Investigations of Filarial Nematode Motility, Response to Drug Treatment, and Pathology

Western Michigan University ScholarWorks at WMU

Dissertations Graduate College

8-2015

Charles Nutting Western Michigan University, [email protected]

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Recommended Citation Nutting, Charles, "Investigations of Filarial Nematode Motility, Response to Drug Treatment, and Pathology" (2015). Dissertations. 745. https://scholarworks.wmich.edu/dissertations/745

This Dissertation-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Dissertations by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. INVESTIGATIONS OF FILARIAL NEMATODE MOTILITY, RESPONSE TO DRUG TREATMENT, AND PATHOLOGY

Charles S. Nutting

A dissertation submitted to the Graduate College in partial fulfillment of the requirements for the degree of Doctor of Philosophy Biological Sciences Western Michigan University August 2015

Doctoral Committee:

Rob Eversole, Ph.D., Chair Charles Mackenzie, Ph.D. Pamela Hoppe, Ph.D. Charles Ide, Ph.D.

INVESTIGATIONS OF FILARIAL NEMATODE MOTILITY, RESPONSE TO DRUG TREATMENT, AND PATHOLOGY

Charles S. Nutting, Ph.D.

Western Michigan University, 2015

More than a billion people live at risk of chronic diseases caused by parasitic filarial nematodes. These diseases: lymphatic filariasis, onchocerciasis, and loaisis cause significant morbidity, degrading the health, quality of life, and economic productivity of those who suffer from them. Though treatable, there is no cure to rid those infected of adult parasites. The parasites can modulate the immune system and live for 10-15 years.

Testing of compounds against filarial nematodes is complicated due to a lack of an objective platform on which to analyze in vitro treatments. There is no published, immunocompetent laboratory model for lymphatic filariasis. This work addresses each of those areas. Imatinib mesylate is shown to have macrofilaricidal potential, killing adult male and female Brugia pahangi worms in-vitro. Histological analysis of rats infected with Brugia pahangi show the same lymphangectasia and inflammatory cellular response seen in humans. The WiggleTron, a light scatter based detection system, can detect and quantify parasite motion; analysis of that motion can be correlated with worm health to study the in-vitro effects of potential anthelminthic drugs. Finally, this work will show the relative uniqueness of secreted microRNAs and discuss their potential as novel therapeutic agents.

My success at WMU would not have been possible without the support of others.

Rob Eversole, thank you for your leadership, mentorship, and friendship far beyond this

research. Your guidance has helped me become a better scientist, a better problem solver,

a better teacher, and a better human (although it seems the monkey will always exert

some control). I am, and will continue to be, grateful for all that you’ve done for me.

Charles Mackenzie, thank you for providing me with opportunities to be a part of

research all over the world. Taking the time to include me in your efforts studying and

combatting filarial diseases has been invaluable to my training and perspective.

Pam Hoppe and Charles Ide, thank you for your critical review of my work. Your comments and insights helped me bridge the gaps from individual experiments to a complete story. Kevin Blair thank you, without your brilliance none of my WT work would be possible. Karim Essani, thank you for giving me my first opportunity to work in a lab and beginning my first real science education. I had no idea what I was doing. The previous statement is now somewhat less accurate thanks to your efforts.

Finally, Rebecca, having a partner who is wholeheartedly committed to the idea that I should pursue something that truly makes me happy, regardless of the privations that you have to suffer, is an incredible thing. I can’t write all that you’ve done to support

this work. I’m overcome with emotion even thinking about it; Thank you.

Charles S. Nutting

ii TABLE OF CONTENTS

ACKNOWLEDGEMENTS ...... ii

LIST OF TABLES ...... vii

LIST OF FIGURES ...... viii

CHAPTER

I. INTRODUCTION ...... 1

Nematode Biology ...... 1

Assessing Nematode Motion ...... 2

Light Scattering Detection ...... 3

Parasitism Involving Nematodes ...... 4

Lymphatic Filariasis ...... 4

Onchocerciasis ...... 20

Loaisis ...... 29

Remaining Areas of Inquiry...... 34

2. RAT LYMPHATIC PATHOLOGY ...... 36

Evaluation of Lymphatic Pathology ...... 36

Previous Work ...... 36

Slide Preparation ...... 37

Nova Red and Hematoxylin Staining ...... 37 iii Table of Contents - continued

CHAPTER

Grading Scale ...... 38

Immunohistochemistry Results ...... 38

Grading Lymphatic Change ...... 42

Statistics ...... 50

Discussion ...... 50

Treatment of Infected Rats with Potential Macrofilariacidal Agents ...... 54

Animals ...... 54

Parasites ...... 54

Infection ...... 55

Monitoring Patency ...... 55

Failure of Infection ...... 55

Confirmation of Protocol ...... 56

Discussion ...... 56

3. DETECTION OF FILARIAL NEMATODE MOTION AND DRUG SCREENING ...... 58

Introduction ...... 58

Motion Sensing Equipment...... 59

Measurement and Analysis ...... 61 iv Table of Contents - continued

CHAPTER

Initial Analysis of Nematode Motion ...... 62

Parasites ...... 63

Initial Drug Testing ...... 65

Statistics ...... 67

Results ...... 67

Detection of Motion ...... 67

Estimation of Worm Number...... 72

Analysis of Worm Health ...... 73

Discussion ...... 77

Field Detection of Microfilariae ...... 79

Microfilaraemic Samples ...... 80

Determining Dilution ...... 80

Determination of Parasite Number ...... 81

Discussion ...... 83

Description of Motion of Different Nematodes ...... 84

Nematodes for Comparison ...... 84

Follow On Drug Testing ...... 87

v Table of Contents - continued

CHAPTER

Drugs ...... 88

Adult Worms ...... 89

Drug Effects ...... 89

Discussion ...... 89

4. FILARIAL MICRO RNA DETECTION IN LOA LOA INFECTED BLOOD ...... 91

Introduction ...... 91

Methods...... 92

DeterminingDilution...... 92

Results ...... 93

Discussion ...... 96

5. CONCLUSION ...... 100

REFERENCES ...... 107

APPENDIX A: COPYRIGHT FOR FIGURE 3 ...... 120

APPENDIX B: COPYRIGHT FOR FIGURE 5 ...... 121

APPENDIX C: COPYRIGHT FOR FIGURES 2, 4, AND 6 ...... 122

APPENDIX D: IACUC ...... 123

vi LIST OF TABLES

1. The number of sections containing each subtype of worm and the levels of lymphangectasia and cellular inflammatory response……..………………………....43

2. Loa loa and Onchocerca ochengi circulating miRNA candidates found in baboon, or cow plasma, respectively…………………………………………………….……...... 95

vii LIST OF FIGURES

1. Prevalence of LF…………………..….………………………………………………..6

2. Life Cycle of Brugia Malayi….………………………………………………………..9

3. Prevalence of Onchocerciasis…………………………...……………………………21

4. Life Cycle of Onchocerca volvulus …………….……………………………………22

5. Prevalence of Loa loa ………………………………………………………………..30

6. Life Cycle of Loa loa ………………………………………………...………………31

7. CD3 T-lymphocyte marker stained panel …...……………………………………….39

8. CD20 B-lymphocyte marker stained panel …………………………………..………39

9. CD68 macrophage marker stained panel …………………………………………….40

10. KI-67 epithelial proliferation marker stained panel…………………….…………...41

11. Representation of zero lymphangectasia and zero cellular inflammatory response....44

12. Representation of level 1 lymphangectasia.…………………………..………….….45

13. Representation of level 2 lymphangectasia.…………..…………………..…………45

14. Representation of level 3 lymphangectasia………………...………………………..46

15. Representation of cellular inflammatory response level 1…………………………..47

16. Representation of cellular inflammatory response level 2…………………………..48

17. Representation of cellular inflammatory response level 3…………………………..49

18. Image of nematodes studied…...... 59

19. Inside view of the WT with top and side view of sample mount and collection apparatus………………………….……………………………………………..…..61

viii List of Figures - continued

20. One second tracing of a single Brugia pahangi L3 motion vs blank………………..68

21. FFT depicting 10 healthy (black) and 10 degraded (red) B. pahangi L3’s. Scaled voltage displayed on y-axis, Hz on the x-axis...... 69

22. Mean returns for 500 live microfilariae, 500 dead microfilariae, and 500 live & dead microfilariae.…………………...…………………………………...... ……..69

23. Mean returns for 100 microfilariae, 100 dead microfilariae, and 100 live and 100 dead microfilariae…………………………………………………………………...70

24. Mean returns for 5000 microfilariae, 5000 dead microfilariae, and 5000 live and 100 dead microfilariae...... 70

25. Mean returns for 100 live L3’s and 100 dead L3’s.……………………………..…..71

26. Mean returns for live and dead adult female and adult male worms………………..71

27. Mean returns over time of L3’s treated at different molar concentrations of imatinib mesylate ………………….……………………………………………...... 74

28. Mean returns of L3’s treated at different molar concentrations of Chloroquine...... 74

29. Mean returns for adult females treated with different molar concentrations of imatinib mesylate……………………………………………………………………75

30. Mean returns for adult females treated with different molar concentrations of Chloroquine……………………………………………………………………….....75

31. Ratios of selected frequency ranges of L3 motion…………………………………..76

32. FFT and ratios of select frequency ranges…………………………….……...….………..77

33. Curve generated from known samples relating mean RMS to Blood microfilaral levels per tube………………………………………………………………...……..82

34. An FFT overlay of 4 different types of microfilarial motion detected within the WT…….…………………………………………………………………………….85

ix List of Figures - continued

35. FFT analysis of B. pahangi adult male (red) motion overlaid with FFT analysis of O. ochengi adult male (black) motion detected within the WT.……………...…87

36. FFT analysis of B. pahangi adult female (red) motion overlaid with FFT analysis of O. ochengi adult female (black) motion detected within the WT…………...…...88

37. Venn diagram showing the distribution of circulating miRNA candidate sequences among four host–parasite scenarios…………………………………...…94 38. Clustal Omega alignments of nine sequences identiﬁed in at least four parasitic ﬁlarial species ……………………………………………………………………..…99

CHAPTER I

INTRODUCTION

Nematode Biology

Nematodes are a diverse group of multicellular roundworms. These worms live in many different environments and have widely varying lifestyles. Most nematodes are free-living worms residing in soil, marine, or fresh water [1]. Some nematodes such as

Heterodera are plant parasites [1]. Some are parasitic to animals and humans; their parasitism causes disease that affects over one-sixth of the world’s population [2].

Despite the diverse lifestyles of nematodes, they share a common anatomy and physiology. Nematodes are surrounded and protected by a semi-permeable cuticle which sits atop a layer of hypodermis. The cuticle is porous, allowing some ions, water and other small molecules to pass and helping to maintain osmotic pressure. The hypodermis contains lateral lines that form chords, the lateral cords containing excretory canals.

Underneath the hypodermis is a layer of spindle-shaped, cholinergic and gamma- aminobutyric acid (GABA) controlled, longitudinal body muscle, innervated by nerves extending outward from a ring of nervous tissue that encircles the pharynx [1,3].

Innervation of the body wall muscle is both inhibitory and excitatory [1].

The alimentary system is a tube that runs the length of the nematode’s body. It includes a mouth, surrounded by six lips, a small, variable cavity in the buccal region, a muscular pharynx, an intestine, and an anus [1]. A nematode can be thought of as a sealed pressure vessel, the internal pressure is great enough that at rest, the intestine

should be flat, however the muscular pharynx is used as a pump to increase pressure,

forcing fluid into the intestine [1].

Female nematodes are normally larger and have two ovarian tubes and a uterus.

Male nematodes have a spermatogenic tube connected to a cloaca through vas deferens.

Some species of nematode can switch sexes due to environmental cues [1]. All

nematodes follow a common life-cycle having four larval stages after hatching prior to

reaching adult status [1].

Nematode motion is relatively similar despite their diversity. As most nematodes

live in aquatic or moist environments gliding across a wet surface or swimming is a

typical motion type. Locomotion in this manner is achieved through a pattern of dorso-

ventral undulation [4]. This movement is the result of the interplay of muscle contraction

along one side of the body countered by the hydrostatic pressure of the internal fluid

acting on the elastic cuticle [1]. The resulting locomotion is perpendicular to the long axis of the worm. This type of locomotion is the most common, however others exist especially within the free-living species of nematodes when dealing with drier environments and parasitic nematodes within their host organisms [1].

Assessing Nematode Motion

Efforts to measure and differentiate parasite motion are for the most part subjective studies using visual analysis to describe and rate the motion of the worm [1,5].

Automation of this study has been attempted to a varying degree of success [6-8]. Initial attempts to automate the measurement of nematodes were limited to the relatively large adult forms of the worms [6]. Impedance based measurements offer the ability to detect differences between live and dead worms and objectively measure changes in worm

2 motion, however are limited to the laboratory or industry setting, further complications arise if the nematode in question will not come to rest at the bottom of the assay plate [7].

Smaller developmental stages offer problems to the video-based measurement system, which at current seems to be limited to the larger adult worms [8].

Light Scattering Detection

Visible light is a form of electromagnetic energy from roughly 400nm to 700nm in wavelength. Insomuch, visible light has both wave-like and particle-like behaviors.

Light exhibits the properties of reflection (wave/particle) [9,10], refraction

(wave/particle) [9,10], interference (wave) [10,11], diffraction (wave) [9,10,12], polarization (wave) [10,13], and photoelectric effect (particle) [10,14].

Reflection, refraction, and the photoelectric effect are the properties of light taken advantage of by light scattering detectors. Reflection is a property of light wherein when light strikes a surface a portion of it will rebound off the surface at an angle equal to the angle of incidence [10]. Refraction is when light strikes a medium with a different speed of light from where it began its travel; the light will bend in the direction of the boundary between the two media, changing the path of light propagation [10]. Photoelectric effect describes the ejection of electrons from a surface that is being bombarded with photons, which when in a circuit will cause a current as electrons move toward a cathode [10,15].

During the 1980s, the first attempt at detecting and quantifying parasite motion using light scattering was initiated by Bennet and Pax [6]. In their setup, a light was passed upward through a tube containing the nematode in a solution toward the meniscus of the fluid. The light would be reflected and refracted off of the meniscus and sensed by detectors at the same level as the meniscus. When the nematode moved, the fluid and

thereby the meniscus would be disturbed, altering the light sensed by the detectors [6].

This change in reflection and refraction pattern of light due to motion was the underlying

physical principle allowing the detection of motion; this is because of the photoelectric

effect [15]. When photons come into contact with the photodetectors, electrons are

displaced generating a current. Current and voltage are positively correlated [15].

Increases in the light absorbed by the photodiode increase the amount of electrons

displaced as photons hit the surface of the detector [15]. This is registered as a positive

voltage. Decreases in the light absorbed by the photodiode decrease the amount of electrons displaced, resulting in a negative voltage. Bennet and Pax went on to test a

number of different nematode types and had success monitoring the motion of larval

Nippostrongylus brasilienis and ascaris, as well as adult C. elegans and Brugia pahangi

[6]. This machine was limited in its ability to detect the motion of smaller nematodes or

larval stages.

Parasitism Involving Nematodes

Parasitic diseases remain a public health problem in developing countries [16-18].

Filarial nematodes are responsible for causing disease in the tropical and subtropical

regions around the world [19,20]. Lymphatic filariasis, onchocerciasis, and loaisis cause

massive economic and health damages in endemic areas; all result from parasitic

nematodes.

Lymphatic Filariasis

Lymphatic Filariasis (LF) in humans is a debilitating and chronic disease caused

by 3 different types of parasitic worms: Wucheria bancrofti, Brugia malayi, and Brugia

timori [21,22]. These parasites are spread through a mosquito vector [23]. In addition to

the human forms, these and other filarial worms cause similar pathologies in other animal species [24,25]. The disease state is characterized by lymphangiectasia, chronic lymphedema, hydrocele of the testis, and acute inflammatory adenolymphangitis [22,26].

Accompanying these symptoms is a widely seen immune dysfunction that allows the healthy parasites to grow relatively unmolested by the immune system [27].

The parasites that cause this condition tend to proliferate in impoverished areas and lymphatic filariasis further contributes to that poverty [17,26,28]. In 1993, the

International Task Force for Disease Eradication characterized as potentially eradicable

[29]. The World Health Organization (WHO) asked its membership to come up with plans for the elimination of LF; these efforts culminated in the establishment of the

Global Programme to Eliminate Lymphatic Filariasis (GPELF) [26]. In the following paragraphs, this section will discuss in further detail: the epidemiology of LF in humans, the organisms that cause LF and vectors involved in its transmission, pathology, host immune response, and the treatment programs and protocols.

Epidemiology:

Over 1.3 billion people in 83 countries live at risk of filarial infection [30-32]

(figure 1). It’s estimated that greater than 120 million people are infected with lymphatic filarial parasites [31,32]. Of that number, 40 million people throughout the world suffer from lymphatic filariasis [21] with damage to extremities and genital areas [32]. The remaining 80 million parasite infected individuals do not clinically show the disease [32].

Of those suffering from LF, roughly 90% are afflicted with bancroftian filariasis and 10% with Brugian filariasis (including both Brugia malayi and Brugia timori) [33].

Figure 1: Prevalence of LF [34].

Though the endemic regions range from South America, Africa, Southeast Asia,

and the Western Pacific [31], some commonalities exist. Climate across these regions is

very similar. The regions endemic for LF form a belt around the world corresponding

more or less to the region in between the Tropic of Cancer and the Tropic of Capricorn.

Therefore, all of the endemic countries fall into the tropical or immediate subtropical

climatic zones [31]. The climate in these areas remains warm through much or all of the year. This warmth, coupled with adequate rainfall sets the general preconditions for vector survival required for development and transmission of the filarial parasites to

humans [35]. Within this area, broadly defined above, there is still considerable variation

in altitude, land-use and demographics. These factors can then be further used to define

the endemic countries into more specific areas of regions of higher risk of LF infection

[26].

Altitude is a natural variable affecting filarial infection risk. Altitude has much the same effect that distance from the equator has on LF risk. A higher, dryer, cooler microclimate provided by increased elevation will lessen the ability of the vector to survive. This in turn lessens the risk for transmission of filarial parasites and rates of infection [36]. Studies in malaria, another vector-borne parasitic disease, show similar trends with increasing altitude [37].

Land-use and demographics also play a large role in the filarial risk in an area. In urban areas, especially urban poor areas, the mosquito Culex quinquefasciatus is more common [33]. The poor sanitation in these areas produces fertile breeding grounds for this insect. Typically in these regions, those suffering from LF are infected with W. bancrofti [33]. In rural areas Anopheles species may also carry W. bancrofti, but are more normally associated with Brugia malayi [33]. Mansonia mosquitos also serve as vectors for Brugia malayi in rural regions as well [33]. In these rural regions, B. malayi has also been found to reside in several different animal types that may serve as a reservoir for human infection [33,38]. Brugia timori is vectored by another mosquito Anopheles barbirostris [33]. The range of Brugia timori is very limited. It has only been noted on a few Indonesioan islands [33,39].

Filarial Parasites:

Wuchereria bancrofti is responsible for roughly 90% of the cases of human LF;

Brugia malayi and Brugia timori make up the other 10% of cases [33], the malayi variant

making up the majority of that balance. These filarial nematodes belong to the subfamily

Onchocercinae, which in turn belongs to the family Onchocercidae, the superfamily

Filarioidea, and the order Spirurida [40]. Wuchereria and Brugia share a common life

cycle and similar morphology. Adult Wuchereria females reach lengths of 100mm with

diameters between 0.24mm and 0.30mm. Adult Wuchereria males reach lengths of

40mm with a diameter around 0.1mm [41]. Adult Brugian females reach lengths between

43mm and 55mm with diameters between 0.13mm and 0.17mm. Adult Brugian males

reach lengths of 13mm to 23mm with a diameter around 5um to 7um [42]. Wuchererian and Brugian microfilariae are sheathed and much smaller than the adults with lengths ranging from 244um to 296um in Wuchereria and 177um to 230um in Brugia [41,42].

Wuchererian microfilariae range from 7.5um to 10um in diameter; Bancroftian microfilariae have diameters from 5um to 7um [41,42].

During a blood meal an infected mosquito will introduce a L3 larval stage parasite to a human host. This parasite then uses the wound caused by the mosquito’s proboscis to pass the human epidermis. These parasites mature within the human host to an adult worm stage and are commonly found in lymphatic vessels. The adults will then begin to produce sheathed microfilariae. These microfilariae leave the lymphatics and make their way through the blood vessels to vessels near the surface of the skin [43]. Another mosquito will then take a blood meal on the infected host and ingest the microfilariae.

Within the mosquito, the microfilariae shed their sheaths. They ultimately reach the

thoracic muscles. In this region, the microfilariae develop into L1 larvae, then L2 larvae,

until finally reaching the L3 larval stage. At this point they then migrate toward the mosquito proboscis to await insertion into a human host [41,42]. The life cycle for Brugia malayi produced by the US CDC is depicted below in figure 2.

Figure 2. Life Cycle of Brugia Malayi [42] http://www.cdc.gov/parasites/lymphaticfilariasis/biology_b_malayi.html

Genome:

Eukaryotic parasites such as B. malayi and W. bancrofti have large complex

genomes. Brugia malayi encodes over 11,500 genes, found through automated gene

prediction using the highly assembled component of the genome [44]. A further 20Mb of

DNA was isolated from B. malayi and estimated to include an additional 3000-6000

genes [44]. Although there is no published genome for Wuchereria bancrofti, it is likely

that its genetic component is similar as other nematodes C. elegans and C briggsae both

have genomes that encode over 19,000 proteins [45,46].

Comparison of the genomes of B. malayi with other nematodes shows a large

overlap, about 48% of orthologous genes from the B. malayi genome [44]. This number

itself may be artificially low as further analysis shows that 8% of the orthologous genes

between B. malayi and C. elegans have undergone expansion through gene duplication events in C. elegans [44]. This expansion of genes could also explain why B. malayi has

a smaller genome than C. elegans or C. briggsae [44]. Comparison between these

nematodes has also yielded a portion of the malayan genome that appears to be unique.

About 20% of the proteins encoded by B. malayi appear to be species specific [44].

Likely, included within this set of genes are some genes that are required for modulation

of the hosts B. malayi inhabits as neither C. elegans or C. briggsae are parasitic to humans or mosquitos [44,45].

B. Malayi also encodes a gene similar to human TGF-β [44,47]. This homolog of a human cytokine may serve as an important immunosuppressive mechanism employed by filarial parasites as TGF-β is thought to be both be involved in suppression of immune effector cells, as well as the conversion of FOXP3+ Treg cells [48]. A homolog of

Macrophage inhibitory factor (MIF) is also found in filarial parasites [49]. Other immunomodulatory genes have been found in filarial parasites, for example Glutathione peroxidase, superoxide dismutase, thioredoxin peroxidase, and glutathione S- transferase are all antioxidative that help protect the parasite from host-induced oxidative stress

[50,51]. Filarial parasites also encode cysteine and serine protease inhibitors, Bm-CPI-2,

and Bm-SPN-2 that block proteases such as papain and neutrophil proteases respectively

[52].

Endosymbiont:

The bacterium Wolbachia pipientis is a type of intracellular bacteria belonging to

the order Rickettsiates [40] that can be found in filarial parasites, as well as arthropods.

Within filarial parasites, wolbachia functions as an endosymbiont, thereby profiting from

its infection of the filarial worm, while providing some beneficial effect [40]. Wolbachia

inhabits many of the species within the subfamilies Onchocercinae and Dirofilarinae

(reviewed in [40]. Further, Wolbachia is found within all the filarial nematodes that cause

LF [53]. Of the species of filarial parasite that have been found to harbor Wolbachia

100% of the population seems to contain the bacterium [54].

Wolbachia is present in each of the larval stages of filarial nematodes [55]. Both

sexes of the parasite harbor Wolbachia within the lateral chords [54,55]. The bacterium is

also found in the ovaries, oocytes, and developing embryos within the female

reproductive tract [54,55]. Wolbachia is not associated with the male reproductive system

[54,55]. The appearance of Wolbachia within the female reproductive system and

apparent lack within the male suggests that Wolbachia is vertically transmitted through

the female gamete.

Though populations of Wolbachia vary between worms, patterns in populations have been noted. Populations are relatively stable within microfilariae, L2, and L3 larval stages inside the mosquito [56]. Upon infection of a mammalian host, Wolbachia population grows substantially (600 fold within a week). This growth continues within the lateral chord region till about 15 months after infection in males [56]. Females show

this growth of population in the lateral chords, as well as a continued growth of the

population of Wolbachia within the ovaries and the developing eggs [56].

Continued Wolbachia growth within the female reproductive tract and studies

using anti-endosymbiont antibiotics show that Wolbachia is important for embryo development within filarial parasites and that endosymbiont depletion can be an effective

target for control of the parasite (reviewed in [40,54]) Wolbachia enhances the filarial

parasites ability to modulate the immune system of its host (reviewed in [57]). There is

also significant evidence that Wolbachia excretes compounds used by its parasite host for

metabolism that the worm may lack the ability to make on its own (reviewed in [57]).

Pathology:

There are number of different pathologies associated with LF. Lymphangiectasia, chronic lymphedema, hydrocele, acute inflammatory adenolymphangitis, chyluria, and tropical pulmonary eosinophilia have all been described as a result of the interplay

between the parasite and the host immune system.

L3 parasites migrate to lymphatics and undergo larval molts until they reach the

adult stage. Once adult, the worms live for a long time unmolested by the host immune

system [19]. Lymphangiectasia is the abnormal dilation and growth of lymphatic vessels

[58]. This endothelial hyperplasia takes place in the presence of healthy adult worms

[59,60], and is likely due to factors produced by the worms themselves to aid in immune

evasion and ensure parasite survival [58]. These worms normally take up residence

within the lymphatics of the arms, legs, or groin area. This lymphatic change is not due to

obstruction [58]. Dilation results in increased volume and allows fluid to pool in these

vessels.

Pooling of fluid within these vessels over time can lead to a chronic state of lymphedema [61]. This swelling eventually puts pressure on the surrounding tissues, including the epidermis. Skin elasticity is lost and fibrosis occurs in the surrounding

tissue. As the edema progresses, folds in the skin develop [61]. These folds represent

fertile breeding grounds for secondary infections and the development of acute

dermatolymphangioadenitis [61]. These secondary infections can cause acute

inflammatory stress that exacerbates local edema. This can cause the formation of dermatosclerosis and ulcerous lesions [62]. Continuing attacks by secondary infections

eventually lead to the development of elephantiasis [63]. Vascular endothelial growth

factor (VEGF)-C contributes to the lymphatic change [64]. It signals endothelial cells

within the lymphatic vessels to proliferate through the induction of the VEGF receptor 3

[65]. Up-regulation of VEGF-C is considered a molecular marker for the disease [66].

Hydrocele is a special case of lymphatic edema that is localized to the area

surrounding the testis resulting from filarial infection. Hydrocele results in pooling of

lymphatic fluid within the scrotum [61]. Hydrocele may begin as acute swelling that goes

away over time, however if left untreated, these repeated attacks can change the tissue in

the tunica vaginalis, a serous membrane extended off the peritoneum that projects into the

testis, leading to chronic swelling [61]. VEGF-A, another lymphangiogenic cytokine [67]

is shown to be up-regulated in hydrocele and contributes to new vessel formation and

increased vessel density in the surrounding tissue that lead to the disease [68]

Acute inflammatory adenolymphangitis due to LF occurs transiently, more often

than not in patients that show chronic lymphedema [69]. It is characterized by fever,

redness, increased swelling and tenderness in the host [69], as well as decreased

movement or death of the parasite, indicating damage to the parasite has occurred [70].

This inflammatory reaction can be caused by the administration of drugs. For this reason,

anthelminthic drugs in development may require a long killing time for adult worms.

Chyluria is simply the presence of chyle in urine [61]. Ruptured lymphatic vessels

leak fluid which is taken up by the excretory system. This fluid causes a milky

appearance of urine [61]. Environmental factors and diet can influence the magnitude and

length of chylous episodes.

In a small percentage of lymphatic filariasis cases, a condition known as tropical

pulmonary eosinophilia is also seen [71]. Tropical pulmonary eosinophilia results from

immune complexes, formed in response to microfilaria, migrating to the vasculature of

the lung and causing inflammatory related damage [71].

Host Immune Response:

The human immune response to filarial infection is very complex. The response

to filarial infection is comprised of a high level of anti-filarial antibodies of the IgE [72]

and IgG4 subtypes [73], accompanied with eosinophilia [74]. Studies have shown that

there is a degraded Th1 response to helminth infection [27,75], along with a

predominantly Th2 type cytokine response in human hosts [76-79]. The Th2 response

includes increases in interleukin (IL) 4, IL-5, and IL-13 [77,78,80]. The regulatory IL-10 is also expressed in a high level in filarial infections [81]. IL-4 and IL-13 traditionally

stimulate the production of IgE and IgG4 type antibodies [82,83]. IL-5 has been shown to

recruit and stimulate eosinophils [84]. IL-10 suppresses effector cell action in both Th1

and Th2 immune responses [85]. In doing this, IL-10 expression may contribute to the

relative inadequacy of the human immune system to successfully clear the filarial

parasites [85,86]. This leads to healthy adult worms being long-lived within the host and

encountering little immune resistance.

Dead or injured worms present a different profile in immune mobilization than

healthy worms. Dead parasites are very inflammatory, promoting a classical Th1 type

response with IFN-γ, IL-6, and TNF-α [87]. This leads to an influx of inflammatory cells:

eosinophils, macrophages, mast cells, lymphocytes, and plasma cells are all found in

tissue surrounding degraded adults within the lymphatics. There is speculation that the

Th1 response is due to not only worm products, but also Wolbachia products [87].

Eosinophilia is a classic reaction to metazoan parasites. During lymphatic filariasis, eosinophilia is stimulated as a result of the Th2 cytokine IL-5. IL-5 has been

shown to stimulate eosinophil differentiation [88] as well as the release of bone marrow

resident eosinophils into the bloodstream along with eotaxin proteins 1-3 [89,90]. Within

areas endemic for lymphatic filariasis, eosinophilia can be seen in the peripheral blood at

levels of 5% to 75% of total blood leukocytes, much higher than the accepted 1% to 6%

of a typical European population [91-93]. In addition to elevated blood eosinophil counts,

eosinophilia can be seen in perivascular areas, (far from the worms themselves),

collocated with dead or dying treated adult worms, or within the lymph nodes [92].

Eosinophils kill parasites through an antibody, complement, or combined factor

mediated release of granules containing basic or cationic proteins or reactive oxygen species [91,94]. These effector molecules, released from the eosinophils, do not differentiate between host and parasite tissue and therefore are the cause of some of the damage to host tissue seen near parasites as well as in atopic conditions such as asthma

[91,93,95]. In patients suffering from LF, eosinophils are not normally found near healthy

adult worms [92,96], but are found in large numbers around injured or dead worms [97].

Eosinophil granule proteins (peroxidase, major basic, cationic) can also be isolated in the

areas surrounding injured or dead parasites allowing the assessment that some tissue

change resultsfrom eosinophil activity [97].

Macrophages are critical effector cells the human immune system marshals in defense against a broad range of microorganisms. When classically activated through IFN

γ, macrophages function as pro-inflammatory [98]. Within lymphatic filariasis,

macrophages acting in this manner have been shown to congregate near adult worms, as

well as dying or degrading worms. These congregations highlight their role in defense

against the parasites as well as in pathology seen as a result of infection [99]. Further,

studies have shown that macrophages can be effective at killing L3 parasites in vitro

[100-102] when classically activated through the use of nitric oxide (NO) [101,103]. In-

vivo studies in jirds show that macrophages from infected animals show increased

phagocytosis and microbial destruction [104]. Further, macrophages seem to be the

dominant cell type surrounding parasites in jirds and contributing to granulomatous

formations around the worms [105].

However, macrophages, monocytes, and other antigen presenting cells have been

linked to parasite induced immunosuppression in vivo [98,106-109]. These conflicting

descriptions show the complicated nature of the interactions between macrophages and

filarial parasites. In summary, the parasites induce an alternatively activated macrophage

[98,110] that operates based partly on the presence of TGF-β [110] as well as IL-4 in

association with macrophage inhibition factor [108,111]. These alternately activated

macrophages contribute to suppression by the production of anti-inflammatory cytokines

and the inhibition of T-cell population expansion [112], thereby having the opposite

effect as the classically activated macrophages mentioned in the paragraph above.

Further, the parasite also negatively affects the trans-endothelial migration of monocytes

as well as neutrophils without altered expression of adhesion molecules [113].

T regulatory cells (T-regs) are a specialized subtype of CD4+ cells, whose job is

the active suppression of other immune cells [48,114-116]. T-regs have been postulated to be one of the reasons that filarial parasites can so adeptly evade the human immune system and live for such a long time within the body [117]. Studies in humans showed high levels of IL-10 in patients with persistent filarial infections [81]. Th1 type inflammatory cytokines are found to be expressed in low levels in individuals suffering from chronic filarial infection [118]. Inhibitory T-reg cells have been successfully harvested from patients with other chronic helminth infections [119], and shown to be involved in hyporesponsiveness to their antigens through the influence of IL-10 and

TGF- β [120].

Further studies in mice have shown that there is an increase in T-reg cell population due to filarial infection with B. malayi [121]. This increase of T-reg cells occurs at the L3 and the adult stage [121] and requires IL-4 [122], although IL-10 has been shown to compel expansion of the T-regulatory population [123]. Antigen specific

T cells harvested from onchocercomas and cultured show a high level of production of the T-reg cytokine IL-10 [119]. Lending further credence to the idea that T-regs are

integral to suppressing the host immune system and allowing the parasite a long life is the

work of Taylor et al, who, using the mouse as a model with antibodies specific to T-reg

cells, showed that neutralizing T-regs led to an increased parasite clearance [124].

Current Treatments:

Ivermectin and albendazole have been used as part of a mass drug administration

in conjunction with diethylcarbamazine (DEC) to treat LF in endemic areas as part of this

program directly targeting the parasites [17,26]. Antibiotics, such as doxycycline have

been used to target the endosymbiont bacteria Wolbachia [125-128]. Unfortunately, none

of these treatment options currently available, whether used alone or in concert with one

another, fully addresses the requirement to kill adult parasites without bringing about a massive inflammatory response with a reasonable treatment regimen.

Ivermectin is a macrocyclic lactone given at 150-200mg/kg; a member of a class of anthelminthic that acts on glutamate coupled chloride channels [129,130]. Ivermectin binding leads to cellular hyperpolarization through an influx of chloride ions which then causes paralysis [131]. In O. volvulus, ivermectin has been shown to reduce the number of microfilaria produced by adult worms [132], through the degradation of microfilaria within the uterus of the adult worm [133]. The actual binding site of ivermectin on the glutamate coupled chloride channels within filarial parasites remains unknown.

Ivermectin shows no lethal effects on the adult worms. Ivermectin has also been shown to interfere with the function of the excretory-secretory apparatus during in-vitro studies with Brugian microfilariae which resulted in a drastic decrease in the amount of protein released from microfilariae [134]. Decreasing the release of protein may be a contributing factor to clearing in-vivo microfilariae as they can no longer secrete potentially immunomodulatory factors at a protective level [134].

Albendazole is part of a class of drugs called benzimidazoles. These drugs typically work by disrupting β-tubulin formation of microtubules [135], therefore

affecting areas of high cellular turnover. This is shown to influence tissue such as

epithelial sheets lining the gut [136]. Albendazole does not effectively kill adult worms

[137].

Antibiotic treatments targeting the endosymbiont Wolbachia result in sterilization

of the adult female worms for a period of up to 2 years and disrupt the development of

microfilariae [125,128,138]. Treatments are given daily for a duration of four to eight

weeks in length [128,130]. Ultrasonography of treated worms showed a marked decrease

in the number of adult parasites present in previously infected people [128]. It took many months to see the effects of the doxycycline treatment, both on the microfilariae and on the adults [128]. This slow kill of adults is a positive in that it lessens the chance of a potentially damaging massive inflammatory reaction in response to rapidly dying adult worms [139]. Antibiotics have also proven to interrupt the molting of L3 to L4 larvae

[140]. Positive as the results might be in killing adults and preventing larval molts, the required duration of treatment makes them unrealistic for use in a mass drug administration such as the one the WHO is currently engaged in.

Diethylcarbamazine (DEC) is added to salt and used in conjunction with albendazole in areas that are not co-endemic for onchocerciasis and loiasis [61]. At high doses DEC kills a percentage of adult parasites, but has no overall effect on pathology

[61]. At lower levels DEC aids in microfilariae clearance through an as of yet unknown mechanism, thought to sensitize them to phagocytosis through targeting of the arachadonic acid, 5-lipoxygenase, and cyclooxygenase-1 pathways [141]. Effects on clearance of microfilariae with DEC are normally short-lived [142]

Flubendazole is another member of the benzimidazole class of drugs.

Flubendazole has potential to aid in the treatment of LF. In O. volvulus, flubendazole

showed a greater ability than DEC to reduce the number of microfilaria found in the skin

and eye 6 months after treatment [143]. In rats, flubendazole has also been shown to

significantly lower the number of detectable microfilaria [144] and drastically lower numbers of adult parasites when sacrificed [144]. It is because of this ability to lower the number of adult parasites that it is a potential new treatment for lymphatic filariasis as none of the current treatment options can effectively kill adult worms.

Onchocerciasis

Onchocerca volvulus is the causative agent of onchocerciasis. In onchocerciasis,

adult female worms live in nodules located within the hypodermis [64]. Upon maturity,

these adult worms release microfilariae which migrate to the skin causing epidermal

dysfunctions and blindness resulting from inflammation [64]. Onchocerciasis is

transmitted by the black fly of genus Simulium [145]. Like the parasites that cause

lymphatic filariasis, O. volvulus seems to modulate the host immune response. The

Onchocerciasis Control Program (OCP) of the WHO coordinates regional programs to

eliminate onchocerciasis [146], the Onchocerciasis Elimination Program for the Americas

(OEPA), and the African Program for Onchocerciasis Control (APOC). The upcoming

section will further describe the epidemiology, causative organisms, vector, pathology,

host immune response, and treatment programs and protocols for onchocerciasis.

Epidemiology:

Nearly 40 million people in sub-Saharan Africa, the Middle East, and parts of

Latin America suffer from onchocerciasis [19,147,148]. Another 120 million are

estimated to live within endemic regions and are therefore at risk for onchocerciasis

(reviewed in [147]).

Onchocerciasis, much like lymphatic filariasis, is a disease found in the tropical and sub-tropical (climates previously discussed) regions that can support year round vector populations. Within sub-Saharan Africa, the Middle East, and Latin America onchocerciasis is found situated near rivers and in forested areas, the preferred habitat of

Simulium [149]. By comparing maps indicating the endemic areas for onchocerciasis

(figure 3) to topographical charts it is clear that high altitude and the associated cooler temperatures that come with high altitude are prohibitive to maintaining a vector population and are thereby free of onchocerciasis.

Figure 3: Prevalence of Onchocerciasis [148]

Parasite:

O. volvulus is the sole causative parasite for onchocerciasis. It is a member of the same sub-family, Onchocercinae as Wucheria and Brugia Spp [40] and therefore has the same phylogeny as previously described. O. volvulus can live up to 15 years within the host [147]. Their life cycle (figure 4) is similar to that of the LF causative parasites. The adult female worm is the largest form of O. volvulus measuring 33-50 cm in length with a diameter of 270-400um [150]. The adult male measures 19-42mm in length and has a diameter of 130-210um. O. volvulus microfilariae are from 220-360um long with a diameter between 5 and 9um.

Figure 4: Life Cycle of Onchocerca volvulus [150] http://www.cdc.gov/dpdx/onchocerciasis/ 22

The adult female worms typically live within induced nodules deep to the skin

with numbers varying from one to sixty coiled worms [147,151]. Males may also be

found within lesions, however may not be permanent tissue residents [151]. Adults within

the human host develop from L3 worms introduced through the bite of a Simulium biting fly. These worms undergo a larval molt to L4 stage worms, before sexually maturing

[150]. Once sexually mature the parasite is considered adult. Adult females within the nodule produce 1000-3000 microfilariae each day [152]. These microfilariae leave the nodule and migrate to the epidermis. Once in the epidermis they live for up to two years waiting to be ingested by another biting fly [150]. Within the fly, microfilariae undergo two larval molts and migrate toward the proboscis as infective L3 larvae.

Genome:

There is currently no full sequence available for the genome of Onchocerca volvulus, but some work has been done to characterize the genetic makeup of the parasite.

The nuclear genome is estimated to be around 1.5 x 10^8 bp in size with a mitochondrial genome of around 13,000 bp [153]. Many of the genes identified seem to be larval stage specific reviewed in [153]. From what is available, the genome of Onchocerca volvulus seems very similar to that of Brugia malayi [52]. Due to this similarity many of the immunomodulatory proteins should be found within Onchocerca volvulus as well.

Endosymbiont:

O. volvulus, like the causative species involved in LF is a host for the symbiotic bacteria Wolbachia pipientis. The relationship between O. volvulus and Wolbachia is identical to that of Wuchereria or the Brugian filarial nematodes and Wolbachia [154].

Pathology:

Adult worms live in nodules beneath the skin, these nodules are formed around healthy adult worms by the immune system [61,155]. These nodules are essentially long- lived granulomas that form protective barriers around the adult worms, without destroying them. These granulomas are formed by the encapsulation of the worms by multiple macrophages, which further mature into epitheloid cells, then into fused giant cells. These macrophages trigger nearby fibroblast to produce a fibrotic capsule of collagen, which then encompasses the worm as well as the giant cells. This nodule formation may be enhanced by the parasite produced fatty acid binding protein Ov-FAR-

1 which can enhance collagen synthesis [156] as well as angiogenic proteins [157]. Other inflammatory cells have been found present in the surrounding tissue adjacent to

encapsulated adult worms. These include eosinophils, neutrophils, and lymphocytes

[155].

Upon taking up residence under the skin, O. volvulus begins to produce proteins

that are considered non-self by the host immune system. It is this triggering of an immune

response, combined with the parasite’s ability to limit the scope of the immune response,

that causes changes in the epidermis and eye of people suffering from onchocerciasis

[147]. A grading system has been employed to differentiate skin lesions in

onchocerciasis, grouping affected individuals into categories based on the appearance of

their skin. Acute papular dermatitis, chronic onchodermatitis, lichenified

onchodermatitis, chronic onchocerciasis, and onchocercal depigmentation are the

categories used to describe epidermal change.

Acute papular dermatitis is normally the first skin change seen and may be

transient in nature, disappearing in a few days [61]. A rash-like area of skin develops due

to the formation of small abscesses, which can progress to larger structures and

generalized edema around skin microfilariae [147]. Filarial itch or pruritus usually

accompanies the rash. Continued irritation caused by scratching can cause lacerations in

the skin and lead to secondary infections that increase local inflammation and can

exacerbate damage to the skin leading to more chronic epidermal dystrophy [61]. Chronic onchodermatitis results from repeated acute episodes resulting from dying parasites.

Larger lesions can be seen on the epidermis [61]. In chronic onchocerciasis this is accompanied by loss of elasticity, due to the breakdown of the dermal extracellular matrix by both host and worm enzymes [158], and general atrophy of the tissue, which in turn makes the skin seem aged beyond unaffected areas and seem to hang down from the rest of the body, especially around enlarged lymph nodes [147].

Lichenified onchodermatitis is characterized by hyperkeratotic plaque formation in affected areas and is traditionally called lizard skin or sowda [61]. These plaques are normally associated with ulcerations in the epidermis and associated enlarged lymph nodes. This type of presentation is normally seen in individual with low parasite loads.

Affected epidermis has abnormally high levels of pigmentation. The breakdown of dermal extracellular matrix seen in chronic onchocerciasis is also seen in lichenified onchodermatitis [147]. Onchocercal depigmentation is also seen in some chronically infected individuals. The same breakdown of dermal extracellular matrix and atrophy of the skin as seen in chronic onchocerciasis, accompanied by a loss of pigment in the epidermis, leading to light patches of epidermis on the individual [61,147].

A special case of epidermal change, called river blindness occurs should

microfilariae migrate to the eye. Microfilariae that invade the conjunctiva, cornea, or

posterior chamber of the eye can cause inflammation and the breakdown of the barrier

that provides immune-privilege to the cornea [159-161]. This can lead to inflammation of many eye tissues and the development of corneal scarring, keratitis of the cornea itself,

leading to loss of visual acuity [162]. Further inflammation in the posterior chamber can

progress to the retina and result in chorioretinitis and degradation of the retinal

epithelium and pigmentation, leading to blindness [163].

Lymphadenitis, briefly mentioned earlier, can be found with chronic

onchocerciasis [147]. Migrating microfilariae have been found in the node, surrounded

by eosinophils and macrophages [164]. Follicular hyperplasia has also been noted to

accompany the lymphadenitis [164].

Host Immune Response:

The preceding pathologies described are all classically considered to be resultant

from chronic inflammatory reactions to the parasites [165]. These inflammatory

responses are resultant from the activation of the immune system by the parasite. As there

are many different pathologies seen in onchocerciasis, there are many different ways in

which the immune system has been seen to engage the parasite [166]. However, for the

majority, estimated around 98% of cases there is a general trend that has been identified

and can be described [167].

In general for most onchocerciasis sufferers, live healthy worms trigger a Th2

response, a Treg response, and a muted Th1 response and moderate inflammation [168].

The Th2 response has been identified looking at cytokines present (IL-4, IL-5, IL-13), the

effector cells involved (eosinophils, mast cells), and the predominant humoral reaction

(IgE and IgG4) [147,169-174]. Treg response has been noted through the increased presence of IL-10 and TGF-β in infected individuals [86] and the ability to isolate suppressive IL-10 and TGF-β producing cells from chronically infected individuals

[175].

In a very small minority of cases, individuals that have been continuously exposed but show no microfilariae or signs of skin changes are called putatively immune.

Putatively immune individuals display increased Th1 type responses including IFN-γ,

GM-CSF, and TNF-α along with the Th2 response and increased levels of IL-5 and show no signs of inflammation [176-178]. Sowda individuals show a Th2 response that is larger than what is seen in the more standard form of onchocerciasis and massive inflammation [168,171,179]. Dead and dying worms show a large Th1 response of the same profile as seen in LF [87].

Eosinophilia is seen in people affected by chronic onchocerciasis, and more pronounced in individuals suffering from the sowda variant of the disease [147].

Eosinophil granule products can be isolated from the serum of infected individuals at elevated levels; sowda patients show even higher concentrations of these granule components [180]. Eosinophilia is stimulated through the Th2 cytokine IL-5. IL-5 has been shown to stimulate eosinophil differentiation [88]. Eosinophils have been found to be adherent to Onchocerca volvulus microfilariae, L3’s, but not L4’s [181]. This mimics what is traditionally found within onchocerciasis patients, where eosinophils have been found adhered to microfilariae from the skin[164], contributing to the pathology seen in the organ [182].

Eosinophil degranulation and degradation is continuous in sowda patients but

transient in chronic onchocerciasis patients, resulting from the death of parasites or the

administration of drugs [147,180]. Within Sowda patients, the action of the eosinophil

seems to have a microfilaricidal effect as microfilariae are isolated from Sowda patients

at a much lower level [147,155]. In chronic onchocerciasis patients, administration of

DEC causes rapid degradation of Onchocerca volvulus, and can trigger eosinophil degranulation through what is called the Mazzotti reaction, causing acute inflammation in the tissue surrounding the worms and the formation of many small abscesses and granulomas around degrading microfilariae [147]. Microfilaraie are also found in the blood and lymphatic system during this reaction and are cleared in the lymph nodes

[147].

Macrophages are critical for the development of the nodules that surround the adult parasites, as discussed earlier. Macrophages are found encircling and devouring parts of degraded microfilariae found in Sowda patients and chronic onchocerciasis sufferers following eosinophil degranulation [147]. Macrophages in this case are classically activated and respond to not only the damaged worms, but the endosymbiont bacteria as well [87].

Much like in LF, macrophages can be converted via worm products and other host immune products to an alternatively activated macrophage subtype. AAM’s can contribute to immune regulation through the production of TGF-β and IL-10.

[81,99,109,112].

Treatment:

Ivermectin is used at 150-200 mg/kg per day to treat onchocerciasis [61].

Ivermectin clears microfilariae through a mechanism that has been previously discussed as it is also used in lymphatic filariasis treatment. DEC is no longer used in areas where onchocerciasis is prevalent, as in high doses it can cause adverse reactions that can cause massive inflammation due to worm degradation and death similar to an expanded

Mazzoti reaction [61]. Similar to treating LF, targeting O. volvulus associated Wolbachia with antibiotics has proven effective to clear microfilariae [183]. The same problem found in treatment of LF also confounds treatment of onchocerciasis: there is no clear macrofilaricidal drug available that has proven safe and effective.

Loaisis

Loaisis is caused by the filarial nematode Loa loa. This nematode, found only in

Central and West Africa, infects about 10 million people, while another 30 million live in endemic areas with either a high or intermediate risk of becoming infected [184,185].

Loa loa migrates transiently through connective tissue underneath epithelial layers in an infected human host [61]. Loa loa is commonly observed passing underneath the cornea; for this reason it is known colloquially as the “eye worm.”

Epidemiology:

Loa loa is found in Sub-Saharan Central and West Africa [186]. Within this region, there are highly endemic foci and areas where the disease is less prevalent [186].

The areas of highest prevalence coincide with vector habitats [61]. These correspond to heavily forested areas with year-round water supplies. All totaled, between 20-50 million people reside within regions where they could possibly contract Loa loa [61,186]. A map showing the distribution of Loa loa is within figure 5.

Figure 5: Prevalence of Loa loa [186].

Parasite:

Loa loa is the only causative agent of loaisis. Loa loa belongs to the family

Onchocercidae, the superfamily Filarioidea, and the order Spirurida [40,187]. Adult worms can live up to 17 years within a human host [61]. Adult females range from 40-70 mm in length with a diameter of 0.5 mm [61,188]. Adult males are 30-35 mm in length with a diameter of 0.35mm [61,188]. The life cycle of Loa loa is similar to that of O. volvulus and the lymphatic filarial nematodes (figure 6). Black flies of the genus

Chrysops serve as an arthropod host for larval stages 1-3 and a vector for transmission to

the human host for larval stage 4 and adulthood [61,188]. Mature adults produce

microfilariae that are taken up in a blood meal with the bite of a Chrysops fly. Unlike the

O. volvulus and the lymphatic filarial nematodes, Loa loa does not host the endosymbiont

Wolbachia.

Figure 6: Life Cycle of Loa loa [188] http://www.cdc.gov/parasites/loiasis/biology.html

Adult Loa loa generally live in the subcutaneous connective tissue [61,188].

Rather than take up permanent residence, they migrate throughout the connective tissue.

Microfilariae produced by mature females migrate to the peripheral blood with a

periodicity that coincides with the most active times of the arthropod vector [61,188].

These microfilariae penetrate through the stomach wall of the fly and migrate to the fat body where they mature [61,188].

Genome:

Loa loa’s genome is comprised of 91.4 Mb pairs [187]. Microfilarial RNA sequencing predicts 14,907 genes [187]. This number is similar to the number of genes thought make up of the B. malayi genome [44]. Unlike Brugian spp, Loa loa lacks the endosymbiont bacteria Wolbachia. While Wolbachia is thought to produce some compounds not found within the genome of endosymbiont carrier filarial nematodes, Loa loa does not appear to have any genes that encode for proteins that would give rise to capabilities endosymbiont carrier filarial nematodes don’t have within their proteome

[44,57,187] Further, although Wolbachia has been shown to transfer genomic DNA to the nucleus of filarial cells [189], however there appears to be no large remnants of transfers from Wolbachia resident within the Loa loa genome.

Much like Bruga spp, Loa loa encodes several proteins that have immunomodulatory capabilities. Loa loa produces proteins that mimic human TGF-β, a macrophage inhibitory factor, an interferon regulatory factor, members of the IL-16 family, an IL-5 receptor antagonist, and cytokine signaling suppressors [187]. It also encodes a number of proteins that are very close to human produced proteins, but may yield the production of autoantibodies [187].

Pathology:

Most people infected with Loa loa are asymptomatic [190]. The hallmark pathology seen in Loa loa infection is the transient, localized swelling that follows the

worm’s migration [61,191]. Called Calabar swelling, this angioedema occurs in the

connective tissue near where the worm is located [61,191]. The swelling can last from a

few minutes to days; however seems to not cause any permanent damage in most cases

[192]. The exception to the previous statement is when the nematode traverses the sub-

corneal region of the eye. When Loa loa traverses the eye, the results can be simple pain and inflammation, but also more seriously, potential blindness [192].

Host Immune Response:

Loa loa, similar to the previously discussed parasitic filarial nematodes, has the ability to live within the human host for a period of greater than 10 years [61]. This long

life would not be possible without evasion and modulation of the host immune system.

The immune response to Loa loa takes one of two phenotypes. Some individuals show a

Th1 response with IL-2 and INF-γ, whereas others show a response that is much more

similar to the more prevalent Th2 type response to O. volvulus and the lymphatic filarial

parasites. There appears to be no real bias towards one response or the other [193].

Although there is significantly less literature on Loa loa, than there is for either O.

volvulus or the lymphatic filarial parasites, genomic analysis shows that Loa loa encodes

both a macrophage inhibitory factor and TGF-β [187]. It is therefore possible to assume

that these cytokine mimics operate in much the same way that they do for the previously

mentioned filarial nematodes, blocking the inflammatory action of macrophages and

compelling the generation of a higher population of antigen specific T-Reg cells. Loa loa

microfilariae also have the ability to bind complement proteins, thereby preventing

complement activation and formation of MAC in response to filarial presence [194]. A

more comprehensive study of the immune response and immunomodulatory capability of

Loa loa is needed.

Treatment:

Treatment of Loaisis involves both surgical and chemotherapeutic approaches.

Once located; adult worms can be excised from the connective tissue underlying the epidermis and dermis. The same procedure can be done with adult worms visualized in the eye with the help of a local anesthetic [195].

Loaisis can also be treated with a number of different drugs. DEC has been shown to be effective against both adult worms and microfilariae at doses of 2mg/kg per day, 3 times a week, for a period of 3 weeks [196]. Benzimidazoles (action described previously) mebendanazole and albendazole (200 mg 2x/day, 3 weeks) have been shown to be effective at reducing microfilarial loads in loaisis [197,198]. Ivermectin has also been shown to reduce microfilarial population in patients with loaisis [199]. However, those patients who present with loaisis and onchocerciasis present a significant problem to treatment with ivermectin. There have been adverse effects reported in people co- infected with both parasites (reviewed in [195,199]). Side effects are thought to be the result of immune activation during a massive microfilarial die off and include: neurological side effects (coma, encephalitis, and retinal hemorrhage), as well as glomeronephritis [195,199,200].

Remaining Areas of Inquiry

Though much is known about the causative agents of filarial disease, there are still many areas of active inquiry. There remains no published immunocompetent laboratory animal model for human lymphatic filariasis. In vitro parasite motion should

be influenced by drug effects; there is no objective and quantifiable method for observing

filarial nematode motion. There is no macrofilaricidal agent that is effective against filarial parasites. There is little understanding about what influence successful drug- induced clearance of the adult parasites would have on the underlying pathology seen in filarial disease. It remains difficult to quickly and decisively diagnose and quantify infection. Finally, screening drugs for use as anthelminthics can be very subjective in early in-vitro testing and difficult to quantify the effect of the drug on the parasite. These areas will be addressed in the coming chapters.

CHAPTER 2

RAT LYMPHATIC PATHOLOGY

Evaluation of Lymphatic Pathology

The purpose of this study was to evaluate the effect of Brugia pahangi on rat

lymphatics and describe the pathology. The idea for this grew out of benchtop

descriptions of worms taking up residence in the rat lymphatic vessel during the course of

infection. Though this is known in the community, no one has fully investigated the

pathology of lymphatic filariasis in the rat model. Once the pathology is fully evaluated, it can be used as a baseline in drug testing to evaluate impacts of different anthelminthic drugs on the underlying pathology.

Previous Work

Throughout his career Dr. Charles Mackenzie has done numerous animal studies

involving filarial nematodes. He has maintained a collection of slides and tissues that go

back to his earliest work. He graciously granted me access to these old slides in order to

review them and interpret the effects of the nematode on an infected rat. Those slides

accounted for over 100 infected animals. Slides were reviewed using brightfield

microscopy. Many were in poor condition, however patent infections with adult worms

resident in the lymphatics were visible. These slides were used to select which blocks

would be recut and restained, and determine what antibodies should be used for

immunohistochemistry (IHC).

Slide Preparation

Selected blocks were chosen and sectioned on a rotary microtome at 4 µm.

Sections were placed on adhesive slides and dried at 56 °C overnight. The slides were subsequently deparaffinized in xylene and hydrated through descending grades of ethanol to distilled water. Slides were placed in Tris buffered saline pH 7.5 for 5 minutes. Slides were then heat treated (in a rice steamer for 30 minutes followed by 10 minutes at room temperature, or in Pascal pressure cooker for 15 minutes at 125C followed by 80°C for 5

minutes and then 30 minutes at room temperature on countertop) or underwent enzyme

induced epitope retrieval (10 minutes at 37C). These processes were followed by

subsequent rinses and blocking for endogenous peroxidase using 3% hydrogen

peroxide/methanol bath (1:4 ratio) for 20 minutes at room temperature followed by

running tap and distilled water rinses.

Immunohistochemistry (IHC):

Specific antibodies were chosen to elucidate cell types in the tissue.

Immunohistochemistry preparations included staining for CD3 (a marker for T

lymphocytes), (CD20 a marker for B lymphocytes), (CD68 a marker for macrophages),

and KI67 (a marker of cellular proliferation).

Nova Red and Hematoxylin Staining:

Reactions were developed with Nova Red (Vector) for 15 minutes; followed by counter-stain in Gill 2 hematoxylin (Richard Allen – Kalamazoo, MI, USA) for 15 seconds, differentiated in 1% aqueous glacial acetic acid and rinsed in running tap water.

Slides were then dehydrated through ascending grades of ethanol, cleared through several changes of xylene, and cover-slipped using flotex permanent mounting medium. 37

Grading Scale

Brightfield microscopy was used to visualize the lumbar lymphatics. This

inspection of the tissue facilitated the development of two scoring scales (0-3); one for

lymphangectasia and one for inflammatory cellular presence. Lymphatic vessels were scored 0 if no lymphatic change was evident, 1 if there was abnormal lymphatic

endothelial growth that encompassed less than 1/3 the circumference of the vessel, 2 if

there was abnormal lymphatic endothelial growth that encompassed more than 1/3 but

less than 2/3 the circumference of the vessel, and 3 if there was abnormal lymphatic

endothelial growth that encompassed more than 2/3 the circumference of the vessel.

Inflammatory cellular presence was scored 0 if there was no inflammatory presence, 1 if

there was minimal inflammatory presence (one group of cells, surrounding less than 1/3

circumference of vessel), 2 if there was an intermediate inflammatory presence (greater

than one grouping of cells, yet still surrounding less than 2/3 the circumference of the

vessel), and 3 if there was a massive inflammatory presence (vessel nearly completely

surrounded or infiltration into the vessel lumen).

Immunohistochemistry Results

Analysis of seven worm containing vessels showed no CD3+ cellular infiltration into the lumen of the lymphatics or the surrounding tissue (figure 7). The health status or

age of the worm in question had no impact on T cell population as degraded (figure 7a),

healthy (figure 7b), and killed and cleared (figure 7c) all lack T lymphocytes.

Figure 7: (left) CD3 T-lymphocyte marker stained panel A. A granuloma encapsulated, degraded worm within a lumbar lymphatic showing no endothelial proliferation. B. A healthy, mature worm within a lumbar lymphatic showing mild lymphangectasia. C. A cleared lymphatic vessel showing complete lymphangectasia

Figure 8: (right) CD20 B-lymphocyte marker stained panel. A. A granuloma encapsulated, degraded worm within a lumbar lymphatic showing no endothelial proliferation. B. A healthy, mature worm within a lumbar lymphatic showing mild lymphangectasia. C. A cleared lymphatic vessel showing complete lymphangectasia

B lymphocytes, marked with CD20 were analyzed in eight different vessels. Of those, B lymphocytes were found in the surrounding tissue in 7 of the eight lymphatics

(figure 8). B lymphocytes are found in the surrounding tissue, regardless of the health of

the worm, degraded (figure 8a), healthy (figure 8b), and killed and cleared (figure 8c).

However, the population of B lymphocytes in the surrounding tissue appears to be greater in the vessels that had worms fully killed and cleared.

Figure 9: CD68 macrophage marker stained panel A. A healthy, mature, microfilariae producing, worm in a lumbar lymphatic showing minor lymphangectasia and a massive cellular inflammatory response. B. A healthy immature worm showing no lymphangectasia and a small cellular inflammatory response. C. A granuloma encapsulated, degraded worm within a lumbar lymphatic showing no endothelial proliferation. D. A cleared lymphatic vessel showing moderate lymphangectasia and a large cellular inflammatory response.

Of the 7 vessels studied, macrophages were found around or in 2 of the

lymphatics (figure 9). Macrophages were seen surrounding the lumen of a lymphatic 40

containing a mature, microfilaria producing worm (figure 9a) and forming a granuloma

around a degraded worm (figure 9c). Macrophages were not normally seen surrounding

healthy worms (figure 9b). Nor were macrophages seen surrounding lymphatics that have

been cleared of the parasite (figure 9d)

Figure 10: KI-67 epithelial proliferation marker stained panel. A. Control. B. Healthy, mature, microfilariae producing worm in a lumbar lymphatic showing minor lymphangectasia with proliferating cells. C. Proliferating endothelial cells of a lumbar lymphatic vessel. 41

To look for cellular proliferation, the KI-67 epithelial proliferation marker was

used as a stain. This KI-67 staining of a worm-infected vessel wall that appeared to be in

the initial stages of lymphangectasia showed that the endothelial cells were proliferating

(figure 10) in close proximity to the healthy worm.

Grading Lymphatic Change

Lymphangectasia does not commonly occur in vessels where immature worms are found. Mature worms are associated with moderate lymphangectasia. Only vessels with degraded or cleared worms showed complete lymphangectasia. Worms were found in 40 of the 253 slides studied. Thirteen lymphatics belonging to animals known to be patent

were also identified. Of these 54 sections (Table 1), 17 had no change in their lymphatic vessels. The vessels were lined with a single layer of lymphatic endothelium with a normal, generally circular appearance (Figure 11). The worm within the lumen appeared to be healthy in 14 of the 17 vessels. Of these 14, only one worm appeared to be a mature microfilaria producing parasite (Figure 11b), meaning that the majority of the healthy worms found within lymphatic vessels were immature. In 3 of the 17 sections studied, the worm within the tube appeared degraded. These worms were surrounded by granulomatous inflammation within the lumen of the vessel, yet the vessel wall remained normal (figure 9c).

Ten animal sections showed worms in lymphatics with slight lymphangectasia

(<1/3 circumference of vessel) (figure 12). Of this group, all of the worms within the lumen appear to be healthy. Further, all but 2 appeared to be mature worms with microfilaria developing in the uterine tubes. Ten animal sections showed worms within lymphatics suffering moderate lymphangectasia (<2/3 circumference of vessel) (figure

13). Of these 10, nine appeared to be healthy and mature worms with developing

microfilaria. One was a degraded worm in a vessel that showed moderate

lymphangectasia.

Table 1

Lymphangectasia Total 0 1 2 3 immature 15 13 2 0 0 mature 18 1 8 9 0 degraded 8 3 0 1 4 cleared 13 0 0 0 13 54

Inflammatory Response Total 0 1 2 3 immature 15 7 8 0 0 mature 18 3 11 1 3 degraded 8 0 0 0 8 cleared 13 0 2 0 11 54

Table 1: The number of sections containing each subtype of worm and the levels of lymphangectasia and cellular inflammatory response. Lymphatic vessels were scored 0 if no lymphatic change was evident, 1 if there was abnormal lymphatic endothelial growth that encompassed less than 1/3 the circumference of the vessel, 2 if there was abnormal lymphatic endothelial growth that encompassed more than 1/3 but less than 2/3 the circumference of the vessel, and 3 if there was abnormal lymphatic endothelial growth that encompassed more than 2/3 the circumference of the vessel. Inflammatory cellular presence was scored 0 if there was no inflammatory presence, 1 if there was minimal inflammatory presence (one group of cells, surrounding less than 1/3 circumference of vessel), 2 if there was an intermediate inflammatory presence (greater than one grouping of cells, yet still surrounding less than 2/3 the circumference of the vessel), and 3 if there was a massive inflammatory presence (vessel nearly completely surrounded or infiltration into the vessel lumen).

Figure 11: Representation of zero lymphangectasia and zero cellular inflammatory response. A. Healthy, immature worm in a lumbar lymphatic. B. Healthy, mature, microfilariae producing worm in a lumbar lymphatic. C. Healthy, immature worm in a lumbar lymphatic.

There were no sections where a healthy worm was present in the lymphatic that showed massive lymphangectasia. Only four degraded worms were found in vessels with complete lymphangectasia (figure 14a). Vessels lacking worms were inspected in animals

known to be infected. Thirteen lymphatic vessels were identified that lacked worms yet came from animals known to be infected through confirmation of microfilaremia or the presence of a worm in another lymphatic vessel (figure 14b,14c). These vessels all showed massive lymphatic endothelial growth.

Figure 12: Representation of level 1 lymphangectasia. A. Healthy, immature worm in a lumbar lymphatic. B. Healthy, mature, microfilariae producing worm in a lumbar lymphatic.

Figure 13: Representation of level 2 lymphangectasia, a healthy, mature, microfilariae producing worm in a lumbar lymphatic. 45

Figure 14: Representation of level 3 lymphangectasia. A. A degraded worm in a lumbar lymphatic. B. A cleared lumbar lymphatic. C. A cleared lumbar lymphatic.

Grading Inflammatory Response:

Cellular inflammatory responses are seen in association with both immature and

mature parasites. In general the responses are minimal. Very few examples of moderate

or massive inflammatory cell infiltration were seen outside of those associated with

degraded worms. There were 10 sections showing vessels with no inflammatory response

(Figure 11). Seven of the sections contained worms that had not matured to the point where they had developing microfilariae visible in the uterine tubes. The remaining three sections had developing microfilariae within the uterine tubes of the worms.

Figure 15: Representation of cellular inflammatory response level 1. A. Healthy, immature worm in a lumbar lymphatic. B. Healthy, immature worm in a lumbar lymphatic. C. Healthy, mature, microfilariae producing worm in a lumbar lymphatic.

There were 21 sections showing vessels with a small inflammatory response, where there was just one grouping of inflammatory cells that did not encircle more than

1/3 the circumference of the lumen (figure 15). Of these 11 contained mature worms with developing microfilariae in their uterine tubes (figure 15c). The remaining 8 were immature worms. Two cleared lymphatic vessels showed a small inflammatory response as well.

Only one section showed moderate inflammatory response (figure 16). This vessel contained a healthy mature worm with microfilaria developing within the uterine tubes.

Figure 16: Representation of level 2 cellular inflammatory response; a healthy, mature, microfilariae producing worm in a lumbar lymphatic.

Twenty-two sections showed sections showed a massive inflammatory response

(figure 17). Eleven of these sections were from cleared lymphatics (figure 8c) Of these,

eight were in clearly degraded worms (figure 17a, 17c). Only three sections showed

healthy worms within the lymphatics, in both cases these were mature worms with

developing microfilariae (figure 17b).

Figure 17: Representation of a level 3 cellular inflammatory response. A. A degraded worm within a lumbar lymphatic. B. Healthy, mature, microfilariae producing worm in a lumbar lymphatic. C. A degraded worm within a lumbar lymphatic

Statistics

In order to evaluate the significance of the non-parametric scores assigned to both

lymphangectasia and cellular inflammatory response a Wilcoxon rank sum test was used.

Based on the scoring different levels of lymphangectasia area associated with different

life stages, immature worms were associated with a significantly different amount of

lymphangectasia than mature worms or degraded/cleared worms (p-value <0.05). Mature

worms area associated with a significantly different amount of lymphangectasia from

cleared/degraded are associated with (p-value <0.05). Cleared and degraded worms

within the lymphatics showed a degree of lymphangectasia that was statistically equal.

Based on the scoring, immature worms showed a smaller cellular inflammatory response

than mature worms or degraded/cleared worms (p-value <0.05). Mature trigger a smaller cellular inflammatory response than degraded/cleared worms (p-value <0.05). Cleared

and degraded worms had statistically equal cellular inflammatory responses.

Discussion

The above results looking at parasite status, lymphatic pathology, and cellular inflammatory response infer a pathogenesis for lymphatic filariasis in the rat that correlates with the pathogenesis of LF in humans. As is the case in human LF, lymphangectasia does not typically occur in vessels with an immature L4 or L5 worm

(figure 11). The immune system responds to the immature worms, albeit minimally.

About half of the immature worms bring about a small inflammatory response in the surrounding tissue (figure 15a,15b). Overall low scores for lymphatic change seem to

correlate with lower scores for inflammatory cell presence; however that is not

necessarily the case. Three specimens were found to have immune cells that had

penetrated into the lumen of the vessel and encapsulated the parasite in a granulomatous

mass, yet the lymphatic endothelium was unchanged (figure 9a).. There is a spectrum of

inflammatory response around vessels that show no lymphangectasia. This infers that the

inflammatory cells do not play a role in lymphatic change along the same lines as what is

seen in SCID mice [201] and that it is the parasite that compels endothelial proliferation.

Lymphangectasia begins as the parasite matures into its reproductive adult form.

These changes persist as the parasite is killed and cleared. While 2 examples of

lymphangectasia near immature worms were noted, lymphatic change was found

predominantly in vessels where there was a mature adult present (figure 11,12). Just as in

human filariasis [62], some degree of lymphatic change was noted around almost every

(17/18) mature adult worm. When a healthy worm is present, lymphatic endothelium does not seem to proliferate around the whole circumference of the vessel. Only vessels containing degraded worms appeared as if proliferation had occurred throughout the entire circumference of the vessel. This infers that though the worm initiates lymphangectasia, the inflammatory cell activity in response to the dying worm has a role in its continuation.

Over eighty percent of the lymphatics with mature worms had an inflammatory response, most common being a small grouping of cells in the surrounding tissue (figure

9c). A few examples of massive inflammatory responses were seen (figure 17b), but only one example of moderate inflammation was noted (figure 16). This leads to the conclusion that the normal state from the perspective of the worm is a small

inflammatory presence that is benign. Divergence from this normal state requires some event. This event could be the activation of the immune system in response to microfilariae, or to physical damage to the adult, or to a wholly unrelated factor. In any case, after that event, inflammatory cell migration to the surrounding tissue proceeds very quickly and culminates in the infiltration of the lymphatic vessel and destruction of the parasite. A quick ramping up of the immune response would explain why there are so few examples of the transition between the normal small response to the massive response seen in degraded worms.

A few degraded worms were found in lymphatic vessels where no change to the endothelium had occurred (figure 9a). The vast majority of damaged worms were found in vessels with a high degree of lymphangectasia (figure 14a). Vessels from known infected animals that had cleared the parasite retained the changes to the lymphatic endothelium resultant from the parasite (figure 17c). Since the cleared vessels maintain the pathology, at least for some time, it is unlikely that the normal-looking vessels associated with damaged worms had healed as the worm was dying. It is more likely that the worm simply died before lymphangectasia could occur. If lymphangectasia truly does occur at or after maturation of the parasite, it would mean that these degraded worms in unchanged vessels died prior to reaching maturity. The fact that inflammatory cells infiltrated the lumen and began breaking down the worm and encapsulating it with no lymphatic change lends credence to the idea that the worm initiates lymphangectasia independent of the host immune response.

Initial IHC shows some interesting points, but is of limited value at this point. T- lymphocytes seem to be absent from the surrounding tissue along the entire spectrum of

infection. B-lymphocytes on the contrary are just the opposite, found throughout the

pathogenesis of the infection. Further IHC work should be done to investigate this

further; however it appears that B-lymphocytes may be activated in rat LF in a T-

lymphocyte independent manner [202]. Macrophage activity also shows what may be an

interesting trend. Macrophages are absent from tissue surrounding most of the healthy

worms; they were predominantly seen encircling degraded worms in granulomatous

lesions. In only one case were macrophages found near a healthy worm; the worm had

matured and had clear microfilariae developing. Further macrophages were not found

post clearance of the parasite, indicating again that once whatever the event is that

triggers the increase in inflammation happens; the immune response is rapid. Further IHC

should be done in the future, incorporating morphometric analysis of the cell types to fully elucidate the cellular inflammatory response. Further KI-67 staining should be done on lymphatic vessels, including those that have been cleared of the parasite to determine if the absence of the worm stops endothelial proliferation.

Brugian infection of rats follows the same pathogenesis as human LF. This is clearly shown by the histological examination presented herewith. The rat therefore represents a potential immunocompetent model for human lymphatic filariasis that could be employed not only to test drug efficacy, but also to study the effects on host tissue which may be predictive of the effects if used in humans. With an immunocompetent model of the human disease the next question becomes can a new treatment clear the adult parasites? And if so, what effect does it have on the pathology of the affected lymphatic vessels?

Treatment of Infected Rats with Potential Macrofilariacidal Agents

In order to investigate the macrofilariacidal efficacy of potential anthelminthic

agents a new infection would need to be established in a population of rats. These rats

would be infected with Brugia pahangi and monitored for patency. Upon reaching

patency, they would have to be treated with flubendazole or imatinib mesylate at multiple

concentrations per bodyweight. Finally, the animals would be sacrificed, fixed and

sectioned to visualize the lumbar lymphatics. Brightfield microscopy would be used to

identify adult worms, lymphangectasia, and cellular inflammatory response, and the

results compared between the treatment groups and controls.

Animals

Lewis rats show the highest rates of patency when infected with Brugia pahangi

[203]. Therefore, male, Lewis rats (aged 6 weeks) were obtained through Charles River

Labs (Portage, MI). Rats were obtained 10 at a time due to parasite availability, with a

study population to not exceed 90 animals. Animals were divided into groups of 10.

Groups included both infected and uninfected controls. Plans were made to have up to seven different treatment groups utilizing flubendazole or imatinib mesylate at different

concentrations.

Parasites

Infective L3 larvae were obtained from the Filariasis Research Reagent Resource

Center (FR3) (Athens, GA). Parasites arrived in 50ml centrifuge tubes containing

medium (RPMI 1640) supplemented with fetal bovine serum. Upon arrival, parasites

were concentrated, counted, and separated into groups of approximately 100 each.

Parasites were used as an infectus the same day that they arrived to ensure maximum

effectiveness.

Infection

100 L3’s were concentrated into a volume of medium between 200 and 300ul.

This medium was transferred to a 1ml syringe fitted to an 18g needle. Rats were

immobilized with the right hind leg exposed. Subcutaneous injection was administered on

the ventral surface of the thigh. Injection was done in a slow/controlled manner to

prevent creating too much pressure too quickly and increasing the likelihood that the injectus would be forced out of the animal. Animals were monitored for an hour post injection to ensure there were no immediate hypersensitivity reactions.

Monitoring Patency

Patency occurs in the rat from about 12-16 weeks post infection [203]. Saphenous

venipuncture was used to retrieve a sample of peripheral blood (<200ul). This blood was captured utilizing Ethylenediaminetetraacetic acid (EDTA) treated capillary tubes

(Sarstedt, Germany) to prevent clotting. Blood was transferred to a 96 well plate and mixed with distilled water to induce lysis of the erythrocytes. Plates were inspected using an inverted microscope for the presence of microfilaria. Animals were monitored weekly from 12 weeks post infection till 22 weeks post infection.

Failure of Infection

Due to the limited availability of parasites, initial infections reached 22 weeks post infection before the entire population could be infected. At this time, 40 rats had been infected. Zero animals from this group of 40 were found to be patent at 22 weeks and the decision was made to not pursue infecting any more rats with this parasite source.

Discussions with FR3 elucidated the fact that there had been speculation that their Brugia pahangi had host-adapted to the animal model used to maintain the population. The rat study here seemed to confirm that.

Confirmation of Protocol

In order to ensure that it was not merely user error that caused a failure of the rat infection, Brugia pahangi L3’s were obtained from Tom Klein at Louisiana State

University. These parasites were regularly used in rat studies, so they should not have any problems due to host adaptation. Five rats from the previous uninfected control group were infected using the same protocol described above. At 12 weeks post infection 3 of the animals were confirmed patent via isolation of microfilaria from peripheral blood.

This confirmed the protocol, but did little to answer the question of drug effects and the impact on lymphatic pathology. While LSU was able to provide some parasites to test the protocol, they could not support a large rat infection. The rat study was at that point abandoned.

Discussion

Though the rat pathology study was ultimately unsuccessful in establishing a patent infection or elucidating the activity of potential anthelminthic drugs, it highlighted the importance of a good animal model and the potential dangers of a poor animal model for human disease. While the gerbil is a good host for Brugia it does not show a correlative pathology with the resultant human disease. It cannot address potential impacts on parasite induced lymphangectasia. Further, as the nematode resides in much different tissue between the gerbil and the human, drug effects seen within the gerbil model may not be applicable in people as the drug may not reach the separate locations in

the same concentration. Finally, dependence on a bad animal model for perpetuation of a

pathogen can have the unintended effect of inducing host adaptation. As generation after

generation of a pathogen is passed within a host species, the immune system of the host

systemically destroys the individuals that are poor pathogens. Conversely, it can be said

that the host immune system is artificially selecting individuals that are better fit to infect

the host. In isolated laboratory populations, this creates a strain of pathogen that is more

and more adapted to its specific host with each generation.

Though pathological examination of rat lymphatics shows that rats share a

common pathological response to lymphatic filariasis, the lack of an infective parasite supply led to the abandonment of further in-vivo studies with the rat model. This setback

did not stop research into potential anthelminthic drugs. On the contrary, it helped focus

subsequent efforts into a much more basic search for macrofilaricidal agents using in-

vitro studies and helped generate momentum for the development and utilization of a new

instrument and analytical techniques for describing nematode health.

CHAPTER 3

DETECTION OF FILARIAL NEMATODE MOTION AND DRUG SCREENING

Introduction

The screening of compounds as potential anti-parasitic agents has increased as

global health programs focus more sharply on eliminating the major neglected tropical

infections caused by helminths including nematodes such as Onchocerca volvulus,

Wuchereria bancrofti and Brugia sp [204]. The effort to find new anthelminthic agents

requires improved technologies, including improvements to the process of evaluating the

commonly used parameter of parasite motion as a predictor of parasite health [8,205-

207]. Current techniques are lacking in utility; some address only the larger stages of parasites and cannot quantify or measure microscopic larval stages [8], whilst others are not compatible with use in remote field settings because of their complexity [8,205-207].

Here a technology is described that improves the detailed capture of the complex motion of these parasites in solution and the characteristics of alterations in this motion.

This system also allows evaluation of potential anti-worm agents in vitro by quantifying the number of viable worms present in test samples. Brugia pahangi, a filarial worm similar to the 3 species that cause human lymphatic filariasis, was primarily used to describe this new system along with C. elegans, the archetypical nematode (Figure 18).

Further, this technology was used to determine the effectiveness of a number of anthelminthic agents against the adult forms of Brugia pahangi.

Figure 18: Image of nematodes studied. Images of Brugia pahangi adult male, bar 5000um (top/left); female, bar 5000um (top/right); L3, bar 800um (bottom left); and microfilaria, bar 350um (bottom/middle); as well as an image of Caenorhabditis elegans L1, bar 350 um (bottom/right).

Motion Sensing Equipment

The WiggleTron (WT) (figure 19) operates on many of the same principles as its

predecessor, the B&P Instruments Micromotility Meter [6]. The WT has, however,

improved sensitivity in detection, decreased noise, better placement of the photo-

detectors, and increased sampling rate as compared to the B&P machine. The WT

ultimately converts sample organism movements into an analog voltage signal which

once sampled is analyzed for its amplitude and frequency composition time. The sample-

containing vial is illuminated from below by a white LED emitting ~5 milliwatts of

visible optical power into the base of the vial. The LED and sample tube are separated by

an opaque ring which retains stray light, reduces thermal conduction into the sample vial,

and prevents damage to the LED lens. Temperature within the sample vial is consistently 59

32 ± 1°C. The light passes up through the sample reflecting dynamically off any

movement within the vial, onto large PIN photo-detectors, connected in parallel, flanking

the sides of the vial. Unlike the original micro-motility meter, these photo- detectors span

vertically from the base of the vial up to just below the meniscus level of the liquid

sample. This reflected light energy is converted to an analog of the movement, amplified

at 0.40, 4.0 or 40 μV/pA to accommodate various sizes of sample organism, using negative feedback resistance to determine the optimal situation. The sample vial is held firmly by support fingers that in turn are stabilized by a superstructure that also supports and aligns the photo-detectors. All samples were evaluated in 31 mmH X 6 mm OD borosilicate glass tubes (Sigma, pn.24715) with 200μl samples. This system could be

miniaturized and made suitable for use in field situations, as well as be constructed to test

multiple samples at the same time allowing for large scale screening of compounds.

The instrument as described above was used to carry out all of the experiments

using the different nematodes. This configuration was achieved through multiple rounds

of testing. Photodetector placement, circuit orientation, vial choice, measurement time,

and optical guidance were all optimized prior to beginning experiments using the

machine.

Figure 19: Inside view of the WT with top and side view of sample mount and collection apparatus.

Measurement and Analysis

Tubes were placed within the WT over the light source and allowed to equilibrate for at least one minute prior to initiating acquisition. Each sample population (containing parasites) as well as control (medium only) was prepared in triplicate. The analog voltage output signal was digitized at 1 kHz with a DT9816 (Data Translation, Inc., Marlboro,

Massachusetts, USA) 16 bit ADC controlled by Quick-DAQ software (Data Translation,

Inc., Marlboro, Massachusetts,USA). The recording duration used for pilot studies was

30 seconds, however after experimentation it was found that to accommodate the 2N time requirement for low frequency FFT resolution of 0.1Hz [208], this testing time be standardized for all samples at 33 seconds. The proprietary Quick-DAQ _.hpf data files were converted to _.csv files containing time interval and voltage amplitude. The voltage

amplitude was multiplied by 3276 then converted to RMS value to represent better the

sample’s bit depth for 16 bit resolution of the ±10 V input range of the DT 9816, making the resulting amplitude values integer numbers and thus easier to interpret and compare quickly. This number (3276) was selected as it is the factor that best converts bit number into an arbitrary unit that allows for easier comparisons; this technique is commonly used in electronic science [209]. Thus it is not a specific “unit” as such but a non-dimensional unit used solely for the comparison between two or more samples studied by this equipment.

Each sample was run 3 times on the WT. The mean and standard deviation for each sample was calculated using the scaled RMS values from these individual runs. This yields a number that can be used to compare the motion of the worms in each sample based on the amplitude of motion. Dead parasites (transferred to 95% ethanol), then transferred back to fresh medium followed the same procedure for sample preparation, measurement, and analysis. Further, the (_.csv) files can be imported into SignalLab

SIGVIEW (Mitov Software LLC, Moorpark, California, USA). This software allows FFT analysis to look at differences in the frequency of motion of the sample and highlight differences graphically at different frequencies of movement.

Initial Analysis of Nematode Motion

The first studies using the WT were designed to answer very basic questions about the capabilities of the WT. First, could the WT actually measure movement of all larval stages of the test nematode B. pahangi? Second, could the WT be used to count nematodes in solution and estimate parasite density? Third, could the WT be used to

differentiate between healthy and unhealthy worms? Finally, could the WT sense changes

in worm motion due to the administration of potential anthelminthic agents?

Parasites

B. pahangi microfilariae were obtained from Filariasis Research Reagent

Resource Center (FR3, Atlanta, Georgia, USA). Upon receipt, microfilariae were placed in approximately 25ml of fresh medium (RPMI 1640 supplemented with 10% fetal bovine serum (FBS) and 1% penicillin and streptomycin) and agitated till at a uniform distribution within the medium. 10 ul of this suspension was then transferred to 100 ul of fresh medium in a well on a 96-well plate. This was repeated 4 times. The contents of the wells were examined under light microscope to determine parasite health (highly active and with normal anatomical appearance). Once parasites were determined to be healthy and free from debris, all 4 wells were counted for living parasites to determine the density of microfilariae in suspension. This density number was then used to generate dilutions to allow us to prepare samples ranging from 10 to 50,000 worms suspended in 200 ul of medium. Each sample was then run on the WT and analyzed as described earlier. The results from each population were averaged to provide a snapshot of motility amplitude of the range of populations. Samples were then prepared using dead microfilariae from

10–50,000 worms and run and analyzed in the same manner; populations of live versus dead worms could then be compared.

Since the samples were prepared in triplicate each population could then be averaged to generate a plot of population as a function of measured and analyzed RMS amplitude. For tube populations from 0–1,500 worms, this plot yielded a function capable of predicting the population of parasites within the sample tube. Unknown population 63

samples were then prepared, run, and analyzed as described above. The equation

resulting from the known population was used to calculate the population of microfilariae in the unknown tubes. The population of each of the unknown tubes was then found using the same method used to find concentrations of microfilariae described previously and compared to the calculated population.

B. pahangi infective larvae (L3’s) were obtained from FR3. Upon receipt, L3’s were placed in approximately 1ml of fresh medium (RPMI 1640 supplemented with 10% fetal bovine serum (FBS) and penicillin and streptomycin) and agitated to mix uniformly within the medium. 20ul of this suspension was then transferred to a small petri dish containing approximately 2ml of medium. The dish was investigated under light microscopy to determine parasite health. Once parasites were determined to be healthy and free of debris, they were counted to determine the density of L3’s in suspension.

Samples containing between 10 and 200 L3’s in 200 ul of medium were then prepared.

Samples with less than 10 worms were also prepared by pipetting a single worm at a time under the stereoscope into the same type of vials described previously; each sample prepared in this manner also had a final volume of 200 ul. Samples were prepared in triplicate. All samples were then covered with Parafilm (Pechiney Plastic Packaging Co.,

Chicago, USA) and placed in the freezer for 2 days after live analysis. Afterward, the tubes were thawed and inspected to make sure the parasites were dead. Tubes with the

dead parasites were then run on the WT and analyzed as previously described. Both live

and dead L3’s were then compared at each worm population level.

Adult B. pahangi, both male and female were obtained from FR3. Upon receipt,

parasites were placed in approximately 5 ml of fresh medium (RPMI 1640 supplemented

with 10% FBS and penicillin and streptomycin) in a large petri dish. Individual worms

were picked up using a glass Pasteur pipette and transferred into 200 ul of medium in the same type of vials described previously, 1 parasite per vial. Samples were run on the WT and analyzed as previously described. These samples were then covered with Parafilm and placed in the freezer for 2 days. Afterward, the tubes were thawed and inspected to make sure the parasites were dead. Tubes with the dead parasites were then run on the

WT and analyzed as previously described and their results compared to living adult worms.

Mature, egg-producing C. elegans were bleached. The eggs were harvested,

washed and allowed to hatch on a plate containing agar with no food, arresting their

development at the L1 stage to ensure a uniform larval stage for analysis. Samples from

0–100 worms were prepared as previously described, however rather than using medium

C. elegans were run in normal saline (0.9% NaCl) to ensure that they remained arrested

in L1. Samples of live and dead C. elegans were run as previously described; FFT

frequency analysis was done as previously described, using 100 L1’s.

Initial Drug Testing

Twenty-one samples, each containing two B. pahangi L3’s were prepared in 198

ul of medium in the same vials described earlier. These 21 samples were grouped into 7

groups of three. These groups included one control group, and three treatment groups for

the drugs imatinib mesylate (Gleevec, Novartis) and chloroquine (Sigma-Aldrich Co,

New Jersey, USA), both at levels of 100nM, 500nM, and 100uM. Each sample was run

prior to treatment on the WT. Two microliters of medium were added to each tube in the

control group, two microliters of a 10uM drug solution were added to the tubes in the

100nM groups, two microliters of a 50uM drug solution added to the tubes in the 500nM groups, and two microliters of a 10mM drug solution were added to the 100uM groups.

Each tube was covered with Parafilm M Barrier Film (Bemis NA, Neenah, Wisconsin,

USA) and then tested at 1, 24, 48 and 72 hour(s) post treatment.

Twenty-one samples, each containing one B. pahangi adult female, were prepared in 198 ul of medium in the same vials described earlier. These 21 samples were grouped into 7 groups of three. These groups included one control group, and three treatment groups for the drugs imatinib mesylate and chloroquine at levels of 100nM, 500nM, and

100uM. Each sample was run pre-treatment, treated, covered, and analyzed at the same time points as described with the L3 treatment.

Frequency Analysis:

Three groups of 10 B. pahangi L3’s were analyzed on theWT immediately upon receipt from FR3. Other L3’s were plated in medium and allowed to slowly degrade while sitting on the bench. After 1 day of monitoring via microscopy, degraded worms showing uncharacteristic and lethargic motion under the scope were then analyzed on the

WT. Instead of the normal fluid motion, seen in healthy worms, these worms appeared to flick only one end of their body. The same process was repeated at 48 hours. These data, and data from the fresh L3’s, were then imported into Sigview (www.sigview.com). Fast

Fourier Transform (FFT) analysis was done to look at spikes at specific frequencies of motion. By comparing FFT diagrams from blank samples and samples with worms we established that worm motion takes place below 16Hz.

Further, visual analysis of many FFT diagrams, specific to the worm type being studied showed some general patterns. Based on these patterns each L3 sample was

broken into frequency ranges of 0.1–2Hz, 2 8Hz, and 8–16Hz. This was also carried out for C. elegans. RMS amplitude for each frequency range was summed for each sample and averaged across the population group. Then a ratio was calculated relating the three frequency ranges to each other.

Statistics

A one-way ANOVA was used, followed by post hoc Tukey’s test to compare the means for each sample group and determine significance of RMS amplitudes for all of the worms run on the WiggleTron [210]. This analysis was done using JMP 11 software

(www.jmp.com).

Results

Detection of Motion

Analysis of the data from the WT shows that the device can detect parasite presence and that detection results from parasite motion within the tube. A real-time trace of motion follows a sinusoidal pattern with the majority of the movement, taking place at frequencies less than 20Hz (Figure 20, 21). All the worms studied, when healthy, showed a periodic motion when viewed under a microscope, bending or twisting around a center point on the worm’s body. This results in a cyclic bending-unbending or twisting- untwisting motion. The detector’s baseline RMS amplitude for no motion is zero. This motion of the worm scatters light, either increasing or decreasing the amount of light received by the photodiodes. This yields an elevated or lessened RMS amplitude based on the direction of motion and nature of the light scattering. Based on the cyclic motion of the worm, a sinusoidal RMS amplitude is detected. Expectedly, due to big physical differences, live worms yield dramatically different RMS amplitudes based on population

size, type/species, and larval stage within each tube. However, despite the difference in their RMS amplitudes, they are all similar in that live worms yield RMS amplitudes that are significantly larger than blank tubes. Results obtained from adults of both sexes, L3’s, microfilariae, and L1’s all show that dead worms are functionally non-existent and give results similar to blank tubes when analyzed within the WT (Figs. 22, 23, 24, 25, 26).

There is however, with parasite numbers well above the normal infection or test levels usually likely to be examined (>500 mf/200ul), a significant impact on RMS amplitude

(Figure 24). Figure 22 and 23 show that at 100 or 500 mf/ 200ul there in no effect of adding an equivalent number of dead similar worms.

B. pahangi L3 Motion vs Blank 0.500 0.400 0.300 0.200 0.100 mV 0.000 0s 1s -0.100 -0.200 -0.300 -0.400 -0.500 Time 0-1s

Figure 20: One second tracing of a single Brugia pahangi L3 motion vs blank.

Figure 21: FFT depicting 10 healthy (black) and 10 degraded (red) B. pahangi L3’s. Scaled voltage displayed on y-axis, Hz on the x-axis.

200 500mf Live vs Dead 180 b a:b, p<0.0001 160 b:c, p<0.0001 140 b:d, p=.2434 d a:d, p=0.0045 120

100

80 c a:c, p=0.9731 60 a c:d, p=0.0023 40

0 Blank 500mf Live 500mf Dead 500mf Live & Dead

Figure 22: Mean returns for 500 live microfilariae, 500 dead microfilariae, and 500 live & dead microfilariae.

100mf Live vs Dead 120 b a:b, p=0.0004 b:c, p=0.0004 d 100 b:d, p=0.1274 a:d, p=0.0404 80 c 60 a:c, p=0.999 a c:d, p=0.036 40

0 Blank 100 mf Live 100 mf Dead 100 mf Live & Dead

Figure 23: Mean returns for 100 microfilariae, 100 dead microfilariae, and 100 live and 100 dead microfilariae.

5000mf Live vs Dead

600 b a:b, p<0.0001 b:c, p<0.0001 500 b:d, p<0.0001 d 400 a:d, p<0.0001

300

200 c a:c, p=0.997 100 c:d, p<0.0001 a 0 Blank Live 5000 mf Dead 5000 mf 5000 mf Live & Dead

Figure 24: Mean returns for 5000 microfilariae, 5000 dead microfilariae, and 5000 live and 100 dead microfilariae.

B. Pahangi L3’s Live and Dead 4000 b 3500 a:b p=0.0001 b:c p=0.0001 3000

2500 Blank 2000 100 Live 1500 100 Dead

1000 c a:c p=0.9976 500 a 0 Blank 100 Live 100 Dead

Figure 25: Mean returns for 100 live L3’s and 100 dead L3’s.

Adult B. pahangi Live vs Dead 2500 b 2000 a:b p=0.0017 b:c p=0.0017 b:d p=0.0794 1500 d d:e p=0.0020 1000

500 c a:c p=1.000 e a c:e p=0.9988 a:e p=1.000 0 Blank Mean Female Mean Female Mean Male Mean Male Live Dead Live Dead

Figure 26: Mean returns for live and dead adult female and adult male worms.

Estimation of Worm Number

Analysis of the WT data from microfilariae shows that this system can estimate different numbers of worms based on the amplitude of RMS amplitude (motion). For microfilariae there is a positive correlation between amplitude and worm number in samples up to 5,000 worms. With numbers of microfilariae greater than 5,000 the signals resulting from worm motion no longer consistently correlate with increases in worm population. However, two further general characteristics of the WT’s ability to capture motion were seen: firstly the maximum RMS amplitude possible for the present experimental conditions occurs at 17,500 microfilariae, and secondly at numbers higher than 17,500 microfilariae there is a decline in signal with an increase in population. With populations of 0–1500 microfilariae, the increase in RMS amplitude resultant from an increase in population is linear with a sensitivity of 300 worms (p = 0.0079). Analysis of data with B. pahangi L3’s, and C. elegans L1’s shows an increase in RMS amplitude along with population from 0–100 worms. The B. pahangi L3 sensitivity is 5 worms (p =

0.0166), whereas the sensitivity for C. elegans L1’s is 50 worms (p = 0.0014). Due to the size of the adult Brugia parasites, multiple worms were not run within the same tube for this study. Analysis of over 400 adult worms from the peritoneal cavity of girds shows that adult worm sex can be determined based on amplitude alone through the use of the

Wiggle- Tron (p<0.0001).

Using known RMS amplitude values for each population, population as a function of RMS amplitude can be plotted and used to estimate the population size of an unknown sample. Microfilariae were used to investigate the predictive nature as there is a need for a quick, easy field test to confirm and quantify microfilariaemia in endemic populations.

Functions generated using results from 0–1,500 microfilariae can estimate within 20% error the population of microfilariae within a tube for numbers of worms less than 200.

Multiple tests yielded an error of 16.7% when testing a population of 175 worms. At higher numbers, the non-linear relationship between RMS amplitude and population failed to estimate the population number with an accuracy of +/- 20%, and this makes prediction using the WT unreliable for this situation.

Analysis of Worm Health

Analysis of the data from the WT shows that after treatment with prospective anti-filarial drugs, there is a significant difference in the amplitude of the RMS amplitude between treated and control groups. Forty-eight hours post treatment, results from L3’s showed a significant decrease in motion across all treatment groups and the control group

(Figure 27, 28). The treatment groups receiving the highest doses, approximately 100x known lethal dosage (LD100) of each drug, yielded results that were nearly identical to that of dead worms or blank tubes. The changes in worm motion were significant earlier,

1hour post treatment (hpt) for the chloroquine 100uM group, and 24 hpt in the imatinib

mesylate 100uM group. The lower treatment levels showed that there was still some

motion in the worms, yet their activity level as compared to the control group was greatly

reduced. This was confirmed by light microscopy. Analysis of treated adults did not show

as drastic results as the L3’s at lower treatment levels, yet the highest treatment groups of

each drug showed a significant decrease in activity after treatment. After 72 hours all but

the highest treatment levels exhibited some activity (Figure 29, 30).

B. pahangi L3's Treated with imatinib mesylate 0-72 hours

600

500

400 CTRL 300 ima 100nM ima 500nM 200 ima 100uM 100 * 0 0 hpt 1 hpt 24 hpt 48 hpt 72 hpt

Figure 27: Mean returns over time of L3’s treated at different molar concentrations of imatinib mesylate, (*) significant change from pretreatment earlier than control or other groups (p=0.0153).

B. pahangi L3's Treated with chloroquine 0- 72 hours 600

500

400 CTRL 300 chlor 100nM chlor 500nM 200 chlor 100uM 100 *

0 0 hpt 1 hpt 24 hpt 48 hpt 72 hpt

Figure 28: Mean returns of L3’s treated at different molar concentrations of Chloroquine, (*) significant change from pretreatment earlier than control or other groups (p<0.0001).

Adult B. pahangi females treated with imatinib mesylate 3500

3000

2500 CTRL 2000 ima 100nM 1500 * ima 500nM 1000 ima 100uM

500

0 0 hpt 1 hpt 24 hpt 48 hpt 72 hpt

Figure 29: Mean returns for adult females treated with different molar concentrations of imatinib mesylate, (*) significant differences from before drug treatment at 1hpt and on (p<0.0291).

Adult B. pahangi females treated with chloroquine 4500 4000 3500 3000 CTRL 2500 chlor 100nM 2000 chlor 500nM 1500 chlor 100uM 1000 500 * 0 0 hpt 1 hpt 24 hpt 48 hpt 72 hpt

Figure 30: Mean returns for adult females treated with different molar concentrations of chloroquine (*) significant differences from before drug treatment at 1hpt and on (p<0.0346).

FFT analysis of fresh B. pahangi L3’s, and naturally degraded L3’s also shows that the WT can be used to analyze parasite health. There is a peak range in the frequency of motion for these worms between 4Hz and 8Hz (Figure 21); degraded L3’s lacked activity at this peak range. This is shown by comparing the summed motion at different frequency ranges. The healthy L3’s had a significantly different ratio of mid-range frequency of motion compared to high frequency motion or low frequency motion than their microscopically confirmed degraded L3 counterparts (Figure 31).

Figure 31: Ratios of selected frequency ranges of L3 motion, healthy (*) significantly different from blank or degraded (all p<0.0001), blank statistically same as degraded (all p>0.1917)

C. elegans showed a peak of motion between the ranges of 3Hz to 8Hz (Figure

32). When compared to similar sized B. pahangi microfilariae, the L1’s showed a different pattern of motion; specifically their peak activity was at higher frequency ranges than the activity of the Brugian microfilariae (Figure 32).When allowed to starve for 48

hours, C. elegans L1’s showed significant changes in the pattern of their motion. This is shown by relating the mid-range frequency component of their motion to the low and high range frequency components, then comparing fresh versus starved worms (Figure

32). The fresh and starved worms had significantly different ratios of mid-range to low

and high-range to low (p<0.0001), whereas the ratios of their mid-range motion

compared to high was similar (p =0.3095). Both the fresh and starved worms showed

significant differences in signal across all frequency ranges from that of the blank tube

(p<0.0001).

Figure 32: FFT and ratios of select frequency ranges. Left panel shows an FFT of 100 C. elegans L1(blue), overlaid with 100 b. pahangi (black), and blank (red). Right panel shows ratios of selected frequency ranges of C. elegans L1 motion, showing significant differences (*) in returns of degraded worms vs blanks (p<0.0001), healthy worms vs blank (p<0.0001), and healthy worms vs degraded in all but the ratio of middle frequency range to high frequency range (p=0.3095).

Discussion

This initial work with the WT shows clearly that the system has the capability to

detect motion from nematodes as small as microfilariae. Basic analysis of this data is able

to generate a reproducible estimation of number of worms present in a small volume.

While not truly a count, this information is valuable in screening of hyper-infected

individuals for the receipt of special treatment regimens. Though the WT’s utility in estimating worm number decreases as the number of worms go up, it is well within the range of normal clinically noted levels of micrfilaraemia. A quick, objective test that is quantitative in nature could prove useful in epidemiological studies. However, most seralogical tests for filarial diseases are poorly quantitative [211-213]. Quantitative field screenings are often complicated requiring the production of blood smear slides, a trained technician, a microscope, and the time required to individually count microfilariae. The

WT has the potential to serve that role. There is nothing preventing the miniaturization of the WT to support field operations. Further testing with fresh samples should be done to better establish its utility.

This work also shows that the WT has the ability to detect changes in motion.

Simple, amplitude based analysis of nematode motion can objectively show changes to the worm resultant from the application of anthelminthic agents. Current global eradication efforts are underway for filarial disease, but there is yet no macrofilaricidal agent capable of meeting those needs. Efficiently and objectively screening compounds to be used against filarial nematodes will continue to be a requirement until this need is met and will have applications long after. This work showed that a one-well sample can effectively accomplish this goal, further it is the first account of macrofilaricidal activity using imatinib mesylate. In its current state, the WT can support drug discovery, but this system has the capability to be expanded. A 96-well plate version of the WT could effectively screen a number of compounds with multiple dilutions in a high throughput screening setup that is impossible with current technology.

Finally, this work shows that it is just scratching the surface of the data recorded by the WT. The RMS amplitude analyzed for most of the study is a crude way of looking the sum of all worm motion. It does not take into consideration patterns in motion, but rather assigns an overall score to the motion. The FFT analysis done in this work shows that underlying that simple analysis is a wealth of data that could be mined to refine our understanding of changes in worm motion. The frequency at which a worm moves, or at which a population of worms moves, changes as they degrade. This begs the question of the impact of anthelminthic drugs on the patterns of motion. Further analysis may be able to elucidate smaller changes in worm motion patterns that could be descriptive of mechanisms of action within the nematode when included with histopathological study of the treated worms.

There are many potential applications for the WT. Fieldwork, drug discovery, future high-throughput screening, and in-depth analysis of the data could all yield future discoveries that contribute to the eradication of filarial diseases in humans.

Field Detection of Microfilariae

Initial work with the WT proved it had the capability to sense worm motion in perfect laboratory conditions. One of the assumptions made with the WT was that it would have potential utility in the field as a way of screening and estimating the number of worms within the blood of an infected individual. There are no naturally occurring filarial infections in the United States, so in order to test this hypothesis, we collaborated with the Research Foundation in Tropical Diseases and Environment at the University of

Buea in Cameroon. The WT was forward deployed to Buea along with a scientist to run

WT experiments in the field. The WT had not been tested in the field as of yet, so work

included both protocol development and experimentation with fresh microfilariae in

whole blood.

Microfilaraemic Samples

The University of Buea provided four samples of Loa loa infected whole baboon

blood treated with EDTA. Microscopy confirmed that only two of the samples contained

microfilariae.

Determining Dilution

Whole blood, with intact red blood cells has shown to be too opaque a medium for the WT. For this reason red blood cells must be lysed and blood must be diluted to allow for motion detection. Deionized water was added to whole blood containing microfilariae to dilute the blood and lyse red blood cells. Solutions containing 50, 25, 10,

5 and 2.5% whole blood were produced and run on the WT according to the protocol already described. Initial results showed no ability to detect microfilarial motion. A portion of each concentration was reviewed on the microscope and the worms were found to be almost motionless. Microfilariae from whole blood analyzed on the microscope were found to be moving quickly with the normal episodic motion expected of filarial worms.

The choice was made to change the diluent/lysing agent. A solution of 85% phosphate buffered saline (PBS), 7.5% deionized water, and 7.5% Saponin (Sigma-

Aldrich, USA) was prepared. This lysing agent was used to produce solutions containing

50, 25, 10, 5 and 2.5% whole blood. The microfilariae were allowed to incubate within the solutions for 5 minutes and then inspected using the microscope. Microfilariae motion from worms in the whole blood and lysing agent solution was compared to that of worms

within 100% whole blood and found to be consistent. Samples were then run on the WT

as described above. Analysis of the measurements was done as described above. The 5%

whole blood solution had the highest mean return. The 5% samples were compared to a

blank solution containing 5% uninfected whole blood and the diluent/lysing agent.

Statistical evaluation as described above determine that there was a significant difference

between the blank and the microfilariae containing samples (p<0.05).

Determination of Parasite Number

Four wells of a 96 well plate were filled with 190ul of the diluent/lysing agent; to

this 10ul of microfilariae containing whole blood was added. Microfilariae were counted

in each well 3x and averaged. The sum of all the wells was averaged to get a

microfilarial density of 110 worms per well. This density 110mf/10ul, was used to

calculate a density at 1ml of blood, 11,000mf/ul. The WT was able to detect significant

differences in motion with a tube containing only 110 microfilariae.

Prediction of Microfilarial Density in Whole Blood:

As only one sample contained microfilariae, and that sample had a common

density, it was necessary to both concentrate and dilute the sample to give different densities to establish a curve. 1ml of whole blood was spun in the centrifuge at 1000 rpm for 10 minutes. The whole blood was removed and the pellet containing microfilaria was

resuspended in medium. This procedure was repeated with the medium. Finally, the

sample was resuspended in 200ul of uninfected whole blood. This sample was further

diluted randomly with more whole blood to create 5 extra samples in triplicate. These 5

samples were diluted to 5% infected whole blood with the diluent/lysing agent.

The density of the samples was determined using microscopy as described earlier for each diluted sample. Sample microfilarial values were 37, 42, 300, 555, and 1620 respectively, along with the data from the initial runs to establish dilution at

110mf/sample. Each of the samples was run on the WT and analyzed as described earlier.

The mean RMS was plotted to establish a linear curve with an R-value of 0.906 (Figure

33). Eight unknown samples were generated using the concentrated infected whole blood.

They were diluted to the same dilution and run and analyzed as before. The mean RMS generated by the WT was used in conjunction with the curve established by the known values. The unknown samples were then counted under the microscope. The curve failed to predict the density in any of the unknown tubes.

Tube Loa loa density via mean RMS 1800 1600 y = 40.973x - 465.94 1400 R² = 0.906 1200 1000 Tube 800 Density 600 400 200 0 0 1020304050 -200 Mean RMS

Figure 33: Curve generated from known samples relating mean RMS to Blood microfilaral levels per tube.

Discussion

The 1:19 dilution required to sense microfilarial motion in whole blood appears to be too dilute. Below 11,000 mf/ml, the WT cannot detect microfilarial motion in a way that is significantly different from a blank tube. That level is reasonable for some microfilaraemic individuals, but the number is highly variable. Many individuals show a much lower level of microfilaeremia. The WT would be of limited utility in the field at this point, simply providing a test that rules in/out the presence of microfilariae above a threshold level. Even lysed and diluted, the sample from whole blood maintains a dark red coloration. This dark coloration is opaque enough to impact detection via the photodiode and thus limits the sensitivity of the WT in its current configuration.

The current configuration depends on white light. This was a simple choice for initial testing in laboratory conditions as white LEDs are cheap, readily available, and easy to provide power for. It unfortunately appears wholly unsuitable for work within whole blood. Future improvements in the WT with the goal of miniaturization for use in the field should also look to optimizing a light source for use with blood. Numerous visible light sources at different wavelengths are available, as are infrared and UV LEDs.

Further, there is potential application for a small laser to be used as an illumination source to mitigate the effects of this darker medium.

The WT, even at parasite densities that gave a non-blank return could not be used to estimate the number of microfilariae in whole blood. This is likely most directly due to the limited ability to detect motion. However, as infected blood availability was extremely limited, numerous steps were required to artificially create samples of different densities. Multiple rounds of pipetting, centrifugation, and resuspension in new media

likely left the microfilariae in poorer condition than when they initially arrived in the lab.

This same lack of test material prevented the experiment from being performed multiple

times. Though there was ample amount of testing done with the WT in laboratory

conditions with B. pahangi and C. elegans, the expected optimization of a new approach to measuring filarial motion in the field, within whole blood, in hindsight appears to have

been overly ambitious. Though ultimately little of value was gained from this work, it

highlighted potential pitfalls that may arise during future attempts to modify the WT

toward both the field and high-throughput models that have been conceptualized.

Further, it provided defined areas of future study to mitigate the decreased sensitivity of

the WT due to darker medium.

Description of Motion of Different Nematodes

Early on in the development of the WT it was hypothesized that it may be able to

determine patterns of motion that were unique to species of nematodes. Testing between

different filarial nematodes was hampered by availability issue. Onchocerca spp, and Loa

loa were only available to us through our collaborative partners in Africa for a short

period of time. Even while there, our access to different types of nematodes was

extremely limited. That being said, it was possible look at a few examples to get

preliminary data to infer whether or not the WT would have the capability to differentiate

parasite species by movement patterns.

Nematodes for Comparison

B. pahangi microfilariae, adult males, and female worms were provided by FR3;

data was used from the original WT motion detection study and drug testing studies. O.

ochengi microfilariae, adult males, and female worms were provided by the University of

Buea. These were severely limited, with only one example of an O. ochengi female. Loa loa microfilariae data was used from the previous study on detection of Loa loa in whole blood. Data from the C. elegans (from the lab of Dr. Pam Hoppe) experiment described earlier was also used.

Microfilariae and C. elegans L1’s were run in the WT as described previously with approximately 100 worms per tube (110 for Loa loa). The resultant files were converted to .csv files as described earlier and imported into SignalLab SIGVIEW software (Mitov Software LLC, Moorpark, California, USA). FFT analysis was performed as previously described. The FFT’s were individually analyzed visually to look for common patterns. Exemplars of common FFT’s from each respective species type chosen and overlaid on the same chart (Figure 34).

Red - L. loa Green - B. pahangi Blue - C. elegans Black - O.ochengi

Figure 34: An FFT overlay of 4 different types of microfilarial motion detected within the WT (x-axis, Hz) (y-axis, mV).

The FFT shows that, though each worm may have different amplitudes of motion, the actual peak frequencies of activity are very similar. Even though at the individual level there may be differences in the frequency of motion, this lack of difference in a population should have been expected. The necessity of using a large number of worms to allow WT detection means that the frequency pattern of each individual worm is obscured. Unless all of the worms are moving in phase, in the same direction, at the same time, there will be interference generated in the overall signal and the tracing will have more peaks and troughs than what an individual would likely have, affecting how frequency of motion is interpreted. Therefore the similarities in the FFT’s are much more likely due to the common population and individual upon individual interference than any similarity of motion at the individual level.

Adult males and females of B. pahangi and O. ochengi were run on the WT as described earlier. The data from WT analysis was imported into Sigview as described earlier. FFT analysis was carried out and each FFT was analyzed to come up with a clear picture of what a normal FFT would look like for each respective type of worm and gender. FFT graphs were overlaid to compare the motion of the worms to each other.

Though there are not enough samplings from O. ochengi to make any determinations of the statistical significance of the difference in motion, the overlays show that there appears to be a difference in the movement patterns of B. pahangi adult males and O. ochengi adult males (Figure 35). The overlays for the female adults of each respective species also appear to show that there is a difference in the movement patterns between the species (Figure 36).

Follow On Drug Testing

Initial drug testing showed the WT’s ability to determine drug effects through the

motion of worms within a tube in the detector. However, this initial testing was limited to

only two different drugs. With the confirmation of the technology’s capability, the decision was made to broaden the screening efforts of the WT and analyze more potential drugs for macrofilaricidal effects.

Figure 35: FFT analysis of B. pahangi adult male (red) motion overlaid with FFT analysis of O. ochengi adult male (black) motion detected within the WT (x-axis, Hz) (y- axis, mV).

Figure 36: FFT analysis of B. pahangi adult female (red) motion overlaid with FFT analysis of O. ochengi adult female (black) motion detected within the WT (x-axis, Hz) (y-axis, mV).

Drugs

Mebendazole (Sigma-Aldrich, USA), albendazole (Sigma-Aldrich, USA),

flubendazole (Sigma-Aldrich, USA), rotenone (Sigma-Aldrich, USA), ivermectin

(Mectizan, Merck) and imatinib mesylate (Gleevec, Novartis), were chosen.

Mebendazole, albendazole, and flubendazole are all benzimidazoles with aromatic ring

structures. Initially, they proved difficult to dissolve; the addition of dimethyl sulfoxide

(DMSO) was required. DMSO was added to a final concentration of 10% for each of the

benzimidazoles. The other drugs were all dissolved in deionized water. Each drug was

prepared in stock solutions of 10mM, 50uM, and 10uM.

Adult Worms

Ninety-five samples, each containing one B. pahangi adult female, were prepared

in 198 ul of medium in the same vials described earlier. These 95 samples were grouped

into 19 groups of five. These groups included one control group and three treatment

groups for each of the drugs previously listed at levels of 100nM, 500nM, and 100uM.

Each sample was run pretreatment as described before. Two microliters of medium were

added to each tube in the control group, two microliters of a 10uM drug solution were

added to the tubes in the 100nM groups, two microliters of a 50uM drug solution added

to the tubes in the 500nM groups, and two microliters of a 10mM drug solution were

added to the 100uM groups. Each tube was covered with Parafilm M Barrier Film (Bemis

NA, Neenah, Wisconsin, USA) and then tested at 1, 4, 12, 24, 48, 72, and 96 hour(s) post

treatment.

Drug Effects

None of the drugs, other than imatinib mesylate, showed any difference between

the test groups and the control group. Imatinib mesylate’s effect on the adult male and

female worms mimicked what was seen and already reported in the original drug testing

study (Figure 29).

Discussion

The majority of the negative results from this study were expected as all of the

compounds tested, besides imatinib mesylate and flubendazole, are currently in use as anthelminthics and have shown no ability to kill the adult parasite in lymphatic filariasis.

Flubendazole is an agent that has shown promise in the past, but in the short time that I

have been involved in filarial research I’ve seen no fewer than 4 different formulations

come and go. One of the variations may very well have macrofilaricidal capabilities; this evaluation of one variant should not be used to paint the entirety of flubendazole as ineffective against Brugia spp.

The work presented in this chapter shows the utility that the WT brings to the study of filarial diseases and filarial nematodes in general. Clearly, it can detect motion, provide an estimate of the number of worms generating that motion, differentiate between different sexes, stages, and species of worms based on analysis of the motion, and through the analysis of worm motion screen for potential drugs to fight filariases.

Though the analytical techniques are in their infancy and remain time consuming, the potential for simplification and software integration could greatly reduce those in future iterations of the machine. Objective measure of worm health has heretofore been unavailable to the research community for smaller parasites. This objective measurement will show provide a great advantage to screening efforts in search of anti-filarial drugs.

The WT can be semi-quantitative in laboratory settings;l however those results do not carry over to use as a field diagnostic at this time. Future iterations need to attempt to get around the dark coloring inherent in patent blood for the WT to function as a diagnostic.

If that can be achieved, then the laboratory data shows that it will be able to function as a semi-quantitative diagnostic tool. Until that is reality, it makes more sense to focus on simple and reliable molecular efforts to improve diagnostics in field.

CHAPTER 4

FILARIAL MICRO RNA DETECTION IN LOA LOA INFECTED BLOOD

Introduction

In the past decade, microRNA (miRNA) research has advanced with significant momentum, illustrated by a rapidly growing list of curated sequences from a broad panel of organisms. Present in eukaryotes, miRNAs are endogenous, short noncoding RNA entities (∼22 nucleotides) with important regulatory roles in gene expression at the posttranscriptional level. Messenger RNAs (mRNA) targeted by partially complementary miRNAs are either degraded or remain untranslated [214]. Not confined to cells, miRNAs are found in biofluids, stabilized within vesicles or in protein complexes [215], and are thought to play important roles in cell–cell communication [216]. The importance of miRNAs for normal functioning of cells and organisms has been acknowledged, as their relative expression has been shown to be dysregulated in many diseases [217]. miRNAs can be species- and tissue-specific. Consequently, miRNAs have become a major focus of diagnostic and biomarker research.

Many parasites express miRNAs, including helminths [218]. The annotation and functional characterization of miRNAs in the free-living nematode Caenorhabditis

elegans (>400 mature sequences in miRBase v. 21) has progressed significantly, whereas miRNA research in filarial parasites has just begun. miRNAs from Brugia malayi, Brugia pahangi, and Dirofilaria immitis whole worm extracts have been described [219-222]. In

addition, previous work has identiﬁed circulating miRNA candidates of nematode origin

in D. immitis-infected dog plasma and in serum from Onchocerca volvulus-infected patients [223]. Here is described a parasite-derived miRNA candidates identiﬁed in

plasma from Loa loa-infected baboons and from an Onchocerca ochengi-infected cow,

and bring new elements to the repertoire of miRNA candidates released by ﬁlarial

nematodes in their hosts’ blood.

Methods

Four milliliters of blood were collected by venipuncture of the cephalic vein from

each of three L. loa-infected baboons (Papio anubis) at two time points one week apart,

in Buea, Cameroon. Eight milliliters of blood were obtained by jugular venipuncture

from an O. ochengi-infected cow (Bos indicus). Approval for these studies was obtained

from the national research authority, the Ministry of Science, Yaoundé, and certiﬁed by

the local REFOTDE animal use committee. The bovine sample came from Kumba

Abattoir; although the speciﬁc infection intensity of the donor is not known, the animal

had more than 15 palpable nodules which were all isolated and dissected to demonstrate

the presence of O. ochengi parasites. Microfilaria were also confirmed in the baboon

blood.

Samples were centrifuged at 2000 × g for 15 min to isolate plasma, ﬁltered, and

subjected to total RNA isolation using a kit (Norgen Biotek, # 50900) immediately after

collection in EDTA tubes. The RNA was stabilized with 1/10th volume of 3 M NaOAc

and 3 volumes of 100% ethanol, and stored at −20 ◦C prior to shipment at 4 ◦C. A pooled

baboon total RNA sample (120 ng) and the single cow total RNA sample (96 ng) were

sent to LC Sciences (Houston, TX, USA) for Illumina deep-sequencing and

bioinformatics analysis using a proprietary pipeline. RNA integrity was recorded by LC

Sciences. Brieﬂy, after removal of low-quality sequences and other RNA population hits

from Rfam and Repbase [224,225], the analysis consisted of mapping high-quality reads

against the P. anubis or B. indicus genomes ﬁrst (ftp://ftp.ncbi.nih.gov/genomes/Papio

anubis/ and http://www.ncbi.nlm.nih.gov/Traces/wgs/?val= AGFL01). Reads unmapped

to the host genomes were further mapped to the L. loa

(ftp://ftp.ncbi.nlm.nih.gov/genbank/genomes/Eukaryotes/invertebrates/Loa loa/Loa loa

V3/Primary Assembly/ unplaced scaffolds/FASTA/unplaced.scaf.fa.gz) or O. ochengi

(http://www.nematodes.org/downloads/959nematodegenomes/ blast/db2/Onchocerca

ochengi nuclear assembly nOo.2.0.fna.gz) genomes, respectively, and registered

nematode miRNAs in miR- Base v. 20 [226]. miRNA names were given according to

homology to known nematode miRNAs. Candidate sequences were assigned to groups reﬂecting their predicted secondary structure and genome mapping properties.

Results

A total of 6,331,705 high quality reads were obtained from the L. loa-infected baboon pooled plasma samples. Mapping to the baboon and mammalian genomes resulted in the identiﬁcation of 767 unique sequences of known and candidate baboon miRNAs. Of the remaining reads, 22 unique sequences were mapped to the L. loa or other nematode genomes and called miRNA candidates (Table 2).

Similarly, 6,078,962 high quality reads were detected in the O. ochengi-infected cow-plasma sample. We predicted 911 unique sequences to originate from the cow and report 10 miRNA candidates of potential nematode origin (Table 2).

Results from a previous study with D. immitis and O. volvulus [223] enabled a multiple-species comparison of ﬁlarial miRNA candidate proﬁles in blood from the different hosts. The four miRNA candidate lists were screened against each other using

BLASTn [227]. Most sequences were unique to the respective host–parasite associations, and no miRNA candidate was common to all four species. In search of homologues sharing 100% sequence identity and the same length, we failed to observe circulating miRNA candidates common to both O. volvulus and O. ochengi (Figure 37).

Figure 37: Venn diagram showing the distribution of circulating miRNA candidate sequences among four host–parasite scenarios. Only 100% sequence identity and identical length were considered for overlapping regions.

miRNA name Sequence Copy # Comment Loa loa miRNA candidates bma-miR-92_R+2 TATTGCACTCGTCCCGGCCTAA 3 bma-miR-100a_R+1 AACCCGTAGTTTCGAACATGTGT 3 Sequences map to nematode miRNAs (without C. elegans) bma-miR-71_R+3 TGAAAGACATGGGTAGTGAGAC 2 and map to the L. loa genome. bma-miR-34 TGGCAGTGTGGTTAGCTGGTTGT 1 bma-let-7_R+1_1ss22TA TGAGGTAGTAGGTTGTATAGTAA 1 bma-miR-100c_R+1_1ss12CT AACCCGTAGAATTGAAATCGTGT 1 bma-lin-4 TCCCTGAGACCTCTGCTGCGA 9 Sequences map to other nematode miRNAs and only mature (not predicted precursor) sequences map to the L. loa bma-miR-36_R-1_1ss19GA TCACCGGGTGCACATTCGA 4 genome. The sequence maps to other nematode miRNA. Only the mature (not predicted precursor) sequence maps to the L. loa bma-miR-100d TACCCGTAGCTCCGAATATGTG 1 genome. The L. loa genome sequence cannot form a hairpin. cel-mir-5548-p3_1ss13AT ACGGCGGTAGGCTAG 2 crm-mir-35c-3-p3_1ss9TA AGGTCCGAACCCATC 1 Sequences map to nematode miRNAs but not to crm-mir-237-p3_1ss13TG AGCAGTCGAGTAGCCT 1 the L. loa genome. cel-miR-39-3p_L-1R-4 CACCGGGTGTAAATCAG 1 asu-miR-36b-5p_L-1R-7_1ss9TA GTGAGTGATTGCGAC 1 bma-mir-36-5-p3_2ss14AC19GA TCACCGGGTGCACCTTCGATC 1 Sequences map to nematode miRNAs, but not to the L. loa bma-mir-36-4-p3_2ss14AC19GA TCACCGGGTGCACCTTCGATC 1 genome. The sequences present further differences (i.e. > 1 prd-let-7-5p_R+2_2ss11GT17AC TGAGGTAGTATGTTGTCTAGTTTTT 1 mismatch or mapped to other species). 95 PC-3p-13651_9 GGTGGCTGTAGTTTAGTGG 9 PC-3p-21742_5 CAAAATAGATCCGTAACT 5 The reads map to the L. loa genome, but not to other PC-3p-21786_5 TCCCGGCTCGTGGCACCA 5 nematode precursor miRNAs. Extended genome sequences PC-3p-70114_2 TACTGGCCTCTCAAACTCTGGGA 2 are predicted to form hairpins. PC-3p-172942_1 GTTCAGCCGGAGATAGGGAC 1 Onchocerca ochengi miRNA candidates The sequence maps to a nematode miRNA (without C. bma-miR-100a_R+1 AACCCGTAGTTTCGAACATGTGT 1 elegans) and maps to the O. ochengi genome. cbn-miR-81_1ss21GC TGAGATCATCGTGAAAGCTACT 6 cel-miR-39-3p_L-1R-4 CACCGGGTGTAAATCAG 3 Sequences map to nematode miRNAs but not to ppc-mir-2264-p3_1ss16TC TCCCCGGATGCGCACC 1 the O. ochengi genome. prd-miR-7911a-5p_L-5R-3_1ss6CA ACGGATGATGCACCA 1 hco-lin-4 TCCCTGAGACCTCAATTGCGA 1 PC-3p-5495_77 ATTATTGGATAACTTGGC 77 The reads map to the O. ochengi genome but not to PC-3p-41557_10 TAGCTGGTTCCCTCCGAA 10 other nematode precursor miRNAs. Extended genome PC-3p-80582_4 AATCGAACCATCTCGTAGCT 4 sequences are predicted to form hairpins. PC-5p-151716_2 GCAACATGTGTAGGATA 2 Table 2: Loa loa and Onchocerca ochengi circulating miRNA candidates found in baboon, or cow plasma, respectively. miRNA names were assigned by homology. asu: Ascaris suum; bma: Brugia malayi; cbn: Caenorhabditis brenneri; cel: Caenorhabditis elegans; crm: Caenorhabditis remanei; hco: Haemonchus contortus; ppc: Pristionchus pacificus; prd: Panagrellus redivivus; PC: predicted candidate. Circulating filarial miRNA candidates identified by deep-sequencing and bioinformatics.

Five sequences were found in both L. loa and D. immitis infections (bma-miR-34, bma-let-7 R+1 1ss22TA, bma-miR-100c R+1 1ss12CT, bma-lin-4. Interestingly, the predicted candidate PC-3p-70114 2 we describe in the context of L. loa infection had also been observed in D. immitis-infected dog plasma (named PC-3p-11263 74 in [223]), supporting the idea that the sequence might represent a true miRNA. The L. loa infection presented one common miRNA with O. volvulus (bma-miR-92 R+2) and one with O. ochengi (cel-miR-39-3p L-1R-4). miR-39 has to date not been reported in D. immitis or

Brugia spp, the closest homologue being found in C. elegans. bma-miR-100a R+1 was found in L. loa, O. ochengi and D. immitis infections. We extended the study of miRNA candidate to non-perfect homologues in length and/or in sequence using Clustal Omega

2.1 and including Brugia malayi (miRBase v. 20) and B. pahangi sequences from whole worm extracts [221]. All sequences tested were highly conserved in sequence, with most of the inter-species variation observed in the miRNA length and at the 3’ end (Figure 38).

Conservation of the seed sequences suggests that functions may have been maintained across species despite the observation that perfect homologues are not commonly found in multiple species. These observed homologies between species support the fact that these miRNA candidates may represent true miRNAs. Onchocerca spp do not release mf into the host bloodstream as is the case for L. loa and D. immitis. As expected, only a short list of miRNA candidates was present in the plasma sample from the O. ochengi- infected cow, and only in low copy numbers.

Discussion

Besides the lack of information regarding the infection intensity (actual number of

adult worms), we suggest that this low number may be due to the absence of any parasite

stage in the blood circulation. D. immitis adults reside in the bloodstream, whereas adult

L. loa and Onchocerca spp. are embedded in tissues. This may not only affect the release

kinetics of mf, but perhaps also the removal of parasite-derived extraneous materials,

such as miRNAs, from the host circulation. Despite the presence of mf in the baboon blood, miRNA candidates in the pooled sample were neither numerous nor abundant. The relatively low and unstable mf counts (<500 to 11,000 mf/ml) measured in baboons might explain the small size of the miRNA candidate library. Indeed, mf counts are known to exhibit signiﬁcant daily and seasonal periodicity [228]. In comparison, the D.

immitis-infected dogs had counts up to 96,000 mf/ml, and as many as 245 miRNA

candidates of presumed nematode origin [223]. The mechanisms behind miRNA release

by worms into the host bloodstream remain largely unknown, while some mf

disintegration during blood removal and processing cannot be excluded. Stage- and sex-

speciﬁc miRNA expression is likely to be an important factor; a recent study on B. malayi

reported that miR-71 and miR-92 (both present in L. loa-infected baboon plasma) are

predominantly expressed in mf [220]. We discovered few miRNA candidates common to

several species, while most were speciﬁc to only one of the four host–parasite pairs.

Present in this study too, it is interesting to note that the miR-100 isoforms, miR-71, and miR-34 ranked among the ten most abundant miRNA candidates in D. immitis-infected dog blood [223]. Little is yet known about the functions of these miRNAs. Members of the miR-100 family, as well as miR-34, let-7 and lin-4, are involved in developmental events or longevity in C. elegans [214,229,230].

Poole and colleagues predicted six putative ﬁlarial-speciﬁc miRNAs based on B.

malayi and B. pahangi published miRNAs and on genome data of O. volvulus,

Wuchereria bancrofti and L. loa that were not found in the present study [220]. The expression of these miRNAs was perhaps too low to be caught by sequencing in the present work, or may not be secretory. The host miRNAs play a signiﬁcant role in developmental timing in helminths [214,231]. As has been suggested, circulating miRNAs could have important functional roles at the host–parasite interface

[219,232,233]. Our intentions behind the present work were to provide preliminary data to compare circulating miRNAs of predicted nematode origin across four host–filarial parasite associations, and through the identified sequences, assess species specificity. As expected, homologous miRNA candidates presented identical seed sequences. It is noteworthy that many sequences were unique to a single host–parasite association.

Further tests, involving more infected individuals, are needed to validate the reported results (i.e. by RT-qPCR). miRNA characterization is crucial in order to better understand their role in host–parasite interactions, and evaluate their potential for therapeutic intervention or diagnosis.

Figure 38: Clustal Omega alignments of nine sequences identiﬁed in at least four parasitic ﬁlarial species. The 5’ ends and hence, the seed sequences, are strongly conserved across species. Data were retrieved from miRBase v. 20 (for B. malayi [226]), the literature (for B. pahangi and D. immitis [221,222]) or a previous study (for D. immitis and O. volvulus [223]). The miRNA length is indicated next to each sequence.

CHAPTER 5

CONCLUSION

Over 1.3 billion people live in regions where filarial disease is endemic. These diseases have both a human and an economic cost that drag down the people infected and the developing countries in which they live. If elimination of these diseases comes to pass

it will require advances in how we model, monitor, and treat these diseases. The work presented here addresses each of these areas.

An appropriate animal model is critical to understanding how disease and treatment will be affected in humans. The work described here shows that the rat is the best option for modeling human lymphatic filariasis. The shared pathology will allow the study of the disease in the same tissue. The failed rat infection and treatment study presented here provides a framework for future research on drug effects. It also highlights a shortcoming in the manner in which B. pahangi are maintained. Passing the parasites, generation after generation, in a certain animal can cause that parasite to host-adapt.

Host-adaptation in general will complicate the use of FR3’s research B. pahangi strain for use in in-vivo work in any animal other than the gerbil. This is unfortunate as FR3 has the funding and infrastructure to supply parasites, yet the application of that support will be in an animal model that does not share the pathology of human LF and therefore is not the best choice for studying the effects of treatment.

Pathological review of rat lymphatics showed a massive inflammatory response to dead worm tissue. This highlights the need to do in-vivo testing on any compound that

100

could be macrofilaricidal. If the compound does work, it must work in a way that does

not trigger an inflammatory response that is more detrimental to the infected individual.

There is no way to model this outside of a living organism. Further, since the

inflammatory response is critical, this should only be done using immunocompetent

animals. Animals such as the SCID mouse do not have a functioning immune system and

therefore will not guarantee an understanding of the effects of any successful

macrofilaricidal treatment-induced immune response.

Though animal studies are paramount for understanding the response to treatment,

the in-vitro work presented here shows what direction they should take. Imatinib

mesylate showed macrofilaricidal activity against adult B. pahangi males and females.

None of the benzimidazoles, including flubendazole, showed any capability to kill the adult parasite in-vitro. Though it had no effect on adult worms in this study, flubendazole showed potential capabilities in past studies [234]. Currently the drug has a number of different formulations which all need to be evaluated. This clearly makes imatinib mesylate the best choice for future animal studies.

The findings of this work outline next steps for future animal studies in lymphatic filariasis. Evaluation of imatinib mesylate in patent rats should give a better understanding of the macrofilaricidal capabilities of the drug in-vivo and address the question of what happens to the underlying pathology that the parasite causes in the rat lymphatic system. The effective concentration (LD100) (100uM) of imatinib mesylate used in this study is low enough to be reproduced in the plasma. To achieve this molar concentration approximately 59 mg of imatinib mesylate need be dissolved in one liter of

solution. This is a 0.0059 percent concentration; alternatively it can be stated as 0.059g/L

101

or 0.000059g/ml. This value is well below serum levels measured from patients undergoing treatments for chronic myeloid leukemia at only 400-800mg dose per day

[235]. Assuming less than 80kg of body mass for those undergoing treatment, this is less than 10mg/kg/day. Based on this value treatment groups should be at 1mg/kg, 5mg/kg,

10mg/kg, and 20mg/kg.

WiggleTron results are at this point limited in scale, analytical techniques, and medium. The associated analysis of the WT output is in its infancy and requires too much operator action to allow for large scale studies. Further, this analysis barely scratches the surface of what may be within the datasets. Finally, the WT lacked the ability to see through more opaque media with the current light source. Even with these issues, the utility of objectively quantifying nematode motion and correlating it with nematode health is clear. This work has shown, that even in its infancy, the WT with the analysis done herewith has been used to screen potential macrofilaricidal capacity.

The scale of the studies and the analytical techniques used to investigate the data are areas where protocol improvements would be easiest to implement. The first step to protocol improvement would be streamlining how data is transferred between programs to yield the results that have been used in this work to describe motion automatically. In doing this analytical time would be greatly reduced. Data would automatically turn into the figures depicted within this work and allow for quick decisions to be made about potential drugs that are just not possible to make at this time. By removing the amount of research time dedicated to manipulating and sorting data, the researcher could spend more time exploring new methods for data analysis. In addition to speeding up analysis,

102

automatic parsing of data to analytical programs would remove an opportunity for user

error.

Scale of study would also be greatly improved by the introduction of more

sensors. With automatic import of data, sensor number would not greatly impact analysis

time. In the current configuration, adding multiple sensors will be difficult. For the WT to

run multiple sensors and multiple tests at the same time, it must have the same basic

physical conditions in every test tube. This means photodiode placement and wiring must

be identical, light source must be identical, and distance from light source must be

identical. In order to do this, the multiple tube WT would benefit from being rebuilt

digitally. Digitally modelling the WT would allow future iterations to be 3D printed to

ensure common dimensions between light and tube holders. The process of creating the multiple-tube WT would further benefit from automation of the circuitry, again removing any differences that may result from manual wiring. The last issue is that of the light source. Each LED is slightly variable in the amount and composition of the light that it produces. Therefore that will either have to be controlled or eliminated.

Control of this would be through the use of a standard signal based on one of the light sources. This standard signal would be compared to the output from each LED. The slight variations in each LED could then be electronically amplified or reduced to adhere to the standard signal.

Eliminating this would mean utilizing one wavelength of light and a standard intensity of that light. An approach to doing this could involve only one laser light source with the wavelength determined based on testing in the single channel device. This laser light source would then be split either using fiber optics or a standard system of mirrored

103

wave guides to direct exactly the same intensity of light through each of the sample tubes.

This type of set up is impossible at this time due to the precision required in manufacture.

With a standard light source and automatic data import and analysis. The WT

could be configured for any different number of samples, though the ubiquity and

standard dimensions of 96-well plates would seem an obvious choice. In this

configuration, the WT would be able to measure and analyze many different drugs, many

different dilutions, controls, and standards at the same time. This would allow mass

sampling of drugs for potential use against parasitic nematodes. The WT could also be of

use in other screening compounds against other types of parasites, monitoring health of

aquatic microscopic biota, and evaluating motion of sperm.

This work also highlights areas for improvement for a possible field version of the

WT. The same discussion of the time required to manipulate and analyze data that

complicates the scale of testing the WT can do also complicates field work. Therefore

field versions would also benefit greatly from enhanced software integration and

automated analysis.

On the hardware side, the white LED light source cannot be used to see through

opaque media such as blood. In order for the WT to truly be used as a diagnostic, future

versions of the WT dedicated to the field must be able to overcome this. Laser flow

cytometers such as the IDEXX Labs Lasercyte are frequently used in clinical settings

with whole blood. They work on much the same light scattering principle that the WT is based on. It is likely that utilization of a laser as the light source would be better for measuring nematode motion in blood.

104

Adding reagents to lyse red blood cells in infected blood changed the way the worms moved. It is possible that with future versions operating a laser light source, there will be no need to lyse erythrocytes, and therefore no effect on the motion of the parasites. Should this prove true, it would yield a much better opportunity to develop a standard curve of microfilaraemia and use it to be quantitative in the field.

Nematode miRNAs harvested from infected individuals have potential application in either a disease monitoring role or as a potential target for therapeutics. The work presented here shows that the yet isolated miRNAs from different filarial infections show specificity to only one parasite. As the miRNAs are only produced when the animal is patent, this would serve as an additional tool to monitor the scope of infection as well as the progress of drug administration.

The highly specific nature of the miRNAs isolated in this work leads to the conjecture that these miRNAs may have evolved due to the uniqueness of the host- parasite relationship. These molecules may contribute to the understanding of the previously discussed ability of filarial worms to modulate the host immune response for long term survival [236]. This activity has already been identified in viral/host interactions [237] and nematode infections [238]. This work shows that filarial worm miRNA secretions are highly species specific. High species specificity suggests a co- evolutionary relationship between the host and pathogen and could explain some of the difficulties encountered during the failed rat infection described above.

Further, should these miRNAs be found to be regulatory molecules inhibiting the host immune system, they would become important targets for therapeutics. Inhibiting the activity of the nematode-produced immune-modulatory miRNAs in would help

105

reinvigorate the host immune response and could allow for the natural clearance of the pathogen. Further, the circulating miRNAs could be reduced in concentration over time to allow for a slow reboot of the immune response allowing a slower kill of the parasite without triggering a massive inflammatory response that could be detrimental to the host.

(can we relate ther miRNAs to the host adaptations seen withn the FR3 jird model failing in rats)

Overall this work is of scientific value to the field because it provides a description of a better way to model human filarial disease, shows potential technology for use in monitoring, describes a potential therapeutic agent’s effect on adult filarial nematodes, discusses a potential therapeutic miRNA target and offers a description of a new technology and analytical technique for evaluating anti-filarial drugs. In doing so, this work is positive progress in the global effort to eradicate the chronic diseases caused by filarial parasites and has important implications in global human health.

106

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APPENDIX A: COPYRIGHT FOR FIGURE 3

Copyright Text Reads: “Copyright: © 2006 Basáñez et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.”

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APPENDIX B: COPYRIGHT FOR FIGURE 5

Copyright Text Reads: “Copyright: _ 2011 Zoure´ et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.”

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APPENDIX C: COPYRIGHT FOR FIGURES 2, 4, AND 6

Copyright Text Reads: “Thank you for your inquiry to CDC-INFO. In response to your request to use life cycle images from the CDC website as part of your dissertation, we are able to provide you with the following information. The image you provided can be found in CDC's Public Health Image Library (PHIL) at: http://phil.cdc.gov/phil/details.asp Most images found in the PHIL are royalty-free and available for personal, professional and educational use in electronic or print media, with appropriate citation. Please credit CDC and the individual photographer if his or her name is given. If used in electronic media, please link back to the PHIL site.”

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APPENDIX D: IACUC

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