Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5): 519-541, Sep./Oct. 1996 519 The Biology of Malarial Parasite in the Mosquito - A Review Amauri Braga Simonetti
Departamento de Microbiologia, Instituto de Biociência Universidade Federal do Rio Grande do Sul, Rua Sarmento Leite 500, 90050-170 Porto Alegre, RS, Brasil The purpose of this review is to summarize the biology of Plasmodium in the mosquito including recent data to contribute to better understanding of the developmental interaction between mosquito and malarial parasite. The entire sporogonic cycle is discussed taking into consideration different para- site/vector interactions and factors affecting parasite development to the mosquito.
Key words: malaria - mosquito - sporogonic cycle - cell biology
The control and prevention of malaria has been et al. 1996). This review foccuses on the cell biol- pursued for a long time. Although campaigns ogy of malarial parasites at different stages of its against malaria were initially successful in some development in the mosquito and also includes areas, the emergence of resistance of the parasite factors that may affect the parasite infectivity. to drugs and of the mosquito vector to insecticides, The sporogonic cycle combined with the difficulties in implementing and Some erythrocytic parasites differentiate into maintaining effective control schemes have led to sexual forms called gametocytes. Mature and func- a resurgence of the disease in many parts of the tional gametocytes ingested by an appropriate spe- world (Wernsdorfer 1991, Schapira et al. 1993, cies of mosquito in a bloodmeal are stimulated to Roush 1993). Much of the current work on ma- transform into the stages which establish the para- laria focuses on immunological aspects of the dis- sites in their vector (Garnham 1966). Under the in- ease and there has been remarkable progress in the fluence of changes in the mosquito midgut environ- identification of a variety of parasite antigens in ment the gametocytes become extracellular within different stages of the parasite development, some 8-15 min of ingestion. After emergence from the of which may be included in a future vaccine red blood cell (exflagellation) the male gametes fer- (Nussenzweig & Nussenzweig 1989, Mitchel 1989, tilize the female gametes within 60 min of ingestion Targett 1989, Nussenzweig 1990, Hommel 1991, of blood. The fertilized macrogamete (zygote) dif- Good 1991a). However, experimental and field ferentiates into a single motile ookinete over the next studies have shown the complexity of the immune 10-25 hr, which migrates from the bloodmeal response to parasites, indicating that an efficient through the midgut wall to form an oocyst under- malaria vaccine is difficult to achieve (Cattani neath the basal lamina of the midgut. Each oocyst 1989, Good 1991b, 1992, Philips 1992). There- produces many thousands of invasive sporozoites fore, for control of the disease greater understand- over a period of 7-12 days. The sporozoites escape ing of the biological mechanisms involved in host/ from the oocyst and then invade the salivary glands, parasite/vector interactions is essential. here they stay for possibly very long periods until In recent years an increasing number of stud- injected into another vertebrate host when the next ies have concentrated on the mosquito stages of bloodmeal is taken (Sinden 1984, Carter & Graves the parasite development. Comprehensive reviews 1988). A diagram of the sporogonic cycle in the on biological, ultrastructural, biochemical, molecu- mosquito is shown in Figure. lar and immunological aspects of the parasite and the vector can be obtained in the literature (Sinden Development of gametocytes (gametocytogen- 1978, 1983, 1984, Carter & Graves 1988, Carter esis) et al. 1988, Alano & Carter 1990, Billingsley 1990, As with other members of the order Crampton et al. 1990, 1994, Alano 1991, Brey Haemosporina, gametocytes of Plasmodium can 1991, Coluzzi 1992, Kaslow et al. 1994a, Sinden arise from merozoites from pre-erythrocytic para- sites. Nevertheless, during natural infections, most gametocytes arise from merozoites of blood-stage origin (Alano & Carter 1990). Two alternative possibilities by which malaria parasites could be- Fax: 55-51-3362779. E.mail: [email protected] come committed to either sexual or asexual devel- Received 20 December 1995 opment have been proposed (Inselburg 1983, Mons Accepted 13 May 1996 1985, 1986, Bruce et al. 1990): first, the merozoite 520 Biology of Malarial Parasites in Mosquito • AB Simonetti
EXOERYTHROCYTIC CYCLE ERYTHROCYTIC IN LIVER CYCLE IN BLOOD
Penetrates red cell
Merozoites
red cells
reinvade
Schizont
Merozoites
Sporozoites Macro- Micro- penetrates gametocyte gametocyte liver cell IN MAN
Gametocytes taken Sporozoites injected into mosquito IN MOSQUITO into man with saliva stomach with (ANOPHELES) of mosquito bloo meal
Sporozoites in Microgametes salivary gland FERTILISATION GAMETOGENESIS
Ookinete
Ookinete penetrates midgut wall of mosquito to develop into oocyst
SPOROGONY
Oocyst ruptures to liberate sporozoites which penetrate salivary gland
Life cycle of the malaria parasite in mammals (from Vickerman & Cox 1972). is not committed at the time of invasion of a red ronmental factors influence it so that at maturity blood cell. During early growth (as a ring form), the schizont produces merozoites that are the parasite is suceptible to factors that will com- precommitted to form asexual parasites or com- mit it to either sexual or asexual development. Sec- mitted to form gametocytes upon subsequent in- ond, during growth of an asexual parasite, envi- vasion of a red blood cell. Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 521
A number of studies have attempted to iden- showed in vitro that induction of exflagellation of tify factors that may influence the differentiation P. berghei is triggered by a rise in the intracellular ++ and production of sexual stage parasites including pH (pHi) which is mediated by Ca and cGMP cAMP, presence of antimalarial drugs and other regulation. pHi can be modulated by alkaline me- environmental factors associated to the host such dia and is controlled by a complex series of inter- as the presence of serum undetermined components dependent ion pumps and channels controlling Na+, + - - (reviewed by Sinden 1983, Mons 1986, Carter & K , Cl and HCO3 transport between the parasite Graves 1988, Dearsly et al. 1990). In a recent re- and the environment. Other influential factors de- port (Schneweis et al. 1991) it was claimed that scribed include cAMP analogues and inhibitors of the production of infective gametocytes in vitro phosphodiesterase (Martin et al. 1978). The dura- can be enhanced by products of haemolysis but tion of microgametogenesis is both temperature and the nature of the erythrocytic factor was not iden- species dependent, e.g. at 20-22°C it may take 7- tified. 15 min for P. falciparum in vitro, although Gametocyte development takes longer than exflagellation may be detected after shorter peri- asexual schizogony, e.g. 26 hr as opposed to 22.5 ods in the fluid excreted by feeding Anopheles hr in P. berghei (Mons et al. 1985) or in the more (Sinden 1983). There is no evidence that extreme case of P. falciparum 8-12 days as op- exflagellation is influenced by factors released by posed to 48 hr (Sinden 1983). The proportion of digestion of the blood meal since digestion nor- parasites that develop into gametocytes varies mally begins several hours later (Graf et al. 1986). greatly during the course of natural infections even Microgamete formation involves three mitotic di- at its peak but is very low in relation to the total visions with a rapid assembly of eight axonemes parasitaemia (Smalley et al. 1981). The growth and on the single microtubule organizing centre that differentiation of gametocytes of P. falciparum has divides and passes to the spindle poles. This divi- been divided into five stages (I to V) covering about sion simultaneously segregates the genome and the eight days from merozoite invasion to mature ga- axoneme so that each of the eight emergent ga- metocyte, each stage being distinguished by suc- metes receives a single axoneme and haploid ge- cessive changes in the organization of the cell nome, both being connected to a common micro- (Hawking et al. 1971). tubule organizing centre. After exflagellation the Little is known about commitment of gameto- microgametes, normally bearing a single axoneme, cytes to be male or female. The fact that both fe- a single condensed nucleus and a single kineto- male and male can be produced by haploid blood- some with its sphere and granule at the distal end, stage parasite, the sex of a gametocyte does not are torn from the microgametocyte surface and result from chromosomal differences between both rapidly move away into the blood meal (Sinden & types of cell but their development must be due to Croll 1975). selective gene expression. In general, the number Macrogametogenesis at the morphological of female gametocytes predominates over the num- level involves little more than escape from the host ber of male, but this predominance may vary at cell (Sinden 1984). At the cellular level there is de different times between cloned infections novo synthesis of the proteins which are expressed (Cornelissen 1988, Schall 1989). on the surface of macrogamete (Kumar & Carter 1984). It was recently identified a gametocyte spe- Gametogenesis Mature and functional gametocytes ingested by cific protein of P. falciparum called Pf11-1 and there is some evidence that this protein might be the mosquito in a bloodmeal are stimulated by the involved in the emergence of gametes from the midgut environment to transform into gametes. infected erythrocyte (Scherf et al. 1992, 1993). Studies indicate that various triggers induce game- Interactions between the vertebrate host and the tocytes to undergo differentiation. Microgameto- parasite do not cease when the blood meal is taken. genesis in vitro is, optimally, dependent upon a rise in pH (Nijhout & Carter 1978), a rise in pCO and Following induction of gametogenesis the parasite 2 is liberated into the blood meal. It has been shown bicarbonate levels (Carter & Nijhout 1977, Nijhout that the gametes are susceptible to the phagocytes & Carter 1978), a fall in temperature of a few de- in the host’s blood (Rutledge et al. 1969, Sinden & grees below that of the vertebrate host (Sinden & Smaley 1976) and that they are susceptible to acti- Croll, 1975) or a very potent factor termed mos- vation of the components of the complement path- quito exflagellation factor (MEF). The latter is a small heat stable molecule from the mosquito head way (Grotendorst et al. 1986, 1987). and gut which stimulates gametogenesis via a bi- Zygote formation (fertilization) and ookinete carbonate- and pH-independent mechanism development (Nijhout 1979). Recently, Kawamoto et al. (1991) Fertilization is rapid usually occurring within 522 Biology of Malarial Parasites in Mosquito • AB Simonetti
1 hr of gamete formation, the plasmalemma of the products in infectivity has been studied in differ- two gametes fuse and the microgamete axoneme ent parasite-vector models. Using a selected line and nucleus enter the macrogamete cytoplasm of An. stephensi, Feldmann and Ponnudurai (1989) (Sinden 1983). During zygote development, struc- found mature P. falciparum ookinetes in the mid- tural changes occur and its transformation to gut lumen of refractory mosquitoes but no further ookinete is in part determined by the gradual as- penetration of the gut epithelium was observed. The sembly of the apical complex including the collar reasons for this limited development in non-com- and pollar rings, rhoptries and micronemes (Can- patible mosquitoes could be related to digestive ning & Sinden 1973, Davies 1974, Sinden 1978). function since early initiation of hemoglobin deg- Intensive protein synthesis also begins in the fer- radation and higher aminopeptidase activity have tilized macrogamete and continues in the zygote been described in refractory strains of An. stephensi and developing ookinete as reported for different (Feldmann et al. 1990). It has also been shown that Plasmodium species (Kaushal et al. 1983a, Kaushal P. gallinaceum develops up to the ookinete stage & Carter 1984, Kumar & Carter 1985, Vermeulen in the non-compatible mosquito An. stephensi, this et al. 1985a, 1986, Sinden et al. 1987). Included in development occurring over the same time period this repertoir of proteins are many of the targets of and with the same success as in the compatible proposed transmission blocking immunity. It has vector Ae. aegypti. However, P. gallinaceum been reported that An. gambiae can concentrate ookinetes did not escape from the midgut lumen the bloodmeal by a factor of 1.2 to 1.8 reducing in An. stephensi mosquitoes (Rudin et al. 1991). the production of ookinetes when compared to An. Possible mechanism inhibiting parasite devel- freeborni which can not concentrate (Sinden et al. opment involves damage of the parasite by diges- 1996). The mature ookinete is a motile cell that tive enzymes present in the vector. Trypsin and varies from 7 to 18 mm in length and 2 to 4 mm in aminopeptidases are the major proteolytic enzymes diameter (Sinden, 1978). Locomotion of the involved in blood digestion by female mosquitoes, ookinete has been described in different Plasmo- and are produced by the midgut cells in direct re- dium species as a linear or snake-like gliding mo- sponse to blood feeding (Briegel & Lea 1975, Graf tion (Freyvogel 1966). Studying P. berghei & Briegel 1982, Billingsley 1990, Billingsley & ookinetes in primary mosquito cell cultures, Speer Hecker 1991). P. gallinaceum ookinetes 0-10 hr et al. (1974) described spiral waves on the surface old (i.e. zygote to ookinete transition) were shown of some ookinetes, especially in the anterior half to be susceptible to mosquito enzymes in double of the body, which might be involved in ookinete feeding experiments (Gass 1977) and in vitro dam- locomotion. age was observed to cultured ookinetes by protein- Some factors could influence the development, ases from Ae. aegypti (Gass & Yeates, 1979). How- survival and infectivity of the parasite during its ever, results found by Shahabuddin et al. (1993) residence in the midgut lumen. Eyles (1952) has using the same parasite/vector system suggest that showed that the parasite development ceases at the the parasite secretes an inactive or partially active ookinete stage unless a macromolecular (non-dia- chitinase that is activated by a mosquito-produced lyzable) component is present in the blood meal. serine protease. In a recent study Chege et al. (1996) Studying the influence of red blood cells on the examined the effect of digestive enzymes on the ability of P. gallinaceum zygotes fertilized in vitro kinetics of P. falciparum ookinete development and to infect Aedes aegypti Rosenberg et al. (1984) oocyst infection rates in An. albimanus, An. found a linear relationship between erythrocyte freeborni and An. gambiae. Their data indicated density and the number of oocysts up to a 50% that proteolytic enzymes alone do not limit the early hematocrit. Furthermore, they deduced that there stages of sporogonic development in these vector are one or more nondialyzable substances (eryth- species of Anopheles. rocytic factors) contained in normal erythrocytes, and released by mosquito digestion, that are es- Peritrophic layer sential for ookinete invasion of the gut epithelium. The peritrophic layer (PL) of the insect midgut When they added trypsin inhibitor to the bloodmeal forms a cylindrical sheet separating the midgut there was an inhibition of midgut penetration by contents from the single cell-layered midgut en- ookinetes. Recent studies have shown that when dothelium. It is secreted within hours of the blood mosquitoes are fed with cultured P. falciparum meal at different rates depending on the mosquito (Ponnudurai et al. 1989) and P. berghei (Sinden species (Billingsley 1990). Apical secretion gran- 1989) gametocytes, upon dilution with fresh red ules are present in the midgut cells of Anopheles cells, more oocysts result at initial (low) dilutions species, which are released into the periphery of whereas further dilution reduces oocyst counts. The the posterior midgut lumen during the feeding pro- involvement of blood factors and/or its digestive cess in response to stretching of the gut wall. The Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 523 vesicle contents coalesce and then condense to form nomena play a role in the orientation of the para- a compacted PL between 8 and 24 hr (Hecker 1977, sites on their way out of the midgut lumen and that Berner et al. 1983). In culicine mosquitoes the PL the PM and/or glycocalyx may be crucial struc- is formed de novo by the posterior midgut cells in tures for the penetration of the gut epithelium by the proventriculus. In A. aegypti, formation starts the ookinete. This does not exclude the possibility immediately after the blood meal, but about 12 hr that ookinetes penetrate the PL by an enzymatic later it is a mature structure (Perrone & Spielman, process (see below). Ultrastructural observations 1988). on Ae. aegypti infected with P. gallinaceum show- The role of the mosquito PL as a barrier to ing an electron dense amorphous material in front ookinete invasion of the gut wall and pathogenic of the parasite were consistent with a blockade of effects of Plasmodium species upon the vector are parasites within the PL (Sieber et al. 1991). The controversial. In ultrastructural studies on the in- ookinetes appeared to disrupt the layers of the PL, teraction of P. falciparum ookinetes with the mid- suggesting an enzymatic mechanism for penetra- gut epithelium of An. stephensi Meis & Ponnudurai tion. These observations were further investigated (1987) frequentely found parasites trapped in the by Huber et al. (1991) who, using the same vector/ membrane. They also observed that if the PL was parasite system, also suggested a possible role for dissected out 36 hr after the blood meal many GlcNAc in the binding of the ookinete to the PL, ookinetes were attached to its external surface. In and demonstrated the presence of chitin in the PL. the same study it was mentioned that the ookinete They observed that mature ookinetes transiently was capable of penetrating the newly formed, but secreted a soluble chitinase, thought to be respon- not the thickened and hardened PL 36 hr after the sible for the digestion of the PL. Recently, feeding. A failure to cross this barrier or retarded Shahabuddin et al. (1993) reported an inhibition penetration might increase the length of exposure of P. gallinaceum chitinase and a transmission of ookinetes to mosquito trypsin to which it is blocking activity of a chitinase inhibitor, known to be sensitive. In contrast, using P. berghei- allosamidin, on the sporogonic development of P. infected An. atroparvus mosquitoes, Sluiters et al. gallinaceum and P. falciparum in the respective (1986) concluded that the PL would not function vectors Ae. aegypti and An. freeborni. However, as physical barrier against migrating ookinetes enzymatic mechanisms of penetration may differ which can pass through fenestrations. Billingsley in other vector/parasite systems since the PL of An. and Rudin (1992) observed that infectivity of An. stephensi appears not to contain chitin (Berner et stephensi by P. berghei, measured by oocyst al. 1983). counts, was unnaffected by the presence or absence of the PL. However, in A. aegypti infected with P. Penetration of midgut epithelium gallinaceum its presence serves to reduce rather Ookinetes found in the epithelial cell layer be- than prevent infection (Ponnudurai et al. 1988, tween 24 and 48 hr post-infection have success- Billingsley & Rudin 1992). These observations fully evaded the obstacles presented by the mid- suggested to the authors that in compatible vector- gut lumen; however, they still might fail to develop parasite combinations, the PL acts as a limiting, at the normal site of development (Sinden 1984, rather than absolute barrier to the penetrating Ponnudurai et al. 1988). It has been shown that the ookinete while in incompatible combinations the midgut wall is negatively charged (Houk et al. PL appears to be an absolute barrier to ookinete 1986), but there is no evidence of electrical charge penetration. interactions between ookinetes and epithelial cells. To reach the midgut epithelium the ookinetes It has been a matter for discussion as to whether must first cross the partially or fully formed PL. the ookinete follows an intra- or intercellular route The PL may act as the recognition site for the pen- to reach the ultimate site of development and en- etrating ookinete via lectin-mediated mechanisms. cystment in the outer wall of the midgut epithe- The occurrence of sugar residues which could be lium. involved in vector recognition by the parasite has Intercellular movement of P. gallinaceum been demonstrated in the PL of An. stephensi and ookinetes was first described by Stohler (1957), Ae. aegypti (Berner et al. 1983). Rudin and Hecker but Mehlhorn et al. (1980) have found the same (1989) showed the presence of binding sites for parasite in an intracellular position. Recently, Torii different lectins in midguts of P. berghei-infected et al. (1992a) observed P. gallinaceum ookinetes An. stephensi, with high specificity for N-acetyl- in both intracellular and intercellular positions in D-galactosamine (GalNAc), and P. gallinaceum- the midgut epithelium of the mosquito Ae. aegypti, infected Ae. aegypti, with high specificity for N- which they interpret as that they first enter into the acetyl-D-glucosamine (GlcNAc). The authors con- epithelium, then exit into the intercellular space cluded that it seems likely that lectin-binding phe- and move to the basal lamina. Garnham et al. 524 Biology of Malarial Parasites in Mosquito • AB Simonetti
(1962) showed that the ookinete of P. cynomolgi Friedman, 1987). They observed similar mortality bastianelli enters the epithelial cell by liquifying rates in infected and uninfected batches of mos- the cell membrane. Davies (1974) again postulated quitoes. However, when ookinetes use an intracel- intercellular movement by P. berghei nigeriensis lular route, as described previously, increased dam- ookinetes. Although describing the ookinete of P. age to midgut cells might occur, resulting in higher berghei in an intracellular position, as did Garnham mosquito mortality. This is probably mediated by et al. (1969), Canning and Sinden (1973) stated invasion of the hemolymph by opportunistic gram- that the parasite might also migrate by an intercel- negative bacteria and/or microsporidia (Maier et lular route. More recently, P. yoelii nigeriensis al. 1987, Seitz et al. 1987). ookinetes have been described to take an intracel- Ultimately the ookinete penetrates the basement lular route to the external wall of the midgut (Maier membrane, but fails to pass through the basal et al. 1987). However, when the same parasite was lamina of the midgut adjacent to hemocoele used to infect An. omorii, an intercellular route was (Sinden 1984). Whether this is due to the inability mostly undertaken, although the intracellular oc- of the ookinete to penetrate the basal lamina, or to currence was also observed (Syaffruddin et al. the specific recognition of the lamina and conse- 1991). Meis and Ponnudurai (1987) presented evi- quent shut-down of the incisive process is not dence that P. falciparum ookinetes migrate between known. Interactions of parasites with vector extra- the epithelial midgut cells. Using a specific mono- cellular matrix proteins (ECM) cannot be dis- clonal antibody they also observed a track in the counted (Kaslow et al. 1994b). PL, which is related to the shedding of a 25 kD surface protein (Pfs25) during movement. The au- Oocyst development thors suggested that this protein may bind to re- Oocyst development is predominantly extracel- ceptors on the epithelial cells prior to an intercel- lular (Duncan et al. 1960, Garnham et al. 1969, lular invasion, since it is reported to have epider- Howells & Davies 1971, Sinden 1975), but occa- mal growth factor (EGF)-like domains (Kaslow et sionally occurs within the midgut epithelial cell al. 1988). It was recently shown that Pfs25 persits (Vanderberg et al. 1967, Bafort 1971, Beaudoin et in the oocyst wall during parasite development in al. 1974). The ookinete usually comes to rest be- the mosquito (Lensen et al. 1993). The same group neath the basal lamina 18-24 hr after the infective studied the migration of P. falciparum and P. blood meal (Sinden 1978). It rapidly rounds up be- berghei ookinetes through the midgut epithelium tween 18 and 72 hr after feeding and the apical in An. stephensi by using ruthenium red staining complex is resorbed into the oocyst cytoplasm (Meis et al. 1989). The results of previous studies (Garnham et al. 1969). There is some evidence were confirmed: P. falciparum ookinetes pen- suggesting a significant role of the basal lamina in etrated by intercellular route, but the rodent para- the development of the ookinete (Kaslow et al. site P. berghei appeared to take an intracellular 1994b). It was found that in vitro-cultured position, confirming that both mechanisms occur ookinetes injected directly into the hemolymph and are species-dependent. In the case of P. berghei form clusters of oocysts adherent to the basal a protein of 21 kD (Pbs21) present on the surface lamina throughout the hemocoele. Furthermore, of the ookinete (Sinden et al. 1987) could play a binding of ookinetes to artificial surfaces, such as role during the intracellular invasion of the mid- plastic, is enhanced at least 10-fold by addition of gut epithelium of An. stephensi mosquitoes. It was various components of basal lamina such as demonstrated in the midgut of P. berghei infected matrigel, collagen IV, and laminin (Warburg & mosquitoes that expression of Pbs21 was predomi- Miller, 1992). The young oocyst is enveloped by a nantly localized on the ookinete surface one day thick plasmalemma that is covered on the after the infectious blood meal and thereafter ex- hemocoelomic surface by a fibrous basal lamina. pression declined to a minimum on days 2 and 3, Oocysts from the second day onwards are also cov- the time of onset of oocyst development (Simonetti ered by an amorphous capsule which becomes re- et al. 1993). duced in thickness at maturity (Vanderberg et al. The mode of penetration by ookinetes can per- 1967, Aikawa 1971, Strome & Beaudoin 1974, haps be related to damage of the epithelial lining Sinden 1975). of the midgut. Intercellular migration may not dam- Despite the usual growth of the oocyst under age cell membranes, and increased mortality does the basal lamina of the midgut, oocyst develop- not occur in P. falciparum-infected An. stephensi ment is not site specific. Weathersby (1952, 1954, and An. gambiae during this period, even with very 1960) has shown by injection of gametocytes di- heavy parasite loads (Meis & Ponnudurai, 1987). rectly into the hemocoele of susceptible mosqui- Similar observations have been reported in P. toes that oocysts would develop to maturity if at- gallinaceum-infected Ae. aegypti (Freier & tached to other parts of the body than the stomach Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 525 or even if they were floating freely in the hemo- Little information is available on the uptake and coel fluid. In his experiments he used different source of nutrients for oocyst development. It is parasite-host combinations and concluded that the assumed that in vivo the source of nutrients is the site of oocyst development is probably not a criti- hemolymph. Mack and Vanderberg (1978) ana- cal factor in the maturation process. Furthermore, lyzed hemolymph of An. stephensi collected from the factors that are responsible for the death of uninfected and P. berghei-infected mosquitoes at parasite in refractory lines are not confined to the different stages of the parasite development. It was stomach wall. These results were supported by found that four days after the blood meal the os- those reported by Ball and Chao (1957, 1960, 1961, motic pressure and the specific gravity were lower 1976) who showed that oocysts of P. relictum may in infected mosquitoes compared with uninfected develop in vitro away from the intact stomach of ones. The difference, however, was attributed to the mosquito. The overall results of this series of indirect effects of the quality of the ingested blood studies by Ball and Chao demonstrated in vitro meal. These studies were complemented by analy- development of all stages from ookinetes to fully sis of the concentration of free amino acids in the infective sporozoites without attachment of oocysts hemolymph collected in similar conditions with to the midgut. However, it was not possible to ob- results showing significantly lower concentrations tain complete sporogonic development in a single in infected mosquitoes with decreases in valine and preparation. Rosenberg and Koontz (1984) injected histidine, and a total loss of detectable methionine cultured P. gallinaceum zygotes into the hemocoele suggesting it is incorporated (Mack et al. 1979). of Ae. aegypti mosquitoes and observed develop- This difference could be due to the utilization of ment of ectopic oocysts in approximately 50% of some of these amino acids by the developing oo- the mosquitoes, with sporozoites being found in cyst as suggested by Ball and Chao (1976) who the salivary glands. These observations suggest that analyzed the uptake of amino acids by P. relictum oocyst metabolism is not dependent upon direct oocysts in vitro, comparing growth of uninfected transfer of nutrients from the midgut epithelium. and infected guts of Culex tarsalis in Grace’s in- Occasional intracellular oocyst development has sect culture medium. They found significant de- been reported for P. berghei in An. stephensi and creases in the concentration of certain amino acids An. quadrimaculatus (Vanderberg et al. 1967). The including arginine, asparagine, proline and histi- same localization was described in P. vinckei by dine, and less marked decrease in concentrations Bafort (1971) who concluded that both mechani- of others like methionine, valine, leucine and iso- cal pressure and physiological mechanisms play a leucine. From these studies it appears that the re- role in the movement of oocysts to the duced amount of free aminoacids in the hemocoelomic surface. Studying the sporogonic hemolymph is due to oocyst metabolism. Autora- development of P. berghei in An. stephensi, diographic studies with P. gallinaceum in Ae. Beaudoin et al. (1974) found oocysts developing aegypti mosquitoes indicated that 3H-leucine is ectopically within the midgut epithelium follow- uniformly incorporated throught the oocyst within ing normal infection, eventually emptying their 15 min of injection into hemocoele (Vanderberg sporozoite content into the tissue itself or the mid- et al. 1967). gut lumen. In addition, they observed no morpho- logical and structural abnormalities in the luminal Sporogony parasites which displayed good viability. In con- With increasing maturation the oocyst under- trast to P. berghei, no ectopic development was goes considerable cytoplasmic subdivision. Ini- seen in P. falciparum-infected An. stephensi mos- tially the plasmalemma forms invaginations and quitoes (Meis et al. 1992b), confirming previous clefts that penetrate even deeper into the cytoplasm, results observed with P. falciparum in naturally thus subdividing the cell (Vanderberg et al. 1967, infected An. gambiae (Sinden & Strong 1978). Terzakis 1971, Posthuma et al. 1988). In a trans- Recent reports described an enhancement of oo- mission electron microscopy study of P. falciparum cyst development in vitro for P. berghei oocysts it was suggested that cleft formation was (Syaffruddin et al. 1992), P. gallinaceum (Warburg due to dilation of endoplasmic reticulum (Sinden & Miller, 1992) and P. falciparum (Warburg & & Strong 1978). Using immunogold labelling tech- Schneider, 1993), when insect cell lines were added nique during sporogonic stage of the same para- into the culture medium. From these observations site, Posthuma et al. (1988) considered the latter it appears that nutritional or other regulatory re- explanation unlikely. With increasing activity the quirements of the developing parasite can be met cytoplasmic clefts become extended and the ex- without a direct contact with midgut epithelium or panding vacuolar space more pronounced leading haemolymph. The question of how the oocyst is to the sporoblast formation. Along the clefts sporo- supplied with nutritive material is an intriguing one. zoites are formed by a budding process at the Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 519
face of the limiting membrane (Vanderberg et species (Collins et al. 1986). The authors demon- al. 1967, Howells & Davies 1971, Canning & strated that refractoriness is manifested by mela- Sinden 1973, Sinden & Strong 1978). nization of the ookinete after its passage through As the sporozoite continues to bud off, a the midgut epithelium. Paskewitz et al. (1989) lo- nucleus and various cytoplasmic components are calized phenoloxidase activity in the basal lamina passed into it from the sporoblast. The membranes of the epithelial cells of both encapsulating and of the developing sporozoite pellicle are formed susceptible mosquitoes prior to blood feeding. and other organelles like microtubules and However, after an infective blood meal, this activ- rhoptries become discernible (Vanderberg et al. ity was still observed close to invading ookinetes 1967, Sinden & Garnham 1973). When sporogony in refractory mosquitos but it was reduced or ab- is completed (about 10-12 days after the infective sent in susceptible mosquitoes. When the non-com- feed), the oocyst is filled with sporozoites and one patible vector An. gambiae was fed with ookinetes or more residual bodies (Sinden 1984). Estimations of P. gallinaceum, invasion of the midgut epithe- of number of sporozoites per oocyst have ranged lium by the ookinetes occurred but oocysts were widely. Garnham (1966) reported that the number infrequentely formed. Using the same system in a single P. vivax oocyst varies from 1,000 to Vernick et al. (1989) and Vernick and Collins 10,000. Pringle (1965) estimated that a single oo- (1989) tried to elucidate mechanisms involved in cyst of P. falciparum contains nearly 10,000 sporo- vector-parasite incompatibility by injecting in vitro- zoites. Studies carried out with mosquitoes fed on cultured ookinetes into the hemocoel of mosqui- infected volunteers from Thailand showed a mean toes and monitoring parasite development using count of approximately 3,700 sporozoites per oo- specific rRNA probes. As no differences were cyst for P. vivax and 3,400 for P. falciparum, found between susceptible and refractory mosqui- whereas for P. cynomolgi-infected mosquitoes a toes the authors suggested that the specific lytic single oocyst contained about 7,500 (Rosenberg factor(s) in the refractory line are intracellular. & Rungsiwongse 1991). Dependent upon species, the mature sporozoite varies from 9 to 16.5 mm in The sporozoite and salivary gland invasion length and from 0.4 to 2.7 mm in diameter; aber- The motile sporozoites emerge into the rant forms have been described up to 40 mm long hemocoele through holes from an area of weak- (Sinden 1978). ness in the oocyst wall. Holes are possibly pro- So far, studies on synthesis and expression of duced by a combination of the muscular action of proteins during sporogonic development have the gut wall and the activity of the sporozoites foccused on a polypeptide called the (Sinden 1978, Meis et al. 1992b). Within the hemo- circumsporozoite protein (CSP) found on the ma- coel the sporozoites are distributed throughout the ture sporozoite. Observations on the origin of CSP mosquito and can initially be found in many parts and its distribution through the mosquito stage were of the insect, even in the maxillary palps; within a reported by several authors. It is now well estab- day or two of their release from oocysts the sporo- lished that these proteins are synthesized in matur- zoites invade the salivary glands where they accu- ing oocysts of different Plasmodium species from mulate and remain until delivery (Vaughan et al. 6-7 days after the infective blood meal, before 1992). Thus, sporozoites do not adhere to most tis- sporozoites are visible (Nagasawa et al. 1987, 1988, sues, except for the salivary glands and rarely the Posthuma et al. 1988, Hamilton et al. 1988, midgut wall, hemocytes or thoracic muscles Boulanger et al. 1988, Torii et al. 1992b, Meis et (Vanderberg 1974, Sinden 1975, 1978, Golenda al. 1992a). At this stage, CSP is present on the plas- et al. 1990, Vaughan et al. 1992). The latter obser- malemma and at various sites within the cytoplasm vation, especially in heavily infected mosquitoes, and endoplasmic reticulum of the sporoblast. When could be associated with an impairment of flight the sporozoites bud from the sporoblast they are activity in malaria-infected An. stephensi vectors already covered with CSP which is also found in demonstrated by some authors (Rowland & salivary gland sporozoites (Yoshida et al. 1981, Boersma 1988). Santoro et al. 1983, Tsuji et al. 1992). It has been estimated that in mosquitoes fed on Humoral encapsulation of oocysts, which in individuals with naturally acquired P. vivax about malaria infected mosquitoes is known as Ross’ 850 sporozoites per oocyst reached the glands black spores, has been described in P. berghei (Sattabongkot et al. 1991) which follows, by cal- nigeriensis and P. vivax and seems to occur mainly culation, that approximately 23 % of all P. vivax in older oocysts which have begun to produce sporozoites released into the hemocoel sporozoites (Sinden & Garnham, 1973). This phe- subsequentely reach the salivary glands (Rosenberg nomenon was studied in a selected line of An. & Rungsiwongse 1991). Vaughan et al. (1992), gambiae that encapsulates different Plasmodium using regression analysis, calculated the approxi- 520 Biology of Malarial Parasites in Mosquito • AB Simonetti mately 650 salivary gland sporozoites were pro- 1988, 1991, 1992). Soluble CSP was shown to be duced per oocyst and reported that virtually all present throughout the hemocoel (Robert et al. oocyst infections produced salivary gland infec- 1988). Beier et al. (1992a) concluded that the re- tions in An. gambiae infected with P. falciparum lease of CSP by sporozoites is a normal but com- by membrane feeding. The same group has found plex mechanism that they interpreted to be associ- a similar number by studying the sporogonic de- ated with sporozoite survival in the host, is not site- velopment of cultured P. falciparum in six species specific and it would be regulated in response to of laboratory-reared Anopheles mosquitoes background levels of soluble CSP in the environ- (Vaughan et al. 1994). This is in contrast to obser- ment (negative feedback mechanism). This idea is vations on wild-caught An. gambiae from Burkino- supported by previous results showing that the Faso (Lombardi et al. 1987) and western Kenya parasites cease to synthesize CSP during their jour- (Beier et al. 1990) where sporozoites failed to en- ney through the hemolymph but shedding still oc- ter the salivary glands in 43% and 10% of infected curs (Posthuma et al. 1988, 1989). There is no evi- mosquitoes, respectively. However, when sporo- dence yet for chemotaxis but the congregation of zoites from P. gallinaceum oocysts were injected sporozoites in the vicinity of the glands before in- into Ae. aegypti female mosquitoes only 6.5 to vasion may support, according to some workers, a 10.4% of inoculated sporozoites invaded the sali- tactile mechanism (Golenda et al. 1990, Meis et vary glands. Interestingly, injected salivary gland al. 1992b). Several polysacharides have been iden- sporozoites did not reinvade the glands (Touray et tified that may orient protozoa towards or away al. 1992). Recently, a laboratory study on An. from a stimulus (Van Houten 1988). tesselatus mosquitoes infected with different iso- The selective invasion of mosquito salivary lates of P. vivax and P. falciparum from patients glands by malarial parasites is not well understood. living in Sri Lanka showed that approximately 15% Specific recognition of the glands was shown in P. of mosquito batches in which oocysts developed knowlesi. Oocysts developed normally on the gut failed to produce salivary gland sporozoites of An. freeborni but sporozoites were never found (Gamage-Mendis et al. 1993). This discrepancy in salivary glands. When glands from the suscep- between naturally and laboratory-infected mosqui- tible vector An. dirus were implanted into the ab- toes could be attributed to different environmental domen, they did become infected (Rosenberg conditions or mixed mosquito populations. 1985). These experiments demonstrated that the It could be expected sporozoites would elicit a salivary glands themselves determined specificity. humoral response in the mosquito by activation of Although invasion of salivary glands seems to re- the prophenoloxidase cascade and as a result be quire specific recognition, the mechanism by which killed by melanization. However, sporozoites in sporozoites recognize, attach to, and penetrate the the hemocoele are rarely seen to be melanized glands remains to be determined. (Brey 1991). Sporozoites might be protected from Sporozoites preferentially invade the medial mosquito defense reactions against ‘non-self’ by lobe and the distal portions of the lateral lobes of antigen sharing. This has been demonstrated as a the salivary glands where the salivary duct is not potential mechanism for avoidance of mosquito chitinous in Anopheles species (Sterling et al. 1973, defence reactions by microfilariae of Brugia James & Rossignol 1991, Ponnudurai et al. 1991). pahangi (Maier et al. 1987). Immunoreactivity to Hence, the occurrence of a specific receptor-me- CSP was observed on the midgut wall of mosqui- diated invasion by sporozoites is plausible. Perrone toes infected with P. falciparum (Boulanger et al. et al. (1986) used lectins to characterize carbohy- 1988) and P. yoelii (Beaudoin et al. 1990). The drate moieties on the basal lamina of Ae. aegypti latter authors also detected reactivity on uninfected salivary glands. As the median and distal lateral midguts and suggest the presence of a common lobes bound a common lectin, RCA 120, whose determinant between the parasite and the mosquito. substrate is b-D-galactose, the authors suggested The migration of sporozoites from oocysts to that sugars that bind this lectin serve as candidate salivary glands could be active (in contact with residues to which sporozoites may attach. In con- basal lamina), passive (in suspension) or both. If trast, the sporozoite coat binds some lectins with active, the parasite would use a gliding motility to very low efficiency (Schulman et al. 1980, Turner move across the basal lamina and reach the gland. & Gregson 1982). However, in a recent scanning Vanderberg (1974) described circular gliding and electron microscopic study Meis et al. (1992b) lo- attached waving locomotion and movement in calized P. falciparum sporozoites in proximal and sporozoites of different species when bovine se- distal parts but were unable to identify any spe- rum albumin was added to Medium 199. Sporo- cific regions on the glands where sporozoites pen- zoites that move over a substratum in vitro leave etrate. These authors also showed sites where the behind trails of CS proteins (Stewart & Vanderberg sporozoites have pierced the basal lamina, which Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 521 probably explains the presence of CSP on the basal zoites could cause pathological vesiculation and lamina induced by shedding during penetration cytoskeletal changes in salivary gland tissues as (Posthuma et al. 1989) and the presence of immu- the infected cells are often deformed and swollen noreactive spots of 1-2 mm on the surface of in- (Sterling et al. 1973, Maier et al. 1987). The effi- fected glands (Golenda et al. 1990). Recently, ciency of salivary gland invasion is poorly under- Touray et al. (1994) developed an in vivo salivary stood. It has been estimated that the median sporo- gland invasion assay and have found that anti-sali- zoite load in the glands is less than 10,000 in colo- vary gland antibodies, sulfated glycosaminogly- nized or wild Anopheles species (Shute 1945, cans and some lectins, particularly Suc-WGA, Pringle 1966, Wirtz et al. 1987, Beier et al. 1991b, block invasion of sporozoites. Although the mecha- Sattabongkot et al. 1991) or slightly higher nism of blocking is not yet known, those lectins (Ponnudurai et al. 1991). that blocked invasion bound to salivary glands but The development of infectivity by the sporo- did not bind to sporozoites. Beier et al. (1992a) zoites appears to be asynchronous, in some cases and Beier (1993) proposed that as sporozoites in- taking place in the hemocoele, while in others not vade the salivary glands, the build-up of CSP is occuring until after they have invaded the salivary the signal for sporozoites to halt their active motil- glands. Thus, it seems to be time-dependent rather ity, and thus their release of CSP (down-regula- than site-dependent (Vanderberg 1975, Daher & tion). The involvement of CSP and other proteins Krettli 1980). It was demonstrated in P. berghei- distinct from CSP such as PySSP2 (Charoenvit et infected mice that populations of salivary gland al. 1987) and PfSSP2 (Robson et al. 1988, Rogers sporozoites were more than 10,000 times as infec- et al. 1992a,b) in binding of sporozoites to the basal tive to the vertebrate host as populations of oocyst lamina of mosquito salivary glands is speculative. sporozoites from the same mosquitoes (Vanderberg As they share similarities in their structure they 1975). Touray et al. (1992) found that as few as might be related to this process since it has been 10-50 salivary gland P. gallinaceum sporozoites suggested region II of CSP is involved in hepato- were required to induce infection in chickens com- cyte invasion (Cerami et al. 1992a,b, Pancake et pared to 5,000 oocyst sporozoites. Sporozoite in- al. 1992). fectivity increases with time during the first week Rosenberg (1985) and King (1988) have sug- after the invasion of the salivary gland (Vanderberg gested that sporozoites invade the salivary gland 1975). Degeneration of sporozoites is not frequent cells using a mechanism similar to invasion of in nature as observed by Barber (1936) who stud- erythrocytes by merozoites although there is no ied anophelines collected in Mediterranean areas. evidence of parasitophorous vacuole membrane When degeneration occurred in a salivary gland formation observed in other stages of the parasite or a lobe of a gland, in another gland or lobe the cycle (Sinden & Strong 1978, Meis & Verhave sporozoites were normal or in a different stage of 1988). Membrane-limited vacuoles beneath the degeneration. plasma membrane in An. stephensi distal salivary The number of sporozoites injected into the tis- gland cells invaded by P. berghei have been de- sue or capillary of the vertebrate is very small com- scribed (Sterling et al. 1973). Penetration could also pared to that found in the salivary glands. It has involve an unusual intercellular route as suggested been estimated, by employing different methods, by Golenda et al. (1990) who detected CSP in the that each bite delivers fewer than 50 sporozoites region between cells of the median lobe of the with a tendency for most sporozoites to be ejected gland. Posthuma et al. (1989) observed many in the first droplets of saliva (Vanderberg 1977, sporozoites on the basal side of the cells, but also Rosenberg et al. 1990, Ponnudurai et al. 1991, found trail-like CSP immunoreactivity at the lat- Beier et al. 1991a,b, Beier et al. 1992b, Li et al. eral space between the cells. 1992). Although a correlation between salivary After penetration, sporozoites are present in gland sporozoite load and sporozoite inoculum has bundles in the accini of gland cells in both proxi- been reported (Rosenberg et al. 1990) ejection of mal and distal areas. Most probably, the sporozoi- sporozoites is probably a random process, more tes which are present in proximal areas of the glands related to the architecture of the salivary gland duct are unable to reach the draining duct because of system than to the number of sporozoites in this the chitinized layer in that area whereas distally organ (Ponnudurai et al. 1991). localized sporozoites reach the draining duct via Some studies reported that P. falciparum-in- the large unchitinized collecting tube (Meis et al. fected mosquitoes deliver sporozoites in an unpre- 1992b). This explanation would not be valid for dictable fashion, sometimes not at all (Ponnudurai Aedes species since the salivary ducts are lined with et al. 1991), and others transmit inconsistently chitin and extend the full length of the glands (Rickman et al. 1990). Clumping of sporozoites (James & Rossignol 1991). Penetration by sporo- has been reported in infected salivary glands (Ster- 522 Biology of Malarial Parasites in Mosquito • AB Simonetti ling et al. 1973) and clusters of sporozoites were of Ae. aegypti result in reduced levels of salivary detected after delivery when An. stephensi mos- apyrase. Mosquitoes deficient in salivary apyrase quitoes infected with P. falciparum were allowed experience difficulty in locating host blood and en- to feed through fresh mouse skin (Ponnudurai et gorging; they therefore probe more often and may al. 1991). It has been observed that salivary glands attempt to feed on several hosts in succession are not depleted of sporozoites even in vectors that (Rossignol et al. 1984, 1986, Ribeiro et al. 1985). feed up to 15 times (Shute 1945), which allows Li et al. (1992) demonstrated that probing time of infected mosquitoes to remain potentially infec- P. berghei-infected An. stephensi is not affected tious for life. by sporozoite invasion of salivary glands. The low sporozoite inoculum and the low en- Blood meal size may influence infectivity since tomological inoculation rates in natural conditions it determines the number of gametocytes ingested (Mendis et al. 1990a, Gordon et al. 1991) demon- and therefore subsequent infection. It has been strates the high efficiency with which injected shown that larger An. dirus females took larger sporozoites will develop malaria. bloodmeals by artificial feeding with cultured P. Factors affecting parasite development to the falciparum and developed significantly more oo- mosquito cysts (Kitthawee et al. 1990). In a field study, The process of infection of mosquitoes is ex- Lyimo and Koella (1992) reported that the pro- ceedingly complex and regulated by a range of portion of An. gambiae mosquitoes infected with factors originating from the parasite, the vertebrate P. falciparum during a blood meal was indepen- host and the mosquito vector, and from the inter- dent of size but the number of oocysts harboured actions between all three (Sinden 1991). Many of by infected mosquitoes increased with size of the these and other factors are known to affect fertili- mosquito. zation and subsequent stages of parasite develop- b) Gametocyte carriers/transmission blocking im- ment, thus having great influence on transmission munity - Malarial infections induce host responses of the disease. To have an idea, when sporogonic to both asexual and sexual stage malaria parasites development of cultured P. falciparum was evalu- that may modulate gametocyte infectivity. Great ated in six species of Anopheles mosquitoes there heterogeneity in infectiousness of different carri- was a total loss of approximately 31,600-fold in ers has been noted, with apparently poor correla- the parasite population from macrogametocyte to tion between infectiousness and gametocyte den- oocyst stage (Vaughan et al. 1994). sity (Graves et al.1988). However, it remains un- a) Host location and feeding behaviour - Of pri- clear whether symptomatic and asymptomatic mary importance in malaria transmission is the asexual infections differ in their ability to influ- proportion of mosquito feeds taken from humans ence gametocyte infectivity. It has been reported and the proportion of these feeds taken from in- that asymptomatic P. falciparum patients were fected individuals. In nature a vector needs to sur- more infectious than symptomatic patients (Boyd vive longer than the sporogonic period after tak- & Kitchen 1937, Jeffery & Eyles 1955, Muirhead- ing an infective blood meal; during this period the Thomson 1957, Carter & Graves 1988) while, in mosquito probably takes blood meals every 2-3 contrast, another report suggested that days, depending on its gonotrophic cycle and the asymptomatic and symptomatic P. malariae pa- availability of breeding sites (Ponnudurai et al. tients were equally infective (Young & Burgess 1989). Parasitemic hosts tend to be sick and often 1961). less irritated by mosquito feeding. Additionally, Specific and non-specific responses are be- the thrombocytopenia which is commonly associ- lieved to modulate parasite transmission. The in- ated with blood-borne parasitic diseases leads to duction of specific immunological responses to facilitation of vessel location, resulting in increased Plasmodium shows marked heterogeneity within feeding success by mosquitoes on parasitemic hosts human populations (Mendis et al. 1987, Graves et (Rossignol et al. 1985). Salivary glands and saliva al. 1988, Targett 1990, Snow et al. 1993). The contain a whole range of components with phar- sexual stages can induce trasmission blocking im- macological activities important for blood feeding munity (TBI) and effective targets include antigens success and subsequent bloodmeal processing, in- identified on the surface of the macro- and/or cluding anticoagulants, anti-inflammatory, microgemetes (‘pre-fertilization’antigens) as well vasodilatory and immunosuppressive compounds as antigens present on the surface of the gamete, (Ribeiro et al. 1984, 1989, Ribeiro 1987, Titus & zygote and ookinete (‘post-fertilization’ antigens). Ribeiro 1990, James & Rossignol 1991). Rossignol Antibodies to ‘pre-fertilization’ antigens of P. et al. (1984) concluded that the lesions caused by falciparum such as Pfs230, Pfs48/50 and Pfs16 P. gallinaceum sporozoites in the salivary glands have been detected in humans (Graves et al. 1988, Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 523
Premawansa et al. 1994, Hogh et al. 1994). A sig- changes in gametocyte infectivity. Acute phase nificant association between lacking of infectivity reactants like C-reactive protein (CRP), which are of P. falciparum gametocyte carriers and recogni- non-specific indicators of inflammatory activity, tion of epitope IIa on Pfs48/50 by antibodies in are elevated in patients with P. falciparum malaria their sera has been observed (Graves et al. 1992). (Ree 1971, Naik & Voller 1984, Chagnon et al. Naturally acquired TBI to P. vivax sexual stage 1992). Some cytokines such as interferon (IFN-g), antigens has also been demonstrated (Mendis et tumor necrosis factor (TNF-a) and interleukin 6 al. 1987, 1990b, Mendis & Carter 1991, Ranawaka (IL-6) are elevated in sera fom patients with P. et al. 1988, Goonewardene et al. 1990, Gamage- falciparum and P. vivax malaria (Grau et al. 1989, Mendis et al. 1992) and appears to play a role on Kern et al. 1989, Kwiatkowski et al. 1990, Mendis transmission of the disease (de Zoysa et al. 1988). et al. 1990c, Karunaweera et al. 1992). Both IFN- In P. vivax malaria antibodies, at low concentra- g and TNF-a appear to cause a transient but marked tions, can also have a transmission-enhancing ef- drop in the infectivity of gametocytes to mosqui- fect on infectivity of malarial parasite to mosqui- toes due to the intraerythrocytic killing of para- toes (Mendis et al. 1987, Peiris et al. 1988, sites (Naotunne et al. 1991, Karunaweera et al. Naotunne et al. 1990, Gamage-Mendis et al. 1992). 1992). However, a recent study has shown no el- A recent report described TBI in P. vivax malaria evation in blood levels of cytokines IL-2, IL-6, when antibodies raised against a peptide blocked TNF-a and IFN-g nor reactive nitrogen intermedi- parasite development in the mosquito An. tesselatus ates (Hogh et al. 1994). The authors suggested that (Snewin et al. 1995). As shown in a variety of Plas- this could be explained by the inability of modium species, within the mosquito vector anti- asymptomatic gametocyte carriers, unlikely to body to the ‘pre-fertilization’ antigens may pre- harbour high asexual parasitaemias, to promote the vent fertilization by any of four mechanisms: (1) responses. the agglutination of macro/microgametes limiting The concept that anti-sexual stage immunity their mobility; (2) antibody coating of macro/ may regulate infection of the moquito vector by microgamentes inhibiting cell-cell recognition; (3) gametocyte-infected malarial blood has gained opsonization in the bloodmeal or (4) complement considerable support and must be considered for dependent/independent lysis (Gwadz 1976, Carter the development of malaria trasmission blocking & Chen 1976, Carter et al. 1979, 1985, 1990, vaccines (Kaslow et al. 1992). Kaushal et al. 1983a,b, Rener et al. 1983, Harte et c) Antibodies against sporozoites - There is evi- al. 1985a, Vermeulen et al. 1985b, Grotendorst et dence that naturally acquired or experimentally al. 1986, Grotendorst & Carter 1987, Quakyi et al. elicited anti-sporozoite antibodies ingested by 1987, Peiris et al. 1988, Premawansa et al. 1990). mosquitoes may affect the dynamics of the Cellular responses are also involved in TBI and sporogonic development in the vector. Several may have some influence on parasite infectivity studies with P. falciparum-infected Anopheles spe- (Harte et al. 1985b, Mendis et al. 1990b, Riley & cies (Vaughan et al. 1988, Beier et al. 1989, Greenwood 1990, Goonewardene et al. 1990). Hollingdale & Rosario 1989) showed that (1) in- Immunity to ‘post-fertilization’ antigens such gested human CSP antibodies were detected in the as Pfs25, Pbs21, Pgs25 and Prs25 also plays an blood meal of field collected mosquitoes up to 36 important role on transmission of the disease by hr after feeding, (2) antibodies crossing the mid- suppressing parasite infectivity at different stages gut into hemocoel persist from 4 to 36 hr post-in- of its development in the mosquito as demonstrated fection in hemolymph, (3) ingested CSP antibod- by many workers in different Plasmodium species ies on day 5 after infection bound to developing (Grotendorst et al. 1984, Vermeulen et al. 1985a, oocysts, (4) enhancement of the sporozoite pro- Sinden et al. 1987, Winger et al. 1988, Fries et al. duction, (5) ingestion of CSP antibodies on day 10 1989, Carter & Kaushal 1984, Carter et al. 1989a,b, after feeding had no effect on oocyst maturation Kaslow et al. 1991, 1992, 1994b, Foo et al. 1991, or sporozoite production, (6) contact between CSP Sieber et al. 1991, Tirawanchai et al. 1991, Duffy antibodies and sporozoites in the hemocoel did not et al. 1993, Paton et al. 1993, Ranawaka et al. 1993, block sporozoite invasion of salivary glands, (7) 1994). The mechanisms of blockade could be the exposure to CSP antibody increased sporozoite same four described above and/or the antibody may infectivity and (8) human IgG antibodies were act by damaging the parasite surface coat present on salivary gland sporozoites from field- (Ponnudurai et al. 1987). collected mosquitoes. It has been recently demon- Non-specific responses to the asexual stages are strated that antibodies to P. gallinaceum CSP pre- believed to modulate parasite trasmission vent sporozoites from invading salivary glands of (Naotunne et al. 1991, Kwiatkowski 1992). Nu- Ae. aegypti (Warburg et al. 1992). Ponnudurai et merous non-specific factors may correlate with al. (1989) did not find any influence of anti-sporo- 524 Biology of Malarial Parasites in Mosquito • AB Simonetti zoite antibodies on the number of salivary gland Coluzzi 1992, Collins 1994, Curtis 1994). Intro- sporozoites but concluded that a second blood duction and expression of genes coding for anti- meal, with or without antibody, simply functions bodies against target antigens present on the as a nutritional stimulus for faster oocyst matura- ookinete surface into the mosquito embryos is one tion. However, when transmission blocking anti- of the possibilities to examine the potential of this bodies anti-Pbs21 (a surface antigen present on the technology (Crampton et al. 1993). surface of P. berghei zygote/ookinete) were added f) Anti-malarial drugs - Sub-therapeutic doses of to second bloodfeeds at different stages of parasite antimalarial drugs have been reported to enhance development in the mosquito, a significant reduc- infectivity of Plasmodium species to their vectors tion in oocyst intensity but no detectable change (Shute & Maryon 1954). Additionally, numerous in prevalence occurred. Furthermore, at all times compounds including chloroquine (Wilkinson et anti-Pbs21 reduced sporozoite number in the tho- al. 1976), sulphamethoxazole-trimethroprim rax but highest gland intensities were obtained (Wilkinson et al. 1973), pyrimethamine (Shute & when the second bloodfeed was given on day 4 Maryon 1951), Fansidar (Carter & Graves 1988) (Ranawaka et al. 1993). These results were inter- and Berenil (Ono et al. 1993) have been suggested preted as two opposing roles of second bloodfeeds to induce gametocyte formation but no influence containing trasmission blocking antibody: (1) in- of chloroquine (Jeffery et al. 1956, Smalley 1977, hibition of parasite development and (2) the sup- Chutmongkonkul et al. 1992, Hogh et al. 1994) ply of nutrients which permit more sporozoites to and Fansidar (Hogh et al. 1994) on gametocyte be produced by each oocyst. Despite some contro- infectivity was observed by some investigators. It versy these results potentially have significant im- was demonstrated that pyrimethamine- and plications for natural malaria transmission and for halofantrine-treated gametocytes of P. falciparum a possible vaccine development. are more infective to An. stephensi mosquitoes than d) Anti-mosquito antibodies - In addition to anti- untreated controls (Chutmongkonkul et al. 1992). parasite antibodies, it has been tested experimen- Other studies examined the effects of some tally the effect on malaria trasmission of antibod- schizontocidal agents on the sporogonic cycle of ies raised against parts of the mosquito which could P. falciparum and P. berghei in anopheline mos- be included in a malaria vaccine. Ramasamy and quitoes (Coleman et al. 1988, do Rosario et al. Ramasamy (1990), studying the P. berghei/An. 1988). It was found that chloroquine, when fed farauti model, found that mosquitoes feeding on during late sporogony (10-12 days post-infection), mice immunised with midgut antigens exhibited a may increase the vectorial capacity of some mos- reduction in mosquito infection rates. Similar re- quito species. The effects of chloroquine on the sults were reported by Billingsley et al. (1990) us- infectivity of chloroquine-sensitive and -resistant ing monoclonal antibodies produced against mos- populations of P. yoelii nigeriensis to An. stephensi quito midgut tissue in P. berghei/An. stephensi mosquitoes were studied by Ichimori et al. (1990). system. The results showed an enhancement of infectivity e) Genetic manipulation of the vector - Experiments in sensitive strains but no effect was detected in with refractory lines of An. gambiae (Collins et al. 1986) and studies on the effects of broad antimi- resistant clones and sublines. Chloroquine use and crobial and antiparasitic components, e.g. the subsequent development of resistance over the magainins and cecropins (Gwadz et al. 1989), past years is associated with an increasing human showed that it may be feasible to induce effective malaria infectiousness (Lines et al. 1991) which disruption in the normal development of Plasmo- may be indirect effects of parasitaemia on the host. dium species in the vector by the introduction and The sporontocidal activity of chloroquine, expression of appropriate genes into the mosquito halofantrine and pyrimethamine was evaluated by genome. Two types of useful target genes can be administration to An. stephensi mosquitoes, either used in transgenic mosquitoes. First, those that ren- in the first bloodmeal containing P. falciparum der populations vulnerable to subsequent control gametocytes from in vitro cultures, or in the sec- measures, such as insecticide susceptibility or tem- ond, parasite-free bloodmeal, given four days af- perature sensitivity, and second, those that inter- ter infection. A sporontocidal effect was observed rupt disease transmission by replacing vector with only when pyrimethamine was administred with non-vector forms (Crampton et al. 1990, Kidwell the infective bloodmeal (Chutmongkonkul et al. & Ribeiro 1992, Crampton 1994). Although many 1992). It has been demonstrated recently an inhibi- technical, and perhaps ethical, problems associated tory action of the anti-malarial Atovaquone with the wild-release of transgenic insects have yet (566C80) against ookinete, oocysts and sporozoi- to be overcome, the potential of this technology tes of Plasmodium berghei in An. stephensi (Fowler has received greater attention recently (Brey 1991, et al.1994, 1995). Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 525
ACKNOWLEDGMENTS J Med Entomol 26: 547-553. Beier JC, Perkins PV, Koros JK, Onyango FK, Gargan Amauri Braga Simonetti was supported by a schol- TP, Wirtz RA, Koech DK, Roberts, CR 1990. Ma- arship from CNPq (Brazil) during his PhD in the Infec- laria sporozoite detection by dissection and ELISA tion and Immunity Section, Department of Biology at to assess infectivity of afrotropical Anopheles Imperial College of Science, Technology and Medicine (Diptera: Culicidae). J Med Entomol 27: 377-384. (London, U.K.). Beier JC, Vaughan JA, Madani A, Noden, BH 1992a. I would like to acknowlegde Professor Robert E Plasmodium falciparum: release of circumsporozoite Sinden for his guidance and helpfull advices which made protein by sporozoites in the mosquito vector. Exp possible this review. Parasitol 75: 248-256. REFERENCES Beier MS, Davis JR, Pumpuni CB, Noden BH, Beier JC 1992b. Ingestion of Plasmodium falciparum sporo- Aikawa M 1971. Plasmodium: The fine structure of zoites during transmission by anopheline mosqui- malarial parasites. Exper Parasitol 30: 284-320. toes. Am J Trop Med Hyg 47: 195-200. Aikawa M Atkinson CT, Beaudoin LM, Sedegah M, Berner R, Rudin W, Hecker H 1983. Peritrophic mem- Charoenvit Y, Beaudoin R 1990. Localization of CS branes and protease activity in the midgut of the and Non-CS Antigens in the Sporogonic Stages of malaria mosquito, Anopheles stephensi (Liston) Plasmodium yoelii. Bull WHO 68: 165-171. (Insecta: Diptera) under normal and experimental Alano P 1991. Plasmodium sexual stage antigens. conditions. J Ultrastruct Res 83: 195-204. Parasitol Today 7: 199-203. Billingsley PF 1990. The midgut ultrastructure of Alano P, Carter R 1990. Sexual differentiation in ma- haematophagous insects. Ann Rev Entomol 35: 219- laria parasites. Ann Rev Microbiol 44: 429-449. 248. Bafort JM 1971. The biology of rodent malaria with Billingsley PF, Hecker H 1991. Blood digestion in the particular reference to Plasmodium vinkei vinkei mosquito, Anopheles stephensi Liston (Diptera: Rhodain 1952. Ann Soc belge de Med Trop 51: 1- Culicidae): activity and distribution of trpsin, ami- 204. nopeptidase, and alpha-glucosidase in the midgut. Ball G H, Chao J 1957. Development in vitro of iso- J Med Entomol 28: 865-871. lated oocysts of Plasmodium relictum. J Parasitol Billingsley PF, Rudin W 1992. The role of the mos- 43: 409-412. quito peritrophic membrane in bloodmeal digestion Ball GH, Chao J 1960. In vitro development of the mos- and infectivity of Plasmodium species. J Parasitol quito phase of Plasmodium relictum. Exp Parasitol 78: 430-440. 9: 47-55. Billingsley PF, Winger L, Simonetti AB, Sinden REE Ball GH, Chao J 1961. Infectivity to canaries of sporo- 1990. Monoclonal antibdies produced against mos- zoites of Plasmodium relictum developing in vitro. quito midgut tissue. VII International Congress of J Parasitol 47: 787-790. Parasitology (COPA), Paris. Ball GH, Chao J 1976. Use of amino acids by Plasmo- Boulanger N, Matile H, Betschart B 1988. Formation dium relictum oocysts in vitro. Exp Parasitol 39: of the circumsporozoite protein of Plasmodium 115-118. falciparum in Anopheles stephensi. Acta Trop 45: Barber MA 1936. Degeneration of the sporozoites of 55-65. the malaria parasite in anopheline mosquitoes in Boyd MF, Kitchen SF 1937. On the infectiousness of nature and its relation to the transmission of malaria. patients infected with Plasmodium vivax and Plas- Am J Hyg 24: 45-56. modium falciparum. Am J Trop Med Hyg 17: 253- Beaudoin RL, Strome CPA, Tubergen TA 1974. Plas- 262. modium berghei berghei: ectopic development of the Brey PT 1991. The Taming of the Anopheles - Current ANKA strain in Anopheles stephensi. Exp Parasitol trends in malaria vector research. Res Immunol 142: 36: 189-201. 712-722. Beier JC 1993. Malaria sporozoites: survival, transmis- Briegel H, Lea AO 1975. Relationship between protein sion and disease control. Parasitol Today 9: 210- and proteolytic activity in the midgut of mosquitoes. 215. J Ins Physiol 21: 1597-1604. Beier JC, Davis JR, Vaughan JA, Noden BH, Beier MS Bruce MC, Alano P, Duthie S, Carter R 1990. Commit- 1991a. Quantitation of Plasmodium falciparum ment of the malaria parasite Plasmodium falciparum sporozoites transmitted in vitro by experimentally to sexual and asexual development. Parasitology infected Anopheles gambiae and Anopheles 100: 191-200. stephensi. Am J Trop Med Hyg 44: 564-570. Canning EU, Sinden RE 1973. The organisation of the Beier JC, Onyango FK, Ramadhan M, Koros JK, Asiago ookinete and observations on nuclear division in C.M, Wirtz RA, Koech DK, Roberts CR 1991b. oocysts of Plasmodium berghei. Parasitology 67: Quantitation of malaria sporozoites in the salivary 29-40. glands of wild afrotropical Anopheles. Med Vet Carter R, Bushell G, Saul A, Graves PM, Kidson C 1985. Entomol 5: 63-70. Two apparently nonrepeated epitopes on gametes Beier JC, Oster CN, Koros JK, Onyango FK, Githeko of Plasmodium falciparum are targets of transmis- AK, Rowton E, Koech DK, Roberts CR 1989. Ef- sion-blocking antibodies. Infect Immun 50: 102-106. fect of human circumsporozoite antibodies in Plas- Carter R, Chen DH 1976. Malaria transmission blocked modium -infected Anopheles (Diptera: Culicidae). 526 Biology of Malarial Parasites in Mosquito • AB Simonetti
by immunisation with gamets of the malaria para- sporogonic development in three species of Anoph- site. Nature 263: 57-60. eles mosquitoes. J Parasitol 82: 11-16. Carter R, Graves PM 1988. Gametocytes. In: Malaria. Chutmongkonkul M, Maier WA, Seitz HM 1992. Plas- Principles and practice of malariology, edited by modium falciparum: effect of chloroquine, Wernsdorfer, W.H. and McGregor, Sir I. Edinburgh: halofantrine and pyrimethamine on the infectivity Chuchill Livingstone, p. 253-306. of gametocytes for An. stephensi mosquitoes. Ann Carter R, Graves PM, Creasey A, Byrne K, Read D, Trop Med Parasitol 86: 103-110. Alano P, Fenton B 1989a. Plasmodium falciparum: Coleman RE, Vaughan JA, Hayes DO, Hollingdale MR, an abundant stage-specific protein expressed during Do Rosario VE 1988. Effect of mefloquine and early gametocyte development. Exp Parasitol 69: artisinin on the sporogonic cycle of Plasmodium 140-149. berghei ANKA in Anopheles stephensi mosquitoes. Carter R, Graves PM, Keister DB, Quakyi IA 1990. Acta Leid 57: 61-74. Properties of epitopes of Pfs 48/45, a target of trans- Collins FH 1994. Prospects for malaria control through mission blocking monoclonal antibodies, on gametes genetic manipulation of its vectors. Parasitol To- of different isolates of Plasmodium falciparum. day 10: 370-371. Paras Immunol 12: 587-603. Collins FH, Sakai RK, Vernick KD, Paskewitz S, Seeley Carter R, Graves P M, Quakyi I, Good MF 1989b. Re- DC, Miller LH, Collins WE, Campbell CC, Gwadz stricted or absent immune responses in human popu- RW 1986. Genetic selection of a Plasmodium re- lations to Plasmodium falciparum gamete antigens fractory strain of the malaria vector Anopheles that are targets of malaria transmission-blocking gambiae. Science 234: 607-610. antibodies. J Exp Med 169: 135-147. Coluzzi M 1992. Malaria vector analysis and control. Carter R, Gwadz RW, Mcauliffe FM 1979. Plasmo- Parasitol Today 8: 113-118. dium gallinaceum: transmission blocking immunity Cornelissen AWCA 1988. Sex determination and sex in chickens. I. Comparative immunogenicity of ga- differentiation in malaria parasites. Biol Rev 63: 379- metocyte and gamete-containing preparations. Exp 394. Parasitol 47: 185-193. Crampton JM 1994. Molecular studies of insect vectors Carter R, Kaushal DC 1984. Characterization of anti- of malaria. Adv Parasitol 34: 1-31. gens on mosquito midgut stages of Plasmodium Crampton JM, Galler R, Sinden RE, Crisanti A 1993. gallinaceum. III. changes in zygote surface proteins La lutte génétique contre les moustiques. La Recher- during transformation to mature ookinete. Mol che 259: 1218-1219. Biochem Parasitol 13: 235-241. Crampton JM, Morris A, Lycett G, Warren A, Eggleston Carter R, Kumar N, Quakyi I, Good M, Mendis K, P 1990. Transgenic mosquitoes: a future vector con- Graves P, Miller LH 1988. Immunity to sexual trol strategy? Parasitol Today 6: 31-36. stages of malaria parasites. Progr Allergy 41: 193- Curtis CF 1994. The case for malaria cntrol by genetic 214. manipulation of its vectors. Parasitol Today 10: 371- Carter R, Nijhout MM 1977. Control of gamete forma- 374. tion (exflagellation) in malaria parasites. Science Daher VR, Krettli AU 1980. Infectivity of Plasmo- 195: 407-409. dium gallinaceum sporozoites from oocysts. J Cattani JA 1989. Malaria vaccines: results of human tri- Protozool 27: 440-442. als and directions of current research. Exp Med 68: Davies EE 1974. Ultrastructural studies on the early 242-247. ookinete stage of Plasmodium berghei nigeriensis Cerami C, Frevert V, Sinnis P, Takacs B, Clavijo P, and its transformation into an oocyst. Ann Trop Med Santos MJ, Nussenzweig V 1992b. The basolateral Parasitol 68: 283-290. domain of the hepatocyte plasma membrane bears Dearsly AL, Sinden RE, Self IA 1990. Sexual develop- receptors for the CSP of Plasmodium falciparum ment in malarial parasites - Gametocyte production, sporozoites. Cell 70: 1021-1033. fertility and infectivity to the mosquito vector. Para- Cerami C, Kwakyeberko F, Nusswenzweig V 1992a. sitology 100: 359-368. Binding of malarial circumsporozoite protein to De Zoysa APK, Herath PRJ, Abhywrana A, Padmalal sulfatides
microscopic observations on malarial oocysts (Plas- motile stages of malaria parasites VI. The ookinete modium relictum). J Protozool 7: 18-26. of Plasmodium berghei yoelii and its transforma- Eyles DE 1952. Studies on Plasmodium gallinaceum II. tion into an early oocyst. Trans R Soc Trop Med Factors in the blood of the vertebrate host influenc- Hyg 63: 187-194. ing mosquito infection. Am J Trop Med Hyg 5: 276- Gass RF 1977. Influences of blood digestion on the de- 290. velopment of Plasmodium gallinaceum (Brumpt) in Feldmann AM, Billingsley PF, Savelkoul A 1990. Blood the midgut of Aedes aegypti (L.). Acta Trop 34: meal digestion by strains of Anopheles stephensi 127-140. Liston (Diptera: Culicidae) of differing susceptibil- Gass RF, Yeates RA 1979. In vitro damage to cultured ity to Plasmodium falciparum. Parasitology 101: ookinetes of Plasmodium gallinaceum by digestive 193-200. proteinases from susceptible Aedes aegypti. Acta Feldmann AM, Ponnudurai T 1989. Selection of Anoph- Trop 36: 243-252. eles stephensi for refractoriness and susceptibility Golenda CF, Starkweather WH, Wirtz RA 1990. The to Plasmodium falciparum. Med Vet Entomol 3: distribution of circumsporozoite protein (Cs) in 41-52. Anopheles stephensi mosquitoes infected with Plas- Foo A, Carter R, Lambros C, Graves P, Quakyi I, Targett modium falciparum malaria. J Histochem Cytochem GAT, Ponnudurai T, Lewis GE 1991. Conserved and 38: 475-481. variant epitopes of target antigens of transmission- Good MF 1991a. Towards the development of the ideal blocking antibodies among isolates of Plasmodium malaria vaccine - A decade of progress in a difficult falciparum from Malaysia. Am J Trop Med Hyg field. Med J Austr 154: 284-289. 44: 623-631. Good MF 1991b. The implications for malaria vaccine Fowler RE, Billingsley PF, Pudney M, Sinden RE 1994. programs if memory T-cells from non-exposed hu- Inhibitoy action of the anti-malarial Atovaquone mans can respond to malaria antigens. Curr Op (566C80) against Plasmodium berghei ANKA in the Immunol 3: 496-502. mosquito Anopheles stephensi. Parasitology 108: Good MF 1992. A malaria vaccine strategy based on 383-388. the induction of cellular immunity. Immunol Today Fowler RE, Sinden RE, Pudney M 1995. Inhibitory 13: 126-129. activity of the anti-malarial Atovaquone (566C80) Goonewardene R, Carter R, Gamage CP, Delgiudice G, against ookinete, oocysts and sporozoites of Plas- David PH, Howie S, Mendis KN 1990. Human T modium berghei. J Parasitology 8: 452-458. cell proliferative responses to Plasmodium vivax Freier J E, Friedman S 1987. Effect of Plasmodium antigens: evidence of immunosuppression follow- gallinaceum infection on the mortality and body ing prolonged exposure to endemic malaria. Europ weight of Aedes aegypti (Diptera : Culicidae). J Med J Immunol 20: 1387-1391. Entomol 24: 6-10. Gordon DM, Davis DR, Lee M, Lambros C, Harrison Freyvogel TA 1966. Shape, movement in situ and loco- BA, Samuel R, Campbell GH, Jeghathesan M, motion of plasmodial ookinetes. Acta Trop 23: 201- Selvarajan K, Lewis GE 1991. Significance of 221. circumsporozoite-specific antibody in the natural Fries HCW, Lamers MBAC, Smits MA, Ponnudurai T, transmission of Plasmodium falciparum, Plasmo- Meuwissen JHET 1989. Characterization of epitopes dium vivax, and Plasmodium malariae in an aborigi- on the 25 kiloDalton protein of the macrogametes/ nal (Orang-Asli) population of central peninsular zygotes of Plasmodium falciparum. Parasite Malaysia. Am J Trop Med Hyg 45: 49-56. Immunol 11: 31-45. Graf R, Briegel H 1982. Comparison between aminopep- Gamage-Mendis AC, Rajakaruna J, Carter R, Mendis tidase and trypsin activity in blood-fed females of KN 1992. Transmission blocking immunity to hu- Aedes aegypti. Rev Suis Zool 89: 845-850. man Plasmodium vivax malaria in an endemic popu- Graf R, Raikhel AS, Brown MR, Lea AO, Briegel H lation in Kataragama, Sri-Lanka. Parasite Immunol 1986. Mosquito trypsin: immunocytochemical lo- 14: 385-396. calization in the midgut of blood-fed Aedes aegypti Gamage-Mendis AC, Rajakaruna J, Weerasinghe S, (L.). Cell Tis Res 245: 19-27. Mendis C, Carter R, Mendis KN 1993. Infectivity Grau GE, Taylor TE, Molyneux ME, Wirima JJ, Vassali P, Hommel M, Lambert PH 1989. Tumor necrosis of Plasmodium vivax and Plasmodium falciparum factor and disease severity in children with to Anopheles tessellatus; relationship between oo- falciparum malaria. N Engl J Med 320: 1586-1591. cyst and sporozoite development. Trans R Soc Trop Graves PM, Carter R, Burkot TR, Quakyi IA, Kumar N Med Hyg 87: 3-6. 1988. Antibodies to Plasmodium falciparum gamete Garnham PCC 1966. Malaria parasites and other surface antigens in Papua New Guinea sera. Paras haemosporidia. Blackwell Scientific Publications, Immunol 10: 209-218. Oxford, 1114 pp. Graves PM, Doubrovsky A, Satabongkot J, Battistutta Garnham PCC, Bird RG, Baker JR 1962. Electron mi- D 1992. Human antibody responses to epitopes on croscopic studies of motile stages of malarial para- the Plasmodium falciparum gametocyte antigen sites III. The ookinetes of Haemamoeba and Plas- PFS48/45 and their relationship to infectivity of ga- modium. Trans R Soc Trop Med Hyg 56: 116-120. metocyte carriers. Am J Trop Med Hyg 46: 711- Garnhm PCC, Bird RG, Baker JR, Desser SS, El-Nahal 719. HMS 1969. Electron microscopic studies on the Grotendorst CA, Carter, R 1987. Complement effects 528 Biology of Malarial Parasites in Mosquito • AB Simonetti
on the infectivity of Plasmodium gallinaceum to 377-381. Aedes aegypti mosquitoes II. changes in sensitivity Iinselburg J 1983. Gametocyte formation by the prog- to complement-like factors during zygote develop- eny of single Plasmodium falciparum schizonts. J ment. J Parasitol 73: 980-984. Parasitol 69: 584-591. Grotendorst CA, Carter R, Rosenberg R, Koontz L 1986. James AA, Rossignol PA 1991. Mosquito salivary glands Complement effects on the infectivity of Plasmo- - Parasitological and molecular aspects. Parasitol dium gallinaceum to Aedes aegypti mosquitoes I. Today 7: 267-271. Resistance of zygotes to the alternative pathway of Jeffery GM, Eyles DE 1955. Infectivity to mosquitoes complement. J Immunol 136: 4270-4274. of Plasmodium falciparum as related to gametocyte Grotendorst CA, Kumar N, Carter R, Kaushal DC 1984. density and duration of infection. Am J Trop Med A surface protein expressed during transformation Hyg 4: 781-789. of zygotes of Plasmodium gallinaceum is a target of Jeffery GM, Young MD, Eyles DE 1956. The treatment transmission-blocking antibodies. Infec Immun 45: of Plasmodium falciparum infection with 775-777. chloroquine, with a note on infectivity to mosqui- Gwadz W 1976. Malaria: successful immunization toes of primaquine-and pyrimethamine-treated cases. against the sexual stages of Plasmodium Am J Hyg 64: 1-11. gallinaceum. Science 193: 1150-1151. Karunaweera ND, Grau GE, Gamage P, Carter R, Mendis Gwadz RW, Kaslow D, Lee J-Y, Maloy WL, Zasloff KN 1992. Dynamics of fever and serum levels of M, Miller LH 1989. Effects of magainins and tumor necrosis factor are closely associated during cercropins on the sporogonic development of ma- clinical paroxysms in Plasmodium vivax malaria. laria parasites in mosquitoes. Infec Immun 57: 2628- Proc Natl Acad Sci USA 89: 3200-3203. 2633. Kaslow DC, Bathurst IC, Barr PJ 1992. Malaria Hamilton AJ, Davies CS, Sinden RE 1988. Expression trasmission-blocking vaccines. Trends Biotechnol of the circumsporozoite proteins revealed in situ in 10: 388-391. the mosquito stages of Plasmodium berghei by the Kaslow DC, Bathurst IC, Lensen T, Ponnudurai T, Barr Lowicryl-immunogold technique. Parasitology 96: PJ, Keister DB 1994. Saccharomyces cerevisiae re- 273-280. combinant Pfs25 adsorbed to alum elecits antibod- Harte PG, Rogers N, Targett GAT 1985a. Vaccination ies that block transmission of Plasmodium with purified microgamete antigens prevents trans- falciparum. Infec Immun 62: 5576-5580. mission of rodent malaria. Nature 316: 258-259. Kaslow DC, Isaacs SN, Quakyi IA, Gwadz RW, Moss Harte PG, Rogers NC, Targett GAT 1985b. Monoclonal B, Keister DB 1991. Induction of Plasmodium anti-gamete antibodies prevent transmission of mu- falciparum transmission blocking antibodies by re- rine malaria. Paras Immunol 7: 607-615. combinant vaccinia virus. Science 252: 1310-1313. Hawking F, Wilson ME, Gammage K 1971. Evidence Kaslow DC, Nussenzweig V, Miller L 1994a. Meeting for the cyclic development and short-lived maturity on parasites and the invertebrate vector. Mem Inst in the gametocytes of Plasmodium falciparum. Oswaldo Cruz 89: 279-295. Trans R Soc Trop Med Hyg 65: 549-559. Kaslow DC, Quakyi IA, Syin C, Raum MG, Keister Hecker H 1977. Structure and function of midgut epi- DB, Coligan JE, McCutchan TF, Miller LH 1988. thelial cells in Culicidae mosquitoes (Insecta, A vaccine candidate from the sexual stage of human Diptera). Cell Tis Res 184: 321-341. malaria that contains EGF-like domains. Nature 333: Hollingdale MR, do Rosario V 1989. Malaria transmis- 74-76. sion-enhancing activity in mosquitoes by Kaushal DC, Carter R 1984. Caracterization of antigens mammalaian host anti-sporozoite antibodies. Exp on the mosquito midgut stages of Plasmodium Parasitol 68: 365-368. gallinaceum . II. Comparison of surface antigens of Hommel M 1991. Steps towards a malaria vaccine. Res male and female gametes and zygotes. Mol Biochem Immunol 142: 618-631. Parasitol 11: 145-156. Houk EJ, Hardy JL, Chiles RE 1986. Mesenteronal epi- Kaushal DC, Carter R, Howard RJ, Macauliffe FM thelial cellsurface charge of the mosquito, Culex 1983a. Characterization of antigens on mosquito tarsalis Coquillett. Binding of colloidal iron hydrox- midgut stages of Plasmodium gallinaceum I. Zygote ide, native ferritin and cationised ferritin. J surface antigens. Mol Biochem Parasitol 8: 53-69. Submicroscop Cytol 18: 385-396. Kaushal DC, Carter R, Rener J, Grotendorst CA, Miller Howells RE, Davies EE 1971. Nuclear division in the LH, Howard RJ 1983b. Monoclonal antibodies oocyst of Plasmodium berghei. Ann Trop Med Hyg against surface determinants on gametes of Plasmo- 65: 451-459. dium gallinaceum block transmission of malaria Huber M, Cabib E, Miller LH 1991. Malaria parasite prasites to mosquitoes. J Immunol 131: 2557-2562. chitinase and penetration of the mosquito peritrophic Kawamoto F, Alejo Blanco R, Fleck SL, Sinden RE membrane. Proc Natl Acad Sci USA 88: 2807- 1991. Plasmodium berghei - Ionic regulation and 2810. the induction of gametogenesis. Exp Parasitol 72: Ichimori K, Curtis CF, Targett GAT 1990. The effects 33-42. of chloroquine on the infectivity of chloroquine-sen- Kern P, Hemmer CJ, Van Damme J, Gruss HJ, Dietrich sitive and -resistant populations of Plasmodium M 1989. Elevated tumor necrosis factor-alfa and yoelii nigeriensis to mosquitoes. Parasitology 100: interleukin-6 serum levels as markers for compli- Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 529
cated Plasmodium falciparum malaria. Am J Med 923. 87: 139-143. Maier WA, Becker-Feldman H, Seitz HM 1987. Pathol- Kidwell MG, Ribeiro JMC 1992. Can transposable ele- ogy of malaria infected mosquitoes. Parasitol To- ments be used to drive disease refractoriness genes day 3: 216-218. into vector populations? Parasitol Today 8: 325- Martin SK, Miller LH, Nijhout MM, Carter R 1978. 329. Plasmodium gallinaceum: induction of male game- King C 1988. Cell motility of sporozoan protozoa. tocyte exflagellation by phosphdiesterase inhibitors. Parasitol Today 4: 315-319. Exp Parasitol 44: 239-242. Kitthawee S, Edman JD, Sattabongkot J 1990. Evalua- Mehlhorn H, Peters W, Haberkorn A 1980. The forma- tion of survival potential and malaria susceptibility tion of ookinetes and oocysts in Plasmodium among different size classes of laboratory-reared gallinaceum (Haemosporidia) and considerations on Anopheles dirus. Am J Trop Med Hyg 43: 328- phylogenetic relationships between Haemosporidia, 332. Piroplasmida and other Coccidia. Protistologica 16: Kumar N, Carter R 1984. Biosynthesis of the target an- 135-154. tigens of antibodies blocking transmission of Plas- Meis JFGM, Croes H, Mons B, Vanbelkum A, modium falciparum. Mol Biochem Parasitol 13: Ponnudurai T 1992a. Localization of circumsporo- 333-342. zoite protein in the sporogonic stages of Plasmo- Kumar N, Carter R 1985. Biosynthesis of two stage- dium vivax. Parasitol Res 78: 165-167. specific membrane proteins during transformation Meis JFGM, Ponnudurai T 1987. Ultrastructural stud- of Plasmodium gallinaceum zygotes into ookinetes. ies on the interaction of Plasmodium falciparum Mol Biochem Parasitol 14: 127-139. ookinetes with the midgut epithelium of Anopheles Kwiatowski D 1992. Malaria: becoming more specific stephensi mosquitoes. Parasitol Res 73: 500-506. about non-specific immunity. Curr Op Immunol 4: Meis JFGM, Pool G, Vangemert GJ, Lensen AHW, 425-431. Ponnudurai T, Meuwissen JHET 1989. Plasmodium Kwiatowski D, Hill AVS, Sambou I, Twumasi P, falciparum ookinetes migrate intercellularly through Castracane J, Manogue KR, Cerami A, Brewster DR, Anopheles stephensi midgut epithelium. Parasitol Greenwood BM 1990. TNF concentrations in fatal Res 76: 13-19. cerebral, non-fatal cerebral, and uncomplicated Plas- Meis JFGM, Verhave JP 1988. Exoerythrocytic devel- modium falciparum malaria. Lancet ii: 1201-1204. opment of malarial parasites. Adv Parasitol 27: 1- Lensen AHW, van Gemert GJA, Bolmer MG, Meis 66. JFGM, Kaslow D, Meuwissen JHE Th, Ponnudurai Meis JFGM, Wismans PGP, Jap PHK, Lensen AHW, T 1993. Transmission blocking antibody of the Plas- Ponnudurai T 1992b. A scanning electron micro- modium falciparum zygote/ookinete surface protein scopic study of the sporogonic development of Plas- Pfs25 also influences sporozoite development. Para- modium falciparum in Anopheles stephensi. Acta site Immunol 14: 471-479. Trop 50: 227-236. Li X, Sina B, Rossignol PA 1992. Probing behaviour Mendis KN, Carter R 1991. Transmission blocking im- and sporozoite delivery by Anopheles stephensi in- munity may provide clues that antimalarial immu- fected with Plasmodium berghei. Med Vet Entomol nity is largely T-independent. Res Immunol 142: 6: 57-61. 687-690. Lines J.D, Wilkes TJ, Lyimo EO 1991. Human malaria Mendis KN, David PH, Carter R 1990b. Human im- infectiousness measured by age-specific sporozoite mune responses against sexual stages of malaria rates in An gambiae in Tanzania. Parasitology 102: parasites: considerations for malaria vaccines. In- 167-177. tern J Parasitol 20: 497-502. Lombardi S, Esposito F, Zavala F, Lamizana L, Rossi Mendis, KN, Ezoysa APK, Abhayawardena TA, Carter R, Herath PRJ, Mendis G 1990a. Characteristics of P, Sabatinelli G, Nussenzweig R, Coluzzi M 1987. malaria transmission in Kataragama, Sri-Lanka - A Detection and anatomical localization of Plasmo- focus for immuno-epidemiological studies. Am J dium falciparum circumsporozoite protein and Trop Med Hyg 42: 298-308. sporozoites in the afrotropical malaria vector Anoph- Mendis KN, Munesinghe YD, DeSilva YNY, Keragalla eles gambiae S.L. Am J Trop Med Hyg 37: 491- I, Carter R 1987. Malaria transmission-blocking 494. immunity induced by natural infections of Plasmo- Lyimo EO, Koella JC 1992. Relatiosnship between body dium vivax in humans. Infec Immun 55: 369-372. size of adult Anopheles gambiae s.l. and infection Mendis KN, Naotunne TD, Karunaweera ND, with the malaria parasite Plasmodium falciparum. Delgiudice G, Grau GE, Carter R 1990c. Anti-para- Parasitology 104: 233-237. site effects of cytokines in malaria. Immunol Lett Mack SR, Samuels S, Vanderberg JP 1979. Hemolymph 25: 217-220. of Anopheles stephensi from uninfected and Plas- Mitchell GH 1989. An update on candidate malaria vac- modium berghei-infected mosquitoes. 2. Free amino cines. Parasitology 98: S29-S47. acids. J Parasitol 65: 130-136. Mons B 1985. Induction of sexual differentiation in Mack SR, Vanderberg JP 1978. Hemolymph of Anoph- malaria. Parasitol Today 1: 87-89. eles stephensi from noninfected and Plasmodium Mons B 1986. Intraerythrocytic differentiation of Plas- berghei-infected mosquitoes. 1. Collection procedure modium berghei. Acta Leid 54: 1-83. and physical characteristics. J Parasitol 64: 918- 530 Biology of Malarial Parasites in Mosquito • AB Simonetti
Mons B, Janse CJ, Boorsma EG 1985. Synchronized CP, Carter R, David PH, Mendis KN 1988. Mono- erythrocytic schizogony and gametocytogenesis of clonal and polyclonal antibodies both block and en- Plasmodium berghei in vivo and in vitro. Parasi- hance transmission of human Plasmodium vivax ma- tology 91: 423-430. laria. Am J Trop Med Hyg 39: 26-32. Muirhead-Thomson RC 1957. The malarial infectivity Perrone JB, DeMaio J, Spielman A 1986. Regions of of an African village population to mosquitoes mosquito salivary glands distinguished by surface (Anopheles gambiae). A random xenodiagnostic sur- lectin-binding characteristics. Insect Biochem 16: vey. Am J Trop Med Hyg 6: 971-979. 313-318. Nagasawa H, Aikawa M, Procell PM, Campbell GH, Perrone JB, Spielman A 1988. Time and site of assem- Collins WE, Campbell CC 1988. Plasmodium bly of the peritrophic membrane of the mosquito malariae: distribution of circumsporozoite protein Aedes aegypti. Cell Tiss Res 252: 473-478. in the oocyst and salivary gland sporozoite. Exp Phillips RS 1992. Vaccination against malaria. Parasitol 66: 27-34. Immunobiology 184: 240-262. Nagasawa H, Procell PM, Atkinson CT, Campbell GH, Ponnudurai T, Billingsley PF, Rudin W 1988. Differen- Collins WE, Aikawa M 1987. Localization of tial infectivity of Plasmodium for mosquitoes. circumsporozoite protein of Plasmodium ovale in Parasitol Today 4: 319-321. midgut oocysts. Infec Immun 55: 2928-2932. Ponnudurai T, Lensen AHW, Van Gemert, GJA, Bensink Naik P, Voller A 1984. Serum C-reactive protein levels MPE, Bolmer M, Meuwissen JHET 1989. Infectiv- and falciparum malaria. Trans R Soc Trop Med Hyg ity of cultured Plasmodium falciparum gametocytes 78: 812-813. to mosquitoes. Parasitology 98: 165-173. Naotunne TD, Karunaweera ND, Delgiudice G, Ponnudurai T, Lensen AHW, Van Gemert GJA, Bolmer Kularatne MU, Grau GE, Carter R, Mendis KN MG, Meuwissen JHET 1991. Feeding behaviour and 1991. Cytokines kill malaria parasites during infec- sporozoite ejection by infected Anopheles stephensi. tion crisis - Extracellular complementary factors are Trans R Soc Trop Med Hyg 85: 175-180. essential. J Exp Med 173: 523-529. Posthuma G, Meis FGM, Verhave JP, Hollingdale MR, Naotunne TD, Rathnayake KDL, Jayasinghe A, Carter Ponnudurai T, Meuwissen JHET 1988. Localiza- R, Mendis KN 1990. Plasmodium cynomolgi - Se- tion of circumsporozoite protein of the malaria para- rum-mediated blocking and enhancement of infec- site Plasmodium falciparum during sporogony in tivity to mosquitoes during infections in the natural Anopheles stephensi midguts using immunoelectron- host, Macaca sinica. Exp Parasitol 71: 305-313. microscopy of ultrathin cryosections. Eur J Cell Biol Nijhout MM 1979. Plasmodium gallinaceum: 46: 18-24. exflagellation stimulated by a mosquito factor. Exp Posthuma G, Meis JFGM, Verhave JP, Gigengak S, Parasitol 48: 75-80. Hollingdale MR, Ponnudurai T, Genze HJ 1989. Nijhout MM, Carter R 1978. Gamete development in Immunogold determination of Plasmodium malarial parasites: bicarbonate-dependent stimula- falciparum circumsporozoite protein in Anopheles tion by pH in vitro. Parasitology 76: 39-53. stephensi salivary gland cells. Eur J Cell Biol 49: Nussenzweig RS 1990. Recombinant proteins and syn- 66-72. thetic peptides as malaria vaccine candidates. Can Premawansa S, Gamage-Mendis A, Perera L, Begarnie J Microbiol 36: 817-820. S, Mendis K, Carter R 1994. Plasmodium falciparum Nussenzweig V, Nussenzweig RS 1989. Rationale for malaria trasmission-blocking immunity under con- the development of an engineered sporozoite ma- ditions of low endemicity as in Sri Lanka. Parasite laria vaccine. Adv Immunol 45: 283-334. Immunol 16: 35-42. Ono T, Onhnishe Y, Nagamune K, Kano M 1993. Premawansa S, Peiris JSM, Perera KLRL, Ariyaratne Gametocytogenesis induction by Berenil in cultured G, Carter R, Mendis KN 1990. Target antigens of Plsmodium falciparum. Exp Parasitol 77: 74-78. transmission blocking immunity of Plasmodium Pancake SJ, Holt GD, Mellouk S, Hoffman SL 1992. vivax malaria - Characterization and polymorphism Malaria sporozoites and circumsporozoite proteins in natural parasite isolates. J Immunol 144: 4376- bind specifically to sulfated glycoconjugates. J Cell 4383. Biol 117: 1351-1357. Pringle G 1965. A count of the sporozoites in an oocyst Paskewitz SM, Brown MR, Collins FH, Lea AO 1989. of Plasmodium falciparum. Trans R Soc Trop Med Ultrastructural localization of phenoloxidase in the Hyg 59: 289-290. midgut of refractory Anopheles gambiae and asso- Pringle G 1966. A quantitative study of naturally ac- ciation of the enzyme with encapsulated Plasmodium quired malaria infections in Anopheles gambiae and cynomolgi. J Parasitol 75: 594-600. Anopheles funestus in a highly malarious area of east Paton MG, Barker GC, Matsuoka H, Ramesar J, Janse Africa. Trans R Soc Trop Med Hyg 60: 626-632. CJ, Waters AP, Sinden RE 1993. Structure and ex- Quakyi IA, Carter R, Rener J, Kumar N, Good MF, pression of a post-transcriptionally regulated malaria Miller LH 1987. The 230-kDa gamete surface pro- gene enconding a surface protein from the sexual tein of Plasmodium falciparum is also a target for stages of Plasmodium berghei. Mol Biochem transmission-blocking antibodies. J Immunol 139: Parasitol 59: 263-276. 4213-4217 Peiris JSM, Premawansa S, Ranawaka MBR, Udagama Ramasamy M S, Ramasamy R 1990. Effect of anti- PV, Munasonghe YD, Nanayakkara MV, Gamage mosquito antibodies on the infectivity of the rodent Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 531
malaria parasite Plasmodium berghei to Anopheles Proc Natl Acad Sci USA 89: 9176-9180. farauti. Med Vet Entomol 4: 161-166. Rogers WO, Rogers MD, Hedstrom RC, Hoffman SL Ranawaka G, Alejo Blanco R, Sinden RE 1993. The 1992a. Characterization of the gene encoding sporo- effect of transmission-blocking antibody ingested in zoite surface protein-2, a protective Plasmodium primary and secondary bloodfeeds, upon the devel- yoelii sporozoite antigen. Mol Biochem Parasitol 53: opment of Plasmodium berghei in the mosquito vec- 45-51. tor. Parasitology 107: 225-231. Rosenberg R 1985. Inability of Plasmodium knowlesi Ranawaka GRR, Fleck SL, Alejo Blanco AR, Sinden sporozoites to invade Anopheles freeborni salivary RE 1994. Characterization of the modes of action of glands. Am J Trop Med Hyg 34: 687-691. anti-Pbs21 malaria transmission-blocking immunity: Rosenberg R, Koontz LC 1984. Plasmodium ookinete to oocyst differentiation in vivo. Parasi- gallinaceum: density dependent limits on infectiv- tology 109: 403-411. ity to Aedes aegypti. Exp Parasitol 57: 234-238. Ranawaka MB, Munesinghe YD, De Silva DMR, Carter Rosenberg R, Koontz LC, Alston K, Friedman FK 1984. R, Mendis KN 1988. Boosting of transmission- Plasmodium gallinaceum: erythrocyte factor essen- blocking immunity during natural Plasmodium vivax tial for zygote infection of Aedes aegypti. Exp infections in humans depends upon frequent rein- Parasitol 57: 158-164. fection. Infec Immun 56: 1820-1824. Rosenberg R, Rungsiwongse J 1991. The number of Ree GH 1971. C-reactive protein in Gambian africans sporozoites produced by individual malaria oocysts. with special reference to P. falciparum malaria. Am J Trop Med Hyg 45: 574-577. Trans R. Soc Trop Med Hyg 65: 574-580. Rosenberg R, Wirtz RA, Scneider I, Burge R 1990. An Rener J, Graves PM, Carter R, Williams JL, Burkot T estimation of the number of malaria sporozoites 1983. Target antigens of transmission-blocking im- ejected by a feeding mosquito. Trans R Soc Trop munity on gametes of Plasmodium falciparum. J Med Hyg 84: 209-212. Exp Med 158: 971-976. Rossignol PA, Ribeiro JMC, Jungery M, Turell MJ, Ribeiro JMC 1987. Role of saliva in blood-feeding by Spielman A, Bailey CL 1985. Enhanced mosquito arthropods. Ann Rev Entomol 32: 463-478. blood-finding success on parasitaemic hosts: evi- Ribeiro JMC, Modi GB, Tesh RB 1989. Salivary apirase dence for vector-parasite mutualism. Proc Natl Acad activity of some old world phlebotomine sand flies. Sci USA 82: 7725-7727. Insect Biochem 19: 409-412. Rossignol PA, Ribeiro JMC, Spielman A 1984. Increased Ribeiro MC, Rossignol PA, Spielman A 1984. Role of intradermal probing time in sporozoite-infected mosquito saliva in blood vessel location. J Exp Biol mosquitoes. Am J Trop Med Hyg 33: 17-20. 108: 1-9. Rossignol PA, Ribeiro JMC, Spielman A 1986. Increased Ribeiro JMC, Rossignol PA, Spielman A 1985. Sali- biting rate and reduced fertility in sporozoite-infected vary gland apyrase activity determines probing time mosquitoes. Am J Trop Med Hyg 35: 277-279. in Anopheline mosquitoes. J Insect Physiol 31: 689- Roush RT 1993. Occurrence, genetics and management 692. of insecticide resistance. Parasitol Today 9: 174- Rickman LS, Jones TR, Long GW, Paparello S, 179. Schneider I, Paul CF, Beaudoin RL, Hoffman SL Rowland M, Boersma E 1988. Changes in the sponta- 1990. Plasmodium falciparum-infected Anopheles neous flight activity of the mosquito Anopheles stephensi inconsistently transmit malaria to humans. stephensi by parasitization with the rodent malaria Am J Trop Med Hyg 43: 441-445. Plasmodium yoelii. Parasitology 97: 221-227. Riley E, Greenwood B 1990. Measuring cellular immune Rudin W, Billingsley PF, Saladin S 1991. The fate of responses to malaria antigens in endemic popula- Plasmodium gallinaceum in Anopheles stephensi tions - Epidemiological, parasitological and physi- Liston and possible barriers to transmission. Ann ological factors which influence in vitro assays. Soc Belg Méd Trop 71: 167-177. Immunol Lett 25: 221-229. Rudin W, Hecker H 1989. Lectin-binding sites in the Robert V, Verhave JP, Ponnudurai T, Louwe L, midgut of the mosquitoes Anopheles stephensi Liston Scholtens P, Carnevale P 1988. Study of the distri- and Aedes aegypti L. (Diptera: Culicidae0. Parasitol bution of circumsporozoite antigen in Anopheles Res 75: 268-279. gambiae infected with Plasmodium falciparum, us- Rutledge LC, Gould DJ, Tantichareon B 1969. Factors ing the enzyme-linked immunosorbent assay. Trans affecting the infection of anophelines with human R Soc Trop Med Hyg 82: 389-391. malaria in Thailand. Trans R Soc Trop Med Hyg 63: Robson KJH, Hall JRS, Jennings MW, Harris TJR, 613-619. Marsh K, Newbold CI, Tate VE, Weatherhall DJ Santoro F, Cochrane AH, Nussenzweig V, Nardin EH, 1988. A highly conserved amino-acid sequence in Nussenzweig R, Gwadz RW, Ferreira A 1983. Struc- thrombospondin, properdin and in proteins from tural similarities among the protective antigens of sporozoites and blood stages of a human malaria spoorzoites from different species oof malaria para- parasite. Nature 335: 79-82. sites. J Biol Chem 258: 3341-3345. Rogers WO, Malik A, Mellouk S, Nakamura K, Rogers Sattabongkot J, Manaeechai N, Rosenberg R 1991. Plas- MD, Szarfman A, Gordon DM, Nussler AK, Aikawa modium vivax: gametocyte infectivity of naturally M, Hoffman SL 1992b. Characterization of Plas- infected Thai adults. Parasitology 102: 27-31. modium falciparum sporozoite surface protein 2. Schall JJ 1989. The sex ratio of Plasmodium gameto- 532 Biology of Malarial Parasites in Mosquito • AB Simonetti
cytes. Parasitology 98: 343-350. R Soc Trop Med Hyg 79: 598-605. Schapira A, Beales PF, Halloran ME 1993. Malaria: liv- Sinden RE 1978. Cell Biology, p. 85-186. In R Killick- ing with drug resistance. Parasitol Today 9: 168-174. Kendrick & WA Peters (eds) Rodent Malaria, New Scherf A, Behr C, Sarthou JL, Pla M, Rogier C, Trape York: Academic Press. JF, Pereira da Silva L, Dubois P 1993. Immune re- Sinden RE 1989. Recent advances in the parasitology sponse in mouse and malaria-exposed humans to of malaria. Trans R Soc Trop Med Hyg 83 Suppl: peptides derived from Pf11-1, a highly repetitive 3-9. megadalton protein of Plasmodium falciparum. Eur Sinden RE 1991. Asexual blood stages of malaria modu- J Immunol 23: 1574-1581. late gametocyte infectivity to the mosquito vector - Scherf A, Petersen C, Carter R, Alano P, Nellson R, possible implications for control strategies. Parasi- Aikawa M, Mattei D, Pereira da Silava, L. 1992. tology 103: 191-196. Characterization of a Plasmodium falciparum mu- Sinden RE, Butcher GA, Billker O, Fleck SL 1996. tant that has deleted the majority of the gametocyte- Regulation of infectivity of Plasmodium to the mos- specific Pf11-1 locus. Mem Inst Oswaldo Cruz quito vector. Adv Parasitology 38: 54 - 117. 87(Suppl. III): 91-94. Sinden RE, Croll NA 1975. Citolology and kinetics of Schneweis S, Maier WA, Seitz HM 1991. Haemolysis microgametogenesis and fertilization of Plasmodium of infected erythrocytes - A trigger for formation of yoelii nigeriensis. Parasitology 70: 53-65. Plasmodium falciparum gametocytes. Parasitol Res Sinden RE, Garnham PCC 1973. A comparative study 77: 458-460. on the ultrastructure of Plasmodium sporozoites Schulman S, Oppenheim JD, Vanderberg JP 1980. Plas- within the oocyst and salivary glands, with particu- modium berghei and Plasmodium knowlesi: serum lar reference to the incidence of the micropore. Trans binding to sporozoites. Exp Parasitol 49: 420-429. R Soc Trop Med Hyg 67: 631-637. Seitz HM, Maier WA, Rottok M, Becker-Feldman H Sinden RE, Smalley ME 1976. Gametocytes of Plas- 1987. Concomittant infections of Anopheles modium falciparum: phagocytosis by leucocytes in stephensi with Plasmodium berghei and Serratia vivo and in vitro. Trans R Soc Trop Med Hyg 70: marcesens additive detrimental effects. Z Bakteriol 344-345. Mikrobiol Hyg 266: 155-166. Sinden RE, Strong K 1978. An ultrastructural study of Shahabuddin M, Toyoshima T, Aikawa M, Kaslow DC the sporogonic development of Plasmodium 1993. Transmission-blocking acitivity of a chitinase falciparum in Anopheles gambiae. Trans R Soc Trop inhibitor activation of malarial parasite chitinase by Med Hyg 27: 477-491. mosquito protease. Proc Natl Acad Sci USA 90: Sinden RE, Winger LA, Hartley RH, Carter HE, 4266-4270. Tirawanchai N, Davies CS, Sluiters JG 1987. Shute PG 1945. An investigation into the number of Ookinete antigens of Plasmodium berghei: a light sporozoites found in the salivary glands of Anoph- and electron microscopic immunogold study of the eles mosquitoes. Trans R Soc Trop Med Hyg 38: 21kD determinant recognised by transmission block- 493-498. ing antibodies. Proc R Soc Lond B 230: 443-458. Shute PG, Marion M 1951. A study of gametocytes in a Sluiters JF, Visser PE, Van Der Kaay, HJ 1986. The West Africa strain of Plamodium falciparum. Trans establishment of Plasmodium berghei in mosquitoes R Soc Trop Med Hyg 44: 421-438. of a refractory and a susceptible line of Anopheles Shute PG, Maryon M 1954. The effect of pyrimethamine atroparvus. Z Parasitenkd 72: 313-322. (Daraprim) on the gametocytes and oocysts of Plas- Smalley ME 1977. Plasmodium falciparum gametocytes: modium falciparum and Plasmodium vivax. Trans the effect of chloroquine on their development. Trans R Soc Trop Med Hyg 48: 50-63. R Soc Trop Med Hyg 71: 523-529. Sieber KP, Huber M, Kaslow D, Banks SM, Torii M, Smalley ME, Brown J, Basset NM 1981. The rate of Aikawa M, Miller LH 1991. The peritrophic mem- production of Plasmodium falciparum gametocytes brane as a barrier: its penetration by Plasmodium during natural infections. Trans R Soc Trop Med gallinaceum and the effect of a monoclonal antibody Hyg 75: 317-319. to ookinetes. Exp Parasitol 72: 145-156. Snewin VA, Premawansa S, Kapilananda GMG, Simonetti AB, Billingsley PF, Winger L, Sinden RE Ratnayaka L, Udagama PV, Mattei DM, Khouri E, 1993. Kinetics of expression of two major Plasmo- DelGiudice G, Peiris JSM, Mendis KN, David PH dium berghei antigens in the msquito vector Anoph- 1995. Transmission blocking immunity in Plasmo- eles stephensi. J Euk Microbiol (J Protozool) 40: dium vivax malaria: antibodies raised against a pep- 569-576. tide block parasite development in the mosquito Sinden RE 1975. The sporogonic cycle of Plasmodium vector. J Exp Med 181: 357-362. yoelii nigeriensis: a scanning electron microscope Snow RW, Schellenberg JRMA, Peshu N, Forster D, study. Protistologica 11: 31-39. Newton CRJC, Winstanley PA, Mwangi I, Warn PA, Sinden RE 1983. The cell biology of sexual develop- Newbold C, Marsh K 1993. Periodicity and space- ment in Plasmodium. Parasitology 86: 7-28. time clustering of severe childhood malaria on the Sinden RE 1984. The biology of Plasmodium in the coast of Kenya. Trans R Soc Trop Med Hyg 87: 386- mosquito. Experientia 40: 1330-1343. 390. Sinden RE 1985. A cell biologist’s view of host cell Speer CA, Rosale-Ronquillo MC, Silverman PH 1974. recognition and invasion by malarial parasites. Trans Scanning electron microscope observations of Plas- Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 533
modium berghei ookinetes in primary mosquito cell bodies recognize a processing dependent epitope cultures. J Invert Pathol 24: 179-183. present in the mature CS protein of various Sterling CR, Aikawa M, Vanderberg JP 1973. The pas- plasmodial species. Parasite Immunol 14: 457-469. sage of Plasmodium berghei sporozoites through the Turner DP, Gregson NA 1982. The cell surface of Plas- salivary glands of Anopheles stephensi: an electron modium gallinaceum sporozoites: microelectro- microscope study. J Parasitol 59: 593-605. phoretic and lectin-binding studies. Parasitology 84: Stewart MJ, Vanderberg JP 1988. Malaria sporozoites 227-238. leave behind trails of circumsporozoite protein dur- Van Houten J 1988. Chemoresponse mechanism toward ing gliding. J Protozool 35:389-393. a molecular level. J Protozool 35: 241-245. Stewart MJ, Vanderberg JP 1991. Malaria sporozoites Vanderberg JP 1974. Studies on the motility of Plasmo- release circumsporozoite protein from their apical dium sporozoites. J Protozool 21: 527-537. end and translocate it along their surface. J Protozool Vanderberg JP 1975. Development of infectivity of the 38: 411-421. Plasmodium berghei sporozoite. J Parasitol 61: 43- Stewart MJ, Vanderberg JP 1992. Electron microscopic 50. analysis of circumsporozoite protein trail formation Vanderberg JP 1977. Plasmodium berghei: quantitation by gliding malaria sporozoites. J Protozool 39: 663- of sporozoites injected by mosquitoes feeding on a 671. rodent host. Exp Parasitol 42: 169-181. Stohler H 1957. Analyse des infektionsverlaufes von Vanderberg JP, Rhodin J, Yoeli M 1967. Electron mi- Plasmodium gallinaceum im darme von Aedes croscopic and histochemical studies of sporozoite aegypti. Acta Trop 14: 302-352. formation in Plasmodium berghei. J Protozool 14: Strome CPA, Beaudoin RL 1974. The surface of the 82-103. malarial parasite I. Scanning electron microscopy Vaughan JA, Do Rosario V, Leland P, Light J, Woolett of the oocyst. Exp Parasitol 36: 131-142. R, Hollingdale MR, Azad AF 1988. Plasmodium Syafruddin A, Arakawa R, Kamimura, Kawamoto F falciparum: ingested anti-sporozoite antibodies af- 1991. Penetration of the mosquito midgut wall by fect sporogony in Anopheles stephensi mosquitoes. the ookinetes of Plasmodium yoelii nigeriensis. Exp Parasitol 66: 171-182. Parasitol Res 77: 230-236. Vaughan JA, Noden BH, Beier JC 1992. Population Syafruddin A, Arakawa R, Kamimura K, Kawamotoo F dynamics of Plasmodium falciparum sporogony in 1992. Development of Plasmodium berghei laboratory-infected Anopheles gambiae. J Parasitol ookinetes to young oocysts in vitro. J Protozool 39: 78: 716-724. 333-338. Vaughan JA, Noden BH, Beier JC 1994. Sporogonic Targett GAT 1989. Status of malaria vaccine research. development of cultured Plasmodium falciparum in J R Soc Med 82: 52-56. six species of laboratory-reared Anopheles mosqui- Targett GAT 1990. Immunity to sexual stages of human toes. Am J Trop Med Hyg 51: 233-243. malaria parasites-Immune modulation during natu- Vermeulen AN, Deursen JV, Brakenhof RH, Lensen ral infections, antigenic determinants, and the induc- THW, Ponnudurai T, Meuwissen JHET 1986. Char- tion of transmission-blocking immunity. Scand J acterization of Plasmodium falciparum sexual stage Infec Dis 76: 79-88. antigens and their biosynthesis in synchronized ga- Terzakis JA 1971. Transformation of the Plasmodium metocyte cultures. Mol Biochem Parasitol 20: 155- cynomolgi oocyst. J Protozool 18: 62-73. 163. Tirawanchai N, Winger LA, Nicholas J, Ssinden RE Vermeulen AN, Ponnudurai T, Beckers PJA, Verhave 1991. Analysis of immunity induced by the affin- JP, Smits MA, Meuwissen JHET 1985a. Sequential ity-purified 21-Kilodalton zygote-ookinete surface expression of antigens on sexual stages of Plasmodium antigen of Plasmodium berghei. Infec Immun 59: falciparum accessible to transmission blocking an- 36-44. tibodies in the mosquito. J Exp Med 162: 1460- Titus RG, Ribeiro JMC 1990. The role of vector saliva 1476. in transmission of arthropod-borne disease. Vermeulen AN, Roeffen WFG, Hendrik JBJ, Ponnudurai Parasitol Today 6: 157-160. T, Beckers PJA, Meuwissen JHET 1985b. Plasmo- Torii M, Nakamura K, Sieber KP, Miller LH, Aikawa dium falciparum transmission blocking antibodies M 1992a. Penetration of the mosquito (Aedes recognize monovalently expressed epitopes. Develop aegypti) midgut wall by the ookinetes of Plasmo- Biol Standard 62: 91-97. dium gallinaceum. J Protozool 39: 449-454. Vernick KD, Collins H, Gwadz RW 1989a. A general Torii M, Yanagi T, Tsuboi T, Kanbara H 1992b. system of resistance to malaria infection in Anoph- Appearence and localization of Plasmodium yoelii eles gambiae controlled by two main genetic loci. circumsporozoite protein during sporogony in Am J Trop Med Hyg 40: 585-592. Anopheles stephensi. J Protozool Res 2: 134-140. Vernick KD, Collins FH 1989b. Association of a Plas- Touray MG, Warburg A, Laughinghouse A, Krettli AU, modium-refractory phenotype with an esterase lo- Miller LH 1992. Developmentally regulated infec- cus in Anopheles gambiae. Am J Trop Med Hyg 40: tivity of malaria sporozoites for mosquito salivary 593-597. glands and the vertebrate host. J Exp Med 175: Vickerman K, Cox FEG 1972. Introductory studies in 1607-1612. Biology. In SW Hurry & J Murray (eds), The Pro- Tsuji M, Corradin G, Zavala F 1992. Monoclonal anti- tozoa, Albemarie Street, London. 534 Biology of Malarial Parasites in Mosquito • AB Simonetti
Warburg A, Miller LH 1992. Sporogonic development Effect of sulphamethoxazole-trimethoprim on the of a malaria parasite in vitro. Science 255: 448- viability of Plasmodium falciparum gametocytes. 450. Trans R Soc Trop Med Hyg 67: 148-149. Warburg A, Schneider I 1993. In vitro culture of the Wilkinson, RN, Neypatimanond, S, Gould DJ 1976. mosquito stages of Plasmodium falciparum. Exp Infectivity of falciparum malaria patients for Parasitol 76: 121-126. anopheline mosquitoes befoore and after chloroquine Warburg A, Touray M, Krettli AU, Miller LH 1992. treatment. Trans R Soc Trop Med Hyg 70: 306-307. Plasmodium gallinaceum: antibodies to Winger LA, Tirawanchai N, Nicholas J, Carter HE, circumsporozoite protein prevent sporozoites from Smith JE, Sinden RE 1988. Ookinete antigens of invading the salivary glands of Aedes aegypti. Exp Plasmodium berghei. Appearance on the zygote of Parasitol 75: 303-307. a Mr 21 kD determinant identified by transmission Weathersby AB 1952. The role of the stomach wall in blocking monoclonal antibodies. Parasite Immunol the exogenous development of Plasmodium 10: 193-207. gallinaceum as studied by means of haemocoel in- Wirtz RA, Burkot TR, Graves PM, Andre RG 1987. Field jections of susceptible and refractory mosquitoes. J evaluation of enzyme-linked immunosorbent assays for Plasmodium falciparum and Plasmodium vivax Infec Dis 91: 198-205. sporozoites in mosquitoes (Diptera: Culicidae) from Weathersby AB 1954. The ectopic development of ma- Papua New Guinea. J Med Entomol 24: 433-437. larial oocysts. Exp Parasitol 3: 538-543. Yoshida N, Potonjak P, Nussenzweig V, Nussenzweig Weathersby AB 1960. Experimental infection of Aedes RS 1981. Biosynthesis of Pb44, the protective anti- aegypti with exoerythrocytic stages of Plasmodium gen of sporozoites of Plasmodium berghei. J Exp gallinaceum. Exp Parasitol 9: 334-337. Med 154: 1225-1236. Wernsdorfer WH 1991. The development and spread of Young MD, Burgess RW 1961. The infectivity to mos- drug-resistant malaria. Parasitol Today 7: 297-303. quitoes of Plasmodium malariae. Am J Hyg 73: 182- Wilkinson RN, Colwell EJ, Neoypatimanond S 1973. 192. Mem Inst Oswaldo Cruz, Rio de Janeiro, Vol. 91(5), Sep./Oct. 1996 535