Immune Responses in Human Necatoriasis: Association Between Interleukin-5 Responses and Resistance to Reinfection
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This is a repository copy of Immune Responses in Human Necatoriasis: Association between Interleukin-5 Responses and Resistance to Reinfection . White Rose Research Online URL for this paper: http://eprints.whiterose.ac.uk/1376/ Article: Quinnell, R.J., Pritchard, D.I., Raiko, A. et al. (2 more authors) (2004) Immune Responses in Human Necatoriasis: Association between Interleukin-5 Responses and Resistance to Reinfection. The Journal of Infectious Diseases, 190 (3). pp. 430-438. ISSN 0022-1899 Reuse See Attached Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing [email protected] including the URL of the record and the reason for the withdrawal request. [email protected] https://eprints.whiterose.ac.uk/ MAJOR ARTICLE Immune Responses in Human Necatoriasis: Association between Interleukin-5 Responses and Resistance to Reinfection Rupert J. Quinnell,1 David I. Pritchard,2 Andrew Raiko,3 Alan P. Brown,2 and Marie-Anne Shaw1 1School of Biology, University of Leeds, Leeds, and 2School of Pharmacy, University of Nottingham, Nottingham, United Kingdom; 3Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea (See the editorial commentary by Maizels and Balic, on pages 427–9.) Cytokine and proliferative responses to Necator americanus infection were measured in a treatment-reinfection study of infected subjects from an area of Papua New Guinea where N. americanus is highly endemic. Before treatment, most subjects produced detectable interleukin (IL)–4 (97%), IL-5 (86%), and interferon (IFN)–g (64%) in response to adult N. americanus antigen. Pretreatment IFN-g responses were negatively associated with hookworm burden, decreasing by 18 pg/mL for each increase of 1000 eggs/gram (epg) (n p 75 ;P ! .01 ). Mean IFN-g responses increased significantly after anthelmintic treatment, from 166 to 322 pg/mL (n p 42 ; P ! .01). The intensity of reinfection was significantly negatively correlated with pretreatment IL-5 responses, decreasing by 551 epg for each 100 pg/mL increase in production of IL-5 (n p 51 ;P ! .01 ). These data indicate that there is a mixed cytokine response in necatoriasis, with worm burden–associated suppression of IFN-g responses to adult N. americanus antigen. Resistance to reinfection is associated with the parasite-specific IL- 5 response. The human hookworms Necator americanus and An- long-term control requires repeated chemotherapy. Re- cylostoma duodenale infect more than a billion people cently, attention has been focused on the possibility of worldwide and are a significant cause of iron-deficiency control by vaccination, and a number of vaccine can- anemia [1]. The global burden of disease due to hook- didates are being tested [7]. Relatively little is known worms has been estimated to be 22 million disability- about protective immune responses to infection with adjusted life-years [2]. Infection usually occurs after hookworms. Infection with hookworm, as with other penetration of the skin by infective larvae, followed by helminths, induces a strong immune response, with a tissue-migratory larval stage. Adult worms are long- elevated levels of total and specific IgE and eosinophilia. lived inhabitants of the small intestine, and, in contrast There is some evidence of a protective effect of anti- to infection with other geohelminths, the intensity of hookworm antibodies [8], and total and specific IgE infection is usually greatest in adults [3, 4]. Infection responses have been shown to correlate negatively with with hookworms is treated easily with a variety of ant- hookworm fecundity [9]. However, the role of cellular helmintics, but, in areas where hookworms are en- and cytokine responses in resistance to reinfection has demic, reinfection after treatment is rapid [5, 6], and not been investigated. Infection with human hookworms is chronic, with adult worms surviving an average of 2–4 years, with a Received 5 September 2003; accepted 13 January 2004; electronically published 25 June 2004. maximum of 18 years [10]. This suggests that infection Financial support: Medical Research Council (Career Development Award to with hookworms may modulate parasite-specific im- R.J.Q.); GlaxoSmithKline and Pfizer (donations of anthelmintics). Reprints or correspondence: Dr. Rupert J. Quinnell, School of Biology, University mune responses. Such immunomodulation is charac- of Leeds, Leeds LS2 9JT, UK ([email protected]). teristic of infection with tissue-dwelling filarial nema- The Journal of Infectious Diseases 2004;190:430–8 todes and schistosomes, resulting in an antigen-specific ᮊ 2004 by the Infectious Diseases Society of America. All rights reserved. 0022-1899/2004/19003-0002$15.00 suppression of cellular immune responses [11–14]. There 430 • JID 2004:190 (1 August) • Quinnell et al. may also be modulation of responses to nonparasite antigens, Table 1. Demographic and parasitological characteristics of Necator americanus such as bacterial antigens [15–17]. Since hookworm-infected subjects enrolled in a study of infection in Papua New Guinea. communities typically harbor other species of helminth and nonhelminth pathogens, there is the potential for a wide variety Characteristic Value of immunological interactions. Such interactions may be of Age, years great importance when considering vaccination against either Mean (95% CI) 24.6 (22.0–27.5) hookworms or other pathogens in areas where hookworms are Range 6–66 endemic. Sex, no. of subjects We report here the results of a study of an N. americanus– Male 50 infected population in Papua New Guinea. The aims of the study Female 31 Hookworm burden, mean (95% CI), epg were to describe the proliferative and cytokine (interferon [IFN]– All ages (n p 81) 3182 (2551–3928) g, interleukin [IL]–4, and IL-5) responses to hookworm antigen 6–13 years old (n p 13) 2356 (1041–4095) in an infected population and to test the hypotheses that (1) 14–20 years old (n p 25) 3233 (2242–4473) infection with hookworms suppresses immune responses to par- 21–34 years old (n p 25) 3742 (2453–5402) asite or mycobacterial antigen, (2) antihookworm immune re- 35–66 years old (n p 18) 2931 (1870–4524) Prevalence of other infections, no. of subjects sponses protect against reinfection, and (3) coinfection with other infected/total no. of subjects (%) parasites affects immune responses to hookworm. Trichuris trichiura 2/81 (2.5) Ascaris lumbricoides 0/81 (0) SUBJECTS, MATERIALS, AND METHODS Filariasis 10/79 (12.7) Plasmodium species 15/77 (19.5) Study population. The study was performed in the village P. falciparum 11/77 (14.3) of Haven, Madang Province, Papua New Guinea. Informed P. vivax 3/77 (3.9) P. malariae 1/77 (1.3) consent was obtained from all subjects or their parents. The study was approved by the Medical Research Advisory Com- NOTE. CI, confidence interval; epg, eggs per gram of feces. mittee of Papua New Guinea. Stool samples were obtained during September 1998, and fecal egg counts were performed obtained from 5 control subjects (21–44 years old) from an by use of a modified McMaster salt-flotation method, with re- area where hookworms are not endemic (University of Leeds, sults expressed as eggs per gram (epg) of feces. Blood samples Leeds, UK). (10–20 mL) were obtained from 81 infected subjects 15 years Preparation of antigens. Adult N. americanus excretory- old during November–December 1998 (table 1); those subjects secretory (ES) products and the mycobacterial antigen purified were then treated with a single dose of pyrantel pamoate (10 protein derivative (PPD; Statens Serum Institute, Copenhagen) mg/kg of body weight) 0–3 days after blood samples were ob- were used. ES products were obtained as described elsewhere tained. Repeat blood samples were obtained from 54 subjects [18]. In brief, N. americanus worms were maintained in syn- a median of 33 days after treatment (range, 24–38 days); the geneic DSN hamsters by percutaneous infection of neonates remaining subjects refused to have a second blood sample ob- with 100 infective N. americanus larvae. Thirty-five days after tained. The efficacy of anthelmintic treatment was assessed in infection, the hamsters were killed, and the small intestine was a nearby village: treatment reduced the mean epg by 83% (n removed, cut along its length, and placed in Hanks’ buffered p44). At the conclusion of sampling, everyone in the village, saline solution at 37ЊC. Adult worms were allowed to detach except children !4 years old and pregnant women, was offered voluntarily from the small intestine, washed extensively with treatment with a single dose of albendazole (400 mg). Perinatal RPMI 1640 medium supplemented with 100 IU/mL penicillin vaccination with bacille Calmette-Gue´rin (BCG) is routinely and 100 mg/mL streptomycin, and incubated for 1 h at 37ЊC. performed in this population. Before treatment, all subjects ES products were collected by culturing overnight in RPMI were tested for malaria infection by use of microscopic ex- 1640 medium supplemented with 100 IU/mL penicillin, 100 amination of Giemsa-stained blood smears and for filarial in- mg/mL streptomycin, and 2 mmol/L l-glutamine. The protein fection by use of circulating antigen ELISA (TropBio). During content of the collected ES products was determined by use of September 2001, ∼33 months after treatment, reinfection hook- bovine serum albumin (BSA) standards (BioRad). ES products worm burden (i.e., epg) was assessed in as many members of were freeze-dried and stored at Ϫ20ЊC until required. the study group as possible (n p 63 ), and treatment with al- Proliferation assays. Peripheral blood mononuclear cells bendazole was offered again. Reinfection epg was not assessed (PBMCs) were isolated from heparinized venous blood by cen- in 14 subjects who were absent from the village and in 4 subjects trifugation over Histopaque 1077 (Sigma). PBMCs were washed who did not provide a fecal sample.