Differential antigen-stimulated proliferation of human mononuclear cells by recombinant Schistosoma japonicum antigens in a Chinese population

Immune correlate study on human Schistosoma japonicum in a well-defined population in Leyte, Philippines: II. Cellular immune responses to S. japonicum recombinant and native antigens

Cellular immune responses to specific Schistosoma japonicum recombinant and native antigens were investigated in a defined study population of 155 individuals in the Philippines, where data collected from a 3-year observation of exposure, infection and reinfection pattern were used to categorically classify putative 'resistant' and 'susceptible' individuals. Using peripheral blood mononuclear cells (PBMC) of individuals enrolled in the study, in vitro lymphocyte proliferation and cytokine (IFN-gamma, IL-5 and IL-10) production in response to defined recombinant antigens (97 kDa paramyosin, 22 kDa tegumental antigen, 37 kDa glyceraldehyde-3-phosphate dehydrogenase, 14 kDa fatty acid binding protein and 28 kDa gluthathione-S-tranferase) and native antigen soluble worm antigen preparation (SWAP) were measured. Cellular responses to the recombinant and SWAP antigens suggest that Th1 type of response appear to be important in predicting resistance in this population. Of the five recombinant antigens tested, rPMY induced significant levels of IFN-gamma. The production of IL-10, a Th2-type cytokine was strongly implicated in immune regulation. Of importance was the evidence found for SWAP and rPMY induced IFN-gamma responses in predicting 'resistance'. It was noted that these associations were significant even after the effect of age and sex were accounted for in a multivariate analysis.

Human T and B cell epitope mapping of Taenia solium paramyosin

Taenia solium paramyosin is an immunodominant antigen in human and porcine cysticercosis that has shown promise as a vaccine candidate against schistosomiasis and some filariasis. There are few studies to identify the immunologically relevant regions of paramyosin. In this work, we characterize the humoral and cellular response of neurocysticercotic patients against T. solium paramyosin. Western blots using different recombinant fragments of T. solium paramyosin, showed that the sera from neurocysticercotic patients were strongly reactive against the carboxyl end region, with poor recognition of the central and amino regions. In contrast, the cellular immune response of patients did not show preferential recognition of any region of paramyosin.

Characterization and protective potential of the immune response to Taenia solium paramyosin in a murine model of cysticercosis

Paramyosin has been proposed as a vaccine candidate in schistosomiasis and filariasis. However, limited information is available about its protective potential against cysticercosis and the immune response it induces. Immunization of mice with recombinant full-length paramyosin of Taenia solium (TPmy) results in about a 52% reduction in parasite burden after a subsequent challenge by intraperitoneal inoculation of Taenia crassiceps cysticerci. Immunization assays using recombinant fragments of TPmy, corresponding approximately to thirds on the amino, central, or carboxyl regions, suggest that protective epitopes are located mostly in the amino-end third. Proliferation assays using T cells obtained from mice immunized with the full-length recombinant TPmy also showed a preferential response to the amino-terminal fragment. In contrast, antibodies in the sera from these mice predominantly recognize epitopes located in the carboxyl-terminal fragment, being the immunoglobulin G1 subclass, the predominant antibody isotype. Characterization of the cellular immune response induced against the protective amino-terminal fragment reveals production of gamma interferon and interleukin-2, but not interleukin-4, suggesting a Th1-like profile.

Schistosomiasis in the People's Republic of China: prospects and challenges for the 21st century

Schistosomiasis japonica is a serious communicable disease and a major disease risk for more than 30 million people living in the tropical and subtropical zones of China. Infection remains a major public health concern despite 45 years of intensive control efforts. It is estimated that 865,000 people and 100,250 bovines are today infected in the provinces where the disease is endemic, and its transmission continues. Unlike the other schistosome species known to infect humans, the oriental schistosome, Schistosoma japonicum, is a true zoonotic organism, with a range of mammalian reservoirs, making control efforts extremely difficult. Clinical features of schistosomiasis range from fever, headache, and lethargy to severe fibro-obstructive pathology leading to portal hypertension, ascites, and hepatosplenomegaly, which can cause premature death. Infected children are stunted and have cognitive defects impairing memory and learning ability. Current control programs are heavily based on community chemotherapy with a single dose of the drug praziquantel, but vaccines (for use in bovines and humans) in combination with other control strategies are needed to make elimination of the disease possible. In this article, we provide an overview of the biology, epidemiology, clinical features, and prospects for control of oriental schistosomiasis in the People's Republic of China.

Is there immunity to Schistosoma japonicum?

The Oriental schistosome, Schistosoma japonicum, unlike the other two major schistosomes that infect humans (S. mansoni and S. haematobium), is a zoonotic species. The transmission dynamics and the potential effects of host-related regulatory factors, including immunity, are likely to be distinct for this parasite. Here, Allen Ross and collaborators from Australia, China and the Philippines discuss recently published and established epidemiological and laboratory data bearing on anti-infection immunity to Asian schistosomiasis, and contrast these findings with the emerging picture of development of anti-infection immunity against the African schistosomes. Implications for vaccines and other control strategies for schistosomiasis japonica are also discussed.

The search for a vaccine against schistosomiasis--a difficult path but an achievable goal

The search for an effective vaccine against schistosomiasis, a parasitic disease currently affecting over 200 million people, remains a desirable but as yet challenging and elusive goal. Progress in the area has been relatively slow but research demonstrating the ability of humans to acquire natural immunity to schistosome infection, together with the successful use in animals of attenuated vaccines, supplemented with encouraging results obtained with defined antigens, suggests that development of a vaccine is achievable. Noteworthy also are recent immune correlate findings which shed light on the complex, putatively protective immune responses in humans, which have improved the prospects of success. With the first human clinical trial having been completed with a schistosome vaccine candidate, this review examines current progress aimed at achieving the objective of a safe and effective vaccine for widespread use against schistosomiasis. The review emphasises work undertaken in the author's laboratory and those of his chief collaborators in the search for a vaccine against schistosomiasis japonica, a disease of major public health significance in The People's Republic of China and The Philippines. Schistosomiasis vaccines should not be considered as the panacea for schistosomiasis control as, when available, it is generally envisaged that they would be used as one component of an integrated strategy complementing currently available and effective tools such as chemotherapy, improvements to sanitation, piped water supply, effective sewage draining and health education.

Production of interleukin-10 by peripheral blood mononuclear cells from residents of a marshland area in China endemic for Schistosoma japonicum

Interleukin-10 (IL-10) cytokine production was assessed using peripheral blood mononuclear cells (PBMC) from 67 individuals living in an area endemic for schistosomiasis japonica in China (Dongting Lake, Hunan Province), and 11 control subjects from a non-endemic part of the same Province. Production of IL-10 was measured following in vitro stimulation of PBMC using whole parasite extract (SWAP) or a panel of recombinant Schistosoma japonicum antigens (22-kDa tegumental membrane-associated antigen, glyceraldehyde-3-phosphate dehydrogenase, paramyosin, 14-kDa fatty acid-binding protein and 28-kDa glutathione S-transferase) which are of recognized interest in the development of protective immunity to schistosomiasis. Significantly, PBMC isolated from the exposed population compared with the non-exposed population produced higher levels of IL-10. There was a trend towards higher mean levels of IL-10 release in putatively resistant (insusceptible) (consistently egg negative but highly exposed) individuals compared with susceptible (egg-positive) subjects from the exposed population. Analysis of individual exposure (the duration of water contact and the percent body surface area in contact with water, expressed as m2 h/day) vs. IL-10 production indicated a weak but consistent and statistically significant inverse correlation, with lower levels of exposure being associated with higher levels of IL-10. These results suggest an association between IL-10 production and resistance to S. japonicum in subjects from this Chinese population exposed to infection.

Antibody isotype responses, infection and re-infection for Schistosoma japonicum in a marshland area of China

Antibody isotype responses to adult worm antigen (AWA) of Schistosoma japonicum and two recombinant proteins (paramyosin (PMY) and a 22 kDa tegumental membrane-associated antigen (TEG)) were analyzed in 137 individuals from an area moderately endemic for schistosomiasis in the Dongting Lake region, Hunan Province, China. The prevalence and geometric mean (GM) intensity of infection before the implementation of curative chemotherapy were 28.5% and 234.4 epg, respectively, but 9 months after treatment the prevalence (6.6%) and intensity (38.3 epg) had decreased. There was no significant difference in either the prevalence or intensity of infection between males and females. Specific IgG (total), IgG4, IgG2, IgA and IgE responses to AWA, PMY and TEG were measured by ELISA. Males produced significantly (P < 0.05) more anti-AWA total IgG, IgE, IgA, IgG4 and IgG2 antibodies, and anti-TEG IgG2 antibody than their female counterparts. The OD450 levels of anti-AWA, PMY and TEG antibody isotypes did not present clear age-dependent trends except for peak levels of anti-AWA IgG4 antibodies evident among subjects 20-29 years of age. The total IgG and IgG4 antibody profiles against AWA correlated well with current S. japonicum infections while anti-AWA IgG2, IgA and IgE antibodies did not show such an association. Anti-AWA-specific IgE antibody levels were positively correlated (r = 0.55) with anti-AWA specific IgG4 antibody levels. In addition, the overall percentage of responders (using a cut-off value obtained from normal controls) to all isotypes to AWA were higher than those observed for both the recombinant antigens. Only 18.2%, 16.8% and 7.3% of the study population were IgE responders to AWA, PMY and TEG. A longer follow-up period is required before we can more fully understand the role of IgE, if any, in protective immunity against schistosomiasis japonica.