Multiple vaccinations with UV- attenuated cercariae in pig enhance protective immunity against Schistosoma japonicum infection as compared to single vaccination

Dandan Lin,Jingjiao Wu,Minjun Ji,Patrick Driguez,Guanling Wu,Haiwei Wu,Yanan Gao,Fang Tian,Donghui Zhang,Donald P Mcmanus

doi:10.1186/1756-3305-4-103

Abstract

BackgroundSchistosomiasis japonica is a major public health problem in the endemic areas of China, the Philippines, and Indonesia. To date, a vaccine has not been developed against this disease but immunization with UV-attenuated cercariae can induce a high level of protective immunity in Landrace/Yorkshire/Duroc crossbred pigs. To compare the efficacy of a single vaccination and multiple vaccinations with UV-attenuated Schistosoma japonicum cercariae, two groups of pigs received either one or three exposures to 10,000 cercariae attenuated with 400 μw UV.ResultsPigs with a single immunization had a 59.33% reduction in adult worm burden, a 89.87% reduction in hepatic eggs and a 86.27% reduction in fecal eggs at eight weeks post-challenge (P < 0.01). After three immunizations, protection increased to 77.62%, 88.8% and 99.78% reduction in adult worms, hepatic eggs and fecal eggs, respectively (P < 0.01). Humoral and cellular immunological parameters measured indicated that schistosome-specific IgG1 and IgG2 levels in the vaccinated groups were higher than in the infection-control group. Triple vaccinations resulted in higher levels of antibodies, especially IgG2, compared with a single vaccination and IFN-γ levels increased with repeated immunization with UV-irradiated cercariae.ConclusionThe high levels of protection against S. japonicum infection can be achieved with a UV-attenuated vaccine in pigs, and that three vaccinations were possibly more effective than a single vaccination. Moreover, triple vaccinations evoked a more vigorous IFN-γ response and a stronger antibody-mediated response, especially an increase in the levels of IgG2 antibodies.

Highlights

Schistosomiasis japonica is a major public health problem in the endemic areas of China, the Philippines, and Indonesia
A high level of protection against Schistosoma japonicum induced by UV-attenuated cercariae (UVAC) vaccination 1.1 Lower adult worm and liver egg burdens in vaccinated pigs The number of adult worms recovered and hepatic eggs per gram at 8 weeks post-challenge are shown in
Humoral response against Schistosoma japonicum infection 2.1 High levels of IgG antibodies induced after triple vaccinations with UVAC As shown in Figure 3, immunization with UVAC followed by challenge with normal cercariae induced schistosome antigen-specific IgM and IgG responses in pigs

Summary

Introduction

Schistosomiasis japonica is a major public health problem in the endemic areas of China, the Philippines, and Indonesia. It is well recognized that the radiation-attenuated (RA) vaccine can induce high and stable protection against Schistosoma mansoni challenge in many animal models, including mice and primates [3]. Both antibody and CD4+ T-cell-mediated, IFN-g-dependent effector mechanisms have been demonstrated in the mouse model against S. mansoni [3]. The pig is a significant reservoir host of S. japonicum, but being a large animal with close biological similarities to humans, it provides a better experimental model than the mouse to study the relevant immune events associated with protection [9,10,11,12,13]. Experimental studies on porcine schistosomiasis japonica can provide novel information about how to make an effective and feasible vaccine applicable to the field

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Conclusion