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

Background: schistosomiasis 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 w uv. results: pigs 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- levels increased with repeated immunization with uv-irradiated cercariae. conclusion: the 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- response and a stronger antibody-mediated response,especially an increase in the levels of igg2 antibodies. © 2011 lin et al; licensee biomed central ltd.