No vaccines are available for human use for any of the parasitic infections including the helminthic disease, schistosomiasis. Sm-p80, the large subunit of Schistosoma mansoni calpain, is a leading antigen candidate for a schistosomiasis vaccine. Prophylactic and antifecundity efficacies of Sm-p80 have been tested using a variety of vaccine approaches in both rodent and nonhuman primate models. However, the therapeutic efficacy of a Sm-p80-based vaccine had not yet been determined. In this study, we have evaluated the therapeutic efficacy of Sm-p80 using two different strategies and three Sm-p80-based vaccine formulations in baboons. Vaccine formulations were able to eliminate 10-36% of established adult worms;... More
No vaccines are available for human use for any of the parasitic infections including the helminthic disease, schistosomiasis. Sm-p80, the large subunit of Schistosoma mansoni calpain, is a leading antigen candidate for a schistosomiasis vaccine. Prophylactic and antifecundity efficacies of Sm-p80 have been tested using a variety of vaccine approaches in both rodent and nonhuman primate models. However, the therapeutic efficacy of a Sm-p80-based vaccine had not yet been determined. In this study, we have evaluated the therapeutic efficacy of Sm-p80 using two different strategies and three Sm-p80-based vaccine formulations in baboons. Vaccine formulations were able to eliminate 10-36% of established adult worms; reduced retention of eggs in tissues from 10-57% and decreased the egg excretion in feces from 13-33%. Marked differences were observed in B and T cell immune correlates between vaccinated and control animals. This is the first report of killing of established adult schistosome worms by a vaccine. In addition to distinct prophylactic efficacy of Sm-p80, this study adds to the potential of Sm-p80 as an important antigen with both substantial prophylactic and therapeutic efficacies. These data reinforce that Sm-p80 should be moved forward through development leading to human clinical trials.
