Potential biomarker and composite efficacy readout for human clinical trials of schistosomiasis vaccine in Africa.

Schistosomiasis is a chronic disease that inflicts high morbidity and significant mortality with an estimated 90% of cases occurring in sub-Saharan Africa. Development of a vaccine against schistosomiasis is a major global health goal. The SchistoShield (Sm-p80 + GLA-SE) vaccine has consistently exhibited robust efficacy in non-human primate pre-clinical trials, has recently completed Phase 1 clinical trials in the US and Phase 1b trials are ongoing in Africa. To delineate a potential clinical/parasitological endpoint to measure the efficacy of schistosomiasis vaccine during human clinical trials, we have designed an in vitro schistosomula killing assay using sera collected from SchistoShield-vaccinated baboons and human volunteers from the Phase 1 clinical trial. Sm-p80-specific antibodies produced by immunized non-human primates and humans induced statistically significant larval schistosomula killing ex vivo. This reproducible functional assay has the potential to serve as one of the biomarkers for the effectiveness of the SchistoShield vaccine in human trials in Africa.