Anti-Transmission DNA Vaccine for Schistosomiasis japonica in China

Despite intensive control efforts, schistosomiasis remains an endemic, zoonotic disease of major public health importance in China. In the marsh and lake regions of China, water buffalo account for approximately 75% of disease transmission. In addition to acting as the major reservoir, infected water buffalo often experience poor growth and weight gain compared to non-infected animals. Thus, interventions which reduce schistosome infection in buffalo will be beneficial to buffalo health and aid in reducing disease prevalence in humans. In this regard, a mathematical model predicted that an anti-fecundity vaccine which reduces fecal egg output in water buffalo by 40-45% in conjunction with praziquantel treatment will significantly lead to reduction in transmission of schistosomiasis. In this study, we tested the ability of four schistosome- DNA vaccine constructs to reach these levels in water buffalo. The DNA vaccine constructs encode the glycolytic enzyme triose phosphate isomerase (SjCTPI) or the tetraspanin 23 kDa integral membrane protein (SjC23) or the same antigens fused to the N-terminus end of the bovine heat shock protein 70 (SjCTPI-Hsp70 and SjC23-Hsp70). We found that compared to buffalo vaccinated with the control plasmid DNA (pVAX), vaccination with SjCTPI-Hsp70 or SjCTPI plasmids reduced worm burdens by 51.2% and 41.5% respectively and importantly, fecal miracidialhatching was reduced by 52.1% and 33.2% respectively. Vaccination with SjC23-Hsp70 and SjC23 plasmids reduced worm burdens by 50.9% and 45.5% respectively and fecal miracidial-hatching by 52.0% and 47.4%. Thus both the SjCTPI-Hsp70 and SjC23-Hsp70 plasmid DNA vaccines exceeded the level of protection predicted by the mathematical model to significantly reduce transmission of schistosomiasis in the lakes and marsh regions of China. These data support the use of either of these two vaccines in a field-based intervention to determine if vaccination of buffalo will reduce transmission of schistosomiasis in China. (ACMCIP Abstract)