Schistosoma egg-induced liver pathology resolution by Sm-p80-based schistosomiasis vaccine in baboons

Schistosomiasis remains a serious chronic debilitating hepato-intestinal disease. Current control measures based on mass drug administration are inadequate due to sustained re-infection rates, low treatment coverage and emergence of drug resistance. Hence, there is an urgent need for a schistosomiasis vaccine for disease control. In this study, we assessed the anti-pathology efficacy of Schistosoma mansoni large subunit of calpain (Sm-p80)-based vaccine against schistosomiasis caused by infections with Schistosoma mansoni in baboons. We also evaluated the disease transmission-blocking potential of Sm-p80 vaccine. Immunisations with Sm-p80-based vaccine resulted in significant reduction of hepatic egg load in vaccinated baboons (67.7% reduction, p = 0.0032) when compared to the control animals, indicative of reduction in pathology. There was also a significant reduction in sizes of egg-induced granulomas in baboons immunised with Sm-p80 vaccine compared to their control counterparts. Egg hatching rate analysis revealed an overall 85.6% reduction (p = 0.0018) in vaccinated animals compared to the controls, highlighting the potential role of Sm-p80 vaccine in disease transmission. The findings on anti-pathology efficacy and transmission-blocking potential presented in this study have formed the basis for a large-scale double-blinded baboon experiment that is currently underway.