Kunitz-type protease inhibitor as a vaccine candidate against schistosomiasis mansoni

Objective: The aim of this study was to develop a vaccine against schistosomiasis, which is a major challenge due to the complex lifecycle of the causative schistosome parasite. Methods: SmKI-1 is a 16-kDa Kunitz-type protease inhibitor present in the excretory–secretory products and tegument of adult worms and eggs of Schistosoma mansoni. Two independent vaccine trials were performed in mice to determine the efficacy of rSmKI-1 in developing protective immunity. Results: The results obtained showed reductions of 23–33% in adult worms, 28–31% in intestinal eggs, 33–39% in faecal eggs, and 20–43% in liver eggs. Furthermore, rSmKI-1 significantly increased the production of interferon gamma, interleukin (IL)-10, and IL-6 in vaccinated mice, maintaining a Th1/Th2-type balanced protective response. Conclusions: rSmKI-1 generated partial protection against schistosomiasis mansoni in the murine model of infection and could be developed as part of a combination vaccine with other vaccine candidates to provide an even more solid level of protection