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.