Vaccine potential of hemocyanin from Oncomelania hupensis against Schistosoma japonicum

Hemocyanin, a giant oxygen transport protein which is usually found in many arthropods and mollusks was isolated and purified from Oncomelania hupensis. In this study, we showed that Oncomelania hupensis hemocyanin (OhH) shared carbohydrate epitopes with different developmental stages of Schistosoma japonicum (Cercaria, Schistosomulum, Adult worm and Egg) and exhibited serological cross-reaction with these stages of S. japonicum immune sera, which had a potential for use in diagnostic and therapeutic studies of schistosomasis. OhH was used as a vaccine in combination with Freund's adjuvant to evaluate the induction of immune responses and protection against S. japonicum infection in mice. Mice immunized with OhH induced a Th1 type of immune responses. Strong protection against S. japonicum were observed in adult worm and egg burdens after 42 days post-challenge, which showed a significant worm reduction of 52.5% and egg reduction of 69.2% compared to the control groups, respectively. These results indicated that OhH was a potential candidate to compose an anti-schistosome vaccine.