Protective immunity and vaccines to schistosomiasis.

Human schistosomiasis is a major health problem in endemic areas and it is estimated that world-wide more than 200 million people are infected. Active infection, exposure to attenuated parasites, or appropriate immunization with parasite extracts or purified antigens can lead to partial protection against challenge infections. Studies of the humoral and cellular mechanisms responsible for these forms of resistance, and the definition, purification or production of recombinant moieties responsible for the induction of immunity are currently the focus of considerable research efforts.