Whether by administration of a vaccine or anti-pathogenesis substances, intervention of schistosomiasis by immunologic means is a major goal of schistosomiasis research efforts today. This application is to renew our program examining the role Schistosoma mansoni irradiated cercariae play as a model for inducing anti-schistosome immunity and anti-pathogenesis, and as candidates for a live vaccine. To determine vaccine effectiveness in situations approximating that to be encountered in the field, immunity will be assessed aginst multiple 'trickle' cercarial challenges. Using mice immunized with irradiated Schistosma japonicum cercariae, the specificity of vaccine induced resistance will be more thoroughly examined by challenge with the homologous or a heterologous schistsome species (S. mansoni). Anti-pathogenic effects of live vaccine administration will be examined in the mouse, along with the possibility that immunologic suppression of protection develops in cases where suboptimal levels of immunity are stimulated. Basic issues related to a recently developed cryopreserved live vaccine will also be addressed. These are: (1) by autoradiographic techniques determine the vaccine's migratory properties in the naive host, and (2) Attempt to enhance the vaccine's efficiency by concurrent administration of immunopotentiators and the cryopreserved vaccine. These experiments should answer pressing questions related to anti-schistosome immune mechanisms, while evaluating more critically the feasibility of irradiated larve as components of a live vaccine.
