Characterization of the immune response to DNA vaccination strategies for schistosomiasis candidate antigen, Sm-p80 in the baboon.

Even though schistosomicidal agents and other control measures, including public hygiene and snail control exist, development of an efficacious vaccine still remains the most potentially powerful method for control of schistosomiasis. In our continuing efforts to develop a vaccine against schistosomiasis, we have selected a vaccine candidate (Sm-p80), which plays an important role in the immune evasion process of the parasite. Sm-p80 has been shown to confer up to 60% protection in mice following experimental infection. In this initial study, we have used Sm-p80 plus the Th1 response promoting cytokine, interleukin-2 (IL-2), in a DNA immunogen formulation. The vaccine was tested for its safety and immunogenicity in a baboon model of schistosomiasis. The vaccine generated a Th1 type Sm-p80-specific response in baboons with IgG(1)/IgG(2) ratios of less than 1.0. No detectable IgG(3) or IgG(4) anti-Sm-p80 responses were present in the immunized baboons. The antibodies to Sm-p80 were able to kill up to 35% schistosomula in vitro in the presence of complement. These results although preliminary suggest the potential of Sm-p80 as a viable vaccine candidate for schistosomiasis.