Murine immune responses to Schistosoma haematobium and the vaccine candidate rSh28GST

Longitudinal studies of Schistosoma haematobium infection in CBA mice revea led a progressive down-regulation of cellular immune responses, as measured by mitogenic and antigenic stimulation of in vitro lymphocyte cultures. An tigen-stimulated production of the Th1 cytokine IFN-gamma by splenocytes in creased progressively up to 14 weeks post infection, (four weeks after the onset of parasite egg production), before declining swiftly. Levels of the Th2 cytokine IL-4 in the same cultures remained low until 14 weeks, after w hich they rose rapidly as IFN-gamma declined. High levels of IL-10 coincide d with the peak in IFN-gamma production, suggesting a non Th2-restricted ro le for this cytokine. Both total and antigen-specific immunoglobulin produc tion confirmed parasite egg deposition as being a major stimulus for host h umoral responses. The S. haematobium infection failed to elicit detectable T cell responses to the antifecundity vaccine candidate rSh28GST. However l ow levels of antibody were detectable in infected mouse serum and strong Ig G and IgA production was induced by vaccination with rSh28GST plus adjuvant .