Human and murine humoral immune recognition of multiple peptides from Schistosoma mansoni glyceraldehyde 3-P dehydrogenase is associated with resistance to Schistosomiasis

Schistosoma mansoni glyceraldehyde 3-phosphate dehydrogenase (SG3PDH) is a target of cellular and humoral immune responses of Brazilian and Egyptian s ubjects putatively resistant to reinfection with S. mansoni. In an aim to d evelop a safe, stable and effective vaccine based on this promising molecul e, six peptides derived from its primary sequence were selected based on th e lowest homology to human G3PDH. The synthetic peptides were tested by ELI SA against plasma of humans putatively susceptible or resistant to reinfect ion with S. mansoni or S'. haematobium following chemotherapeutic cure of p revious infection. Repeat experiments indicated that the six peptides bear human B-cell epitopes that bind immunoglobulin (Ig)M, IgGl and IgG3 antibod ies. Resistance to reinfection appeared to be significantly associated with humoral immune responses to multiple peptides. This contention was support ed by studies in the murine model, whereby we examined the B cell immune re sponses of Swiss and inbred BALB/c and C57BL/6 mice immunized with recombin ant SG3PDH (rSG3PDH) to the six SG3PDH-derived peptides. The serum antibodi es of rSG3PDH-immunized Swiss mice were directed to only one of the six pep tides tested by ELISA. Antibodies from rSG3PDH-immunized C57BL/6 and BALB/c mice bound, respectively, to four and six out of six peptides. In contrast to Swiss mice, immunization of C57BL/6 and BALB/c mice with rSG3PDH induce d protection against challenge cercariae which reached the level of signifi cance (P<0.05) for BALB/c mice. The data together indicate that host recogn ition of multiple peptides of a candidate vaccine antigen is necessary for the expression of its ability to contribute to protective immunity against Schistosomiasis.