Paramyosin is a major target of the human IgA response against Schistosomajaponicum

Human resistance and susceptibility to schistosomiasis is associated with a ge and specific antibody isotype responses against worm (SWAP) and egg (SEA ) antigens. In a cross-sectional study of 176 individuals infected with Sch istosoma japonicum in the Philippines, strikingly similar isotype response patterns against SWAP and SEA was observed when compared to other endemic a reas. Interestingly, IgA titres to SWAP correlated with older age among S. japonicum-infected individuals (n = 176, P < 0.01), suggesting a role for t his isotype in protective immunity. To identify the molecular targets of hu man IgA, 17 high-IgA/SWAP responders were identified from the said populati on. IgA antibodies from the majority (14/17) of these individuals recognize d a band of 97 kDa (Sj97), comigrating in immunoblots with the myofibrillar protein paramyosin. The antigen was confirmed as paramyosin by expressed s equence tag (EST)-analysis of four clones obtained by screening an adult S. japonicum cDNA library with pooled IgA antisera and mouse antiparamyosin p olyclonal antibodies. The identification of paramyosin as a major target of human IgA raises its potential as a vaccine candidate that targets mucosal immune responses. Since this antigen is exposed on the parasite surface on ly during the lung stages, we propose that human IgA contributes to parasit e attrition during schistosome migration in the lungs.