HUMAN IGE RESPONSES TO SCHISTOSOMA-MANSONI AND RESISTANCE TO REINFECTION

Schistosoma mansoni infected Kenyan patients were treated and the inte nsities of their reinfections were followed over the next two years. I n addition, their pre- and six month post-treatment serum levels of Ig G1-4, IgM, and IgE, specific for schistosomula, egg and adult worm, we re measured in ELISA. No reinfection took place before six months post -treatment. Reinfection intensities varied with age; the younger child ren becoming reinfected at significantly higher intensities than older individuals. When antibody and reinfection levels were compared, only the six month post-treatment IgE reponse against adult worm correlate d negatively with intensities of reinfection and, therefore, was predi ctive of resistance or immunity to reinfection. IgE and IgG specific W estern Blots were carried out. The adult worm antigens recognized by I gE were restricted compared with the IgG responses of the same patient s, although no individual antigen was uniquely recognized by the IgE i sotype. A dominant 22 kDa antigen was recognized by most but not all h igh IgE responders. Patients with IgE responses against this antigen s uffered significantly lower subsequent levels of reinfection, compared with non-responders. A monospecific rabbit antiserum against the 22 k Da adult worm antigen showed that this antigen is specifically located in the tegument of the adult worm and of 'lung' and 'liver' stage sch istosomula, but is absent from the early 'skin' schistosomula. It is p ossible that this antigen is a target for human IgE mediated immune ef fector mechanisms active against the post skin stage schistosomula and that this is boosted by the death of adult worms.