Schistosomiasis mansoni: Immunoblot analysis to diagnose and differentiaterecent and chronic infection

One hundred seven patients classified into three different groups (11 with acute schistosomiasis, 58 with chronic schistosomiasis, and 38 children wit h high IgM-specific antibody titers against schistosome gut-associated anti gens living in an endemic schistosomiasis area) were studied by immunoblott ing for the presence of IgG, IgM, and IgA antibodies against Schistosoma ma nsoni soluble adult worm antigen preparation. We used sera from 15 individu als infected with various intestinal parasites, as well as sera from 19 uni nfected individuals, as controls. An immunogenic fraction with a molecular weight of 31-32 kD (Sm31/32) was the most frequently recognized by the diff erent antibody isotypes. In the group with acute disease, this fraction was recognized by IgG and IgM antibodies of all patients, and by 10 (90.9%) of 11 samples for IgA antibodies. Approximately 98% of the patients with chro nic infections had IgG antibodies against Sm31/32, but only about 10% had I gM and IgA antibodies against this fraction. The IgG immunoblot profiles of the children from the endemic area were similar to those obtained for the group with acute schistosomiasis. This observation suggests recent infectio n of these children. Our data show that the Sm31/32 protein fraction is hig hly immunogenic and may be a useful serologic marker for diagnosing and dif ferentiating between acute and chronic schistosomiasis infection.