Human susceptibility to Schistosoma japonicum in China correlates with antibody isotypes to native antigens

Antibody isotypic responses (IgE, IgA, IgG1, IgG2, IgG3 and IgG4) to Schist osoma japonicum antigens-adult worm (AWA), soluble egg (SEA) and the recomb inant proteins TEG (22.6-kDa tegumental antigen, Sj22) and PMY (paramyosin, Sj97)-were measured (in 1998) in a cohort of 179 Chinese subjects 2 years post-treatment. Subjects in the highest intensity re-infection group (> 100 eggs per gram faeces) had significantly higher levels of IgG1 and IgG4 aga inst AWA. Analysis of IgG4/IgE ratios for AWA and SEA linked IgG4 excess to re-infection and IgE excess to non-re-infection. Two years after chemother apeutic cure, 29 subjects, who were re-infected or never infected but highl y water-exposed, were classified as epidemiologically susceptible (n = 15) or epidemiologically insusceptible to infection (n = 14). IgG4 levels again st native antigens (AWA and SEA) were higher in susceptibles and IgE levels were higher in insusceptibles but antibody responses to the recombinant pr oteins (PMY and TEG) showed no clear pattern or difference between suscepti bility groups. These and earlier findings provide evidence that immunity de velops against schistosomiasis japonica in China and that susceptibility/re sistance correlates with antibody isotypes against native schistosome antig ens.