Immunoblot analysis of Schistosoma japonicum egg antigens with sera from patients with acute and chronic schistosomiasis japonica.

Humoral immune responses of IgG, IgM, IgA, IgE and IgG subclass antibodies to Schistosoma japonicum egg antigens were determined by immunoblotting with serum samples from individuals in China with acute (n=24) or chronic (n=35) schistosomiasis. In general, IgM, IgA, and IgE in sera from acute patients exhibited strong binding to antigens but binding was much weaker in chronic cases. Reaction of IgG4 of chronic cases was stronger than that of IgG4 of acute cases. The recognition profile of each antibody isotype in sera was analyzed for 11 major antigen molecules (antigens with apparent molecular weights of 82, 76, 61, 57, 53, 46, 40, 32, 27, 10 and less than 6.5 kDa). Except for the 10 kDa molecule, they were well-recognized by IgA and IgE in sera of acute cases. In other combinations of antibody class and clinical phase, recognition patterns against these molecules differed among individuals. Notably, the 10 kDa molecule was specifically recognized by total IgG and IgG4 in sera from most of the chronic patients, but in sera from only one acute case. This result suggests that the 10 kDa molecule is one of the major target antigens of IgG4 and may be useful as a marker antigen to characterize the clinical phases of S. japonicum infection.