FACTORS AFFECTING HIGH AND LOW HUMAN IGE RESPONSES TO SCHISTOSOME WORM ANTIGENS IN AN AREA OF BRAZIL ENDEMIC FOR SCHISTOSOMA-MANSONI AND HOOKWORM

We have previously examined the antibody isotype responses to schistos ome worm and egg antigens in human populations living in areas of Keny a and the Philippines endemic for Schistosoma mansoni and S. japonicum , respectively. Here, we have analyzed antibody isotype responses to S . mansoni adult worm (AW) antigen and soluble egg antigen (SEA) in mor e than 500 Brazilian individuals, an found similar relationships with age and sex as in the Kenyan and Filipino populations. Isotype respons es to AW antigen broadly increased with age whereas isotype responses to SEA decreased, and a higher proportion of males than females had de tectable IgE against AW antigen. Most isotype responses to AW antigen and SEA correlated positively with intensity of infection with S. mans oni except AW antigen-specific IgG(2), which correlated negatively. Th e overall prevalence of infection with S. mansoni in this area was rel atively low at only 39.5%; hookworm prevalence was higher at 57.4%. Th e majority of those infected with S. mansoni were also infected with h ookworm (76%). Those individuals with high IgE responses to AW antigen were matched for sex, age, and total IgG to AW antigen as closely as possible with individuals with low levels of AW antigen-specific IgE. The two groups were compared for factors potentially influential in Ig E production. No difference was found between the high and low IgE res ponders for 1) intensity or prevalence of infection with S. mansoni, 2 ) relative exposure to S. mansoni, 3) number of previous treatments fo r schistosomiasis, or 4) prevalence of infection with hookworm, but di fferences were found in other isotype responses to S. mansoni. The hig h IgE responders had higher IgA and IgG(4) against both AW antigen and SEA but lower IgG(3) responses to AW antigen than the low IgE respond ers. The IgE responses to three S. mansoni antigens (paramyosin, Sm22. 6, and a 12-kD AW antigen band) were detected in individuals with IgE against AW antigen only.