HUMAN IGE RESPONSES TO RSM22.6 ARE ASSOCIATED WITH INFECTION INTENSITY RATHER THAN AGE PER SE, IN A RECENTLY ESTABLISHED FOCUS OF SCHISTOSOMASIS MANSONI

In studies of schistosomasis mansoni-endemic communities, individuals with IgE responses to a 22 kD adult worm antigen (rSm22.6) suffered lo wer intensities of reinfection after treatment. It is of interest to d efine the factors that lead to the production of rSm22.6-specific IgE because it is a marker for resistant individuals and it may be involve d in the development of resistance to reinfection. In endemic populati ons rSm22.6-spccific IgE increases linearly with age. However, it is n ot possible to distinguish between age per se and 'history of infectio n' in endemic populations because individuals are exposed to the paras ite at an early age. We have, therefore, quantified pre-and post-treat ment isotype responses to rSm22.6 in a comparatively 'epidemic' Senega lese community where the patients were infected at different ages and where pre-treatment intensity of infection can be taken as a reasonabl e measure of antigen exposure. Pose-treatment isotype responses to rSm 22.6 correlated positively with pre-treatment intensities of infection but were nor shown to be related to age. IgG1, IgG4 and IgE responses to rSm22.6 were significantly higher after treatment with the differe nce increasing with the pre-treatment level of infection. These result s from a recently established focus of infection suggest that isotype responses to rSm22.6 are antigen-exposure dependent rather than depend ent on age per se.