A COMPARISON OF HUMORAL RESPONSES TO SCHISTOSOMA-HAEMATOBIUM IN AREASWITH LOW AND HIGH-LEVELS OF INFECTION

Antibody responses to Schistosoma haematobium of 280 Zimbabweans were studied in two areas of differing infection levels. 133 of the subject s came from a low infection area with a prevalence of 33.8% and geomet ric mean infection intensity of 0.8 eggs per 10 ml of urine, while 147 of the subjects came from a high infection area with a prevalence of 62.7% and geometric mean intensity of 3.2 eggs per 10 ml of urine. Bot h the age-prevalence and age-intensity curves exhibited a peak shift. IgA, IgE, IgG, IgG1, IgG2, lgG3, IgG4, and IgM antibody levels against soluble egg antigen (SEA) and whole worm homogenate (WWH) were assaye d by ELISA. Females produced significantly more anti SEA IgG1, IgG4, I gM, anti-WWH IgE and IgG1. People from the high infection area produce d significantly more anti-SEA IgE, lgG3 and anti-WWH IgG3 and signific antly lower levels of anti-SEA IgA, IgM and anti-WWH IgM when the effe cts of infection intensity, sex and age had been allowed for. The age profiles of anti-SEA IgA, IgG and anti-WWH IgA and IgM reflected curre nt levels of infection while anti-WWH IgG1, IgG2 and anti-SEA IgG1 evo lved more slowly with age, and anti-WWH IgE rose with age in both area s. Some antibody responses, anti-SEA/WWH IgM, anti-SEA IgG1 and possib ly anti-SEA/WWH IgA showed different age profiles in the two areas, wi th changes in antibody levels occurring at a younger age in the high i nfection area suggesting that immune responses are evolving more rapid ly in residents of this area. This result clearly demonstrates that an tibody levels are not a function of age alone.