Age-dependency of serum isotype responses and antigen recognition in human whipworm (Trichuris trichiura) infection.

The present study examines the age-dependency of parasite-specific isotype responses and antigen recognition profiles of individuals within a Trichuris trichiura endemic community, in order to evaluate the significance of serum antibodies as determinants of observed age-related patterns of infection intensity. A high degree of individual heterogeneity is observed in isotype responses to separated T. trichiura antigens by Western blot. Recognition by IgG1 antibodies exhibits marked age-dependency. The age-profiles of IgG1 responses to selected antigens of 16-17 kDa and 90 kDa molecular weight reflect the age-related changes in current infection intensity at the population level. Similarly, mean age patterns of IgG2 responses to a 90 kDa antigen, and mean IgG4 responses to a 16-17 kDa antigen reflect mean infection levels. IgG3 responses are negligible, and for methodological reasons, both IgE and IgM specificities are not presented. IgA responses to separated antigens of 16-17 kDa and 90 kDa, exhibit age-profiles which may suggest the development of an IgA-mediated acquired resistance to T. trichiura with age. IgA levels remain elevated throughout early adulthood, when infection intensity levels markedly decrease, supporting the hypothesis that IgA antibodies may be significant in generating the convex nature of the age-infection profile of T. trichiura.