ACQUISITION AND EXPRESSION OF HUMORAL REACTIVITY TO ANTIGENS OF INFECTIVE STAGES OF FILARIAL LARVAE

Measurement of anti-larval responses in filaria-exposed populations ma y shed light on the natural history of exposure to Wuchereria bancroft i. Using serum samples obtained by a cross-sectional survey of 172 ind ividuals from two neighbourhoods in Leogane, Haiti, antibody responses directed against infective stage filarial larvae (L(3)) were assayed by enzyme-linked immmunosorbent assay (ELISA), immunofluorescence (IFA ), and immunoblot for the presence of anti-larval antibodies. ELISA re sults indicated that virtually all members of both neighborhoods mount ed an anti-larval antibody response within the first five years of lif e, suggesting that exposure to infection is universal. In a multiple l inear regression analysis that modelled antibody levels as a function of age, gender, microfilaria status, and neighbourhood (as a proxy for transmission intensity), isotype-specific antibody levels were found to be significantly influenced by both age and neighbourhood. Antibodi es directed against the surface of L(3) also were age-dependent; the p revalence of IgG antibodies detected by IFA was significantly higher i n children than in adults. The prevalence of antibody recognition of 1 6.7 and 72.3 kDa L(3) antigens on immunoblots was significantly greate r for serum samples from microfilaraemic than amicrofilaraemic persons . These results suggest that antibody responses to larval antigens are influenced to varying degrees by age, transmission intensity, and mic rofilaraemia status.