LONGITUDINAL ANALYSIS OF THE DEVELOPMENT OF FILARIAL INFECTION AND ANTIFILARIAL IMMUNITY IN A COHORT OF HAITIAN CHILDREN

Longitudinal studies are being conducted in Leogane, Haiti to investig ate the relationship between acquisition of filarial infection and dev elopment of antifilarial immunity as well as the impact of maternal in fection on this relationship. Children (0-24 months of age) residing i n Leogane were enrolled and were examined periodically to monitor para sitologic status and to collect serum for antigen and antifilarial ant ibody determinations. To examine the development of filarial antigenem ia and antifilarial antibody responses in this cohort, serum samples w ere selected from a cross section of the population at two (n = 82) an d four years of age (n = 76). Antigen prevalence increased from 6% amo ng two-year-olds to more than 30% among four-year-olds, but in only on e four-year-old child were microfilaria detected in a 20-mu l smear. T he proportion of antigen-positive children born to antigen-positive mo thers was higher than the proportion of antigen-positive children born to antigen-negative mothers (9.8% versus 0% for two-year-olds; P = 0. 15; and 39.6% versus 22.7% for four-year-olds; P = 0.18). Antifilarial IgG4 levels were significantly higher among antigen-positive children at both two and four years of age (P < 0.001). In analyses of paired samples, antifilarial IgG4 responses increased significantly more amon g children who acquired infection by four years of age than among chil dren who remained antigen negative, whereas antifilarial IgG1 and IgG2 responses changed equally for antigen-positive and -negative children . Antifilarial antibody levels were not influenced by maternal infecti on status, but were significantly influenced by age, antigen status, a nd the neighborhood within the community. These results provide eviden ce that children acquire infection early in life and suggest that anti filarial antibody responses may peak in early childhood.