AGE-RELATED PREVALENCE OF ANTIBODIES TO INFECTIVE LARVAE OF WUCHERERIA-BANCROFTI IN NORMAL INDIVIDUALS FROM A FILARIA-ENDEMIC REGION

Antibody isotypic levels (IgM, IgE and IgG subclasses) to infective larvae (L(3)) of Wuchereria bancrofti were measured in 104 normal individuals from a filaria-endemic region in Otissa. The titres of antibodies were considerably higher in adults (n=25, 25.1+/-3.8 year) than in children (n=52, 7.1+/-2.1 year). Young children (n=14) less than four years were seronegative to all isotypes other than IgM, the sere-conversion to which was achieved in the children (n=15) by the age of 7.5+/-1.2 years. The prevalence of other isotypes increased with age and reached a maximum in early adulthood (18.6+/-1.6 years), which persisted in older adults (>30 years). However, the increase in IgG(3) prevalence with age was less marked. IgG(2) was detected only after 10 years of age. Compared to the high prevalence (100%) of IgM, IgE, IgG(1) and IgG(2) in adults. IgG(3) and IgG(4) prevalences were low, 35% and 28% respectively. IgA level to L(3) antigen was found to be extremely low even in adults. These data indicate that the prevalence of L(3) antibodies was different for different isotypes and the acquisition of antibody response essentially followed an age dependent pattern.