Worm burden and host responsiveness in Wuchereria bancrofti infection: Useof antigen detection to refine earlier assessments from the South Pacific

A population from the Witchereria bancrofti-endemic island of Mauke was ree valuated retrospectively by use of the Og4C3 circulating antigen (CAg) enzy me-link-ed immunosorbent assay to assess active infection in relation to ho st responses by age and gender. Use of microfilaremia (Mf) alone misclassif ied similar to 50% of infected people, although CAg and Mf levels were posi tively correlated. Levels of CAg peaked between those aged 31-60 years; men aged > 60 years had a significantly higher CAg prevalence (> 90%) than wom en. Filaria-specific immunoglobulin (Ig) G4 reached maximum levels in both genders at age 51-60 years. By analysis of variance, both age and gender si gnificantly influenced CAg and IgG4, with men having higher levels of both in the total Population. Individuals positive for CAg had significantly low er lymphocyte proliferation responses to parasite antigen than did CAg-nega tive people, regardless of clinical status. This study reemphasizes the imp ortance of CAg measurements for accurately assessing filarial prevalence an d clinical status and demonstrates the relationship between active infectio n and immune responsiveness.