Enhanced Diagnostic Specificity in Human Filariasis by IgG4 Antibody Assessment

By configuring an enzyme immunoassay to assess antibodies of the IgG4 subclass only, this work was able to eliminate serological false-positive results in 32 of 34 cross-reactive sera from patients with non-filarial parasitic infections and greatly enhanced specificity with minimal loss of sensitivity.

Abstract

Phosphocholine (PC), an immunodominant molecule present on a wide range of organisms, including filariae, evokes antibody responses that lead to false-positive reactions in routine serological assays. Humans essentially do not respond to PC in the IgG4 subclass; therefore, by configuring an enzyme immunoassay to assess antibodies of the IgG4 subclass only, we were able to eliminate serological false-positive results in 32 of 34 cross-reactive sera from patients with non-filarial parasitic infections. Specificity was thus greatly enhanced with minimal loss of sensitivity. Because preadsorption of these cross-reactive sera to remove antibodies to PC eliminated only approximately 50% of the original cross-reactivity, other shared epitopes (perhaps similar to PC) are also likely to be restricted by IgG subclass.