Detection of Wuchereria bancrofti specific antigens in the serum of endemic residents.

A sandwich enzyme-linked immunosorbent assay (s-ELISA) is developed for detecting circulatory antigens in individuals infected with Wuchereria bancrofti in an endemic area using antibody (Ig) against excretory-secretory-metabolic antigens of the microfilariae raised in rabbit (anti-mf-ESM) and labelled with alkaline phosphatase (ESM-Ig-conjugate). An optical density reading of a sample greater than 0.075 (after subtracting the background) was taken as positive in the s-ELISA. When homologous (WbmfESM) and heterologous (sonicated antigens of human and model intestinal helminths-Ascaris lumbricoides. Trichuris muris, Necator americanus and Strongyloides ratti) antigens were spiked at 2.5, 5, and 7.5 microgram/well, rabbit ESM-Ig-conjugate reacted specifically with the samples containing homologous antigens. Amongst 21 sera in five different categories of non-endemic group, only four (two in helminth-ve and two in mixed intestinal helminthic group) were found to be positive. Out of 19 sera from endemic residents, three of 7 endemic normals (ENS), all microfilaraemics (mf+) (n = 7) and 4 out of 5 elephantoid patient sera were positive. This preliminary data show that rabbit mfESM-Ig-conjugate is efficient in detecting sera samples containing antigenic components of microfilariae. This assay was found to be discriminatory in detecting individuals carrying current infection. This test requires further validation with larger number of samples and it may prove of value for detecting lymphatic filarial infection.