Demonstration of immunoglobulin G antibodies against Onchocerca volvulus excretory-secretory antigens in different forms and stages of onchocerciasis

Abstract
The excretory-secretory (E-S) products of helminths are considered to comprise immunogenic molecules of high diagnostic value. In the present study, the serodiagnostic potential of the E-S products released in vitro by cultured female Onchocerca volvulus was investigated by enzyme-linked immunosorbent assay (elisa) and Western blotting using 190 serum samples from persons infected with O. volvulus and unexposed persons. The sensitivity of detection of anti-O. volvulus E-S antibodies was 94% for sera from patients with the generalized form of onchocerciasis and 100% for sera from patients with the chronic hyperreactive form (sowda). 95% of the sera from amicrofilaridermic persons, who subsequently became microfilaridermic within 2 years, reacted with O. volvulus E-S antigens and the donors were therefore regarded as having had a prepatent infection when first examined. These sera gave higher (P < 0·05) elisa optical densities than sera from the same persons obtained when they had become patent, indicating a loss of antibody reactivity after emergence of microfilariae. The specificity of the E-S elisa was 100% when sera of subjects infected with Wuchereria bancrofti were used, and at least 88% for Mansonella perstans sera. In Western blot analysis, the sera of persons with generalized onchocerciasis recognized 7 protein bands. Many E-S proteins were stained less intensely by the sera of subjects with generalized onchocerciasis than by the sera of sowda patients. Similar antigen bands were demonstrated using sera from the persons with prepatent infections.