DEMONSTRATION OF IMMUNOGLOBULIN-G ANTIBODIES AGAINST ONCHOCERCA-VOLVULUS EXCRETORY-SECRETORY ANTIGENS IN DIFFERENT FORMS AND STAGES OF ONCHOCERCIASIS

The excretory-secretory (E-S) products of helminths are considered to comprise immunogenic molecules of high diagnostic value. In the presen t study the serodiagnostic potential of the E-S products released in v itro by cultured female Onchocerca volvulus was investigated by enzyme -linked immunosorbent assay (ELISA) and Western blotting using 190 ser um samples from persons infected with O. volvulus and unexposed person s. The sensitivity of detection of anti-O. volvulus E-S antibodies was 94% for sera from patients with the generalized form of onchocerciasi s and 100% for sera from patients with the chronic hyperreactive form (sowda). 95% of the sera from amicrofilaridermic persons, who subseque ntly became microfilaridermic within 2 years, reacted with O. volvulus E-S antigens and the donors were therefore regarded as having had a p repatent infect-ion when first examined. These sera gave higher (P<0.0 5) ELISA optical densities than sera from the same persons obtained wh en they had become patent, indicating a loss of antibody reactivity af ter emergence of microfilariae. The specificity of the E-S ELISA was 1 00% when sera of subjects infected with Wuchereria bancrofti were used , and at least 88% for Mansonella perstans sera. In Western blot analy sis, the sera of persons with generalized onchocerciasis recognized 7 protein bands. Many E-S proteins were stained less intensely by the se ra of subjects with generalized onchocerciasis than by the sera of sow da patients. Similar antigen bands were demonstrated using sera from t he persons with prepatent infections.