Immunodiagnostic studies on Onchocerca volvulus and Mansonella perstans infections using a recombinant 33 kDa O. volvulus protein (Ov33).

A total detergent-soluble extract of adult female Onchocerca volvulus (OvAg) and a recombinant O. volvulus protein (Ov33) linked to glutathione-S-transferase (GST) were compared with regard to their serodiagnostic suitability for differentiating between O. volvulus and Mansonella perstans infections in a region endemic for both filarial worms in western Uganda. Using OvAg in an enzyme-linked immunosorbent assay (ELISA), 98.8% sensitivity was obtained examining 84 O. volvulus microfilariae (mf) carriers living in the hyperendemic area. However, 5 of 18 (28%) sera from M. perstans mf carriers without O. volvulus mf, from another area hypoendemic for O. volvulus, cross-reacted with OvAg. Using the recombinant antigen Ov33-GST in an ELISA and Western blot assay, sensitivity for O. volvulus remained high (97.2% and 98.8% respectively) while none of 90 sera from M. perstans mf carriers reacted positively. Both antigens were used to examine a batch of sera from 260 persons living in the onchocerciasis hyperendemic area who did not have mf in their skin snips (9.5% of 2728 persons examined); 116 of these sera (44.6%) were positive in the OvAg ELISA, compared to 85 (32.7%) and 69 (26.5%) which were positive in Ov33-GST ELISA and Ov33-GST Western blot, respectively. Reaction with GST alone was minimal. The recombinant antigen Ov33 efficiently differentiates between O. volvulus and M. perstans infections, and is sensitive when used to detect patent and prepatent or low-level O. volvulus infections.