Impaired antibody responses and loss of reactivity to Onchocerca volvulus antigens by HIV-seropositive onchocerciasis patients.

The impact of concomitant human immunodeficiency virus (HIV) infection on the antibody response of onchocerciasis patients to Onchocerca volvulus antigens (OvAg) was studied by Western blotting and enzyme linked immunosorbent assay (ELISA). Immunoglobulin G (IgG) antibodies in sera from 45 HIV-sero-positive O. volvulus microfilariae (mf) carriers (HIV+/Ov+) recognized significantly fewer distinct O. volvulus antigenic bands, and responded less frequently to all detected bands compared to sera from 61 matched HIV-seronegative mf carriers (HIV-/Ov+). 29% of 31 follow-up sera from the HIV+/Ov+ patients failed to react to many of the antigenic bands recognized by initial sera from the same patients. Among 4 HIV+/Ov+ persons examined for total CD4+ cells, loss of reactivity corresponded with low CD4+ total cell counts. In an OvAg ELISA, sera from the HIV+/Ov+ individuals had significantly lower IgG+IgM antibody levels than sera from the HIV-/Ov+ persons, and the sensitivity of the assay was 87% for the HIV+/Ov+ subjects compared to 100% for those who were HIV-/Ov+. It is concluded that HIV-infected onchocerciasis patients exhibit significantly impaired antibody responses to O. volvulus antigens, and tend to lose their reactivity to these antigens over time due to immune response abnormalities caused by the concomitant HIV infection.

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.