Sensitivity of some Immunoglobulin G class and subclass antibodies to adult Onchocerca volvulus SDS-extracted antigens.

Indirect sandwich enzyme-linked immunosorbent assay (ELISA) was used to measure serum antibody responses in onchocerciasis patients. Apparently, IgG antibody class was more sensitive than IgG1, IgG3 and IgG4 responses to Onchocerca volvulus adult worms sodium duodecyl sulphate (SDS) extracted crude antigens in proven clinical and parasitological cases (n=95). Sensitivity varied slightly among the IgG1, IgG3 and IgG4 isotypes. All cases were positive for IgG, with 98%, 97% and 96% for the IgG isotypes respectively. Those with evidences of palpable nodule and skin microfilariae (n=32) were all seropositive (100%) for the three IgG isotypes-assays. A decrease in seropositivity was recorded among the assumed endemic normals or those with no evidence of infection (n=19), yet IgG recorded the highest with 90% and IgG4 was the least with 58%. It is concluded that the IgG1 and IgG3 assays have great potential as a screening test, while IgG4 could serve as a confirmatory test. These assays could be useful in detecting cases elusive to parasitological and clinical prognosis particularly in post-control surveillance situations. Keywords: Onchocerca volvulus, Serology, sensitivity, Screening, Diagnosis, Antigens and Antibodies