Onchocerca volvulus: Characterization of the clinical status of onchocerciasis patients using antibodies reactivity in enzyme-linked immunosorbent assays

Abstract

Serum anti-bodies, IgA, IgG class and subclasses (excluding IgG2) and IgM responses to crude sodium-duodecyl sulphate (SDS) extract of Onchocerca volvulus female adult worms, were tested with indirect enzyme-linked immunosorbent assay (ELISA). Antigenic epitopes defined by monoclonal anti-bodies (mAbs) designated CAM8, CAM22 and CAM28 were measured using inhibition (competitive) ELISA. Generally, cases (n=95) with proven parasitological and or clinical evidences had the highest mean optical density (OD) values for IgG, IgG1, IgG3 and IgG4 anti-bodies compared to the endemic normal (n=19) and non-endemic control (n=7) groups. Reactivity varied with infection status and was more in those having skin microfilariae than those without skin mf. Individuals with chronic skin diseases (n-20) had higher anti-body levels than those with optic nerve disease (OND, n=12). Serum inhibition of Cam22 was higher, while Cam28 was lower in those with, than without skin microfilariae. Those manifesting chronic skin diseases showed a remarkable increase in percentage inhibition of both mAbs in sharp contrast to the OND group. There were very few Cam8 responders which did not show any apparent clinical trend. It is not known whether this is an indication of selective tolerance or immunosupression. The study showed that anti-body responses to the parasite antigens had strong positive association (p<0.5) with the development of onchocercal skin diseases than eye-related lesions.