Purification and characterization of circulating <em>Onchocerca volvulus</em> antigens from epileptic and non-epileptic onchocerciasis patient sera

Abstract

Studies conducted during the past 25 years to investigate the possible relationship between onchocerciasis and epilepsy have led to contradictory results. In the present study aimed at contributing to the investigation of a possible relationship between onchocerciasis and epilepsy, we proceeded to purify and characterize circulating O. volvulus antigens from sera of onchocerciasis patients with and without epilepsy. Out of 539 onchocerciasis patients included in the study, sera from 78 epileptics and 20 non epileptics with high antigen titres were separately pooled and subjected to affinity purification using immunosorbent columns prepared using human and rabbit anti-O. volvulus IgG antibodies. Eluates of purified circulating O. volvulus antigens were concentrated, and then the protein contents were determined using the Bradford method. The antigenicity of the purified antigens was evaluated in a direct ELISA using onchocerciasis patient sera. Finally, the molecular composition of the purified proteins was determined by SDS-PAGE. The purified antigens were highly antigenic and there was no significant difference in the reaction profiles of the two groups or categories of patients. SDS-PAGE analysis showed that the purified antigens ranged from 31.63 to 102.40 KDa and there was no difference in the molecular composition of antigens purified from sera of the two classes of patients. Based on this antigen profiling between epileptic and non-epileptic onchocerciasis patients, we cannot conclude with certainty whether onchocerciasis is really a cause of epilepsy in areas where it is hyperendemic as predicted by some epidemiological studies.

Keywords: Antigen-detection ELISA, Immunoadsorbent columns, Affinity chromatography, Antigenicity, SDS-PAGE