Use of monoclonal antibodies for the characterization of Onchocerca volvulus antigens

In order to identify Onchocerca volvulus antigens that could be considered as either diagnostic and/or immunoprophylactic, mouse monoclonal antibodies were produced against O. volvulus soluble antigens. Three were selected on the basis of their staining patterns in an indirect fluorescent antibody assay carried out on cryosections of adult O. volvulus. The first monoclonal antibody (K1-159) recognized a cuticular antigen which appeared in IFA to be restricted to the genus Onchocerca. However, neither Western blotting, nor the immunoprecipitation experiments performed on radiolabelled O. volvulus soluble antigen allowed detection of the corresponding antigen(s). The second monoclonal antibody (K1-126) bound to the muscle cells of adults. A 30,000 Mr antigen was detected by Western blot analysis of adult O. volvulus homogenate. This antigen was also recognised by sera from infected patients and corresponding antigenic determinants were detected in extracts of O. gutturosa, Acanthocheilonema viteae and Ascaris suum, but not in Brugia malayi. The third monoclonal antibody (K1-143) recognized egg shells and the surface of adult worms. The target epitope was not species specific and could be found in O. gutturosa, A. viteae, B. malayi and A. suum. The electrophoretic analysis of I-125 labelled soluble antigens and radiolabelled surface antigens of adult O. volvulus, showed numerous antigens (molecular weights ranging from 30,000 to 120,000 Mr) precipitated by K1-143. In an inhibition radioimmunoassay, K1-143 allowed the detection of corresponding antibodies in 79% of the O. volvulus patient sera tested.