IMMUNOLOGICAL CROSS-REACTIVITY IN THE PATHOGENESIS OF OCULAR ONCHOCERCIASIS

Purpose. Onchocerca volvulus, a filarial worm, is a major cause of inf ectious blindness and inflammatory eye disease. An autoimmune cause fo r ocular onchocerciasis has been suggested since the identification of a recombinant antigen of O. volvulus that shows immunologic cross-rea ctivity with a host ocular component of 44,000 M(r). The aim of this s tudy was to establish the distribution of the cross-reactive antigens in both host tissues and the parasite, and to determine if significant autoantibody responses to the host antigen could be detected in infec ted persons. Methods. The tissue and organ distribution of the 44,000 M(r) antigen was determined by immunocytochemistry and Western blot an alysis. Human autoantibody responses to the ocular antigen were demons trated by Western blot analysis using sera collected from persons with onchocerciasis, with and without posterior segment pathology, Bancrof tian filariasis, and Europeans with no filarial infection. Results. Th e tissue distribution of the 44,000 M(r) antigen correlates with the s ites of pathology in onchocerciasis and antibody reactivity against th is antigen could be detected in all persons with onchocerciasis and po sterior segment pathology. The antigen is also recognized by sera from persons with Bancroftian filariasis, but not from normal persons. Con clusions. A role is proposed for immunologic cross-reactivity in the p athogenesis of onchocerciasis and it is suggested that intraocular pre sentation of the cross-reactive parasite antigen by microfilariae is e ssential for the development of disease.