MOLECULAR CHARACTERIZATION OF A PARASITE ANTIGEN IN SERA FROM ONCHOCERCIASIS PATIENTS THAT IS IMMUNOLOGICALLY CROSS-REACTIVE WITH HUMAN KERATIN

Onchocerca volvulus is a nematode that causes severe dermatitis and bl indness in humans. Prior studies have shown that immune complexes in s era from onchocerciasis patients contain parasite antigens with M(r) o f 23,000 and 65,000-70,000. Monoclonal antibody OV-1 binds to these an tigens and to corresponding antigens in adult worm extracts and in vit ro culture supernatants. OV-1 was used to immunoscreen an O. volvulus adult worm cDNA library. Clone OV1CF contains a 1632-bp open-reading f rame that codes for a protein with a predicted M(r) of 63,000. The ded uced protein sequence of OV1CF has 78% identity with Ascaris lumbricoi des intermediate filament A and 40%-50% identity with several mammalia n intermediate filaments. Antibodies raised to OV1CF bind to human ker atin, and some sera from onchocerciasis patients contain antibodies to OV1CF and to keratin. Thus, immune complexes from onchocerciasis pati ents contain a parasite antigen that is immunologically cross-reactive with human intermediate filament proteins.