EPITOPE RECOGNITION OF RECOVERIN IN CANCER-ASSOCIATED RETINOPATHY - EVIDENCE FOR CALCIUM-DEPENDENT CONFORMATIONAL EPITOPES

Recoverin, a photoreceptor-specific calcium-binding protein, is a targ et for antibodies in human cancer-associated retinopathy. We have stud ied the binding properties of antirecoverin human autoantibodies and r at monoclonal antibodies (MAbs). The majority of antibodies to recover in, both in human disease and in animals immunized with recoverin, are directed against the same major immunodominant region, the sequence w ithin the residue 64-70 in proximity to the calcium-binding domain EF- hand 2. The immuno-dominant epitopes consist of linear and conformatio nal components. Our data demonstrate that the reactivity of autoantibo dies was dependent on conformational changes induced by the binding of calcium to recoverin. Some patients' antibodies could be detected by immunocytochemical methods and enzyme linked immunosorbent assay (ELIS A); however, their binding was abolished on Western blots; their epito pes were sensitive to SDS treatment, Immunization of Lewis rat with pu rified recoverin induces antibodies with properties strikingly similar to human autoantibodies. Comparison between the monoclonal antibodies (MAbs) and native autoantibodies showed that the calcium-induced chan ges in conformation were critical for specificities of the antibody ge nerated, The recoverin region within the sequence 61-82 is a key regio n for antibody binding; it also contains a major T-cell epitope, and i t is highly uveitogenic in Lewis rats. (C) 1996 Wiley-Liss, Inc.