Cross-Reactivity of Antibodies against Leptospiral Recurrent Uveitis-Associated Proteins A and B (LruA and LruB) with Eye Proteins

Abstract

Infection by Leptospira interrogans has been causally associated with human and equine uveitis. Studies in our laboratories have demonstrated that leptospiral lipoprotein LruA and LruB are expressed in the eyes of uveitic horses, and that antibodies directed against LruA and LruB react with equine lenticular and retinal extracts, respectively. These reactivities were investigated further by performing immunofluorescent assays on lenticular and retinal tissue sections. Incubation of lens tissue sections with LruA-antiserum and retinal sections with LruB-antiserum resulted in positive fluorescence. By employing two-dimensional gel analyses followed by immunoblotting and mass spectrometry, lens proteins cross-reacting with LruA antiserum were identified to be α-crystallin B and vimentin. Similarly, mass spectrometric analyses identified β-crystallin B2 as the retinal protein cross-reacting with LruB-antiserum. Purified recombinant human α-crystallin B and vimentin were recognized by LruA-directed antiserum, but not by control pre-immune serum. Recombinant β-crystallin B2 was likewise recognized by LruB-directed antiserum, but not by pre-immune serum. Moreover, uveitic eye fluids contained significantly higher levels of antiibodies that recognized α-crystallin B, β-crystallin B2 and vimentin than did normal eye fluids. Our results indicate that LruA and LruB share immuno-relevant epitopes with eye proteins, suggesting that cross-reactive antibody interactions with eye antigens may contribute to immunopathogenesis of Leptospira-associated recurrent uveitis. Leptospira is the most common infectious cause of uveitis, a potentially debilitating inflammation of the eye. In our earlier work, we discovered that eye fluids of uveitic horses contain high levels of antibodies directed against novel leptospiral proteins, which we named LruA and LruB (Leptospiral recurrent uveitis associated proteins A and B). Significantly, antibodies raised against LruA and LruB also recognize lens and retinal tissue. We have now identified the cross-reactive eye proteins as alpha-crystallin B, vimentin and beta-crystallin B2. We also demonstrated that ocular fluids from uveitic horses contain high levels of antibodies recognizing alpha-crystallin B, vimentin and beta-crystallin B2. These data suggest that antibodies directed against leptospiral LruA and LruB during infection can also react with eye proteins, alpha-crystallin B, vimentin and beta-crystallin B2, potentially contributing to the severity of this eye disease.