Characterization of two corneal epithelium-derived antigens associated with vasculitis

PURPOSE. In a previous investigation into corneal autoimmunity, it tvas dem onstrated that a putative autoantigen, a protein of 66 kDa, present in bovi ne corneal epithelium, binds circulating autoantibodies in approximately 60 % of patients with Wegener's granulomatosis (WG). The aim of the present st udy was to characterize and identify the 66-kDa protein. METHODS. A purification protocol was established for the 66-kDa protein usi ng standard chromatography techniques. During the purification procedure it became clear that the 66-kDa protein detected in patients' sera was in fac t two proteins, both running at 66 kDa on sodium dodecyl sulfate-polyacryla mide gel electrophoresis, that eluted in different fractions on DE-52 chrom atography columns. These two proteins have been labeled bovine corneal epit helial antigen-A and -B (BCEA-A and BCEA-B). Further investigations of anti body binding have demonstrated that patients' sera bind to either one or th e other of these proteins with no cross-reactivity between them. Separated BCEA-A and BCEA-B protein extracts were immunoblotted with 27 WG patients' sera, 10 Churg-Strauss syndrome (CSS) patients' sera, 31 rheumatoid arthrit is (RA) patients' sera, and 40 healthy control subjects' sera from the bloo d bank. RESULTS. Forty-six percent of WG patients' sera had antibodies to one of th e 66-kDa antigens, whereas none of the healthy control subjects' sera had 6 6-kDa antibodies (P < 10(-5)). In the WG group, 31% were positive to BCEA-A (versus controls, P = 0.0023), and 15% were positive to BCEA-B. WG patient s with peripheral ulcerative keratitis (PUK) had a significant association with anti-BCEA-A antibodies when compared with healthy control subjects (50 %, P < 10(-6)). However, in the RA group with no eye disease there was an a ssociation with BCEA-A (25%, P = 0.011) but not in the RA group with PUK. T he frequency of anti-BCEA-B antibodies was significantly increased in patie nts with CSS (60%, P < 10(-7)). CONCLUSIONS. In summary, it has been shown that vasculitis patients have an tibodies to two 66-kDa corneal antigens and that autoantibodies to these an tigens are mutually exclusive. It has also been shown that antibodies to BC EA-B are associated with CSS, whereas BCEA-A antibodies are associated with WG and RA.