alpha-enolase is an antigenic target in primary Sjogren's syndrome.

OBJECTIVES: Although anti-cyclic citrullinated peptides antibodies are specific markers for rheumatoid arthritis (RA), they might be present in other diseases. Our aim was to assess the native or citrullinated antigens recognised by patients with primary Sjogren's syndrome (pSS) and to evaluate their association with clinical and serological features. METHODS: In an initial screening, we assessed the serum reactivity of 12 patients with pSS against native or in vitro citrullinated antigens of HEp-2 cells by immunoblotting. We identified a 47kDa band, which was preferentially recognised and corresponded to alpha-enolase. Thus, levels of IgA and IgG anti-native and citrullinated alpha-enolase antibodies were measured in 50 pSS patients, 20 RA patients and 20 healthy subjects (HS) by ELISA. RESULTS: We identified alpha-enolase as a predominant antigen recognised in pSS. These patients had higher levels of anti-citrullinated alpha-enolase IgG antibodies compared with RA or HS (p=0.003 and p<0.0001, respectively). Furthermore, there was an increase of IgG anti-citrullinated alpha-enolase vs IgG anti-non-citrullinated alpha-enolase antibodies in pSS patients (p=0.001), by contrast no difference was found in RA. The presence of IgA and IgG anti-non-citrullinated and anti-citrullinated alpha-enolase antibodies were not associated with any clinical manifestation whatsoever, including non-erosive arthritis among pSS, but an association of IgA anti-citrullinated alpha-enolase with anti-Ro/SSA antibodies was found. CONCLUSIONS: We characterised alpha-enolase as a dominant antigen in lysates of HEp- 2 cells in pSS. Nevertheless, their precise role in pSS remains to be elucidated.