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Summary Background Anticentromere antibodies (ACAs) have been observed in patients with autoimmune hepatitis (AIH) and hepatitis C virus (HCV)-related chronic liver disease (CLD-C) as well as those with primary biliary cirrhosis (PBC). However, little is known about the differences in immune responses to the centromere proteins among these liver diseases. Objective By synthesizing recombinant proteins consisting of the N- and C-termini of major centromere proteins, we investigated the humoral responses against them in each disease. Results Eight of the 754 (1%) patients with CLD-C, 14 of the 57 (25%) patients with PBC and six of the 38 (16%) patients with AIH were seropositive for ACAs. There were no significant differences in ACA titers determined by an indirect immunofluorescent method among the groups of patients with CLD-C, PBC and AIH. However, the analysis of immunoreactivities against each recombinant protein revealed that the titers of IgG-subclass autoantibodies against the C-terminus of centromere protein (CENP)-B were significantly higher in the CLD-C patients than in the AIH patients. Likewise, the titers of IgM-subclass autoantibodies against the N-terminus of CENP-A were significantly higher in the PBC group than in the CLD-C group. The ACA-positive patients who developed liver cirrhosis had significantly higher titers of the IgA-subclass autoantibodies against the C-terminus of CENP-C than those who did not. Conclusion These findings suggest that immunoreactivities against the fragments of centromere proteins show distinct patterns among CLD-C, PBC and AIH and that the determination of immunoreactivities against the centromere proteins may be useful for the prediction of disease progression.

Anticentromere antibody (ACA) is generally considered to be a serological marker for systemic sclerosis (SSc). ACA-positive patients with primary Sjögren's syndrome (pSS) have also been reported. ACA often recognizes centromere proteins (CENPs): CENP-A, CENP-B, and CENP-C, and sometimes reacts to heterochromatin protein 1 (HP1)α. We compared the reactivity against six different epitopes for three ACA-positive clinical subgroups: 29 patients with pSS, 36 SSc patients with sicca symptoms, and 28 SSc patients without sicca symptoms.We utilized enzyme-linked immunosorbent assays (ELISAs) with recombinant proteins covering six different epitope regions of ACA (the amino terminus (Nt) of CENP-A, CENP-B, and CENP-C, the carboxyl terminus (Ct) of CENP-B and CENP-C, and HP1α).The patients with pSS were found to have IgG-class autoantibodies against CENP-C-Nt and HP1α, and IgA-class autoantibodies against CENP-C-Ct with significantly higher frequencies than the SSc patients with or without sicca symptoms. The positive predictive value and the negative predictive value of the combination of these three autoantibodies for pSS were 73% and 82%, respectively, for pSS.Based on the result that reactivities against CENP-C and HP1α in patients with pSS differ from those in patients with SSc, we propose ACA-positive pSS as a clinical subset of SS that is independent of SSc.

We evaluated the utility of HEp-2 cells transfected with the 60 kDa SS-A/Ro as a substrate for indirect immunofluorescence (IIF-HEp-2000) to compare several methods for screening Japanese serum samples for anti-SS-A/Ro antibodies. Serum samples from 243 Japanese patients were analyzed by IIF for anti-nuclear antibodies (ANAs), using HEp-2 cells (IIF-HEp-2), and for anti-SS-A/Ro 60 kDa antibodies, using IIF-HEp-2000 and enzyme-linked immunosorbent assay (ELISA). We performed double immunodiffusion and immunoprecipitation experiments, using the products of in vitro transcription and translation, to analyze sera for which there were discrepancies in the results of the IIF-HEp-2000 assay and ELISA. A total of 93 of the 243 serum samples showed findings positive for anti-SS-A/Ro antibodies. Notably, eight of the 93 sera gave positive findings for anti-SS-A/Ro antibodies by IIF-HEp-2000 but ANA-negative by IIF-HEp-2 analysis. Seven sera possessing anti-SS-A/Ro antibodies gave false negative results by IIF-HEp-2000; however, those samples were all ANA positive. ELISA for anti-SS-A/Ro antibodies showed that five and two samples gave false positive and negative results, respectively. Analysis by IIF-HEp-2000 was useful for primary screening of patients for ANAs, especially for anti-SS-A/Ro antibodies; the test could detect anti-SS-A/Ro antibodies not identified on standard substrates in samples obtained from the Japanese population, as reported for the Caucasian population.