The HLA-DRB1 shared epitope is not associated with antibodies against cyclic citrullinated peptide in Chinese patients with rheumatoid arthritis

Objective: Rheumatoid arthritis (RA) is a destructive autoimmune polyarthritis that has been associated with a group of human leucocyte antigen (HLA)-DRB1 alleles that share a common amino-acid sequence at residues 70-74 called the shared epitope (SE). Recently, anti-cyclic citrullinated peptide (CCP) antibodies have also been reported to be associated with HLA-DR4 and have gained wide acceptance as early diagnostic markers for RA in Caucasian patients. The current study was performed to investigate whether the association between the SE (HLA-DRB1*0401/04/05/10) and anti-CCP antibodies is also present in Chinese Han patients with RA. Methods: One hundred and four RA patients and 122 healthy controls were recruited. HLA-DR4 was detected by the sequence-specific primer polymerase chain reaction (SSP-PCR) phototyping method. Anti-CCP antibodies and immunoglobulin M rheumatoid factor (IgM-RF) were measured by enzyme-linked immunosorbent assay (ELISA) and laser nephelometry, respectively. Results: Of the Chinese patients with RA, 76.5% exhibited anti-CCP antibodies compared with none of the controls (76.5% vs. 0%, p<0.001). The prevalence of the SE was significantly higher in patients with RA compared with controls [p=0.010, odds ratio (OR)=2.42, 95% confidence interval (CI)=1.16-5.07]. Among the HLA-DR4 alleles, the presence of HLA-DRB1*0401 was significantly higher in RA patients than in controls (p=0.0118, OR=9.68, 95% CI=1.13-448.8). In our study we found that the SE was not associated with production of anti-CCP antibodies (p=0.2899, OR= 1.920, 95% CI=0.52-8.89). Conclusions: The prevalence of the SE is significantly lower in Chinese RA patients, as compared with previous reports of a study using a Caucasian cohort, indicating that distinct genetic risk factors might be associated with anti-CCP antibody production. These data emphasized the complexity of the genetic effects of the major histocompatibility complex on the RA phenotype.