[Association between the synovial expression of cyclic citrullinated peptide and susceptibility variants of HLA-DRB1 shared epitope alleles and PADI 4 gene single nucleotide polymorphisms in patients with rheumatoid arthritis].

Objective: To analyze the association between the synovial expression of cyclic citrullinated peptide (CCP) and susceptibility variants of HLA-DRB1 shared epitope (SE) alleles and/or peptidylarginine deiminase 4 (PADI4) gene single nucleotide polymorphisms (SNP) in patients with rheumatoid arthritis (RA).

Methods: From October 2008 to December 2011, 53 RA patients and 42 controls were enrolled. The expression of CCP in RA synovial tissues was detected by immunohistochemical assay with 6×His tagged anti-CCP single chain fragment V (ScFv) antibodies generated by pHEN2 phagemid recombinant antibodies display system. PADI4 SNP was genotyped by reverse transcription cDNA sequencing and heterozygote was DNA haplotype was mapped by TA clone sequencing. HLA-DRB1 SE alleles were analyzed by sequence specific primer-polymerase chain reaction (SSP-PCR).

Results: The prevalence of synovial CCP expression was significantly different between RA group and the control (76.9% and 11.4% respectively, P < 0.01). The frequencies of 2 SNPs (PADI4_89 G+ and PADI4_104 T+) varied significantly between the groups(P < 0.05). Compared with the major haplotypes, only these two minor alleles were associated with the increased RA susceptibility (OR = 3.67 and 2.53, P < 0.05). SE+ alleles was strongly associated with RA susceptibility (OR = 5.57, P < 0.01). The synovial expression of CCP in RA was strongly associated with SE+ alleles, only 2 minor SNPs (PADI4_89 G+ and PADI4_104T+) and the combination. Serum anti-CCP titers were significantly associated with SE+ alleles, PADI4_104T+, SE+/PADI4_89 G+ and SE+/PADI4_104T+ haplotype.

Conclusion: The synovial expression of CCP and the generation of anti-CCP antibodies are strongly associated with SE alleles and/or certain PADI4 gene SNP in RA.