A majority of Brazilian patients with rheumatoid arthritis HLA-DRB1 alleles carry both the HLA-DRB1 shared epitope and anti-citrunillated peptide antibodies

• Main Authors: P. Louzada-Júnior, M.V.C. Freitas, R.D.R. Oliveira, N.H.S. Deghaide, R.A. Conde, M.B. Bertolo, E.A. Donadi
• Format: Article
• Language: English
• Published: Associação Brasileira de Divulgação Científica 2008-06-01
• Series: Brazilian Journal of Medical and Biological Research
• Subjects: Susceptibility to rheumatoid arthritis; HLA; Brazilians; Shared epitope; Anti-cyclic citrullinated peptide
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2008000600010

The objective of the present study was to evaluate the contribution of the shared epitope (SE), the rheumatoid arthritis (RA) protection model, and the occurrence of anti-cyclic citrullinated peptide (anti-CCP) antibodies in RA patients from a genetically diverse population. One hundred and forty Brazilian RA patients and 161 matched controls were typed for HLA-DRB1 alleles using amplified DNA hybridized with sequence-specific oligonucleotide probes or primers. Patients were stratified according to the presence or absence of SE (DRB1*0401, *0404, *0405, *0101, *1001, and *1402), of the DERAA alleles (DRB1*0103, *0402, *1102, *1103, *1301, *1302, and *1304), and X (all other alleles). Anti-CCP antibodies were measured by ELISA. The combined frequency of SE-positive alleles was significantly greater (76.4 vs 23.6%, P < 0.0001) than the controls. The SE/SE and SE/X genotypes were over-represented (P < 0.0001, OR = 6.02) and DERAA/X was under-represented in RA patients (P < 0.001, OR = 0.49), whereas the frequencies of the SE/DERAA, X/X and X/DERAA genotypes were not significantly different from controls. The frequency of anti-CCP antibodies was higher in SE-positive patients than in SE-negative patients (64.6 vs 44.7%, P = 0.03; OR = 2.25). Although the Brazilian population is highly miscegenated, the results of this study support the findings observed in most genetically homogeneous populations with RA; however, they are not mutually exclusive but rather complementary. The participation of DRB1-DERAA alleles in protection against RA was also observed (OR = 0.4; 95%CI = 0.23-0.68).