Background Rheumatoid Arthritis (RA) is one of the commonest forms of inflammatory arthritis affecting 0.5-1% of population worldwide. One of the poor prognostic features (PPFs) that has been set by the American College of Rheumatology in 2008 is the presence of specific sequence of amino acids at positions 70-74 in the third hypervariable region of the beta chain which is one of the constituents of the second class HLA haplotypes; DR. This sequence is called Shared Epitope (SE) and it facilitates the citrullination or deamination (i.e. post-translational modification) of Arginine into Citrulline and the formation of Anti-citrullinated peptides antibodies (ACPAs) which are the main pathogenic factor in RA.(1)
Objectives The aim of this case-control study was to detect the presence and patterns of Shared epitope in 150 Egyptian Rheumatoid arthritis patients admitted to the Alexandria Main University Hospital between June 2010 & May 2011. We then compared these patterns to those encountered in 200 control subjects who resided in the same city during the same period.
Methods We assigned study subjects into 2 groups; RA group (150 RA patients diagnosed based on the ACR/EULAR criteria 2010) and Control group (200 healthy subjects who were prepared to be living organ donors by our Transplantation Unit). We then used Dynal RELI TM SSO HLA-DRB Test and polymerase Chain Reaction (PCR) to detect the amino acid sequence at positions 70-74 on the DRB1 chain (shared epitope;SE) in both groups. We then tabulated and compared the data with proper methods.
Results We found that DR15 (with 70-74 sequence of QARAA) was the commonest allele (95/150=63.3%) among RA group when compared to control group with Odds Ratio (OR) of 8.45, while alleles other than the recognized shared epitopes (e.g. DR1, DR4, DR10, DR14) were more prevalent in control group and were even protective.
Conclusions DRB*1 1501/1502 (QARAA)was the commonest epitope among Egyptian RA patients included in our study and we concluded that it might be a new Shared Epitope (SE) in our population as it differs racially from other populations in which SE had been detected.
Gregersen PK et al. The shared epitope hypothesis. Arthritis Rheum 1987,30:2642-6.
Disclosure of Interest None Declared