Background Several genes have been identified so far in the pathogenesis of rheumatoid arthritis (RA). The most important region is the Human Leukocyte Antigen (HLA) that contributes to approximately half of the genetic susceptibility for RA. The association seems to be stronger or specific for anti-citrullinated protein antibodies (ACPA) positive disease. More than 30 other variants in potentially pathogenic genes located in non-MHC regions have been identified by recently performed genome wide analysis studies among individuals of European ancestry. These alleles explain about 23% of the RA genetic burden.
Objectives The aim of our study was to analyze the association of previously confirmed RA risk alleles in Slovak population and to determine their relationship and involvement in the increase of disease risk.
Methods Genetic analysis was conducted in 1224 samples (494 RA patients, 728 controls; 83% females, 17% males) with balanced geographic distribution. The presence of HLA-DRB1 alleles (DRB1*04:01, 04:04, 04:05, 04:08, 04:10, 01:01, 01:02, 10:01) considered as shared epitope (SE) was analysed by ELPHA (Enzyme Linked Probe Hybridization Assay). Eight non-MHC single nucleotide polymorphysms (SNPs): PTPN22 (rs2476601), STAT4 (rs75744865), CTLA4 (rs3087243), PADI4 (rs2240340), AFF3 (rs11676922), IRF5 (rs10488631), TNFAIP3 (rs5029937) and TRAF1/C5 (rs3761847) were genotyped by real-time PCR using the TaqMan 5′-allele discrimination assay. Principal component analysis (PCA) followed by discrimination analysis were applied to reveal the relations between these genetic factors and disease.
Results Our results show that of all genes analysed, the distribution of PTPN22, STAT4, IRF5 and PADI4 risk alleles and genotypes was significantly different between RA patients and healthy subjects in Slovak population (P< 0.05, chi-square test). The principal component analysis showed that the most important variables for sample discrimination are SE followed by STAT4, PADI4 and CTLA4. The discrimination analysis with forward selection have chosen SE as the most important variable for RA presence and showed that non-risk genotypes in STAT4, PTPN22, IRF5, PADI4, respectively are predictors for classifying subjects into healthy controls (F = 127.373; p = 0.0002).
Conclusions Genetic factors explain 11.1% of data variability in our cohort. The RA diagnose is significantly affected by presence of SE risk allele and RA associated alleles in genes STAT4, PTPN22, IRF5 and PADI4 with emphasis on heterozygozyty being sufficient to increase the risk of disease.
Acknowledgements Study was supported by grants: ATMOS N00024, VEGA 2/0018/12, ITMS 26240220058
Disclosure of Interest None Declared