HLA-B, DR and DQ antigens polymorphism in Tunisian patients with ankylosing spondylitis (a case-control study).

The objective of the study is to assess the distribution of HLA-B genes, HLA-B27 subtypes, HLA-DRB1 and HLA-DQB1 alleles in patients with ankylosing spondylitis (AS) and in control subjects in the Tunisian population and to compare their distribution with that found in other countries. This is a case-control study that included 100 consecutive patients (85 males/15 females) with AS according to the modified New York criteria and 100 control individuals. HLA-B, B27 subtypes and class II (DR and DQ) typing of all subjects was performed by polymerase chain reaction amplification with sequence-specific primers (PCR-SSP). HLA-B27 was found in 62% of patients against 3% in controls (P = 0.0000, OR = 52.6, 15.6 < CI < 166.7). On the other hand, B07 and B51 were significantly decreased in comparison with controls (P = 0.01, OR = 0.3, 0.1 < CI < 0.8 and P = 0.0000, OR = 0.2, 0.1 < CI < 0.4, respectively). Eight B27 subtypes were identified in the AS group, but the most frequent ones were B2702 (32%) and B2705 (24%). Among HLA-DRB1 alleles, a significant increase in DRB111 was found in comparison with controls (P = 0.01, OR = 2.2, 1.2 < CI < 4.5). However, DRB113 had a negative association with AS (P = 0.01, OR = 0.4, 0.2 < CI < 0.8). For HLA-DQB1 alleles, a significant positive association with DQB103 was observed in AS group (P = 0.03, OR = 1.8, 1.0 < CI < 3.4). Multivariate analysis by logistic regression revealed that DRB111 and DQB103 had no direct links with the disease, but were dependent on the presence of HLA-B27. Moreover, B07 and B51 seemed to have independently a negative correlation with AS, but DRB113 seemed to depend on B51. Haplotypes carrying B27 were significantly associated with AS and those carrying B07 or B51 were negatively correlated with the disease. In conclusion, our study confirms that B27 predisposes to AS while B07 and B51 are negatively correlated with the disease.