Relationship between γ-interferon gene polymorphisms and susceptibility to brucellosis infection

Interferon-gamma (IFN-) is a pro-inflammatory cytokine that plays a pivotal role in the defense mechanism against Brucella infection. It was hypothesized that the IFN- in (+874 A/T in intron 1) TT and +5644 T/A, TT genotypes, which are reportedly associated with high IFN production, are associated with susceptibility to brucellosis in Iranian subjects. Genotyping of these IFN- variants by an allele-specific polymerase chain reaction method was performed in 281 subjects, comprising 153 patients with active brucellosis and 128 healthy controls. It was found that the +874 minor allele (A) and homozygote genotype (AA) were significantly more frequently present in brucellosis patients than in controls (OR=2.588; 95% CI, 1.313-5.104; P=0.006 for the AA genotype; OR=1.575; 95% CI, 1.124-2.216; P=0.010 for the A allele). However, the allelic and genotypic distribution of the IFN- polymorphism at position UTR5644 A>T did not differ significantly between patients and controls (P>0.05). The distribution of haplotypes in this study suggests that the T/A haplotype (+874/UTR5644), which was present more frequently in controls than in patients, may protect subjects against Brucella infection. It is suggested that IFN- +874 AA genotype and A allele are risk factors for developing brucellosis infection in Iranian subjects.