TNF-alpha, TGF-beta, IL-10, IL-6 and IFN-gamma gene polymorphisms as risk factors for brucellosis.

Polymorphisms in the regulatory regions of cytokine genes can affect the level of cytokine production, and may be associated with predisposition to infectious diseases as well as different clinical outcomes. The aim of this study was to investigate the association of the polymorphisms of IL-6 (-174), IL-10 (-1082, -819), IFN gamma (+874), TGF beta (codon 10, codon 25) and TNF alpha (-308) genes with brucellosis in terms of susceptibility and resistance to the disease or occurrence of focal complications. A case control study was carried out in 85 patients with brucellosis and 85 healthy controls. We studied the polymorphisms of IL-6, IL-10, IFN-gamma, TGF-beta 1 and TNF alpha genes, using the polymerase chain reaction with sequence-specific primers. The IL-10 CT, TGF-beta 1 codon 10 CC and TGF-beta 1 codon 25 GG genotypes were significantly more frequent in the patients compared to the controls. The IL-10 CC genotype was higher in the controls than in the patients. In addition, the IL-6 (-174) GG genotype was more frequent in the patients without focal forms, while the GC genotype was more frequent in the patients with focal forms. Our results showed that polymorphisms of IL-10 (-819) and TGF beta 1 codons 10 and 25 were associated with susceptibility or resistance to brucellosis. The IL-6 (-174) GC genotype may be a risk factor for the development of focal complications of brucellosis, whereas the GG genotype may be a protective factor against brucellosis.