Gene Polymorphism of Tumor Necrosis Factor-Alpha in a Sample of Iraqi Pulmonary Tuberculosis Patients

The study aimed to investigate the association between tumor necrosis factor (TNF gene) alleles and pulmonary tuberculosis (PTB) in a sample of Iraqi patients, in which a total of 94 patients were investigated, in addition to 80 age, gender and ethnicity matched controls. All subjects were genotyped by polymerase chain reaction with sequence specific primers (SSP-PCR) method at two positions of TNF gene; -308 and -238 (TNF-308 and TNF-238), which were presented with three genotypes (GG, GA and AA) at both positions. At position -308, a significant (P = 6.9 x 10-5) decreased frequency of GG genotype was observed in PTB patients compared to controls (60.6 vs. 87.5%), and the preventive fraction of such difference was 0.68. In contrast, the genotype GA was significantly (P = 1.3 x 10-4) increased in patients (38.2 vs. 12.5%), and the associated relative risk and etiological fraction were 4.34 and 0.30, respectively. The corresponding TNF-308 alleles (G and A) also showed variations between patients and controls. Allele G was decreased (79.8 vs. 93.8%), while C allele was increased (20.2 vs. 6.2%) in patients, and both differences were significant at a P of 1.5 x 10-4. However, at position -238, neither TNF-238 genotypes nor alleles demonstrated a significant difference between patients and controls. The present results suggest that the GG genotype and G allele of TNF gene at position -306 may be associated with a protection against PTB in Iraqi population. Keywords: Tumor necrosis factor; Gene polymorphism, PCR; Pulmonary tuberculosis