Objective: To investigate the possible association between the SNP in the 5' untranslated region (5' UTR) of the human beta defensin 1 (DEFB1) gene and the susceptibility to pulmonary tuberculosis (PTB) in Chinese Han population.
Methods: In this case-control study, venous blood was collected from 102 patients with PTB and 148 healthful persons. Genomic DNA was extracted using whole blood DNA extraction kit. The -52A/G, -44C/G and -20A/G SNP were genotyped by PCR-directed sequencing. The genotypes and allele frequency were analyzed using the χ(2) test. The linkage disequilibrium and haplotype were analyzed by SHEsis software.
Results: A total of 102 patients with PTB (69 males and 33 females, (53.42 ± 20.22) years old) and 148 healthy control cases (95 males and 53 females, (50.67 ± 14.53) years old) were enrolled, with no difference in gender and age (all P values > 0.05). DEFB1 -44 CC genotype was significantly more frequently found in PTB patients than in control group (81.4% (83/102) vs 66.9% (99/148), χ(2) = 5.114, P < 0.05, OR = 2.096, 95%CI: 1.095 - 4.011), so was -44C allele (89.2% (182/204) vs 80.4% (238/296), χ(2) = 6.975, P < 0.05, OR = 1.576, 95%CI: 1.086 - 2.286). No difference in -52 A/G and -20 A/G SNP was observed between the two groups. The proportion of the GGG (-52/-44/-20) haplotype was lower in PTB patients than in the control group (0.030 vs 0.081, χ(2) = 5.629, P < 0.05, OR = 0.348, 95%CI: 0.140 - 0.863). No linkage disequilibrium was found among the SNP of the three sites (D' values were 0.132, 0.064, 0.088; r(2) values were 0.003, 0.002, 0.003; all P values > 0.05).
Conclusion: These results suggest that the SNP of DEFB1 5' UTR is associated with susceptibility to PTB in Chinese Han population. -44 C→G SNP and the related haplotype (GGG) might play a protective role in the pathogenesis of PTB.