Association of the rs4646994 in ACE gene with susceptibility to tuberculosis in a region of the Brazilian Amazon.

Background: Tuberculosis (TB) is an infectious disease caused by the bacterium Mycobacterium tuberculosis and represents an important global public health issue. Single-nucleotide polymorphisms and INDELs are common genetic variations that can be located in genes associated with immune response and, therefore, they may have direct implications over the phenotype of susceptibility to infections like tuberculosis. This study aimed to investigate the association between the 17 genetic polymorphisms and susceptibility to tuberculosis in a Brazilian population.

Methods: This case-control study enrolled 283 individuals with active tuberculosis and 145 health care workers. Four INDELs and 13 single nucleotide polymorphisms and were genotyped using Multiplex PCR method and TaqMan SNP Genotyping Assays. Group comparisons for categorical variables were performed using the chi-squared test, whilst the t-Student test was used to analyze the continuous variables. Multiple logistic regression analyses were performed to estimate the odds ratio (OR) with 95% confidence intervals (CI). Deviation from Hardy-Weinberg equilibrium was assessed using chi-squared tests with Bonferroni correction. The results were analyzed comparing the genotypic distributions adopting the dominant model and the estimated values ​​of p corrected for multiple tests through FDR (False Discovery Rate) test.

Results: The HWE test confirmed that the genotypic frequencies for polymorphisms were balanced. The frequency of Del allele was 73 and 75%, in cases and controls respectively. Frequency of Del allele was significantly higher in the control group than TB group. The homozygous Del/Del genotype was present in 51.6% of cases and 58.6% of controls. The rare Ins/Ins genotype was present in only 7.6% of controls and 6% of cases. The ACE Del/Del genotype was significantly higher in the cases than in controls revealing significant protection for TB in the domain model (OR = 0.465; p < 0.005).

Conclusions: The Del/Del genotype of the rs4646994 in ACE gene was associated with susceptibility to tuberculosis. The identification of genetic variants responsible for susceptibility to tuberculosis will allow the development of new diagnostic tools for tuberculosis infection. These studies will help improve control and the future eradication of this disease.