Background : Pulmonary tuberculosis is caused by
Mycobacterium tuberculosis
. It is a multifactorial disease with both host as well as pathogen factors contributing to susceptibility and protection from the disease. Various reports have highlighted important roles of lung surfactant protein D (SP-D), mannan-binding lectin (MBL) and I-NOS in innate immune defense against
M. tuberculosis
Aims : The present study investigated the role of polymorphisms in three candidate genes encoding Lung surfactant protein D, Mannan binding lectin and Inducible Nitric oxide synthase, in susceptibility and protection to pulmonary tuberculosis.
Settings and Design : A case-control association study of SNP's in lung surfactant protein D (SP-D), mannan-binding lectin (MBL) and
I-NOS with pulmonary tuberculosis in Indian population was carried out. This involved sequencing of all the coding exons of lung surfactant protein D (SP-D)
, while, exon 1 (collagen region) and exon 4 (carbohydrate recognition domain) of mannan-binding lectin (MBL) and exons 2, 8 and 16 of
I-NOS and their flanking intronic regions for single nucleotide polymorphisms in DNA samples isolated from 30 pulmonary tuberculosis patients and 30 controls of Indian population.
Statistical analysis: Various allele frequencies were calculated using online two by two table (home.clara.net/sisa/). Odds ratio and
P values were calculated at 95% confidence interval (CI).
Results : A total of fourteen single nucleotide polymorphisms (5 in
SP-D , 5 in
MBL and 4 in
I-NOS ) were observed of which four (G459A
SP-D , G274T
I-NOS , G1011A and T357G
MBL ) have not been reported earlier. Four single nucleotide polymorphisms
viz. G459A of exon 7 of SP-D (
P =0.00, odds ratio (OR) = 4.96, 2.18 OR< 11.31), G875A of exon 1 of MBL (
P = 0.00 or= 3.85 1.66 OR< 8.88), G300A of intron 8 (
P =0.00 or=4.04, 2.20< OR< 7.42) and G274T of intron 16 of I-NOS (
P =0.00 or=4.46, 2.40 OR< 8.28) showed significant association with TB in Indian population.
Conclusion: The present study has led to identification of 4 SNP's in
SP-D ,
MBL and
I-NOS associated with pulmonary tuberculosis in Indian population.
