Genetic polymorphism in Mannose Binding Lectin-2 (MBL-2) and Vitamin D Receptor (VDR) is known to influence the susceptibility to tuberculosis. The objective of the present study was to evaluate the frequency distribution of the MBL-2 promoter and structural polymorphism (−550 H/L, −221 Y/X, and +4 P/Q; R52C, G54D, and G57F) and VDR polymorphism (FokI, BsmI, TaqI, and ApaI) in healthy individuals of Indian population and comparative analysis with the global population. In Indian population, the frequency of VDR mutant alleles “f” for FokI, “b” for BsmI, “t” for TaqI, and “a” for ApaI was 25%, 54%, 30%, and 61%, respectively. The allelic frequency of MBL-2 promoter polymorphism −550 H/L was H versus L: 32% versus 68%, −221 Y/X was Y versus X: 68% versus 32%, and +4 P/Q was P versus Q: 78% versus 22%. Mutant allelic frequencies of the MBL-2 exon 1 D, B, and C allele were 6%, 11%, and 3%, respectively. Comparative analysis with global populations showed a noteworthy difference for MBL-2 and VDR polymorphism frequency distribution, indicating the ethnic variability of Indians. The study signifies the differential distribution of susceptibility genes in Indian population, which can influence the understanding of the pathophysiology of tuberculosis in Indian population.
1. Introduction
Mycobacterium tuberculosis is one of the most ancient and life-threatening pathogens for mankind. More than one-third of the world’s population harbours the tubercle bacilli asymptomatically. However, only 5–10% of the infected individuals develop the disease [1]. In 2012, one-third of the global deaths occurring due to tuberculosis were reported in India and South Africa [2]. The interindividual variation in disease susceptibility and progression is a consequence of the varied extent of host response to M. tuberculosis. Genetic polymorphism in Mannose Binding Lectin-2 (MBL-2), a central player in the innate immune response and Vitamin D Receptor (VDR), an immunomodulator has been found to influence the susceptibility to tuberculosis [3, 4].
The MBL-2, a pattern recognition receptor of the innate immune system [5], acts as the first line of defense against infectious agents including M. tuberculosis. The MBL-2 enhances the opsonization and facilitates phagocytosis of infectious agents. Variations in MBL-2 gene influences tuberculosis susceptibility and the reports of MBL-2 gene involvement have been contradictory [6, 7]. Low levels of MBL-2 have been associated with protection against tuberculosis [8–10] while others have reported its association with tuberculosis susceptibility [11–13]. The lower levels of MBL-2 have been attributed to the structural gene variants in the first exon of the gene: MBL-2 D (C>T transition, Arg52Cys), B (G>A transition, Gly54Asp), and C (G>A transition, Gly57Glu) are collectively referred to as O allele while wild type is referred to as A allele [14, 15]. These results in the amino acid substitution in collagen like domain, significantly decreasing the functional MBL-2 serum levels [16]. The Single Nucleotide Polymorphisms (SNPs) in the promoter region, MBL-2 H/L (C>G transition, −550 bp in promoter region), Y/X (G>C transition, −221 bp in promoter region), and P/Q (C>T transition, +4 bp in 5′ UTR region) [17], influence the MBL-2 transcription thus modulating the MBL-2 protein levels in serum.
The role of 1,25-dihydroxyvitamin D3, an active metabolite of vitamin D in the calcium metabolism regulation, is well established. Vitamin D3 plays a key role of an immunomodulatory hormone, whose actions are mediated through binding to a nuclear receptor, Vitamin D Receptor (VDR). Vitamin D3 activates macrophages enhancing the phagocytosis and thus restricts the M. tuberculosis proliferation [18]. The polymorphism in the VDR gene may influence the VDR activity, subsequently associating it with increased susceptibility to tuberculosis and various clinical outcomes [3, 19]. Several polymorphisms have been identified in VDR genes recognized by restriction endonucleases. These include FokI in the coding region and BsmI, ApaI, and TaqI in the 3′ untranslated region. The FokI polymorphism (F/f, C>T) in exon 2 results in VDR length differentiation by three amino acids producing a less active 3 amino acid-elongated VDR when encoded by the “f” allele [20]. BsmI polymorphism (B/b, T>G) and ApaI polymorphism (A/a, T>G) occur in the intron separating exons 8 and 9. TaqI polymorphism (T/t, T>C) in exon 9, a synonymous SNP coding for isoleucine, enhances the VDR mRNA stability [21].
The aim of the present study was to estimate the allele and the genotype frequency distribution for MBL-2 and VDR gene polymorphism in Indian population and comparative analysis of the observed data with global population reported previously to get a glimpse of ethnic variability among different populations across the world.
2. Materials and Methods2.1. Study Population
The unrelated disease-free healthy subjects’ samples were recruited at B. V. Patel PERD Centre, Ahmedabad, Gujarat. The age of healthy subjects was in the range of 19–50 years with male/female ratio of 5.4. The control individuals had no known history of tuberculosis. Healthy group comprised of individuals from western and northern parts of the country. Populations within Indian subcontinent are heterogeneous and represent elements of several ancestries. However, ancestry lineages are no longer demarcated in present geographical regions. Separate methods were used for the genotyping studies for MBL-2 and VDR. Samples which did not meet particular quality parameters for analysis were not included. This resulted in variation of sample size for all the polymorphisms studied. The MBL-2 polymorphisms were studied by sequencing of samples in 96-well plate; two of the samples failed to amplify. Genomic DNA of healthy subjects was extracted using phenol-chloroform extraction method [22]. Institutional ethical clearance and written informed consent of the blood donors were obtained prior to blood collection from the individuals.
2.2. Genotyping
The six SNPs in the MBL-2 gene promoter and exon 1 (GenBank accession: rs11003125, rs7096206, rs7095891, rs5030737, rs1800450, and rs1800451) were genotyped by directly sequencing the 964 bp region amplified from genomic DNA samples of 94 disease-free healthy subjects. A preamplified PCR product of amplicon size 964 bp bracketing the region surrounding the polymorphic sites was sent for direct sequencing to Macrogen Inc., Korea, using a pair of specific primers (mentioned in Table 1).
Primers and annealing temperature used in genotyping MBL-2 and VDR polymorphism.
The PCR amplification was performed for the VDR gene (FokI, BsmI, TaqI, and ApaI) polymorphism in a volume of 50 µL in presence of 5 µL of 10x PCR buffer provided with the Taq polymerase, 1.5 mM MgCl2, 0.2 mM dNTP mix, 0.2 µM of each primer (mentioned in Table 1), 1-2 µL of 1 U/µL Taq polymerase, and 280 ng of genomic DNA and subjected to thermal cycler at annealing temperatures mentioned in Table 1. The amplified products were electrophoresed and visualized in ethidium bromide stained 1.5–2% agarose gels. The amplified PCR products were subjected to restriction fragment length polymorphism (RFLP) using respective restriction enzymes. The genotypes were assigned in accordance with the number of bands obtained after the digestion for each of the four polymorphisms (for details see Table 2).
The restriction digestion reaction conditions and genotype assignment after the digestion.
SNP
Incubation Temperature
Homozygous wild type
Heterozygote
Homozygous mutant
% agarose gel
FokI
37°C
265 bp
265 bp, 195 bp, 70 bp
195 bp, 70 bp
2%
BsmI
37°C
160 bp, 235 bp
388 bp, 160 bp, 235 bp
388 bp
2%
TaqI
65°C
485 bp
485 bp, 297 bp, 188 bp
297 bp, 188 bp
2%
ApaI
37°C
1174 bp, 217 bp
1391 bp, 1174 bp, 217 bp
1391 bp
1.5%
2.3. Statistical Analysis
MBL-2 and VDR alleles and genotype frequencies in disease-free healthy subjects were calculated by direct counting. The Hardy-Weinberg equilibrium (HWE) was determined. Chi-square test was performed to compare the allelic frequencies of different populations and p values were calculated by unconditional logistic regression and p < 0.05 was considered to be significant. Linkage disequilibrium and haplotype analysis was performed by Haploview version 4.2 software developed at The Broad Institute, Cambridge, MA (http://www.broadinstitute.org). The LD plot construction and haplotype frequencies were calculated using the same software [23]. The standardized disequilibrium coefficient (D′) analysis between the MBL-2 SNPs was also performed using the LD plot function of this software.
3. Results
In the present study, MBL-2 promoter polymorphism (−550 H/L, −221 Y/X, and +4 P/Q) and exon 1 polymorphism (R52C: D allele, G54D: B allele, and G57F: C allele) were analyzed in 94 healthy subjects of Indian population shown in Table 3. All polymorphism with the exception of R52C were in Hardy-Weinberg equilibrium. The genotype and the allele frequency of MBL-2 polymorphism are represented in Table 3. The allelic frequency of MBL-2 promoter polymorphism −550 H/L was H versus L: 32% versus 68%, −221 Y/X was Y versus X: 68% versus 32%, and +4 P/Q was P versus Q: 78% versus 22%. The MBL-2 exon 1 polymorphism mutant allelic frequency obtained for D, B, and C allele was 6%, 11%, and 3%, respectively. The observed genotype and allele frequencies in Indian population were compared with the previously reported different populations worldwide by using chi-square tests to elucidate the differences in the distribution of MBL-2 structural variant alleles (D, B, and C) and promoter variants (Figure 1). The observations for MBL-2 structural polymorphisms were similar to the findings reported in South Indian population [11], Europeans [24, 25], Denmark [4], and Brazilian population [26] (p>0.05) (Figure 1). A significant difference was observed between the Indian (present study) and East African (Kenya) population for B (p=0.002) and C (p<0.0001) structural variants [24]. In comparison to MBL-2 promoter polymorphism distribution, a statistical significant genotype frequency distribution difference between the Indians (present study) and Chinese Han population (p<0.01) was observed [10].
The allele and genotype frequencies of MBL-2 polymorphism among the disease-free healthy subjects in Indian population.
Polymorphism
Genotype frequency (%)
Allele frequency
rs11003125 (H/L)
HH
HL
LL
H
L
9 (9.6)
43 (45.7)
42 (44.7)
0.32
0.68
rs7096206 (Y/X)
YY
YX
XX
Y
X
42 (44.7)
44 (46.8)
8 (8.7)
0.68
0.32
rs7095891 (P/Q)
PP
PQ
QQ
P
Q
55 (58.5)
36 (38.3)
3 (3.2)
0.78
0.22
rs5030737 (A/D)
AA
AD
DD
A
D
85 (90.4)
7 (7.4)
2 (2.2)
0.94
0.06
rs1800450 (A/B)
AA
AB
BB
A
B
74 (78.7)
19 (20.2)
1 (1)
0.89
0.11
rs1800451 (A/C)
AA
AC
CC
A
C
89 (94.7)
5 (5.3)
0 (0)
0.97
0.03
A/O allele
AA
AO
OO
A
O
61 (64.9)
29 (30.9)
4 (4.2)
0.89
0.11
D, B, and C: less frequent alleles for 52-, 54-, and 57-codon polymorphism, respectively
L, X, and Q: less frequent alleles of −550, −221, and +4 polymorphism, respectively
H, Y, and P: common alleles of −550, −221, and +4 polymorphism, respectively
AA genotype represents homozygous wild genotypes for structural polymorphism
AO genotype represents heterozygous genotypes of structural polymorphism
OO genotype represents homozygous mutant genotypes of structural polymorphism as well as double heterozygous genotypes (D/B, B/C) of structural polymorphism.
Graphical representation of MBL-2 structural polymorphism mutant alleles (B, C, and D) variations across the global populations [4, 11, 24, 26].
The sequence data generated for 964 bp MBL-2 promoter region and exon 1 was analyzed for the patterns wherein the presence of a polymorphism at one position would be consistently associated with polymorphism at one or more other positions. The examination of pairwise linkage disequilibrium (LD) between the MBL-2 variants was performed by construction of LD plot which revealed the presence of a single haplotype block (Figure 2). Seven putative haplotypes spanning the length of the sequenced region have been identified with a frequency of more than 1% (CCCCG = 29.4%, GGCCG = 23.8%, CGTCG = 21.4%, CGCCA = 11.7%, GGCTG = 5.9%, CGCCG = 5%, and GCCCG =1.9%) [27].
Graphical representation of Haploview LD graph of MBL-2 gene. Squares without numbers represent D′ values of 1.0; all numbers represent the D′ value expressed as a percentile. Standard color scheme of Haploview was applied to LD color display (logarithm of odds [LOD] score ≥2 and D′ = 1, shown in bright red; LOD score ≥2 and D′ <1 shown in purple; LOD score <2 and D′ <1 shown in white).
The distribution of VDR genotypes and allele frequencies of FokI, BsmI, TaqI, and ApaI in Indian population is shown in Table 4. The allelic frequency of “f,” “b,” “t,” and “a” alleles was 25%, 54%, 30%, and 61% obtained in Indian population. The genotype frequency of FokI and TaqI was in agreement with Hardy-Weinberg equilibrium. The observed VDR polymorphism genotype frequency distribution was compared individually with the different populations worldwide by using χ2 tests (Figure 3). There was a statistically significant difference between Indians (present study) and the West Africans in FokI, BsmI, and ApaI polymorphism (p<0.01) but nonsignificant difference in TaqI polymorphism (p=0.142) [28]. Japanese population differs significantly from Indians (present study) in TaqI and ApaI (p<0.05) and FokI (p<0.001) polymorphism [29]. VDR polymorphism frequency distribution differs significantly from the Korean population in TaqI and BsmI (p<0.01) but is similar in ApaI and FokI (p>0.05) polymorphism [30]. The frequency of the VDR genotypes in the present study also differs from that of studies conducted in North Indian and East Indian populations [31, 32]. Upon comparative analysis, there was a significant difference in our data from East Indians in TaqI, FokI, and BsmI polymorphism (p<0.01) and from North Indians in ApaI and FokI except TaqI polymorphism (p<0.01). The frequency observed was however similar to the Turkish population for VDR FokI, BsmI, and TaqI polymorphism [33]. There was a statistically significant difference between Indians (present study) and the Europeans (Finnish, French, Austrians, and Swedes) (p<0.01), as well as with Asians (Thais and Chinese) (p<0.05), for VDR FokI, ApaI, and TaqI polymorphism (Figure 3) [29, 31]. This demonstrates the genetic diversity within Indian population and also between different populations globally.
The genotype and allele frequencies of VDR polymorphism in healthy subjects in Indian population.
VDR polymorphism
N
Genotype frequency (%)
Allele frequency
FokI
228
FF
Ff
ff
F
f
128 (56.1)
88 (38.6)
12 (5.3)
0.75
0.25
BsmI
150
BB
Bb
bb
B
b
19 (12.7)
100 (66.6)
31 (20.7)
0.46
0.54
TaqI
236
TT
Tt
tt
T
t
110 (46.6)
110 (46.6)
16 (6.8)
0.70
0.30
ApaI
137
AA
Aa
aa
A
a
5 (3.7)
98 (71.5)
34 (24.8)
0.39
0.61
(N = number of individuals studied.)
The graphical representation of VDR polymorphisms (FokI, BsmI, TaqI, and ApaI) variations across the global population [28, 30–33, 37, 38].
4. Discussion
The innate immunity is the first line of defense against infectious microorganisms. There are several key players of the innate immune system that interact, coordinate, and act against these infectious agents. Genetic variations in these key players can influence their mechanism of action leading to variable immune response. MBL-2 and VDR are among these key players which influence the susceptibility to M. tuberculosis infection and disease development. The present study involved the frequency distribution analyses of MBL-2 and VDR polymorphisms, two molecules known to play a key role in tuberculosis susceptibility. The study also included haplotype study for MBL-2 polymorphisms and evaluation of global frequency distribution disparity among different populations worldwide.
Frequency distribution of genotype and alleles of VDR and MBL-2 gene varies among different ethnic population, which may lead to variable susceptibility to the infection. For VDR FokI “f” allele, the frequency varies from 43% in Finland to 21% in West Africa. The occurrence of “f” allele was much higher in Caucasian population. The VDR TaqI “t” allele frequency was found to be higher in Caucasians than Asian and African populations. The polymorphism VDR BsmI demonstrates a significant difference from the West African and other Asian populations. VDR ApaI “a” allele frequency varies from 35% in West Africa to 83% in Korea. TaqI, ApaI, and BsmI nonfunctional VDR polymorphisms show linkage disequilibrium and thus influence disease association indirectly [34]. Studies by Selvaraj et al. reported genotypes FF of FokI, TT of TaqI, and Bb of BsmI in males and tt of TaqI in females to be associated with pulmonary tuberculosis susceptibility in South Indian population [21, 35]. On the contrary, Sharma et al. (2011) reported the protective association of FF and TT genotype against the Mycobacterium tuberculosis infection in Central India [34]. A study conducted in Gujarati Indians living in London showed strong association of ff genotype with pulmonary tuberculosis [36]. Therefore, we are not able to draw any conclusion.
In summary, a lot of studies have been conducted through the years to understand the role of Vitamin D Receptor polymorphism in susceptibility to infectious diseases. Unfortunately, the results have been conflicting and still the role of VDR in tuberculosis susceptibility is not clear: the polymorphism determines susceptibility to the development of clinical disease or susceptibility to infection. Therefore the use of VDR polymorphism as marker for tuberculosis susceptibility is under debate. MBL-2 variant alleles have been associated with lower serum MBL levels and contrasting associations for MBL-2 variant alleles and mycobacterial infection have been reported in different populations. VDR and MBL-2 polymorphisms’ global and regional distribution, widely studied in several populations worldwide, varies significantly in each population, thus making it unique for the tuberculosis susceptibility studies. The differences in genotype and allele frequencies observed between populations could have been result of different selective pressures such as differences in diet, climate, latitude, or exposure to pathogens leading to adaptations. The efforts should be placed on a molecular understanding of the pathogenic processes, allowing a clear insight of genetic influences on the infectious diseases. The population based studies are important to reveal the population specific component to tuberculosis susceptibility which can prove effective in incorporating this into treatment and prevention strategies specifically. The study needs to be validated in larger samples to get a clearer picture of frequency distribution of MBL-2 and VDR genetic variants and their association to tuberculosis susceptibility in different parts of India.
Ethical Approval
Institutional ethical clearance was obtained.
Consent
Written informed consent of the blood donors was obtained prior to blood collection from the individuals.
Conflict of Interests
The authors declare no conflict of interests.
Acknowledgments
The authors thank Industries Commissionerate, Government of Gujarat, India, for funding this project. They also thank Council of Scientific and Industrial Research (CSIR) New Delhi, India, for providing Senior Research Fellowship to Ms. Anuroopa Gupta. They acknowledge all the volunteers for participation in the study.
BloomB. R.SmallP. M.The evolving relation between humans and Mycobacterium tuberculosis19983381067767810.1056/nejm1998030533810082-s2.0-0032485526World Health Organization (WHO)2013Geneva, SwitzerlandWorld Health Organization (WHO)BellamyR.Evidence of gene-environment interaction in development of tuberculosis2000355920458858910.1016/s0140-6736(99)00426-22-s2.0-0034685155SøborgC.MadsenH. O.AndersenÅ. B.LillebaekT.Kok-JensenA.GarredP.Mannose-binding lectin polymorphisms in clinical tuberculosis2003188577778210.1086/3771832-s2.0-0141724527JanewayC. A.Jr.The immune system evolved to discriminate infectious nonself from noninfectious self1992131111610.1016/0167-5699(92)90198-G2-s2.0-0026791975EisenD. P.MinchintonR. M.Impact of mannose-binding lectin on susceptibility to infectious diseases200337111496150510.1086/3793242-s2.0-0345550400YimJ.-J.SelvarajP.Genetic susceptibility in tuberculosis201015224125610.1111/j.1440-1843.2009.01690.x2-s2.0-76249122956DenholmJ. T.McBrydeE. S.EisenD. P.Mannose-binding lectin and susceptibility to tuberculosis: a meta-analysis20101621849010.1111/j.1365-2249.2010.04221.x2-s2.0-77956530119Garcia-LaordenM. I.PenaM. J.CamineroJ. A.Garcia-SaavedraA.Campos-HerreroM. I.CaballeroA.Rodriguez-GallegoC.Influence of mannose-binding lectin on HIV infection and tuberculosis in a Western-European population200643142143215010.1016/j.molimm.2006.01.0082-s2.0-33744826814LiuW.ZhangF.XinZ.-T.ZhaoQ.-M.WuX.-M.ZhangP.-H.De VlasS.RichardusJ. H.HabbemaJ. D. F.YangH.CaoW.-C.Sequence variations in the MBL gene and their relationship to pulmonary tuberculosis in the Chinese Han population20061010109811032-s2.0-33749491447AlagarasuK.SelvarajP.SwaminathanS.RaghavanS.NarendranG.NarayananP. R.Mannose binding lectin gene variants and susceptibility to tuberculosis in HIV-1 infected patients of South India200787653554310.1016/j.tube.2007.07.0072-s2.0-35348812504CapparelliR.IannacconeM.PalumboD.MedagliaC.MoscarielloE.RussoA.IannelliD.Role played by human mannose-binding lectin polymorphisms in pulmonary tuberculosis2009199566667210.1086/5966582-s2.0-61849168928SelvarajP.JawaharM. S.RajeswariD. N.AlagarasuK.VidyaraniM.NarayananP. R.Role of mannose binding lectin gene variants on its protein levels and macrophage phagocytosis with live Mycobacterium tuberculosis in pulmonary tuberculosis200646343343710.1111/j.1574-695x.2006.00053.x2-s2.0-33645071570MadsenH. O.GarredP.KurtzhalsJ. A. L.LammL. U.RyderL. P.ThielS.SvejgaardA.A new frequent allele is the missing link in the structural polymorphism of the human mannan-binding protein1994401374410.1007/bf001639622-s2.0-0028236241TurnerM. W.Mannose-binding lectin: the pluripotent molecule of the innate immune system1996171153254010.1016/0167-5699(96)10062-12-s2.0-0030297443NuytinckL.ShapiroF.Mannose-binding lectin: laying the stepping stones from clinical research to personalized medicine200411355210.1517/17410541.1.1.35SteffensenR.ThielS.VarmingK.JersildC.JenseniusJ. C.Detection of structural gene mutations and promoter polymorphisms in the mannan-binding lectin (MBL) gene by polymerase chain reaction with sequence-specific primers20002411-2334210.1016/S0022-1759(00)00198-82-s2.0-0034738657RookG. A. W.SteeleJ.FraherL.Vitamin D3, gamma interferon, and control of proliferation of Mycobacterium tuberculosis by human monocytes19865711591632-s2.0-0022560726SelvarajP.ChandraG.JawaharM. S.RaniM. V.RajeshwariD. N.NarayananP. R.Regulatory role of vitamin D receptor gene variants of BsmI, ApaI, TaqI, and FokI polymorphisms on macrophage phagocytosis and lymphoproliferative response to Mycobacterium tuberculosis antigen in pulmonary tuberculosis200424552353210.1023/b:joci.0000040923.07879.312-s2.0-4544219889GrossC.EccleshallT. R.MalloyP. J.VillaM. L.MarcusR.FeldmanD.The presence of a polymorphism at the translation initiation site of the vitamin D receptor gene is associated with low bone mineral density in postmenopausal Mexican-American women199611121850185510.1002/jbmr.5650111204SelvarajP.NarayananP. R.ReethaA. M.Association of vitamin D receptor genotypes with the susceptibility to pulmonary tuberculosis in female patients and resistance in female contacts20001111721792-s2.0-0033931647DhawanD.PanchalH.ShuklaS.PadhH.Genetic variability & chemotoxicity of 5-fluorouracil & cisplatin in head & neck cancer patients: a preliminary study201313711251292-s2.0-84874722411BarrettJ. C.FryB.MallerJ.DalyM. J.Haploview: analysis and visualization of LD and haplotype maps200521226326510.1093/bioinformatics/bth4572-s2.0-13444269543GarredP.LarsenF.SeyfarthJ.FujitaR.MadsenH. O.Mannose-binding lectin and its genetic variants200672859410.1038/sj.gene.63642832-s2.0-33644772194Ocejo-VinyalsJ.-G.Lavín-AlconeroL.Sánchez-VelascoP.Guerrero-AlonsoM.-Á.AusínF.FariñasM.-C.Leyva-CobiánF.Mannose-binding lectin promoter polymorphisms and gene variants in pulmonary tuberculosis patients from Cantabria (Northern Spain)20122012646912810.1155/2012/4691282-s2.0-84876509847da CruzH. L. A.da SilvaR. C.SegatL.de CarvalhoM. S. Z. D. M. G.BrandãoL. A. C.GuimarãesR. L.SantosF. C. F.De LiraL. A. S.MontenegroL. M. L.SchindlerH. C.CrovellaS.MBL2 gene polymorphisms and susceptibility to tuberculosis in a northeastern Brazilian population20131932332910.1016/j.meegid.2013.03.0022-s2.0-84885170834LewontinR. C.The interaction of selection and linkage. I. General considerations; heterotic models19644914967BornmanL.CampbellS. J.FieldingK.BahB.SillahJ.GustafsonP.MannehK.LisseI.AllenA.SirugoG.SyllaA.AabyP.McAdamK. P. W. J.Bah-SowO.BennettS.LienhardtC.HillA. V. S.Vitamin D receptor polymorphisms and susceptibility to tuberculosis in West Africa: a case-control and family study200419091631164110.1086/4244622-s2.0-5444259819BhanushaliA. A.LajpalN.KulkarniS. S.ChavanS. S.BagadiS. S.DasB. R.Frequency of fokI and taqI polymorphism of vitamin D receptor gene in Indian population and its association with 25-hydroxyvitamin D levels200915310811310.4103/0971-6866.601862-s2.0-77949585230KangT. J.JinS. H.YeumC. E.Vitamin D receptor gene TaqI, BsmI and FokI polymorphisms in Korean patients with tuberculosis201111525325710.4110/in.2011.11.5.253BidH. K.MishraD. K.MittalR. D.Vitamin-D receptor (VDR) gene (Fok-I, Taq-I and Apa-I) polymorphisms in healthy individuals from north indian population2005621471522-s2.0-24944573144SinghA.GaughanJ. P.KashyapV. K.SLC11A1 and VDR gene variants and susceptibility to tuberculosis and disease progression in East India201115111468147510.5588/ijtld.11.00892-s2.0-80053961523AtesO.DolekB.DalyanL.MusellimB.OngenG.Topal-SarikayaA.The association between BsmI variant of vitamin D receptor gene and susceptibility to tuberculosis20113842633263610.1007/s11033-010-0404-82-s2.0-79960945724SharmaP. R.SinghS.JenaM.MishraG.PrakashR.DasP. K.BamezaiR. N. K.TiwariP. K.Coding and non-coding polymorphisms in VDR gene and susceptibility to pulmonary tuberculosis in tribes, castes and Muslims of Central India20111161456146110.1016/j.meegid.2011.05.0192-s2.0-79960437218SelvarajP.ChandraG.KurianS. M.ReethaA. M.NarayananP. R.Association of vitamin D receptor gene variants of BsmI, ApaI and FokI polymorphisms with susceptibility or resistance to pulmonary tuberculosis20038412156415682-s2.0-1642576781WilkinsonR. J.LlewelynM.ToossiZ.PatelP.PasvolG.LalvaniA.WrightD.LatifM.DavidsonR. N.Influence of vitamin D deficiency and vitamin D receptor polymorphisms on tuberculosis among Gujarati Asians in west London: a case-control study2000355920461862110.1016/s0140-6736(99)02301-62-s2.0-0034685157LiuW.CaoW.-C.ZhangC.-Y.TianL.WuX.-M.HabbemaJ. D. F.ZhaoQ.-M.ZhangP.-H.XinZ.-T.LiC.-Z.YangH.VDR and NRAMP1 gene polymorphisms in susceptibility to pulmonary tuberculosis among the Chinese Han population: a case-control study2004844284342-s2.0-2442594129MerzaM.FarniaP.AnooshehS.VarahramM.KazampourM.PajandO.SaeifS.MirsaeidiM.MasjediM. R.VelayatiA. A.HoffnerS.The NRAMPI, VDR and TNF-α gene polymorphisms in Iranian tuberculosis patients: the study on host susceptibility200913425225610.1590/s1413-867020090004000022-s2.0-77950007042