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. 2019 Jun 7;98(23):e15955. doi: 10.1097/MD.0000000000015955

3’UTR polymorphisms in NRAMP1 are associated with the susceptibility to pulmonary tuberculosis: A MOOSE-compliant meta-analysis

Yang Liu a,∗, Erjiang Zhao b, Lin Zhu a, Danning Zhang c, Zhe Wang a
Editor: Meixia Lu
PMCID: PMC6571362  PMID: 31169721

Abstract

Many studies have investigated the association between the 3’UTR polymorphism in natural resistance-associated macrophage protein 1 (NRAMP1) and the risk of pulmonary tuberculosis (PTB), Revealing inconclusive results. This study aimed to investigate the correlation between the NRAMP1 3’UTR polymorphism and the risk of PTB.

This meta-analysis included 29 case–control studies to better and comprehensively assess this correlation. Pooled odds ratios (ORs) and 95% confidence interval (95% CIs) were calculated to assess the strength of the association.

These 29 case–control studies included 4672 cases and 6177 controls. The NRAMP1 3’UTR polymorphism displayed a significant positive correlation with the risk of PTB in 3 models (for del/del vs ins/ins: OR = 1.22, 95% CI = 1.01–1.47; for Ins/del vs ins/ins: OR = 1.19, 95% CI 1.08–1.30; for Ins/del + del/del vs ins/ins: OR = 1.25, 95% CI = 1.08–1.45). A stratified analysis by ethnicity revealed that the NRAMP1 3’UTR polymorphism was associated with an increased risk of PTB in the Asian population, but not in Caucasian, African, and South American populations.

The present results indicate that the NRAMP1 3’UTR polymorphism may be considered a risk factor for PTB in the Asian population.

Keywords: meta-analysis, NRAMP1, polymorphism, pulmonary tuberculosis

1. Introduction

Tuberculosis (TB), a chronic infectious disease caused by Mycobacterium tuberculosis, is a major cause of worldwide mortality and morbidity. In 2016, 10.4 million new cases were reported, and 1.7 million individuals died of TB. Most of the individuals with TB reportedly reside in India China, Philippines, Pakistan, Nigeria, and South Africa.[1] The precise mechanisms underlying TB pathogenesis remain unknown. Weakened immunity, human immunodeficiency virus (HIV) infections, alcohol abuse, advanced age, chronic corticosteroid therapy, diabetes, socio-economic status, and malnutrition are the prominent risk factors of TB.[2] Not all individuals exposed to the similar risk factors develop tuberculosis, thus suggesting the involvement of genetic factors, including single-nucleotide polymorphisms, in TB pathogenesis.

When M tuberculosis infects the body, the immune system produces a barrage of defensive protein molecules, recruiting phagocytic cells, which eliminate the pathogen. Natural resistance-associated macrophage protein 1 (NRAMP1) is also referred to as the solute carrier family 11 proton-coupled divalent metal ion transporter membrane1 (SLC11A1), which plays an important role in the immune response to mycobacterial infections. NRAMP1 encodes a divalent transition metal (Fe and Mn) transporter that localizes on the lysosomal membrane.[3] Iron is an essential mycobacterial nutrient that also influences the generation of reactive oxygen and nitrogen intermediates. Therefore, NRAMP1 is involved in resistance to intracellular pathogens, including Leishmania, Salmonella, and Mycobacteria. NRAMP1 is associated with various infectious diseases and inflammatory diseases. It primarily contains 4 polymorphisms, rs17235416 (3’UTR), rs17235409 (D543N), rs3731865 (INT4), and rs34448891 (5=(GT)n). Among these polymorphisms, 3’UTR polymorphisms have been widely investigated for their association with TB. A functionally significant TGTG del allele in NRAMP1 leads to reduced production of NRAMP1 when compared to the TGTG+ allele and may be correlated with the risk of TB.

Numerous studies have investigated the association between the NRAMP1 3’UTR polymorphism and the risk of pulmonary tuberculosis (PTB) in different regions,[4–29] revealing inconclusive results. A case–control study by Medapati et al[29] reported that the NRAMP1 3’UTR polymorphism is significantly associated with the susceptibility to TB among Indian individuals. However, Jafari[28] reported no significant association between these 2 aspects. Hence, the present meta-analysis aimed to better and comprehensively assess the correlation between the NRAMP1 3’UTR polymorphism and the risk of PTB.

2. Materials and methods

2.1. Search strategy

We performed a comprehensive search in PubMed, Elsevier, and the Cochrane Library (update till January 1, 2019), using the following keywords

(“tuberculosis” or “TB” or “mycobacteria”), (“polymorphism” or “mutation” or “variant”), and (“Natural resistance associated macrophage protein 1” or “NRAMP1” or “Solute carrier family 11A member 1 or SLC11A1” or “rs17235416”). Articles in all languages were included. Furthermore, additional related articles were identified through screening of the references of relevant articles. In case of a duplicate publication, the largest study was selected. The present study was conducted in accordance with the PRISMA guidelines for systematic reviews and meta-analyses.[30] Ethical approval was not necessary since this study is a meta-analysis.

2.2. Inclusion and exclusion criteria

Following were the inclusion criteria of this meta-analysis:

  • (1)

    case–control or cohort studies on the NRAMP1 3’UTR polymorphism and the risk of PTB;

  • (2)

    sufficient data estimating odds ratios (ORs) with 95% confidence intervals (95% CIs).

The major exclusion criteria were as follows:

  • (1)

    meta-analyses, letters, reviews, or editorial comments;

  • (2)

    studies were not irrelevant to TGTG ins/del;

  • (3)

    not PTB;

  • (4)

    studies with insufficient data;

  • (5)

    other than case–control study;

  • (6)

    genotype distributions were not in accordance with Hardy–Weinberg equilibrium (HWE) in the control group.

2.3. Data extraction and quality assessment

For all studies, EZ and LZ extracted the data independently and reached a consensus. Any disagreement was resolved through discussion among the 3 authors. The following information was collected from all eligible studies: the first author, year of publication, country of origin, ethnicity, source of controls, number of case and control subjects, HIV status, genotype frequencies in case and control groups, and HWE. We evaluated the quality of all of the studies included according to Newcastle–Ottawa scale (NOS).[31] The NOS contains 3 categories which are selection(0–4 points), comparability(0–2 points), and exposure (0–3 points). The total scores ranged from 0 to 9.

2.4. Statistical analysis

The association between the NRAMP1 3’UTR polymorphism and the risk of PTB was evaluated using crude ORs with 95% CIs. To assess heterogeneity, the Cochrane Q test and the I-squared (I2) metric were used. If the I2 metric was <50%, indicating a lack of heterogeneity among studies, A fixed-effects model (the Mantel–Haenszel method) was used. Otherwise, the random-effects model (the DerSimonian and Laird method) was applied.[32] In addition, subgroup analyses based on ethnicity (Asian, Caucasian, African, and South American) were carried out. Funnel plot analysis and Egger test were conducted to identify a publication bias of the meta-analysis.[33] All statistical analyses were performed using STATA 11.0 software (STATA Corp., College Station, TX) and P values were 2-tailed.

3. Results

3.1. Characteristics of eligible studies

In accordance with the flowchart shown in Figure 1, 211 studies were retrieved through our initial literature search. After excluding duplicate articles, reviews, letters, comments, and irrelevant studies, 50 studies remained for further evaluation. After reading full-text articles, 24 studies were excluded. Finally, 26 eligible studies including 29 case–control studies, including 4672 cases and 6177 controls were included (Fig. 1). The major characteristics of identified studies were summarized in Table 1. These studies included 18 studies on Asians, 4 studies on Caucasians, 5 studies on Africans, and 2 studies on South American populations.

Figure 1.

Figure 1

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Flow chart of included studies in the current meta-analysis.

Table 1.

Main characteristics of studies included in this meta-analysis.

3.1.

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3.2. Quantitative synthesis

Table 2 summarizes the results of this meta-analysis. Overall, the NRAMP1 3’UTR polymorphism was significantly associated with the risk of PTB in 3 models (for del/del vs ins/ins: OR = 1.22, 95% CI = 1.01–1.47; for Ins/del vs ins/ins: OR = 1.19, 95% CI 1.08–1.30; for Ins/del + del/del vs ins/ins: OR = 1.25, 95% CI = 1.08–1.45); however, the recessive model did not reveal this significant association (for del/del vs ins/ins + Ins/del: OR = 1.18, 95% CI 0.98–1.42). In a stratified analysis by ethnicity, the present meta-analysis revealed that the NRAMP1 3’UTR polymorphism was associated with an increased risk of PTB in the Asian population (for del/del vs ins/ins: OR = 2.08, 95% CI = 1.45–2.98; for Ins/del vs ins/ins: OR = 1.49, 95% CI 1.29–1.73, Figure 2; for Ins/del + del/del vs ins/ins: OR = 1.57, 95% CI = 1.36–1.18; for del/del vs ins/ins + Ins/del: OR = 1.89, 95% CI 1.33–2.69), but not in the Caucasian, African, and South American populations. In a stratified analysis by HIV status, the NRAMP1 3’UTR polymorphism was significantly associated with the risk of PTB in HIV- individuals in 2 models (for Ins/del vs ins/ins: OR = 1.26, 95% CI = 1.06–1.49; for Ins/del + del/del vs ins/ins: OR = 1.28, 95% CI = 1.07–1.54), but not in the HIV+ individuals.

Table 2.

Summary ORs and 95% CI of Association between 3’UTR polymorphism and pulmonary tuberculosis risk.

3.2.

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Figure 2.

Figure 2

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Forest plot for the association between 3’UTR polymorphism and pulmonary tuberculosis risk for the Ins/del genotype compared with the ins/ins genotype In a stratified analysis by ethnicity. CI = confidence interval, OR = odds ratio.

3.3. Publication bias

Funnel plot analysis and Egger's test were conducted to assess publication bias. Egger test did not reveal any evidence of publication bias in the Ins/del versus ins/ins models (t = 0.14, P = .888) and in the dominant model (t = 0.81, P = .423); however, publication bias was detected in the del/del vs. ins/ins models (t = 2.65, P = .014, Fig. 3) and in the recessive model (t = 2.43, P = .023).

Figure 3.

Figure 3

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Funnel plot of the association 3’UTR polymorphism and pulmonary tuberculosis risk for the del/del genotype compared with the ins/ins genotype in overall populations. OR = odds ratio, se = standard error.

4. Discussion

The innate immune response activates early events during a M tuberculosis infection. NRAMP1 plays an important role in the immune response to a mycobacterial infection. Therefore, this meta-analysis aimed to better and comprehensively assess the correlation between the NRAMP1 3’UTR polymorphism and the risk of PTB. The present study reports a significant correlation between the NRAMP1 3’UTR polymorphism and the risk of PTB in overall and Asian populations.

Many epidemiological studies have investigated the association between the NRAMP1 3’UTR polymorphism and the risk of PTB. In 2006, a meta-analysis by Li et al[34] reported that 3’UTR polymorphisms are significantly associated with the risk of PTB. Subsequently, a meta-analysis by Meilang et al[35] on PTB and extra-PTB reported that 3’UTR polymorphisms increased the risk of TB in comparison with their corresponding common alleles. Furthermore, stratified analyses by ethnicity, which assessed the forms of TB, confirmed the results of Li et al. This meta-analysis includes 29 recent case–control studies including 4672 cases and 6177 controls to better and comprehensively assess the correlation between the NRAMP1 3’UTR polymorphism and the risk of PTB. The present results are similar to those of 2 previous meta-analyses. The 3’UTR del/del and ins/del genotypes were significantly associated with a higher risk than the 3’UTR ins/ins genotype.

In 2000, the association between the NRAMP1 3’UTR polymorphism and the risk of PTB was first investigated by Ryu et al.[5] They revealed a significant relationship of the ins/del genotype variant with the risk of PTB among Koreans, but not in the del/del genotype. A case–control study by Medapati et al[29] reported that the NRAMP1 3’UTR polymorphism is significantly associated with the susceptibility to TB in the Indian population. However, Taype et al[9] reported did not report an association in the Peruvian population. These contradictory results may be explained on the basis of the present results, suggesting that the risk of PTB conferred by the variant allele may be modified by race. The present meta-analysis reported that the NRAMP1 3’UTR polymorphism was associated with an increased risk of PTB in the Asian population, but not in Caucasian, African, and South American populations.

Despite the strengths of the present study, some limitations should be acknowledged. First, upon subgroup analysis by ethnicity, the NRAMP1 3’UTR polymorphism was not associated with the risk of PTB in Caucasian, African, and South American populations. However, the sample size was relatively small in Caucasian, South American, and African populations, thus potentially decreasing the statistical power of the results to establish an actual association. Second, publication bias was detected in the del/del versus ins/ins models and the recessive model in overall analysis; hence, the present results should be considered with caution. Third, PTB is a complex disease; however, we did not carry out subgroup analysis to analyze potential gene-gene and gene-environment interactions because of insufficient data. Fourth, this meta-analysis was performed with a candidate gene strategy. Genome-wide association studies (GWAS) scanning entire genomes for genetic variation include immense amounts of SNPs and have been designed for the same ethnic background and study design. A GWAS by Zheng et al[36] reported that 2 loci 14q24.3 (rs12437118, Pcombined = 1.72 × 10−11, OR = 1.277, ESRRB) and 20p13(rs6114027, Pcombined = 2.37 × 10.11, OR = 1.339, TGM6) were significantly associated with TB in Han Chinese individuals. Miao et al[37] reported that rs9272461 is significantly associated with the risk of PTB in various genetic models. Hence, GWAS are required to further validate the present results.

In conclusion, the present results indicate that the NRAMP1 3’UTR polymorphism may be associated with an increased risk of PTB in the Asian population, but not in the Caucasian, African, and South American populations. Well-designed epidemiological studies with larger sample sizes are needed to verify the present findings.

Acknowledgments

We would like to thank Editage [www.editage.cn] for English language editing.

Author contributions

Data extraction: Erjiang Zhao, Lin Zhu

Formal analysis: Erjiang Zhao, Danning Zhang

Investigation: Yang Liu, Lin Zhu, Dan Ning Zhang.

Methodology: Yang Liu, Erjiang Zhao, Dan Ning Zhang, Zhe Wang, Danning Ding.

Resources: Yang Liu.

Software: Erjiang Zhao, Lin Zhu.

Writing – original draft: Yang Liu, Erjiang Zhao.

Writing – review & editing: Yang Liu.

Yang Liu orcid: 0000-0002-3877-9203.

Footnotes

Abbreviations: 95% CI = 95% confidence interval, GWAS = genome-wide association studies, HIV = human immunodeficiency virus, HWE = Hardy–Weinberg equilibrium, NOS = Newcastle–Ottawa scale, NRAMP1 = natural resistance associated macrophage protein 1, OR = odds ratios, PTB = pulmonary tuberculosis, SLC11A1 = solute carrier family 11A member 1, TB = tuberculosis.

YL and EZ equally contribute to this work.

The authors have no conflicts of interest to disclose.

References

  • [1].World Health Organization (WHO), Global Tuberculosis Report 2018. 2018. Available at: https://www.who.int/en/news-room/fact-sheets/detail/tuberculosis Accessed September 18, 2018. [Google Scholar]
  • [2].Güneylioglu D, Yilmaz A, Bilgin S, et al. Factors affecting delays in diagnosis and treatment of pulmonary tuberculosis in a tertiary care hospital in Istanbul, Turkey. Med Sci Monit 2004;10:CR62–7. [PubMed] [Google Scholar]
  • [3].Goswami T, Bhattacharjee A, Babal P, et al. Naturalresistance -associated macrophage protein 1 is an H+/bivalent cation antiporter. Biochem J 2001;354(Pt3):511–9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [4].Ryu S, Park YK, Bai GH, et al. 3’UTR polymorphisms in the NRAMP1 gene are associated with susceptibility to tuberculosis in Koreans. Int J Tuberc Lung Dis 2000;4:577–80. [PubMed] [Google Scholar]
  • [5].Liaw YS, Tsai-Wu JJ, Wu CH, et al. Variations in the NRAMP1 gene and susceptibility of tuberculosis in Taiwanese. Int J Tuberc Lung Dis 2002;6:454–60. [PubMed] [Google Scholar]
  • [6].Abe T, Iinuma Y, Ando M, et al. NRAMP1 polymorphisms, susceptibility and clinical features of tuberculosis. J Infect 2003;46:215–20. [DOI] [PubMed] [Google Scholar]
  • [7].Liu W, Cao WC, Zhang CY CY, et al. VDR and NRAMP1 gene polymorphisms in susceptibility to pulmonary tuberculosis among the Chinese Han population: a case-control study. Int J Tuberc Lung Dis 2004;8:428–34. [PubMed] [Google Scholar]
  • [8].Fitness J, Floyd S, Warndorff DK, et al. Large-scale candidate gene study of tuberculosis susceptibility in the Karonga district of northern Malawi. Am J Trop Med Hyg 2004;71:341–9. [PubMed] [Google Scholar]
  • [9].Taype CA, Castro JC, Accinelli RA, et al. Association between SLC11A1 polymorphisms and susceptibility to different clinical forms of tuberculosis in the Peruvian population. Infect Genet Evol 2006;6:361–7. [DOI] [PubMed] [Google Scholar]
  • [10].Hsu YH, Chen CW, Sun HS, et al. Association of NRAMP 1 gene polymorphism with susceptibility to tuberculosis in Taiwanese aboriginals. J Formos Med Assoc 2006;105:363–9. [DOI] [PubMed] [Google Scholar]
  • [11].Vejbaesya S, Chierakul N, Luangtrakool P, et al. NRAMP1 and TNF-alpha polymorphisms and susceptibility to tuberculosis in Thais. Respirology 2007;12:202–6. [DOI] [PubMed] [Google Scholar]
  • [12].Sborg C, Andersen AB, Range N, et al. Influence of candidate susceptibility genes on tuberculosis in a high endemic region. Mol Immunol 2007;44:2213–20. [DOI] [PubMed] [Google Scholar]
  • [13].Sahiratmadja E, Wieringa FT, van Crevel R, et al. Iron deficiency and NRAMP1 polymorphisms (INT4, D543N and 3’UTR) do not contribute to severity of anaemia in tuberculosis in the Indonesian population. Br J Nutr 2007;98:684–90. [DOI] [PubMed] [Google Scholar]
  • [14].Satomi A, Yoshiyuki A, Tadahiko F, et al. Association of the SLC11A1 gene polymorphisms with susceptibility to mycobacterium infections in a Japanese population. Infect Dis Clin Pract 2008;16:230–4. [Google Scholar]
  • [15].Parisa F, Omid P, Saber A, et al. Comparison of Nramp1 gene polymorphism among TB health care workers and recently infected cases; assessment of host susceptibility. Tanaffos 2008;7:19–24. [Google Scholar]
  • [16].Chen XR, Feng YL, Ma Y, et al. A study on the haplotype of the solute carrier family 11 member 1 gene in Tibetan patients with pulmonary tuberculosis in China. Zhonghua Jie He He Hu Xi Za Zhi 2009;32:360–4. [PubMed] [Google Scholar]
  • [17].Merza M, Farnia P, Anoosheh S, et al. The NRAMPI, VDR and TNF-alpha gene polymorphisms in Iranian tuberculosis patients: the study on host susceptibility. Braz J Infect Dis 2009;13:252–6. [DOI] [PubMed] [Google Scholar]
  • [18].Hatta M, Ratnawati M, Tanaka J, et al. NRAMP1/SLC11A1 gene polymorphisms and host susceptibility to Mycobacterium tuberculosis and M. leprae in South Sulawesi, Indonesia. Southeast Asian J Trop Med Public Health 2010;41:386–94. [PubMed] [Google Scholar]
  • [19].de Wit E, van der Merwe L, van Helden PD, et al. Gene-gene interaction between tuberculosis candidate genes in a South African population. Mamm Genome 2011;22:100–10. [DOI] [PubMed] [Google Scholar]
  • [20].Solgun HA, Tastemir D, Aksaray N, et al. Polymorphisms in NRAMP1 and MBL2 genes and their relations with tuberculosis in Turkish children. Tuberk Toraks 2011;59:48–53. [DOI] [PubMed] [Google Scholar]
  • [21].Nugraha J, Anggraini R. NRAMP1 polymorphism and susceptibility to lung tuberculosis in Surabaya, Indonesia. Southeast Asian J Trop Med Public Health 2011;42:338–41. [PubMed] [Google Scholar]
  • [22].Ben-Selma W, Harizi H, Letaief M, et al. Age- and gender-specific effects on NRAMP1 gene polymorphisms and risk of the development of active tuberculosis in Tunisian populations. Int J Infect Dis 2012;16:543–50. [DOI] [PubMed] [Google Scholar]
  • [23].Sapkota BR, Hijikata M, Matsushita I, et al. Association of SLC11A1 (NRAMP1) polymorphisms with pulmonary Mycobacterium avium complex infection. Hum Immunol 2012;73:529–36. [DOI] [PubMed] [Google Scholar]
  • [24].Tiksnadi B B, Herman H. The NRAMP1 polymorphism as a risk factor for tuberculous spondylitis. Malays Orthop J 2013;7:25–9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [25].Wu F, Zhang W, Zhang L, et al. NRAMP1, VDR, HLA-DRB1, and HLA-DQB1 gene polymorphisms in susceptibility to tuberculosis among the Chinese Kazakh population: a case-control study. Biomed Res Int 2013;2013: 484535. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [26].Fernández-Mestre M, Villasmil A, Takiff H, et al. NRAMP1 and VDR Gene polymorphisms in susceptibility to tuberculosis in venezuelan population. Dis Markers 2015;2015: 860628. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [27].Wu L, Deng H, Zheng Y, et al. An association study of NRAMP1, VDR, MBL and their interaction with the susceptibility to tuberculosis in a Chinese population. Int J Infect Dis 2015;38:129–35. [DOI] [PubMed] [Google Scholar]
  • [28].Jafari M, Nasiri MR, Sanaei RS, et al. The NRAMP1, VDR, TNF-α, ICAM1, TLR2 and TLR4 gene polymorphisms in Iranian patients with pulmonary tuberculosis: a case–control study. Infect Genet Evol 2016;39:92–8. [DOI] [PubMed] [Google Scholar]
  • [29].Medapati RV, Suvvari S, Godi S, et al. NRAMP1 and VDR gene polymorphisms in susceptibility to pulmonary tuberculosis among Andhra Pradesh population in India: a case-control study. BMC Pulm Med 2017;17: 89. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [30].Moher D, Liberati A, Tetzlaff J, et al. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. Ann Intern Med 2009;151:264–9. [DOI] [PubMed] [Google Scholar]
  • [31].Stang A. Critical evaluation of the Newcastle-Ottawa scale for the assessment of the quality of nonrandomized studies in meta-analyses. Eur J Epidemiol 2010;25:603–5. [DOI] [PubMed] [Google Scholar]
  • [32].Mantel N, Haenszel W. Statistical aspects of the analysis of data from retrospective studies of disease. J Natl Cancer Inst 1959;22:719–48. [PubMed] [Google Scholar]
  • [33].Egger M, Davey Smith G, Schneider M, et al. Bias in meta-analysis detected by a simple, graphical test. BMJ 1997;315:629–34. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [34].Li HT, Zhang TT, Zhou YQ, et al. SLC11A1 (formerly NRAMP1) gene polymorphisms and tuberculosis susceptibility: a meta-analysis. Int J Tuberc Lung Dis 2006;10:3–12. [PubMed] [Google Scholar]
  • [35].Meilang Q, Zhang Y, Zhang J, et al. Polymorphisms in the SLC11A1 gene and tuberculosis risk: a meta-analysis update. Int J Tuberc Lung Dis 2012;16:437–46. [DOI] [PubMed] [Google Scholar]
  • [36].Zheng R, Li Z, He F F, et al. Genome-wide association study identifies two risk loci for tuberculosis in Han Chinese. Nat Commun 2018;9: 4072. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • [37].Miao R, Huang S, Li C, et al. An HLA class II locus, previously identified by a genome-wide association study, is also associated with susceptibility to pulmonary tuberculosis in a Chinese population. Infect Genet Evol 2018;64:164–7. [DOI] [PubMed] [Google Scholar]

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