MBL2 gene polymorphisms and susceptibility to tuberculosis in a northeastern Brazilian population

Association Study of MBL2 Gene Polymorphisms and Risk of Tuberculosis in Southeast of Iran

Mannose-binding lectin (MBL) is an acute phase protein which recognizes the pathogens through its carbohydrate recognition domain. It is an important part of human innate immunity. The aim of the current study was to evaluate the impact of MBL2 polymorphism on pulmonary tuberculosis in a number of patients from the southeast of Iran. In this case-control study, 2 MBL gene polymorphisms (rs1800450, rs7095891) were genotyped using PCR-RFLP method and polymerase chain reaction for detection of 34bp ins/del of MBL2 gene (rs777980157) polymorphism. The study included 170 patients with PTB (pulmonary tuberculosis) and 175 control subjects. The findings indicated that the GA (GA vs. GG: OR=0.172, 95% CI=0.107-0.275, P<0.001) (OR - odds ratio; CI - confidence interval) genotype as well as GA+AA (GA+AA vs. GG: OR=0.191, 95% CI=0.120-0.302, P<0.001) genotype of rs1800450 reduced the risk of PTB compared to GG genotype. The rs7095891 variant significantly decreased the risk of PTB in codominant (GA vs. GG: OR=0.118, 95% CI=0.054-0.258, P<0.001; and AA vs. GG: OR=0.029, 95% CI=0.01-0.082, P<0.001), dominant (GA+AA vs. GG: OR=0.095, 95% CI=0.044-0.207, P<0.001) and recessive (AA vs. GA+GG: OR=0.172, CI=0.081-0.365, P<0.001) inheritance models. No significant relationship was identified between the rs777980157 variant and PTB risk/protection. In conclusion, we found that the MBL2 rs1800450 and rs7095891 polymorphisms provide relative protection against PTB. Additional studies on larger populations with different ethnicities are required to verify our findings.

Association between polymorphisms in mannose-binding lectin 2 gene with pulmonary tuberculosis susceptibility

Background

Mannose-binding lectin (MBL2) is considered to play a role in the human innate immune response to tuberculosis (TB) infections, and 4 common single nucleotide polymorphisms (SNPs) may be associated with pulmonary tuberculosis (PTB) risk. To examine these potential associations, we performed a comprehensive analysis to assess the relationships between MBL2 polymorphisms and PTB.

Methods

The PubMed, Embase, and SinoMed databases were searched for articles published prior to June 13, 2019. Odds ratios with 95% confidence intervals were calculated to evaluate the strength of the relationships.

Results

There were 37 case-control studies examining the effects of the four SNPs in MBL2 on PTB. A positive association between rs11003125 and PTB risk was observed in the hospital-based subgroup. Moreover, for the combined polymorphism and PTB risk, positive associations were detected not only in the total population but also in those with Asian origins across all source of control subgroups. No associations were found for rs7096206 or rs7095891.

Conclusions

Our current study indicated that several SNPs in MBL2 may be associated with susceptibility to PTB.

Myeloid C-Type Lectin Receptors in Tuberculosis and HIV Immunity: Insights Into Co-infection?

C-type lectin receptors (CLRs) are carbohydrate binding pattern recognition receptors (PRRs) which play a central role in host recognition of pathogenic microorganisms. Signaling through CLRs displayed on antigen presenting cells dictates important innate and adaptive immune responses. Several pathogens have evolved mechanisms to exploit the receptors or signaling pathways of the CLR system to gain entry or propagate in host cells. CLR responses to high priority pathogens such as Mycobacterium tuberculosis (Mtb), HIV, Ebola, and others are described and considered potential avenues for therapeutic intervention. Mtb and HIV are the leading causes of death due to infectious disease and have a synergistic relationship that further promotes aggressive disease in co-infected persons. Immune recognition through CLRs and other PRRs are important determinants of disease outcomes for both TB and HIV. Investigations of CLR responses to Mtb and HIV, to date, have primarily focused on single infection outcomes and do not account for the potential effects of co-infection. This review will focus on CLRs recognition of Mtb and HIV motifs. We will describe their respective roles in protective immunity and immune evasion or exploitation, as well as their potential as genetic determinants of disease susceptibility, and as avenues for development of therapeutic interventions. The potential convergence of CLR-driven responses of the innate and adaptive immune systems in the setting of Mtb and HIV co-infection will further be discussed relevant to disease pathogenesis and development of clinical interventions.

Selected factors of the innate immunity in Polish patients suffering from pulmonary tuberculosis

We conducted a prospective study of 453 Polish patients suffering from pulmonary tuberculosis and 267 healthy controls. Selected polymorphisms of the genes encoding for collectins, ficolins and MBL-associated serine protease 2 were investigated as were serum concentrations of mannose-binding lectin, surfactant protein D, ficolin-1 and ficolin-3. The number of MBL2 gene exon 1 variant allele carriers was significantly higher in patients, compared with controls. The homozygosity for SFTPA2 +26 C > A SNP variant allele occurred less commonly within TB, while homozygosity for the FCN1 -542 G > A major allele was less frequent within the control group. Two patients were found MASP-2-deficient. Serum concentrations of MBL, SP-D and ficolin-1 were higher amongst patients while the converse was found for ficolin-3. Ficolin-1 had high specificity to differentiate between individuals with tuberculosis and healthy persons and therefore may be considered potential disease marker.

Association between -221 X/Y polymorphism of mannose-binding lectin (MBL) gene and susceptibility to HTLV-1 infection among people from an endemic region in the Northeast of Iran

BACKGROUND

The role of (MBL) gene single nucleotide polymorphisms (SNPs) has been well documented in susceptibility to several infectious diseases. This study aimed to investigate the association between two MBL promoter variants, -550 H/L and -221 X/Y, and susceptibility to HTLV-1 infection.

METHODS

A total of 153 subjects infected with HTLV-1 and 169 healthy controls were recruited. SSP-PCR method was applied to genotype -550 H/L and -221 X/Y polymorphisms. Associations between genotypes or alleles and susceptibility to HTLV-1 infection were analyzed by Pearson's Chi-Square. p ≤ .05 was considered statistically significant.

RESULTS

Statistical analysis revealed significant differences between the two groups in the -221 position (χ2 = 19.709; p = .000). The MBL YX genotype was significantly associated with increased susceptibility to HTLV-1 (OR = 2.73, %95 CI = 1.74-4.30). Combined genotype of the two loci showed that the HYHX genotype (OR = 2.20, 95% CI = 1.95-2.48) and LYLX (OR = 1.97, 95% CI = 1.13-3.45) were associated with an increased risk of HTLV-1 infection.

CONCLUSION

Our results represent the importance of -221 X > Y variants in acquisition of HTLV-1 as this is the case for several other viral and bacterial infections.

Association of MBL2 gene polymorphisms with pulmonary tuberculosis susceptibility: trial sequence meta-analysis as evidence

Background

Mannose-binding lectin (MBL) or mannose-binding protein (MBP), encoded by MBL2 gene and secreted by the liver, activates complement system through lectin pathway in innate immunity against the host’s infection. Conflictingly, a number of MBL2 variants, rs1800450 (A>B), rs1800451 (A>C), rs5030737 (A>D), rs7096206 (Y>X), rs11003125 (H>L), and rs7095891 (P>Q) allele, have been found to be associated with compromised serum levels and pulmonary tuberculosis (PTB) susceptibility. The present meta-analysis study was performed to evaluate the potential association of these MBL2 gene variants with PTB susceptibility.

Materials and methods

A quantitative synthesis was performed on PubMed (Medline), EMBASE, and Google Scholar web database searches. A meta-analysis was performed to calculate the pooled odds ratios and 95% CIs for all the genetic models.

Results

A total of 14 eligible studies were included to analyze their pooled data for associations between alleles, genotypes, and minor allele carriers. The statistical analysis revealed the significant reduced PTB risk with homozygous variant genotype of rs1800451 polymorphism (CC vs AA: P=0.043; OR =0.828, 95% CI =0.689–0.994). Contrary to this, the variant allele of rs5030737 polymorphism showed association with increased PTB risk (D vs A: P=0.026; OR =1.563, 95% CI =1.054–2.317). However, the other genetic models of rs1800450 (A>B), rs7096206 (Y>X), and rs11003125 (H>L) MBL2 gene polymorphisms did not divulge any association with PTB susceptibility.

Conclusion

The current meta-analysis concludes that rs1800451 (A>C) and rs5030737 (A>D) polymorphisms of MBL2 gene play a significant role in PTB susceptibility. Further, well-designed epidemiological studies with larger sample size including consideration of environmental factors are warranted for the future.

CTLA-4 gene polymorphisms are associated with obesity in Turner Syndrome

Turner syndrome (TS) is characterized by a set of clinical conditions, including autoimmune/inflammatory diseases and infectious conditions, that can compromise a patient’s quality of life. Here we assessed polymorphisms in CTLA-4 +49A/G (rs231775), PTPN22 +1858G/A (rs2476601), and MBL2 -550 (H/L) (rs11003125), -221(X/Y) (rs7096206) and exon 1 (A/O) in women from northeastern Brazil to determine whether polymorphisms within these key immune response genes confer differential susceptibility to clinical conditions in TS. A case-control genetic association study was performed, including 86 female TS patients and 179 healthy women. An association was observed for the A/G genotype of CTLA-4 +49A/G in TS patients (p=0.043, odds ratio [OR]=0.54). In addition, an association between the CTLA-4 G/G genotype and obesity was detected in TS patients (p=0.02, OR=6.04). Regarding, the -550(H/L) polymorphism in the MBL2 promoter, the frequency of the H/L genotype was significantly higher in the TS group than healthy controls (p=0.01, OR=1.96). The H/H genotype indicated a protective effect in TS patients (p=0.01, OR=0.23). No differences were observed in the distribution of -221(X/Y), MBL2 exon 1 variants, and PTPN22 +1858G/A in any assessed groups. CTLA-4 variants are potentially involved in obesity in this cohort of TS patients from northeastern Brazil.

MBL2 gene polymorphisms in HHV-8 infection in people living with HIV/AIDS

Background

Host genetic factors such as MBL2 gene polymorphisms cause defects in the polymerization of MBL protein and result in a functional deficiency and/or in low serum levels that can influence susceptibility to various viral infections. The aim of this study was to estimate the frequency of alleles, genotypes and haplotypes related to -550, -221 and exon 1 polymorphisms of the MBL2 gene and investigate their association with HHV-8 in people living with HIV/AIDS (PLWHA), as well as the impacts on CD4 cell count and HIV viral load in HIV/HHV-8 coinfected and HIV monoinfected patients.

Results

A cross sectional study in PLWHA, with and without HHV-8 infection, exploring associations between different factors, was performed in the outpatient infectious and parasitic diseases clinic at a referral hospital. Genomic DNA extractions from leukocytes were performed using a commercial Wizard^®Genomic DNA Purification kit (Promega, Madison, WI). The promoter region (-550 and -221) was genotyped with the TaqMan system (Applied TaqMan Biosystems^® genotyping Assays), and the structural region (exon1) was genotyped with Express Sybr Greener Supermix kit (Invitrogen, USA). In total, 124 HIV/HHV-8 coinfected and 213 HIV monoinfected patients were analysed. Median TCD4 counts were significantly lower in HIV/HHV-8 coinfected patients, whereas the mean of the first and last viral load of HIV did not present significant difference. There was no difference in frequency between the LL, YY and AA genotypes between the HIV/HHV-8 coinfected or HIV monoinfected patients. However, in a multivariate analysis, coinfected patients with the intermediate expression haplotype of the MBL2 gene had an odds ratio of 3.1-fold (CI = 1.2–7.6) of their last CD4 cell count being below 350 cells/mm³. Among the coinfected individuals, four developed KS and presented the intermediate expression MBL haplotype, with three being HYA/LXA and one being LYA/LYO.

Conclusions

Host genetic factors, such as -550, -221 and exon 1 polymorphisms, can be related to the may modify coinfections and/or to the development clinical manifestations caused by HHV-8, especially in HIV/HHV-8 coinfected patients who present the intermediate expression haplotypes of MBL.

Genetic polymorphisms of MBL2 and tuberculosis susceptibility: a meta-analysis of 22 case-control studies

INTRODUCTION

The association of mannose-binding lectin gene (MBL2) polymorphisms with tuberculosis susceptibility was inconclusive. In this study, a meta-analysis of 22 case-control studies was carried out to assess the effect of MBL2 polymorphisms on tuberculosis risk.

MATERIAL AND METHODS

A search was performed in Embase, PubMed and Web of Science up to Sep 30, 2015. Odds ratio (OR) and 95% confidence interval (95% CI) were used to assess the association. Statistical analyses were performed using STATA 12.0 software.

RESULTS

rs1800451 was associated with a decreased tuberculosis risk in the allele model (C vs. A: OR = 0.93, 95% CI: 0.86-1.00, p = 0.050). In analyses stratified by ethnicity, rs7096206 (C/G: OR = 1.31, 95% CI: 1.10-1.57, p = 0.003; GG vs. GC + CC: OR = 0.69, 95% CI: 0.56-0.85, p < 0.001) and A/O (O/A: OR = 1.34, 95% CI: 1.10-1.64, p = 0.004) were associated with tuberculosis risk in Asians, A/O (AA vs. AO + OO: OR = 0.71, 95% CI: 0.51-0.99, p = 0.041) and rs1800451 (AC vs. AA + CC: OR = 2.70, 95% CI: 1.27-5.74, p = 0.010) were associated with tuberculosis risk in Americans, and rs1800451 (C/A: OR = 0.92, 95% CI: 0.86-0.99, p = 0.035) was associated with tuberculosis risk in Africans. Additionally, rs1800450 (B/A: OR = 0.42, 95% CI: 0.25-0.72, p = 0.001) was associated with tuberculosis risk in Europeans.

CONCLUSIONS

The MBL2 rs1800451 polymorphism is associated with decreased TB risk in the general population, and A/O, rs7096206, rs1800450 and rs1800451 are likely to be associated with the risk for some specific ethnic groups.

Genetic polymorphisms of exon 1 of MBL2 contribute to tuberculosis risk especially in Asian populations: an updated meta-analysis of 26 studies

Background

Evidence suggests that genetic variations of exon 1 of mannose-binding lectin 2 (MBL2) may contribute to tuberculosis (TB) risk. Many studies have investigated the association between MBL2 exon 1 polymorphisms (rs1800450, rs1800451, and rs5030737) and TB risk, but yielded inconclusive results.

Method

We conducted this meta-analysis of 26 eligible case–control studies that included 7952 cases and 9328 controls to identify the strength of association. Odds ratio (OR) and 95% CI were used to evaluate the strength of association. Statistical analyses were performed by using STATA 12.1.

Results

We found a statistically significant correlation between MBL2 exon 1 polymorphisms and increased TB risk among three models: allele model (O vs A: OR =1.18, 95% CI: 1.01–1.38, P_{heterogeneity}<0.0001, I²=85.8%), homozygote comparison (OO vs AA: OR =1.49, 95%CI: 1.02–2.18, P_{heterogeneity}<0.0001, I²=79.1%), dominant model (AO/OO vs AA: OR =1.20, 95% CI: 1.01–1.43, P_{heterogeneity}<0.0001, I²=83.5%), especially in studies based on Asian populations among five models: allele model (O vs A: OR =1.29, 95% CI: 1.11–1.51, P_{heterogeneity}<0.0001, I²=66.0%), homozygote comparison (OO vs AA: OR =1.67, 95% CI: 1.09–2.55, P_{heterogeneity}=0.008, I²=54.2%), heterozygote comparison (AO vs AA: OR =1.26, 95% CI: 1.05–1.50, P_{heterogeneity}=0.001, I²=62.9%), dominant model (AO/OO vs. AA: OR =1.31, 95% CI: 1.10–1.56, P_{heterogeneity}=0.001, I²=64.2%), and recessive model (OO vs AO/AA: OR =1.50, 95% CI: 1.01–2.22, P_{heterogeneity}=0.023, I²=48.0%). Meta-regression results revealed that source of controls (p=0.009), but not ethnicity (p=0.687), genotyping method (p=0.231), and sample size (p=0.451) contributed to the source of heterogeneity.

Conclusion

This meta-analysis suggests that MBL2 exon 1 polymorphisms may contribute to TB risk, especially in Asian populations.

Influence of Genetic Polymorphism Towards Pulmonary Tuberculosis Susceptibility

Tuberculosis (TB) is still remains the major threat for human health worldwide. Several case-control, candidate-gene, family studies and genome-wide association studies (GWAS) suggested the association of host genetic factors to TB susceptibility or resistance in various ethnic populations. Moreover, these factors modulate the host immune responses to tuberculosis. Studies have reported genetic markers to predict TB development in human leukocyte antigen (HLA) and non-HLA genes like killer immunoglobulin-like receptor (KIR), toll-like receptors (TLRs), cytokine/chemokines and their receptors, vitamin D receptor (VDR) and SLC11A1 etc. Highly polymorphic HLA loci may influence antigen presentation specificities by modifying peptide binding motifs. The recent meta-analysis studies revealed the association of several HLA alleles in particular class II HLA-DRB1 with TB susceptibility and valuable marker for disease development especially in Asian populations. Case-control studies have found the association of HLA-DR2 in some populations, but not in other populations, this could be due to an ethnic specific association of gene variants. Recently, GWAS conducted in case-control and family based studies in Russia, Chinese Han, Morocco, Uganda and Tanzania revealed the association of genes such as ASAP1, Alkylglycerol monooxygenase (AGMO), Forkhead BoxP1 (FOXP1), C-terminal domain phosphatase 1 (UBLCP1) and intergenic SNP rs932347C/T with TB. Whereas, SNP rs10956514A/G were not associated with TB in western Chinese Han and Tibetan population. In this review, we summarize the recent findings of genetic variants with susceptibility/resistance to TB.

Correlation between MBL2/CD14/TNF-α gene polymorphisms and susceptibility to spinal tuberculosis in Chinese population

Objective: The present study investigated the clinical significance of mannose-binding lectin 2 (MBL2), cluster of differentiation 14 (CD14) and tumour necrosis factor-α (TNF-α) gene polymorphisms in patients with spinal tuberculosis (TB) in Chinese population. Methods: A total of 240 patients with spinal TB were enrolled in the present study from May 2013 to August 2016 at Hangzhou Red Cross Hospital. A total of 150 age- and sex-matched healthy subjects were enrolled as controls. The genomic DNA was extracted from the peripheral blood of all subjects, and the MBL2, CD14 and TNF-α gene polymorphisms were detected by direct DNA sequencing. Results: (1) Compared with controls, patients with spinal TB exhibited a significantly higher frequency of the XY genotype at the −221G>C polymorphism as well as the Q allele and PQ genotype or an association with the QQ genotype at the +4C>T polymorphism in the MBL2 gene. (2) Compared with controls, patients with spinal TB exhibited a significantly higher frequency of the T allele and TT genotype or an association with the CT genotype at the −159C>T polymorphism in the CD14 gene. (3) Compared with controls, patients with spinal TB exhibited a significantly higher frequency of the T allele and the CT genotype or an association with the TT genotype at the TNF-857 polymorphism in the TNF-α gene. Conclusion: The −221G>C polymorphism of MBL2, the −159C>T polymorphism of CD14 and the TNF-857 polymorphism of TNF-α are risk factors for spinal TB and may be involved in the development of spinal TB in the Chinese population. These factors are indicators of susceptibility to spinal TB and require clinical attention.

Genomics of human pulmonary tuberculosis: from genes to pathways

Purpose of review

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), remains a major public health threat globally. Several lines of evidence support a role for host genetic factors in resistance/susceptibility to TB disease and MTB infection. However, results across candidate gene and genome-wide association studies (GWAS) are largely inconsistent, so a cohesive genetic model underlying TB risk has not emerged.

Recent Findings

Despite the difficulties in identifying consistent genetic associations, genetic studies of TB and MTB infection have revealed a few well-documented loci. These well validated genes are presented in this review, but there remains a large gap in how these genes translate into better understanding of TB. To address this, we present a pathway based extension of standard association analyses, seeding the results with the best validated genes from candidate gene and GWAS studies.

Summary

Several pathways were significantly enriched using pathway analyses that may help to explain population patterns of TB risk. In conclusion, we advocate for novel approaches to the study of host genetic analysis of TB that extend traditional association approaches.

Association of IFNG gene polymorphisms with pulmonary tuberculosis but not with spinal tuberculosis in a Chinese Han population

Spinal tuberculosis (STB) is an extrapulmonary form of tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb), which accounts for around 2% of all TB cases and can lead to spine degeneration. It is widely accepted that host genetic factors participate in the pathogenesis of active TB, but the factors controlling which TB form will manifest after Mtb infection remain unknown. We hypothesized that a genetic difference may exist between the development of STB and pulmonary tuberculosis (PTB). Here, three single nucleotide polymorphisms (SNPs) in the IFNG gene (rs2069718), IRGM gene (rs10065172), and MBL2 gene (rs11003125) were genotyped among 183 PTB patients, 177 STB patients, and 360 healthy controls from the Chinese Han population. We found that rs2069718 genotypes were significantly associated with PTB (TT, p = 0.007; CT, p = 0.008) but not STB, and the TT genotype (p = 0.046) of rs2069718 were less common in PTB than in STB. In contrast, neither PTB nor STB were found to be associated with rs10065172 and rs11003125. Overall, we found a difference in the rs2069718 genetic distribution between the STB and PTB patients in a Chinese Han population. The rs2069718 TT genotype was associated with a protective role in PTB but not STB development during active Mtb infection.

Mannose-Binding Lectin (MBL) gene polymorphisms in susceptibility to pulmonary tuberculosis among the Lur population of Lorestan Province of Iran

OBJECTIVE

Tuberculosis (TB) is caused by infection of Mycobacterium tuberculosis. Host genetic variability is an important determinant of the risk of developing TB in humans. Although the association between MBL polymorphisms and TB has been studied in various populations, the results are controversial. The aim of this study was to investigate mannose-binding lectin (MBL) gene polymorphisms with susceptibility to pulmonary tuberculosis (PTB) in a Lur population of Iran.

METHODS

In this case-control study, four functional MBL gene polymorphisms (HL, XY, PQ and AB) were genotyped by using PCR Single Strand Conformation Polymorphism (SSCP) technique in a Lur population living in Lorestan Province, consisting of 100 patients with pulmonary tuberculosis (PTB) age and sex matched 100 healthy controls (HCs). Association analyses were performed with the SPSS 21 statistical software.

RESULTS

We found that MBL (HH) genotype polymorphism significantly was associated with increased susceptibility to TB (35% in patients vs. 22% in controls, P = 0.0417, OR = 1.909, %95 CI = 1.020-3.573). Additionally, H allele showed a significant association with increased risk of TB (56.5% in patients vs. 46% in controls, P = 0.0357, OR = 1.525, %95 CI = 1.028-2.262). Also, the distribution of L allele in patients was significantly lower frequency in TB patients compared to controls (43.5% vs. 54%, P = 0.0357, OR = 0.656, %95 CI = 0.442-0.973). However, the allelic and genotypic frequencies of AB, XY and PQ polymorphisms were not significantly different between the patients and the controls. We couldn't detect any significant differences between haplotypes among TB patients and healthy controls.

CONCLUSIONS

Our findings demonstrated that HH genotype and H allele may increase the susceptibility to pulmonary TB in the Lur population of Iran, although L allele may decrease the susceptibility to pulmonary TB in this population. We suggest that it is necessary to further more studies with larger sample size and other ethnic population.

Association of mannose-binding lectin gene polymorphisms with the development of pulmonary tuberculosis in China

Background

Mannose-binding lectin (MBL) is an important protein in the lectin pathway of the immune system. This study explores the association between MBL polymorphism and the susceptibility to tuberculosis (TB). The association between the MBL2 polymorphisms and serum MBL levels is also analyzed in the present study.

Methods

A total of 112 inpatients with pulmonary TB and 120 healthy controls were recruited to participate in this case–control study. Polymerase Chain Reaction-Restriction Fragment Length Polymorphism(PCR-RFLP) technology was used to genotype MBL gene (variants in −221Y/X and exon l codons 54 A/B). Serum MBL level was assayed by human MBL ELISA kit. Demographic data and exposure information were also obtained from the study participants.

Results

Genotypes YA/YA of MBL gene were more prevalent in the healthy control group than in the TB patient (P =0.038, OR, 0.57; 95% CI, 0.34-0.97) and genotypes XA/XA were less frequent in the healthy control group (P =0.007, OR, 6.42; 95% CI, 1.39-29.67). The resistant diplotype was more frequently found in the younger patients and retreatment cases with TB in MBL gene sites −221Y/X or codon 54 A/B. X/Y and A/B polymorphisms were strong determinants of serum MBL levels.

Conclusion

The polymorphisms of MBL gene may be associated with susceptibility to TB and the recurrence of TB. The YA/YA may be a protected diplotype against TB.

A Meta-analysis of MBL2 Polymorphisms and Tuberculosis Risk

MBL2 gene encodes mannose-binding lectin, is a member of innate immune system. Earlier studies revealed that MBL2 gene variants, rs1800451, rs1800450, rs5030737, rs7096206, rs11003125 and rs7095891 are associated with impaired serum level and susceptibility to TB, but their results are inconsistent. A meta-analysis was performed by including 22 studies (7095 TB-patients and 7662 controls) and data were analyzed with respect to associations between alleles, genotypes and minor allele carriers to evaluate the potential association between MBL2 polymorphisms and TB risk. Statistically significant results were found only for the homozygous variant genotype (CC vs. AA: p = 0.045; OR = 0.834, 95% CI = 0.699 to 0.996) of rs1800451 and showed reduced risk of TB in overall population. However, other genetic models of rs1800450, rs5030737, rs7096206, rs11003125, rs7095891 and combined rs1800450, rs1800451, rs5030737 polymorphisms of MBL2 gene did not reveal any association with TB risk. Stratified analysis by ethnicity showed decreased risk of TB in African population for rs1800450 and rs1800451. Whereas, no association was observed between other MBL2 polymorphisms and TB risk in all the evaluated ethnic populations. In conclusion, MBL2 rs1800450 and rs1800451 polymorphisms play a protective role in TB infection and reinforce their critical significance as a potential genetic marker for TB resistance.

Association of Mannose-binding Lectin Polymorphisms with Tuberculosis Susceptibility among Chinese

Tuberculosis (TB) is caused by infection of Mycobacterium tuberculosis. Host genetic variability is an important determinant of the risk of developing TB in humans. Although the association between MBL2 polymorphisms and TB has been studied in various populations, the results are controversial. In this study four functional single-nucleotide polymorphisms (SNPs, H/L, X/Y, P/Q and A/B) across the MBL2 gene were genotyped by direct DNA sequencing of PCR products in a case-control population of Chinese Han origin, consisting of 1,020 patients with pulmonary TB and 1,020 controls. We found that individuals carrying variant allele at A/B (namely BB or AB genotypes) was associated with increased susceptibility to TB (odds ratios [OR] = 1.57, 95% confidence interval [CI] 1.30–1.91, P = 1.3 × 10⁻⁶). Additionally, LYPB haplotype showed a significant association with increased risk of TB (OR = 1.54, 95% CI 1.27–1.87, P = 4.2 × 10⁻⁶; global haplotype association P = 3.5 × 10⁻⁵). Furthermore, individuals bearing low- or medium- MBL expression haplotype pairs had an increased risk of TB (OR = 1.56, 95% CI 1.29–1.90, P = 1.4 × 10⁻⁶). Thus, the reduced expression of functional MBL secondary to having MBL2 variants may partially mediate the increased susceptibility to TB risk.

The Role of Host Genetics (and Genomics) in Tuberculosis

Familial risk of tuberculosis (TB) has been recognized for centuries. Largely through studies of mono- and dizygotic twin concordance rates, studies of families with Mendelian susceptibility to mycobacterial disease, and candidate gene studies performed in the 20th century, it was recognized that susceptibility to TB disease has a substantial host genetic component. Limitations in candidate gene studies and early linkage studies made the robust identification of specific loci associated with disease challenging, and few loci have been convincingly associated across multiple populations. Genome-wide and transcriptome-wide association studies, based on microarray (commonly known as genechip) technologies, conducted in the past decade have helped shed some light on pathogenesis but only a handful of new pathways have been identified. This apparent paradox, of high heritability but few replicable associations, has spurred a new wave of collaborative global studies. This review aims to comprehensively review the heritability of TB, critically review the host genetic and transcriptomic correlates of disease, and highlight current studies and future prospects in the study of host genomics in TB. An implicit goal of elucidating host genetic correlates of susceptibility to Mycobacterium tuberculosis infection or TB disease is to identify pathophysiological features amenable to translation to new preventive, diagnostic, or therapeutic interventions. The translation of genomic insights into new clinical tools is therefore also discussed.

Frequency Distribution of Mannose Binding Lectin-2 and Vitamin D Receptor Gene Variants: Putative Markers for Tuberculosis

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.

MBL-associated serine proteases (MASPs) and infectious diseases

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MASP-1 and MASP-2 are central players of the lectin pathway of complement.

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MASP1 and MASP2 gene polymorphisms regulate protein serum levels and activity.

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MASP deficiencies are associated with increased infection susceptibility.

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MASP polymorphisms and serum levels are associated with disease progression.

The lectin pathway of the complement system has a pivotal role in the defense against infectious organisms. After binding of mannan-binding lectin (MBL), ficolins or collectin 11 to carbohydrates or acetylated residues on pathogen surfaces, dimers of MBL-associated serine proteases 1 and 2 (MASP-1 and MASP-2) activate a proteolytic cascade, which culminates in the formation of the membrane attack complex and pathogen lysis. Alternative splicing of the pre-mRNA encoding MASP-1 results in two other products, MASP-3 and MAp44, which regulate activation of the cascade. A similar mechanism allows the gene encoding MASP-2 to produce the truncated MAp19 protein. Polymorphisms in MASP1 and MASP2 genes are associated with protein serum levels and functional activity. Since the first report of a MASP deficiency in 2003, deficiencies in lectin pathway proteins have been associated with recurrent infections and several polymorphisms were associated with the susceptibility or protection to infectious diseases. In this review, we summarize the findings on the role of MASP polymorphisms and serum levels in bacterial, viral and protozoan infectious diseases.

Impact of MBL and MASP-2 gene polymorphism and its interaction on susceptibility to tuberculosis

Background

Mannose-binding lectin (MBL) and MBL-associated serine proteases 2 (MASP-2) are important proteins in the lectin pathway of the immune system. Polymorphism of MBL and MASP-2 genes may affect the serum concentration of MBL and MASP-2. This study explores the association between MBL and MASP-2 gene polymorphism and their interactions and the susceptibility to tuberculosis (TB).

Method

A total of 503 patients with TB and 419 healthy controls were recruited to participate in this case-control study. PCR-SSP technology was applied to genotype rs7096206 of MBL genes and rs2273346 and rs6695096 of MASP-2 genes. Demographic data and some exposure information were also obtained from study participants. Unconditional logistic regression analysis was used to identify association between the various factors and TB whilst Marginal Structural Linear Odds Models were used to estimate the interactions.

Results

Both genotype GC at rs7096206 of MBL genes and genotype TC at rs2273346 and rs6695096 of MASP-2 genes were more prevalent in the TB patient group than the healthy control group (P < 0.05, OR 1.393, 1.302 and 1.426 respectively). The relative excess risk of interaction (RERI) between rs7096206 of MBL genes and rs2273346 and rs6695096 of MASP-2 genes was 0.897 (95% CI: 0.282, 1.513) and 1.142 (95% CI: 0.755, 1.530) respectively (P < 0.05).

Conclusion

Polymorphisms of MBL (rs7096206) and MASP-2 (rs2273346 and rs6695096) were associated with the susceptibility of TB, and there were gene-gene interactions among them.

Impact of passive smoking, cooking with solid fuel exposure, and MBL/MASP-2 gene polymorphism upon susceptibility to tuberculosis

BACKGROUND

To explore the impact of passive smoking, cooking with solid fuel, mannose-binding lectin (MBL) gene, MBL-associated serine proteases 2 (MASP-2) gene, and gene-environment interactions on the susceptibility to tuberculosis (TB) in non-smokers.

METHODS

A total of 205 TB patients and 216 healthy controls were recruited to participate in this case-control study. PCR with sequence-specific primers (PCR-SSP) technology was leveraged to genotype rs7096206 of MBL genes and rs2273346 and rs6695096 of MASP-2 genes. Demographic data and information on exposures of participants were collected. Unconditioned logistic regression analysis was conducted to identify associations between the various factors and TB, and marginal structural linear odds models were used to estimate the interactions.

RESULTS

Passive smoking and cooking with solid fuel were associated with the risk of TB, with odds ratios (OR) of 1.58 and 2.93, respectively (p<0.05). Genotype CG at rs7096206 of MBL genes (OR 2.02) and genotype TC at rs6695096 of MASP-2 genes (OR 1.67) were more prevalent in the TB patients than in healthy controls (p<0.05). The relative excess risk of interaction (RERI) between rs7096206 of MBL genes and passive smoking or cooking with solid fuel exposure was 1.86 (95% confidence interval (CI) 0.59-3.16) and 2.66 (95% CI 1.85-3.47), respectively. The RERI between rs6695096 of MASP-2 genes and cooking with solid fuel exposure was 3.70 (95% CI 2.63-4.78), which was also a positive interaction. However, the RERI between rs6695096 of MASP-2 genes and passive smoking was not statistically significant.

CONCLUSIONS

Passive smoking, cooking with solid fuel, and polymorphisms of MBL (rs7096206) and MASP-2 (rs6695096) genes were associated with susceptibility to TB in non-smokers, and there were gene-environment interactions among them. Further studies are needed to explore details of the mechanisms of association.