Impact Of MBL/MASP-2Gene Polymorphism And Related Factors On Susceptibility To Tuberculosis Among Hans Population In Hunan Province

Background:Tuberculosis (TB) is a global public health issue posing serious harm to the human health. It is estimated that there were8.6million TB patients in2012globally. China has the second highest TB burden in the world. According to the5th TB epidemiological sampling survey in2010in China, the TB prevalence was459/100,000among people aged15years and above.Many studies have suggested that smoking, excessive alcohol consumption and cooking with solid fuel are risk factors for TB. Laboratory evidence suggests that EGCG in tea leaves can arrest the growth of tubercle bacillus by inhibiting the activity of InhA, the enoyl-acyl carrier protein reductase in tubercle bacillus. It can also inhibit the survival of tubercle bacillus within macrophages by inhibiting the TACO (tryptophan-aspartate containing coat protein) gene transcription within macrophages. Previous studies suggest that the polymorphism of MBL genes in promoter region and structural region affects the formation of MBL multimer and the serum MBL concentration. The reduction of MBL multimer results in the impaired binding with ligand and the increased likelihood of being degraded by metalloproteinase. MASP-2gene mutation also facilitates the changes in the serum concentration of the proteins it encodes (namely, MASP2and Map19), and results in the impaired binding with MBL and ficolin molecules, consequently blocking the lectin pathway of complement activation and resulting in the impaired non-specific body immune system functioning.Objective:This study explores the impact of MBL/MASP-2gene polymorphism and environmental factors on susceptibility to tuberculosis among Hans population in Hunan province.Methods:Sources of cases:A two-step stratified sampling was conducted to randomly select cases. First, four county-level CDCs (i.e. Qidong County CDC, Yueyanglou District CDC, Yueyang County CDC and Hongjiang City CDC) was chosen using the random number table containing122counties/cities/districts in Hunan Province. Then, cases were randomly selected from all new TB patients registered in2009in the four county-level CDCs. All cases were TB patients confirmed following the TB diagnosis criteria developed by the Chinese Ministry of Health.Sources of healthy controls:Controls were selected following the similar stratified sampling strategy. First, one community health service center (i.e. Xingang Community Health Service Center) was selected using the random number table containing14community health service centers in Kaifu District, Changsha City. Next, one of the six communities (i.e. Xin’ansi Community) covered by the Xingang Community Health Service Center was randomly selected. Finally, healthy controls with a history of mycobacterium tuberculosis contact were randomly selected from the permanent residents in the Xin’ansi Community, the number of which was equal to the cases. Among the healthy controls with a BCG scar, the average diameter of PPD (purified protein derivative) induration was≥10mm. In those without a BCG scar and without a history of BCG vaccination, the average diameter of PPD (purified protein derivative) induration was≥5mm. No abnormalities were found in the chest X-ray of all healthy controls.After each subject signed the written informed consent form, self-developed questionnaire was used to collect data. We used EDTA anticoagulant tubeto collect5ml to extract peripheral white blood cell genome.Genotyping:In our study, we used PCR-SSP to genotype the rs7096206of MBL genes, as well as the rs2273346and rs6695096of MASP-2genes.Statistical Analysis:Epidata3.0was used to input data, and SAS9.2was used to analyze the data.Χ2test was conducted for comparing grouped data and detecting Hardy-Weinberg equilibrium. Logistic regression was used for multivariate analysis. Marginal Structural Linear Odds Models were used for the point and interval estimation of the relative excess risk of the interaction (RERI). RERI>0indicate a positive interaction. RER1<0indicate a negative interaction.Results:Smoking was associated with the risk of TB, OR=1.605(1.121,2.296), P<0.05. Tea drinking was a protective factor against TB, OR=0.674(0.476,0.955), P<0.05. The genotype GC at rs7096206of MBL genes and the genotype TC at rs2273346and rs6695096of MASP-2genes in the TB patient group were both more prevalent than those in the healthy control group (P<0.05), with OR1.427,1.379and1.396respectively. The interactions between rs7096206of MBL genes and rs2273346and rs6695096of MASP-2genes were positive, with the relative excess risk of interactions (RERI)0.7675(0.1521,1.3831) and1.0429(0.6556,1.4301) respectively (P<0.05). The interaction between rs7096206of MBL genes and smoking was positive with the RERI0.5360(0.2996,0.7728), P<0.05. There was a positive interaction between rs2273346of MASP-2genes and smoking with the RERI0.4570(0.1522,0.7619), P<0.05. There were negative interactions between rs7096206of MBL genes, rs2273346and rs6695096of MASP-2genes and tea drinking, with RERIs-0.6530(-0.9830,-0.3230),-0.2862(-0.5393,-0.03319) and-0.4907(-0.8356,-0.1455) respectively (P<0.05). Passive smoking and cooking with solid fuel were associated with the risk of TB in non-smokers, with the OR1.51(1.02-2.26) and2.78(1.81-4.28) respectively (P<0.05). There were positive interactions between rs7096206of MBL genes and passive smoking or cooking with solid fuel exposure, with the RERIs1.857(0.594,3.150) and2.45(1.66,3.24) respectively (P<0.05). The interaction between rs6695096of MASP-2genes and cooking with solid fuel exposure was negative, with the RERI2.60(1.57,3.61), P<0.05.Conclusion:Smoking, passive smoking, cooking with solid fuel exposure could increase the risk of TB. Tea drinking could decrease the risk of TB. The heterozygous mutations at rs7096206of MBL genes, rs2273346and rs6695096of MASP-2genes were associated with the susceptibility to TB. There were positive interactions between rs7096206of MBL genes and rs2273346or rs6695096of MASP-2genes. There were positive interactions between rs7096206of MBL genes or rs2273346of MASP-2genes and smoking. There were negative interactions between rs7096206of MBL genes or rs6695096of MASP-2genes and tea drinking. There were positive interactions between rs7096206of MBL genes and smoking in non-smokers. There were positive interactions between rs7096206of MBL genes or rs6695096of MASP-2genes and smoking in non-smokers.