| Objective: Tuberculous meningitis(TBM) is one of the most severe forms of infectious diseases caused by Mycobacterium tuberculosis(M. tuberculosis), which is mostly involved of meninges and parenchyma of the brain and spinal cord and membrane can be involved at the same time. It’s estimated that one third of wold’s population are potentially infected with M. tuberculosis, while only 10% of that develop into clinical disease. WHO estimated that in 2013, an estimated 9.0 million people developed TB and 1.5 million died from the disease, 360 000 of whom were HIV-positive. According to the WHO report 2014, the incidence rate of TB was 70 per 100,000 population in China in 2013. TBM results from the haematogenous dissemination of M. tuberculosis from the lung to the meninges and parenchyma of the brain or spinal cord and represents around 1% of all forms of TB. The reason why some patients with PTB develop TBM, but most do not and why some patients develop TBM without PTB has not yet been established These clinical situations suggest that besides environmental or bacterial factors, the host response to the pathogen may play a major role in the development of TB disease. The optimal antituberculosis chemotherapy of TBM is also uncertain and the regimen is the same used for PTB. A number of studies have suggested that host genetics play an important role in TB susceptibility though the results were controversial in different ethnic groups and most of them are limited to PTB. The solute carrier family 11 A member 1(SLC11A1) has been shown to be a critical element in the regulation of intracellular membrane vesicle trafficking of macrophages. SLC11A1 gene has been studied extensively for genetic association with TB, especially with PTB. This study was for the first time to evaluate the possible association between SLC11A1 D543 N polymorphism and TBM in a sample of Chinese adult population.Methods: Case group included 346 subjects, of which 113 patients with TBM were enrolled consecutively from Department of Neurology, the Second Hospital of Hebei Medical University between January 2014 and September 2014. Of the 113 subjects with TBM in the study, all of them had a positive stain for acid fast bacilli at least for one time. A total of 233 patients diagnosed with active PTB were enrolled between January 2014 and September 2014 at Hebei Chest Disease Hospital and The fifth hospital of Shijiazhuang City. All of them were bacteriologically confirmed. 395 control subjects were from hospital patients of neurology department without history and clinical manifestations of tuberculosis. Venous blood samples from all subjects were collected and DNA was extracted. The typing of D543 N was performed using polymerase chain reaction-restriction fragment length polymorphism(PCR-RFLP) technique. Ten percent of individuals from each study group were randomly chosen, directly sequenced and used as genotyping positive controls. A case-control study was designed to compare the distribution of alleles and genotypes.All subjects with TBM were underwent lumbar puncture and CSF specimens were submitted to take cerebrospinal fluid routine, biochemical examination, MGG pigmentation, alcian blue pigmentation and modified Ziehl-Neelsen stain. All TBM patients had clinical manifestation of fever and headache while PTB patients had cough and low fever.Results:1 Cases and controls: The case group included 346 subjects. Of which 232(67.1%) were male while 114(32.9%) were female. The median age for case group was 36.9±17.4 years. The case group included subgroups of TBM group and PTB group. TBM group included 113 subjects, Of which 70(61.9%) were male while 43(38.1%) were female. PTB group included 233 subjects, of which 162(69.5%) were male while 71(30.5%)were female. There was no statistical difference between control and case group in gender comparison(χ2=3.675,P=0.055). There was significant difference between control and case group in age comparison(t=18.898,P<0.001). TBM group and PTB group are younger than control group(TBM vs control, t=13.111,P<0.001; PTB vs control, t=18.898,P<0.001). There was no difference between TBM group and control group when compared with gender(χ2=0.106,P=0.745) while there was difference between PTB group and control group(χ2=5.452,P=0.020).2 The detection of Hardy-Weinberg equilibrium(HWE): The genotypes of control were in Hardy-Weinberg equilibrium(HWE)(P>0.05).3 The analysis of allele frequency and genotype distribution of SLC11A1 gene D543 N locus: The A allele was a predisposing risk factor for TB group(OR=1.453, 95% CI: 1.076-1.961, P=0.014). The results of Chi-square test without considering age and sex are as following: D543 N polymorphism was a risk predisposing factor for TB in additive tested inheritance model(OR=1.571, 95% CI: 1.127-2.190, P=0.007). This study also showed that D543 N polymorphism was significantly associated with susceptibility to TB in dominant tested inheritance model(OR=1.564, 95% CI: 1.125-2.175, P=0.008). Multivariate logistic regression analysis was used when age and sex were adjusted: D543 N polymorphism was a risk predisposing factor for TB in additive tested inheritance model(OR=2.127, 95% CI: 1.403-3.225, P<0.001) and dominant tested inheritance model(OR=2.125, 95% CI: 1.405-3.212, P<0.001).4 The analysis of allele frequency and genotype distribution of SLC11A1 gene D543 N locus stratified by clinical forms: The A allele was a predisposing risk factor for TBM group(OR=1.770, 95% CI: 1.181-2.654, P=0.005). The results of Chi-square test without considering age and sex are as following: D543 N polymorphism was a risk predisposing factor for TBM in additive tested inheritance model(OR=1.981, 95% CI: 1.249-3.141, P=0.003). This study also showed that D543 N polymorphism was significantly associated with susceptibility to TBM in dominant tested inheritance model(OR=1.985, 95% CI: 1.257-3.136, P=0.003). Multivariate logistic regression analysis was used when age and sex were adjusted: D543 N polymorphism was a risk predisposing factor for TBM in additive tested inheritance model(OR=2.706, 95% CI: 1.509-4.851, P=0.001) and dominant tested inheritance model(OR=2.647, 95% CI: 1.484-4.720, P=0.001). This study also showed that D543 N polymorphism was a risk predisposing factor for PTB in additive tested inheritance model(OR=1.925, 95% CI: 1.207-3.070, P =0.006) and dominant tested inheritance model(OR=1.934, 95% CI: 1.217-3.075, P=0.005) while there was no difference of A allele frequency between PTB group and control group(OR=1.313, 95% CI: 0.937-1.840, P=0.112).5 The analysis of allele frequency and genotype distribution of SLC11A1 gene D543 N locus stratified by sex and used by Multivariate logistic regression: We identified statistically significant difference between the TB and control groups among male subjects(OR=1.722, 95% CI: 1.053-2.817, P=0.030) and female subjects(OR=3.371, 95% CI: 1.557-7.296, P=0.002) with regard to the frequency of genotype variants AG and AA at the D543 N locus in additive tested inheritance model. When TBM group was compared with control group, the significant association regarding to the frequency of variant genotypes at the D543 N locus was only seen in female subjects(OR=6.064, 95% CI: 2.207-16.657, P<0.001). There was a higher frequency of variant genotypes at the D543 N locus in the PTB group than in the control group only among male subjects(OR=1.802, 95% CI: 1.049-3.096, P=0.033).6 Variant genotype AG at the D543 N locus was more strongly associated with susceptibility to TBM(OR=2.725, 95% CI: 1.612-4.606, P<0.001) than to pulmonary TB(OR=1.885, 95% CI: 1.208-2.942, P=0.005) proved by multinomial logistic regression when age and sex were adjusted.Conclusions:1 The increase of allele A frequency may increase the occurrence of tuberculosis.2 The variant genotype AG at the D543 N locus is more strongly associated with susceptibility to TBM than to PTB.3 Patient gender may affect the susceptibility of SLC11A1 gene D543 N polymorphism to TBM and PTB given that frequencies of genotype distribution in male subjects and female subjects are different. |
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