IFNG +874T/A polymorphism and cytokine plasma levels are associated with susceptibility to Mycobacterium tuberculosis infection and clinical manifestation of tuberculosis

Differential combination of cytokine and interferon- γ +874 T/A polymorphisms determines disease severity in pulmonary tuberculosis

BACKGROUND

Mycobacterium tuberculosis infects nearly 1/3 of the world population and this reservoir forms the largest pool from which new cases arise. Among the cytokines, IFN-γ is a key determinant in protection against tuberculosis. Single nucleotide polymorphisms (SNPs) in IFN-γ gene (+874 T/A) which determine TT high ((hi)), AA low ((lo)) and TA intermediate ((int)) responder phenotypes have shown variable associations with tuberculosis disease outcome in different ethnic populations. The objective of the current study was to analyze IFN-γ gene combinations with other IFN-γ regulating cytokine genes (IL-10, TNF -α, IL-6) to see the effect of gene- combinations on disease severity outcome in pulmonary tuberculosis.

METHODS AND FINDINGS

Study groups comprised of pulmonary TB patients stratified according to lung tissue involvement into mild (Pmd = 74) or advance (Pad = 23) lung disease and compared with healthy controls (TBNA = 166). Genotype analysis was carried out using amplification refractory mutation system-PCR (ARMS-PCR). IFN-γ gene (+874 T/A) functional SNP combinations in TNFα (-308 G/A), IL-10 (-1082 A/G) and IL-6 (-174 G/C) were analyzed. Single gene analysis (Pearson χ²) showed a dominant association of IFN-γ TT (hi) genotype (p = 0.001) and T allele (p = 0.001) with mild disease. IFN-γ(lo) -IL-10(lo) genotype combination was associated with advanced disease (p = 0.002). IFN-γ(hi) -IL-6(hi) combination was associated with mild disease (p = 0.0005) while IFN-γ(lo) -IL-6(int) was associated with protection against both forms of pulmonary disease (p = 0.002).

CONCLUSION

Our results show that a limited number of IFN-γ gene combinations with other cytokine functional SNPs determine the outcome of disease severity in tuberculosis.

Increased interleukin-10 and interferon-γ levels in Plasmodium vivax malaria suggest a reciprocal regulation which is not altered by IL-10 gene promoter polymorphism

Background

In human malaria, the naturally-acquired immune response can result in either the elimination of the parasite or a persistent response mediated by cytokines that leads to immunopathology. The cytokines are responsible for all the symptoms, pathological alterations and the outcome of the infection depends on the reciprocal regulation of the pro and anti-inflammatory cytokines. IL-10 and IFN-gamma are able to mediate this process and their production can be affected by single nucleotide polymorphisms (SNPs) on gene of these cytokines. In this study, the relationship between cytokine IL-10/IFN-gamma levels, parasitaemia, and their gene polymorphisms was examined and the participation of pro-inflammatory and regulatory balance during a natural immune response in Plasmodium vivax-infected individuals was observed.

Methods

The serum levels of the cytokines IL-4, IL-12, IFN-gamma and IL-10 from 132 patients were evaluated by indirect enzyme-linked immunosorbent assays (ELISA). The polymorphism at position +874 of the IFN-gamma gene was identified by allele-specific polymerase chain reaction (ASO-PCR) method, and the polymorphism at position -1082 of the IL-10 gene was analysed by PCR-RFLP (PCR-Restriction Fragment Length Polymorphism).

Results

The levels of a pro- (IFN-gamma) and an anti-inflammatory cytokine (IL-10) were significantly higher in P. vivax-infected individuals as compared to healthy controls. The IFN-gamma levels in primoinfected patients were significantly higher than in patients who had suffered only one and more than one previous episode. The mutant alleles of both IFN-gamma and IL-10 genes were more frequent than the wild allele. In the case of the IFNG+874 polymorphism (IFN-gamma) the frequencies of the mutant (A) and wild (T) alleles were 70.13% and 29.87%, respectively. Similar frequencies were recorded in IL-10-1082, with the mutant (A) allele returning a frequency of 70.78%, and the wild (G) allele a frequency of 29.22%. The frequencies of the alleles associated with reduced production of both IFN-gamma and IL-10 were high, but this effect was only observed in the production of IFN-gamma.

Conclusions

This study has shown evidence of reciprocal regulation of the levels of IL-10 and IFN-gamma cytokines in P. vivax malaria, which is not altered by the presence of polymorphism in the IL-10 gene.

The +874T/A polymorphism in the interferon-γ gene and tuberculosis risk: an update by meta-analysis

The +874T/A polymorphism in the interferon-γ (IFN-γ) gene has been extensively examined for association to tuberculosis (TB); however, results of different studies have been inconsistent. The aim of this study was to comprehensively analyze the genetic risk of the +874T/A polymorphism in IFN-γ gene for TB by meta-analysis. A total of 4553 cases and 4631 controls in 21 case-control studies were included in this meta-analysis. The results indicated that the variant T allele carriers had a 27% decreased risk of TB, when compared with the homozygote AA (odds ratio [OR] = 0.73, 95% confidence interval [CI] = 0.61-0.87 for TT + TA versus AA). In the subgroup analysis by ethnicity, significant decreased risks were associated with T allele carriers in Asians (OR= 0.71, 95% CI = 0.52-0.97, p = 0.03) but not in Caucasians (OR = 0.87, 95% CI = 0.65-1.17, p = 0.37). Our results suggest that the IFN-γ +874T/A polymorphism contributes to susceptibility to TB.

Polymorphisms in the RANTES gene increase susceptibility to active tuberculosis in Tunisia

RANTES plays a pivotal role in attracting and activating various leukocyte populations that control Mycobacterium tuberculosis infection. The present study investigated the relationship between the RANTES polymorphisms (-28C/G; rs2280788, and -403G/A; rs2107538) and susceptibility to active tuberculosis (TB) in Tunisian populations. A total of 168 patients with pulmonary TB (pTB), 55 with extrapulmonary TB (epTB), and 150 control subjects were studied. Genotype analyses were carried out using polymerase chain reaction-restriction fragment length polymorphism method. We found that the -28 GG genotype was significantly associated with susceptibility to pTB (odds ratio [OR]=11.19; 95% confidence intervals [CI], 5.14-25; P corrected for the number of genotypes [Pc]=10(-8)) and epTB (OR=11.67; 95% CI, 4.74-29.33; Pc=10(-8)). However, the -28 CC genotype was found to be significantly associated with resistance to pTB (OR=0.08; 95% CI, 0.04-0.16; Pc=10(-8)) and epTB development (OR=0.11; 95% CI, 0.05-0.27; Pc=10(-8)). -403A allele was associated with increased risk development of epTB (OR=2.21; 95% CI, 1.18-4.14; p=0.007). G-G and A-C haplotypes and the AG/GC diplotype were associated with increase susceptibility to pTB (OR=7.88, 95% CI, 5.38-11.55; Pc=3.10(-8); OR=2.32, 95% CI, 1.32-4.11; Pc=3.10(-3); OR=13.26, 95% CI, 6.06-29.89; Pc=3.10(-8); respectively) and epTB (OR=6.64, 95% CI, 4-11.05; Pc=3.10(-8); OR=2.6, 95% CI, 1.26-5.35; Pc=12.10(-3); OR=11.26, 95% CI, 4.44-29.28; Pc=3.10(-8); respectively). Collectively, our findings suggested an association of the RANTES -28C/G and -403G/A functional polymorphisms with susceptibility to Mycobacterium tuberculosis infection in Tunisian populations.

Differential serum cytokine levels are associated with cytokine gene polymorphisms in north Indians with active pulmonary tuberculosis

Globally only 5-10% of people encountering Mycobacterium tuberculosis have a lifetime risk of active disease indicating a strong host genetic bias towards development of tuberculosis. In the current study we investigated genotype variants pertaining to five cytokine genes namely IFNG, TNFA, IL4, IL10 and IL12 in the north Indian population with active pulmonary tuberculosis (APTB) and correlated the serum cytokine levels with the corresponding genotypes. Twenty five single nucleotide polymorphisms (SNPs) including six loci examined for the first time in tuberculosis were selected for genotyping in 108 patients with APTB from north India and 48 healthy regional controls (HC). Applying exclusion criteria 12 SNPs passed all the filters and were analysed further. The serum cytokine concentrations were measured by ELISA. Compared to HC mean serum IFN-γ, IL-12, IL-4, and IL-10 levels were higher in APTB (p = 0.3661, p = 0.0186, p = 0.003, p = 0.7, respectively). In contrast the mean serum TNF-α level was higher in HC (p = 0.007). Comparison of genotypes and serum levels of the corresponding cytokine genes reveal that though IFN-γ and IL-4 levels were higher in APTB the genotype variants showed no difference between HC and APTB. In contrast the genotypes of the selected rsIDs in the TNFA, IL12 and IL10 genes showed significant association with the varying serum levels of corresponding cytokines. The variant of the TNFA gene at rs3093662, the IL12 gene at rs3213094 and rs3212220 and the IL10 gene at rs3024498 did show a strong indication to be of relevance to the immunity to tuberculosis. To our knowledge this is the first report from this region relating genotypes and serum cytokine levels in north Indian population.

MCP-1 -2518 A/G functional polymorphism is associated with increased susceptibility to active pulmonary tuberculosis in Tunisian patients

Monocyte chemoattractant protein-1 (MCP-1) plays crucial role in protective immunity against Mycobacterium tuberculosis (MT). In this study, we examined whether single nucleotide polymorphism (SNP) -2518 A/G (rs 1024611) of MCP-1 affect the susceptibility to active tuberculosis (TB) in Tunisian populations. Genomic DNA from patients with active TB (168 cases of pulmonary TB and 55 cases of extrapulmonary TB) and ethnically controls (150 cases) was genotyped for the MCP-1 -2518 A/G SNP by polymerase chain reaction fragment length polymorphism (PCR-RFLP). We observed that -2518 G allele and GG genotype (high MCP-1 producer) frequencies were significantly more elevated in active pulmonary TB group in comparison to control group [34 vs. 22%; P = 0.0007; 15 vs. 5%, P corrected for the number of genotypes (Pc) = 0.015; respectively]. Additionally, they were associated with increased risk development of this clinical form of TB [odds ratio (OR) = 1.83, 95% confidence intervals (CI) = 1.26-2.66; OR = 3.1, 95% CI = 1.28-7.76; respectively]. However, wild type allele -2518 A and AA genotype were over-represented in control group (78 and 62%) and seem to be protective factors against TB. Moreover, -2518 AA genotype was more frequent in control group and was associated with resistance against development of active pulmonary TB (OR = 0.56, 95% CI = 0.35-0.89, Pc = 0.03). Our findings confirm the key role of -2518 A/G SNP of MCP-1 and support its association with resistance/susceptibility to the development of active pulmonary TB in the Tunisian population.

Specific T cell frequency and cytokine expression profile do not correlate with protection against tuberculosis after bacillus Calmette-Guérin vaccination of newborns

RATIONALE

Immunogenicity of new tuberculosis (TB) vaccines is commonly assessed by measuring the frequency and cytokine expression profile of T cells.

OBJECTIVES

We tested whether this outcome correlates with protection against childhood TB disease after newborn vaccination with bacillus Calmette-Guérin (BCG).

METHODS

Whole blood from 10-week-old infants, routinely vaccinated with BCG at birth, was incubated with BCG for 12 hours, followed by cryopreservation for intracellular cytokine analysis. Infants were followed for 2 years to identify those who developed culture-positive TB-these infants were regarded as not protected against TB. Infants who did not develop TB disease despite exposure to TB in the household, and another group of randomly selected infants who were never evaluated for TB, were also identified-these groups were regarded as protected against TB. Cells from these groups were thawed, and CD4, CD8, and γδ T cell-specific expression of IFN-γ, TNF-α, IL-2, and IL-17 measured by flow cytometry.

MEASUREMENTS AND MAIN RESULTS

A total of 5,662 infants were enrolled; 29 unprotected and two groups of 55 protected infants were identified. There was no difference in frequencies of BCG-specific CD4, CD8, and γδ T cells between the three groups of infants. Although BCG induced complex patterns of intracellular cytokine expression, there were no differences between protected and unprotected infants.

CONCLUSIONS

The frequency and cytokine profile of mycobacteria-specific T cells did not correlate with protection against TB. Critical components of immunity against Mycobacterium tuberculosis, such as CD4 T cell IFN-γ production, may not necessarily translate into immune correlates of protection against TB disease.