Single nucleotide polymorphisms in toll-like receptor 6 are associated with altered lipopeptide- and mycobacteria-induced interleukin-6 secretion

Polymorphisms of inflammation-related genes and susceptibility to childhood leukemia: evidence from a meta-analysis of 16 published studies

OBJECTIVE

This study was to comprehensively clarify the associations between single nucleotide polymorphisms (SNPs) in inflammatory genes and the susceptibility to childhood leukemia.

METHODS

Eligible articles were collected from the databases of PubMed, EMBASE, Cochrane Library, CNKI and Wan Fang. The pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated to estimate the association strength by using the STATA 15.0 software.

RESULTS

Sixteen studies were enrolled. These studies mainly evaluated SNPs in 13 genes, including C-X-C motif chemokine ligand 12 (CXCL12), toll-like receptor (TLR)-4, TLR6, TLR9, CD14, interleukin (IL)-1β, NLR family pyrin domain containing 3, IL-4, interleukin 4 receptor, IL-10, IL-13, macrophage migration inhibitory factor (MIF) and tumor necrosis factor-α. The meta-analysis indicated that CXCL12 rs1801157 (AG vs GG: OR = 1.99; 95%CI = 1.20-3.30; p = 0.008; AA + AG vs GG: OR = 1.92; 95%CI = 1.18-3.12; p = 0.009), TLR6 rs5743810 (TC vs TT: OR = 0.58; 95%CI = 0.39-0.85; p = 0.005), IL-10 rs1800871 (TC vs CC: OR = 1.19; 95%CI = 1.01-1.41; p = 0.044), rs1800872 (AC vs AA: OR = 1.53; 95%CI = 1.22-1.92; p < 0.001) and MIF rs755622 (CG versus GG: OR = 1.33; 95%CI = 1.07-1.67; p = 0.012) polymorphisms were associated with the risk of childhood leukemia. No significant correlations were found between SNPs in other genes and the childhood leukemia risk. Subgroup analyses of rs1800871 and rs1800872 confirmed the conclusions obtained in their overall meta-analytical processes.

CONCLUSION

CXCL12 rs1801157, TLR6 rs5743810, IL-10 rs1800871, rs1800872 and MIF rs755622 polymorphisms may represent candidate biomarkers for the risk prediction of childhood leukemia.

Association between polymorphisms of TLR2-1-6 and bipolar disorder in a tunisian population

BACKGROUND

Bipolar disorder (BD) is a complex neuropsychiatric disease that has been strongly linked to immune dysregulation. In particular, an abnormal inflammatory response mediated by toll-like receptor 2 - 1/6 (TLR2-1/6) was described in BD. Nevertheless, genetic factors' contribution is still unknown. Thus, we suggested that functional polymorphisms of TLR2, 1 and 6 could be involved in BD predisposition.

METHODS AND RESULTS

TLR2, 1 and 6 polymorphisms were genotyped by PCR-RFLP in 292 controls and 131 patients from a Tunisian population. Polymorphisms and haplotype associations were explored in BD and binary logistic regression analysis was performed for more powerful associations. In dominant model, we found a significantly higher genotype and minor allele frequencies in healthy females compared to patients for TLR2-196-174Ins/Del (p = 0.04; OR = 0.3, p = 0.04; OR = 0.3, respectively) and for TLR6-S249P only with minor allele (p = 0.03; OR = 0.2). In contrast, TLR2-R677W CT + TT and T allele frequencies were significantly higher in BD (padjusted<10- 4; ORadjusted =46.6, p < 10- 4; OR = 6.3, respectively), specifically in females (CT + TT: 100%). Similarly, TLR1-R80T showed significantly increased GC + CC and C allele frequencies in patients compared to controls (padjusted=0.04; ORadjusted=4, p = 0.009; OR = 4.3, respectively). Moreover, haplotype investigation demonstrated that InsGTCGT (p < 10- 4, OR = 275) and delGCCGT (p = 0.03, OR = 18.5) were significantly overrepresented in BD patients compared to controls.

CONCLUSIONS

We suggest that TLR2-196-174Ins/Del and TLR6-S249P could be protective factors of females against BD. However, TLR2-R677W and TLR1-R80T could be strongly associated with higher risk of BD. Interestingly, TLR2-R677W could be a genetic marker for BD in females. However, further studies with larger groups are needed to confirm these findings.

Single Nucleotide Variants in the TLR1, TLR2 and TLR6 Genes: A Case-Control Study in a Colombian Population

BACKGROUND

Single nucleotide variants in toll-like receptor genes play a crucial role in leprosy susceptibility or resistance.

METHODS

With an epidemiology case-control study, associations between SNVs rs5743618 in TLR1, rs5743708 in TLR2, and rs5743810 in TLR6 and overall susceptibility for leprosy were estimated in 114 cases and 456 controls. Following that, stratified analysis was performed. DNA was extracted from peripheral blood. Genotyping was performed using predesigned TaqMan probes.

RESULTS

The A/G genotype of rs5743810 behaved as a protective factor for the development of leprosy in the codominant (OR= 0.37; 95% CI = 016-0.86, p = 0.049) and over-dominant (OR = 0.38; 95% CI = 0.16-0.88, p = 0.019) inheritance models. The A/G and A/A genotypes behaved as a protective factor (OR = 0.39; 95% CI = 0.17-0.87, p = 0.016) in the dominant model. The SNVs rs5743618 and rs5743708 showed no association with any of the models. The CGG haplotype (rs5743618-rs5743708-rs5743810) behaved as a susceptibility factor for developing leprosy (OR = 1.86; 95% CI = 1.11-3.10, p = 0.019). The latter haplotype behaved as a susceptibility factor for leprosy development in women (OR = 2.39; 95% CI = 1.21-4.82, p = 0.013).

CONCLUSIONS

The identified variants in the genes encoding TLRs, specifically rs5743810 in TLR6 and CGG (rs5743618-rs5743708-rs5743810) haplotypes, may somehow explain leprosy susceptibility in the studied population in a leprosy endemic region in Colombia.

Association of Toll-like Receptors 1, 2, 4, 6, 8, 9 and 10 Genes Polymorphisms and Susceptibility to Pulmonary Tuberculosis in Sudanese Patients

Background

Genetic factors are important contributors to the development of a wide range of complex disease. Polymorphisms in genes encoding for toll-like receptors (TLRs) usually influence the efficiency of the immune response to infection and are associated with disease susceptibility and progression. Therefore, we aim to describe the first association between TLR1, TLR2, TLR4 TLR6, TLR8, TLR9 and TLR10 genes polymorphisms and susceptibility to pulmonary tuberculosis (PTB) in Sudanese patients.

Methodology

Here we performed a case study which included 160 tuberculosis patients and 220 healthy matched controls from Sudan. In the study population, we evaluated the possible association between 86 markers in TLR1, TLR2, TLR4 TLR6, TLR8, TLR9 and TLR10 genes polymorphisms and susceptibility to PTB disease in Sudanese population using polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP).

Results

From our results it appeared that in the PTB population the TLR1 (rs5743557, rs4833095, rs5743596), TLR2 (rs5743704, rs5743708, rs3804099), TLR4 (rs4986790, rs4986791), TLR6 (rs5743810), TLR8 (rs3764879, rs3764880), TLR9 (rs352165, rs352167, rs187084) and TLR10 (rs4129009) were significantly more often encountered (p<0.0001) than in the control population and were associated with PTB in the Sudanese population. For the other polymorphisms tested, no association with PTB was found in the population tested.

Conclusion

The work describes novel mutations in TLR1, TLR2, TLR4, TLR6, TLR8, TLR9 and TLR10 genes and their association with PTB infection in Sudanese population. These results will enhance our ability to determine the risk of developing the disease by targeting specific TLR pathways to reduce the severity of the disease. Future studies are needed in a larger sample to replicate our findings and understand the mechanism of association of TLR polymorphism in PTB.

High-expression of the innate-immune related gene UNC93B1 predicts inferior outcomes in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous hematological malignancy with dismal prognosis. Identification of better biomarkers remained a priority to improve established stratification and guide therapeutic decisions. Therefore, we extracted the RNA sequence data and clinical characteristics of AML from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression database (GTEx) to identify the key factors for prognosis. We found UNC93B1 was highly expressed in AML patients and significantly linked to poor clinical features (p < 0.05). We further validated the high expression of UNC93B1 in another independent AML cohort from GEO datasets (p < 0.001) and performed quantitative PCR of patient samples to confirm the overexpression of UNC93B1 in AML (p < 0.005). Moreover, we discovered high level of UNC93B1 was an independent prognostic factor for poorer outcome both in univariate analysis and multivariate regression (p < 0.001). Then we built a nomogram model based on UNC93B1 expression, age, FAB subtype and cytogenetic risk, the concordance index of which for predicting overall survival was 0.729 (p < 0.001). Time-dependent ROC analysis for predicting survival outcome at different time points by UNC93B1 showed the cumulative 2-year survival rate was 43.7%, and 5-year survival rate was 21.9%. The differentially expressed genes (DEGs) between two groups divided by UNC93B1 expression level were enriched in innate immune signaling and metabolic process pathway. Protein-protein interaction (PPI) network indicated four hub genes (S100A9, CCR1, MRC1 and CD1C) interacted with UNC93B1, three of which were also significantly linked to inferior outcome. Furthermore, we discovered high UNC93B1 tended to be infiltrated by innate immune cells, including Macrophages, Dendritic cells, Neutrophils, Eosinophils, and NK CD56dim cells. We also found UNC93B1 had a significantly positive correlation with CD14, CD68 and almost all Toll-like receptors. Finally, we revealed negatively correlated expression of UNC93B1 and BCL2 in AML and conjectured that high-UNC93B1 monocytic AML is more resistant to venetoclax. And we found high MCL-1 expression compensated for BCL-2 loss, thus, we proposed MCL-1 inhibitor might overcome the resistance of venetoclax in AML. Altogether, our findings demonstrated the utility of UNC93B1 as a powerful poor prognostic predictor and alternative therapeutic target.

Association of Single Nucleotide Polymorphisms from Angiogenesis-Related Genes, ANGPT2, TLR2 and TLR9, with Spontaneous Preterm Labor

In this study, we hypothesized that the changes localized at angiopoietin-2 (ANGPT2), granulocyte-macrophage colony-stimulating factor (CSF2), fms-related tyrosine kinase 1 (FLT1) and toll-like receptor (TLR) 2, TLR6 and TLR9 genes were associated with spontaneous preterm labor (PTL), as well as with possible genetic alterations on PTL-related coagulation. This case-control genetic association study aimed to identify single nucleotide polymorphisms (SNPs) for the aforementioned genes, which are correlated with genetic risk or protection against PTL in Polish women. The study was conducted in 320 patients treated between 2016 and 2020, including 160 women with PTL and 160 term controls in labor. We found that ANGPT2 rs3020221 AA homozygotes were significantly less common in PTL cases than in controls, especially after adjusting for activated partial thromboplastin time (APTT) and platelet (PLT) parameters. TC heterozygotes for TLR2 rs3804099 were associated with PTL after correcting for anemia, vaginal bleeding, and history of threatened miscarriage or PTL. TC and CC genotypes in TLR9 rs187084 were significantly less common in women with PTL, compared to the controls, after adjusting for bleeding and gestational diabetes. For the first time, it was shown that three polymorphisms-ANGPT2 rs3020221, TLR2 rs3804099 and TLR9 rs187084 -were significantly associated with PTL, adjusted by pregnancy development influencing factors.

The Genetic Association Between TLR-1, -2, -4, and -6 Gene Polymorphisms and Rheumatoid Arthritis Susceptibility in a Chinese Han Population

Aims: The toll-like receptor (TLR) genes were shown to be involved in the pathogenesis of rheumatoid arthritis (RA). We aimed to investigate the genetic associations between the TLR-1, -2, -4, and -6 genes polymorphisms and RA susceptibility in a Chinese Han population. Methods: Six polymorphisms [TLR-1 (rs5743610, rs5743618), -2 (rs5743708), -4 (rs4986790, rs4986791), and -6 (rs5743810)] in TLRs genes were genotyped in 360 patients with RA and 560 matched healthy controls by using direct sequencing method. The odds ratios (ORs) and 95% confidence intervals (CIs) were evaluated using a standard logistic regression analysis. Results: No significant association between the allelic, dominant, and recessive models of TLR-1 rs5743610, TLR-2 rs5743708, TLR-4 rs4986790 and rs4986791, and TLR-6 rs5743810 polymorphisms and RA risk was observed (p > 0.05). However, significant associations were detected between the allelic, dominant, and recessive models of TLR-1 rs5743618 and RA risk (allelic: OR [95% CI] = 2.21 [1.73-2.81], p < 0.0001; dominant: OR [95% CI] = 2.33 [1.75-3.09], p < 0.0001; recessive models: OR [95% CI] = 3.70 [1.85-7.41], p = 0.0002). In addition, the TLR6 rs5743810 was found to be associated with the rheumatoid factor (RF)^- and anticyclic citrullinated peptide (anti-CCP)^- antibody in RA group (RF: OR [95% CI] = 2.29 [1.42-3.69], p = 0.0007; anti-CCP: OR [95% CI] = 2.33 [1.39-3.89], p = 0.001). Conclusions: The allelic, dominant, and recessive models of TLR1 rs5743618 might be associated with RA susceptibility. Also, the TLR6 rs5743810 might be associated with RF and anti-CCP antibody of RA in Chinese Han population.

Evaluation of Polymorphisms in Toll-Like Receptor Genes as Biomarkers of the Response to Treatment of Erythema Nodosum Leprosum

Erythema nodosum leprosum (ENL) is an inflammatory complication caused by a dysregulated immune response to Mycobacterium leprae. Some Toll-like receptors (TLRs) have been identified as capable of recognizing antigens from M. leprae, triggering a wide antimicrobial and inflammatory response. Genetic polymorphisms in these receptors could influence in the appearance of ENL as well as in its treatment. Thus, the objective of this work was to evaluate the association of genetic variants of TLRs genes with the response to treatment of ENL with thalidomide and prednisone. A total of 162 ENL patients were recruited from different regions of Brazil and clinical information was collected from their medical records. Genomic DNA was isolated from blood and saliva samples and genetic variants in TLR1 (rs4833095), TLR2 (rs3804099), TLR4 (rs1927914), and TLR6 (rs5743810) genes were genotyped by TaqMan real-time PCR system. In order to evaluate the variants' association with the dose of the medications used during the treatment, we applied the Generalized Estimating Equations (GEE) analysis. In the present sample, 123 (75.9%) patients were men and 86 (53.1%) were in treatment for leprosy during the ENL episode. We found an association between polymorphisms in TLR1/rs4833095, TLR2/rs3804099, TLR4/rs1927914, and TLR6/rs5783810 with the dose variation of thalidomide in a time-dependent manner, i.e., the association with the genetic variant and the dose of the drug was different depending on the moment of the treatment evaluated. In addition, we identified that the association of polymorphisms in TLR1/rs4833095, TLR2/rs3804099, and TLR6/rs5783810 with the dose variation of prednisone also were time-dependent. Despite these associations, in all the interactions found, the influence of genetic variants on dose variation was not clinically relevant for therapeutic changes. The results obtained in this study show that TLRs polymorphism might play a role in the response to ENL treatment, however, in this context, they could not be considered as useful biomarkers in the clinical setting due small differences in medication doses. A larger sample size with patients with a more genetic profile is fundamental in order to estimate the association of genetic variants with the treatment of ENL and their clinical significance.

Variants of Toll-like receptor 6 associated with tuberculosis susceptibility in the Chinese Tibetan population

BACKGROUND

Our investigation attempted to understand the role of innate immunity related genes played in tuberculosis. The relationship between single-nucleotide polymorphisms (SNPs) of three innate immunity-related genes (TLR6, MyD88, and TIRAP) and tuberculosis (TB) risk in two Chinese populations were explored.

METHODS

Totally 1185 Chinese Han, consisting of 580 active TB cases and 605 healthy controls (HCs), and 1216 Chinese Tibetan individuals including 613 TB patients and 603 HCs were enrolled to conduct two case-control studies. TagSNPs of the three genes were selected based on the HapMap database and genotyped by the SNPscan™ Kit. Haploview software 4.2 was applied to perform linkage disequilibrium (LD) analysis and online software SHEsis was used to discover significant haplotype block. RegulomeDB and HaploReg were applied to predict potential functional SNPs of the three genes.

RESULTS

The results showed that minor alleles of rs5743808 and rs5743827 of TLR6 were related with increased TB risk (p = 0.001, OR 95%CI = 1.51 (1.18-1.95) and p = 0.002, OR 95%CI = 1.42 (1.14-1.77)), and significant association was also observed between rs5743827 and TB risk in male subgroup (p = 0.003, OR 95%CI = 1.67 (1.91-2.35)) in the Tibetan population. For the Tibetan population, frequency of haplotype ACGT of rs1039559-rs3775073-rs5743808-rs5743827 of TLR6 was significantly higher in the TB group (p = 0.0008), while haplotype ATAC was significantly higher in the control group (p = 0.0002). The above associations remained after permutation and Bonferroni correction. No significant association was found in the Han population. Probable functions of tagSNPs of TLR6 and some other linked variants were discovered after bioinformatic analysis.

CONCLUSIONS

This study suggested that variants of TLR6 might be associated with TB risk in the Tibetan population, while not in the Han population. The difference between Chinese Han and Tibetan people will provide better understanding of tuberculosis.

Synergistic effect of genetic polymorphisms in TLR6 and TLR10 genes on the risk of pulmonary tuberculosis in a Moldavian population

Polymorphisms in genes that control immune function and regulation may influence susceptibility to pulmonary tuberculosis (TB). In this study, 14 polymorphisms in 12 key genes involved in the immune response (VDR, MR1, TLR1, TLR2, TLR10, SLC11A1, IL1B, IL10, IFNG, TNF, IRAK1, and FOXP3) were tested for their association with pulmonary TB in 271 patients with TB and 251 community-matched controls from the Republic of Moldova. In addition, gene-gene interactions involved in TB susceptibility were analyzed for a total of 43 genetic loci. Single nucleotide polymorphism (SNP) analysis revealed a nominal association between TNF rs1800629 and pulmonary TB (Fisher exact test P = 0.01843). In the pairwise interaction analysis, the combination of the genotypes TLR6 rs5743810 GA and TLR10 rs11096957 GT was significantly associated with an increased genetic risk of pulmonary TB (OR = 2.48, 95% CI = 1.62-3.85; Fisher exact test P value = 1.5 × 10^-5, significant after Bonferroni correction). In conclusion, the TLR6 rs5743810 and TLR10 rs11096957 two-locus interaction confers a significantly higher risk for pulmonary TB; due to its high frequency in the population, this SNP combination may serve as a novel biomarker for predicting TB susceptibility.

Donor UNC-93 Homolog B1 genetic polymorphism predicts survival outcomes after unrelated bone marrow transplantation

UNC-93 homolog B1 (UNC93B1) is a key regulator of toll-like receptors (TLRs), pattern recognition receptors that sense invading pathogens and manage the innate immune response and deliver them from the endoplasmic reticulum to their respective endosomal signaling compartments. Several types of TLRs are known to contribute to the inflammatory process after allogeneic hematopoietic stem cell transplantation (SCT), so UNC93B1 might play integral roles there. We investigated the influence of the UNC93B1 single-nucleotide polymorphism (SNP) rs308328 (T>C) on transplant outcomes in a cohort of 237 patients undergoing unrelated HLA-matched bone marrow transplantation (BMT) for hematologic malignancies through the Japan Marrow Donor Program. The donor UNC93B1 C/C genotype was associated with a better 3-year overall survival than the donor UNC93B1 C/T or T/T genotype. An analysis of the UNC93B1 rs308328 genotype may therefore be useful for selecting the donor, estimating the prognosis, and creating therapeutic strategies after allogeneic SCT.

The impact of human single nucleotide polymorphisms on Bacillus Calmette-Guérin responses

The influence of genetic variability on human immune responses has major implications for the understanding of disease mechanisms and host-pathogen interactions. Bacillus Calmette-Guérin (BCG) vaccine, which is given globally to protect against tuberculosis, has high variability in its protective efficacy against mycobacteria and its beneficial off-target (heterologous) effects. Single nucleotide polymorphisms (SNPs) are major cause of genetic variation and have been strongly associated with susceptibility to tuberculosis and outcomes following BCG immunotherapy for cancer. This review discusses the contribution of SNPs to the variability in mycobacterial-specific and off-target BCG responses, and the implications for this on development of novel TB vaccines and strategies to harness the beneficial off-target effects of BCG.

Single Nucleotide Polymorphisms in TLR4 Affect Susceptibility to Tuberculosis in Mexican Population from the State of Veracruz

Tuberculosis is still a global public health problem, with an estimated 10 million new cases and 1.6 million deaths in 2017. Of all humans infected with M. tuberculosis, only 10-15% will develop active tuberculosis disease during their lifetime, and data suggest that along with environmental factors, genetic factors influence susceptibility to develop active disease. Toll-like receptors (TLRs) are pattern recognition receptors that play a central role in the initiation and shaping of adaptive immune responses, and several TLRs have been shown to recognize mycobacterial components. In this work, we performed a case-control study to determine if common single nucleotide polymorphisms (SNPs) in genes encoding TLRs 1, 2, 4, 6, and 10 are associated with susceptibility to develop active tuberculosis in population from the state of Veracruz, Mexico. The study included 279 cases and 569 controls. The results show that the frequency of two SNPs in TLR4 was significantly higher in controls than in tuberculosis patients. The minor allele (G) of rs4986790 in TLR4 (D299G) decreased the risk of active tuberculosis in the allelic (A vs. G, OR = 0.31, 95%CI = 0.09‐0.81, p = 0.01) and in the dominant genetic model (AA vs. GG+AG, OR = 0.26, 95%CI = 0.09‐0.77, p = 0.02). Similarly, the minor allele (T) of rs4986791 in TLR4 (T399I) decreased the risk of active disease in the allelic model (C vs. T, OR = 0.29, 95%CI = 0.10‐0.90, p = 0.03). We did not find an association of SNPs in TLR1 (N248S), TLR2 (R753Q), TLR6 (S249P), and TLR10 (A153S and V298I) with tuberculosis disease. These results suggest that in this population, genetic variants of TLR4 affect the susceptibility for suffering active tuberculosis disease.

N-terminal diversity of Litopenaeus vannamei hemocyanin and immunity

Hemocyanin is primarily a respiratory copper-containing glycoprotein present in the hemolymph of mollusks and arthropods. Recently, hemocyanin has attracted huge research interest due to its multifunctionality and polymorphism. Most previous immune-related studies on shrimp hemocyanin have focused on the C-terminal. Moreover, we previously reported that the C-terminal domain of Litopenaeus vannamei hemocyanin possesses single nucleotide polymorphisms (SNPs), but little is known about the molecular diversity of the N-terminal domain. In the current study, diversity within the N-terminal domain of L. vannamei hemocyanin (LvHMC-N) was explored using bioinformatics and molecular biology techniques as well as immune challenge. Twenty-five LvHMC-N variants were identified using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and DNA sequencing, with multiple sequence alignment showing that the 25 variants shared 87%-99 % sequence homology with LvHMC (AJ250830.1). In different shrimp individuals and different shrimp tissues (i.e., hemocytes, stomach, muscle and hepatopancreas), the LvHMC-N variants were expressed differently. Pathogen challenge could modulate the molecular diversity of LvHMC-N, as three LvHMC-Nr variants (LvHMC-Nr1, LvHMC-Nr2 and LvHMC-Nr3) were identified by sequencing following Vibrio parahaemolyticus challenge. Most importantly, recombinant proteins of these three variants (rLvHMC-Nr1, rLvHMC-Nr2 and rLvHMC- Nr3) had relatively high in vitro agglutinative activities against V. parahaemolyticus, Vibrio alginolyticus and Streptoccocus iniae. Our present data indicates that the N-terminus of L. vannamei hemocyanin also possess molecular diversity, which seems to be associated with immune resistance to pathogenic infections.

Association of the TLR1 variant rs5743557 with susceptibility to tuberculosis

Background

Toll-like receptor 1 (TLR1) and TLR6 play important roles in the innate immune response against Mycobacterium tuberculosis (M.TB) via interactions with TIR domain-containing adaptor protein (TIRAP) and myeloid differentiation primary response 88 (MYD88). The aim of this study was to investigate the relationship of TLR1, TLR6, MYD88 and TIRAP polymorphisms with susceptibility to latent tuberculosis infection (LTBI) and tuberculosis (TB).

Methods

In total, 204 uninfected healthy controls (HC), 201 individuals with LTBI and 209 TB patients were enrolled. Two interferon-γ release assays were used to differentiate individuals with LTBI from uninfected controls. TagSNPs of the four genes were genotyped by the SNPscan^TM Kit. The Haploview 4.2 and SHEsis software packages were combined to perform linkage disequilibrium (LD) and haplotype analyses. Multifactor dimensionality reduction (MDR) software was used to investigate gene-gene interaction. The Stata 12.0 software was used to perform meta-analysis of the relationship between rs5743557 and TB susceptibility.

Results

The AA genotype of rs5743557 was associated with reduced TB risk (P=0.006) and the AA/GA genotypes of TLR1 rs5743604 were associated with increased TB risk (P=0.017) when the LTBI group was compared with the TB group. The frequency of TLR1 haplotype rs4833095-rs5743604 CG was significantly higher in the LTBI group than in the TB group (P=0.019877). However, only the relationship between rs5743557 and TB susceptibility remained significant after 1000-fold permutation testing (P=0.023). The meta-analysis suggested that rs5743557_A was associated with decreased TB risk in the Chinese adult population (P<0.001, OR 0.80, 95% CI: 0.72-0.88). No significant gene-gene interactions were found.

Conclusions

The results of our study suggest that the tagSNP rs5743557 of TLR1 is associated with the risk of TB.

SNPs in the Toll1 receptor of Litopenaeus vannamei are associated with immune response

Tolls and Toll-like receptors (TLRs) are important regulators in the innate immune system and their genetic variations usually affect the host's susceptibility/resistance to pathogen infections. In this study, we report on the single nucleotide polymorphisms (SNPs) of Toll1 in Litopenaeus vannamei (LvToll1) and how this is associated with immune response. PCR-DGGE analysis revealed genetic polymorphisms in LvToll1 at both the genomic DNA (gDNA) and cDNA levels. Using high-throughput sequencing, 223 SNPs were identified at the gDNA level, of which 145 were non-synonymous SNP (nsSNP), with 3 nsSNPs having frequency over 1%. On the other hand, 60 SNPs were identified at the cDNA level including 38 nsSNPs and 4 nsSNPs with frequency over 1%. Upon challenging shrimps with Streptococcus iniae, Vibrio parahaemolyticus and white spot syndrome virus (WSSV), LvToll1 was shown to generate 6, 4 and 4 novel bands, respectively when analyzed with PCR-DGGE. Sequencing analysis of these bands showed that they contained 6, 4 and 2 nsSNPs, respectively. Moreover, the nsSNP C1526T was detected in S. iniae-resistant but not in susceptible shrimps. Most significantly, the C1526T mutation could shorten the α-helix of the LRR domain and was predicted to affect the function of LvToll1, indicating that SNP C1526T might be associated with shrimp's resistance to pathogen infections. In sum, our findings here reveal that the genetic polymorphisms of Toll receptor are linked with the immune response to pathogen infections in L. vannamei.

The interaction between farming/rural environment and TLR2, TLR4, TLR6 and CD14 genetic polymorphisms in relation to early- and late-onset asthma

Asthma phenotypes based on age-of-onset may be differently influenced by the interaction between variation in toll-like receptor (TLR)/CD14 genes and environmental microbes. We examined the associations between single-nucleotide polymorphisms (SNP) in the TLR/CD14 genes and asthma, and their interaction with proxies of microbial exposure (childhood farm exposure and childhood rural environment). Ten SNPs in four genes (TLR2, TLR4, TLR6, CD14) were genotyped for 1,116 participants from the Tasmanian Longitudinal Health Study (TAHS). Using prospectively collected information, asthma was classified as never, early- (before 13 years) or late-onset (after 13 years). Information on childhood farm exposure/childhood rural environment was collected at baseline. Those with early-onset asthma were more likely to be males, had a family history of allergy and a personal history of childhood atopy. We found significant interaction between TLR6 SNPs and childhood farm exposure. For those with childhood farm exposure, carriers of the TLR6-rs1039559 T-allele (p-interaction = 0.009) and TLR6-rs5743810 C-allele (p-interaction = 0.02) were associated with lower risk of early-onset asthma. We suggest the findings to be interpreted as hypothesis-generating as the interaction effect did not withstand correction for multiple testing. In this large, population-based longitudinal study, we found that the risk of early- and late-onset asthma is differently influenced by the interaction between childhood farming exposure and genetic variations.

Whole genome sequencing of an African American family highlights toll like receptor 6 variants in Kawasaki disease susceptibility

Kawasaki disease (KD) is the most common acquired pediatric heart disease. We analyzed Whole Genome Sequences (WGS) from a 6-member African American family in which KD affected two of four children. We sought rare, potentially causative genotypes by sequentially applying the following WGS filters: sequence quality scores, inheritance model (recessive homozygous and compound heterozygous), predicted deleteriousness, allele frequency, genes in KD-associated pathways or with significant associations in published KD genome-wide association studies (GWAS), and with differential expression in KD blood transcriptomes. Biologically plausible genotypes were identified in twelve variants in six genes in the two affected children. The affected siblings were compound heterozygous for the rare variants p.Leu194Pro and p.Arg247Lys in Toll-like receptor 6 (TLR6), which affect TLR6 signaling. The affected children were also homozygous for three common, linked (r² = 1) intronic single nucleotide variants (SNVs) in TLR6 (rs56245262, rs56083757 and rs7669329), that have previously shown association with KD in cohorts of European descent. Using transcriptome data from pre-treatment whole blood of KD subjects (n = 146), expression quantitative trait loci (eQTL) analyses were performed. Subjects homozygous for the intronic risk allele (A allele of TLR6 rs56245262) had differential expression of Interleukin-6 (IL-6) as a function of genotype (p = 0.0007) and a higher erythrocyte sedimentation rate at diagnosis. TLR6 plays an important role in pathogen-associated molecular pattern recognition, and sequence variations may affect binding affinities that in turn influence KD susceptibility. This integrative genomic approach illustrates how the analysis of WGS in multiplex families with a complex genetic disease allows examination of both the common disease–common variant and common disease–rare variant hypotheses.

Epistatic effect of TLR-1, -6 and -10 polymorphisms on organic dust-mediated cytokine response

Exposure to organic dust from agricultural environments is associated with inflammatory respiratory conditions. The putative causal agents in organic dust include viral, microbial and fungal components, which are recognized by the family of toll-like receptors and drive host innate and adaptive responses. Our aim in this study was to determine whether responsiveness to organic dust among agricultural workers was dependent on polymorphisms in the TLR10-TLR1-TLR6 gene cluster. We stimulated whole blood from 509 agricultural workers with organic dust, triacyl lipopeptide N-palmitoyl-S-dipalmitoylglyceryl Cys-Ser-(Lys)₄ (Pam3CSK4) and the diacyl- lipopeptide peptidoglycan. Several of the tagging polymorphisms and haplotypes conferred hyper-responsiveness to organic dust with an increase in IL-6 (p < 0.005), but not TNF-α, secretion. We conclude that genetic variation in the TLR10-TLR1-TLR6 gene cluster mediates responsiveness to organic dust, but indicates different signaling pathways for IL-6 and TNF-α. These studies provide new insight into the role of the TLR10-TLR1-TLR6 gene cluster and the innate immune response to organic dust.

Associations of Toll-Like Receptor and β-Defensin Polymorphisms with Measures of Periodontal Disease (PD) in HIV+ North American Adults: An Exploratory Study

Polymorphisms in toll-like receptor (TLR) and β-defensin (DEFB) genes have been recognized as potential genetic factors that can influence susceptibility to and severity of periodontal diseases (PD). However, data regarding associations between these polymorphisms and PD are still scarce in North American populations, and are not available in HIV+ North American populations. In this exploratory study, we analyzed samples from HIV+ adults (n = 115), who received primary HIV care at 3 local outpatient HIV clinics and were monitored for PD status. We genotyped a total of 41 single nucleotide polymorphisms (SNPs) in 8 TLR genes and copy number variation (CNV) in DEFB4/103A. We performed regression analyses for levels of 3 periodontopathogens in subgingival dental plaques (Porphyromonas gingivalis [Pg], Treponema denticola [Td], and Tannerella forsythia [Tf]) and 3 clinical measures of PD (periodontal probing depth [PPD], gingival recession [REC], and bleeding on probing [BOP]). In all subjects combined, 2 SNPs in TLR1 were significantly associated with Td, and one SNP in TLR2 was significantly associated with BOP. One of the 2 SNPs in TLR1 was significantly associated with Td in Caucasians. In addition, another SNP in TLR1 and a SNP in TLR6 were also significantly associated with Td and Pg, respectively, in Caucasians. All 3 periodontopathogen levels were significantly associated with PPD and BOP, but none was associated with REC. Instrumental variable analysis showed that 8 SNPs in 6 TLR genes were significantly associated with the 3 periodontopathogen levels. However, associations between the 3 periodontopathogen levels and PPD or BOP were not driven by associations with these identified SNPs. No association was found between DEFB4/103A CNV and any periodontopathogen level or clinical measure in all samples, Caucasians, or African Americans. Our exploratory study suggests a role of TLR polymorphisms, particularly TLR1 and TLR6 polymorphisms, in PD in HIV+ North Americans.

TLR-6 SNP P249S is associated with healthy aging in nonsmoking Eastern European Caucasians - A cohort study

BACKGROUND

To investigate mechanisms that determine healthy aging is of major interest in the modern world marked by longer life expectancies. In addition to lifestyle and environmental factors genetic factors also play an important role in aging phenotypes. The aged immune system is characterized by a chronic micro-inflammation, known as inflamm-aging, that is suspected to trigger the onset of age-related diseases such as cardiovascular disease, Alzheimer's disease, cancer, and Diabetes Mellitus Type 2 (DMT2). We have recently shown that a Toll-like receptor 6 variant (P249S) is associated with susceptibility to cardiovascular disease and speculated that this variant may also be associated with healthy aging in general by decreasing the process of inflamm-aging.

RESULTS

Analyzing the PolSenior cohort we show here that nonsmoking S allele carriers are significantly protected from age-related diseases (P = 0.008, OR: 0.654). This association depends not only on the association with cardiovascular diseases (P = 0.018, OR: 0.483) for homozygous S allele carriers, but is also driven by a protection from Diabetes Mellitus type 2 (P = 0.010, OR: 0.486) for S allele carriers. In addition we detect a trend but no significant association of this allele with inflamm-aging in terms of baseline IL-6 levels.

CONCLUSION

We confirm our previous finding of the TLR-6 249S variant to be protective regarding cardiovascular diseases. Furthermore, we present first evidence of TLR-6 249S being involved in DMT2 susceptibility and may be in general associated with healthy aging possibly by reducing the process of inflamm-aging.

Genetic variation in pattern recognition receptors: functional consequences and susceptibility to infectious disease

Cells of the innate immune system are equipped with surface and cytoplasmic receptors for microorganisms called pattern recognition receptors (PRRs). PRRs recognize specific pathogen-associated molecular patterns and as such are crucial for the activation of the immune system. Currently, five different classes of PRRs have been described: Toll-like receptors, C-type lectin receptors, nucleotide-binding oligomerization domain-like receptors, retinoic acid-inducible gene I-like receptors and absent in melanoma 2-like receptors. Following their discovery, many sequence variants in PRR genes have been uncovered and shown to be implicated in human infectious diseases. In this review, we will discuss the effect of genetic variation in PRRs and their signaling pathways on susceptibility to infectious diseases in humans.

Toll-Like Receptor Family Polymorphisms Are Associated with Primary Renal Diseases but Not with Renal Outcomes Following Kidney Transplantation

Toll-like receptors (TLRs) play a crucial role in innate- and adaptive immunity. The TLR pathways were shown to play key functional roles in experimental acute and chronic kidney injury, including the allo-immune response after experimental renal transplantation. Data about the precise impact of TLRs and their negative regulators on human renal transplant outcomes however are limited and contradictory. We studied twelve non-synonymous single nucleotide polymorphisms (SNPs) of which eleven in TLR1-8 and one in SIGIRR in a final cohort comprising 1116 matching donors and recipients. TLR3 p.Leu412Phe and SIGIRR p.Gln312Arg significantly deviated from Hardy-Weinberg equilibrium and were excluded. The frequency distribution of the minor alleles of the remaining 10 TLR variants were compared between patients with end-stage renal disease (recipients) and controls (kidney donors) in a case-control study. Secondly, the associations between the minor allele frequency of the TLR variants and delayed graft function, biopsy-proven acute rejection and death-censored graft failure after transplantation were investigated with Cox regression. Carrier frequencies of the minor alleles of TLR1 p.His305Leu (OR = 4.79, 95% CI = 2.35–9.75, P = 0.0002), TLR1 p.Asn248Ser (OR = 1.26, 95% CI = 1.07–1.47, P = 0.04) and TLR8 p.Met1Val (OR = 1.37, 95% CI = 1.14–1.64, P = 0.008) were significantly higher in patients with ESRD, with little specificity for the underlying renal disease entity (adjusted for age, gender and donor-recipient relatedness). The minor allele frequency of none of the TLR variants significantly associated with the surrogate and definite outcomes, even when multivariable models were created that could account for TLR gene redundancy. In conclusion, genetic variants in TLR genes were associated with the prevalence of ESRD but not renal transplant outcomes. Therefore, our data suggests that specific TLR signaling routes might play a role in the final common pathway of primary renal injury. A role for TLR signaling in the context of renal transplantation is probably limited.

TLR1, 2, 4, 6 and 9 Variants Associated with Tuberculosis Susceptibility: A Systematic Review and Meta-Analysis

BACKGROUND

Studies investigating the influence of toll-like receptor (TLR) polymorphisms and tuberculosis susceptibility have yielded varying and often contradictory results in different ethnic groups. A meta-analysis was conducted to investigate the relationship between TLR variants and susceptibility to tuberculosis, both across and within specific ethnic groups.

METHODS

An extensive database search was performed for studies investigating the relationship between TLR and tuberculosis (TB) susceptibility. Data was subsequently extracted from included studies and statistically analysed.

RESULTS

32 articles involving 18907 individuals were included in this meta-analysis, and data was extracted for 14 TLR polymorphisms. Various genetic models were employed. An increased risk of TB was found for individuals with the TLR2 rs3804100 CC and the TLR9 rs352139 GA and GG genotypes, while decreased risk was identified for those with the AG genotype of TLR1 rs4833095. The T allele of TLR6 rs5743810 conferred protection across all ethnic groups. TLR2 rs5743708 subgroup analysis identified the A allele to increase susceptibility to TB in the Asian ethnic group, while conferring protection in the Hispanic group. The T allele of TLR4 rs4986791 was also found to increase the risk of TB in the Asian subgroup. All other TLR gene variants investigated were not found to be associated with TB in this meta-analysis.

DISCUSSION

Although general associations were identified, most TLR variants showed no significant association with TB, indicating that additional studies investigating a wider range of pattern recognition receptors is required to gain a better understanding of this complex disease.

Less functional variants of TLR-1/-6/-10 genes are associated with age

BACKGROUND

Determining the prerequisites for healthy aging is a major task in the modern world characterized by a longer lifespan of the individuals. Besides lifestyle and environmental influences genetic factors are involved as shown by several genome-wide association studies. Older individuals are known to have an impaired immune response, a condition recently termed "inflamm-aging". We hypothesize that the induction of this condition in the elderly is influenced by the sensitivity of the innate immune system. Therefore, we investigated genetic variants of the Toll-like receptor (TLR) family, one of the major family of innate immune receptors, for association with age in two cohorts of healthy, disease-free subjects.

RESULTS

According to sex we found a positive association of loss-of-function variants of TLR-1 and -6 with healthy aging with odds ratios of 1.54 in males for TLR-6 (249 S/S), and 1.41, 1.66, and 1.64 in females for TLR-1 prom., TLR-1 (248 S/S), and TLR-1 (602 S/S), respectively. Thus, the presence of these variants increases the probability of achieving healthy old age and indicates that a reduced TLR activity may be beneficial in the elderly.

CONCLUSIONS

This is the first report showing an association of TLR variants with age. While a loss of function of an important immune receptor may be a risk factor for acute infections as has been shown previously, in the setting of healthy ageing it appears to be protective, which may relate to "inflamm-aging". These first results should be reproduced in larger trials to confirm this hypothesis.

Toll-like receptor 2 subfamily gene polymorphisms are associated with Bacillus Calmette-Guérin osteitis following newborn vaccination

AIM

Toll-like receptor (TLR) 1, 2, 6 and 10, the TLR2 subfamily, are known to be associated with immunity against tuberculosis. We evaluated whether polymorphisms in genes encoding TLR1, TLR2 and TLR6 were associated with osteitis in infants who received the Bacillus Calmette-Guérin (BCG) vaccination soon after birth.

METHODS

Blood samples from 132 adults aged 21-49 who had BCG osteitis in early childhood were analysed in a controlled study for TLR1 T1805G (rs5743618), TLR2 G2258A (rs5743708) and TLR6 C745T (rs5743810) gene single nucleotide polymorphisms.

RESULTS

The frequencies of the variant genotypes differed between the cases and controls: 11.4% versus 5.7% for TLR2 G2258A (p = 0.033) and 77.3% versus 61.6% for TLR6 C745T (p = 0.001). The TLR2 and TLR6 variant genotypes were associated with a higher risk of BCG osteitis, with adjusted odds ratios (aOR) of 2.154 (95%CI 1.026-4.521) and 1.907 (95%CI 1.183-3.075), respectively. The frequency of the TLR1 T1805G variant genotype was 19.7% in the cases and 33.6% in the controls (p = 0.003). The TLR1 variant genotype was associated with a lower risk of BCG osteitis (aOR 0.554, 95%CI 0.336-0.911).

CONCLUSION

Gene polymorphisms that regulate the function of the TLR2 subfamily play a role in the development of BCG osteitis in vaccinated infants.

Role of cytokines and other factors involved in the Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (Mtb) is a pathogen that is widely distributed geographically and continues to be a major threat to world health. Bacterial virulence factors, nutritional state, host genetic condition and immune response play an important role in the evolution of the infection. The genetically diverse Mtb strains from different lineages have been shown to induce variable immune system response. The modern and ancient lineages strains induce different cytokines patterns. The immunity to Mtb depends on Th1-cell activity [interferon-γ (IFN-γ), interleukin-12 (IL-12) and tumor necrosis factor-α (TNF-α)]. IL-1β directly kills Mtb in murine and human macrophages. IL-6 is a requirement in host resistance to Mtb infection. IFN-γ, TNF-α, IL-12 and IL-17 are participants in Mycobacterium-induced granuloma formation. Other regulating proteins as IL-27 and IL-10 can prevent extensive immunopathology. CXCL 8 enhances the capacity of the neutrophil to kill Mtb. CXCL13 and CCL19 have been identified as participants in the formation of granuloma and control the Mtb infection. Treg cells are increased in patients with active tuberculosis (TB) but decrease with anti-TB treatment. The increment of these cells causes down- regulation of adaptive immune response facilitating the persistence of the bacterial infection. Predominance of Th2 phenotype cytokines increases the severity of TB. The evolution of the Mtb infection will depend of the cytokines network and of the influence of other factors aforementioned.

The human IL-23 receptor rs11209026 A allele promotes the expression of a soluble IL-23R-encoding mRNA species

The human IL23R gene single nucleotide polymorphism rs11209026 A allele confers protection against inflammatory diseases. However, although this difference has been associated with reductions in IL-23-induced IL-17A production and STAT3 phosphorylation, the molecular mechanism underlying these changes remains undefined. Th17 cell maturation depends on IL-23 signaling. Multiple splice forms of the human IL23R transcript exist, and one, Δ9, encodes a soluble form of the receptor. In this study, we asked whether this protective allele was associated with mRNA splicing. Using mini-gene constructs and competitive oligonucleotide binding, we showed that the A allele alters IL-23R α-chain mRNA splicing and favors exon 9 skipping by reducing the binding of the splicing enhancer SF2. This enhances expression of the Δ9 mRNA and consequently diminishes IL-23 signaling. Thus, the presence of the A allele increases expression of the soluble form of IL23R mRNA (which then functions as a decoy receptor) and lowers the ability to develop a Th17 phenotype upon IL-23 stimulation. We further showed that antisense oligonucleotides targeting the SF2 binding site could efficiently induce exon 9 skipping in the presence of the G allele, and thereby replicate the effect of the A allele. Antisense oligonucleotide treatment caused dose-responsive induction of the IL23RΔ9 mRNA and interfered with in vitro differentiation of human Th17 cells, reducing their expression of the signature Th17 cytokines IL-17A and IL-17F. This may represent a novel approach to therapy of Th17-mediated diseases by elevating soluble IL-23R while simultaneously reducing the remaining cell surface receptor density.

Polymorphisms in TICAM2 and IL1B are associated with TB

Background

Human genetic susceptibility for tuberculosis (TB) has been demonstrated by several studies, but few have examined multiple innate and adaptive immunity genes comprehensively, age-specific effects, and/or resistance to Mycobacterium tuberculosis (Mtb) infection (RSTR). We hypothesized that RSTR, defined by a persistently negative tuberculin skin test, may have different genetic influences than Mtb disease.

Methods

We examined 29 candidate genes in pathways that mediate immune responses to Mtb in subjects in a household contact study in Kampala, Uganda. We genotyped 546 haplotype-tagging single nucleotide polymorphisms (SNPs) in 835 individuals from 481 families; 28.7% had TB, 10.5% were RSTR, and the remaining 60.8% had latent Mtb infection.

Results

Among our most significant findings were SNPs in TICAM2 (p=3.6×10⁻⁶) and IL1B (p=4.3×10⁻⁵) associated with TB. Multiple SNPs in IL4 and TOLLIP were associated with TB (p<0.05). Age-genotype interaction analysis revealed SNPs in IL18 and TLR6 that were suggestively associated with TB in children ≤ 10 years old (p=2.9×10⁻³). By contrast, RSTR was associated with SNPs in NOD2, SLC6A3 and TLR4 (nominal p < 0.05); these genes were not associated with TB, suggesting distinct genetic influences.

Conclusions

We report the first association between TICAM2 polymorphisms and TB, and between IL18 and pediatric TB.

Toll-like receptor 6 V327M polymorphism is associated with an increased risk of Klebsiella pneumoniae infection

BACKGROUND

Klebsiella pneumoniae is a common cause of nosocomial pneumonia, especially in children. Toll-like receptors plays an important role in defense against this pathogen. The impact of human TLR6 polymorphisms on susceptibility to K. pneumoniae infection is poorly understood. The aim of the present work was to determine whether single nucleotide polymorphisms in TLR6 are associated with altered immune responses to K. pneumoniae.

METHODS

The TLR6 coding region was sequenced in 126 K. pneumoniae culture-positive patients and 142 hospitalized K. pneumoniae culture-negative controls.

RESULTS

The frequency of V327M polymorphism was found to be significantly higher in patients than that in controls (16.7% vs. 7.7%). In vitro studies showed that V327M polymorphism did not impair TLR6 expression in transfected HEK 293T cells. Further studies demonstrated that V327M polymorphism was associated with increased IL-8 mRNA expression in transfected HEK 293T cells when stimulated with K. pneumoniae and the specific ligand for TLR2/TLR6 heterodimers known as Pam2CSK4. The present data showed V327M polymorphism to be associated with increased apoptosis of HEK 293T cells when challenged with K. pneumoniae.

CONCLUSIONS

Taken together, these data indicated that TLR6 V327M may be involved in mediating deleterious inflammatory responses and modulating host susceptibility to K. pneumoniae. These results provide new insight into the pathophysiologic role of TLR6 V327M in the innate immune response to bacterial infection in human.

Association of Toll-like receptor polymorphisms with HIV status in North Americans

Single nucleotide polymorphisms (SNPs) in toll-like receptor (TLR) genes TLR2-4 and TLR7-9, but not in TLR1 and TLR6, have been previously evaluated regarding HIV acquisition and disease progression in various populations, most of which were European. In the present study, we examined associations between a total of 41 SNPs in 8 TLR genes (TLR1-4, TLR6-9) and HIV status in North American subjects (total n = 276 [Caucasian, n = 102; African American, n = 150; other, n = 24]). Stratification of the data by self-identified race revealed that a total of 9 SNPs in TLR1, TLR4, TLR6, and TLR8 in Caucasians, and 2 other SNPs, one each in TLR4 and TLR8, in African Americans were significantly associated with HIV status at P < 0.05. Concordant with the odds ratios of these SNPs, significant differences were observed in the SNP allele frequencies between HIV+ and HIV− subjects. Finally, in Caucasians, certain haplotypes of single (TLR1, TLR4) and heterodimer (TLR2_TLR6) genes may be inferred as “susceptible” or “protective”. Our study provides in-depth insight into the associations between TLR variants, particularly TLR1 and TLR6, and HIV status in North Americans, and suggests that these associations may be race-specific.

Genetic variants of innate immune receptors and infections after liver transplantation

Infection is the leading cause of complication after liver transplantation, causing morbidity and mortality in the first months after surgery. Allograft rejection is mediated through adaptive immunological responses, and thus immunosuppressive therapy is necessary after transplantation. In this setting, the presence of genetic variants of innate immunity receptors may increase the risk of post-transplant infection, in comparison with patients carrying wild-type alleles. Numerous studies have investigated the role of genetic variants of innate immune receptors and the risk of complication after liver transplantation, but their results are discordant. Toll-like receptors and mannose-binding lectin are arguably the most important studied molecules; however, many other receptors could increase the risk of infection after transplantation. In this article, we review the published studies analyzing the impact of genetic variants in the innate immune system on the development of infectious complications after liver transplantation.

Toll-like receptor polymorphisms are associated with increased neurosyphilis risk

BACKGROUND

Single-nucleotide polymorphisms (SNPs) in toll-like receptors (TLR) 1, 2, and 6 impair cell signaling in response to spirochetal lipoproteins. We investigated whether common SNPs in TLR1, TLR2, or TLR6 were associated with laboratory- or clinically-defined neurosyphilis.

METHODS

Polymorphisms in the genes for TLR1 (a T→G mutation at position 1805), TLR2 (a G→A mutation at position 2258), and TLR6 (a C→T mutation at position 745) were sought in 456 white patients with syphilis. Laboratory-defined neurosyphilis included a reactive cerebrospinal fluid (CSF)-Venereal Disease Research Laboratory (VDRL) test. Clinically-defined neurosyphilis included new vision or hearing loss. Controls had CSF white blood cells of 5/μL or less, nonreactive CSF-Venereal Disease Research Laboratory, and no vision or hearing loss.

RESULTS

Overall, 26.2% of patients had laboratory-defined and 36.2% had clinically-defined neurosyphilis. Compared with controls, patients with any of the 3 SNPs were more likely to have laboratory-defined neurosyphilis. Those with TLR2 or TLR6 SNPs were more likely to have clinically-defined neurosyphilis. These associations were independent of serum rapid plasma reagin titer.

CONCLUSIONS

A common TLR1 polymorphism is associated with an increased risk of laboratory-defined neurosyphilis, and common TLR2 and TLR6 polymorphisms are associated with an increased risk of both laboratory- and clinically-defined neurosyphilis. These data suggest that host factors impact the natural history of syphilis.

Influence of Toll-like receptor gene polymorphisms to tuberculosis susceptibility in humans

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (M. tb), and it remains one of the major bacterial infections worldwide. Innate immunity is an important arm of antimycobacterial host defence mechanism that senses various pathogen-associated molecular patterns (PAMP) of microbes by a variety of pattern recognition receptors (PRRs). As per the recent discovery, Toll-like receptors (TLRs) play a crucial role in the recognition of M. tb, this immune activation occurs only in the presence of functional TLRs. Variants of TLRs may influence their expression, function and alters the recognition or signalling mechanism, which leads to the disease susceptibility. Hence, the identification of mutations in these receptors could be used as a marker to screen the individuals who are at risk. In this review, we discuss TLR SNPs and their signalling mechanism to understand the susceptibility to TB for better therapeutic approaches.

Distinct T-cell responses when BCG vaccination is delayed from birth to 6 weeks of age in Ugandan infants

BACKGROUND

In Uganda, the tuberculosis vaccine BCG is administered on the first day of life. Infants delivered at home receive BCG vaccine at their first healthcare facility visit at 6 weeks of age. Our aim was to determine the effect of this delay in BCG vaccination on the induced immune response.

METHODS

We assessed CD4(+) and CD8(+) T-cell responses with a 12-hour whole-blood intracellular cytokine/cytotoxic marker assay, and with a 6-day proliferation assay.

RESULTS

We enrolled 92 infants: 50 had received BCG vaccine at birth and 42 at 6 weeks of age. Birth vaccination was associated with (1) greater induction of CD4(+) and CD8(+) T cells expressing either interferon γ (IFN-γ) alone or IFN-γ together with perforin and (2) induction of proliferating cells that had greater capacity to produce IFN-γ, tumor necrosis factor α (TNF-α), and interleukin 2 together, compared with delayed vaccination.

CONCLUSIONS

Distinct patterns of T-cell induction occurred when BCG vaccine was given at birth and at 6 weeks of age. We propose that this diversity might impact protection against tuberculosis. Our results differ from those of studies of delayed BCG vaccination in South Africa and the Gambia, suggesting that geographical and population heterogeneity may affect the BCG vaccine-induced T-cell response.

Association of a common TLR-6 polymorphism with coronary artery disease - implications for healthy ageing?

BACKGROUND

The pro-inflammatory status of the elderly triggers most of the age-related diseases such as cancer and atherosclerosis. Atherosclerosis, the leading cause world wide of morbidity and death, is an inflammatory disease influenced by life-style and genetic host factors. Stimuli such as oxLDL or microbial ligands have been proposed to trigger inflammation leading to atherosclerosis. It has recently been shown that oxLDL activates immune cells via the Toll-like receptor (TLR) 4/6 complex. Several common single nucleotide polymorphisms (SNPs) of the TLR system have been associated with atherosclerosis. To investigate the role of TLR-6 we analyzed the association of the TLR-6 SNP Pro249Ser with atherogenesis.

RESULTS

Genotyping of two independent groups with CAD, as well as of healthy controls revealed a significant association of the homozygous genotype with a reduced risk for atherosclerosis (odds ratio: 0.69, 95% CI 0.51-0.95, P = 0.02). In addition, we found a trend towards an association with the risk of restenosis after transluminal coronary angioplasty (odds ratio: 0.53, 95% CI 0.24-1.16, P = 0.12). In addition, first evidence is presented that the frequency of this protective genotype increases in a healthy population with age. Taken together, our results define a role for TLR-6 and its genetic variations in modulating the inflammatory response leading to atherosclerosis.

CONCLUSIONS

These results may lead to a better risk stratification, and potentially to an improved prophylactic treatment of high-risk populations. Furthermore, the protective effect of this polymorphism may lead to an increase of this genotype in the healthy elderly and may therefore be a novel genetic marker for the well-being during aging.

A TLR6 polymorphism is associated with increased risk of Legionnaires' disease

Legionella pneumophila (Lp), the etiologic agent of Legionnaires’ Disease (LD), is an important cause of community-acquired and nosocomial pneumonia. However, the host immune and genetic determinants of human susceptibility to Lp are poorly understood. Here we show that both TLR6 and TLR1 cooperate with TLR2 to recognize Lp in transfected HEK293 cells. We also perform a human genetic association study of 14 candidate single nucleotide polymorphisms in Toll-like receptors (TLRs) 1, 2, and 6 in 98 LD cases and 268 controls from the Netherlands. No polymorphisms in TLR1 or TLR2 were associated with LD. A TLR6 polymorphism, 359T>C (rs5743808), was associated with an elevated risk of LD in genotypic and dominant (OR 5.83, p=7.9×10⁻⁵) models. The increased risk in persons with 359 TC or CC genotypes was further enhanced among smokers. In a multivariate model, 359T>C was associated with a higher risk of LD (OR 4.24, p=0.04), than any other variable, including age and smoking. Together, these data suggest that the human TLR6 variant, 359T>C, is an independent risk factor for LD.

Toll-like receptor 6 senses Mycobacterium avium and is required for efficient control of mycobacterial infection

Mycobacterium avium has been reported to signal through both Toll-like receptor (TLR2) and TLR9. To investigate the role of TLR6 in innate immune responses to M. avium, TLR6, MyD88, TLR2, and TLR2/6 KO mice were infected with this pathogen. Bacterial burdens were higher in the lungs and livers of infected TLR6, TLR2, TLR2/6, and MyD88 KO mice compared with those in C57BL/6 mice, which indicates that TLR6 is required for the efficient control of M. avium infection. However, TLR6 KO spleen cells presented with normal M. avium induced IFN-γ responses as measured by ELISA and flow cytometry. In contrast, the production of IFN-γ in lung tissue was diminished in all studied KO mice. Furthermore, only MyD88 deficiency reduced granuloma areas in mouse livers. Moreover, we determined that TLR6 plays an important role in controlling bacterial growth within macrophages and in the production of TNF-α, IL-12, and IL-6 by M. avium infected DCs. Finally, the lack of TLR6 reduced activation of MAPKs and NF-κB in DCs. In summary, TLR6 is required for full resistance to M. avium and for the activation of DCs to produce proinflammatory cytokines.

Toll-like receptor -1, -2, and -6 polymorphisms and pulmonary tuberculosis susceptibility: a systematic review and meta-analysis

Background

A large number of studies have investigated whether polymorphisms in the Toll-like receptor (TLR) genes are implicated in susceptibility to tuberculosis (TB) in different populations. However, the results are inconsistent and inconclusive.

Methods

A literature search was conducted using the PubMed, EMBASE, Medline (Ovid), ISI Web of Knowledge and Chinese National Knowledge Infrastructure (CNKI). A meta-analysis on the associations between the TLR1 G1805T, TLR2 T597C, T1350C, G2258A, and TLR6 C745T polymorphisms and TB risk was carried out by comparison using different genetic models.

Results

In total, 16 studies from 14 articles were included in this review. In meta-analysis, significant associations were observed between the TLR2 2258AA (AA vs. AG+AG, OR 5.82, 95% CI 1.30–26.16, P = 0.02) and TLR6 745TT (TT vs. CT+CC, OR 0.61, 95% CI 0.39–0.97, P = 0.04) polymorphisms and TB risk. In the subgroup analysis by ethnicity, Africans and American Hispanic subjects with the TLR1 1805T allele had an increased susceptibility, whereas Asian and European subjects with the TLR2 2258A allele had an increased susceptibility to TB.

Conclusions

The meta-analysis indicated that TLR2 G2258A is associated with increased TB risk, especially in Asians and Europeans. TLR1 G1805T is associated with increased TB in Africans and American Hispanics. TLR6 C745T is associated with decreased TB risk. Our systematic review and meta-analysis reported an interesting preliminary conclusion, but this must be validated by future large-scale and functional studies in different populations.

Toll-like receptor 6 plays an important role in host innate resistance to Brucella abortus infection in mice

Brucella abortus is recognized by several Toll-like receptor (TLR)-associated pathways triggering proinflammatory responses that affect both the nature and intensity of the immune response. Previously, we demonstrated that B. abortus-mediated dendritic cell (DC) maturation and control of infection are dependent on the adaptor molecule MyD88. However, the involvement of all TLRs in response to B. abortus infection is not completely understood. Therefore, we decided to evaluate the requirement for TLR6 in host resistance to B. abortus. Here, we demonstrated that TLR6 is an important component for triggering an innate immune response against B. abortus. An in vitro luciferase assay indicated that TLR6 cooperates with TLR2 to sense Brucella and further activates NF-κB signaling. However, in vivo analysis showed that TLR6, not TLR2, is required for the efficient control of B. abortus infection. Additionally, B. abortus-infected dendritic cells require TLR6 to induce tumor necrosis factor alpha (TNF-α) and interleukin-12 (IL-12). Furthermore, our findings demonstrated that the mitogen-activated protein kinase (MAPK) signaling pathway is impaired in TLR2, TLR6, and TLR2/6 knockout (KO) DCs when infected with B. abortus, which may account for the lower proinflammatory cytokine production observed in TLR6 KO mouse dendritic cells. In summary, the results presented here indicate that TLR6 is required to trigger innate immune responses against B. abortus in vivo and is required for the full activation of DCs to induce robust proinflammatory cytokine production.

Genetic variation in TLR genes in Ugandan and South African populations and comparison with HapMap data

Genetic epidemiological studies of complex diseases often rely on data from the International HapMap Consortium for identification of single nucleotide polymorphisms (SNPs), particularly those that tag haplotypes. However, little is known about the relevance of the African populations used to collect HapMap data for study populations conducted elsewhere in Africa. Toll-like receptor (TLR) genes play a key role in susceptibility to various infectious diseases, including tuberculosis. We conducted full-exon sequencing in samples obtained from Uganda (n = 48) and South Africa (n = 48), in four genes in the TLR pathway: TLR2, TLR4, TLR6, and TIRAP. We identified one novel TIRAP SNP (with minor allele frequency [MAF] 3.2%) and a novel TLR6 SNP (MAF 8%) in the Ugandan population, and a TLR6 SNP that is unique to the South African population (MAF 14%). These SNPs were also not present in the 1000 Genomes data. Genotype and haplotype frequencies and linkage disequilibrium patterns in Uganda and South Africa were similar to African populations in the HapMap datasets. Multidimensional scaling analysis of polymorphisms in all four genes suggested broad overlap of all of the examined African populations. Based on these data, we propose that there is enough similarity among African populations represented in the HapMap database to justify initial SNP selection for genetic epidemiological studies in Uganda and South Africa. We also discovered three novel polymorphisms that appear to be population-specific and would only be detected by sequencing efforts.

Human TOLLIP regulates TLR2 and TLR4 signaling and its polymorphisms are associated with susceptibility to tuberculosis

Tuberculosis, one of the leading causes of death worldwide, stimulates inflammatory responses with beneficial and pathologic consequences. The regulation and nature of an optimal inflammatory response to Mycobacterium tuberculosis remains poorly understood in humans. Insight into mechanisms of negative regulation of the TLR-mediated innate immune response to M. tuberculosis could provide significant breakthroughs in the design of new vaccines and drugs. We hypothesized that TOLLIP and its common variants negatively regulate TLR signaling in human monocytes and are associated with susceptibility to tuberculosis. Using short hairpin RNA knockdown of TOLLIP in peripheral blood human monocytes, we found that TOLLIP suppresses TNF and IL-6 production after stimulation with TLR2 and TLR4 ligands. In contrast, secretion of the anti-inflammatory cytokine IL-10 was induced by TOLLIP. We also discovered two common polymorphisms that are associated with either decreased levels of mRNA expression (rs3750920) or increased IL-6 production (rs5743899) in a sample of 56 healthy volunteers. Furthermore, in a case-population study in Vietnam with 760 cord blood samples and 671 TB case patients, we found that SNPs rs3750920 and rs5743899 were associated with susceptibility to tuberculosis (p = 7.03 × 10(-16) and 6.97 × 10(-7), respectively). These data demonstrate that TOLLIP has an anti-inflammatory effect on TLR signaling in humans and that TOLLIP deficiency is associated with an increased risk of tuberculosis. To our knowledge, these data also show the first associations of TOLLIP polymorphisms with any infectious disease. These data also implicate an unexpected mechanism of negative regulation of TLR signaling in human tuberculosis pathogenesis.

The Role of TLR2 in Infection and Immunity

Toll-like receptors (TLRs) are recognition molecules for multiple pathogens, including bacteria, viruses, fungi, and parasites. TLR2 forms heterodimers with TLR1 and TLR6, which is the initial step in a cascade of events leading to significant innate immune responses, development of adaptive immunity to pathogens and protection from immune sequelae related to infection with these pathogens. This review will discuss the current status of TLR2 mediated immune responses by recognition of pathogen-associated molecular patterns (PAMPS) on these organisms. We will emphasize both canonical and non-canonical responses to TLR2 ligands with emphasis on whether the inflammation induced by these responses contributes to the disease state or to protection from diseases.

Common polymorphisms in the PKP3-SIGIRR-TMEM16J gene region are associated with susceptibility to tuberculosis

BACKGROUND

Tuberculosis has been associated with genetic variation in host immunity. We hypothesized that single-nucleotide polymorphisms (SNPs) in SIGIRR, a negative regulator of Toll-like receptor/IL-1R signaling, are associated with susceptibility to tuberculosis.

METHODS

We used a case-population study design in Vietnam with cases that had either tuberculous meningitis or pulmonary tuberculosis. We genotyped 6 SNPs in the SIGIRR gene region (including the adjacent genes PKP3 and TMEM16J) in a discovery cohort of 352 patients with tuberculosis and 382 controls. Significant associations were genotyped in a validation cohort (339 patients with tuberculosis, 376 controls).

RESULTS

Three SNPs (rs10902158, rs7105848, rs7111432) were associated with tuberculosis in discovery and validation cohorts. The polymorphisms were associated with both tuberculous meningitis and pulmonary tuberculosis and were strongest with a recessive genetic model (odds ratios, 1.5-1.6; P = .0006-.001). Coinheritance of these polymorphisms with previously identified risk alleles in Toll-like receptor 2 and TIRAP was associated with an additive risk of tuberculosis susceptibility.

CONCLUSIONS

These results demonstrate a strong association of SNPs in the PKP3-SIGIRR-TMEM16J gene region and tuberculosis in discovery and validation cohorts. To our knowledge, these are the first associations of polymorphisms in this region with any disease.

Evolution of the bovine TLR gene family and member associations with Mycobacterium avium subspecies paratuberculosis infection

Members of the Toll-like receptor (TLR) gene family occupy key roles in the mammalian innate immune system by functioning as sentries for the detection of invading pathogens, thereafter provoking host innate immune responses. We utilized a custom next-generation sequencing approach and allele-specific genotyping assays to detect and validate 280 biallelic variants across all 10 bovine TLR genes, including 71 nonsynonymous single nucleotide polymorphisms (SNPs) and one putative nonsense SNP. Bayesian haplotype reconstructions and median joining networks revealed haplotype sharing between Bos taurus taurus and Bos taurus indicus breeds at every locus, and specialized beef and dairy breeds could not be differentiated despite an average polymorphism density of 1 marker/158 bp. Collectively, 160 tagSNPs and two tag insertion-deletion mutations (indels) were sufficient to predict 100% of the variation at 280 variable sites for both Bos subspecies and their hybrids, whereas 118 tagSNPs and 1 tagIndel predictively captured 100% of the variation at 235 variable sites for B. t. taurus. Polyphen and SIFT analyses of amino acid (AA) replacements encoded by bovine TLR SNPs indicated that up to 32% of the AA substitutions were expected to impact protein function. Classical and newly developed tests of diversity provide strong support for balancing selection operating on TLR3 and TLR8, and purifying selection acting on TLR10. An investigation of the persistence and continuity of linkage disequilibrium (r²≥0.50) between adjacent variable sites also supported the presence of selection acting on TLR3 and TLR8. A case-control study employing validated variants from bovine TLR genes recognizing bacterial ligands revealed six SNPs potentially eliciting small effects on susceptibility to Mycobacterium avium spp paratuberculosis infection in dairy cattle. The results of this study will broadly impact domestic cattle research by providing the necessary foundation to explore several avenues of bovine translational genomics, and the potential for marker-assisted vaccination.