Genomic variants of TLR1--it takes (TLR-)two to tango

Identification and validation of hub differential genes in pulmonary sarcoidosis

A total of 138 cDEGs were screened from mediastinal lymph nodes and peripheral whole blood. Among them, 6 hub cDEGs including CTSS, CYBB, FPR2, MNDA, TLR1 and TLR8 with elevated degree and betweenness levels were illustrated in protein-protein interaction network. In comparison to healthy controls, CTSS (1.61 vs. 1.05), CYBB (1.68 vs. 1.07), FPR2 (2.77 vs. 0.96), MNDA (2.14 vs. 1.23), TLR1 (1.56 vs. 1.09), and TLR8 (2.14 vs. 0.98) displayed notably elevated expression levels within pulmonary sarcoidosis PBMC samples (P < 0.0001 for FPR2 and P < 0.05 for others), echoing with prior mRNA microarray findings. The most significant functional pathways were immune response, inflammatory response, plasma membrane and extracellular exosome, with 6 hub cDEGs distributing along these pathways. CTSS, CYBB, FPR2, MNDA, TLR1, and TLR8 could be conducive to improving the diagnostic process and understanding the underlying mechanisms of pulmonary sarcoidosis.

Genetic polymorphism in European and African sheep breeds reared in Hungary based on 48 SNPs associated with resistance to gastrointestinal parasite infection using KASP-PCR technique

This pilot study used an alternative and economically efficient technique, the Kompetitive Allele-Specific Polymerase Chain Reaction (KASP-PCR) to examine 48 SNPs from 11 parasite-resistance genes found on 8 chromosomes in 110 animals from five sheep breeds reared in Hungary; Hungarian Tsigai, White Dorper, Dorper, Ile de France, and Hungarian Merino. Allele and genotype frequencies, fixation index, observed heterozygosity, expected heterozygosity, F statistic, and their relationship with the Hardy-Weinberg equilibrium (WHE) and the polymorphic information content (PIC) were determined, followed by principal component analysis (PCA). As much as 32 SNPs out of the 48 initially studied were successfully genotyped. A total of 9 SNPs, 4 SNPs in TLR5, 1 SNP in TLR8, and 4 SNPs in TLR2 genes, were polymorphic. The variable genotype and allele frequency of the TLRs gene indicated genetic variability among the studied sheep breeds, with the Hungarian Merino exhibiting the most polymorphisms, while Dorper was the population with the most SNPs departing from the HWE. According to the PIC value, the rs430457884-TLR2, rs55631273-TLR2, and rs416833129-TLR5 were found to be informative in detecting polymorphisms among individuals within the populations, whereas the rs429546187-TLR5 and rs424975389-TLR5 were found to have a significant influence in clustering the population studied. This study reported a moderate level of genetic variability and that a low to moderate within-breed diversity was maintained in the studied populations.

Toll-Like Receptor 1 Locus Re-examined in a Genome-Wide Association Study Update on Anti-Helicobacter pylori IgG Titers

BACKGROUND & AIMS

A genome-wide significant association between anti-Helicobacter pylori (H pylori) IgG titers and Toll-like receptor (TLR1/6/10) locus on 4p14 was demonstrated for individuals of European ancestry, but not uniformly replicated. We re-investigated this association in an updated genome-wide association study (GWAS) meta-analysis for populations with low gastric cancer incidence, address potential causes of cohort heterogeneity, and explore functional implications of genetic variation at the TLR1/6/10 locus.

METHODS

The dichotomous GWAS (25% individuals exhibiting highest anti-H pylori IgG titers vs remaining 75%) included discovery and replication sampls of, respectively, n = 15,685 and n = 9676, all of European ancestry. Longitudinal analysis of serologic data was performed on H pylori-eradicated subjects (n = 132) and patients under surveillance for premalignant gastric lesions (n = 107). TLR1/6/10 surface expression, TLR1 mRNA, and cytokine levels were measured in leukocyte subsets of healthy subjects (n = 26) genotyped for TLR1/6/10 variants.

RESULTS

The association of the TLR1/6/10 locus with anti-H pylori IgG titers (rs12233670; β = -0.267 ± SE 0.034; P = 4.42 × 10-15) presented with high heterogeneity and failed replication. Anti-H pylori IgG titers declined within 2-4 years after eradication treatment (P = 0.004), and decreased over time in patients with premalignant gastric lesions (P < 0.001). Variation at the TLR1/6/10 locus affected TLR1-mediated cytokine production and TLR1 surface expression on monocytes (P = 0.016) and neutrophils (P = 0.030), but not mRNA levels.

CONCLUSIONS

The association between anti-H pylori IgG titers and TLR1/6/10 locus was not replicated across cohorts, possibly owing to dependency of anti-H pylori IgG titers on therapy, clearance, and antibody decay. H pylori-mediated immune cell activation is partly mediated via TLR1 signaling, which in turn is affected by genetic variation.

Induction of Foxp3 and activation of Tregs by HSP gp96 for treatment of autoimmune diseases

Upregulation and stabilization of Foxp3 expression in Tregs are essential for regulating Treg function and immune homeostasis. In this study, gp96 immunization showed obvious therapeutic effects in a Lyn^–/– mouse model of systemic lupus erythematosus. Moreover, gp96 alleviated the initiation and progression of MOG-induced experimental autoimmune encephalomyelitis. Immunization of gp96 increased Treg frequency, expansion, and suppressive function. Gene expression profiling identified the NF-κB family member p65 and c-Rel as the key transcription factors for enhanced Foxp3 expression in Treg by gp96. Mutant gp96 within its Toll-like receptor (TLR) binding domain, TLR2 knockout mice, and mice with cell-specific deletion of MyD88, were used to demonstrate that gp96 activated Tregs and induced Foxp3 expression via a TLR2-MyD88-mediated NF-κB signaling pathway. Taken together, these results show that gp96 immunization restricted antibody-induced and Th-induced autoimmune diseases by integrating Treg expansion and activation, indicating its potential clinical usefulness against autoimmune diseases.

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SLE symptoms in Lyn^–/– mice are ameliorated by gp96 immunization

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Tregs expanded by gp96 provide potential in suppressing Th-mediated EAE

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Gp96 promotes Treg proliferation, stability, and suppressive function

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Gp96 binds to and activates Treg in a TLR2-MyD88-NF-кB-Foxp3 pathway

Bacterial lipoproteins and other factors released by Francisella tularensis modulate human neutrophil lifespan: Effects of a TLR1 SNP on apoptosis inhibition

Francisella tularensis infects several cell types including neutrophils, and aberrant neutrophil accumulation contributes to tissue destruction during tularaemia. We demonstrated previously that F. tularensis strains Schu S4 and live vaccine strain markedly delay human neutrophil apoptosis and thereby prolong cell lifespan, but the bacterial factors that mediate this aspect of virulence are undefined. Herein, we demonstrate that bacterial conditioned medium (CM) can delay apoptosis in the absence of direct infection. Biochemical analyses show that CM contained F. tularensis surface factors as well as outer membrane components. Our previous studies excluded roles for lipopolysaccharide and capsule in apoptosis inhibition, and current studies of [¹⁴C] acetate‐labelled bacteria argue against a role for other bacterial lipids in this process. At the same time, studies of isogenic mutants indicate that TolC and virulence factors whose expression requires FevR or MglA were also dispensable, demonstrating that apoptosis inhibition does not require Type I or Type VI secretion. Instead, we identified bacterial lipoproteins (BLPs) as active factors in CM. Additional studies of isolated BLPs demonstrated dose‐dependent neutrophil apoptosis inhibition via a TLR2‐dependent mechanism that is significantly influenced by a common polymorphism, rs5743618, in human TLR1. These data provide fundamental new insight into pathogen manipulation of neutrophil lifespan and BLP function.

Genetic and Metabolic Signals during Acute Enteric Bacterial Infection Alter the Microbiota and Drive Progression to Chronic Inflammatory Disease

Chronic inflammatory disorders are thought to arise due to an interplay between predisposing host genetics and environmental factors. For example, the onset of inflammatory bowel disease is associated with enteric proteobacterial infection, yet the mechanistic basis for this association is unclear. We have shown previously that genetic defiency in TLR1 promotes acute enteric infection by the proteobacteria Yersinia enterocolitica. Examining that model further, we uncovered an altered cellular immune response that promotes the recruitment of neutrophils which in turn increases metabolism of the respiratory electron acceptor tetrathionate by Yersinia. These events drive permanent alterations in anti-commensal immunity, microbiota composition, and chronic inflammation, which persist long after Yersinia clearence. Deletion of the bacterial genes involved in tetrathionate respiration or treatment using targeted probiotics could prevent microbiota alterations and inflammation. Thus, acute infection can drive long term immune and microbiota alterations leading to chronic inflammatory disease in genetically predisposed individuals.

Association of toll-like receptors with susceptibility to tuberculosis suggests sex-specific effects of TLR8 polymorphisms

BACKGROUND

Toll-like receptors (TLRs) are involved in the recognition of conserved microbial structures, leading to activation of an inflammatory response and formation of an adaptive immune response.

METHODS

Twenty-three polymorphisms in five TLR genes were genotyped in 729 tuberculosis cases and 487 healthy controls in a population-based case-control association study in a South African population.

RESULTS

We detected sex-specific associations for TLR8 polymorphisms, with rs3761624 (OR=1.54, p<0.001), rs3764879 (OR=1.41, p=0.011) and rs3764880 (OR=1.42, p=0.011) associated in females and rs3764879 (OR=0.72, p=0.013) and rs3764880 (OR=0.75, p=0.036) associated in males. Epistatic interactions between the TLR genes were investigated and the TLR1_rs4833095 polymorphism was shown to interact with TLR2_rs3804100 and (GT)n microsatellite (p=0.002) and alter susceptibility to TB. We also studied the role of TLRs in disease caused by different Mycobacterium tuberculosis genotypes in 257 tuberculosis cases, and identified associations between specific TLR polymorphisms and disease caused by specific strains.

CONCLUSION

This study provides further evidence that the TLRs play an important role in the outcome of tuberculosis disease, and suggests a partial explanation for the male bias in tuberculosis ratios.

Expression pattern of Toll-like receptors (TLRs) in different organs and effects of lipopolysaccharide on the expression of TLR 2 and 4 in reproductive organs of female rabbit

Toll-like receptors (TLRs) are vital for innate immunity, and they were expressed in various immune cells, tissues and organs. Moreover, TLRs specific expression pattern in different cells, tissue and organs have been confirmed to have correlation with the ability to resistance to pathogenic challenges. The present study aimed to determine the expression profiles and levels of TLR2, 3, 4, 5, 6, 8 and 10 in the lung, trachea, intestine, stomach, liver, spleen, uterine horn and body, cervix, ovary, oviduct and hypothalamus of female rabbits, and whether the expression level of TLR2 and 4 in the ovary, oviduct, uterine horn and body, and cervix were affected by lipopolyasaccharide (LPS). The tissues of the lung, trachea, intestine, stomach, liver, spleen, uterine horn and body, cervix, ovary, oviduct and hypothalamus were collected from four rabbits which didn't be treated as 0 h. 16 rabbits in LPS group were injected with LPS (according to 0.5mg/kg body weight) and 16 rabbits in control group were injected with saline (LPS carrier), hereafter the tissues of the uterine horn and body, cervix, ovary and oviduct from 32 rabbits were collected after 1.5, 3, 6, and 12h (n=4 each group) postinjection. The expression profiles of TLRs were analyzed by reverse transcriptase polymerase chain reaction (RT-PCR), and expression level of TLRs were examined using quantitative real-time PCR (qRT-PCR). The results shown: TLR2, 3, 4, 5, 6, 8 and 10 were expressed in lung, trachea, intestine, stomach, liver, spleen, uterine horn and body, cervix, ovary, oviduct and hypothalamus of female rabbits, but their expression level had great difference in the same organs, and each TLR has different expression level in the different organs. After LPS-stimulation, the expression of TLR2 in the uterine body and horn was significantly higher than that in control group by 3h and 12h of postinjection (P<0.05) respectively. The expression of TLR4 in ovary and uterine body was significantly higher than that in control group by 3 and 12h of postinjection (P<0.05), and the expression of TLR4 in uterine body was greater than that in control by 3h postinjection (P<0.05). The results suggested LPS upregulated the expression of TLR2 and 4 in uterine body and horn, and the expression of TLR4 in ovary.

Role of cytokines and Toll-like receptors in the immunopathogenesis of Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an autoimmune disease of the peripheral nervous system, mostly triggered by an aberrant immune response to an infectious pathogen. Although several infections have been implicated in the pathogenesis of GBS, not all such infected individuals develop this disease. Moreover, infection with a single agent might also lead to different subtypes of GBS emphasizing the role of host factors in the development of GBS. The host factors regulate a broad range of inflammatory processes that are involved in the pathogenesis of autoimmune diseases including GBS. Evidences suggest that systemically and locally released cytokines and their involvement in immune-mediated demyelination and axonal damage of peripheral nerves are important in the pathogenesis of GBS. Toll-like receptors (TLRs) link innate and adaptive immunity through transcription of several proinflammatory cytokines. TLR genes may increase susceptibility to microbial infections; an attenuated immune response towards antigen and downregulation of cytokines occurs due to mutation in the gene. Herein, we discuss the crucial role of host factors such as cytokines and TLRs that activate the immune response and are involved in the pathogenesis of the disease.

The oxidative stress product carboxyethylpyrrole potentiates TLR2/TLR1 inflammatory signaling in macrophages

Oxidative stress is key in the pathogenesis of several diseases including age-related macular degeneration (AMD), atherosclerosis, diabetes, and Alzheimer's disease. It has previously been established that a lipid peroxidation product, carboxyethylpyrrole (CEP), accumulates in the retinas of AMD patients. Retinal infiltrating macrophages also accumulate in the retinas of both AMD patients and in a murine model of AMD. We therefore investigated the ability of CEP-adducts to activate innate immune signaling in murine bone-marrow derived macrophages (BMDMs). We found that CEP specifically synergizes with low-dose TLR2-agonists (but not agonists for other TLRs) to induce production of inflammatory cytokines. Moreover, CEP selectively augments TLR2/TLR1-signaling instead of TLR2/TLR6-signaling. These studies uncover a novel synergistic inflammatory relationship between an endogenously produced oxidation molecule and a pathogen-derived product, which may have implications in the AMD disease process and other oxidative stress-driven pathologies.

Toll-like receptor 2-blocking antibodies promote angiogenesis and induce ERK1/2 and AKT signaling via CXCR4 in endothelial cells

OBJECTIVE

Toll-like receptor 2 (TLR2) inhibition by function blocking antibodies (ABs) is associated with enhanced preservation of endothelial cell function during vascular disease. In the present study, we investigated the capacity of TLR2-blocking ABs to modulate the angiogenic response of endothelial cells in vitro and in vivo.

APPROACH AND RESULTS

Incubation of endothelial cells with mono- or polyclonal anti-TLR2 ABs resulted in increased tube formation, sprouting, and migration of endothelial cells compared with controls. In a mouse model of hindlimb ischemia, using TLR2-deficient or anti-TLR2 AB-treated wild-type mice resulted in increased new capillary formation and enhanced reperfusion. The effects of anti-TLR2 ABs were similar to those exerted by stromal cell-derived factor-1, and we show that anti-TLR2 ABs yet not TLR2 ligands lead to comparable activation of extracellular signal-regulated kinase1/2 and AKT but not p38 mitogen-activated protein kinase as activation of the CXCR4 canonical signal transduction pathways by stromal cell-derived factor-1. Immunoprecipitation of TLR2 revealed that anti-TLR2 ABs initiate an association of TLR2 with CXCR4 and mitogen-activated protein kinase activation. The proangiogenic properties of anti-TLR2 ABs were abolished by both G-protein inhibition and CXCR4 knockdown in endothelial cells.

CONCLUSIONS

Our results provide evidence for a proangiogenic effect of TLR2-blocking ABs on endothelial cells in vitro and in vivo. They identify a novel molecular mechanism linking TLR2 to angiogenic processes that is independent from the activation of inflammatory cascades and further support the concept of a beneficial effect of TLR2 inhibition for endothelial cell function in vascular disease.

Effects of human Toll-like receptor 1 polymorphisms on ageing

Background

Advanced age results in crucial alterations of the innate and adaptive immune system leading to functional defects resulting in infection and chronic diseases. Toll-like receptors (TLR) recognize pathogenic structures and are important in the immune response to infections and vaccination. However, the role of TLR single nucleotide polymorphisms (SNP) is poorly understood in the setting of human ageing. This study investigated the impact of the TLR1 SNPs A743G and T1805G on ageing in different age groups from two European populations.

Results

The TLR1 genotypes 743AA/1805GG (TLR1neg) are associated with a TLR1 negative phenotype, impaired function and susceptibility to tuberculosis. Carriers of heterozygous 743AG/1805TG and homozygous 743GG/1805TT genotypes (TLR1pos) have a TLR1 positive phenotype. By comparing healthy young and old German donors, the old group showed a tendency to carry more TLR1neg and less homozygous TLR1pos genotypes. Anti-inflammatory Interleukin (IL)-1 receptor antagonist (Ra) was significantly elevated in supernatants of mononuclear cells from old German subjects with a TLR1pos genotype in contrast to those with the 743AA genotype. Healthy old individuals and nonagenarians from Italy displayed significantly higher frequencies of TLR1pos genotypes than the old group from Germany. The data show that tumor-necrosis-factor (TNF)α, CXCL8 and CCL2 levels were higher in old donors from Germany than in plasma levels from old Italian donors. TNFα and CCL2 levels were significantly raised in old German individuals compared to Italian nonagenarians. German and Italian donors with the TLR1neg genotype basically produced more CCL2 than older European donors with TLR1pos genotypes.

Conclusion

The higher frequency of the TLR1pos genotype in elderly Italian subjects may result from different ethnic populations. Lower inflammatory mediator release of aged Italian individuals is probably due to different background in nutrition, diet, genetics and to psychological aspects. Elderly donors carrying TLR1pos genotypes basically release more anti-inflammatory IL-1Ra and less inflammatory CCL2 suggesting a decline of the pro-inflammatory status found in ageing and, therefore, this may define an anti-inflammatory phenotype. Future studies are needed to elucidate the association of a TLRpos genotype with decreased susceptibility to infections and reduced risk to develop artherosclerosis.

Differential trafficking of TLR1 I602S underlies host protection against pathogenic mycobacteria

We recently identified I602S as a frequent single-nucleotide polymorphism of human TLR1 that greatly inhibits cell surface trafficking, confers hyporesponsiveness to TLR1 agonists, and protects against the mycobacterial diseases leprosy and tuberculosis. Because mycobacteria are known to manipulate the TLR system to their advantage, we hypothesize that the hyporesponsive 602S variant may confer protection by enabling the host to overcome this immune subversion. We report that primary human monocytes and macrophages from homozygous TLR1 602S individuals are resistant to mycobacterial-induced downregulation of macrophage MHC class II, CD64, and IFN-γ responses compared with individuals who harbor the TLR1 602I variant. Additionally, when challenged with mycobacterial agonists, macrophages from TLR1 602S/S individuals resist induction of host arginase-1, an enzyme that depletes cellular arginine stores required for the production of antimicrobial reactive nitrogen intermediates. The differences in cell activation mediated by TLR1 602S and TLR1 602I are observed upon stimulation with soluble mycobacterial-derived agonists but not with whole mycobacterial cells. Taken together, these results suggest that the TLR1 602S variant protects against mycobacterial disease by preventing soluble mycobacterial products, perhaps released from granulomas, from disarming myeloid cells prior to their encounter with whole mycobacteria.

Toll-like receptor signaling in liver ischemia and reperfusion

Liver ischemia-reperfusion (I/R) injuries are significant clinical challenges implicated in various hepatic surgical procedures and transplantations. Associated with varying degrees of insult, the hallmark of I/R is the excessive inflammatory response potentiated by the host immune system. Toll-like receptors (TLRs), known to play an important role in pathogen-derived inflammation, are now thought to participate in I/R injury-derived inflammation signaling pathways. Endogenous particles (proteins, cytokines, nucleic acids) that are released from damaged host cells bind to TLR2, TLR4, and TLR9, resulting in even further injury by subsequent inflammatory reactions and activation of the innate immune system. This review aims to systematically examine the current literature about TLR signaling mechanisms, allowing for a greater understanding of the precise role of TLRs in hepatic I/R injuries.

Cell surface trafficking of TLR1 is differentially regulated by the chaperones PRAT4A and PRAT4B

The subcellular localization of Toll-like receptors (TLRs) is critical to their ability to function as innate immune sensors of microbial infection. We previously reported that an I602S polymorphism of human TLR1 is associated with aberrant trafficking of the receptor to the cell surface, loss of responses to TLR1 agonists, and differential susceptibility to diseases caused by pathogenic mycobacteria. Through an extensive analysis of receptor deletion and point mutants we have discovered that position 602 resides within a short 6 amino acid cytoplasmic region that is required for TLR1 surface expression. This short trafficking motif, in conjunction with the adjacent transmembrane domain, is sufficient to direct TLR1 to the cell surface. A serine at position 602 interrupts this trafficking motif and prevents cell surface expression of TLR1. Additionally, we have found that ER-resident TLR chaperones, PRAT4A and PRAT4B, act as positive and negative regulators of TLR1 surface trafficking, respectively. Importantly, either over-expression of PRAT4A or knock-down of PRAT4B rescues cell surface expression of the TLR1 602S variant. We also report that IFN-γ treatment of primary human monocytes derived from homozygous 602S individuals rescues TLR1 cell surface trafficking and cellular responses to soluble agonists. This event appears to be mediated by PRAT4A whose expression is strongly induced in human monocytes by IFN-γ. Collectively, these results provide a mechanism for the differential trafficking of TLR1 I602S variants, and highlight the distinct roles for PRAT4A and PRAT4B in the regulation of TLR1 surface expression.

Toll-like receptor 2 signaling in CD4(+) T lymphocytes promotes T helper 17 responses and regulates the pathogenesis of autoimmune disease

Toll-like receptors (TLRs) have previously been shown to play critical roles in the activation of innate immunity. Here, we describe that T cell expression of TLR2 regulates T helper 17 (Th17) cell responses. Stimulation with TLR2 agonists promoted Th17 differentiation in vitro and led to more robust proliferation and Th17 cytokine production. Using the experimental autoimmune encephalomyelitis (EAE) model, we found that TLR2 regulated Th17 cell-mediated autoimmunity in vivo and that loss of TLR2 in CD4(+) T cells dramatically ameliorated EAE. This study thus reveals a critical role of a TLR in the direct regulation of adaptive immune response and pathogenesis of autoimmune diseases.

The expression and function of Nod-like receptors in neutrophils

Neutrophils make up an essential part of the innate immune system, and are involved both in the initial responses to pathogens, and in orchestrating later immune responses. Neutrophils recognize pathogens through pattern-recognition receptors (PRRs), which are activated by microbial motifs. The Nod-like receptors (nucleotide-binding domain leucine-rich repeat containing family; NLRs) constitute a recently discovered group of PRRs whose role in the neutrophil immune responses is not yet characterized. The present study aimed to investigate the expression and function of NLRs in neutrophils. Neutrophils were isolated from human peripheral blood, and the presence of nucleotide-binding oligomerization domain 1 (NOD1), NOD2 and NACHT-LRR-PYD-containing protein 3 (NLRP3) was evaluated with flow cytometry and immunohistochemistry. The expression of NOD1, NOD2 and NLRP3 messenger RNA was determined using real-time reverse transcription-polymerase chain reaction. Changes in neutrophil cytokine secretion, phenotype and migration following agonist-induced activation were studied using enzyme-linked immunosorbent assay, flow cytometry and a chemotaxis assay, respectively. No expression of NOD1 was found in isolated neutrophils and stimulation with the NOD1 ligand gamma-d-glutamyl-meso-diaminopimelic acid induced no signs of activity. In contrast, a marked expression of NOD2 and NLRP3 was found. NOD2 activation with MurNAc-l-Ala-d-isoGln (MDP) resulted in interleukin-8 secretion, CD62 ligand down-regulation, CD11b up-regulation and increased migration towards an inflammatory stimulus. NLRP3 activation with alum caused interleukin-1beta secretion and facilitated migration. Altogether, this suggests that NLRs may be a previously unknown pathway for neutrophil activation.

Association of the toll-like receptor 2 A-16934T promoter polymorphism with severe atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disease with a multifactorial pathogenesis and increasing incidence in the Western world. A genetically determined defective function of pattern recognition receptors such as toll-like receptors (TLRs) has been proposed as a candidate mechanism in the pathogenesis of AD.

AIM

To study the impact of genetic predisposition of five genes encoding for pattern recognition-related molecules for the phenotype of AD.

METHODS

We examined nine different single-nucleotide polymorphism (SNP) frequencies in the genes encoding TLR1, -2, -4, -9 and the adapter molecule TIRAP by PCR with subsequent melting curve analysis in a case/control cohort of 136 adult AD patients and 129 age and gender matched non-atopic, healthy individuals. TLR2-expression and -function in cells from genotyped individuals were analysed.

RESULTS

For the SNPs examined, similar genotype frequencies were found in both groups. In a subgroup of patients suffering from severe AD (SCORAD >50), a significantly increased representation of the A-allele in position -16934 of the tlr2 gene was present (P = 0.004). Constitutive tlr2 mRNA expression in peripheral monocytes was independent of this tlr2 promoter SNP. Stimulation assays indicated that IL-6, but not TNF-alpha secretion following TLR2 stimulation is reduced in homozygous tlr2-16934-A allele carriers.

CONCLUSION

These data indicate that TLR2 is relevant for the phenotype of severe AD in adults.

A TIR domain variant of MyD88 adapter-like (Mal)/TIRAP results in loss of MyD88 binding and reduced TLR2/TLR4 signaling

The adapter protein MyD88 adapter-like (Mal), encoded by TIR-domain containing adapter protein (Tirap) (MIM 606252), is the most polymorphic of the five adapter proteins involved in Toll-like receptor signaling, harboring eight non-synonymous single nucleotide polymorphisms in its coding region. We screened reported mutations of Mal for activity in reporter assays to test the hypothesis that variants of Mal existed with altered signaling potential. A TIR domain variant, Mal D96N (rs8177400), was found to be inactive. In reconstituted cell lines, Mal D96N acted as a hypomorphic mutation, with impaired cytokine production and NF-kappaB activation upon lipopolysaccharide or PAM2CSK4 stimulation. Moreover, co-immunoprecipitation studies revealed that Mal D96N is unable to interact with MyD88, a prerequisite for downstream signaling to occur. Computer modeling data suggested that residue 96 resides in the MyD88 binding site, further supporting these findings. Genotyping of Mal D96N in three different cohorts suggested that it is a rare mutation. We, thus, describe a rare variant in Mal that exerts its effect via its inability to bind MyD88.

Toll-like receptors in ischemia-reperfusion injury

Ischemia-reperfusion (I/R) injuries are implicated in a large array of pathological conditions such as myocardial infarction, cerebral stroke, and hepatic, renal, and intestinal ischemia, as well as following cardiovascular and transplant surgeries. The hallmark of these pathologies is excessive inflammation. Toll-like receptors (TLRs) are recognized as one of the main contributors to pathogen-induced inflammation and, more recently, injury-induced inflammation. Endogenous ligands such as low-molecular hyaluronic acid, fibronectin, heat shock protein 70, and heparin sulfate were all found to be cleaved in the inflamed tissue and to activate TLR2 and TLR4, initiating an inflammatory response even in the absence of pathogens and infiltrating immune cells. In this review, we discuss the contribution of TLR activation in hepatic, renal, cerebral, intestinal, and myocardial I/R injuries. A greater understanding of the role of TLRs in I/R injuries may aid in the development of specific TLR-targeted therapeutics to treat these conditions.

Novel mutations in TLR genes cause hyporesponsiveness to Mycobacterium avium subsp. paratuberculosis infection

BACKGROUND

Toll like receptors (TLR) play the central role in the recognition of pathogen associated molecular patterns (PAMPs). Mutations in the TLR1, TLR2 and TLR4 genes may change the ability to recognize PAMPs and cause altered responsiveness to the bacterial pathogens.

RESULTS

The study presents association between TLR gene mutations and increased susceptibility to Mycobacterium avium subsp. paratuberculosis (MAP) infection. Novel mutations in TLR genes (TLR1- Ser150Gly and Val220Met; TLR2 - Phe670Leu) were statistically correlated with the hindrance in recognition of MAP legends. This correlation was confirmed subsequently by measuring the expression levels of cytokines (IL-4, IL-8, IL-10, IL-12 and IFN-gamma) in the mutant and wild type moDCs (mocyte derived dendritic cells) after challenge with MAP cell lysate or LPS. Further in silico analysis of the TLR1 and TLR4 ectodomains (ECD) revealed the polymorphic nature of the central ECD and irregularities in the central LRR (leucine rich repeat) motifs.

CONCLUSION

The most critical positions that may alter the pathogen recognition ability of TLR were: the 9th amino acid position in LRR motif (TLR1-LRR10) and 4th residue downstream to LRR domain (exta-LRR region of TLR4). The study describes novel mutations in the TLRs and presents their association with the MAP infection.

Molecular cloning and characterization of Toll-like receptors 1-10 in sheep

Toll-like receptors (TLRs) are pattern-recognition receptors that trigger innate immune responses and stimulate adaptive immunity. Currently, only partial information is available for sheep TLR genes. The aims of this study were to clone and sequence the coding regions of all 10 ovine TLR genes and compare the sequences with those of other mammalian species. The coding sequences for ovine TLRs 1-10 and the 3'-untranslated sequences for ovine TLR1, 6 and 10 have been obtained. Ovine TLR6 exhibited a distinctive 3'-end sequence that resembled a rare splice variant of bovine TLR6, but appeared to represent the major TLR6 transcript in the sheep. qRT-PCR confirmed the presence of TLR transcripts in blood mononuclear cells, alveolar macrophages, keratinocytes and lymph node tissues. Comparative sequence analysis showed that the sheep TLRs share high sequence similarity with the respective cattle, pig, human and mouse genes and are likely derived from the same ancestral sequence.

STAT2*C related genotypes and allele but not TLR4 and CD40 gene polymorphisms are associated with higher susceptibility for asthma

Objective: Asthma is caused by a complex interaction between multiple genes and environmental factors. Herein we aimed to investigate whether signal transducer and activator of transcription (STAT2), toll-like receptors 4 (TLRs4) and CD40-related polymorphisms are associated with asthma susceptibility.

Design: Children were divided: (1) asthma (n=117); (2) normal controls (n=60). The polymorphisms of STAT2, TLR4 and CD40 polymorphism were analyzed by PCR-RFLP genotyping. Genotypes, allelic frequencies and association of haplotypes in both groups were compared.

Results: STAT2*C related genotypes, but not TLR4 and CD40 polymorphism, are associated with higher susceptibility for asthma. Distributions of STAT2*CC/CG/GG and C/G allele in both groups are: (1) 0/11.1/88.9 % and 5.6/94.4%; (2) 0/1.7/98.3% and 0.8/99.2% (p<0.05). Proportions of TLR4*rs10983755 AA/AG/GG and rs1927914 CC/CT/TT homozygote are: (1) 35.1/8.5/56.4% and 9.4/56.4/34.2%; (2) 35/8.3/56.7% and 16.7/48.3/35% (non-difference). Proportions of CD40*rs1883832 CC/CT/TT, rs3765459 AA/AG/GG, and rs4810485 TT/GT/GG are: (1) 29.9/53/17.1%, 6.8/47.9/45.3 and 18.8/62.4/18.8%; (2) 36.7/41.7/21.6%, 1.6/46.7/ 51.7 and 15/51.7/33.3% (non-difference). Haplotype analyses for TLR4 and CD40 genes revealed their non-association and non-additional effect upon asthma susceptibilities.

Conclusion: STAT2*C related genotypes and alleles are associated with asthma susceptibilities and pathogenesis. There were non-association and non-additional effects of TLR4/CD40 gene polymorphisms and haplotypes upon asthma risk.

Toll-like receptors TLR1, TLR2 and TLR4 gene mutations and natural resistance to Mycobacterium avium subsp. paratuberculosis infection in cattle

Toll like receptors (TLRs) are a class of pattern recognition receptors belonging to the innate immune system. Mutations in the protein coding region of TLRs are associated with altered responsiveness to pathogen-associated molecular patterns (PAMPs). A search was performed for novel mutations in bovine TLR1, TLR2 and TLR4 genes associated with the Mycobacterium avium subsp. paratuberculosis (MAP) infection. The work was also focused on the assessment of linkage between well known mutations in TLR genes (TLR2: Arg677Trp, Pro681His and Arg753Gln; TLR4: Asp299Gly and Thr399Ile), and the susceptibility of cattle to MAP infection. Detection of MAP infection in cattle population (n=711) was based on IS900 PCR, which revealed 22.50% (n=160) MAP positivity. Known mutations in TLR2 and TLR4 genes were not found in cattle population. A novel mutation Val220Met was associated (Odd's ratio, OR-3.459) with increased susceptibility to MAP infection. Toll/interleukin-1 receptor (TIR) domain of TLR2 was screened for the presence of mutations, wherein a novel Ile680Val mutation was linked with MAP infection. In silico analysis of the bovine TLR4 ectodomain (ECD) revealed the polymorphic nature of the central ECD and irregularities in the central LRR motifs. LRR11 of the TLR4 showed five missense mutations possibly linked with the increased susceptibility to MAP infection. The most critical position that may alter the pathogen recognition of TLR molecule was 4th residue downstream to LRR domain. Two such missense mutations in TLR4 (Asp299Asn downstream to LRR11, and Gly389Ser downstream to LRR15) were associated with MAP infection. Briefly, the work describes novel mutations in the bovine TLRs and presents their association with the MAP infection.

Full-exon resequencing reveals toll-like receptor variants contribute to human susceptibility to tuberculosis disease

Tuberculosis (TB) is the leading cause of death worldwide due to an infectious agent. Data have accumulated over decades suggesting that variability in human susceptibility to TB disease has a genetic component. Toll-like receptors (TLRs) play a critical role in initiating the innate immune response to many pathogens in mouse models, but little is known about their role in human infections. Human TLRs have been reported to recognize mycobacterial antigens and initiate an immune response. We tested the hypothesis that amino acid-altering polymorphisms in five TLRs were associated with susceptibility to TB disease using a population-based case-control study with 1,312 adult TB patients and controls. Full-coding region sequencing of the five TLR genes in all 1,312 subjects yielded a data set in excess of 16 Mb. Rare nonsynonymous polymorphisms in TLR6-TLR1-TLR10 were significantly overrepresented among African-American TB cases compared with ethnically-matched control subjects. Common nonsynonymous polymorphisms in TLR6-TLR1-TLR10 also were significantly associated with TB disease in certain ethnic groups. Among African Americans, homozygotes for the common-variant haplotype TLR1-248S, TLR1-602I, and TLR6-249S had a significantly increased TB disease risk. A transmission/disequilibrium test on an independent sample found that the TLR1-248S variant was preferentially transmitted to diseased children, thereby confirming disease association. These results are consistent with recent reports implicating TLR1 variants, including TLR1-602, in significantly altered innate immune responses. Also consistent with disease association, rare TLR6 variants were defective in their ability to mediate NF-kappaB signal transduction in transfected human cells. Taken together, the data suggest that variant TLRs contribute to human susceptibility to TB disease. Extensive full-exon resequencing was critical for revealing new information about the role of TLRs in human-pathogen interactions and the genetic basis of innate immune function.

Genetic polymorphisms within the human Toll-like receptor 2 subfamily

Infectious disease is a formidable selective force in Nature as is evident from the complexity of immune systems across multicellular species. TLRs (Toll-like receptors) constitute central pattern-recognition molecules of the innate immune system that sense bacterial, viral, fungal, protozoan and helminth organisms and activate responses that provide immediate as well as long-term protection for the host. The present article reviews the function and evolution of vertebrate TLRs with an emphasis on the subfamily of receptors comprising human TLR1, 2, 6 and 10. The idea that TLRs undergo strong purifying selection provides the framework for the discussion of single nucleotide polymorphisms, many of which are associated with the incidence of infectious disease.