Detection of Toll-like receptor 2 (TLR2) mutation in the lepromatous leprosy patients

Human Toll-like receptor 2 genetic polymorphisms with tuberculosis susceptibility: A systematic review and meta-analysis

BACKGROUND

Toll-like receptor 2 (TLR2) is a crucial factor in the development of tuberculosis. However, no studies have explored the association between TLR2 polymorphisms and tuberculosis susceptibility.

OBJECTIVES

This study aimed to explore the correlation between tuberculosis susceptibility and TLR2 polymorphisms (rs3804099, rs3804100, rs1898830, rs5743708, rs121917864, and (-196-174) del).

METHODS

All relevant online databases including PubMed, CNKI, WANFANG DATA, and METSTR-FMRS were systematically searched. STATA17.0 (Stata Corp LP, College Station, Texas, USA) was used.

RESULTS

A total of 37 studies, covering six polymorphisms and comprising 9,474 cases and 10,295 controls, were included in this analysis. rs3804099(C vs T: OR = 1.00, 95 % CI: 0.93-1.08, CC + TC vs TT: OR = 1.04, 95 % CI: 0.98-1.10), rs3804100 (C vs T: OR = 1.19, 95 % CI: 0.93-1.07, CC + TC vs TT: OR = 0.97, 95 % CI: 0.89-1.06), rs1898830(G vs A: OR = 0.90, 95 % CI: 0.81-1.00, GG + AG vs AA: OR = 0.87, 95 % CI: 0.67-1.12), (-196 ∼174) del polymorphism (Del vs Ins: OR = 0.93,95 % CI: 0.76-1.14, DD + DI vs II: OR = 0.92,95 % CI: 0.72-1.17).

CONCLUSIONS

This study indicated that only the TLR2 rs5743708 polymorphism exhibited a significant association with a higher tuberculosis risk, while TLR2 rs3804099, rs3804100, rs1898830, rs121917864, and (-196-174) del polymorphisms were not associated with tuberculosis susceptibility.

Macrophage Biology in Human Granulomatous Skin Inflammation

Cutaneous granulomatoses represent a heterogeneous group of diseases, which are defined by macrophage infiltration in the skin. Skin granuloma can be formed in the context of infectious and non-infectious conditions. Recent technological advances have deepened our understanding of the pathophysiology of granulomatous skin inflammation, and they provide novel insights into human tissue macrophage biology at the site of ongoing disease. Here, we discuss findings on macrophage immune function and metabolism derived from three prototypic cutaneous granulomatoses: granuloma annulare, sarcoidosis, and leprosy.

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.

The Keratinocyte as a Crucial Cell in the Predisposition, Onset, Progression, Therapy and Study of the Atopic Dermatitis

The keratinocyte (KC) is the main functional and structural component of the epidermis, the most external layer of the skin that is highly specialized in defense against external agents, prevention of leakage of body fluids and retention of internal water within the cells. Altered epidermal barrier and aberrant KC differentiation are involved in the pathophysiology of several skin diseases, such as atopic dermatitis (AD). AD is a chronic inflammatory disease characterized by cutaneous and systemic immune dysregulation and skin microbiota dysbiosis. Nevertheless, the pathological mechanisms of this complex disease remain largely unknown. In this review, we summarize current knowledge about the participation of the KC in different aspects of the AD. We provide an overview of the genetic predisposing and environmental factors, inflammatory molecules and signaling pathways of the KC that participate in the physiopathology of the AD. We also analyze the link among the KC, the microbiota and the inflammatory response underlying acute and chronic skin AD lesions.

Association between TLR2 polymorphisms (- 196-174 Ins/Del, R677W, R753Q, and P631H) and schizophrenia in a Tunisian population

Since immune dysregulation has been well studied in schizophrenia pathophysiology, recent studies showed a potent role of TLR2 in neuroinflammation process underlying schizophrenia pathogenesis. However, the genetic predisposition is still unclear. Thus, we hypothesized that TLR2 polymorphisms - 196-174 Ins/Del (rs111200466), R753Q (rs5743708), R677W (rs121917864), and P631H (rs5743704) could be involved in schizophrenia predisposition. A case-control study was performed on a Tunisian population composed of 250 healthy controls and 250 patients genotyped by PCR-RFLP. Genotype and allele distribution were evaluated with sex, schizophrenia subtypes, and other clinical features. We also assessed a haplotype analysis for TLR2 polymorphisms with schizophrenia. Our results showed higher ins/del genotype frequency in healthy women compared to patients (p = 0.006; OR = 0.2). In the other hand, logistic regression showed higher ins/del genotype frequency in controls compared to paranoid patients (p = 0.05; OR = 0.48, adjusted). Frequencies of CT and T allele of R677W were significantly higher in patients compared to controls (p < 10^-4, OR = 10.39; p < 10^-4, OR = 4, adjusted, respectively). R753Q polymorphism was exclusively detected in patients (GA + AA = 2.5%) particularly in men with disorganized subtype. P631H did not show any association with schizophrenia. Finally, haplotype analysis showed that InsGTC and delGTC were associated with higher risk of schizophrenia (p = 0.0001, OR = 8.58; p = 0.04, OR = 5.01, respectively). In the Tunisian population, our results suggested that TLR2 R677W could be associated with susceptibility for schizophrenia, while - 196-174 Ins/Del suggested a trend of protection in women. Otherwise, R753Q could have an effect on schizophrenia especially for disorganized subgroup.

Genetic polymorphisms as multi-biomarkers in severe acute respiratory syndrome (SARS) by coronavirus infection: A systematic review of candidate gene association studies

The Severe acute respiratory syndrome may be caused by coronavirus disease which has resulted in a global pandemic. Polymorphisms in the population play a role in susceptibility to severity. We aimed to perform a systematic review related to the effect of single nucleotide polymorphisms in the development of severe acute respiratory syndrome (SARS). Twenty-eight eligible articles published were identified in PubMed, ScienceDirect, Web of Science, PMC Central and Portal BVS and additional records, with 20 studies performed in China. Information on study characteristics, genetic polymorphisms, and comorbidities was extracted. Study quality was assessed by the STrengthening the REporting of Genetic Association (STREGA) guideline. Few studies investigated the presence of polymorphisms in HLA, ACE1, OAS-1, MxA, PKR, MBL, E-CR1, FcγRIIA, MBL2, L-SIGN (CLEC4M), IFNG, CD14, ICAM3, RANTES, IL-12 RB1, TNFA, CXCL10/IP-10, CD209 (DC-SIGN), AHSG, CYP4F3 and CCL2 with the susceptibility or protection to SARS-Cov. This review provides comprehensive evidence of the association between genetic polymorphisms and susceptibility or protection to severity SARS-CoV. The literature about coronavirus infection, susceptibility to severe acute respiratory syndrome (SARS) and genetic variations is scarce. Further studies are necessary to provide more concrete evidence, mainly related to Covid-19.

Immunology of leprosy

Leprosy is a disease caused by Mycobacterium leprae (ML) with diverse clinical manifestations, which are strongly correlated with the host's immune response. Skin lesions may be accompanied by peripheral neural damage, leading to sensory and motor losses, as well as deformities of the hands and feet. Both innate and acquired immune responses are involved, but the disease has been classically described along a Th1/Th2 spectrum, where the Th1 pole corresponds to the most limited presentations and the Th2 to the most disseminated ones. We discuss this dichotomy in the light of current knowledge of cytokines, Th subpopulations and regulatory T cells taking part in each leprosy presentation. Leprosy reactions are associated with an increase in inflammatory activity both in limited and disseminated presentations, leading to a worsening of previous symptoms or the development of new symptoms. Despite the efforts of many research groups around the world, there is still no adequate serological test for diagnosis in endemic areas, hindering the eradication of leprosy in these regions.

Higher Levels of Serum TLR2 and TLR4 in Patients with Hashimoto's Thyroiditis

OBJECTIVE

Hashimoto's thyroiditis (HT) is an autoimmune disorder caused by the interaction between genes and environmental triggers. HT is the most common endocrine disorder, as well as the most common cause of hypothyroidism. Autoimmunity plays a crucial role in the pathogenesis of HT and recent studies suggest that Toll-like receptor (TLR) signals lead to increased inflammatory response. The aim of our study is to investigate whether TLR-2 and TLR-4 levels and gene polymorphisms contribute to the damaged immune response leading to HT.

METHODS

Using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, single-nucleotide polymorphisms (SNPs) of TLR2 gene Arg677Trp, Arg753Gln, 196-174 del and TLR4 gene Asp299Gly, Thr399Ile were studied in 100 patients with HT and 100 healthy controls. Also, we investigated serum levels of TLR-2 and TLR-4 in the immunopathogenesis of HT. TLR-2 and TLR-4 serum levels were found to be significantly higher in HT patients than the control group. However, no statistical significance was found between patient and control groups in terms of genotype frequencies and allele frequency distribution of TLR2 gene Arg677Trp, Arg753Gln, 196-174 del and TLR4 gene Asp299Gly, Thr399Ile polymorphisms.

RESULT

TLR2 gene Arg677Trp, Arg753Gln, 196-174 del and TLR4 gene Asp299Gly, Thr399Ile polymorphism do not appear to have a role in the development of HT disease. However, in our study, serum levels of TLR-2 and TLR-4 were found to be higher in HT patients than control groups.

CONCLUSION

These findings suggest that TLR-2 and TLR-4 play an important role in the immunopathologic mechanism of disease by causing an increase in proinflammatory response.

Role of Toll-Like Receptors 2 and 4 Genes Polymorphisms in Neonatal Sepsis in a Developing Country: A Pilot Study

Objective Toll-like receptors (TLR) are one of the key molecules that alert the immune system to the presence of microbial infections. This study attempts to elucidate the role of TLR2 and TLR4 polymorphisms in neonatal sepsis.

Methods A case–control study including 30 neonates with confirmed sepsis compared with 20 neonates in a control group. TLR2 and TLR24 gene polymorphisms were confirmed by polymerase chain reaction.

Results The majority of infections were attributed to gram-negative organisms (72.5%) namely Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia coli. Results also revealed that incidence of TLR polymorphism was significantly different between the sepsis and control groups (p = 0.016). The most common polymorphism was TLR2; Arg 753 Gln (16.7%). Presence of TLR polymorphism was also associated with a longer duration of therapy (a median of 10 days for cases with positive polymorphism compared with 6.5 days for negative cases; p = 0.001).

Conclusion This pilot study suggests that any polymorphisms in TLR2 and TLR4 might have a role that interferes with the innate immune response of newborn.

4,4'-Diaminodiphenyl Sulfone (DDS) as an Inflammasome Competitor

The aim of this study is to examine the use of an inflammasome competitor as a preventative agent. Coronaviruses have zoonotic potential due to the adaptability of their S protein to bind receptors of other species, most notably demonstrated by SARS-CoV. The binding of SARS-CoV-2 to TLR (Toll-like receptor) causes the release of pro-IL-1β, which is cleaved by caspase-1, followed by the formation and activation of the inflammasome, which is a mediator of lung inflammation, fever, and fibrosis. The NLRP3 (NACHT, LRR and PYD domains-containing protein 3) inflammasome is implicated in a variety of human diseases including Alzheimer's disease (AD), prion diseases, type 2 diabetes, and numerous infectious diseases. By examining the use of 4,4'-diaminodiphenyl sulfone (DDS) in the treatment of patients with Hansen's disease, also diagnosed as Alzheimer's disease, this study demonstrates the diverse mechanisms involved in the activation of inflammasomes. TLRs, due to genetic polymorphisms, can alter the immune response to a wide variety of microbial ligands, including viruses. In particular, TLR2Arg677Trp was reported to be exclusively present in Korean patients with lepromatous leprosy (LL). Previously, mutation of the intracellular domain of TLR2 has demonstrated its role in determining the susceptibility to LL, though LL was successfully treated using a combination of DDS with rifampicin and clofazimine. Of the three tested antibiotics, DDS was effective in the molecular regulation of NLRP3 inflammasome activators that are important in mild cognitive impairment (MCI), Parkinson's disease (PD), and AD. The specific targeting of NLRP3 itself or up-/downstream factors of the NLRP3 inflammasome by DDS may be responsible for its observed preventive effects, functioning as a competitor.

Toll-like receptor polymorphism in host immune response to infectious diseases: A review

Immunopolymorphism is considered as an important aspect behind the resistance or susceptibility of the host to an infectious disease. Over the years, researchers have explored many genetic factors for their role in immune surveillance against infectious diseases. Polymorphic characters in the gene encoding Toll-like receptors (TLRs) play profound roles in inducing differential immune responses by the host against parasitic infections. Protein(s) encoded by TLR gene(s) are immensely important due to their ability of recognizing different types of pathogen associated molecular patterns (PAMPs). This study reviews the polymorphic residues present in the nucleotide or in the amino acid sequence of TLRs and their influence on alteration of inflammatory signalling pathways promoting either susceptibility or resistance to major infectious diseases, including tuberculosis, leishmaniasis, malaria and filariasis. Population-based studies exploring TLR polymorphisms in humans are primarily emphasized to discuss the association of the polymorphic residues with the occurrence and epidemiology of the mentioned infectious diseases. Principal polymorphic residues in TLRs influencing immunity to infection are mostly single nucleotide polymorphisms (SNPs). I602S (TLR1), R677W (TLR2), P554S (TLR3), D299G (TLR4), F616L (TLR5), S249P (TLR6), Q11L (TLR7), M1V (TLR8), G1174A (TLR9) and G1031T (TLR10) are presented as the major influential SNPs in shaping immunity to pathogenic infections. The contribution of these SNPs in the structure-function relationship of TLRs is yet not clear. Therefore, molecular studies on such polymorphisms can improve our understanding on the genetic basis of the immune response and pave the way for therapeutic intervention in a more feasible way.

Association of TLR4 Polymorphisms, Expression, and Vitamin D with Helicobacter pylori Infection

Helicobacter pylori (H. pylori) infection is the strongest recognized risk factor for gastric adenocarcinoma. Since previous observations have shown that polymorphisms in innate immune system genes, as well as vitamin D (VitD) levels, could modify the risk of infection with Helicobacterpylori (H. pylori), we analyzed the relation between single nucleotide polymorphisms (SNPs) in TLRs (TLR1, TLR2, TLR4) CD14, RUNX3 and VitD levels with H. pylori infection. A case-control study on four hundred sixty Lebanese individuals was conducted. Eleven SNPs in total were genotyped and gene expression analysis using real-time PCR was performed in white blood cells of a subsample of eight individuals. A total of 49% of the participants were affected. Although no direct association was found between the SNPs and H. pylori infection, rs4986790G>A and rs4986791T>C in TLR4 were negatively associated with VitD levels (β = −0.371, p = 5 × 10⁻³ and β = −0.4, p = 2 × 10⁻³, respectively), which was negatively associated with H. pylori infection (OR = 0.01, p < 1 × 10⁻³). TLR4 expression was 3× lower in individuals with H. pylori compared with non-infected (p = 0.01). TLR4 polymorphisms, expression, and VitD could be implicated in H. pylori infection and further development of gastric adenocarcinoma.

Toll-Like Receptor Evolution in Birds: Gene Duplication, Pseudogenization, and Diversifying Selection

Toll-like receptors (TLRs) are key sensor molecules in vertebrates triggering initial phases of immune responses to pathogens. The avian TLR family typically consists of ten receptors, each adapted to distinct ligands. To understand the complex evolutionary history of each avian TLR, we analyzed all members of the TLR family in the whole genome assemblies and target sequence data of 63 bird species covering all major avian clades. Our results indicate that gene duplication events most probably occurred in TLR1 before synapsids diversified from sauropsids. Unlike mammals, ssRNA-recognizing TLR7 has duplicated independently in several avian taxa, while flagellin-sensing TLR5 has pseudogenized multiple times in bird phylogeny. Our analysis revealed stronger positive, diversifying selection acting in TLR5 and the three-domain TLRs (TLR10 [TLR1A], TLR1 [TLR1B], TLR2A, TLR2B, TLR4) that face the extracellular space and bind complex ligands than in single-domain TLR15 and endosomal TLRs (TLR3, TLR7, TLR21). In total, 84 out of 306 positively selected sites were predicted to harbor substitutions dramatically changing the amino acid physicochemical properties. Furthermore, 105 positively selected sites were located in the known functionally relevant TLR regions. We found evidence for convergent evolution acting between birds and mammals at 54 of these sites. Our comparative study provides a comprehensive insight into the evolution of avian TLR genetic variability. Besides describing the history of avian TLR gene gain and gene loss, we also identified candidate positions in the receptors that have been likely shaped by direct molecular host-pathogen coevolutionary interactions and most probably play key functional roles in birds.

Innate Immune Responses in Leprosy

Leprosy is an infectious disease that may present different clinical forms depending on host immune response to Mycobacterium leprae. Several studies have clarified the role of various T cell populations in leprosy; however, recent evidences suggest that local innate immune mechanisms are key determinants in driving the disease to its different clinical manifestations. Leprosy is an ideal model to study the immunoregulatory role of innate immune molecules and its interaction with nervous system, which can affect homeostasis and contribute to the development of inflammatory episodes during the course of the disease. Macrophages, dendritic cells, neutrophils, and keratinocytes are the major cell populations studied and the comprehension of the complex networking created by cytokine release, lipid and iron metabolism, as well as antimicrobial effector pathways might provide data that will help in the development of new strategies for leprosy management.

Pattern recognition receptors and coordinated cellular pathways involved in tuberculosis immunopathogenesis: Emerging concepts and perspectives

Pattern Recognition Receptors (PRRs) play a central role in the recognition of numerous pathogens, including Mycobacterium tuberculosis, resulting in activation of innate and adaptive immune responses. Besides Toll Like Receptors, C-type Lectin Receptors and Nod Like Receptors are now being recognized for their involvement in inducing immune response against M. tuberculosis infection. Although, a functional redundancy of the PRRs has also been reported in many studies, emerging evidences support the notion that a cooperative and coordinated response generated by these receptors is critical to sustain the full immune control of M. tuberculosis infection. Many of the PRRs are now found to be involved in various cellular host defenses, such as inflammasome activation, phagosome biogenesis, endosomal trafficking, and antigen processing pathways that are all very critical for an effective immune response against M. tuberculosis. In support, polymorphism in several of these receptors has also been found associated with increased susceptibility to tuberculosis in humans. Nonetheless, increasing evidences also show that in order to enhance its intracellular survival, M. tuberculosis has also evolved multiple strategies to subvert and reprogram PPR-mediated immune responses. In light of these findings, this review analyzes the interaction of bacterial and host factors at the intersections of PRR signaling pathways that could provide integrative insights for the development of better vaccines and therapeutics for tuberculosis.

Autophagy Is an Innate Mechanism Associated with Leprosy Polarization

Leprosy is a chronic infectious disease that may present different clinical forms according to the immune response of the host. Levels of IFN-γ are significantly raised in paucibacillary tuberculoid (T-lep) when compared with multibacillary lepromatous (L-lep) patients. IFN-γ primes macrophages for inflammatory activation and induces the autophagy antimicrobial mechanism. The involvement of autophagy in the immune response against Mycobacterium leprae remains unexplored. Here, we demonstrated by different autophagic assays that LC3-positive autophagosomes were predominantly observed in T-lep when compared with L-lep lesions and skin-derived macrophages. Accumulation of the autophagic receptors SQSTM1/p62 and NBR1, expression of lysosomal antimicrobial peptides and colocalization analysis of autolysosomes revealed an impairment of the autophagic flux in L-lep cells, which was restored by IFN-γ or rapamycin treatment. Autophagy PCR array gene-expression analysis revealed a significantly upregulation of autophagy genes (BECN1, GPSM3, ATG14, APOL1, and TPR) in T-lep cells. Furthermore, an upregulation of autophagy genes (TPR, GFI1B and GNAI3) as well as LC3 levels was observed in cells of L-lep patients that developed type 1 reaction (T1R) episodes, an acute inflammatory condition associated with increased IFN-γ levels. Finally, we observed increased BCL2 expression in L-lep cells that could be responsible for the blockage of BECN1-mediated autophagy. In addition, in vitro studies demonstrated that dead, but not live M. leprae can induce autophagy in primary and lineage human monocytes, and that live mycobacteria can reduce the autophagy activation triggered by dead mycobacteria, suggesting that M. leprae may hamper the autophagic machinery as an immune escape mechanism. Together, these results indicate that autophagy is an important innate mechanism associated with the M. leprae control in skin macrophages.

Leprosy is an interesting model to study immune responses in humans due to the dichotomy observed among the poles of the disease. While in the self-limited tuberculoid form (T-lep) there are high systemic levels of the cytokine IFN-γ, in the clinically progressive lepromatous form (L-lep) low IFN-γ levels are found. IFN-γ activates an antimicrobial mechanism called autophagy, which has been implicated in control of Mycobacterium tuberculosis infection. However, the role played by autophagy in the immunopathogenesis of leprosy remains unknown. Here we show that autophagy was differentially regulated in T-lep and L-lep patients. In T-lep skin lesion cells autophagy contributes for bacilli control, whereas in L-lep cells the BCL2-mediated block of autophagy promotes the mycobacterial persistence. We also observed that IFN-γ may counteract the inhibition of autophagy triggered by M. leprae infection in L-lep macrophages. In addition, the levels of autophagy were restored in L-lep patients who developed the reversal reaction, an inflammatory state associated with augmented IFN-γ, which is the most important cause of nerve damage and deformities in leprosy. These findings suggest that the modulation of autophagy has the potential to be useful in the treatment of the disease, and provides new insights to prevent leprosy reactional episodes.

CD14 and TLR4 Gene Polymorphisms in Adult Periodontitis

Bacterial deposits, smoking, and host genetic factors play a major role in an individual’s predisposition to periodontitis. Bacterial components are recognized by CD14 and toll-like receptor 4 (TLR4), resulting in a NF-κB-based inflammatory response. We hypothesized that functional CD14 and TLR4 polymorphisms contribute to periodontitis susceptibility. We aimed to investigate the occurrence of CD14-260C>T, TLR4 299Asp>Gly, and 399Thr>Ile gene polymorphisms in adult periodontititis. DNA was collected from 100 patients with severe periodontitis and from 99 periodontally healthy controls. The gene polymorphisms were determined by the PCR technique. The presence of the periodontal pathogens Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans, and whether the subjects smoked, was included in the analyses. The CD14-260T/T genotype was found in 34.0% of periodontitis patients and in 20.2% of controls. Logistic regression analysis adjusted for gender, age, smoking, and prevalence of P. gingivalis and A. actinomycetemcomitans showed an association between the CD14-260T/T genotype and periodontitis (P = 0.004, OR 3.0, 95% CI 1.4–6.9). We conclude that the CD14-260T/T genotype contributes to the susceptibility to severe periodontitis in Dutch Caucasians.

The TLR2 and TLR4 gene polymorphisms in Moroccan visceral leishmaniasis patients

Visceral leishmaniasis (VL) is endemic in the Mediterranean basin and leads to the most severe form of Leishmania infection, lethal if left untreated. However, most infections are sub-clinical or asymptomatic, reflecting the influence of host genetic background on disease outcome. This study aimed to investigate possible association of TLR4 Asp299Gly, TLR4 Thr399Ile and TLR2 Arg753Gln polymorphisms with VL in Moroccan children. We enrolled 119 children with VL caused by Leishmania infantum as well as 138 unrelated children, 95 asymptomatic subjects and 43 healthy individuals who had no evidence of present or past infection. Polymorphisms were genotyped by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) and amplification refractory mutation system assay (ARMS-PCR). Results showed significant differences in genotype Thr399Ile and recessive model frequencies between VL and delayed-type hypersensitivity (DTH+) groups (p=0.018, OR=0.414CI 0.195-0.880; p=0.029, OR=0.448CI 0.214-0.938], respectively) by having the amino-acid threonine polymorphism as a reference in the VL group. Concerning the Asp299Gly there were a significant associations when comparing VL vs DTH+ (Asp299Gly genotype p=0.002, OR=0.326CI 0.158-0.671, allele frequencies p=0.033, OR=0.396CI 0.164-0.959, recessive model p=0.002, OR=0.343CI 0.172-0.681) and DTH+ vs DTH- groups (Asp299Gly genotype p=2.160E-4, OR=3.065CI 1.672-5.618, Gly299Gly genotype p=0.047, OR=0.368CI 0.299-0.452, allele frequencies p=1.406E-7, OR=29.571CI 3.907-223.8, recessive model p=4.370E-14, OR=36.965CI 8.629-158.3), by having the aspartic acid polymorphism as a reference these results suggest that the allele A (savage) confer protection against the clinical manifestations but not against the infection. Furthermore, there was a significant association regarding the Arg753Gln genotype (p=0.002, OR=0.326CI 0.158-0.671), allele frequencies (p=0.033, OR=0.396CI 0.164-0.959) and when applying a recessive model (p=0.002, OR=0.343CI 0.172-0.681) in the VL vs DTH+ groups. The same results was observed when comparing DTH+ vs DTH- groups (p=4.136E-6, OR=0.211CI 0.104-0.428), allele frequencies (p=0.008, OR=0.327CI 0.137-0.779) and recessive model (p=1.748E-5, OR=0.244CI 0.124-0.480). The results provide evidence that allele C in Thr399Ile and allele G in Arg753Gln polymorphisms may lead to protection against the clinical disease. Our data provide insights into the possible role of TLR2 and TLR4 variations in VL susceptibility.

Toll-like receptor cascade and gene polymorphism in host-pathogen interaction in Lyme disease

Lyme disease (LD) risk occurs in North America and Europe where the tick vectors of the causal agent Borrelia burgdorferi sensu lato are found. It is associated with local and systemic manifestations, and has persistent posttreatment health complications in some individuals. The innate immune system likely plays a critical role in both host defense against B. burgdorferi and disease severity. Recognition of B. burgdorferi, activation of the innate immune system, production of proinflammatory cytokines, and modulation of the host adaptive responses are all initiated by Toll-like receptors (TLRs). A number of Borrelia outer-surface proteins (eg, OspA and OspB) are recognized by TLRs. Specifically, TLR1 and TLR2 were identified as the receptors most relevant to LD. Several functional single-nucleotide polymorphisms have been identified in TLR genes, and are associated with varying cytokines types and synthesis levels, altered pathogen recognition, and disruption of the downstream signaling cascade. These single-nucleotide polymorphism-related functional alterations are postulated to be linked to disease development and posttreatment persistent illness. Elucidating the role of TLRs in LD may facilitate a better understanding of disease pathogenesis and can provide an insight into novel therapeutic targets during active disease or postinfection and posttreatment stages.

Evidence for adaptation of porcine Toll-like receptors

Naturally endemic infectious diseases provide selective pressures for pig populations. Toll-like receptors (TLRs) represent the first line of immune defense against pathogens and are likely to play a crucial adaptive role for pig populations. This study was done to determine whether wild and domestic pig populations representing diverse global environments demonstrate local TLR adaptation. The genomic sequence encoding the ectodomain, responsible for interacting with pathogen ligands of bacterial (TLR1, TLR2 and TLR6) and viral (TLR3, TLR7 and TLR8) receptors, was obtained. Mitochondrial D-loop region sequences were obtained and a phylogenetic analysis using these sequences revealed a clear separation of animals into Asian (n = 27) and European (n = 40) clades. The TLR sequences were then analyzed for population-specific positive selection signatures within wild boars and domesticated pig populations derived from Asian and European clades. Using within-population and between-population tests for positive selection, a TLR2-derived variant 376A (126Thr), estimated to have arisen in 163,000 years ago with a frequency of 83.33 % within European wild boars, 98.00 % within domestic pig breeds of European origin, 40.00 % within Asian wild boars, and 11.36 % within Asian domestic pigs, was identified to be under positive selection in pigs of European origin. The variant is located within the N terminal domain of the TLR2 protein 3D crystal structure and could affect ligand binding. This study suggests the TLR2 gene contributing to responses to bacterial pathogens has been crucial in adaptation of pigs to pathogens.

Toll-like receptor signaling in primary immune deficiencies

Toll-like receptors (TLRs) recognize common microbial or host-derived macromolecules and have important roles in early activation of the immune system. Patients with primary immune deficiencies (PIDs) affecting TLR signaling can elucidate the importance of these proteins to the human immune system. Defects in interleukin-1 receptor-associated kinase-4 and myeloid differentiation factor 88 (MyD88) lead to susceptibility to infections with bacteria, while mutations in nuclear factor-κB essential modulator (NEMO) and other downstream mediators generally induce broader susceptibility to bacteria, viruses, and fungi. In contrast, TLR3 signaling defects are specific for susceptibility to herpes simplex virus type 1 encephalitis. Other PIDs induce functional alterations of TLR signaling pathways, such as common variable immunodeficiency in which plasmacytoid dendritic cell defects enhance defective responses of B cells to shared TLR agonists. Dampening of TLR responses is seen for TLRs 2 and 4 in chronic granulomatous disease (CGD) and X-linked agammaglobulinemia (XLA). Enhanced TLR responses, meanwhile, are seen for TLRs 5 and 9 in CGD, TLRs 4, 7/8, and 9 in XLA, TLRs 2 and 4 in hyper IgE syndrome, and for most TLRs in adenosine deaminase deficiency.

Toll-like receptors TLR4 (Asp299Gly and Thr399Ile) and TLR2 (Arg677Trp and Arg753Gln) gene polymorphisms in end-stage renal disease patients on peritoneal dialysis

BACKGROUND

Toll-like receptors (TLRs), expressed on cells of the innate immune system, are the first line of host defense. Recognition of bacterial pathogens by the peritoneum is mediated in part by TLR. In this study, we investigated the role of TLR4 (Asp299Gly and Thr399Ile) and TLR2 (Arg677Trp and Arg753Gln) gene polymorphisms in end-stage renal disease (ESRD) patients on peritoneal dialysis (PD).

METHOD

A total of 100 ESRD patients on PD and 150 healthy controls were enrolled in the study. The patients were divided into two groups: ESRD patients on PD with peritonitis (n = 38) and without peritonitis (n = 62). Genotyping of TLR4 (Asp299Gly and Thr399Ile) and TLR2 (Arg677Trp and Arg753Gln) genes were performed by polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP).

RESULTS

Heterozygous variant of TLR4 (Thr399Ile) Thr/Ile genotype showed significant association with both groups of patients (patients with and without peritonitis) with no difference between the groups. Overall, TLR4 (Thr399Ile) Thr/Ile genotype demonstrated an association with ESRD on PD (OR 3.9). Further, TLR4 (Thr399Ile) polymorphism showed significant association with PD patients having two or more episodes of peritonitis compared to patients with no peritonitis. No such association of increased risk of ESRD was observed with TLR4 (Asp299Gly) Asp/Gly genotype and TLR2 polymorphisms. Haplotype frequencies, Gly/Ile and Asp/Ile, conferred 2.46- and 4.62-fold increased risk of ESRD, respectively.

CONCLUSIONS

TLR4 Thr399Ile genotype was associated with ESRD patients on PD; however, the genotype frequency was similar in PD patients with and without peritonitis.

Association of Toll-like receptor 2 Arg753Gln and Toll-like receptor 1 Ile602Ser single-nucleotide polymorphisms with leptospirosis in an Argentine population

Toll-like receptor 2 (TLR2), a member of the Toll-like receptor family, plays an important role in the recognition of and subsequent immune response activation against leptospirosis in humans. The genetic polymorphism in TLR2 of an arginine to glutamine substitution at residue 753 (Arg753Gln) has been associated with a negative influence on TLR2 function, which may, in turn, determine the innate host response to Leptospira spp. This bacterium signals through TLR2/TLR1 heterodimers in human cells. The aim of the present study was to investigate the Arg753Gln single-nucleotide polymorphism (SNP) of the TLR2 gene, and the isoleucine to serine transversion at position 602 (Ile602Ser) of the TLR1 gene (previously associated with Lyme disease), in leptospirosis patients compared to healthy controls, carrying out a retrospective case/control study. The TLR2 polymorphism adenine (A) allele was observed in 7.3% of leptospirosis patients but was not found in the control group, whereas the guanine (G) allele of the TLR1 polymorphism was found in 63.6% of patients and 41.6% of controls. Susceptibility to leptospirosis disease was increased 10.57-fold for carriers of the TLR2 G/A genotype (P=0.0493) and 3.85-fold for carriers of the TLR1 G/G genotype (P=0.0428). Furthermore, the risk of developing hepatic insufficiency and jaundice was increased 18.86- and 27.60-fold for TLR2 G/A carriers, respectively. Similarly, the risk of developing jaundice was increased 12.67-fold for TLR1 G allele carriers (G/G and T/G genotypes). In conclusion, the present data suggest that the TLR2 Arg753Gln and TLR1 Ile602Ser SNPs influence the risk of developing leptospirosis and its severity.

Single nucleotide polymorphisms of Toll-like receptors and susceptibility to infectious diseases

Toll-like receptors (TLRs) are the best-studied family of pattern-recognition receptors (PRRs), whose task is to rapidly recognize evolutionarily conserved structures on the invading microorganisms. Through binding to these patterns, TLRs trigger a number of proinflammatory and anti-microbial responses, playing a key role in the first line of defence against the pathogens also promoting adaptive immunity responses. Growing amounts of data suggest that single nucleotide polymorphisms (SNPs) on the various human TLR proteins are associated with altered susceptibility to infection. This review summarizes the role of TLRs in innate immunity, their ligands and signalling and focuses on the TLR SNPs which have been linked to infectious disease susceptibility.

Tyrosine phosphorylation in Toll-like receptor signaling

There is a wealth of knowledge about how different Ser/Thr protein kinases participate in Toll-like receptor (TLR) signaling. In many cases, we know the identities of the Ser/Thr residues of various components of the TLR-signaling pathways that are phosphorylated, the functional consequences of the phosphorylation and the responsible protein kinases. In contrast, the analysis of Tyr-phosphorylation of TLRs and their signaling proteins is currently incomplete, because several existing analyses are not systematic or they do not rely on robust experimental data. Nevertheless, it is clear that many TLRs require, for signaling, ligand-dependent phosphorylation of specific Tyr residues in their cytoplasmic domains; the list includes TLR2, TLR3, TLR4, TLR5, TLR8 and TLR9. In this article, we discuss the current status of knowledge of the effect of Tyr-phosphorylation of TLRs and their signaling proteins on their biochemical and biological functions, the possible identities of the relevant protein tyrosine kinases (PTKs) and the nature of regulations of PTK-mediated activation of TLR signaling pathways.

Most influential FEMS publications

A selection of influential FEMS publications to celebrate the 40th anniversary of FEMS.

Human neutrophils produce IL-12, IL-10, PGE2 and LTB4 in response to Paracoccidioides brasiliensis. Involvement of TLR2, mannose receptor and dectin-1

The functions of phagocytic cells against pathogens are initiated by the interaction between membrane receptors and molecular structures which compose the cell wall of these microorganisms. Thus our study aimed to identify the neutrophil receptors involved in the recognition of different strains of Paracoccidioides brasiliensis and the consequent modulation of immune response through the production of cytokines and inflammatory mediators. Neutrophils did not produce TNF-alfa in response to both strains. However, these cells produce IL-12, mainly in response to Pb 265, with participation of TLR2 and dectin-1. These cells also produce L-10, whose levels were higher for Pb 18 with involvement of TLR2 and MR and only TLR2 for Pb 265. The production of PGE2 and LTB4 was detected similarly for the two strains. For PGE2, MR and dectin-1 were involved, while in relation to LTB4, none of them. In summary, we demonstrated that neutrophils have a dynamic role during host immune response to P. brasiliensis, since in addition to their role as effector cells of innate immunity; they have the capacity to modulate innate and adaptative immune response against this fungus by producing cytokines and lipidic mediators. This modulation may be toward a pró- or anti-inflammatory pattern in a dependence of P. brasiliensis strains and PRR involved in fungus recognition by these cells.

Leprosy as a model of immunity

ABSTRACT: Leprosy displays a spectrum of clinical manifestations, such as lepromatous and tuberculoid leprosy, and type I and II lepra reactions, which are thought to be a reflection of the host’s immunological response against Mycobacterium leprae. Therefore, differential recognition of M. leprae, as well as its degraded components, and subsequent activation of cellular immunity will be an important factor for the clinical manifestation of leprosy. Although M. leprae mainly parasitizes tissue macrophages in the dermis and the Schwann cells of peripheral nerves, the presence of M. leprae in other organs, such as the liver, may also play important roles in the further modification of seesaw-like bipolar phenotypes of leprosy. Thus, leprosy is an exciting model for investigating the role of the human immune system in host defense and susceptibility to infection.

Insights from animal models on the immunogenetics of leprosy: a review

A variety of host immunogenetic factors appear to influence both an individual's susceptibility to infection with Mycobacterium leprae and the pathologic course of the disease. Animal models can contribute to a better understanding of the role of immunogenetics in leprosy through comparative studies helping to confirm the significance of various identified traits and in deciphering the underlying mechanisms that may be involved in expression of different disease related phenotypes. Genetically engineered mice, with specific immune or biochemical pathway defects, are particularly useful for investigating granuloma formation and resistance to infection and are shedding new light on borderline areas of the leprosy spectrum which are clinically unstable and have a tendency toward immunological complications. Though armadillos are less developed in this regard, these animals are the only other natural hosts of M. leprae and they present a unique opportunity for comparative study of genetic markers and mechanisms associable with disease susceptibility or resistance, especially the neurological aspects of leprosy. In this paper, we review the recent contributions of genetically engineered mice and armadillos toward our understanding of the immunogenetics of leprosy.

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.

The genetics of innate immunity sensors and human disease

Since their discovery, innate immunity microbial sensors have been increasingly studied and shown to play a critical role in innate responses to microbes in several experimental in vitro, ex vivo, and animal models. However, their role in the human response to infection in natural conditions has just started to be deciphered, by means of clinical studies of primary immunodeficiencies and epidemiological genetic studies. Here, we summarize the major findings concerning the genetic diversity of the various families of microbial sensors in humans, and of other molecules involved in the signaling pathways they trigger. Specifically, we review the genetic associations, revealed by both clinical and epidemiological genetics studies, of microbial sensors from five different families: Toll-like receptors, C-type lectin receptors, NOD-like receptors, RIG-I-like receptors, and cytosolic DNA sensors. In particular, we consider the relationships between variation at the genes encoding these molecules and susceptibility to and the severity of infectious diseases and other clinical conditions associated with immune dysfunction, including autoimmunity, inflammation, allergy, and cancer. Despite the fact that the genetic links between innate immunity sensors and human disorders remain still limited, human genetics studies are increasingly improving our understanding of the genuine functions of microbial sensors and downstream signaling molecules in the natural setting.

Toll-like receptor polymorphisms, inflammatory and infectious diseases, allergies, and cancer

Toll-like receptors (TLRs) are germ-line-encoded innate immune sensors that recognize conserved microbial structures and host alarmins and signal expression of MHC proteins, costimulatory molecules, and inflammatory mediators by macrophages, neutrophils, dendritic cells, and other cell types. These processes activate immediate and early mechanisms of innate host defense, as well as initiate and orchestrate adaptive immune responses. Several single-nucleotide polymorphisms (SNPs) within the TLR genes have been associated with altered susceptibility to infectious, inflammatory, and allergic diseases, and have been found to play a role in tumorigenesis. Critical advances in our understanding of innate immune functions and genome-wide association studies (GWAS) have uncovered complex interactions of genetic polymorphisms within TLRs and environmental factors. However, conclusions obtained in the course of such analyses are restricted by limited power of many studies that is likely to explain controversial findings. Further, linkages to certain ethnic backgrounds, gender, and the presence of multigenic effects further complicate the interpretations of how the TLR SNPs affect immune responses. For many TLRs, the molecular mechanisms by which SNPs impact receptor functions remain unknown. In this review, I have summarized current knowledge about the TLR polymorphisms, their impact on TLR signaling, and associations with various inflammatory, infectious, allergic diseases and cancers, and discussed the directions of future scientific research.

Divergent roles of amino acid residues inside and outside the BB loop affect human Toll-like receptor (TLR)2/2, TLR2/1 and TLR2/6 responsiveness

TLR2 specifically recognizes a wide range of ligands by homodimerizing or heterodimerizing with TLR1 or TLR6. However, the molecular basis of the specific signalling transduction induced by TLR2 homodimerization or heterodimerization with TLR1 or TLR6 is largely unknown. In this study, we found three amino acid residues, two (663L and 688N) outside and one (681P) inside the BB loop, which were conserved in all of the TLRs, except for the TLR3 toll/IL-1R(TIR) domain. The responsiveness of human TLR2/2, TLR2/1 or TLR2/6 was completely lost when 663L and 688N were replaced with the corresponding amino acid residues in the TLR3 TIR domain, respectively. However, the response of TLR2 (P681A) to the high concentration of TLR2/TLR6 agonist was almost intact, but the activity of TLR2 (P681A) was greatly reduced when stimulated with the TLR2/1 agonist or the TLR2/2 agonist. Although the surface expression of TLR2 (L663E) was sharply reduced, both the intracellular distribution and the surface expression of all of the other TLR2 mutants were unchanged. The ability of all three TLR2 mutants to recruit MyD88, was consistent with their responsivenesses. Computer modelling indicated that the surface negative charge of all of the TLR2 mutants' BB loops was reduced. Thus, our data demonstrated that the 663L and 688N residues outside of the BB loop were essential for the responsiveness of TLR2/2, TLR2/1 and TLR2/6, but the 681P residue inside of the BB loop exhibited divergent roles in TLR2/2, TLR2/1 and TLR2/6 signalling transduction, thereby providing clues regarding the specific signalling transduction of TLR2/2, TLR2/1 and TLR2/6.

Hypothalamic neuronal toll-like receptor 2 protects against age-induced obesity

Toll-like receptors (TLRs) are traditionally associated with immune-mediated host defense. Here, we ascribe a novel extra-immune, hypothalamic-associated function to TLR2, a TLR-family member known to recognize lipid components, in the protection against obesity. We found that TLR2-deficient mice exhibited mature-onset obesity and susceptibility to high-fat diet (HFD)-induced weight gain, via modulation of food intake. Age-related obesity was still evident in chimeric mice, carrying comparable TLR2⁺ immune cells, suggesting a non-hematopoietic-related involvement of this receptor. TLR2 was up-regulated with age or HFD in pro-opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus, a brain area participating in central-metabolic regulation, possibly modulating the hypothalamic-anorexigenic peptide, α-melanocyte-stimulating hormone (α-MSH). Direct activation of TLR2 in a hypothalamic-neuronal cell-line via its known ligands, further supports its capacity to mediate non-immune related metabolic regulation. Thus, our findings identify TLR2 expressed by hypothalamic neurons as a potential novel regulator of age-related weight gain and energy expenditure.

Toll like receptor 2 and 4 polymorphisms in malaria endemic populations of India

Toll like receptors (TLRs) play a pivotal role in recognizing the invading malaria parasite Plasmodium, thus genetic makeup of the exposed population can be of utmost importance for its predisposition to malaria. In this study 264 malaria patients from seven different eco epidemiological regions of India were genotyped for TLR2 and TLR4 polymorphisms using DNA sequencing methods. No variation was observed at residue positions 677 and 753 in TLR2 whereas residue positions 299 and 399 in TLR4 were highly polymorphic. The GC haplotype (Asp299Gly/Thr399Thr) was observed at the highest frequency in populations of East Singhbhum, Vizianagaram and North Goa and absent in Kolkata, Dakshin Kannada and Nicobar district. All polymorphisms were in Hardy Weinberg equilibrium. Populations of Kolkata, Nicobar district, Sundergarh and Dakshin Kannada were observed to be closely related. TLR2 polymorphism was absent in the Indian population and an overall heterogeneous pattern of TLR4 polymorphism can be attributed to genetic drift. However it can be inferred that GC haplotype is under the process of natural selection in the Indian population and one of the factors contributing to its selection could be predominance of Plasmodium falciparum in these regions.

Human beta-defensin 3 is up-regulated in cutaneous leprosy type 1 reactions

Background

Leprosy, a chronic granulomatous disease affecting the skin and nerves, is caused by Mycobacterium leprae (M. leprae). The type of leprosy developed depends upon the host immune response. Type 1 reactions (T1Rs), that complicate borderline and lepromatous leprosy, are due to an increase in cell-mediated immunity and manifest as nerve damage and skin inflammation. Owing to the increase in inflammation in the skin of patients with T1Rs, we sought to investigate the activation of the innate immune system during reactionary events. Specifically, we investigated the expression levels of human beta-defensins (hBDs) 2 and 3 in the skin of patients with T1Rs, in keratinocytes, and in macrophages stimulated with M. leprae and corticosteroids.

Results

Skin biopsies from twenty-three patients with Type 1 reactions were found to have higher transcript levels of hBD3 as compared to fifteen leprosy patients without Type 1 reactions, as measured by qPCR. Moreover, we observed that keratinocytes but not macrophages up-regulated hBD2 and hBD3 in response to M. leprae stimulation in vitro. Corticosteroid treatment of patients with T1Rs caused a suppression of hBD2 and hBD3 in skin biopsies, as measured by qPCR. In vitro, corticosteroids suppressed M. leprae-dependent induction of hBD2 and hBD3 in keratinocytes.

Conclusions

This study demonstrates that hBD3 is induced in leprosy Type 1 Reactions and suppressed by corticosteroids. Furthermore, our findings demonstrate that keratinocytes are responsive to M. leprae and lend support for additional studies on keratinocyte innate immunity in leprosy and T1Rs.

Trial Registration

Controlled-Trials.com ISRCTN31894035

Leprosy, caused by Mycobacterium leprae (M. leprae), is a chronic infection leading to potentially debilitating nerve damage. Although the infection is curable with multi-drug therapy, many patients continue to suffer from episodes of inflammation, called Type 1 reactions. These reactions may lead to nerve damage and deformation. Patients with Type 1 reactions are treated with corticosteroids to reduce the inflammation. Elucidating the immune factors contributing to leprosy Type 1 reactions will further clarify why many leprosy patients develop nerve and skin inflammation. We conducted a study to understand whether the antimicrobial peptides, human beta-defensins (hBD) 2 and 3, are increased in the skin of leprosy patients with Type 1 reactions. We also investigated keratinocyte expression of hBD2 and hBD3 in response to M. leprae. In this study, we found that hBD3 was significantly increased in the skin of leprosy patients with Type 1 reactions. Moreover, we demonstrated that corticosteroid treatment reduced the expression of hBD3 in patients with Type 1 reactions. We also found that keratinocytes incubated with M. leprae upregulated hBD2 and hBD3 in vitro; corticosteroids were found to suppress this response. These studies suggest a role for the innate immune system in leprosy Type 1 reactions.

Genomics in cardiovascular diseases: analysis of the importance of the toll-like receptor signaling pathway

The development of techniques for genomics study makes it possible for us to further our knowledge about the physiopathology of various immunological or infectious diseases. These techniques improve our understanding of the development and evolution of such diseases, including those of cardiovascular origin, whilst they help to bring about the design of new therapeutic strategies. We are reviewing the genetic alterations of immunity in said field, and focusing on the signaling pathway of toll-like receptors because not only does this play a decisive role in response to microorganisms, it is also heavily involved in modulating the inflammatory response to tissue damage, a side effect of numerous cardiovascular diseases. These alterations in tissue homeostasis are present under a wide range of circumstances, such as reperfusion ischemia (myocardial infarction) phenomena, arteriosclerosis, or valvulopathy.

Allele-specific primer polymerase chain reaction for a single nucleotide polymorphism (C1205T) of swine toll-like receptor 5 and comparison of the allelic frequency among several pig breeds in Japan and the Czech Republic

In the present study, an allele-specific primer-polymerase chain reaction (ASP-PCR) for genotyping a single nucleotide polymorphism (SNP) of swine Toll-like receptor 5 (TLR5) (C1205T; P402L) that is related to the impaired recognition of Salmonella enterica serovar Choleraesuis (SC) was developed. The allele frequencies in several pig breeds in Japan and the Czech Republic were also compared. The swine TLR5 C1205T mutation was successfully determined by ASP-PCR using genomic DNA samples in Japan that had previously been genotyped by a sequencing method. Using the PCR condition determined, genomic DNA samples from blood obtained from 110 pigs from seven different breeds in the Czech Republic were genotyped by the ASP-PCR. The genotyping results from the ASP-PCR completely matched the results from the sequencing method. The allele frequency of the swine TLR5 C1205T mutation was 27.5% in the Landrace breed of the Czech Republic compared with 50.0% in Japanese Landrace. In Japan, the C1205T mutation was found only in the Landrace breed, whereas in the Czech Republic it was found in both the Landrace and Piétrain breeds. These results indicate the usefulness of ASP-PCR for detecting a specific SNP for swine TLR5 affecting ligand recognition. They also suggest the possibility of genetically improving pigs to enhance their resistance against SC infection by eliminating or selecting this specific SNP of swine TLR5.

R753Q polymorphism inhibits Toll-like receptor (TLR) 2 tyrosine phosphorylation, dimerization with TLR6, and recruitment of myeloid differentiation primary response protein 88

The R753Q polymorphism in the Toll-IL-1 receptor domain of Toll-like receptor 2 (TLR2) has been linked to increased incidence of tuberculosis and other infectious diseases, but the mechanisms by which it affects TLR2 functions are unclear. Here, we studied the impact of the R753Q polymorphism on TLR2 expression, hetero-dimerization with TLR6, tyrosine phosphorylation, and recruitment of myeloid differentiation primary response protein (MyD) 88 and MyD88 adapter-like (Mal). Complementation of HEK293 cells with transfected WT or R753Q TLR2 revealed their comparable total levels and only minimal changes in cell surface expression of the mutant species. Notably, even a 100-fold increase in amounts of transfected R753Q TLR2 versus WT variant did not overcome the compromised ability of the mutant TLR2 to activate nuclear factor κB (NF-κB), indicating that a minimal decrease in cell surface levels of the R753Q TLR2 cannot account for the signaling deficiency. Molecular modeling studies suggested that the R753Q mutation changes the electrostatic potential of the DD loop and results in a discrete movement of the residues critical for protein-protein interactions. Confirming these predictions, biochemical assays demonstrated that R753Q TLR2 exhibits deficient agonist-induced tyrosine phosphorylation, hetero-dimerization with TLR6, and recruitment of Mal and MyD88. These proximal signaling deficiencies correlated with impaired capacities of the R753Q TLR2 to mediate p38 phosphorylation, NF-κB activation, and induction of IL-8 mRNA in transfected HEK293 cells challenged with inactivated Mycobacterium tuberculosis or mycobacterial components. Thus, the R753Q polymorphism renders TLR2 signaling-incompetent by impairing its tyrosine phosphorylation, dimerization with TLR6, and recruitment of Mal and MyD88.

Pattern recognition receptors in infectious skin diseases

During the last decade, multiple pattern recognition receptors (PRRs) have been identified. These are involved in the innate immune response against a plethora of pathogens. However, PRR functioning can also be detrimental, even during infections. This review discusses the current knowledge on PRRs that recognize dermatotropic pathogens, and potential therapeutical implications.

NOD2 triggers an interleukin-32-dependent human dendritic cell program in leprosy

It is unclear whether the ability of the innate immune system to recognize distinct ligands from a single microbial pathogen via multiple pattern recognition receptors (PRRs) triggers common pathways or differentially triggers specific host responses. In the human mycobacterial infection leprosy, we found that activation of monocytes via nucleotide-binding oligomerization domain-containing protein 2 (NOD2) by its ligand muramyl dipeptide, as compared to activation via heterodimeric Toll-like receptor 2 and Toll-like receptor 1 (TLR2/1) by triacylated lipopeptide, preferentially induced differentiation into dendritic cells (DCs), which was dependent on a previously unknown interleukin-32 (IL-32)-dependent mechanism. Notably, IL-32 was sufficient to induce monocytes to rapidly differentiate into DCs, which were more efficient than granulocyte-macrophage colony-stimulating factor (GM-CSF)-derived DCs in presenting antigen to major histocompatibility complex (MHC) class I-restricted CD8(+) T cells. Expression of NOD2 and IL-32 and the frequency of CD1b(+) DCs at the site of leprosy infection correlated with the clinical presentation; they were greater in patients with limited as compared to progressive disease. The addition of recombinant IL-32 restored NOD2-induced DC differentiation in patients with the progressive form of leprosy. In conclusion, the NOD2 ligand-induced, IL-32-dependent DC differentiation pathway contributes a key and specific mechanism for host defense against microbial infection in humans.

Polymorphisms of the TLR2 and TLR4 genes are associated with risk of gastric cancer in a Brazilian population

AIM: To investigate toll-like receptor 2 (TLR2) -196 to -174 del, and TLR4 (+896A/G rs4986790 and +1196C/T rs4986791) polymorphisms at risk of chronic gastritis and gastric cancer in a Brazilian population and association of gastric lesions with risk factors such as smoking, alcohol intake and Helicobacter pylori infection.

METHODS: In this case-control study, polymorphism at TLR2 -196 to -174 del was investigated by using the allele-specific polymerase chain reaction (PCR) method, while the PCR-restriction fragment length polymorphism technique was carried out to identify the TLR4 (rs4986790 and rs4986791) genotypes in 607 Brazilian individuals (208 with chronic gastritis-CG, 174 with gastric cancer-GC and 225 controls -C).

RESULTS: The single nucleotide polymorphisms TLR4+1196C/T was not associated with risk of chronic gastritis or gastric cancer and the homozygous genotypes TLR4+896GG and TLR4+1196TT were absent in the studied population. However, the frequency of TLR2 -196 to -174 ins/del + del/del and TLR4+896AG genotypes was significantly higher (P < 0.01 and P = 0.01, respectively) in the cancer group (33.4% and 11.5%, respectively) than in the control group (16.9% and 4.5%, respectively). It was also observed that the G-C haplotype of the TLR4+896A/G+1196C/T (P = 0.02) and the combination of variant alleles of the TLR2/TLR4+896G (P = 0.02) are associated with susceptibility to gastric cancer. In addition, the multiple logistic regression showed that male gender [odds ratio (OR) = 2.70; 95% CI: 1.66-4.41; P < 0.01], alcohol intake (OR = 2.93; 95% CI: 1.76-4.87; P < 0.01), TLR2 -196 to -174 del (OR = 2.64; 95% CI: 1.56-4.44; P < 0.01) and TLR4+896G (OR = 3.19; 95% CI: 1.34- 7.61; P < 0.01) polymorphisms were associated with a higher susceptibility to developing this neoplasm.

CONCLUSION: Our data indicate that TLR2 -196 to -174 del and TLR4+896G may increase the risk of gastric cancer in a Brazilian population.

Polymorphisms of innate immunity receptors in infection by parasites

The innate immune system is the first line of defence against infection by pathogenic bacteria, virus and parasites and is also responsible for initiating an adaptive immune response. In contrast to the receptors of adaptive immunity (TCRs and antibodies) which are generated by gene recombination, receptors of the innate immune system are encoded in the germline and are thus inherited from generation to generation. Although evolutionarily selected, the genes encoding the innate recognition receptors show variations among individuals, and these polymorphisms may have an impact on the ability of an individual to deal with an infection. In recent years, several polymorphisms have been identified in innate recognition receptors, and efforts are being made to determine whether these polymorphisms are associated with a higher or lower susceptibility to infectious diseases. These studies will allow a better understanding of the role of innate receptors in specific diseases and are valuable in the design of preventive or therapeutic interventions to fight the disease. In this review, we summarize studies aimed at determining the influence of polymorphisms in innate recognition receptors on the susceptibility to diseases caused by parasites.

Different patterns of Toll-like receptor 2 polymorphisms in populations of various ethnic and geographic origins

Upon the invasion of the host by microorganisms, innate immunity is triggered through pathogen recognition by pattern recognition receptors (PRRs). Toll-like receptors (TLRs) are the best-studied class of PRRs, and they recognize specific pathogen-associated molecular patterns (PAMPs) from various microorganisms. A large number of studies have shown that genetic variation in TLRs may influence susceptibility to infections. We assessed the genetic variation of TLR2, which encodes one of the most important TLRs, in various populations around the globe and correlated it with changes in the function of the molecule. The three best-known nonsynonymous TLR2 polymorphisms (1892C>A, 2029C>T, and 2258G>A) were assessed in different populations from the main continental masses: Romanians, Vlax-Roma, Dutch (European populations), Han Chinese (East Asia), Dogon, Fulani (Africa), and Trio Indians (America). The 2029C>T polymorphism was absent in both European and non-European populations, with the exception of the Vlax-Roma, suggesting that this polymorphism most likely arose in Indo-Aryan people after migration into South Asia. The 1892C>A polymorphism that was found exclusively in European populations, but not in Asian, African, or American volunteers, probably occurred in proto-Indo-Europeans. Interestingly, 2258G>A was present only in Europeans, including Vlax-Roma, but at a very low frequency. The differential pattern of the TLR2 polymorphisms in various populations may explain some of the differences in susceptibility to infections between these populations.