Cutting edge: a Toll-like receptor 2 polymorphism that is associated with lepromatous leprosy is unable to mediate mycobacterial signaling

The contribution of pattern recognition receptor signalling in the development of age related macular degeneration: the role of toll-like-receptors and the NLRP3-inflammasome

Age-related macular degeneration (AMD) is a leading cause of irreversible vision loss, characterised by the dysfunction and death of the photoreceptors and retinal pigment epithelium (RPE). Innate immune cell activation and accompanying para-inflammation have been suggested to contribute to the pathogenesis of AMD, although the exact mechanism(s) and signalling pathways remain elusive. Pattern recognition receptors (PRRs) are essential activators of the innate immune system and drivers of para-inflammation. Of these PRRs, the two most prominent are (1) Toll-like receptors (TLR) and (2) NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3)-inflammasome have been found to modulate the progression of AMD. Mutations in TLR2 have been found to be associated with an increased risk of developing AMD. In animal models of AMD, inhibition of TLR and NLRP3 has been shown to reduce RPE cell death, inflammation and angiogenesis signalling, offering potential novel treatments for advanced AMD. Here, we examine the evidence for PRRs, TLRs2/3/4, and NLRP3-inflammasome pathways in macular degeneration pathogenesis.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Pathogenicity and virulence of Mycobacterium leprae

Leprosy is caused by Mycobacterium leprae (M. leprae) and M. lepromatosis, an obligate intracellular organism, and over 200,000 new cases occur every year. M. leprae parasitizes histiocytes (skin macrophages) and Schwann cells in the peripheral nerves. Although leprosy can be treated by multidrug therapy, some patients relapse or have a prolonged clinical course and/or experience leprosy reaction. These varying outcomes depend on host factors such as immune responses against bacterial components that determine a range of symptoms. To understand these host responses, knowledge of the mechanisms by which M. leprae parasitizes host cells is important. This article describes the characteristics of leprosy through bacteriology, genetics, epidemiology, immunology, animal models, routes of infection, and clinical findings. It also discusses recent diagnostic methods, treatment, and measures according to the World Health Organization (WHO), including prevention. Recently, the antibacterial activities of anti-hyperlipidaemia agents against other pathogens, such as M. tuberculosis and Staphylococcus aureus have been investigated. Our laboratory has been focused on the metabolism of lipids which constitute the cell wall of M. leprae. Our findings may be useful for the development of future treatments.

Single nucleotide polymorphisms in genes involved in immune responses and outcome of tegumentary leishmaniasis

Leishmaniases are neglected tropical diseases with a broad clinical spectrum. Tegumentary leishmaniasis (TL) is a disease caused by different Leishmania species, transmitted by phlebotomine sand flies and distributed worldwide. TL can present a cutaneous (CL) or mucocutaneous (MCL) clinical form depending on factors inherent to the parasite, the host and the vector. Polymorphisms in the immune response genes are host genetic factors that influence the pathogenesis or control of leishmaniasis. Single nucleotide polymorphisms (SNPs) in immune genes have been evaluated in several countries where leishmaniasis is endemic. In this review, we report studies on SNPs in several immune genes that might be associated with susceptibility or resistance to TL. We summarize studies from around the world and in Brazil, highlight the difficulties of these studies and future analyses needed to enhance our knowledge regarding host genetic factors in TL. Understanding the genetic characteristics of the host that facilitate resistance or susceptibility to leishmaniasis can contribute to the development of immunotherapy schedules for this disease. The current treatment methods are toxic, and no human vaccine is available.

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.

The Paratuberculosis Paradigm Examined: A Review of Host Genetic Resistance and Innate Immune Fitness in Mycobacterium avium subsp. Paratuberculosis Infection

Paratuberculosis, or Johne's Disease (JD) is a debilitating chronic enteritis mainly affecting ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). This organism causes worldwide economic losses to the livestock industry, and is of public health importance due to the potential zoonotic risk between MAP and Crohn's disease (CD) in humans. Without economical treatments, or a vaccine capable of preventing infection without causing cross-reactions with bovine tuberculosis, test-and-cull methods for disease control are imperative. Unfortunately, difficulties in diagnostics and long subclinical stage hinder adequate control and is further complicated by variation in MAP exposure outcome. Interestingly, the majority of infections result in asymptomatic presentation and never progress to clinical disease. One contributing factor is host genetics, where polymorphisms in innate immune genes have been found to influence resistance and susceptibility to disease. Candidate genes identified across studies overlap with those found in CD and tuberculosis including; Solute carrier family 11 member 1 gene (SLC11A1), Nucleotide-binding-oligomerization domain containing gene 2 (NOD2), Major histocompatibility complex type II (MHC-II), and Toll-like receptor (TLR) genes. This review will highlight evidence supporting the vital role of these genes in MAP infection outcome, associated challenges, and implications for the future of JD research.

Increased oxidative stress in elderly leprosy patients is related to age but not to bacillary load

BACKGROUND

Leprosy continues to be a public health problem in Brazil. Furthermore, detection rates in elderly people have increased, particularly those of multibacillary (L-Lep) patients, who are responsible for transmitting M. leprae. Part of the decline in physiological function during aging is due to increased oxidative damage and change in T cell subpopulations, which are critical in defense against the disease. It is not still clear how age-related changes like those related to oxidation affect elderly people with leprosy. The aim of this work was to verify whether the elderly leprosy patients have higher ROS production and how it can impact the evolution of leprosy.

METHODOLOGY/PRINCIPAL FINDINGS

87 leprosy patients, grouped according to age range and clinical form of leprosy, and 25 healthy volunteers were analyzed. Gene expression analysis of antioxidant and oxidative burst enzymes were performed in whole blood using Biomark's microfluidic-based qPCR. The same genes were evaluated in skin lesion samples by RT-qPCR. The presence of oxidative damage markers (carbonylated proteins and 4-hydroxynonenal) was analyzed by a DNPH colorimetric assay and immunofluorescence. Carbonylated protein content was significantly higher in elderly compared to young patients. One year after multidrug therapy (MDT) discharge and M. leprae clearance, oxidative damage increased in young L-Lep patients but not in elderly ones. Both elderly T and L-Lep patients present higher 4-HNE in cutaneous lesions than the young, mainly surrounding memory CD8+ T cells. Furthermore, young L-Lep demonstrated greater ability to neutralize ROS compared to elderly L-Lep patients, who presented lower gene expression of antioxidant enzymes, mainly glutathione peroxidase.

CONCLUSIONS/SIGNIFICANCE

We conclude that elderly patients present exacerbated oxidative damage both in blood and in skin lesions and that age-related changes can be an important factor in leprosy immunopathogenesis. Ultimately, elderly patients could benefit from co-supplementation of antioxidants concomitant to MDT, to avoid worsening of the disease.

Toll-Like Receptor 4 Protects Against Clostridium perfringens Infection in Mice

Toll-like receptor 4 (TLR4) has been reported to protect against Gram-negative bacteria by acting as a pathogen recognition receptor that senses mainly lipopolysaccharide (LPS) from Gram-negative bacteria. However, the role of TLR4 in Gram-positive bacterial infection is less well understood. Clostridium perfringens type A is a Gram-positive bacterium that causes gas gangrene characterized by severe myonecrosis. It was previously demonstrated that C. perfringens θ-toxin is a TLR4 agonist, but the role of TLR4 in C. perfringens infection is unclear. Here, TLR4-defective C3H/HeJ mice infected with C. perfringens showed a remarkable decrease in survival rate, an increase in viable bacterial counts, and accelerated destruction of myofibrils at the infection site compared with wild-type C3H/HeN mice. These results demonstrate that TLR4 plays an important role in the elimination of C. perfringens. Remarkable increases in levels of inflammatory cytokines, such as interleukin-1β (IL-1β), interleukin-6 (IL-6), and granulocyte colony-stimulating factor (G-CSF), were observed in C. perfringens-infected C3H/HeN mice, whereas the increases were limited in C3H/HeJ mice. Generally, increased G-CSF accelerates granulopoiesis in the bone marrow and the spleen to exacerbate neutrophil production, resulting in elimination of bacteria. The number of neutrophils in the spleen was increased in C. perfringens-infected C3H/HeN mice compared with non-infected mice, while the increase was lower in C. perfringens-infected C3H/HeJ mice. Furthermore, DNA microarray analysis revealed that the mutation in TLR4 partially affects host gene expression during C. perfringens infection. Together, our results illustrate that TLR4 is crucial for the innate ability to eliminate C. perfringens.

Pathogenesis and Host Immune Response in Leprosy

Leprosy is an ancient insidious disease caused by Mycobacterium leprae, where the skin and peripheral nerves undergo chronic granulomatous infections, leading to sensory and motor impairment with characteristic deformities. Susceptibility to leprosy and its disease state are determined by the manifestation of innate immune resistance mediated by cells of monocyte lineage. Due to insufficient innate resistance, granulomatous infection is established, influencing the specific cellular immunity. The clinical presentation of leprosy ranges between two stable polar forms (tuberculoid to lepromatous) and three unstable borderline forms. The tuberculoid form involves Th1 response, characterized by a well demarcated granuloma, infiltrated by CD4⁺ T lymphocytes, containing epitheloid and multinucleated giant cells. In the lepromatous leprosy, there is no characteristic granuloma but only unstructured accumulation of ineffective macrophages containing engulfed pathogens. Th1 response, characterised by IFN-γ and IL-2 production, activates macrophages in order to kill intracellular pathogens. Conversely, a Th2 response, characterized by the production of IL-4, IL-5 and IL-10, helps in antibody production and consequently downregulates the cell-mediated immunity induced by the Th1 response. M. lepare has a long generation time and its inability to grow in culture under laboratory conditions makes its study challenging. The nine-banded armadillo still remains the best clinical and immunological model to study host-pathogen interaction in leprosy. In this chapter, we present cellular morphology and the genomic uniqueness of M. leprae, and how the pathogen shows tropism for Schwann cells, macrophages and dendritic cells.

Targeting Toll like Receptors in Cancer: Role of TLR Natural and Synthetic Modulators

Background:

Toll like receptors (TLRs) are a group of transmembrane receptors belonging to the broad class pattern recognition receptors (PRR), involved in recognition of Pathogen Associated Molecular Patterns (PAMPs) thereby inducing an immune response. Apart from these exogenous PAMPs, numerous endogenous PAMPs are also ligands for various TLRs thereby activating the TLR dependent immune response, subsequently leading to the onset of an inflammatory response. Prolonged activation of TLR by these endogenous PAMPs leads to chronic inflammatory insults to the body and which in turn alters the proliferative patterns of the cells, which ultimately leads to the development of cancer.

Objectives:

The present review aims to provide a detailed outline of the differential roles of various TLRs in cancer and the possible use of them as a therapeutic target.

Methods:

Data were collected from PubMed/Sciencedirect/Web of Science database and sorted; the latest literature on TLRs was incorporated in the review.

Results:

Among the different TLRs, few are reported to be anti-neoplastic, which controls the cell growth and multiplication in response to the endogenous signals. On the contrary, numerous studies have reported the procarcinogenic potentials of TLRs. Hence, TLRs have emerged as a potential target for the prevention and treatment of various types of cancers. Several molecules, such as monoclonal antibodies, small molecule inhibitors and natural products have shown promising anticancer potential by effectively modulating the TLR signalling.

Conclusion:

Toll-like receptors play vital roles in the process of carcinogenesis, hence TLR targeting is a promising approach for cancer prevention.

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 gene polymorphisms in patients with keratitis

OBJECTIVE

To investigate differences in SNPs in TLR genes between people who had keratitis and controls in an Indian population.

METHODS

145 cases of keratitis and 189 matched controls were recruited. DNA was extracted from peripheral blood. Single nucleotide polymorphisms (SNP) in TLR2 (n = 6), TLR4 (n = 15), TLR5 (n = 13) and TLR9 (n = 10) were analysed. The risk of developing keratitis was assessed based on allele, genotype and haplotype associations.

RESULTS

For all cases of keratitis, the TLR4 SNP rs4986791 TC genotype frequency was significantly higher in cases (p = 0.006, OR = 1.96, 95 % CI 1.19-3.2). Including cases of only microbial keratitis (MK) revealed that genotypes in TLR2 SNP rs5743706 TA (p = 0.0001; OR = 8.61; 95 % CI 2.59-28.56)), TLR4 SNP s4986791 TC (p = 0.002; OR = 2.65; 95 % CI 1.39-5.07) were significantly more common for MK, whereas the TLR5 SNP rs2241096 A allele (p = 0.00316, OR = 0.42, 95 % CI 0.2-0.9286) and GA genotype (p = 0.016; OR = 0.45; 95 % CI 0.23-0.86) was significantly less common in MK cases. The TLR2 SNP rs5743706 genotype TA was significantly less common in the sterile keratitis (SK) group (p = 0.004, OR = 0.43, 95 %CI 0.24-0.77). Haplotype analysis of MK compared to controls showed that TLR2 AT was more common in controls (p = 0.003); TLR4 ACAC was more common in cases (p = 0.004); TLR5 TGGCA was more common in controls (p = 0.001).

CONCLUSION

The present study revealed multiple associations between variants across TLR genes, which may have implications for understanding the underlying host factors, risk of developing keratitis and molecular pathogenesis in keratitis.

Expression of NLRP3 inflammasome in leprosy indicates immune evasion of Mycobacterium leprae

BACKGROUND

Leprosy is an infectious-contagious disease caused by Mycobacterium leprae that remain endemic in 105 countries. This neglected disease has a wide range of clinical and histopathological manifestations that are related to the host inflammatory and immune responses. More recently, the inflammasome has assumed a relevant role in the inflammatory response against microbiological agents. However, the involvement of inflammasome in leprosy remains poorly understood.

OBJECTIVES

The aim is to associate biomarkers of inflammasome with the different immunopathological forms of leprosy.

METHODS

We performed an observational, cross-sectional, and comparative study of the immunophenotypic expression of inflammasome-associated proteins in immunopathological forms of leprosy of 99 skin lesion samples by immunohistochemistry. The intensity and percentage of NLRP3, Caspase-1, Caspases-4/5, interleukin-1β and interleukin-18 immunoreactivities in the inflammatory infiltrate of skin biopsies were evaluated.

FINDINGS

Strong expression of NLRP3 and inflammatory Caspases-4/5 were observed in lepromatous leprosy (lepromatous pole). In addition, were observed low expression of caspase-1, interleukin-1β, and interleukin-18 in tuberculoid and lepromatous leprosy. The interpolar or borderline form showed immunophenotype predominantly similar to the lepromatous pole.

MAIN CONCLUSIONS

Our results demonstrate that the NLRP3 inflammasome is inactive in leprosy, suggesting immune evasion of M. leprae.

Unique etiologic, demographic, and pathologic characteristics of localized aggressive periodontitis support classification as a distinct subcategory of periodontitis

BACKGROUND

Localized aggressive periodontitis (LAgP) occurs in 2% of African-American adolescents but only 0.15% of white adolescents. First molars and incisors are affected by rapid onset and progression.

METHODS

This nonsystematic critical review evaluated published data for LAgP and chronic periodontitis (CP), focusing on potential differences in epidemiology, microbiology, immunology, genetics, and response to therapy.

RESULTS

LAgP differs from CP by localization to incisors and first molars, early onset and rapid progression in adolescents and young adults, and a 10-fold higher prevalence in populations of African or Middle Eastern origin, often with strong familial aggregation. The bacterium Aggregatibacter actinomycetemcomitans and hyperresponsive neutrophils are frequently observed. Antibiotic and nonsurgical therapies are highly effective.

CONCLUSIONS

LAgP differs in many ways from the far more common CP that affects older adults. The substantial evidence of dissimilarities summarized in this review strongly supports the classification of LAgP as a distinct form of periodontitis.

PRACTICAL IMPLICATIONS

Classifying LAgP as a distinct subcategory of periodontitis will encourage future research and does not conflict with the newly proposed "staging and grading" system. The silent onset and rapid progression of LAgP make early diagnosis and frequent follow-up with patients essential for effective treatment.

Leprosy As a Complex Infection: Breakdown of the Th1 and Th2 Immune Paradigm in the Immunopathogenesis of the Disease

Leprosy is a chronic infectious disease whose evolution involves complex immune mechanisms of the host that influence the clinical presentation of the disease. For many years, the main interpretation of the host defense response was based on characterization of the established immune paradigm between T helper (Th) 1 and Th2 lymphocytes. However, with advances in the knowledge of immunology, new approaches have emerged along with the development of new immunological pathways that have changed the interpretation of the long-established paradigm of the polar forms of the disease, especially with the identification of new subtypes of T lymphocytes such as Th9, Th17, Th22, and Tregs. Thus, this review discusses the role of these new subtypes of T helper lymphocytes and how the development of the immune response of these cells modifies the pattern of the Th1/Th2 response in the immunopathogenesis of leprosy.

Peptidoglycan accelerates granulopoiesis through a TLR2- and MyD88-dependent pathway

Granulopoiesis is accelerated during Gram-negative bacterial infection through activation of toll-like receptor 4 (TLR4). In this study, we tested whether activation of TLR2 promotes granulopoiesis by using the well-known TLR2 agonist, peptidoglycan (PGN). Neutrophils in bone marrow and spleen, and plasma granulocyte colony-stimulating factor (G-CSF) were increased in mice that had received intraperitoneal PGN administration. Incorporation of BrdU into bone marrow neutrophils increased, demonstrating that PGN accelerated granulopoiesis. Treatment of bone marrow cells (BMCs) with PGN increased neutrophils in vitro and promoted the secretion of G-CSF from Ly-6G^-Ly-6C⁺ monocytes. The accelerated granulopoiesis caused by PGN was not seen in TLR2-deficient and MyD88-deficient BMCs. Additionally, PGN induced G-CSF production in human umbilical vein endothelial cells. These findings demonstrate that PGN promotes the secretion of G-CSF from monocytes and endothelial cells, leading to the acceleration of granulopoiesis. Our results illustrate that bacterial recognition by TLR2 facilitates granulopoiesis during Gram-positive bacterial infection.

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.

TLR2, TLR4 and TLR9 genotypes and haplotypes in the susceptibility to and clinical course of Chlamydia trachomatis infections in Dutch women

Chlamydia trachomatis infections demonstrate remarkable differences in clinical course that are approximately 40% based on host genetic variation. Here, we study the single nucleotide polymorphisms (SNPs) and their haplotypes in TLR2, TLR4 and TLR9 (TLR2 +2477G>A; TLR2 -16934T>A; TLR4+896A>G; TLR9 -1237T>C and TLR9 +2848G>A) in relation to the susceptibility to, and severity of C. trachomatis infections. We analysed the five SNPs in a cohort of 770 Dutch Caucasian women either attending a sexually transmitted diseases outpatient clinic (n = 731) or having complaints of subfertility (n = 39). Haplotype analyses showed a trend for TLR2 haplotype I (-16934T/+2477G) to protect against the development of symptoms and tubal pathology (Ptrend = 0.03) after Chlamydia infection. In the susceptibility cohort, TLR9 haplotype III (-1237C/+2848A) showed a significant decreasing trend in the development of symptoms after C. trachomatis infection (P = 0.02, OR: 0.55, 95%CI: 0.33-0.91). Logistic regression of the TLR2 haplotypes, TLR4+896A>G, and TLR9 haplotypes showed that the TLR2 haplotype combinations AG-TA and AG-TG confer risk (OR 3.4 (P = 0.01) and 1.6 (P = 0.03)), while the TLR9 haplotype combination TG-TA protects against C. trachomatis infections (OR: 0.4, P = 0.004). Our study shows that both TLR2 and TLR9 genes and SNP combinations do influence the clinical course of Chlamydia infections.

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.

Quantitative defects in invariant NKT cells and TLR responses in patients with hyper-IgE syndrome

BACKGROUND

Autosomal dominant hyper-IgE syndrome (AD-HIES) is a primary immunodeficiency mainly caused by mutations in STAT3, a signalling molecule implicated in the development of appropriate immune responses. We aimed to characterise the innate immune response in AD-HIES.

METHODS

The frequency of innate immune cells in peripheral blood (PB) from seven AD-HIES patients and healthy controls were determined. CD80/CD86 surface expression and cytokine levels in supernatants from PBMC after stimulation with TLR-2, -4 and -9 agonists were also measured by flow cytometry. In addition, several SNPs within these TLR genes in genomic DNA samples from patients and controls were examined.

RESULTS

A significantly reduced number of PB iNKT cells was observed in the AD-HIES group. CpG-stimulated pDC and mDC from patients exhibited a lower increase in the expression of the costimulatory molecule CD80. We also observed an increase in the secretion of IL-12p70, TNF-alpha and IL-10 in PBMC from HIES patients after LTA or LPS stimuli. No association was found between the different SNPs detected and the HIES phenotype.

CONCLUSIONS

These findings demonstrate that important mediators of the innate immunity responses are affected in AD-HIES. More studies are necessary to investigate how the STAT3 function interferes with development of iNKT cells and TLR-mediated responses.

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.

Immunology of leprosy and diagnostic challenges

Leprosy, caused by noncultivable Mycobacterium leprae (ML), has varied manifestations, which are associated with the host immune responses. The dermal involvement is accompanied by peripheral nerve damage, which leads to sensory motor loss and deformities. Both innate and acquired immune responses are involved. The main cell to be compromised is the CD4 + T helper cell, which shows antigen specific unresponsiveness to only ML and not to other common antigens in the bacilliferous generalized lepromatous form of the disease. In contrast, the paucibacillary localized tuberculoid form shows appropriate T cell functions and poor antibody response. The dichotomy between T cell functions and antibodies are discussed against the current information on cytokines, Th subsets, and regulatory T cells. During lepromatous reactions, there is a temporary, heightened T cell immunity, even in lepromatous subjects. The dermal lesions confirm many features observed with peripheral blood mononuclear cells and give additional information on local immune responses. Nerve damage involves both immune and nonimmune mechanisms. Leprosy is a model disease for understanding host immune responses to intracellular bacilli. There are challenges in diagnosing early leprosy. In spite of intensive efforts by many groups, consensus on a universal test suitable for endemic areas is awaited.

Investigation of Toll-Like Receptor-2 (2258G/A) and Interferon Gamma (+874T/A) Gene Polymorphisms among Infertile Women with Female Genital Tuberculosis

BACKGROUND

Toll-like receptor 2 (TLR2) and interferon-gamma (IFN-γ) coordinate with a diverse array of cellular programs through the transcriptional regulation of immunologically relevant genes and play an important role in immune system, reproductive physiology and basic pathology. Alterations in the functions of TLR2 2258G (guanine)/ A, IFN-γ (+874T/A) and signalling molecules that result from polymorphisms are often associated with susceptibility or resistance, which may, in turn, establish the innate host response to various infectious diseases. Presently, we proposed to investigate the risk of common single nucleotide polymorphism (SNP) of TLR2 and IFN-γ genes, for their effect on infertility in women with female genital tuberculosis (FGTB) and healthy women as controls.

METHODOLOGY/PRINCIPAL FINDINGS

Genotyping of TLR2 and IFN-γ gene polymorphisms was performed by amplification refractory mutation system multi-gene/multi-primer polymerase chain reaction followed by restriction fragment length polymorphism in 175 FGTB patients and 100 healthy control women (HCW). The TLR2 polymorphism [adenine (A) allele] was observed in 57.7 and 58.0% of FGTB patients and HCW, respectively. The IFN-γ (+874T/A) polymorphism (A allele) was significant in 74.3 and 71.0% of FGTB patients and HCW, respectively, while the odds ratios for the AA and TA genotypes for predisposition of FGTB were found to be 0.304 and 1.650 in HCW, respectively. The SNP of TLR2 was not associated with FGTB but the SNP of IFN-γ was found to be associated with mycobacteria infections and to induce infertility.

CONCLUSIONS/SIGNIFICANCE

At present, we hypothesize that infertile women with FGTB and HCW without tuberculosis (TB) have identical frequency of TLR variants, which may be adequate in the production of IFN-γ in response to Mycobacterium tuberculosis infections. Thus, the study appears to be the first of its kind reporting a mutation in the IFN-γ gene [+874 T (thymine) to A] responsible for susceptibility to TB infections and further inducing infertility.

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.

Relationship between toll-like receptor 2 Arg677Trp and Arg753Gln and toll-like receptor 4 Asp299Gly polymorphisms and cytomegalovirus infection

OBJECTIVES

The association among specific single-nucleotide polymorphisms (SNPs) in TLR2 (Arg677Trp, Arg753Gln) and TLR4 (Asp299Gln) and human cytomegalovirus (CMV) infection was studied in infants and adults.

METHODS

The TLR2 and TLR4 polymorphisms were genotyped in 151 patients with CMV infections and in 78 unrelated healthy individuals. Genotyping was performed by restriction fragment length polymorphism (RFLP) analysis of PCR-amplified fragments. The viral load was measured by quantitative real-time PCR.

RESULTS

Almost all of the patients with CMV infections were wild-type homozygotes without TLR2 and TLR4 polymorphisms. No significant differences in TLR2 and TLR4 polymorphisms were observed between infants with or without CMV infection. Compared with adults with CMV infections, heterozygosity for the TLR2 Arg677Trp and TLR4 Asp299Gly SNPs was detected more frequently in healthy individuals (p<0.05). Logistic regression analysis showed that the wild-type TLR2 genotype was associated with an increased risk of CMV infection and that heterozygosity for TLR2 and TLR4 SNPs diminished the risk of CMV infection in adult patients. An association between CMV load and the TLR4 SNP was found.

CONCLUSION

Our results suggest that the wild-type TLR2 genotype may be a risk factor for CMV replication in adult patients.

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.

Toll-like receptors and human disease: lessons from single nucleotide polymorphisms

Toll-like receptors (TLRs), a large group of proteins which recognize various pathogen-associated molecular patterns, are critical for the normal function of the innate immune system. Following their discovery many single nucleotide polymorphisms within TLRs and components of their signaling machinery have been discovered and subsequently implicated in a wide range of human diseases including atherosclerosis, sepsis, asthma, and immunodeficiency. This review discusses the effect of genetic variation on TLR function and how they may precipitate disease.

Management and prevention of ventilator-associated pneumonia caused by multidrug-resistant pathogens

Ventilator-associated pneumonia (VAP) due to multidrug-resistant (MDR) pathogens is a leading healthcare-associated infection in mechanically ventilated patients. The incidence of VAP due to MDR pathogens has increased significantly in the last decade. Risk factors for VAP due to MDR organisms include advanced age, immunosuppression, broad-spectrum antibiotic exposure, increased severity of illness, previous hospitalization or residence in a chronic care facility and prolonged duration of invasive mechanical ventilation. Methicillin-resistant Staphylococcus aureus and several different species of Gram-negative bacteria can cause MDR VAP. Especially difficult Gram-negative bacteria include Pseudomonas aeruginosa, Acinetobacter baumannii, carbapenemase-producing Enterobacteraciae and extended-spectrum β-lactamase producing bacteria. Proper management includes selecting appropriate antibiotics, optimizing dosing and using timely de-escalation based on antiimicrobial sensitivity data. Evidence-based strategies to prevent VAP that incorporate multidisciplinary staff education and collaboration are essential to reduce the burden of this disease and associated healthcare costs.

Toll like receptor 9 (TLR9) polymorphism G520R in sheep is associated with seropositivity for Small Ruminant Lentivirus

Infectious diseases of sheep are of major economic importance causing direct and indirect losses. Among the major sheep infectious agents are Small Ruminant Lentivirus, Chlamydophila abortus and Mycobacterium avium subsp. paratuberculosis infections, mainly due to their worldwide distribution and economic impact that they cause. Based on the differential susceptibility to infectious diseases between and within breeds and on the recent findings regarding the putative involvement of TLR9 in disease susceptibility, the aim of this study was to evaluate the levels of nucleotide variation of TLR9 and its mediator MyD88 in three sheep flocks originated from different breeds and assess their possible association with seropositivity/seronegativity for different infectious agents. The analysis indicated that the change of G to R at codon 520 of TLR9 polypeptide shows a significant association with Small Ruminant Lentivirus seropositivity. This amino-acid substitution, which can result in polarity change, might influence structure and function of LRR17, interfering with ligand binding and thus could be used in studies investigating susceptibility/resistance to Small Ruminant Lentivirus infections in sheep.

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.

Molecular mechanisms for the subversion of MyD88 signaling by TcpC from virulent uropathogenic Escherichia coli

The Toll/IL-1 receptor (TIR) domains are crucial signaling modules during innate immune responses involving the Toll-like receptors (TLRs) and IL-1 receptor (IL-1R). Myeloid differential factor 88 (MyD88) is a central TIR domain-containing adapter molecule responsible for nearly all TLR-mediated signaling and is targeted by a TIR domain-containing protein C (TcpC) from virulent uropathogenic Escherichia coli, a common human pathogen. The mechanism of such molecular antagonism has remained elusive. We present the crystal structure of the MyD88 TIR domain with distinct loop conformations that underscore the functional specialization of the adapter, receptor, and microbial TIR domains. Our structural analyses shed light on the genetic mutations at these loops as well as the Poc site. We demonstrate that TcpC directly associates with MyD88 and TLR4 through its predicted DD and BB loops to impair the TLR-induced cytokine induction. Furthermore, NMR titration experiments identify the unique CD, DE, and EE loops from MyD88 at the TcpC-interacting surface, suggesting that TcpC specifically engages these MyD88 structural elements for immune suppression. These findings thus provide a molecular basis for the subversion of TLR signaling by the uropathogenic E. coli virulence factor TcpC and furnish a framework for the design of novel therapeutic agents that modulate immune activation.

Surface expression and genotypes of Toll-like receptors 2 and 4 in patients with juvenile idiopathic arthritis and systemic lupus erythematosus

BACKGROUND

Chronic arthritis is a common feature of juvenile idiopathic arthritis (JIA) and systemic lupus erythematosus (SLE). It was subsequently discovered that Toll-like receptors (TLRs) are able to upregulate cytokine production in response to endogenous ligands released after tissue damage, suggesting that TLRs can maintain an inflammatory response even in absence of pathogen. Thus, TLRs may contribute to increased inflammation in JIA and SLE patients. The aim of this study was to investigate the role of TLRs in JIA and SLE. We examined the in vivo expression and polymorphisms of TLR2 and TLR4 in peripheral monocytes of patients with JIA and SLE during active and inactive disease phases.

METHODS

This single center cohort study consisted of JIA and SLE affected children and control subjects. TLR2 and TLR4 protein expression on CD14+ monocytes was examined by flow cytometry. TLR2 and TLR4 genotypes were determined using the polymerase chain reaction-restriction fragment length polymorphism method (RFLP-PCR).

RESULTS

A significant reduction in the level of TLR4 expression (p ≤ 0.001) was observed on monocytes of patients with JIA and SLE compared with that of healthy control subjects. There was no correlation between the TLR2 or TLR4 genotypes and the observed differential TLR protein expression on monocytes.

CONCLUSIONS

To conclude, our observations suggest involvement of investigated TLRs in the pathogenesis of JIA and SLE. It still remains to be elucidated whether reduced TLR4 expression is cause of chronic arthritis or a result of some feedback loop.

Susceptibility to leprosy is associated with M-ficolin polymorphisms

PURPOSE

Mycobacterium leprae exploits complement activation and opsonophagocytosis to infect phagocytes. M-ficolin is encoded by the FCN1 gene and initiates the lectin pathway on monocyte surfaces. We investigated FCN1 promoter polymorphisms that could be responsible for the high interindividual variability of M-ficolin levels and for modulating leprosy susceptibility.

METHODS

We genotyped rs2989727 (-1981 G > A), rs28909068 (-791 G > A), rs10120023 (-542 G > A), rs17039495 (-399 G > A), rs28909976 (-271IndelT), rs10117466 (-144C > A) and rs10858293 (+33 T > G) in 400 controls and 315 leprosy patients from Southern Brazil, and in 296 Danish healthy individuals with known M-ficolin levels.

RESULTS

Ten haplotypes were identified with sequence-specific PCR and/or haplotype-specific sequencing. We found evidence for a protective codominant additive effect of FCN1*-542A-144C with leprosy in Euro-Brazilians (P=0.003, PBf =0.021, OR=0.243 [CI95% =0.083-0.71]), which was independent of age, ethnic group and gender effects (P=0.029). There was a trend for a positive association of the -399A variant in Afro-Brazilians (P=0.022, PBf =0.154, OR=4.151 [CI95% =1.115-15.454], as well as for a negative association of the FCN1*3A haplotype with lepromatous leprosy, compared with less severe forms of the disease (P=0.016, PBf =0.112, OR=0.324 [CI95% =0.123-0.858]). Danish individuals with this haplotype presented M-ficolin levels higher than the population average of circa 1,000 ng/ml, and -542A-144C, which is able to modify the recognition of transcription factors in silico, occurred in individuals with levels under the 25 percentil (P=0.031).

CONCLUSIONS

Our data provide the first evidence that FCN1 polymorphisms are associated with leprosy. M-ficolin may represent a novel key to understand the immunopathogenesis of M. leprae infection.

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.

Toll-like receptor (TLR2 and TLR4) polymorphisms and chronic obstructive pulmonary disease

Toll-like receptors (TLRs) participate in the defence against bacterial infections that are common in patients with Chronic Obstructive Pulmonary Disease (COPD). We studied all tagging SNPs in TLR2 and TLR4 and their associations with the level and change over time of both FEV(1) and sputum inflammatory cells in moderate-to-severe COPD. Nine TLR2 SNPs and 17 TLR4 SNPs were genotyped in 110 COPD patients. Associations of SNPs with lung function and inflammatory cells in induced sputum were analyzed cross-sectionally with linear regression and longitudinally with linear mixed-effect models. Two SNPs in TLR2 (rs1898830 and rs11938228) were associated with a lower level of FEV(1) and accelerated decline of FEV(1) and higher numbers of sputum inflammatory cells. None of the TLR4 SNPs was associated with FEV(1) level. Eleven out of 17 SNPs were associated with FEV(1) decline, including rs12377632 and rs10759931, which were additionally associated with higher numbers of sputum inflammatory cells at baseline and with increase over time. This is the first longitudinal study showing that tagging SNPs in TLR2 and TLR4 are associated with the level and decline of lung function as well as with inflammatory cell numbers in induced sputum in COPD patients, suggesting a role in the severity and progression of COPD.

The tuberculous granuloma: an unsuccessful host defence mechanism providing a safety shelter for the bacteria?

One of the main features of the immune response to M. Tuberculosis is the formation of an organized structure called granuloma. It consists mainly in the recruitment at the infectious stage of macrophages, highly differentiated cells such as multinucleated giant cells, epithelioid cells and Foamy cells, all these cells being surrounded by a rim of lymphocytes. Although in the first instance the granuloma acts to constrain the infection, some bacilli can actually survive inside these structures for a long time in a dormant state. For some reasons, which are still unclear, the bacilli will reactivate in 10% of the latently infected individuals, escape the granuloma and spread throughout the body, thus giving rise to clinical disease, and are finally disseminated throughout the environment. In this review we examine the process leading to the formation of the granulomatous structures and the different cell types that have been shown to be part of this inflammatory reaction. We also discuss the different in vivo and in vitro models available to study this fascinating immune structure.

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 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.

Species-specific recognition of Aspergillus fumigatus by Toll-like receptor 1 and Toll-like receptor 6

BACKGROUND

Aspergillus fumigatus causes invasive aspergillosis, a potentially fatal infection in oncohematological patients. Innate immune detection of A. fumigatus involves Toll-like receptor (TLR) 4 and TLR2, which forms a heterodimer with either TLR1 or TLR6. The role of those coreceptors in Aspergillus sensing is unknown.

METHODS

Cytokine production was measured in bone marrow-derived macrophages (BMDMs) from wild-type (WT) and TLR-deficient mice after incubation with a WT and an immunogenic RodA-deficient (ΔrodA-47) strain of A. fumigatus and in lungs from these mice after intranasal mold inoculation. Aspergillus fumigatus-mediated NF-κB activation was measured in HEK293T cells transfected with plasmids expressing mouse or human TLRs.

RESULTS

Bone marrow-derived macrophages from TLR1- and TLR6-deficient mice produced lower amounts of interleukin 12p40, CXCL2, interleukin 6, and tumor necrosis factor α than BMDMs from WT mice after stimulation with A. fumigatus. Lungs from TLR1- and TLR6-deficient mice had diminished CXCL1 and CXCL2 production and increased fungal burden after intranasal inoculation of ΔrodA A. fumigatus compared with lungs from WT mice. ΔrodA strain-mediated NF-κB activation was observed in HEK293T cells expressing mouse TLR2/1, mouse TLR2/6, and human TLR2/1 but not human TLR2/6.

CONCLUSIONS

Innate immune detection of A. fumigatus is mediated by TLR4 and TLR2 together with TLR1 or TLR6 in mice and TLR1 but not TLR6 in humans.