Navigating through the maze of TLR2 mediated signaling network for better mycobacterium infection control

miR-146a is critical for orchestrating Mycobacterium fortuitum survival through anti-inflammatory and M2 macrophage responses in fish

The significance of microRNAs (miRNAs) in host response to non-tuberculoid mycobacteria like Mycobacterium fortuitum remains nascent. Using zebrafish kidney macrophages (ZFKM), we elucidate a novel function of miR-146a, orchestrated by the TLR-2-PI3K-NF-κB pathway, in M. fortuitum pathogenesis. We demonstrate that miR-146a facilitates anti-inflammatory response by targeting IRAK-1 and TRAF-6 in M. fortuitum-infected ZFKM. Moreover, miR-146a mitigates M1 macrophage activity by suppressing the iNOS-NO axis while enhancing M2-specific TGF-β mRNA expression and subsequent inhibition of M. fortuitum eradication. These findings collectively suggest that miR-146a diminishes macrophage-mediate M. fortuitum clearance. Our study provides novel insights into the intricate interplay between miRNAs and mycobacterial infections. We propose a mechanistic model wherein the TLR-2/NF-κB axis initiates miR-146a expression, which, in turn, suppresses irak-1 and traf-6, fostering the development of M2 macrophages. Consequently, this creates an anti-inflammatory environment conducive to M. fortuitumsurvival. Our findings provide novel insights into the intricate interplay between miRNAs and mycobacterial persistence, a concerning aspect of pathogenesis.

Protein Expression of TLR2, TLR4, and TLR9 on Monocytes in TB, HIV, and TB/HIV

Toll-like receptors (TLRs) have a critical role in recognizing pathogenic patterns and initiating immune responses against TB and HIV. Previously, studies described the gene expression of TLRs in patients with TB and HIV. Here, we demonstrated TLRs protein expressions and their association with clinical status and plasma markers in TB, HIV, and TB/HIV coinfection. The phenotyping of TLR2, TLR4, and TLR9 on CD14+ monocytes and their subsets were determined by multicolor flow cytometry. Host plasma biomarkers and microbial indices were measured using Luminex Multiplex assay and standard of care tools, respectively. TLR2 expression significantly enhanced in TB, slightly increased in HIV but slightly reduced in TB/HIV coinfection compared to apparently health controls (HC). On the other hand, TLR4 expression was significantly increased in TB, HIV, and TB/HIV compared to HC. Expression of TLR4 was equally enhanced on classical and intermediate monocytes while higher TLR2 expression on intermediate than classical monocytes. TLR4 had a positive correlation pattern with plasma biomarkers while TLR2 had an inverse correlation pattern. TLR4 is associated with disease severity while TLR2 is with the immune-competent status of patients. Our findings demonstrated that the pattern of TLR expression is disease as well as monocyte subset specific and distinct factors drive these differences.

Pathogenicity and virulence of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis, an infectious disease with one of the highest morbidity and mortality rates worldwide. Leveraging its highly evolved repertoire of non-protein and protein virulence factors, Mtb invades through the airway, subverts host immunity, establishes its survival niche, and ultimately escapes in the setting of active disease to initiate another round of infection in a naive host. In this review, we will provide a concise synopsis of the infectious life cycle of Mtb and its clinical and epidemiologic significance. We will also take stock of its virulence factors and pathogenic mechanisms that modulate host immunity and facilitate its spread. Developing a greater understanding of the interface between Mtb virulence factors and host defences will enable progress toward improved vaccines and therapeutics to prevent and treat tuberculosis.

Clinical isolates of Mycobacterium tuberculosis with different genotypes exhibit distinct host macrophage responses in vitro

Introduction. Mycobacterium tuberculosis (M.tb), the causative agent of tuberculosis, can survive as an intracellular parasite after entering macrophages via phagocytosis. M.tb strains are genotypically distinct and engage in diverse pathogen-host interactions, with different host immune responses triggered by different M.tb strains. Importantly, differences in intracellular accumulation and triggering of host macrophage responses during early infection stages are key determinants that shape the final outcomes of host innate immune responses to different M.tb strains.Hypothesis/Gap Statement. Clinical M.tb strains with different genotypes elicit different host innate immune responses in vitro.Aim. This work aimed to compare host innate immune responses elicited by genotypically diverse, clinically derived M.tb strains in vitro.Methodology. RAW264.7 cells were infected with three lineage 2 and lineage 4 clinically derived M.tb strains and strain H37Rv. Strains were evaluated for differences in intracellular growth, induction of macrophage apoptosis, and induction of expression of proinflammatory cytokines and associated pattern recognition receptors.Results. Highly variable cytokine profiles were observed subsequent to RAW264.7 cell infection with the different strains. The Beijing genotype strain, a modern Beijing strain belonging to lineage 2, induced milder host proinflammatory responses and less apoptosis and exhibited greater intracellular growth as compared to the other strains. Moreover, mRNA expression levels of iNOS in Beijing and MANU2 genotype strains exceeded corresponding levels obtained for the T1 genotype strain. Meanwhile, mRNA expression levels of toll-like receptor (TLR)-encoding genes TLR2 and TLR7 in macrophages infected with the Beijing genotype strain were higher than corresponding levels observed in MANU2 genotype strain-infected macrophages.Conclusion. The higher intracellular survival rate and lower level of host cell apoptosis associated with macrophage infection with the Beijing genotype strain indicated greater virulence of this strain relative to that of the other strains. Furthermore, in vitro immune responses induced by the Beijing genotype strain were unique in that this strain induced a weaker inflammatory response than was induced by T1 or MANU2 genotype strains. Nevertheless, additional evidence is needed to confirm that Beijing genotype strains possess greater virulence than strains with other genotypes.

Mycobacterium tuberculosis Induces Irg1 in Murine Macrophages by a Pathway Involving Both TLR-2 and STING/IFNAR Signaling and Requiring Bacterial Phagocytosis

Irg1 is an enzyme that generates itaconate, a metabolite that plays a key role in the regulation of inflammatory responses. Previous studies have implicated Irg1 as an important mediator in preventing excessive inflammation and tissue damage in Mycobacterium tuberculosis (Mtb) infection. Here, we investigated the pattern recognition receptors and signaling pathways by which Mtb triggers Irg1 gene expression by comparing the responses of control and genetically deficient BMDMs. Using this approach, we demonstrated partial roles for TLR-2 (but not TLR-4 or -9), MyD88 and NFκB signaling in Irg1 induction by Mtb bacilli. In addition, drug inhibition studies revealed major requirements for phagocytosis and endosomal acidification in Irg1 expression triggered by Mtb but not LPS or PAM3CSK4. Importantly, the Mtb-induced Irg1 response was highly dependent on the presence of the bacterial ESX-1 secretion system, as well as host STING and Type I IFN receptor (IFNAR) signaling with Type II IFN (IFN-γ) signaling playing only a minimal role. Based on these findings we hypothesize that Mtb induces Irg1 expression in macrophages via the combination of two independent triggers both dependent on bacterial phagocytosis: 1) a major signal stimulated by phagocytized Mtb products released by an ESX-1-dependent mechanism into the cytosol where they activate the STING pathway leading to Type I-IFN production, and 2) a secondary TLR-2, MyD88 and NFκB dependent signal that enhances Irg1 production independently of Type I IFN induction.

Correlation between innate and adaptive immunity response in TB children post BCG vaccination. Is it effective or not?: Cross-sectional study

BACKGROUND

How far the role of innate immunity and adaptive immunity do in children who have been BCG vaccinated in controlling the course and the severity of the TB disease has not been completely known. Mycobacterium tuberculosis entry to the body will be recognized by Toll-like receptors found on macrophages, neutrophils, and dendritic cells as part of the innate immune response, after which the dendritic cells will then present the antigen to lymphocyte T0 cells and initiate the adaptive immune response (of which CD4 T cells have an important role in). Was one or were both of these immune responses function well or not in a BCG Vaccinated Children with TB?

OBJECTIVE

This study aim to find a better understanding of the role of innate immune response assessed by TLR2/TLR4 mRNA gene expression and serum TLR2/TLR4 levels, while the role of adaptive immune response is assessed by analyzing serum CD4 level in children with TB who have had BCG vaccination.

METHODS

This cross-sectional study was conducted among children with TB at the outpatient and inpatient wards at Bhakti Medicare and Jakarta Islamic Hospital. Expression of mRNA gene was measured using the Boom method and protein serum levels were measured using the ELISA method. The results were analyzed by using the SPSS v.23 program.

RESULTS

Sixty-nine children were recruited as subjects. In this study, 68.1% of whom had BCG scars. TLR4 mRNA gene expression was found to be higher than TLR2 mRNA gene expression. Serum CD4 level was found to be highest out of TLR2 and TLR4 level, but serum TLR2 level was higher than TLR4 level. TLR2/TLR4 mRNA gene expression, serum TLR2/TLR4 levels, and CD4 levels in subjects with BCG scar were also found to be significantly higher than in subjects without BCG scar (p < 0.001). There was a significant positive correlation between TLR2/TLR4 mRNA gene expression and serum TLR2/TLR4 levels (r = 0.860; r = 0.864; p < 0.001) and between serum levels TLR2/TLR4 with serum CD4 levels (r = 0.822; r = 0.832 p < 0.001).

CONCLUSION

As early as possible, BCG vaccine administration is needed in endemic countries, but it must be ensured that scars can be formed. It is also important to control Latent TB Infection (LTBI) to prevent transmission and relapse of disease.

LAPped in Proof: LC3-Associated Phagocytosis and the Arms Race Against Bacterial Pathogens

Cells of the innate immune system continuously patrol the extracellular environment for potential microbial threats that are to be neutralized by phagocytosis and delivery to lysosomes. In addition, phagocytes employ autophagy as an innate immune mechanism against pathogens that succeed to escape the phagolysosomal pathway and invade the cytosol. In recent years, LC3-associated phagocytosis (LAP) has emerged as an intermediate between phagocytosis and autophagy. During LAP, phagocytes target extracellular microbes while using parts of the autophagic machinery to label the cargo-containing phagosomes for lysosomal degradation. LAP contributes greatly to host immunity against a multitude of bacterial pathogens. In the pursuit of survival, bacteria have developed elaborate strategies to disarm or circumvent the LAP process. In this review, we will outline the nature of the LAP mechanism and discuss recent insights into its interplay with bacterial pathogens.

Nontuberculous Mycobacteria, Macrophages, and Host Innate Immune Response

Although nontuberculous mycobacteria (NTM) are considered opportunistic infections, incidence and prevalence of NTM infection are increasing worldwide becoming a major public health threat. Innate immunity plays an essential role in mediating the initial host response against these intracellular bacteria. Specifically, macrophages phagocytose and eliminate NTM and act as antigen-presenting cells, which trigger downstream activation of cellular and humoral adaptive immune responses. Identification of macrophage receptors, mycobacterial ligands, phagosome maturation, autophagy/necrosis, and escape mechanisms are important components of this immunity network. The role of the macrophage in mycobacterial disease has mainly been studied in tuberculosis (TB), but limited information exists on its role in NTM. In this review, we focus on NTM immunity, the role of macrophages, and host interaction in NTM infection.

Respiratory Epithelial Cells Respond to Lactobacillus plantarum but Provide No Cross-Protection against Virus-Induced Inflammation

Virus-induced inflammation plays a critical role in determining the clinical outcome of an acute respiratory virus infection. We have shown previously that the administration of immunobiotic Lactobacillus plantarum (Lp) directly to the respiratory tract prevents lethal inflammatory responses to subsequent infection with a mouse respiratory virus pathogen. While Lp-mediated protective responses involve non-redundant contributions of both Toll-like receptor 2 (TLR2) and NOD2, the cellular basis of these findings remains unclear. Here, we address the impact of Lp and its capacity to suppress inflammation in virus-infected respiratory epithelial cells in two cell culture models. We found that both MLE-12 cells and polarized mouse tracheal epithelial cells (mTECs) were susceptible to infection with Influenza A and released proinflammatory cytokines, including CCL2, CCL5, CXCL1, and CXCL10, in response to replicating virus. MLE-12 cells express NOD2 (81 ± 6.3%) and TLR2 (19 ± 4%), respond to Lp, and are TLR2-specific, but not NOD2-specific, biochemical agonists. By contrast, we found that mTECs express NOD2 (81 ± 17%) but minimal TLR2 (0.93 ± 0.58%); nonetheless, mTECs respond to Lp and the TLR2 agonist, Pam2CSK4, but not NOD2 agonists or the bifunctional TLR2-NOD2 agonist, CL-429. Although MLE-12 cells and mTECS were both activated by Lp, little to no cytokine suppression was observed in response to Lp followed by virus infection via a protocol that replicated experimental conditions that were effective in vivo. Further study and a more complex approach may be required to reveal critical factors that suppress virus-induced inflammatory responses.

Mycobacterium tuberculosis induces connective tissue growth factor expression through the TLR2-JNK-AP-1 pathway in human lung fibroblasts

Mycobacterium tuberculosis (M.tb) infection in lung causes pulmonary fibrosis, which leads to the irreversible reduction of pulmonary function. Fibrotic protein connective tissue growth factor (CTGF) expression has been confirmed to play a crucial role in lung fibrosis. However, the underlying signal pathway and effect of M.tb on CTGF expression in human lung fibroblasts are unclear. Our results revaled that M.tb caused time- and concentration-dependent increases in CTGF expression in human lung fibroblasts. A mechanistic investigation revealed that M.tb induced CTGF expression through TLR2 but not TLR4. The promoter activity assay indicated that M.tb-induced CTGF activity was mainly controlled by the promoter region at -747 to -184 bp, which contained signal transducer and activator of transcription 3 and activator protein 1 (AP-1) binding sites. Moreover, curcumin (AP-1 inhibitor) restrained M.tb-induced CTGF expression. M.tb also induced increases in AP-1 luciferase activity and DNA binding activity of c-Jun and c-Fos on the CTGF promoter. Furthermore, the knockdown of c-Jun by small interfering RNA attenuated M.tb-induced CTGF expression and AP-1 luciferase activity. A JNK inhibitor (SP600125) and a JNK dominant-negative mutant suppressed M.tb-induced CTGF expression. We also discovered that M.tb could induce the phosphorylation of JNK and c-Jun. Furthermore, SP600125 inhibited M.tb-induced c-Jun phosphorylation and AP-1- luciferase activity. M.tb-induced fibronectin expression was inhibited by anti-CTGF antibody. These results demonstrate that M.tb is activated through TLR2 to induce JNK activation, further increasing the DNA binding activity of c-Jun and c-Fos and finally inducing CTGF expression and extracellular matrix production.-Lee, H.-S., Hua, H.-S., Wang, C.-H., Yu, M.-C., Chen, B.-C., Lin, C.-H. Mycobacterium tuberculosis induces connective tissue growth factor expression through the TLR2-JNK-AP-1 pathway in human lung fibroblasts.

Chronic Inflammation Contributes to Tumor Growth: Possible Role of L-Selectin-Expressing Myeloid-Derived Suppressor Cells (MDSCs)

Recent data have demonstrated that chronic inflammation is a crucial component of tumor initiation and progression. We previously reported that immature myeloid-derived suppressor cells (MDSCs) with immunosuppressive activity toward effector T cells were expanded in experimental chronic inflammation. We hypothesized that elevated levels of MDSCs, induced by chronic inflammation, may contribute to the progression of tumor growth. Using the Ehrlich carcinoma animal model, we found increased tumor growth in mice with chronic adjuvant arthritis, which was accompanied by a persistent increase in the proportion of splenic monocytic and granulocytic MDSCs expressing CD62L (L-selectin), when compared to tumor mice without adjuvant arthritis. Depletion of inflammation-induced MDSCs resulted in decreased tumor growth. In vitro studies demonstrated that increased expression of CD62L by MDSCs was mediated by TNFα, elevated concentrations of which were found in tumor mice subjected to chronic inflammation. Moreover, the addition of exogenous TNFα markedly enhanced the suppressive activity of bone marrow-derived MDSCs, as revealed by the ability to impair the proliferation of CD8⁺ T cells in vitro. This study provides evidence that chronic inflammation may promote tumor growth via induction of CD62L expression by MDSCs that can facilitate their migration to tumor and lymph nodes and modulation of their suppressor activity.

TLR1/2 orchestrate human plasmacytoid predendritic cell response to gram+ bacteria

Gram+ infections are worldwide life-threatening diseases in which the pathological role of type I interferon (IFN) has been highlighted. Plasmacytoid predendritic cells (pDCs) produce high amounts of type I IFN following viral sensing. Despite studies suggesting that pDCs respond to bacteria, the mechanisms underlying bacterial sensing in pDCs are unknown. We show here that human primary pDCs express toll-like receptor 1 (TLR1) and 2 (TLR2) and respond to bacterial lipoproteins. We demonstrated that pDCs differentially respond to gram+ bacteria through the TLR1/2 pathway. Notably, up-regulation of costimulatory molecules and pro-inflammatory cytokines was TLR1 dependent, whereas type I IFN secretion was TLR2 dependent. Mechanistically, we demonstrated that these differences relied on diverse signaling pathways activated by TLR1/2. MAPK and NF-κB pathways were engaged by TLR1, whereas the Phosphoinositide 3-kinase (PI3K) pathway was activated by TLR2. This dichotomy was reflected in a different role of TLR2 and TLR1 in pDC priming of naïve cluster of differentiation 4+ (CD4+) T cells, and T helper (Th) cell differentiation. This work provides the rationale to explore and target pDCs in bacterial infection.

Association of VDR gene polymorphisms and 22 bp deletions in the promoter region of TLR2Δ22 (-196-174) with increased risk of pulmonary tuberculosis: A case-control study in tea garden communities of Assam

BACKGROUND

A high number of pulmonary tuberculosis (PTB) cases have been reported from tea garden communities of Assam. Till date, no molecular epidemiological study was performed to investigate the association of candidate gene(s) with the risk PTB in this region. The present case-control study was aimed to investigate the association of vitamin D receptor (VDR) gene polymorphisms and 22 bp deletion in the promoter region of toll-like receptor 2 (TLR2) gene with the risk of PTB in tea garden communities of Assam.

METHODS

Genotyping of VDR polymorphisms and TLR2Δ22 (-196-174) gene was carried out for 169 PTB cases and 227 apparently healthy community controls using blood samples by PCR-RFLP followed by DNA sequencing. For association study, both univariate and multivariate logistic regression analyses were performed.

RESULTS

This study has shown that BsmI and FokI polymorphisms of VDR gene significantly associated with an increased risk of PTB (AOR = 3.58, 95% CI = 1.64-7.80, P < .01 for B/b genotype of BsmI and AOR = 2.44, 95% CI = 1.40-4.24, P < .01 for F/f genotype of FokI polymorphism). No significant association of TaqI and ApaI polymorphism of VDR gene was found with the risk of PTB. Moreover, this study has revealed that person carrying deletion allele in their TLR2Δ22 (-196-174) gene is significantly associated with an increased risk of PTB having b/b or F/f genotypes in BsmI or FokI polymorphisms of VDR gene.

CONCLUSION

This study has revealed that BsmI and FokI polymorphisms of VDR gene significantly associated with an increased risk of PTB.

TLR2 contributes to trigger immune response of pleural mesothelial cells against Mycobacterium bovis BCG and M. tuberculosis infection

Mycobacterium tuberculosis is a causative agent leading to pleural effusion, characterized by the accumulation of fluid and immune cells in the pleural cavity. Although this phenomenon has been described before, detailed processes or mechanisms associated with the pleural effusion are still not well understood. Pleural mesothelial cells (PMCs) are specialized epithelial cells that cover the body wall and internal organs in pleural cavity playing a central role in pleural inflammation. Toll-like receptors are expressed in various cell types including mesothelial cells and initiate the recognition and defense against mycobacterial infection. In the present study, we investigated direct immune responses of PMCs against two mycobacterial strains, M. bovis vaccine strain Bacille Calmette-Guérin (BCG) and M. tuberculosis virulent strain H37Rv, and the role of TLR2 in such responses. Infection with BCG and H37Rv increased the production of IL-6, CXCL1, and CCL2 in WT PMCs, which was partially impaired in TLR2-deficient cells. In addition, the activation of NF-κB and MAPKs induced by BCG and H37Rv was suppressed in TLR2-deficient PMCs, as compared with the WT cells. TLR2 deficiency led to the decrease of nitric oxide (NO) production through the delayed gene expression of iNOS in PMCs. TLR2 was also shown to be essential for optimal expression of cellular adhesion molecules such as ICAM-1 and VCAM-1 in PMCs in response to BCG and H37Rv. These findings strongly suggest that TLR2 participates in mycobacteria-induced innate immune responses in PMCs and may play a role in pathogenesis of tuberculosis pleural effusion.

Mycobacterium tuberculosis Molecular Determinants of Infection, Survival Strategies, and Vulnerable Targets

Mycobacterium tuberculosis is the causative agent of tuberculosis, an ancient disease which, still today, represents a major threat for the world population. Despite the advances in medicine and the development of effective antitubercular drugs, the cure of tuberculosis involves prolonged therapies which complicate the compliance and monitoring of drug administration and treatment. Moreover, the only available antitubercular vaccine fails to provide an effective shield against adult lung tuberculosis, which is the most prevalent form. Hence, there is a pressing need for effective antitubercular drugs and vaccines. This review highlights recent advances in the study of selected M. tuberculosis key molecular determinants of infection and vulnerable targets whose structures could be exploited for the development of new antitubercular agents.

Protein O-mannosylation deficiency increases LprG-associated lipoarabinomannan release by Mycobacterium tuberculosis and enhances the TLR2-associated inflammatory response

Protein O-mannosylation is crucial for the biology of Mycobacterium tuberculosis but the key mannosylated protein(s) involved and its(their) underlying function(s) remain unknown. Here, we demonstrated that the M. tuberculosis mutant (Δpmt) deficient for protein O-mannosylation exhibits enhanced release of lipoarabinomannan (LAM) in a complex with LprG, a lipoprotein required for LAM translocation to the cell surface. We determined that LprG is O-mannosylated at a unique threonine position by mass spectrometry analyses of the purified protein. However, although replacement of this amino acid by an alanine residue completely abolished LprG O-mannosylation, the increased release of the LAM/LprG complex was preserved. We found that the increased secretion of this complex is due to enhanced LAM production in the Δpmt M. tuberculosis and M. smegmatis mutants relative to their wild-type counterparts. This abnormal release of LAM/LprG has functional consequences on the induction of inflammatory responses and provides a possible explanation for the reduced virulence of the M. tuberculosis Δpmt mutant.

Particulate matter air pollution from the city of Quito, Ecuador, activates inflammatory signaling pathways in vitro

Automobile traffic, industrial processes and natural phenomena cause notable air pollution, including gaseous and particulate contaminants, in urban centers. Exposure to particulate matter (PM) air pollution affects human health, and has been linked to respiratory, cardiovascular and neurological diseases. The mechanisms underlying inflammation in these diverse diseases, and to what extent health effects are different for PM obtained from different sources or locations, are still unclear. This study investigated the in vitro toxicity of ambient course (PM₁₀) and fine (PM_2.5) particulate matter collected at seven sites in the urban and periurban zones of Quito, Ecuador. Material from all sites was capable of activating TLR2 and TLR4 signaling pathways, with differences in the activation related to particle size. Additionally, airborne particulate matter from Quito is an effective activator of the NLRP3 inflammasome.

Signaling via pattern recognition receptors NOD2 and TLR2 contributes to immunomodulatory control of lethal pneumovirus infection

Pattern recognition receptors (PRRs) engage microbial components in the lung, although their role in providing primary host defense against respiratory virus infection is not fully understood. We have previously shown that Gram-positive Lactobacillus plantarum (Lp) administered to the respiratory tract promotes full and sustained protection in response to an otherwise lethal mouse pneumovirus (PVM) infection, a robust example of heterologous immunity. While Lp engages PRRs TLR2 and NOD2 in ex vivo signaling assays, we found that Lp-mediated protection was unimpaired in single gene-deleted TLR2(-/-) and NOD2(-/-) mice. Here we demonstrate substantial loss of Lp-mediated protection in a double gene-deleted NOD2(-/-)TLR2(-/-) strain. Furthermore, we demonstrate protection against PVM infection by administration of the bi-functional NOD2-TLR2 agonist, CL-429. The bi-functional NOD2-TLR2 ligand CL-429 not only suppresses virus-induced inflammation, it is significantly more effective at preventing lethal infection than equivalent amounts of mono-molecular TLR2 and NOD2 agonists. Interestingly, and in contrast to biochemical NOD2 and/or TLR2 agonists, Lp remained capable of eliciting primary proinflammatory responses from NOD2(-/-)TLR2(-/-) mice in vivo and from alveolar macrophages challenged ex vivo. Taken together, we conclude that coordinate engagement of NOD2 and TLR2 constitutes a key step in the genesis of Lp-mediated protection from a lethal respiratory virus infection, and represents a critical target for modulation of virus-induced inflammatory pathology.

Mannan Derivatives Instruct Dendritic Cells to Induce Th1/Th2 Cells Polarization via Differential Mitogen-Activated Protein Kinase Activation

Mannan derived from fungal cell walls have potential uses as immunomodulating agents and vaccine adjuvants. Immunization with antigen conjugated to oxidized mannan (OM) or reduced mannan (RM) have induced differential immune responses in mice. Yet, the adjuvant effect and differences in molecular profiles of OM and RM on APCs is unresolved. Here, we investigated the response of mouse bone marrow-derived DCs to OM and RM. OM and RM stimulated DCs to produce differential Th1/Th2-inducing cytokines in vitro. OM and RM-activated DCs stimulated allogeneic T-cell Th1 and Th2 polarization reaction. OM instruct DCs to stimulate Th1 responses via IL-12p70 production, which depends on the phosphorylation of p38, RM barely induce IL-12p70, but IL-10 and IL-4, and magnitude of ERK phosphorylation, which results in a Th2 bias. These findings indicate that OM and RM were potent adjuvant capable of directly initiating DC activation Th1 and Th2 polarization respectively.

Sensing of Mycobacterium tuberculosis and consequences to both host and bacillus

Mycobacterium tuberculosis (Mtb), the primary causative agent of human tuberculosis, has killed more people than any other bacterial pathogen in human history and remains one of the most important transmissible diseases worldwide. Because of the long-standing interaction of Mtb with humans, it is no surprise that human mucosal and innate immune cells have evolved multiple mechanisms to detect Mtb during initial contact. To that end, the cell surface of human cells is decorated with numerous pattern recognition receptors for a variety of mycobacterial ligands. Furthermore, once Mtb is ingested into professional phagocytes, other host molecules are engaged to report on the presence of an intracellular pathogen. In this review, we discuss the role of specific mycobacterial products in modulating the host's ability to detect Mtb. In addition, we describe the specific host receptors that mediate the detection of mycobacterial infection and the role of individual receptors in mycobacterial pathogenesis in humans and model organisms.

Aberrant Toll-like receptor 2 promoter methylation in blood cells from patients with pulmonary tuberculosis

OBJECTIVES

Toll-like receptor 2 (TLR2) is a major mediator of innate immunity against tuberculosis (TB). This study aimed to determine if TLR2 promoter DNA methylation is associated with pulmonary TB.

METHODS

The DNA methylation levels of 20 CpG sites over the TLR2 promoter region and TLR2 gene/protein expressions of immune cells of the blood were examined in 99 sputum culture-positive pulmonary TB patients and 77 healthy subjects (HS).

RESULTS

TB patients had higher methylation levels over five CpG sites (3, 7, 9, 13, and 18), lower TLR2 gene expression, lower TLR2 expression on monocyte, higher TLR2 expression on NK cell, and higher serum TNF-α/IFN-γ levels than HS after adjusting for confounding factors. Patients with a high bacillary load had lower methylation levels at CpG-15, -17, and -20. Patients with drug-resistant TB had higher CpG-18 methylation levels and lower TLR2 expression on NK cell. Patients with far advanced lesion on chest radiograph had higher serum TNF-α level and higher TLR2 expression on NK cell. Patients with a high TLR2 expression on NK cell had lower one-year survival. CpG-18 methylation level, TLR2 expressions on monocyte/NK cell, and TNF-α/IFN-γ levels were all reversed to normal after 6-month anti-TB treatment.

CONCLUSIONS

Aberrant methylation of certain CpG sites over TLR2 promoter region is associated with active pulmonary TB or its phenotypes, probably through the down-regulation of TLR2 expression.