Corticosteroid therapy for the management of paradoxical inflammatory reaction in patients with pulmonary tuberculosis.

BACKGROUND: Paradoxical reaction after the initiation of tuberculosis treatment is defined as increased inflammation following effective antimycobacterial treatment. This is a phenomenon that can severely complicate a patient's recovery, potentially leading to further morbidity and residual deficits. Paradoxical reaction remains poorly understood regarding its pathophysiology and management. Only a limited number of reports look critically at the available therapeutic options, with evidence of the efficacy of prednisolone therapy being primarily limited to extrapulmonary PR only. CASE: We describe two HIV negative patients who were admitted to our department with pulmonary tuberculosis, presenting with inflammatory patterns attributable to PR and their response to adjunctive steroid therapy. DISCUSSION AND CONCLUSIONS: The presented cases further highlight the need for immunological studies and randomized trials for corticosteroid therapy are needed to better understand this phenomenon as well as provide an evidence-base for anti-inflammatory treatment. Furthermore, by means of this case series, we are also able to highlight the potential variability in the symptomatology of the lesser known PR phenomenon, in which we observed a hypotensive shock-like syndrome not previously described in literature.

Autophagy controls BCG-induced trained immunity and the response to intravesical BCG therapy for bladder cancer.

The anti-tuberculosis-vaccine Bacillus Calmette-Guérin (BCG) is the most widely used vaccine in the world. In addition to its effects against tuberculosis, BCG vaccination also induces non-specific beneficial effects against certain forms of malignancy and against infections with unrelated pathogens. It has been recently proposed that the non-specific effects of BCG are mediated through epigenetic reprogramming of monocytes, a process called trained immunity. In the present study we demonstrate that autophagy contributes to trained immunity induced by BCG. Pharmacologic inhibition of autophagy blocked trained immunity induced in vitro by stimuli such as ß-glucans or BCG. Single nucleotide polymorphisms (SNPs) in the autophagy genes ATG2B (rs3759601) and ATG5 (rs2245214) influenced both the in vitro and in vivo training effect of BCG upon restimulation with unrelated bacterial or fungal stimuli. Furthermore, pharmacologic or genetic inhibition of autophagy blocked epigenetic reprogramming of monocytes at the level of H3K4 trimethylation. Finally, we demonstrate that rs3759601 in ATG2B correlates with progression and recurrence of bladder cancer after BCG intravesical instillation therapy. These findings identify a key role of autophagy for the nonspecific protective effects of BCG.

Bacille Calmette-Guerin induces NOD2-dependent nonspecific protection from reinfection via epigenetic reprogramming of monocytes.

Adaptive features of innate immunity, recently described as "trained immunity," have been documented in plants, invertebrate animals, and mice, but not yet in humans. Here we show that bacille Calmette-Guérin (BCG) vaccination in healthy volunteers led not only to a four- to sevenfold increase in the production of IFN-γ, but also to a twofold enhanced release of monocyte-derived cytokines, such as TNF and IL-1ß, in response to unrelated bacterial and fungal pathogens. The enhanced function of circulating monocytes persisted for at least 3 mo after vaccination and was accompanied by increased expression of activation markers such as CD11b and Toll-like receptor 4. These training effects were induced through the NOD2 receptor and mediated by increased histone 3 lysine 4 trimethylation. In experimental studies, BCG vaccination induced T- and B-lymphocyte-independent protection of severe combined immunodeficiency SCID mice from disseminated candidiasis (100% survival in BCG-vaccinated mice vs. 30% in control mice). In conclusion, BCG induces trained immunity and nonspecific protection from infections through epigenetic reprogramming of innate immune cells.

BCG-induced trained immunity in NK cells: Role for non-specific protection to infection.

Adaptive features of innate immunity, also termed 'trained immunity', have recently been shown to characterize monocytes of BCG vaccinated healthy volunteers. Trained immunity leads to increased cytokine production in response to non-related pathogens via epigenetic reprogramming of monocytes. Recently, memory-like properties were also observed in NK cells during viral infections, but it is unknown if memory properties of NK cells contribute to trained immunity due to BCG vaccination. BCG vaccination of healthy volunteers increased proinflammatory cytokine production following ex vivo stimulation of NK cells with mycobacteria and other unrelated pathogens up until at least three months after vaccination. In addition, in a murine model of disseminated candidiasis, BCG vaccination led to an increased survival in SCID mice, which was partially dependent on NK cells. These findings suggest that NK cells may contribute to the non-specific (heterologous) beneficial effects of BCG vaccination.

Low induction of proinflammatory cytokines parallels evolutionary success of modern strains within the Mycobacterium tuberculosis Beijing genotype.

One of the most widespread clades of Mycobacterium tuberculosis worldwide, the Beijing genotype family, consists of ancient (atypical) and modern (typical) strains. Modern Beijing strains outcompete ancient strains in terms of prevalence, while reserving a higher degree of genetic conservation. We hypothesize that their selective advantage lies in eliciting a different host immune response. Bead-disrupted lysates of a collection of different M. tuberculosis strains of the modern (n = 7) or ancient (n = 7) Beijing genotype, as well as the Euro-American lineage (n = 6), were used for induction of ex vivo cytokine production in peripheral blood mononuclear cells (PBMCs) from 10 healthy individuals. Hierarchical clustering and multivariate regression analyses were used to study possible differences in production of nine cytokines. Modern and ancient M. tuberculosis Beijing genotypes induced different cytokine signatures. Overall induction of interleukin-1ß (IL-1ß), gamma interferon (IFN-γ), and IL-22 was 38 to 40% lower after stimulation with modern Beijing strains (corrected P values of <0.0001, 0.0288, and 0.0002, respectively). Euro-American reactivation strains induced 2-fold more TNF-α production than both types of Beijing strains. The observed differences in cytokine induction point to a reduction in proinflammatory cytokine response as a possible contributing factor to the evolutionary success of modern Beijing strains.

Autophagy modulates the Mycobacterium tuberculosis-induced cytokine response.

Both autophagy and pro-inflammatory cytokines are involved in the host defence against mycobacteria, but little is known regarding the effect of autophagy on Mycobacterium tuberculosis (MTB)-induced cytokine production. In the present study, we assessed the effect of autophagy on production of monocyte-derived and T-cell-derived cytokines, and examined whether two functional polymorphisms in autophagy genes led to altered cytokine production. Blocking autophagy inhibited tumour necrosis factor-α (TNF-α) production, while enhancing interleukin-1ß (IL-1ß) production in peripheral blood mononuclear cells stimulated with MTB. Induction of autophagy by starvation or interferon-γ (IFN-γ) had the opposite effect. The modulation of both TNF-α and IL-1ß production by autophagy was induced at the level of gene transcription. Functional polymorphisms in the autophagy genes ATG16L1 and IRGM did not have a major impact on MTB-induced cytokine production in healthy volunteers, although a moderate effect was observed on IFN-γ production by the ATG16L1 T300A polymorphism. These data demonstrate the interplay between autophagy and inflammation during host defence against mycobacteria, and future studies to investigate the clinical implications of these effects for the susceptibility to tuberculosis are warranted.

Innate immune recognition of Mycobacterium tuberculosis.

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is a major health problem, with 10 million new cases diagnosed each year. Innate immunity plays an important role in the host defense against M. tuberculosis, and the first step in this process is recognition of MTB by cells of the innate immune system. Several classes of pattern recognition receptors (PPRs) are involved in the recognition of M. tuberculosis, including Toll-like receptors (TLRs), C-type lectin receptors (CLRs), and Nod-like receptors (NLRs). Among the TLR family, TLR2, TLR4, and TLR9 and their adaptor molecule MyD88 play the most prominent roles in the initiation of the immune response against tuberculosis. In addition to TLRs, other PRRs such as NOD2, Dectin-1, Mannose receptor, and DC-SIGN are also involved in the recognition of M. tuberculosis. Human epidemiological studies revealed that genetic variation in genes encoding for PRRs and downstream signaling products influence disease susceptibility, severity, and outcome. More insight into PRRs and the recognition of mycobacteria, combined with immunogenetic studies in TB patients, does not only lead to a better understanding of the pathogenesis of tuberculosis but also may contribute to the design of novel immunotherapeutic strategies.

Transcriptional and inflammasome-mediated pathways for the induction of IL-1beta production by Mycobacterium tuberculosis.

Proinflammatory cytokines of the IL-1 family play an important role for the anti-mycobacterial host defense mechanisms. In the present study we have deciphered the pathways leading from recognition of Mycobacterium tuberculosis to the production and release of IL-1beta, the most important member of the IL-1 family. By stimulating cells defective in various pattern recognition receptors, we could demonstrate that IL-1beta production is induced by M. tuberculosis through pathways involving TLR2/TLR6 and NOD2 receptors. In contrast, TLR4, TLR9 and TLR1 receptors are not involved in IL-1beta induction. Recognition of M. tuberculosis by TLR and NOD2 leads to transcription of proIL-1beta through mechanisms involving ERK, p38 and Rip2, but not JNK. Interestingly, although caspase-1 is necessary for the processing of proIL-1beta, activation of caspase-1 is not dependent on the stimulation of cells by M. tuberculosis. Monocytes expressed constitutively active caspase-1. The secretion of IL-1beta is dependent on the activation of P2X7-induced pathways by endogenously released ATP. In conclusion, we have dissected the molecular mechanisms responsible for IL-1beta production by M. tuberculosis, and that may contribute to a deeper knowledge of the mechanisms of cell activation by M. tuberculosis.

Efficacy of ivermectin mass-drug administration to control scabies in asylum seekers in the Netherlands: A retrospective cohort study between January 2014 - March 2016.

Scabies is a skin infestation with the mite Sarcoptes scabiei causing itch and rash and is a major risk factor for bacterial skin infections and severe complications. Here, we evaluated the treatment outcome of 2866 asylum seekers who received (preventive) scabies treatment before and during a scabies intervention programme (SIP) in the main reception centre in the Netherlands between January 2014 and March 2016. A SIP was introduced in the main national reception centre based on frequent observations of scabies and its complications amongst Eritrean and Ethiopian asylum seekers in the Netherlands. On arrival, all asylum seekers from Eritrea or Ethiopia were checked for clinical scabies signs and received ivermectin/permethrin either as prevention or treatment. A retrospective cohort study was conducted to compare the reinfestations and complications of scabies in asylum seekers who entered the Netherlands before and during the intervention and who received ivermectin/permethrin. In total, 2866 asylum seekers received treatment during the study period (January 2014 -March 2016) of which 1359 (47.4%) had clinical signs of scabies. During the programme, most of the asylum seekers with scabies were already diagnosed on arrival as part of the SIP screening (580 (64.7%) of the 897). Asylum seekers with more than one scabies episode reduced from 42.0% (194/462) before the programme to 27.2% (243/897) during the programme (RR = 0.64, 95% CI = 0.55-0.75). Development of scabies complications later in the asylum procedure reduced from 12.3% (57/462) to 4.6% (41/897). A scabies prevention and treatment programme at start of the asylum procedure was feasible and effective in the Netherlands; patients were diagnosed early and risk of reinfestations and complications reduced. To achieve a further decrease of scabies, implementation of the programme in multiple asylum centres may be needed.

Delayed versus standard assessment for excision surgery in patients with Buruli ulcer in Benin: a randomised controlled trial.

BACKGROUND: Surgical intervention was once the mainstay of treatment for Buruli ulcer disease, a neglected tropical disease caused by Mycobacterium ulcerans. Since the introduction of streptomycin and rifampicin for 8 weeks as standard care, surgery has persisted as an adjunct therapy, but its role is uncertain. We investigated the effect of delaying the decision to operate to 14 weeks on rates of healing without surgery. METHODS: In this randomised controlled trial, we enrolled patients aged 3 years or older with confirmed disease at one hospital in Lalo, Benin. Patients were randomly assigned (1:1) to groups assessing the need for excision surgery 8 weeks (standard care) or 14 weeks after initiation of antimicrobial treatment. The primary endpoint was the number of patients healed without the need for surgery (not including skin grafting), assessed in all patients in follow-up at 50 weeks (or last observation for those healed for >10 weeks). A doctor masked to treatment assignment checked the indications for surgery according to predefined criteria. This study is registered with ClinicalTrials.gov, number NCT01432925. FINDINGS: Between July 1, 2011, and Jan 15, 2015, 119 patients were enrolled, with two patients per group lost to follow-up. 55 (96%) of 57 participants in the delayed-decision group and 52 (90%) of 58 participants in the standard-care group had healed lesions 1 year after start of antimicrobial treatment (relative risk [RR] 1·08, 95% CI 0·97-1·19). 37 (67%) of 55 patients in the delayed-decision group had their lesions healed without surgical intervention, as did 25 (48%) of 52 in the standard-care group (RR 1·40, 95% CI 1·00-1·96). The time to heal and residual functional limitations did not differ between the two groups (median time to heal 21 weeks [IQR 10-27] in the delayed-decision group and 21 weeks [10-39] in the standard-care group; functional limitations in six [11%] of 57 and three [5%] of 58 patients; p=0·32). Postponing the decision to operate resulted in reduced median duration of hospitalisation (5 days [IQR 0-187] vs 131 days [0-224]; p=0·024) and wound care (153 days [IQR 56-224] vs 182 days [94-307]; p=0·036). INTERPRETATION: In our study, patients treated for Buruli ulcer benefited from delaying the decision to operate. Even large ulcers can heal with antibiotics alone, without delaying healing rate and without an increase in residual functional limitations. FUNDING: NWO-VENI grant 241500, BUG Foundation, and UBS OPTIMUS.

Whole Blood Profiling of Bacillus Calmette-Guérin-Induced Trained Innate Immunity in Infants Identifies Epidermal Growth Factor, IL-6, Platelet-Derived Growth Factor-AB/BB, and Natural Killer Cell Activation.

Vaccination of infants with bacillus Calmette-Guérin (BCG) activates both the innate and adaptive arms of the immune response. The antimycobacterial effects of these responses most likely account for the ability of BCG to protect against childhood forms of tuberculosis (TB). There is also evidence for a heterologous protective effect of BCG vaccination against TB-unrelated mortality in low birth weight infants. A possible mechanism of action of this effect, the induction of trained innate immunity, has been demonstrated when cells from BCG-vaccinated adults are restimulated in vitro with non-related microbial stimuli. Our aim was to examine an extensive panel of secreted immune biomarkers to characterize the profile of trained innate immunity in infants. Stimulation of whole blood for 48 h was performed 4 months after BCG vaccination, or in control unvaccinated infants. Stimulants were lipopolysaccharide; Pam3Cys (P3C); heat-killed Candida albicans, Staphylococcus aureus, Escherichia coli, and a lysate of Mycobacterium tuberculosis. Culture supernatants were tested for secreted cytokines and chemokines by 42-plex bead array and monocytes and natural killer (NK) cells assessed for expression of activation markers by flow cytometry. BCG-vaccinated infants displayed increases in 11 cytokines and chemokines in response to different non-specific innate immunity stimuli: epidermal growth factor (EGF); eotaxin; IL-6; IL-7; IL-8; IL-10; IL-12p40; monocyte chemotactic protein-3; macrophage inflammatory protein-1α; soluble CD40 ligand and platelet-derived growth factor (PDGF)-AB/BB. Although each stimulant induced a distinct response profile, three analytes, EGF, IL-6, and PDGF-AB/BB, were commonly higher after stimulation with Pam3Cys, C. albicans, and S. aureus. Conversely, certain cytokines such as interferon gamma-inducible protein-10, IL-2, IL-13, IL-17, GM-CSF, and GRO were suppressed in BCG-vaccinated infants, while no increases in TNFα or IL-1ß production were detected. We did not observe a concomitant, BCG-associated change in monocyte surface activation markers in response to non-specific stimuli, but we detected a significant increase in CD69 expression on NK cells in response to Pam3Cys. Pam3Cys-induced NK cell activation correlated with the magnitude of IL-12p40 and IL-10 responses to the same stimulant. This study reveals a novel cytokine/chemokine biomarker signature of BCG-induced trained innate immunity in infants and the involvement of NK cells in these responses.

Immunometabolic Pathways in BCG-Induced Trained Immunity.

The protective effects of the tuberculosis vaccine Bacillus Calmette-Guerin (BCG) on unrelated infections are thought to be mediated by long-term metabolic changes and chromatin remodeling through histone modifications in innate immune cells such as monocytes, a process termed trained immunity. Here, we show that BCG induction of trained immunity in monocytes is accompanied by a strong increase in glycolysis and, to a lesser extent, glutamine metabolism, both in an in-vitro model and after vaccination of mice and humans. Pharmacological and genetic modulation of rate-limiting glycolysis enzymes inhibits trained immunity, changes that are reflected by the effects on the histone marks (H3K4me3 and H3K9me3) underlying BCG-induced trained immunity. These data demonstrate that a shift of the glucose metabolism toward glycolysis is crucial for the induction of the histone modifications and functional changes underlying BCG-induced trained immunity. The identification of these pathways may be a first step toward vaccines that combine immunological and metabolic stimulation.

Effect of low-dose ritonavir (100 mg twice daily) on the activity of cytochrome P450 2D6 in healthy volunteers.

OBJECTIVE: In the treatment of human immunodeficiency virus infection, the protease inhibitor ritonavir is used in a low dose (100 mg twice daily) to inhibit cytochrome P450 (CYP) 3A4 and thereby increase plasma concentrations of coadministered protease inhibitors. When applied in a therapeutic dose (600 mg twice daily), ritonavir also inhibits CYP2D6. The effect of low-dose ritonavir on CYP2D6 is unknown and was investigated in this study. METHODS: This was a 1-arm, 2-period, fixed-order study in 13 healthy male volunteers who were extensive metabolizers of CYP2D6. The first period examined baseline CYP2D6 activity by evaluating the pharmacokinetics of a single dose of desipramine and by metabolic phenotyping with dextromethorphan. During the second period, participants took ritonavir, 100 mg twice daily, for 2 weeks, followed by repeat assessment of desipramine pharmacokinetics and the dextromethorphan metabolic phenotype in the presence of ritonavir. RESULTS: Low-dose ritonavir (100 mg twice daily) significantly increased the exposure to single-dose desipramine, as reflected in a geometric mean ratio (with ritonavir/without ritonavir) of 1.26 (95% confidence interval, 1.13-1.40) for the desipramine area under the concentration versus time curve from time 0 to infinity (P < .001). Coadministration of low-dose ritonavir did not significantly affect the dextromethorphan/dextrorphan urinary metabolic ratio and did not convert any extensive metabolizer to a poor metabolizer. CONCLUSIONS: Low-dose ritonavir (100 mg twice daily) exerts a modest inhibitory effect on the activity of CYP2D6 in extensive metabolizers, as assessed with desipramine as the index substrate. This effect was not apparent with the dextromethorphan/dextrorphan metabolic ratio as an indicator for CYP2D6 activity. It is expected that the effect of low-dose ritonavir on CYP2D6 will not require standard dose reductions for CYP2D6 substrates.

Trained immunity: consequences for the heterologous effects of BCG vaccination.

A growing body of evidence from epidemiologic and immunologic studies have shown that in addition to target disease-specific effects, vaccines have heterologous effects towards unrelated pathogens. Like some other vaccines, bacille Calmette-Guerin (BCG) has shown in observational studies and randomized clinical trials to increase survival beyond the disease burden of the target disease. The immunologic substrate for these non-specific protective effects have been ascertained to heterologous T cell effects on the one hand, and to priming of innate immunity on the other hand. The term 'trained immunity' has been proposed to describe these potentiating effects of vaccines on innate immune responses. This process can explain the rapid effects of BCG vaccination and has been suggested to be mediated by epigenetic programming of monocytes or macrophages. This novel concept has important implications for the possible use of vaccines, for vaccination policy and even for the design of novel immunotherapeutic approaches.

Accumulation of heparan sulfate proteoglycans in cerebellar senile plaques.

Alzheimer's disease (AD) brains are characterized by the presence of senile plaques (SPs), which primarily consist of amyloid beta protein (Abeta). Besides Abeta, several other proteins with the ability to modulate amyloid fibril formation accumulate in SPs, e.g. heparan sulfate proteoglycans (HSPGs). Cerebellar SPs are predominantly of the diffuse type, whereas fibrillar SPs are rarely observed. Furthermore, because of the spatial separation of non-fibrillar and fibrillar SPs in the cerebellum, this brain region provides a model for the study of the association of Abeta-associated factors with various stages of SP formation. In the present study, we performed an immunohistochemical analysis to investigate the expression of the HSPG species agrin, perlecan, glypican-1 and the syndecans 1-3 as well as glycosaminoglycan side-chains in cerebellar SPs. We demonstrated that agrin and glypican-1 were expressed in both non-fibrillar and fibrillar cerebellar SPs, whereas the syndecans were only associated with fibrillar cerebellar SPs. Perlecan expression was absent in all cerebellar SPs. Since fibrillar and non-fibrillar SPs may develop independently in the cerebellum, it is likely that agrin, glypican-1 as well as heparan sulfate glycosaminoglycans may contribute to the formation of both cerebellar plaque types, whereas syndecan only seems to play a role in the generation of cerebellar fibrillar plaques.

Long-lasting effects of BCG vaccination on both heterologous Th1/Th17 responses and innate trained immunity.

We have recently shown that BCG (Bacillus Calmette-Guérin) vaccination in healthy volunteers induces epigenetic reprogramming of monocytes, leading to increased cytokine production in response to nonrelated pathogens for up to 3 months after vaccination. This phenomenon was named 'trained immunity'. In the present study we assessed whether BCG was able to induce long-lasting effects on both trained immunity and heterologous T helper 1 (Th1) and Th17 immune responses 1 year after vaccination. The production of TNFα and IL-1ß to mycobacteria or unrelated pathogens was higher after 2 weeks and 3 months postvaccination, but these effects were less pronounced 1 year after vaccination. However, monocytes recovered 1 year after vaccination had an increased expression of pattern recognition receptors such as CD14, Toll-like receptor 4 (TLR4) and mannose receptor, and this correlated with an increase in proinflammatory cytokine production after stimulation with the TLR4 ligand lipopolysaccharide. The heterologous production of Th1 (IFN-γ) and Th17 (IL-17 and IL-22) immune responses to nonmycobacterial stimulation remained strongly elevated even 1 year after BCG vaccination. In conclusion, BCG induces sustained changes in the immune system associated with a nonspecific response to infections both at the level of innate trained immunity and at the level of heterologous Th1/Th17 responses.

The role of autophagy in host defence against Mycobacterium tuberculosis infection.

Autophagy is a vital homeostatic process triggered by starvation and other cellular stresses, in which cytoplasmatic cargo is targeted for degradation in specialized structures termed autophagosomes. Autophagy is involved in nutrient regeneration, protein and organelle degradation, but also in clearance of intracellular pathogens such as Mycobacterium tuberculosis, the causative agent of tuberculosis. Recent studies suggest that induction of autophagy in macrophages is an effective mechanism to enhance intracellular killing of M. tuberculosis, and that the ability of the pathogen to inhibit this process is of paramount importance for its survival. Patient studies have shown genetic associations between tuberculosis and the autophagy gene IRGM, as well as with several genes indirectly involved in autophagy. In this review we will discuss the complex interplay between M. tuberculosis and autophagy, as well as the effect of polymorphisms in autophagy-related genes on susceptibility to tuberculosis.

Polymorphisms in autophagy genes and susceptibility to tuberculosis.

Recent data suggest that autophagy is important for intracellular killing of Mycobacterium tuberculosis, and polymorphisms in the autophagy gene IRGM have been linked with susceptibility to tuberculosis (TB) among African-Americans, and with TB caused by particular M. tuberculosis genotypes in Ghana. We compared 22 polymorphisms of 14 autophagy genes between 1022 Indonesian TB patients and 952 matched controls, and between patients infected with different M. tuberculosis genotypes, as determined by spoligotyping. The same autophagy polymorphisms were studied in correlation with ex-vivo production of TNF, IL-1ß, IL-6, IL-8, IFN-γ and IL-17 in healthy volunteers. No association was found between TB and polymorphisms in the genes ATG10, ATG16L2, ATG2B, ATG5, ATG9B, IRGM, LAMP1, LAMP3, P2RX7, WIPI1, MTOR and ATG4C. Associations were found between polymorphisms in LAMP1 (p = 0.02) and MTOR (p = 0.02) and infection with the successful M. tuberculosis Beijing genotype. The polymorphisms examined were not associated with M. tuberculosis induced cytokines, except for a polymorphism in ATG10, which was linked with IL-8 production (p = 0.04). All associations found lost statistical significance after correction for multiple testing. This first examination of a broad set of polymorphisms in autophagy genes fails to show a clear association with TB, with M. tuberculosis Beijing genotype infection or with ex-vivo pro-inflammatory cytokine production.

Mycobacterium tuberculosis induces IL-17A responses through TLR4 and dectin-1 and is critically dependent on endogenous IL-1.

In the present study, we dissected the pathways that trigger the IL-17A responses by MTB. Dectin-1 and TLR4 were shown to be involved in MTB-induced IL-17A production, and blockade of the NOD2, TLR2, or MR had no effect on IL-17A. The MAPK Erk, known to mediate transcription of IL-1beta mRNA, was strongly involved in the IL-17A production induced by MTB. The intracellular enzymes caspase-1 and serine proteases, which process pro-IL-1beta into the active IL-1beta, were also crucial for the induction of IL-17A. Lastly, the MTB-induced IL-17A response was strongly dependent on signaling through the IL-1R but not the IL-6R pathway. In conclusion, the MTB-induced IL-17A response relies strongly on the endogenous IL-1 pathway and IL-1R signaling. TLR4 and dectin-1 are the main receptors responsible for mediating the signals responsible for IL-17A production by MTB. These findings contribute to a better understanding of the host response to mycobacteria and provide the opportunity to explore potential, novel, therapeutic strategies against TB.