M2 macrophages or IL-33 treatment attenuate ongoing Mycobacterium tuberculosis infection

Biomarkers of mortality in adults and adolescents with advanced HIV in sub-Saharan Africa

One-third of people with HIV in sub-Saharan Africa start antiretroviral therapy (ART) with advanced disease. We investigated associations between immune biomarkers and mortality in participants with advanced HIV randomised to cotrimoxazole or enhanced antimicrobial prophylaxis in the Reduction of Early Mortality in HIV-Infected Adults and Children Starting Antiretroviral Therapy (REALITY) trial (ISRCTN43622374). Biomarkers were assayed using ELISA and Luminex. Associations between baseline values and all-cause 24-week mortality were analysed using Cox models, and for cause-specific mortality used Fine & Gray models, including prophylaxis randomisation, viral load, CD4, WHO stage, age, BMI, and site as covariates; and weighted according to inverse probability of selection into the substudy. Higher baseline CRP, IFN-γ, IL-6 and IP-10 were associated with higher all-cause mortality; and higher IL-23, IL-2 and RANTES with lower all-cause mortality. Associations varied by cause of death: tuberculosis-associated mortality was most strongly associated with higher CRP and sST2, and cryptococcosis-associated mortality with higher IL-4 and lower IL-8. Changes in I-FABP (p = 0.002), faecal alpha-1 antitrypsin (p = 0.01) and faecal myeloperoxidase (p = 0.005) between baseline and 4 weeks post-ART were greater in those receiving enhanced versus cotrimoxazole prophylaxis. Our findings highlight how the immune milieu shapes outcomes following ART initiation, and how adjunctive antimicrobials can modulate the gut environment in advanced HIV.

Leishmania exploits host cAMP/EPAC/calcineurin signaling to induce an IL-33-mediated anti-inflammatory environment for the establishment of infection

Host anti-inflammatory responses are critical for the progression of visceral leishmaniasis, and the pleiotropic cytokine interleukin (IL)-33 was found to be upregulated in infection. Here, we documented that IL-33 induction is a consequence of elevated cAMP-mediated exchange protein activated by cAMP (EPAC)/calcineurin-dependent signaling and essential for the sustenance of infection. Leishmania donovani-infected macrophages showed upregulation of IL-33 and its neutralization resulted in decreased parasite survival and increased inflammatory responses. Infection-induced cAMP was involved in IL-33 production and of its downstream effectors PKA and EPAC, only the latter was responsible for elevated IL-33 level. EPAC initiated Rap-dependent phospholipase C activation, which triggered the release of intracellular calcium followed by calcium/calmodulin complex formation. Screening of calmodulin-dependent enzymes affirmed involvement of the phosphatase calcineurin in cAMP/EPAC/calcium/calmodulin signaling-induced IL-33 production and parasite survival. Activated calcineurin ensured nuclear localization of the transcription factors, nuclear factor of activated T cell 1 and hypoxia-inducible factor 1 alpha required for IL-33 transcription, and we further confirmed this by chromatin immunoprecipitation assay. Administering specific inhibitors of nuclear factor of activated T cell 1 and hypoxia-inducible factor 1 alpha in BALB/c mouse model of visceral leishmaniasis decreased liver and spleen parasite burden along with reduction in IL-33 level. Splenocyte supernatants of inhibitor-treated infected mice further documented an increase in tumor necrosis factor alpha and IL-12 level with simultaneous decrease of IL-10, thereby indicating an overall disease-escalating effect of IL-33. Thus, this study demonstrates that cAMP/EPAC/calcineurin signaling is crucial for the activation of IL-33 and in effect creates anti-inflammatory responses, essential for infection.

FDA-Approved Amoxapine Effectively Promotes Macrophage Control of Mycobacteria by Inducing Autophagy

Antibiotic resistance poses a significant hurdle in combating global public health crises, prompting the development of novel therapeutics. Strategies to enhance the intracellular killing of mycobacteria by targeting host defense mechanisms offer numerous beneficial effects, which include reducing cytotoxicity caused by current lengthy anti-tubercular treatment regimens and slowing or circumventing the development of multidrug-resistant strains. The intracellular pathogen Mycobacterium tuberculosis infects macrophages and exploits host machinery to survive and multiply. Using a cell-based screen of FDA-approved drugs, we identified an antidepressant, Amoxapine, capable of inhibiting macrophage cytotoxicity during mycobacterial infection. Notably, this reduced cytotoxicity was related to the enhanced intracellular killing of Mycobacterium bovis BCG and M. tuberculosis within human and murine macrophages. Interestingly, we discovered that postinfection treatment with Amoxapine inhibited mTOR (mammalian target of rapamycin) activation, resulting in the induction of autophagy without affecting autophagic flux in macrophages. Also, inhibition of autophagy by chemical inhibitor 3-MA or knockdown of an essential component of the autophagic pathway, ATG16L1, significantly diminished Amoxapine's intracellular killing effects against mycobacteria in the host cells. Finally, we demonstrated that Amoxapine treatment enhanced host defense against M. tuberculosis in mice. In conclusion, our study identified Amoxapine as a novel host-directed drug that enhances the intracellular killing of mycobacteria by induction of autophagy, with concomitant protection of macrophages against death. IMPORTANCE The emergence and spread of multidrug-resistant (MDR) and extensive drug-resistant (XDR) TB urges the development of new therapeutics. One promising approach to combat drug resistance is targeting host factors necessary for the bacteria to survive or replicate while simultaneously minimizing the dosage of traditional agents. Moreover, repurposing FDA-approved drugs presents an attractive avenue for reducing the cost and time associated with new drug development. Using a cell-based screen of FDA-approved host-directed therapies (HDTs), we showed that Amoxapine inhibits macrophage cytotoxicity during mycobacterial infection and enhances the intracellular killing of mycobacteria within macrophages by activating the autophagy pathway, both in vitro and in vivo. These findings confirm targeted autophagy as an effective strategy for developing new HDT against mycobacteria.

Vitamin D3 alters macrophage phenotype and endosomal trafficking markers in dairy cattle naturally infected with Mycobacterium avium subsp. paratuberculosis

Macrophages are important host defense cells in ruminant paratuberculosis (Johne’s Disease; JD), a chronic enteritis caused by Mycobacterium avium subsp. paratuberculosis (MAP). Classical macrophage functions of pathogen trafficking, degradation, and antigen presentation are interrupted in mycobacterial infection. Immunologic stimulation by 25-hydroxyvitamin D₃ (25(OH)D₃) and 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) enhances bovine macrophage function. The present study aimed to investigate the role of vitamin D₃ on macrophage phenotype and endosomal trafficking of MAP in monocyte-derived macrophages (MDMs) cultured from JD-, JD+ subclinical, and JD+ clinically infected cattle. MDMs were pre-treated 100 ng/ml 25(OH)D₃ or 4 ng/ml 1,25(OH)₂D₃ and incubated 24 hrs with MAP at 10:1 multiplicity of infection (MOI). In vitro MAP infection upregulated pro-inflammatory (M1) CD80 and downregulated resolution/repair (M2) CD163. Vitamin D₃ generally decreased CD80 and increased CD163 expression. Furthermore, early endosomal marker Rab5 was upregulated 140× across all stages of paratuberculosis infection following in vitro MAP infection; however, Rab5 was reduced in MAP-activated MDMs from JD+ subclinical and JD+ clinical cows compared to healthy controls. Rab7 expression decreased in control and clinical cows following MDM infection with MAP. Both forms of vitamin D₃ reduced Rab5 expression in infected MDMs from JD- control cows, while 1,25(OH)₂D₃ decreased Rab7 expression in JD- and JD+ subclinical animals regardless of MAP infection in vitro. Vitamin D₃ promoted phagocytosis in MDMs from JD- and JD+ clinical cows treated with either vitamin D₃ analog. Results from this study show exogenous vitamin D₃ influences macrophage M1/M2 polarization and Rab GTPase expression within MDM culture.

Inflammasome genetic variants are associated with tuberculosis, HIV-1 infection, and TB/HIV-immune reconstitution inflammatory syndrome outcomes

Background

Tuberculosis (TB) and AIDS are the leading causes of infectious diseases death worldwide. Here, we investigated the relationship between from single nucleotide polymorphisms (SNPs) of the NLRP3, CARD8, AIM2, CASP-1, IFI16, and IL-1β inflammasome genes, as well as the profiles of secreted proinflammatory cytokines (e.g., IL-1β, IL-18, IL-33, and IL-6) with the TB clinical profiles, TB-HIV coinfection, and IRIS onset.

Methods

The individuals were divided into four groups: TB-HIV group (n=88; 11 of them with IRIS), HIV-1 group (n=20), TB group (n=24) and healthy volunteers (HC) group (n=10), and were followed up at INI/FIOCRUZ and HGNI (Rio de Janeiro/Brazil) from 2006 to 2016. Real-time PCR was used to determine the genotypes of the Single Nucleotide Polymorphism (SNPs), and ELISA was used to measure the plasma cytokine levels. Unconditional logistic regression models were used to perform risk estimations.

Results

A higher risk for extrapulmonary TB was associated with the TT genotype (aOR=6.76; P=0.026) in the NLRP3 rs4612666 Single Nucleotide Polymorphism (SNP) and the C-C-T-G-C haplotype (aOR=4.99; P= 0.017) in the NLRP3 variants. This same Single Nucleotide Polymorphism (SNP) was associated with lower risk against extrapulmonary TB when the carrier allele C (aOR=0.15; P=0.021) was present. Among those with HIV-1 infections, a higher risk for TB onset was associated with the GA genotype (aOR=5.5; P=0.044) in the IL1-β rs1143634 Single Nucleotide Polymorphism (SNP). In contrast, lower risk against TB onset was associated with the A-G haplotype (aOR=0.17; P= 0.026) in the CARD8 variants. Higher IL-6 and IL-33 levels were observed in individuals with TB. A higher risk for IRIS onset was associated with CD8 counts ≤ 500 cells/mm3 (aOR=12.32; P=0.010), the presence of extrapulmonary TB (aOR=6.6; P=0.038), and the CT genotype (aOR=61.06; P=0.026) or carrier allele T (aOR=61.06; P=0.026) in the AIM2 rs2276405 Single Nucleotide Polymorphism (SNP), whereas lower risk against IRIS onset was associated with the AT genotype (aOR=0.02; P=0.033) or carrier allele T (aOR=0.02; P=0.029) in the CARD8 rs2043211 Single Nucleotide Polymorphism (SNP) and the T-G haplotype (aOR=0.07; P= 0.033) in the CARD8 variants. No other significant associations were observed.

Conclusions

Our results depict the involvement of genetic polymorphisms of crucial innate immunity genes and proinflammatory cytokines in the clinical outcomes related to TB-HIV coinfection.

Exacerbation of Mycobacterium avium pulmonary infection by comorbid allergic asthma is associated with diminished mycobacterium-specific Th17 responses

Accumulating evidence suggests that two chronic respiratory diseases, nontuberculous mycobacterium (NTM)-pulmonary disease (PD) and allergic asthma, are frequently present together and that they likely influence the disease development and progression of each other. However, their precise interactions regarding the pathogenesis of comorbid diseases versus that of individual diseases are not well understood. In this study, comorbid diseases (i.e., Mycobacteria avium (Mav) pulmonary infection (PI) (Mav-PI) and ovalbumin-induced allergic asthma) were established in mice in different orders and at different time periods. Individual disease-specific characteristics, including alterations in immune cell populations and antigen-specific immune responses, were analyzed and compared. To assess Mav-PI pathogenesis, lung inflammation and bacterial burden levels were also determined. Allergic asthma induction in the presence of Mav-PI markedly aggravated Mav-PI pathogenesis by increasing the bacterial burden and the severity of lung inflammation. Interestingly, the general outcome of allergic asthma with goblet cell hyperplasia was alleviated at a chronic stage in the comorbid mouse model. Overall, the increase in the number of Mav CFUs was inversely correlated with the Mav-specific Th17 response, as confirmed by comparing BALB/c and C57BL/6J mice. Overall, the pathogenesis of existing Mav-PI is more severely affected by allergen exposure than vice versa. This Mav-PI exacerbation is associated with disruption of Mav-specific Th17 responses. This study provides the first evidence that the Mav-specific Th17 response plays an important role in the control of Mav pathogenesis in the presence of allergic asthma, indicating that targeting the Th17 response has therapeutic potential for NTM-PD accompanied by allergic asthma.

Serum levels of inhibitory costimulatory molecules and correlations with levels of innate immune cytokines in patients with pulmonary tuberculosis

Objective

To analyze serum levels of inhibitory costimulatory molecules and their correlations with innate immune cytokine levels in patients with pulmonary tuberculosis (PTB).

Methods

Data for 280 PTB patients and 280 healthy individuals were collected. Serum levels of immune molecules were measured using ELISA. Univariate, multivariate, subgroup, matrix correlation, and receiver operating characteristic curve analyses were performed.

Results

Host, environment, lifestyle, clinical features, and medical history all influenced PTB. Serum levels of soluble programmed death ligand 1 (sPD-L1), soluble T-cell immunoglobulin- and mucin-domain–containing molecule 3 (sTim-3), soluble galectin-9 (sGal-9), interleukin (IL)-4, and IL-33 were significantly higher in patients with PTB, while levels of IL-12, IL-23, IL-18, and interferon (IFN)-γ were significantly lower. Serum levels of sTim-3 were higher in alcohol users. Levels of sTim-3 were negatively correlated with those of IL-12. Levels of IL-12, IL-23, and IL-18 were positively correlated with those of IFN-γ, while levels of IL-12 were negatively correlated with those of IL-4. The areas under the curve of sPD-L1, sTim-3, sGal-9, IL-12, IL-23, IL-18, IFN-γ, IL-4, and IL-33 for identifying PTB were all >0.77.

Conclusions

Inhibitory costimulatory molecules may be targets for controlling PTB. Immune molecules may be helpful for diagnosis of PTB.

Evolutionary Views of Tuberculosis: Indoleamine 2,3-Dioxygenase Catalyzed Nicotinamide Synthesis Reflects Shifts in Macrophage Metabolism: Indoleamine 2,3-Dioxygenase Reflects Altered Macrophage Metabolism During Tuberculosis Pathogenesis

Indoleamine 2,3-dioxygenase (IDO) is the rate-limiting enzyme in conversion of tryptophan to kynurenines, feeding de novo nicotinamide synthesis. IDO orchestrates materno-foetal tolerance, increasing human reproductive fitness. IDO mediates immune suppression through depletion of tryptophan required by T lymphocytes and other mechanisms. IDO is expressed by alternatively activated macrophages, suspected to play a key role in tuberculosis (TB) pathogenesis. Unlike its human host, Mycobacterium tuberculosis can synthesize tryptophan, suggesting possible benefit to the host from infection with the microbe. Intriguingly, nicotinamide analogues are used to treat TB. In reviewing this field, it is postulated that flux through the nicotinamide synthesis pathway reflects switching between aerobic glycolysis and oxidative phosphorylation in M. tuberculosis-infected macrophages. The evolutionary cause of such shifts may be ancient mitochondrial behavior related to reproductive fitness. Evolutionary perspectives on the IDO pathway may elucidate why, after centuries of co-existence with the Tubercle bacillus, humans still remain susceptible to TB disease.

Obesity-Induced Dysbiosis Exacerbates IFN-γ Production and Pulmonary Inflammation in the Mycobacterium tuberculosis Infection

The microbiota of the gut-lung axis affects local and far-reaching immune responses and might also trigger chronic and inflammatory diseases. We hypothesized that gut dysbiosis induced by obesity, which coexists in countries with a high tuberculosis burden, aggravates the host susceptibility and the pulmonary damage tolerance. To assess our hypothesis, we used a model of high-fat diet (HFD)-induced obesity, followed by infection of C57BL/6 mice with Mycobacterium tuberculosis. We showed that obesity increased the susceptibility, the pulmonary inflammation and IFN-γ levels in M. tuberculosis-infected mice. During the comorbidity obesity and tuberculosis, there is an increase of Bacteroidetes and Firmicutes in the lungs, and an increase of Firmicutes and butyrate in the feces. Depletion of gut microbiota by antibiotic treatment in the obese infected mice reduced the frequencies of CD4+IFN-γ+IL-17- cells and IFN-γ levels in the lungs, associated with an increase of Lactobacillus. Our findings reinforce the role of the gut-lung axis in chronic infections and suggest that the gut microbiota modulation may be a potential host-directed therapy as an adjuvant to treat TB in the context of IFN-γ-mediated immunopathology.

Decitabine Promotes Modulation in Phenotype and Function of Monocytes and Macrophages That Drive Immune Response Regulation

Decitabine is an approved hypomethylating agent used for treating hematological malignancies. Although decitabine targets altered cells, epidrugs can trigger immunomodulatory effects, reinforcing the hypothesis of immunoregulation in treated patients. We therefore aimed to evaluate the impact of decitabine treatment on the phenotype and functions of monocytes and macrophages, which are pivotal cells of the innate immunity system. In vitro decitabine administration increased bacterial phagocytosis and IL-8 release, but impaired microbicidal activity of monocytes. In addition, during monocyte-to-macrophage differentiation, treatment promoted the M2-like profile, with increased expression of CD206 and ALOX15. Macrophages also demonstrated reduced infection control when exposed to Mycobacterium tuberculosis in vitro. However, cytokine production remained unchanged, indicating an atypical M2 macrophage. Furthermore, when macrophages were cocultured with lymphocytes, decitabine induced a reduction in the release of inflammatory cytokines such as IL-1β, TNF-α, and IFN-γ, maintaining IL-10 production, suggesting that decitabine could potentialize M2 polarization and might be considered as a therapeutic against the exacerbated immune response.

Immune Subtyping in Latent Tuberculosis

Latent tuberculosis infection (LTBI) poses a major roadblock in the global effort to eradicate tuberculosis (TB). A deep understanding of the host responses involved in establishment and maintenance of TB latency is required to propel the development of sensitive methods to detect and treat LTBI. Given that LTBI individuals are typically asymptomatic, it is challenging to differentiate latently infected from uninfected individuals. A major contributor to this problem is that no clear pattern of host response is linked with LTBI, as molecular correlates of latent infection have been hard to identify. In this study, we have analyzed the global perturbations in host response in LTBI individuals as compared to uninfected individuals and particularly the heterogeneity in such response, across LTBI cohorts. For this, we constructed individualized genome-wide host response networks informed by blood transcriptomes for 136 LTBI cases and have used a sensitive network mining algorithm to identify top-ranked host response subnetworks in each case. Our analysis indicates that despite the high heterogeneity in the gene expression profiles among LTBI samples, clear patterns of perturbation are found in the immune response pathways, leading to grouping LTBI samples into 4 different immune-subtypes. Our results suggest that different subnetworks of molecular perturbations are associated with latent tuberculosis.

Helminth Antigen Exposure Enhances Early Immune Control of Mycobacterium tuberculosis in Monocytes and Macrophages

Helminth and Mycobacterium tuberculosis (Mtb) coinfection is common and suggested to influence the risk of developing active tuberculosis (TB). It is known that helminths in contrast to TB induce a strong Th2 response in the host. However, the direct impact of helminth antigen exposure on host immunity against TB is largely unknown. Our aim was to explore the effects of helminth antigen exposure on the early immune control of Mtb in monocytes and macrophages. Ascaris lumbricoides (ASC) and Schistosoma mansoni (SM) protein antigens were used to study the immediate effect of helminth antigen exposure in monocytes, on monocyte-to-macrophage differentiation, or mature macrophages, in the control of virulent Mtb H37Rv. Pre-exposure of peripheral blood mononuclear cells reduced Mtb growth in monocytes, especially with SM, but no Th1/Th2 cytokines or activation markers indicated involvement of T cells. Monocytes exposed before maturing into macrophages reduced Mtb growth in macrophages (ASC), and pre-exposure of mature macrophages reduced (ASC) or kept Mtb growth at control levels (SM). This in vitro model shows how helminth infection directly affects the monocyte-macrophage axis at an early stage before cell-mediated immunity develops. During acute helminth coinfection or when helminth antigen concentration is elevated at the site of Mtb infection, these helminths provide an enhanced control and killing of Mtb owing to the direct stimulatory effect of helminth antigens on phagocytic cells.

Evidence for the Effect of Vaccination on Host-Pathogen Interactions in a Murine Model of Pulmonary Tuberculosis by Mycobacterium tuberculosis

The global control of Tuberculosis remains elusive, and Bacillus Calmette-Guérin (BCG) -the most widely used vaccine in history-has proven insufficient for reversing this epidemic. Several authors have suggested that the mass presence of vaccinated hosts might have affected the Mycobacterium tuberculosis (MTB) population structure, and this could in turn be reflected in a prevalence of strains with higher ability to circumvent BCG-induced immunity, such as the recent Beijing genotype. The effect of vaccination on vaccine-escape variants has been well-documented in several bacterial pathogens; however the effect of the interaction between MTB strains and vaccinated hosts has never been previously described. In this study we show for the first time the interaction between MTB Beijing-genotype strains and BCG-vaccinated hosts. Using a well-controlled murine model of progressive pulmonary tuberculosis, we vaccinated BALB/c mice with two different sub-strains of BCG (BCG-Phipps and BCG-Vietnam). Following vaccination, the mice were infected with either one of three selected MTB strains. Strains were selected based on lineage, and included two Beijing-family clinical isolates (strains 46 and 48) and a well-characterized laboratory strain (H37Rv). Two months after infection, mice were euthanized and the bacteria extracted from their lungs. We characterized the genomic composite of the bacteria before and after exposure to vaccinated hosts, and also characterized the local response to the bacteria by sequencing the lung transcriptome in animals during the infection. Results from this study show that the interaction within the lungs of the vaccinated hosts results in the selection of higher-virulence bacteria, specifically for the Beijing genotype strains 46 and 48. After exposure to the BCG-induced immune response, strains 46 and 48 acquire genomic mutations associated with several virulence factors. As a result, the bacteria collected from these vaccinated hosts have an increased ability for immune evasion, as shown in both the host transcriptome and the histopathology studies, and replicates far more efficiently compared to bacteria collected from unvaccinated hosts or to the original-stock strain. Further research is warranted to ascertain the pathways associated with the genomic alterations. However, our results highlight novel host-pathogen interactions induced by exposure of MTB to BCG vaccinated hosts.

Green propolis increases myeloid suppressor cells and CD4+Foxp3+ cells and reduces Th2 inflammation in the lungs after allergen exposure

ETHNOPHARMACOLOGICAL RELEVANCE

Propolis is a natural product produced by honeybees used as a medicine at least to 300 BC. In the last decades, several studies showed biological and pharmacological properties of propolis, witch scientifically explains the empirical use for centuries. The anti-inflammatory activity of propolis with the purpose to reduce Th2 inflammation has been evaluated in allergic asthma. However, it remains to be determined how propolis negatively regulates the immune response after allergen re-exposure.

AIM OF THE STUDY

We hypothesized that the anti-inflammatory activity of propolis is dependent on the induction of myeloid derived suppressor cells (MDSC) and regulatory T cells.

MATERIALS AND METHODS

To assess this hypothesis, we used an ovalbumin-induced asthma model to evaluate the effect of EPP-AF® dry extract from Brazilian green propolis.

RESULTS

Propolis treatment decreased pulmonary inflammation and mucus production as well as eosinophils and IL-5 in the broncoalveolar lavage. Propolis enhanced also in vitro differentiation and in vivo frequency of lung MDSC and CD4⁺Foxp3⁺ regulatory T cells.

CONCLUSIONS

Together these results confirm the immunomodulatory potential of propolis during sensitization and challenge with allergen. In addition, the collecting findings show, for the first time, that propolis increases the frequency of MDSC and CD4⁺Foxp3⁺ regulatory T cells in the lungs, and suggest that it could be use as target for development of new immunotherapy or adjuvant immunotherapy for asthma.

Filarial Coinfection Is Associated With Higher Bacterial Burdens and Altered Plasma Cytokine and Chemokine Responses in Tuberculous Lymphadenitis

Filarial infections are known to modulate cytokine responses in pulmonary tuberculosis by their propensity to induce Type 2 and regulatory cytokines. However, very little is known about the effect of filarial infections on extra-pulmonary forms of tuberculosis. Thus, we have examined the effect of filarial infections on the plasma levels of various families of (IL-1, IL-12, γC, and regulatory) cytokines and (CC and CXC) chemokines in tuberculous lymphadenitis coinfection. We also measured lymph node culture grades in order to assess the burden of Mycobacterium tuberculosis in the two study groups [Fil+ (n = 67) and Fil– (n = 109)]. Our data reveal that bacterial burden was significantly higher in Fil+ compared to Fil– individuals. Plasma levels of IL-1 family (IL-1α, IL-β, IL-18) cytokines were significantly lower with the exception of IL-33 in Fil+ compared to Fil– individuals. Similarly, plasma levels of IL-12 family cytokines -IL-12 and IL-23 were significantly reduced, while IL-35 was significantly elevated in Fil+ compared to Fil– individuals. Filarial infection was also associated with diminished levels of IL-2, IL-9 and enhanced levels of IL-4, IL-10, and IL-1Ra. Similarly, the Fil+ individuals were linked to elevated levels of different CC (CCL-1, CCL-2, CCL-3, CCL-11) and CXC (CXCL-2, CXCL-8, CXCL-9, CXCL-11) chemokines. Therefore, we conclude that filarial infections exert powerful bystander effects on tuberculous lymphadenitis, effects including modulation of protective cytokines and chemokines with a direct impact on bacterial burdens.

AMPK-Targeted Effector Networks in Mycobacterial Infection

AMP-activated protein kinase (AMPK), a key metabolic regulator, plays an essential role in the maintenance of energy balance in response to stress. Tuberculosis (TB), primarily caused by the pathogen Mycobacterium tuberculosis (Mtb), remains one of the most important infectious diseases worldwide, characterized by both high incidence and mortality. Development of new preventive and therapeutic strategies against TB requires a profound understanding of the various host-pathogen interactions that occur during infection. Emerging data suggest that AMPK plays an essential regulatory role in host autophagy, mitochondrial biogenesis, metabolic reprogramming, fatty acid β-oxidation, and the control of pathologic inflammation in macrophages during Mtb infection. As described in this review, recent studies have begun to define the functional properties of AMPK modulators capable of restricting intracellular bacteria and promoting host defenses. Several host defense factors in the context of AMPK activation also participate in autophagic and non-autophagic pathways in a coordinated manner to enhance antimicrobial responses against Mtb infection. A better understanding of these AMPK-targeted effector networks offers significant potential for the development of novel therapeutics for human TB and other infectious diseases.

CCR4-dependent reduction in the number and suppressor function of CD4+Foxp3+ cells augments IFN-γ-mediated pulmonary inflammation and aggravates tuberculosis pathogenesis

Chronic pulmonary inflammation marked predominantly by CD4⁺IFN-γ⁺ cells is the hallmark of tuberculosis pathogenesis in immunocompetent adults, who are substantially affected by this disease. Moreover, CD4⁺Foxp3⁺ cell-mediated suppression contributes to infection susceptibility. We addressed the role of CD4⁺Foxp3⁺ cells in tuberculosis pathogenesis, because this aspect has not been addressed during chronic infection. We targeted CCR4, which induces the influx of CD4⁺Foxp3⁺ cells into the lungs. CCR4^−/− mice exhibited a lower frequency of CD4⁺Foxp3⁺ cells at 15, 30, and 70 days of infection than their wild-type counterparts. However, only at 70 days of infection was an exacerbated IFN-γ-mediated immune response associated with apparent tuberculosis pathogenesis and susceptibility. In addition, CCR4^−/− mice exhibited a decrease in the suppressor function of CD4⁺Foxp3⁺ cells. Adoptive transfer of Foxp3⁺ cells into infected CCR4^−/− mice restored pulmonary inflammation and bacterial load to levels observed in wild-type mice. Our findings suggest that CD4⁺Foxp3⁺ cells play a time-dependent role in tuberculosis and highlight that CCR4 plays a critical role in the balance of IFN-γ-mediated inflammation by regulating the influx and function of CD4⁺Foxp3⁺ cells. Our findings are translationally relevant, as CD4⁺Foxp3⁺ cells or CCR4 could be a target for immunotherapy, considering the heterogeneity of tuberculosis in immunocompetent adults.

Inhibitor of apoptosis proteins, NAIP, cIAP1 and cIAP2 expression during macrophage differentiation and M1/M2 polarization

Monocytes and macrophages constitute the first line of defense of the immune system against external pathogens. Macrophages have a highly plastic phenotype depending on environmental conditions; the extremes of this phenotypic spectrum are a pro-inflammatory defensive role (M1 phenotype) and an anti-inflammatory tissue-repair one (M2 phenotype). The Inhibitor of Apoptosis (IAP) proteins have important roles in the regulation of several cellular processes, including innate and adaptive immunity. In this study we have analyzed the differential expression of the IAPs, NAIP, cIAP1 and cIAP2, during macrophage differentiation and polarization into M1 or M2. In polarized THP-1 cells and primary human macrophages, NAIP is abundantly expressed in M2 macrophages, while cIAP1 and cIAP2 show an inverse pattern of expression in polarized macrophages, with elevated expression levels of cIAP1 in M2 and cIAP2 preferentially expressed in M1. Interestingly, treatment with the IAP antagonist SMC-LCL161, induced the upregulation of NAIP in M2, the downregulation of cIAP1 in M1 and M2 and an induction of cIAP2 in M1 macrophages.

MicroRNA 27a-3p Regulates Antimicrobial Responses of Murine Macrophages Infected by Mycobacterium avium subspecies paratuberculosis by Targeting Interleukin-10 and TGF-β-Activated Protein Kinase 1 Binding Protein 2

Mycobacterium avium subspecies paratuberculosis (MAP) persistently survive and replicate in mononuclear phagocytic cells by adopting various strategies to subvert host immune response. Interleukin-10 (IL-10) upregulation via inhibition of macrophage bactericidal activity is a critical step for MAP survival and pathogenesis within the host cell. Mitogen-activated protein kinase p38 signaling cascade plays a crucial role in the elevation of IL-10 and progression of MAP pathogenesis. The contribution of microRNAs (miRNAs) and their influence on the activation of macrophages during MAP pathogenesis are still unclear. In the current study, we found that miRNA-27a-3p (miR-27a) expression is downregulated during MAP infection both in vivo and in vitro. Moreover, miR-27a is also downregulated in toll-like receptor 2 (TLR2)-stimulated murine macrophages (RAW264.7 and bone marrow-derived macrophage). ELISA and real-time qRT-PCR results confirm that overexpression of miR-27a inhibited MAP-induced IL-10 production in macrophages and upregulated pro-inflammatory cytokines, while miR-27a inhibitor counteracted these effects. Luciferase reporter assay results revealed that IL-10 and TGF-β-activated protein kinase 1 binding protein 2 (TAB 2) are potential targets of miR-27a. In addition, we demonstrated that miR-27a negatively regulates TAB 2 expression and diminishes TAB 2-dependent p38/JNK phosphorylation, ultimately downregulating IL-10 expression in MAP-infected macrophages. Furthermore, overexpression of miR-27a significantly inhibited the intracellular survival of MAP in infected macrophages. Our data show that miR-27a augments antimicrobial activities of macrophages and inhibits the expression of IL-10, demonstrating that miR-27a regulates protective innate immune responses during MAP infection and can be exploited as a novel therapeutic target in the control of intracellular pathogens, including paratuberculosis.

Protective immunity against tuberculosis: what does it look like and how do we find it?

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An absence of immune correlates of protection is a barrier to vaccine development.

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The immune mechanisms behind tuberculosis progression are not understood.

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Fluorescent Mtb reporter strains identify permissive and controller host cells.

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Bacterial burden can be impacted by the magnitude of host cell population.

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Bacterial reporter strains offer new insights into host immune mechanisms.

Progress towards the development of an effective vaccine against tuberculosis is hampered by the lack of correlative readouts of immune protection, coupled with our limited understanding of the immune mechanisms that determine disease progression versus containment. In this article we discuss the value of microbial readouts of bacterial fitness to probe the host immune environments and determine those host cell subsets that promote or control bacterial growth. Ultimately, we feel that these bacterial reporters will prove to be key in understanding the immune mechanisms underpinning disease outcome, and that this knowledge is critical to any program developing vaccines or immune-modulatory therapeutics as a means of controlling tuberculosis.