Induction of TNF in human alveolar macrophages as a potential evasion mechanism of virulent Mycobacterium tuberculosis

Elucidating the effect of pro and anti-inflammatory recombinant cytokines TNF-α and TGF-β in tuberculosis

Tuberculosis (TB) is a leading cause of death caused by Mycobacterium tuberculosis (M tb) and about one-third of the world's population is infected with TB. The household contacts of TB patients are at higher risk towards TB than general population. During the initial stages of infection, pro and anti-inflammatory cytokines are induced by innate immune cells, and the course of infection is influenced by general cytokine environment. These cytokines play an important role in the regulation of host immune responses against M tb. Therefore, it is necessary to understand the cytokines role in the immune mechanism to evaluate the correlation between the disease and the immune responses involved in TB. Our current study has focused on recombinant cytokines to understand their effects on cell proliferation and cytokine levels in culture supernatants. We observed that the mean proliferative responses to recombinant rhTNF-α were high and TNF-α levels were significantly low in APTB patients compared to their HHC and HC with p < 0.0375 and p < 0.0051 respectively. The mean proliferative responses to recombinant rhTGF-β were significantly low in APTB when compared to HHC and HC with p < 0.0376, p < 0.0247 respectively, and TGF-β levels were also significantly low in APTB and HHC compared to HC with p < 0.0468 and p < 0.0001 respectively. The lower cytokine secretions in culture supernatants might be due the autocrine signaling by recombinant cytokines towards the inflammatory response. Further, to validate these recombinant cytokines, a larger sample size could aid in identifying individuals at high risk for TB.

A new tractable method for generating human alveolar macrophage-like cells in vitro to study lung inflammatory processes and diseases

Alveolar macrophages (AMs) are unique lung resident cells that contact airborne pathogens and environmental particulates. The contribution of human AMs (HAMs) to pulmonary diseases remains poorly understood due to the difficulty in accessing them from human donors and their rapid phenotypic change during in vitro culture. Thus, there remains an unmet need for cost-effective methods for generating and/or differentiating primary cells into a HAM phenotype, particularly important for translational and clinical studies. We developed cell culture conditions that mimic the lung alveolar environment in humans using lung lipids, that is, Infasurf (calfactant, natural bovine surfactant) and lung-associated cytokines (granulocyte macrophage colony-stimulating factor, transforming growth factor-β, and interleukin 10) that facilitate the conversion of blood-obtained monocytes to an AM-like (AML) phenotype and function in tissue culture. Similar to HAM, AML cells are particularly susceptible to both Mycobacterium tuberculosis and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. This study reveals the importance of alveolar space components in the development and maintenance of HAM phenotype and function and provides a readily accessible model to study HAM in infectious and inflammatory disease processes, as well as therapies and vaccines. IMPORTANCE Millions die annually from respiratory disorders. Lower respiratory track gas-exchanging alveoli maintain a precarious balance between fighting invaders and minimizing tissue damage. Key players herein are resident AMs. However, there are no easily accessible in vitro models of HAMs, presenting a huge scientific challenge. Here, we present a novel model for generating AML cells based on differentiating blood monocytes in a defined lung component cocktail. This model is non-invasive, significantly less costly than performing a bronchoalveolar lavage, yields more AML cells than HAMs per donor, and retains their phenotype in culture. We have applied this model to early studies of M. tuberculosis and SARS-CoV-2. This model will significantly advance respiratory biology research.

A new tractable method for generating Human Alveolar Macrophage Like cells in vitro to study lung inflammatory processes and diseases

Alveolar macrophages (AMs) are unique lung resident cells that contact airborne pathogens and environmental particulates. The contribution of human AMs (HAM) to pulmonary diseases remains poorly understood due to difficulty in accessing them from human donors and their rapid phenotypic change during in vitro culture. Thus, there remains an unmet need for cost-effective methods for generating and/or differentiating primary cells into a HAM phenotype, particularly important for translational and clinical studies. We developed cell culture conditions that mimic the lung alveolar environment in humans using lung lipids, i.e. , Infasurf (calfactant, natural bovine surfactant) and lung-associated cytokines (GM-CSF, TGF-β, and IL-10) that facilitate the conversion of blood-obtained monocytes to an AM-Like (AML) phenotype and function in tissue culture. Similar to HAM, AML cells are particularly susceptible to both Mycobacterium tuberculosis and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. This study reveals the importance of alveolar space components in the development and maintenance of HAM phenotype and function, and provides a readily accessible model to study HAM in infectious and inflammatory disease processes, as well as therapies and vaccines.

IMPORTANCE

Millions die annually from respiratory disorders. Lower respiratory track gas-exchanging alveoli maintain a precarious balance between fighting invaders and minimizing tissue damage. Key players herein are resident AMs. However, there are no easily accessible in vitro models of HAMs, presenting a huge scientific challenge. Here we present a novel model for generating AML cells based on differentiating blood monocytes in a defined lung component cocktail. This model is non-invasive, significantly less costly than performing a bronchoalveolar lavage, yields more AML cells than HAMs per donor and retains their phenotype in culture. We have applied this model to early studies of M. tuberculosis and SARS-CoV-2. This model will significantly advance respiratory biology research.

Lumpfish (Cyclopterus lumpus) Is Susceptible to Renibacterium salmoninarum Infection and Induces Cell-Mediated Immunity in the Chronic Stage

Renibacterium salmoninarum is a Gram-positive, intracellular pathogen that causes Bacterial Kidney Disease (BKD) in several fish species in freshwater and seawater. Lumpfish (Cyclopterus lumpus) is utilized as a cleaner fish to biocontrol sea lice infestation in Atlantic salmon (Salmo salar) farms. Atlantic salmon is susceptible to R. salmoninarum, and it can transfer the infection to other fish species. Although BKD outbreaks have not been reported in lumpfish, its susceptibility and immune response to R. salmoninarum is unknown. In this study, we evaluated the susceptibility and immune response of lumpfish to R. salmoninarum infection. Groups of lumpfish were intraperitoneally (i.p.) injected with either R. salmoninarum (1×10⁷, 1×10⁸, or 1×10⁹ cells dose^-1) or PBS (control). R. salmoninarum infection kinetics and mortality were followed for 98 days post-infection (dpi). Transcript expression levels of 33 immune-relevant genes were measured in head kidney (n = 6) of fish infected with 1×10⁹ cells/dose and compared to the control at 28 and 98 dpi. Infected lumpfish displayed characteristic clinical signs of BKD. Lumpfish infected with high, medium, and low doses had a survival rate of 65%, 93%, and 95%, respectively. Mortality in the high-dose infected group stabilized after 50 dpi, but R. salmoninarum persisted in the fish tissues until 98 dpi. Cytokines (il1β, il8a, il8b), pattern recognition receptors (tlr5a), interferon-induced effectors (rsad2, mxa, mxb, mxc), and iron regulation (hamp) and acute phase reactant (saa5) related genes were up-regulated at 28 dpi. In contrast, cell-mediated adaptive immunity-related genes (cd4a, cd4b, ly6g6f, cd8a, cd74) were down-regulated at 28 dpi, revealing the immune suppressive nature of R. salmoninarum. However, significant upregulation of cd74 at 98 dpi suggests induction of cell-mediated immune response. This study showed that R. salmoninarum infected lumpfish in a similar fashion to salmonid fish species and caused a chronic infection, enhancing cell-mediated adaptive immune response.

Characterization of bacterial DNA identified in abscessed and non-abscessed bovine hepatic tissue at the time of harvest

Bacteriological characterization of bovine liver abscesses has been accomplished by cultural methods but DNA methods are still needed, as many bacteria are not conducive to laboratory culture. In addition to this gap in research, there have been no studies which identify the bacterial presence within healthy, non-abscessed liver tissue. The objective of this study was to compare the bacteriome of both abscessed and non-abscessed bovine livers in an observational case-control study design. Fifty-six livers, obtained from Holstein steers, were scored according to a modified Elanco liver abscess score description where A- was partitioned into active abscesses or scarred where only scars were present. Parenchyma tissue was collected from non-abscessed livers (n = 22) and scarred livers (n = 7), and purulent material was collected from abscessed livers (n = 24), and DNA was extracted for 16s rRNA gene sequence-based bacterial analysis. Across liver samples, 21 total phyla were identified with a mean of 14. Predominant phyla, accounting for >98% of reads, were Fusobacteria (51.7%), Bacteroidetes (26.9%), Proteobacteria (8.03%), Firmicutes (5.39%), Cyanobacteria (3.85%), and Actinobacteria (2.21%). Proteobacteria, Cyanobacteria, and Firmicutes were greater in non-abscessed and scarred livers, whereas Fusobacteria and Bacteroidetes prevailed in abscessed livers. Non-abscessed livers shared 3,059 operational taxonomic units (OTU) with abscessed livers (total OTU of all livers = 4,167), but non-abscessed livers had greater richness and evenness, whereas abscessed livers had greater dominance (P ≤ 0.0014). Liver score affected the relative abundance of OTU (R = 0.463; P = 0.001) but abscessed livers shared ≥ 40% similarity and were not different from each other (P ≥ 0.370). Of the predominant OTU (top 10 as a % of reads), three OTU (Fusobacteria necrophorum, Bacteroides spp., and Trueperella pyogenes) were shared across both abscessed and non-abscessed livers. Fusobacterium necrophorum was the dominant OTU regardless of liver score, and the single most abundant OTU, even among non-abscessed livers. We describe bacterial DNA detected in non-abscessed bovine liver tissue for the first time, which indicates possible presence of viable bacteria with pathogenic potential in apparently healthy liver tissue.

Should isoniazid prophylaxis be prescribed to the patients under tumor necrosis factor-alpha antagonists independent of tuberculin skin test?

INTRODUCTION

The aim of this study was to present the follow-up results of 110 patients who were given anti-tumor necrosis factor alpha (TNF-α) therapy for rheumatic and dermatologic diseases in a country with a high rates of active and latent tuberculosis bacillus infection.

MATERIAL AND METHODS

Between February 2008 and January 2015, 110 cases in the age range of 23-77 who are using anti-TNF-α were included in the study retro-prospectively.

RESULTS

52.7% of them (n = 58) were male. The most common diagnoses were rheumatoid arthritis (42.7%) and ankylosing spondylitis (38.2%). Most frequently given treatment were infliximab 37.3% and etanercept 30.9%, respectively. The 65 patients whose first tuberculin skin test (TST) value "5 mm and above" was started daily 300 mg INH prophylaxis for 9 months but 3 patients had not been started because of refusing treatment. In only one case chemoprophylaxis has had to be interrupted because of high liver function test due to the INH prophylaxis. TST conversion was observed in 14 patients. Further follow-up, it was observed that 4 patients had TST's positivity. Isoniazide (INH) prophylaxis was started these 18 patients (42.9%). Although INH prophylaxis has been given in two patients, they developed active tuberculosis in follow-up.

CONCLUSION

Considering the INH resistance in our country, all patients especially the ones with residual lesion and history of previous exposure, should be followed up closely during the anti-TNF-α treatment.

A Modular Microscale Granuloma Model for Immune-Microenvironment Signaling Studies in vitro

Tuberculosis (TB) is one of the most potent infectious diseases in the world, causing more deaths than any other single infectious agent. TB infection is caused by inhalation of Mycobacterium tuberculosis (Mtb) and subsequent phagocytosis and migration into the lung tissue by innate immune cells (e.g., alveolar macrophages, neutrophils, and dendritic cells), resulting in the formation of a fused mass of immune cells known as the granuloma. Considered the pathological hallmark of TB, the granuloma is a complex microenvironment that is crucial for pathogen containment as well as pathogen survival. Disruption of the delicate granuloma microenvironment via numerous stimuli, such as variations in cytokine secretions, nutrient availability, and the makeup of immune cell population, can lead to an active infection. Herein, we present a novel in vitro model to examine the soluble factor signaling between a mycobacterial infection and its surrounding environment. Adapting a newly developed suspended microfluidic platform, known as Stacks, we established a modular microscale infection model containing human immune cells and a model mycobacterial strain that can easily integrate with different microenvironmental cues through simple spatial and temporal "stacking" of each module of the platform. We validate the establishment of suspended microscale (4 μL) infection cultures that secrete increased levels of proinflammatory factors IL-6, VEGF, and TNFα upon infection and form 3D aggregates (granuloma model) encapsulating the mycobacteria. As a proof of concept to demonstrate the capability of our platform to examine soluble factor signaling, we cocultured an in vitro angiogenesis model with the granuloma model and quantified morphology changes in endothelial structures as a result of culture conditions (P < 0.05 when comparing infected vs. uninfected coculture systems). We envision our modular in vitro granuloma model can be further expanded and adapted for studies focusing on the complex interplay between granulomatous structures and their surrounding microenvironment, as well as a complementary tool to augment in vivo signaling and mechanistic studies.

Towards new TB vaccines

Mycobacterium tuberculosis remains the leading cause of death attributed to a single infectious organism. Bacillus Calmette-Guerin (BCG), the standard vaccine against M. tuberculosis, is thought to prevent only 5% of all vaccine-preventable deaths due to tuberculosis, thus an alternative vaccine is required. One of the principal barriers to vaccine development against M. tuberculosis is the complexity of the immune response to infection, with uncertainty as to what constitutes an immunological correlate of protection. In this paper, we seek to give an overview of the immunology of M. tuberculosis infection, and by doing so, investigate possible targets of vaccine development. This encompasses the innate, adaptive, mucosal and humoral immune systems. Though MVA85A did not improve protection compared with BCG alone in a large-scale clinical trial, the correlates of protection this has revealed, in addition to promising results from candidate such as VPM1002, M72/ASO1E and H56:IC31 point to a brighter future in the field of TB vaccine development.

Anti-PD-1 immunotherapy leads to tuberculosis reactivation via dysregulation of TNF-α

Previously, we developed a 3-dimensional cell culture model of human tuberculosis (TB) and demonstrated its potential to interrogate the host-pathogen interaction (Tezera et al., 2017a). Here, we use the model to investigate mechanisms whereby immune checkpoint therapy for cancer paradoxically activates TB infection. In patients, PD-1 is expressed in Mycobacterium tuberculosis (Mtb)-infected lung tissue but is absent in areas of immunopathology. In the microsphere model, PD-1 ligands are up-regulated by infection, and the PD-1/PD-L1 axis is further induced by hypoxia. Inhibition of PD-1 signalling increases Mtb growth, and augments cytokine secretion. TNF-α is responsible for accelerated Mtb growth, and TNF-α neutralisation reverses augmented Mtb growth caused by anti-PD-1 treatment. In human TB, pulmonary TNF-α immunoreactivity is increased and circulating PD-1 expression negatively correlates with sputum TNF-α concentrations. Together, our findings demonstrate that PD-1 regulates the immune response in TB, and inhibition of PD-1 accelerates Mtb growth via excessive TNF-α secretion.

Rv1273c, an ABC transporter of Mycobacterium tuberculosis promotes mycobacterial intracellular survival within macrophages via modulating the host cell immune response

Mycobacterium proteins, especially cell wall associated proteins, interact with host macrophage to regulate the functions and cytokine production. So, identification and characterization of such proteins is essential for understanding tuberculosis pathogenesis. The role of the ABC transporter proteins in the pathophysiology and virulence of Mycobacterium tuberculosis is not clearly understood. In the present study, Rv1273c, an ABC transporter, has been expressed in a non-pathogenic and fast growing Mycobacterium smegmatis strain to explore its role in host pathogen interactions. Over expression of Rv1273c resulted in enhanced intracellular survival in macrophage as well as modified cell wall architecture. We found altered colony morphology and cell surface properties that might be linked with remodelling of bacterial cell wall which may help in the intracellular survival of mycobacterium. However, the enhanced intracellular survival was not found to be the consequence of an increased resistance to intracellular stresses. The activation of macrophage by Rv1273c was associated with perturbed cytokine production. Pharmacological inhibition experiment and western immunoblotting suggested that this altered cytokine profile was mediated possibly by NF-kB and p38 pathway in macrophage. Overall, the present findings indicated that Rv1273c enhanced mycobacterium persistence and mediated the evasion of immune responses during infection.

Interleukin 10 knock-down in bovine monocyte-derived macrophages has distinct effects during infection with two divergent strains of Mycobacterium bovis

Mycobacterium bovis is the causative agent of bovine tuberculosis (TB), a cattle disease of global importance. M. bovis infects bovine macrophages (Mø) and subverts the host cell response to generate a suitable niche for survival and replication. We investigated the role of the anti-inflammatory cytokine interleukin (IL) 10 during in vitro infection of bovine monocyte-derived Mø (bMDM) with two divergent UK strains of M. bovis, which differentially modulate expression of IL10. The use of IL10-targeting siRNA revealed that IL10 inhibited the production of IL1B, IL6, tumour necrosis factor (TNF) and interferon gamma (IFNG) during infection of bMDM with the M. bovis strain G18. In contrast, IL10 only regulated a subset of these genes; TNF and IFNG, during infection with the M. bovis reference strain AF2122/97. Furthermore, nitric oxide (NO) production was modulated by IL10 during AF2122/97 infection, but not at the nitric oxide synthase 2 (NOS2) mRNA level, as observed during G18 infection. However, IL10 was found to promote survival of both M. bovis strains during early bMDM infection, but this effect disappeared after 24 h. The role of IL10-induced modulation of TNF, IFNG and NO production in M. bovis survival was investigated using siRNA targeting TNF, IFNG receptor 1 (IFNGR1) and NOS2. Knock-down of these genes individually did not promote survival of either M. bovis strain and therefore modulation of these genes does not account for the effect of IL10 on M. bovis survival. However, TNF knock-down was found to be detrimental to the survival of the M. bovis strain G18 during early infection. The results provide further evidence for the importance of IL10 during M. bovis infection of Mø. Furthermore, they highlight M. bovis strain specific differences in the interaction with the infected bMDM, which may influence the course of infection and progression of bovine TB.

Association of the TNF-α-308, TNF-α-238 gene polymorphisms with risk of bone-joint and spinal tuberculosis: a meta-analysis

The aim of the present study was to investigate the association of TNF-α-308 and TNF-α-238 gene polymorphisms with the risk of bone-joint and spinal tuberculosis (TB) by meta-analysis. By searching PubMed, Web of Science, Wanfang databases, CNKI, Medline, and Cochrane Library, the published articles about studies of the association of the TNF-α-308, TNF-α-238 gene polymorphisms with risk of bone-joint and spinal tuberculosis were collected by two reviewers. Begg’s and Egger’s tests were performed to assess publication bias. Stata 12.0 software was used for data analysis. The symmetry of the funnel plot indicated no significant publication bias in the Begg’s test (A: P=1.00, B: P=0.764), and the results of the Egger’s test showed no evidence of publication bias (A: P=0.954, B: P=0.626). Seven studies assessed the relationship between TNF-α-308 gene polymorphisms and risk of bone-joint and spinal tuberculosis risk. The heterogeneity (I²) of GG vs. AA or AG was 0% and there was no heterogeneity (χ² = 0.06 and P=0.944) in a fixed-effects model. There was also a lack of association between TNF-α-308 polymorphism and bone-joint and spinal tuberculosis risk under the recessive model. The remaining models of the TNF-α-308 genotype and further studies of TNF-α-238 did not show a noteworthy association. Overall, there was no significant association between TNF-α-308, TNF-α-238 gene polymorphisms and bone-joint and spinal tuberculosis risk. Our study suggests that tumor necrosis factor α (TNF-α) gene polymorphisms may not contribute to bone-joint and spinal tuberculosis based on the current evidence.

Crohn's Disease: Potential Drugs for Modulation of Autophagy

Autophagy is an intracellular process whereby cytoplasmic constituents are degraded within lysosomes. Autophagy functions to eliminate unwanted or damaged materials such as proteins and organelles as their accumulation would be harmful to the cellular system. Autophagy also acts as a defense mechanism against invading pathogens and plays an important role in innate and adaptive immunity. In physiological processes, autophagy is involved in the regulation of tissue development, differentiation and remodeling, which are essential for maintaining cellular homeostasis. Recent studies have demonstrated that autophagy is linked to various diseases and involved in pathophysiological roles, such as adaptation during starvation, anti-aging, antigen presentation, tumor suppression and cell death. The modulation of autophagy has shown greatest promise in Crohn’s disease as most of autophagy drugs involved in these diseases are currently under clinical trials and some has been approved by Food and Drug Administration. This review article discusses autophagy and potential drugs that are currently available for its modulation in Crohn’s disease.

Polymorphisms of cytokine genes and tuberculosis in two independent studies

Cytokine gene single nucleotide polymorphisms (SNPs) can influence cytokine levels, which may be associated with tuberculosis (TB) susceptibility. There is evidence that interleukin 1B (IL1B), tumor necrosis factor-alpha (TNF-alpha), and IL6 may be involved in the progression of TB. Using a self-validating case-control design, we selected eleven functional SNPs in IL1B, TNF and IL6 to detect their association with TB in Chinese Han and Tibetan populations. The associations between SNPs and TB were estimated by computing the odds ratios (ORs) and 95% confidence intervals (95% CI) using logistic regression analyses. We found that the IL1B rs16944 polymorphism was associated with decreased risk of TB in the two studies. The G allele at rs2069837 of IL6 was significantly more common in controls than in TB patients in the Han population. Moreover, TNF rs1799964 and rs1800630 were risk factors for susceptibility to TB, which were validated in the Chinese Tibetan population. In addition, TNF rs1799724 and rs1800629 were associated with TB, but only in the Tibetan population. In conclusion, SNPs of the IL1B and TNF gene were associated with TB susceptibility in Chinese Han and Tibetan populations. IL6 polymorphism may be considered as a protective factor for TB in the Chinese Han population, but not the Tibetan population.

ATP redirects cytokine trafficking and promotes novel membrane TNF signaling via microvesicles

Cellular stress or injury induces release of endogenous danger signals such as ATP, which plays a central role in activating immune cells. ATP is essential for the release of nonclassically secreted cytokines such as IL-1β but, paradoxically, has been reported to inhibit the release of classically secreted cytokines such as TNF. Here, we reveal that ATP does switch off soluble TNF (17 kDa) release from LPS-treated macrophages, but rather than inhibiting the entire TNF secretion, ATP packages membrane TNF (26 kDa) within microvesicles (MVs). Secretion of membrane TNF within MVs bypasses the conventional endoplasmic reticulum- and Golgi transport-dependent pathway and is mediated by acid sphingomyelinase. These membrane TNF-carrying MVs are biologically more potent than soluble TNF in vivo, producing significant lung inflammation in mice. Thus, ATP critically alters TNF trafficking and secretion from macrophages, inducing novel unconventional membrane TNF signaling via MVs without direct cell-to-cell contact. These data have crucial implications for this key cytokine, particularly when therapeutically targeting TNF in acute inflammatory diseases.-Soni, S., O'Dea, K. P., Tan, Y. Y., Cho, K., Abe, E., Romano, R., Cui, J., Ma, D., Sarathchandra, P., Wilson, M. R., Takata, M. ATP redirects cytokine trafficking and promotes novel membrane TNF signaling via microvesicles.

Emodin Alleviates Liver Fibrosis of Mice by Reducing Infiltration of Gr1hi Monocytes

Emodin, as a major active component of Rheum palmatum L. and Polygonum cuspidatum, has been reported to have antifibrotic effect. However, the mechanism of emodin on antifibrotic effect for liver fibrosis was still obscure. In the present study, we aimed to investigate whether emodin can alleviate carbon tetrachloride- (CCl₄-) induced liver fibrosis through reducing infiltration of Gr1^hi monocytes. Liver fibrosis was induced by intraperitoneal CCl₄ injection in mice. Mice in the emodin group received emodin treatment by gavage. Pretreatment with emodin significantly protected mice from liver inflammation and fibrosis revealed by the decreased elevation of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST), as well as reduced hepatic necrosis and fibrosis by analysis of hematoxylin-eosin (HE) staining, Masson staining, α-smooth muscle actin (α-SMA), and collagen-I immunohistochemistry staining. Further, compared to CCl₄ group, mice in the emodin group showed significantly less intrahepatic infiltration of Gr1^hi monocytes. Moreover, emodin significantly inhibited hepatic expression of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGF-β1), granulin (GRN), monocyte chemoattractant protein 1 (MCP-1), and chemokine ligand 7 (CCL7), which was in line with the decreased numbers of intrahepatic Gr1^hi monocytes. In conclusion, emodin can alleviate the degree of liver fibrosis by reducing infiltration of Gr1^hi monocytes. These results suggest that emodin is a promising candidate to prevent and treat liver fibrosis.

Mycobacterium tuberculosis hypoxic response protein 1 (Hrp1) augments the pro-inflammatory response and enhances the survival of Mycobacterium smegmatis in murine macrophages

PURPOSE

The DosR/DosS two-component regulatory system of Mycobacterium tuberculosis regulates the expression of numerous genes under stress conditions and is important for the long-term survival of M. tuberculosis in the host. The rv2626c gene of M. tuberculosis is one of the most strongly induced transcripts of the dormancy regulon. This study focused on the immunological effects and possible function of Rv2626c in maintaining mycobacterial survival under various stress conditions.

METHODOLOGY

We heterologously expressed the Rv2626c protein in Mycobacterium smegmatis by constructing a recombinant strain Ms_rv2626c. The viability of Ms_rv2626c was evaluated both in vivo and ex vivo. Different stress conditions, including acidified sodium nitrite, malachite green, low pH, SDS and lysozyme, were used to evaluate the effect of Rv2626c on bacterial resistance. An in vitro assay using a macrophage infection model was utilized to investigate the potential effect of Rv2626c to alter the immune response of host cell and its associated pathways. The effect of Rv2626c on cell necrosis was also explored.

RESULTS

The expression of Rv2626c-enhanced M. smegmatis survival under hypoxia and nitric oxide stress in vitro, and this enhancement was maintained within macrophages and in mouse tissues. In addition, macrophages infected with M. smegmatis expressing Rv2626c showed significantly higher interleukin-1β (IL-1β), IL-6, tumour necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) expression, as well as a higher level of cell necrosis, compared with the control.

CONCLUSION

M. tuberculosis protein Rv2626c plays a significant role in stimulating macrophages to provoke a pro-inflammatory response and in mycobacterial survival during infection.

Influence of lung CT changes in chronic obstructive pulmonary disease (COPD) on the human lung microbiome

BACKGROUND

Changes in microbial community composition in the lung of patients suffering from moderate to severe COPD have been well documented. However, knowledge about specific microbiome structures in the human lung associated with CT defined abnormalities is limited.

METHODS

Bacterial community composition derived from brush samples from lungs of 16 patients suffering from different CT defined subtypes of COPD and 9 healthy subjects was analyzed using a cultivation independent barcoding approach applying 454-pyrosequencing of 16S rRNA gene fragment amplicons.

RESULTS

We could show that bacterial community composition in patients with changes in CT (either airway or emphysema type changes, designated as severe subtypes) was different from community composition in lungs of patients without visible changes in CT as well as from healthy subjects (designated as mild COPD subtype and control group) (PC1, Padj = 0.002). Higher abundance of Prevotella in samples from patients with mild COPD subtype and from controls and of Streptococcus in the severe subtype cases mainly contributed to the separation of bacterial communities of subjects. No significant effects of treatment with inhaled glucocorticoids on bacterial community composition were detected within COPD cases with and without abnormalities in CT in PCoA. Co-occurrence analysis suggests the presence of networks of co-occurring bacteria. Four communities of positively correlated bacteria were revealed. The microbial communities can clearly be distinguished by their associations with the CT defined disease phenotype.

CONCLUSION

Our findings indicate that CT detectable structural changes in the lung of COPD patients, which we termed severe subtypes, are associated with alterations in bacterial communities, which may induce further changes in the interaction between microbes and host cells. This might result in a changed interplay with the host immune system.

Topical nitric oxide releasing nanoparticles are effective in a murine model of dermal Trichophyton rubrum dermatophytosis

Systemic therapies are preferred for treating dermal dermatophytosis due to inadequate penetration of topical agents. However, systemic antifungals are associated with off-target effects and limited tissue penetration, and antimicrobial resistance is a growing concern. To address this, we investigated topical nitric oxide-releasing nanoparticles (NO-np), which have been used against superficial fungal infections and bacterial abscesses. In addition to enhanced penetration and permeation conferred by nanoparticles, nitric oxide, a broad-spectrum multi-mechanistic antimicrobial agent, offers decreased likelihood of resistance development. In the current study, NO-np inhibited Trichophyton rubrum in vitro, as well as in a murine model of dermal dermatophytosis. In mice, NO-np reduced fungal burden after three days, with complete clearance after seven. Furthermore, NO-np decreased tissue IL-2, 6, 10 and TNFα, indicating earlier attenuation of the host inflammatory response and decreased tissue morbidity. Thus, topical NO-np represent an attractive alternative to systemic therapy against dermal T. rubrum infection.

Human Immunology of Tuberculosis

Immunology is a central theme when it comes to tuberculosis (TB). The outcome of human infection with Mycobacterium tuberculosis is dependent on the ability of the immune response to clear or contain the infection. In cases where this fails, the bacterium replicates, disseminates within the host, and elicits a pathologic inflammatory response, and disease ensues. Clinical presentation of TB disease is remarkably heterogeneous, and the disease phenotype is largely dependent on host immune status. Onward transmission of M. tuberculosis to new susceptible hosts is thought to depend on an excessive inflammatory response causing a breakdown of the lung matrix and formation of lung cavities. But this varies in cases of underlying immunological dysfunction: for example, HIV-1 infection is associated with less cavitation, while diabetes mellitus comorbidity is associated with increased cavitation and risk of transmission. In compliance with the central theme of immunology in tuberculosis, we rely on detection of an adaptive immune response, in the form of interferon-gamma release assays or tuberculin skin tests, to diagnose infection with M. tuberculosis. Here we review the immunology of TB in the human host, focusing on cellular and humoral adaptive immunity as well as key features of innate immune responses and the underlying immunological dysfunction which associates with human TB risk factors. Our review is restricted to human immunology, and we highlight distinctions from the immunological dogma originating from animal models of TB, which pervade the field.

Human Lung Mononuclear Phagocytes in Health and Disease

The lungs are vulnerable to attack by respiratory insults such as toxins, allergens, and pathogens, given their continuous exposure to the air we breathe. Our immune system has evolved to provide protection against an array of potential threats without causing collateral damage to the lung tissue. In order to swiftly detect invading pathogens, monocytes, macrophages, and dendritic cells (DCs)-together termed mononuclear phagocytes (MNPs)-line the respiratory tract with the key task of surveying the lung microenvironment in order to discriminate between harmless and harmful antigens and initiate immune responses when necessary. Each cell type excels at specific tasks: monocytes produce large amounts of cytokines, macrophages are highly phagocytic, whereas DCs excel at activating naïve T cells. Extensive studies in murine models have established a division of labor between the different populations of MNPs at steady state and during infection or inflammation. However, a translation of important findings in mice is only beginning to be explored in humans, given the challenge of working with rare cells in inaccessible human tissues. Important progress has been made in recent years on the phenotype and function of human lung MNPs. In addition to a substantial population of alveolar macrophages, three subsets of DCs have been identified in the human airways at steady state. More recently, monocyte-derived cells have also been described in healthy human lungs. Depending on the source of samples, such as lung tissue resections or bronchoalveolar lavage, the specific subsets of MNPs recovered may differ. This review provides an update on existing studies investigating human respiratory MNP populations during health and disease. Often, inflammatory MNPs are found to accumulate in the lungs of patients with pulmonary conditions. In respiratory infections or inflammatory diseases, this may contribute to disease severity, but in cancer patients this may improve clinical outcomes. By expanding on this knowledge, specific lung MNPs may be targeted or modulated in order to attain favorable responses that can improve preventive or treatment strategies against respiratory infections, lung cancer, or lung inflammatory diseases.

Mycobacterium tuberculosis Peptidyl-Prolyl Isomerases Are Immunogenic, Alter Cytokine Profile and Aid in Intracellular Survival

Mycobacterium tuberculosis (M. tb) has two peptidyl-prolyl isomerases (Ppiases) PpiA and PpiB, popularly known as cyclophilin A and cyclophilin B. The role of cyclophilins in processes such as signaling, cell surface recognition, chaperoning, and heat shock response has been well-documented. We present evidence that M. tb Ppiases modulate the host immune response. ELISA results revealed significant presence of antibodies to M. tb Ppiases in patient sera as compared to sera from healthy individuals. Treatment of THP-1 cells with increasing concentrations of rPpiA, induced secretion of pro-inflammatory cytokines TNF-α and IL-6. Alternatively, treatment with rPpiB inhibited secretion of TNF-α and induced secretion of IL-10. Furthermore, heterologous expression of M. tb PpiA and PpiB in Mycobacterium smegmatis increased bacterial survival in THP-1 cells as compared to those transformed with the vector control. Our results demonstrate that M. tb Ppiases are immunogenic proteins that can possibly modulate host immune response and enhance persistence of the pathogen within the host by subverting host cell generated stresses.

Low Dose BCG Infection as a Model for Macrophage Activation Maintaining Cell Viability

Mycobacterium bovis BCG, the current vaccine against tuberculosis, is ingested by macrophages promoting the development of effector functions including cell death and microbicidal mechanisms. Despite accumulating reports on M. tuberculosis, mechanisms of BCG/macrophage interaction remain relatively undefined. In vivo, few bacilli are sufficient to establish a mycobacterial infection; however, in vitro studies systematically use high mycobacterium doses. In this study, we analyze macrophage/BCG interactions and microenvironment upon infection with low BCG doses and propose an in vitro model to study cell activation without affecting viability. We show that RAW macrophages infected with BCG at MOI 1 activated higher and sustained levels of proinflammatory cytokines and transcription factors while MOI 0.1 was more efficient for early stimulation of IL-1β, MCP-1, and KC. Both BCG infection doses induced iNOS and NO in a dose-dependent manner and maintained nuclear and mitochondrial structures. Microenvironment generated by MOI 1 induced macrophage proliferation but not MOI 0.1 infection. In conclusion, BCG infection at low dose is an efficient in vitro model to study macrophage/BCG interactions that maintains macrophage viability and mitochondrial structures. This represents a novel model that can be applied to BCG research fields including mycobacterial infections, cancer immunotherapy, and prevention of autoimmunity and allergies.

The Role of Interleukin-23 in the Early Development of Emphysema in HIV1(+) Smokers

Rationale. Matrix metalloproteinase-9 (MMP-9) expression is upregulated in alveolar macrophages (AM) of HIV1⁺ smokers who develop emphysema. Knowing that lung epithelial lining fluid (ELF) of HIV1⁺ smokers contains increased levels of inflammatory cytokines compared to HIV1⁻ smokers, we hypothesized that upregulation of lung cytokines in HIV1⁺ smokers may be functionally related to increased MMP-9 expression. Methods. Cytokine arrays evaluated cytokine protein levels in ELF obtained from 5 groups of individuals: HIV1⁻ healthy nonsmokers, HIV1⁻ healthy smokers, HIV1⁻ smokers with low diffusing capacity (DL_CO), HIV1⁺ nonsmokers, and HIV1⁺ smokers with low DL_CO. Results. Increased levels of the Th17 related cytokine IL-23 were found in HIV1⁻ smokers with low DL_CO and HIV1⁺ smokers and nonsmokers. Relative IL-23 gene expression was increased in AM of HIV1⁺ individuals, with greater expression in AM of HIV1⁺ smokers with low DL_CO. Infection with HIV1 in vitro induced IL-23 expression in normal AM. IL-23 stimulation of AM/lymphocyte cocultures in vitro induced upregulation of MMP-9. Lung T lymphocytes express receptor IL-23R and interact with AM in order to upregulate MMP-9. Conclusion. This mechanism may contribute to the increased tissue destruction in the lungs of HIV1⁺ smokers and suggests that Th17 related inflammation may play a role.

TNF-α -238, -308, -863 polymorphisms, and brucellosis infection

BACKGROUND

Brucella abortus is an intracellular bacterium that affects humans and domestic animals. Tumor necrosis factor-alpha (TNF-α) has been shown as a key player in the induction of cell-mediated resistance against Brucella infection. We aimed to evaluate the possible influence of the TNF-α promoter polymorphisms (-308 G/A, -238 G/A, and -863 C/A) on the susceptibility of human brucellosis.

METHODOLOGY

A total of 153 patients with active brucellosis and 128 healthy individuals were recruited. All subjects were genotyped for the polymorphisms in the TNF-α gene by Allele-Specific polymerase chain reaction analysis.

RESULTS

Our results showed that the TNF-α -308 GG genotype was significantly more frequently present in controls than in brucellosis patients (91% vs. 75%), thus was a protective factor against developing brucellosis (OR=0.313, p=0.001). In contrast, the -308 GA genotype (OR=3.026, p=0.002) and minor allele (A) (OR=3.058, p=0.001) as well as AAG haplotype (OR=4.014, p=0.001) conferred an increased risk of brucellosis. However, the -238 G/A and -863 C/A polymorphisms were not associated with the risk of brucellosis at both allelic and genotypic levels (p>0.05).

CONCLUSION

Our study revealed that the TNF-α -308 A allele or GA heterozygosity or AAG haplotype were associated with an increased risk of brucellosis in our population.

Lipoarabinomannan, and its related glycolipids, induce divergent and opposing immune responses to Mycobacterium tuberculosis depending on structural diversity and experimental variations

Exposure to Mycobacterium tuberculosis (Mtb) may lead to active or latent tuberculosis, or clearance of Mtb, depending essentially on the quality of the host's immune response. This response is initiated through the interaction of Mtb cell wall surface components, mostly glycolipids, with cells of the innate immune system, particularly macrophages (Mφs) and dendritic cells (DCs). The way Mφs and DC alter their cytokine secretome, activate or inhibit different microbicidal mechanisms and present antigens and consequently trigger the T cell-mediated immune response impacts the host immune response against Mtb. Lipoarabinomannan (LAM) is one of the major cell wall components of Mtb. Mannosyl-capped LAM (ManLAM), and its related cell wall-associated types of glycolipids/lipoglycans, namely phosphatidylinositol mannosides (PIMs) and lipomannan (LM), exhibit important and distinct immunomodulatory properties. The structure, internal heterogeneity and abundance of these molecules vary between Mtb strains exhibiting distinct degrees of virulence. Thus ManLAM, LM and PIMs may be considered crucial Mtb-associated virulence factors in the pathogenesis of tuberculosis. Of particular relevance for this review, there is controversy about the specific immunomodulatory properties of these distinct glycolipids, particularly when tested as purified molecules in vitro. In addition to the variability in the glycolipid composition conflicting reports may also result from differences in the protocols used for glycolipid isolation and for in vitro experiments including immune cell types and procedures to generate them. Understanding the immunomodulatory properties of these cell wall glycolipids, how they differ between distinct Mtb strains, and how they influence the degree of Mtb virulence, is of utmost relevance to understand how the host mounts a protective or otherwise pathologic immune response. This is essential for the design of preventive strategies against tuberculosis. Thus, since clarifying the controversy on this matter is crucial we here review, summarize and discuss reported data from in vitro stimulation with the three major Mtb complex cell wall glycolipids (ManLAM, PIMs and LM) in an attempt to conciliate the conflicting findings.

Lymphangiogenesis is induced by mycobacterial granulomas via vascular endothelial growth factor receptor-3 and supports systemic T-cell responses against mycobacterial antigen

Granulomatous inflammation is characteristic of many autoimmune and infectious diseases. The lymphatic drainage of these inflammatory sites remains poorly understood, despite an expanding understanding of lymphatic role in inflammation and disease. Here, we show that the lymph vessel growth factor Vegf-c is up-regulated in Bacillus Calmette-Guerin- and Mycobacterium tuberculosis-induced granulomas, and that infection results in lymph vessel sprouting and increased lymphatic area in granulomatous tissue. The observed lymphangiogenesis during infection was reduced by inhibition of vascular endothelial growth factor receptor 3. By using a model of chronic granulomatous infection, we also show that lymphatic remodeling of tissue persists despite resolution of acute infection and a 10- to 100-fold reduction in the number of bacteria and tissue-infiltrating leukocytes. Inhibition of vascular endothelial growth factor receptor 3 decreased the growth of new vessels, but also reduced the proliferation of antigen-specific T cells. Together, our data show that granuloma-up-regulated factors increase granuloma access to secondary lymph organs by lymphangiogenesis, and that this process facilitates the generation of systemic T-cell responses to granuloma-contained antigens.

Factors affecting the tuberculosis risk in patients receiving anti-tumor necrosis factor-α treatment

BACKGROUND

Tumor necrosis factor (TNF)-α inhibitors are known to increase the risk of tuberculosis (TB).

OBJECTIVES

To examine the factors associated with an increased risk of TB in patients receiving anti-TNF-α treatment (aTNF-α-T).

METHOD

Of 3,094 patients who received aTNF-α-T between 2003 and 2013, a total of 1,964 subjects with a follow-up time longer than 6 months were identified and included in this retrospective analysis. Potential risk factors for the development of TB in patients receiving aTNF-α-T were evaluated.

RESULTS

Of the 1,964 patients, 1,009 (51%) were male and 955 (49%) were female, with a mean age of 39.7 ± 13.9 years. The primary conditions requiring aTNF-α-T included ankylosing spondylitis (n = 875), rheumatoid arthritis (n = 711), Behçet's disease (n = 83), and others (n = 295). Sixteen patients [8 (50%) males and 8 (50%) females; 5 (31.2%) with pulmonary TB and 11 (68.8%) with extrapulmonary TB] developed TB, with a corresponding TB incidence of 466/100,000. No significant associations were found between age, gender, smoking history, pack-years of smoking, isoniazid (INH) chemoprophylaxis, type of anti-TNF-α agent, use of other immunosuppressive drugs, and the risk of TB (p > 0.05). Multivariate logistic regression analysis showed a significantly higher risk of TB in patients diagnosed with Behçet's disease, and a significantly lower risk of TB in patients with a tuberculin skin test wheal ≥10 mm in diameter (p < 0.05).

CONCLUSION

aTNF-α-T is associated with an increased risk of pulmonary or extrapulmonary TB, even when follow-up protocols and INH chemoprophylaxis are implemented, and TB often develops in the later stages of treatment. The risk of TB was higher in patients with Behçet's disease and lower in patients who had a strong tuberculin skin test reaction.

Mycobacterium tuberculosis RecA is indispensable for inhibition of the mitogen-activated protein kinase-dependent bactericidal activity of THP-1-derived macrophages in vitro

Our knowledge about the mechanisms utilized by Mycobacterium tuberculosis to survive inside macrophages is still incomplete. One of the mechanism that protects M. tuberculosis from the host's microbicidal products and allows bacteria to survive involves DNA repair systems such as the homologous recombination (HR) and nonhomologous end-joining (NHEJ) pathways. It is accepted that any pathway that contributes to genome maintenance should be considered as potentially important virulence factor. In these studies, we investigated reactive oxygen species, nitric oxide and tumor necrosis factor-α production by macrophages infected with wild-type M. tuberculosis, with an HR-defective mutant (∆recA), with an NHEJ-defective mutant [∆(ku,ligD)], with a mutant defective for both HR and NHEJ [∆(ku,ligD,recA)], or with appropriate complemented strains. We also assessed the involvement of extracellular signal-regulated kinases (ERKs) 1 and 2 in the response of macrophages to infection with the above-mentioned strains, and ERK1/2 phosphorylation in M. tuberculosis-infected macrophages. We found that mutants lacking RecA induced a greater bactericidal response by macrophages than did the wild-type strain or an NHEJ-defective mutant, and activated ERK1/2 was involved only in the response of macrophages to recA deletion mutants [∆(ku,ligD,recA) and ∆recA]. We also demonstrated that only the triple mutant induced ERK1/2 phosphorylation in phorbol-12-myristate-13-acetate-stimulated macrophages. Moreover, HR-defective mutants induced lower amounts of tumor necrosis factor-α secretion than did the wild-type or ∆(ku,ligD). Our results indicate that RecA contributes to M. tuberculosis virulence, and also suggest that diminished ERK1/2 activation in macrophages infected with M. tuberculosis possessing recA may be an important mechanism by which wild-type mycobacteria escape intracellular killing.

Higher risk of tuberculosis reactivation when anti-TNF is combined with immunosuppressive agents: a systematic review of randomized controlled trials

OBJECTIVE

Treatment with tumour necrosis factor antagonists (anti-TNF) has been recognized as a risk factor for tuberculosis (TB) reactivation. Our aim was to evaluate risk of TB reactivation in rheumatologic and non-rheumatologic diseases treated with the same anti-TNF agents with and without concomitant therapies.

METHODS

We searched for randomized controlled trials (RCTs) evaluating infliximab, adalimumab, and certolizumab in both rheumatologic and non-rheumatologic diseases until 2012. Results were calculated as pooled rates and/or pooled odd ratios (OR).

RESULTS

Overall, 40 RCTs with a total of 14,683 patients (anti-TNF: 10,010; placebo: 4673) were included. TB reactivation was 0.26% (26/10,010) in the anti-TNF group and 0% (0/4673) in the control group, corresponding to an OR of 24.8 (95% CI 2.4-133). TB risk was higher when anti-TNF agents were combined with methotrexate or azathioprine as compared with either controls (24/4241 versus 0/4673; OR 54; 95% CI 5.3-88) or anti-TNF monotherapy (24/4241 versus 2/5769; OR 13.3; 95% CI 3.7-100). When anti-TNF was used as monotherapy, TB risk tended to be higher than placebo (2/5769 versus 0/4673; OR 4; 95% CI 0.2-15.7).

CONCLUSIONS

TB risk with anti-TNF agents appeared to be increased when these agents were used in combination with methotrexate or azathioprine as compared with monotherapy regimen. TB risk seemed to be higher than placebo, even when monotherapy is prescribed.

MRP8/14 induces autophagy to eliminate intracellular Mycobacterium bovis BCG

OBJECTIVE

To explore the role of myeloid-related protein 8/14 in mycobacterial infection.

METHODS

The mRNA and protein expression levels of MRP8 or MRP14 were measured by real-time PCR and flow cytometry, respectively. Role of MRP8/14 was tested by overexpression or RNA interference assays. Flow cytometry and colony forming unit were used to test the phagocytosis and the survival of intracellular Mycobacterium bovis BCG (BCG), respectively. Autophagy mediated by MRP8/14 was detected by Western blot and immunofluorescence. The colocalization of BCG phagosomes with autophagosomes or lysosomes was by detected by confocal microscopy. ROS production was detected by flow cytometry.

RESULTS

MRP8/14 expressions were up-regulated in human monocytic THP1 cells and primary macrophages after mycobacterial challenge. Silencing of MRP8/14 suppressed bacterial killing, but had no influence on the phagocytosis of BCG. Importantly, silencing MRP8/14 decreased autophagy and BCG phagosome maturation in THP1-derived macrophages, thereby increasing the BCG survival. Additionally, we demonstrated that MRP8/14 promoted autophagy in a ROS-dependent manner.

CONCLUSIONS

The present study revealed a novel role of MRP8/14 in the autophagy-mediated elimination of intracellular BCG by promoting ROS generation, which may provide a promising therapeutic target for tuberculosis and other intracellular bacterial infectious diseases.

Mycobacterium tuberculosis Rv3402c enhances mycobacterial survival within macrophages and modulates the host pro-inflammatory cytokines production via NF-kappa B/ERK/p38 signaling

Intracellular survival plays a central role in the pathogenesis of Mycobacterium tuberculosis, a process which depends on an array of virulence factors to colonize and replicate within the host. The M. tuberculosis iron regulated open reading frame (ORF) rv3402c, encoding a conserved hypothetical protein, was shown to be up-regulated upon infection in both human and mice macrophages. To explore the function of this ORF, we heterologously expressed the rv3402c gene in the non-pathogenic fast-growing Mycobacterium smegmatis strain, and demonstrated that Rv3402c, a cell envelope-associated protein, was able to enhance the intracellular survival of recombinant M. smegmatis. Enhanced growth was not found to be the result of an increased resistance to intracellular stresses, as growth of the Rv3402c expressing strain was unaffected by iron depletion, H₂O₂ exposure, or acidic conditions. Colonization of macrophages by M. smegmatis expressing Rv3402c was associated with substantial cell death and significantly greater amount of TNF-α and IL-1β compared with controls. Rv3402c-induced TNF-α and IL-1β production was found to be mediated by NF-κB, ERK and p38 pathway in macrophages. In summary, our study suggests that Rv3402c delivered in a live M. smegmatis vehicle can modify the cytokines profile of macrophage, promote host cell death and enhance the persistence of mycobacterium within host cells.

Soluble TNFRp75 regulates host protective immunity against Mycobacterium tuberculosis

Development of host protective immunity against Mycobacterium tuberculosis infection is critically dependent on the inflammatory cytokine TNF. TNF signals through 2 receptors, TNFRp55 and TNFRp75; however, the role of TNFRp75-dependent signaling in immune regulation is poorly defined. Here we found that mice lacking TNFRp75 exhibit greater control of M. tuberculosis infection compared with WT mice. TNFRp75-/- mice developed effective bactericidal granulomas and demonstrated increased pulmonary recruitment of activated DCs. Moreover, IL-12p40-dependent migration of DCs to lung draining LNs of infected TNFRp75-/- mice was substantially higher than that observed in WT M. tuberculosis-infected animals and was associated with enhanced frequencies of activated M. tuberculosis-specific IFN-γ-expressing CD4+ T cells. In WT mice, TNFRp75 shedding correlated with markedly reduced bioactive TNF levels and IL-12p40 expression. Neutralization of TNFRp75 in M. tuberculosis-infected WT BM-derived DCs (BMDCs) increased production of bioactive TNF and IL-12p40 to a level equivalent to that produced by TNFRp75-/- BMDCs. Addition of exogenous TNFRp75 to TNFRp75-/- BMDCs infected with M. tuberculosis decreased IL-12p40 synthesis, demonstrating that TNFRp75 shedding regulates DC activation. These data indicate that TNFRp75 shedding downmodulates protective immune function and reduces host resistance and survival; therefore, targeting TNFRp75 may be beneficial for improving disease outcome.

Prominent role for T cell-derived tumour necrosis factor for sustained control of Mycobacterium tuberculosis infection

Tumour Necrosis Factor (TNF) is critical for host control of M. tuberculosis, but the relative contribution of TNF from innate and adaptive immune responses during tuberculosis infection is unclear. Myeloid versus T-cell-derived TNF function in tuberculosis was investigated using cell type-specific TNF deletion. Mice deficient for TNF expression in macrophages/neutrophils displayed early, transient susceptibility to M. tuberculosis but recruited activated, TNF-producing CD4⁺ and CD8⁺ T-cells and controlled chronic infection. Strikingly, deficient TNF expression in T-cells resulted in early control but susceptibility and eventual mortality during chronic infection with increased pulmonary pathology. TNF inactivation in both myeloid and T-cells rendered mice critically susceptible to infection with a phenotype resembling complete TNF deficient mice, indicating that myeloid and T-cells are the primary TNF sources collaborating for host control of tuberculosis. Thus, while TNF from myeloid cells mediates early immune function, T-cell derived TNF is essential to sustain protection during chronic tuberculosis infection.

Identification of a new tuberculosis antigen recognized by γδ T cell receptor

The immune protection initiated by γδ T cells plays an important role in mycobacterial infection. The γδ T cells activated by Mycobacterium tuberculosis-derived nonpeptidic, phosphorylated biometabolites (phosphoantigens) provide only partial immune protection against mycobacterium, while evidence has suggested that protein antigen-activated γδ T cells elicit effective protective immune responses. To date, only a few distinct mycobacterial protein antigens have been identified. In the present study, we screened protein antigens recognized by γδ T cells using cells transfected with the predominant pulmonary tuberculosis γδ T cell receptor (TCR) CDR3 fragment. We identified two peptides, TP1 and TP2, which not only bind to the pulmonary tuberculosis predominant γδ TCR but also effectively activate γδ T cells isolated from pulmonary tuberculosis patients. Moreover, 1-deoxy-d-xylulose 5-phosphate synthase 2 (DXS2), the TP1-matched mycobacterial protein, was confirmed as a ligand for the γδ TCR and was found to activate γδ T cells from pulmonary tuberculosis patients. The extracellular region (extracellular peptide [EP]) of Rv2272, a TP2-matched mycobacterial transmembrane protein, was also shown to activate γδ T cells from pulmonary tuberculosis patients. Both DXS2- and EP-expanded γδ T cells from pulmonary tuberculosis patients could secrete gamma interferon (IFN-γ) and monocyte chemoattractant protein 1 (MCP-1), which play important roles in mediating cytotoxicity against mycobacterium and stimulating monocyte chemotaxis toward the site of infection. In conclusion, our study identified novel mycobacterial protein antigens recognized by γδ TCR cells that could be candidates for the development of vaccines or adjuvants against mycobacterium infection.

Association between tumor necrosis factor alpha-238G/a polymorphism and tuberculosis susceptibility: a meta-analysis study

Background

Tumor necrosis factor alpha (TNF-α) plays a key role in the containment of tuberculosis. The relationship between the TNF -238G/A polymorphism and tuberculosis susceptibility remains inconclusive. A comprehensive meta-analysis was made to provide a more precise estimate of the relationship between them.

Methods

Multiple search strategies were used. A fixed effect model was takentook to estimate pooled OR with 95% confidence interval (CI) for the association between the TNF -238G/A polymorphism and tuberculosis susceptibility. The Chi-squared-based Q-test and I-squaredI² statistic were calculated to examine heterogeneity. Begg’s funnel plot and Egger’s test were used to assess publication bias.

Results

9 case-control studies were included in this meta-analysis. No significant heterogeneity was demonstrated, and no obvious publication bias was detected among the included studies. The meta-analysis indicated that there was no significant association between the TNF -238G/A polymorphism and tuberculosis susceptibility (GA+AA versus GG model: OR=1.005, 95% CI: 0.765-1.319; A versus G model: OR=1.000, 95% CI: 0.769-1.300). In the subgroup analyses by ethnicity, types of TB and human immunodeficiency virus (HIV) status, no significant association were identified.

Conclusions

The meta-analysis involving 2723 subjects did not detect any association between the TNF -238G/A polymorphism and tuberculosis susceptibility.

Divergent effects of mycobacterial cell wall glycolipids on maturation and function of human monocyte-derived dendritic cells

BACKGROUND

Mycobacterium tuberculosis (Mtb) is able to evade the immune defenses and may persist for years, decades and even lifelong in the infected host. Mtb cell wall components may contribute to such persistence by modulating several pivotal types of immune cells. Dendritic cells (DCs) are the most potent antigen-presenting cells and hence play a crucial role in the initial immune response to infections by connecting the innate with the adaptive immune system.

PRINCIPAL FINDINGS

We investigated the effects of two of the major mycobacterial cell wall-associated types of glycolipids, mannose-capped lipoarabinomannan (ManLAM) and phosphatidylinositol mannosides (PIMs) purified from the Mtb strains H37Rv and Mycobacterium bovis, on the maturation and cytokine profiles of immature human monocyte-derived DCs. ManLAM from Mtb H37Rv stimulated the release of pro-inflammatory cytokines TNF, IL-12, and IL-6 and expression of co-stimulatory (CD80, CD86) and antigen-presenting molecules (MHC class II). ManLAM from M. bovis also induced TNF, IL-12 and IL-6 but at significantly lower levels. Importantly, while ManLAM was found to augment LPS-induced DC maturation and pro-inflammatory cytokine production, addition of PIMs from both Mtb H37Rv and M. bovis strongly reduced this stimulatory effect.

CONCLUSIONS

These results indicate that the mycobacterial cell wall contains macromolecules of glycolipid nature which are able to induce strong and divergent effects on human DCs; i.e while ManLAM is immune-stimulatory, PIMs act as powerful inhibitors of DC cytokine responses. Thus PIMs may be important Mtb-associated virulence factors contributing to the pathogenesis of tuberculosis disease. These findings may also aid in the understanding of some earlier conflicting reports on the immunomodulatory effects exerted by different ManLAM preparations.

Evaluation of the cell growth of mycobacteria using Mycobacterium smegmatis mc2 155 as a representative species

The study of the in vitro cell growth of mycobacteria still remains a fastidious, difficult, and time-consuming procedure. In addition, assessing mycobacterial growth in the laboratory is often complicated by cell aggregation and slow growth-rate. We now report that the use of a stainless steel spring in the culture led to an absence of large cell clumps, to a decrease of dead cells in the exponential phase and to growth of a more homogeneous population of large cells. We also report that flow cytometry is a rapid, simple and reliable approach to monitor mycobacterial cell growth and viability. Here, we monitored Mycobacterium smegmatis cellular growth by optical density, dry cell mass, and colony forming units; in addition, viability, cell size and granularity profiles were analyzed by flow cytometry, and cell morphology by electron microscopy. Cultures monitored by flow cytometry may lead to a better understanding of the physiology of mycobacteria. Moreover, this methodology may aid in characterizing the cell growth of other fastidious species of microorganisms.

Replication of Crohn's disease-associated AIEC within macrophages is dependent on TNF-α secretion

Adherent and invasive Escherichia coli (AIEC) associated with Crohn's disease are able to survive and to replicate extensively in active phagolysosomes within macrophages. AIEC-infected macrophages release large amounts of tumour necrosis factor-alpha (TNF-α) and do not undergo cell death. The aim of the present study was to determine what benefit AIEC bacteria could gain from inducing the release of large amounts of TNF-α by infected macrophages and to what extent the neutralization of TNF-α could affect AIEC intramacrophagic replication. Our results showed that the amount of TNF-α released by infected macrophages is correlated with the load of intramacrophagic AIEC bacteria and their intracellular replication. TNF-α secretion was not related to the number of bacteria entering host cells because when the number of bacteria internalized in macrophage was decreased by blocking lipid raft-dependent and clathrin-coated pits-dependent endocytosis, the amount of TNF-α secreted by infected macrophages was not modified. Interestingly, dose-dependent increases in the number of intracellular AIEC LF82 bacteria were observed when infected macrophages were stimulated with exogenous TNF-α, and neutralization of TNF-α secreted by AIEC-infected macrophages using anti-TNF-α antibodies induced a significant decrease in the number of intramacrophagic bacteria. These results indicate that AIEC bacteria use TNF-α as a Trojan horse to ensure their intracellular replication because replication of AIEC bacteria within macrophages induces the release of TNF-α, which in turn increases the intramacrophagic replication of AIEC. Neutralizing TNF-α secreted by infected macrophages may represent an effective strategy to control AIEC intracellular replication.

Inhaled therapies for tuberculosis and the relevance of activation of lung macrophages by particulate drug-delivery systems

Pathogenic strains of Mycobacterium tuberculosis (Mtb) induce ‘alternative activation’ of lung macrophages that they colonize, in order to create conditions that promote the establishment and progression of infection. There is some evidence to indicate that such macrophages may be rescued from alternative activation by inhalable microparticles containing a variety of drugs. This review summarizes the experience of various groups of researchers, relating to observations of induction of a number of classical macrophage activation pathways. Restoration of a ‘respiratory burst’ and upregulation of reactive oxygen species and nitrogen intermediates through the phagocyte oxidase and nitric oxide synthetase enzyme systems; induction of proinflammatory macrophage cytokines; and finally induction of apoptosis rather than necrosis of the infected macrophage are discussed. It is suggested that there is scope to co-opt host responses in the management of tuberculosis, through the route of pulmonary drug delivery.