Promotion of Anti-Tuberculosis Macrophage Activity by L-Arginine in the Absence of Nitric Oxide.

Macrophages are indispensable immune cells tasked at eliminating intracellular pathogens. Mycobacterium tuberculosis (Mtb), one of the most virulent intracellular bacterial pathogens known to man, infects and resides within macrophages. While macrophages can be provoked by extracellular stimuli to inhibit and kill Mtb bacilli, these host defense mechanisms can be blocked by limiting nutritional metabolites, such as amino acids. The amino acid L-arginine has been well described to enhance immune function, especially in the context of driving macrophage nitric oxide (NO) production in mice. In this study, we aimed to establish the necessity of L-arginine on anti-Mtb macrophage function independent of NO. Utilizing an in vitro system, we identified that macrophages relied on NO for only half of their L-arginine-mediated host defenses and this L-arginine-mediated defense in the absence of NO was associated with enhanced macrophage numbers and viability. Additionally, we observed macrophage glycolysis to be driven by both L-arginine and mechanistic target of rapamycin (mTOR), and inhibition of glycolysis or mTOR reduced macrophage control of Mtb as well as macrophage number and viability in the presence of L-arginine. Our data underscore L-arginine as an essential nutrient for macrophage function, not only by fueling anti-mycobacterial NO production, but also as a central regulator of macrophage metabolism and additional host defense mechanisms.

Potential benefit of vitamin D supplementation in people with respiratory illnesses, during the COVID-19 pandemic.

This review describes the evidence for the potential benefit of vitamin D supplementation in people with respiratory diseases who may have a higher susceptibility to coronavirus disease 2019 (COVID-19) infection and its consequences. Clinical evidence indicates that vitamin D may reduce the risk of both upper and lower respiratory tract infections and offers benefit particularly in people with vitamin D deficiency. Some evidence exists for a higher incidence of active tuberculosis (TB) in patients who are deficient in vitamin D. An association between low levels of 25(OH)D (the active form of vitamin D) and COVID-19 severity of illness and mortality has also been reported. In addition, low 25(OH)D levels are associated with poor outcomes in acute respiratory distress syndrome (ARDS). The cytokine storm experienced in severe COVID-19 infections results from excessive release of pro-inflammatory cytokines. Due to its immunomodulatory effects, adequate vitamin D levels may cause a decrease in the pro-inflammatory cytokines and an increase in the anti-inflammatory cytokines during COVID-19 infections. Vitamin D deficiency was found in 82.2% of hospitalized COVID-19 cases and 47.2% of population-based controls (p < 0.0001). The available evidence warrants an evaluation of vitamin D supplementation in susceptible populations with respiratory diseases, such as TB, and particularly in those who are deficient in vitamin D. This may mitigate against serious complications of COVID-19 infections or reduce the impact of ARDS in those who have been infected.

The Effects of Oral Liposomal Glutathione and In Vitro Everolimus in Altering the Immune Responses against Mycobacterium bovis BCG Strain in Individuals with Type 2 Diabetes.

Tuberculosis (TB) caused by Mycobacterium tuberculosis (M. tb) still remains a devastating infectious disease in the world. There has been a daunting increase in the incidence of Type 2 Diabetes Mellitus (T2DM) worldwide. T2DM patients are three times more vulnerable to M. tb infection compared to healthy individuals. TB-T2DM coincidence is a challenge for global health control. Despite some progress in the research, M. tb still has unexplored characteristics in successfully evading host defenses. The lengthy duration of treatment, the emergence of multi-drug-resistant strains and extensive-drug-resistant strains of M. tb have made TB treatment very challenging. Previously, we have tested the antimycobacterial effects of everolimus within in vitro granulomas generated from immune cells derived from peripheral blood of healthy subjects. However, the effectiveness of everolimus treatment against mycobacterial infection in individuals with T2DM is unknown. Furthermore, the effectiveness of the combination of in vivo glutathione (GSH) supplementation in individuals with T2DM along with in vitro treatment of isolated immune cells with everolimus against mycobacterial infection has never been tested. Therefore, we postulated that liposomal glutathione (L-GSH) and everolimus would offer great hope for developing adjunctive therapy for mycobacterial infection. L-GSH or placebo was administered to T2DM individuals orally for three months. Study subjects' blood was drawn pre- and post-L-GSH/or placebo supplementation, where Peripheral Blood Mononuclear Cells (PBMCs) were isolated from whole blood to conduct in vitro studies with everolimus. We found that in vitro treatment with everolimus, an mTOR (membrane target of rapamycin) inhibitor, significantly reduced intracellular M. bovis BCG infection alone and in conjunction with L-GSH supplementation. Furthermore, we found L-GSH supplementation coupled with in vitro everolimus treatment produced a greater effect in inhibiting the growth of intracellular Mycobacterium bovis BCG, than with the everolimus treatment alone. We also demonstrated the functions of L-GSH along with in vitro everolimus treatment in modulating the levels of cytokines such as IFN-γ, TNF-α, and IL-2 and IL-6, in favor of improving control of the mycobacterial infection. In summary, in vitro everolimus-treatment alone and in combination with oral L-GSH supplementation for three months in individuals with T2DM, was able to increase the levels of T-helper type 1 (Th1) cytokines IFN-γ, TNF-α, and IL-2 as well as enhance the abilities of granulomas from individuals with T2DM to improve control of a mycobacterial infection.

Immune variations throughout the course of tuberculosis treatment and its relationship with adrenal hormone changes in HIV-1 patients co-infected with Mycobacterium tuberculosis.

HIV infection is a major risk factor predisposing for Mycobacterium tuberculosis infection and progression to active tuberculosis (TB). As host immune response defines the course of infection, we aimed to identify immuno-endocrine changes over six-months of anti-TB chemotherapy in HIV+ people. Plasma levels of cortisol, DHEA and DHEA-S, percentages of CD4+ regulatory T cell subsets and number of IFN-γ-secreting cells were determined. Several cytokines, chemokines and C-reactive protein levels were measured. Results were correlated with clinical parameters as predictors of infection resolution and compared to similar data from HIV+ individuals, HIV-infected persons with latent TB infection and healthy donors. Throughout the course of anti-TB/HIV treatment, DHEA and DHEA-S plasma levels raised while cortisol diminished, which correlated to predictive factors of infection resolution. Furthermore, the balance between cortisol and DHEA, together with clinical assessment, may be considered as an indicator of clinical outcome after anti-TB treatment in HIV+ individuals. Clinical improvement was associated with reduced frequency of unconventional Tregs, increment in IFN-γ-secreting cells, diminution of systemic inflammation and changes of circulating cytokines and chemokines. This study suggests that the combined anti-HIV/TB therapies result in partial restoration of both, immune function and adrenal hormone plasma levels.

Heme oxygenase-1 inhibition promotes IFNγ- and NOS2-mediated control of Mycobacterium tuberculosis infection.

Mycobacterium tuberculosis (Mtb) infection induces pulmonary expression of the heme-degrading enzyme heme oxygenase-1 (HO-1). We have previously shown that pharmacological inhibition of HO-1 activity in experimental tuberculosis results in decreased bacterial loads and unexpectedly that this outcome depends on the presence of T lymphocytes. Here, we extend these findings by demonstrating that IFNγ production by T lymphocytes and NOS2 expression underlie this T-cell requirement and that HO-1 inhibition potentiates IFNγ-induced NOS2-dependent control of Mtb by macrophages in vitro. Among the products of heme degradation by HO-1 (biliverdin, carbon monoxide, and iron), only iron supplementation reverted the HO-1 inhibition-induced enhancement of bacterial control and this reversal was associated with decreased NOS2 expression and NO production. In addition, we found that HO-1 inhibition results in decreased labile iron levels in Mtb-infected macrophages in vitro and diminished iron accumulation in Mtb-infected lungs in vivo. Together these results suggest that the T-lymphocyte dependence of the therapeutic outcome of HO-1 inhibition on Mtb infection reflects the role of the enzyme in generating iron that suppresses T-cell-mediated IFNγ/NOS2-dependent bacterial control. In broader terms, our findings highlight the importance of the crosstalk between iron metabolism and adaptive immunity in determining the outcome of infection.

Levofloxacin based non-rifampicin anti-tuberculous therapy: An effective alternative in renal transplant recipients in resource limited setting.

INTRODUCTION: Rifampicin is one of the most effective components of anti-tuberculous therapy (ATT). Since rifampicin is a hepatic enzyme (CYP3A4) inducer, in a post-renal transplant recipient, the dose of calcineurin inhibitors needs to be up-regulated and frequently monitored. In resource-limited (low- and lower-middle-income countries) setting this is not always feasible. Therefore, we evaluated a non-rifampicin-based ATT using levofloxacin in kidney transplant recipients. METHODS: We retrospectively studied the medical records of renal transplant recipients diagnosed with tuberculosis in our institute between 2014 and 2017. After a brief discussion with patients regarding the nature and course of ATT, those who opted for a non-rifampicin based therapy due to financial constraints were included in the study and followed for a minimum of 6 months period after the completion of ATT. RESULTS: Out of the 550 renal transplant recipients, 67 (12.2%) developed tuberculosis after a median period of 24 (1-228) months following transplantation, of them, 64 patients opted for non-rifampicin-based ATT. The mean age was 37.6 years. Only 25% were given anti-thymocyte globulin based induction, while the majority (56; 87.5%) of them were on tacrolimus-based triple-drug maintenance therapy. Extrapulmonary tuberculosis was noted in 33% of cases, while 12 (18.7%) had disseminated disease. The median duration of treatment was 12 months and the cure rate of 93.7% (n = 60) was achieved at the end of therapy. CONCLUSION: Levofloxacin based ATT appears to be a safe and effective alternative of rifampicin in kidney transplant recipients who cannot afford heightened tacrolimus dosage.

Potential role of adjuvant drugs on efficacy of first line oral antitubercular therapy: Drug repurposing.

Despite the availability of potent antitubercular drugs, tuberculosis (TB) still remains one of the world's leading causes of death. The current antitubercular therapy (ATT) suffers from a drawback of longer duration that imposes a major challenge of patient non compliance and resistance development. The current scenario necessitates alternative strategies with potential to shorten treatment duration that could pave the way for improved clinical outcomes. In recent years, host directed adjunctive therapies have raised considerable attention and emerged as a promising intervention which targets clinically relevant biological pathways in hosts to modulate pathological immune responses. Few of the approved drugs namely statins, metformin, ibuprofen, aspirin, valproic acid, adalimumab, bevacizumab, zileuton and vitamin D3 have shown promising results in clinical outcomes during their preliminary screening in TB patients and can be potentially repurposed as antitubercular drugs. This review highlights clinical and non clinical evidences of some already existing drug and their targets in hosts that could help in shortening treatment duration and reducing bacterial burden at minimal doses.

Minipigs as a neonatal animal model for tuberculosis vaccine efficacy testing.

Many vaccines against childhood diseases are administered early after birth, but vaccine development studies frequently test efficacy in adult rather than in neonatal animal models. In countries with endemic tuberculosis (TB), Bacillus Calmette-Guerin (BCG) is administered as part of the neonatal vaccine regimen because it prevents against the disseminated form of TB in children, although it has variable efficacy against pulmonary TB. Several promising new vaccines against TB are currently being tested in adult animal models. Here we evaluated neonatal piglets as an animal model to test vaccine efficacy. For this purpose, minipigs were vaccinated or not with BCG 48 h after birth and their immune response followed longitudinally until adolescence. We characterized the memory and activation phenotype of T cells, cytokine profile, and monocyte activation in response to BCG stimulation from 4 weeks of age into adolescence- age of 24 weeks. Immunological responses in vaccinated and non-vaccinated animals were further monitored upon infection with a low dose exposure to Mycobacterium tuberculosis strain HN878 via the aerosol route. Comparing the immunological response elicited by BCG vaccination in minipigs vs similar studies in infants, suggest that minipigs have the potential to serve as an effective neonatal animal model for vaccine development.

Scale-Independent Microfluidic Production of Cationic Liposomal Adjuvants and Development of Enhanced Lymphatic Targeting Strategies.

Cationic liposomes prepared from dimethyldioctadecylammonium bromide (DDAB) and trehalose 6,6'-dibehenate (TDB) are strong liposomal adjuvants. As with many liposome formulations, within the laboratory DDAB:TDB is commonly prepared by the thin-film method, which is difficult to scale-up and gives high batch-to-batch variability. In contrast, controllable technologies such as microfluidics offer robust, continuous, and scale-independent production. Therefore, within this study, we have developed a microfluidic production method for cationic liposomal adjuvants that is scale-independent and produces liposomal adjuvants with analogous biodistribution and immunogenicity compared to those produced by the small-scale lipid hydration method. Subsequently, we further developed the DDAB:TDB adjuvant system to include a lymphatic targeting strategy using microfluidics. By exploiting a biotin-avidin complexation strategy, we were able to manipulate the pharmacokinetic profile and enhance targeting and retention of DDAB:TDB and antigen within the lymph nodes. Interestingly, redirecting these cationic liposomal adjuvants did not translate into notably improved vaccine efficacy.

Compounding effect of vitamin D3 diet, supplementation, and alcohol exposure on macrophage response to mycobacterium infection.

Vitamin D3 is known to be a key component in the defense against Mycobacterium tuberculosis (Mtb) infection through the regulation of cytokine and effector molecules. Conversely, alcohol exposure has been recognized as an immune dysregulator. Macrophages were extracted from D3 deficient and sufficient diet mice and supplemented with D3 or exposed to ethanol during ex vivo infection using M. bovis BCG, as a surrogate for Mtb. Results of our study indicate that while exogenous supplementation or alcohol exposure did alter immune response, in vivo diet was the greatest determinant of cytokine and effector molecule production. Alcohol exposure was found to profoundly dysregulate primary murine macrophages, with ethanol-exposed cells generally characterized as hyper- or hyporesponsive. Exogenous D3 supplementation had a normative effect for diet deficient host, however supplementation was not sufficient to compensate for the effects of diet deficiency. Vitamin D3 sufficient diet resulted in reduced cell cytotoxicity for the majority of time points. Results provide insight into the ramifications of both the individual and combined health risks of D3 deficiency or alcohol exposure. Given the clinical relevance of D3 deficiency and alcohol use comorbidities, outcomes of this study have implications in therapeutic approaches for the treatment of tuberculosis disease.

Active Tuberculosis in Patients with Psoriasis Receiving Biologic Therapy: A Systematic Review.

BACKGROUND: Biologic therapies pose a risk for opportunistic infections, especially for reactivating latent tuberculosis infection (LTBI). OBJECTIVE: The aim was to describe the clinical features and mortality rate of active Mycobacterium tuberculosis (TB) in psoriasis patients receiving biologic therapies. METHODS: A systematic review of PubMed, Google Scholar, ScienceDirect, Cochrane Library, and ClinicalTrials.gov databases was performed. Studies describing active TB in patients with psoriasis receiving biologic therapy from inception to May 31, 2018 were included. Clinical data as well as mortality rates were recorded. RESULTS: Fifty-one studies were included, evaluating 78 patients with active TB: 11 prospective studies, 13 retrospective, and 27 case reports/series. Most patients (73%) with active TB were male, the mean age was 48 ± 13 years, and 85% were of European or Asian origin. Pre-treatment LTBI screening was negative for 63% of patients. Disease presented in 33% of patients within the first 3 months of treatment, and in 51% within the first 6 months. Most patients (72%) presented with extra-pulmonary TB, and 49% had disseminated disease. The mortality rate was 7%. LIMITATIONS: Limitations of this review are its small sample size and inclusion of case reports. CONCLUSIONS: Some patients develop active TB despite LTBI screening. Clinicians initiating biologic therapy in patients with psoriasis should be aware of the clinical features of active TB in this scenario.

Malnutrition and Associated Disorders in Tuberculosis and Its Therapy.

Tuberculosis (TB) has become the most important infectious disease to see resurgence worldwide. In 2014, there were 9.6 million documented cases worldwide with a mortality of almost 1.5 million (Global Tuberculosis Report 2014). One of the Millennium Development Goals set by the United Nations was the reversal of the TB epidemic, which has been achieved worldwide with an 18% lower incidence of TB globally compared to the incidence in the year 2000. Though efficient intervention has brought down the relative incidence and mortality of TB globally, the fact remains that one third of the world population has latent TB infection, and 10% of people with latent TB infection develop active TB at some point in their life (The Facts about Tuberculosis 1995). Risk factors that prompt the reactivation of latent TB into active TB are a compromised immune system, HIV, malnutrition, and use of tobacco. In developing and underdeveloped economies, malnutrition and undernutrition play a major role in subverting the immune system and reactivating the latent TB infection. Undernutrition is one of the major factors in India and Southeast Asia leading to an increase in TB infections. Once tuberculosis sets in, it leads to an increase in metabolism and a decrease in appetite that compounds the already present malnutrition. Drawing on previous studies, we have aimed at understanding the relationship between malnutrition and TB infection and making minimal recommendations for corrective action.

Allicin enhances antimicrobial activity of macrophages during Mycobacterium tuberculosis infection.

ETHNOPHARMACOLOGICAL RELEVANCE: The emergence of drug-resistant Mycobacterium tuberculosis (M.tb) strains has severely hampered global efforts towards tuberculosis (TB) eradication. The internationally accepted therapy "Directly Observed Treatment Short-course (DOTS)" is lengthy, and incorporates risks for the generation of drug-resistant M.tb variants. Multiple and extremely drug-resistant (MDR and XDR) variants of TB are now widespread throughout the globe, and totally drug-resistant (TDR) strains have appeared. Therefore, new classes of antibiotics are urgently needed to combat these deadly organisms. Historically, garlic is known to kill mycobacterial strains, and its active compound, allicin, kills various microorganisms. Here we have shown that allicin not only reduced the bacterial burden in the lungs of mice infected with Mycobacterium tuberculosis (M.tb), but also induces strong anti-tubercular immunity. MATERIALS AND METHODS: In the present study, the anti-mycobacterial and immunomodulatory activity of garlic extract and its pure constituent allicin were demonstrated based on several in vitro and in vivo experiments in murine model of tuberculosis. Furthermore, the validation of study was done by immunoblots showing the modulation of MAPK and SAPK/JNK signaling by allicin in macrophages. RESULTS: Here, we report that allicin/garlic extract exhibits strong anti-mycobacterial responses in vitro and in vivo against drug-sensitive, MDR and XDR strains of TB. In addition to direct killing, allicin also induced pro-inflammatory cytokines in macrophages. Moreover, allicin/garlic extract treatment in murine models of infection resulted in induction of strong protective Th1 response, leading to drastic reduction in mycobacterial burden. These results indicated that allicin/garlic extract has both antibacterial and immunomodulatory activity. Furthermore, garlic extract reversed the immune dampening effects of frontline anti-TB drugs. CONCLUSION: Allicin/garlic extract alone or as an adjunct to classical antibiotics holds great promise for treatment of drug-sensitive as well as drug-resistant TB. These results warrant further study and validation of allicin for treatment of TB.

Vitamin B1 Helps to Limit Mycobacterium tuberculosis Growth via Regulating Innate Immunity in a Peroxisome Proliferator-Activated Receptor-γ-Dependent Manner.

It is known that vitamin B1 (VB1) has a protective effect against oxidative retinal damage induced by anti-tuberculosis drugs. However, it remains unclear whether VB1 regulates immune responses during Mycobacterium tuberculosis (MTB) infection. We report here that VB1 promotes the protective immune response to limit the survival of MTB within macrophages and in vivo through regulation of peroxisome proliferator-activated receptor γ (PPAR-γ). VB1 promotes macrophage polarization into classically activated phenotypes with strong microbicidal activity and enhanced tumor necrosis factor-α and interleukin-6 expression at least in part by promoting nuclear factor-κB signaling. In addition, VB1 increases mitochondrial respiration and lipid metabolism and PPAR-γ integrates the metabolic and inflammatory signals regulated by VB1. Using both PPAR-γ agonists and deficient mice, we demonstrate that VB1 enhances anti-MTB activities in macrophages and in vivo by down-regulating PPAR-γ activity. Our data demonstrate important functions of VB1 in regulating innate immune responses against MTB and reveal novel mechanisms by which VB1 exerts its function in macrophages.

Adjuvant Potential of Poly-α-l-Glutamine from the Cell Wall of Mycobacterium tuberculosis.

Novel adjuvants are in demand for improving the efficacy of human vaccines. The immunomodulatory properties of Mycobacterium tuberculosis cell wall components have been highlighted in the formulation of complete Freund's adjuvant (CFA). We have explored the adjuvant potential of poly-α-l-glutamine (PLG), a lesser-known constituent of the pathogenic mycobacterial cell wall. Immune parameters indicated that the adjuvant potency of PLG was statistically comparable to that of CFA and better than that of alum in the context of H1 antigen (Ag85B and ESAT-6 fusion). At 1 mg/dose, PLG augmented the immune response of Ag85B, BP26, and protective antigen (PA) by increasing serum antibodies and cytokines in the culture supernatant of antigen-stimulated splenocytes. PLG modulated the humoral response of vaccine candidate ESAT-6, eliciting significantly higher levels of total IgG and isotypes (IgG1, IgG2a, and IgG2b). Additionally, the splenocytes from PLG-adjuvanted mice displayed a robust increase in the Th1-specific gamma interferon, tumor necrosis factor alpha, interleukin-2 (IL-2), Th2-specific IL-6 and IL-10, and Th17-specific IL-17A cytokines upon antigenic stimulation. PLG improved the protective efficacy of ESAT-6 by reducing bacillary load in the lung and spleen as well as granuloma formation, and it helped in maintaining vital health parameters of mice challenged with M. tuberculosis The median survival time of PLG-adjuvanted mice was 205 days, compared to 146 days for dimethyl-dioctadecyl ammonium bromide-monophosphoryl lipid A (DDA-MPL)-vaccinated groups and 224 days for Mycobacterium bovis BCG-vaccinated groups. PLG enhanced the efficiency of the ESAT-6 vaccine to the level of BCG and better than that of DDA-MPL (P < 0.05), with no ill effect in C57BL/6J mice. Our results propose that PLG is a promising adjuvant candidate for advanced experimentation.

Cigarette Smoking Impairs the Bioenergetic Immune Response to Mycobacterium tuberculosis Infection.

Smoking is a major risk factor driving the tuberculosis epidemic, and smokers' alveolar macrophages (AM) demonstrate significant immune defects after infection. Recently, macrophage glycolytic reprogramming has emerged as crucial in the early host immune response to Mycobacterium tuberculosis (Mtb) infection. In the present study, we sought to compare baseline metabolic characteristics and the glycolytic response to infection of human AM from smokers and nonsmokers. AM were obtained at bronchoscopy, and extracellular flux analyses were performed to determine baseline metabolic characteristics compared with human monocyte-derived macrophages (MDM). Metabolic characterization of AM from smokers and nonsmokers was performed similarly. After infection with Mtb, differences in glycolytic response were measured by extracellular flux analyses and gene expression analyses and correlated with production of glycolysis-driven IL-1ß and prostaglandin E2. Similar experiments were performed in cigarette smoke extract-treated MDM as an alternative model. At baseline, human AM from nonsmokers have a significantly lower extracellular acidification rate/oxygen consumption rate ratio than MDM (P < 0.05), but they retain substantial glycolytic reserve. Compared with nonsmokers' AM, smokers' AM demonstrate reduced metabolic activity, reduced glycolytic reserve (P = 0.051), and reduced spare respiratory capacity (P < 0.01). After infection with Mtb, smokers' AM have significantly reduced glycolytic response, as measured by extracellular flux analyses (P < 0.05) and glycolytic gene expression analyses. Cigarette smoke extract-treated MDM similarly demonstrate reduced metabolic activity and reserves, as well as impaired glycolytic response to infection. Human AM demonstrate metabolic plasticity that allows glycolytic reprogramming to occur after Mtb infection. In smokers, this metabolic reserve is significantly attenuated, with consequent impairment of the glycolytic response to infection.

Vitamin B5 Reduces Bacterial Growth via Regulating Innate Immunity and Adaptive Immunity in Mice Infected with Mycobacterium tuberculosis.

The mechanisms by which vitamins regulate immunity and their effect as an adjuvant treatment for tuberculosis have gradually become very important research topics. Studies have found that vitamin B5 (VB5) can promote epithelial cells to express inflammatory cytokines. We aimed to examine the proinflammatory and antibacterial effect of VB5 in macrophages infected with Mycobacterium tuberculosis (MTB) strain H37Rv and the therapeutic potential of VB5 in vivo with tuberculosis. We investigated the activation of inflammatory signal molecules (NF-κB, AKT, JNK, ERK, and p38), the expression of two primary inflammatory cytokines (tumor necrosis factor and interleukin-6) and the bacterial burdens in H37Rv-infected macrophages stimulated with VB5 to explore the effect of VB5 on the inflammatory and antibacterial responses of macrophages. We further treated the H37Rv-infected mice with VB5 to explore VB5's promotion of the clearance of H37Rv in the lungs and the effect of VB5 on regulating the percentage of inflammatory cells. Our data showed that VB5 enhanced the phagocytosis and inflammatory response in macrophages infected with H37Rv. Oral administration of VB5 decreased the number of colony-forming units of H37Rv in lungs of mice at 1, 2, and 4 weeks after infection. In addition, VB5 regulated the percentage of macrophages and promoted CD4+ T cells to express interferon-γ and interleukin-17; however, it had no effect on the percentage of polymorphonuclear neutrophils, CD4+ and CD8+ T cells. In conclusion, VB5 significantly inhibits the growth of MTB by regulating innate immunity and adaptive immunity.

Usefulness of Chinese Herbal Medicines as Host-Directed Therapeutics against Mycobacterial Infections: A Review.

The high incidence of tuberculosis (TB) in developing countries, the resurgence of TB in industrialized countries, and the worldwide increase in the prevalence of Mycobacterium avium complex infections have prompted the quest for new antimycobacterial drugs. However, the development of such chemotherapeutics is currently making very slow progress. It therefore appears that devising improved administration protocols for clinical treatment against intractable mycobacteriosis using existing chemotherapeutics is more practical than awaiting the development of novel antimycobacterial drugs. The modulation of host immune responses using immunoadjunctive agents may increase the efficacy of antimicrobial treatment against mycobacteriosis. Particularly, the mild and long-term up-regulation of host immune reactions against mycobacterial pathogens using Chinese herbal medicines (CHMs) may be beneficial for immunoadjunctive therapy. This review focuses on the current status and future prospects regarding the development of CHMs that can be useful for the clinical control of intractable mycobacterial infections.

An Iron-Rich Diet Decreases the Mycobacterial Burden and Correlates With Hepcidin Upregulation, Lower Levels of Proinflammatory Mediators, and Increased T-Cell Recruitment in a Model of Mycobacterium bovis Bacille Calmette-Guerin Infection.

Background: Recent evidence indicates a robust competition between the host and mycobacteria for iron acquisition during mycobacterial infection. Variable effects of iron supplementation on the susceptibility to mycobacterial infection have been reported. In this study, we revisited the effects of an experimental iron-enriched diet on Mycobacterium bovis bacille Calmette-Guerin (BCG) infection. Methods: Mice fed a standard diet or a diet moderately enriched with iron were infected with M. bovis BCG expressing green fluorescent protein. Colony-forming unit numbers, host myeloid cell counts, cell recruitment, cytokine production, and iron gene expression were determined at different stages of infection. Bone marrow-derived macrophages incubated with or without iron were also used to measure bacterial uptake, levels of inflammation markers, and iron gene expression. Results: In vivo analysis of BCG-infected mice revealed that moderate iron supplementation reduced inflammation, as measured by decreased proinflammatory cytokine levels and neutrophil recruitment and enhanced T-cell recruitment in granulomas, and decreased the bacterial load. Enhanced bacterial clearance in the liver correlated with upregulation of the gene encoding hepcidin, which is known to have antimicrobial proprieties, and with sequestration of iron in tissues. In cultured macrophages, iron supplementation induced reactive oxygen species and reduced uptake and intracellular growth of BCG. Conclusion: Moderate iron diet supplementation diminished inflammation and growth of M. bovis BCG via enhanced reactive oxygen species production, immune cell activation, and local hepcidin expression.