Innate immunity to mycobacteria: vitamin D and autophagy

Mycobacterium tuberculosis and host interactions in the manifestation of tuberculosis

The final step of epigenetic processes is changing the gene expression in a new microenvironment in the body, such as neuroendocrine changes, active infections, oncogenes, or chemical agents. The case of tuberculosis (TB) is an outcome of Mycobacterium tuberculosis (M.tb) and host interaction in the manifestation of active and latent TB or clearance. This comprehensive review explains and interprets the epigenetics findings regarding gene expressions on the host-pathogen interactions in the development and progression of tuberculosis. This review introduces novel insights into the complicated host-pathogen interactions, discusses the challengeable results, and shows the gaps in the clear understanding of M.tb behavior. Focusing on the biological phenomena of host-pathogen interactions, the epigenetic changes, and their outcomes provides a promising future for developing effective TB immunotherapies when converting gene expression toward appropriate host immune responses gradually becomes attainable. Overall, this review may shed light on the dark sides of TB pathogenesis as a life-threatening disease. Therefore, it may support effective planning and implementation of epigenetics approaches for introducing proper therapies or effective vaccines.

Vitamin D3 improved erectile function recovery by regulating autophagy and apoptosis in a rat model of cavernous nerve injury

Vitamin D3 is an important element in improving erectile function. However, the mechanisms of vitamin D3 remain unknown. Thus, we explored the effect of vitamin D3 on erectile function recovery after nerve injury in a rat model and investigated its possible molecular mechanisms. Eighteen male Sprague-Dawley rats were used in this study. The rats were randomly divided into three groups: the control, bilateral cavernous nerve crush (BCNC), and BCNC + vitamin D3 groups. BCNC model was established in rats by surgery. The intracavernosal pressure and the ratio of intracavernosal pressure to mean arterial pressure were utilized to evaluate erectile function. Masson trichrome staining, immunohistochemistry, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling and western blot analysis were performed on penile tissues to elucidate the molecular mechanism. The results indicated that vitamin D3 alleviated hypoxia and suppressed the fibrosis signalling pathway by upregulating the expression of eNOS (p = 0.001), nNOS (p = 0.018) and α-SMA (p = 0.025) and downregulating the expression of HIF-1α (p = 0.048) and TGF-β1 (p = 0.034) in BCNC rats. Vitamin D3 promoted erectile function restoration by enhancing the autophagy process through decreases in the p-mTOR/mTOR ratio (p = 0.02) and p62 (p = 0.001) expression and increases in Beclin1 expression (p = 0.001) and the LC3B/LC3A ratio (p = 0.041). Vitamin D3 application improved erectile function rehabilitation by suppressing the apoptotic process through decreases in the expression of Bax (p = 0.002) and caspase-3 (p = 0.046) and an increase in the expression of Bcl2 (p = 0.004). Therefore, We concluded that vitamin D3 improved the erectile function recovery in BCNC rats by alleviating hypoxia and fibrosis, enhancing autophagy and inhibiting apoptosis in the corpus cavernosum.

Vitamin D and autophagy in knee osteoarthritis: A review

Knee osteoarthritis (KOA), the highly prevalent degenerative disease affecting the joint, perpetually devastates the health of the elderly. Of various mechanisms known to participate in KOA etiology, apoptosis of chondrocytes is widely regarded as the primary cause of cartilage degradation. It has been suggested that the induction of autophagy in chondrocytes could potentially prolong the progression of KOA by modulating intracellular metabolic processes, which may be helpful for ameliorating chondrocyte apoptosis and eventual cartilage degeneration. Autophagy, a physiological process characterized by intracellular self-degradation, has been reportedly implicated in various pathologic conditions including KOA. Interestingly, vitamin D has been shown to regulate autophagy in human chondrocytes through multiple pathways, specifically AMPK/mTOR signaling pathway. This observation underscores the potential of vitamin D as a novel approach for restoring the functionality and survivability of chondrocytes in KOA. Supporting vitamin D's clinical significance, previous studies have demonstrated its substantial involvement in the symptoms and irregular joint morphology observed in KOA patients, strengthening potential therapeutic efficacy of vitamin D in treatment of KOA. Herein, the purpose of this review was to determine the mechanisms underlying the multi-processes of vitamin D implicated in autophagy in several cells including chondrocytes, which would bring unique insights into KOA pathogenesis.

The relationship between host defense peptides and adrenal steroids. An account of reciprocal influences

AIM

β-defensins 2 and -3 (HBD-2 and HBD-3) and cathelicidin LL-37 are host defense peptides (HDPs) that play a crucial role in the immune response against mycobacteria. Given our former studies in tuberculosis patients wherein their plasma levels of such peptides correlated with steroid hormone concentrations, we now studied the reciprocal influence of cortisol and/or dehydroepiandrosterone (DHEA) on HDPs biosynthesis and LL-37 on adrenal steroidogenesis.

MAIN METHODS

Cultures of macrophages derived from the THP-1 line were treated with cortisol (10^-6M) and/or DHEA (10^-6M and 10^-7M) and stimulated with irradiated M. tuberculosis (Mi) or infected M. tuberculosis strain H37Rv to assess cytokine production, HDPs, reactive oxygen species (ROS) and colony forming units. Cultures of NCI-H295-R adrenal line were treated with LL37 (5, 10, and 15 µg/ml) for 24 h to further measure cortisol and DHEA levels together with steroidogenic enzyme transcripts.

KEY FINDINGS

In macrophages, M. tuberculosis produced an increase of IL-1β, TNFα, IL-6, IL-10, LL-37, HBD-2, and HBD-3 levels, irrespective of DHEA treatment. Adding cortisol to M. tuberculosis-stimulated cultures (with or without DHEA) decreased the amounts of these mediators, compared to only stimulated cultures. Although M. tuberculosis reduced ROS levels, DHEA increased these values in addition to diminishing intracellular mycobacterial growth (no matter cortisol treatment). In turn, studies on adrenal cells showed that LL-37 reduced the production of cortisol and DHEA besides modifying transcripts for some steroidogenic enzymes.

SIGNIFICANCE

while adrenal steroids seem to influence the production of HDPs, the former compounds are also likely to modulate adrenal biogenesis.

1α,25(OH)2D3 Promotes the Autophagy of Porcine Ovarian Granulosa Cells as a Protective Mechanism against ROS through the BNIP3/PINK1 Pathway

Vitamin D (VD) is one of the important nutrients required by livestock; however, VD deficiency is reported to be widespread. Earlier studies have suggested a potential role for VD in reproduction. Studies on the correlation between VD and sow reproduction are limited. The aim of the current study was aimed to determine the role of 1,25-dihydroxy vitamin D₃ (1α,25(OH)₂D₃) on porcine ovarian granulosa cells (PGCs) in vitro to provide a theoretical basis for improving the reproductive efficiency of sows. We used chloroquine (autophagy inhibitor) and reactive oxygen species (ROS) scavenger N-acetylcysteine in conjunction with 1α,25(OH)₂D₃ to explore the effect on PGCs. The results showed that 10 nM of 1α,25(OH)₂D₃ increased PGC viability and ROS content. In addition, 1α,25(OH)₂D₃ induces PGC autophagy according to the gene transcription and protein expression levels of LC3, ATG7, BECN1, and SQSTM1 and promotes the generation of autophagosomes. 1α,25(OH)₂D₃-induced autophagy affects the synthesis of E₂ and P₄ in PGCs. We investigated the relationship between ROS and autophagy, and the results showed that 1α,25(OH)₂D₃-induced ROS promoted PGC autophagy. The ROS-BNIP3-PINK1 pathway was involved in PGC autophagy induced by 1α,25(OH)₂D₃. In conclusion, this study suggests that 1α,25(OH)₂D₃ promotes PGC autophagy as a protective mechanism against ROS via the BNIP3/PINK1 pathway.

Modulating macrophage function to reinforce host innate resistance against Mycobacterium avium complex infection

Mycobacterium avium complex (MAC) is the main causative agent of infectious diseases in humans among nontuberculous mycobacteria (NTM) that are ubiquitous organisms found in environmental media such as soil as well as in domestic and natural waters. MAC is a primary causative agent of NTM-lung disease that threaten immunocompromised or structural lung disease patients. The incidence and the prevalence of M. tuberculosis infection have been reduced, while MAC infections and mortality rates have increased, making it a cause of global health concern. The emergence of drug resistance and the side effects of long-term drug use have led to a poor outcome of treatment regimens against MAC infections. Therefore, the development of host-directed therapy (HDT) has recently gained interest, aiming to accelerate mycobacterial clearance and reversing lung damage by employing the immune system using a novel adjuvant strategy to improve the clinical outcome of MAC infection. Therefore, in this review, we discuss the innate immune responses that contribute to MAC infection focusing on macrophages, chief innate immune cells, and host susceptibility factors in patients. We also discuss potential HDTs that can act on the signaling pathway of macrophages, thereby contributing to antimycobacterial activity as a part of the innate immune response during MAC infection. Furthermore, this review provides new insights into MAC infection control that modulates and enhances macrophage function, promoting host antimicrobial activity in response to potential HDTs and thus presenting a deeper understanding of the interactions between macrophages and MACs during infection.

Association Between Vitamin D Deficiency and Autoimmune Thyroid Disorder: A Systematic Review

Despite recent evidence that low serum 25-hydroxyvitamin D (25(OH)D) levels and deflects may influence the emergence of autoimmune thyroid disorders (AITD), the relationship between vitamin D deficiency and Graves’ disease (GD) and Hashimoto's thyroiditis (HT), which comprise AITD, remains unclear. We retrieved studies that described vitamin D association with HT and GD from PubMed/Medline, Google Scholar, and the Cochrane Library. We included research studies that compared vitamin D levels and deficiency or sufficiency between AITD cases such as HT and GD cases and control subjects. The final assessment comprised 11 studies that recruited 1952 AITD cases (HT and GD) that were published between 2011 and 2021; these were included in the final review. All the included studies were observational, and more precisely, case-control studies that recruited healthy subjects as well as controls. The majority of the studies reviewed indicated that HT and GD patients have a greater prevalence of vitamin D deficiency or low serum 25 (OH)-D levels. Two studies failed to establish an association between vitamin D deficiency and HT and GD disease. In conclusion, vitamin D deficiency or insufficiency can increase the rate of autoimmune diseases such as HT and GD. Randomized controlled trials with a longer follow-up period are needed to confirm the causal relationship between autoimmune thyroid disorder and vitamin D and to provide more reliable insights into the relevance of treatment effects of vitamin D therapy or supplementation.

Reduced levels of serum 25(OH)D3 are associated with tuberculosis positive cattle under conditions of high natural exposure to Mycobacterium bovis

Serum vitamin D (25(OH)D₃) concentrations of < 30 ng/mL in cattle are insufficient to induce an adequate immune response against intracellular pathogens, which suggests that the efficacy of the immune response may be highly dependent on the bioavailability of 25(OH)D₃. This study shows an overview of both in vitro and in vivo 25(OH)D3-mediated immune modulation amongst dairy cattle naturally exposed to M. bovis. Tuberculin status was confirmed by interferon gamma release assay (IGRA), and natural exposure was demonstrated by polymerase chain reaction (PCR). Tuberculin (-) cattle have a higher serum concentration of 25(OH)D₃ (X¯= 87.12 ng/mL) when compared to tuberculin (+) cattle (X¯ = 45.86 ng/mL). Reduced serum 25(OH)D₃ levels are associated with the presence of bovine TB, and serum 25(OH)D₃ levels of > 80 ng/mL are necessary to counteract infection by M. bovis. Kill assays were performed to evaluate in vitro 25(OH)D₃ modulation of intracellular M. bovis growth in bovine macrophages, which showed that reduced serum 25(OH)D₃ levels are associated with diminished mycobactericidal capacity in this experimental model. On the other hand, increased 25(OH)D₃ in culture media enhances phagocytosis and nitric oxide production, which in turn improves capacity to combat M. bovis.

Vitamin d and leishmaniasis: Neither seasonal nor risk factor in canine host but potential adjuvant treatment through cbd103 expression

Vitamin D (VitD) deficiency has been shown to be a risk factor for a plethora of disorders. We have shown that dogs with clinical leishmaniasis presented lower VitD serum levels than non-infected dogs, and even lower than those with asymptomatic infection. However, if VitD deficiency is a risk factor to develop clinical leishmaniasis remains to be answered. It is also unknown if VitD participates in Leishmania control. First, we retrospectively analysed VitD concentration in serum samples from 36 healthy dogs collected in different periods of the year concluding that there isn't a seasonal variation of this vitamin in dogs. We also included 9 dogs with clinical leishmaniasis and 10 non-infected healthy dogs, in which we measured VitD levels at the beginning of the study, when all dogs were negative for serology and qPCR, and 1 year later. Whereas non-infected dogs showed no change in VitD levels along the study, those developing clinical leishmaniasis showed a significant VitD reduction at the end of the study (35%). When we compared VitD concentration between the two groups at the beginning of the study, no differences were detected (43.6 (38-59) ng/mL, P = 0.962). Furthermore, an in vitro model using a canine macrophage cell line proved that adding active VitD leads to a significant reduction in L. infantum load (31.4%). Analyzing expression of genes related to VitD pathway on primary canine monocytes, we showed that CBD103 expression was significantly enhanced after 1,25(OH)2D addition. Our results show that VitD concentration is neither seasonal nor a risk factor for developing canine leishmaniasis, but it diminishes with the onset of clinical disease suggesting a role in parasitic control. Our in vitro results corroborate this hypothesis and point out that VitD regulates infection through CBD103 expression. These results open the possibility for studies testing VitD as an adjuvant in leishmaniasis therapy.

Cumulative Signaling Through NOD-2 and TLR-4 Eliminates the Mycobacterium Tuberculosis Concealed Inside the Mesenchymal Stem Cells

For a long time, tuberculosis (TB) has been inflicting mankind with the highest morbidity and mortality. Although the current treatment is extremely potent, a few bacilli can still hide inside the host mesenchymal stem cells (MSC). The functional capabilities of MSCs are known to be modulated by TLRs, NOD-2, and RIG-1 signaling. Therefore, we hypothesize that modulating the MSC activity through TLR-4 and NOD-2 can be an attractive immunotherapeutic strategy to eliminate the Mtb hiding inside these cells. In our current study, we observed that MSC stimulated through TLR-4 and NOD-2 (N2.T4) i) activated MSC and augmented the secretion of pro-inflammatory cytokines; ii) co-localized Mtb in the lysosomes; iii) induced autophagy; iv) enhanced NF-κB activity via p38 MAPK signaling pathway; and v) significantly reduced the intracellular survival of Mtb in the MSC. Overall, the results suggest that the triggering through N2.T4 can be a future method of immunotherapy to eliminate the Mtb concealed inside the MSC.

Autophagy as a Target for Drug Development Of Skin Infection Caused by Mycobacteria

Pathogenic mycobacteria species may subvert the innate immune mechanisms and can modulate the activation of cells that cause disease in the skin. Cutaneous mycobacterial infection may present different clinical presentations and it is associated with stigma, deformity, and disability. The understanding of the immunopathogenic mechanisms related to mycobacterial infection in human skin is of pivotal importance to identify targets for new therapeutic strategies. The occurrence of reactional episodes and relapse in leprosy patients, the emergence of resistant mycobacteria strains, and the absence of effective drugs to treat mycobacterial cutaneous infection increased the interest in the development of therapies based on repurposed drugs against mycobacteria. The mechanism of action of many of these therapies evaluated is linked to the activation of autophagy. Autophagy is an evolutionary conserved lysosomal degradation pathway that has been associated with the control of the mycobacterial bacillary load. Here, we review the role of autophagy in the pathogenesis of cutaneous mycobacterial infection and discuss the perspectives of autophagy as a target for drug development and repurposing against cutaneous mycobacterial infection.

Steroid hormone modulates the production of cathelicidin and human β-defensins in lung epithelial cells and macrophages promoting Mycobacterium tuberculosis killing

Several studies have documented the interaction between the immune and endocrine systems as an effective defense strategy against tuberculosis, involving the production of several molecules and immunological processes. In this study, we determined the effect of cortisol and dehydroepiandrosterone (DHEA) on the production of antimicrobial peptides such as cathelicidin and human β-defensin (HBD) -2, and HBD-3 and their effect on intracellular growth of Mycobacterium tuberculosis (Mtb) in lung epithelial cells and macrophages. Our results showed that DHEA promotes the production of these antimicrobial peptides in infected cells, correlating with the decrease of Mtb bacilli loads. These results suggest the use of exogenous DHEA as an adjuvant for tuberculosis therapy.

Targeting Autophagy as a Strategy for Developing New Vaccines and Host-Directed Therapeutics Against Mycobacteria

Mycobacterial disease is an immense burden worldwide. This disease group includes tuberculosis, leprosy (Hansen's disease), Buruli Ulcer, and non-tuberculous mycobacterial (NTM) disease. The burden of NTM disease, both pulmonary and ulcerative, is drastically escalating globally, especially in developed countries such as America and Australia. Mycobacteria's ability to inhibit or evade the host immune system has contributed significantly to its continued prevalence. Pre-clinical studies have highlighted promising candidates that enhance endogenous pathways and/or limit destructive host responses. Autophagy is a cell-autonomous host defense mechanism by which intracytoplasmic cargos can be delivered and then destroyed in lysosomes. Previous studies have reported that autophagy-activating agents, small molecules, and autophagy-activating vaccines may be beneficial in restricting intracellular mycobacterial infection, even with multidrug-resistant strains. This review will examine how mycobacteria evade autophagy and discusses how autophagy could be exploited to design novel TB treatment strategies, such as host-directed therapeutics and vaccines, against Mycobacterium tuberculosis and NTMs.

Regulatory Mechanisms of Autophagy-Targeted Antimicrobial Therapeutics Against Mycobacterial Infection

Mycobacterium tuberculosis (Mtb) is an intracellular pathogen causing human tuberculosis, an infectious disease that still remains as a global health problem. Autophagy, a lysosomal degradative process, has emerged as a critical pathway to restrict intracellular Mtb growth through enhancement of phagosomal maturation. Indeed, several autophagy-modulating agents show promise as host-directed therapeutics for Mtb infection. In this Review, we discuss recent progress in our understanding the molecular mechanisms underlying the action of autophagy-modulating agents to overcome the immune escape strategies mediated by Mtb. The factors and pathways that govern such mechanisms include adenosine 5'-monophosphate-activated protein kinase, Akt/mammalian TOR kinase, Wnt signaling, transcription factor EB, cathelicidins, inflammation, endoplasmic reticulum stress, and autophagy-related genes. A further understanding of these mechanisms will facilitate the development of host-directed therapies against tuberculosis as well as infections with other intracellular bacteria targeted by autophagic degradation.

The relationship between maternal vitamin D deficiency and glycolipid metabolism and adverse pregnancy outcome

OBJECTIVE

Maternal vitamin D deficiency is associated with glucose and lipid metabolism in the mother and offspring. Meanwhile, it can also lead to adverse pregnancy outcomes. The aim of this case-control study was to document maternal, umbilical arterial glucose and lipid metabolic levels and correlations in pregnancies with or without vitamin D deficiency, while also investigating adverse pregnancy outcomes.

DESIGN/PARTICIPANTS/MEASUREMENTS

A total of 425 pregnant women who received antenatal care and delivered at Wenzhou People's Hospital were enrolled. According to their serum 25-hydroxyvitamin D [25(OH)D] level, the pregnant women were divided into the vitamin D deficiency group [25(OH)D < 20 ng/mL, 185 participants] and the control group [25(OH)D ≥ 20 ng/mL, 240 participants]. Maternal blood samples were collected at 24-28 weeks of gestation and delivery for 75-g oral glucose tolerance test (OGTT), and measurements of glucose and lipid metabolite levels and 25(OH)D levels. Umbilical arterial samples were collected during delivery (33.57-41.43 gestational weeks).

RESULTS

Compared with control participants, vitamin D deficiency women had significantly higher concentrations of fasting blood-glucose (P < .01), 1-h OGTT plasma glucose (P < .01), 2-h OGTT plasma glucose (P < .01), insulin (P < .01), HOMA-IR (P < .01), LDL (P < .01) and triglycerides (P = .02) and lower concentrations of HOMA-S (P < .01). Compared with the control group, vitamin D deficiency women had higher concentrations of triglycerides (P < .01) and lower concentrations of HDL-C (P < .01) and HOMA-β (P = .01) in infant umbilical arterial blood. Pearson's correlation analysis demonstrated that the maternal 25(OH)D level was negatively correlated with maternal plasma glucose, insulin, LDL-C, cholesterol, triglyceride and HOMA-IR (r = -.38, -.27, -.2, -.11, -.11, -.33 and .11; P < .01, <.01, <.01, <.05, <.05 and <.01, respectively), while there was a positive correlation between maternal serum 25(OH)D and HOMA-S (r = .11, P < .05). The triglyceride level in the umbilical artery was negatively correlated with maternal serum 25(OH)D concentration (r = -.286, P < .01), while the HDL-C and HOMA-β in umbilical artery were positively related (r = .154, .103, P < .01). Compared with the control group, the incidences of pre-eclampsia [4.8% (9/185) vs 1.25% (3/240), P = .03], gestational diabetes mellitus [19.45% (36/185) vs 12.08% (29/240), P = .04] and premature rupture of membranes [15.68% (29/185) vs 5.42% (13/240), P < .01] were higher in the vitamin D deficiency group.

CONCLUSION

Vitamin D deficiency during pregnancy is associated with maternal glucose and lipid metabolism and pregnancy outcomes. Therefore, it is worth recommending to maintain vitamin D status at an optimal level in pregnant women to prevent metabolic disorders and pregnancy complications.

Synthesis and Antibacterial Evaluation of New Pyrazolo[3,4-d]pyrimidines Kinase Inhibitors

Pyrazolo[3,4-d]pyrimidines represent an important class of heterocyclic compounds well-known for their anticancer activity exerted by the inhibition of eukaryotic protein kinases. Recently, pyrazolo[3,4-d]pyrimidines have become increasingly attractive for their potential antimicrobial properties. Here, we explored the activity of a library of in-house pyrazolo[3,4-d]pyrimidines, targeting human protein kinases, against Staphylococcus aureus and Escherichia coli and their interaction with ampicillin and kanamycin, representing important classes of clinically used antibiotics. Our results represent a first step towards the potential application of dual active pyrazolo[3,4-d]pyrimidine kinase inhibitors in the prevention and treatment of bacterial infections in cancer patients.

Vitamin D - A host directed autophagy mediated therapy for tuberculosis

According to the WHO report 2019, Tuberculosis (TB) is an ancient disease of humanity that is curable. TB has caused significant morbidity and mortality even in 2018. The etiological agent of TB, Mycobacterium tuberculosis (MTB) exploits its virulence factors to escape from host immunity and therapeutic drugs. Host Directed Therapy (HDT) is an adjunctive therapy where repurposed drugs, small molecules, vitamins, cytokines, and monoclonal antibodies are used to overcome the pathogen exploited pathways in the host. One of the HDTs, i.e. induction of autophagy is a highly regulated intracellular self-degradative process in which pathogens are sequestered in double-layered autophagosomes and targeted to the lysosome for degradation. Apart from the pathogen clearance, autophagy involves the release of nutrients during starvation, removal of damaged organelles and aggregated proteins, antigen presentation, tumor suppression, and anti-aging mechanisms. Xenophagy is a type of selective autophagy against microbes induced by ubiquitin receptors (p62/SQSTM1, NDP52, NBR1, OPTN, Parkin and Smurf proteins) after pathogen recognition. ULK1/2, Beclin-1, ATG5-ATG12-ATG16 L and LC-II-PE complexes along with two nutrient-sensing protein complexes, mTOR and AMPK activate autophagy mechanisms to limit infection. Pattern Recognition Receptors (PRRs) such as TLR2, recognize lipopolysaccharide (LPS) of MTB and triggers vitamin D₃ activating enzymes. Activated vitamin D₃ induces the synthesis of antimicrobial peptide, LL-37, which further enhances xenophagy. Apart from vitamin D, few micronutrients such as zinc and iron also regulate autophagy. In this review, we discuss current knowledge, advances and perspectives of autophagy against TB.

Vitamin D increases killing of intracellular Leishmania amazonensis in vitro independently of macrophage oxidative mechanisms

Vitamin D has been reported to activate macrophage microbicidal mechanisms by inducing the production of antimicrobial peptides and nitric oxide (NO), but conversely has been shown to contribute to a greater susceptibility to Leishmania amazonensis infection in mice. Thus, this study aimed to evaluate the role of vitamin D during intracellular infection with L. amazonensis by examining its effect on macrophage oxidative mechanisms and parasite survival in vitro. Vitamins D2 and D3 significantly inhibited promastigote and amastigote growth in vitro. Vitamin D3 was not able to induce NO and reactive oxygen species (ROS) production in uninfected macrophages or macrophages infected with L. amazonensis. In addition, vitamin D3 in combination with interferon (IFN)-γ did not enhance amastigote killing and in fact, significantly reduced NO and ROS production when compared with the effect of IFN-γ alone. In this study, we demonstrated that vitamin D directly reduces parasite growth in infected macrophages (approximately 50-60% at 50 μm) but this effect is independent of the activation of macrophage oxidative mechanisms. These findings will contribute to a better understanding of the role of vitamin D in cutaneous leishmaniasis.

Nuclear Receptors as Autophagy-Based Antimicrobial Therapeutics

Autophagy is an intracellular process that targets intracellular pathogens for lysosomal degradation. Autophagy is tightly controlled at transcriptional and post-translational levels. Nuclear receptors (NRs) are a family of transcriptional factors that regulate the expression of gene sets involved in, for example, metabolic and immune homeostasis. Several NRs show promise as host-directed anti-infectives through the modulation of autophagy activities by their natural ligands or small molecules (agonists/antagonists). Here, we review the roles and mechanisms of NRs (vitamin D receptors, estrogen receptors, estrogen-related receptors, and peroxisome proliferator-activated receptors) in linking immunity and autophagy during infection. We also discuss the potential of emerging NRs (REV-ERBs, retinoic acid receptors, retinoic acid-related orphan receptors, liver X receptors, farnesoid X receptors, and thyroid hormone receptors) as candidate antimicrobials. The identification of novel roles and mechanisms for NRs will enable the development of autophagy-adjunctive therapeutics for emerging and re-emerging infectious diseases.

ESAT-6 regulates autophagous response through SOD-2 and as a result induces intracellular survival of Mycobacterium bovis BCG

Mycobacterium is known for subverting the host defense machinery, and one such mechanism is the inhibition of autophagy. Here, we have demonstrated that Mycobacterium tuberculosis (MTB) secretes a virulence factor; an early secretory antigenic target protein (ESAT-6) into the phagosome, which induces the expression and activity of mitochondrial superoxide dismutase (SOD-2) of macrophages. Using a series of experiments, and Mycobacterium bovis BCG as a model strain (where ESAT-6 protein is not expressed), we have delineated that the protein regulates SOD-2 of macrophages. The expression and augmentation of SOD-2 activity were confirmed by either incubating the macrophages with ESAT-6 protein, transfection of macrophage by esat6 gene using a eukaryotic promoter vector, or by infection with different mycobacterial strains. The induction of acidification of phagosomal compartment containing bacteria was observed in cells that express low levels of SOD-2. This was further confirmed by observing a significant decrease in the M. bovis BCG intracellular load in the sod-2 knocked-down macrophages.

Immunomodulatory significance of natural peptides in mammalians: Promising agents for medical application

Modulation of immune responses by immunoregulatory agents, such as the natural or synthetic immunomodulatory peptides, has been suggested as a potential strategy to modulate immune system against infection and other immune-related diseases. These compositionally simple peptides have attracted much attention for many drug developers, due to their high activity, low toxicity and clear target specificity. Host defence peptides and milk-derived peptides are two kinds of natural immunomodulatory peptides which have been widely studied in mammalians. They could participate at the interface of innate and adaptive immunity by regulating immune effector cells. This review summarizes the recent advances in host defence peptides and milk-derived peptides as well as their general characteristics, immunomodulatory functions and possible applications.

Vitamin D-Cathelicidin Axis: at the Crossroads between Protective Immunity and Pathological Inflammation during Infection

Vitamin D signaling plays an essential role in innate defense against intracellular microorganisms via the generation of the antimicrobial protein cathelicidin. In addition to directly binding to and killing a range of pathogens, cathelicidin acts as a secondary messenger driving vitamin D-mediated inflammation during infection. Recent studies have elucidated the biological and clinical functions of cathelicidin in the context of vitamin D signaling. The vitamin D-cathelicidin axis is involved in the activation of autophagy, which enhances antimicrobial effects against diverse pathogens. Vitamin D studies have also revealed positive and negative regulatory effects of cathelicidin on inflammatory responses to pathogenic stimuli. Diverse innate and adaptive immune signals crosstalk with functional vitamin D receptor signals to enhance the role of cathelicidin action in cell-autonomous effector systems. In this review, we discuss recent findings that demonstrate how the vitamin D-cathelicidin pathway regulates autophagy machinery, protective immune defenses, and inflammation, and contributes to immune cooperation between innate and adaptive immunity. Understanding how the vitamin D-cathelicidin axis operates in the host response to infection will create opportunities for the development of new therapeutic approaches against a variety of infectious diseases.

Role Of Vitamin-D Supplementation In TB/HIV Co-Infected Patients

OBJECTIVE

This review aimed to assess the role of vitamin D supplementation on the decrement of mortality and morbidity rate among tuberculosis (TB)/human immune deficiency virus (HIV) co-infected clients.Method: Pub Med, google scholar and google search were accessed to find out all document to describe this review article.

RESULTS

Nowadays TB/HIV co-infection has become a major global concern, particularly in low and middle-income countries. Mycobacterium tuberculosis and HIV infections are co-endemic and more susceptible to the progression of TB. Immunosuppression associated with HIV is a strong risk factor for the reactivation of latent TB to the active form. Immune cells like macrophages recognized Mycobacterium tuberculosis through TLR2/1, and it increases the expression of the vitamin D receptor (VDR) and CYP27B1. The synthesis of 1,25-dihydroxy vitamin D promotes VDR-mediated transactivation of the antimicrobial peptide cathelicidin and the killing of intracellular Mycobacterium tuberculosis. Cathelicidins have a direct antimicrobial effect through membrane disruption. Besides, it has also antiviral effects via inhibition of retrovirus (HIV) replication. In fact, as some studies showed, there was a lower induction of cathelicidin in monocytes who have low vitamin D levels.Conclusion: Therefore, vitamin D supplementation can be directly involved in the reduction of TB/HIV co-infection and its progression.

Induction of autophagy through CLEC4E in combination with TLR4: an innovative strategy to restrict the survival of Mycobacterium tuberculosis

Host-directed therapies are gaining considerable impetus because of the emergence of drug-resistant strains of pathogens due to antibiotic therapy. Therefore, there is an urgent need to exploit alternative and novel strategies directed at host molecules to successfully restrict infections. The C-type lectin receptor CLEC4E and Toll-like receptor TLR4 expressed by host cells are among the first line of defense in encountering pathogens. Therefore, we exploited signaling of macrophages through CLEC4E in association with TLR4 agonists (C₄.T₄) to control the growth of Mycobacterium tuberculosis (Mtb). We observed significant improvement in host immunity and reduced bacterial load in the lungs of Mtb-infected mice and guinea pigs treated with C₄.T₄ agonists. Further, intracellular killing of Mtb was achieved with a 10-fold lower dose of isoniazid or rifampicin in conjunction with C₄.T₄ than the drugs alone. C₄.T₄ activated MYD88, PtdIns3K, STAT1 and RELA/NFKB, increased lysosome biogenesis, decreased Il10 and Il4 gene expression and enhanced macroautophagy/autophagy. Macrophages from autophagy-deficient (atg5 knockout or Becn1 knockdown) mice showed elevated survival of Mtb. The present findings also unveiled the novel role of CLEC4E in inducing autophagy through MYD88, which is required for control of Mtb growth. This study suggests a unique immunotherapeutic approach involving CLEC4E in conjunction with TLR4 to restrict the survival of Mtb through autophagy.

ABBREVIATIONS

3MA: 3 methyladenine; AO: acridine orange; Atg5: autophagy related 5; AVOs: acidic vesicular organelles; BECN1: beclin 1, autophagy related; BMDMs: bone marrow derived macrophages; bw: body weight; C₄.T₄: agonists of CLEC4E (C₄/TDB) and TLR4 (T₄/ultra-pure-LPS); CFU: colony forming unit; CLEC4E/Mincle: C-type lectin domain family 4, member e; CLR: c-type lectin receptor; INH: isoniazid; LAMP1: lysosomal-associated membrane protein 1; Mφ^C4.T4: Mtb-infected C₄.T₄ stimulated macrophages; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MDC: monodansylcadaverine; MTOR: mechanistic target of rapamycin kinase; MYD88: myeloid differentiation primary response 88; NFKB: nuclear factor of kappa light polypeptide gene enhance in B cells; NLR: NOD (nucleotide-binding oligomerization domain)-like receptors; PFA: paraformaldehyde; PPD: purified protein derivative; PtdIns3K: class III phosphatidylinositol 3-kinase; RELA: v-rel reticuloendotheliosis viral oncogene homolog A (avian); RIF: rifampicin; RLR: retinoic acid-inducible gene-I-like receptors; TDB: trehalose-6,6´-dibehenate; TLR4: toll-like receptor 4; Ultra-pure-LPS: ultra-pure lipopolysaccharide-EK; V-ATPase: vacuolar-type H⁺ ATPase.

25-Hydroxyvitamin D concentrations in dogs with naturally acquired blastomycosis

Background

Hypovitaminosis D is common in humans with tuberculosis, and adequate serum 25‐hydroxyvitamin D [25(OH)D] concentrations may improve response to therapy. The pathomechanism of Blastomyces dermatitidis is similar to that of Mycobacterium tuberculosis, but the 25(OH)D status of dogs with blastomycosis has not been investigated.

Objectives

To determine if dogs with blastomycosis have lower 25(OH)D concentrations compared with healthy controls and to explore the prognostic value of 25(OH)D concentrations in blastomycosis.

Animals

35 control dogs (16 client‐owned, healthy dogs and 19 healthy, random‐source hound mixes) and 22 dogs with blastomycosis.

Methods

Prospective study. Serum concentrations of 25(OH)D, parathyroid hormone (PTH), ionized calcium were measured, and biochemistry and hematology profiles were performed. The 25‐hydroxyvitamin D concentrations were compared between groups, and factors associated with 25(OH)D variation were investigated in dogs with blastomycosis. Dogs with blastomycosis were followed for up to 5 years after discharge and factors associated with survival were investigated.

Results

Dogs with blastomycosis had significantly lower concentrations of 25(OH)D and PTH and higher concentrations of ionized calcium than did control dogs. In dogs with blastomycosis, 25(OH)D concentrations were independently associated with neutrophil count, pCO₂, and with bone and skin involvement. The 25‐hydroxyvitamin D concentration was not associated with survival in dogs with blastomycosis, whereas lactate concentrations; bone, skin, and lymph node involvement; number of affected sites; and, presence of respiratory signs were associated with survival.

Conclusions and Clinical Importance

Dogs with blastomycosis had lower 25(OH)D concentrations than did healthy controls. Despite no impact on survival, investigating the effect of 25(OH)D supplementation on recovery is warranted.

Autophagy, apoptosis, vitamin D, and vitamin D receptor in hepatocellular carcinoma associated with hepatitis C virus

The aims of this study were to investigate the interplay between autophagy and apoptosis and to investigate the association between both of autophagy and apoptosis and vitamin D and its receptor in hepatitis C virus (HCV) viral infection and its implication in the progression into hepatocellular carcinoma (HCC).A cross-sectional study where serum levels of microtubule-associated protein 1A/1B-light chain 3 (LC3); marker of autophagy, caspase-3; marker of apoptosis, vitamin D3 and vitamin D receptor (VDR) were measured in healthy subjects as well as HCV and HCV-HCC patients using enzyme-linked immunosorbent assay technique.Collectively, the liver profile revealed hepatic dysfunctions in HCV patients with or without HCC. A significant reduction in the serum concentration levels LC3 and caspase-3 were observed referring to the down regulation of autophagy and host-mediated apoptosis in HCV patients with or without HCC. Deficiency of vitamin D and decreased levels of its receptor were observed in HCV and HCV-HCC patients.The perturbation in vitamin D/VDR axis, which modulates both of autophagy and apoptosis in HCV infection, may point out to its involvement and implication in the pathogenesis of HCV infection and the development of HCV-related HCC. Therefore, supplementation with vitamin D may not be the only solution to restore the vital biological functions of vitamin D but VDR-targeted therapy may be of great importance in this respect.

Innate immunity in tuberculosis: host defense vs pathogen evasion

The major innate immune cell types involved in tuberculosis (TB) infection are macrophages, dendritic cells (DCs), neutrophils and natural killer (NK) cells. These immune cells recognize the TB-causing pathogen Mycobacterium tuberculosis (Mtb) through various pattern recognition receptors (PRRs), including but not limited to Toll-like receptors (TLRs), Nod-like receptors (NLRs) and C-type lectin receptors (CLRs). Upon infection by Mtb, the host orchestrates multiple signaling cascades via the PRRs to launch a variety of innate immune defense functions such as phagocytosis, autophagy, apoptosis and inflammasome activation. In contrast, Mtb utilizes numerous exquisite strategies to evade or circumvent host innate immunity. Here we discuss recent research on major host innate immune cells, PRR signaling, and the cellular functions involved in Mtb infection, with a specific focus on the host's innate immune defense and Mtb immune evasion. A better understanding of the molecular mechanisms underlying host-pathogen interactions could provide a rational basis for the development of effective anti-TB therapeutics.

Canine Leishmaniasis Progression is Associated with Vitamin D Deficiency

The relationship between vitamin D deficiency and the risk of suffering from a plethora of health disorders, ranging from autoimmune processes to infectious diseases has been widely described. Nonetheless, the potential role of vitamin D in visceral leishmaniasis remains uncharacterized. In the Mediterranean basin, where the dog is leishmania’s main peri-domestic reservoir, control measures against the canine disease have shown beneficial effects on the incidence of human leishmaniasis. In this study, we measured the vitamin D levels in serum samples from a cohort of 68 healthy and disease dogs from a highly endemic area and we have also studied the relationship of these levels with parasitological and immunological parameters. The sick dogs presented significantly lower (P < 0.001) vitamin D levels (19.6 ng/mL) than their non-infected (31.8 ng/mL) and the asymptomatic counterparts (29.6 ng/mL). In addition, vitamin D deficiency correlated with several parameters linked to leishmaniasis progression. However, there was no correlation between vitamin D levels and the Leishmania-specific cellular immune response. Moreover, both the leishmanin skin test and the IFN-γ levels displayed negative correlations with serological, parasitological and clinical signs. Further studies to determine the functional role of vitamin D on the progression and control of canine leishmaniasis are needed.

Dual antiplasmodial activity of vitamin D3 and its analog, 22-oxacalcitriol, by direct and indirect mechanisms

Recent evidence suggests that 1α,25-dihydroxyvitamin D3 (calcitriol, VD3), the active form of vitamin D (VD), can inhibit the proliferation of microorganisms. In the present study, we conducted in vitro experiments and utilized in vivo murine models to investigate the antimalarial activity of VD3 and its analog, 22-oxacalcitriol (22-OCT), which was designed to cause less hypercalcemia than VD3. VD3 and 22-OCT treatments effectively resolved a Plasmodium chabaudi (Pc) infection in wild-type mice. Reduced parasitemia was observed during the acute phase of infection in the presence of VD3 and 22-OCT, followed by a delayed peak during the chronic stage of infection. Some anti-Pc activity was observed in VD receptor knockout (KO) mice. VD3 and 22-OCT also completely inhibited the proliferation of P. falciparum (Pf) in human red blood cells in vitro. Plasma levels of interferon (IFN)-γ in VD3-treated B10 and B6 mice were lower than those in vehicle-treated animals, and VD3 resolved a Pc infection in IFN-γ-KO mice, which greatly improved survival. These data suggest that the protective effects of VD3 are elicited through an IFN-γ-independent mechanism. Effective antiplasmodial doses of VD3 and 22-OCT resulted in a loss of body weight in mice. This loss in body weight occurred concomitantly with the development of hypercalcemia. Zoledronic acid partially attenuated VD3-induced hypercalcemia and abrogated the antiparasitic effects of VD3. This study highlights a potential therapeutic role for VD3 in the treatment of malarial infections and shows that hypercalcemia is excellent indicator of the antiplasmodial activity of VD3.

Mammalian host defense peptides and their implication on combating Leishmania infection

Infection with parasites of the genus Leishmania is a health problem in many countries around the world. No effective vaccine is available against leishmaniasis, so chemotherapy is the only alternative for treatment of all forms of the disease. However, drawbacks including toxicity and severe adverse reactions restrain the use of currently available chemotherapeutics. Therefore development of new drugs and therapeutic approaches is highly demanded. Mammalian host defense peptides (mHDP) and/or mammalian antimicrobial peptides (mAMP) are among promising compounds considered effective to control the infectious diseases. These are potential multifunctional molecules that modulate the immune response besides direct killing of pathogens. Here we have reviewed the hallmark characteristics of the mHDPs in respect to the potential role they can play against leishmaniasis.

Vitamin D and airway infections: a European perspective

Vitamin D has immuno-modulatory properties, and deficient levels of circulating 25-hydroxyvitamin D (<30 nmol/l) may contribute to increased risk of infectious illnesses. This narrative review summarises data on vitamin D status in Europe and updates results of randomised controlled trials (RCTs) regarding vitamin D and airway infections such as tuberculosis (TB) and acute upper respiratory tract infection. In Europe, the prevalence of vitamin D deficiency is up to 37% in the general population and up to 80% in nursing home residents and non-European immigrants. Half of TB patients have a migration background. While results of RCTs do not support the concept of beneficial adjunctive effects of vitamin D supplements in anti-TB treatment [odds ratio (OR) = 0.86; 95% CI 0.62-1.19], the few published RCTs on the prophylaxis of TB suggest some protective vitamin D effects in individuals with deficient circulating 25-hydroxyvitamin D levels. Regarding acute respiratory tract infection, RCTs indicate a significant risk reduction by vitamin D supplements [OR = 0.65; 95% confidence interval (CI) 0.50-0.85]. There is evidence that daily administration is more effective than high-dose bolus administration [OR = 0.48 (95% CI 0.30-0.77) vs. OR = 0.87 (95% CI 0.67-1.14)] and that individuals with deficient or insufficient (30-50 nmol/l) circulating 25-hydroxyvitamin D levels benefit most. Several vitamin D effects on innate immunity may explain these protective effects. In summary, there is possible evidence from RCTs for protective vitamin D effects on TB and likely evidence for protective effects on acute airway infection. Since vitamin D deficiency is prevalent in Europe, especially in institutionalised individuals and non-European immigrants, daily oral vitamin D intake, e.g. 1000 international units, is an inexpensive measure to ensure adequate vitamin D status in individuals at risk.

Transcriptional regulation of cathelicidin genes in chicken bone marrow cells

Cathelicidins form a family of vertebrate-specific immune molecules with an evolutionarily conserved gene structure. We analyzed the expression patterns of cathelicidin genes (CAMP, CATH3, and CATHB1) in chicken bone marrow cells (BMCs) and chicken embryonic fibroblasts (CEFs). We found that CAMP and CATHB1 were significantly up-regulated in BMCs, whereas the expression of CATH3 did not differ significantly between BMCs and CEFs. To study the mechanism underlying the up-regulation of cathelicidin genes in BMCs, we predicted the transcription factors (TFs) that bind to the 5'-flanking regions of cathelicidin genes. CEBPA, EBF1, HES1, MSX1, and ZIC3 were up-regulated in BMCs compared to CEFs. Subsequently, when a siRNA-mediated knockdown assay was performed for MSX1, the expression of CAMP and CATHB1 was decreased in BMCs. We also showed that the transcriptional activity of the CAMP promoter was decreased by mutation of the MSX1-binding sites present within the 5'-flanking region of CAMP. These results increase our understanding of the regulatory mechanisms controlling cathelicidin genes in BMCs.

The Sculpting of the Mycobacterium tuberculosis Genome by Host Cell-Derived Pressures

Mycobacterium tuberculosis is an incredibly successful pathogen with an extraordinary penetrance of its target host population. The ability to infect many yet cause disease in few is undoubtedly central to this success. This ability relies on sensing and responding to the changing environments encountered during the course of disease in the human host. This chapter discusses these environmental cues and stresses, and explores how the genome of Mtb has evolved under the purifying selections that they exert. In analyzing the response of Mtb to a broad range of intracellular pressures it is clear that, despite genome down-sizing, Mtb has retained an extraordinary flexibility in central carbon metabolism. We believe that it is this metabolic plasticity, more than any of the virulence factors, that is the foundation for Mtb's qualities of endurance.

The cooperation between the autophagy machinery and the inflammasome to implement an appropriate innate immune response: do they regulate each other?

Autophagy is originally described as the main catabolic pathway responsible for maintaining intracellular nutritional homeostasis that involves the formation of a unique vacuole, the autophagosome, and the interaction with the endosome-lysosome pathways. This conserved machinery plays a key role in immune-protection against different invaders, including pathogenic bacteria, intracellular parasites, and some viruses like herpes simplex and hepatitis C virus. Importantly, autophagy is linked to a number of human diseases and disorders including neurodegenerative disease, Crohn's disease, type II diabetes, tumorigenesis, cardiomyopathy, and fatty liver disease. On the other hand, inflammasomes are multiprotein platforms stimulated upon several environmental conditions and microbial infection. Once assembled, the inflammasomes mediate the maturation of pro-inflammatory cytokines and promote phagosome-lysosome fusion to sustain an innate immune response. The intersections between autophagy and inflammasome have been observed in various diseases and microbial infections. This review highlights the molecular aspects involved in autophagy and inflammasome interactions during different medical conditions and microbial infections.

NOD-2 and TLR-4 Signaling Reinforces the Efficacy of Dendritic Cells and Reduces the Dose of TB Drugs against Mycobacterium tuberculosis

Tuberculosis (TB) is one of the leading killer infectious diseases. TB patients are inflicted with devastating side effects and the toxicity of a lengthy drug regime, accentuating an urgent need to explore newer and safer treatment methods. Recently, an improved understanding of host-pathogen interaction has opened new avenues for TB treatment, including immunotherapy. This has emboldened us to devise a novel strategy to restrict Mycobacterium tuberculosis(Mtb) growth by activating dendritic cells (DCs) through the NOD-2 and TLR-4 molecules of innate immunity. Triggered DCs show a robust release of cytokines and nitric oxide, autophagy and improved migration towards the lymph nodes, and consequently impede the intracellular survival of Mtb. Of note, this approach enhanced the efficacy of TB drugs by reducing their dose to a 5-fold lesser concentration than recommended. In vivo administration of ligands of NOD-2 (NOD-2L) and TLR-4 (TLR-4L) substantially increased the pool of effector memory CD4 and CD8 T cells. Additionally, NOD-2L and TLR-4L, in conjunction with the reduced dose of isoniazid, substantially declined the Mtb burden in the lungs. In the future, adjunct therapy involving NOD-2L, TLR-4L and TB drugs may have enough potential to reduce the dose and duration of treatment of TB patients.

Autophagy in Mycobacterium tuberculosis and HIV infections

Human Immunodeficiency Virus (HIV) and Mycobacterium tuberculosis (M.tb) are among the most lethal human pathogens worldwide, each being responsible for around 1.5 million deaths annually. Moreover, synergy between acquired immune deficiency syndrome (AIDS) and tuberculosis (TB) has turned HIV/M.tb co-infection into a major public health threat in developing countries. In the past decade, autophagy, a lysosomal catabolic process, has emerged as a major host immune defense mechanism against infectious agents like M.tb and HIV. Nevertheless, in some instances, autophagy machinery appears to be instrumental for HIV infection. Finally, there is mounting evidence that both pathogens deploy various countermeasures to thwart autophagy. This mini-review proposes an overview of the roles and regulations of autophagy in HIV and M.tb infections with an emphasis on microbial factors. We also discuss the role of autophagy manipulation in the context of HIV/M.tb co-infection. In future, a comprehensive understanding of autophagy interaction with these pathogens will be critical for development of autophagy-based prophylactic and therapeutic interventions for AIDS and TB.

Vitamin D: Immuno-modulation and tuberculosis treatment

Tuberculosis (TB) is a major global health problem and often coincides with vitamin D deficiency. High doses of vitamin D were widely used to treat TB during the pre-antibiotic era. Vitamin D exerts its action through vitamin D receptor (VDR), and VDR gene polymorphisms are associated with susceptibility or resistance to tuberculosis as well as sputum smear and culture conversion during anti-TB treatment. In-vitro studies have revealed that 1,25-dihydroxyvitamin D3 enhances innate immunity by increased expression of various antimicrobial peptides, including cathelicidin, and induction of autophagy of the infected cells thus restricts the intracellular growth of Mycobacterium tuberculosis in macrophages. On the other hand, vitamin D has been shown to suppress the pro-inflammatory cytokine response and enhance the anti-inflammatory response. Supplementation with vitamin D in concert with treatment for TB may be beneficial with respect to minimizing the excessive tissue damage that occurs during the active stage of tuberculosis disease. Several clinical trials have evaluated vitamin D supplementation as an adjunct therapy in the treatment for tuberculosis. However, results are conflicting, owing to variations in dose regimens and outcomes. Further investigations are needed to find the optimal concentration of vitamin D for supplementation with standard anti-TB drugs to optimize treatment, which could help to effectively manage both drug-sensitive and drug-resistant tuberculosis.

Macrophage defense mechanisms against intracellular bacteria

Macrophages and neutrophils play a decisive role in host responses to intracellular bacteria including the agent of tuberculosis (TB), Mycobacterium tuberculosis as they represent the forefront of innate immune defense against bacterial invaders. At the same time, these phagocytes are also primary targets of intracellular bacteria to be abused as host cells. Their efficacy to contain and eliminate intracellular M. tuberculosis decides whether a patient initially becomes infected or not. However, when the infection becomes chronic or even latent (as in the case of TB) despite development of specific immune activation, phagocytes have also important effector functions. Macrophages have evolved a myriad of defense strategies to combat infection with intracellular bacteria such as M. tuberculosis. These include induction of toxic anti-microbial effectors such as nitric oxide and reactive oxygen intermediates, the stimulation of microbe intoxication mechanisms via acidification or metal accumulation in the phagolysosome, the restriction of the microbe's access to essential nutrients such as iron, fatty acids, or amino acids, the production of anti-microbial peptides and cytokines, along with induction of autophagy and efferocytosis to eliminate the pathogen. On the other hand, M. tuberculosis, as a prime example of a well-adapted facultative intracellular bacterium, has learned during evolution to counter-balance the host's immune defense strategies to secure survival or multiplication within this otherwise hostile environment. This review provides an overview of innate immune defense of macrophages directed against intracellular bacteria with a focus on M. tuberculosis. Gaining more insights and knowledge into this complex network of host-pathogen interaction will identify novel target sites of intervention to successfully clear infection at a time of rapidly emerging multi-resistance of M. tuberculosis against conventional antibiotics.

Soluble mediators regulating immunity in early life

Soluble factors in blood plasma have a substantial impact on both the innate and adaptive immune responses. The complement system, antibodies, and anti-microbial proteins and peptides can directly interact with potential pathogens, protecting against systemic infection. Levels of these innate effector proteins are generally lower in neonatal circulation at term delivery than in adults, and lower still at preterm delivery. The extracellular environment also has a critical influence on immune cell maturation, activation, and effector functions, and many of the factors in plasma, including hormones, vitamins, and purines, have been shown to influence these processes for leukocytes of both the innate and adaptive immune systems. The ontogeny of plasma factors can be viewed in the context of a lower effectiveness of immune responses to infection and immunization in early life, which may be influenced by the striking neonatal deficiency of complement system proteins or enhanced neonatal production of the anti-inflammatory cytokine IL-10, among other ontogenic differences. Accordingly, we survey here a number of soluble mediators in plasma for which age-dependent differences in abundance may influence the ontogeny of immune function, particularly direct innate interaction and skewing of adaptive lymphocyte activity in response to infectious microorganisms and adjuvanted vaccines.

Phagocyte NADPH oxidase, chronic granulomatous disease and mycobacterial infections

Infection of humans with Mycobacterium tuberculosis remains frequent and may still lead to death. After primary infection, the immune system is often able to control M. tuberculosis infection over a prolonged latency period, but a decrease in immune function (from HIV to immunosenescence) leads to active disease. Available vaccines against tuberculosis are restricted to BCG, a live vaccine with an attenuated strain of M. bovis. Immunodeficiency may not only be associated with an increased risk of tuberculosis, but also with local or disseminated BCG infection. Genetic deficiency in the reactive oxygen species (ROS)-producing phagocyte NADPH oxidase NOX2 is called chronic granulomatous disease (CGD). CGD is among the most common primary immune deficiencies. Here we review our knowledge on the importance of NOX2-derived ROS in mycobacterial infection. A literature review suggests that human CGD patient frequently have an increased susceptibility to BCG and to M. tuberculosis. In vitro studies and experiments with CGD mice are incomplete and yielded - at least in part - contradictory results. Thus, although observations in human CGD patients leave little doubt about the role of NOX2 in the control of mycobacteria, further studies will be necessary to unequivocally define and understand the role of ROS.

Levels of 1,25(OH)2D3 for patients with pulmonary tuberculosis and correlations of 1,25(OH)2D3 with the clinical features of TB

BACKGROUND

To determine the 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] concentrations to patients with tuberculosis (TB) and whether it influenced the patient's clinical features.

METHODS

For the first part, a total of 153 healthy adults and 74 patients with pulmonary TB (PTB) were enrolled. Serum concentrations of 1,25(OH)2D3 were determined by liquid chromatography-tandem mass spectroscopy to examine the 1,25(OH)2D3 concentrations of the two groups from the peripheral blood. If there are differences between the two groups, what follow will increase the experimental group numbers to examine the relationship among the 1,25(OH)2D3 concentrations with the numbers of the lesion area, the tubercule bacilli in sputum and the CD4/CD8 ratio of T lymphocytes in the peripheral blood.

RESULTS

In the first part, the 1,25(OH)2D3 concentrations was lower in patients with TB than in those healthy adults [365.9 (SD 235.7) vs. 464.3 (SD 335.6), P<0.05]. In the second part, we increased the sample size to 134 (male 91 cases, female 43 cases). we found that the plasma levels of 1,25(OH)2D3 are not correlated with the numbers of the lesion area and the tubercule bacilli in sputum, but the 1,25(OH)2D3 levels can interact the ratio of CD4/CD8 T lymphocytes, it shows a positive correlation with the ratio of CD4/CD8 T lymphocytes.

CONCLUSIONS

The 1,25(OH)2D3 concentrations in TB patients lower than the healthy adults, it might exist as a risk factor during the development of TB or TB might affect the levels of 1,25(OH)2D3. But the different status vitamin D concentration might not affect the numbers of the lesion area, the tubercule bacilli in sputum. It shows a positive correlation with the ratio of CD4/CD8 T lymphocytes. The study will have a significance value to clinical medicine, but further study will need to study the levels of 1,25(OH)2D3 with the TB.

The role of vitamin D in regulating the iron-hepcidin-ferroportin axis in monocytes

Chronic kidney disease affects 40% of adults aged 65 and older. Anemia of CKD is present in 30% of patients with CKD and is associated with increased cardiovascular risk, decreased quality of life, and increased mortality. Hepcidin-25 (hepcidin), the key iron regulating hormone, prevents iron egress from macrophages and thus prevents normal recycling of the iron needed to support erythropoiesis. Hepcidin levels are increased in adults and children with CKD. Vitamin D insufficiency is highly prevalent in CKD and is associated with erythropoietin hyporesponsiveness. Recently, hepcidin levels were found to be inversely correlated with vitamin D status in CKD. The aim of this study was to investigate the role of vitamin D in the regulation of hepcidin expression in vitro and in vivo. This study reports that 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), the hormonally active form of vitamin D, is associated with decreased hepcidin and increased ferroportin expression in lipopolysaccharide (LPS) stimulated THP-1 cells. 1,25(OH)₂D₃ also resulted in a dose-dependent decrease in pro-hepcidin cytokines, IL-6 and IL-1β, release in vitro. Further, we show that high-dose vitamin D therapy impacts systemic hepcidin levels in subjects with early stage CKD. These data suggest that improvement in vitamin D status is associated with lower systemic concentrations of hepcidin in subjects with CKD. In conclusion, vitamin D regulates the hepcidin-ferroportin axis in macrophages which may facilitate iron egress. Improvement in vitamin D status in patients with CKD may reduce systemic hepcidin levels and may ameliorate anemia of CKD.

Autophagy adaptor protein p62/SQSTM1 and autophagy-related gene Atg5 mediate autophagosome formation in response to Mycobacterium tuberculosis infection in dendritic cells

Mycobacterium tuberculosis is an intracellular pathogen that can survive within phagocytic cells by inhibiting phagolysosome biogenesis. However, host cells can control the intracellular M. tuberculosis burden by the induction of autophagy. The mechanism of autophagosome formation to M. tuberculosis has been well studied in macrophages, but remains unclear in dendritic cells. We therefore characterized autophagosome formation in response to M. tuberculosis infection in dendritic cells. Autophagy marker protein LC3, autophagy adaptor protein p62/SQSTM1 (p62) and ubiquitin co-localized to M. tuberculosis in dendritic cells. Mycobacterial autophagosomes fused with lysosomes during infection, and major histcompatibility complex class II molecules (MHC II) also localized to mycobacterial autophagosomes. The proteins p62 and Atg5 function in the initiation and progression of autophagosome formation to M. tuberculosis, respectively; p62 mediates ubiquitination of M. tuberculosis and Atg5 is involved in the trafficking of degradative vesicles and MHC II to mycobacterial autophagosomes. These results imply that the autophagosome formation to M. tuberculosis in dendritic cells promotes the antigen presentation of mycobacterial peptides to CD4⁺ T lymphocytes via MHC II.

Elevated 1- α hydroxylase activity in monocytes from patients with active tuberculosis

A uremic patient developed hypercalcemia after tuberculosis infection, and his ionized calcium levels correlated with 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) levels. We performed further studies to determine whether monocytes are alternative sites of 1,25(OH)₂D₃ conversion beyond renal tubular cells. Using an ex vivo bioassay, in this study, we found that 1-α hydroxylase (CYP27B1) activity in monocytes is significantly higher in patients with active tuberculosis (TB) than in those with frequent TB contact. However, when monocytes from patients with active TB were restimulated with antigen derived from Mycobacterium tuberculosis, less 1,25(OH)₂D₃ was observed. In contrast, the level of 1,25(OH)₂D₃ was unchanged in those with frequent TB contact. We conclude that monocytes may be an alternative source of 1-α hydroxylase that could convert 25-hydroxyvitamin D₃ to the more active 1,25(OH)₂D₃.

Vitamin D-related host genetic variants alter HIV disease progression in children

BACKGROUND

Vitamin D deficiency is common in HIV infection and has been associated with advanced disease. This study investigated whether vitamin D-related genetic variants were associated with disease progression in HIV-infected children.

METHODS

The Fok-I (C/T), Bsm-I (G/A), GC (A/C), DHCR7 (G/T) and CYP2R1 (G/A) genetic variants were detected by real-time polymerase chain reaction in HIV-infected children who participated in the Pediatric AIDS Clinical Trials Group P152 and P300 protocols, which predated the availability of effective combination antiretroviral therapy. The primary endpoints included time to progression to the first HIV-related disease endpoint (≥2 opportunistic infection, weight growth failure) or death, which constituted the progression-free survival. Analyses were performed for age>2 years and ≤2 years separately adjusting for race and treatment effect.

RESULTS

Of the 998 children evaluated, 139 experienced HIV disease progression. For children>2 years, rapid disease progression was associated with the DHCR7 G allele compared with the T allele (G/G vs. T/T: hazard ratio [HR]=5.0, P = 0.035; G/T vs. T/T: HR=4.5, P=0.042; G/G+G/T vs. T/T: HR=4.8, P=0.036) and the Bsm-I A allele compared with the G allele (A/G vs. G/G: HR=2.2, P=0.014 and A/G+A/A vs. G/G: HR=2.0, P=0.026). In children≤2 years, the Bsm-I A allele increased the risk of disease progression in Hispanics (A/A vs. G/A+G/G: HR=2.8, P=0.03 and A/A vs. G/G: HR=2.8, P=0.046) and whites (A/A vs. G/G: HR=6.6, P=0.025 and A/A vs. G/A+G/G: HR=3.6, P=0.038).

CONCLUSIONS

Vitamin D-related host genetic variants that alter the availability and activity of vitamin D are associated with risk of HIV disease progression in children and may vary by age and race.

Autophagy as an innate defense against mycobacteria

Over the past several years, much has been revealed about the roles of autophagy and the mechanisms by which the autophagic pathway activates the host innate effector response against Mycobacterium tuberculosis (Mtb) infection. In response to invading mycobacteria, the host innate immune system not only recognizes pathogen motifs through innate receptors, it also produces appropriate effector proteins, including cytokines. These innate signals activate or regulate autophagic pathways during infection. It is now clear that vitamin D and functional vitamin D receptor signaling are critical in the activation of autophagic defenses against Mtb in human cells. Immunity-related GTPase family M proteins, including the cationic antimicrobial protein cathelicidin and autophagic receptor p62, participate in autophagic pathways that enhance antimicrobial activity against mycobacteria. Moreover, reactive oxygen species mediate antibacterial autophagy and successful antimicrobial responses during antibiotic chemotherapy. Recent work has also shown that pathogenic Mtb can be targeted by selective autophagy through an ESX-1 type VII secretion system. Here, we review the triggers, host factors, and intracellular pathways that regulate host autophagy and its impact on antimicrobial host defenses during mycobacterial infection.

Autophagy during Mycobacterium tuberculosis infection and implications for future tuberculosis medications

Autophagy is a cellular homeostasis mechanism to eliminate unwanted or excessive organelles, or for the turnover of long-life cytosolic macromolecules. During Mycobacterium tuberculosis infection, autophagy represents not only an antimicrobial mechanism for the clearance of the intracellular pathogen, but also prevents excessive inflammation, avoiding the adverse effects on host. Here we focus on the anti-tuberculosis autophagy and signal pathways involved, and attempt to depict an integrative map of the interaction between autophagy and cytokine, ROS production, vitamin D, and inflammatory response. Novel autophagy-based therapy is also summarized. This integrative insight might add some novel thoughts for better tuberculosis medications.