Low doses of imatinib induce myelopoiesis and enhance host anti-microbial immunity

Inducible antibacterial responses in macrophages

Macrophages destroy bacteria and other microorganisms through phagocytosis-coupled antimicrobial responses, such as the generation of reactive oxygen species and the delivery of hydrolytic enzymes from lysosomes to the phagosome. However, many intracellular bacteria subvert these responses, escaping to other cellular compartments to survive and/or replicate. Such bacterial subversion strategies are countered by a range of additional direct antibacterial responses that are switched on by pattern-recognition receptors and/or host-derived cytokines and other factors, often through inducible gene expression and/or metabolic reprogramming. Our understanding of these inducible antibacterial defence strategies in macrophages is rapidly evolving. In this Review, we provide an overview of the broad repertoire of antibacterial responses that can be engaged in macrophages, including LC3-associated phagocytosis, metabolic reprogramming and antimicrobial metabolites, lipid droplets, guanylate-binding proteins, antimicrobial peptides, metal ion toxicity, nutrient depletion, autophagy and nitric oxide production. We also highlight key inducers, signalling pathways and transcription factors involved in driving these different antibacterial responses. Finally, we discuss how a detailed understanding of the molecular mechanisms of antibacterial responses in macrophages might be exploited for developing host-directed therapies to combat antibiotic-resistant bacterial infections.

Therapeutic Drug Monitoring of Imatinib and N-Desmethyl Imatinib in Chronic Myeloid Leukemia Patients Using LC-MS/MS in a Cohort Study

Imatinib is an oral tyrosine kinase inhibitor (TKI) and first-line therapy for patients with chronic myeloid leukemia (CML). There is a positive correlation between serum imatinib concentrations and treatment response. However, the specific relationship between the blood concentration of imatinib and its influencing factors remains unclear. This study collected basic information from 102 patients using imatinib as first-line treatment for CML. Further, we analyzed the individual differences in imatinib concentration and explored its influencing factors. Through intra-day and inter-day precision studies, we found that the precision for the imatinib assay methodology was within ±13% and that the recovery rate was above 85%. There is notable individual variation in the blood concentration of imatinib; the recommended treatment concentration is 860-1500 ng/mL, with only 41.40% of patients achieving this concentration. Also, there was a negative correlation between age and imatinib trough concentration (Ctrough ), as is observed between age and N-desmethyl imatinib. Moreover, compared with the adolescent group, the serum imatinib Ctrough for groups aged 17-47 and 48-68 years was significantly reduced. Further analysis shows that imatinib Ctrough values reaching therapeutic concentrations (59%) increased dramatically for patients with CML aged 17-47 years. Moreover, groups dosed with 400 mg/day resulted in therapeutic imatinib concentrations for 68% of patients with CML, which was the best performance. The established method was validated, with acceptable accuracy, precision, linearity, and stability, as required, and then successfully applied to the therapeutic drug monitoring of imatinib. Age, dose, and metabolites can influence the imatinib concentration and its therapeutic effect in patients with CML.

Potential Repurposed Drug Candidates for Tuberculosis Treatment: Progress and Update of Drugs Identified in Over a Decade

The devastating impact of Tuberculosis (TB) has been a menace to mankind for decades. The World Health Organization (WHO) End TB Strategy aims to reduce TB mortality up to 95% and 90% of overall TB cases worldwide, by 2035. This incessant urge will be achieved with a breakthrough in either a new TB vaccine or novel drugs with higher efficacy. However, the development of novel drugs is a laborious process involving a timeline of almost 20-30 years with huge expenditure; on the other hand, repurposing previously approved drugs is a viable technique for overcoming current bottlenecks in the identification of new anti-TB agents. The present comprehensive review discusses the progress of almost all the repurposed drugs that have been identified to the present day (∼100) and are in the development or clinical testing phase against TB. We have also emphasized the efficacy of repurposed drugs in combination with already available frontline anti-TB medications along with the scope of future investigations. This study would provide the researchers a detailed overview of nearly all identified anti-TB repurposed drugs and may assist them in selecting the lead compounds for further in vivo/clinical research.

The host-directed therapeutic imatinib mesylate accelerates immune responses to Mycobacterium marinum infection and limits pathology associated with granulomas

Infections caused by members of the mycobacterium tuberculosis complex [MTC] and nontuberculous mycobacteria [NTM] can induce widespread morbidity and mortality in people. Mycobacterial infections cause both a delayed immune response, which limits rate of bacterial clearance, and formation of granulomas, which contain bacterial spread, but also contribute to lung damage, fibrosis, and morbidity. Granulomas also limit access of antibiotics to bacteria, which may facilitate development of resistance. Bacteria resistant to some or all antibiotics cause significant morbidity and mortality, and newly developed antibiotics readily engender resistance, highlighting the need for new therapeutic approaches. Imatinib mesylate, a cancer drug used to treat chronic myelogenous leukemia [CML] that targets Abl and related tyrosine kinases, is a possible host-directed therapeutic [HDT] for mycobacterial infections, including those causing TB. Here, we use the murine Mycobacterium marinum [Mm] infection model, which induces granulomatous tail lesions. Based on histological measurements, imatinib reduces both lesion size and inflammation of surrounding tissue. Transcriptomic analysis of tail lesions indicates that imatinib induces gene signatures indicative of immune activation and regulation at early time points post infection that resemble those seen at later ones, suggesting that imatinib accelerates but does not substantially alter anti-mycobacterial immune responses. Imatinib likewise induces signatures associated with cell death and promotes survival of bone marrow-derived macrophages [BMDMs] in culture following infection with Mm. Notably, the capacity of imatinib to limit formation and growth of granulomas in vivo and to promote survival of BMDMs in vitro depends upon caspase 8, a key regulator of cell survival and death. These data provide evidence for the utility of imatinib as an HDT for mycobacterial infections in accelerating and regulating immune responses, and limiting pathology associated with granulomas, which may mitigate post-treatment morbidity.

Host-directed immunotherapy of viral and bacterial infections: past, present and future

The advent of COVID-19 and the persistent threat of infectious diseases such as tuberculosis, malaria, influenza and HIV/AIDS remind us of the marked impact that infections continue to have on public health. Some of the most effective protective measures are vaccines but these have been difficult to develop for some of these infectious diseases even after decades of research. The development of drugs and immunotherapies acting directly against the pathogen can be equally challenging, and such pathogen-directed therapeutics have the potential disadvantage of selecting for resistance. An alternative approach is provided by host-directed therapies, which interfere with host cellular processes required for pathogen survival or replication, or target the host immune response to infection (immunotherapies) to either augment immunity or ameliorate immunopathology. Here, we provide a historical perspective of host-directed immunotherapeutic interventions for viral and bacterial infections and then focus on SARS-CoV-2 and Mycobacterium tuberculosis, two major human pathogens of the current era, to indicate the key lessons learned and discuss candidate immunotherapeutic approaches, with a focus on drugs currently in clinical trials.

A Pleurocidin-Like Peptide from Poecilia Mexicana Fish Induces Selective Cytotoxicity in Leukemia Jurkat Cells Through The Apoptosis Pathway

OBJECTIVE

Some cationic anti-microbial peptides show a wide range of cytotoxic action versus malignant cells, which may lead to developing a novel group of antitumor medications. In the present study, the anticancer activity of pleurocidin-like peptide WF3 isoform X2 (AMP-WF3), from the Poecilia Mexicana fish, against leukemic cell line Jurkat was evaluated, and the cytotoxicity compared with the effects on normal cells, including peripheral blood mononuclear cells (PBMCs) and human dermal fibroblast (HDF) cells.

MATERIALS AND METHODS

In this experimental study, cells were treated with various dosages of AMP-WF3 for 24 hours. Using methyl thiazole tetrazolium salt reduction (MTT test), the effects of the AMP-WF3 on cell viability and toxicity were evaluated. The impact of this peptide on apoptotic pathways was examined using flow cytometry and Annexin V-PI stains. Additionally, the relative expression of the P53, P21 and BCL-2 genes was evaluated using a real-time polymerase chain reaction.

RESULTS

The Jurkat cell line was more susceptible to AMP-WF3 cytotoxicity [half-maximal inhibitory concentration (IC₅₀)=50 μM], while normal cells (PBMCs and HDF) were less susceptible. Flow cytometry verified that the apoptotic activity of AMP-WF3 on Jurkat cells was significantly higher than that of HDF and PBMCs. Peptide-treated Jurkat cells were associated with increased expression of P21, and P53 genes. In contrast, the changes in P21, P53, and BCL-2 genes differed in PBMCs and HDF cells. In HDF cells, simultaneous increase of P21, P53, and BCL-2, and in PBMCs, only the increase of BCL-2 was observed.

CONCLUSION

Our research showed that AMP-WF3 could be developed as a novel treatment agent with minimum side effects for ALL patients.

Inhibition of indoleamine dioxygenase leads to better control of tuberculosis adjunctive to chemotherapy

The expression of indoleamine 2,3-dioxygenase (IDO), a robust immunosuppressant, is significantly induced in macaque tuberculosis (TB) granulomas, where it is expressed on IFN-responsive macrophages and myeloid-derived suppressor cells. IDO expression is also highly induced in human TB granulomas, and products of its activity are detected in patients with TB. In vivo blockade of IDO activity resulted in the reorganization of the granuloma with substantially greater T cells being recruited to the core of the lesions. This correlated with better immune control of TB and reduced lung M. tuberculosis burdens. To study if the IDO blockade strategy can be translated to a bona fide host-directed therapy in the clinical setting of TB, we studied the effect of IDO inhibitor 1-methyl-d-tryptophan adjunctive to suboptimal anti-TB chemotherapy. While two-thirds of controls and one-third of chemotherapy-treated animals progressed to active TB, inhibition of IDO adjunctive to the same therapy protected macaques from TB, as measured by clinical, radiological, and microbiological attributes. Although chemotherapy improved proliferative T cell responses, adjunctive inhibition of IDO further enhanced the recruitment of effector T cells to the lung. These results strongly suggest the possibility that IDO inhibition can be attempted adjunctive to anti-TB chemotherapy in clinical trials.

Inflammation-mediated tissue damage in pulmonary tuberculosis and host-directed therapeutic strategies

Treatment of tuberculosis (TB) involves the administration of anti-mycobacterial drugs for several months. The emergence of drug-resistant strains of Mycobacterium tuberculosis (Mtb, the causative agent) together with increased disease severity in people with co-morbidities such as diabetes mellitus and HIV have hampered efforts to reduce case fatality. In severe disease, TB pathology is largely attributable to over-exuberant host immune responses targeted at controlling bacterial replication. Non-resolving inflammation driven by host pro-inflammatory mediators in response to high bacterial load leads to pulmonary pathology including cavitation and fibrosis. The need to improve clinical outcomes and reduce treatment times has led to a two-pronged approach involving the development of novel antimicrobials as well as host-directed therapies (HDT) that favourably modulate immune responses to Mtb. HDT strategies incorporate aspects of immune modulation aimed at downregulating non-productive inflammatory responses and augmenting antimicrobial effector mechanisms to minimise pulmonary pathology and accelerate symptom resolution. HDT in combination with existing antimycobacterial agents offers a potentially promising strategy to improve the long-term outcome for TB patients. In this review, we describe components of the host immune response that contribute to inflammation and tissue damage in pulmonary TB, including cytokines, matrix metalloproteinases, lipid mediators, and neutrophil extracellular traps. We then proceed to review HDT directed at these pathways.

Treatment of infection-induced vascular pathologies is protective against persistent rough morphotype Mycobacterium abscessus infection in zebrafish

Mycobacterium abscessus infections are of increasing global prevalence and are often difficult to treat due to complex antibiotic resistance profiles. While there are similarities between the pathogenesis of M. abscessus and tuberculous mycobacteria, including granuloma formation and stromal remodelling, there are distinct molecular differences at the host-pathogen interface. Here we have used a zebrafish-M. abscessus model and host-directed therapies that were previously identified in the zebrafish-M. marinum model to identify potential host-directed therapies against M. abscessus infection. We find efficacy of anti-angiogenic and vascular normalizing therapies against rough M. abscessus infection, but no effect of anti-platelet drugs.

Repurposing diphenylbutylpiperidine-class antipsychotic drugs for host-directed therapy of Mycobacterium tuberculosis and Salmonella enterica infections

The persistent increase of multidrug-resistant (MDR) Mycobacterium tuberculosis (Mtb) infections negatively impacts Tuberculosis treatment outcomes. Host-directed therapies (HDT) pose an complementing strategy, particularly since Mtb is highly successful in evading host-defense by manipulating host-signaling pathways. Here, we screened a library containing autophagy-modulating compounds for their ability to inhibit intracellular Mtb-bacteria. Several active compounds were identified, including two drugs of the diphenylbutylpiperidine-class, Fluspirilene and Pimozide, commonly used as antipsychotics. Both molecules inhibited intracellular Mtb in pro- as well as anti-inflammatory primary human macrophages in a host-directed manner and synergized with conventional anti-bacterials. Importantly, these inhibitory effects extended to MDR-Mtb strains and the unrelated intracellular pathogen, Salmonella enterica serovar Typhimurium (Stm). Mechanistically Fluspirilene and Pimozide were shown to regulate autophagy and alter the lysosomal response, partly correlating with increased bacterial localization to autophago(lyso)somes. Pimozide's and Fluspirilene's efficacy was inhibited by antioxidants, suggesting involvement of the oxidative-stress response in Mtb growth control. Furthermore, Fluspirilene and especially Pimozide counteracted Mtb-induced STAT5 phosphorylation, thereby reducing Mtb phagosome-localized CISH that promotes phagosomal acidification. In conclusion, two approved antipsychotic drugs, Pimozide and Fluspirilene, constitute highly promising and rapidly translatable candidates for HDT against Mtb and Stm and act by modulating the autophagic/lysosomal response by multiple mechanisms.

Tuberculosis: An Update on Pathophysiology, Molecular Mechanisms of Drug Resistance, Newer Anti-TB Drugs, Treatment Regimens and Host- Directed Therapies

Human tuberculosis (TB) is primarily caused by Mycobacterium tuberculosis (Mtb) that inhabits inside and amidst immune cells of the host with adapted physiology to regulate interdependent cellular functions with intact pathogenic potential. The complexity of this disease is attributed to various factors such as the reactivation of latent TB form after prolonged persistence, disease progression specifically in immunocompromised patients, advent of multi- and extensivelydrug resistant (MDR and XDR) Mtb strains, adverse effects of tailor-made regimens, and drug-drug interactions among anti-TB drugs and anti-HIV therapies. Thus, there is a compelling demand for newer anti-TB drugs or regimens to overcome these obstacles. Considerable multifaceted transformations in the current TB methodologies and molecular interventions underpinning hostpathogen interactions and drug resistance mechanisms may assist to overcome the emerging drug resistance. Evidently, recent scientific and clinical advances have revolutionised the diagnosis, prevention, and treatment of all forms of the disease. This review sheds light on the current understanding of the pathogenesis of TB disease, molecular mechanisms of drug-resistance, progress on the development of novel or repurposed anti-TB drugs and regimens, host-directed therapies, with particular emphasis on underlying knowledge gaps and prospective for futuristic TB control programs.

Comprehensive review on mechanism of action, resistance and evolution of antimycobacterial drugs

Tuberculosis is one of the deadliest infectious diseases existing in the world since ancient times and still possesses serious threat across the globe. Each year the number of cases increases due to high drug resistance shown by Mycobacterium tuberculosis (Mtb). Available antimycobacterial drugs have been classified as First line, Second line and Third line antibiotics depending on the time of their discoveries and their effectiveness in the treatment. These antibiotics have a broad range of targets ranging from cell wall to metabolic processes and their non-judicious and uncontrolled usage in the treatment for years has created a significant problem called multi-drug resistant (MDR) tuberculosis. In this review, we have summarized the mechanism of action of all the classified antibiotics currently in use along with the resistance mechanisms acquired by Mtb. We have focused on the new drug candidates/repurposed drugs, and drug in combinations, which are in clinical trials for either treating the MDR tuberculosis more effectively or involved in reducing the time required for the chemotherapy of drug sensitive TB. This information is not discussed very adequately on a single platform. Additionally, we have discussed the recent technologies that are being used to discover novel resistance mechanisms acquired by Mtb and for exploring novel drugs. The story of intrinsic resistance mechanisms and evolution in Mtb is far from complete. Therefore, we have also discussed intrinsic resistance mechanisms of Mtb and their evolution with time, emphasizing the hope for the development of novel antimycobacterial drugs for effective therapy of tuberculosis.

Host-directed Therapy: A New Arsenal to Come

The emergence of drug-resistant strains among the variety of pathogens worsens the situation in today's scenario. In such a situation, a very heavy demand for developing the new antibiotics has arisen, but unfortunately, very limited success has been achieved in this arena till now. Infectious diseases usually make their impression in the form of severe pathology. Intracellular pathogens use the host's cell machinery for their survival. They alter the gene expression of several host's pathways and endorse to shut down the cell's innate defense pathway like apoptosis and autophagy. Intracellular pathogens are co-evolved with hosts and have a striking ability to manipulate the host's factors. They also mimic the host molecules and secrete them to prevent the host's proper immune response against them for their survival. Intracellular pathogens in chronic diseases create excessive inflammation. This excessive inflammation manifests in pathology. Host directed therapy could be alternative medicine in this situation; it targets the host factors, and abrogates the replication and persistence of pathogens inside the cell. It also provokes the anti-microbial immune response against the pathogen and reduces the exacerbation by enhancing the healing process to the site of pathology. HDT targets the host's factor involved in a certain pathway that ultimately targets the pathogen life cycle and helps in eradication of the pathogen. In such a scenario, HDT could also play a significant role in the treatment of drugsensitive as well with drug resistance strains because it targets the host's factors, which favors the pathogen survival inside the cell.

Are losartan and imatinib effective against SARS-CoV2 pathogenesis? A pathophysiologic-based in silico study

Proposing a theory about the pathophysiology of cytokine storm in COVID19, we were to find the potential drugs to treat this disease and to find any effect of these drugs on the virus infectivity through an in silico study. COVID-19-induced ARDS is linked to a cytokine storm phenomenon not explainable solely by the virus infectivity. Knowing that ACE2, the hydrolyzing enzyme of AngII and SARS-CoV2 receptor, downregulates when the virus enters the host cells, we hypothesize that hyperacute AngII upregulation is the eliciting factor of this ARDS. We were to validate this theory through reviewing previous studies to figure out the role of overzealous activation of AT1R in ARDS. According to this theory losartan may attenuate ARDS in this disease. Imatinib, has previously been elucidated to be promising in modulating lung inflammatory reactions and virus infectivity in SARS and MERS. We did an in silico study to uncover any probable other unconsidered inhibitory effects of losartan and imatinib against SARS-CoV2 pathogenesis. Reviewing the literature, we could find that over-activation of AT1R could explain precisely the mechanism of cytokine storm in COVID19. Our in silico study revealed that losartan and imatinib could probably: (1) decline SARS-CoV2 affinity to ACE2. (2) inhibit the main protease and furin, (3) disturb papain-like protease and p38MAPK functions. Our reviewing on renin-angiotensin system showed that overzealous activation of AT1R by hyper-acute excess of AngII due to acute downregulation of ACE2 by SARS-CoV2 explains precisely the mechanism of cytokine storm in COVID-19. Besides, based on our in silico study we concluded that losartan and imatinib are promising in COVID19.

Diurnal expression of MRP4 in bone marrow cells underlies the dosing-time dependent changes in the oxaliplatin-induced myelotoxicity

The expression and function of some xenobiotic transporters varies according to the time of day, causing the dosing time-dependent changes in drug disposition and toxicity. Multidrug resistance-associated protein-4 (MRP4), an ATP­binding cassette (ABC) efflux transporter encoded by the Abcc4 gene, is highly expressed in bone marrow cells (BMCs) and protects them against xenobiotics, including chemotherapeutic drugs. In this study, we demonstrated that MRP4 was responsible for the extrusion of oxaliplatin (L-OHP), a platinum (Pt)-based chemotherapeutic drug, from BMCs of mice, and that the efflux transporter expression exhibited significant diurnal variation. Therefore, we investigated the relevance of the diurnal expression of MRP4 in BMCs for L-OHP-induced myelotoxicity in mice maintained under standardized light/dark cycle conditions. After intravenous injection of L-OHP, the Pt content in BMCs varied according to the injection time. Lower Pt accumulation in BMCs was detected in mice after injection of L-OHP at the mid-dark phase, during which the expression levels of MRP4 increased. Consistent with these observations, the myelotoxic effects of L-OHP were attenuated when mice were injected with L-OHP during the dark phase. This dosing schedule also alleviated the L-OHP-induced reduction of the peripheral white blood cell count. The present results suggest that the myelotoxicity of L-OHP is attenuated by optimizing the dosing schedule. Diurnal expression of MRP4 in BMCs is associated with the dosing time-dependent changes in L-OHP-induced myelotoxicity.

Pyoderma gangrenosum-like necrotizing panniculitis associated with Imatinib: A case report

Imatinib mesylate is a small tyrosine kinase inhibitor that targets BCR-ABL, ckit and platelet-derived growth factor receptor. It is prescribed by hematologists for chronic myeloid leukemia and acute lymphoblastic leukemia and by oncologists for Gastrointestinal Stromal Tumors (GIST). Cutaneous reactions to Imatinib are common but their incidence and severity widely varies between patients. A self-limited skin rash is the most common adverse effect but there have been reported cases of patients with maculopapular rash, pigmentary changes, superficial edema and rarer and clinically distinctive features such as lichenoid reactions or psoriasis. We here describe for the first time a case of pyoderma gangrenosum-like necrotizing panniculitis, a rare dermatological condition, after initiating therapy with Imatinib.

COVID-19-driven endothelial damage: complement, HIF-1, and ABL2 are potential pathways of damage and targets for cure

COVID-19 pandemia is a major health emergency causing hundreds of deaths worldwide. The high reported morbidity has been related to hypoxia and inflammation leading to endothelial dysfunction and aberrant coagulation in small and large vessels. This review addresses some of the pathways leading to endothelial derangement, such as complement, HIF-1α, and ABL tyrosine kinases. This review also highlights potential targets for prevention and therapy of COVID-19-related organ damage and discusses the role of marketed drugs, such as eculizumab and imatinib, as suitable candidates for clinical trials.

Importance of protein Ser/Thr/Tyr phosphorylation for bacterial pathogenesis

Protein phosphorylation regulates a large variety of biological processes in all living cells. In pathogenic bacteria, the study of serine, threonine, and tyrosine (Ser/Thr/Tyr) phosphorylation has shed light on the course of infectious diseases, from adherence to host cells to pathogen virulence, replication, and persistence. Mass spectrometry (MS)-based phosphoproteomics has provided global maps of Ser/Thr/Tyr phosphosites in bacterial pathogens. Despite recent developments, a quantitative and dynamic view of phosphorylation events that occur during bacterial pathogenesis is currently lacking. Temporal, spatial, and subpopulation resolution of phosphorylation data is required to identify key regulatory nodes underlying bacterial pathogenesis. Herein, we discuss how technological improvements in sample handling, MS instrumentation, data processing, and machine learning should improve bacterial phosphoproteomic datasets and the information extracted from them. Such information is expected to significantly extend the current knowledge of Ser/Thr/Tyr phosphorylation in pathogenic bacteria and should ultimately contribute to the design of novel strategies to combat bacterial infections.

Circulating myeloid cells invade the central nervous system to mediate cachexia during pancreatic cancer

Weight loss and anorexia are common symptoms in cancer patients that occur prior to initiation of cancer therapy. Inflammation in the brain is a driver of these symptoms, yet cellular sources of neuroinflammation during malignancy are unknown. In a mouse model of pancreatic ductal adenocarcinoma (PDAC), we observed early and robust myeloid cell infiltration into the brain. Infiltrating immune cells were predominately neutrophils, which accumulated at a unique central nervous system entry portal called the velum interpositum, where they expressed CCR2. Pharmacologic CCR2 blockade and genetic deletion of Ccr2 both resulted in significantly decreased brain-infiltrating myeloid cells as well as attenuated cachexia during PDAC. Lastly, intracerebroventricular blockade of the purinergic receptor P2RX7 during PDAC abolished immune cell recruitment to the brain and attenuated anorexia. Our data demonstrate a novel function for the CCR2/CCL2 axis in recruiting neutrophils to the brain, which drives anorexia and muscle catabolism.

In Situ Mannosylated Nanotrinity-Mediated Macrophage Remodeling Combats Candida albicans Infection

Deep Candida albicans infection is one of the major causes of death in immunosuppressed hosts. Remodeling macrophages to phenotype M1 can decrease fungus burden and facilitate combating C. albicans under an immunosuppressive state. In this study, a nanotrinity was exploited to direct fungicidal macrophage polarization by leveraging the regulation pathways in macrophage redifferentiation. Conventional chemotherapeutic imatinib, which can abrogate M2 macrophage polarization via "shutting off" the STAT6 phosphorylation pathway, was encapsulated in biodegradable polymeric nanoparticles. In house-customized dual functional mannosylated chitosan oligosaccharides were then coated on the surface of the imatinib-laden nanoparticles, and thus, a mannosylated nanotrinity was achieved with ternary functions for macrophage remodeling: (i) imatinib-blocked STAT6 phosphorylation pathway for decreasing M2 macrophage population; (ii) chitosan oligosaccharides-mediated TLR-4 pathway activation that could promote macrophage redifferentiation to M1 phenotype; (iii) mannose motif-enhanced macrophage targeting. After physiochemical characterization, regulatory effects of the mannosylated nanotrinity on macrophages and the anti-C. albicans efficacy were evaluated at the cellular level and animal level, respectively. The results demonstrated that our mannosylated nanotrinity could efficiently induce macrophage polarization toward the M1 phenotype, decrease M2 phenotype production, and markedly lessen fungus burden and increased the median survival time of mice infected with C. albicans. Therefore, the mannosylated nanotrinity developed in this study could significantly induce macrophage remodeling in situ by the two-pronged process, "turning on" M1 phenotype polarization meanwhile "shutting off" M2 phenotype polarization, and thus allowed to eradicate C. albicans infection.

The current state of animal models and genomic approaches towards identifying and validating molecular determinants of Mycobacterium tuberculosis infection and tuberculosis disease

Animal models are important in understanding both the pathogenesis of and immunity to tuberculosis (TB). Unfortunately, we are beginning to understand that no animal model perfectly recapitulates the human TB syndrome, which encompasses numerous different stages. Furthermore, Mycobacterium tuberculosis infection is a very heterogeneous event at both the levels of pathogenesis and immunity. This review seeks to establish the current understanding of TB pathogenesis and immunity, as validated in the animal models of TB in active use today. We especially focus on the use of modern genomic approaches in these models to determine the mechanism and the role of specific molecular pathways. Animal models have significantly enhanced our understanding of TB. Incorporation of contemporary technologies such as single cell transcriptomics, high-parameter flow cytometric immune profiling, proteomics, proteomic flow cytometry and immunocytometry into the animal models in use will further enhance our understanding of TB and facilitate the development of treatment and vaccination strategies.

Effects of host-directed therapies on the pathology of tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), has co-evolved with the human immune system and utilizes multiple strategies to persist within infected cells, to hijack several immune mechanisms, and to cause severe pathology and tissue damage in the host. This delays the efficacy of current antibiotic therapy and contributes to the evolution of multi-drug-resistant strains. These challenges led to the development of the novel approach in TB treatment that involves therapeutic targeting of host immune response to control disease pathogenesis and pathogen growth, namely, host-directed therapies (HDTs). Such HDT approaches can (1) enhance the effect of antibiotics, (2) shorten treatment duration for any clinical form of TB, (3) promote development of immunological memory that could protect against relapse, and (4) ameliorate the immunopathology including matrix destruction and fibrosis associated with TB. In this review we discuss TB-HDT candidates shown to be of clinical relevance that thus could be developed to reduce pathology, tissue damage, and subsequent impairment of pulmonary function. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Therapeutic host-directed strategies to improve outcome in tuberculosis

Bacille Calmette-Guérin (BCG) is the only licenced tuberculosis (TB) vaccine, but has limited efficacy against pulmonary TB disease development and modest protection against extrapulmonary TB. Preventative antibiotic treatment for Mycobacterium tuberculosis (Mtb) infections in high-prevalence settings is unfeasible due to unclear treatment durability, drug toxicity, logistical constraints related to directly observed treatment strategy (DOTS) and the lengthy treatment protocols. Together, these factors promote non-adherence, contributing to relapse and establishment of drug-resistant Mtb strains. Although antibiotic treatment of drug-susceptible Mtb is generally effective, drug-resistant TB has a treatment efficacy below 50% and can, in a proportion, develop into progressive, untreatable disease. Other immune compromising co-infections and/or co-morbidities require more complex prevention/treatment approaches, posing huge financial burdens to national health services. Novel TB treatment strategies, such as host-directed therapeutics, are required to complement pathogen-targeted approaches. Pre-clinical studies have highlighted promising candidates that enhance endogenous pathways and/or limit destructive host responses. This review discusses promising pre-clinical candidates and forerunning compounds at advanced stages of clinical investigation in TB host-directed therapeutic (HDT) efficacy trials. Such approaches are rationalized to improve outcome in TB and shorten treatment strategies.

Remembering the Host in Tuberculosis Drug Development

New therapeutics to augment current approaches and shorten treatment duration are of critical importance for combating tuberculosis (TB), especially those with novel mechanisms of action to counter the emergence of drug-resistant TB. Host-directed therapy (HDT) offers a novel strategy with mechanisms that include activating immune defense mechanisms or ameliorating tissue damage. These and related concepts will be discussed along with issues that emerged from the workshop organized by the Stop TB Working Group on New Drugs, held at the Gordon Research Conference for Tuberculosis Drug Development in Lucca, Italy in June 2017, titled "Strategic Discussion on Repurposing Drugs & Host Directed Therapies for TB." In this review, we will highlight recent data regarding drugs, pathways, and concepts that are important for successful development of HDTs for TB.

Combating biothreat pathogens: ongoing efforts for countermeasure development and unique challenges

Research to discover and develop antibacterial and antiviral drugs with potent activity against pathogens of biothreat concern presents unique methodological and process-driven challenges. Herein, we review laboratory approaches for finding new antibodies, antibiotics, and antiviral molecules for pathogens of biothreat concern. Using high-throughput screening techniques, molecules that directly inhibit a pathogen’s entry, replication, or growth can be identified. Alternatively, molecules that target host proteins can be interesting targets for development when countering biothreat pathogens, due to the modulation of the host immune response or targeting proteins that interfere with the pathways required by the pathogen for replication. Monoclonal and cocktail antibody therapies approved by the Food and Drug Administration for countering anthrax and under development for treatment of Ebola virus infection are discussed. A comprehensive tabular review of current in vitro, in vivo, pharmacokinetic and efficacy datasets has been presented for biothreat pathogens of greatest concern. Finally, clinical trials and animal rule or traditional drug approval pathways are also reviewed.

Opinions; interpretations; conclusions; and recommendations are those of the authors and are not necessarily endorsed by the US Army.

Host-Targeted Therapeutics against Multidrug Resistant Intracellular Staphylococcus aureus

Staphylococcus aureus is a facultative intracellular pathogen that invades and replicates within many types of human cells. S. aureus has shown to rapidly overcome traditional antibiotherapy by developing multidrug resistance. Furthermore, intracellular S. aureus is protected from the last-resort antibiotics—vancomycin, daptomycin, and linezolid—as they are unable to achieve plasma concentrations sufficient for intracellular killing. Therefore, there is an urgent need to develop novel anti-infective therapies against S. aureus infections. Here, we review the current state of the field and highlight the exploitation of host-directed approaches as a promising strategy going forward.

Evaluation of Different Concentrations of Imatinib on the Viability of Leishmania major: An In Vitro Study

BACKGROUND

Leishmaniasis is an infectious disease caused by an intracellular parasite of Leishmania and is transmitted through the female sandflies bite and may lead to severe skin lesions. Although drugs such as antimony compounds are available, their side effects such as toxicity, low efficacy, and emergence of resistance have raised the importance of effective replacement. Imatinib, as an inhibitor of tyrosine kinase (TK) of Leishmania, stops abnormal function of TK such as Bcr-Abl through assembling into transmembrane pores in a sterol-dependent manner. Hence, the evaluation of killing effects of different concentrations of imatinib against Leishmania major amastigotes and promastigotes in vitro were the objectives of the present study.

MATERIALS AND METHODS

The killing effects of different concentrations of imatinib (25, 50, and 100 μg) and 25 μg amphotericin B (as positive control) were evaluated against RPMI 1640-cultured promastigotes and the amastigote/macrophage model by MTS cell proliferation assay kit (ab197010) and Giemsa staining method during 24, 48, and 72 h.

RESULTS

The results showed anti-Leishmania effect of imatinib in concentration and time-dependent manner. The lowest number of live promastigotes and amastigotes were obtained due to treat with 100 μg/ml imatinib at 72 h. Furthermore, 100 μg concentration of imatinib had the same effect as 25 μg amphotericin B on both L. major promastigotes and amastigotes (P < 0.001).

CONCLUSION

The anti-Leishmania effect of imatinib was confirmed by MTS and direct microscopy. Further study is recommended for evaluating possible therapeutic effects of imatinib on leishmaniasis in vivo.

B Cell-Based Vaccine Transduced With ESAT6-Expressing Vaccinia Virus and Presenting α-Galactosylceramide Is a Novel Vaccine Candidate Against ESAT6-Expressing Mycobacterial Diseases

Early secretory antigenic target-6 (ESAT6) is a potent immunogenic antigen expressed in Mycobacterium tuberculosis as well as in some non-tuberculous mycobacteria (NTM), such as M. kansasii. M. kansasii is one of the most clinically relevant species of NTM that causes mycobacterial lung disease, which is clinically indistinguishable from tuberculosis. In the current study, we designed a novel cell-based vaccine using B cells that were transduced with vaccinia virus expressing ESAT6 (vacESAT6), and presenting α-galactosylceramide (αGC), a ligand of invariant NKT cells. We found that B cells loaded with αGC had increased levels of CD80 and CD86 after in vitro stimulation with NKT cells. Immunization of mice with B/αGC/vacESAT6 induced CD4⁺ T cells producing TNF-α and IFN-γ in response to heat-killed M. tuberculosis. Immunization of mice with B/αGC/vacESAT6 ameliorated severe lung inflammation caused by M. kansasii infection. We also confirmed that immunization with B/αGC/vacESAT6 reduced M. kansasii bacterial burden in the lungs. In addition, therapeutic administration of B/αGC/vacESAT6 increased IFN-γ⁺ CD4⁺ T cells and inhibited the progression of lung pathology caused by M. kansasii infection. Thus, B/αGC/vacESAT6 could be a potent vaccine candidate for the prevention and treatment of ESAT6-expressing mycobacterial infection caused by M. kansasii.

Nilotinib: A Tyrosine Kinase Inhibitor Mediates Resistance to Intracellular Mycobacterium Via Regulating Autophagy

Nilotinib, a tyrosine kinase inhibitor, has been studied extensively in various tumor models; however, no information exists about the pharmacological action of nilotinib in bacterial infections. Mycobacterium bovis (M. bovis) and Mycobacterium avium subspecies paratuberculosis (MAP) are the etiological agents of bovine tuberculosis and Johne's disease, respectively. Although M. bovis and MAP cause distinct tissue tropism, both of them infect, reside, and replicate in mononuclear phagocytic cells of the infected host. Autophagy is an innate immune defense mechanism for the control of intracellular bacteria, regulated by diverse signaling pathways. Here we demonstrated that nilotinib significantly inhibited the intracellular survival and growth of M. bovis and MAP in macrophages by modulating host immune responses. We showed that nilotinib induced autophagic degradation of intracellular mycobacterium occurred via the inhibition of PI3k/Akt/mTOR axis mediated by abelson (c-ABL) tyrosine kinase. In addition, we observed that nilotinib promoted ubiquitin accumulation around M. bovis through activation of E3 ubiquitin ligase parkin. From in-vivo experiments, we found that nilotinib effectively controlled M. bovis growth and survival through enhanced parkin activity in infected mice. Altogether, our data showed that nilotinib regulates protective innate immune responses against intracellular mycobacterium, both in-vitro and in-vivo, and can be exploited as a novel therapeutic remedy for the control of M. bovis and MAP infections.

Host-directed kinase inhibitors act as novel therapies against intracellular Staphylococcus aureus

Host-directed therapeutics are a promising anti-infective strategy against intracellular bacterial pathogens. Repurposing host-targeted drugs approved by the FDA in the US, the MHRA in the UK and/or regulatory equivalents in other countries, is particularly interesting because these drugs are commercially available, safe doses are documented and they have been already approved for other clinical purposes. In this study, we aimed to identify novel therapies against intracellular Staphylococcus aureus, an opportunistic pathogen that is able to exploit host molecular and metabolic pathways to support its own intracellular survival. We screened 133 host-targeting drugs and found three host-directed tyrosine kinase inhibitors (Ibrutinib, Dasatinib and Crizotinib) that substantially impaired intracellular bacterial survival. We found that Ibrutinib significantly increased host cell viability after S. aureus infection via inhibition of cell invasion and intracellular bacterial proliferation. Using phosphoproteomics data, we propose a putative mechanism of action of Ibrutinib involving several host factors, including EPHA2, C-JUN and NWASP. We confirmed the importance of EPHA2 for staphylococcal infection in an EPHA2-knock-out cell line. Our study serves as an important example of feasibility for identifying host-directed therapeutics as candidates for repurposing.

Western diet regulates immune status and the response to LPS-driven sepsis independent of diet-associated microbiome

Sepsis is a deleterious immune response to infection that leads to organ failure and is the 11th most common cause of death worldwide. Despite plaguing humanity for thousands of years, the host factors that regulate this immunological response and subsequent sepsis severity and outcome are not fully understood. Here we describe how the Western diet (WD), a diet high in fat and sucrose and low in fiber, found rampant in industrialized countries, leads to worse disease and poorer outcomes in an LPS-driven sepsis model in WD-fed mice compared with mice fed standard fiber-rich chow (SC). We find that WD-fed mice have higher baseline inflammation (metaflammation) and signs of sepsis-associated immunoparalysis compared with SC-fed mice. WD mice also have an increased frequency of neutrophils, some with an "aged" phenotype, in the blood during sepsis compared with SC mice. Importantly, we found that the WD-dependent increase in sepsis severity and higher mortality is independent of the microbiome, suggesting that the diet may be directly regulating the innate immune system through an unknown mechanism. Strikingly, we could predict LPS-driven sepsis outcome by tracking specific WD-dependent disease factors (e.g., hypothermia and frequency of neutrophils in the blood) during disease progression and recovery. We conclude that the WD is reprogramming the basal immune status and acute response to LPS-driven sepsis and that this correlates with alternative disease paths that lead to more severe disease and poorer outcomes.

Mastocytosis: from a Molecular Point of View

Mast cells (MCs) are physiologically activated by binding of stem cell factor (SCF) to the extracellular domains of the Kit receptor. This binding increases the proliferation and prolongs the survival of normal mature MCs, as well as intensifies the release of mediators. In mastocytosis, somatic mutations of the coding Kit gene cause autocrine dysregulation and lead to constitutive KIT activation even in the absence of its ligand SCF. Clinical symptoms are caused by MC-mediator release and/or infiltration of MCs into tissues. Aberrant KIT activation may result in increased production of MCs in the skin and extracutaneous organs. Depending on the affected organ(s), the disease can be divided into cutaneous mastocytosis (CM), systemic mastocytosis (SM), and localized MC tumors. The updated classification of WHO discriminates between several distinct subvariants of CM and SM. While the prognosis in CM and indolent SM (ISM) is excellent with (almost) normal life expectancy, the prognosis in aggressive SM (ASM) and MC leukemia (MCL) is dismal. The symptoms may comprise urticaria, angioedema, flush, pruritus, abdominal pain, diarrhea, hypotension, syncope, and musculoskeletal pain and are the results of MC infiltration and mediator release into target organs, i.e., the skin, gastrointestinal tract, liver, spleen, lymph nodes, and bone marrow. Mastocytosis differs from a lot of other hematological disorders because its pathology is not only based on the lack of normal function of a specific pathway or of a specific cell type but additionally is a proliferative disease. Currently available treatments of mastocytosis include symptomatic, antimediator and cytoreductive targeted therapies.

The tyrosine kinase inhibitor dasatinib reduces the growth of intracellular Mycobacterium tuberculosis despite impairing T-cell function

Tyrosine kinases are checkpoints for multiple cellular pathways and dysregulation induces malignancies, most notably chronic myeloid leukemia (CML). Inhibition of Abl-tyrosine kinases has evolved as a new concept for the treatment of CML and other malignant diseases. Due to the multiple immune-modulatory pathways controlled by tyrosine kinases, treatment with tyrosine kinase inhibitors (TKIs) will not only affect the biology of malignant cells but also modulate physiological immune functions. To understand the effects of TKIs on host defense against intracellular bacteria, we investigated the immunological impact of the dual Abl/Src TKI dasatinib on the cellular immune response to Mycobacterium tuberculosis (Mtb). Our results demonstrate that dasatinib impaired proliferation, cytokine release (IFN-γ, TNF-α, GM-CSF), expression of granulysin and degranulation of cytotoxic effector molecules of human Mtb-specific T-lymphocytes by inhibition of lymphocyte-specific protein tyrosine kinase (Lck) phosphorylation. Despite this profound inhibition of T-cell function, dasatinib suppressed growth of virulent Mtb in human macrophages co-cultured with autologous Mtb-specific T-cells (49±15%). Functional analysis suggested that growth inhibition is due to dasatinib-triggered lysosomal acidification in Mtb-infected macrophages. These results highlight the significance of innate immune responses, i.e. acidification of lysosomes, which control the multiplication of intracellular bacteria despite the lack of efficient T-cell support.

The Immune Response to Mycobacterium tuberculosis in HIV-1-Coinfected Persons

Globally, about 36.7 million people were living with HIV infection at the end of 2015. The most frequent infection co-occurring with HIV-1 is Mycobacterium tuberculosis-374,000 deaths per annum are attributable to HIV-tuberculosis, 75% of those occurring in Africa. HIV-1 infection increases the risk of tuberculosis by a factor of up to 26 and alters its clinical presentation, complicates diagnosis and treatment, and worsens outcome. Although HIV-1-induced depletion of CD4⁺ T cells underlies all these effects, more widespread immune deficits also contribute to susceptibility and pathogenesis. These defects present a challenge to understand and ameliorate, but also an opportunity to learn and optimize mechanisms that normally protect people against tuberculosis. The most effective means to prevent and ameliorate tuberculosis in HIV-1-infected people is antiretroviral therapy, but this may be complicated by pathological immune deterioration that in turn requires more effective host-directed anti-inflammatory therapies to be derived.

Development of New Preventive and Therapeutic Vaccines for Tuberculosis

Tuberculosis (TB) is a contagious disease that has been responsible for the death of one billion people in the last 200 years. Until now, the only vaccine approved for the prevention of TB is Bacillus Calmette-Guérin (BCG), which is prepared by attenuating Mycobacterium bovis. However, one of the limitations of BCG is that its preventive effect against pulmonary TB varies from person to person. Therefore, there arises a need for a new TB vaccine to replace or supplement BCG. In this review, we have summarized the findings of current clinical trials on preventive and therapeutic TB vaccine candidates. In addition, we have discussed a novel vaccination approach using the cell-based vaccine presenting early secretory antigenic target-6 (ESAT-6), which is a potent immunogenic antigen. The role of ESAT-6 in hosts has also been described.

Optimization of the tumor microenvironment and nanomedicine properties simultaneously to improve tumor therapy

Effective delivery of nanomedicines to tumor tissues depends on both the tumor microenvironment and nanomedicine properties. Accordingly, tumor microenvironment modification or advanced design of nanomedicine was emerging to improve nanomedicine delivery to tumors. However, few studies have emphasized the necessity to optimize the tumor microenvironment and nanomedicine properties simultaneously to improve tumor treatment. In the present study, imatinib mesylate (IMA) was used to normalize the tumor microenvironment including platelet-derived growth factor receptor-β expression inhibition, tumor vessel normalization, and tumor perfusion improvement as demonstrated by immunofluorescence staining. In addition, the effect of tumor microenvironment normalization on tumor delivery of nanomedicines with different sizes was carefully investigated. It was shown that IMA treatment significantly reduced the accumulation of nanoparticles (NPs) around 110 nm but enhanced the accumulation of micelles around 23 nm by in vivo fluorescence imaging experiment. Furthermore, IMA treatment limited the distribution of NPs inside tumors but increased that of micelles with a more homogeneous pattern. Finally, the anti-tumor efficacy study displayed that IMA pretreatment could significantly increase the therapeutic effects of paclitaxel-loaded micelles. All-together, a new strategy to improve nanomedicine delivery to tumor was provided by optimizing both nanomedicine size and the tumor microenvironment simultaneously, and it will have great potential in clinics for tumor treatment.

Tuberculosis: progress and advances in development of new drugs, treatment regimens, and host-directed therapies

Tuberculosis remains the world's leading cause of death from an infectious disease, responsible for an estimated 1 674 000 deaths annually. WHO estimated 600 000 cases of rifampicin-resistant tuberculosis in 2016-of which 490 000 were multidrug resistant (MDR), with less than 50% survival after receiving recommended treatment regimens. Concerted efforts of stakeholders, advocates, and researchers are advancing further development of shorter course, more effective, safer, and better tolerated treatment regimens. We review the developmental pipeline and landscape of new and repurposed tuberculosis drugs, treatment regimens, and host-directed therapies (HDTs) for drug-sensitive and drug-resistant tuberculosis. 14 candidate drugs for drug-susceptible, drug-resistant, and latent tuberculosis are in clinical stages of drug development; nine are novel in phase 1 and 2 trials, and three new drugs are in advanced stages of development for MDR tuberculosis. Specific updates are provided on clinical trials of bedaquiline, delamanid, pretomanid, and other licensed or repurposed drugs that are undergoing investigation, including trials aimed at shortening duration of tuberculosis treatment, improving treatment outcomes and patient adherence, and reducing toxic effects. Ongoing clinical trials for shortening tuberculosis treatment duration, improving treatment outcomes in MDR tuberculosis, and preventing disease in people with latent tuberculosis infection are reviewed. A range of HDTs and immune-based treatments are under investigation as adjunctive therapy for shortening duration of therapy, preventing permanent lung injury, and improving treatment outcomes of MDR tuberculosis. We discuss the HDT development pipeline, ongoing clinical trials, and translational research efforts for adjunct tuberculosis treatment.

c-Abl-TWIST1 Epigenetically Dysregulate Inflammatory Responses during Mycobacterial Infection by Co-Regulating Bone Morphogenesis Protein and miR27a

Mycobacteria propelled modulation of host responses is of considerable interest in the face of emerging drug resistance. Although it is known that Abl tyrosine kinases affect entry and persistence of mycobacteria, mechanisms that couple c-Abl to proximal signaling pathways during immunity are poorly understood. Loss-of-function of c-Abl through Imatinib, in a mouse model of tuberculosis or RNA interference, identified bone morphogenesis protein (BMP) signaling as its cellular target. We demonstrate that c-Abl promotes mycobacterial survival through epigenetic modification brought about by KAT5-TWIST1 at Bmp loci. c-Abl-BMP signaling deregulated iNOS, aggravating the inflammatory balance. Interestingly, BMP signaling was observed to have far-reaching effects on host immunity, as it attenuated TLR3 pathway by engaging miR27a. Significantly, these events were largely mediated via WhiB3 and DosR/S/T but not SecA signaling pathway of mycobacteria. Our findings suggest molecular mechanisms of host pathways hijacked by mycobacteria and expand our understanding of c-Abl inhibitors in potentiating innate immune responses.

The impact of Mir-9 regulation in normal and malignant hematopoiesis

MicroRNA-9 (MiR-9) dysregulation has been observed in various cancers. Recently, MiR-9 is considered to have a part in hematopoiesis and hematologic malignancies. However, its importance in blood neoplasms is not yet well defined. Thus, this study was conducted in order to assess the significance of MiR-9 role in the development of hematologic neoplasia, prognosis, and treatment approaches. We have shown that a large number of MiR-9 targets (such as FOXOs, SIRT1, CCND1, ID2, CCNG1, Ets, and NFkB) play essential roles in leukemogenesis and that it is overexpressed in different leukemias. Our findings indicated MiR-9 downregulation in a majority of leukemias. However, its overexpression was reported in patients with dysregulated MiR-9 controlling factors (such as MLLr). Additionally, prognostic value of MiR-9 has been reported in some types of leukemia. This study generally emphasizes on the critical role of MiR-9 in hematologic malignancies as a prognostic factor and a therapeutic target.

TLR5 signaling in murine bone marrow induces hematopoietic progenitor cell proliferation and aids survival from radiation

Administration of the bacterial protein flagellin to mice activates innate immune signaling that protects against an array of challenges, including ionizing radiation. Herein, we define the underlying mechanism for this protection. We report that flagellin treatment induces proliferation and mobilization of bone marrow cells that aid survival following irradiation. Specifically, treatment of mice or bone marrow cells ex vivo with flagellin induced Toll-like receptor 5 (TLR5)-dependent and NOD-like receptor C4-independent proliferation of Lin^-Sca-1⁺Kit⁺ (LSK) cells, which includes both hematopoietic stem cells that provide long-term repopulation (LTR) and multipotent progenitor cells (MPPs) that transiently proliferate and differentiate into a range of blood cell types. TLR5 expression on bone marrow cells was necessary and sufficient for flagellin-induced LSK proliferation. Flagellin treatment stimulated LSK proliferation by inducing a 10-fold increase in type 3 MPP (MPP3) without a concomitant increase in LTR cells. Cotransfer of 5 × 10³ fluorescence-activated cell sorted flagellin-induced MPP3 cells along with 1 × 10⁵ whole bone marrow cells to lethally irradiated mice revealed that such cells predominantly repopulated the neutrophil compartment for up to 4 week, and dramatically increased the survival rate of the bone marrow transplantation procedure. Hence, we propose the administration of MPP3 cells, elicited by flagellin, as a novel approach to prevent life-threatening neutropenia that can accompany bone marrow transplant and other myeloablative therapeutic procedures.

Drug-induced pyoderma gangrenosum: a model to understand the pathogenesis of pyoderma gangrenosum

Pyoderma gangrenosum (PG) is a rare autoinflammatory condition in which the alteration of neutrophil function and the innate immune response play key roles in its pathogenesis. Cases of PG have been reported in patients being treated with certain medications, which may help us to understand some of the possible pathways involved in the aetiology of PG. The aim of this review is to review the cases of PG triggered by certain drugs and try to thoroughly understand the pathogenesis of the disease. To accomplish this, a PubMed search was completed using the following words: pyoderma gangrenosum, neutrophilic dermatosis, pathophysiology, drug-induced pyoderma gangrenosum. In total, we found 43 cases of drug-induced PG. Most of them were caused by colony-stimulating factors and small-molecule tyrosine kinase inhibitors. We propose that drugs induce PG through various mechanisms such as dysfunctional neutrophil migration and function, dysregulated inflammatory response, promotion of keratinocyte apoptosis and alteration of epigenetic mechanisms. PG is a rare condition with complex pathophysiology and drug-induced cases are even more scarce; this is the main limitation of this review. Understanding the possible mechanisms of drug-induced PG, via abnormal neutrophil migration and function, abnormal inflammation, keratinocyte apoptosis and alteration of epigenetic mechanisms would help to better understand the pathogenesis of PG and ultimately to optimize targeted therapy.

Tuberculosis--advances in development of new drugs, treatment regimens, host-directed therapies, and biomarkers

Tuberculosis is the leading infectious cause of death worldwide, with 9·6 million cases and 1·5 million deaths reported in 2014. WHO estimates 480,000 cases of these were multidrug resistant (MDR). Less than half of patients who entered into treatment for MDR tuberculosis successfully completed that treatment, mainly due to high mortality and loss to follow-up. These in turn illustrate weaknesses in current treatment regimens and national tuberculosis programmes, coupled with operational treatment challenges. In this Review we provide an update on recent developments in the tuberculosis drug-development pipeline (including new and repurposed antimicrobials and host-directed drugs) as they are applied to new regimens to shorten and improve outcomes of tuberculosis treatment. Several new or repurposed antimicrobial drugs are in advanced trial stages for MDR tuberculosis, and two new antimicrobial drug candidates are in early-stage trials. Several trials to reduce the duration of therapy in MDR and drug-susceptible tuberculosis are ongoing. A wide range of candidate host-directed therapies are being developed to accelerate eradication of infection, prevent new drug resistance, and prevent permanent lung injury. As these drugs have been approved for other clinical indications, they are now ready for repurposing for tuberculosis in phase 2 clinical trials. We assess risks associated with evaluation of new treatment regimens, and highlight opportunities to advance tuberculosis research generally through regulatory innovation in MDR tuberculosis. Progress in tuberculosis-specific biomarkers (including culture conversion, PET and CT imaging, and gene expression profiles) can support this innovation. Several global initiatives now provide unique opportunities to tackle the tuberculosis epidemic through collaborative partnerships between high-income countries and middle-income and low-income countries for clinical trials training and research, allowing funders to coordinate several national and regional programmes for greatest overall effect.

Host-directed therapies for infectious diseases: current status, recent progress, and future prospects

Despite extensive global efforts in the fight against killer infectious diseases, they still cause one in four deaths worldwide and are important causes of long-term functional disability arising from tissue damage. The continuing epidemics of tuberculosis, HIV, malaria, and influenza, and the emergence of novel zoonotic pathogens represent major clinical management challenges worldwide. Newer approaches to improving treatment outcomes are needed to reduce the high morbidity and mortality caused by infectious diseases. Recent insights into pathogen–host interactions, pathogenesis, inflammatory pathways, and the host's innate and acquired immune responses are leading to identification and development of a wide range of host-directed therapies with different mechanisms of action. Host-directed therapeutic strategies are now becoming viable adjuncts to standard antimicrobial treatment. Host-directed therapies include commonly used drugs for non-communicable diseases with good safety profiles, immunomodulatory agents, biologics (eg monoclonal antibodies), nutritional products, and cellular therapy using the patient's own immune or bone marrow mesenchymal stromal cells. We discuss clinically relevant examples of progress in identifying host-directed therapies as adjunct treatment options for bacterial, viral, and parasitic infectious diseases.

Immune Cell Regulatory Pathways Unexplored as Host-Directed Therapeutic Targets for Mycobacterium tuberculosis: An Opportunity to Apply Precision Medicine Innovations to Infectious Diseases

The lack of novel antimicrobial drugs in development for tuberculosis treatment has provided an impetus for the discovery of adjunctive host-directed therapies (HDTs). Several promising HDT candidates are being evaluated, but major advancement of tuberculosis HDTs will require understanding of the master or "core" cell signaling pathways that control intersecting immunologic and metabolic regulatory mechanisms, collectively described as "immunometabolism." Core regulatory pathways conserved in all eukaryotic cells include poly (ADP-ribose) polymerases (PARPs), sirtuins, AMP-activated protein kinase (AMPK), and mechanistic target of rapamycin (mTOR) signaling. Critical interactions of these signaling pathways with each other and their roles as master regulators of immunometabolic functions will be addressed, as well as how Mycobacterium tuberculosis is already known to influence various other cell signaling pathways interacting with them. Knowledge of these essential mechanisms of cell function regulation has led to breakthrough targeted treatment advances for many diseases, most prominently in oncology. Leveraging these exciting advances in precision medicine for the development of innovative next-generation HDTs may lead to entirely new paradigms for treatment and prevention of tuberculosis and other infectious diseases.

Sharpening nature's tools for efficient tuberculosis control: A review of the potential role and development of host-directed therapies and strategies for targeted respiratory delivery

Centuries since it was first described, tuberculosis (TB) remains a significant global public health issue. Despite ongoing holistic measures implemented by health authorities and a number of new oral treatments reaching the market, there is still a need for an advanced, efficient TB treatment. An adjunctive, host-directed therapy designed to enhance endogenous pathways and hence compliment current regimens could be the answer. The integration of drug repurposing, including synthetic and naturally occurring compounds, with a targeted drug delivery platform is an attractive development option. In order for a new anti-tubercular treatment to be produced in a timely manner, a multidisciplinary approach should be taken from the outset including stakeholders from academia, the pharmaceutical industry, and regulatory bodies keeping the patient as the key focus. Pre-clinical considerations for the development of a targeted host-directed therapy are discussed here.

Potential of immunomodulatory agents as adjunct host-directed therapies for multidrug-resistant tuberculosis

Treatment of multidrug-resistant tuberculosis (MDR-TB) is extremely challenging due to the virulence of the etiologic strains of Mycobacterium tuberculosis (M. tb), the aberrant host immune responses and the diminishing treatment options with TB drugs. New treatment regimens incorporating therapeutics targeting both M. tb and host factors are urgently needed to improve the clinical management outcomes of MDR-TB. Host-directed therapies (HDT) could avert destructive tuberculous lung pathology, facilitate eradication of M. tb, improve survival and prevent long-term functional disability. In this review we (1) discuss the use of HDT for cancer and other infections, drawing parallels and the precedent they set for MDR-TB treatment, (2) highlight preclinical studies of pharmacological agents commonly used in clinical practice which have HDT potential, and (3) outline developments in cellular therapy to promote clinically beneficial immunomodulation to improve treatment outcomes in patients with pulmonary MDR-TB. The use of HDTs as adjuncts to MDR-TB therapy requires urgent evaluation.

Imatinib Triggers Phagolysosome Acidification and Antimicrobial Activity against Mycobacterium bovis Bacille Calmette-Guérin in Glucocorticoid-Treated Human Macrophages

Glucocorticoids are extensively used to treat inflammatory diseases; however, their chronic intake increases the risk for mycobacterial infections. Meanwhile, the effects of glucocorticoids on innate host responses are incompletely understood. In this study, we investigated the direct effects of glucocorticoids on antimycobacterial host defense in primary human macrophages. We found that glucocorticoids triggered the expression of cathelicidin, an antimicrobial critical for antimycobacterial responses, independent of the intracellular vitamin D metabolism. Despite upregulating cathelicidin, glucocorticoids failed to promote macrophage antimycobacterial activity. Gene expression profiles of human macrophages treated with glucocorticoids and/or IFN-γ, which promotes induction of cathelicidin, as well as antimycobacterial activity, were investigated. Using weighted gene coexpression network analysis, we identified a module of highly connected genes that was strongly inversely correlated with glucocorticoid treatment and associated with IFN-γ stimulation. This module was linked to the biological functions autophagy, phagosome maturation, and lytic vacuole/lysosome, and contained the vacuolar H(+)-ATPase subunit a3, alias TCIRG1, a known antimycobacterial host defense gene, as a top hub gene. We next found that glucocorticoids, in contrast with IFN-γ, failed to trigger expression and phagolysosome recruitment of TCIRG1, as well as to promote lysosome acidification. Finally, we demonstrated that the tyrosine kinase inhibitor imatinib induces lysosome acidification and antimicrobial activity in glucocorticoid-treated macrophages without reversing the anti-inflammatory effects of glucocorticoids. Taken together, we provide evidence that the induction of cathelicidin by glucocorticoids is not sufficient for macrophage antimicrobial activity, and identify the vacuolar H(+)-ATPase as a potential target for host-directed therapy in the context of glucocorticoid therapy.