Host-directed therapies for bacterial and viral infections

Identification of miR-29a as a novel biomarker for lumpy skin disease virus exposure in cattle

Micro RNAs (miRNAs) have been implicated in the regulation of maturation, proliferation, differentiation, and activation of immune cells. In this study, we demonstrated that miR-29a antagonizes IFN-γ production at early times post-LSDV infection in cattle. miR-29a was predicted to target upstream IFN-γ regulators, and its inhibition resulted in enhanced IFN-γ production in sensitized peripheral blood mononuclear cells (PBMCs). Further, stimulation of PBMCs with LSDV antigen exhibited lower levels of miR-29a, concomitant with a potent cell-mediated immune response (CMI), characterized by an increase in LSDV-specific CD8+ T cell counts and enhanced levels of IFN-γ, which eventually facilitated virus clearance. In addition, a few immunocompromised cattle (developed secondary LSDV infection at ~ 6 months) that failed to mount a potent cell-mediated immune response, were shown to maintain higher miR-29a levels. Furthermore, as compared to the sensitized crossbred cattle, PBMCs from sensitized Rathi (a native Indian breed) animals exhibited lower levels of miR-29a along with an increase in CD8+ T cell counts and enhanced levels of IFN-γ. Finally, we analysed that a ≥ 60% decrease in miR-29a expression levels in the PBMCs of sensitized cattle correlated with a potent CMI response. In conclusion, miR-29a expression is involved in antagonizing the IFN-γ response in LSDV-infected cattle and may serve as a novel biomarker for the acute phase of LSDV infection, as well as predicting the functionality of T cells in sensitized cattle. In addition, Rathi cattle mount a more potent CMI response against LSDV than crossbred cattle.

Photosensitive AIEgens sensitize bacteria to oxidative damage and modulate the inflammatory responses of macrophages to salvage the photodynamic therapy against MRSA

The urgent need for antimicrobial agents to combat infections caused by multidrug-resistant bacteria facilitates the exploration of alternative strategies such as photosensitizer (PS)-mediated photoinactivation. However, increasing studies have discovered uncorrelated bactericidal activities among PSs possessing similar photodynamic and pathogen-targeted properties. To optimize the photodynamic therapy (PDT) against infections, we investigated three type-I PSs of D-π-A AIEgens TI, TBI, and TTI. The capacities of reactive oxygen species (ROS) generation of TI, TBI, and TTI did not align with their bactericidal activities. Despite exhibiting the lowest photodynamic efficiency, TI exhibited the highest activities against methicillin-resistant Staphylococcus aureus (MRSA) by impairing the anti-oxidative responses of bacteria. By comparison, TTI, characterized by the strongest ROS production, inactivated intracellular MRSA by potentiating the inflammatory response of macrophages. Unlike TI and TTI, TBI, despite possessing moderate photodynamic activities and inducing ROS accumulation in both MRSA and macrophages, did not exhibit any antibacterial activity. Therefore, relying on the disturbed anti-oxidative metabolism of pathogens or potentiated host immune responses, transient ROS bursts can effectively control bacterial infections. Our study reevaluates the contribution of photodynamic activities of PSs to bacterial elimination and provides new insights into discovering novel antibacterial targets and agents.

Advances in bioinspired nanomaterials managing microbial biofilms and virulence: A critical analysis

Microbial virulence and biofilm formation stand as a big concern against the goal of achieving a green and sustainable future. Microbial pathogenesis is the process by which the microbes (bacterial, fungal, and viral) cause illness in their respective host organism. 'Nanotechnology' is a state-of-art discipline to address this problem. The use of conventional techniques against microbial proliferation has been challenging against the environment. To tackle this problem, there has been a revolution in this multi-disciplinary field, to address the aspect of bioinspired nanomaterials in the antibiofilm and antimicrobial sector. Bioinspired nanomaterials prove to be a potential antibiofilm and antimicrobial agent as they are non-hazardous to the environment and mostly synthesized using a single-step reduction protocol. They exhibit synergistic effects against bacterial, fungal, and viral pathogens and thereby, control the virulence. In this literature review, we have elucidated the potential of bioinspired nanoparticles as well as nanomaterials as a promising anti-microbial treatment pedagogy and throw light on the advancements in how smart photo-switchable platforms have been designed to exhibit both bacterial releasing as well as bacterial-killing properties. Certain limitations and possible outcomes of these bio-based nanomaterials have been discussed in the hope of achieving a green and sustainable ecosystem.

Advances in the targeted theragnostics of osteomyelitis caused by Staphylococcus aureus

Bone infections caused by Staphylococcus aureus may lead to an inflammatory condition called osteomyelitis, which results in progressive bone loss. Biofilm formation, intracellular survival, and the ability of S. aureus to evade the immune response result in recurrent and persistent infections that present significant challenges in treating osteomyelitis. Moreover, people with diabetes are prone to osteomyelitis due to their compromised immune system, and in life-threatening cases, this may lead to amputation of the affected limbs. In most cases, bone infections are localized; thus, early detection and targeted therapy may prove fruitful in treating S. aureus-related bone infections and preventing the spread of the infection. Specific S. aureus components or overexpressed tissue biomarkers in bone infections could be targeted to deliver active therapeutics, thereby reducing drug dosage and systemic toxicity. Compounds like peptides and antibodies can specifically bind to S. aureus or overexpressed disease markers and combining these with therapeutics or imaging agents can facilitate targeted delivery to the site of infection. The effectiveness of photodynamic therapy and hyperthermia therapy can be increased by the addition of targeting molecules to these therapies enabling site-specific therapy delivery. Strategies like host-directed therapy focus on modulating the host immune mechanisms or signaling pathways utilized by S. aureus for therapeutic efficacy. Targeted therapeutic strategies in conjunction with standard surgical care could be potential treatment strategies for S. aureus-associated osteomyelitis to overcome antibiotic resistance and disease recurrence. This review paper presents information about the targeting strategies and agents for the therapy and diagnostic imaging of S. aureus bone infections.

A pan-respiratory antiviral chemotype targeting a transient host multi-protein complex

We present a novel small molecule antiviral chemotype that was identified by an unconventional cell-free protein synthesis and assembly-based phenotypic screen for modulation of viral capsid assembly. Activity of PAV-431, a representative compound from the series, has been validated against infectious viruses in multiple cell culture models for all six families of viruses causing most respiratory diseases in humans. In animals, this chemotype has been demonstrated efficacious for porcine epidemic diarrhoea virus (a coronavirus) and respiratory syncytial virus (a paramyxovirus). PAV-431 is shown to bind to the protein 14-3-3, a known allosteric modulator. However, it only appears to target the small subset of 14-3-3 which is present in a dynamic multi-protein complex whose components include proteins implicated in viral life cycles and in innate immunity. The composition of this target multi-protein complex appears to be modified upon viral infection and largely restored by PAV-431 treatment. An advanced analog, PAV-104, is shown to be selective for the virally modified target, thereby avoiding host toxicity. Our findings suggest a new paradigm for understanding, and drugging, the host-virus interface, which leads to a new clinical therapeutic strategy for treatment of respiratory viral disease.

Effect of Metformin on systemic chemokine responses during anti-tuberculosis chemotherapy

BACKGROUND

Metformin (MET), by boosting immunity, has been suggested as a host-adjunctive therapy to anti-tuberculosis treatment (ATT).

METHODS

We evaluated whether adding MET to the standard ATT can alter the host chemokine response. We investigated the influence of metformin on the plasma levels of a wide panel of chemokines in a group of active tuberculosis patients before treatment, at 2nd month of ATT and at 6-months of ATT as part of our clinical study to examine the effect of metformin on ATT.

RESULTS

Our results demonstrated that addition of metformin resulted in diminished CC (CCL1 and CCL3) and CXC (CXCL-2 and CXCL-10) chemokines in MET arm as compared to non-MET arm at the 2nd month and 6th month of ATT. In addition to this, MET arm showed significantly diminished chemokines in individuals with high bacterial burden and cavitary disease.

CONCLUSION

Our current data suggest that metformin alters chemokines responses that could potentially curb excessive inflammation during ATT.

Dengue virus exploits autophagy vesicles and secretory pathways to promote transmission by human dendritic cells

Dengue virus (DENV), transmitted by infected mosquitoes, is a major public health concern, with approximately half the world's population at risk for infection. Recent decades have increasing incidence of dengue-associated disease alongside growing frequency of outbreaks. Although promising progress has been made in anti-DENV immunizations, post-infection treatment remains limited to non-specific supportive treatments. Development of antiviral therapeutics is thus required to limit DENV dissemination in humans and to help control the severity of outbreaks. Dendritic cells (DCs) are amongst the first cells to encounter DENV upon injection into the human skin mucosa, and thereafter promote systemic viral dissemination to additional human target cells. Autophagy is a vesicle trafficking pathway involving the formation of cytosolic autophagosomes, and recent reports have highlighted the extensive manipulation of autophagy by flaviviruses, including DENV, for viral replication. However, the temporal profiling and function of autophagy activity in DENV infection and transmission by human primary DCs remains poorly understood. Herein, we demonstrate that mechanisms of autophagosome formation and extracellular vesicle (EV) release have a pro-viral role in DC-mediated DENV transmission. We show that DENV exploits early-stage canonical autophagy to establish infection in primary human DCs. DENV replication enhanced autophagosome formation in primary human DCs, and intrinsically-heightened autophagosome biogenesis correlated with relatively higher rates of DC susceptibility to DENV. Furthermore, our data suggest that viral replication intermediates co-localize with autophagosomes, while productive DENV infection introduces a block at the late degradative stages of autophagy in infected DCs but not in uninfected bystander cells. Notably, we identify for the first time that approximately one-fourth of DC-derived CD9/CD81/CD63+ EVs co-express canonical autophagy marker LC3, and demonstrate that DC-derived EV populations are an alternative, cell-free mechanism by which DCs promote DENV transmission to additional target sites. Taken together, our study highlights intersections between autophagy and secretory pathways during viral infection, and puts forward autophagosome accumulation and viral RNA-laden EVs as host determinants of DC-mediated DENV infection in humans. Host-directed therapeutics targeting autophagy and exocytosis pathways thus have potential to enhance DC-driven resistance to DENV acquisition and thereby limit viral dissemination by initial human target cells following mosquito-to-human transmission of DENV.

T Cell and Natural Killer Cell Membrane-Camouflaged Nanoparticles for Cancer and Viral Therapies

Extensive research has been conducted on the application of nanoparticles in the treatment of cancer and infectious diseases. Due to their exceptional characteristics and flexible structure, they are classified as highly efficient drug delivery systems, ensuring both safety and targeted delivery. Nevertheless, nanoparticles still encounter obstacles, such as biological instability, absence of selectivity, recognition as unfamiliar elements, and quick elimination, which restrict their remedial capacity. To surmount these drawbacks, biomimetic nanotechnology has been developed that utilizes T cell and natural killer (NK) cell membrane-encased nanoparticles as sophisticated methods of administering drugs. These nanoparticles can extend the duration of drug circulation and avoid immune system clearance. During the membrane extraction and coating procedure, the surface proteins of immunological cells are transferred to the biomimetic nanoparticles. Such proteins present on the surface of cells confer several benefits to nanoparticles, including prolonged circulation, enhanced targeting, controlled release, specific cellular contact, and reduced in vivo toxicity. This review focuses on biomimetic nanosystems that are derived from the membranes of T cells and NK cells and their comprehensive extraction procedure, manufacture, and applications in cancer treatment and viral infections. Furthermore, potential applications, prospects, and existing challenges in their medical implementation are highlighted.

Sepsis in surgical patients: Personalized medicine in the future treatment of sepsis

Sepsis results when a severe infection overwhelms the normal regulatory mechanisms of the immune system, resulting in a dysregulated host response characterized by new-onset organ failure. A wide range of infectious challenges can induce sepsis, resulting in an even wider range of maladaptive immune responses. This makes sepsis a syndromic diagnosis without a unifying, underlying molecular mechanism. The next step toward personalized medicine for sepsis is to resolve the heterogeneity across the universe of septic patients in order to establish pathobiologically homogenous sepsis "endotypes" that have uniformly defined changes in physiology and immunology. Defining the mechanisms of immune dysfunction within these endotypes will provide a roadmap for the application of immunomodulatory therapies for sepsis. This approach can drive in a paradigm shift in sepsis treatment, moving beyond supportive care and toward active efforts to restore normal immune function.

Synergistic peptide combinations designed to suppress SARS-CoV-2

The SARS-CoV-2, responsible for the COVID-19 pandemic, poses a significant threat to global healthcare. Peptide and peptide-based inhibitors, known for their safety, efficacy, and selectivity, have recently emerged as promising candidates for treating late-developing viral infections. In this study, three peptides were selected to target different stages of viral invasion, specifically ACE2 and S protein binding, as well as membrane fusion. The objective was to assess their ability to impede the entry of the SARS-CoV-2 Spike pseudotyped virus. Our findings revealed that a combination of these three peptides demonstrated enhanced antiviral effects. This outcome substantiates the feasibility of developing effective peptide combinations to combat diseases related to SARS-CoV-2. Moreover, the three-peptide combinations, designed to target multiple aspects of SARS-CoV-2 viral entry, exhibited heightened viral inhibition and broad-spectrum antiviral properties.

Dehydrozaluzanin C- derivative protects septic mice by alleviating over-activated inflammatory response and promoting the phagocytosis of macrophages

Host-directed therapy (HDT) is a new adjuvant strategy that interfere with host cell factors that are required by a pathogen for replication or persistence. In this study, we assessed the effect of dehydrozaluzanin C-derivative (DHZD), a modified compound from dehydrozaluzanin C (DHZC), as a potential HDT agent for severe infection. LPS-induced septic mouse model and Carbapenem resistant Klebsiella pneumoniae (CRKP) infection mouse model was used for testing in vivo. RAW264.7 cells, mouse primary macrophages, and DCs were used for in vitro experiments. Dexamethasone (DXM) was used as a positive control agent. DHZD ameliorated tissue damage (lung, kidney, and liver) and excessive inflammatory response induced by LPS or CRKP infection in mice. Also, DHZD improved the hypothermic symptoms of acute peritonitis induced by CRKP, inhibited heat-killed CRKP (HK-CRKP)-induced inflammatory response in macrophages, and upregulated the proportions of phagocytic cell types in lungs. In vitro data suggested that DHZD decreases LPS-stimulated expression of IL-6, TNF-α and MCP-1 via PI3K/Akt/p70S6K signaling pathway in macrophages. Interestingly, the combined treatment group of DXM and DHZD had a higher survival rate and lower level of IL-6 than those of the DXM-treated group; the combination of DHZD and DXM played a synergistic role in decreasing IL-6 secretion in sera. Moreover, the phagocytic receptor CD36 was increased by DHZD in macrophages, which was accompanied by increased bacterial phagocytosis in a clathrin- and actin-dependent manner. This data suggests that DHZD may be a potential drug candidate for treating bacterial infections.

Diving into drug-screening: zebrafish embryos as an in vivo platform for antimicrobial drug discovery and assessment

The rise of multidrug-resistant bacteria underlines the need for innovative treatments, yet the introduction of new drugs has stagnated despite numerous antimicrobial discoveries. A major hurdle is a poor correlation between promising in vitro data and in vivo efficacy in animal models, which is essential for clinical development. Early in vivo testing is hindered by the expense and complexity of existing animal models. Therefore, there is a pressing need for cost-effective, rapid preclinical models with high translational value. To overcome these challenges, zebrafish embryos have emerged as an attractive model for infectious disease studies, offering advantages such as ethical alignment, rapid development, ease of maintenance, and genetic manipulability. The zebrafish embryo infection model, involving microinjection or immersion of pathogens and potential antibiotic hit compounds, provides a promising solution for early-stage drug screening. It offers a cost-effective and rapid means of assessing the efficacy, toxicity and mechanism of action of compounds in a whole-organism context. This review discusses the experimental design of this model, but also its benefits and challenges. Additionally, it highlights recently identified compounds in the zebrafish embryo infection model and discusses the relevance of the model in predicting the compound's clinical potential.

Plant phenolics inhibit focal adhesion kinase and suppress host cell invasion by uropathogenic Escherichia coli

Traditional folk treatments for the prevention and management of urinary tract infections (UTIs) and other infectious diseases often include plants and plant extracts that are rich in phenolic compounds. These have been ascribed a variety of activities, including inhibition of bacterial interactions with host cells. Here, we tested a panel of four well-studied phenolic compounds-caffeic acid phenethyl ester (CAPE), resveratrol, catechin, and epigallocatechin gallate-for the effects on host cell adherence and invasion by uropathogenic Escherichia coli (UPEC). These bacteria, which are the leading cause of UTIs, can bind and subsequently invade bladder epithelial cells via an actin-dependent process. Intracellular UPEC reservoirs within the bladder are often protected from antibiotics and host defenses and likely contribute to the development of chronic and recurrent infections. In cell culture-based assays, only resveratrol had a notable negative effect on UPEC adherence to bladder cells. However, both CAPE and resveratrol significantly inhibited UPEC entry into the host cells, coordinate with attenuated phosphorylation of the host actin regulator Focal Adhesion Kinase (FAK or PTK2) and marked increases in the numbers of focal adhesion structures. We further show that the intravesical delivery of resveratrol inhibits UPEC infiltration of the bladder mucosa in a murine UTI model and that resveratrol and CAPE can disrupt the ability of other invasive pathogens to enter host cells. Together, these results highlight the therapeutic potential of molecules like CAPE and resveratrol, which could be used to augment antibiotic treatments by restricting pathogen access to protective intracellular niches.IMPORTANCEUrinary tract infections (UTIs) are exceptionally common and increasingly difficult to treat due to the ongoing rise and spread of antibiotic-resistant pathogens. Furthermore, the primary cause of UTIs, uropathogenic Escherichia coli (UPEC), can avoid antibiotic exposure and many host defenses by invading the epithelial cells that line the bladder surface. Here, we identified two plant-derived phenolic compounds that disrupt activation of the host machinery needed for UPEC entry into bladder cells. One of these compounds, resveratrol, effectively inhibited UPEC invasion of the bladder mucosa in a mouse UTI model, and both phenolic compounds significantly reduced host cell entry by other invasive pathogens. These findings suggest that select phenolic compounds could be used to supplement existing antibacterial therapeutics by denying uropathogens shelter within host cells and tissues and help explain some of the benefits attributed to traditional plant-based medicines.

Preventive nasal administration of flagellin restores antimicrobial effect of gentamicin and protects against a multidrug-resistant strain of Pseudomonas aeruginosa

The increasing prevalence of multidrug-resistant Pseudomonas aeruginosa (PA) is a significant concern for chronic respiratory disease exacerbations. Host-directed drugs, such as flagellin, an agonist of toll-like receptor 5 (TLR5), have emerged as a promising solution. In this study, we evaluated the prophylactic intranasal administration of flagellin against a multidrug-resistant strain of PA (PAMDR) in mice and assessed the possible synergy with the antibiotic gentamicin (GNT). The results indicated that flagellin treatment before infection decreased bacterial load in the lungs, likely due to an increase in neutrophil recruitment, and reduced signs of inflammation, including proinflammatory cytokines. The combination of flagellin and GNT showed a synergistic effect, decreasing even more the bacterial load and increasing mice survival rates, in comparison to mice pre-treated only with flagellin. These findings suggest that preventive nasal administration of flagellin could restore the effect of GNT against MDR strains of PA, paving the way for the use of flagellin in vulnerable patients with chronic respiratory diseases.

Regulation of immune responses to infection through interaction between stem cell-derived exosomes and toll-like receptors mediated by microRNA cargoes

Infectious diseases are among the factors that account for a significant proportion of disease-related deaths worldwide. The primary treatment approach to combat microbial infections is the use of antibiotics. However, the widespread use of these drugs over the past two decades has led to the emergence of resistant microbial species, making the control of microbial infections a serious challenge. One of the most important solutions in the field of combating infectious diseases is the regulation of the host's defense system. Toll-like receptors (TLRs) play a crucial role in the first primary defense against pathogens by identifying harmful endogenous molecules released from dying cells and damaged tissues as well as invading microbial agents. Therefore, they play an important role in communicating and regulating innate and adaptive immunity. Of course, excessive activation of TLRs can lead to disruption of immune homeostasis and increase the risk of inflammatory reactions. Targeting TLR signaling pathways has emerged as a new therapeutic approach for infectious diseases based on host-directed therapy (HDT). In recent years, stem cell-derived exosomes have received significant attention as factors regulating the immune system. The regulation effects of exosomes on the immune system are based on the HDT strategy, which is due to their cargoes. In general, the mechanism of action of stem cell-derived exosomes in HDT is by regulating and modulating immunity, promoting tissue regeneration, and reducing host toxicity. One of their most important cargoes is microRNAs, which have been shown to play a significant role in regulating immunity through TLRs. This review investigates the therapeutic properties of stem cell-derived exosomes in combating infections through the interaction between exosomal microRNAs and Toll-like receptors.

Phloretin inhibits transmissible gastroenteritis virus proliferation via multiple mechanisms

Transmissible gastroenteritis virus (TGEV), an enteropathogenic coronavirus, has caused huge economic losses to the pig industry, with 100% mortality in piglets aged 2 weeks and intestinal injury in pigs of other ages. However, there is still a shortage of safe and effective anti-TGEV drugs in clinics. In this study, phloretin, a naturally occurring dihydrochalcone glycoside, was identified as a potent antagonist of TGEV. Specifically, we found phloretin effectively inhibited TGEV proliferation in PK-15 cells, dose-dependently reducing the expression of TGEV N protein, mRNA, and virus titer. The anti-TGEV activity of phloretin was furthermore refined to target the internalization and replication stages. Moreover, we also found that phloretin could decrease the expression levels of proinflammatory cytokines induced by TGEV infection. In addition, we expanded the potential key targets associated with the anti-TGEV effect of phloretin to AR, CDK2, INS, ESR1, ESR2, EGFR, PGR, PPARG, PRKACA, and MAPK14 with the help of network pharmacology and molecular docking techniques. Furthermore, resistant viruses have been selected by culturing TGEV with increasing concentrations of phloretin. Resistance mutations were reproducibly mapped to the residue (S242) of main protease (Mpro). Molecular docking analysis showed that the mutation (S242F) significantly disrupted phloretin binding to Mpro, suggesting Mpro might be a potent target of phloretin. In summary, our findings indicate that phloretin is a promising drug candidate for combating TGEV, which may be helpful for developing pharmacotherapies for TGEV and other coronavirus infections.

The antimicrobial activity of innate host-directed therapies: A systematic review

Intracellular human pathogens are the deadliest infectious diseases and are difficult to treat effectively due to their protection inside the host cell and the development of antimicrobial resistance (AMR). An emerging approach to combat these intracellular pathogens is host-directed therapies (HDT), which harness the innate immunity of host cells. HDT rely on small molecules to promote host protection mechanisms that ultimately lead to pathogen clearance. These therapies are hypothesized to: (1) possess indirect yet broad, cross-species antimicrobial activity, (2) effectively target drug-resistant pathogens, (3) carry a reduced susceptibility to the development of AMR and (4) have synergistic action with conventional antimicrobials. As the field of HDT expands, this systematic review was conducted to collect a compendium of HDT and their characteristics, such as the host mechanisms affected, the pathogen inhibited, the concentrations investigated and the magnitude of pathogen inhibition. The evidential support for the main four HDT hypotheses was assessed and concluded that HDT demonstrate robust cross-species activity, are active against AMR pathogens, clinical isolates and laboratory-adapted pathogens. However, limited information exists to support the notion that HDT are synergistic with canonical antimicrobials and are less predisposed to AMR development.

Microfluidics produced ATRA-loaded PLGA NPs reduced tuberculosis burden in alveolar epithelial cells and enabled high delivered dose under simulated human breathing pattern in 3D printed head models

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is second only to COVID-19 as the top infectious disease killer worldwide. Multi-drug resistant TB (MDR-TB) may arise because of poor patient adherence to medications due to lengthy treatment duration and side effects. Delivering novel host directed therapies (HDT), like all trans retinoic acid (ATRA) may help to improve drug regimens and reduce the incidence of MDR-TB. Local delivery of ATRA to the site of infection leads to higher bioavailability and reduced systemic side effects. ATRA is poorly soluble in water and has a short half-life in plasma. Therefore, it requires a formulation step before it can be administered in vivo. ATRA loaded PLGA nanoparticles suitable for nebulization were manufactured and optimized using a scalable nanomanufacturing microfluidics (MF) mixing approach (MF-ATRA-PLGA NPs). MF-ATRA-PLGA NPs demonstrated a dose dependent inhibition of Mtb growth in TB-infected A549 alveolar epithelial cell model while preserving cell viability. The MF-ATRA-PLGA NPs were nebulized with the Aerogen Solo vibrating mesh nebulizer, with aerosol droplet size characterized using laser diffraction and the estimated delivered dose was determined. The volume median diameter (VMD) of the MF-ATRA-PLGA NPs was 3.00 ± 0.18 μm. The inhaled dose delivered in adult and paediatric 3D printed head models under a simulated normal adult and paediatric breathing pattern was found to be 47.05 ± 3 % and 20.15 ± 3.46 % respectively. These aerosol characteristics of MF-ATRA-PLGA NPs supports its suitability for delivery to the lungs via inhalation. The data generated on the efficacy of an inhalable, scalable and regulatory friendly ATRA-PLGA NPs formulation provides a foundation on which further pre-clinical testing can be built. Overall, the results of this project are promising for future research into ATRA loaded NPs formulations as inhaled host directed therapies for TB.

Screening Peptide Drug Candidates To Neutralize Whole Viral Agents: A Case Study with Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)

The COVID-19 pandemic revealed the need for therapeutic and pharmaceutical molecule development in a short time with different approaches. Although boosting immunological memory by vaccination was the quickest and robust strategy, still medication is required for the immediate treatment of a patient. A popular approach is the mining of new therapeutic molecules. Peptide-based drug candidates are also becoming a popular avenue. To target whole pathogenic viral agents, peptide libraries can be employed. With this motivation, we have used the 12mer M13 phage display library for selecting SARS-CoV-2 targeting peptides as potential neutralizing molecules to prevent viral infections. Panning was applied with four iterative cycles to select SARS-CoV-2 targeting phage particles displaying 12-amino acid-long peptides. Randomly selected peptide sequences were synthesized by a solid-state peptide synthesis method. Later, selected peptides were analyzed by the quartz crystal microbalance method to characterize their molecular interaction with SARS-CoV-2's S protein. Finally, the neutralization activity of the selected peptides was probed with an in-house enzyme-linked immunosorbent assay. The results showed that scpep3, scpep8, and scpep10 peptides have both binding and neutralizing capacity for S1 protein as a candidate for therapeutic molecule. The results of this study have a translational potential with future in vivo and human studies.

Host-Directed Virus-Mimicking Particles Interacting with the ACE2 Receptor Competitively Block Coronavirus SARS-CoV-2 Entry

Herein, we fabricate host-directed virus-mimicking particles (VMPs) to block the entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into host cells through competitive inhibition enabled by their interactions with the angiotensin-converting enzyme 2 (ACE2) receptor. A microfluidic platform is developed to fabricate a lipid core of the VMPs with a narrow size distribution and a low level of batch-to-batch variation. The resultant solid lipid nanoparticles are decorated with an average of 231 or 444 Spike S1 RBD protrusions mimicking either the original SARS-CoV-2 or its delta variant, respectively. Compared with that of the nonfunctionalized core, the cell uptake of the functionalized VMPs is enhanced with ACE2-expressing cells due to their strong interactions with the ACE2 receptor. The fabricated VMPs efficiently block the entry of SARS-CoV-2 pseudovirions into host cells and suppress viral infection. Overall, this study provides potential strategies for preventing the spread of SARS-CoV-2 or other coronaviruses employing the ACE2 receptor to enter into host cells.

Evaluation of the antimalarial properties of Solanum incanum L. leaf extract fractions and its ability to downregulate delta aminolevulinate dehydratase to prevent the establishment of malaria infection

ETHNOPHARMACOLOGICAL RELEVANCE

Solanum incanum L. is commonly used in traditional herbal medicine (THM) in Kenya for treating various ailments. Recent developments in disease treatment have introduced the concept of host-directed therapy (HDT). This approach involves targeting factors within the host cell that can impede the growth or replication of a pathogen. One such host factor is delta aminolevulinate dehydratase (δ-ALAD), the second enzyme in the heme biosynthesis pathway utilized by Plasmodium for growth. Studies using mice models have shown an increase in δ-ALAD expression during Plasmodium berghei infection. Another plant in the Solanum genus, S. guaranticum, has been found to inhibit δ-ALAD in red blood cells in vitro and in the brain in vivo. Is it possible that the bioactive compounds in S. incanum extracts could also be effective in HDT for malaria treatment?

AIM OF STUDY

To better assess the effectiveness of S. incanum leaf extracts as a curative and prophylaxis in malaria parasite infection, and to test the plant's ability to decrease δ-ALAD expression.

MATERIALS AND METHODS

The leaves of S. incanum were collected, dried, and pulverized before being subjected to a successive extraction protocol to obtain crude, hexane, ethyl acetate, and aqueous extract fractions. Phytochemical analysis was conducted on all extract fractions, followed by GC-MS analysis of the fraction with the most potent antimalarial activity. An acute toxicity study was also performed on the extracted fractions. The potency of the extract fractions as curative and prophylactic antimalarial was then evaluated in THM using Plasmodium berghei-infected mice at a dose of 100 mg/kg. The extract fraction with the highest activity was further evaluated at varying doses and its effect on δ-ALAD was measured using RT-qPCR. The percentage of parasitemia and chemosuppression, and mean survival time were used as indices of activity.

RESULTS

Phytochemical analysis revealed that the ethyl acetate and aqueous extract fractions contained high terpenoids, flavonoids, and phenols levels. However, alkaloids were only present in moderate quantities in the aqueous extract, and quinones were found in high levels only in the crude extract. Additionally, all extract fractions contained saponins in high levels but lacked tannins. While the plant extracts were found to be non-toxic, they did not exhibit curative antimalarial activity. However, all extract fractions showed prophylactic antimalarial activity, with the ethyl acetate extract having the highest percentage of chemosuppression even at doses of 250 and 1000 mg/kg. In the negative control, the expression of δ-ALAD was 5.4-fold, but this was significantly reduced to 2.3-fold when mice were treated with 250 mg/kg of the ethyl acetate fraction. GC-MS analysis of the ethyl acetate fraction revealed high percentages of 2-methyloctacosane, tetracosane, and decane.

CONCLUSION

The fractions extracted from S. incanum leaves have been found to possess only antimalarial prophylactic properties, with the ethyl acetate extract fraction showing the most effective results. The activity of this fraction may be attributed to its ability to decrease the expression of δ-ALAD, as it contains an alkane compound implicated with enzyme-inhibitory activity.

Pathogen- and host-directed pharmacologic strategies for control of Vairimorpha (Nosema) spp. infection in honey bees

Microsporidia are obligate intracellular parasites of the Fungal Kingdom that cause widespread infections in nature, with important effects on invertebrates involved in food production systems. The two microsporidian species Vairimorpha (Nosema) ceranae (and the less common Vairimorpha (Nosema) apis) can cause individual disease in honey bees and contribute to colony collapse. The efficacy, safety, and availability of fumagillin, the only drug currently approved to treat microsporidia infection in bees, is uncertain. In this review, we will discuss some of the most promising alternative strategies for the mitigation of Vairimorpha spp. with an emphasis on infection by V. ceranae, now the dominant species infecting bees. We will focus on pharmacologic interventions where the mechanism of action is known and examine both pathogen-directed and host-directed approaches. As limiting toxicity to host cells has been especially emphasized in treating bees that are already facing numerous stressors, strategies that disrupt pathogen-specific targets may be especially advantageous. Therefore, efforts to increase the knowledge and tools for facilitating the discovery of such targets and pharmacologic agents directed against them should be prioritized.

A host-directed oxadiazole compound potentiates antituberculosis treatment via zinc poisoning in human macrophages and in a mouse model of infection

Antituberculosis drugs, mostly developed over 60 years ago, combined with a poorly effective vaccine, have failed to eradicate tuberculosis. More worryingly, multiresistant strains of Mycobacterium tuberculosis (MTB) are constantly emerging. Innovative strategies are thus urgently needed to improve tuberculosis treatment. Recently, host-directed therapy has emerged as a promising strategy to be used in adjunct with existing or future antibiotics, by improving innate immunity or limiting immunopathology. Here, using high-content imaging, we identified novel 1,2,4-oxadiazole-based compounds, which allow human macrophages to control MTB replication. Genome-wide gene expression analysis revealed that these molecules induced zinc remobilization inside cells, resulting in bacterial zinc intoxication. More importantly, we also demonstrated that, upon treatment with these novel compounds, MTB became even more sensitive to antituberculosis drugs, in vitro and in vivo, in a mouse model of tuberculosis. Manipulation of heavy metal homeostasis holds thus great promise to be exploited to develop host-directed therapeutic interventions.

Postantibiotic leukocyte enhancement-mediated reduction of intracellular bacteria by macrophages

INTRODUCTION

Potentiation of the bactericidal activities of leukocytes, including macrophages, upon antibacterial agent administration has been observed for several decades and is summarized as the postantibiotic leukocyte enhancement (PALE) theory. Antibiotics-induced bacterial sensitization to leukocytes is commonly recognized as the mechanism of PALE. However, the degree of sensitization drastically varies with antibiotic classes, and little is known about whether and how the potentiation of leukocytes contributes to PALE.

OBJECTIVES

In this study, we aim to develop a mechanistic understanding of PALE by investigating the immunoregulation of traditional antibiotics on macrophages.

METHODS

Interaction models between bacteria and macrophages were constructed to identify the effects of different antibiotics on the bactericidal activities of macrophages. Oxygen consumption rate, expression of oxidases, and antioxidants were then measured to evaluate the effects of fluoroquinolones (FQs) on the oxidative stress of macrophages. Furthermore, the modulation in endoplasmic reticulum stress and inflammation upon antibiotic treatment was detected to analyze the mechanisms. At last, the peritoneal infection model was utilized to verify the PALE in vivo.

RESULTS

Enrofloxacin significantly reduced the intracellular burden of diverse bacterial pathogens through promoting the accumulation of reactive oxygen species (ROS). The upregulated oxidative response accordingly reprograms the electron transport chain with decreased production of antioxidant enzymes to reduce internalized pathogens. Additionally, enrofloxacin modulated the expression and spatiotemporal localization of myeloperoxidase (MPO) to facilitate ROS accumulation to target invaded bacteria and downregulated inflammatory response to alleviate cellular injury.

CONCLUSION

Our findings demonstrate the crucial role of leukocytes in PALE, shedding light on the development of new host-directed antibacterial therapies and the design of rational dosage regimens.

Targeting host deoxycytidine kinase mitigates Staphylococcus aureus abscess formation

Host-directed therapy (HDT) is an emerging approach to overcome antimicrobial resistance in pathogenic microorganisms. Specifically, HDT targets host-encoded factors required for pathogen replication and survival without interfering with microbial growth or metabolism, thereby eliminating the risk of resistance development. By applying HDT and a drug repurposing approach, we demonstrate that (R)-DI-87, a clinical-stage anticancer drug and potent inhibitor of mammalian deoxycytidine kinase (dCK), mitigates Staphylococcus aureus abscess formation in organ tissues upon invasive bloodstream infection. Mechanistically, (R)-DI-87 shields phagocytes from staphylococcal death-effector deoxyribonucleosides that target dCK and the mammalian purine salvage pathway-apoptosis axis. In this manner, (R)-DI-87-mediated protection of immune cells amplifies macrophage infiltration into deep-seated abscesses, a phenomenon coupled with enhanced pathogen control, ameliorated immunopathology, and reduced disease severity. Thus, pharmaceutical blockade of dCK represents an advanced anti-infective intervention strategy against which staphylococci cannot develop resistance and may help to fight fatal infectious diseases in hospitalized patients.

Inhibition of malaria and babesiosis parasites by putative red blood cell targeting small molecules

Background

Chemotherapies for malaria and babesiosis frequently succumb to the emergence of pathogen-related drug-resistance. Host-targeted therapies are thought to be less susceptible to resistance but are seldom considered for treatment of these diseases.

Methods

Our overall objective was to systematically assess small molecules for host cell-targeting activity to restrict proliferation of intracellular parasites. We carried out a literature survey to identify small molecules annotated for host factors implicated in Plasmodium falciparum infection. Alongside P. falciparum, we implemented in vitro parasite susceptibility assays also in the zoonotic parasite Plasmodium knowlesi and the veterinary parasite Babesia divergens. We additionally carried out assays to test directly for action on RBCs apart from the parasites. To distinguish specific host-targeting antiparasitic activity from erythrotoxicity, we measured phosphatidylserine exposure and hemolysis stimulated by small molecules in uninfected RBCs.

Results

We identified diverse RBC target-annotated inhibitors with Plasmodium-specific, Babesia-specific, and broad-spectrum antiparasitic activity. The anticancer MEK-targeting drug trametinib is shown here to act with submicromolar activity to block proliferation of Plasmodium spp. in RBCs. Some inhibitors exhibit antimalarial activity with transient exposure to RBCs prior to infection with parasites, providing evidence for host-targeting activity distinct from direct inhibition of the parasite.

Conclusions

We report here characterization of small molecules for antiproliferative and host cell-targeting activity for malaria and babesiosis parasites. This resource is relevant for assessment of physiological RBC-parasite interactions and may inform drug development and repurposing efforts.

Activin A levels are raised during human tuberculosis and blockade of the activin signaling axis influences murine responses to M. tuberculosis infection

Activin A strongly influences immune responses; yet, few studies have examined its role in infectious diseases. We measured serum activin A levels in two independent tuberculosis (TB) patient cohorts and in patients with pneumonia and sarcoidosis. Serum activin A levels were increased in TB patients compared to healthy controls, including those with positive tuberculin skin tests, and paralleled severity of disease, assessed by X-ray scores. In pneumonia patients, serum activin A levels were also raised, but in sarcoidosis patients, levels were lower. To determine whether blockade of the activin A signaling axis could play a functional role in TB, we harnessed a soluble activin type IIB receptor fused to human IgG1 Fc, ActRIIB-Fc, as a ligand trap in a murine TB model. The administration of ActRIIB-Fc to Mycobacterium tuberculosis-infected mice resulted in decreased bacterial loads and increased numbers of CD4 effector T cells and tissue-resident memory T cells in the lung. Increased frequencies of tissue-resident memory T cells corresponded with downregulated T-bet expression in lung CD4 and CD8 T cells. Altogether, the results suggest a disease-exacerbating role of ActRIIB signaling pathways. Serum activin A may be useful as a biomarker for diagnostic triage of active TB or monitoring of anti-tuberculosis therapy.

IMPORTANCE

Tuberculosis remains the leading cause of death by a bacterial pathogen. The etiologic agent of tuberculosis, Mycobacterium tuberculosis, can remain dormant in the infected host for years before causing disease. Significant effort has been made to identify biomarkers that can discriminate between latently infected and actively diseased individuals. We found that serum levels of the cytokine activin A were associated with increased lung pathology and could discriminate between active tuberculosis and tuberculin skin-test-positive healthy controls. Activin A signals through the ActRIIB receptor, which can be blocked by administration of the ligand trap ActRIIB-Fc, a soluble activin type IIB receptor fused to human IgG1 Fc. In a murine model of tuberculosis, we found that ActRIIB-Fc treatment reduced mycobacterial loads. Strikingly, ActRIIB-Fc treatment significantly increased the number of tissue-resident memory T cells. These results suggest a role for ActRIIB signaling pathways in host responses to Mycobacterium tuberculosis and activin A as a biomarker of ongoing disease.

Repurposing of SARS-CoV-2 compounds against Marburg Virus using MD simulation, mm/GBSA, PCA analysis, and free energy landscape

The significant mortality rate associated with Marburg virus infection made it the greatest hazard among infectious diseases. Drug repurposing using in silico methods has been crucial in identifying potential compounds that could prevent viral replication by targeting the virus's primary proteins. This study aimed at repurposing the drugs of SARS-CoV-2 for identifying potential candidates against the matrix protein VP40 of the Marburg virus. Virtual screening was performed where the control compound, Nilotinib, showed a binding score of -9.99 kcal/mol. Based on binding scores, hit compounds 9549298, 11960895, 44545852, 51039094, and 89670174 were selected that had a lower binding score than the control. Subsequent molecular dynamics (MD) simulation revealed that compound 9549298 consistently formed a hydrogen bond with the residue Gln290. This was observed both in molecular docking and MD simulation poses, indicating a strong and significant interaction with the protein. 11960895 had the most stable and consistent RMSD pattern exhibited in 100 ns simulation, while 9549298 had the most identical RMSD plot compared to the control molecule. MM/PBSA analysis showed that the binding free energy (ΔG) of 9549298 and 11960895 was lower than the control, with -30.84 and -38.86 kcal/mol, respectively. It was observed by the PCA (principal component analysis) and FEL (free energy landscape) analysis that compounds 9549298 and 11960895 had lesser conformational variation. Overall, this study proposed 9549298 and 11960895 as potential binders of VP40 MARV that can cause its inhibition, however it inherently lacks experimental validation. Furthermore, the study proposes in-vitro experiments as the next step to validate these computational findings, offering a practical approach to further explore these compounds' potential as antiviral agents.Communicated by Ramaswamy H. Sarma.

In silico identification and validation of phenolic lipids as potential inhibitor against bacterial and viral strains

The recurrence of coronavirus disease and bacterial resistant strains has drawn attention to naturally occurring bioactive molecules that can demonstrate broad-spectrum efficacy against bacteria as well as viral strains. The drug-like abilities of naturally available "anacardic acids" (AA) and their derivatives against different bacterial and viral protein targets through in-silico tools were explored. Three viral protein targets [P DB: 6Y2E (SARS-CoV-2), 1AT3 (Herpes) and 2VSM (Nipah)] and four bacterial protein targets [P DB: 2VF5 (Escherichia coli), 2VEG (Streptococcus pneumoniae), 1JIJ (Staphylococcus aureus) and 1KZN (E. coli)] were selected to evaluate the activity of bioactive AA molecules. The potential ability to inhibit the progression of microbes has been discussed based on the structure, functionality and interaction ability of these molecules on the selected protein targets for multi-disease remediation. The number of interactions, full-fitness value and energy of the ligand-target system were determined from the docked structure in SwissDock and Autodock Vina. In order to compare the efficacy of these active derivatives to that of commonly used drugs against bacteria and viruses, a few of the selected molecules were subjected to 100 ns long MD simulations. It was found that the phenolic groups and alkyl chains of AA derivatives are more likely to bind with microbial targets, that could be responsible for the improved activity against these targets. The results suggest that the proposed AA derivatives have demonstrated potential to become active drug ingredients against microbial protein targets. Further, experimental investigations are essential for clinical verification of the drug-like abilities of AA derivatives.Communicated by Ramaswamy H. Sarma.

Evaluation of the therapeutic effect of a novel bacteriophage in the healing process of infected wounds with Klebsiella pneumoniae in mice

OBJECTIVE

Bacterial wound infections have recently become a threat to public health. The emergence of multidrug-resistant (MDR) strains of Klebsiella pneumoniae highlights the need for a new treatment method. The effectiveness of bacteriophages has been observed for several infections in animal models and human trials. In this study, we assessed the effectiveness of bacteriophages in the treatment of wound infections associated with MDR and biofilm-producing K. pneumoniae and compared its effectiveness with that of gentamicin.

METHODS

A lytic phage against MDR K. pneumoniae was isolated and identified. The effectiveness of phages in the treatment of wound infection in mice was investigated and its effectiveness was compared with gentamicin.

RESULTS

The results showed that the isolated phage belonged to the Drexlerviridae family. This phage acts like gentamicin and effectively eliminates bacteria from wounds. In addition, mice in the phage therapy group were in better physical condition.

CONCLUSION

Our results demonstrated the success of phage therapy in the treatment of mice wounds infected with K. pneumoniae. These results indicate the feasibility of topical phage therapy for the safe treatment of wound infections.

Relationship between metformin use and mortality in tuberculosis patients with diabetes: a nationwide cohort study

BACKGROUND/AIMS

To determine whether metformin, which is considered a host-directed therapy for tuberculosis (TB), is effective in improving the prognosis of patients with TB and diabetes mellitus (DM), who have higher mortality than those without DM.

METHODS

This cohort study included patients who were registered as having TB in the National Tuberculosis Surveillance System. The medical and death records of matched patients were obtained from the National Health Information Database and Statistics Korea, respectively, and data from 2011 to 2017 were collected retrospectively. We classified patients according to metformin use among participants who used diabetes drugs for more than 28 days. The primary outcome was all-cause mortality during TB treatment. Double propensity score adjustment was applied to reduce the effects of confounding and multivariable Cox proportional hazard models were used to estimate adjusted hazard ratio (aHR) with 95% confidence interval (CI).

RESULTS

The all-cause mortality rate during TB treatment was lower (9.5% vs. 12.4%, p < 0.01) in the metformin user group. The hazard of death due to all causes after double propensity score adjustment was also lower in the metformin user group (aHR 0.76, 95% CI 0.67-0.86, p < 0.01). There was no significant difference in mortality between metformin users and non-users for TB-related deaths (p = 0.22); however, there was a significant difference in the non-TB-related deaths (p < 0.01).

CONCLUSION

Metformin use in patients with TB-DM co-prevalence is associated with reduced all-cause mortality, suggesting the potential for metformin adjuvant therapy in these patients.

TRIM27 elicits protective immunity against tuberculosis by activating TFEB-mediated autophagy flux

Infectious diseases, such as Mycobacterium tuberculosis (Mtb)-caused tuberculosis (TB), remain a global threat exacerbated by increasing drug resistance. Host-directed therapy (HDT) is a promising strategy for infection treatment through targeting host immunity. However, the limited understanding of the function and regulatory mechanism of host factors involved in immune defense against infections has impeded HDT development. Here, we identify the ubiquitin ligase (E3) TRIM27 (tripartite motif-containing 27) as a host protective factor against Mtb by enhancing host macroautophagy/autophagy flux in an E3 ligase activity-independent manner. Mechanistically, upon Mtb infection, nuclear-localized TRIM27 increases and functions as a transcription activator of TFEB (transcription factor EB). Specifically, TRIM27 binds to the TFEB promoter and the TFEB transcription factor CREB1 (cAMP responsive element binding protein 1), thus enhancing CREB1-TFEB promoter binding affinity and promoting CREB1 transcription activity toward TFEB, eventually inducing autophagy-related gene expression as well as autophagy flux activation to clear the pathogen. Furthermore, TFEB activator 1 can rescue TRIM27 deficiency-caused decreased autophagy-related gene transcription and attenuated autophagy flux, and accordingly suppressed the intracellular survival of Mtb in cell and mouse models. Taken together, our data reveal that TRIM27 is a host defense factor against Mtb, and the TRIM27-CREB1-TFEB axis is a potential HDT-based TB target that can enhance host autophagy flux.

Antibiotic resistance: a global crisis, problems and solutions

Healthy state is priority in today's world which can be achieved using effective medicines. But due to overuse and misuse of antibiotics, a menace of resistance has increased in pathogenic microbes. World Health Organization (WHO) has announced ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) as the top priority pathogens as these have developed resistance against certain antibiotics. To combat such a global issue, it is utmost important to identify novel therapeutic strategies/agents as an alternate to such antibiotics. To name certain antibiotic adjuvants including: inhibitors of beta-lactamase, efflux pumps and permeabilizers for outer membrane can potentially solve the antibiotic resistance problems. In this regard, inhibitors of lytic domain of lytic transglycosylases provide a novel way to not only act as an alternate to antibiotics but also capable of restoring the efficiency of previously resistant antibiotics. Further, use of bacteriophages is another promising strategy to deal with antibiotic resistant pathogens. Taking in consideration the alternatives of antibiotics, a green synthesis nanoparticle-based therapy exemplifies a good option to combat microbial resistance. As horizontal gene transfer (HGT) in bacteria facilitates the evolution of new resistance strains, therefore identifying the mechanism of resistance and development of inhibitors against it can be a novel approach to combat such problems. In our perspective, host-directed therapy (HDT) represents another promising strategy in combating antimicrobial resistance (AMR). This approach involves targeting specific factors within host cells that pathogens rely on for their survival, either through replication or persistence. As many new drugs are under clinical trials it is advisable that more clinical data and antimicrobial stewardship programs should be conducted to fully assess the clinical efficacy and safety of new therapeutic agents.

Monitoring host-pathogen interactions using chemical proteomics

With the rapid emergence and the dissemination of microbial resistance to conventional chemotherapy, the shortage of novel antimicrobial drugs has raised a global health threat. As molecular interactions between microbial pathogens and their mammalian hosts are crucial to establish virulence, pathogenicity, and infectivity, a detailed understanding of these interactions has the potential to reveal novel therapeutic targets and treatment strategies. Bidirectional molecular communication between microbes and eukaryotes is essential for both pathogenic and commensal organisms to colonise their host. In particular, several devastating pathogens exploit host signalling to adjust the expression of energetically costly virulent behaviours. Chemical proteomics has emerged as a powerful tool to interrogate the protein interaction partners of small molecules and has been successfully applied to advance host-pathogen communication studies. Here, we present recent significant progress made by this approach and provide a perspective for future studies.

Broad-spectrum antiviral strategy: Host-targeting antivirals against emerging and re-emerging viruses

Viral infections are amongst the most prevalent diseases that pose a significant threat to human health. Targeting viral proteins or host factors represents two primary strategies for the development of antiviral drugs. In contrast to virus-targeting antivirals (VTAs), host-targeting antivirals (HTAs) offer advantages in terms of overcoming drug resistance and effectively combating a wide range of viruses, including newly emerging ones. Therefore, targeting host factors emerges as an extremely promising strategy with the potential to address critical challenges faced by VTAs. In recent years, extensive research has been conducted on the discovery and development of HTAs, leading to the approval of maraviroc, a chemokine receptor type 5 (CCR5) antagonist used for the treatment of HIV-1 infected individuals, with several other potential treatments in various stages of development for different viral infections. This review systematically summarizes advancements made in medicinal chemistry regarding various host targets and classifies them into four distinct catagories based on their involvement in the viral life cycle: virus attachment and entry, biosynthesis, nuclear import and export, and viral release.

Microtubule disruption synergizes with STING signaling to show potent and broad-spectrum antiviral activity

The activation of stimulator of interferon genes (STING) signaling induces the production of type I interferons (IFNs), which play critical roles in protective innate immunity for the host to defend against viral infections. Therefore, achieving sustained or enhanced STING activation could become an antiviral immune strategy with potential broad-spectrum activities. Here, we discovered that various clinically used microtubule-destabilizing agents (MDAs) for the treatment of cancer showed a synergistic effect with the activation of STING signaling in innate immune response. The combination of a STING agonist cGAMP and a microtubule depolymerizer MMAE boosted the activation of STING innate immune response and showed broad-spectrum antiviral activity against multiple families of viruses. Mechanistically, MMAE not only disrupted the microtubule network, but also switched the cGAMP-mediated STING trafficking pattern and changed the distribution of Golgi apparatus and STING puncta. The combination of cGAMP and MMAE promoted the oligomerization of STING and downstream signaling cascades. Importantly, the cGAMP plus MMAE treatment increased STING-mediated production of IFNs and other antiviral cytokines to inhibit viral propagation in vitro and in vivo. This study revealed a novel role of the microtubule destabilizer in antiviral immune responses and provides a previously unexploited strategy based on STING-induced innate antiviral immunity.

Engineering Antimicrobial Metal-Phenolic Network Nanoparticles with High Biocompatibility for Wound Healing

Antibiotic-resistant bacteria pose a global health threat by causing persistent and recurrent microbial infections. To address this issue, antimicrobial nanoparticles (NPs) with low drug resistance but potent bactericidal effects have been developed. However, many of the developed NPs display poor biosafety and their synthesis often involves complex procedures and the antimicrobial modes of action are unclear. Herein, a simple strategy is reported for designing antimicrobial metal-phenolic network (am-MPN) NPs through the one-step assembly of a seeding agent (diethyldithiocarbamate), natural polyphenols, and metal ions (e.g., Cu2+ ) in aqueous solution. The Cu2+ -based am-MPN NPs display lower Cu2+ antimicrobial concentrations (by 10-1000 times) lower than most reported nanomaterials and negligible toxicity across various models, including, cells, blood, zebrafish, and mice. Multiple antimicrobial modes of the NPs have been identified, including bacterial wall disruption, reactive oxygen species production, and quinoprotein formation, with the latter being a distinct pathway identified for the antimicrobial activity of the polyphenol-based am-MPN NPs. The NPs exhibit excellent performance against multidrug-resistant bacteria (e.g., methicillin-resistant Staphylococcus aureus (MRSA)), efficiently inhibit and destroy bacterial biofilms, and promote the healing of MRSA-infected skin wounds. This study provides insights on the antimicrobial properties of metal-phenolic materials and the rational design of antimicrobial metal-organic materials.

mSphere of Influence: How host genetics impact microbial pathogenesis and treatment of infectious disease

Emily Rosowski works in the field of host-pathogen interactions, studying how host innate immune mechanisms control pathogens. In this mSphere of Influence article, she reflects on how "Host genotype-specific therapies can optimize the inflammatory response to mycobacterial infections" by D. M. Tobin, F. J. Roca, S. F. Oh, R. McFarland, et al. (Cell 148:434-446, 2012, https://doi.org/10.1016/j.cell.2011.12.023) made an impact on her by investigating how differences in host genetics can affect modes of microbial pathogenesis and inform treatments for infectious disease.

The Hazards of Probiotics on Gut-Derived Pseudomonas aeruginosa Sepsis in Mice Undergoing Chemotherapy

Pseudomonas aeruginosa (P. aeruginosa) is a leading cause of nosocomial infections associated with a high mortality rate and represents a serious threat to human health and the increasing frequency of antimicrobial resistance. Cancer patients are more vulnerable to invasive infection due to ulcerative lesions in mucosal surfaces and immune suppression secondary to chemotherapy. In our in vitro study, we observed that probiotics have the potential to yield beneficial effects on intestinal epithelial cells infected with P. aeruginosa. Additionally, probiotics were found to confer advantageous effects on the innate immunity of mice suffering from Salmonella-induced colitis. As a result, we sought to investigate the impact of probiotics on gut-derived P. aeruginosa sepsis induced by chemotherapy. Following chemotherapy, gut-derived P. aeruginosa sepsis was induced in female C57BL/6 mice aged 6-8 weeks, which were raised under specific-pathogen-free (SPF) conditions in an animal center. Prior to the induction of the sepsis model, the mice were administered 1 × 108 colony-forming units (CFU) of the probiotics, namely Lactobacillus rhamnosus GG (LGG) and Bifidobacterium longum (BL) via oral gavage. We observed that LGG or BL amplified the inflammatory mRNA expression in mice undergoing chemotherapy and suffering from gut-derived P. aeruginosa sepsis. This led to a heightened severity of colitis, as indicated by histological examination. Meanwhile, there was a notable decrease in the expression of antimicrobial peptide mRNA along with reduced levels of zonulin and claudin-2 protein staining within mucosal tissue. These alterations facilitated the translocation of bacteria to the liver, spleen, and bloodstream. To our astonishment, the introduction of probiotics exacerbated gut-derived P. aeruginosa sepsis in mice undergoing chemotherapy. Conclusively, we must be prudent when using probiotics in mice receiving chemotherapy complicated with gut-derived P. aeruginosa sepsis.

Irisflorentin promotes bacterial phagocytosis and inhibits inflammatory responses in macrophages during bacterial infection

Bacterial infection remains a big concern in the patients of ICU, which is the main cause of life-threatening organ dysfunction, or even sepsis. The poor control of bacterial infection caused by antibiotic resistance, etc. or the overwhelming immune response are the most important patho genic factors in intensive care unit (ICU) patients. As main pathogens, antibiotic-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), impose serious challenges during sepsis and require alternative therapeutic options. Irisflorentin (IFL) is one of the major bioactive compounds isolated from the roots of Belamcanda chinensis (Shegan). In this study, IFL could suppress inflammatory response induced by MRSA or a synthetic mimic of bacterial lipoprotein (Pam3CSK4). IFL treatment enhanced the ability of macrophages to phagocytose bacteria likely through up-regulating the expression of phagocytic receptors SR-A1 and FcγR2a. Furthermore, IFL inhibited Pam3CSK4-induced production of pro-inflammatory cytokines, including IL-6 and TNF-α in Raw 264.7 cells, mouse primary macrophages or dendritic cells. IFL treatment also inhibited heat-killed MRSA-induced secretion of IL-6 and TNF-α in mouse bone marrow-derived macrophages. Moreover, IFL attenuated M1 polarization of macrophages as indicated by the down-regulated expression of its polarization markers CD86 and iNOS. Mechanistically, IFL markedly decreased the Pam3CSK4-induced activation of ERK, JNK or p38 MAPK pathways in macrophages. Taken together, IFL may serve as a promising compound for the therapy of bacterial infection, particularly those caused by antibiotic-resistant bacteria, such as MRSA.

Eliminating the invading extracellular and intracellular FnBp+ bacteria from respiratory epithelial cells by autophagy mediated through FnBp-Fn-Integrin α5β1 axis

Background

We previously found that the respiratory epithelial cells could eliminate the invaded group A streptococcus (GAS) through autophagy induced by binding a fibronectin (Fn) binding protein (FnBp) expressed on the surface of GAS to plasma protein Fn and its receptor integrin α5β1 of epithelial cells. Is autophagy initiated by FnBp+ bacteria via FnBp-Fn-Integrin α5β1 axis a common event in respiratory epithelial cells?

Methods

We chose Staphylococcus aureus (S. aureus/S. a) and Listeria monocytogenes (L. monocytogenes/L. m) as representatives of extracellular and intracellular FnBp+ bacteria, respectively. The FnBp of them was purified and the protein function was confirmed by western blot, viable bacteria count, confocal and pull-down. The key molecule downstream of the action axis was detected by IP, mass spectrometry and bio-informatics analysis.

Results

We found that different FnBp from both S. aureus and L. monocytogenes could initiate autophagy through FnBp-Fn-integrin α5β1 axis and this could be considered a universal event, by which host tries to remove invading bacteria from epithelial cells. Importantly, we firstly reported that S100A8, as a key molecule downstream of integrin β1 chain, is highly expressed upon activation of integrin α5β1, which in turn up-regulates autophagy.

Conclusions

Various FnBp from FnBp+ bacteria have the ability to initiate autophagy via FnBp-Fn-Integrin α5β1 axis to promote the removal of invading bacteria from epithelial cells in the presence of fewer invaders. S100A8 is a key molecule downstream of Integrin α5β1 in this autophagy pathway.

Host-directed therapy against mycobacterium tuberculosis infections with diabetes mellitus

Tuberculosis (TB) is caused by the bacterial pathogen Mycobacterium tuberculosis (MTB) and is one of the principal reasons for mortality and morbidity worldwide. Currently, recommended anti-tuberculosis drugs include isoniazid, rifampicin, ethambutol, and pyrazinamide. TB treatment is lengthy and inflicted with severe side-effects, including reduced patient compliance with treatment and promotion of drug-resistant strains. TB is also prone to other concomitant diseases such as diabetes and HIV. These drug-resistant and complex co-morbid characteristics increase the complexity of treating MTB. Host-directed therapy (HDT), which effectively eliminates MTB and minimizes inflammatory tissue damage, primarily by targeting the immune system, is currently an attractive complementary approach. The drugs used for HDT are repositioned drugs in actual clinical practice with relative safety and efficacy assurance. HDT is a potentially effective therapeutic intervention for the treatment of MTB and diabetic MTB, and can compensate for the shortcomings of current TB therapies, including the reduction of drug resistance and modulation of immune response. Here, we summarize the state-of-the-art roles and mechanisms of HDT in immune modulation and treatment of MTB, with a special focus on the role of HDT in diabetic MTB, to emphasize the potential of HDT in controlling MTB infection.

Construction of cellulose acetate-based composite nanofiber films with effective antibacterial and filtration properties

In recent years, the safety of public health has attracted more and more attention. In order to avoid the spread of bacteria and reduce the diseases caused by their invasion of the human body, novel filtration and antibacterial materials have attracted more and more attention. In this work, the antibacterial agents silver nanoparticles (AgNPs) and cetylpyridine bromide (CPB) were introduced into a cellulose acetate (CA) nanofiber film by electrospinning technology to prepare CA-based composite films with good antibacterial and filtration properties. The results of the antibacterial test of the composite nanofiber films showed that AgNPs and CPB had synergistic antibacterial effects and exhibited good antibacterial properties against a variety of bacteria. In addition, in vitro cytotoxicity, skin irritation and skin sensitization experiments proved that the CA/AgNPs, CA/CPB and CA/CPB/AgNPs films produced no skin irritation or sensitization in the short term. These are expected to become potential materials for the preparation of new antibacterial masks. This work provides a new idea for developing materials with good antibacterial properties for enhancing protection via filtration masks.

Unlocking the enigma of phenotypic drug tolerance: Mechanisms and emerging therapeutic strategies

In the ongoing battle against antimicrobial resistance, phenotypic drug tolerance poses a formidable challenge. This adaptive ability of microorganisms to withstand drug pressure without genetic alterations further complicating global healthcare challenges. Microbial populations employ an array of persistence mechanisms, including dormancy, biofilm formation, adaptation to intracellular environments, and the adoption of L-forms, to develop drug tolerance. Moreover, molecular mechanisms like toxin-antitoxin modules, oxidative stress responses, energy metabolism, and (p)ppGpp signaling contribute to this phenomenon. Understanding these persistence mechanisms is crucial for predicting drug efficacy, developing strategies for chronic bacterial infections, and exploring innovative therapies for refractory infections. In this comprehensive review, we dissect the intricacies of drug tolerance and persister formation, explore their role in acquired drug resistance, and highlight emerging therapeutic approaches to combat phenotypic drug tolerance. Furthermore, we outline the future landscape of interventions for persistent bacterial infections.

Targeting host deoxycytidine kinase mitigates Staphylococcus aureus abscess formation

Host-directed therapy (HDT) is an emerging approach to overcome antimicrobial resistance in pathogenic microorganisms. Specifically, HDT targets host-encoded factors required for pathogen replication and survival without interfering with microbial growth or metabolism, thereby eliminating the risk of resistance development. By applying HDT and a drug repurposing approach, we demonstrate that (R)-DI-87, a clinical-stage anti-cancer drug and potent inhibitor of mammalian deoxycytidine kinase (dCK), mitigates Staphylococcus aureus abscess formation in organ tissues upon invasive bloodstream infection. Mechanistically, (R)-DI-87 shields phagocytes from staphylococcal death-effector deoxyribonucleosides that target dCK and the mammalian purine salvage pathway-apoptosis axis. In this manner, (R)-DI-87-mediated protection of immune cells amplifies macrophage infiltration into deep-seated abscesses, a phenomenon coupled with enhanced pathogen control, ameliorated immunopathology, and reduced disease severity. Thus, pharmaceutical blockade of dCK represents an advanced anti-infective intervention strategy against which staphylococci cannot develop resistance and may help to fight fatal infectious diseases in hospitalized patients.

Metabolism Shapes Immune Responses to Staphylococcus aureus

BACKGROUND

Staphylococcus aureus (S. aureus) is a common cause of hospital- and community-acquired infections that can result in various clinical manifestations ranging from mild to severe disease. The bacterium utilizes different combinations of virulence factors and biofilm formation to establish a successful infection, and the emergence of methicillin- and vancomycin-resistant strains introduces additional challenges for infection management and treatment.

SUMMARY

Metabolic programming of immune cells regulates the balance of energy requirements for activation and dictates pro- versus anti-inflammatory function. Recent investigations into metabolic adaptations of leukocytes and S. aureus during infection indicate that metabolic crosstalk plays a crucial role in pathogenesis. Furthermore, S. aureus can modify its metabolic profile to fit an array of niches for commensal or invasive growth.

KEY MESSAGES

Here we focus on the current understanding of immunometabolism during S. aureus infection and explore how metabolic crosstalk between the host and S. aureus influences disease outcome. We also discuss how key metabolic pathways influence leukocyte responses to other bacterial pathogens when information for S. aureus is not available. A better understanding of how S. aureus and leukocytes adapt their metabolic profiles in distinct tissue niches may reveal novel therapeutic targets to prevent or control invasive infections.

Plant Phenolics Inhibit Focal Adhesion Kinase and Suppress Host Cell Invasion by Uropathogenic Escherichia coli

Traditional folk treatments for the prevention and management of urinary tract infections (UTIs) and other infectious diseases often include plants and plant extracts that are rich in phenolic and polyphenolic compounds. These have been ascribed a variety of activities, including inhibition of bacterial interactions with host cells. Here we tested a panel of four well-studied phenolic compounds - caffeic acid phenethyl ester (CAPE), resveratrol, catechin, and epigallocatechin gallate - for effects on host cell adherence and invasion by uropathogenic Escherichia coli (UPEC). These bacteria, which are the leading cause of UTIs, can bind and subsequently invade bladder epithelial cells via an actin-dependent process. Intracellular UPEC reservoirs within the bladder are often protected from antibiotics and host defenses, and likely contribute to the development of chronic and recurrent infections. Using cell culture-based assays, we found that only resveratrol had a notable negative effect on UPEC adherence to bladder cells. However, both CAPE and resveratrol significantly inhibited UPEC entry into the host cells, coordinate with attenuated phosphorylation of the host actin regulator Focal Adhesion Kinase (FAK, or PTK2) and marked increases in the numbers of focal adhesion structures. We further show that the intravesical delivery of resveratrol inhibits UPEC infiltration of the bladder mucosa in a murine UTI model, and that resveratrol and CAPE can disrupt the ability of other invasive pathogens to enter host cells. Together, these results highlight the therapeutic potential of molecules like CAPE and resveratrol, which could be used to augment antibiotic treatments by restricting pathogen access to protective intracellular niches.

Deciphering the mechanism of action of VP343, an antileishmanial drug candidate, in Leishmania infantum

Antileishmanial chemotherapy is currently limited due to severe toxic side effects and drug resistance. Hence, new antileishmanial compounds based on alternative approaches, mainly to avoid the emergence of drug resistance, are needed. The present work aims to decipher the mechanism of action of an antileishmanial drug candidate, named VP343, inhibiting intracellular Leishmania infantum survival via the host cell. Cell imaging showed that VP343 interferes with the fusion of parasitophorous vacuoles and host cell late endosomes and lysosomes, leading to lysosomal cholesterol accumulation and ROS overproduction within host cells. Proteomic analyses showed that VP343 perturbs host cell vesicular trafficking as well as cholesterol synthesis/transport pathways. Furthermore, a knockdown of two selected targets involved in vesicle-mediated transport, Pik3c3 and Sirt2, resulted in similar antileishmanial activity to VP343 treatment. This work revealed potential host cell pathways and targets altered by VP343 that would be of interest for further development of host-directed antileishmanial drugs.