bims-bac4me 2023-11-12 papers

bims-bac4me

Biomed News

on Microbiome and trained immunity

Issue of 2023‒11‒12
37 papers selected by
Chun-Chi Chang, University Hospital Zurich

Macrophage phenotypes and functions: resolving inflammation and restoring homeostasis.
Trained immunity: Target for prophylaxis and therapy.
Early-life microbiota-immune homeostasis.
Hyperglycemia potentiates increased Staphylococcus aureus virulence and resistance to growth inhibition by Pseudomonas aeruginosa.
Efferocytosis: a double-edged sword in microbial immunity.
Ginsenoside Rg3 enriches SCFA-producing commensal bacteria to confer protection against enteric viral infection via the cGAS-STING-type I IFN axis.
Colonic macrophages eat and feed.
Regulated cell death in neutrophils: From apoptosis to NETosis and pyroptosis.
Tissue-resident B cells orchestrate macrophage polarisation and function.
Monocyte differentiation within tissues: a renewed outlook.
Epigenetic modulations of immune cells: from normal development to tumor progression.
Dexamethasone impairs the expression of antimicrobial mediators in lipopolysaccharide-activated primary macrophages by inhibiting both expression and function of interferon β.
Specialized phosphate transport is essential for Staphylococcus aureus nitric oxide resistance.
Bacterial quorum sensing orchestrates longitudinal interactions to shape microbiota assembly.
Purification, characterization, and cloning of a novel pro-inflammatory secreted protein from Staphylococcus aureus.
"Training immunity" against nosocomial pathogens.
Antibiotic failure: Beyond antimicrobial resistance.
The contribution of DNA repair pathways to Staphylococcus aureus fitness and fidelity during nitric oxide stress.
Potent antibodies have surprise source: people with chronic infections.
Tackling antimicrobial resistance to protect healthy ageing.
Host-microbe interactions in chronic rhinosinusitis biofilms and models for investigation.
From microbiome composition to functional engineering, one step at a time.
Ferroptosis triggers airway inflammation in asthma.
Characterization of polarization states of canine monocyte derived macrophages.
Diagnostic and commensal Staphylococcus pseudintermedius genomes reveal niche adaptation through parallel selection of defense mechanisms.
The PI3K-Akt pathway is a multifaceted regulator of the macrophage response to diverse group B Streptococcus isolates.
Reframing macrophage diversity with network motifs.
Endotype evaluation of Hispanic/Latinx-American patients with chronic rhinosinusitis with nasal polyps.
Enterohaemorrhagic E. coli utilizes host- and microbiota-derived L-malate as a signaling molecule for intestinal colonization.
Postbiotic Fractions of Probiotics Lactobacillus plantarum 299v and Lactobacillus rhamnosus GG Show Immune-Modulating Effects.
Host Lipid Manipulation by Intracellular Bacteria: Moonlighting for Immune Evasion.
Airway and blood monocyte transcriptomic profiling reveals an antiviral phenotype in RSV-infected infants with severe disease.
Neutrophils sing "IL[-10] be seeing you" in the lungs during pneumonia.
Interferon signaling drives epithelial metabolic reprogramming to promote secondary bacterial infection.
Generation of Monocyte-Derived Dendritic Cells with Differing Sialylated Phenotypes.
Exogenous L-Alanine promotes phagocytosis of multidrug-resistant bacterial pathogens.
A human urothelial microtissue model reveals shared colonization and survival strategies between uropathogens and commensals.

Trends Immunol. 2023 Nov 06. pii: S1471-4906(23)00211-9. [Epub ahead of print]

Macrophage phenotypes and functions: resolving inflammation and restoring homeostasis.

Patricia Rodríguez-Morales, Ruth A Franklin.

  Inflammation must be tightly regulated to both defend against pathogens and restore tissue homeostasis. The resolution of inflammatory responses is a dynamic process orchestrated by cells of the immune system. Macrophages, tissue-resident innate immune cells, are key players in modulating inflammation. Here, we review recent work highlighting the importance of macrophages in tissue resolution and the return to homeostasis. We propose that enhancing macrophage pro-resolution functions represents a novel and widely applicable therapeutic strategy to dampen inflammation, promote repair, and restore tissue integrity and function.

Keywords:  SARS-CoV-2; efferocytosis; fibrosis; inflammation; macrophages; tissue repair

DOI:  https://doi.org/10.1016/j.it.2023.10.004
Cell Host Microbe. 2023 Nov 08. pii: S1931-3128(23)00419-5. [Epub ahead of print]31(11): 1776-1791

Trained immunity: Target for prophylaxis and therapy.

Athanasios Ziogas, Mariolina Bruno, Roy van der Meel, Willem J M Mulder, Mihai G Netea.

Trained immunity is a de facto memory for innate immune responses, leading to long-term functional reprogramming of innate immune cells. In physiological conditions, trained immunity leads to adaptive states that enhance resistance against pathogens and contributes to immunosurveillance. Dysregulated trained immunity can however lead either to defective innate immune responses in severe infections or cancer or to inflammatory and autoimmune diseases if trained immunity is inappropriately activated. Here, we review the immunological and molecular mechanisms that mediate trained immunity induction and propose that trained immunity represents an important target for prophylactic and therapeutic approaches in human diseases. On the one hand, we argue that novel approaches that induce trained immunity may enhance vaccine efficacy. On the other hand, induction of trained immunity in cancer, and inhibition of exaggerated induction of trained immunity in inflammatory disorders, are viable targets amenable for new therapeutic approaches.

DOI: https://doi.org/10.1016/j.chom.2023.10.015
Front Immunol. 2023 ;14 1266876

Early-life microbiota-immune homeostasis.

Hayley M Reynolds, Matthew L Bettini.

  As the prevalence of allergy and autoimmune disease in industrialized societies continues to rise, improving our understanding of the mechanistic roles behind microbiota-immune homeostasis has become critical for informing therapeutic interventions in cases of dysbiosis. Of particular importance, are alterations to intestinal microbiota occurring within the critical neonatal window, during which the immune system is highly vulnerable to environmental exposures. This review will highlight recent literature concerning mechanisms of early-life microbiota-immune homeostasis as well as discuss the potential for therapeutics in restoring dysbiosis in early life.

Keywords:  dysbiosis; early-life; fecal microbiota transplant; gut microbiota; immune homeostasis; prebiotics; probiotics

DOI:  https://doi.org/10.3389/fimmu.2023.1266876
Microbiol Spectr. 2023 Nov 07. e0229923

Hyperglycemia potentiates increased Staphylococcus aureus virulence and resistance to growth inhibition by Pseudomonas aeruginosa.

Christopher J Genito, Benjamin P Darwitz, Matthew A Greenwald, Matthew C Wolfgang, Lance R Thurlow.

  Diabetes is associated with several health consequences, including increased susceptibility to more frequent and severe infections. Bacterial infections associated with diabetes are typically polymicrobial, with Staphylococcus aureus and Pseudomonas aeruginosa frequently isolated from the same infection site. S. aureus and P. aeruginosa are frequently found in diabetic skin and soft tissue infections, in the lungs of people with cystic fibrosis, and in indwelling device infections. Numerous studies have investigated interactions between these two pathogens primarily using in vitro systems. These models have several limitations as they do not accurately reflect the complexities of an immune response nor the nutrient dynamics in a diabetic infection microenvironment. Here, we describe a novel murine indwelling device co-infection model that allows us to study the interactions between S. aureus and P. aeruginosa within the context of an immune response during both normal and diabetic infections. Our data shows that P. aeruginosa significantly inhibits S. aureus growth during co-infection in a normal mouse and that inhibition is not dependent on the P. aeruginosa PQS quorum sensing system. Conversely, in a diabetic co-infection, S. aureus overcomes inhibition by P. aeruginosa and this phenotype is reliant on S. aureus glycolysis. We also demonstrate that both organisms display increased virulence potential in a diabetic co-infection as we observe increased dissemination to peripheral tissues. This study revealed novel in vivo interactions between S. aureus and P. aeruginosa and advances our understanding of the complex interactions between microorganisms in polymicrobial infections in clinically relevant infection microenvironments.IMPORTANCEIndividuals with diabetes are prone to more frequent and severe infections, with many of these infections being polymicrobial. Polymicrobial infections are frequently observed in skin infections and in individuals with cystic fibrosis, as well as in indwelling device infections. Two bacteria frequently co-isolated from infections are Staphylococcus aureus and Pseudomonas aeruginosa. Several studies have examined the interactions between these microorganisms. The majority of these studies use in vitro model systems that cannot accurately replicate the microenvironment of diabetic infections. We employed a novel murine indwelling device model to examine interactions between S. aureus and P. aeruginosa. Our data show that competition between these bacteria results in reduced growth in a normal infection. In a diabetic infection, we observe increased growth of both microbes and more severe infection as both bacteria invade surrounding tissues. Our results demonstrate that diabetes changes the interaction between bacteria resulting in poor infection outcomes.

Keywords:  USA300; diabetes; dissemination; glycolysis; indwelling medical devices

DOI:  https://doi.org/10.1128/spectrum.02299-23
Arch Microbiol. 2023 Nov 05. 205(12): 370

Efferocytosis: a double-edged sword in microbial immunity.

Fatemeh Mohammad-Rafiei, Fatemeh Moadab, Ali Mahmoudi, Jamshid Gholizadeh Navashenaq, Seyed Mohammad Gheibihayat.

  Efferocytosis is characterized as the rapid and efficient process by which dying or dead cells are removed. This type of clearance is initiated via "find-me" signals, and then, carries on by "eat-me" and "don't-eat-me" ones. Efferocytosis has a critical role to play in tissue homeostasis and innate immunity. However, some evidence suggests it as a double-edged sword in microbial immunity. In other words, some pathogens have degraded efferocytosis by employing efferocytic mechanisms to bypass innate immune detection and promote infection, despite the function of this process for the control and clearance of pathogens. In this review, the efferocytosis mechanisms from the recognition of dying cells to phagocytic engulfment are initially presented, and then, its diverse roles in inflammation and immunity are highlighted. In this case, much focus is also laid on some bacterial, viral, and parasitic infections caused by Mycobacterium tuberculosis (M. tb), Mycobacterium marinum (M. marinum), Listeria monocytogenes (L. monocytogenes), Chlamydia pneumoniae (CP), Klebsiella pneumoniae (KP), Influenza A virus (IAV), human immunodeficiency virus (HIV), and Leishmania, respectively.

Keywords:  Apoptosis; Eat-me; Efferocytosis; Find-me; Pathogen clearance

DOI:  https://doi.org/10.1007/s00203-023-03704-8
ISME J. 2023 Nov 10.

Ginsenoside Rg3 enriches SCFA-producing commensal bacteria to confer protection against enteric viral infection via the cGAS-STING-type I IFN axis.

Gan Wang, Jingtianyi Liu, Yanan Zhang, Jinyan Xie, Shuxian Chen, Yuhua Shi, Fushan Shi, Shu Jeffrey Zhu.

The microbiota-associated factors that influence host susceptibility and immunity to enteric viral infections remain poorly defined. We identified that the herbal monomer ginsenoside Rg3 (Rg3) can shape the gut microbiota composition, enriching robust short-chain fatty acid (SCFA)-producing Blautia spp. Colonization by representative Blautia coccoides and Blautia obeum could protect germ-free or vancomycin (Van)-treated mice from enteric virus infection, inducing type I interferon (IFN-I) responses in macrophages via the MAVS-IRF3-IFNAR signaling pathway. Application of exogenous SCFAs (acetate/propionate) reproduced the protective effect of Rg3 and Blautia spp. in Van-treated mice, enhancing intracellular Ca2+- and MAVS-dependent mtDNA release and activating the cGAS-STING-IFN-I axis by stimulating GPR43 signaling in macrophages. Our findings demonstrate that macrophage sensing of metabolites from specific commensal bacteria can prime the IFN-I signaling that is required for antiviral functions.

DOI: https://doi.org/10.1038/s41396-023-01541-7
Cell Metab. 2023 Nov 07. pii: S1550-4131(23)00375-3. [Epub ahead of print]35(11): 1847-1848

Colonic macrophages eat and feed.

Jan Van den Bossche.

Macrophages not only secure host defense via phagocytosis but also play a key role in tissue homeostasis. A comprehensive study by Fritsch et al. reveals a novel mechanism by which macrophages in the colon deliver polyamines to epithelial cells to support self-renewal of the epithelium during periods of high proliferation.

DOI: https://doi.org/10.1016/j.cmet.2023.10.006
Semin Immunol. 2023 Nov 06. pii: S1044-5323(23)00140-9. [Epub ahead of print]70 101849

Regulated cell death in neutrophils: From apoptosis to NETosis and pyroptosis.

Léonie Dejas, Karin Santoni, Etienne Meunier, Mohamed Lamkanfi.

  Neutrophils are among the most abundant immune cells, representing about 50%- 70% of all circulating leukocytes in humans. Neutrophils rapidly infiltrate inflamed tissues and play an essential role in host defense against infections. They exert microbicidal activity through a variety of specialized effector mechanisms, including phagocytosis, production of reactive oxygen species, degranulation and release of secretory vesicles containing broad-spectrum antimicrobial factors. In addition to their homeostatic turnover by apoptosis, recent studies have revealed the mechanisms by which neutrophils undergo various forms of regulated cell death. In this review, we will discuss the different modes of regulated cell death that have been described in neutrophils, with a particular emphasis on the current understanding of neutrophil pyroptosis and its role in infections and autoinflammation.

Keywords:  Apoptosis; Cell death; Infection; Inflammation; Netosis; Neutrophil; Pyroptosis

DOI:  https://doi.org/10.1016/j.smim.2023.101849
Nat Commun. 2023 Nov 04. 14(1): 7081

Tissue-resident B cells orchestrate macrophage polarisation and function.

Ondrej Suchanek, John R Ferdinand, Zewen K Tuong, Sathi Wijeyesinghe, Anita Chandra, Ann-Katrin Clauder, Larissa N Almeida, Simon Clare, Katherine Harcourt, Christopher J Ward, Rachael Bashford-Rogers, Trevor Lawley, Rudolf A Manz, Klaus Okkenhaug, David Masopust, Menna R Clatworthy.

B cells play a central role in humoral immunity but also have antibody-independent functions. Studies to date have focused on B cells in blood and secondary lymphoid organs but whether B cells reside in non-lymphoid organs (NLO) in homeostasis is unknown. Here we identify, using intravenous labeling and parabiosis, a bona-fide tissue-resident B cell population in lung, liver, kidney and urinary bladder, a substantial proportion of which are B-1a cells. Tissue-resident B cells are present in neonatal tissues and also in germ-free mice NLOs, albeit in lower numbers than in specific pathogen-free mice and following co-housing with 'pet-store' mice. They spatially co-localise with macrophages and regulate their polarization and function, promoting an anti-inflammatory phenotype, in-part via interleukin-10 production, with effects on bacterial clearance during urinary tract infection. Thus, our data reveal a critical role for tissue-resident B cells in determining the homeostatic 'inflammatory set-point' of myeloid cells, with important consequences for tissue immunity.

DOI: https://doi.org/10.1038/s41467-023-42625-4
Trends Immunol. 2023 Nov 08. pii: S1471-4906(23)00212-0. [Epub ahead of print]

Monocyte differentiation within tissues: a renewed outlook.

Alessandra Rigamonti, Javiera Villar, Elodie Segura.

When recruited to mammalian tissues, monocytes differentiate into macrophages or dendritic cells (DCs). In the past few years, the existence of monocyte-derived DCs (moDCs) was questioned by the discovery of new DC populations with overlapping phenotypes. Here, we critically review the evidence for monocyte differentiation into DCs in tissues and highlight their specific functions. Recent studies have shown that monocyte-derived macrophages (moMacs) with distinct life cycles coexist in tissues, both at steady state and upon inflammation. Integrating studies in mice and humans, we highlight specific features of moMacs during inflammation and tissue repair. We also discuss the notion of monocyte differentiation occurring via a binary fate decision. Deciphering monocyte-derived cell properties is essential for understanding their role in nonresolving inflammation and how they might be targeted for therapies.

DOI: https://doi.org/10.1016/j.it.2023.10.005
Int J Biol Sci. 2023 ;19(16): 5120-5144

Epigenetic modulations of immune cells: from normal development to tumor progression.

Yuanchun Xu, Zongsheng He, Jing Du, Ziqiang Chen, John W M Creemers, Bin Wang, Fan Li, Yaling Wang.

  The dysfunction of immune cell development often impairs immunological homeostasis, thus causing various human diseases. Accumulating evidence shows that the development of different immune cells from hematopoietic stem cells are highly fine-tuned by different epigenetic mechanisms including DNA methylation, histone modifications, chromatin remodeling and RNA-related regulations. Understanding how epigenetic regulators modulate normal development of immune cells contributes to the identification of new strategies for various diseases. Here, we review recent advances suggesting that epigenetic modulations can orchestrate immune cell development and functions through their impact on critical gene expression. We also discuss the aberrations of epigenetic modulations in immune cells that influence tumor progression, and the fact that underlying mechanisms affect how epigenetic drugs interfere with tumor progression in the clinic.

Keywords:  DNA methylation; Innate immune cells; RNA-associated modulations; adaptive immune cells; cancer treatment; chromatin remodeling; histone modifications

DOI:  https://doi.org/10.7150/ijbs.88327
Front Immunol. 2023 ;14 1190261

Dexamethasone impairs the expression of antimicrobial mediators in lipopolysaccharide-activated primary macrophages by inhibiting both expression and function of interferon β.

John D O'Neil, Oliwia O Bolimowska, Sally A Clayton, Tina Tang, Kalbinder K Daley, Samuel Lara-Reyna, Jordan Warner, Claire S Martin, Rahul Y Mahida, Rowan S Hardy, J Simon C Arthur, Andrew R Clark.

  Glucocorticoids potently inhibit expression of many inflammatory mediators, and have been widely used to treat both acute and chronic inflammatory diseases for more than seventy years. However, they can have several unwanted effects, amongst which immunosuppression is one of the most common. Here we used microarrays and proteomic approaches to characterise the effect of dexamethasone (a synthetic glucocorticoid) on the responses of primary mouse macrophages to a potent pro-inflammatory agonist, lipopolysaccharide (LPS). Gene ontology analysis revealed that dexamethasone strongly impaired the lipopolysaccharide-induced antimicrobial response, which is thought to be driven by an autocrine feedback loop involving the type I interferon IFNβ. Indeed, dexamethasone strongly and dose-dependently inhibited the expression of IFNβ by LPS-activated macrophages. Unbiased proteomic data also revealed an inhibitory effect of dexamethasone on the IFNβ-dependent program of gene expression, with strong down-regulation of several interferon-induced antimicrobial factors. Surprisingly, dexamethasone also inhibited the expression of several antimicrobial genes in response to direct stimulation of macrophages with IFNβ. We tested a number of hypotheses based on previous publications, but found that no single mechanism could account for more than a small fraction of the broad suppressive impact of dexamethasone on macrophage type I interferon signaling, underlining the complexity of this pathway. Preliminary experiments indicated that dexamethasone exerted similar inhibitory effects on primary human monocyte-derived or alveolar macrophages.

Keywords:  SARS-CoV-2; dexamethasone; glucocorticoid; innate immunity; interferon β; macrophage; type I interferon; virus

DOI:  https://doi.org/10.3389/fimmu.2023.1190261
mBio. 2023 Nov 08. e0245123

Specialized phosphate transport is essential for Staphylococcus aureus nitric oxide resistance.

Amelia C Stephens, Srijon K Banerjee, Anthony R Richardson.

  Staphylococcus aureus is a major human pathogen capable of causing a variety of diseases ranging from skin and soft tissue infections to systemic presentations such as sepsis, endocarditis, and osteomyelitis. For S. aureus to persist as a pathogen in these environments, it must be able to resist the host immune response, including the production of reactive oxygen and nitrogen species (e.g., nitric oxide, NO·). Extensive work from our lab has shown that S. aureus is highly resistant to NO·, especially in the presence of glucose. RNA-seq performed on S. aureus exposed to NO· in the presence and absence of glucose showed a new system important for NO· resistance-phosphate transport. The phosphate transport systems pstSCAB and nptA are both upregulated upon NO·-exposure, particularly in the presence of glucose. Both are key for phosphate transport at an alkaline pH, which the cytosol of S. aureus becomes under NO· stress. Accordingly, the ΔpstSΔnptA mutant is attenuated under NO stress in vitro as well as in macrophage and murine infection models. This work defines a new role in infection for two phosphate transporters in S. aureus and provides insight into the complex system that is NO· resistance in S. aureus.IMPORTANCEStaphylococcus aureus is a bacterial pathogen capable of causing a wide variety of disease in humans. S. aureus is unique in its ability to resist the host immune response, including the antibacterial compound known as nitric oxide (NO·). We used an RNA-sequencing approach to better understand the impact of NO· on S. aureus in different environments. We discovered that inorganic phosphate transport is induced by the presence of NO·. Phosphate is important for the generation of energy from glucose, a carbon source favored by S. aureus. We show that the absence of these phosphate transporters causes lowered energy levels in S. aureus. We find that these phosphate transporters are essential for S. aureus to grow in the presence of NO· and to cause infection. Our work here contributes significantly to our understanding of S. aureus NO· resistance and provides a new context in which S. aureus phosphate transporters are essential.

Keywords:  S. aureus; nitric oxide; pathogenesis; phosphate

DOI:  https://doi.org/10.1128/mbio.02451-23
Microbiome. 2023 Nov 06. 11(1): 241

Bacterial quorum sensing orchestrates longitudinal interactions to shape microbiota assembly.

Ying Su, Ming-Ying Xu, Ying Cui, Run-Zhi Chen, Li-Xiang Xie, Jing-Xiang Zhang, Yong-Qiu Chen, Tao Ding.

  BACKGROUND: The mechanism of microbiota assembly is one of the main problems in microbiome research, which is also the primary theoretical basis for precise manipulation of microbial communities. Bacterial quorum sensing (QS), as the most common means for bacteria to exchange information and interactions, is characterized by universality, specificity, and regulatory power, which therefore may influence the assembly processes of human microbiota. However, the regulating role of QS in microbiota assembly is rarely reported. In this study, we developed an optimized in vitro oral biofilm microbiota assembling (OBMA) model to simulate the time-series assembly of oral biofilm microbiota (OBM), by which to excavate the QS network and its regulating power in the process.RESULTS: By using the optimized OBMA model, we were able to restore the assembly process of OBM and generate time-series OBM metagenomes of each day. We discovered a total of 2291 QS protein homologues related to 21 QS pathways. Most of these pathways were newly reported and sequentially enriched during OBM assembling. These QS pathways formed a comprehensive longitudinal QS network that included successively enriched QS hubs, such as Streptococcus, Veillonella-Megasphaera group, and Prevotella-Fusobacteria group, for information delivery. Bidirectional cross-talk among the QS hubs was found to play critical role in the directional turnover of microbiota structure, which in turn, influenced the assembly process. Subsequent QS-interfering experiments accurately predicted and experimentally verified the directional shaping power of the longitudinal QS network in the assembly process. As a result, the QS-interfered OBM exhibited delayed and fragile maturity with prolonged membership of Streptococcus and impeded membership of Prevotella and Fusobacterium.
CONCLUSION: Our results revealed an unprecedented longitudinal QS network during OBM assembly and experimentally verified its power in predicting and manipulating the assembling process. Our work provides a new perspective to uncover underlying mechanism in natural complex microbiota assembling and a theoretical basis for ultimately precisely manipulating human microbiota through intervention in the QS network. Video Abstract.

Keywords:  Bacterial communication; Bacterial interaction; Interspecies cross-talk; Microbiota assembly; Microbiota manipulation; Quorum sensing

DOI:  https://doi.org/10.1186/s40168-023-01699-4
Microbiol Spectr. 2023 Nov 08. e0289823

Purification, characterization, and cloning of a novel pro-inflammatory secreted protein from Staphylococcus aureus.

Patrick M Schlievert, Jacob D Nelson, Samuel H Kilgore, Lilliana Radoshevich, Aloysius J Klingelhutz, Donald Y M Leung.

  Staphylococcus aureus is a human pathogen, causing infections ranging from benign skin and soft tissue infections to life-threatening pneumonia, sepsis/infective endocarditis, and toxic shock syndrome (TSS). The organisms cause infections through production of both cell-surface and secreted virulence factors. We focus primarily on secreted virulence factors, having done scans for such proteins for many years. We have purified and characterized TSS toxin-1; staphylococcal enterotoxin-like superantigens K, L, and Q; an operon of six serine proteases, epsilon cytotoxin; and enterotoxin-associated ampicillin resistance protein. The current study clones and characterizes another novel secreted factor that we tentatively refer to as methionine-rich protein (MRP) because its gene encodes a protein with ten methionine residues and eight in the small mature protein. The MRP gene encodes a protein of 199 amino acids with the first 28 being a signal peptide. The mature protein has 171 amino acids and has a molecular weight of approximately 18,800. MRP has an unusual isoelectric point (pI) for staphylococcal secreted virulence factors of approximately 5.3, whereas other secreted virulence factors have neutral or basic pIs. MRP was listed as a hypothetical protein in the NCBI database. We tested MRP for biological activities that characterize S. aureus and observed that the protein has no detectable superantigen, cytolytic (hemolytic), lipase, or protease activity. MRP induced chemokine (interleukin-8) production from human vaginal epithelial cells. This activity potentially facilitates S. aureus provoking harmful mucosal and skin inflammatory responses.IMPORTANCEStaphylococcus aureus causes a myriad of human diseases, ranging from relatively mild soft tissue infections to highly fatal pneumonia, sepsis, and toxic shock syndrome. The organisms primarily cause diseases across mucosal and skin barriers. In order to facilitate penetration of barriers, S. aureus causes harmful inflammation by inducing chemokines from epithelial cells. We report the cloning and characterization of a novel secreted S. aureus protein that induces chemokine production from epithelial cells as its major demonstrable function. This secreted protein possibly helps S. aureus and its secreted proteins to penetrate host barriers.

Keywords:  Staphylococcus aureus; chemokines; epithelial cells; virulence factors

DOI:  https://doi.org/10.1128/spectrum.02898-23
Sci Immunol. 2023 Nov 10. 8(89): eadl5685

"Training immunity" against nosocomial pathogens.

Alexandra Schäfer, David R Martinez.

Non-antigen vaccines that broadly activate innate immune responses reduce mortality against hospital-acquired bacterial and fungal pathogens.

DOI: https://doi.org/10.1126/sciimmunol.adl5685
Drug Resist Updat. 2023 Oct 18. pii: S1368-7646(23)00095-X. [Epub ahead of print]71 101012

Antibiotic failure: Beyond antimicrobial resistance.

Cesar de la Fuente-Nunez, Angela Cesaro, Robert E W Hancock.

  Despite significant progress in antibiotic discovery, millions of lives are lost annually to infections. Surprisingly, the failure of antimicrobial treatments to effectively eliminate pathogens frequently cannot be attributed to genetically-encoded antibiotic resistance. This review aims to shed light on the fundamental mechanisms contributing to clinical scenarios where antimicrobial therapies are ineffective (i.e., antibiotic failure), emphasizing critical factors impacting this under-recognized issue. Explored aspects include biofilm formation and sepsis, as well as the underlying microbiome. Therapeutic strategies beyond antibiotics, are examined to address the dimensions and resolution of antibiotic failure, actively contributing to this persistent but escalating crisis. We discuss the clinical relevance of antibiotic failure beyond resistance, limited availability of therapies, potential of new antibiotics to be ineffective, and the urgent need for novel anti-infectives or host-directed therapies directly addressing antibiotic failure. Particularly noteworthy is multidrug adaptive resistance in biofilms that represent 65 % of infections, due to the lack of approved therapies. Sepsis, responsible for 19.7 % of all deaths (as well as severe COVID-19 deaths), is a further manifestation of this issue, since antibiotics are the primary frontline therapy, and yet 23 % of patients succumb to this condition.

Keywords:  Antibiotic resistance; Biofilm; Global health; Infectious Diseases; Sepsis

DOI:  https://doi.org/10.1016/j.drup.2023.101012
mBio. 2023 Nov 10. e0215623

The contribution of DNA repair pathways to Staphylococcus aureus fitness and fidelity during nitric oxide stress.

Kelly E Hurley, Srijon K Banerjee, Amelia C Stephens, Michelle R Scribner, Vaughn S Cooper, Anthony R Richardson.

  Staphylococcus aureus is a major human pathogen that causes a variety of illnesses, ranging from minor skin and soft tissue infections to more severe systemic infections. Although the primary host immune response can typically clear bacterial infections, S. aureus is uniquely resistant to inflammation. For instance, our laboratory has determined that S. aureus is highly resistant to nitric oxide (NO⋅), an important component of the innate immune response that plays a role in both immunomodulatory and antibacterial processes. Additionally, NO⋅ and its derivatives can cause damage to S. aureus DNA, more specifically, deamination and/or oxidation of DNA bases; however, regulation and repair mechanisms of DNA in S. aureus are understudied. Thus, we hypothesize that several DNA repair mechanisms may account for the replication fidelity of S. aureus and may contribute to fitness in the presence of NO⋅. Here, we show the role of several DNA repair mechanisms in S. aureus. More specifically, we found that recombinational repair genes recJ, recG, and polA may play a role in the repair of NO⋅-induced replication fork collapses. We also show the role of the base excision repair pathway protein, MutY, in reducing NO⋅-mediated mutagenesis. Overall, our results suggest that NO⋅ leads to DNA damage, which subsequently induces the activity of several DNA repair pathways, contributing to the replication fidelity and fitness of S. aureus.IMPORTANCEPathogenic bacteria must evolve various mechanisms in order to evade the host immune response that they are infecting. One aspect of the primary host immune response to an infection is the production of an inflammatory effector component, nitric oxide (NO⋅). Staphylococcus aureus has uniquely evolved a diverse array of strategies to circumvent the inhibitory activity of nitric oxide. One such mechanism by which S. aureus has evolved allows the pathogen to survive and maintain its genomic integrity in this environment. For instance, here, our results suggest that S. aureus employs several DNA repair pathways to ensure replicative fitness and fidelity under NO⋅ stress. Thus, our study presents evidence of an additional strategy that allows S. aureus to evade the cytotoxic effects of host NO⋅.

Keywords:  DNA repair; Staphylococcus aureus; nitric oxide

DOI:  https://doi.org/10.1128/mbio.02156-23
Nature. 2023 Nov;623(7986): 227

Potent antibodies have surprise source: people with chronic infections.



Keywords:  Microbiology

DOI:  https://doi.org/10.1038/d41586-023-03352-4
Lancet Healthy Longev. 2023 Nov;pii: S2666-7568(23)00218-0. [Epub ahead of print]4(11): e584

Tackling antimicrobial resistance to protect healthy ageing.

The Lancet Healthy Longevity.

DOI: https://doi.org/10.1016/S2666-7568(23)00218-0
Biofilm. 2023 Dec 15. 6 100160

Host-microbe interactions in chronic rhinosinusitis biofilms and models for investigation.

Emily J Vanderpool, Kendra P Rumbaugh.

  Chronic rhinosinusitis (CRS) is a debilitating condition characterized by long-lasting inflammation of the paranasal sinuses. It affects a significant portion of the population, causing a considerable burden on individuals and healthcare systems. The pathogenesis of CRS is multifactorial, with bacterial infections playing a crucial role in CRS development and persistence. In recent years, the presence of biofilms has emerged as a key contributor to the chronicity of sinusitis, further complicating treatment and exacerbating symptoms. This review aims to explore the role of biofilms in CRS, focusing on the involvement of the bacterial species Staphylococcus aureus and Pseudomonas aeruginosa, their interactions in chronic infections, and model systems for studying biofilms in CRS. These species serve as an example of how microbial interplay can influence disease progression and exemplify the need for continued investigation and innovation in CRS research.

Keywords:  Biofilm models; Chronic rhinosinusitis; Host-microbe interactions; Pseudomonas aeruginosa; Staphylococcus aureus

DOI:  https://doi.org/10.1016/j.bioflm.2023.100160
Microbiol Mol Biol Rev. 2023 Nov 10. e0006323

From microbiome composition to functional engineering, one step at a time.

Sebastian Dan Burz, Senka Causevic, Alma Dal Co, Marija Dmitrijeva, Philipp Engel, Daniel Garrido-Sanz, Gilbert Greub, Siegfried Hapfelmeier, Wolf-Dietrich Hardt, Vassily Hatzimanikatis, Clara Margot Heiman, Mathias Klaus-Maria Herzog, Alyson Hockenberry, Christoph Keel, Andreas Keppler, Soon-Jae Lee, Julien Luneau, Lukas Malfertheiner, Sara Mitri, Bidong Ngyuen, Omid Oftadeh, Alan R Pacheco, François Peaudecerf, Grégory Resch, Hans-Joachim Ruscheweyh, Asli Sahin, Ian R Sanders, Emma Slack, Shinichi Sunagawa, Janko Tackmann, Robin Tecon, Giovanni Stefano Ugolini, Jordan Vacheron, Jan Roelof van der Meer, Evangelia Vayena, Pascale Vonaesch, Julia A Vorholt.

  SUMMARYCommunities of microorganisms (microbiota) are present in all habitats on Earth and are relevant for agriculture, health, and climate. Deciphering the mechanisms that determine microbiota dynamics and functioning within the context of their respective environments or hosts (the microbiomes) is crucially important. However, the sheer taxonomic, metabolic, functional, and spatial complexity of most microbiomes poses substantial challenges to advancing our knowledge of these mechanisms. While nucleic acid sequencing technologies can chart microbiota composition with high precision, we mostly lack information about the functional roles and interactions of each strain present in a given microbiome. This limits our ability to predict microbiome function in natural habitats and, in the case of dysfunction or dysbiosis, to redirect microbiomes onto stable paths. Here, we will discuss a systematic approach (dubbed the N+1/N-1 concept) to enable step-by-step dissection of microbiome assembly and functioning, as well as intervention procedures to introduce or eliminate one particular microbial strain at a time. The N+1/N-1 concept is informed by natural invasion events and selects culturable, genetically accessible microbes with well-annotated genomes to chart their proliferation or decline within defined synthetic and/or complex natural microbiota. This approach enables harnessing classical microbiological and diversity approaches, as well as omics tools and mathematical modeling to decipher the mechanisms underlying N+1/N-1 microbiota outcomes. Application of this concept further provides stepping stones and benchmarks for microbiome structure and function analyses and more complex microbiome intervention strategies.

Keywords:  focal strains; inoculants; microbiome development; microbiota; modeling; systems’ analysis

DOI:  https://doi.org/10.1128/mmbr.00063-23
Ther Adv Respir Dis. 2023 Jan-Dec;17:17 17534666231208628

Ferroptosis triggers airway inflammation in asthma.

Minming Li, Min Li, Yunjiao Hou, Huilin He, Ruonan Jiang, Chu Wang, Shibo Sun.

  Ferroptosis is a regulatory cell death characterized by intracellular iron accumulation and lipid peroxidation that leads to oxidative stress. Many signaling pathways such as iron metabolism, lipid metabolism, and amino acid metabolism precisely regulate the process of ferroptosis. Ferroptosis is involved in a variety of lung diseases, such as acute lung injury, chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis. Increasing studies suggest that ferroptosis is involved in the development of asthma. Ferroptosis plays an important role in asthma. Iron metabolism disorders, lipid peroxidation, amino acid metabolism disorders lead to the occurrence of ferroptosis in airway epithelial cells, and then aggravate clinical symptoms in asthmatic patients. Moreover, several regulators of ferroptosis are involved in the pathogenesis of asthma, such as Nrf2, heme oxygenase-1, mevalonate pathway, and ferroptosis inhibitor protein 1. Importantly, ferroptosis inhibitors improve asthma. Thus, the pathogenesis of ferroptosis and its contribution to the pathogenesis of asthma help us better understand the occurrence and development of asthma, and provide new directions in asthma treatment. This article aimed to review the role and mechanism of ferroptosis in asthma, describing the relationship between ferroptosis and asthma based on signaling pathways and related regulatory factors. At the same time, we summarized current observations of ferroptosis in eosinophils, airway epithelial cells, and airway smooth muscle cells in asthmatic patients.

Keywords:  Nrf2; airway epithelial cells; asthma; ferroptosis; lipid peroxidation

DOI:  https://doi.org/10.1177/17534666231208628
PLoS One. 2023 ;18(11): e0292757

Characterization of polarization states of canine monocyte derived macrophages.

Qingkang Lyu, Edwin J A Veldhuizen, Irene S Ludwig, Victor P M G Rutten, Willem van Eden, Alice J A M Sijts, Femke Broere.

Macrophages can reversibly polarize into multiple functional subsets depending on their micro-environment. Identification and understanding the functionality of these subsets is relevant for the study of immune‑related diseases. However, knowledge about canine macrophage polarization is still in its infancy. In this study, we polarized canine monocytes using GM-CSF/IFN- γ and LPS towards M1 macrophages or M-CSF and IL-4 towards M2 macrophages and compared them to undifferentiated monocytes (M0). Polarized M1 and M2 macrophages were thoroughly characterized for morphology, surface marker features, gene profiles and functional properties. Our results showed that canine M1-polarized macrophages obtained a characteristic large, roundish, or amoeboid shape, while M2-polarized macrophages were smaller and adopted an elongated spindle-like morphology. Phenotypically, all macrophage subsets expressed the pan-macrophage markers CD14 and CD11b. M1-polarized macrophages expressed increased levels of CD40, CD80 CD86 and MHC II, while a significant increase in the expression levels of CD206, CD209, and CD163 was observed in M2-polarized macrophages. RNAseq of the three macrophage subsets showed distinct gene expression profiles, which are closely associated with immune responsiveness, cell differentiation and phagocytosis. However, the complexity of the gene expression patterns makes it difficult to assign clear new polarization markers. Functionally, undifferentiated -monocytes, and M1- and M2- like subsets of canine macrophages can all phagocytose latex beads. M2-polarized macrophages exhibited the strongest phagocytic capacity compared to undifferentiated monocytes- and M1-polarized cells. Taken together, this study showed that canine M1 and M2-like macrophages have distinct features largely in parallel to those of well-studied species, such as human, mouse and pig. These findings enable future use of monocyte derived polarized macrophages particularly in studies of immune related diseases in dogs.

DOI: https://doi.org/10.1371/journal.pone.0292757
Nat Commun. 2023 Nov 03. 14(1): 7065

Diagnostic and commensal Staphylococcus pseudintermedius genomes reveal niche adaptation through parallel selection of defense mechanisms.

Sanjam S Sawhney, Rhiannon C Vargas, Meghan A Wallace, Carol E Muenks, Brian V Lubbers, Stephanie A Fritz, Carey-Ann D Burnham, Gautam Dantas.

Staphylococcus pseudintermedius is historically understood as a prevalent commensal and pathogen of dogs, though modern clinical diagnostics reveal an expanded host-range that includes humans. It remains unclear whether differentiation across S. pseudintermedius populations is driven primarily by niche-type or host-species. We sequenced 501 diagnostic and commensal isolates from a hospital, veterinary diagnostic laboratory, and within households in the American Midwest, and performed a comparative genomics investigation contrasting human diagnostic, animal diagnostic, human colonizing, pet colonizing, and household-surface S. pseudintermedius isolates. Though indistinguishable by core and accessory gene architecture, diagnostic isolates harbor more encoded and phenotypic resistance, whereas colonizing and surface isolates harbor similar CRISPR defense systems likely reflective of common household phage exposures. Furthermore, household isolates that persist through anti-staphylococcal decolonization report elevated rates of base-changing mutations in - and parallel evolution of - defense genes, as well as reductions in oxacillin and trimethoprim-sulfamethoxazole susceptibility. Together we report parallel niche-specific bolstering of S. pseudintermedius defense mechanisms through gene acquisition or mutation.

DOI: https://doi.org/10.1038/s41467-023-42694-5
Front Cell Infect Microbiol. 2023 ;13 1258275

The PI3K-Akt pathway is a multifaceted regulator of the macrophage response to diverse group B Streptococcus isolates.

Yadira S De-Leon-Lopez, Michelle E Thompson, Jessica J Kean, Rebecca A Flaherty.

  Group B Streptococcus (GBS), also known as Streptococcus agalactiae, is a common member of the microbial flora in healthy individuals. However, problems may arise when GBS-colonized mothers become pregnant. GBS may be transferred from a colonized mother to her newborn or developing fetus, which may result in complications such as miscarriage, pre-term birth, meningitis, pneumonia, or sepsis. Macrophages play an especially important role in the fetal and newborn response to GBS due to the limited development of the adaptive immune system early in life. The goal of this study was to expand what is currently known about how GBS manipulates macrophage cell signaling to evade the immune system and cause disease. To this end, we investigated whether the PI3K-Akt pathway was involved in several key aspects of the macrophage response to GBS. We explored whether certain GBS strains, such as sequence type (ST)-17 strains, rely on this pathway for the more rapid macrophage uptake they induce compared to other GBS strains. Our findings suggest that this pathway is, indeed, important for macrophage uptake of GBS. Consistent with these findings, we used immunofluorescence microscopy to demonstrate that more virulent strains of GBS induce more actin projections in macrophages than less virulent strains. Additionally, we explored whether PI3K-Akt signaling impacted the ability of GBS to survive within macrophages after phagocytosis and whether this pathway influenced the survival rate of macrophages themselves following GBS infection. The PI3K-Akt pathway was found to promote the survival of both macrophages and intracellular GBS following infection. We also observed that inhibition of the PI3K-Akt pathway significantly reduced GBS-mediated activation of NFκB, which is a key regulator of cell survival and inflammatory responses. Overall, these insights into strain-dependent GBS-mediated manipulation of the PI3K-Akt pathway and its downstream targets in infected macrophages may provide new insights for the development of diagnostic and therapeutic tools to combat severe GBS disease.

Keywords:  PI3K-Akt pathway; cell death; group B streptococcus; inflammatory response; intracellular signaling; macrophage; phagocytosis

DOI:  https://doi.org/10.3389/fcimb.2023.1258275
Trends Immunol. 2023 Nov 09. pii: S1471-4906(23)00216-8. [Epub ahead of print]

Reframing macrophage diversity with network motifs.

Gabriela A Pizzurro, Kathryn Miller-Jensen.

  A binary classification of macrophage activation as inflammatory or resolving does not capture the diversity of macrophage states observed in tissues. However, framing macrophage activation as a continuous spectrum of states overlooks the intracellular and extracellular networks that regulate and coordinate macrophage responses. Here, we suggest that the systems biology concept of network motifs, which incorporate rules of local molecular interactions, is useful for reframing macrophage activation. Because network motifs can be used to regulate distinct biological functions, they offer a simplified unit that can be compared across organismal, tissue, and disease contexts. Moreover, defining macrophage states as combinations of functional modules regulated by network motifs offers a framework to ultimately predict and target macrophage responses arising in complex environments.

Keywords:  activation states; functional modules; macrophages; networks motifs

DOI:  https://doi.org/10.1016/j.it.2023.10.009
Int Forum Allergy Rhinol. 2023 Nov 07.

Endotype evaluation of Hispanic/Latinx-American patients with chronic rhinosinusitis with nasal polyps.

Arthur W Wu, Dennis M Tang, Kevin Hur, Aria Jafari, Philip G Chen, Masayoshi Takashima, Elena E Chang, Bonnie Balzer, Anna Mathew, Mukul Divatia, Haodong Xu, Juliana Robledo, Luv Amin, Benjamin Tam, David J Cvancara, Amisheila G Kinua, Tariq A Syed, Dominique L Paderin, Missael Vasquez, Omar G Ahmed.

  KEY POINTS: Hispanic-American patients with chronic rhinosinusitis with nasal polyps have a comparable level of tissue eosinophilia compared to their Caucasian counterparts in the United States. Mixed inflammation involving both neutrophils and eosinophils is more common in this population compared to Caucasians. Findings from this study may indicate that Hispanic-American patients have a unique endotype or endotypes that deserves further investigation.

Keywords:  Allergic; Chronic Rhinosinusitis; Eosinophilic rhinitis and nasal polyposis; sinusitis

DOI:  https://doi.org/10.1002/alr.23298
Nat Commun. 2023 Nov 09. 14(1): 7227

Enterohaemorrhagic E. coli utilizes host- and microbiota-derived L-malate as a signaling molecule for intestinal colonization.

Bin Liu, Lingyan Jiang, Yutao Liu, Hongmin Sun, Jun Yan, Chenbo Kang, Bin Yang.

The mammalian gastrointestinal tract is a complex environment that hosts a diverse microbial community. To establish infection, bacterial pathogens must be able to compete with the indigenous microbiota for nutrients, as well as sense the host environment and modulate the expression of genes essential for colonization and virulence. Here, we found that enterohemorrhagic Escherichia coli (EHEC) O157:H7 imports host- and microbiota-derived L-malate using the DcuABC transporters and converts these substrates into fumarate to fuel anaerobic fumarate respiration during infection, thereby promoting its colonization of the host intestine. Moreover, L-malate is important not only for nutrient metabolism but also as a signaling molecule that activates virulence gene expression in EHEC O157:H7. The complete virulence-regulating pathway was elucidated; the DcuS/DcuR two-component system senses high L-malate levels and transduces the signal to the master virulence regulator Ler, which in turn activates locus of enterocyte effacement (LEE) genes to promote EHEC O157:H7 adherence to epithelial cells of the large intestine. Disruption of this virulence-regulating pathway by deleting either dcuS or dcuR significantly reduced colonization by EHEC O157:H7 in the infant rabbit intestinal tract; therefore, targeting these genes and altering physiological aspects of the intestinal environment may offer alternatives for EHEC infection treatment.

DOI: https://doi.org/10.1038/s41467-023-43149-7
Cells. 2023 Oct 28. pii: 2538. [Epub ahead of print]12(21):

Postbiotic Fractions of Probiotics Lactobacillus plantarum 299v and Lactobacillus rhamnosus GG Show Immune-Modulating Effects.

Agnieszka Magryś, Mateusz Pawlik.

  Probiotic bacteria belonging to Lactobacillus spp. are important producers of bioactive molecules, known as postbiotics, that play essential roles in the immunological support of the intestinal mucosa. In this study, the system of co-culture of intestinal epithelial cells with macrophage cells in vitro was used to study the potential effect of postbiotic fractions of L. rhamonosus and L. plantarum on the modulation of the immune response induced by pro-inflammatory stimuli. This study's results revealed that the presence of probiotic bacterial components on the mucosal surface in the early and late stage of inflammatory conditions is based on cellular interactions that control inflammation and consequent damage to the intestinal epithelium. In our studies, heat killed fractions of probiotic bacteria and their extracted proteins showed a beneficial effect on controlling inflammation, regardless of the strain tested, consequently protecting intestinal barrier damage. In conclusion, the presented results emphasize that the fractions of probiotic bacteria of L. plantarum and L. rhamnosus may play a significant role in the regulation of LPS-mediated cytotoxic activity in intestinal epithelial cells. The fractions of probiotic strains of L. rhamnosus and L. plantarum showed the potential to suppress inflammation, effectively activating the anti-inflammatory cytokine IL-10 and modulating the IL-18-related response.

Keywords:  Lactobacillus plantarum 299v; Lactobacillus rhamnosus GG; co-culture; gut inflammation; postbiotics; probiotics

DOI:  https://doi.org/10.3390/cells12212538
J Membr Biol. 2023 Nov 08.

Host Lipid Manipulation by Intracellular Bacteria: Moonlighting for Immune Evasion.

Naveen Challagundla, Deepti Phadnis, Aakriti Gupta, Reena Agrawal-Rajput.

  Lipids are complex organic molecules that fulfill energy demands and sometimes act as signaling molecules. They are mostly found in membranes, thus playing an important role in membrane trafficking and protecting the cell from external dangers. Based on the composition of the lipids, their fluidity and charge, their interaction with embedded proteins vary greatly. Bacteria can hijack host lipids to satisfy their energy needs or to conceal themselves from host cells. Intracellular bacteria continuously exploit host, from their entry into host cells utilizing host lipid machinery to exiting through the cells. This acquisition of lipids from host cells helps in their disguise mechanism. The current review explores various mechanisms employed by the intracellular bacteria to manipulate and acquire host lipids. It discusses their role in manipulating host membranes and the subsequence impact on the host cells. Modulating these lipids in macrophages not only serve the purpose of the pathogen but also modulates the macrophage energy metabolism and functional state. Additionally, we have explored the intricate pathogenic relationship and the potential prospects of using this knowledge in lipid-based therapeutics to disrupt pathogen dominance.

Keywords:  Lipid metabolism; Lipids; Macrophage polarization; Membrane; Pathogen-containing vacuole

DOI:  https://doi.org/10.1007/s00232-023-00296-8
J Infect Dis. 2023 Nov 06. pii: jiad487. [Epub ahead of print]

Airway and blood monocyte transcriptomic profiling reveals an antiviral phenotype in RSV-infected infants with severe disease.

PROMISE investigators

  BACKGROUND: Respiratory syncytial virus (RSV) infection is the primary cause of lower respiratory tract infections in children under 5 years of age. Monocytes, especially in the respiratory tract are suggested to contribute to RSV pathology but their role is incompletely understood. With transcriptomic profiling of blood and airway monocytes, we describe the role of monocytes in severe RSV infection.METHODS: Tracheobronchial aspirates and blood samples were collected from both control (n=9) and RSV infected (n=14) patients admitted to the paediatric intensive care unit. Monocytes (CD14+) were sorted and analysed by RNA-sequencing for transcriptomic profiling.
RESULTS: Both peripheral blood and airway monocytes of RSV patients showed an increased expression of antiviral and interferon-responsive genes compared to controls. Cytokine signalling showed a shared response between blood and airway monocytes, while also displaying responses that were more pronounced based on the tissue of origin. Airway monocytes upregulated additional genes related to migration and inflammation.
CONCLUSIONS: We found that the RSV-induced interferon response extends from the airways to the peripheral blood. Moreover, RSV induces a migration-promoting transcriptional program in monocytes. Unravelling the monocytic response and its role in the immune response to RSV infection could help the development of therapeutics to prevent severe disease.

Keywords:  RSV infection; innate immunity; interferon response; monocytes; pediatric disease; transcriptomics

DOI:  https://doi.org/10.1093/infdis/jiad487
J Leukoc Biol. 2023 Nov 01. pii: qiad134. [Epub ahead of print]

Neutrophils sing "IL[-10] be seeing you" in the lungs during pneumonia.

Matthew K McPeek, John C Gomez, Claire M Doerschuk.

DOI: https://doi.org/10.1093/jleuko/qiad134
PLoS Pathog. 2023 Nov;19(11): e1011719

Interferon signaling drives epithelial metabolic reprogramming to promote secondary bacterial infection.

Grace P Carreno-Florez, Brian R Kocak, Matthew R Hendricks, Jeffrey A Melvin, Katrina B Mar, Jessica Kosanovich, Rachel L Cumberland, Greg M Delgoffe, Sruti Shiva, Kerry M Empey, John W Schoggins, Jennifer M Bomberger.

Clinical studies report that viral infections promote acute or chronic bacterial infections at multiple host sites. These viral-bacterial co-infections are widely linked to more severe clinical outcomes. In experimental models in vitro and in vivo, virus-induced interferon responses can augment host susceptibility to secondary bacterial infection. Here, we used a cell-based screen to assess 389 interferon-stimulated genes (ISGs) for their ability to induce chronic Pseudomonas aeruginosa infection. We identified and validated five ISGs that were sufficient to promote bacterial infection. Furthermore, we dissected the mechanism of action of hexokinase 2 (HK2), a gene involved in the induction of aerobic glycolysis, commonly known as the Warburg effect. We report that HK2 upregulation mediates the induction of Warburg effect and secretion of L-lactate, which enhances chronic P. aeruginosa infection. These findings elucidate how the antiviral immune response renders the host susceptible to secondary bacterial infection, revealing potential strategies for viral-bacterial co-infection treatment.

DOI: https://doi.org/10.1371/journal.ppat.1011719
J Vis Exp. 2023 Oct 20.

Generation of Monocyte-Derived Dendritic Cells with Differing Sialylated Phenotypes.

Vanessa C C Luz, Zélia Silva, Patrícia Sobral, Ankit Tanwar, Rachel L Paterson, Paula A Videira.

Sialic acids are negatively charged monosaccharides typically found at the termini of cell surface glycans. Due to their hydrophilicity and biophysical characteristics, they are involved in numerous biological processes, such as modulation of the immune response, recognition of self and non-self antigens, carbohydrate-protein interactions, etc. The cellular content of sialic acid is regulated by sialidase, which catalyzes the removal of sialic acid residues. Several studies have shown that sialo-glycans are critical in monitoring immune surveillance by engaging with cis and trans inhibitory Siglec receptors on immune cells. Likewise, glyco-immune checkpoints in cancer are becoming crucial targets for developing immunotherapies. Additionally, dendritic cells (DCs) are envisioned as an important component in immunotherapies, especially in cancer research, due to their unique role as professional antigen-presenting cells (APC) and their capacity to trigger adaptive immune responses and generate immunologic memory. Nevertheless, the function of DCs is dependent on their full maturation. Immature DCs have an opposing function to mature DCs and a high sialic acid content, which further dampens their maturation level. This downregulates the ability of immature DCs to activate T-cells, leading to a compromised immune response. Consequently, removing sialic acid from the cell surface of human DCs induces their maturation, thus increasing the expression of MHC molecules and antigen presentation. In addition, it can restore the expression of co-stimulatory molecules and IL-12, resulting in DCs having a higher ability to polarize T-cells toward a Th1 phenotype and specifically activate cytotoxic T-cells to kill tumor cells. Therefore, sialic acid has emerged as a key modulator of DCs and is being used as a novel target to advance their therapeutic use. This study provides a unique approach to treat in vitro monocyte-derived DCs with sialidase, aimed at generating DC populations with different cell surface sialic acid phenotypes and tailored maturation and co-stimulatory profiles.

DOI: https://doi.org/10.3791/65525
EMBO Rep. 2023 Nov 09. e49561

Exogenous L-Alanine promotes phagocytosis of multidrug-resistant bacterial pathogens.

Ming Jiang, Xin-Hai Chen, Hui Li, Xuan-Xian Peng, Bo Peng.

  Multidrug-resistant bacteria present a major threat to public health that urgently requires new drugs or treatment approaches. Here, we conduct integrated proteomic and metabolomics analyses to screen for molecular candidates improving survival of mice infected with Vibrio parahaemolyticus, which indicate that L-Alanine metabolism and phagocytosis are strongly correlated with mouse survival. We also assess the role of L-Alanine in improving mouse survival by in vivo bacterial challenge experiments using various bacteria species, including V. parahaemolyticus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Functional studies demonstrate that exogenous L-Alanine promotes phagocytosis of these multidrug-resistant pathogen species. We reveal that the underlying mechanism involves two events boosted by L-Alanine: TLR4 expression and L-Alanine-enhanced TLR4 signaling via increased biosynthesis and secretion of fatty acids, including palmitate. Palmitate enhances binding of lipopolysaccharide to TLR4, thereby promoting TLR4 dimer formation and endocytosis for subsequent activation of the PI3K/Akt and NF-κB pathways and bacteria phagocytosis. Our data suggest that modulation of the metabolic environment is a plausible approach for combating multidrug-resistant bacteria infection.

Keywords:  L-Alanine; PI3K/Akt and NF-κB pathway; TLR-4; metabolic regulation; phagocytosis

DOI:  https://doi.org/10.15252/embr.201949561
Sci Adv. 2023 Nov 10. 9(45): eadi9834

A human urothelial microtissue model reveals shared colonization and survival strategies between uropathogens and commensals.

Carlos Flores, Jefferson Ling, Amanda Loh, Ramón G Maset, Angeline Aw, Ian J White, Raymond Fernando, Jennifer L Rohn.

Urinary tract infection is among the most common infections worldwide, typically studied in animals and cell lines with limited uropathogenic strains. Here, we assessed diverse bacterial species in a human urothelial microtissue model exhibiting full stratification, differentiation, innate epithelial responses, and urine tolerance. Several uropathogens invaded intracellularly, but also commensal Escherichia coli, suggesting that invasion is a shared survival strategy, not solely a virulence hallmark. The E. coli adhesin FimH was required for intracellular bacterial community formation, but not for invasion. Other shared lifestyles included filamentation (Gram-negatives), chaining (Gram-positives), and hijacking of exfoliating cells, while biofilm-like aggregates were formed mainly with Pseudomonas and Proteus. Urothelial cells expelled invasive bacteria in Rab-/LC3-decorated structures, while highly cytotoxic/invasive uropathogens, but not commensals, disrupted host barrier function and strongly induced exfoliation and cytokine production. Overall, this work highlights diverse species-/strain-specific infection strategies and corresponding host responses in a human urothelial microenvironment, providing insights at the microtissue, cell, and molecular level.

DOI: https://doi.org/10.1126/sciadv.adi9834