ABSTRACT
Live attenuated vaccines are generally highly efficacious and often superior to inactivated vaccines, yet the underlying mechanisms of this remain largely unclear. Here we identify recognition of microbial viability as a potent stimulus for follicular helper T cell (TFH cell) differentiation and vaccine responses. Antigen-presenting cells (APCs) distinguished viable bacteria from dead bacteria through Toll-like receptor 8 (TLR8)-dependent detection of bacterial RNA. In contrast to dead bacteria and other TLR ligands, live bacteria, bacterial RNA and synthetic TLR8 agonists induced a specific cytokine profile in human and porcine APCs, thereby promoting TFH cell differentiation. In domestic pigs, immunization with a live bacterial vaccine induced robust TFH cell and antibody responses, but immunization with its heat-killed counterpart did not. Finally, a hypermorphic TLR8 polymorphism was associated with protective immunity elicited by vaccination with bacillus Calmette-Guérin (BCG) in a human cohort. We have thus identified TLR8 as an important driver of TFH cell differentiation and a promising target for TFH cell-skewing vaccine adjuvants.
Subject(s)
Lymphocyte Activation/immunology , Microbial Viability/immunology , T-Lymphocytes, Helper-Inducer/immunology , Toll-Like Receptor 8/immunology , Vaccines, Attenuated/immunology , Adult , Animals , Antibody Formation/immunology , Cell Differentiation/immunology , Female , Humans , Male , SwineABSTRACT
IL-22 plays a critical role in defending against mucosal infections, but how IL-22 production is regulated is incompletely understood. Here, we show that mice lacking IL-33 or its receptor ST2 (IL-1RL1) were more resistant to Streptococcus pneumoniae lung infection than wild-type animals and that single-nucleotide polymorphisms in IL33 and IL1RL1 were associated with pneumococcal pneumonia in humans. The effect of IL-33 on S. pneumoniae infection was mediated by negative regulation of IL-22 production in innate lymphoid cells (ILCs) but independent of ILC2s as well as IL-4 and IL-13 signaling. Moreover, IL-33's influence on IL-22-dependent antibacterial defense was dependent on housing conditions of the mice and mediated by IL-33's modulatory effect on the gut microbiota. Collectively, we provide insight into the bidirectional crosstalk between the innate immune system and the microbiota. We conclude that both genetic and environmental factors influence the gut microbiota, thereby impacting the efficacy of antibacterial immune defense and susceptibility to pneumonia.
Subject(s)
Immunity, Innate , Interleukin-1 Receptor-Like 1 Protein , Interleukin-22 , Interleukin-33 , Interleukins , Streptococcus pneumoniae , Animals , Interleukin-33/immunology , Interleukin-33/genetics , Interleukin-33/metabolism , Interleukins/metabolism , Interleukins/immunology , Interleukins/genetics , Mice , Streptococcus pneumoniae/immunology , Interleukin-1 Receptor-Like 1 Protein/metabolism , Interleukin-1 Receptor-Like 1 Protein/genetics , Interleukin-1 Receptor-Like 1 Protein/immunology , Humans , Mice, Knockout , Microbiota/immunology , Mice, Inbred C57BL , Pneumonia, Pneumococcal/immunology , Pneumonia, Pneumococcal/microbiology , Gastrointestinal Microbiome/immunology , Lymphocytes/immunology , Lymphocytes/metabolism , Polymorphism, Single NucleotideABSTRACT
Legionella pneumophila is an intracellular pathogen that can cause severe pneumonia after the inhalation of contaminated aerosols and replication in alveolar macrophages. Several pattern recognition receptors (PRRs) have been identified that contribute to the recognition of L. pneumophila by the innate immune system. However, the function of the C-type lectin receptors (CLRs), which are mainly expressed by macrophages and other myeloid cells, remains largely unexplored. Here, we used a library of CLR-Fc fusion proteins to search for CLRs that can bind the bacterium and identified the specific binding of CLEC12A to L. pneumophila. Subsequent infection experiments in human and murine macrophages, however, did not provide evidence for a substantial role of CLEC12A in controlling innate immune responses to the bacterium. Consistently, antibacterial and inflammatory responses to Legionella lung infection were not significantly influenced by CLEC12A deficiency. Collectively, CLEC12A is able to bind to L. pneumophila-derived ligands but does not appear to play a major role in the innate defense against L. pneumophila.
Subject(s)
Host-Pathogen Interactions , Immunity, Innate , Lectins, C-Type , Legionella pneumophila , Legionnaires' Disease , Receptors, Mitogen , Animals , Humans , Mice , Lectins, C-Type/metabolism , Legionella pneumophila/immunology , Legionnaires' Disease/immunology , Legionnaires' Disease/microbiology , Macrophages/metabolism , Macrophages, Alveolar/metabolism , Receptors, Mitogen/immunologyABSTRACT
PURPOSE: To investigate antimicrobial use and primary and nosocomial infections in hospitalized COVID-19 patients to provide data for guidance of antimicrobial therapy. METHODS: Prospective observational cohort study conducted at Charité-Universitätsmedizin Berlin, including patients hospitalized with SARS-CoV-2-infection between March and November 2020. RESULTS: 309 patients were included, 231 directly admitted and 78 transferred from other centres. Antimicrobial therapy was initiated in 62/231 (26.8%) of directly admitted and in 44/78 (56.4%) of transferred patients. The rate of microbiologically confirmed primary co-infections was 4.8% (11/231). Although elevated in most COVID-19 patients, C-reactive protein and procalcitonin levels were higher in patients with primary co-infections than in those without (median CRP 110 mg/l, IQR 51-222 vs. 36, IQR 11-101, respectively; p < 0.0001). Nosocomial bloodstream and respiratory infections occurred in 47/309 (15.2%) and 91/309 (29.4%) of patients, respectively, and were associated with need for invasive mechanical ventilation (OR 45.6 95%CI 13.7-151.8 and 104.6 95%CI 41.5-263.5, respectively), extracorporeal membrane oxygenation (OR 14.3 95%CI 6.5-31.5 and 16.5 95%CI 6.5-41.6, respectively), and haemodialysis (OR 31.4 95%CI 13.9-71.2 and OR 22.3 95%CI 11.2-44.2, respectively). The event of any nosocomial infection was significantly associated with in-hospital death (33/99 (33.3%) with nosocomial infection vs. 23/210 (10.9%) without, OR 4.1 95%CI 2.2-7.3). CONCLUSIONS: Primary co-infections are rare, yet antimicrobial use was frequent, mostly based on clinical worsening and elevated inflammation markers without clear evidence for co-infection. More reliable diagnostic prospects may help to reduce overtreatment. Rates of nosocomial infections are substantial in severely ill patients on organ support and associated with worse patient outcome.
Subject(s)
Anti-Infective Agents , COVID-19 Drug Treatment , COVID-19 , Coinfection , Cross Infection , Humans , COVID-19/epidemiology , Coinfection/drug therapy , Coinfection/epidemiology , SARS-CoV-2 , Hospital Mortality , Prospective Studies , Anti-Infective Agents/therapeutic use , Cross Infection/drug therapy , Cross Infection/epidemiologyABSTRACT
Pneumonia is a life-threatening disease often caused by infection with Streptococcus pneumoniae and Pseudomonas aeruginosa. Many of the mediators (e.g., TNF, IL-6R) and junction molecules (e.g., E-cadherin) orchestrating inflammatory cell recruitment and loss of barrier integrity are proteolytically cleaved through a disintegrin and metalloproteinases (ADAMs). We could show by Western blot, surface expression analysis and measurement of proteolytic activity in cell-based assays, that ADAM10 in epithelial cells is upregulated and activated upon infection with Pseudomonas aeruginosa and Exotoxin A (ExoA), but not upon infection with Streptococcus pneumoniae. Targeting ADAM10 by pharmacological inhibition or gene silencing, we demonstrated that this activation was critical for cleavage of E-cadherin and modulated permeability and epithelial integrity. Stimulation with heat-inactivated bacteria revealed that the activation was based on the toxin repertoire rather than the interaction with the bacterial particle itself. Furthermore, calcium imaging experiments showed that the ExoA action was based on the induction of calcium influx. Investigating the extracellular vesicles and their proteolytic activity, we could show that Pseudomonas aeruginosa triggered exosomal release of ADAM10 and proteolytic cleavage in trans. This newly described mechanism could constitute an essential mechanism causing systemic inflammation in patients suffering from Pseudomonas aeruginosa-induced pneumonia stimulating future translational studies.
Subject(s)
ADAM10 Protein/metabolism , Amyloid Precursor Protein Secretases/metabolism , Antigens, CD/metabolism , Cadherins/metabolism , Membrane Proteins/metabolism , Proteolysis , A549 Cells , Epithelium/metabolism , Exosomes/metabolism , Exosomes/physiology , Humans , Inflammation/microbiology , Pseudomonas aeruginosa/metabolism , Pseudomonas aeruginosa/pathogenicity , THP-1 CellsABSTRACT
Rationale: Platelets are generated in the capillaries of the lung, control hemostasis, and display immunological functions. Tuberculosis primarily affects the lung, and patients show platelet changes and hemoptysis. A role of platelets in immunopathology of pulmonary tuberculosis requires careful assessment.Objectives: To identify the dynamics and interaction partners of platelets in the respiratory tissue and establish their impact on the outcome of pulmonary tuberculosis.Methods: Investigations were primarily performed in murine models of primary progressive pulmonary tuberculosis, by analysis of mouse strains with variable susceptibility to Mycobacterium tuberculosis infection using platelet depletion and delivery of antiplatelet drugs.Measurements and Main Results: Platelets were present at the site of infection and formed aggregates with different myeloid subsets during experimental tuberculosis. Such aggregates were also detected in patients with tuberculosis. Platelets were detrimental during the early phase of infection, and this effect was uncoupled from their canonical activation. Platelets left lung cell dynamics and patterns of antimycobacterial T-cell responses unchanged but hampered antimicrobial defense by restricting production of reactive oxygen species in lung-residing myeloid cells.Conclusions: Platelets are detrimental in primary progressive pulmonary tuberculosis, orchestrate lung immunity by modulating innate immune responsiveness, and may be amenable to new interventions for this deadly disease.
Subject(s)
Blood Platelets/metabolism , Mycobacterium tuberculosis/immunology , Phagocytes/pathology , Respiratory Burst/physiology , T-Lymphocytes/immunology , Tuberculosis, Pulmonary/metabolism , Animals , Disease Models, Animal , Disease Progression , Female , Flow Cytometry , Male , Mice , Mice, Inbred C57BL , Phagocytes/metabolism , Tuberculosis, Pulmonary/immunology , Tuberculosis, Pulmonary/pathologyABSTRACT
The cyclic GMP-AMP synthase (cGAS)-STING pathway is central for innate immune sensing of various bacterial, viral and protozoal infections. Recent studies identified the common HAQ and R232H alleles of TMEM173/STING, but the functional consequences of these variants for primary infections are unknown. Here we demonstrate that cGAS- and STING-deficient murine macrophages as well as human cells of individuals carrying HAQ TMEM173/STING were severely impaired in producing type I IFNs and pro-inflammatory cytokines in response to Legionella pneumophila, bacterial DNA or cyclic dinucleotides (CDNs). In contrast, R232H attenuated cytokine production only following stimulation with bacterial CDN, but not in response to L. pneumophila or DNA. In a mouse model of Legionnaires' disease, cGAS- and STING-deficient animals exhibited higher bacterial loads as compared to wild-type mice. Moreover, the haplotype frequency of HAQ TMEM173/STING, but not of R232H TMEM173/STING, was increased in two independent cohorts of human Legionnaires' disease patients as compared to healthy controls. Our study reveals that the cGAS-STING cascade contributes to antibacterial defense against L. pneumophila in mice and men, and provides important insight into how the common HAQ TMEM173/STING variant affects antimicrobial immune responses and susceptibility to infection. TRIAL REGISTRATION: ClinicalTrials.gov DRKS00005274, German Clinical Trials Register.
Subject(s)
Anti-Bacterial Agents/therapeutic use , Immunity, Innate/genetics , Legionella pneumophila/immunology , Legionnaires' Disease/drug therapy , Legionnaires' Disease/genetics , Membrane Proteins/genetics , Nucleotidyltransferases/physiology , Adult , Aged , Aged, 80 and over , Animals , Case-Control Studies , Cells, Cultured , Female , Genetic Predisposition to Disease , HEK293 Cells , Humans , Immunity, Innate/drug effects , Male , Mice , Mice, Inbred C57BL , Middle Aged , Polymorphism, Genetic , Treatment OutcomeABSTRACT
Although Moraxella catarrhalis and Neisseria meningitidis are important human pathogens, they often colonize the human respiratory tract without causing overt clinical symptoms. Both pathogens express structurally unrelated proteins that share the ability to stimulate the adhesion molecule CEACAM1 expressed on human cells. Here we demonstrate that the interaction of CEACAM1 with ubiquitous surface protein A1 expressed on M. catarrhalis or with opacity-associated proteins on N. meningitidis resulted in reduced Toll-like receptor 2-initiated transcription factor NF-kappaB-dependent inflammatory responses of primary pulmonary epithelial cells. These inhibitory effects were mediated by tyrosine phosphorylation of the immunoreceptor tyrosine-based inhibitory motif of CEACAM1 and by recruitment of the phosphatase SHP-1, which negatively regulated Toll-like receptor 2-dependent activation of the phosphatidylinositol 3-OH kinase-Akt kinase pathway. Our results identify a CEACAM1-dependent immune-evasion strategy.
Subject(s)
Antigens, CD/immunology , Bronchi/immunology , Cell Adhesion Molecules/immunology , Moraxella catarrhalis/immunology , Neisseria meningitidis/immunology , Respiratory Mucosa/immunology , Toll-Like Receptor 2/immunology , Amino Acid Motifs/physiology , Antigens, Bacterial/immunology , Antigens, Bacterial/metabolism , Antigens, CD/chemistry , Bacterial Outer Membrane Proteins/immunology , Bacterial Outer Membrane Proteins/metabolism , Bronchi/metabolism , Bronchi/microbiology , Cell Adhesion Molecules/chemistry , Cells, Cultured , Cytokines/metabolism , Down-Regulation , Humans , NF-kappa B/antagonists & inhibitors , NF-kappa B/metabolism , Phosphatidylinositol 3-Kinases/metabolism , Protein Tyrosine Phosphatase, Non-Receptor Type 6/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Respiratory Mucosa/metabolism , Respiratory Mucosa/microbiology , Signal Transduction/immunology , Toll-Like Receptor 2/metabolismABSTRACT
PURPOSE: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread worldwide causing a global health emergency. Pa-COVID-19 aims to provide comprehensive data on clinical course, pathophysiology, immunology and outcome of COVID-19, to identify prognostic biomarkers, clinical scores, and therapeutic targets for improved clinical management and preventive interventions. METHODS: Pa-COVID-19 is a prospective observational cohort study of patients with confirmed SARS-CoV-2 infection treated at Charité - Universitätsmedizin Berlin. We collect data on epidemiology, demography, medical history, symptoms, clinical course, and pathogen testing and treatment. Systematic, serial blood sampling will allow deep molecular and immunological phenotyping, transcriptomic profiling, and comprehensive biobanking. Longitudinal data and sample collection during hospitalization will be supplemented by long-term follow-up. RESULTS: Outcome measures include the WHO clinical ordinal scale on day 15 and clinical, functional, and health-related quality-of-life assessments at discharge and during follow-up. We developed a scalable dataset to (i) suit national standards of care, (ii) facilitate comprehensive data collection in medical care facilities with varying resources, and (iii) allow for rapid implementation of interventional trials based on the standardized study design and data collection. We propose this scalable protocol as blueprint for harmonized data collection and deep phenotyping in COVID-19 in Germany. CONCLUSION: We established a basic platform for harmonized, scalable data collection, pathophysiological analysis, and deep phenotyping of COVID-19, which enables rapid generation of evidence for improved medical care and identification of candidate therapeutic and preventive strategies. The electronic database accredited for interventional trials allows fast trial implementation for candidate therapeutic agents. TRIAL REGISTRATION: Registered at the German registry for clinical studies (DRKS00021688).
Subject(s)
Coronavirus Infections/physiopathology , Pneumonia, Viral/physiopathology , Registries , Berlin/epidemiology , Betacoronavirus , Biological Specimen Banks , COVID-19 , Coronavirus Infections/epidemiology , Disease Management , Humans , Observational Studies as Topic , Pandemics , Phenotype , Pneumonia, Viral/epidemiology , Prospective Studies , Risk Assessment , Risk Factors , SARS-CoV-2 , Time Factors , Treatment Outcome , World Health OrganizationABSTRACT
Several body sites, including the intestinal and respiratory tracts, are colonized with a myriad of bacteria, archaea, fungi, and viruses, which are collectively referred to as the "microbiota." The bacterial component of the microbiota in particular has been recognized to influence a multitude of physiological functions, including innate and adaptive immune responses. Germ-free and microbiota-depleted animals display an impaired antimicrobial defense and are therefore highly susceptible to various infections, including those affecting the lung. In this review, we summarize current understanding of how the microbiota affects antimicrobial immunity and disease tolerance during viral and bacterial pulmonary infections. A better understanding of these mechanisms could help to refine clinical approaches to preserve or rescue the microbiota-immune system interplay and protect patients against lung infections.
Subject(s)
Adaptive Immunity/drug effects , Anti-Infective Agents/pharmacology , Immunity, Innate/drug effects , Lung/drug effects , Microbiota/drug effects , Adaptive Immunity/immunology , Animals , Gastrointestinal Microbiome/drug effects , Gastrointestinal Microbiome/immunology , Humans , Immunity, Innate/immunology , Lung/immunologyABSTRACT
TMEM173 encodes MPYS/STING and is an innate immune sensor for cyclic dinucleotides (CDNs) playing a critical role in infection, inflammation, and cancer. The R71H-G230A-R293Q (HAQ) of TMEM173 is the second most common human TMEM173 allele. In this study, using data from the 1000 Genomes Project we found that homozygous HAQ individuals account for â¼16.1% of East Asians and â¼2.8% of Europeans whereas Africans have no homozygous HAQ individuals. Using B cells from homozygous HAQ carriers, we found, surprisingly, that HAQ/HAQ carriers express extremely low MPYS protein and have a decreased TMEM173 transcript. Consequently, the HAQ/HAQ B cells do not respond to CDNs. We subsequently generated an HAQ knock-in mouse expressing a mouse equivalent of the HAQ allele (mHAQ). The mHAQ mouse has decreased MPYS protein in B cells, T cells, Ly6Chi monocytes, bone marrow-derived dendritic cells, and lung tissue. The mHAQ mouse also does not respond to CDNs in vitro and in vivo. Lastly, Pneumovax 23, with an efficacy that depends on TMEM173, is less effective in mHAQ mice than in wild type mice. We conclude that HAQ is a null TMEM173 allele. Our findings have a significant impact on research related to MPYS-mediated human diseases and medicine.
Subject(s)
Immunity, Innate/genetics , Membrane Proteins/genetics , Alleles , Animals , Gene Knock-In Techniques , Genotype , Humans , Mice , Mice, Inbred C57BL , Nucleotides, Cyclic/immunology , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
BACKGROUND: Aging is a multifactorial process driven by several conditions. Among them, inflamm-aging is characterized by chronic low-grade inflammation driving aging-related diseases. The aged immune system is characterized by the senescence-associated secretory phenotype, resulting in the release of proinflammatory cytokines contributing to inflamm-aging. Another possible mechanism resulting in inflamm-aging could be the increased release of danger- associated molecular patterns (DAMPs) by increased cell death in the elderly, leading to a chronic low-grade inflammatory response. Several pattern recognition receptors of the innate immune system are involved in recognition of DAMPs. The DNA-sensing cGAS-STING pathway plays a pivotal role in combating viral and bacterial infections and recognizes DNA released by cell death during the process of aging, which in turn may result in increased inflamm-aging. OBJECTIVE: The aim of this study was to investigate whether a variation within the STING gene with known impaired function may be associated with protection from aging-related diseases by decreasing the process of inflamm-aging. METHODS: STING (Tmem173) R293Q was genotyped in a cohort of 3,397 aged subjects (65-103 years). The distribution of the variant allele in healthy subjects and subjects suffering from aging-associated diseases was compared by logistic regression analysis. RESULTS: We show here that STING 293Q allele carriers were protected from aging-associated diseases (OR = 0.823, p = 0.038). This effect was much stronger in the subgroup of subjects suffering from chronic lung diseases (OR = 0.730, p = 0.009). CONCLUSION: Our results indicate that decreased sensitivity of the innate immune receptors is associated with healthy aging, most likely due to a decreased process of inflamm-aging.
Subject(s)
Aging/genetics , Cellular Senescence/genetics , Inflammation/metabolism , Membrane Proteins , Aged , Aged, 80 and over , Cell Death/genetics , Cognition , Cohort Studies , Female , Geriatric Assessment/methods , Health Status Disparities , Humans , Male , Membrane Proteins/genetics , Membrane Proteins/metabolism , Poland/epidemiology , Polymorphism, Single Nucleotide , Protective Factors , Risk Factors , Signal TransductionABSTRACT
Streptococcus pneumoniae is a frequent colonizer of the upper respiratory tract and a leading cause of bacterial pneumonia. The innate immune system senses pneumococcal cell wall components, toxin, and nucleic acids, which leads to production of inflammatory mediators to initiate and control antibacterial defense. Here, we show that the cGAS (cyclic GMP-AMP [cGAMP] synthase)-STING pathway mediates detection of pneumococcal DNA in mouse macrophages to primarily stimulate type I interferon (IFN) responses. Cells of human individuals carrying HAQ TMEM173, which encodes a common hypomorphic variant of STING, were largely or partly defective in inducing type I IFNs and proinflammatory cytokines upon infection. Subsequent analyses, however, revealed that STING was dispensable for restricting S. pneumoniae during acute pneumonia in mice. Moreover, explorative analyses did not find differences in the allele frequency of HAQ TMEM173 in nonvaccinated pneumococcal pneumonia patients and healthy controls or an association of HAQ TMEM173 carriage with disease severity. Together, our results indicate that the cGAS/STING pathway senses S. pneumoniae but plays no major role in antipneumococcal immunity in mice and humans.
Subject(s)
Membrane Proteins/immunology , Nucleotidyltransferases/immunology , Pneumococcal Infections/immunology , Streptococcus pneumoniae/immunology , Adult , Aged , Animals , Cohort Studies , Female , Humans , Immunity, Innate , Interferon Type I/genetics , Interferon Type I/immunology , Macrophages/immunology , Male , Membrane Proteins/genetics , Mice , Mice, Inbred C57BL , Mice, Knockout , Middle Aged , Nucleotidyltransferases/genetics , Pneumococcal Infections/genetics , Pneumococcal Infections/microbiology , Streptococcus pneumoniae/geneticsABSTRACT
Macrophages can be niches for bacterial pathogens or antibacterial effector cells depending on the pathogen and signals from the immune system. Here we show that type I and II IFNs are master regulators of gene expression during Legionella pneumophila infection, and activators of an alveolar macrophage-intrinsic immune response that restricts bacterial growth during pneumonia. Quantitative mass spectrometry revealed that both IFNs substantially modify Legionella-containing vacuoles, and comparative analyses reveal distinct subsets of transcriptionally and spatially IFN-regulated proteins. Immune-responsive gene (IRG)1 is induced by IFNs in mitochondria that closely associate with Legionella-containing vacuoles, and mediates production of itaconic acid. This metabolite is bactericidal against intravacuolar L. pneumophila as well as extracellular multidrug-resistant Gram-positive and -negative bacteria. Our study explores the overall role IFNs play in inducing substantial remodeling of bacterial vacuoles and in stimulating production of IRG1-derived itaconic acid which targets intravacuolar pathogens. IRG1 or its product itaconic acid might be therapeutically targetable to fight intracellular and drug-resistant bacteria.
Subject(s)
Hydro-Lyases/immunology , Interferons/immunology , Legionella pneumophila/immunology , Legionnaires' Disease/immunology , Macrophages, Alveolar/immunology , Proteome , Animals , Disease Models, Animal , Female , Gene Expression Regulation , Gene Ontology , Hydro-Lyases/genetics , Hydro-Lyases/metabolism , Immunity, Innate , Interferons/metabolism , Legionella pneumophila/genetics , Legionella pneumophila/metabolism , Legionnaires' Disease/metabolism , Mice , Mice, Inbred C57BL , Mice, Transgenic , Mitochondria/metabolism , Models, Immunological , Reactive Oxygen Species/metabolism , Succinates/metabolism , Vacuoles/metabolism , Vacuoles/microbiologyABSTRACT
Legionella pneumophila is a facultative intracellular bacterium which can cause a severe pneumonia called Legionnaires' disease after inhalation of contaminated water droplets and replication in alveolar macrophages. The innate immune system is generally able to sense and -in most cases- control L. pneumophila infection. Comorbidities and genetic risk factors, however, can compromise the immune system and high infection doses might overwhelm its capacity, thereby enabling L. pneumophila to grow and disseminate inside the lung. The innate immune system mediates sensing of L. pneumophila by employing e.g. NOD-like receptors (NLRs), Toll-like receptors (TLRs), as well as the cGAS/STING pathway to stimulate death of infected macrophages as well as production of proinflammatory cytokines and interferons (IFNs). Control of pulmonary L. pneumophila infection is largely mediated by inflammasome-, TNFα- and IFN-dependent macrophage-intrinsic resistance mechanisms. This article summarizes the current knowledge of innate immune responses to L. pneumophila infection in general, and of macrophage-intrinsic defense mechanisms in particular.
Subject(s)
Immunity, Innate , Legionella pneumophila/immunology , Legionnaires' Disease/immunology , Macrophages, Alveolar/immunology , Signal Transduction/immunology , Cytokines/metabolism , Host-Pathogen Interactions/immunology , Humans , Inflammasomes/metabolism , Legionnaires' Disease/microbiology , Macrophages, Alveolar/metabolism , Macrophages, Alveolar/microbiologyABSTRACT
BACKGROUND: Antibiotic exposure alters the microbiota, which can impact the inflammatory immune responses. Critically ill patients frequently receive antibiotic treatment and are often subjected to mechanical ventilation, which may induce local and systemic inflammatory responses and development of ventilator-induced lung injury (VILI). The aim of this study was to investigate whether disruption of the microbiota by antibiotic therapy prior to mechanical ventilation affects pulmonary inflammatory responses and thereby the development of VILI. METHODS: Mice underwent 6-8 weeks of enteral antibiotic combination treatment until absence of cultivable bacteria in fecal samples was confirmed. Control mice were housed equally throughout this period. VILI was induced 3 days after completing the antibiotic treatment protocol, by high tidal volume (HTV) ventilation (34 ml/kg; positive end-expiratory pressure = 2 cmH2O) for 4 h. Differences in lung function, oxygenation index, pulmonary vascular leakage, macroscopic assessment of lung injury, and leukocyte and lymphocyte differentiation were assessed. Control groups of mice ventilated with low tidal volume and non-ventilated mice were analyzed accordingly. RESULTS: Antibiotic-induced microbiota depletion prior to HTV ventilation led to aggravation of VILI, as shown by increased pulmonary permeability, increased oxygenation index, decreased pulmonary compliance, enhanced macroscopic lung injury, and increased cytokine/chemokine levels in lung homogenates. CONCLUSIONS: Depletion of the microbiota by broad-spectrum antibiotics prior to HTV ventilation renders mice more susceptible to developing VILI, which could be clinically relevant for critically ill patients frequently receiving broad-spectrum antibiotics.
Subject(s)
Anti-Bacterial Agents/adverse effects , Microbiota/drug effects , Ventilator-Induced Lung Injury/physiopathology , Animals , Anti-Bacterial Agents/therapeutic use , Blood Gas Analysis/methods , Disease Models, Animal , Lung/physiopathology , Mice , Mice, Inbred C57BL , Respiration, Artificial/adverse effects , Respiration, Artificial/methods , Ventilator-Induced Lung Injury/complications , Ventilator-Induced Lung Injury/drug therapyABSTRACT
Streptococcus pneumoniae frequently colonizes the upper respiratory tract of healthy individuals, but also commonly causes severe invasive infections such as community-acquired pneumonia and meningitis. One of the key virulence factors of pneumococci is the pore-forming toxin pneumolysin which stimulates cell death and is involved in the evasion of some defense mechanisms. The immune system, however, employs different inflammasomes to sense pneumolysin-induced pore formation, cellular membrane damage, and/or subsequent leakage of bacterial nucleic acid into the host cell cytosol. Canonical inflammasomes are cytosolic multiprotein complexes consisting of a receptor molecule such as NLRP3 or AIM2, the adapter ASC, and caspase-1. NLRP3 and AIM2 inflammasomes mediate cell death and production of important IL-1 family cytokines to recruit leukocytes and defend against S. pneumoniae. Here, we review recent evidence that highlights inflammasomes as critical sensors of S. pneumoniae-induced cellular perturbations, summarize their role in pneumococcal infections, and discuss potential evasion strategies of some emerging pneumococcal strains.
Subject(s)
Immune Evasion , Immunity, Innate , Inflammasomes/immunology , Pneumococcal Infections/immunology , Streptococcus pneumoniae/immunology , Animals , Humans , Inflammasomes/genetics , Pneumococcal Infections/microbiology , Streptococcus pneumoniae/genetics , Streptococcus pneumoniae/physiologyABSTRACT
Hospital-acquired infections are an increasingly serious health concern. Infections caused by carpabenem-resistant Klebsiella pneumoniae (CR-Kp) are especially problematic, with a 50 % average survival rate. CR-Kp are isolated from patients with ever greater frequency, 7 % within the EU but 62 % in Greece. At a time when antibiotics are becoming less effective, no vaccines to protect from this severe bacterial infection exist. Herein, we describe the convergent [3+3] synthesis of the hexasaccharide repeating unit from its capsular polysaccharide and related sequences. Immunization with the synthetic hexasaccharide 1 glycoconjugate resulted in high titers of cross-reactive antibodies against CR-Kp CPS in mice and rabbits. Whole-cell ELISA was used to establish the surface staining of CR-Kp strains. The antibodies raised were found to promote phagocytosis. Thus, this semi-synthetic glycoconjugate is a lead for the development of a vaccine against a rapidly progressing, deadly bacterium.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacterial Vaccines/immunology , Carbapenems/pharmacology , Glycoconjugates/chemical synthesis , Klebsiella pneumoniae/drug effects , Klebsiella pneumoniae/immunology , Vaccines, Synthetic/immunology , Animals , Antibodies, Bacterial/biosynthesis , Antibodies, Bacterial/immunology , Drug Resistance, Bacterial , Enzyme-Linked Immunosorbent Assay , Glycoconjugates/chemistry , Glycoconjugates/immunology , Klebsiella Infections/prevention & control , Mice , Oligosaccharides/chemistry , Phagocytosis/immunology , RabbitsABSTRACT
Pulmonary vascular hyperresponsiveness is a main characteristic of pulmonary arterial hypertension (PAH). In PAH patients, elevated levels of the vasoconstrictors thromboxane A2 (TXA2), endothelin (ET)-1 and serotonin further contribute to pulmonary hypertension. Protein kinase C (PKC) isozyme alpha (PKCα) is a known modulator of smooth muscle cell contraction. However, the effects of PKCα deficiency on pulmonary vasoconstriction have not yet been investigated. Thus, the role of PKCα in pulmonary vascular responsiveness to the TXA2 analog U46619, ET-1, serotonin and acute hypoxia was investigated in isolated lungs of PKCα-/- mice and corresponding wild-type mice, with or without prior administration of the PKC inhibitor bisindolylmaleimide I or Gö6976. mRNA was quantified from microdissected intrapulmonary arteries. We found that broad-spectrum PKC inhibition reduced pulmonary vascular responsiveness to ET-1 and acute hypoxia and, by trend, to U46619. Analogously, selective inhibition of conventional PKC isozymes or PKCα deficiency reduced ET-1-evoked pulmonary vasoconstriction. The pulmonary vasopressor response to serotonin was unaffected by either broad PKC inhibition or PKCα deficiency. Surprisingly, PKCα-/- mice showed pulmonary vascular hyperresponsiveness to U46619 and increased TXA2 receptor (TP receptor) expression in the intrapulmonary arteries. To conclude, PKCα regulates ET-1-induced pulmonary vasoconstriction. However, PKCα deficiency leads to pulmonary vascular hyperresponsiveness to TXA2, possibly via increased pulmonary arterial TP receptor expression.