Polymorphisms in the gene encoding the transcription factor IRF5 that lead to higher mRNA expression are associated with many autoimmune diseases. Here we show that IRF5 expression in macrophages was reversibly induced by inflammatory stimuli and contributed to the plasticity of macrophage polarization. High expression of IRF5 was characteristic of M1 macrophages, in which it directly activated transcription of the genes encoding interleukin 12 subunit p40 (IL-12p40), IL-12p35 and IL-23p19 and repressed the gene encoding IL-10. Consequently, those macrophages set up the environment for a potent T helper type 1 (TH1)-TH17 response. Global gene expression analysis demonstrated that exogenous IRF5 upregulated or downregulated expression of established phenotypic markers of M1 or M2 macrophages, respectively. Our data suggest a critical role for IRF5 in M1 macrophage polarization and define a previously unknown function for IRF5 as a transcriptional repressor.

Irf5 promotes inflammatory macrophage polarization and th1/th17 response

Macrophages mediate crucial innate immune responses via caspase-1-dependent processing and secretion of IL-1β and IL-18. While wild type Salmonella typhimurium infection is lethal to mice, a strain that persistently expresses flagellin was cleared by the cytosolic flagellin detection pathway via NLRC4 activation of caspase-1; however, this clearance was independent of IL-1β and IL-18. Instead, caspase-1 induced pyroptotic cell death released bacteria from macrophages, exposing them to uptake and killing by reactive oxygen species in neutrophils. Similarly, caspase-1 cleared Legionella and Burkholderia by cytokine independent mechanisms. Our results show, for the first time, that caspase-1 can clear intracellular bacteria in vivo independent of IL-1β and IL-18, and establish pyroptosis as an efficient mechanism of bacterial clearance by the innate immune system.

Caspase-1-induced pyroptosis is an innate immune effector mechanism against intracellular bacteria (111.33)

The pandemic of coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused an unprecedented global social and economic impact, and high numbers of deaths. Many risk factors have been identified in the progression of COVID-19 into a severe and critical stage, including old age, male gender, underlying comorbidities such as hypertension, diabetes, obesity, chronic lung diseases, heart, liver and kidney diseases, tumors, clinically apparent immunodeficiencies, local immunodeficiencies, such as early type I interferon secretion capacity, and pregnancy. Possible complications include acute kidney injury, coagulation disorders, thoromboembolism. The development of lymphopenia and eosinopenia are laboratory indicators of COVID-19. Laboratory parameters to monitor disease progression include lactate dehydrogenase, procalcitonin, high-sensitivity C-reactive protein, proinflammatory cytokines such as interleukin (IL)-6, IL-1β, Krebs von den Lungen-6 (KL-6), and ferritin. The development of a cytokine storm and extensive chest computed tomography imaging patterns are indicators of a severe disease. In addition, socioeconomic status, diet, lifestyle, geographical differences, ethnicity, exposed viral load, day of initiation of treatment, and quality of health care have been reported to influence individual outcomes. In this review, we highlight the scientific evidence on the risk factors of severity of COVID-19.

Risk factors for severe and critically ill COVID-19 patients: A review.

Cationic host defence peptides (CHDP), also known as antimicrobial peptides, are naturally occurring peptides that can combat infections through their direct microbicidal properties and/or by influencing the host's immune responses. The unique ability of CHDP to control infections as well as resolve harmful inflammation has generated interest in harnessing the properties of these peptides to develop new therapies for infectious diseases, chronic inflammatory disorders and wound healing. Various strategies have been used to design synthetic optimized peptides, with negligible toxicity. Here, we focus on the progress made in understanding the scope of functions of CHDP and the emerging potential clinical applications of CHDP-based therapies.

/pdf/antimicrobial-host-defence-peptides-functions-and-clinical-48oa63nlrk.pdf

Antimicrobial host defence peptides: functions and clinical potential

No studies have examined the relationships between bacterial communities along sites of the upper aerodigestive tract of an individual subject. Our objective was to perform an intrasubject and intersite analysis to determine the contributions of two upper mucosal sites (mouth and nose) as source communities for the bacterial microbiome of lower sites (lungs and stom- ach). Oral wash, bronchoalveolar lavage (BAL)fluid, nasal swab, and gastric aspirate samples were collected from 28 healthy subjects. Extensive analysis of controls and serial intrasubject BALfluid samples demonstrated that sampling of the lungs by bronchoscopy was not confounded by oral microbiome contamination. By quantitative PCR, the oral cavity and stomach con- tained the highest bacterial signal levels and the nasal cavity and lungs contained much lower levels. Pyrosequencing of 16S rRNA gene amplicon libraries generated from these samples showed that the oral and gastric compartments had the greatest species richness, which was significantly greater in both than the richness measured in the lungs and nasal cavity. The bacterial communities of the lungs were significantly different from those of the mouth, nose, and stomach, while the greatest similarity was between the oral and gastric communities. However, the bacterial communities of healthy lungs shared significant member- ship with the mouth, but not the nose, and marked subject-subject variation was noted. In summary, microbial immigration from the oral cavity appears to be the significant source of the lung microbiome during health, but unlike the stomach, the lungs exhibit evidence of selective elimination of Prevotellabacteria derived from the upper airways. IMPORTANCE We have demonstrated that the bacterial communities of the healthy lung overlapped those found in the mouth but were found at lower concentrations, with lower membership and a different community composition. The nasal microbiome, which was distinct from the oral microbiome, appeared to contribute little to the composition of the lung microbiome in healthy subjects. Our studies of the nasal, oral, lung, and stomach microbiomes within an individual illustrate the microbiological conti- nuity of the aerodigestive tract in healthy adults and provide culture-independent microbiological support for the concept that microaspiration is common in healthy individuals.

Analysis of the Upper Respiratory Tract Microbiotas as the Source of the Lung and Gastric Microbiotas in Healthy Individuals

Rhinovirus (RV) infection is the most common cause of asthma exacerbations (AE), however mechanisms are poorly understood. Conventional sampling techniques such as bronchoalveolar lavage dilute many cytokines below limits of detection and consequently it has not been possible to measure key mediators of Th1, Th2 and Th17 pathways during virus-induced AE’s . In addition, IL-33, an epithelial-derived alarmin, has recently been shown to be essential for mouse virus-induced airway hyperresponsiveness, however the relationship between IL-33 and exacerbations in human asthma remains unknown. Using the human model of experimental RV induced AE along with novel techniques to sample upper and lower airway mucosal lining fluid (MLF) we investigated the roles of IL-33 and several other prominent cytokines in virus-induced AE’s. Methods 32 mild-to-moderate asthmatics and 14 healthy subjects were inoculated nasally with RV-16. Symptom scores were recorded daily. Bronchoscopies were performed 2 weeks prior to inoculation and on d4 post-inoculation. Novel techniques to sample MLF called ‘bronchosorption’ and ‘nasosorption’ were performed. Cytokines were measured in both bronchial and nasal samples at baseline and on d4 with further nasal sampling on days 2, 3, 5, 7, 10 and 42. Results In asthma, nasal IL-4, –5, –13, –17, –33, and IFN-γ levels were significantly increased during infection compared to baseline (all P Conclusion Sampling MLF permits the direct measurement of previously undetectable mediators across multiple inflammatory pathways. Increased IL-33 and Th2 induction are associated with increased AE severity. IL-33 correlated strongly with Th2 cytokine levels and may represent a novel target for the treatment of virus-induced AE’s. In addition, nasal Th2 inflammation correlated with bronchial levels whilst baseline levels predicted the magnitude of Th2 induction during the AE. Therefore it may be possible to use nasosorption to guide therapy with anti-IL-5 and anti-IL-13 mAb treatments.

https://thorax.bmj.com/content/thoraxjnl/67/Suppl_2/A3.1.full.pdf

T5 Sampling Airway Mucosal Lining Fluid Identifies Roles For IL-33 and Multiple Inflammatory Pathways in Virus-Induced Asthma Exacerbations

Asthma is a heterogeneous condition and it is vital to accurately predict responders to targeted therapies. However, difficulties in measuring IL5 and IL13 have forced reliance on indirect markers of Th2 inflammation with limited success. Using the human model of experimental rhinovirus (RV) induced asthma exacerbation (AE) and new techniques to absorb nasal (nasosorption) and bronchial (bronchosorption) mucosal lining fluid (MLF), we explored Th2 inflammation during a RV-induced AE. Methods: 32 mild-to-moderate asthmatics and 14 healthy subjects were inoculated with RV-16. Bronchoscopies were performed 2 weeks prior to inoculation and on d4 post-inoculation. Cytokines were measured in both bronchial and nasal samples at baseline and on d4 with further nasal sampling on days 2,3,5,7,10 and 42. Results: Nasal IL5 and IL13 were significantly increased in asthma during infection compared to baseline (p Conclusion: RV induced Th2 inflammation correlated with AE severity. Nasal Th2 inflammation correlated with bronchial levels whilst baseline Th2 levels predicted the magnitude of Th2 induction during the AE. Nasosorption is a non-invasive, rapid technique capable of measuring Th2 inflammation directly. It may be possible to use this technique as a biomarker to guide therapy with anti-IL5 and anti-IL13 mAb treatments.

https://erj.ersjournals.com/content/erj/40/Suppl_56/346.full.pdf

Nasal and bronchial levels of Th2 cytokines correlate during a virus induced asthma exacerbation

Introduction and Objectives Histone deacetylase (HDAC) enzymes have a role in suppressing inflammatory gene transcription. There is evidence for reduced HDAC activity in COPD which correlates with the severity of airflow obstruction. Increased inflammation found during exacerbations of COPD may result from a reduction in HDAC activity but this has not been studied in virus induced exacerbations. We sought to investigate HDAC activity following rhinovirus infection in an experimental model of COPD exacerbations. Methods Experimental rhinovirus challenge was performed in GOLD stage II COPD subjects and non-obstructed control smokers and non-smokers. Rhinovirus infection was confirmed with quantitative PCR performed on nasal lavage and sputum samples collected at baseline and days 3, 5, 9, 12, 15, 21 and 42 post virus inoculation. Sputum macrophages were isolated by adhesion and HDAC2 isoenzyme immunoprecipitated, prior to performing a HDAC activity assay. Results 11 non-smokers (NS), 10 smokers (Smk) and 9 COPD subjects were recruited. The mean (SEM) % predicted baseline FEV1 was 103 (4), 98 (4) and 69 (2)% for NS, Smk and COPD respectively. At baseline there was no difference in HDAC2 activity between the three study groups, the geometric mean (95% CI) activity was NS 22.39 (12.45 to 40.25); Smk 22.91 (18.28 to 28.71) and COPD 48.98 (26.04 to 92.13) (p=0.095). Following rhinovirus infection, in NS HDAC2 activity increased, in Smk it remained largely unchanged and there was a fall from baseline levels in COPD subjects at all time points, Abstract S14 figure 1. Conclusions HDAC2 activity was not reduced in stable COPD subjects compared to controls. This may reflect the mild disease state of the study population. During a rhinovirus induced exacerbation HDAC2 activity fell in COPD subjects, this represents a potential mechanism of excessive inflammation. The same pattern is not seen in control subjects.

https://thorax.bmj.com/content/thoraxjnl/66/Suppl_4/A9.3.full.pdf

Maria-Belen Trujillo-Torralbo

Papers

T5 Sampling Airway Mucosal Lining Fluid Identifies Roles For IL-33 and Multiple Inflammatory Pathways in Virus-Induced Asthma Exacerbations

Nasal and bronchial levels of Th2 cytokines correlate during a virus induced asthma exacerbation

S14 Histone deacetylase activity is reduced in COPD subjects during rhinovirus induced exacerbations