Long term exposure of cigarette smoke condensate (CSC) mediates transcriptomic changes in normal human lung epithelial Beas-2b cells and protection by garlic compounds.

Chronic cigarette smoke condensate (CSC) exposure is one of the preventable risk factors in the CS-induced lung cancer. However, understanding the mechanism of cellular transformation induced by CS in the lung remains limited. We investigated the effect of long term exposure of CSC in human normal lung epithelial Beas-2b cells, and chemopreventive mechanism of organosulphur garlic compounds, diallyl sulphide (DAS) and diallyl disulphide (DADS) using Next Generation Sequencing (NGS) transcriptomic analysis. CSC regulated 1077 genes and of these 36 genes are modulated by DAS while 101 genes by DADS. DAS modulated genes like IL1RL1 (interleukin-1 receptor like-1), HSPA-6 (heat shock protein family A, member 6) while DADS demonstrating ADTRP (Androgen-Dependent TFPI Regulating Protein), ANGPT4 (Angiopoietin 4), GFI1 (Growth Factor-Independent 1 Transcriptional Repressor), TBX2 (T-Box Transcription Factor 2), with some common genes like NEURL-1 (Neuralized E3-Ubiquitin Protein Ligase 1), suggesting differential effects between these two garlic compounds. They regulate genes by influencing pathways including HIF-1alpha, STAT-3 and matrix metalloproteases, contributing to the chemoprotective ability of organosulfur garlic compounds against CSC-induced cellular transformation. Taken together, we demonstrated CSC induced global gene expression changes pertaining to cellular transformation which potentially can be delayed with dietary chemopreventive phytochemicals like DS and DADS influencing alterations at the transcriptomic level.

Inhaled modified angiotensin converting enzyme 2 (ACE2) as a decoy to mitigate SARS-CoV-2 infection

COVID-19 is a new zoonotic disease caused by the SARS-CoV-2 virus. Since its emergence in Wuhan City, China, the virus has rapidly spread across the globe causing calamitous health, economic and societal consequences. It causes disproportionately severe disease in the elderly and those with co-morbidities, such as hypertension and diabetes. There is currently no proven treatment for COVID-19 and a safe and effective vaccine is at least a year away. The virus gains access to the respiratory epithelium through cell surface angiotensin converting enzyme 2 (ACE2). The receptor binding domain (RBD) of the virus is unlikely to mutate without loss of pathogenicity and thus represents an attractive target for antiviral treatment. Inhaled modified recombinant human ACE2, may bind SARS-CoV-2 and mitigate lung damage. This decoy strategy is unlikely to provoke an adverse immune response and may reduce morbidity and mortality in high-risk groups. Copyright © 2020 New Zealand Medical Association. All rights reserved.

Silver nanoparticles with excellent biocompatibility block pseudotyped SARS-CoV-2 in the presence of lung surfactant.

Silver (Ag) is known to possess antimicrobial properties which is commonly attributed to soluble Ag ions. Here, we showed that Ag nanoparticles (NPs) potently inhibited SARS-CoV-2 infection using two different pseudovirus neutralization assays. We also evaluated a set of Ag nanoparticles of different sizes with varying surface properties, including polyvinylpyrrolidone (PVP)-coated and poly (ethylene glycol) (PEG)-modified Ag nanoparticles, and found that only the bare (unmodified) nanoparticles were able to prevent virus infection. For comparison, TiO2 nanoparticles failed to intercept the virus. Proteins and lipids may adsorb to nanoparticles forming a so-called bio-corona; however, Ag nanoparticles pre-incubated with pulmonary surfactant retained their ability to block virus infection in the present model. Furthermore, the secondary structure of the spike protein of SARS-CoV-2 was perturbed by the Ag nanoparticles, but not by the ionic control (AgNO3) nor by the TiO2 nanoparticles. Finally, Ag nanoparticles were shown to be non-cytotoxic towards the human lung epithelial cell line BEAS-2B and this was confirmed by using primary human nasal epithelial cells. These results further support that Ag nanoparticles may find use as anti-viral agents.

Development of an In Vitro Model of SARS-CoV-Induced Acute Lung Injury for Studying New Therapeutic Approaches.

One of the causes of death of patients infected by SARS-CoV-2 is the induced respiratory failure caused by excessive activation of the immune system, the so-called "cytokine storm", leading to damage to lung tissue. In vitro models reproducing various stages of the disease can be used to explore the pathogenetic mechanisms and therapeutic approaches to treating the consequences of a cytokine storm. We have developed an in vitro test system for simulating damage to the pulmonary epithelium as a result of the development of a hyperinflammatory reaction based on the co-cultivation of pulmonary epithelial cells (A549 cells) and human peripheral blood mononuclear cells (PBMC) primed with lipopolysaccharide (LPS). In this model, after 24 h of co-cultivation, a sharp decrease in the rate of proliferation of A549 cells associated with the intrinsic development of oxidative stress and, ultimately, with the induction of PANoptotic death were observed. There was a significant increase in the concentration of 40 cytokines/chemokines in a conditioned medium, including TNF-α, IFN-α, IL-6, and IL-1a, which corresponded to the cytokine profile in patients with severe manifestation of COVID-19. In order to verify the model, the analysis of the anti-inflammatory effects of well-known substances (dexamethasone, LPS from Rhodobacter sphaeroides (LPS-RS), polymyxin B), as well as multipotent mesenchymal stem cells (MSC) and MSC-derived extracellular vesicles (EVs) was carried out. Dexamethasone and polymyxin B restored the proliferative activity of A549 cells and reduced the concentration of proinflammatory cytokines. MSC demonstrated an ambivalent effect through stimulated production of both pro-inflammatory cytokines and growth factors that regenerate lung tissue. LPS-RS and EVs showed no significant effect. The developed test system can be used to study molecular and cellular pathological processes and to evaluate the effectiveness of various therapeutic approaches for the correction of hyperinflammatory response in COVID-19 patients.

Microbial Dysbiosis and Epithelial Dysfunction in Vitamin A-Deficient Lungs

Once believed to be sterile, recent studies now show microbes inhabiting healthy lungs that are dysregulated in patients with chronic obstructive pulmonary disease (COPD), asthma, tuberculosis (TB), and SARS-CoV-2 infection. Other studies have shown an increase in pulmonary disease and recurrent respiratory infections in malnourished patients. According to the World Health Organization, vitamin A deficiency (VAD) is now a major public health issue in low-income communities and many developing countries. While VAD has been shown to alter gene expression and tissue morphology in humans and mice, research suggests the lung microbiome plays an intimate role in the metabolic regulation, pathogen inhibition, and inflammatory responses in the lung. Whether dysbiosis is a cause or consequence of chronic respiratory conditions, or whether retinoic acid (RA) - the bioactive metabolite of Vitamin A - is essential for lung microbiome homeostasis, remains unknown. Therefore, we hypothesize that dietary VAD leads to epithelial remodeling which promotes microbial dysbiosis;the dysbiosis then perpetuates epithelial remodeling via host-microbe interactions. Our preliminary results show anatomical/pathological changes to the epithelium in VAD adult mouse lungs compared to controls (VAS). Using our Nkx2- 1creERT2/dnRAR Rosa26 tdTomato transgenic mouse model that selectively induces VAD in the adult lung epithelium following tamoxifen injections, our data supports the hypothesis that host epithelial aberration associated with dietary VAD is induced locally in the lung and not via distal or systemic mechanisms. Our data also indicates the onset of dysbiosis in adult mouse lungs as early as three weeks post-diet modulation as observed through changes in microbial composition in VAD mice compared to controls. Finally, our bulk RNAseq analysis of host and microbial gene signatures has uncovered mechanisms associated with microbial metabolic functions, ciliopathy, host cellular polarity, and immune response to infection, that are dysregulated in the absence of vitamin A. Further, we have also identified altered transcriptional activity of microbes that are traditionally symbiotic or pathobiotic under normal homeostasis. This work indicates the presence of specific host-microbe interactions that are essential for lung homeostasis and protection against lung infection and disease that are dysregulated or lost in the absence of dietary vitamin A.

Transcriptional Interaction Between RelA and cJUN

Rationale: The SARS-CoV-2 pandemic has underscored the need for novel anti-infectious strategies, including host-directed therapeutics, against existing and emerging respiratory pathogens. We have reported that an aerosolized therapeutic comprised of a Toll-like receptor (TLR)-2/6 agonist, Pam2CSK4, and a TLR-9 agonist, ODN M362, stimulate pathogen-agnostic innate immune responses in lung epithelial cells. This therapeutic (“Pam2-ODN”) promotes synergistic microbicidal activity and host survival benefit against pneumonia caused by a wide range of pathogens. Here, we study the immunomodulatory signaling mechanisms required to effect this inducible epithelial resistance. Methods: Bioinformatic analysis of transcriptional responses from human and mouse lung epithelium al cells to influenza A H1N1 or SARS-CoV-2 (GSE147507) or Pam2-ODN (GSE289984, GSE26864) were analyzed using R and IPA software to identify essential transcription factors (TFs). Lung cell population dynamics were studied for TFs related to Pam2-ODN immunomodulatory signaling using high-throughput imaging flow cytometry (IFC). Human or mouse lung epithelial cells were stimulated with PBS or Pam2-ODN and single or dual inhibitors of TFs before challeng with influenza A H3N2 (IAV) or coronavirus OC43 (CoV) to compare the epithelium-specific transcriptional control of relevant TFs using in-cell western blotting, IFC and hemagglutination for viral burdens. Results: Functional enrichment analysis revealed RelA and cJUN to be major immunomodulatory TFs of Pam2-ODN and activators of leukocyte- and epithelial-derived antiviral immune mechanisms targeting replication of influenza A and SARS-CoV-2. Cell population dynamics studied from mouse lungs confirmed activation of RelA and cJUN in CD45+, EpCAM- leukocytes and in CD45-, EpCAM+ epithelial cells, with predominant activation of the lung epithelium and none or minimal activation of structural cell populations such as fibroblasts or endothelial cells. Studies of epithelium-specific signaling in vitro revealed co-activation of RelA-(pS536) and cJun- (pS73) TFs with Pam2-ODN, and earlier onset of cJUN phosphorylation and nuclear translocation with Pam2-ODN after IAV or CoV infection. Individual or dual inhibition of RelA and/or cJUN activity in vitro disrupted the antiviral activity of Pam2-ODN of IAV infected cells. Conclusion: Pam2-ODN induces unique, pathogen-agnostic protective signaling in lung epithelial cells that involves cooperative activation of RelA and cJUN. This combined TF signaling mechanism is not observed in other structural lung cell populations after Pam2-ODN exposure. Further, the phospho-regulation dynamics of RelA and cJUN are not replicated by IAV or CoV infection alone, suggesting a novel therapeutic process that can be leveraged to protect individuals against pneumonia. (Figure Presented).

Molecular Landscape of Lung Epithelium Contributes to High Severity and Comorbidities for COVID-19 and Lung Cancer

The heterogeneous and complex nature of cancer is extensively revealed at molecular, genetic, and tissue microenvironment levels. Currently, co-occurrence of coronavirus disease 2019 (COVID-19) to lung cancer patients and severity of infections by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been understood at preclinical and clinical levels. However, molecular and cellular insights are not discussed in those papers that support the increased COVID-19 severity and comorbidities in several cancer types, including lung cancer patients. Therefore, this perspective highlights the basis of high severity and comorbidities among lung cancer patients infected by COVID-19 with an emphasis on translational aspects.

Multi-Arm Trial of Inflammatory Signal Inhibitors (MATIS) for Hospitalised Patients with Mild or Moderate COVID-19 Pneumonia: A Structured Summary of a Study Protocol for a Randomised Controlled Trial

Introduction: Severe COVID-19 pneumonia is characterised by respiratory and multi-organ failure in the context of marked systemic inflammation. This hyperinflammatory syndrome is reflected by the elevation of several inflammatory molecules, such as C-reactive protein (CRP), ferritin, IL-6, troponin, and D-dimer. In a subset of patients, early intervention with signal inhibitors may treat the Covid-19 hyperinflammatory syndrome before the development of acute lung injury and organ failure. We present a summary of a study protocol for a randomised controlled, multi-arm trial with two novel inflammatory signal inhibitors;Ruxolitinib (RUX) and Fostamatinib (FOS) for the treatment of Covid-19 pneumonia. RUX is an oral Janus Associated Kinase (JAK1/JAK2) inhibitor approved for the treatment of splenomegaly, myelofibrosis and polycythaemia vera. Inhibition of STAT3 downregulates IL-6 and IL-23, which are important for the inflammatory effects of Th17 cells. Further, JAK2 inhibition has been shown to reduce levels of TNFa and CRP, as well as reducing viral cellular entry and assembly. FOS is an oral spleen tyrosine kinase (SYK) inhibitor approved for the treatment of chronic immune thrombocytopenia. Studies of severe acute respiratory distress syndrome (ARDS) suggest that the pathogenesis relies on a series of SYK events leading to cytokine and chemokine release. FOS acts by inhibiting SYK activity, blocking the production and release of cytokines induced via C-lectin receptors and Fc receptor activation, ameliorating the cytokine storm which precedes ARDS. Primary Objective: The primary objective of MATIS is to determine the efficacy of RUX or FOS compared to standard of care (SOC) to reduce the proportion of hospitalised patients progressing from mild or moderate to severe COVID-19 pneumonia at 14 days from baseline. Secondary objectives at 7, 14 and 28 days: - Determine the efficacy of RUX or FOS to reduce mortality - Determine the efficacy of RUX or FOS to reduce the need for invasive ventilation or ECMO - Determine the efficacy of RUX or FOS to reduce the need for non-invasive ventilation - Determine the efficacy of RUX or FOS to reduce the proportion of patients suffering significant oxygen desaturation - Determine the efficacy of RUX or FOS to reduce the need for renal replacement therapy - Determine the efficacy of RUX and FOS to reduce the incidence of venous thromboembolism COVID-19 pneumonia - Determine the efficacy of RUX and FOS to reduce the severity of COVID-19 pneumonia [graded by a modified WHO Ordinal Scale] - Determine the efficacy of RUX or FOS to reduce the level of inflammatory biomarkers - Determine the efficacy of RUX or FOS to reduce the duration of hospital admission - Evaluate the safety of RUX and FOS for COVID-19 pneumonia Study Design: This is a multi-arm, two-stage, open-label, randomised (1:1:1) controlled trial. Participants will be recruited during hospitalisation for COVID-19 in multiple centres in the UK. Eligible participants (table 1) are randomised to one of the three interventions (RUX, FOS, SOC) by a central web-based randomisation service. This uses randomisation sequences with random block sizes, stratified by age (<65 and ≥65 years) and site. The treatment duration is 14 days from baseline. Patients receiving RUX will be administered 10mg BD for Day 1-7 and 5mg BD for Day 8-14. FOS will be administered as 150mg BD day 1-7 and 100mg BD day 8-14. Participants receive follow up assessments on days 7, 14 and 28 after the first dose. Outcomes: Primary endpoints will be assessed with a pairwise comparison (FOS vs SOC and RUX vs SOC) of the proportion of participants diagnosed with severe COVID-19 pneumonia within 14 days. Severe COVID-19 pneumonia is defined by a modified WHO COVID-19 Ordinal Score 5, comprising the following indicators of disease severity: - Death - Requirement for invasive ventilation - Requirement for non-invasive ventilation including CPAP or high flow oxygen - O2 saturation < 90% on 60% inspired oxygen Samples size: In stage 1 of this multi-arm study, 171 parti ipants will be randomised (57 per arm). Following an interim analysis, if either intervention shows a signal of efficacy, stage 2 will recruit a further 95 participants per arm (Fig 1). Trial Status: Recruitment is ongoing and commenced 2nd October 2020. Currently 127 patients are recruited and stage 1 is projected to be completed by 1st September 2021. The full protocol can be accessed via the trial's website. [Formula presented] Disclosures: Milojkovic: Novartis: Honoraria, Speakers Bureau;Incyte: Honoraria, Speakers Bureau;Bristol-Myers Squibb: Honoraria, Speakers Bureau;Pfizer: Honoraria, Speakers Bureau. Cooper: Principia and Sanofi: Consultancy;Sanofi and Principia: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel, accommodations expenses. OffLabel Disclosure: Fostamatanib - is a tyrosine kinase inhibitor with activity against spleen tyrosine kinase (SYK). In the context of treating COVID-19, Fostamatanib acts by inhibiting SYK activist, blocking the production and release of cytokines induced via C-lectin receptors and Fc receptor activation, ameliorating the cytokine storm which precedes ARDS. Studies of severe acute respiratory syndrome induced by coronavirus, suggest that pathogenesis relies on a series of SYK events. SYK medicates ctuokine and chemokine release, induced by the activation of C-lectin receptors and immunoglobulin Fc receptors, resulting in neutrophil and monocyte lung ingress, sequential activation of neutrophil extracellular traps and activation of lung epithelium and multiple myeloid cell. This is followed by inflammation and tissue destruction that contribute to ARDS. Ruxolitinib - A JAK1/JAK2 inhibitor. JAK and STAT molecules are proteins that trance extracellular stimulation into intracellular signalling, leading to expression of host inflammatory cytokines and a variety of immune cells. In the context of MATIS, we use low dose ruxolitinib to treat COVID-19 by targeting key signalling pathways implicated in the hyper-inflammatory response of patients with COVID-19 infection. The mechanisms of Ruxolitinib to act in COVID-19 is through inhibition of STAT3 activation, down regulating IL-6 and IL-23, signalling important for the inflammatory effects of Th17 cells. Furthermore it leads to reductions of TNFa and CRP.

SARS-CoV-2 Ion Channel ORF3a Enables TMEM16F-Dependent Phosphatidylserine Externalization to Augment Procoagulant Activity of the Tenase and Prothrombinase Complexes

Severe SARS-CoV-2 infection is complicated by dysregulation of the blood coagulation system and high rates of thrombosis, but virus-intrinsic mechanisms underlying this phenomenon are poorly understood. Increased intracellular calcium concentrations promote externalization of phosphatidylserine (PS), the membrane anionic phospholipid required for assembly and activation of the tenase and prothrombinase complexes to drive blood coagulation. TMEM16F is a ubiquitous phospholipid scramblase that mediates externalization of PS in a calcium-dependent manner. As SARS-CoV-2 ORF3a encodes a presumed cation channel with the ability to transport calcium, we hypothesized that ORF3a expression by infected host cells perturbs the cellular calcium rheostat, driving TMEM16F-dependent externalization of PS and enhancing procoagulant activity. Using a doxycycline-inducible system, synchronized expression of ORF3a in A549 pulmonary epithelial cells resulted in a time-dependent augmentation of tissue factor (TF) procoagulant activity exceeding 9-fold by 48 hours (p < 0.0001), with no change in TF cell-surface expression. This enhancement was dependent upon PS as determined by inhibition with the PS-binding protein lactadherin. Over 2-fold enhancement of prothrombinase activity (p < 0.0001) was also observed by 48 hours. ORF3a increased intracellular calcium levels by 18-fold at 48 hours (p < 0.0001), as determined by the intracellular calcium indicator fluo-4. After 16 hours of ORF3a expression, more than 60% of cells had externalized PS (p < 0.001) without increased cell death, as quantified by flow cytometry following annexin V binding. Immunofluorescence microscopy staining for ORF3a, annexin V, and nuclei confirmed ORF3a expression within internal and cell surface membranes and increased PS externalization. PS externalization was insensitive to the pan-caspase inhibitor z-VAD-FMK, and there was no evidence of apoptotic activation as determined by caspase-3 cleavage. By contrast, ORF3a expression did not augment coagulation in cells deficient in the calcium-dependent phospholipid scramblase TMEM16F. Similarly, ORF3a-enhanced TF procoagulant activity (p < 0.01) and prothrombinase activity (p<0.05) was completely abrogated using TMEM16 inhibitors, including the uricosuric agent benzbromarone that has been registered for human use in over 20 countries. Live SARS-CoV-2 infection of A549-ACE2 cells increased cell surface factor Xa generation at MOI 0.1 (p < 0.01) but not MOI 0.01 or following heat inactivation of the virus, and RNA sequencing confirmed ORF3a induction without increased F3 expression. RNA sequencing of human SARS-CoV-2 infected lung autopsy and control tissue (n= 53) confirmed these findings in vivo. Immunofluorescence staining for ORF3a and KRT8/18 and CD31 in SARS-CoV-2 infected human lung autopsy specimens demonstrated ORF3a expression in pulmonary epithelium and endothelial cells, highlighting the potential pathologic relevance of this mechanism. Here we demonstrate that expression of the SARS-CoV-2 accessory protein ORF3a increases the intracellular calcium concentration and TMEM16F-dependent PS scrambling to augment procoagulant activity of the tenase and prothrombinase complexes. Our studies of human cells and tissues infected with SARS-CoV-2 support the pathologic relevance of this mechanism. We highlight the therapeutic potential to target the ORF3a-TMEM16F axis as with benzbromarone to mitigate dysregulation of coagulation and thrombosis during severe SARS-CoV-2 infection. Disclosures: Schwartz: Miromatrix Inc: Membership on an entity's Board of Directors or advisory committees;Alnylam Inc.: Consultancy, Speakers Bureau. Schulman: CSL Behring: Consultancy, Research Funding.

SARS-CoV-2 activates lung epithelial cell proinflammatory signaling and leads to immune dysregulation in COVID-19 patients.

BACKGROUND: The outbreak of Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 infection has become a global health emergency. We aim to decipher SARS-CoV-2 infected cell types, the consequent host immune response and their interplay in lung of COVID-19 patients. METHODS: We analyzed single-cell RNA sequencing (scRNA-seq) data of bronchoalveolar lavage fluid (BALF) samples from 10 healthy donors, 6 severe COVID-19 patients and 3 mild recovered patients. The expressions of SARS-CoV-2 receptors (ACE2 and TMPRSS2) were examined among different cell types. The immune cells infiltration patterns, their expression profiles, and interplays between immune cells and SARS-CoV-2 target cells were further investigated. FINDINGS: Compared to healthy controls, ACE2 and TMPRSS2 expressions were significantly higher in lung epithelial cells of COVID-19 patients, in particular club and ciliated cells. SARS-CoV-2 activated pro-inflammatory genes and interferon/cytokine signaling in these cells. In severe COVID-19 patients, significantly higher neutrophil, but lower macrophage in lung was observed along with markedly increased cytokines expression compared with healthy controls and mild patients. By contrast, neutrophil and macrophage returned to normal level whilst more T and NK cells accumulation were observed in mild patients. Moreover, SARS-CoV-2 infection altered the community interplays of lung epithelial and immune cells: interactions between the club and immune cells were higher in COVID-19 patients compared to healthy donors; on the other hand, immune-immune cells interactions appeared the strongest in mild patients. INTERPRETATION: SARS-CoV-2 could infect lung epithelium, alter communication patterns between lung epithelial cells and immune system, and drive dysregulated host immune response in COVID-19 patients. FUNDING: This project was supported by National Key R&D Program of China (No. 2018YFC1315000/2018YFC1315004), Science and Technology Program Grant Shenzhen (JCYJ20170413161534162), HMRF Hong Kong (17160862), RGC-CRF Hong Kong (C4039-19G), RGC-GRF Hong Kong (14163817), Vice-Chancellor's Discretionary Fund CUHK and CUHK direct grant, Shenzhen Virtual University Park Support Scheme to CUHK Shenzhen Research Institute.

SARS-CoV-2 infection of primary human lung epithelium for COVID-19 modeling and drug discovery.

Coronavirus disease 2019 (COVID-19) is the latest respiratory pandemic caused by severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2). Although infection initiates in the proximal airways, severe and sometimes fatal symptoms of the disease are caused by infection of the alveolar type 2 (AT2) cells of the distal lung and associated inflammation. In this study, we develop primary human lung epithelial infection models to understand initial responses of proximal and distal lung epithelium to SARS-CoV-2 infection. Differentiated air-liquid interface (ALI) cultures of proximal airway epithelium and alveosphere cultures of distal lung AT2 cells are readily infected by SARS-CoV-2, leading to an epithelial cell-autonomous proinflammatory response with increased expression of interferon signaling genes. Studies to validate the efficacy of selected candidate COVID-19 drugs confirm that remdesivir strongly suppresses viral infection/replication. We provide a relevant platform for study of COVID-19 pathobiology and for rapid drug screening against SARS-CoV-2 and emergent respiratory pathogens.

First contact: the role of respiratory cilia in host-pathogen interactions in the airways.

Respiratory cilia are the driving force of the mucociliary escalator, working in conjunction with secreted airway mucus to clear inhaled debris and pathogens from the conducting airways. Respiratory cilia are also one of the first contact points between host and inhaled pathogens. Impaired ciliary function is a common pathological feature in patients with chronic airway diseases, increasing susceptibility to respiratory infections. Common respiratory pathogens, including viruses, bacteria, and fungi, have been shown to target cilia and/or ciliated airway epithelial cells, resulting in a disruption of mucociliary clearance that may facilitate host infection. Despite being an integral component of airway innate immunity, the role of respiratory cilia and their clinical significance during airway infections are still poorly understood. This review examines the expression, structure, and function of respiratory cilia during pathogenic infection of the airways. This review also discusses specific known points of interaction of bacteria, fungi, and viruses with respiratory cilia function. The emerging biological functions of motile cilia relating to intracellular signaling and their potential immunoregulatory roles during infection will also be discussed.

Human Induced Pluripotent Stem Cell-Derived Lung Epithelial System for SARS-CoV-2 Infection Modeling and Its Potential in Drug Repurposing.

The lung is the most vulnerable target for the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, and respiratory failure causing acute respiratory distress syndrome is its foremost outcome. However, the current primary in vitro models in use for SARS-CoV-2 display apparent limitations for modeling such complex human respiratory disease. Although patient cells can directly model the effects of a drug, their availability and capacity for expansion are limited compared with transformed/immortalized cells or tumor-derived cell lines. An additional caveat is that the latter may harbor genetic and metabolic abnormalities making them unsuitable for drug screening. Therefore, it is important to create physiologically relevant human-cell models that can replicate the pathophysiology of SARS-CoV-2, thus facilitating drug testing. In this study, we show preliminary data on how human induced pluripotent stem cells-derived lung epithelial cell system could emerge as a relevant and sensitive platform for modeling SARS-CoV-2 infection and drug screening.