Direct Exposure to SARS-CoV-2 and Cigarette Smoke Increases Infection Severity and Alters the Stem Cell-Derived Airway Repair Response

Airway Basal Stem Cells Inflammatory Alterations in COVID-19 and Mitigation by Mesenchymal Stem Cells

SARS-CoV-2 infection and the resultant COVID-19 pneumonia cause significant damage to the airway and lung epithelium. This damage manifests as mucus hypersecretion, pulmonary inflammation and fibrosis, which often lead to long-term complications collectively referred to as long COVID or post-acute sequelae of COVID-19 (PASC). The airway epithelium, as the first line of defence against respiratory pathogens, depends on airway basal stem cells (BSCs) for regeneration. Alterations in BSCs are associated with impaired epithelial repair and may contribute to the respiratory complications observed in PASC. Given the critical role of BSCs in maintaining epithelial integrity, understanding their alterations in COVID-19 is essential for developing effective therapeutic strategies. This study investigates the intrinsic properties of BSCs derived from COVID-19 patients and evaluates the modulatory effects of mesenchymal stem cells (MSCs). Through a combination of functional assessments and transcriptomic profiling, we identified key phenotypic and molecular deviations in COVID-19 patient-derived BSCs, including goblet cell hyperplasia, inflammation and fibrosis, which may underlie their contribution to PASC. Notably, MSC co-culture significantly mitigated these adverse effects, potentially through modulation of the interferon signalling pathway. This is the first study to isolate BSCs from COVID-19 patients in the Chinese population and establish a COVID-19 BSC-based xenograft model. Our findings reveal critical insights into the role of BSCs in epithelial repair and their inflammatory alterations in COVID-19 pathology, with potential relevance to PASC and virus-induced respiratory sequelae. Additionally, our study highlights MSC-based therapies as a promising strategy to address respiratory sequelae and persistent symptoms.

Association of Endothelial Nitric Oxide Synthase Polymorphisms with Clinical Severity in Patients with COVID-19

Background/Objectives: To elucidate the factors that contribute to individual variability in the progression of COVID-19, experiments on endothelial nitric oxide synthase polymorphisms have been reported. Nitric oxide synthase (NOS3) is located in the endothelium and is involved in the regulation of inflammation and vascular homeostasis. In this study, we investigated the association between COVID-19 severity and NOS3 G894T and NOS3 27-bp VNTR 4b/a genetic polymorphisms. Methods: Patients with COVID-19 (n = 178) were divided into Group 1 (mild disease) and Group 2 (severe disease) based on oxygen saturation levels in room air (Group 1, SpO2 ≥ 93%, n = 107; and Group 2, SpO2 < 93%, n = 73) and hospitalization requirements. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism analysis. Results: Overall, genotype and allele frequencies of the NOS3 genetic polymorphisms were similar across the two study groups (p > 0.05). However, the subgroup analysis showed a notable trend for the 4b/4a allele distribution between Groups 1 and 2. In the younger subgroup of patients (≤50 years old) without chronic obstructive pulmonary disease, Group 2 tended to have a higher frequency of the 4b allele than Group 1 (97.4% vs. 85.4% p = 0.06) and a higher occurrence of 4b/4b genotype (94.7% vs. 74.0%, p = 0.05). Additionally, a rarely observed 4c allele was detected only in two subjects within Group 2 but not in Group 1. Conclusions: These findings suggest a trend of association between COVID-19 severity and NOS3 27-bp VNTR 4b/a genetic polymorphism. Genetic analysis may reveal patient susceptibility to disease, prognosis risk factors, and drug responsiveness.

Airway basal stem cell therapy for lung diseases: an emerging regenerative medicine strategy

Chronic pulmonary diseases pose a prominent health threat globally owing to their intricate pathogenesis and lack of effective reversal therapies. Nowadays, lung transplantation stands out as a feasible treatment option for patients with end-stage lung disease. Unfortunately, the use of this this option is limited by donor organ shortage and severe immunological rejection reactions. Recently, airway basal stem cells (BSCs) have emerged as a novel therapeutic strategy in pulmonary regenerative medicine because of their substantial potential in repairing lung structure and function. Airway BSCs, which are strongly capable of self-renewal and multi-lineage differentiation, can effectively attenuate airway epithelial injury caused by environmental factors or genetic disorders, such as cystic fibrosis. This review comprehensively explores the efficacy and action mechanisms of airway BSCs across various lung disease models and describes potential strategies for inducing pluripotent stem cells to differentiate into pulmonary epithelial lineages on the basis of the original research findings. Additionally, the review also discusses the technical and biological challenges in translating these research findings into clinical applications and offers prospective views on future research directions, therefore broadening the landscape of pulmonary regenerative medicine.

Optimization of a micro-scale air-liquid-interface model of human proximal airway epithelium for moderate throughput drug screening for SARS-CoV-2

BACKGROUND

Many respiratory viruses attack the airway epithelium and cause a wide spectrum of diseases for which we have limited therapies. To date, a few primary human stem cell-based models of the proximal airway have been reported for drug discovery but scaling them up to a higher throughput platform remains a significant challenge. As a result, most of the drug screening assays for respiratory viruses are performed on commercial cell line-based 2D cultures that provide limited translational ability.

METHODS

We optimized a primary human stem cell-based mucociliary airway epithelium model of SARS-CoV-2 infection, in 96-well air-liquid-interface (ALI) format, which is amenable to moderate throughput drug screening. We tested the model against SARS-CoV-2 parental strain (Wuhan) and variants Beta, Delta, and Omicron. We applied this model to screen 2100 compounds from targeted drug libraries using a high throughput-high content image-based quantification method.

RESULTS

The model recapitulated the heterogeneity of infection among patients with SARS-CoV-2 parental strain and variants. While there were heterogeneous responses across variants for host factor targeting compounds, the two direct-acting antivirals we tested, Remdesivir and Paxlovid, showed consistent efficacy in reducing infection across all variants and donors. Using the model, we characterized a new antiviral drug effective against both the parental strain and the Omicron variant.

CONCLUSION

This study demonstrates that the 96-well ALI model of primary human mucociliary epithelium can recapitulate the heterogeneity of infection among different donors and SARS-CoV-2 variants and can be used for moderate throughput screening. Compounds that target host factors showed variability among patients in response to SARS-CoV-2, while direct-acting antivirals were effective against SARS-CoV-2 despite the heterogeneity of patients tested.

Live imaging of airway epithelium reveals that mucociliary clearance modulates SARS-CoV-2 spread

SARS-CoV-2 initiates infection in the conducting airways, where mucociliary clearance inhibits pathogen penetration. However, it is unclear how mucociliary clearance impacts SARS-CoV-2 spread after infection is established. To investigate viral spread at this site, we perform live imaging of SARS-CoV-2 infected differentiated primary human bronchial epithelium cultures for up to 12 days. Using a fluorescent reporter virus and markers for cilia and mucus, we longitudinally monitor mucus motion, ciliary motion, and infection. Infected cell numbers peak at 4 days post infection, forming characteristic foci that tracked mucus movement. Inhibition of MCC using physical and genetic perturbations limits foci. Later in infection, mucociliary clearance deteriorates. Increased mucus secretion accompanies ciliary motion defects, but mucociliary clearance and vectorial infection spread resume after mucus removal, suggesting that mucus secretion may mediate MCC deterioration. Our work shows that while MCC can facilitate SARS-CoV-2 spread after initial infection, subsequent MCC decreases inhibit spread, revealing a complex interplay between SARS-CoV-2 and MCC.

Cell Culture Differentiation and Proliferation Conditions Influence the In Vitro Regeneration of the Human Airway Epithelium

The human airway mucociliary epithelium can be recapitulated in vitro using primary cells cultured in an air-liquid interface (ALI), a reliable surrogate to perform pathophysiological studies. As tremendous variations exist among media used for ALI-cultured human airway epithelial cells, the aim of our study was to evaluate the impact of several media (BEGM, PneumaCult, Half & Half, and Clancy) on cell type distribution using single-cell RNA sequencing and imaging. Our work revealed the impact of these media on cell composition, gene expression profile, cell signaling, and epithelial morphology. We found higher proportions of multiciliated cells in PneumaCult-ALI and Half & Half, stronger EGF signaling from basal cells in BEGM-ALI, differential expression of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry factor ACE2, and distinct secretome transcripts depending on the media used. We also established that proliferation in PneumaCult-Ex Plus favored secretory cell fate, showing the key influence of proliferation media on late differentiation epithelial characteristics. Altogether, our data offer a comprehensive repertoire for evaluating the effects of culture conditions on airway epithelial differentiation and will aid in choosing the most relevant medium according to the processes to be investigated, such as cilia, mucus biology, or viral infection. We detail useful parameters that should be explored to document airway epithelial cell fate and morphology.

ACE-2 Blockade & TMPRSS2 Inhibition Mitigate SARS-CoV-2 Severity Following Cigarette Smoke Exposure in Airway Epithelial Cells In Vitro

Cigarette smoking is associated with COVID-19 prevalence and severity, but the mechanistic basis for how smoking alters SARS-CoV-2 pathogenesis is unknown. A potential explanation is that smoking alters the expression of the SARS-CoV-2 cellular receptor and point of entry, angiotensin converting enzyme-2 (ACE-2), and its cofactors including transmembrane protease serine 2 (TMPRSS2). We investigated the impact of cigarette smoking on the expression of ACE-2, TMPRSS2, and other known cofactors of SARS-CoV-2 infection and the resultant effects on infection severity in vitro. Cigarette smoke extract (CSE) exposure increased ACE-2 and TMPRSS2 mRNA expression compared to air control in ferret airway cells, Calu-3 cells, and primary human bronchial epithelial (HBE) cells derived from normal and COPD donors. CSE-exposed ferret airway cells inoculated with SARS-CoV-2 had a significantly higher intracellular viral load versus vehicle-exposed cells. Likewise, CSE-exposure increased both SARS-CoV-2 intracellular viral load and viral replication in both normal and COPD HBE cells over vehicle control. Apoptosis was increased in CSE-exposed, SARS-CoV-2-infected HBE cells. Knockdown of ACE-2 via an antisense oligonucleotide (ASO) reduced SARS-CoV-2 viral load and infection in CSE-exposed ferret airway cells that was augmented by co-administration of camostat mesylate to block TMPRSS2 activity. Smoking increases SARS-CoV-2 infection via upregulation of ACE2 and TMPRSS2.

The Relation Between Cigarette Smoking and Development of Sepsis: A 10-Year Follow-Up Study of Four Million Adults from the National Health Screening Program

BACKGROUND

Sepsis remains a growing global health concern with soaring mortality and no direct anti-sepsis drug. Although smoking has distinct deleterious effects on chronic inflammatory illnesses and can impair immune function, a comprehensive analysis of the connection between sepsis and smoking is lacking.

METHODS

This large-scale longitudinal cohort study retrospectively assessed adults aged ≥ 20 years who underwent national health checkups under the Korean National Health Insurance Service between January and December 2009 (N = 4,234,415) and were followed up for 10 years. Sepsis was identified based on the International Classification of Diseases, 10th Revision codes, and smoking status, including accumulated amount, was collected through a self-administered questionnaire. The Cox proportional hazard regression model was used, adjusting for age, sex, household income, body mass index, drinking, exercise, diabetes, hypertension, dyslipidemia, and chronic renal disease.

RESULTS

After excluding cases with sepsis occurring before follow-up or after ≤ 1 year of follow-up, 3,881,958 participants, including non-smokers (N = 2,342,841), former smokers (N = 539,850), and active smokers (N = 999,267), were included. Compared to non-smokers, all active smokers (adjust hazard ratio: 1.41, 95% confidence interval 1.38-1.44) and former smokers (1.10, 1.07-1.14) with ≥ 20 pack-years exhibited a significantly higher risk of sepsis (p < 0.001). Smoking of ≥ 30 pack-years in former and active smokers groups significantly increased sepsis incidence (adjust hazard ratio [95% confidence interval] 1.34 [1.31-1.38], p < 0.001).

CONCLUSIONS

Smoking is closely associated with the incidence of sepsis. Smoking cessation may help in the primary prevention of sepsis.

Does vaping increase the likelihood of SARS-CoV-2 infection? Paradoxically yes and no

Data on the relationship between electronic cigarettes (ECs) and SARS-CoV-2 infection are limited and contradictory. Our objectives were to investigate the impact of EC aerosols on SARS-CoV-2 infection of human bronchial epithelial cells and identify the causative chemical(s). Fully differentiated human bronchial epithelial tissues (hBETs) were exposed at the air-liquid interface (ALI) to aerosols produced from JUUL "Virginia Tobacco" and BLU ECs, as well as nicotine, propylene glycol (PG), vegetable glycerin (VG), and benzoic acid, and infection was then evaluated with SARS-CoV-2 pseudoparticles. Pseudoparticle infection of hBETs increased with aerosols produced from PG/VG, PG/VG plus nicotine, or BLU ECs; however, JUUL EC aerosols did not increase infection compared with controls. Increased infection in PG/VG alone was due to enhanced endocytosis, whereas increased infection in PG/VG plus nicotine or in BLU ECs was caused by nicotine-induced elevation of the aerosol's pH, which correlated with increased transmembrane protease, serine 2 (TMPRSS2) activity. Notably, benzoic acid in JUUL aerosols mitigated the enhanced infection caused by PG/VG or nicotine, offering protection that lasted for at least 48 h after exposure. In conclusion, the study demonstrates that EC aerosols can impact susceptibility to SARS-CoV-2 infection depending on their specific ingredients. PG/VG alone or PG/VG plus nicotine enhanced infection through different mechanisms, whereas benzoic acid in JUUL aerosols mitigated the increased infection caused by certain ingredients. These findings highlight the complex relationship between ECs and SARS-CoV-2 susceptibility, emphasizing the importance of considering the specific aerosol ingredients when evaluating the potential effects of ECs on infection risk.NEW & NOTEWORTHY Data on the relationship between electronic cigarettes (ECs) and SARS-CoV-2 infection are limited and contradictory. We investigated the impact of EC aerosols and their ingredients on SARS-CoV-2 infection of human bronchial epithelial cells. Our data show that specific ingredients in EC aerosols impact the susceptibility to SARS-CoV-2 infection. Propylene glycol (PG)/vegetable glycerin (VG) alone or PG/VG plus nicotine enhanced infection through different mechanisms, whereas benzoic acid in JUUL aerosols mitigated the increased infection caused by these ingredients.

Development of lung tissue models and their applications

The lungs are important organs that play a critical role in the development of specific diseases, as well as responding to the effects of drugs, chemicals, and environmental pollutants. Due to the ethical concerns around animal testing, alternative methods have been sought which are more time-effective, do not pose ethical issues for animals, do not involve species differences, and provide easy investigation of the pathobiology of lung diseases. Several national and international organizations are working to accelerate the development and implementation of structurally and functionally complex tissue models as alternatives to animal testing, particularly for the lung. Unfortunately, to date, there is no lung tissue model that has been accepted by regulatory agencies for use in inhalation toxicology. This review discusses the challenges involved in developing a relevant lung tissue model derived from human cells such as cell lines, primary cells, and pluripotent stem cells. It also introduces examples of two-dimensional (2D) air-liquid interface and monocultured and co-cultured three-dimensional (3D) culture techniques, particularly organoid culture and 3D bioprinting. Furthermore, it reviews development of the lung-on-a-chip model to mimic the microenvironment and physiological performance. The applications of lung tissue models in various studies, especially disease modeling, viral respiratory infection, and environmental toxicology will be also introduced. The development of a relevant lung tissue model is extremely important for standardizing and validation the in vitro models for inhalation toxicity and other studies in the future.

The Apolipoprotein E neutralizing antibody inhibits SARS-CoV-2 infection by blocking cellular entry of lipoviral particles

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causal agent for coronavirus disease 2019 (COVID-19). Although vaccines have helped to prevent uncontrolled viral spreading, our understanding of the fundamental biology of SARS-CoV-2 infection remains insufficient, which hinders effective therapeutic development. Here, we found that Apolipoprotein E (ApoE), a lipid binding protein, is hijacked by SARS-CoV-2 for infection. Preincubation of SARS-CoV-2 with a neutralizing antibody specific to ApoE led to inhibition of SARS-CoV-2 infection. The ApoE neutralizing antibody efficiently blocked SARS-CoV-2 infection of human iPSC-derived astrocytes and air-liquid interface organoid models in addition to human ACE2-expressing HEK293T cells and Calu-3 lung cells. ApoE mediates SARS-CoV-2 entry through binding to its cellular receptors such as the low density lipoprotein receptor (LDLR). LDLR knockout or ApoE mutations at the receptor binding domain or an ApoE mimetic peptide reduced SARS-CoV-2 infection. Furthermore, we detected strong membrane LDLR expression on SARS-CoV-2 Spike-positive cells in human lung tissues, whereas no or low ACE2 expression was detected. This study provides a new paradigm for SARS-CoV-2 cellular entry through binding of ApoE on the lipoviral particles to host cell receptor(s). Moreover, this study suggests that ApoE neutralizing antibodies are promising antiviral therapies for COVID-19 by blocking entry of both parental virus and variants of concern.

Mechanical stretch promotes apoptosis and impedes ciliogenesis of primary human airway basal stem cells

BACKGROUND

Airway basal stem cells (ABSCs) have self-renewal and differentiation abilities. Although an abnormal mechanical environment related to chronic airway disease (CAD) can cause ABSC dysfunction, it remains unclear how mechanical stretch regulates the behavior and structure of ABSCs. Here, we explored the effect of mechanical stretch on primary human ABSCs.

METHODS

Primary human ABSCs were isolated from healthy volunteers. A Flexcell FX-5000 Tension system was used to mimic the pathological airway mechanical stretch conditions of patients with CAD. ABSCs were stretched for 12, 24, or 48 h with 20% elongation. We first performed bulk RNA sequencing to identify the most predominantly changed genes and pathways. Next, apoptosis of stretched ABSCs was detected with Annexin V-FITC/PI staining and a caspase 3 activity assay. Proliferation of stretched ABSCs was assessed by measuring MKI67 mRNA expression and cell cycle dynamics. Immunofluorescence and hematoxylin-eosin staining were used to demonstrate the differentiation state of ABSCs at the air-liquid interface.

RESULTS

Compared with unstretched control cells, apoptosis and caspase 3 activation of ABSCs stretched for 48 h were significantly increased (p < 0.0001; p < 0.0001, respectively), and MKI67 mRNA levels were decreased (p < 0.0001). In addition, a significant increase in the G0/G1 population (20.2%, p < 0.001) and a significant decrease in S-phase cells (21.1%, p < 0.0001) were observed. The ratio of Krt5+ ABSCs was significantly higher (32.38% vs. 48.71%, p = 0.0037) following stretching, while the ratio of Ac-tub+ cells was significantly lower (37.64% vs. 21.29%, p < 0.001). Moreover, compared with the control, the expression of NKX2-1 was upregulated significantly after stretching (14.06% vs. 39.51%, p < 0.0001). RNA sequencing showed 285 differentially expressed genes, among which 140 were upregulated and 145 were downregulated, revealing that DDIAS, BIRC5, TGFBI, and NKX2-1 may be involved in the function of primary human ABSCs during mechanical stretch. There was no apparent difference between stretching ABSCs for 24 and 48 h compared with the control.

CONCLUSIONS

Pathological stretching induces apoptosis of ABSCs, inhibits their proliferation, and disrupts cilia cell differentiation. These features may be related to abnormal regeneration and repair observed after airway epithelium injury in patients with CAD.

Wet-adhesive γ-PGA/ε-PLL hydrogel loaded with EGF for tracheal epithelial injury repair

Following the global COVID-19 pandemic, the incidence of tracheal epithelial injury is increasing. However, the repair of tracheal epithelial injury remains a challenge due to the slow renewal rate of tracheal epithelial cells (TECs). In traditional nebulized inhalation treatments, drugs are enriched in the lungs or absorbed into the blood, reducing drug concentration at the tracheal injury site. In this study, we prepared an epidermal growth factor (EGF)-loaded gamma-polyglutamic acid (γ-PGA)/epsilon-poly-L-lysine (ε-PLL) (PP) hydrogel (EGF@PP) to promote the repair of tracheal epithelial injury. Epidermal growth factor promotes the proliferation of TECs and enhances vascularization, thereby accelerating injury repair. The PP hydrogel exhibits outstanding wet adhesion, slow drug release, and antibacterial and anti-inflammatory properties, making it suitable for application in the airways and creating an environment conducive to epithelial repair. Here, we established a rabbit model of tracheal injury using a laser to destroy the tracheal epithelium and delivered EGF@PP powder to the injury site under fiberoptic bronchoscopy guidance. Our findings revealed that this was an effective therapeutic strategy for accelerating the repair of tracheal epithelial injury.

Live imaging of the airway epithelium reveals that mucociliary clearance modulates SARS-CoV-2 spread

SARS-CoV-2 initiates infection in the conducting airways, which rely on mucocilliary clearance (MCC) to minimize pathogen penetration. However, it is unclear how MCC impacts SARS-CoV-2 spread after infection is established. To understand viral spread at this site, we performed live imaging of SARS-CoV-2 infected differentiated primary human bronchial epithelium cultures for up to 9 days. Fluorescent markers for cilia and mucus allowed longitudinal monitoring of MCC, ciliary motion, and infection. The number of infected cells peaked at 4 days post-infection in characteristic foci that followed mucus movement. Inhibition of MCC using physical and genetic perturbations limited foci. Later in infection, MCC was diminished despite relatively subtle ciliary function defects. Resumption of MCC and infection spread after mucus removal suggests that mucus secretion mediates this effect. We show that MCC facilitates SARS-CoV-2 spread early in infection while later decreases in MCC inhibit spread, suggesting a complex interplay between SARS-CoV-2 and MCC.

Antiviral CD8+ T-cell immune responses are impaired by cigarette smoke and in COPD

BACKGROUND

Virus infections drive COPD exacerbations and progression. Antiviral immunity centres on the activation of virus-specific CD8+ T-cells by viral epitopes presented on major histocompatibility complex (MHC) class I molecules of infected cells. These epitopes are generated by the immunoproteasome, a specialised intracellular protein degradation machine, which is induced by antiviral cytokines in infected cells.

METHODS

We analysed the effects of cigarette smoke on cytokine- and virus-mediated induction of the immunoproteasome in vitro, ex vivo and in vivo using RNA and Western blot analyses. CD8+ T-cell activation was determined in co-culture assays with cigarette smoke-exposed influenza A virus (IAV)-infected cells. Mass-spectrometry-based analysis of MHC class I-bound peptides uncovered the effects of cigarette smoke on inflammatory antigen presentation in lung cells. IAV-specific CD8+ T-cell numbers were determined in patients' peripheral blood using tetramer technology.

RESULTS

Cigarette smoke impaired the induction of the immunoproteasome by cytokine signalling and viral infection in lung cells in vitro, ex vivo and in vivo. In addition, cigarette smoke altered the peptide repertoire of antigens presented on MHC class I molecules under inflammatory conditions. Importantly, MHC class I-mediated activation of IAV-specific CD8+ T-cells was dampened by cigarette smoke. COPD patients exhibited reduced numbers of circulating IAV-specific CD8+ T-cells compared to healthy controls and asthmatics.

CONCLUSION

Our data indicate that cigarette smoke interferes with MHC class I antigen generation and presentation and thereby contributes to impaired activation of CD8+ T-cells upon virus infection. This adds important mechanistic insight on how cigarette smoke mediates increased susceptibility of smokers and COPD patients to viral infections.

A single-cell atlas of in vitro multiculture systems uncovers the in vivo lineage trajectory and cell state in the human lung

We present an in-depth single-cell atlas of in vitro multiculture systems on human primary airway epithelium derived from normal and diseased lungs of 27 individual donors. Our large-scale single-cell profiling identified new cell states and differentiation trajectories of rare airway epithelial cell types in human distal lungs. By integrating single-cell datasets of human lung tissues, we discovered immune-primed subsets enriched in lungs and organoids derived from patients with chronic respiratory disease. To demonstrate the full potential of our platform, we further illustrate transcriptomic responses to various respiratory virus infections in vitro airway models. Our work constitutes a single-cell roadmap for the cellular and molecular characteristics of human primary lung cells in vitro and their relevance to human tissues in vivo.

Airborne fine particles drive H1N1 viruses deep into the lower respiratory tract and distant organs

Mounting data suggest that environmental pollution due to airborne fine particles (AFPs) increases the occurrence and severity of respiratory virus infection in humans. However, it is unclear whether and how interactions with AFPs alter viral infection and distribution. We report synergetic effects between various AFPs and the H1N1 virus, regulated by physicochemical properties of the AFPs. Unlike infection caused by virus alone, AFPs facilitated the internalization of virus through a receptor-independent pathway. Moreover, AFPs promoted the budding and dispersal of progeny virions, likely mediated by lipid rafts in the host plasma membrane. Infected animal models demonstrated that AFPs favored penetration of the H1N1 virus into the distal lung, and its translocation into extrapulmonary organs including the liver, spleen, and kidney, thus causing severe local and systemic disorders. Our findings revealed a key role of AFPs in driving viral infection throughout the respiratory tract and beyond. These insights entail stronger air quality management and air pollution reduction policies.

New insights into how popular electronic cigarette aerosols and aerosol constituents affect SARS-CoV-2 infection of human bronchial epithelial cells

The relationship between the use of tobacco products and SARS-CoV-2 infection is poorly understood and controversial. Few studies have examined the effect of electronic cigarettes (ECs) on SARS-CoV-2 infection. We tested the hypothesis that EC fluids and aerosols with nicotine promote SARS-COV-2 infection by increasing viral entry into human respiratory epithelial cells. Responses of BEAS-2B cells to JUUL aerosols or their individual constituents were compared using three exposure platforms: submerged culture, air-liquid-interface (ALI) exposure in a cloud chamber, and ALI exposure in a Cultex system, which produces authentic heated EC aerosols. In general, nicotine and nicotine + propylene glycol/vegetable glycerin aerosols increased ACE2 (angiotensin converting enzyme 2) levels, the SARS-CoV-2 receptor; and increased the activity of TMPRSS2 (transmembrane serine protease 2), an enzyme essential for viral entry. Lentivirus pseudoparticles with spike protein were used to test viral penetration. Exposure to nicotine, EC fluids, or aerosols altered the infection machinery and increased viral entry into cells. While most data were in good agreement across the three exposure platforms, cells were more responsive to treatments when exposed at the ALI in the Cultex system, even though the exposures were brief and intermittent. While both nicotine and JUUL aerosols increased SARS-CoV-2 infection, JUUL significantly decreased the effect of nicotine alone. These data support the idea that vaping can increase the likelihood of contracting COVID-19 and that e-liquid composition may modulate this effect.

The Isolation and In Vitro Differentiation of Primary Fetal Baboon Tracheal Epithelial Cells for the Study of SARS-CoV-2 Host-Virus Interactions

The mucociliary airway epithelium lines the human airways and is the primary site of host-environmental interactions in the lung. Following virus infection, airway epithelial cells initiate an innate immune response to suppress virus replication. Therefore, defining the virus-host interactions of the mucociliary airway epithelium is critical for understanding the mechanisms that regulate virus infection, including Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Non-human primates (NHP) are closely related to humans and provide a model to study human disease. However, ethical considerations and high costs can restrict the use of in vivo NHP models. Therefore, there is a need to develop in vitro NHP models of human respiratory virus infection that would allow for rapidly characterizing virus tropism and the suitability of specific NHP species to model human infection. Using the olive baboon (Papio anubis), we have developed methodologies for the isolation, in vitro expansion, cryopreservation, and mucociliary differentiation of primary fetal baboon tracheal epithelial cells (FBTECs). Furthermore, we demonstrate that in vitro differentiated FBTECs are permissive to SARS-CoV-2 infection and produce a potent host innate-immune response. In summary, we have developed an in vitro NHP model that provides a platform for the study of SARS-CoV-2 infection and other human respiratory viruses.

De-novo reconstruction and identification of transcriptional gene regulatory network modules differentiating single-cell clusters

Single-cell RNA sequencing (scRNA-seq) technology provides an unprecedented opportunity to understand gene functions and interactions at single-cell resolution. While computational tools for scRNA-seq data analysis to decipher differential gene expression profiles and differential pathway expression exist, we still lack methods to learn differential regulatory disease mechanisms directly from the single-cell data. Here, we provide a new methodology, named DiNiro, to unravel such mechanisms de novo and report them as small, easily interpretable transcriptional regulatory network modules. We demonstrate that DiNiro is able to uncover novel, relevant, and deep mechanistic models that not just predict but explain differential cellular gene expression programs. DiNiro is available at https://exbio.wzw.tum.de/diniro/.

Cigarette smoke preferentially induces full length ACE2 expression in differentiated primary human airway cultures but does not alter the efficiency of cellular SARS-CoV-2 infection

Cigarette smoking has many serious negative health consequences. The relationship between smoking and SARS-CoV-2 infection is controversial, specifically whether smokers are at increased risk of infection. We investigated the impact of cigarette smoke on ACE2 isoform expression and SARS-CoV-2 infection in differentiated primary human bronchial epithelial cells at the air-liquid-interface (ALI). We assessed the expression of ACE2 in response to CSE and therapeutics reported to modulate ACE2. We exposed ALI cultures to cigarette smoke extract (CSE) and then infected them with SARS-CoV-2. We measured cellular infection using flow cytometry and whole-transwell immunofluorescence. We found that CSE increased expression of full-length ACE2 (flACE2) but did not alter the expression of a Type I-interferon sensitive truncated isoform (dACE2) that lacks the capacity to bind SARS-CoV-2. CSE did not have a significant impact on key mediators of the innate immune response. Importantly, we show that, despite the increase in flACE2, CSE did not alter airway cell infection after CSE exposure. We found that nicotine does not significantly alter flACE2 expression but that NRF2 agonists do lead to an increase in flACE2 expression. This increase was not associated with an increase in SARS-CoV-2 infection. Our results are consistent with the epidemiological data suggesting that current smokers do not have an excess of SARS-CoV-2 infection. but that those with chronic respiratory or cardiovascular disease are more vulnerable to severe COVID-19. They suggest that, in differentiated conducting airway cells, flACE2 expression levels may not limit airway SARS-CoV-2 infection.

The lung employs an intrinsic surfactant-mediated inflammatory response for viral defense

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) causes an acute respiratory distress syndrome (ARDS) that resembles surfactant deficient RDS. Using a novel multi-cell type, human induced pluripotent stem cell (hiPSC)-derived lung organoid (LO) system, validated against primary lung cells, we found that inflammatory cytokine/chemokine production and interferon (IFN) responses are dynamically regulated autonomously within the lung following SARS-CoV-2 infection, an intrinsic defense mechanism mediated by surfactant proteins (SP). Single cell RNA sequencing revealed broad infectability of most lung cell types through canonical (ACE2) and non-canonical (endocytotic) viral entry routes. SARS-CoV-2 triggers rapid apoptosis, impairing viral dissemination. In the absence of surfactant protein B (SP-B), resistance to infection was impaired and cytokine/chemokine production and IFN responses were modulated. Exogenous surfactant, recombinant SP-B, or genomic correction of the SP-B deletion restored resistance to SARS-CoV-2 and improved viability.

Human Coronavirus Cell Receptors Provide Challenging Therapeutic Targets

Coronaviruses interact with protein or carbohydrate receptors through their spike proteins to infect cells. Even if the known protein receptors for these viruses have no evolutionary relationships, they do share ontological commonalities that the virus might leverage to exacerbate the pathophysiology. ANPEP/CD13, DPP IV/CD26, and ACE2 are the three protein receptors that are known to be exploited by several human coronaviruses. These receptors are moonlighting enzymes involved in several physiological processes such as digestion, metabolism, and blood pressure regulation; moreover, the three proteins are expressed in kidney, intestine, endothelium, and other tissues/cell types. Here, we spot the commonalities between the three enzymes, the physiological functions of the enzymes are outlined, and how blocking either enzyme results in systemic deregulations and multi-organ failures via viral infection or therapeutic interventions is addressed. It can be difficult to pinpoint any coronavirus as the target when creating a medication to fight them, due to the multiple processes that receptors are linked to and their extensive expression.

Risk Factors of Severe COVID-19: A Review of Host, Viral and Environmental Factors

The clinical course and outcome of COVID-19 are highly variable, ranging from asymptomatic infections to severe disease and death. Understanding the risk factors of severe COVID-19 is relevant both in the clinical setting and at the epidemiological level. Here, we provide an overview of host, viral and environmental factors that have been shown or (in some cases) hypothesized to be associated with severe clinical outcomes. The factors considered in detail include the age and frailty, genetic polymorphisms, biological sex (and pregnancy), co- and superinfections, non-communicable comorbidities, immunological history, microbiota, and lifestyle of the patient; viral genetic variation and infecting dose; socioeconomic factors; and air pollution. For each category, we compile (sometimes conflicting) evidence for the association of the factor with COVID-19 outcomes (including the strength of the effect) and outline possible action mechanisms. We also discuss the complex interactions between the various risk factors.

Transmission of Human Influenza A Virus in Pigs Selects for Adaptive Mutations on the HA Gene

Influenza A viruses (FLUAV) cause respiratory diseases in many host species, including humans and pigs. The spillover of FLUAV between swine and humans has been a concern for both public health and the swine industry. With the emergence of the triple reassortant internal gene (TRIG) constellation, establishment of human-origin FLUAVs in pigs has become more common, leading to increased viral diversity. However, little is known about the adaptation processes that are needed for a human-origin FLUAV to transmit and become established in pigs. We generated a reassortant FLUAV (VIC11pTRIG) containing surface gene segments from a human FLUAV strain and internal gene segments from the 2009 pandemic and TRIG FLUAV lineages and demonstrated that it can replicate and transmit in pigs. Sequencing and variant analysis identified three mutants that emerged during replication in pigs, which were mapped near the receptor binding site of the hemagglutinin (HA). The variants replicated more efficiently in differentiated swine tracheal cells compared to the virus containing the wildtype human-origin HA, and one of them was present in all contact pigs. These results show that variants are selected quickly after replication of human-origin HA in pigs, leading to improved fitness in the swine host, likely contributing to transmission. IMPORTANCE Influenza A viruses cause respiratory disease in several species, including humans and pigs. The bidirectional transmission of FLUAV between humans and pigs plays a significant role in the generation of novel viral strains, greatly impacting viral epidemiology. However, little is known about the evolutionary processes that allow human FLUAV to become established in pigs. In this study, we generated reassortant viruses containing human seasonal HA and neuraminidase (NA) on different constellations of internal genes and tested their ability to replicate and transmit in pigs. We demonstrated that a virus containing a common internal gene constellation currently found in U.S. swine was able to transmit efficiently via the respiratory route. We identified a specific amino acid substitution that was fixed in the respiratory contact pigs that was associated with improved replication in primary swine tracheal epithelial cells, suggesting it was crucial for the transmissibility of the human virus in pigs.

Hippo signaling pathway activation during SARS-CoV-2 infection contributes to host antiviral response

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), responsible for the Coronavirus Disease 2019 (COVID-19) pandemic, causes respiratory failure and damage to multiple organ systems. The emergence of viral variants poses a risk of vaccine failures and prolongation of the pandemic. However, our understanding of the molecular basis of SARS-CoV-2 infection and subsequent COVID-19 pathophysiology is limited. In this study, we have uncovered a critical role for the evolutionarily conserved Hippo signaling pathway in COVID-19 pathogenesis. Given the complexity of COVID-19-associated cell injury and immunopathogenesis processes, we investigated Hippo pathway dynamics in SARS-CoV-2 infection by utilizing COVID-19 lung samples and human cell models based on pluripotent stem cell-derived cardiomyocytes (PSC-CMs) and human primary lung air-liquid interface (ALI) cultures. SARS-CoV-2 infection caused activation of the Hippo signaling pathway in COVID-19 lung and in vitro cultures. Both parental and Delta variant of concern (VOC) strains induced Hippo pathway. The chemical inhibition and gene knockdown of upstream kinases MST1/2 and LATS1 resulted in significantly enhanced SARS-CoV-2 replication, indicating antiviral roles. Verteporfin, a pharmacological inhibitor of the Hippo pathway downstream transactivator, YAP, significantly reduced virus replication. These results delineate a direct antiviral role for Hippo signaling in SARS-CoV-2 infection and the potential for this pathway to be pharmacologically targeted to treat COVID-19.

New Insights into How JUUL™ Electronic Cigarette Aerosols and Aerosol Constituents Affect SARS-CoV-2 Infection of Human Bronchial Epithelial Cells

Background

The relationship between the use of tobacco products and SARS-CoV-2 infection is poorly understood and controversial. Most studies have been done with tobacco cigarettes, while few have examined the effect of electronic cigarettes (ECs) on SARS-CoV-2 infection. We tested the hypothesis that EC fluids and aerosols with high concentrations of nicotine promote SARS-COV-2 infection by increasing viral entry into human respiratory epithelial cells.

Methods

Responses of BEAS-2B cells to authentic JUUL™ aerosols or their individual constituents (propylene glycol (PG)/vegetable glycerin (VG) and nicotine) were compared using three exposure platforms: submerged culture, air-liquid-interface (ALI) exposure in a cloud chamber, and ALI exposure in a Cultex® system, which produces authentic heated EC aerosols. SARS-CoV-2 infection machinery was assessed using immunohistochemistry and Western blotting. Specifically, the levels of the SARS-CoV-2 receptor ACE2 (angiotensin converting enzyme 2) and a spike modifying enzyme, TMPRSS2 (transmembrane serine protease 2), were evaluated. Following each exposure, lentivirus pseudoparticles with spike protein and a green-fluorescent reporter were used to test viral penetration and the susceptibility of BEAS-2B cells to infection.

Results

Nicotine, EC fluids, and authentic JUUL™ aerosols increased both ACE2 levels and TMPRSS2 activity, which in turn increased viral particle entry into cells. While most data were in good agreement across the three exposure platforms, cells were more responsive to treatments when exposed at the ALI in the Cultex system, even though the exposures were brief and intermittent. In the Cultex system, PG/VG, PG/VG/nicotine, and JUUL™ aerosols significantly increased infection above clean air controls. However, both the PG/VG and JUUL™ treatments were significantly lower than nicotine/PG/VG. PG/VG increased infection only in the Cultex® system, which produces heated aerosol.

Conclusion

Our data are consistent with the conclusion that authentic JUUL™ aerosols or their individual constituents (nicotine or PG/VG) increase SARS-CoV-2 infection. The strong effect produced by nicotine was modulated in authentic JUUL aerosols, demonstrating the importance of studying mixtures and aerosols from actual EC products. These data support the idea that vaping increases the likelihood of contracting COVID-19.

Association between smoking and COVID-19 severity: A multicentre retrospective observational study

The relationship between smoking and coronavirus disease 2019 (COVID-19) severity remains unclear. This study aimed to investigate the effect of smoking status (current smoking and a smoking history) on the clinical severity of COVID-19. Data of all enrolled 588 patients, who were referred to 25 hospitals in Jiangsu province between January 10, 2020 and March 14, 2020, were retrospectively reviewed. Univariate and multivariate regression, random forest algorithms, and additive interaction were used to estimate the importance of selective predictor variables in the relationship between smoking and COVID-19 severity. In the univariate analysis, the proportion of patients with a current smoking status in the severe group was significantly higher than that in the non-severe group. In the multivariate analysis, current smoking remained a risk factor for severe COVID-19. Data from the interaction analysis showed a strong interaction between the number of comorbidities in patients with COVID-19 and smoking. However, no significant interaction was found between smoking and specific comorbidities, such as hypertension, diabetes, etc. In the random forest model, smoking history was ranked sixth in mean decrease accuracy. Active smoking may be significantly associated with an enhanced risk of COVID-19 progression towards severe disease. However, additional prospective studies are needed to clarify the complex relationship between smoking and COVID-19 severity.

Brief training in regulation of craving reduces cigarette smoking

INTRODUCTION

Craving is an important contributing factor in cigarette smoking and has been added as a diagnostic criterion for addiction in the DSM-5. Cognitive-behavioral therapy and other treatments that incorporate craving regulation strategies reduce smoking and the likelihood of relapse. Although this finding suggests that the regulation of craving is an important mechanism underlying smoking cessation, whether targeted interventions that train smokers to regulate craving can directly impact real-world smoking behaviors is unclear.

METHOD

Across two pilot studies (N = 33; N = 60), we tested whether a brief, computer-delivered training session in the cognitive regulation of craving altered subsequent smoking behaviors in daily life. The study first randomly assigned participants to either a no training (control) group, or one of two Regulation of Craving Training (ROC-T) conditions. Next, all participants came into the lab and those assigned to ROC-T conditions were trained to implement a cognitive strategy to regulate their craving, by either focusing on the negative consequences of smoking, or by distracting themselves. Then, these participants underwent ROC-T during which they practiced using the strategy to regulate their craving during cue exposure. The study subsequently assessed participants' smoking via daily diaries for 3-6 days, and via self-report up to 1-month follow-up.

RESULTS

Across both studies, ROC-T conditions were associated with significant reductions in average cigarettes smoked per day, with effects persisting through follow-up.

CONCLUSION

These results confirm that the regulation of craving is an important mechanism of smoking cessation, and can be targeted via easily administered training procedures, such as ROC-T.

The adverse inflammatory response of tobacco smoking in COVID-19 patients: biomarkers from proteomics and metabolomics

Whether tobacco smoking affects the occurrence and development of COVID-19 is still a controversial issue, and potential biomarkers to predict the adverse outcomes of smoking in the progression of COVID-19 patients have not yet been elucidated. To further uncover their linkage and explore the effective biomarkers, three proteomics and metabolomics databases (i.e. smoking status, COVID-19 status, and basic information of population) from human serum proteomic and metabolomic levels were established by literature search. Bioinformatics analysis was then performed to analyze the interactions of proteins or metabolites among the above three databases and their biological effects. Potential confounding factors (age, BMI, and gender) were controlled to improve the reliability. The obtained data indicated that smoking may increase the relative risk of conversion from non-severe to severe COVID-19 patients by inducing the dysfunctional immune response. Seven interacting proteins (C8A, LBP, FCN2, CRP, SAA1, SAA2, and VTN) were found to promote the deterioration of COVID-19 by stimulating the complement pathway and macrophage phagocytosis as well as inhibiting the associated negative regulatory pathways, which can be biomarkers to reflect and predict adverse outcomes in smoking COVID-19 patients. Three crucial pathways related to immunity and inflammation, including tryptophan, arginine, and glycerophospholipid metabolism, were considered to affect the effect of smoking on the adverse outcomes of COVID-19 patients. Our study provides novel evidence and corresponding biomarkers as potential predictors of severe disease progression in smoking COVID-19 patients, which is of great significance for preventing further deterioration in these patients.

Hallmarks of Severe COVID-19 Pathogenesis: A Pas de Deux Between Viral and Host Factors

Two years into Coronavirus Disease 2019 (COVID-19) pandemic, a comprehensive characterization of the pathogenesis of severe and critical forms of COVID-19 is still missing. While a deep dysregulation of both the magnitude and functionality of innate and adaptive immune responses have been described in severe COVID-19, the mechanisms underlying such dysregulations are still a matter of scientific debate, in turn hampering the identification of new therapies and of subgroups of patients that would most benefit from individual clinical interventions. Here we review the current understanding of viral and host factors that contribute to immune dysregulation associated with COVID-19 severity in the attempt to unfold and broaden the comprehension of COVID-19 pathogenesis and to define correlates of protection to further inform strategies of targeted therapeutic interventions.

Mitoquinone mesylate targets SARS-CoV-2 infection in preclinical models

To date, there is no effective oral antiviral against SARS-CoV-2 that is also anti-inflammatory. Herein, we show that the mitochondrial antioxidant mitoquinone/mitoquinol mesylate (Mito-MES), a dietary supplement, has potent antiviral activity against SARS-CoV-2 and its variants of concern in vitro and in vivo . Mito-MES had nanomolar in vitro antiviral potency against the Beta and Delta SARS-CoV-2 variants as well as the murine hepatitis virus (MHV-A59). Mito-MES given in SARS-CoV-2 infected K18-hACE2 mice through oral gavage reduced viral titer by nearly 4 log units relative to the vehicle group. We found in vitro that the antiviral effect of Mito-MES is attributable to its hydrophobic dTPP+ moiety and its combined effects scavenging reactive oxygen species (ROS), activating Nrf2 and increasing the host defense proteins TOM70 and MX1. Mito-MES was efficacious reducing increase in cleaved caspase-3 and inflammation induced by SARS-CoV2 infection both in lung epithelial cells and a transgenic mouse model of COVID-19. Mito-MES reduced production of IL-6 by SARS-CoV-2 infected epithelial cells through its antioxidant properties (Nrf2 agonist, coenzyme Q10 moiety) and the dTPP moiety. Given established safety of Mito-MES in humans, our results suggest that Mito-MES may represent a rapidly applicable therapeutic strategy that can be added in the therapeutic arsenal against COVID-19. Its potential long-term use by humans as diet supplement could help control the SARS-CoV-2 pandemic, especially in the setting of rapidly emerging SARS-CoV-2 variants that may compromise vaccine efficacy.

One-Sentence Summary

Mitoquinone/mitoquinol mesylate has potent antiviral and anti-inflammatory activity in preclinical models of SARS-CoV-2 infection.

Predictors of COVID-19 perceived susceptibility: insights from population-based self-reported survey during lockdown in the United States

BACKGROUND

The COVID-19 pandemic during lockdown has highlighted the importance of identifying individuals most at risk of infection with SARS-CoV-2, underscoring the need to assess factors contributing to susceptibility to disease. With the rapidly evolving nature of the pandemic and its new variants, there is an inadequate understanding on whether there are certain factors such as a specific symptom or collection of symptoms that combined with life-style behaviors may be useful to predict susceptibility. The study aims to explore such factors from pre-vaccination data to guide public health response to potential new waves.

METHODS

An anonymous electronic survey was distributed through social media during the lockdown period in the United States from April to June 2020. Respondents were questioned regarding COVID testing, presenting symptoms, demographic information, comorbidities, and confirmation of COVID-19 test results. Stepwise logistic regression was used to identify predictors for COVID-19 perceived susceptibility. Selected classifiers were assessed for prediction performance using area under receiver operating characteristic (AUROC) curve analysis.

RESULTS

A total of 130 participants deemed as susceptible because they self-reported their perception of having COVID-19 (but without the evidence of positive test) were compared with 130 individuals with documented negative test results. Participants had a mean age of 45 years, and 165 (63%) were female. Final multivariable model showed significant associations with perceived susceptibility for the following variables: fever (OR:33.5; 95%CI: 3.9,85.9), body ache (OR:3.0; 95%CI:1.1,6.4), contact history (OR:2.7; 95%CI:1.1,6.4), age> 50 (OR:2.7; 95%CI:1.1, 6.6) and smoking (OR:3.3; 95%CI: 1.2,9.1) after adjusting for other symptoms and presence of comorbid conditions. The AUROC ranged from poor to fair (0.65-0.76) for cluster of symptoms but improved to a good model (AUROC = 0.803) after inclusion of sociodemographic and lifestyle behaviors e.g., age and smoking tobacco.

CONCLUSIONS

Fever and body aches suggest association with perceived COVID-19 susceptibility in the presence of demographic and lifestyle behaviors. Using other constitutional and respiratory symptoms with fever and body aches, the parsimonious classifier correctly predicts 80.3% of COVID-19 perceived susceptibility. A larger cohort of respondents will be needed to study and refine classifier performance in future lockdowns and with expected surge of new variants of COVID-19 pandemic.

Three-dimensional models of the lung: past, present and future: a mini review

Respiratory diseases are a major reason for death in both men and women worldwide. The development of therapies for these diseases has been slow and the lack of relevant human models to understand lung biology inhibits therapeutic discovery. The lungs are structurally and functionally complex with many different cell types which makes designing relevant lung models particularly challenging. The traditional two-dimensional (2D) cell line cultures are, therefore, not a very accurate representation of the in vivo lung tissue. The recent development of three-dimensional (3D) co-culture systems, popularly known as organoids/spheroids, aims to bridge the gap between 'in-dish' and 'in-tissue' cell behavior. These 3D cultures are modeling systems that are widely divergent in terms of culturing techniques (bottom-up/top-down) that can be developed from stem cells (adult/embryonic/pluripotent stem cells), primary cells or from two or more types of cells, to build a co-culture system. Lung 3D models have diverse applications including the understanding of lung development, lung regeneration, disease modeling, compound screening, and personalized medicine. In this review, we discuss the different techniques currently being used to generate 3D models and their associated cellular and biological materials. We further detail the potential applications of lung 3D cultures for disease modeling and advances in throughput for drug screening.

Hippo Signaling Pathway Activation during SARS-CoV-2 Infection Contributes to Host Antiviral Response

SARS-CoV-2, responsible for the COVID-19 pandemic, causes respiratory failure and damage to multiple organ systems. The emergence of viral variants poses a risk of vaccine failures and prolongation of the pandemic. However, our understanding of the molecular basis of SARS-CoV-2 infection and subsequent COVID-19 pathophysiology is limited. In this study, we have uncovered a critical role for the evolutionarily conserved Hippo signaling pathway in COVID-19 pathogenesis. Given the complexity of COVID-19 associated cell injury and immunopathogenesis processes, we investigated Hippo pathway dynamics in SARS-CoV-2 infection by utilizing COVID-19 lung samples, and human cell models based on pluripotent stem cell-derived cardiomyocytes (PSC-CMs) and human primary lung air-liquid interface (ALI) cultures. SARS-CoV-2 infection caused activation of the Hippo signaling pathway in COVID-19 lung and in vitro cultures. Both parental and Delta variant of concern (VOC) strains induced Hippo pathway. The chemical inhibition and gene knockdown of upstream kinases MST1/2 and LATS1 resulted in significantly enhanced SARS-CoV-2 replication, indicating antiviral roles. Verteporfin a pharmacological inhibitor of the Hippo pathway downstream transactivator, YAP, significantly reduced virus replication. These results delineate a direct antiviral role for Hippo signaling in SARS-CoV-2 infection and the potential for this pathway to be pharmacologically targeted to treat COVID-19.

Topical TMPRSS2 inhibition prevents SARS-CoV-2 infection in differentiated human airway cultures

BACKGROUND

There are limited effective prophylactic/early treatments for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Viral entry requires spike protein binding to the angiotensin-converting enzyme-2 receptor and cleavage by transmembrane serine protease 2 (TMPRSS2), a cell surface serine protease. Targeting of TMPRSS2 by either androgen blockade or direct inhibition is in clinical trials in early SARS-CoV-2 infection.

METHODS

We used differentiated primary human airway epithelial cells at the air-liquid interface to test the impact of targeting TMPRSS2 on the prevention of SARS-CoV-2 infection.

RESULTS

We first modelled the systemic delivery of compounds. Enzalutamide, an oral androgen receptor antagonist, had no impact on SARS-CoV-2 infection. By contrast, camostat mesylate, an orally available serine protease inhibitor, blocked SARS-CoV-2 entry. However, oral camostat is rapidly metabolised in the circulation, with poor airway bioavailability. We therefore modelled local airway administration by applying camostat to the apical surface of differentiated airway cultures. We demonstrated that a brief exposure to topical camostat effectively restricts SARS-CoV-2 infection.

CONCLUSION

These experiments demonstrate a potential therapeutic role for topical camostat for pre- or post-exposure prophylaxis of SARS-CoV-2, which can now be evaluated in a clinical trial.

Angiotensin-converting enzyme 2 in peripheral lung club cells modulates the susceptibility to SARS-CoV-2 in chronic obstructive pulmonary disease

Accumulating evidence has confirmed that chronic obstructive pulmonary disease (COPD) is a risk factor for development of severe pathological changes in the peripheral lungs of patients with COVID-19. However, the underlying molecular mechanisms remain unclear. Because bronchiolar club cells are crucial for maintaining small airway homeostasis, we sought to explore whether the altered susceptibility to SARS-CoV-2 infection of the club cells might have contributed to the severe COVID-19 pneumonia in COPD patients. Our investigation on the quantity and distribution patterns of angiotensin-converting enzyme 2 (ACE2) in airway epithelium via immunofluorescence staining revealed that the mean fluorescence intensity of the ACE2-positive epithelial cells was significantly higher in club cells than those in other epithelial cells (including ciliated cells, basal cells, goblet cells, neuroendocrine cells, and alveolar type 2 cells). Compared with nonsmokers, the median percentage of club cells in bronchiolar epithelium and ACE2-positive club cells was significantly higher in COPD patients. In vitro, SARS-CoV-2 infection (at a multiplicity of infection of 1.0) of primary small airway epithelial cells, cultured on air-liquid interface, confirmed a higher percentage of infected ACE2-positive club cells in COPD patients than in nonsmokers. Our findings have indicated the role of club cells in modulating the pathogenesis of SARS-CoV-2-related severe pneumonia and the poor clinical outcomes, which may help physicians to formulate a novel therapeutic strategy for COVID-19 patients with coexisting COPD.

Mechanisms of Lung Injury Induced by SARS-CoV-2 Infection

The lung is the major target organ of SARS-CoV-2 infection, which causes COVID-19. Here, we outline the multistep mechanisms of lung epithelial and endothelial injury induced by SARS-CoV-2: direct viral infection, chemokine/cytokine-mediated damage, and immune cell-mediated lung injury. Finally, we discuss the recent progress in terms of antiviral therapeutics as well as the development of anti-inflammatory or immunomodulatory therapeutic approaches. This review also provides a systematic overview of the models for studying SARS-CoV-2 infection and discusses how an understanding of mechanisms of lung injury will help identify potential targets for future drug development to mitigate lung injury.

E-cigarette and food flavoring diacetyl alters airway cell morphology, inflammatory and antiviral response, and susceptibility to SARS-CoV-2

Diacetyl (DA) is an α-diketone that is used to flavor microwave popcorn, coffee, and e-cigarettes. Occupational exposure to high levels of DA causes impaired lung function and obstructive airway disease. Additionally, lower levels of DA exposure dampen host defenses in vitro. Understanding DA’s impact on lung epithelium is important for delineating exposure risk on lung health. In this study, we assessed the impact of DA on normal human bronchial epithelial cell (NHBEC) morphology, transcriptional profiles, and susceptibility to SARS-CoV-2 infection. Transcriptomic analysis demonstrated cilia dysregulation, an increase in hypoxia and sterile inflammation associated pathways, and decreased expression of interferon-stimulated genes after DA exposure. Additionally, DA exposure resulted in cilia loss and increased hyaluronan production. After SARS-CoV-2 infection, both genomic and subgenomic SARS-CoV-2 RNA were increased in DA vapor- compared to vehicle-exposed NHBECs. This work suggests that transcriptomic and physiologic changes induced by DA vapor exposure damage cilia and increase host susceptibility to SARS-CoV-2.

Symptoms COVID 19 Positive Vapers Compared to COVID 19 Positive Non-vapers

Objectives:

The purpose of the present study was to assess and describe the severity of symptoms reported by Covid-19 positive patients who vaped (smoked e-cigarettes) when compared to those who did not vape or smoke at the time of the diagnosis of Covid-19.

Methods:

Patients from this study are from a well-characterized patient cohort collected at Mayo Clinic between March 1, 2020 and February 28, 2021; with confirmed COVID-19 diagnosis defined as a positive result on reverse-transcriptase–polymerase-chain-reaction (RT-PCR) assays from nasopharyngeal swab specimens. Among the 1734 eligible patients, 289 patients reported current vaping. The cohort of vapers (N = 289) was age and gender matched to 1445 covid-19 positive patients who did not vape. The data analyzed included: date of birth, gender, ethnicity, race, marital status, as well as lifestyle history such as vaping and smoking and reported covid-19 symptoms experienced.

Results:

A logistic regression analysis was performed separately for each symptom using generalized estimating equations (GEE) with robust variance estimates in order to account for the 1:5 age, sex, and race matched set study design. Patients who vaped and developed Covid-19 infection were more likely to have chest pain or tightness (16% vs 10%, vapers vs non vapers, P = .005), chills (25% vs 19%, vapers vs non vapers, P = .0016), myalgia (39% vs 32%, vapers vs non vapers, P = .004), headaches (49% vs 41% vapers vs non vapers, P = .026), anosmia/dysgeusia (37% vs 30%, vapers vs non vapers, P = .009), nausea/vomiting/abdominal pain (16% vs 10%, vapers vs non vapers, P = .003), diarrhea (16% vs 10%, vapers vs non vapers, P = .004), and non-severe light-headedness (16% vs 9%, vapers vs non vapers, P < .001).

Conclusion:

Vapers experience higher frequency of covid-19 related symptoms when compared with age and gender matched non-vapers. Further work should examine the impact vaping has on post-covid symptom experience.

The seven constitutive respiratory defense barriers against SARS-CoV-2 infection

Before eliciting an adaptive immune response, SARS-CoV-2 must overcome seven constitutive respiratory defense barriers. The first is the mucus covering the respiratory tract's luminal surface, which entraps inhaled particles, including infectious agents, and eliminates them by mucociliary clearance. The second barrier comprises various components present in the airway lining fluid, the surfactants. Besides providing low surface tension that allows efficient gas exchange at the alveoli, surfactants inhibit the invasion of epithelial cells by respiratory viruses, enhance pathogen uptake by phagocytes, and regulate immune cells' functions. The respiratory tract microbiota constitutes the third defense barrier against SARS-CoV-2. It activates the innate and adaptive immune cells and elicits anti-infectious molecules such as secretory IgA antibodies, defensins, and interferons. The fourth defense barrier comprises the antimicrobial peptides defensins, and lactoferrin. They show direct antiviral activity, inhibit viral fusion, and modulate the innate and adaptive immune responses. Secretory IgA antibodies, the fifth defense barrier, besides protecting the local microbiota against noxious agents, also inhibit SARS-CoV-2 cell invasion. If the virus overcomes this barrier, it reaches its target, the respiratory epithelial cells. However, these cells also act as a defense barrier, the sixth one, since they hinder the virus' access to receptors and produce antiviral and immunomodulatory molecules such as interferons, lactoferrin, and defensins. Finally, the sensing of the virus by the cells of innate immunity, the last constitutive defense barrier, elicits a cascade of signals that activate adaptive immune cells and may inhibit the development of productive infection. The subject of the present essay is discussing these mechanisms.

Delayed induction of type I and III interferons mediates nasal epithelial cell permissiveness to SARS-CoV-2

The nasal epithelium is a plausible entry point for SARS-CoV-2, a site of pathogenesis and transmission, and may initiate the host response to SARS-CoV-2. Antiviral interferon (IFN) responses are critical to outcome of SARS-CoV-2. Yet little is known about the interaction between SARS-CoV-2 and innate immunity in this tissue. Here we apply single-cell RNA sequencing and proteomics to a primary cell model of human nasal epithelium differentiated at air-liquid interface. SARS-CoV-2 demonstrates widespread tropism for nasal epithelial cell types. The host response is dominated by type I and III IFNs and interferon-stimulated gene products. This response is notably delayed in onset relative to viral gene expression and compared to other respiratory viruses. Nevertheless, once established, the paracrine IFN response begins to impact on SARS-CoV-2 replication. When provided prior to infection, recombinant IFNβ or IFNλ1 induces an efficient antiviral state that potently restricts SARS-CoV-2 viral replication, preserving epithelial barrier integrity. These data imply that the IFN-I/III response to SARS-CoV-2 initiates in the nasal airway and suggest nasal delivery of recombinant IFNs to be a potential chemoprophylactic strategy.

Human Stem Cell Models of SARS-CoV-2 Infection in the Cardiovascular System

The virus responsible for coronavirus disease 2019 (COVID-19), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has infected over 190 million people to date, causing a global pandemic. SARS-CoV-2 relies on binding of its spike glycoprotein to angiotensin-converting enzyme 2 (ACE2) for infection. In addition to fever, cough, and shortness of breath, severe cases of SARS-CoV-2 infection may result in the rapid overproduction of pro-inflammatory cytokines. This overactive immune response is known as a cytokine storm, which leads to several serious clinical manifestations such as acute respiratory distress syndrome and myocardial injury. Cardiovascular disorders such as acute coronary syndrome (ACS) and heart failure not only enhance disease progression at the onset of infection, but also arise in hospitalized patients with COVID-19. Tissue-specific differentiated cells and organoids derived from human pluripotent stem cells (hPSCs) serve as an excellent model to address how SARS-CoV-2 damages the lungs and the heart. In this review, we summarize the molecular basis of SARS-CoV-2 infection and the current clinical perspectives of the bidirectional relationship between the cardiovascular system and viral progression. Furthermore, we also address the utility of hPSCs as a dynamic model for SARS-CoV-2 research and clinical translation.

Impact of inhaled pollutants on response to viral infection in controlled exposures

Air pollutants are a major source of increased risk of disease, hospitalization, morbidity, and mortality worldwide. The respiratory tract is a primary target of potential concurrent exposure to both inhaled pollutants and pathogens, including viruses. Although there are various associative studies linking adverse outcomes to co- or subsequent exposures to inhaled pollutants and viruses, knowledge about causal linkages and mechanisms by which pollutant exposure may alter human respiratory responses to viral infection is more limited. In this article, we review what is known about the impact of pollutant exposure on antiviral host defense responses and describe potential mechanisms by which pollutants can alter the viral infection cycle. This review focuses on evidence from human observational and controlled exposure, ex vivo, and in vitro studies. Overall, there are a myriad of points throughout the viral infection cycle that inhaled pollutants can alter to modulate appropriate host defense responses. These alterations may contribute to observed increases in rates of viral infection and associated morbidity and mortality in areas of the world with high ambient pollution levels or in people using tobacco products. Although the understanding of mechanisms of interaction is advancing through controlled in vivo and in vitro exposure models, more studies are needed because emerging infectious pathogens, such as severe acute respiratory syndrome coronavirus 2, present a significant threat to public health.

Clinical characteristics of COVID-19 patients with complications: implications for management

Background:

A novel coronavirus disease 2019 (COVID-19) has caused outbreaks worldwide, and the number of cases is rapidly increasing through human-to-human transmission. Because of the greater transmission capacity and possible subsequent multi-organ damage caused by the virus, it is crucial to understand precisely and manage COVID-19 patients. However, the underlying differences in the clinical features of COVID-19 with and without comorbidities are not fully understood.

Aim:

The objective of this study was to identify the clinical features of COVID-19 patients with and without complications to guide treatment and predict the prognosis.

Method:

We collected the clinical characteristics of COVID-19 patients with and without different complications, including hypertension, cardiovascular disease and diabetes. Next, we performed a baseline comparison of each index and traced the dynamic changes in these factors during hospitalization to explore the potential associations.

Result:

A clinical index of differential expression was used for the regression to select top-ranking factors. The top-ranking clinical characteristics varied in each subgroup, such as indices of liver function, renal function and inflammatory markers. Among them, the indices of renal function were highly ranked in all subgroups and displayed significant differences during hospitalization.

Conclusion:

Organ functions of COVID-19 patients, particularly renal function, should be cautiously taken care of during management and might be a crucial factor for a poor prognosis of these patients with complications.

A comprehensive review of the analysis and integration of omics data for SARS-CoV-2 and COVID-19

Since the first report of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in December 2019, over 100 million people have been infected by COVID-19, millions of whom have died. In the latest year, a large number of omics data have sprung up and helped researchers broadly study the sequence, chemical structure and function of SARS-CoV-2, as well as molecular abnormal mechanisms of COVID-19 patients. Though some successes have been achieved in these areas, it is necessary to analyze and mine omics data for comprehensively understanding SARS-CoV-2 and COVID-19. Hence, we reviewed the current advantages and limitations of the integration of omics data herein. Firstly, we sorted out the sequence resources and database resources of SARS-CoV-2, including protein chemical structure, potential drug information and research literature resources. Next, we collected omics data of the COVID-19 hosts, including genomics, transcriptomics, microbiology and potential drug information data. And subsequently, based on the integration of omics data, we summarized the existing data analysis methods and the related research results of COVID-19 multi-omics data in recent years. Finally, we put forward SARS-CoV-2 (COVID-19) multi-omics data integration research direction and gave a case study to mine deeper for the disease mechanisms of COVID-19.

Recent Advances of COVID-19 Modeling Based on Regenerative Medicine

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has caused a pandemic since December 2019 that originated in Wuhan, China. Soon after that, the world health organization declared Coronavirus disease-2019 a global health concern. SARS-CoV-2 is responsible for a lethal respiratory infection as well as the involvement of other organs due to its large tropism spectrum such as neurologic, cardiovascular, endocrine, gastrointestinal, and renal systems. Since the behavior of the virus is not fully understood, a new manifestation of the infection is revealed every day. In order to be able to design more efficient drugs and vaccines to treat the infection, finding out the exact mechanism of pathogenicity would be necessary. Although there have been some big steps toward understanding the relevant process, there are still some deficiencies in this field. Accordingly, regenerative medicine (RM), can offer promising opportunities in discovering the exact mechanisms and specific treatments. For instance, since it is not always possible to catch the pathophysiology mechanisms in human beings, several modeling methods have been introduced in this field that can be studied in three main groups: stem cell-based models, organoids, and animal models. Regarding stem cell-based models, induced pluripotent stem cells are the major study subjects, which are generated by reprogramming the somatic stem cells and then directing them into different adult cell populations to study their behavior toward the infection. In organoid models, different cell lines can be guided to produce a 3D structure including liver, heart, and brain-like platforms. Among animal models, mice are the most common species in this field. However, in order for mice models to be permissive to the virus, angiotensin-converting enzyme 2 receptors, the main receptor involved in the pathogenicity of the virus, should be introduced to the host cells through different methods. Here, the current known mechanism of SARS-CoV-2 infection, different suggested models, the specific response toward different manipulation as well as challenges and shortcomings in each case have been reviewed. Finally, we have tried to provide a quick summary of the present available RM-based models for SARS-CoV-2 infection, as an essential part of developing drugs, for future therapeutic goals.

Determinants of SARS-CoV-2 entry and replication in airway mucosal tissue and susceptibility in smokers

Understanding viral tropism is an essential step toward reducing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission, decreasing mortality from coronavirus disease 2019 (COVID-19) and limiting opportunities for mutant strains to arise. Currently, little is known about the extent to which distinct tissue sites in the human head and neck region and proximal respiratory tract selectively permit SARS-CoV-2 infection and replication. In this translational study, we discover key variabilities in expression of angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2), essential SARS-CoV-2 entry factors, among the mucosal tissues of the human proximal airways. We show that SARS-CoV-2 infection is present in all examined head and neck tissues, with a notable tropism for the nasal cavity and tracheal mucosa. Finally, we uncover an association between smoking and higher SARS-CoV-2 viral infection in the human proximal airway, which may explain the increased susceptibility of smokers to developing severe COVID-19. This is at least partially explained by differences in interferon (IFN)-β1 levels between smokers and non-smokers.

Therapeutic application of estrogen for COVID-19: Attenuation of SARS-CoV-2 spike protein and IL-6 stimulated, ACE2-dependent NOX2 activation, ROS production and MCP-1 upregulation in endothelial cells

The outbreak of COVID-19 has remained uncontained with urgent need for robust therapeutics. We have previously reported sex difference of COVID-19 for the first time indicating male predisposition. Males are more susceptible than females, and more often to develop into severe cases with higher mortality. This predisposition is potentially linked to higher prevalence of cigarette smoking. Nonetheless, we found for the first time that cigarette smoking extract (CSE) had no effect on angiotensin converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) expression in endothelial cells. The otherwise observed worse outcomes in smokers is likely linked to baseline respiratory diseases associated with chronic smoking. Instead, we hypothesized that estrogen mediated protection might underlie lower morbidity, severity and mortality of COVID-19 in females. Of note, endothelial inflammation and barrier dysfunction are major mediators of disease progression, and development of acute respiratory distress syndrome (ARDS) and multi-organ failure in patients with COVID-19. Therefore, we investigated potential protective effects of estrogen on endothelial cells against oxidative stress induced by interleukin-6 (IL-6) and SARS-CoV-2 spike protein (S protein). Indeed, 17β-estradiol completely reversed S protein-induced selective activation of NADPH oxidase isoform 2 (NOX2) and reactive oxygen species (ROS) production that are ACE2-dependent, as well as ACE2 upregulation and induction of pro-inflammatory gene monocyte chemoattractant protein-1 (MCP-1) in endothelial cells to effectively attenuate endothelial dysfunction. Effects of IL-6 on activating NOX2-dependent ROS production and upregulation of MCP-1 were also completely attenuated by 17β-estradiol. Of note, co-treatment with CSE had no additional effects on S protein stimulated endothelial oxidative stress, confirming that current smoking status is likely unrelated to more severe disease in chronic smokers. These data indicate that estrogen can serve as a novel therapy for patients with COVID-19 via inhibition of initial viral responses and attenuation of cytokine storm induced endothelial dysfunction, to substantially alleviate morbidity, severity and mortality of the disease, especially in men and post-menopause women. Short-term administration of estrogen can therefore be readily applied to the clinical management of COVID-19 as a robust therapeutic option.