Pathogenesis of influenza-induced acute respiratory distress syndrome

Lactobacillus plantarum GUANKE modulate anti-viral function of dendritic cells in mice

GUANKE is a Lactobacillus plantarum isolated from the feces of healthy volunteer. We have previously shown that GUANKE enhances the efficacy of the SARS-CoV-2 vaccine and prolongs the duration of vaccine protection by upregulating the IFN pathway and T and B lymphocyte functions of the host. The purpose of this study was to evaluate the protective effects and mechanism of oral administration of Lactobacillus plantarum GUANKE in the influenza (A virus A/Puerto Rico/8/34) infection mouse model. In our experiment, oral administration of GUANKE significantly decreased viral load and increased tight junction proteins expression in lung tissues of influenza-infected mice. After GUANKE was co-cultured with mBMDCs in vitro, mBMDCs' maturity and antiviral ability were enhanced, and matured mBMDCs induced polarization of naïve CD4+ T cells into T helper (Th) 1 cells. Adoptive transfer of GUANKE-treated mBMDCs could protect mice from influenza infections. This study suggests that oral administration of Lactobacillus plantarum GUANKE could provide protection against influenza infection in mice, and this protective effect may be mediated, at least in part, by dendritic cells.

Molecular Basis for Surface-Initiated Non-Thrombin-Generated Clot Formation Following Viral Infection

In this paper, we propose a model that connects two standard inflammatory responses to viral infection, namely, elevation of fibrinogen and the lipid drop shower, to the initiation of non-thrombin-generated clot formation. In order to understand the molecular basis for the formation of non-thrombin-generated clots following viral infection, human epithelial and Madin-Darby Canine Kidney (MDCK, epithelial) cells were infected with H1N1, OC43, and adenovirus, and conditioned media was collected, which was later used to treat human umbilical vein endothelial cells and human lung microvascular endothelial cells. After direct infection or after exposure to conditioned media from infected cells, tissue surfaces of both epithelial and endothelial cells, exposed to 8 mg/mL fibrinogen, were observed to initiate fibrillogenesis in the absence of thrombin. No fibers were observed after direct viral exposure of the endothelium or when the epithelium cells were exposed to SARS-CoV-2 isolated spike proteins. Heating the conditioned media to 60 °C had no effect on fibrillogenesis, indicating that the effect was not enzymatic but rather associated with relatively thermally stable inflammatory factors released soon after viral infection. Spontaneous fibrillogenesis had previously been reported and interpreted as being due to the release of the alpha C domains due to strong interactions of the interior of the fibrinogen molecule in contact with hydrophobic material surfaces rather than cleavage of the fibrinopeptides. Contact angle goniometry and immunohistochemistry were used to demonstrate that the lipids produced within the epithelium and released in the conditioned media, probably after the death of infected epithelial cells, formed a hydrophobic residue responsible for fibrillogenesis. Hence, the standard inflammatory response constitutes the ideal conditions for surface-initiated clot formation.

Vascular endothelial-derived SPARCL1 exacerbates viral pneumonia through pro-inflammatory macrophage activation

Inflammation induced by lung infection is a double-edged sword, moderating both anti-viral and immune pathogenesis effects; the mechanism of the latter is not fully understood. Previous studies suggest the vasculature is involved in tissue injury. Here, we report that expression of Sparcl1, a secreted matricellular protein, is upregulated in pulmonary capillary endothelial cells (EC) during influenza-induced lung injury. Endothelial overexpression of SPARCL1 promotes detrimental lung inflammation, with SPARCL1 inducing 'M1-like' macrophages and related pro-inflammatory cytokines, while SPARCL1 deletion alleviates these effects. Mechanistically, SPARCL1 functions through TLR4 on macrophages in vitro, while TLR4 inhibition in vivo ameliorates excessive inflammation caused by endothelial Sparcl1 overexpression. Finally, SPARCL1 expression is increased in lung ECs from COVID-19 patients when compared with healthy donors, while fatal COVID-19 correlates with higher circulating SPARCL1 protein levels in the plasma. Our results thus implicate SPARCL1 as a potential prognosis biomarker for deadly COVID-19 pneumonia and as a therapeutic target for taming hyperinflammation in pneumonia.

In Vivo Immune-Modulatory Activity of Lefamulin in an Influenza Virus A (H1N1) Infection Model in Mice

Lefamulin is a first-in-class systemic pleuromutilin antimicrobial and potent inhibitor of bacterial translation, and the most recent novel antimicrobial approved for the treatment of community-acquired pneumonia (CAP). It exhibits potent antibacterial activity against the most prevalent bacterial pathogens that cause typical and atypical pneumonia and other infectious diseases. Early studies indicate additional anti-inflammatory activity. In this study, we further investigated the immune-modulatory activity of lefamulin in the influenza A/H1N1 acute respiratory distress syndrome (ARDS) model in BALB/c mice. Comparators included azithromycin, an anti-inflammatory antimicrobial, and the antiviral oseltamivir. Lefamulin significantly decreased the total immune cell infiltration, specifically the neutrophils, inflammatory monocytes, CD4+ and CD8+ T-cells, NK cells, and B-cells into the lung by Day 6 at both doses tested compared to the untreated vehicle control group (placebo), whereas azithromycin and oseltamivir did not significantly affect the total immune cell counts at the tested dosing regimens. Bronchioalveolar lavage fluid concentrations of pro-inflammatory cytokines and chemokines including TNF-α, IL-6, IL-12p70, IL-17A, IFN-γ, and GM-CSF were significantly reduced, and MCP-1 concentrations were lowered (not significantly) by lefamulin at the clinically relevant 'low' dose on Day 3 when the viral load peaked. Similar effects were also observed for oseltamivir and azithromycin. Lefamulin also decreased the viral load (TCID50) by half a log10 by Day 6 and showed positive effects on the gross lung pathology and survival. Oseltamivir and lefamulin were efficacious in the suppression of the development of influenza-induced bronchi-interstitial pneumonia, whereas azithromycin did not show reduced pathology at the tested treatment regimen. The observed anti-inflammatory and immune-modulatory activity of lefamulin at the tested treatment regimens highlights a promising secondary pharmacological property of lefamulin. While these results require confirmation in a clinical trial, they indicate that lefamulin may provide an immune-modulatory activity beyond its proven potent antibacterial activity. This additional activity may benefit CAP patients and potentially prevent acute lung injury (ALI) and ARDS.

Next generation single-domain antibodies against respiratory zoonotic RNA viruses

The global impact of zoonotic viral outbreaks underscores the pressing need for innovative antiviral strategies, particularly against respiratory zoonotic RNA viruses. These viruses possess a high potential to trigger future epidemics and pandemics due to their high mutation rate, broad host range and efficient spread through airborne transmission. Recent pandemics caused by coronaviruses and influenza A viruses underscore the importance of developing targeted antiviral strategies. Single-domain antibodies (sdAbs), originating from camelids, also known as nanobodies or VHHs (Variable Heavy domain of Heavy chain antibodies), have emerged as promising tools to combat current and impending zoonotic viral threats. Their unique structure, coupled with attributes like robustness, compact size, and cost-effectiveness, positions them as strong alternatives to traditional monoclonal antibodies. This review describes the pivotal role of sdAbs in combating respiratory zoonotic viruses, with a primary focus on enhancing sdAb antiviral potency through optimization techniques and diverse administration strategies. We discuss both the promises and challenges within this dynamically growing field.

Endothelial cell dynamics in sepsis-induced acute lung injury and acute respiratory distress syndrome: pathogenesis and therapeutic implications

Sepsis, a prevalent critical condition in clinics, continues to be the leading cause of death from infections and a global healthcare issue. Among the organs susceptible to the harmful effects of sepsis, the lungs are notably the most frequently affected. Consequently, patients with sepsis are predisposed to developing acute lung injury (ALI), and in severe cases, acute respiratory distress syndrome (ARDS). Nevertheless, the precise mechanisms associated with the onset of ALI/ARDS remain elusive. In recent years, there has been a growing emphasis on the role of endothelial cells (ECs), a cell type integral to lung barrier function, and their interactions with various stromal cells in sepsis-induced ALI/ARDS. In this comprehensive review, we summarize the involvement of endothelial cells and their intricate interplay with immune cells and stromal cells, including pulmonary epithelial cells and fibroblasts, in the pathogenesis of sepsis-induced ALI/ARDS, with particular emphasis placed on discussing the several pivotal pathways implicated in this process. Furthermore, we discuss the potential therapeutic interventions for modulating the functions of endothelial cells, their interactions with immune cells and stromal cells, and relevant pathways associated with ALI/ARDS to present a potential therapeutic strategy for managing sepsis and sepsis-induced ALI/ARDS.

Triggering Degradation of Host Cellular Proteins for Robust Propagation of Influenza Viruses

Following infection, influenza viruses strive to establish a new host cellular environment optimized for efficient viral replication and propagation. Influenza viruses use or hijack numerous host factors and machinery not only to fulfill their own replication process but also to constantly evade the host's antiviral and immune response. For this purpose, influenza viruses appear to have formulated diverse strategies to manipulate the host proteins or signaling pathways. One of the most effective tactics is to specifically induce the degradation of the cellular proteins that are detrimental to the virus life cycle. Here, we summarize the cellular factors that are deemed to have been purposefully degraded by influenza virus infection. The focus is laid on the mechanisms for the protein ubiquitination and degradation in association with facilitated viral amplification. The fate of influenza viral infection of hosts is heavily reliant on the outcomes of the interplay between the virus and the host antiviral immunity. Understanding the processes of how influenza viruses instigate the protein destruction pathways could provide a foundation for the development of advanced therapeutics to target host proteins and conquer influenza.

Clinical characteristics and assessment of risk factors in patients with influenza A-induced severe pneumonia after the prevalence of SARS-CoV-2

Purpose

The aim of this study is to describe the novel epidemiological and clinical characteristics of influenza A-induced severe pneumonia occurring after the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and to further assess its potential risk factors for mortality.

Methods

We retrospectively studied the consecutive case series of 30 patients with confirmed influenza A-induced severe pneumonia treated in the intensive care unit at Dazhou Central Hospital in Sichuan, China, from March 1 to April 30, 2023. Logistic regression was used to analyze the independent risk factors, and receiver operating characteristic (ROC) curves were applied to evaluate the predictive efficacy of associated risk factors for mortality.

Results

The mortality rate was 33.3% in this study. Independent risk factors for mortality of patients were acute respiratory distress syndrome (ARDS) (p = 0.044) and septic shock (p = 0.012). ROC statistics for ARDS and septic shock to predict mortality in patients with influenza A-induced severe pneumonia demonstrated an area under the curve of 0.800 (sensitivity 80.0%, specificity 80.0%) and 0.825 (sensitivity 70.0%, specificity 95.0%), respectively.

Conclusion

ARDS and septic shock were the independent risk factors for mortality in patients with influenza A-induced severe pneumonia following the end of the SARS-CoV-2 pandemic. But high level of next generation sequencing reads Aspergillus coinfection, and comorbidities did not increase death risk of the study population.

Runx3 Regulates CD8+ T Cell Local Expansion and CD43 Glycosylation in Mice by H1N1 Influenza A Virus Infection

We have recently reported that transcription factor Runx3 is required for pulmonary generation of CD8+ cytotoxic T lymphocytes (CTLs) that play a crucial role in the clearance of influenza A virus (IAV). To understand the underlying mechanisms, we determined the effects of Runx3 knockout (KO) on CD8+ T cell local expansion and phenotypes using an inducible general Runx3 KO mouse model. We found that in contrast to the lungs, Runx3 general KO promoted enlargement of lung-draining mediastinal lymph node (mLN) and enhanced CD8+ and CD4+ T cell expansion during H1N1 IAV infection. We further found that Runx3 deficiency greatly inhibited core 2 O-glycosylation of selectin ligand CD43 on activated CD8+ T cells but minimally affected the cell surface expression of CD43, activation markers (CD44 and CD69) and cell adhesion molecules (CD11a and CD54). Runx3 KO had a minor effect on lung effector CD8+ T cell death by IAV infection. Our findings indicate that Runx3 differently regulates CD8+ T cell expansion in mLNs and lungs by H1N1 IAV infection. Runx3 is required for CD43 core 2 O-glycosylation on activated CD8+ T cells, and the involved Runx3 signal pathway may mediate CD8+ T cell phenotype for pulmonary generation of CTLs.

Viral Pneumonia: From Influenza to COVID-19

Respiratory viruses are increasingly recognized as a cause of community-acquired pneumonia (CAP). The implementation of new diagnostic technologies has facilitated their identification, especially in vulnerable population such as immunocompromised and elderly patients and those with severe cases of pneumonia. In terms of severity and outcomes, viral pneumonia caused by influenza viruses appears similar to that caused by non-influenza viruses. Although several respiratory viruses may cause CAP, antiviral therapy is available only in cases of CAP caused by influenza virus or respiratory syncytial virus. Currently, evidence-based supportive care is key to managing severe viral pneumonia. We discuss the evidence surrounding epidemiology, diagnosis, management, treatment, and prevention of viral pneumonia.

Utilizing network pharmacology and experimental validation to investigate the underlying mechanism of Denglao Qingguan decoction against HCoV-229E

Background

Denglao Qingguan decoction (DLQGD) has been extensively utilized for the treatment of colds, demonstrating significant therapeutic efficacy. Human Coronavirus 229E (HCoV-229E) is considered a crucial etiological agent of influenza. However, the specific impact and underlying mechanisms of DLQGD on HCoV-229E remain poorly understood.

Methods

Active ingredients and targets information of DLQGD were collected from Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP), literature search, and Swiss ADEM database. The Genecard database was used to collect HCoV-229E related targets. We built an "ingredient-target network" through Cytoscape. Protein - Protein interaction (PPI) networks were mapped using the String database. The Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) were enriched using the DAVID database. Then, we used molecular docking techniques to verify the binding activity between the core compounds and the core gene targets. Finally, in vitro experiments were conducted to validate DLQGD's antiviral activity against HCoV-229E and assess its anti-inflammatory effects.

Results

In total, we identified 227 active components in DLQGD. 18 key targets involved in its activity against HCoV-229E. Notably, the core active ingredients including quercetin, luteolin, kaempferol, β-sitosterol, and apigenin, and the core therapeutic targets were CXCL8, RELA, MAPK14, NFKB1, and CXCL10, all associated with HCoV-229E. KEGG enrichment results included IL-17 signaling pathway, Toll-like receptor signaling pathway, RIG-I-like receptor signaling pathway and so on. The core active ingredients and the core therapeutic targets and Human Aminopeptidase N (ANPEP) all showed good binding activity by molecular docking verification. In vitro, DLQGD exhibited anti-HCoV-229E activity and anti-inflammatory effects.

Conclusion

Our study suggests that DLQGD has both effects of anti-HCoV-229E and anti-inflammatory. The core active ingredients (quercetin, luteolin, kaempferol, β-sitosterol, apigenin) and the core therapeutic targets (CXCL8, RELA, MAPK14, NFKB1, CXCL10) may play key roles in the pharmacological action of DLQGD against HCoV-229E.

Indole-3-carbinol attenuates lipopolysaccharide-induced acute respiratory distress syndrome through activation of AhR: role of CCR2+ monocyte activation and recruitment in the regulation of CXCR2+ neutrophils in the lungs

Introduction

Indole-3-carbinol (I3C) is found in cruciferous vegetables and used as a dietary supplement. It is known to act as a ligand for aryl hydrocarbon receptor (AhR). In the current study, we investigated the role of AhR and the ability of I3C to attenuate LPS-induced Acute Respiratory Distress Syndrome (ARDS).

Methods

To that end, we induced ARDS in wild-type C57BL/6 mice, Ccr2gfp/gfp KI/KO mice (mice deficient in the CCR2 receptor), and LyZcreAhRfl/fl mice (mice deficient in the AhR on myeloid linage cells). Additionally, mice were treated with I3C (65 mg/kg) or vehicle to investigate its efficacy to treat ARDS.

Results

I3C decreased the neutrophils expressing CXCR2, a receptor associated with neutrophil recruitment in the lungs. In addition, LPS-exposed mice treated with I3C revealed downregulation of CCR2+ monocytes in the lungs and lowered CCL2 (MCP-1) protein levels in serum and bronchoalveolar lavage fluid. Loss of CCR2 on monocytes blocked the recruitment of CXCR2+ neutrophils and decreased the total number of immune cells in the lungs during ARDS. In addition, loss of the AhR on myeloid linage cells ablated I3C-mediated attenuation of CXCR2+ neutrophils and CCR2+ monocytes in the lungs from ARDS animals. Interestingly, scRNASeq showed that in macrophage/monocyte cell clusters of LPS-exposed mice, I3C reduced the expression of CXCL2 and CXCL3, which bind to CXCR2 and are involved in neutrophil recruitment to the disease site.

Discussion

These findings suggest that CCR2+ monocytes are involved in the migration and recruitment of CXCR2+ neutrophils during ARDS, and the AhR ligand, I3C, can suppress ARDS through the regulation of immune cell trafficking.

Influenza A virus replicates productively in primary human kidney cells and induces factors and mechanisms related to regulated cell death and renal pathology observed in virus-infected patients

Introduction

Influenza A virus (IAV) infection can cause the often-lethal acute respiratory distress syndrome (ARDS) of the lung. Concomitantly, acute kidney injury (AKI) is frequently noticed during IAV infection, correlating with an increased mortality. The aim of this study was to elucidate the interaction of IAV with human kidney cells and, thereby, to assess the mechanisms underlying IAV-mediated AKI.

Methods

To investigate IAV effects on nephron cells we performed infectivity assays with human IAV, as well as with human isolates of either low or highly pathogenic avian IAV. Also, transcriptome and proteome analysis of IAV-infected primary human distal tubular kidney cells (DTC) was performed. Furthermore, the DTC transcriptome was compared to existing transcriptomic data from IAV-infected lung and trachea cells.

Results

We demonstrate productive replication of all tested IAV strains on primary and immortalized nephron cells. Comparison of our transcriptome and proteome analysis of H1N1-type IAV-infected human primary distal tubular cells (DTC) with existing data from H1N1-type IAV-infected lung and primary trachea cells revealed enrichment of specific factors responsible for regulated cell death in primary DTC, which could be targeted by specific inhibitors.

Discussion

IAV not only infects, but also productively replicates on different human nephron cells. Importantly, multi-omics analysis revealed regulated cell death as potential contributing factor for the clinically observed kidney pathology in influenza.

Nasal Delivery of Haemophilus haemolyticus Is Safe, Reduces Influenza Severity, and Prevents Development of Otitis Media in Mice

BACKGROUND

Despite vaccination, influenza and otitis media (OM) remain leading causes of illness. We previously found that the human respiratory commensal Haemophilus haemolyticus prevents bacterial infection in vitro and that the related murine commensal Muribacter muris delays OM development in mice. The observation that M muris pretreatment reduced lung influenza titer and inflammation suggests that these bacteria could be exploited for protection against influenza/OM.

METHODS

Safety and efficacy of intranasal H haemolyticus at 5 × 107 colony-forming units (CFU) was tested in female BALB/cARC mice using an influenza model and influenza-driven nontypeable Haemophilus influenzae (NTHi) OM model. Weight, symptoms, viral/bacterial levels, and immune responses were measured.

RESULTS

Intranasal delivery of H haemolyticus was safe and reduced severity of influenza, with quicker recovery, reduced inflammation, and lower lung influenza virus titers (up to 8-fold decrease vs placebo; P ≤ .01). Haemophilus haemolyticus reduced NTHi colonization density (day 5 median NTHi CFU/mL = 1.79 × 103 in treatment group vs 4.04 × 104 in placebo, P = .041; day 7 median NTHi CFU/mL = 28.18 vs 1.03 × 104; P = .028) and prevented OM (17% OM in treatment group, 83% in placebo group; P = .015).

CONCLUSIONS

Haemophilus haemolyticus has potential as a live biotherapeutic for prevention or early treatment of influenza and influenza-driven NTHi OM. Additional studies will deem whether these findings translate to humans and other respiratory infections.

CT findings of 144 in-hospital patients with influenza pneumonia: A retrospective analysis

BACKGROUND/PURPOSE

Patients with influenza infection during their period of admission may have worse computed tomography (CT) manifestation according to the clinical status. This study aimed to evaluate the CT findings of in-hospital patients due to clinically significant influenza pneumonia with correlation of clinical presentations.

METHODS

In this retrospective, single center case series, 144 patients were included. All in-hospital patients were confirmed influenza infection and underwent CT scan. These patients were divided into three groups according to the clinical status of the most significant management: (1) without endotracheal tube and mechanical ventilator (ETTMV) or extracorporeal membrane oxygenation (ECMO); (2) with ETTMV; (3) with ETTMV and ECMO. Pulmonary opacities were scored according to extent. Spearman rank correlation analysis was used to evaluate the correlation between clinical parameters and CT scores.

RESULTS

The predominant CT manifestation of influenza infection was mixed ground-glass opacity (GGO) and consolidation with both lung involvement. The CT scores were all reach significant difference among all three groups (8.73 ± 6.29 vs 12.49 ± 6.69 vs 18.94 ± 4.57, p < 0.05). The chest CT score was correlated with age, mortality, and intensive care unit (ICU) days (all p values were less than 0.05). In addition, the CT score was correlated with peak lactate dehydrogenase (LDH) level and peak C-reactive protein (CRP) level (all p values were less than 0.05). Concomitant bacterial infection had higher CT score than primary influenza pneumonia (13.02 ± 7.27 vs 8.95 ± 5.99, p < 0.05).

CONCLUSION

Thin-section chest CT scores correlated with clinical and laboratory parameters in in-hospital patients with influenza pneumonia.

Prevalence, Risk Factors, Clinical Features, and Outcome of Influenza-Associated Pulmonary Aspergillosis in Critically Ill Patients: A Systematic Review and Meta-Analysis

BACKGROUND

Influenza-associated pulmonary aspergillosis (IAPA) increasingly is being reported in critically ill patients. We conducted this systematic review and meta-analysis to examine the prevalence, risk factors, clinical features, and outcomes of IAPA.

STUDY QUESTION

What are the prevalence, risk factors, clinical features, and outcomes of IAPA in critically ill patients?

STUDY DESIGN AND METHODS

Studies reporting IAPA were searched in the following databases: PubMed MEDLINE, CINAHL, Cochrane Library, Embase, Scopus, Cochrane Trials, and ClinicalTrials.gov. We performed one-group meta-analysis on risk factors, clinical features, morbidity, and mortality using random effects models.

RESULTS

We included 10 observational studies with 1,720 critically ill patients with influenza, resulting in an IAPA prevalence of 19.2% (331 of 1,720). Patients who had undergone organ transplantation (OR, 4.8; 95% CI, 1.7-13.8; I2 = 45%), harbored a hematogenous malignancy (OR, 2.5; 95% CI, 1.5-4.1; I2 = 0%), were immunocompromised (OR, 2.2; 95% CI, 1.6-3.1; I2 = 0%), and underwent prolonged corticosteroid use before admission (OR, 2.4; 95% CI, 1.4-4.3; I2 = 51%) were found to be at a higher risk of IAPA developing. Commonly reported clinical and imaging features were not particularly associated with IAPA. However, IAPA was associated with more severe disease progression, a higher complication rate, and longer ICU stays and required more organ supports. Overall, IAPA was associated with a significantly elevated ICU mortality rate (OR, 2.6; 95% CI, 1.8-3.8; I2 = 0%).

INTERPRETATION

IAPA is a common complication of severe influenza and is associated with increased mortality. Early diagnosis of IAPA and initiation of antifungal treatment are essential, and future research should focus on developing a clinical algorithm.

TRIAL REGISTRY

International Prospective Register of Systematic Reviews; No.: CRD42022284536; URL: https://www.crd.york.ac.uk/prospero/.

Tiny Guides, Big Impact: Focus on the Opportunities and Challenges of miR-Based Treatments for ARDS

Acute Respiratory Distress Syndrome (ARDS) is characterized by lung inflammation and increased membrane permeability, which represents the leading cause of mortality in ICUs. Mechanical ventilation strategies are at the forefront of supportive approaches for ARDS. Recently, an increasing understanding of RNA biology, function, and regulation, as well as the success of RNA vaccines, has spurred enthusiasm for the emergence of novel RNA-based therapeutics. The most common types of RNA seen in development are silencing (si)RNAs, antisense oligonucleotide therapy (ASO), and messenger (m)RNAs that collectively account for 80% of the RNA therapeutics pipeline. These three RNA platforms are the most mature, with approved products and demonstrated commercial success. Most recently, miRNAs have emerged as pivotal regulators of gene expression. Their dysregulation in various clinical conditions offers insights into ARDS pathogenesis and offers the innovative possibility of using microRNAs as targeted therapy. This review synthesizes the current state of the literature to contextualize the therapeutic potential of miRNA modulation. It considers the potential for miR-based therapeutics as a nuanced approach that incorporates the complexity of ARDS pathophysiology and the multifaceted nature of miRNA interactions.

Fighting flu: novel CD8+ T-cell targets are required for future influenza vaccines

Seasonal influenza viruses continue to cause severe medical and financial complications annually. Although there are many licenced influenza vaccines, there are billions of cases of influenza infection every year, resulting in the death of over half a million individuals. Furthermore, these figures can rise in the event of a pandemic, as seen throughout history, like the 1918 Spanish influenza pandemic (50 million deaths) and the 1968 Hong Kong influenza pandemic (~4 million deaths). In this review, we have summarised many of the currently licenced influenza vaccines available across the world and current vaccines in clinical trials. We then briefly discuss the important role of CD8+ T cells during influenza infection and why future influenza vaccines should consider targeting CD8+ T cells. Finally, we assess the current landscape of known immunogenic CD8+ T-cell epitopes and highlight the knowledge gaps required to be filled for the design of rational future influenza vaccines that incorporate CD8+ T cells.

Risk factors for prolonged mechanical ventilation in critically ill patients with influenza-related acute respiratory distress syndrome

BACKGROUND

Patients with influenza-related acute respiratory distress syndrome (ARDS) are critically ill and require mechanical ventilation (MV) support. Prolonged mechanical ventilation (PMV) is often seen in these cases and the optimal management strategy is not established. This study aimed to investigate risk factors for PMV and factors related to weaning failure in these patients.

METHODS

This retrospective cohort study was conducted by eight medical centers in Taiwan. All patients in the intensive care unit with virology-proven influenza-related ARDS requiring invasive MV from January 1 to March 31, 2016, were included. Demographic data, critical illness data and clinical outcomes were collected and analyzed. PMV is defined as mechanical ventilation use for more than 21 days.

RESULTS

There were 263 patients with influenza-related ARDS requiring invasive MV enrolled during the study period. Seventy-eight patients had PMV. The final weaning rate was 68.8% during 60 days of observation. The mortality rate in PMV group was 39.7%. Risk factors for PMV were body mass index (BMI) > 25 (kg/m2) [odds ratio (OR) 2.087; 95% confidence interval (CI) 1.006-4.329], extracorporeal membrane oxygenation (ECMO) use (OR 6.181; 95% CI 2.338-16.336), combined bacterial pneumonia (OR 4.115; 95% CI 2.002-8.456) and neuromuscular blockade use over 48 h (OR 2.8; 95% CI 1.334-5.879). In addition, risk factors for weaning failure in PMV patients were ECMO (OR 5.05; 95% CI 1.75-14.58) use and bacteremia (OR 3.91; 95% CI 1.20-12.69).

CONCLUSIONS

Patients with influenza-related ARDS and PMV have a high mortality rate. Risk factors for PMV include BMI > 25, ECMO use, combined bacterial pneumonia and neuromuscular blockade use over 48 h. In addition, ECMO use and bacteremia predict unsuccessful weaning in PMV patients.

Sigma-1 receptor regulates the endoplasmic reticulum stress pathway in the protective mechanism of dexmedetomidine against hyperoxia-induced lung injury

Perioperative hyperoxia therapy is of great significance to save the lives of patients, but little is known about the possible mechanisms that induce hyperoxia-induced acute lung injury (HALI) and the measures for clinical prevention and treatment. In this experiment, the models were established with a feeding chamber with automatic regulation of oxygen concentration. The results showed that with the increase in inhaled oxygen concentration and the prolongation of exposure time, the severity of lung injury also increases significantly, reaching the diagnostic indication of HALI after 48 h of inhaling 95 % oxygen concentration. Subsequently, according to the dynamic changes of apoptosis in lung specimens, and the expression changes in Sig-1R-regulated ER stress pathway proteins (Sig-1R, GRP78, p-PERK, ATF6, IRE1, Caspase-12, ATF4, CHOP, Caspase-3 and p-JNK), it was confirmed that the Sig-1R-regulated ER stress signaling pathway was involved in the occurrence of HALI. To explore the preventive and therapeutic effects of routine clinical medication on HALI during the perioperative period, our research group selected dexmedetomidine (Dex) with lung protection. The experimental results revealed that Dex partially reversed the changes in the expression levels of Sig-1R-regulated ER stress pathway proteins. These results preliminarily confirmed that Dex may inhibit apoptosis induced by high oxygen concentration through the Sig-1R-regulated ER stress signaling pathway, thus playing a protective role in HALI.

Pleural macrophages translocate to the lung during infection to promote improved influenza outcomes

Seasonal influenza results in 3 to 5 million cases of severe disease and 250,000 to 500,000 deaths annually. Macrophages have been implicated in both the resolution and progression of the disease, but the drivers of these outcomes are poorly understood. We probed mouse lung transcriptomic datasets using the Digital Cell Quantifier algorithm to predict immune cell subsets that correlated with mild or severe influenza A virus (IAV) infection outcomes. We identified a unique lung macrophage population that transcriptionally resembled small serosal cavity macrophages and whose presence correlated with mild disease. Until now, the study of serosal macrophage translocation in the context of viral infections has been neglected. Here, we show that pleural macrophages (PMs) migrate from the pleural cavity to the lung after infection with IAV. We found that the depletion of PMs increased morbidity and pulmonary inflammation. There were increased proinflammatory cytokines in the pleural cavity and an influx of neutrophils within the lung. Our results show that PMs are recruited to the lung during IAV infection and contribute to recovery from influenza. This study expands our knowledge of PM plasticity and identifies a source of lung macrophages independent of monocyte recruitment and local proliferation.

GLUT1 contributes to impaired epithelial tight junction in the late phase of acute lung injury

Dysfunction of epithelial barrier is crucial for the development of acute lung injury (ALI). This study was aimed to evaluate the role of glucose transporter 1 (GLUT1) in dysregulation of epithelial tight junction in ALI. GLUT1 was inhibited with specific antagonists WZB117 or BAY876 to see the effects on epithelial tight junction in a well-established LPS-induced mouse ALI model as well as in vitro cultured epithelial cells. Pharmacological inhibition of GLUT1 with WZB117 at either a low or high dose had no effects on lung injury and inflammation 24 h after LPS challenge, but significantly decreased the pulmonary inflammatory responses induced by LPS at 72 h with a high dose, which was verified by treatment with BAY876. WZB117 or BAY876 also recovered the expression of epithelial tight junction proteins ZO-1 and occludin. In cultured BEAS-2B and A549 cells, LPS induced increased GLUT1 expression, accompanied by decreased expression of tight junction protein ZO-1 and occludin. Blockade of GLUT1 restored LPS-induced disruption of ZO-1 and occludin in BEAS-2B rather than A549. Taken together, our results showed that GLUT1 is responsible for dysfunction of epithelial tight junctions in the late phase of LPS-induced ALI.

A combination of oxygenation and driving pressure can provide valuable information in predicting the risk of mortality in ARDS patients

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a common life-threatening condition in critically ill patients. Itis also an important public health issue because it can cause substantial mortality and health care burden worldwide. The objective of this study was to investigate therisk factors that impact ARDS mortality in a medical center in Taiwan.

METHODS

This was a single center, observational study thatretrospectively analyzed data from adults in 6 intensive care units (ICUs) at Taichung Veterans General Hospital in Taiwan from 1st October, 2018to30th September, 2019. Patients needing invasive mechanical ventilation and meeting the Berlin definition criteria were included for analysis.

RESULTS

A total of 1,778 subjects were screened in 6 adult ICUs and 370 patients fulfilled the criteria of ARDS in the first 24 hours of the ICU admission. Among these patients, the prevalenceof ARDS was 20.8% and the overall hospital mortality rate was 42.2%. The mortality rates of mild, moderate and severe ARDS were 35.9%, 43.9% and 46.5%, respectively. In a multivariate logistic regression model, combination of driving pressure (DP) > 14cmH2O and oxygenation (P/F ratio)≤150 was an independent predictor of mortality (OR2.497, 95% CI 1.201-5.191, p = 0.014). Patients with worse oxygenation and a higher driving pressure had the highest hospital mortality rate(p<0.0001).

CONCLUSIONS

ARDS is common in ICUs and the mortality rate remains high. Combining oxygenation and respiratory mechanics may better predict the outcomes of these ARDS patients.

Gasdermin D promotes hyperinflammation and immunopathology during severe influenza A virus infection

Excessive inflammation and tissue damage during severe influenza A virus (IAV) infection can lead to the development of fatal pulmonary disease. Pyroptosis is a lytic and pro-inflammatory form of cell death executed by the pore-forming protein gasdermin D (GSDMD). In this study, we investigated a potential role for GSDMD in promoting the development of severe IAV disease. IAV infection resulted in cleavage of GSDMD in vivo and in vitro in lung epithelial cells. Mice genetically deficient in GSDMD (Gsdmd-/-) developed less severe IAV disease than wildtype mice and displayed improved survival outcomes. GSDMD deficiency significantly reduced neutrophil infiltration into the airways as well as the levels of pro-inflammatory cytokines TNF, IL-6, MCP-1, and IL-1α and neutrophil-attracting chemokines CXCL1 and CXCL2. In contrast, IL-1β and IL-18 responses were not largely impacted by GSDMD deficiency. In addition, Gsdmd-/- mice displayed significantly improved influenza disease resistance with reduced viral burden and less severe pulmonary pathology, including decreased epithelial damage and cell death. These findings indicate a major role for GSDMD in promoting damaging inflammation and the development of severe IAV disease.

Interesting effects of interleukins and immune cells on acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a medical condition characterized by widespread inflammation in the lungs with consequent proportional loss of gas exchange function. ARDS is linked with severe pulmonary or systemic infection. Several factors, including secretory cytokines, immune cells, and lung epithelial and endothelial cells, play a role in the development and progression of this disease. The present study is based on Pubmed database information (1987-2022) using the words "Acute respiratory distress syndrome", "Interleukin", "Cytokines" and "Immune cells". Cytokines and immune cells play an important role in this disease, with particular emphasis on the balance between pro-inflammatory and anti-inflammatory factors. Neutrophils are one of several important mediators of Inflammation, lung tissue destruction, and malfunction during ARDS. Some immune cells, such as macrophages and eosinophils, play a dual role in releasing inflammatory mediators, recruitment inflammatory cells and the progression of ARDS, or releasing anti-inflammatory mediators, clearing the lung of inflammatory cells, and helping to improve the disease. Different interleukins play a role in the development or inhibition of ARDS by helping to activate various signaling pathways, helping to secrete other inflammatory or anti-inflammatory interleukins, and playing a role in the production and balance between immune cells involved in ARDS. As a result, immune cells and, inflammatory cytokines, especially interleukins play an important role in the pathogenesis of this disease Therefore, understanding the relevant mechanisms will help in the proper diagnosis and treatment of this disease.

Cytomegalovirus durably primes neutrophil oxidative burst

Cytomegalovirus (CMV) is a ubiquitous herpes virus that infects most humans, thereafter persisting lifelong in tissues of the host. It is a known pathogen in immunosuppressed patients, but its impact on immunocompetent hosts remains less understood. Recent data have shown that CMV leaves a significant and long-lasting imprint in host immunity that may confer some protection against subsequent bacterial infection. Such innate immune activation may come at a cost, however, with potential to cause immunopathology. Neutrophils are central to many models of immunopathology, and while acute CMV infection is known to influence neutrophil biology, the impact of chronic CMV infection on neutrophil function remains unreported. Using our murine model of CMV infection and latency, we show that chronic CMV causes persistent enhancement of neutrophil oxidative burst well after resolution of acute infection. Moreover, this in vivo priming of marrow neutrophils is associated with enhanced formyl peptide receptor expression, and ultimately constitutive c-Jun N-terminal kinase phosphorylation and enhanced CD14 expression in/on circulating neutrophils. Finally, we show that neutrophil priming is dependent on viral load, suggesting that naturally infected human hosts will show variability in CMV-related neutrophil priming. Altogether, these findings represent a previously unrecognized and potentially important impact of chronic CMV infection on neutrophil responsiveness in immunocompetent hosts.

ZBP1 Drives IAV-Induced NLRP3 Inflammasome Activation and Lytic Cell Death, PANoptosis, Independent of the Necroptosis Executioner MLKL

Influenza A virus (IAV) continues to pose a significant global health threat, causing severe respiratory infections that result in substantial annual morbidity and mortality. Recent research highlights the pivotal role of innate immunity, cell death, and inflammation in exacerbating the severity of respiratory viral diseases. One key molecule in this process is ZBP1, a well-recognized innate immune sensor for IAV infection. Upon activation, ZBP1 triggers the formation of a PANoptosome complex containing ASC, caspase-8, and RIPK3, among other molecules, leading to inflammatory cell death, PANoptosis, and NLRP3 inflammasome activation for the maturation of IL-1β and IL-18. However, the role for other molecules in this process requires further evaluation. In this study, we investigated the role of MLKL in regulating IAV-induced cell death and NLRP3 inflammasome activation. Our data indicate IAV induced inflammatory cell death through the ZBP1-PANoptosome, where caspases and RIPKs serve as core components. However, IAV-induced lytic cell death was only partially dependent on RIPK3 at later timepoints and was fully independent of MLKL throughout all timepoints tested. Additionally, NLRP3 inflammasome activation was unaffected in MLKL-deficient cells, establishing that MLKL and MLKL-dependent necroptosis do not act upstream of NLRP3 inflammasome activation, IL-1β maturation, and lytic cell death during IAV infection.

Reactive oxygen species trigger inflammasome activation after intracellular microbial interaction

The intracellular production of reactive oxygen species (ROS), composed of oxygen-reduced molecules, is important not only because of their lethal effects on microorganisms but also due to their potential inflammatory and metabolic regulation properties. The ROS pro-inflammatory properties are associated with the second signal to inflammasome activation, leading to cleaving pro-IL-1β and pro-IL18 before their secretion, as well as gasdermin-D, leading to pyroptosis. Some microorganisms can modulate NLRP3 and AIM-2 inflammasomes through ROS production: whilst Mycobacterium bovis, Mycobacterium kansasii, Francisella novicida, Brucella abortus, Listeria monocytogenes, Influenza virus, Syncytial respiratory virus, Porcine reproductive and respiratory syndrome virus, SARS-CoV, Mayaro virus, Leishmania amazonensis and Plasmodium sp. enhance inflammasome assembly, Hepatitis B virus, Mycobacterium marinum, Mycobacterium tuberculosis, Francisella tularensis and Leishmania sp. disrupt it. This process represents a recent cornerstone in our knowledge of the immunology of intracellular pathogens, which is reviewed in this mini-review.

Preventing occludin tight-junction disruption via inhibition of microRNA-193b-5p attenuates viral load and influenza-induced lung injury

Virus-induced lung injury is associated with loss of pulmonary epithelial-endothelial tight junction integrity. While the alveolar-capillary membrane may be an indirect target of injury, viruses may interact directly and/or indirectly with miRs to augment their replication potential and evade the host antiviral defense system. Here, we expose how the influenza virus (H1N1) capitalizes on host-derived interferon-induced, microRNA (miR)-193b-5p to target occludin and compromise antiviral defenses. Lung biopsies from patients infected with H1N1 revealed increased miR-193b-5p levels, marked reduction in occludin protein, and disruption of the alveolar-capillary barrier. In C57BL/6 mice, the expression of miR-193b-5p increased, and occludin decreased, 5-6 days post-infection with influenza (PR8). Inhibition of miR-193b-5p in primary human bronchial, pulmonary microvascular, and nasal epithelial cells enhanced antiviral responses. miR-193b-deficient mice were resistant to PR8. Knockdown of occludin, both in vitro and in vivo, and overexpression of miR-193b-5p reconstituted susceptibility to viral infection. miR-193b-5p inhibitor mitigated loss of occludin, improved viral clearance, reduced lung edema, and augmented survival in infected mice. Our results elucidate how the innate immune system may be exploited by the influenza virus and how strategies that prevent loss of occludin and preserve tight junction function may limit susceptibility to virus-induced lung injury.

Immune response in influenza virus infection and modulation of immune injury by viral neuraminidase

Influenza A viruses cause severe respiratory illnesses in humans and animals. Overreaction of the innate immune response to influenza virus infection results in hypercytokinemia, which is responsible for mortality and morbidity. The influenza A virus surface glycoprotein neuraminidase (NA) plays a vital role in viral attachment, entry, and virion release from infected cells. NA acts as a sialidase, which cleaves sialic acids from cell surface proteins and carbohydrate side chains on nascent virions. Here, we review progress in understanding the role of NA in modulating host immune response to influenza virus infection. We also discuss recent exciting findings targeting NA protein to interrupt influenza-induced immune injury.

The β6 Integrin Negatively Regulates TLR7-Mediated Epithelial Immunity via Autophagy During Influenza A Virus Infection

Integrins are essential surface receptors that sense extracellular changes to initiate various intracellular signaling cascades. The rapid activation of the epithelial-intrinsic β6 integrin during influenza A virus (IAV) infection has been linked to innate immune impairments. Yet, how β6 regulates epithelial immunity remains undefined. Here, we identify the role of β6 in mediating the Toll-like receptor 7 (TLR7) through the regulation of intracellular trafficking. We demonstrate that deletion of the β6 integrin in lung epithelial cells significantly enhances the TLR7-mediated activation of the type I interferon (IFN) response during homeostasis and respiratory infection. IAV-induced β6 facilitates TLR7 trafficking to lysosome-associated membrane protein (LAMP2a) components, leading to a reduction in endosomal compartments and associated TLR7 signaling. Our findings reveal an unappreciated role of β6-induced autophagy in influencing epithelial immune responses during influenza virus infection.

Depression, worry, and loneliness are associated with subsequent risk of hospitalization for COVID-19: a prospective study

BACKGROUND

Pre-pandemic psychological distress is associated with increased susceptibility to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, but associations with the coronavirus disease 2019 (COVID-19) severity are not established. The authors examined the associations between distress prior to SARS-CoV-2 infection and subsequent risk of hospitalization.

METHODS

Between April 2020 (baseline) and April 2021, we followed 54 781 participants from three ongoing cohorts: Nurses' Health Study II (NHSII), Nurses' Health Study 3 (NHS3), and the Growing Up Today Study (GUTS) who reported no current or prior SARS-CoV-2 infection at baseline. Chronic depression was assessed during 2010-2019. Depression, anxiety, worry about COVID-19, perceived stress, and loneliness were measured at baseline. SARS-CoV-2 infection and hospitalization due to COVID-19 was self-reported. Relative risks (RRs) were calculated by Poisson regression.

RESULTS

3663 participants reported a positive SARS-CoV-2 test (mean age = 55.0 years, standard deviation = 13.8) during follow-up. Among these participants, chronic depression prior to the pandemic [RR = 1.72; 95% confidence interval (CI) 1.20-2.46], and probable depression (RR = 1.81, 95% CI 1.08-3.03), being very worried about COVID-19 (RR = 1.79; 95% CI 1.12-2.86), and loneliness (RR = 1.81, 95% CI 1.02-3.20) reported at baseline were each associated with subsequent COVID-19 hospitalization, adjusting for demographic factors and healthcare worker status. Anxiety and perceived stress were not associated with hospitalization. Depression, worry about COVID-19, and loneliness were as strongly associated with hospitalization as were high cholesterol and hypertension, established risk factors for COVID-19 severity.

CONCLUSIONS

Psychological distress may be a risk factor for hospitalization in patients with SARS-CoV-2 infection. Assessment of psychological distress may identify patients at greater risk of hospitalization. Future work should examine whether addressing distress improves physical health outcomes.

Roles and Mechanisms of NLRP3 in Influenza Viral Infection

Pathogenic viral infection represents a major challenge to human health. Due to the vast mucosal surface of respiratory tract exposed to the environment, host defense against influenza viruses has perpetually been a considerable challenge. Inflammasomes serve as vital components of the host innate immune system and play a crucial role in responding to viral infections. To cope with influenza viral infection, the host employs inflammasomes and symbiotic microbiota to confer effective protection at the mucosal surface in the lungs. This review article aims to summarize the current findings on the function of NACHT, LRR and PYD domains-containing protein 3 (NLRP3) in host response to influenza viral infection involving various mechanisms including the gut-lung crosstalk.

Investigational Use of Mesenchymal Stem/Stromal Cells and Their Secretome as Add-On Therapy in Severe Respiratory Virus Infections: Challenges and Perspectives

Serious manifestations of respiratory virus infections such as influenza and coronavirus disease 2019 (COVID-19) are associated with a dysregulated immune response and systemic inflammation. Treating the immunological/inflammatory dysfunction with glucocorticoids, Janus kinase inhibitors, and monoclonal antibodies against the interleukin-6 receptor has significantly reduced the risk of respiratory failure and death in hospitalized patients with severe COVID-19, but the proportion of those requiring invasive mechanical ventilation (IMV) and dying because of respiratory failure remains elevated. Treatment of severe influenza-associated pneumonia and acute respiratory distress syndrome (ARDS) with available immunomodulators and anti-inflammatory compounds is still not recommended. New therapies are therefore needed to reduce the use of IMV and the risk of death in hospitalized patients with rapidly increasing oxygen demand and systemic inflammation who do not respond to the current standard of care. This paper provides a critical assessment of the published clinical trials that have tested the investigational use of intravenously administered allogeneic mesenchymal stem/stromal cells (MSCs) and MSC-derived secretome with putative immunomodulatory/antiinflammatory/regenerative properties as add-on therapy to improve the outcome of these patients. Increased survival rates are reported in 5 of 12 placebo-controlled or open-label comparative trials involving patients with severe and critical COVID-19 and in the only study concerning patients with influenza-associated ARDS. Results are encouraging but inconclusive for the following reasons: small number of patients tested in each trial; differences in concomitant treatments and respiratory support; imbalances between study arms; differences in MSC source, MSC-derived product, dosing and starting time of the investigational therapy; insufficient/inappropriate reporting of clinical data. Solutions are proposed for improving the clinical development plan, with the aim of facilitating regulatory approval of the MSC-based investigational therapy for life-threatening respiratory virus infections in the future. Major issues are the absence of a biomarker predicting responsiveness to MSCs and MSC-derived secretome and the lack of pharmacoeconomic evaluations.

Vascular Endothelial-derived SPARCL1 Exacerbates Viral Pneumonia Through Pro-Inflammatory Macrophage Activation

Inflammation upon infectious lung injury is a double-edged sword: while tissue-infiltrating immune cells and cytokines are necessary to control infection, these same factors often aggravate injury. Full appreciation of both the sources and targets of inflammatory mediators is required to facilitate strategies to maintain antimicrobial effects while minimizing off-target epithelial and endothelial damage. Recognizing that the vasculature is centrally involved in tissue responses to injury and infection, we observed that pulmonary capillary endothelial cells (ECs) exhibit dramatic transcriptomic changes upon influenza injury punctuated by profound upregulation of Sparcl1 . Endothelial deletion and overexpression of SPARCL1 implicated this secreted matricellular protein in driving key pathophysiologic symptoms of pneumonia, which we demonstrate result from its effects on macrophage polarization. SPARCL1 induces a shift to a pro-inflammatory "M1-like" phenotype (CD86 + CD206 - ), thereby increasing associated cytokine levels. Mechanistically, SPARCL1 acts directly on macrophages in vitro to induce the pro-inflammatory phenotype via activation of TLR4, and TLR4 inhibition in vivo ameliorates inflammatory exacerbations caused by endothelial Sparcl1 overexpression. Finally, we confirmed significant elevation of SPARCL1 in COVID-19 lung ECs in comparison with those from healthy donors. Survival analysis demonstrated that patients with fatal COVID-19 had higher levels of circulating SPARCL1 protein compared to those who recovered, indicating the potential of SPARCL1 as a biomarker for prognosis of pneumonia and suggesting that personalized medicine approaches might be harnessed to block SPARCL1 and improve outcomes in high-expressing patients.

Simultaneous co-infection with swine influenza A and porcine reproductive and respiratory syndrome viruses potentiates adaptive immune responses

Porcine respiratory disease is multifactorial and most commonly involves pathogen co-infections. Major contributors include swine influenza A (swIAV) and porcine reproductive and respiratory syndrome (PRRSV) viruses. Experimental co-infection studies with these two viruses have shown that clinical outcomes can be exacerbated, but how innate and adaptive immune responses contribute to pathogenesis and pathogen control has not been thoroughly evaluated. We investigated immune responses following experimental simultaneous co-infection of pigs with swIAV H3N2 and PRRSV-2. Our results indicated that clinical disease was not significantly exacerbated, and swIAV H3N2 viral load was reduced in the lung of the co-infected animals. PRRSV-2/swIAV H3N2 co-infection did not impair the development of virus-specific adaptive immune responses. swIAV H3N2-specific IgG serum titers and PRRSV-2-specific CD8β⁺ T-cell responses in blood were enhanced. Higher proportions of polyfunctional CD8β⁺ T-cell subset in both blood and lung washes were found in PRRSV-2/swIAV H3N2 co-infected animals compared to the single-infected groups. Our findings provide evidence that systemic and local host immune responses are not negatively affected by simultaneous swIAV H3N2/PRRSV-2 co-infection, raising questions as to the mechanisms involved in disease modulation.

Analysis of cytokine levels, cytological findings, and MP-DNA level in bronchoalveolar lavage fluid of children with Mycoplasma pneumoniae pneumonia

BACKGROUND

The present study was conducted to determine the inflammatory response in the lungs of children with Mycoplasma pneumoniae pneumonia (MPP).

METHODS

This study retrospectively analyzed cytokine levels, cytological findings, and M. pneumoniae (MP)-DNA level in the bronchoalveolar lavage fluid (BALF) of 96 children with MPP. The study utilized Spearman's correlation method to evaluate the contribution of BALF and blood parameters in MPP children.

RESULTS

(1) A total of 96 MPP children were classified into the Low MP-DNA MPP group (BALF MP-DNA ≤ 105 copies/mL) and the High MP-DNA MPP group (BALF MP-DNA > 105 copies/mL); the Non-fever MPP group (no fever during the entire course of pneumonia) and the Fever MPP group; the Defervescence MPP group (fever had subsided at the time of bronchoscopy) and the Fervescence MPP group; and the Mild MPP group and the Severe MPP group. (2) The High MP-DNA MPP, Fever MPP, Fervescence MPP, and Severe MPP groups had higher levels of interleukin (IL)-6, IL-10, and tumor necrosis factor-α (TNF-α) in their BALF (all p < .05). (3) The proportions of neutrophils and macrophages in the BALF of the High MP-DNA MPP and Fever MPP groups increased and decreased, respectively (all p < .05). (4) In the BALF of MPP children, MP-DNA, IL-6, IL-10, TNF-α, and interferon gamma (IFN-γ) levels positively correlated with neutrophil proportion while negatively correlated with macrophage proportion (all p < .05). (5) The MP-DNA, IL-6, IL-10, TNF-α, and IFN-γ levels in the BALF of MPP children were positively correlated with the levels of C-reactive protein, procalcitonin, lactic dehydrogenase, fibrinogen, and d-dimer, while they were negatively correlated with the albumin level (all p < .05).

CONCLUSIONS

In children with MPP, the pulmonary inflammatory immune response was stronger in the High MP-DNA MPP, Fever MPP, Fervescence MPP, and Severe MPP groups. The relationship between pulmonary cytokine levels, MP-DNA load, and serum inflammatory parameters were found to be weak.

PGE2 Produced by Exogenous MSCs Promotes Immunoregulation in ARDS Induced by Highly Pathogenic Influenza A through Activation of the Wnt-β-Catenin Signaling Pathway

Acute respiratory distress syndrome is an acute respiratory failure caused by cytokine storms; highly pathogenic influenza A virus infection can induce cytokine storms. The innate immune response is vital in this cytokine storm, acting by activating the transcription factor NF-κB. Tissue injury releases a danger-associated molecular pattern that provides positive feedback for NF-κB activation. Exogenous mesenchymal stem cells can also modulate immune responses by producing potent immunosuppressive substances, such as prostaglandin E2. Prostaglandin E2 is a critical mediator that regulates various physiological and pathological processes through autocrine or paracrine mechanisms. Activation of prostaglandin E2 results in the accumulation of unphosphorylated β-catenin in the cytoplasm, which subsequently reaches the nucleus to inhibit the transcription factor NF-κB. The inhibition of NF-κB by β-catenin is a mechanism that reduces inflammation.

Cancer and COVID-19: unravelling the immunological interplay with a review of promising therapies against severe SARS-CoV-2 for cancer patients

Cancer patients, due to their immunocompromised status, are at an increased risk for severe SARS-CoV-2 infection. Since severe SARS-CoV-2 infection causes multiple organ damage through IL-6-mediated inflammation while stimulating hypoxia, and malignancy promotes hypoxia-induced cellular metabolic alterations leading to cell death, we propose a mechanistic interplay between both conditions that results in an upregulation of IL-6 secretion resulting in enhanced cytokine production and systemic injury. Hypoxia mediated by both conditions results in cell necrosis, dysregulation of oxidative phosphorylation, and mitochondrial dysfunction. This produces free radicals and cytokines that result in systemic inflammatory injury. Hypoxia also catalyzes the breakdown of COX-1 and 2 resulting in bronchoconstriction and pulmonary edema, which further exacerbates tissue hypoxia. Given this disease model, therapeutic options are currently being studied against severe SARS-COV-2. In this study, we review several promising therapies against severe disease supported by clinical trial evidence-including Allocetra, monoclonal antibodies (Tixagevimab-Cilgavimab), peginterferon lambda, Baricitinib, Remdesivir, Sarilumab, Tocilizumab, Anakinra, Bevacizumab, exosomes, and mesenchymal stem cells. Due to the virus's rapid adaptive evolution and diverse symptomatic manifestation, the use of combination therapies offers a promising approach to decrease systemic injury. By investing in such targeted interventions, cases of severe SARS-CoV-2 should decrease along with its associated long-term sequelae and thereby allow cancer patients to resume their treatments.

Naturally derived cytokine peptides limit virus replication and severe disease during influenza A virus infection

Objectives

Novel host‐targeted therapeutics could treat severe influenza A virus (IAV) infections, with reduced risk of drug resistance. LAT8881 is a synthetic form of the naturally occurring C‐terminal fragment of human growth hormone. Acting independently of the growth hormone receptor, it can reduce inflammation‐induced damage and promote tissue repair in an animal model of osteoarthritis. LAT8881 has been assessed in clinical trials for the treatment of obesity and neuropathy and has an excellent safety profile. We investigated the potential for LAT8881, its metabolite LAT9991F and LAT7771 derived from prolactin, a growth hormone structural homologue, to treat severe IAV infection.

Methods

LAT8881, LAT9991F and LAT7771 were evaluated for their effects on cell viability and IAV replication in vitro, as well as their potential to limit disease in a preclinical mouse model of severe IAV infection.

Results

In vitro LAT8881 treatment enhanced cell viability, particularly in the presence of cytotoxic stress, which was countered by siRNA inhibition of host lanthionine synthetase C‐like proteins. Daily intranasal treatment of mice with LAT8881 or LAT9991F, but not LAT7771, from day 1 postinfection significantly improved influenza disease resistance, which was associated with reduced infectious viral loads, reduced pro‐inflammatory cytokines and increased abundance of protective alveolar macrophages. LAT8881 treatment in combination with the antiviral oseltamivir phosphate led to more pronounced reduction in markers of disease severity than treatment with either compound alone.

Conclusion

These studies provide the first evidence identifying LAT8881 and LAT9991F as novel host‐protective therapies that improve survival, limit viral replication, reduce local inflammation and curtail tissue damage during severe IAV infection. Evaluation of LAT8881 and LAT9991F in other infectious and inflammatory conditions of the airways is warranted.

Immunomodulatory and antiviral effects of Lycium barbarum glycopeptide on influenza a virus infection

Influenza is caused by a respiratory virus and has a major global impact on human health. Influenza A viruses in particular are highly pathogenic to humans and have caused multiple pandemics. An important consequence of infection is viral pneumonia, and with serious complications of excessive inflammation and tissue damage. Therefore, simultaneously reducing direct damage caused by virus infection and relieving indirect damage caused by excessive inflammation would be an effective treatment strategy. Lycium barbarum glycopeptide (LbGp) is a mixture of five highly branched polysaccharide-protein conjuncts (LbGp1-5) isolated from Lycium barbarum fruit. LbGp has pro-immune activity that is 1-2 orders of magnitude stronger than that of other plant polysaccharides. However, there are few reports on the immunomodulatory and antiviral activities of LbGp. In this study, we evaluated the antiviral and immunomodulatory effects of LbGp in vivo and in vitro and investigated its therapeutic effect on H1N1-induced viral pneumonia and mechanisms of action. In vitro, cytokine secretion, NF-κB p65 nuclear translocation, and CD86 mRNA expression in LPS-stimulated RAW264.7 cells were constrained by LbGp treatment. In A549 cells, LbGp can inhibit H1N1 infection by blocking virus attachment and entry action. In vivo experiments confirmed that administration of LbGp can effectively increase the survival rate, body weight and decrease the lung index of mice infected with H1N1. Compared to the model group, pulmonary histopathologic symptoms in lung sections of mice treated with LbGp were obviously alleviated. Further investigation revealed that the mechanism of LbGp in the treatment of H1N1-induced viral pneumonia includes reducing the viral load in lung, regulating the phenotype of pulmonary macrophages, and inhibiting excessive inflammation. In conclusion, LbGp exhibits potential curative effects against H1N1-induced viral pneumonia in mice, and these effects are associated with its good immuno-regulatory and antiviral activities.

Risk Factors for Influenza-Induced Exacerbations and Mortality in Non-Cystic Fibrosis Bronchiectasis

Influenza infection is a cause of exacerbations in patients with chronic pulmonary diseases. The aim of this study was to investigate the clinical outcomes and identify risk factors associated with hospitalization and mortality following influenza infection in adult patients with bronchiectasis. Using the Chang Gung Research Database, we identified patients with bronchiectasis and influenza-related infection (ICD-9-CM 487 and anti-viral medicine) between 2008 and 2017. The main outcomes were influenza-related hospitalization and in-hospital mortality rate. Eight hundred sixty-five patients with bronchiectasis and influenza infection were identified. Five hundred thirty-six (62%) patients with bronchiectasis were hospitalized for influenza-related infection and 118 (22%) patients had respiratory failure. Compared to the group only seen in clinic, the hospitalization group was older, with more male patients, a lower FEV_1, higher bronchiectasis aetiology comorbidity index (BACI), and more acute exacerbations in the previous year. Co-infections were evident in 55.6% of hospitalized patients, mainly caused by Pseudomonas aeruginosa (15%), fungus (7%), and Klebsiella pneumoniae (6%). The respiratory failure group developed acute kidney injury (36% vs. 16%; p < 0.001), and shock (47% vs. 6%; p < 0.001) more often than influenza patients without respiratory failure. The overall mortality rate was 10.8% and the respiratory failure group exhibited significantly higher in-hospital mortality rates (27.1% vs. 6.2%; p < 0.001). Age, BACI, and previous exacerbations were independently associated with influenza-related hospitalization. Age, presence of shock, and low platelet counts were associated with increased hospital mortality. Influenza virus caused severe exacerbation in bronchiectasis, especially in those who were older and who had high BACI scores and previous exacerbations. A high risk of respiratory failure and mortality were observed in influenza-related hospitalization in bronchiectasis. We highlight the importance of preventing or treating influenza infection in bronchiectasis.

The synergistic effect and mechanisms of flavonoids and polysaccharides from Houttuynia cordata on H1N1-induced pneumonia in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Houttuynia cordata Thunb. (HC, Saururaceae family) is a classical Traditional Chinese Medicine used to treat pneumonia clinically. The total flavonoids (HCF) and polysaccharides (HCP) are key medicinal components of H. cordata involved in its beneficial effect on viral pneumonia.

AIM OF THE STUDY

The purpose of the study is to investigate the synergistic or complementary effects of combination of HCF and HCP on viral pneumonia as well as the mechanisms underlying.

MATERIALS AND METHODS

HCF or HCP were administrated separately or combined in different proportions on influenza virus H1N1 - infected mice. The survival and lung weight of mice were recorded. The synergistic effect on HCF and HCP combination was calculated by Chou-Talalay method. H&E staining was performed to detect lung histomorphology. Western blot, immunohistochemistry and enzyme linked immunosorbent assay were done to analyze the representative protein expression in lung and intestine tissues. AB - PAS staining on intestine tissue sections was performed to evaluate the histopathology of intestines. Bacterial genomic DNA was extracted and sequenced for gut microbiota analysis.

RESULTS

In H1N1 lethally infected mice, the combined administration of HCF and HCP significantly increased the survival rate and prolonged the life span of mice, compared with mono-drug therapy. The viral pneumonia was remarkably improved by HCF and HCP combination reflected by lower lung index, more intact lung morphology, and less inflammatory cells and mediators. Furthermore, the combination of HCF and HCP regulated intestinal microbiota, significantly reduced the proportion of pathogenic Proteobacteria and the secretion of proinflammatory cytokine in gut. The combined HCF and HCP showed synergistic effect on reducing lung and intestine injury. The complementary interaction was also found in HCF and HCP combined therapy, as HCF provided the significant antiviral activity and HCP markedly improved intestinal physical barrier and increased the protein expression involving removal of edema.

CONCLUSIONS

Our findings indicated that combination of HCF and HCP from H. cordata synergistically alleviated H1N1-induced viral pneumonia in mice via multimodal regulation of both pulmonary and intestinal homeostasis, which might imply novel therapeutic strategy for treating viral pneumonia.

Moderate to severe ARDS: COVID-19 patients compared to influenza patients for ventilator parameters and mortality

Background

This study aimed to compare ventilatory parameters recorded the first days of ARDS, and mortality at day 60 between COVID-19 and influenza ARDS patients with PaO2/FiO2≤150 mmHg.

Methods

We compared 244 COVID-19 ARDS patients with 106 influenza ARDS patients. Driving pressure (DP), respiratory system compliance (CRs), ventilator ratio (VR), corrected minute ventilation (VEcorr), and surrogate of mechanical power [index=(4×DP)+respiratory rate] were calculated from day1 to day 5 of ARDS. A propensity score analysis and a principal component analysis (PCA) were performed.

Results

On day 1 of ARDS, COVID-19 patients had significantly higher PaO2/FiO2ratio (median [IQR], 97 mmHg [79–129]versus83 [62.2–114]), p=0.001), and lower DP (13 cmH20 [11–16.0]versus14 [12.0–16.7], p=0.01), VR (2.08 [1.73–2.49versus2.52 [1.97–3.03], p<0.001), VEcorr (12.7 L·mn−1[10.2–14.9]versus14.9 [11.6–18.6], p<0.001), index (80 [70–89]versus84 [75–94], p=0.004). PCA demonstrated an important overlap of ventilatory parameters recorded on day 1 between the two groups. From day 1 to day 5 repeated values of PaO2/FiO2ratio, PaCO2, VR and VEcorr differed significantly between influenza and COVID-19 patients in the unmatched and matched populations. Mortality at day 60 did not differ significantly after matching (29%versus21.7%, p=0.43).

Conclusions

Ventilation was more impaired in influenza than in COVID-19 ARDS patients the first day of ARDS with important overlap of values. However, mortality at day 60 did not differ significantly in the matched population.

COVID-19: Diabetes Perspective-Pathophysiology and Management

Recent evidence relating to the impact of COVID-19 on people with diabetes is limited but continues to emerge. COVID-19 pneumonia is a newly identified illness spreading rapidly throughout the world and causes many disabilities and fatal deaths. Over the ensuing 2 years, the indirect effects of the pandemic on healthcare delivery have become prominent, along with the lingering effects of the virus on those directly infected. Diabetes is a commonly identified risk factor that contributes not only to the severity and mortality of COVID-19 patients, but also to the associated complications, including acute respiratory distress syndrome (ARDS) and multi-organ failure. Diabetic patients are highly affected due to increased viral entry into the cells and decreased immunity. Several hypotheses to explain the increased incidence and severity of COVID-19 infection in people with diabetes have been proposed and explained in detail recently. On the other hand, 20-50% of COVID-19 patients reported new-onset hyperglycemia without diabetes and new-onset diabetes, suggesting the two-way interactions between COVID-19 and diabetes. A systematic review is required to confirm diabetes as a complication in those patients diagnosed with COVID-19. Diabetes and diabetes-related complications in COVID-19 patients are primarily due to the acute illness caused during the SARS-CoV-2 infection followed by the release of glucocorticoids, catecholamines, and pro-inflammatory cytokines, which have been shown to drive hyperglycemia positively. This review provides brief insights into the potential mechanisms linking COVID-19 and diabetes, and presents clinical management recommendations for better handling of the disease.

Spatial transcriptomic characterization of COVID-19 pneumonitis identifies immune circuits related to tissue injury

Severe lung damage resulting from COVID-19 involves complex interactions between diverse populations of immune and stromal cells. In this study, we used a spatial transcriptomics approach to delineate the cells, pathways, and genes present across the spectrum of histopathological damage in COVID-19-affected lung tissue. We applied correlation network-based approaches to deconvolve gene expression data from 46 areas of interest covering more than 62,000 cells within well-preserved lung samples from 3 patients. Despite substantial interpatient heterogeneity, we discovered evidence for a common immune-cell signaling circuit in areas of severe tissue that involves crosstalk between cytotoxic lymphocytes and pro-inflammatory macrophages. Expression of IFNG by cytotoxic lymphocytes was associated with induction of chemokines, including CXCL9, CXCL10, and CXCL11, which are known to promote the recruitment of CXCR3+ immune cells. The TNF superfamily members BAFF (TNFSF13B) and TRAIL (TNFSF10) were consistently upregulated in the areas with severe tissue damage. We used published spatial and single-cell SARS-CoV-2 data sets to validate our findings in the lung tissue from additional cohorts of patients with COVID-19. The resulting model of severe COVID-19 immune-mediated tissue pathology may inform future therapeutic strategies.

Regulatory T cell and macrophage crosstalk in acute lung injury: future perspectives

Acute lung injury (ALI) describes the injury to endothelial cells in the lungs and associated vessels due to various factors. Furthermore, ALI accompanied by inflammation and thrombosis has been reported as a common complication of SARS-COV-2 infection. It is widely accepted that inflammation and the cytokine storm are main causes of ALI. Two classical anti-inflammatory cell types, regulatory T cells (Tregs) and M2 macrophages, are theoretically capable of resisting uncontrolled inflammation. Recent studies have indicated possible crosstalk between Tregs and macrophages involving their mutual activation. In this review, we discuss the current findings related to ALI pathogenesis and the role of Tregs and macrophages. In particular, we review the molecular mechanisms underlying the crosstalk between Tregs and macrophages in ALI pathogenesis. Understanding the role of Tregs and macrophages will provide the potential targets for treating ALI.

Anti-inflammatory effects of theaflavin-3'-gallate during influenza virus infection through regulating the TLR4/MAPK/p38 pathway

Severe pathological damage caused by the influenza virus is one of the leading causes of death. However, the prevention and control strategies for influenza virus infection have certain limitations, and the exploration for new influenza antiviral drugs has become the major research direction. This study evaluated the antiviral activities of four theaflavin derivatives (TFs). Cytopathic effect (CPE) reduction assay revealed that theaflavin-3'-gallate (TF2b) and theaflavin (TF1) could effectively inhibit the replication of influenza viruses H1N1-UI182, H1N1-PR8, H3N2, and H5N1, and TF2b exhibited the most significant antiviral activity in vivo. Intraperitoneal injection of TF2b at 40 mg/kg/d effectively alleviated viral pneumonia, maintained body weight, and improved the survival rate of mice infected with a lethal dose of H1N1-UI182 to 55.56%. Hematological analysis of peripheral blood further showed that TF2b increased the number of lymphocytes and decreased the number of neutrophils, monocytes, and platelets in the blood of infected mice. RT-qPCR results showed that TF2b reduced the mRNA expression levels of inflammatory cytokines (IL-6, TNF-α, and IL-1β), chemokines (CXCL-2 and CCL-3), and interferons (IFN-α and IFN-γ) after influenza virus infection. In addition, TF2b significantly down-regulated the expression levels of TLR4, p-p38, p-ERK, and cytokines IL-6, TNF-α, IL-1β, and IL-10. These results suggest that TF2b not only significantly inhibits viral replication and proliferation in vitro, but also alleviates pneumonia injury in vivo. Its antiviral effect might be attributed to the down-regulation of influenza virus-induced inflammatory cytokines by regulating the TLR4/MAPK/p38 signaling pathway.

SLC38A6 expression in macrophages exacerbates pulmonary inflammation

Pulmonary inflammation involves complex changes of the immune cells, in which macrophages play important roles and their function might be influenced by metabolism. Slc38a6 acts as a carrier of nutrient for macrophages (Mφ) to exert the function. In this study, pneumonia patient blood was found up-regulated SLC38A6 expression, which correlated with monocytes number and white blood cell number. The similar result was also shown in LPS induced sepsis mice. To reveal the key role of Slc38a6, we used systemic and conditional knock-out mice. Either systemic or Lyz^CRE specific knock-out could alleviate the severity of sepsis mice, reduce the proinflammatory cytokine TNF-α and IL-1β expression in serum and decrease the monocytes number in bronchial alveolar lavage and peritoneal lavage via flow cytometry. In order to reveal the signal of up-regulated Slc38a6, the Tlr4 signal inhibitor TAK242 and TLR4 knock-out mice were used. By blocking Tlr4 signal in macrophages via TAK242, the expression of Slc38a6 was down-regulated synchronously, and the same results were also found in Tlr4 knock-out macrophages. However, in the overexpressed Slc38a6 macrophages, blocking Tlr4 signal via TAK242, 20% of the mRNA expression of IL-1β still could be expressed, indicating that up-regulated Slc38a6 participates in IL-1β expression process. Collectively, it is the first time showed that an amino acid transporter SLC38A6 up-regulated in monocytes/macrophages promotes activation in pulmonary inflammation. SLC38A6 might be a promising target molecule for pulmonary inflammation treatment.