Essential role of IL-6 in protection against H1N1 influenza virus by promoting neutrophil survival in the lung

Inhibition of influenza virus infection in mice by pulmonary administration of a spray dried antiviral drug

Increasing resistance to antiviral drugs approved for the treatment of influenza urges the development of novel compounds. Ideally, this should be complemented by a careful consideration of the administration route. 6'siallyllactosamine-functionalized β-cyclodextrin (CD-6'SLN) is a novel entry inhibitor that acts as a mimic of the primary attachment receptor of influenza, sialic acid. In this study, we aimed to develop a dry powder formulation of CD-6'SLN to assess its in vivo antiviral activity after administration via the pulmonary route. By means of spray drying the compound together with trileucine, a dispersion enhancer, we created a powder that retained the antiviral effect of the drug, remained stable under elevated temperature conditions and performed well in a dry powder inhaler. To test the efficacy of the dry powder drug against influenza infection in vivo, infected mice were treated with CD-6'SLN using an aerosol generator that allowed for the controlled administration of powder formulations to the lungs of mice. CD-6'SLN was effective in mitigating the course of the disease compared to the control groups, reflected by lower disease activity scores and by the prevention of virus-induced IL-6 production. Our data show that CD-6'SLN can be formulated as a stable dry powder that is suitable for use in a dry powder inhaler and is effective when administered via the pulmonary route to influenza-infected mice.

Local receptor-interacting protein kinase 2 inhibition mitigates house dust mite-induced asthma

BACKGROUND

House dust mite is the most frequent trigger of allergic asthma, with innate and adaptive immune mechanisms playing critical roles in outcomes. We recently identified the nucleotide-binding oligomerisation domain 1 (NOD1)/receptor-interacting serine/threonine protein kinase 2 (RIPK2) signalling pathway as a relevant contributor to murine house dust mite-induced asthma. This study aimed to evaluate the effectiveness of a pharmacological RIPK2 inhibitor administered locally as a preventive and therapeutic approach using a house dust mite-induced asthma model in wild-type and humanised NOD1 mice harbouring an asthma-associated risk allele, and its relevance using air-liquid interface epithelial cultures from asthma patients.

METHODS

A RIPK2 inhibitor was administered intranasally either preventively or therapeutically in a murine house dust mite-induced asthma model. Airway hyperresponsiveness, bronchoalveolar lavage composition, cytokine/chemokine expression and mucus production were evaluated, as well as the effect of the inhibitor on precision-cut lung slices. Furthermore, the inhibitor was tested on air-liquid interface epithelial cultures from asthma patients and controls.

RESULTS

While local preventive administration of the RIPK2 inhibitor reduced airway hyperresponsiveness, eosinophilia, mucus production, T-helper type 2 cytokines and interleukin 33 (IL-33) in wild-type mice, its therapeutic administration failed to reduce the above parameters, except IL-33. By contrast, therapeutic RIPK2 inhibition mitigated all asthma features in humanised NOD1 mice. Results in precision-cut lung slices emphasised an early role of thymic stromal lymphopoietin and IL-33 in the NOD1-dependent response to house dust mite, and a late effect of NOD1 signalling on IL-13 effector response. RIPK2 inhibitor downregulated thymic stromal lymphopoietin and chemokines in house dust mite-stimulated epithelial cultures from asthma patients.

CONCLUSION

These data support that local interference of the NOD1 signalling pathway through RIPK2 inhibition may represent a new therapeutic approach in house dust mite-induced asthma.

Treatment with lipoxin A4 improves influenza A infection outcome, induces macrophage reprogramming, anti-inflammatory and pro-resolutive responses

INTRODUCTION

Influenza A is a virus from the Orthomixoviridae family responsible for high lethality rates and morbidity, despite clinically proven vaccination strategies and some anti-viral therapies. The eicosanoid Lipoxin A4 (LXA4) promotes the resolution of inflammation by decreasing cell recruitment and pro-inflammatory cytokines release, but also for inducing activation of apoptosis, efferocytosis, and macrophage reprogramming.

OBJECTIVE

Here, we evaluated whether a synthetic lipoxin mimetic, designated AT-01-KG, would improve the course of influenza A infection in a murine model.

METHOD

Mice were infected with influenza A/H1N1 and treated with AT-01-KG (1.7 μg/kg/day, i.p.) at day 3 post-infection.

RESULTS

AT-01-KG attenuated mortality, reducing leukocyte infiltration and lung damage at day 5 and day 7 post-infection. AT-01-KG is a Formyl Peptide Receptor 2 (designated FPR2/3 in mice) agonist, and the protective responses were not observed in fpr2/3 -/- animals. In mice treated with LXA4 (50 μg/kg/day, i.p., days 3-6 post-infection), at day 7, macrophage reprogramming was observed, as seen by a decrease in classically activated macrophages and an increase in alternatively activated macrophages in the lungs. Furthermore, the number of apoptotic cells and cells undergoing efferocytosis was increased in the lavage of treated mice. Treatment also modulated the adaptive immune response, increasing the number of T helper 2 cells (Th2) and regulatory T (Tregs) cells in the lungs of the treated mice.

CONCLUSION

Therefore, treatment with a lipoxin A4 analog was beneficial in a model of influenza A infection in mice. The drug decreased inflammation and promoted resolution and beneficial immune responses, suggesting it may be useful in patients with severe influenza.

Harnessing Endogenous Peptide Compounds as Potential Therapeutics for Severe Influenza

BACKGROUND

Excessive pulmonary inflammation and damage are characteristic features of severe influenza virus infections. LAT8881 is a synthetic 16-amino acid cyclic peptide form of a naturally occurring C-terminal fragment of human growth hormone with therapeutic efficacy against influenza. Shorter linear peptides are typically easier to manufacture and formulate for delivery than larger cyclic peptides. A 6-amino acid linear peptide fragment of LAT8881, LAT9997, was investigated as a potential influenza therapy.

METHODS

LAT9997 was evaluated for its potential to limit disease in a preclinical mouse model of severe influenza infection.

RESULTS

Intranasal treatment of mice with either LAT8881 or LAT9997 from day 1 following influenza infection significantly improved survival outcomes. Initiating LAT9997 treatment at the onset of severe disease also significantly improved disease severity. Greater disease resistance in LAT9997-treated mice correlated with reduced lung immunopathology, damage markers, vascular leak, and epithelial cell death. Treatment reduced viral loads, cytokines, and neutrophil infiltration in the airways yet maintained protective alveolar macrophages in a dose-dependent manner. Sequential trimming of N- and C-terminal amino acids from LAT9997 revealed a structure-activity relationship.

CONCLUSIONS

These findings provide preclinical evidence that therapeutic LAT9997 treatment limits viral burden and characteristic features of severe influenza, including hyperinflammation and lung damage.

SUMMARY

Excessive pulmonary inflammation and damage are characteristic features of severe influenza virus infections. LAT9997 is a linear peptide fragment derived from human growth hormone. This study provides preclinical evidence that therapeutic LAT9997 treatment limits viral burden, hyperinflammation, and lung damage.

Treatment with lipoxin A 4 improves influenza A infection outcome through macrophage reprogramming, anti-inflammatory and pro-resolutive responses

Objective and design

Here, we evaluated whether a synthetic lipoxin mimetic, designated AT-01-KG, would improve the course of influenza A infection in a murine model.

Treatment

Mice were infected with influenza A/H1N1 and treated with AT-01-KG (1.7 mg/kg/day, i.p.) at day 3 post-infection.

Methods

Mortality rate was assessed up to day 21 and inflammatory parameters were assessed at days 5 and 7.

Results

AT-01-KG attenuated mortality, reducing leukocyte infiltration and lung damage at day 5 and day 7 post-infection. AT-01-KG is a Formyl Peptide Receptor 2 (designated FPR2/3 in mice) agonist, and the protective responses were not observed in FPR2/3 -/- animals. In mice treated with LXA4 (50mg/kg/day, i.p., days 3-6 post-infection), at day 7, macrophage reprogramming was observed, as seen by a decrease in classically activated macrophages and an increase in alternatively activated macrophages in the lungs. Furthermore, the number of apoptotic cells and cells undergoing efferocytosis was increased in the lavage of treated mice. Treatment also modulated the adaptive immune response, increasing the number of anti-inflammatory T cells (Th2) and regulatory T (Tregs) cells in the lungs of the treated mice.

Conclusions

Therefore, treatment with a lipoxin A4 analog was beneficial in a model of influenza A infection in mice. The drug decreased inflammation and promoted resolution and beneficial immune responses, suggesting it may be useful in patients with severe influenza.

Diet-induced obesity affects influenza disease severity and transmission dynamics in ferrets

Obesity, and the associated metabolic syndrome, is a risk factor for increased disease severity with a variety of infectious agents, including influenza virus. Yet, the mechanisms are only partially understood. As the number of people, particularly children, living with obesity continues to rise, it is critical to understand the role of host status on disease pathogenesis. In these studies, we use a diet-induced obese ferret model and tools to demonstrate that, like humans, obesity resulted in notable changes to the lung microenvironment, leading to increased clinical disease and viral spread to the lower respiratory tract. The decreased antiviral responses also resulted in obese animals shedding higher infectious virus for a longer period, making them more likely to transmit to contacts. These data suggest that the obese ferret model may be crucial to understanding obesity's impact on influenza disease severity and community transmission and a key tool for therapeutic and intervention development for this high-risk population.

Exposure to PM2.5 modulate the pro-inflammatory and interferon responses against influenza virus infection in a human 3D bronchial epithelium model

Epidemiological studies showed a positive association between exposure to PM2.5 and the severity of influenza virus infection. However, the mechanisms by which PM2.5 can disrupt antiviral defence are still unclear. From this perspective, the objective of this study was to evaluate the effects of PM2.5 on antiviral signalling in the respiratory epithelium using the bronchial Calu-3 cell line grown at the air-liquid interface. Pre-exposure to PM2.5 before infection with the influenza virus was investigated, as well as a co-exposure. Although a physical interaction between the virus and the particles seems possible, no effect of PM2.5 on viral replication was observed during co-exposure, although a downregulation of IFN-β release was associated to PM2.5 exposure. However, pre-exposure slightly increased the viral nucleoprotein production and the pro-inflammatory response. Conversely, the level of the myxovirus resistance protein A (MxA), an interferon-stimulated gene (ISG) induced by IFN-β, was reduced. Therefore, these results suggest that pre-exposure to PM2.5 could alter the antiviral response of bronchial epithelial cells, increasing their susceptibility to viral infection.

Treatment with inhaled aerosolised ethanol reduces viral load and potentiates macrophage responses in an established influenza mouse model

AIM

Treatment options for viral lung infections are currently limited. We aimed to explore the safety and efficacy of inhaled ethanol in an influenza-infection mouse model.

MATERIALS AND METHODS

In a safety and tolerability experiment, 80 healthy female BALB/c mice (20 per group) were exposed to nebulized saline (control) or three concentrations of ethanol (40/60/80% ethanol v/v in water) for 3x30-minute periods, with a two-hour break between exposures. In a separate subsequent experiment, 40 Female BALB/c mice were nasally inoculated with 104.5 plaque-forming units of immediate virulence "Mem71" influenza. Infection was established for 48-h before commencing treatment in 4 groups of 10 mice with either nebulized saline (control) or one of 3 different concentrations of ethanol (40/60/80% ethanol v/v in water) for 3x30-minute periods daily over three consecutive days. In both experiments, mouse behavior, clinical scores, weight change, bronchoalveolar lavage cell viability, cellular composition, and cytokine levels, were assessed 24-h following the final exposure, with viral load also assessed after the second experiment.

RESULTS

In uninfected BALB/c mice, 3x30-minute exposures to nebulized 40%, 60%, and 80% ethanol resulted in no significant differences in mouse weights, cell counts/viability, cytokines, or morphometry measures. In Mem71-influenza infected mice, we observed a dose-dependent reduction in viral load in the 80%-treated group and potentiation of macrophage numbers in the 60%- and 80%-treated groups, with no safety concerns.

CONCLUSIONS

Our data provides support for inhaled ethanol as a candidate treatment for respiratory infections.

Respiratory viral infection promotes the awakening and outgrowth of dormant metastatic breast cancer cells in lungs

Breast cancer is the second most common cancer globally. Most deaths from breast cancer are due to metastatic disease which often follows long periods of clinical dormancy1. Understanding the mechanisms that disrupt the quiescence of dormant disseminated cancer cells (DCC) is crucial for addressing metastatic progression. Infection with respiratory viruses (e.g. influenza or SARS-CoV-2) is common and triggers an inflammatory response locally and systemically2,3. Here we show that influenza virus infection leads to loss of the pro-dormancy mesenchymal phenotype in breast DCC in the lung, causing DCC proliferation within days of infection, and a greater than 100-fold expansion of carcinoma cells into metastatic lesions within two weeks. Such DCC phenotypic change and expansion is interleukin-6 (IL-6)-dependent. We further show that CD4 T cells are required for the maintenance of pulmonary metastatic burden post-influenza virus infection, in part through attenuation of CD8 cell responses in the lungs. Single-cell RNA-seq analyses reveal DCC-dependent impairment of T-cell activation in the lungs of infected mice. SARS-CoV-2 infected mice also showed increased breast DCC expansion in lungs post-infection. Expanding our findings to human observational data, we observed that cancer survivors contracting a SARS-CoV-2 infection have substantially increased risks of lung metastatic progression and cancer-related death compared to cancer survivors who did not. These discoveries underscore the significant impact of respiratory viral infections on the resurgence of metastatic cancer, offering novel insights into the interconnection between infectious diseases and cancer metastasis.

Newcastle disease virus suppresses antigen presentation via inhibiting IL-12 expression in dendritic cells

As a potential vectored vaccine, Newcastle disease virus (NDV) has been subject to various studies for vaccine development, while relatively little research has outlined the immunomodulatory effect of the virus in antigen presentation. To elucidate the key inhibitory factor in regulating the interaction of infected dendritic cells (DCs) and T cells, DCs were pretreated with the NDV vaccine strain LaSota as an inhibitor and stimulated with lipopolysaccharide (LPS) for further detection by enzyme-linked immunosorbent assay (ELISA), flow cytometry, immunoblotting, and quantitative real-time polymerase chain reaction (qRT-PCR). The results revealed that NDV infection resulted in the inhibition of interleukin (IL)-12p40 in DCs through a p38 mitogen-activated protein kinase (MAPK)‍-dependent manner, thus inhibiting the synthesis of IL-12p70, leading to the reduction in T cell proliferation and the secretion of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and IL-6 induced by DCs. Consequently, downregulated cytokines accelerated the infection and viral transmission from DCs to T cells. Furthermore, several other strains of NDV also exhibited inhibitory activity. The current study reveals that NDV can modulate the intensity of the innate‍‒‍adaptive immune cell crosstalk critically toward viral invasion improvement, highlighting a novel mechanism of virus-induced immunosuppression and providing new perspectives on the improvement of NDV-vectored vaccine.

Aryl hydrocarbon receptor activation alters immune cell populations in the lung and bone marrow during coronavirus infection

Respiratory viral infections are one of the major causes of illness and death worldwide. Symptoms associated with respiratory infections can range from mild to severe, and there is limited understanding of why there is large variation in severity. Environmental exposures are a potential causative factor. The aryl hydrocarbon receptor (AHR) is an environment-sensing molecule expressed in all immune cells. Although there is considerable evidence that AHR signaling influences immune responses to other immune challenges, including respiratory pathogens, less is known about the impact of AHR signaling on immune responses during coronavirus (CoV) infection. In this study, we report that AHR activation significantly altered immune cells in the lungs and bone marrow of mice infected with a mouse CoV. AHR activation transiently reduced the frequency of multiple cells in the mononuclear phagocyte system, including monocytes, interstitial macrophages, and dendritic cells in the lung. In the bone marrow, AHR activation altered myelopoiesis, as evidenced by a reduction in granulocyte-monocyte progenitor cells and an increased frequency of myeloid-biased progenitor cells. Moreover, AHR activation significantly affected multiple stages of the megakaryocyte lineage. Overall, these findings indicate that AHR activation modulates multiple aspects of the immune response to a CoV infection. Given the significant burden of respiratory viruses on human health, understanding how environmental exposures shape immune responses to infection advances our knowledge of factors that contribute to variability in disease severity and provides insight into novel approaches to prevent or treat disease.NEW & NOTEWORTHY Our study reveals a multifaceted role for aryl hydrocarbon receptor (AHR) signaling in the immune response to coronavirus (CoV) infection. Sustained AHR activation during in vivo mouse CoV infection altered the frequency of mature immune cells in the lung and modulated emergency hematopoiesis, specifically myelopoiesis and megakaryopoiesis, in bone marrow. This provides new insight into immunoregulation by the AHR and extends our understanding of how environmental exposures can impact host responses to respiratory viral infections.

Beneficial and Detrimental Effects of Cytokines during Influenza and COVID-19

Cytokines are signaling molecules that play a role in myriad processes, including those occurring during diseases and homeostasis. Their homeostatic function begins during embryogenesis and persists throughout life, including appropriate signaling for the cell and organism death. During viral infections, antiviral cytokines such as interferons and inflammatory cytokines are upregulated. Despite the well-known benefits of these cytokines, their levels often correlate with disease severity, linking them to unfavorable outcomes. In this review, we discuss both the beneficial and pathological functions of cytokines and the potential challenges in separating these two roles. Further, we discuss challenges in targeting these cytokines during disease and propose a new method for quantifying the cytokine effect to limit the pathological consequences while preserving their beneficial effects.

Self-Assembled Nanostructures Presenting Repetitive Arrays of Subunit Antigens for Enhanced Immune Response

Infectious diseases pose persistent threats to public health, demanding advanced vaccine technologies. Nanomaterial-based delivery systems offer promising solutions to enhance immunogenicity while minimizing reactogenicity. We introduce a self-assembled vaccine (SAV) platform employing antigen-polymer conjugates designed to facilitate robust immune responses. The SAVs exhibit efficient cellular uptake by dendritic cells (DCs) and macrophages, which are crucial players in the innate immune system. The high-density antigen presentation of this SAV platform enhances the affinity for DCs through multivalent recognition, significantly augmenting humoral immunity. SAV induced high levels of immunoglobulin G (IgG), IgG1, and IgG2a, suggesting that mature DCs efficiently induced B cell activation through multivalent antigen recognition. Universality was confirmed by applying it to respiratory viruses, showcasing its potential as a versatile vaccine platform. Furthermore, we have also demonstrated strong protection against influenza A virus infection with SAV containing hemagglutinin, which is used in influenza A virus subunit vaccines. The efficacy and adaptability of this nanostructured vaccine present potential utility in combating infectious diseases.

Mcl-1 Protein and Viral Infections: A Narrative Review

MCL-1 is the prosurvival member of the Bcl-2 family. It prevents the induction of mitochondria-dependent apoptosis. The molecular mechanisms dictating the host cell viability gain importance in the context of viral infections. The premature apoptosis of infected cells could interrupt the pathogen replication cycle. On the other hand, cell death following the effective assembly of progeny particles may facilitate virus dissemination. Thus, various viruses can interfere with the apoptosis regulation network to their advantage. Research has shown that viral infections affect the intracellular amount of MCL-1 to modify the apoptotic potential of infected cells, fitting it to the "schedule" of the replication cycle. A growing body of evidence suggests that the virus-dependent deregulation of the MCL-1 level may contribute to several virus-driven diseases. In this work, we have described the role of MCL-1 in infections caused by various viruses. We have also presented a list of promising antiviral agents targeting the MCL-1 protein. The discussed results indicate targeted interventions addressing anti-apoptotic MCL1 as a new therapeutic strategy for cancers as well as other diseases. The investigation of the cellular and molecular mechanisms involved in viral infections engaging MCL1 may contribute to a better understanding of the regulation of cell death and survival balance.

Cytokine storm and translating IL-6 biology into effective treatments for COVID-19

As of May 3, 2023, the Coronavirus disease 2019 (COVID-19) pandemic has resulted in more than 760 million confirmed cases and over 6.9 million deaths. Several patients have developed pneumonia, which can deteriorate into acute respiratory distress syndrome. The primary etiology may be attributed to cytokine storm, which is triggered by the excessive release of proinflammatory cytokines and subsequently leads to immune dysregulation. Considering that high levels of interleukin-6 (IL-6) have been detected in several highly pathogenic coronavirus-infected diseases, such as severe acute respiratory syndrome in 2002, the Middle East respiratory syndrome in 2012, and COVID-19, the IL-6 pathway has emerged as a key in the pathogenesis of this hyperinflammatory state. Thus, we review the history of cytokine storm and the process of targeting IL-6 signaling to elucidate the pivotal role played by tocilizumab in combating COVID-19.

Effects of Glucose Levels on Inflammation and Amino Acid Utilization in Lipopolysaccharide-Induced Bovine Mammary Epithelial Cells

Glucose and amino acids are important sources of nutrients in the synthetic milk of dairy cows, and understanding the fate of amino acids is essential to optimize the utilization of amino acids in milk protein synthesis, thereby reducing nutrient inefficiencies during lactation. The purpose of this study was to investigate the effects of LPS and different concentrations of glucose on (1) the expression of inflammatory factors and genes, (2) the glucose metabolism, and (3) amino acid utilization in BMECs. The results showed that there was an interaction (LPS × glucose, p < 0.05) between LPS and glucose content in the inflammatory cytokine genes (IL-6 and TNF-α) and the inflammatory regulatory genes (CXCL2, CXCL8, and CCL5). With the addition of LPS, the HG + LPS group caused downregulated (p < 0.05) expression of IL-6 and TNF-α, compared with the LG + LPS group. Interestingly, compared with the LG + LPS group, the HG + LPS group upregulated (p < 0.05) the expression of CXCL2, CXCL8, and CCL5. LPS supplementation increased (p = 0.056) the consumption of glucose and GLUT1 gene expression (p < 0.05) and tended to increase (p = 0.084) the LDHA gene expression of BMECs under conditions of different concentrations of glucose culture. High glucose content increased (p < 0.001) the consumption of glucose and enhanced (p < 0.05) the GLUT1, HK1, HK2, and LDHA gene expression of BMECs with or without LPS incubation, and there was an interaction (LPS × glucose, p < 0.05) between LPS and glucose concentrations in GLUT1 gene expression. In this study, LPS enhanced (p < 0.05) the consumption of amino acids such as tryptophan, leucine, isoleucine, methionine, valine, histidine, and glutamate, while high levels of glucose decreased (p < 0.01) consumption, except in the case of tyrosine. For histidine, leucine, isoleucine, and valine consumption, there was an interaction (LPS × glucose, p < 0.05) between LPS and glucose levels. Overall, these findings suggest that relatively high glucose concentrations may lessen the LPS-induced BMEC inflammatory response and reduce amino acid consumption, while low glucose concentrations may increase the demand for most amino acids through proinflammatory responses.

Understanding COVID-19 progression with longitudinal peripheral blood mononuclear cell proteomics: Changes in the cellular proteome over time

The clinical presentation of COVID-19 is highly variable, and understanding the underlying biological processes is crucial. This study utilized a proteomic analysis to investigate dysregulated processes in the peripheral blood mononuclear cells of patients with COVID-19 compared to healthy volunteers. Samples were collected at different stages of the disease, including hospital admission, after 7 days of hospitalization, and 30 days after discharge. Metabolic pathway alterations and increased abundance of neutrophil-related proteins were observed in patients. Patients progressing to critical illness had significantly low-abundance proteins in the pentose phosphate and glycolysis pathways compared with those presenting clinical recovery. Important biological processes, such as fatty acid concentration and glucose metabolism disorder, remained altered even after 30 days of hospital discharge. Temporal proteomic changes revealed distinct pathways in critically ill and non-critically ill patients. Our study emphasizes the significance of longitudinal cellular proteomic studies in identifying disease progression-related pathways and persistent protein changes post-hospitalization.

Expression of IFN-Gamma is significantly reduced during severity of covid-19 infection in hospitalized patients

Cytokines play an important role in SARS-CoV-2 infection progression and severity. A number of inflammatory cytokines have been directly associated with disease severity including IL-6 (interleukin-6), IL-10, TNF-α (tumor necrosis factor alpha), IFN-γ (interferon-gamma). Here, in this study, the aim was to better understand the interplay between host immune response mediated by cytokines and severity of SARS-CoV-2 infection by assessing cytokine expression. Therefore, we measured expression levels of a total of 12 genes (IFNA-1, IFN-γ, IL-1α, IL-1β, IL-4, IL-6, IL-7, IL-10, IL-11, IL-13, IL-15, and IL-27) encoding inflammatory, anti-inflammatory and regulatory cytokines using QRT-PCR in hospitalized patients with severe infection compared to mildly infected. IFN-γ was identified as a potent marker of disease severity as indicated previously. Moreover, levels of IL-7 were also found to be partially reduced in patients compared to the healthy controls and linked negatively to disease severity. Identification of these cytokines may be helpful in not only understanding disease pathogenesis but also in better management of the patients after covid infection.

Diet-induced obesity impacts influenza disease severity and transmission dynamics in ferrets

Obesity, and the associated metabolic syndrome, is a risk factor for increased disease severity with a variety of infectious agents, including influenza virus. Yet the mechanisms are only partially understood. As the number of people, particularly children, living with obesity continues to rise, it is critical to understand the role of host status on disease pathogenesis. In these studies, we use a novel diet-induced obese ferret model and new tools to demonstrate that like humans, obesity resulted in significant changes to the lung microenvironment leading to increased clinical disease and viral spread to the lower respiratory tract. The decreased antiviral responses also resulted in obese animals shedding higher infectious virus for longer making them more likely to transmit to contacts. These data suggest the obese ferret model may be crucial to understanding obesity's impact on influenza disease severity and community transmission, and a key tool for therapeutic and intervention development for this high-risk population.

Teaser

A new ferret model and tools to explore obesity's impact on respiratory virus infection, susceptibility, and community transmission.

Efficacy of an isoxazole-3-carboxamide analog of pleconaril in mouse models of Enterovirus-D68 and Coxsackie B5

Enteroviruses (EV) cause a number of life-threatening infectious diseases. EV-D68 is known to cause respiratory illness in children that can lead to acute flaccid myelitis. Coxsackievirus B5 (CVB5) is commonly associated with hand-foot-mouth disease. There is no antiviral treatment available for either. We have developed an isoxazole-3-carboxamide analog of pleconaril (11526092) which displayed potent inhibition of EV-D68 (IC50 58 nM) as well as other enteroviruses including the pleconaril-resistant Coxsackievirus B3-Woodruff (IC50 6-20 nM) and CVB5 (EC50 1 nM). Cryo-electron microscopy structures of EV-D68 in complex with 11526092 and pleconaril demonstrate destabilization of the EV-D68 MO strain VP1 loop, and a strain-dependent effect. A mouse respiratory model of EV-D68 infection, showed 3-log decreased viremia, favorable cytokine response, as well as statistically significant 1-log reduction in lung titer reduction at day 5 after treatment with 11526092. An acute flaccid myelitis neurological infection model did not show efficacy. 11526092 was tested in a mouse model of CVB5 infection and showed a 4-log TCID50 reduction in the pancreas. In summary, 11526092 represents a potent in vitro inhibitor of EV with in vivo efficacy in EV-D68 and CVB5 animal models suggesting it is worthy of further evaluation as a potential broad-spectrum antiviral therapeutic against EV.

Exercise With a Novel Digital Device Increased Serum Anti-influenza Antibody Titers After Influenza Vaccination

It has been reported that some exercise could enhance the anti-viral antibody titers after vaccination including influenza and coronavirus disease 2019 vaccines. We developed SAT-008, a novel digital device, consists of physical activities and activities related to the autonomic nervous system. We assessed the feasibility of SAT-008 to boost host immunity after an influenza vaccination by a randomized, open-label, and controlled study on adults administered influenza vaccines in the previous year. Among 32 participants, the SAT-008 showed a significant increase in the anti-influenza antibody titers assessed by hemagglutination-inhibition test against antigen subtype B Yamagata lineage after 4 wk of vaccination and subtype B Victoria lineage after 12 wk (p<0.05). There was no difference in the antibody titers against subtype "A." The SAT-008 also showed significant increase in the plasma cytokine levels of IL-10, IL-1β, and IL-6 at weeks 4 and 12 after the vaccination (p<0.05). A new approach using the digital device may boost host immunity against virus via vaccine adjuvant-like effects.

Trial Registration

ClinicalTrials.gov Identifier: NCT04916145.

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.

Neutrophils in host defense, healing, and hypersensitivity: Dynamic cells within a dynamic host

Neutrophils are cells of the innate immune system that are extremely abundant in vivo and respond quickly to infection, injury, and inflammation. Their constant circulation throughout the body makes them some of the first responders to infection, and indeed they play a critical role in host defense against bacterial and fungal pathogens. It is now appreciated that neutrophils also play an important role in tissue healing after injury. Their short life cycle, rapid response kinetics, and vast numbers make neutrophils a highly dynamic and potentially extremely influential cell population. It has become clear that they are highly integrated with other cells of the immune system and can thus exert critical effects on the course of an inflammatory response; they can further impact tissue homeostasis and recovery after challenge. In this review, we discuss the fundamentals of neutrophils in host defense and healing; we explore the relationship between neutrophils and the dynamic host environment, including circadian cycles and the microbiome; we survey the field of neutrophils in asthma and allergy; and we consider the question of neutrophil heterogeneity-namely, whether there could be specific subsets of neutrophils that perform different functions in vivo.

B-cell lymphoma-2 family proteins-activated proteases as potential therapeutic targets for influenza A virus and severe acute respiratory syndrome coronavirus-2: Killing two birds with one stone?

The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has led to a global health emergency. There are many similarities between SARS-CoV-2 and influenza A virus (IAV); both are single-stranded RNA viruses infecting airway epithelial cells and have similar modes of replication and transmission. Like IAVs, SARS-CoV-2 infections poses serious challenges due to the lack of effective therapeutic interventions, frequent appearances of new strains of the virus, and development of drug resistance. New approaches to control these infectious agents may stem from cellular factors or pathways that directly or indirectly interact with viral proteins to enhance or inhibit virus replication. One of the emerging concepts is that host cellular factors and pathways are required for maintaining viral genome integrity, which is essential for viral replication. Although IAVs have been studied for several years and many cellular proteins involved in their replication and pathogenesis have been identified, very little is known about how SARS-CoV-2 hijacks host cellular proteins to promote their replication. IAV induces apoptotic cell death, mediated by the B-cell lymphoma-2 (Bcl-2) family proteins in infected epithelia, and the pro-apoptotic members of this family promotes viral replication by activating host cell proteases. This review compares the life cycle and mode of replication of IAV and SARS-CoV-2 and examines the potential roles of host cellular proteins, belonging to the Bcl-2 family, in SARS-CoV-2 replication to provide future research directions.

Anti-inflammatory actions of Pentosan polysulfate sodium in a mouse model of influenza virus A/PR8/34-induced pulmonary inflammation

Introduction

There is an unmet medical need for effective anti-inflammatory agents for the treatment of acute and post-acute lung inflammation caused by respiratory viruses. The semi-synthetic polysaccharide, Pentosan polysulfate sodium (PPS), an inhibitor of NF-kB activation, was investigated for its systemic and local anti-inflammatory effects in a mouse model of influenza virus A/PR8/1934 (PR8 strain) mediated infection.

Methods

Immunocompetent C57BL/6J mice were infected intranasally with a sublethal dose of PR8 and treated subcutaneously with 3 or 6 mg/kg PPS or vehicle. Disease was monitored and tissues were collected at the acute (8 days post-infection; dpi) or post-acute (21 dpi) phase of disease to assess the effect of PPS on PR8-induced pathology.

Results

In the acute phase of PR8 infection, PPS treatment was associated with a reduction in weight loss and improvement in oxygen saturation when compared to vehicle-treated mice. Associated with these clinical improvements, PPS treatment showed a significant retention in the numbers of protective SiglecF+ resident alveolar macrophages, despite uneventful changes in pulmonary leukocyte infiltrates assessed by flow cytometry. PPS treatment in PR8- infected mice showed significant reductions systemically but not locally of the inflammatory molecules, IL-6, IFN-g, TNF-a, IL-12p70 and CCL2. In the post-acute phase of infection, PPS demonstrated a reduction in the pulmonary fibrotic biomarkers, sICAM-1 and complement factor C5b9.

Discussion

The systemic and local anti-inflammatory actions of PPS may regulate acute and post-acute pulmonary inflammation and tissue remodeling mediated by PR8 infection, which warrants further investigation.

The impact of supervised physical exercise on chemokines and cytokines in recovered COVID-19 patients

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus, which induces a high release of pro-inflammatory chemokines and cytokines, leading to severe systemic disorders. Further, evidence has shown that recovered COVID-19 patients still have some symptoms and disorders from COVID-19. Physical exercise can have many health benefits. It is known to be a potent regulator of the immune system, which includes frequency, intensity, duration, and supervised by a professional. Given the confinement and social isolation or hospitalization of COVID-19 patients, the population became sedentary or opted for physical exercise at home, assuming the guarantee of the beneficial effects of physical exercise and reducing exposure to SARS-CoV-2. This study aimed to investigate the effects of a supervised exercise protocol and a home-based unsupervised exercise protocol on chemokine and cytokine serum levels in recovered COVID-19 patients. This study was a prospective, parallel, two-arm clinical trial. Twenty-four patients who had moderate to severe COVID-19 concluded the intervention protocols of this study. Participants were submitted to either supervised exercise protocol at the Clinical Hospital of the Federal University of Pernambuco or home-based unsupervised exercise for 12 weeks. We analyzed serum levels of chemokines (CXCL8/IL-8, CCL5/RANTES, CXCL9/MIG, CCL2/MCP-1, and CXCL10/IP-10) and cytokines (IL-2, IL-4, IL-6, IL-10, IL-17A, TNF-α, and IFN-γ). Before the interventions, no significant differences were observed in the serum levels of chemokines and cytokines between the supervised and home-based unsupervised exercise groups. The CXCL8/IL-8 (p = 0.04), CCL2/MCP-1 (p = 0.03), and IFN-γ (p = 0.004) levels decreased after 12 weeks of supervised exercise. In parallel, an increase in IL-2 (p = 0.02), IL-6 (p = 0.03), IL-4 (p = 0.006), and IL-10 (p = 0.04) was observed after the supervised protocol compared to pre-intervention levels. No significant differences in all the chemokines and cytokines were found after 12 weeks of the home-based unsupervised exercise protocol. Given the results, the present study observed that supervised exercise was able to modulate the immune response in individuals with post-COVID-19, suggesting that supervised exercise can mitigate the inflammatory process associated with COVID-19 and its disorders.

Clinical trial registration

https://ensaiosclinicos.gov.br/rg/RBR-7z3kxjk, identifier U1111-1272-4730.

Alloferon and Zanamivir Show Effective Antiviral Activity against Influenza A Virus (H1N1) Infection In Vitro and In Vivo

The use of vaccines is the most effective and reliable method for the prevention of viral infections. However, research on evaluation of effective therapeutic agents for use in treatment after infection is necessary. Zanamivir was administered through inhalation for treatment of pandemic influenza A/H1N1 in 2009. However, the emergence of drug-resistant strains can occur rapidly. Alloferon, an immunomodulatory drug developed as an NK cell activator, exerts antiviral effects against various viruses, particularly influenza viruses. Therefore, alloferon and zanamivir were administered in combination in an effort to improve the antiviral effect of zanamivir by reducing H1N1 resistance. First, we confirmed that administration of combined treatment would result in effective inhibition of viral proliferation in MDCK and A549 cells infected with H1N1. Production of IL-6 and MIP-1α in these cells and the activity of p38 MAPK and c-Jun that are increased by H1N1 were inhibited by combined treatment. Mice were then infected intranasally with H1N1, and examination of the antiviral efficacy of the alloferon/zanamivir combination was performed. The results showed that combined treatment after infection with H1N1 prevented weight loss, increased the survival rate, and improved lung fibrosis. Combined treatment also resulted in reduced infiltration of neutrophils and macrophages into the lungs. Combined treatment effectively inhibited the activity of p38 MAPK and c-Jun in lung tissue, which was increased by infection with H1N1. Therefore, the combination of alloferon/zanamivir effectively prevents the development of H1N1-mediated inflammation in the lungs by inhibiting the production of inflammatory mediators and migration of inflammatory cells into lung tissue.

Could treatment with immunomodulatory agents targeting IL-1, IL-6, or JAK signalling improve outcomes in patients with severe influenza pneumonia? A systematic and narrative review

Background: Influenza is a global cause of morbidity and mortality and a significant risk for a future pandemic infection. Host hyperinflammation, similar to that seen in COVID-19, may occur in response to influenza virus pneumonia, with Janus kinase (JAK) signalling and proinflammatory cytokines Interleukin (IL)-1 and IL-6 involved. Immune modulation treatment of hospitalised and critically ill COVID-19 patients, including with IL-6 and JAK inhibitors, has been found to be beneficial. Significant interest exists in the use of immunomodulatory agents targeting these pathways in the treatment of severe influenza pneumonia. Methods: We conducted a review with both systematic and narrative methods to assess whether, in patients with severe influenza pneumonia, treatment with immunomodulatory agents targeting IL-1, IL-6 or JAK signalling, in comparison to no immune modulation, is beneficial and improves clinical outcomes. Results: Our systematic search screened 5409 records and found no randomised controlled trials of IL-1, IL-6 or JAK immunomodulatory agents in patients with severe influenza pneumonia. To support this systematic search, we provide a narrative review of the biological rationale, previous use of these agents, including in hospitalised patients with COVID-19, and an overview of their safety profiles. Conclusions: Although immune modulation has proven successful in treating hospitalised and critically ill patients with COVID-19 and a biological rationale exists for testing these agents in influenza, no agents targeting IL-1, IL-6 or JAK signalling have been assessed in randomised controlled trials of patients with severe influenza pneumonia. This highlights a significant evidence gap.

Intestinal microbiota analysis and network pharmacology reveal the mechanism by which Lianhua Qingwen capsule improves the immune function of mice infected with influenza A virus

Objective

Lianhua Qingwen capsule (LHQW) can attenuate lung injury caused by influenza virus infection. However, it is unclear whether the intestinal microbiota plays a role in LHQW activity in ameliorating viral infectious pneumonia. This study aimed to investigate the role of intestinal microbiota in LHQW activity in ameliorating viral infectious pneumonia and its possible mechanisms.

Research design and methods

A mouse model of influenza A viral pneumonia was established by intranasal administration in BALB/c mice. Detection of influenza virus in the lungs, pathological examination of the lungs and small intestine, and biochemical detection of inflammatory indices were performed. The effects of LHQW on intestinal microbiota were evaluated by 16S rRNA gene sequencing. The key components and targets of LHQW were screened via network pharmacology and verified through molecular docking, molecular dynamics simulation, and free binding energy calculations.

Results

Body weight decreased, inflammatory factor levels were disturbed, and the lung and intestinal mucosal barriers were significantly injured in the infected group. The alpha diversity of the intestinal microbiota decreased, and the abundance of Bacteroidetes, Muribaculaceae_unclassified, and Streptococcus decreased significantly. LHQW treatment reduced the viral load in the lungs, rescued body weight and survival, alleviated lung and intestinal mucosal barrier injury, reversed the reduction in the intestinal microbiota alpha diversity, and significantly increased the abundance of Bacteroidetes and Muribaculaceae. Network pharmacological analysis showed that six active herbal medicinal compounds from LHQW could regulate the intestinal microbiota and inhibit the immune-inflammatory response through the Toll-like receptor (TLR) and nuclear factor-κB (NF-κB) signalling pathways in the lungs.

Conclusion

These results suggest that LHQW is effective for treating influenza A virus infectious pneumonia, and the mechanism is associated with the regulation of the TLR4/NF-κB signalling pathway in the lungs by restoring intestinal microbiota and repairing the intestinal wall.

The Il6 -39 kb enhancer containing clustered GATA2- and PU.1-binding sites is essential for Il6 expression in murine mast cells

Mast cells serve as a first-line defense of innate immunity. Interleukin-6 (IL-6) induced by bacterial lipopolysaccharide (LPS) in mast cells plays a crucial role in antibacterial protection. The zinc finger transcription factor GATA2 cooperatively functions with the ETS family transcription factor PU.1 in multiple mast cell activities. However, the regulatory landscape directed by GATA2 and PU.1 under inflammation remains elusive. We herein showed that a large proportion of GATA2-binding peaks were closely located with PU.1-binding peaks in distal cis-regulatory regions of inflammatory cytokine genes in mast cells. Notably, GATA2 and PU.1 played crucial roles in promoting LPS-mediated inflammatory cytokine production. Genetic ablation of GATA2-PU.1-clustered binding sites at the Il6 -39 kb region revealed its central role in LPS-induced Il6 expression in mast cells. We demonstrate a novel collaborative activity of GATA2 and PU.1 in cytokine induction upon inflammatory stimuli via the GATA2-PU.1 overlapping sites in the distal cis-regulatory regions.

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GATA2- and PU.1-binding peaks are closely located in distal enhancers of cytokine genes

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GATA2 and PU.1 play crucial roles in promoting LPS-mediated cytokine induction

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The Il6 -39 kb enhancer containing GATA2 and PU.1 motifs are crucial for Il6 induction

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GATA2 inhibitor exerts anti-inflammatory effects via reducing cytokine induction

Transcriptome analysis of pre-immune state induced by interferon gamma inhibiting the replication of H9N2 avian influenza viruses in chicken embryo fibroblasts

Interferon (IFN), a critical antiviral cytokine produced by pathogens-induced cells, plays an important role in host innate immune system. In this study, to investigate the inhibition effect of IFN on avian influenza virus (AIV), Chicken Embryo Fibroblasts (CEFs) was infected by H₉N₂ AIV. The pre-immune state and transcriptome analysis have been observed and performed. The result showed chicken interferon gamma (chIFN-γ) have the most inhibitory effect on H₉N₂ virus among three types of chicken interferons (chIFNs). Inhibition of chIFN-γ on H₉N₂ virus was verified by indirect immunofluorescence, RT-qPCR and western blot. The possible signaling pathways induced by chIFN-γ with or without virus were analyzed by transcriptome. The transcriptome data were compared among H₉N₂-infected, chIFN-γ-treated, chIFN-γ + H₉N₂-treated, and Control groups. In summary, RNA-sequencing (RNA-seq) data suggested that H₉N₂ virus infection resulted in corresponding response of certain defensive, inflammatory and metabolism pathways to the virus replication in CEFs. Furthermore, while CEFs were treated with chIFN-γ, many immune-related signaling pathways in cells are affected and altered. Antiviral genes involved in these immune pathways such as interferon regulatory factors, chemokines, interferon-stimulated genes (ISGs) and transcription factors were significantly up-regulated, and showed significant antiviral responses. Compared with virus infected CEFs alone, pretreatment with IFN induced the expression of antiviral genes and activated related antiviral pathways, inhibited the viral replication as result. Our study provided functional annotations for antiviral genes and the basis for studying the mechanism of chIFN-γ mediated response against H₉N₂ AIV.

Cigarette smoke augments CSF3 expression in neutrophils to compromise alveolar-capillary barrier function during influenza infection

BACKGROUND

Cigarette smokers are at increased risk of acquiring influenza, developing severe disease and requiring hospitalisation/intensive care unit admission following infection. However, immune mechanisms underlying this predisposition are incompletely understood, and therapeutic strategies for influenza are limited.

METHODS

We used a mouse model of concurrent cigarette smoke exposure and H1N1 influenza infection, colony-stimulating factor (CSF)3 supplementation/receptor (CSF3R) blockade and single-cell RNA sequencing (scRNAseq) to investigate this relationship.

RESULTS

Cigarette smoke exposure exacerbated features of viral pneumonia such as oedema, hypoxaemia and pulmonary neutrophilia. Smoke-exposed infected mice demonstrated an increase in viral (v)RNA, but not replication-competent viral particles, relative to infection-only controls. Interstitial rather than airspace neutrophilia positively predicted morbidity in smoke-exposed infected mice. Screening of pulmonary cytokines using a novel dysregulation score identified an exacerbated expression of CSF3 and interleukin-6 in the context of smoke exposure and influenza. Recombinant (r)CSF3 supplementation during influenza aggravated morbidity, hypothermia and oedema, while anti-CSF3R treatment of smoke-exposed infected mice improved alveolar-capillary barrier function. scRNAseq delineated a shift in the distribution of Csf3 + cells towards neutrophils in the context of cigarette smoke and influenza. However, although smoke-exposed lungs were enriched for infected, highly activated neutrophils, gene signatures of these cells largely reflected an exacerbated form of typical influenza with select unique regulatory features.

CONCLUSION

This work provides novel insight into the mechanisms by which cigarette smoke exacerbates influenza infection, unveiling potential therapeutic targets (e.g. excess vRNA accumulation, oedematous CSF3R signalling) for use in this context, and potential limitations for clinical rCSF3 therapy during viral infectious disease.

Interleukin-6-dependent epithelial fluidization initiates fibrotic lung remodeling

Chronic disease results from the failure of tissues to maintain homeostasis. In the lung, coordinated repair of the epithelium is essential for preserving homeostasis. In animal models and human lung disease, airway epithelial cells mobilize in response to lung injury, resulting in the formation of airway-like cysts with persistent loss of functional cell types and parenchymal architecture. Using live-cell imaging of human lung epithelial cultures and mouse precision-cut lung slices, we demonstrated that distal airway epithelia are aberrantly fluidized both after injury and in fibrotic lung disease. Through transcriptomic profiling and pharmacologic stimulation of epithelial cultures, we identified interleukin-6 (IL-6) signaling as a driver of tissue fluidization. This signaling cascade occurred independently of canonical Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling but instead was dependent on a downstream SRC family kinase (SFK)-yes-associated protein (YAP) axis. Airway epithelial-fibroblast cocultures revealed that the fibrotic mesenchyme acts as a source of IL-6 family cytokines, which drive airway fluidization. Inhibition of the IL-6-SFK-YAP cascade was sufficient to prevent fluidization in both in vitro and ex vivo models. Last, we demonstrated a reduction in fibrotic lung remodeling in mice through genetic or pharmacologic targeting of IL-6-related signaling. Together, our findings illustrate the critical role of airway epithelial fluidization in coordinating the balance between homeostatic lung repair and fibrotic airspace remodeling.

The hormetic and hermetic role of IL-6

Interleukin-6 is a pleiotropic cytokine regulating different tissues and organs in diverse and sometimes discrepant ways. The dual and sometime hermetic nature of IL-6 action has been highlighted in several contexts and can be explained by the concept of hormesis, in which beneficial or toxic effects can be induced by the same molecule depending on the intensity, persistence, and nature of the stimulation. According with hormesis, a low and/or controlled IL-6 release is associated with anti-inflammatory, antioxidant, and pro-myogenic actions, whereas increased systemic levels of IL-6 can induce pro-inflammatory, pro-oxidant and pro-fibrotic responses. However, many aspects regarding the multifaceted action of IL-6 and the complex nature of its signal transduction remains to be fully elucidated. In this review we collect mechanistic insight into the molecular networks contributing to normal or pathologic changes during advancing age and in chronic diseases. We point out the involvement of IL-6 deregulation in aging-related diseases, dissecting the hormetic action of this key mediator in different tissues, with a special focus on skeletal muscle. Since IL-6 can act as an enhancer of detrimental factor associated with both aging and pathologic conditions, such as chronic inflammation and oxidative stress, this cytokine could represent a "Gerokine", a determinant of the switch from physiologic aging to age-related diseases.

Neutrophil subsets and their differential roles in viral respiratory diseases

Neutrophils play significant roles in immune homeostasis and as neutralizers of microbial infections. Recent evidence further suggests heterogeneity of neutrophil developmental and activation states that exert specialized effector functions during inflammatory disease conditions. Neutrophils can play multiple roles during viral infections, secreting inflammatory mediators and cytokines that contribute significantly to host defense and pathogenicity. However, their roles in viral immunity are not well understood. In this review, we present an overview of neutrophil heterogeneity and its impact on the course and severity of viral respiratory infectious diseases. We focus on the evidence demonstrating the crucial roles neutrophils play in the immune response toward respiratory infections, using influenza as a model. We further extend the understanding of neutrophil function with the studies pertaining to COVID-19 disease and its neutrophil-associated pathologies. Finally, we discuss the relevance of these results for future therapeutic options through targeting and regulating neutrophil-specific responses.

In vitro anti-influenza assessment of anionic compounds ascorbate, acetate and citrate

BACKGROUND

Influenza A virus (IAV) infection remains a serious public health threat. Due to drug resistance and side effects of the conventional antiviral drugs, repurposing the available natural compounds with high tolerability and fewer side effects has attracted researchers' attention. The aim of this study was to screen in vitro anti-influenza activity of three anionic compounds ascorbate, acetate, and citrate.

METHODS

The non-cytotoxic concentration of the compounds was determined by MTT assay and examined for the activity against IAV in simultaneous, pre-, and post-penetration combination treatments over 1 h incubation on Madin-Darby Canine Kidney (MDCK) cell line. The virus titer and viral load were determined using hemagglutination assay (HA) and qPCR, respectively. Few pro-inflammatory and anti-inflammatory cytokines were evaluated at RNA and protein levels by qPCR and ELISA, respectively.

RESULTS

The non-cytotoxic concentrations of the ascorbate (200 mg/ml), acetate and citrate (both 3 mg/ml) reduced the viral titer by 6.5, 4.5, and 1.5 logs in the simultaneous combination treatment. The M protein gene copy number decreased significantly in simultaneous treatment (P < 0.01). The expression of cytokines was also affected by the treatment of these compounds.

CONCLUSIONS

These anionic compounds could affect the influenza virus load, thereby reducing pro-inflammatory cytokines and increasing anti-inflammatory cytokines levels.

Mesenchymal Stem Cells and Their Small Extracellular Vesicles as Crucial Immunological Efficacy for Hepatic Diseases

Mesenchymal stem cell small extracellular vesicles (MSC-sEVs) are a priority for researchers because of their role in tissue regeneration. sEVs act as paracrine factors and carry various cargos, revealing the state of the parent cells and contributing to cell–cell communication during both physiological and pathological circumstances. Hepatic diseases are mainly characterized by inflammatory cell infiltration and hepatocyte necrosis and fibrosis, bringing the focus onto immune regulation and other regulatory mechanisms of MSCs/MSC-sEVs. Increasing evidence suggests that MSCs and their sEVs protect against acute and chronic liver injury by inducing macrophages (MΦ) to transform into the M2 subtype, accelerating regulatory T/B (Treg/Breg) cell activation and promoting immunosuppression. MSCs/MSC-sEVs also prevent the proliferation and differentiation of T cells, B cells, dendritic cells (DCs), and natural killer (NK) cells. This review summarizes the potential roles for MSCs/MSC-sEVs, including immunomodulation and tissue regeneration, in various liver diseases. There is also a specific focus on the use of MSC-sEVs for targeted drug delivery to treat hepatitis.

Type I interferon regulates proteolysis by macrophages to prevent immunopathology following viral infection

The ability to treat severe viral infections is limited by our understanding of the mechanisms behind virus-induced immunopathology. While the role of type I interferons (IFNs) in early control of viral replication is clear, less is known about how IFNs can regulate the development of immunopathology and affect disease outcomes. Here, we report that absence of type I IFN receptor (IFNAR) is associated with extensive immunopathology following mucosal viral infection. This pathology occurred independent of viral load or type II immunity but required the presence of macrophages and IL-6. The depletion of macrophages and inhibition of IL-6 signaling significantly abrogated immunopathology. Tissue destruction was mediated by macrophage-derived matrix metalloproteinases (MMPs), as MMP inhibition by doxycycline and Ro 28–2653 reduced the severity of tissue pathology. Analysis of post-mortem COVID-19 patient lungs also displayed significant upregulation of the expression of MMPs and accumulation of macrophages. Overall, we demonstrate that IFNs inhibit macrophage-mediated MMP production to prevent virus-induced immunopathology and uncover MMPs as a therapeutic target towards viral infections.

T helper type (Th1/Th2) responses to SARS-CoV-2 and influenza A (H1N1) virus: From cytokines produced to immune responses

Cytokines produced by T helper cells (Th cells) have essential roles in the body's defense against viruses. Type 1 T helper (Th1) cells are essential for the host defense toward intracellular pathogens while T helper type 2 (Th2) cells are considered to be critical for the helminthic parasites' elimination swine-origin influenza A (H1N1) virus, a disease led to an epidemic in 2009 and rapidly spread globally via human-to-human transmission. Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused a global pandemic in 2020 and is a serious threat to the public health. Pulmonary immunopathology is the leading cause of death during influenza and SARS-CoV-2 epidemics and pandemics. Influenza and SARS-CoV-2 cause high levels of cytokines in the lung. Both inadequate levels and high levels of specific cytokines can have side effects. In this literature review article, we want to compare the Th1 and Th2 cells responses in SARS-CoV-2 and H1N1.

Gammaherpesvirus Alters Alveolar Macrophages According to the Host Genetic Background and Promotes Beneficial Inflammatory Control over Pneumovirus Infection

Human respiratory syncytial virus (hRSV) infection brings a wide spectrum of clinical outcomes, from a mild cold to severe bronchiolitis or even acute interstitial pneumonia. Among the known factors influencing this clinical diversity, genetic background has often been mentioned. In parallel, recent evidence has also pointed out that an early infectious experience affects heterologous infections severity. Here, we analyzed the importance of these two host-related factors in shaping the immune response in pneumoviral disease. We show that a prior gammaherpesvirus infection improves, in a genetic background-dependent manner, the immune system response against a subsequent lethal dose of pneumovirus primary infection notably by inducing a systematic expansion of the CD8+ bystander cell pool and by modifying the resident alveolar macrophages (AMs) phenotype to induce immediate cyto/chemokinic responses upon pneumovirus exposure, thereby drastically attenuating the host inflammatory response without affecting viral replication. Moreover, we show that these AMs present similar rapid and increased production of neutrophil chemokines both in front of pneumoviral or bacterial challenge, confirming recent studies attributing a critical antibacterial role of primed AMs. These results corroborate other recent studies suggesting that the innate immunity cells are themselves capable of memory, a capacity hitherto reserved for acquired immunity.

Neutrophil Homeostasis and Emergency Granulopoiesis: The Example of Systemic Juvenile Idiopathic Arthritis

Neutrophils are key pathogen exterminators of the innate immune system endowed with oxidative and non-oxidative defense mechanisms. More recently, a more complex role for neutrophils as decision shaping cells that instruct other leukocytes to fine-tune innate and adaptive immune responses has come into view. Under homeostatic conditions, neutrophils are short-lived cells that are continuously released from the bone marrow. Their development starts with undifferentiated hematopoietic stem cells that pass through different immature subtypes to eventually become fully equipped, mature neutrophils capable of launching fast and robust immune responses. During severe (systemic) inflammation, there is an increased need for neutrophils. The hematopoietic system rapidly adapts to this increased demand by switching from steady-state blood cell production to emergency granulopoiesis. During emergency granulopoiesis, the de novo production of neutrophils by the bone marrow and at extramedullary sites is augmented, while additional mature neutrophils are rapidly released from the marginated pools. Although neutrophils are indispensable for host protection against microorganisms, excessive activation causes tissue damage in neutrophil-rich diseases. Therefore, tight regulation of neutrophil homeostasis is imperative. In this review, we discuss the kinetics of neutrophil ontogenesis in homeostatic conditions and during emergency myelopoiesis and provide an overview of the different molecular players involved in this regulation. We substantiate this review with the example of an autoinflammatory disease, i.e. systemic juvenile idiopathic arthritis.

Characterizing the Neutrophilic Inflammation in Chronic Rhinosinusitis With Nasal Polyps

The mechanisms underlying neutrophilic inflammation in chronic rhinosinusitis with nasal polyps (CRSwNP) remain poorly investigated. This study aimed to examine the factors that contribute to tissue neutrophilia in CRSwNP. The numbers of neutrophils and active caspase-3-positive apoptotic neutrophils in sinonasal tissues were assessed via immunofluorescence staining. The 95th percentile of tissue neutrophil numbers in control subjects was selected as a cut-off to define neutrophil-high (Neu-high) or neutrophil-low (Neu-low) nasal polyps (NPs). The levels of 34 inflammatory mediators in sinonasal tissues were analyzed using Bio-Plex assay. Purified human peripheral blood neutrophils were incubated with nasal tissue homogenates, and the apoptotic neutrophils were assessed via flow cytometry. The cut-off for Neu-high NPs was >10 myeloperoxidase positive cells/high-power field. Compared with Neu-low NPs, Neu-high NPs had higher tissue levels of IL-1β, IL-1Ra, IL-6, IL-8, G-CSF, MCP-1, and MIP-1α, but lower levels of IL-5, IL-13, IgE, and eosinophils. Principal component and multiple correspondence analyses revealed mixed type 1, type 2, and type 3 endotypes for Neu-low NPs, and predominant type 1 and type 3 endotypes for Neu-high NPs. Neu-high NPs had lower percentages of apoptotic neutrophils than Neu-low NPs. The numbers of neutrophils and the percentages of apoptotic neutrophils correlated with G-CSF and IL-6 levels in the NPs. Tissue homogenates from Neu-high NPs, but not those from Neu-low NPs, suppressed neutrophil apoptosis in vitro, which was reversed by anti-G-CSF treatment. Tissue neutrophil numbers were associated with difficult-to-treat disease in patients with CRSwNP after surgery. We propose that G-CSF promotes neutrophilic inflammation by inhibiting neutrophil apoptosis in CRSwNP.

Phenotypes, Lung Microbiota and Cytokine Responses in Pneumonia After Hematopoietic Stem Cell Transplantation

Objective

We aim to identify phenotypes of hematopoietic stem cell transplantation (HSCT) patients with pneumonia, discover relations of microbiota composition, cytokine profile, and outcomes between phenotypes. Specific cytokines will be evaluated for their role in lung injury in a murine model.

Methods

HSCT patients with pneumonia were included, and clustering of variables including cytokine levels provided the phenotypes. Outcomes were compared between phenotypes. Analysis of lung microbiota identified marker species of phenotypes. In the murine model, marker species-related cytokine regulations and the role of cytokines in lung injury were evaluated.

Results

Seventy-two patients were included, and two phenotypes were identified, namely "reactive" (N=21) and "nonreactive" (N=51) phenotype. Compared to their counterparts, patients with nonreactive phenotype had lower serum IL-6, IL-8, less severe inflammation, worse outcomes and more viruses as marker species in lung microbiota. The animal study validated the pathogens specific cytokine responses that presented in the human study and the potential protective role of IL-6 in these patients.

Conclusion

HSCT patients with pneumonia can be clustered into two phenotypes with different marker species and outcomes: the "nonreactive" phenotype and the "reactive" phenotype. Serum cytokine levels were different between the two phenotypes, which indicate the existence of the pathogen-related cytokine responses. For patients with the "nonreactive" phenotype, IL-6 therapy may improve their prognosis, which should be further tested in clinical studies.

A brief molecular insight of COVID-19: epidemiology, clinical manifestation, molecular mechanism, cellular tropism and immuno-pathogenesis

In December 2019, the emergence and expansion of novel and infectious respiratory virus SARS-CoV-2 originated from Wuhan, China caused an unprecedented threat to the public health and became a global pandemic. SARS-CoV-2 is an enveloped, positive sense and single stranded RNA virus belonging to genera betacoronavirus, of Coronaviridae family. The viral genome sequencing studies revealed 75-80% similarity with SARS-CoV. SARS-CoV-2 mainly affects the lower respiratory system and may progress to pneumonia and Acute Respiratory Distress Syndrome (ARDS). Apart from life-threatening situations and burden on the global healthcare system, the COVID-19 pandemic has imposed several challenges on the worldwide economics and livelihood. The novel pathogen is highly virulent, rapidly mutating and has a tendency to cross the species boundaries such as from bats to humans through the evolution and natural selection from intermediate host. In this review we tried to summarize the overall picture of SARS-CoV-2 including origin/ emergence, epidemiology, pathogenesis, genome organization, comparative analysis with other CoVs, infection and replication mechanism along with cellular tropism and immunopathogenesis which will provide a brief panoramic view about the virus and disease.

Innate immune responses at the asymptomatic stage of influenza A viral infections of Streptococcus pneumoniae colonized and non-colonized mice

Seasonal Influenza A virus (IAV) infections can promote dissemination of upper respiratory tract commensals such as Streptococcus pneumoniae to the lower respiratory tract resulting in severe life-threatening pneumonia. Here, we aimed to compare innate immune responses in the lungs of healthy colonized and non-colonized mice after IAV challenge at the initial asymptomatic stage of infection. Responses during a severe bacterial pneumonia were profiled for comparison. Cytokine and innate immune cell imprints of the lungs were analyzed. Irrespective of the colonization status, mild H1N1 IAV infection was characterized by a bi-phasic disease progression resulting in full recovery of the animals. Already at the asymptomatic stage of viral infection, the pro-inflammatory cytokine response was as high as in pneumococcal pneumonia. Flow cytometry analyses revealed an early influx of inflammatory monocytes into the lungs. Neutrophil influx was mostly limited to bacterial infections. The majority of cells, except monocytes, displayed an activated phenotype characterized by elevated CCR2 and MHCII expression. In conclusion, we show that IAV challenge of colonized healthy mice does not automatically result in severe co-infection. However, a general local inflammatory response was noted at the asymptomatic stage of infection irrespective of the infection type.

Tpl2 Ablation Leads to Hypercytokinemia and Excessive Cellular Infiltration to the Lungs During Late Stages of Influenza Infection

Tumor progression locus 2 (Tpl2) is a serine-threonine kinase known to promote inflammation in response to various pathogen-associated molecular patterns (PAMPs), inflammatory cytokines and G-protein-coupled receptors and consequently aids in host resistance to pathogens. We have recently shown that Tpl2-/- mice succumb to infection with a low-pathogenicity strain of influenza (x31, H3N2) by an unknown mechanism. In this study, we sought to characterize the cytokine and immune cell profile of influenza-infected Tpl2-/- mice to gain insight into its host protective effects. Although Tpl2-/- mice display modestly impaired viral control, no virus was observed in the lungs of Tpl2-/- mice on the day of peak morbidity and mortality suggesting that morbidity is not due to virus cytopathic effects but rather to an overactive antiviral immune response. Indeed, increased levels of interferon-β (IFN-β), the IFN-inducible monocyte chemoattractant protein-1 (MCP-1, CCL2), Macrophage inflammatory protein 1 alpha (MIP-1α; CCL3), MIP-1β (CCL4), RANTES (CCL5), IP-10 (CXCL10) and Interferon-γ (IFN-γ) was observed in the lungs of influenza-infected Tpl2-/- mice at 7 days post infection (dpi). Elevated cytokine and chemokines were accompanied by increased infiltration of the lungs with inflammatory monocytes and neutrophils. Additionally, we noted that increased IFN-β correlated with increased CCL2, CXCL1 and nitric oxide synthase (NOS2) expression in the lungs, which has been associated with severe influenza infections. Bone marrow chimeras with Tpl2 ablation localized to radioresistant cells confirmed that Tpl2 functions, at least in part, within radioresistant cells to limit pro-inflammatory response to viral infection. Collectively, this study suggests that Tpl2 tempers inflammation during influenza infection by constraining the production of interferons and chemokines which are known to promote the recruitment of detrimental inflammatory monocytes and neutrophils.

Neuraminidase in Virus-like Particles Contributes to the Protection against High Dose of Avian Influenza Virus Challenge Infection

Neuraminidase is an important target for influenza vaccination. In this study, we generated avian influenza VLPs, expressing hemagglutinin (HA), neuraminidase (NA), HA and NA co-expressed (HANA), to evaluate the protective role of NA against a high (10LD₅₀) and low (2LD₅₀) dose of avian influenza virus challenge infections. A single immunization with HANA VLPs elicited the highest level of virus-specific IgG, IgG1, and IgG2a responses from the sera post-vaccination and the lungs post-challenge-infection. Potent antibody-secreting cell responses were observed from the spleens and lungs of HANA-VLP-immunized mice post-challenge-infection. HANA VLPs induced the highest CD4⁺ T cell, CD8⁺ T cell, and germinal center B cells, while strongly limiting inflammatory cytokine production in the lungs compared to other VLP immunization groups. In correlation with these findings, the lowest bodyweight losses and lung virus titers were observed from HANA VLP immunization, and all of the immunized mice survived irrespective of the challenge dose. Contrastingly, VLPs expressing either HA or NA alone failed to elicit complete protection. These results indicated that NA in VLPs played a critical role in inducing protection against a high dose of the challenge infection.

Potential Immunomodulatory Properties of Biologically Active Components of Spices Against SARS-CoV-2 and Pan β-Coronaviruses

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced COVID-19 has emerged as a defining global health crisis in current times. Data from the World Health Organization shows demographic variations in COVID-19 severity and lethality. Diet may play a significant role in providing beneficial host cell factors contributing to immunity against deadly SARS-CoV-2 pathogenesis. Spices are essential components of the diet that possess anti-inflammatory, antioxidant, and antiviral properties. Hyperinflammation, an aberrant systemic inflammation associated with pneumonia, acute respiratory failure, and multiorgan dysfunction, is a major clinical outcome in COVID-19. Knowing the beneficial properties of spices, we hypothesize that spice-derived bioactive components can modulate host immune responses to provide protective immunity in COVID-19. This study emphasizes that biologically active components of spices might alleviate the sustained pro-inflammatory condition by inhibiting the activity of tumor necrosis factor-alpha (TNF-α), interleukins (IL6, IL8), and chemokine (CCL2) known to be elevated in COVID-19. Spices may potentially prevent the tissue damage induced by oxidative stress and pro-inflammatory mediators during SARS-CoV-2 infection. The current study also highlights the effects of spices on the antioxidant pathways mediated by Nrf2 (nuclear factor erythroid 2-related factor 2) and Hmox1 (heme oxygenase 1) to restore oxidative homeostasis and protect from aberrant tissue damage. Taken together, the anti-inflammatory and antioxidant activities of bioactive components of spices may hold a promise to target the cellular pathways for developing antivirals against SARS-CoV-2 and pan β-coronaviruses.

Role of neutrophils in acute viral infection

Neutrophils play multiple roles in acute viral infections. They restrict viral replication and diffusion through phagocytosis, degranulation, respiratory burst, secretion of cytokines, and the release of neutrophil extracellular traps, as well as, activate the adaptive immune response. However, the overactivation of neutrophils may cause tissue damage and lead to poor outcomes. Additionally, some characteristics and functions of neutrophils, such as cell number, lifespan, and antiviral capability, can be influenced while eliminating viruses. This review provides a general description of the protective and pathological roles of neutrophils in acute viral infection.