Pandemic H1N1 2009 influenza A virus induces weak cytokine responses in human macrophages and dendritic cells and is highly sensitive to the antiviral actions of interferons

Characteristics of two zoonotic swine influenza A(H1N1) viruses isolated in Germany from diseased patients

Interspecies transmission of influenza A viruses (IAV) from pigs to humans is a concerning event as porcine IAV represent a reservoir of potentially pandemic IAV. We conducted a comprehensive analysis of two porcine A(H1N1)v viruses isolated from human cases by evaluating their genetic, antigenic and virological characteristics. The HA genes of those human isolates belonged to clades 1C.2.1 and 1C.2.2, respectively, of the A(H1N1) Eurasian avian-like swine influenza lineage. Antigenic profiling revealed substantial cross-reactivity between the two zoonotic H1N1 viruses and human A(H1N1)pdm09 virus and some swine viruses, but did not reveal cross-reactivity to H1N2 and earlier human seasonal A(H1N1) viruses. The solid-phase direct receptor binding assay analysis of both A(H1N1)v showed a predominant binding to α2-6-sialylated glycans similar to human-adapted IAV. Investigation of the replicative potential revealed that both A(H1N1)v viruses grow in human bronchial epithelial cells to similar high titers as the human A(H1N1)pdm09 virus. Cytokine induction was studied in human alveolar epithelial cells A549 and showed that both swine viruses isolated from human cases induced higher amounts of type I and type III IFN, as well as IL6 compared to a seasonal A(H1N1) or a A(H1N1)pdm09 virus. In summary, we demonstrate a remarkable adaptation of both zoonotic viruses to propagate in human cells. Our data emphasize the needs for continuous monitoring of people and regions at increased risk of such trans-species transmissions, as well as systematic studies to quantify the frequency of these events and to identify viral molecular determinants enhancing the zoonotic potential of porcine IAV.

The inflammatory spectrum of cardiomyopathies

Infiltration of the myocardium with various cell types, cytokines and chemokines plays a crucial role in the pathogenesis of cardiomyopathies including inflammatory cardiomyopathies and myocarditis. A more comprehensive understanding of the precise immune mechanisms involved in acute and chronic myocarditis is essential to develop novel therapeutic approaches. This review offers a comprehensive overview of the current knowledge of the immune landscape in cardiomyopathies based on etiology. It identifies gaps in our knowledge about cardiac inflammation and emphasizes the need for new translational approaches to improve our understanding thus enabling development of novel early detection methods and more effective treatments.

Lactiplantibacillus pentoses CCFM1227 Produces Desaminotyrosine to Protect against Influenza Virus H1N1 Infection through the Type I Interferon in Mice

Microbiota-derived desaminotyrosine (DAT) protects the host from influenza by modulating the type I interferon (IFN) response. The aim of this study was to investigate the antivirus effects of a DAT-producing bacteria strain. A comparative genomics analysis and UHPLC Q-Exactive MS were used to search for potential strains and confirm their ability to produce DAT, respectively. The anti-influenza functions of the DAT producer were evaluated using an antibiotic-treated mouse model by orally administering the specific strain before viral infection. The results showed the Lactiplantibacillus pentosus CCFM1227 contained the phy gene and produced DAT by degrading phloretin. In vivo, L. pentosus CCFM1227 re-inoculation increased the DAT level in feces, and protected from influenza through inhibiting viral replication and alleviating lung immunopathology. Furthermore, CCFM1227-derived DAT was positively correlated with the IFN-β level in the lung. The transcriptome results showed that CCFM1227 activated gene expression in the context of the defense response to the virus, and the response to interferon-beta. Moreover, CCFM1227 treatment upregulated the expression of MHC-I family genes, which regulate the adaptive immune response. In conclusion, L. pentosus CCFM1227 exerted antiviral effects by producing DAT in the gut, and this may provide a potential solution for creating effective antiviral probiotics.

Differential Leukocyte Expression of IFITM1 and IFITM3 in Patients with Severe Pandemic Influenza A(H1N1) and COVID-19

Interferon-induced transmembrane (IFITM) proteins mediate protection against enveloped viruses by blocking membrane fusion at endosomes. IFITM1 and IFITM3 are crucial for protection against influenza, and various single nucleotide polymorphisms altering their function have been linked to disease susceptibility. However, bulk IFITM1 and IFITM3 mRNA expression dynamics and their correlation with clinical outcomes have not been extensively addressed in patients with respiratory infections. In this study, we evaluated the expression of IFITM1 and IFITM3 in peripheral leukocytes from healthy controls and individuals with severe pandemic influenza A(H1N1) or coronavirus disease 2019 (COVID-19). Comparisons between participants grouped according to their clinical characteristics, underlying disease, and outcomes showed that the downregulation of IFITM1 was a distinctive characteristic of severe pandemic influenza A(H1N1) that correlated with outcomes, including mortality. Conversely, increased IFITM3 expression was a common feature of severe pandemic influenza A(H1N1) and COVID-19. Using a high-dose murine model of infection, we confirmed not only the downregulation of IFITM1 but also of IFITM3 in the lungs of mice with severe influenza, as opposed to humans. Analyses in the comparative cohort also indicate the possible participation of IFITM3 in COVID-19. Our results add to the evidence supporting a protective function of IFITM proteins against viral respiratory infections in humans.

Pleiotropic Effects of Influenza H1, H3, and B Baloxavir-Resistant Substitutions on Replication, Sensitivity to Baloxavir, and Interferon Expression

Baloxavir is an anti-influenza endonuclease inhibitor that targets the polymerase acidic (PA) protein of influenza A and B viruses. Our knowledge regarding the pleiotropic effects of baloxavir resistance-associated substitutions is limited. We generated recombinant A/California/04/09 (H1N1)-, A/Hong Kong/218849/2006 (H3N2)-, and B/Victoria/504/2000-like viruses that contained PA substitutions identified in baloxavir clinical trials and surveillance that could potentially be associated with baloxavir resistance. We characterized their susceptibility to baloxavir, impact on polymerase activity, viral growth, and ability to induce interferon (IFN) and IFN-stimulated genes expression in vitro. Four PA substitutions, H1N1 I38L/T, E199D, and B G199R, significantly reduced the sensitivity of the recombinant viruses to baloxavir (14.1-fold). We confirmed our findings by using the luciferase-based ribonucleoprotein minigenome assay and by using virus yield reduction assay in Calu-3 and normal human bronchial epithelial (NHBE) cells. We observed that I38L and E199D resulted in decreased viral replication of the H1N1 wild-type virus (1.4-fold) but the H1N1 I38T and B G199R substitutions did not significantly alter replication capacity in Calu-3 cells. In addition, H1N1 variants with PA I38L/T and E199D induced significantly higher levels of IFNB1 gene expression compared to the wild-type virus (4.2-fold). In contrast, the B variant, G199R, triggered the lowest levels of IFN genes in Calu-3 cells (1.6-fold). Because baloxavir is a novel anti-influenza therapeutic agent, identifying and characterizing substitutions associated with reduced sensitivity to baloxavir, as well as the impact of these substitutions on viral fitness, is paramount to the strategic implementation of this novel countermeasure.

Immune Responses to IAV Infection and the Roles of L-Selectin and ADAM17 in Lymphocyte Homing

Influenza A virus (IAV) infection is a global public health burden causing up to 650,000 deaths per year. Yearly vaccination programmes and anti-viral drugs currently have limited benefits; therefore, research into IAV is fundamental. Leukocyte trafficking is a crucial process which orchestrates the immune response to infection to protect the host. It involves several homing molecules and receptors on both blood vessels and leukocytes. A key mediator of this process is the transmembrane glycoprotein L-selectin, which binds to vascular addressins on blood vessel endothelial cells. L-selectin classically mediates homing of naïve and central memory lymphocytes to lymph nodes via high endothelial venules (HEVs). Recent studies have found that L-selectin is essential for homing of activated CD8⁺ T cells to influenza-infected lungs and reduction in virus load. A disintegrin and metalloproteinase 17 (ADAM17) is the primary regulator of cell surface levels of L-selectin. Understanding the mechanisms that regulate these two proteins are central to comprehending recruitment of T cells to sites of IAV infection. This review summarises the immune response to IAV infection in humans and mice and discusses the roles of L-selectin and ADAM17 in T lymphocyte homing during IAV infection.

Roles of Glycans and Non-glycans on the Epithelium and in the Immune System in H1-H18 Influenza A Virus Infections

The large variation of influenza A viruses (IAVs) in various susceptible hosts and their rapid evolution, which allows host/tissue switching, host immune escape, vaccine escape, and drug resistance, are difficult challenges for influenza control in all countries worldwide. Access and binding of the IAV to actual receptors at endocytic sites is critical for the establishment of influenza infection. In this chapter, the progress in identification of and roles of glycans and non-glycans on the epithelium and in the immune system in H1-H18 IAV infections are reviewed. The first part of the review is on current knowledge of H1-H16 IAV receptors on the epithelium including sialyl glycans, other negatively charged glycans, and annexins. The second part of the review focuses on H1-H16 IAV receptors in the immune system including acidic surfactant phospholipids, Sia on surfactant proteins, the carbohydrate recognition domain (CRD) of surfactant proteins, Sia on mucins, Sia and C-type lectins on macrophages and dendritic cells, and Sia on NK cells. The third part of the review is about a possible H17-H18 IAV receptor. Binding of these receptors to IAVs may result in inhibition or enhancement of IAV infection depending on their location, host cell type, and IAV strain. Among these receptors, host sialyl glycans are key determinants of viral hemagglutinin (HA) lectins for H1-H16 infections. HA must acquire mutations to bind to sialyl glycans that are dominant on a new target tissue when switching to a new host for efficient transmission and to bind to long sialyl glycans found in the case of seasonal HAs with multiple glycosylation sites as a consequence of immune evasion. Although sialyl receptors/C-type lectins on immune cells are decoy receptors/pathogen recognition receptors for capturing viral HA lectin/glycans protecting HA antigenic sites, some IAV strains do not escape, such as by release with neuraminidase, but hijack these molecules to gain entry and replication in immune cells. An understanding of the virus-host battle tactics at the receptor level might lead to the establishment of novel strategies for effective control of influenza.

Pharmacokinetics and Pharmacodynamics of Huanglian-Houpo Decoction Based on Berberine Hydrochloride and Magnolol Against H1N1 Influenza Virus

BACKGROUND AND OBJECTIVES

Huanglian-Houpo decoction (HH), which is recorded in the famous traditional Chinese medicine monograph "Puji Fang," contains two individual herbs, Huanglian (Rhizoma coptidis) and Houpo (Magnoliae officinalis cortex). It was regularly used to treat seasonal epidemic colds and influenzas in ancient China. Our laboratory discovered that HH has a significant anti-H1N1 influenza virus effect. However, no pharmacokinetic and pharmacodynamic data concerning the anti-H1N1 influenza virus activity of HH are available to date. In the current study, the concentration-time profiles of two major components of HH, berberine and magnolol, in rat plasma were investigated.

METHODS

An integrate pharmacokinetic approach was developed for evaluating the holistic pharmacokinetic characteristics of berberine and magnolol from HH. Additionally, the inhibition rate and levels of IFN-β in MDCK cells infected by influenza virus were analyzed. Data were calculated using 3p97 with pharmacokinetic analysis.

RESULTS

The estimated pharmacokinetic parameters were maximum plasma concentration (C_max) 0.9086 μg/ml, area under the concentration-time curve (AUC) 347.74 μg·min/ml, and time to reach C_max (T_max) 64.69 min for berberine and C_max = 0.9843 μg/ml, AUC= 450.64 μg·min/ml, T_max = 56.86 min for magnolol, respectively. Furthermore, integrated pharmacokinetic and pharmacodynamic analysis showed that the highest plasma concentration, inhibition rate and interferon-β (IFN-β) secretion of HH first increased and then weakened over time, reaching their peaks at 60 min. The plasma concentration of HH is directly related to the anti-influenza virus effect.

CONCLUSION

The results indicated that berberine and magnolol are the main active ingredients of HH related to its anti-influenza virus effect, which is related to the improvement of IFN-β secretion.

RNA-Seq Analysis of Influenza A Virus-Induced Transcriptional Changes in Mice Lung and Its Possible Implications for the Virus Pathogenicity in Mice

The influenza A virus (IAV) is an important cause of respiratory disease worldwide. It is well known that alveolar epithelial cells are the target cells for the IAV, but there is relatively limited knowledge regarding the role of macrophages during IAV infection. Here, we aimed to analyze transcriptome differences in mouse lungs and macrophage (RAW264.7) cell lines infected with either A/California/04/2009 H1N1 (CA09) or A/chicken/SD/56/2015 H9N2 (SD56) using deep sequencing. The uniquely differentially expressed genes (UDEGs) were analyzed with the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases; the results showed that the lungs infected with the two different viruses had different enrichments of pathways and terms. Interestingly, CA09 virus infection in mice was mostly involved with genes related to the extracellular matrix (ECM), while the most significant differences after SD56 infection in mice were in immune-related genes. Gene set enrichment analysis (GSEA) of RAW264.7 cells revealed that regulation of the cell cycle was of great significance after CA09 infection, whereas the regulation of the immune response was most enriched after SD56 infection, which was consistent with analysis results in the lung. Similar results were obtained from weighted gene co-expression network analysis (WGCNA), where cell cycle regulation was extensively activated in RAW264.7 macrophages infected with the CA09 virus. Disorder of the cell cycle is likely to affect their normal immune regulation, which may be an important factor leading to their different prognoses. These results provide insight into the mechanism of the CA09 virus that caused a pandemic and explain the different reactivities of monocytes/macrophages infected by H9N2 and H1N1 IAV subtypes.

Bioprinted Multi-Cell Type Lung Model for the Study of Viral Inhibitors

Influenza A virus (IAV) continuously causes epidemics and claims numerous lives every year. The available treatment options are insufficient and the limited pertinence of animal models for human IAV infections is hampering the development of new therapeutics. Bioprinted tissue models support studying pathogenic mechanisms and pathogen-host interactions in a human micro tissue environment. Here, we describe a human lung model, which consisted of a bioprinted base of primary human lung fibroblasts together with monocytic THP-1 cells, on top of which alveolar epithelial A549 cells were printed. Cells were embedded in a hydrogel consisting of alginate, gelatin and collagen. These constructs were kept in long-term culture for 35 days and their viability, expression of specific cell markers and general rheological parameters were analyzed. When the models were challenged with a combination of the bacterial toxins LPS and ATP, a release of the proinflammatory cytokines IL-1β and IL-8 was observed, confirming that the model can generate an immune response. In virus inhibition assays with the bioprinted lung model, the replication of a seasonal IAV strain was restricted by treatment with an antiviral agent in a dose-dependent manner. The printed lung construct provides an alveolar model to investigate pulmonary pathogenic biology and to support development of new therapeutics not only for IAV, but also for other viruses.

Fueling influenza and the immune response: Implications for metabolic reprogramming during influenza infection and immunometabolism

Recent studies support the notion that glycolysis and oxidative phosphorylation are rheostats in immune cells whose bioenergetics have functional outputs in terms of their biology. Specific intrinsic and extrinsic molecular factors function as molecular potentiometers to adjust and control glycolytic to respiratory power output. In many cases, these potentiometers are used by influenza viruses and immune cells to support pathogenesis and the host immune response, respectively. Influenza virus infects the respiratory tract, providing a specific environmental niche, while immune cells encounter variable nutrient concentrations as they migrate in response to infection. Immune cell subsets have distinct metabolic programs that adjust to meet energetic and biosynthetic requirements to support effector functions, differentiation, and longevity in their ever-changing microenvironments. This review details how influenza coopts the host cell for metabolic reprogramming and describes the overlap of these regulatory controls in immune cells whose function and fate are dictated by metabolism. These details are contextualized with emerging evidence of the consequences of influenza-induced changes in metabolic homeostasis on disease progression.

Type I Interferon Susceptibility Distinguishes SARS-CoV-2 from SARS-CoV

SARS-CoV-2, a novel coronavirus (CoV) that causes COVID-19, has recently emerged causing an ongoing outbreak of viral pneumonia around the world. While distinct from SARS-CoV, both group 2B CoVs share similar genome organization, origins to bat CoVs, and an arsenal of immune antagonists. In this report, we evaluate type I interferon (IFN-I) sensitivity of SARS-CoV-2 relative to the original SARS-CoV. Our results indicate that while SARS-CoV-2 maintains similar viral replication to SARS-CoV, the novel CoV is much more sensitive to IFN-I. In Vero E6 and in Calu3 cells, SARS-CoV-2 is substantially attenuated in the context of IFN-I pretreatment, whereas SARS-CoV is not. In line with these findings, SARS-CoV-2 fails to counteract phosphorylation of STAT1 and expression of ISG proteins, while SARS-CoV is able to suppress both. Comparing SARS-CoV-2 and influenza A virus in human airway epithelial cultures, we observe the absence of IFN-I stimulation by SARS-CoV-2 alone but detect the failure to counteract STAT1 phosphorylation upon IFN-I pretreatment, resulting in near ablation of SARS-CoV-2 infection. Next, we evaluated IFN-I treatment postinfection and found that SARS-CoV-2 was sensitive even after establishing infection. Finally, we examined homology between SARS-CoV and SARS-CoV-2 in viral proteins shown to be interferon antagonists. The absence of an equivalent open reading frame 3b (ORF3b) and genetic differences versus ORF6 suggest that the two key IFN-I antagonists may not maintain equivalent function in SARS-CoV-2. Together, the results identify key differences in susceptibility to IFN-I responses between SARS-CoV and SARS-CoV-2 that may help inform disease progression, treatment options, and animal model development.IMPORTANCE With the ongoing outbreak of COVID-19, differences between SARS-CoV-2 and the original SARS-CoV could be leveraged to inform disease progression and eventual treatment options. In addition, these findings could have key implications for animal model development as well as further research into how SARS-CoV-2 modulates the type I IFN response early during infection.

Investigation of the Potential Mechanism Governing the Effect of the Shen Zhu San on COVID-19 by Network Pharmacology

BACKGROUND

Since December 2019, coronavirus disease 2019 (COVID-19) due to SARS-CoV-2 infection has emerged in Wuhan and rapidly spread throughout China and even to other countries. Combined therapy with modern medicine and traditional Chinese medicine has been proposed, in which Shen Zhu San (SZS) was regarded as one of the basic prescriptions.

METHODS

Network pharmacological approaches along with candidate compound screening, target prediction, target tissue location, protein-protein interaction network, gene ontology (GO), KEGG enrichment analyses, and gene microarray analyses were applied.

RESULTS

A total of 627 targets of the 116 active ingredients of SZS were identified. Targets in immune cells and tissues were much more abundant than those in other tissues. A total of 597 targets were enriched in the GO biological cellular process, while 153 signaling pathways were enriched according to the KEGG analysis. A total of 450 SARS-related targets were integrated and intersected with the targets of SZS to identify 40 common targets that were significantly enriched in five immune function aspects of the immune system process during GO analysis. Several inflammation-related pathways were found to be significantly enriched throughout the study.

CONCLUSIONS

The therapeutic mechanisms of the effects of SZS on COVID-19 potentially involve four effects: suppressing cytokine storms, protecting the pulmonary alveolar-capillary barrier, regulating the immune response, and mediating cell death and survival.

Adjuvantation of an Influenza Hemagglutinin Antigen with TLR4 and NOD2 Agonists Encapsulated in Poly(D,L-Lactide-Co-Glycolide) Nanoparticles Enhances Immunogenicity and Protection against Lethal Influenza Virus Infection in Mice

Along with their excellent safety profiles, subunit vaccines are typically characterized by much weaker immunogenicity and protection efficacy compared to whole-pathogen vaccines. Here, we present an approach aimed at bridging this disadvantage that is based on synergistic collaboration between pattern-recognition receptors (PRRs) belonging to different families. We prepared a model subunit vaccine formulation using an influenza hemagglutinin antigen incorporated into poly-(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles adjuvanted with monophosphoryl lipid A (TLR4 agonist) and muramyl dipeptide (NOD2 agonist). The efficacy studies were conducted in comparison to control vaccine formulations containing individual PRR agonists. We show that the complex adjuvant based on TLR4 and NOD2 agonists potentiates proinflammatory cell responses (measured by activity of transcription factors and cytokine production both in vitro and in vivo) and enhances the phagocytosis of vaccine particles up to comparable levels of influenza virus uptake. Finally, mice immunized with vaccine nanoparticles containing both PRR agonists exhibited enhanced humoral (IgG, hemagglutination-inhibition antibody titers) and cellular (percentage of proliferating CD4+ T-cells, production of IFNɣ) immunity, leading to increased resistance to lethal influenza challenge. These results support the idea that complex adjuvants stimulating different PRRs may present a better alternative to individual PAMP-based adjuvants and could further narrow the gap between the efficacy of subunit versus whole-pathogen vaccines.

Extracorporeal Hemoperfusion as a Potential Therapeutic Option for Severe COVID-19 patients; a Narrative Review

The 2019 novel coronavirus (officially known as severe acute respiratory syndrome coronavirus 2, SARS-CoV2) was first found in Wuhan, China. On February 11, 2020, the World Health Organization (WHO) has declared the outbreak of the disease caused by SARS-CoV2, named coronavirus disease 2019 (COVID-19), as an emergency of international concern. Based on the current epidemiological surveys, some COVID-19 patients with severe infection gradually develop impairment of the respiratory system, acute kidney injury (AKI), multiple organ failure, and ultimately, death. Currently, there is no established pharmacotherapy available for COVID-19. As seen in influenza, immune damage mediated by excessive production of inflammatory mediators contributes to high incidence of complications and poor prognosis. Thus, removal or blocking the overproduction of these mediators potentially aids in reducing the deleterious cytokine storm and improving critically ill patients' outcomes. Based on previous experience of blood purification to treat cytokine storm syndrome (CSS) in severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), here we aimed to review the current literature on extracorporeal hemoperfusion as a potential therapeutic option for CSS-associated conditions, with a focus on severe COVID-19.

Type I interferon susceptibility distinguishes SARS-CoV-2 from SARS-CoV

SARS-CoV-2, a novel coronavirus (CoV) that causes COVID-19, has recently emerged causing an ongoing outbreak of viral pneumonia around the world. While distinct from SARS-CoV, both group 2B CoVs share similar genome organization, origins to bat CoVs, and an arsenal of immune antagonists. In this report, we evaluate type-I interferon (IFN-I) sensitivity of SARS-CoV-2 relative to the original SARS-CoV. Our results indicate that while SARS-CoV-2 maintains similar viral replication to SARS-CoV, the novel CoV is much more sensitive to IFN-I. In Vero and in Calu3 cells, SARS-CoV-2 is substantially attenuated in the context of IFN-I pretreatment, while SARS-CoV is not. In line with these findings, SARS-CoV-2 fails to counteract phosphorylation of STAT1 and expression of ISG proteins, while SARS-CoV is able to suppress both. Comparing SARS-CoV-2 and influenza A virus in human airway epithelial cultures (HAEC), we observe the absence of IFN-I stimulation by SARS-CoV-2 alone, but detect failure to counteract STAT1 phosphorylation upon IFN-I pretreatment resulting in near ablation of SARS-CoV-2 infection. Next, we evaluated IFN-I treatment post infection and found SARS-CoV-2 was sensitive even after establishing infection. Finally, we examined homology between SARS-CoV and SARS-CoV-2 in viral proteins shown to be interferon antagonists. The absence of an equivalent open reading frame (ORF) 3b and changes to ORF6 suggest the two key IFN-I antagonists may not maintain equivalent function in SARS-CoV-2. Together, the results identify key differences in susceptibility to IFN-I responses between SARS-CoV and SARS-CoV-2 that may help inform disease progression, treatment options, and animal model development.

Diverse and Unexpected Roles of Human Monocytes/Macrophages in the Immune Response to Influenza Virus

Human monocytes/macrophages play a central role in the immune response and defense of the host from influenza virus infection. They classically act as antigen-presenting cells for lymphocytes in the context of an immune cell cluster. In that setting, however, monocytes/macrophages exhibit additional, unexpected, roles. They are required for influenza virus infection of the lymphocytes in the cluster, and they are responsible for lymphocyte apoptosis via their synthesis and expression of the viral neuraminidase. Surprisingly, human alveolar macrophages, expected to be among the first cells to encounter the virus, are not susceptible to direct infection by a human influenza virus but can be infected when the virus is complexed with an antibody. Such monocyte/macrophage responses to influenza virus challenge should be considered part of a very complex but quite effective defense, since the common outcome is recovery of the host with development of immunity to the challenging strain of virus.

Hemagglutinin Stability Regulates H1N1 Influenza Virus Replication and Pathogenicity in Mice by Modulating Type I Interferon Responses in Dendritic Cells

Hemagglutinin (HA) stability, or the pH at which HA is activated to cause membrane fusion, has been associated with the replication, pathogenicity, transmissibility, and interspecies adaptation of influenza A viruses. Here, we investigated the mechanisms by which a destabilizing HA mutation, Y17H (activation pH, 6.0), attenuates virus replication and pathogenicity in DBA/2 mice compared to wild-type (WT) virus (activation pH, 5.5). The extracellular lung pH was measured to be near neutral (pH 6.9 to 7.5). WT and Y17H viruses had similar environmental stability at pH 7.0; thus, extracellular inactivation was unlikely to attenuate the Y17H virus. The Y17H virus had accelerated replication kinetics in MDCK, A549, and RAW 264.7 cells when inoculated at a multiplicity of infection (MOI) of 3 PFU/cell. The destabilizing mutation also increased early infectivity and type I interferon (IFN) responses in mouse bone marrow-derived dendritic cells (DCs). In contrast, the HA-Y17H mutation reduced virus replication in murine airway murine nasal epithelial cell and murine tracheal epithelial cell cultures and attenuated virus replication, virus spread, the severity of infection, and cellular infiltration in the lungs of mice. Normalizing virus infection and weight loss in mice by inoculating them with Y17H virus at a dose 500-fold higher than that of WT virus revealed that the destabilized mutant virus triggered the upregulation of more host genes and increased type I IFN responses and cytokine expression in DBA/2 mouse lungs. Overall, HA destabilization decreased virulence in mice by boosting early infection in DCs, resulting in the greater activation of antiviral responses, including the type I IFN response. These studies reveal that HA stability may regulate pathogenicity by modulating IFN responses.IMPORTANCE Diverse influenza A viruses circulate in wild aquatic birds, occasionally infecting farm animals. Rarely, an avian- or swine-origin influenza virus adapts to humans and starts a pandemic. Seasonal and many universal influenza vaccines target the HA surface protein, which is a key component of pandemic influenza viruses. Understanding the HA properties needed for replication and pathogenicity in mammals may guide response efforts to control influenza. Some antiviral drugs and broadly reactive influenza vaccines that target the HA protein have suffered resistance due to destabilizing HA mutations that do not compromise replicative fitness in cell culture. Here, we show that despite not compromising fitness in standard cell cultures, a destabilizing H1N1 HA stalk mutation greatly diminishes viral replication and pathogenicity in vivo by modulating type I IFN responses. This encourages targeting the HA stalk with antiviral drugs and vaccines as well as reevaluating previous candidates that were susceptible to destabilizing resistance mutations.

Insights into species-specific regulation of ANP32A on the mammalian-restricted influenza virus polymerase activity

The ANP32A is responsible for mammalian-restricted influenza virus polymerase activity. However, the mechanism of ANP32A modulation of polymerase activity remains poorly understood. Here, we report that chicken ANP32A (chANP32A) -X1 and -X2 stimulated mammalian-restricted PB2 627E polymerase activity in a dose-dependent manner. Distinct effects of ANP32A constructs suggested that the ¹⁸⁰VK¹⁸¹ residues within chANP32A-X1 are necessary but not sufficient to stimulate PB2 627E polymerase activity. The PB2 N567D, T598V, A613V or F636L mutations promoted PB2 627E polymerase activity and chANP32A-X1 showed additive effects, providing further support that species-specific regulation of ANP32A might be only relevant with the PB2 E627K mutation. Rescue of cycloheximide-mediated inhibition showed that ANP32A is species-specific for modulation of vRNA but not mRNA and cRNA, demonstrating chANP32A-X1 compensated for defective cRNPs produced by PB2 627E virus in mammalian cells. The promoter mutations of cRNA enhanced the restriction of PB2 627E polymerase in mammalian cells, which could be restored by chANP32A-X1, indicating that ANP32A is likely to regulate the interaction of viral polymerase with RNA promoter. Coimmunoprecipitation showed that ANP32A did not affect the primary cRNPs assembly. We propose a model that chANP32A-X1 regulates PB2 627E polymerase for suitable interaction with cRNA promoter for vRNA replication.

A Single-Stranded Oligonucleotide Inhibits Toll-Like Receptor 3 Activation and Reduces Influenza A (H1N1) Infection

The initiation of an immune response is dependent on the activation and maturation of dendritic cells after sensing pathogen associated molecular patterns by pattern recognition receptors. However, the response needs to be balanced as excessive pro-inflammatory cytokine production in response to viral or stress-induced pattern recognition receptor signaling has been associated with severe influenza A virus (IAV) infection. Here, we use an inhibitor of Toll-like receptor (TLR)3, a single-stranded oligonucleotide (ssON) with the capacity to inhibit certain endocytic routes, or a TLR3 agonist (synthetic double-stranded RNA PolyI:C), to evaluate modulation of innate responses during H1N1 IAV infection. Since IAV utilizes cellular endocytic machinery for viral entry, we also assessed ssON's capacity to affect IAV infection. We first show that IAV infected human monocyte-derived dendritic cells (MoDC) were unable to up-regulate the co-stimulatory molecules CD80 and CD86 required for T cell activation. Exogenous TLR3 stimulation did not overcome the IAV-mediated inhibition of co-stimulatory molecule expression in MoDC. However, TLR3 stimulation using PolyI:C led to an augmented pro-inflammatory cytokine response. We reveal that ssON effectively inhibited PolyI:C-mediated pro-inflammatory cytokine production in MoDC, notably, ssON treatment maintained an interferon response induced by IAV infection. Accordingly, RNAseq analyses revealed robust up-regulation of interferon-stimulated genes in IAV cultures treated with ssON. We next measured reduced IAV production in MoDC treated with ssON and found a length requirement for its anti-viral activity, which overlapped with its capacity to inhibit uptake of PolyI:C. Hence, in cases wherein an overreacting TLR3 activation contributes to IAV pathogenesis, ssON can reduce this signaling pathway. Furthermore, concomitant treatment with ssON and IAV infection in mice resulted in maintained weight and reduced viral load in the lungs. Therefore, extracellular ssON provides a mechanism for immune regulation of TLR3-mediated responses and suppression of IAV infection in vitro and in vivo in mice.

Anti-H7N9 avian influenza A virus activity of interferon in pseudostratified human airway epithelium cell cultures

BACKGROUND

Since H7N9 influenza A virus (H7N9) was first reported in 2013, five waves of outbreaks have occurred, posing a huge threat to human health. In preparation for a potential H7N9 epidemic, it is essential to evaluate the efficacy of anti-H7N9 drugs with an appropriate model.

METHODS

Well-differentiated pseudostratified human airway epithelium (HAE) cells were grown at the air-liquid interface, and the H7N9 cell tropism and cytopathic effect were detected by immunostaining and hematoxylin-eosin (HE) staining. The H7N9 replication kinetics and anti-H7N9 effect of recombinant human α2b (rhIFN-α2b) and rhIFN-λ1 were compared with different cell lines. The H7N9 viral load and interferon-stimulated gene (ISG) expression were quantified by real-time PCR assays.

RESULTS

H7N9 could infect both ciliated and non-ciliated cells within the three-dimensional (3D) HAE cell culture, which reduced the number of cilia and damaged the airways. The H7N9 replication kinetics differed between traditional cells and 3D HAE cells. Interferon had antiviral activity against H7N9 and alleviated epithelial cell lesions; the antiviral activity of rhIFN-α2b was slightly better than that of rhIFN-λ1. In normal cells, rhIFN-α2b induced a greater amount of ISG expression (MX1, OAS1, IFITM3, and ISG15) compared with rhIFN-λ1, but in 3D HAE cells, this trend was reversed.

CONCLUSIONS

Both rhIFN-α2b and rhIFN-λ1 had antiviral activity against H7N9, and this protection was related to the induction of ISGs. The 3D cell culture model is suitable for evaluating interferon antiviral activity because it can demonstrate realistic in vivo-like effects.

A comparison of interferon gene expression induced by influenza A virus infection of human airway epithelial cells from two different donors

Influenza is an acute respiratory disease that can cause local annual epidemics and worldwide pandemics of different morbidity and mortality. Our understanding of host factors that modulate the frequency and severity of influenza virus infections is less than complete. In this study, we examined the inter-individual variations in the innate immune responses to H1N1 and H3N2 influenza A viruses (IAV) using primary cultures of normal human bronchial epithelial (NHBE) cells derived from two different donors (D1 and D2). Although IAV replication kinetics were similar in cultures derived from these two donors, the levels of type III interferons (IFNs) were significantly higher in D1 cells compared to D2 cells (˜31-fold↑ in D1 cells versus D2 cells; P < 0.05). The levels of IFN-λ1 protein at individual time points as well as the total amounts of IFN-λ1 secreted over 72 h were also significantly higher in D1 than in D2 NHBE cells (0.7-7.7-fold↑, P < 0.05). The relative levels of IFN-stimulated gene (ISG) expression also differed significantly between D1 and D2 cells. Our data indicate that donor-specific differences can result in significant differences in IFN and ISG induction by human airway epithelium.

Influenza and the Surgeon

BACKGROUND

The influenza virus is a pathogenic virus responsible for large numbers of deaths and long-term disabilities worldwide. Although the very young, the very old, and immunocompromised individuals are most susceptible, the effects of the influenza virus can be observed across the entire spectrum of individuals.

DISCUSSION

Infection with the influenza virus induces a substantial inflammatory and immunologic response and induces marked pulmonary inflammation. Many aspects of influenza affect surgical patients directly. Vaccines are one of the most effective measures aimed at reducing the prevalence and severity of many infectious diseases, including the influenza virus. Vaccination programs remain one of the highest priorities across the spectrum of countries, research institutions such as the National Institutes of Health, international health agencies such as the World Health Organization (WHO), and major non-profit organizations.

CONCLUSION

This review addresses aspects of the immune and inflammatory response to influenza, with a focus on the elderly population and healthcare providers who may act as reservoirs for virus transmission to the vulnerable surgical population.

The induction and consequences of Influenza A virus-induced cell death

Infection with Influenza A virus (IAV) causes significant cell death within the upper and lower respiratory tract and lung parenchyma. In severe infections, high levels of cell death can exacerbate inflammation and comprise the integrity of the epithelial cell barrier leading to respiratory failure. IAV infection of airway and alveolar epithelial cells promotes immune cell infiltration into the lung and therefore, immune cell types such as macrophages, monocytes and neutrophils are readily exposed to IAV and infection-induced death. Although the induction of cell death through apoptosis and necrosis following IAV infection is a well-known phenomenon, the molecular determinants responsible for inducing cell death is not fully understood. Here, we review the current understanding of IAV-induced cell death and critically evaluate the consequences of cell death in aiding either the restoration of lung homoeostasis or the progression of IAV-induced lung pathologies.

Strand-Specific Dual RNA Sequencing of Bronchial Epithelial Cells Infected with Influenza A/H3N2 Viruses Reveals Splicing of Gene Segment 6 and Novel Host-Virus Interactions

Host-influenza virus interplay at the transcript level has been extensively characterized in epithelial cells. Yet, there are no studies that simultaneously characterize human host and influenza A virus (IAV) genomes. We infected human bronchial epithelial BEAS-2B cells with two seasonal IAV/H3N2 strains, Brisbane/10/07 and Perth/16/09 (reference strains for past vaccine seasons) and the well-characterized laboratory strain Udorn/307/72. Strand-specific RNA sequencing (RNA-seq) of the infected BEAS-2B cells allowed for simultaneous analysis of host and viral transcriptomes, in addition to pathogen genomes, to reveal changes in mRNA expression and alternative splicing (AS). In general, patterns of global and immune gene expression induced by the three IAVs were mostly shared. However, AS of host transcripts and small nuclear RNAs differed between the seasonal and laboratory strains. Analysis of viral transcriptomes showed deletions of the polymerase components (defective interfering-like RNAs) within the genome. Surprisingly, we found that the neuraminidase gene undergoes AS and that the splicing event differs between seasonal and laboratory strains. Our findings reveal novel elements of the host-virus interaction and highlight the importance of RNA-seq in identifying molecular changes at the genome level that may contribute to shaping RNA-based innate immunity.IMPORTANCE The use of massively parallel RNA sequencing (RNA-seq) has revealed insights into human and pathogen genomes and their evolution. Dual RNA-seq allows simultaneous dissection of host and pathogen genomes and strand-specific RNA-seq provides information about the polarity of the RNA. This is important in the case of negative-strand RNA viruses like influenza virus, which generate positive (complementary and mRNA) and negative-strand RNAs (genome) that differ in their potential to trigger innate immunity. Here, we characterize interactions between human bronchial epithelial cells and three influenza A/H3N2 strains using strand-specific dual RNA-seq. We focused on this subtype because of its epidemiological importance in causing significant morbidity and mortality during influenza epidemics. We report novel elements that differ between seasonal and laboratory strains highlighting the complexity of the host-virus interplay at the RNA level.

A Three-Dimensional Human Tissue-Engineered Lung Model to Study Influenza A Infection

Influenza A virus (IAV) claims ∼250,000-500,000 lives annually worldwide. Currently, there are a few in vitro models available to study IAV immunopathology. Monolayer cultures of cell lines and primary lung cells (two-dimensional [2D] cell culture) is the most commonly used tool, however, this system does not have the in vivo-like structure of the lung and immune responses to IAV as it lacks the three-dimensional (3D) tissue structure. To recapitulate the lung physiology in vitro, a system that contains multiple cell types within a 3D environment that allows cell movement and interaction would provide a critical tool. In this study, as a first step in designing a 3D-Human Tissue-Engineered Lung Model (3D-HTLM), we describe the 3D culture of primary human small airway epithelial cells (HSAEpCs) and determined the immunophenotype of this system in response to IAV infections. We constructed a 3D chitosan-collagen scaffold and cultured HSAEpCs on these scaffolds at air-liquid interface (ALI). These 3D cultures were compared with 2D-cultured HSAEpCs for viability, morphology, marker protein expression, and cell differentiation. Results showed that the 3D-cultured HSAEpCs at ALI yielded maximum viable cells and morphologically resembled the in vivo lower airway epithelium. There were also significant increases in aquaporin-5 and cytokeratin-14 expression for HSAEpCs cultured in 3D compared to 2D. The 3D culture system was used to study the infection of HSAEpCs with two major IAV strains, H1N1 and H3N2. The HSAEpCs showed distinct changes in marker protein expression, both at mRNA and protein levels, and the release of proinflammatory cytokines. This study is the first step in the development of the 3D-HTLM, which will have wide applicability in studying pulmonary pathophysiology and therapeutics development.

Casein Kinase 1α Mediates the Degradation of Receptors for Type I and Type II Interferons Caused by Hemagglutinin of Influenza A Virus

Although influenza A virus (IAV) evades cellular defense systems to effectively propagate in the host, the viral immune-evasive mechanisms are incompletely understood. Our recent data showed that hemagglutinin (HA) of IAV induces degradation of type I IFN receptor 1 (IFNAR1). Here, we demonstrate that IAV HA induces degradation of type II IFN (IFN-γ) receptor 1 (IFNGR1), as well as IFNAR1, via casein kinase 1α (CK1α), resulting in the impairment of cellular responsiveness to both type I and II IFNs. IAV infection or transient HA expression induced degradation of both IFNGR1 and IFNAR1, whereas HA gene-deficient IAV failed to downregulate the receptors. IAV HA caused the phosphorylation and ubiquitination of IFNGR1, leading to the lysosome-dependent degradation of IFNGR1. Influenza viral HA strongly decreased cellular sensitivity to type II IFNs, as it suppressed the activation of STAT1 and the induction of IFN-γ-stimulated genes in response to exogenously supplied recombinant IFN-γ. Importantly, CK1α, but not p38 MAP kinase or protein kinase D2, was proven to be critical for HA-induced degradation of both IFNGR1 and IFNAR1. Pharmacologic inhibition of CK1α or small interfering RNA (siRNA)-based knockdown of CK1α repressed the degradation processes of both IFNGR1 and IFNAR1 triggered by IAV infection. Further, CK1α was shown to be pivotal for proficient replication of IAV. Collectively, the results suggest that IAV HA induces degradation of IFN receptors via CK1α, creating conditions favorable for viral propagation. Therefore, the study uncovers a new immune-evasive pathway of influenza virus.IMPORTANCE Influenza A virus (IAV) remains a grave threat to humans, causing seasonal and pandemic influenza. Upon infection, innate and adaptive immunity, such as the interferon (IFN) response, is induced to protect hosts against IAV infection. However, IAV seems to be equipped with tactics to evade the IFN-mediated antiviral responses, although the detailed mechanisms need to be elucidated. In the present study, we show that IAV HA induces the degradation of the type II IFN receptor IFNGR1 and thereby substantially attenuates cellular responses to IFN-γ. Of note, a cellular kinase, casein kinase 1α (CK1α), is crucial for IAV HA-induced degradation of both IFNGR1 and IFNAR1. Accordingly, CK1α is proven to positively regulate IAV propagation. Thus, this study unveils a novel strategy employed by IAV to evade IFN-mediated antiviral activities. These findings may provide new insights into the interplay between IAV and host immunity to impact influenza virus pathogenicity.

NS1 Protein of 2009 Pandemic Influenza A Virus Inhibits Porcine NLRP3 Inflammasome-Mediated Interleukin-1 Beta Production by Suppressing ASC Ubiquitination

The inflammasome represents a molecular platform for innate immune regulation and controls proinflammatory cytokine production. The NLRP3 inflammasome is comprised of NLRP3, ASC, and procaspase-1. When the NLRP3 inflammasome is activated, it causes ASC speck formation and caspase-1 activation, resulting in the maturation of interleukin-1β (IL-1β). The NLRP3 inflammasome is regulated at multiple levels, with one level being posttranslational modification. Interestingly, ubiquitination of ASC has been reported to be indispensable for the activation of the NLRP3 inflammasome. Influenza A virus (IAV) infection induces NLRP3 inflammasome-dependent IL-1β secretion, which contributes to the host antiviral defense. However, IAVs have evolved multiple antagonizing mechanisms, one of which is executed by viral NS1 protein to suppress the NLRP3 inflammasome. In this study, we compared IL-1β production in porcine alveolar macrophages in response to IAV infection and found that the 2009 pandemic H1N1 induced less IL-1β than swine influenza viruses (SIVs). Further study revealed that the NS1 C terminus of pandemic H1N1 but not that of SIV was able to significantly inhibit NLRP3 inflammasome-mediated IL-1β production. This inhibitory function was attributed to impaired ASC speck formation and suppression of ASC ubiquitination. Moreover, we identified two target lysine residues, K110 and K140, which are essential for both porcine ASC ubiquitination and NLRP3 inflammasome-mediated IL-1β production. These results revealed a novel mechanism by which the NS1 protein of the 2009 pandemic H1N1 suppresses NLRP3 inflammasome activation.IMPORTANCE Influenza A virus (IAV) infection activates the NLRP3 inflammasome, resulting in the production of IL-1β, which contributes to the host innate immune response. ASC, an adaptor protein of NLRP3, forms specks that are critical for inflammasome activation. Here, we report that the NS1 C terminus of the 2009 pandemic H1N1 has functions to suppress porcine IL-1β production by inhibiting ASC speck formation and ASC ubiquitination. Furthermore, the ubiquitination sites on porcine ASC were identified. The information gained here may contribute to an in-depth understanding of porcine inflammasome activation and regulation in response to different IAVs, helping to further enhance our knowledge of innate immune responses to influenza virus infection in pigs.

Lactoferrin: A Natural Glycoprotein Involved in Iron and Inflammatory Homeostasis

Human lactoferrin (hLf), an iron-binding multifunctional cationic glycoprotein secreted by exocrine glands and by neutrophils, is a key element of host defenses. HLf and bovine Lf (bLf), possessing high sequence homology and identical functions, inhibit bacterial growth and biofilm dependently from iron binding ability while, independently, bacterial adhesion to and the entry into cells. In infected/inflamed host cells, bLf exerts an anti-inflammatory activity against interleukin-6 (IL-6), thus up-regulating ferroportin (Fpn) and transferrin receptor 1 (TfR1) and down-regulating ferritin (Ftn), pivotal actors of iron and inflammatory homeostasis (IIH). Consequently, bLf inhibits intracellular iron overload, an unsafe condition enhancing in vivo susceptibility to infections, as well as anemia of inflammation (AI), re-establishing IIH. In pregnant women, affected by AI, bLf oral administration decreases IL-6 and increases hematological parameters. This surprising effect is unrelated to iron supplementation by bLf (80 μg instead of 1-2 mg/day), but to its role on IIH. AI is unrelated to the lack of iron, but to iron delocalization: cellular/tissue overload and blood deficiency. BLf cures AI by restoring iron from cells to blood through Fpn up-expression. Indeed, anti-inflammatory activity of oral and intravaginal bLf prevents preterm delivery. Promising bLf treatments can prevent/cure transitory inflammation/anemia/oral pathologies in athletes.

Lactoferrin: A Natural Glycoprotein Involved in Iron and Inflammatory Homeostasis

Human lactoferrin (hLf), an iron-binding multifunctional cationic glycoprotein secreted by exocrine glands and by neutrophils, is a key element of host defenses. HLf and bovine Lf (bLf), possessing high sequence homology and identical functions, inhibit bacterial growth and biofilm dependently from iron binding ability while, independently, bacterial adhesion to and the entry into cells. In infected/inflamed host cells, bLf exerts an anti-inflammatory activity against interleukin-6 (IL-6), thus up-regulating ferroportin (Fpn) and transferrin receptor 1 (TfR1) and down-regulating ferritin (Ftn), pivotal actors of iron and inflammatory homeostasis (IIH). Consequently, bLf inhibits intracellular iron overload, an unsafe condition enhancing in vivo susceptibility to infections, as well as anemia of inflammation (AI), re-establishing IIH. In pregnant women, affected by AI, bLf oral administration decreases IL-6 and increases hematological parameters. This surprising effect is unrelated to iron supplementation by bLf (80 μg instead of 1-2 mg/day), but to its role on IIH. AI is unrelated to the lack of iron, but to iron delocalization: cellular/tissue overload and blood deficiency. BLf cures AI by restoring iron from cells to blood through Fpn up-expression. Indeed, anti-inflammatory activity of oral and intravaginal bLf prevents preterm delivery. Promising bLf treatments can prevent/cure transitory inflammation/anemia/oral pathologies in athletes.

IFNAR2-dependent gene expression profile induced by IFN-α in Pteropus alecto bat cells and impact of IFNAR2 knockout on virus infection

Bats are important reservoirs of many viruses, which are capable of infecting the host without inducing obvious clinical diseases. Interferon and the downstream interferon regulated genes (IRGs) are known to act as the first line of defense against viral infections. Little is known about the transcriptional profile of genes being induced by interferon in bats and their role in controlling virus infection. In this study, we constructed IFNAR2 knockout bat cell lines using CRISPR technology and further characterized gene expression profiles induced by the most abundant IFN-α (IFN-α3). Firstly, we demonstrated that the CRISPR/Cas9 system is applicable for bat cells as this represents the first CRIPSR knockout cell line for bats. Our results showed the pleiotropic effect of IFN-α3 on the bat kidney cell line, PaKiT03. As expected, we confirmed that IFNAR2 is indispensable for IFN-a signaling pathway and plays an important role in antiviral immunity. Unexpectedly, we also identified novel IFNAR2-dependent IRGs which are enriched in pathways related to cancer. To our knowledge, this seems to be bat-specific as no such observation has been reported for other mammalian species. This study expands our knowledge about bat immunology and the cell line established can provide a powerful tool for future study into virus-bat interaction and cancer biology.

Generation and characterization of interferon-lambda 1-resistant H1N1 influenza A viruses

Influenza A viruses pose a constant potential threat to human health. In view of the innate antiviral activity of interferons (IFNs) and their potential use as anti-influenza agents, it is important to know whether viral resistance to these antiviral proteins can arise. To examine the likelihood of emergence of IFN-λ1-resistant H1N1 variants, we serially passaged the A/California/04/09 (H1N1) strain in a human lung epithelial cell line (Calu-3) in the presence of increasing concentrations of recombinant IFN-λ1 protein. To monitor changes associated with adaptation of this virus to growth in Calu-3 cells, we also passaged the wild-type virus in the absence of IFN-λ1. Under IFN-λ1 selective pressure, the parental virus developed two neuraminidase (NA) mutations, S79L and K331N, which significantly reduced NA enzyme activity (↓1.4-fold) and sensitivity to IFN-λ1 (↓˃20-fold), respectively. These changes were not associated with a reduction in viral replication levels. Mutants carrying either K331N alone or S79L and K331N together induced weaker phosphorylation of IFN regulatory factor 3 (IRF3), and, as a consequence, much lower expression of the IFN genes (IFNB1, IFNL1 and IFNL2/3) and proteins (IFN-λ1 and IFN-λ2/3). The lower levels of IFN expression correlated with weaker induction of tyrosine-phosphorylated STAT1 and reduced RIG-I protein levels. Our findings demonstrate that influenza viruses can develop increased resistance to the antiviral activity of type III interferons.

Influenza virus NS1 protein mutations at position 171 impact innate interferon responses by respiratory epithelial cells

The influenza virus NS1 protein interacts with a wide range of proteins to suppress the host cell immune response and facilitate virus replication. The amino acid sequence of the 2009 pandemic virus NS1 protein differed from sequences of earlier related viruses. The functional impact of these differences has not been fully defined. Therefore, we made mutations to the NS1 protein based on these sequence differences, and assessed the impact of these changes on host cell interferon (IFN) responses. We found that viruses with mutations at position 171 replicated efficiently but did not induce expression of interferon genes as effectively as wild-type viruses in A459 lung epithelial cells. The decreased ability of these NS1 mutant viruses to induce IFN gene and protein expression correlated with decreased activation of STAT1 and lower levels of IFN-stimulated gene (ISG) expression. These findings demonstrate that mutations at position 171 in the NS1 protein result in decreased expression of IFN and ISGs by A549 cells. Consequently, these viruses may be more virulent than the parental strains that do not contain mutations at position 171 in the NS1 protein.

Systems-based approach to examine the cytokine responses in primary mouse lung macrophages infected with low pathogenic avian Influenza virus circulating in South East Asia

Background

Influenza A virus (IAV) is a major public health concern, being responsible for the death of approximately half a million people each year. Zoonotic transmissions of the virus from swine and avian origin have occurred in the past, and can potentially lead to the emgergence of new IAV stains in future pandemics. Pulmonary macrophages have been implicated in disease severity in the lower airway, and understanding the host response of macrophages infected with avian influenza viruses should provide new therapeutic strategies.

Results

We used a systems-based approach to investigate the transcriptome response of primary murine lung macrophages (PMФ) infected with the mouse-adapted H1N1/WSN virus and low pathogenic avian influenza (LPAI) viruses H5N2 and H5N3. The results showed that the LPAI viruses H5N2 and H5N3 can infect PMФ with similar efficiency to the H1N1/WSN virus. While all viruses induced antiviral responses, the H5N3 virus infection resulted in higher expression levels of cytokines and chemokines associated with inflammatory responses.

Conclusions

The LPAI H5N2 and H5N3 viruses are able to infect murine lung macrophages. However, the H5N3 virus was associated with increased expression of pro-inflammatory mediators. Although the H5N3 virus it is capable of inducing high levels of cytokines that are associated with inflammation, this property is distinct from its inability to efficiently replicate in a mammalian host.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3803-6) contains supplementary material, which is available to authorized users.

THERAPEUTIC POTENTIAL OF ALPHA-INTERFERON PREPARATIONS DURING SOCIALLY-SIGNIFICANT HUMAN DISEASES OF VIRAL ETIOLOGY

Interferons (IFN) belong to key cytokine? of innate and adaptive immune response and play an important role in anti-viral and anti-tumor protection. At the same time, they possess a pronounced immune-modulating, anti-proliferative and anti-fibrotic effect. A general comparative characteristic of human IFN type I (a/(3), IFN type II (y) and IFN type III (X) and nosological directionality of contemporary drugs created on their base is examined in the review. Epidemiologic parameters for main socially-significant human diseases of viral etiology are presented: influenza and other ARVis, herpes infection, chronic viral hepatitis В, C and D. Main attention is given to analysis of effectiveness of therapeutic application of preparations based on IFNa during the indicated infections, a specter of main IFNa induced side effects is listed. Recent achievements on the path of creation of principally new drugs based on IFN, that have lower toxicity and higher clinical effectiveness, as well as perspectives of application of preparations based on recombinant IFN for therapy of potentially dangerous diseases are examined.

Mechanisms of replacement of circulating viruses by seasonal and pandemic influenza A viruses

BACKGROUND

Seasonal influenza causes annual epidemics by the accumulation of antigenic changes. Pandemic influenza occurs through a major antigenic change of the influenza A virus, which can originate from other hosts. Although new antigenic variants of the influenza A virus replace formerly circulating seasonal and pandemic viruses, replacement mechanisms remain poorly understood.

METHODS

A stochastic individual-based SEIR (susceptible-exposed-infectious-recovered) model with two viral strains (formerly circulating old strain and newly emerged strain) was developed for simulations to elucidate the replacement mechanisms.

RESULTS

Factors and conditions of virus and host populations affecting the replacement were identified. Replacement is more likely to occur in tropical regions than temperate regions. The magnitude of the ongoing epidemic by the old strain, herd immunity against the old strain, and timing of appearance of the new strain are not that important for replacement. It is probable that the frequency of replacement by a pandemic virus is higher than a seasonal virus because of the high initial susceptibility and high basic reproductive number of the pandemic virus.

CONCLUSIONS

The findings of this study on replacement mechanisms could lead to a better understanding of virus transmission dynamics and may possibly be helpful in establishing an effective strategy to mitigate the impact of seasonal and pandemic influenza.

Influenza Virus Hemagglutinin Glycoproteins with Different N-Glycan Patterns Activate Dendritic Cells In Vitro

Influenza virus hemagglutinin (HA) N-glycans play important regulatory roles in the control of virus virulence, antigenicity, receptor-binding specificity, and viral escape from the immune response. Considered essential for controlling innate and adaptive immune responses against influenza virus infections, dendritic cells (DCs) trigger proinflammatory and adaptive immune responses in hosts. In this study, we engineered Chinese hamster ovary (CHO) cell lines expressing recombinant HA from pandemic H1, H5, and H7 influenza viruses. rH1HA, rH5HA, and rH7HA were obtained as wild-type proteins or in the presence of kifunensine (KIF) or further with endo-β-N-acetylglucosaminidase-treated KIF (KIF+E) to generate single-N-acetylglucosamine (GlcNAc) N-glycans consisting of (i) terminally sialylated complex-type N-glycans, (ii) high-mannose-type N-glycans, and (iii) single-GlcNAc-type N-glycans. Our results show that high-mannose-type and single-GlcNAc-type N-glycans, but not complex-type N-glycans, are capable of inducing more active hIL12 p40, hIL12 p70, and hIL-10 production in human DCs. Significantly higher HLA-DR, CD40, CD83, and CD86 expression levels, as well reduced endocytotic capacity in human DCs, were noted in the high-mannose-type rH1HA and single-GlcNAc-type rH1HA groups than in the complex-type N-glycan rH1HA group. Our data indicate that native avian rHA proteins (H5N1 and H7N9) are more immunostimulatory than human rHA protein (pH1N1). The high-mannose-type or single-GlcNAc-type N-glycans of both avian and human HA types are more stimulatory than the complex-type N-glycans. HA-stimulated DC activation was accomplished partially through a mannose receptor(s). These results provide more understanding of the contribution of glycosylation of viral proteins to the immune responses and may have implications for vaccine development.

IMPORTANCE

Influenza viruses trigger seasonal epidemics or pandemics with mild-to-severe consequences for human and poultry populations. DCs are the most potent professional antigen-presenting cells, which play a crucial role in the link between innate and adaptive immunity. In this study, we obtained stable-expression CHO cells to produce rH1HA, rH5HA, and rH7HA proteins containing distinct N-glycan patterns. These rHA proteins, each with a distinct N-glycan pattern, were used to investigate interactions with mouse and human DCs. Our data indicate that native avian rHA proteins (H5N1 and H7N9) are more immunostimulatory than human rHA protein (pH1N1). High-mannose-type and single-GlcNAc-type N-glycans were more effective than complex-type N-glycans in triggering mouse and human DC activation and maturation. We believe these results provide some useful information for influenza vaccine development regarding how influenza virus HA proteins with different types of N-glycans activate DCs.

Hemagglutinin of Influenza A Virus Antagonizes Type I Interferon (IFN) Responses by Inducing Degradation of Type I IFN Receptor 1

Influenza A virus (IAV) employs diverse strategies to circumvent type I interferon (IFN) responses, particularly by inhibiting the synthesis of type I IFNs. However, it is poorly understood if and how IAV regulates the type I IFN receptor (IFNAR)-mediated signaling mode. In this study, we demonstrate that IAV induces the degradation of IFNAR subunit 1 (IFNAR1) to attenuate the type I IFN-induced antiviral signaling pathway. Following infection, the level of IFNAR1 protein, but not mRNA, decreased. Indeed, IFNAR1 was phosphorylated and ubiquitinated by IAV infection, which resulted in IFNAR1 elimination. The transiently overexpressed IFNAR1 displayed antiviral activity by inhibiting virus replication. Importantly, the hemagglutinin (HA) protein of IAV was proved to trigger the ubiquitination of IFNAR1, diminishing the levels of IFNAR1. Further, influenza A viral HA1 subunit, but not HA2 subunit, downregulated IFNAR1. However, viral HA-mediated degradation of IFNAR1 was not caused by the endoplasmic reticulum (ER) stress response. IAV HA robustly reduced cellular sensitivity to type I IFNs, suppressing the activation of STAT1/STAT2 and induction of IFN-stimulated antiviral proteins. Taken together, our findings suggest that IAV HA causes IFNAR1 degradation, which in turn helps the virus escape the powerful innate immune system. Thus, the research elucidated an influenza viral mechanism for eluding the IFNAR signaling pathway, which could provide new insights into the interplay between influenza virus and host innate immunity.

IMPORTANCE

Influenza A virus (IAV) infection causes significant morbidity and mortality worldwide and remains a major health concern. When triggered by influenza viral infection, host cells produce type I interferon (IFN) to block viral replication. Although IAV was shown to have diverse strategies to evade this powerful, IFN-mediated antiviral response, it is not well-defined if IAV manipulates the IFN receptor-mediated signaling pathway. Here, we uncovered that influenza viral hemagglutinin (HA) protein causes the degradation of type I IFN receptor subunit 1 (IFNAR1). HA promoted phosphorylation and polyubiquitination of IFNAR1, which facilitated the degradation of this receptor. The HA-mediated elimination of IFNAR1 notably decreased the cells' sensitivities to type I IFNs, as demonstrated by the diminished expression of IFN-induced antiviral genes. This discovery could help us understand how IAV regulates the host innate immune response to create an environment optimized for viral survival in host cells.

Differential Immune Profiles in Two Pandemic Influenza A(H1N1)pdm09 Virus Waves at Pandemic Epicenter

Background and Aims

Severe influenza A(H1N1)pdm2009 virus infection cases are characterized by sustained immune activation during influenza pandemics. Seasonal flu data suggest that immune mediators could be modified by wave-related changes. Our aim was to determine the behavior of soluble and cell-related mediators in two waves at the epicenter of the 2009 influenza pandemic.

Methods

Leukocyte surface activation markers were studied in serum from peripheral blood samples, collected from the 1^st (April–May, 2009) and 2^nd (October 2009–February 2010) pandemic waves. Patients with confirmed influenza A(H1N1)pdm2009 virus infection (H1N1), influenza-like illness (ILI) or healthy donors (H) were analyzed.

Results

Serum IL-6, IL-4 and IL-10 levels were elevated in H1N1 patients from the 2^nd pandemic wave. Additionally, the frequency of helper and cytotoxic T cells was reduced during the 1^st wave, whereas CD69 expression in helper T cells was increased in the 2^nd wave for both H1N1 and ILI patients. In contrast, CD62L expression in granulocytes from the ILI group was increased in both waves but in monocytes only in the 2^nd wave. Triggering Receptor Expressed on Myeloid cells (TREM)-1 expression was elevated only in H1N1 patients at the 1^st wave.

Conclusions

Our results show that during the 2009 influenza pandemic a T cell activation phenotype is observed in a wave-dependent fashion, with an expanded activation in the 2^nd wave, compared to the 1^st wave. Conversely, granulocyte and monocyte activation is infection-dependent. This evidence collected at the pandemic epicenter in 2009 could help us understand the differences in the underlying cellular mechanisms that drive the wave-related immune profile behaviors that occur against influenza viruses during pandemics.

Infectious Progeny of 2009 A (H1N1) Influenza Virus Replicated in and Released from Human Neutrophils

Various reports have indicated that a number of viruses could infect neutrophils, but the multiplication of viruses in neutrophils was abortive. Based on our previous finding that avian influenza viral RNA and proteins were present in the nucleus of infected human neutrophils in vivo, we investigated the possibility of 2009 A (H1N1) influenza viral synthesis in infected neutrophils and possible release of infectious progeny from host cells. In this study we found that human neutrophils in vitro without detectable level of sialic acid expression could be infected by this virus strain. We also show that the infected neutrophils can not only synthesize 2009 A (H1N1) viral mRNA and proteins, but also produce infectious progeny. These findings suggest that infectious progeny of 2009 A (H1N1) influenza virus could be replicated in and released from human neutrophils with possible clinical implications.

Middle East respiratory syndrome coronavirus shows poor replication but significant induction of antiviral responses in human monocyte-derived macrophages and dendritic cells

In this study we assessed the ability of Middle East respiratory syndrome coronavirus (MERS-CoV) to replicate and induce innate immunity in human monocyte-derived macrophages and dendritic cells (MDDCs), and compared it with severe acute respiratory syndrome coronavirus (SARS-CoV). Assessments of viral protein and RNA levels in infected cells showed that both viruses were impaired in their ability to replicate in these cells. Some induction of IFN-λ1, CXCL10 and MxA mRNAs in both macrophages and MDDCs was seen in response to MERS-CoV infection, but almost no such induction was observed in response to SARS-CoV infection. ELISA and Western blot assays showed clear production of CXCL10 and MxA in MERS-CoV-infected macrophages and MDDCs. Our data suggest that SARS-CoV and MERS-CoV replicate poorly in human macrophages and MDDCs, but MERS-CoV is nonetheless capable of inducing a readily detectable host innate immune response. Our results highlight a clear difference between the viruses in activating host innate immune responses in macrophages and MDDCs, which may contribute to the pathogenesis of infection.

Intranasal administration of poly-gamma glutamate induced antiviral activity and protective immune responses against H1N1 influenza A virus infection

BACKGROUND

The global outbreak of a novel swine-origin strain of the 2009 H1N1 influenza A virus and the sudden, worldwide increase in oseltamivir-resistant H1N1 influenza A viruses highlight the urgent need for novel antiviral therapy.

METHODS

Here, we investigated the antiviral efficacy of poly-gamma glutamate (γ-PGA), a safe and edible biomaterial that is naturally synthesized by Bacillus subtilis, against A/Puerto Rico/8/1934 (PR8) and A/California/04/2009 (CA04) H1N1 influenza A virus infections in C57BL/6 mice.

RESULTS

Intranasal administration of γ-PGA for 5 days post-infection improved survival, increased production of antiviral cytokines including interferon-beta (IFN-β) and interleukin-12 (IL-12), and enhanced activation of natural killer (NK) cells and influenza antigen-specific cytotoxic T lymphocytes (CTL) activity.

CONCLUSIONS

These results suggest that γ-PGA protects mice against H1N1 influenza A virus by enhancing antiviral immune responses.

Human Dendritic Cell Response Signatures Distinguish 1918, Pandemic, and Seasonal H1N1 Influenza Viruses

Influenza viruses continue to present global threats to human health. Antigenic drift and shift, genetic reassortment, and cross-species transmission generate new strains with differences in epidemiology and clinical severity. We compared the temporal transcriptional responses of human dendritic cells (DC) to infection with two pandemic (A/Brevig Mission/1/1918, A/California/4/2009) and two seasonal (A/New Caledonia/20/1999, A/Texas/36/1991) H1N1 influenza viruses. Strain-specific response differences included stronger activation of NF-κB following infection with A/New Caledonia/20/1999 and a unique cluster of genes expressed following infection with A/Brevig Mission/1/1918. A common antiviral program showing strain-specific timing was identified in the early DC response and found to correspond with reported transcript changes in blood during symptomatic human influenza virus infection. Comparison of the global responses to the seasonal and pandemic strains showed that a dramatic divergence occurred after 4 h, with only the seasonal strains inducing widespread mRNA loss.

IMPORTANCE

Continuously evolving influenza viruses present a global threat to human health; however, these host responses display strain-dependent differences that are incompletely understood. Thus, we conducted a detailed comparative study assessing the immune responses of human DC to infection with two pandemic and two seasonal H1N1 influenza strains. We identified in the immune response to viral infection both common and strain-specific features. Among the stain-specific elements were a time shift of the interferon-stimulated gene response, selective induction of NF-κB signaling by one of the seasonal strains, and massive RNA degradation as early as 4 h postinfection by the seasonal, but not the pandemic, viruses. These findings illuminate new aspects of the distinct differences in the immune responses to pandemic and seasonal influenza viruses.

Dual effect of Thymosin α 1 on human monocyte-derived dendritic cell in vitro stimulated with viral and bacterial toll-like receptor agonists

OBJECTIVES

Thymosin α 1 (Tα1) recently gained interest as immune adjuvant for vaccines because of its ability to modulate the T-cell/dendritic cell (DC) axis and to improve antibody production. The objective of this study was to determine whether Tα1 would address in vitro the response of human primary monocyte-derived DC, crucial regulators of vaccine-induced immunity, upon exposure to different toll-like receptor (TLR) agonists or infection with viruses or bacteria.

METHODS

DC maturation and production of pro-inflammatory cytokines were analyzed.

RESULTS

Our data revealed a dual effect of Tα1 on DC biology upon viral or bacterial stimulation. Interestingly, Tα1 enhanced human leukocyte antigen (HLA)-I and II surface expression and secretion of IL-6, TNF-α and IL-8 when DCs were treated with viral TLR3 and TLR7/8 agonists. Similarly, in pandemic H1N1 influenza A-infected DCs, Tα1 raised the expression of maturation markers and type I and III Interferon (IFN). In contrast, following bacterial TLR2 and 4 stimulation, as well as upon Bacillus Calmette-Guerin infection, the presence of Tα1 in DC cultures drastically lowered the analyzed cellular parameters.

CONCLUSION

The knowledge that Tα1 pleiotropic effect might ameliorate anti-viral immune responses and, at the same time, dampen inflammation caused by bacterial infections could lay the groundwork for a more appropriate therapeutic application of this molecule.

The effects of H3N2 swine influenza virus infection on TLRs and RLRs signaling pathways in porcine alveolar macrophages

Background

Swine influenza is an economically important respiratory disease of swine resulting from infection with influenza A virus. Swine influenza virus (SIV) becomes the focus as pigs have been hypothesized to serve as an intermediate host for the adaptation of avian influenza viruses to humans or as mixing vessels for the generation of genetically reassortant viruses. The ability of the innate immune system to detect and respond to pathogens is important for survival. Therefore, there is a critical need to evaluate the immediate response to viral infection, especially the role of the toll-like receptors (TLRs) and RNA helicase RIG-I-like receptors (RLRs) innate immunity signaling pathways in H3N2 swine influenza virus infection.

Method

In this study, porcine alveolar macrophages (PAMs) were obtained from porcine lungs and were infected with SIV at a multiplicity of infection (MOI) of 5 in vitro. The changes of the related receptors, signaling proteins and effector molecules of TLRs and RLRs signaling pathways post H3N2 virus infection of PAMs were quantified by Real-time quantitative RT-PCR and western blotting.

Results

The results showed that H3N2 SIV infection significantly increased mRNA expression of TLR-3, TLR-7, RIG- I and MDA5 after 4 hpi (P < 0.05). Western blotting showed that the protein levels of TLR-3, TLR-7 and RIG-I also had a significantly increase after PAM exposed to virus. A significant change of MyD88, MAVS, IRF-3 and IRF-7 mRNA expression were present at 8 hpi. More than a 4-fold increase was induced for TNF-α and IL-1β mRNA expression. And the concentration of TNF-α and IL-1β peaked at 12 and 24 hpi, respectively. IFN-α, IFN-β mRNA and protein levels increased after SIV infection and significant differences was observed at 8, 12 and 24 hpi.

Conclusion

These results indicate that H3N2 swine influenza virus infection significantly influences the expression of the receptors, adapter proteins and downstream effector molecules of RLRs and TLRs signaling pathways. This study enhances our understanding of innate immunity signaling pathways in PAM anti-infection of H3N2 SIV.

Twenty-five years of type I interferon-based treatment: a critical analysis of its therapeutic use

The clinical exploitation of type I interferon (IFN) as an antiviral and antineoplastic agent is based on the properties originally attributed to this cytokine family, with schedules reflecting only their antiviral and antiproliferative activities. Nevertheless, type I IFN has emerged as a central activator of the innate immunity. As current schedules of treatment for chronic hepatitis C and for hematological and solid tumors, based on the continuous administration of recombinant type I IFN or pegylated formulations, disregard viral resistance, host genetic variants predicting treatment outcome and mechanisms of refractoriness, new administration schedules, the combination of type I IFN with new drugs and the increased monitoring of patients' susceptibility to type I IFN are expected to provide a new life to this valuable cytokine.

Protection of human myeloid dendritic cell subsets against influenza A virus infection is differentially regulated upon TLR stimulation

The proinflammatory microenvironment in the respiratory airway induces maturation of both resident and infiltrating dendritic cells (DCs) upon influenza A virus (IAV) infection. This results in upregulation of antiviral pathways as well as modulation of endocytic processes, which affect the susceptibility of DCs to IAV infection. Therefore, it is highly relevant to understand how IAV interacts with and infects mature DCs. To investigate how different subsets of human myeloid DCs (MDCs) involved in tissue inflammation are affected by inflammatory stimulation during IAV infection, we stimulated primary blood MDCs and inflammatory monocyte-derived DCs (MDDCs) with TLR ligands, resulting in maturation. Interestingly, MDDCs but not MDCs were protected against IAV infection after LPS (TLR4) stimulation. In contrast, stimulation with TLR7/8 ligand protected MDCs but not MDDCs from IAV infection. The reduced susceptibility to IAV infection correlated with induction of type I IFNs. We found that differential expression of TLR4, TRIF, and MyD88 in the two MDC subsets regulated the ability of the cells to enter an antiviral state upon maturation. This difference was functionally confirmed using small interfering RNA and inhibitors. Our data show that different human MDC subsets may play distinct roles during IAV infection, as their capacity to induce type I IFNs is dependent on TLR-specific maturation, resulting in differential susceptibility to IAV infection.

Upper airway stem cells: understanding the nose and role for future cell therapy

The nose together with the paranasal sinuses has an approximate surface area of 100 to 200 cm(2) in adults, which is lined with pseudostratified columnar ciliated epithelium. It serves several important physiological functions such as conditioning and filtration of the inspired air and the provision of end organ for the sense of smell. It is also a physical and immunological barrier as it is the first site of interaction between the host tissue and foreign invaders (viruses, bacteria, and allergens). Our understanding of the complex cellular events occurring in response to inhaled agents during the development of common airway diseases has been significantly enhanced by the current status of in vivo and in vitro nasal experimental models. This will allow the development of novel therapeutic strategies designed to improve the physiological and immune defense functions of the nasal epithelium, as well as novel therapies for other common nasal diseases.

Innate immune sensing and response to influenza

Influenza viruses pose a substantial threat to human and animal health worldwide. Recent studies in mouse models have revealed an indispensable role for the innate immune system in defense against influenza virus. Recognition of the virus by innate immune receptors in a multitude of cell types activates intricate signaling networks, functioning to restrict viral replication. Downstream effector mechanisms include activation of innate immune cells and, induction and regulation of adaptive immunity. However, uncontrolled innate responses are associated with exaggerated disease, especially in pandemic influenza virus infection. Despite advances in the understanding of innate response to influenza in the mouse model, there is a large knowledge gap in humans, particularly in immunocompromised groups such as infants and the elderly. We propose here, the need for further studies in humans to decipher the role of innate immunity to influenza virus, particularly at the site of infection. These studies will complement the existing work in mice and facilitate the quest to design improved vaccines and therapeutic strategies against influenza.