Expression of cytokines on human bronchial epithelial cells induced by influenza virus A

Efficient symptomatic treatment and viral load reduction for children with influenza virus infection by nasal-spraying Bacillus spore probiotics

Influenza virus is a main cause of acute respiratory tract infections (ARTIs) in children. This is the first double-blind, randomized, and controlled clinical trial examining the efficacy of nasal-spraying probiotic LiveSpo Navax, which contains 5 billion of Bacillus subtilis and B. clausii spores in 5 mL, in supporting treatment of influenza viral infection in pediatric patients. We found that the nasal-spraying Bacillus spores significantly shortened the recovery period and overall treatment by 2 days and increased treatment effectiveness by 58% in resolving all ARTIs' symptoms. At day 2, the concentrations of influenza virus and co-infected bacteria were reduced by 417 and 1152 folds. Additionally, the levels of pro-inflammatory cytokines IL-8, TNF-α, and IL-6 in nasopharyngeal samples were reduced by 1.1, 3.7, and 53.9 folds, respectively. Compared to the standard control group, treatment regimen with LiveSpo Navax demonstrated significantly greater effectiveness, resulting in 26-fold reduction in viral load, 65-fold reduction in bacterial concentration, and 1.1-9.5-fold decrease in cytokine levels. Overall, nasal-spraying Bacillus spores can support the symptomatic treatment of influenza virus-induced ARTIs quickly, efficiently and could be used as a cost-effective supportive treatment for respiratory viral infection in general.Clinical trial registration no: NCT05378022 on 17/05/2022.

XiaoEr LianHuaQinqGan alleviates viral pneumonia in mice infected by influenza A and respiratory syncytial viruses

CONTEXT

Xiaoer lianhuaqinqgan (XELH), developed based on Lianhua Qingwen (LHQW) prescription, contains 13 traditional Chinese medicines. It has completed the investigational new drug application to treat respiratory viral infections in children in China.

OBJECTIVE

This study demonstrates the pharmacological effects of XELH against viral pneumonia.

MATERIALS AND METHODS

The antiviral and anti-inflammatory effects of XELH were investigated in vitro using H3N2-infected A549 and LPS-stimulated RAW264.7 cells and in vivo using BALB/c mice models of influenza A virus (H3N2) and respiratory syncytial virus (RSV)-infection. Mice were divided into 7 groups (n = 20): Control, Model, LHQW (0.5 g/kg), XELH-low (2 g/kg), XELH-medium (4 g/kg), XELH-high (8 g/kg), and positive drug (20 mg/kg oseltamivir or 60 mg/kg ribavirin) groups. The anti-inflammatory effects of XELH were tested in a rat model of LPS-induced fever and a mouse model of xylene-induced ear edoema.

RESULTS

In vitro, XELH inhibited the pro-inflammatory cytokines and replication of H1N1, H3N2, H1N1, FluB, H9N2, H6N2, H7N3, RSV, and HCoV-229E viruses, with (IC₅₀ 47.4, 114, 79, 250, 99.2, 170, 79, 62.5, and 93 μg/mL, respectively). In vivo, XELH reduced weight loss and lung index, inhibited viral replication and macrophage M1 polarization, ameliorated lung damage, decreased inflammatory cell infiltration and pro-inflammatory cytokines expression in lung tissues, and increased the CD4⁺/CD8⁺ ratio. XELH inhibited LPS-induced fever in rats and xylene-induced ear edoema in mice.

CONCLUSION

XELH efficacy partially depends on integrated immunoregulatory effects. XELH is a promising therapeutic option against childhood respiratory viral infections.

Knockdown of Transmembrane Protein 150A (TMEM150A) Results in Increased Production of Multiple Cytokines

Lipopolysaccharide (LPS)-induced signaling through Toll-like receptor 4 (TLR4) is mediated by the plasma membrane lipid, phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P₂] and its derivatives diacylglycerol and inositol trisphosphate. Levels of PI(4,5)P₂ are controlled enzymatically and fluctuate in LPS-stimulated cells. Recently, transmembrane protein 150A (TMEM150A/TM6P1/damage-regulated autophagy modulator 5) has been shown to regulate PI(4,5)P₂ production at the plasma membrane by modifying the composition of the phosphatidylinositol 4-kinase enzyme complex. To determine if TMEM150A function impacts TLR4 signaling, TMEM150A was knocked down in TLR4-expressing epithelial cells and cytokine expression quantified after LPS stimulation. In general, decreased expression of TMEM150A led to increased levels of LPS-induced cytokine secretion and transcript levels. Unexpectedly, knockdown of TMEM150A in a lung epithelial cell line (H292) also led to increased cytokine levels in the unstimulated conditions suggesting TMEM150A plays an important role in cellular homeostasis. Future studies will investigate if TMEM150A plays a similar role for other TLR agonists and in other cell lineages.

Differential Expression of Serum Exosome microRNAs and Cytokines in Influenza A and B Patients Collected in the 2016 and 2017 Influenza Seasons

MicroRNAs (miRNAs) have remarkable stability and are key regulators of mRNA transcripts for several essential proteins required for the survival of cells and replication of the virus. Exosomes are thought to play an essential role in intercellular communications by transporting proteins and miRNAs, making them ideal in the search for biomarkers. Evidence suggests that miRNAs are involved in the regulation of influenza virus replication in many cell types. During the 2016 and 2017 influenza season, we collected blood samples from 54 patients infected with influenza and from 30 healthy volunteers to identify the potential role of circulating serum miRNAs and cytokines in influenza infection. Data comparing the exosomal miRNAs in patients with influenza B to healthy volunteers showed 76 miRNAs that were differentially expressed (p < 0.05). In contrast, 26 miRNAs were differentially expressed between patients with influenza A (p < 0.05) and the controls. Of these miRNAs, 11 were commonly expressed in both the influenza A and B patients. Interferon (IFN)-inducing protein 10 (IP-10), which is involved in IFN synthesis during influenza infection, showed the highest level of expression in both influenza A and B patients. Influenza A patients showed increased expression of IFNα, GM-CSF, interleukin (IL)-13, IL-17A, IL-1β, IL-6 and TNFα, while influenza B induced increased levels of EGF, G-CSF, IL-1α, MIP-1α, and TNF-β. In addition, hsa-miR-326, hsa-miR-15b-5p, hsa-miR-885, hsa-miR-122-5p, hsa-miR-133a-3p, and hsa-miR-150-5p showed high correlations to IL-6, IL-15, IL-17A, IL-1β, and monocyte chemoattractant protein-1 (MCP-1) with both strains of influenza. Next-generation sequencing studies of H1N1-infected human lung small airway epithelial cells also showed similar pattern of expression of miR-375-5p, miR-143-3p, 199a-3p, and miR-199a-5p compared to influenza A patients. In summary, this study provides insights into the miRNA profiling in both influenza A and B virus in circulation and a novel approach to identify the early infections through a combination of cytokines and miRNA expression.

Modelling within-host macrophage dynamics in influenza virus infection

Human respiratory disease associated with influenza virus infection is of significant public health concern. Macrophages, as part of the front line of host innate cellular defence, have been shown to play an important role in controlling viral replication. However, fatal outcomes of infection, as evidenced in patients infected with highly pathogenic viral strains, are often associated with prompt activation and excessive accumulation of macrophages. Activated macrophages can produce a large amount of pro-inflammatory cytokines, which leads to severe symptoms and at times death. However, the mechanism for rapid activation and excessive accumulation of macrophages during infection remains unclear. It has been suggested that the phenomena may arise from complex interactions between macrophages and influenza virus. In this work, we develop a novel mathematical model to study the relationship between the level of macrophage activation and the level of viral load in influenza infection. Our model combines a dynamic model of viral infection, a dynamic model of macrophages and the essential interactions between the virus and macrophages. Our model predicts that the level of macrophage activation can be negatively correlated with the level of viral load when viral infectivity is sufficiently high. We further identify that temporary depletion of resting macrophages in response to viral infection is a major driver in our model for the negative relationship between the level of macrophage activation and viral load, providing new insight into the mechanisms that regulate macrophage activation. Our model serves as a framework to study the complex dynamics of virus-macrophage interactions and provides a mechanistic explanation for existing experimental observations, contributing to an enhanced understanding of the role of macrophages in influenza viral infection.

Complexes of Oligoribonucleotides with d-Mannitol Modulate the Innate Immune Response to Influenza A Virus H1N1 (A/FM/1/47) In Vivo

Rapid replication of the influenza A virus and lung tissue damage caused by exaggerated pro-inflammatory host immune responses lead to numerous deaths. Therefore, novel therapeutic agents that have anti-influenza activities and attenuate excessive pro-inflammatory responses that are induced by an influenza virus infection are needed. Oligoribonucleotides-d-mannitol (ORNs-d-M) complexes possess both antiviral and anti-inflammatory activities. The current research was aimed at studying the ORNs-d-M effects on expression of innate immune genes in mice lungs during an influenza virus infection. Expression of genes was determined by RT-qPCR and Western blot assays. In the present studies, we found that the ORNs-d-M reduced the influenza-induced up-expression of Toll-like receptors (TLRs) (tlr3, tlr7, tlr8), nuclear factor NF-kB (nfkbia, nfnb1), cytokines (ifnε, ifnk, ifna2, ifnb1, ifnγ, il6, il1b, il12a, tnf), chemokines (ccl3, ccl4, сcl5, cxcl9, cxcl10, cxcl11), interferon-stimulated genes (ISGs) (oas1a, oas2, oas3, mx1), and pro-oxidation (nos2, xdh) genes. The ORNs-d-M inhibited the mRNA overexpression of tlr3, tlr7, and tlr8 induced by the influenza virus, which suggests that they impair the upregulation of NF-kB, cytokines, chemokines, ISGs, and pro-oxidation genes induced by the influenza virus by inhibiting activation of the TLR-3, TLR-7, and TLR-8 signaling pathways. By impairing activation of the TLR-3, TLR-7, and TLR-8 signaling pathways, the ORNs-d-M can modulate the innate immune response to an influenza virus infection.

Adaptation of influenza A (H7N9) virus in primary human airway epithelial cells

Influenza A (H7N9) is an emerging zoonotic pathogen with pandemic potential. To understand its adaptation capability, we examined the genetic changes and cellular responses following serial infections of A (H7N9) in primary human airway epithelial cells (hAECs). After 35 serial passages, six amino acid mutations were found, i.e. HA (R54G, T160A, Q226L, H3 numbering), NA (K289R, or K292R for N2 numbering), NP (V363V/I) and PB2 (L/R332R). The mutations in HA enabled A(H7N9) virus to bind with higher affinity (from 39.2% to 53.4%) to sialic acid α2,6-galactose (SAα2,6-Gal) linked receptors. A greater production of proinflammatory cytokines in hAECs was elicited at later passages together with earlier peaking at 24 hours post infection of IL-6, MIP-1α, and MCP-1 levels. Viral replication capacity in hAECs maintained at similar levels throughout the 35 passages. In conclusion, during the serial infections of hAECs by influenza A(H7N9) virus, enhanced binding of virion to cell receptors with subsequent stronger innate cell response were noted, but no enhancement of viral replication could be observed. This indicates the existence of possible evolutional hurdle for influenza A(H7N9) virus to transmit efficiently from human to human.

Influenza Virus Infection Induces Platelet-Endothelial Adhesion Which Contributes to Lung Injury

Lung injury after influenza infection is characterized by increased permeability of the lung microvasculature, culminating in acute respiratory failure. Platelets interact with activated endothelial cells and have been implicated in the pathogenesis of some forms of acute lung injury. Autopsy studies have revealed pulmonary microthrombi after influenza infection, and epidemiological studies suggest that influenza vaccination is protective against pulmonary thromboembolism; however, the effect of influenza infection on platelet-endothelial interactions is unclear. We demonstrate that endothelial infection with both laboratory and clinical strains of influenza virus increased the adhesion of human platelets to primary human lung microvascular endothelial cells. Platelets adhered to infected cells as well as to neighboring cells, suggesting a paracrine effect. Influenza infection caused the upregulation of von Willebrand factor and ICAM-1, but blocking these receptors did not prevent platelet-endothelial adhesion. Instead, platelet adhesion was inhibited by both RGDS peptide and a blocking antibody to platelet integrin α5β1, implicating endothelial fibronectin. Concordantly, lung histology from infected mice revealed viral dose-dependent colocalization of viral nucleoprotein and the endothelial marker PECAM-1, while platelet adhesion and fibronectin deposition also were observed in the lungs of influenza-infected mice. Inhibition of platelets using acetylsalicylic acid significantly improved survival, a finding confirmed using a second antiplatelet agent. Thus, influenza infection induces platelet-lung endothelial adhesion via fibronectin, contributing to mortality from acute lung injury. The inhibition of platelets may constitute a practical adjunctive strategy to the treatment of severe infections with influenza.IMPORTANCE There is growing appreciation of the involvement of the lung endothelium in the pathogenesis of severe infections with influenza virus. We have recently shown that the virus can infect human lung endothelial cells, but the functional consequences of this infection are unknown (S. M. Armstrong, C. Wang, J. Tigdi, X. Si, C. Dumpit, S. Charles, A. Gamage, T. J. Moraes, and W. L. Lee, PLoS One 7:e47323, 2012, http://dx.doi.org/10.1371/journal.pone.0047323). Here, we show that this infection causes platelets to adhere to the lung endothelium. Importantly, blocking platelets using two distinct antiplatelet drugs improved survival in a mouse model of severe influenza infection. Thus, platelet inhibition may constitute a novel therapeutic strategy to improve the host response to severe infections with influenza.

Induction of the cellular miR-29c by influenza virus inhibits the innate immune response through protection of A20 mRNA

Influenza A viruses (IAVs) are negative-sense, single-stranded, segmented RNA viruses, which primarily targets respiratory epithelial cells and produces clinical outcomes ranging from mild upper respiratory infection to severe pneumonia. MicroRNAs (miRNAs) represent a family of small noncoding RNAs controlling translation and transcription of many genes. The human miR-29 family of miRNAs has three mature members, miR-29a, miR-29b, and miR-29c. Recent studies have revealed that miR-29 is involved in regulation of the innate and adaptive immune responses. However, the function of miR-29 in the immune response to IAV infection remains to be further explored. Our previous study has shown that miR-29 family members are up-regulated during IAV infection, especially miR-29c. Here we report that miR-29c is involved in inhibition of IAV-induced innate immune responses. We found that posttranscriptional regulation was involved in IAV-induced A20 expression in A549 cells. Consistent with a previous report, miR-29c functionally protected A20 transcripts in A549 cells. Overexpression of miR-29c with miR-29c mimic enhanced IAV-induced A20 protein expression and conversely that miR-29c inhibitor significantly blocked IAV-induced A20 protein expression in A549 cells. Furthermore, functional results showed that IAV-induced miR-29c expression correlated with decreased NF-κB activity and expression of several antiviral and proinflammatory cytokines via up-regulation of A20. Together, the findings indicate a new role of miR-29c in IAV infection and suggest its induction may contribute to counteract the innate immune response.

Cytokine Expression at Different Stages of Influenza A(H1N1)pdm09 Virus Infection in the Porcine Lung, Using Laser Capture Microdissection

Pandemic influenza A(H1N1)pdm09 virus has retained its ability to infect swine whilst developing the ability to transmit effectively between humans, thus making the pig a valuable model for studying disease pathogenesis in both species. Lung lesions in pigs caused by infection with influenza A viruses vary in both their severity and distribution with individual lung lobes exhibiting lesions at different stages of infection pathogenic development and disease resolution. Consequently, investigating interactions between the virus and host and their implications for disease pathogenesis can be complicated. Studies were undertaken to investigate the discrete expression of pro- and anti-inflammatory mediators during lung lesion formation in pigs during infection with influenza A(H1N1)pdm09 (A/Hamburg/05/09) virus. Laser capture microdissection was used to identify and select lung lobules containing lesions at different stages of development. Dissected samples were analysed using quantitative RT-PCR to assess pro- and anti-inflammatory cytokine mRNA transcripts. Differential expression of the immune mediators IL-8, IL-10 and IFN-γ was observed depending upon the lesion stage assessed. Upregulation of IFN-γ, IL-8 and IL-10 mRNA was observed in stage 2 lesions, whereas decreased mRNA expression was observed in stage 3 lesions, with IL-8 actively downregulated when compared with controls in both stage 3 and stage 4 lesions. This study highlighted the value of using laser capture microdissection to isolate specific tissue regions and investigate subtle differences in cytokine mRNA expression during lesion development in pigs infected with influenza A(H1N1)pdm09.

Baicalin inhibits TLR7/MYD88 signaling pathway activation to suppress lung inflammation in mice infected with influenza A virus

The present study aimed to investigate the protective effects and underlying mechanisms of baicalin on imprinting control region mice infected with influenza A/FM/1/47 (H1N1) virus. Oral administration of baicalin into mice infected with H1N1 prevented death, increased the mean time to death and inhibited lung index and lung consolidation. Subsequently, fluorescence quantitative polymerase chain reaction was used to assess the mRNA expression of toll-like receptor 7 (TLR7) and myeloid differentiation primary response gene 88 (MYD88), and western blot analysis was used to determine the expression of phosphorylated nuclear factor κB (NF-κB)-P65 and c-jun/activator protein 1 (AP-1). An enzyme-linked immunosorbent assay was applied to test for the inflammatory cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-1β and IL-6, in the lung tissue. The findings indicated that baicalin downregulated the mRNA expression of TLR7 and MYD88, significantly downregulated the protein expression of NF-κB-P65 and AP-1 and also inhibited the secretion of TNF-α, IL-1β and IL-6. In conclusion, baicalin effectively reduced the pathological damage and inflammation of the lungs by downregulating the TLR7/MYD88-mediated signaling pathway.

Early host responses of seasonal and pandemic influenza A viruses in primary well-differentiated human lung epithelial cells

Replication, cell tropism and the magnitude of the host's antiviral immune response each contribute to the resulting pathogenicity of influenza A viruses (IAV) in humans. In contrast to seasonal IAV in human cases, the 2009 H1N1 pandemic IAV (H1N1pdm) shows a greater tropism for infection of the lung similar to H5N1. We hypothesized that host responses during infection of well-differentiated, primary human bronchial epithelial cells (wd-NHBE) may differ between seasonal (H1N1 A/BN/59/07) and H1N1pdm isolates from a fatal (A/KY/180/10) and nonfatal (A/KY/136/09) case. For each virus, the level of infectious virus and host response to infection (gene expression and apical/basal cytokine/chemokine profiles) were measured in wd-NHBE at 8, 24, 36, 48 and 72 hours post-infection (hpi). At 24 and 36 hpi, KY/180 showed a significant, ten-fold higher titer as compared to the other two isolates. Apical cytokine/chemokine levels of IL-6, IL-8 and GRO were similar in wd-NHBE cells infected by each of these viruses. At 24 and 36 hpi, NHBE cells had greater levels of pro-inflammatory cytokines including IFN-α, CCL2, TNF-α, and CCL5, when infected by pandemic viruses as compared with seasonal. Polarization of IL-6 in wd-NHBE cells was greatest at 36 hpi for all isolates. Differential polarized secretion was suggested for CCL5 across isolates. Despite differences in viral titer across isolates, no significant differences were observed in KY/180 and KY/136 gene expression intensity profiles. Microarray profiles of wd-NHBE cells diverged at 36 hpi with 1647 genes commonly shared by wd-NHBE cells infected by pandemic, but not seasonal isolates. Significant differences were observed in cytokine signaling, apoptosis, and cytoskeletal arrangement pathways. Our studies revealed differences in temporal dynamics and basal levels of cytokine/chemokine responses of wd-NHBE cells infected with each isolate; however, wd-NHBE cell gene intensity profiles were not significantly different between the two pandemic isolates suggesting post-transcriptional or later differences in viral-host interactions.

Pathogenesis of influenza-induced acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a fatal complication of influenza infection. In this Review we provide an integrated model for its pathogenesis. ARDS involves damage to the epithelial-endothelial barrier, fluid leakage into the alveolar lumen, and respiratory insufficiency. The most important part of the epithelial-endothelial barrier is the alveolar epithelium, strengthened by tight junctions. Influenza virus targets these epithelial cells, reducing sodium pump activity, damaging tight junctions, and killing infected cells. Infected epithelial cells produce cytokines that attract leucocytes--neutrophils and macrophages--and activate adjacent endothelial cells. Activated endothelial cells and infiltrated leucocytes stimulate further infiltration, and leucocytes induce production of reactive oxygen species and nitric oxide that damage the barrier. Activated macrophages also cause direct apoptosis of epithelial cells. This model for influenza-induced ARDS differs from the classic model, which is centred on endothelial damage, and provides a rationale for therapeutic intervention to moderate host response in influenza-induced ARDS.

Culturing of human nasal epithelial cells at the air liquid interface

In vitro models using human primary epithelial cells are essential in understanding key functions of the respiratory epithelium in the context of microbial infections or inhaled agents. Direct comparisons of cells obtained from diseased populations allow us to characterize different phenotypes and dissect the underlying mechanisms mediating changes in epithelial cell function. Culturing epithelial cells from the human tracheobronchial region has been well documented, but is limited by the availability of human lung tissue or invasiveness associated with obtaining the bronchial brushes biopsies. Nasal epithelial cells are obtained through much less invasive superficial nasal scrape biopsies and subjects can be biopsied multiple times with no significant side effects. Additionally, the nose is the entry point to the respiratory system and therefore one of the first sites to be exposed to any kind of air-borne stressor, such as microbial agents, pollutants, or allergens. Briefly, nasal epithelial cells obtained from human volunteers are expanded on coated tissue culture plates, and then transferred onto cell culture inserts. Upon reaching confluency, cells continue to be cultured at the air-liquid interface (ALI), for several weeks, which creates more physiologically relevant conditions. The ALI culture condition uses defined media leading to a differentiated epithelium that exhibits morphological and functional characteristics similar to the human nasal epithelium, with both ciliated and mucus producing cells. Tissue culture inserts with differentiated nasal epithelial cells can be manipulated in a variety of ways depending on the research questions (treatment with pharmacological agents, transduction with lentiviral vectors, exposure to gases, or infection with microbial agents) and analyzed for numerous different endpoints ranging from cellular and molecular pathways, functional changes, morphology, etc. In vitro models of differentiated human nasal epithelial cells will enable investigators to address novel and important research questions by using organotypic experimental models that largely mimic the nasal epithelium in vivo.

Adding protein context to the human protein-protein interaction network to reveal meaningful interactions

Interactions of proteins regulate signaling, catalysis, gene expression and many other cellular functions. Therefore, characterizing the entire human interactome is a key effort in current proteomics research. This challenge is complicated by the dynamic nature of protein-protein interactions (PPIs), which are conditional on the cellular context: both interacting proteins must be expressed in the same cell and localized in the same organelle to meet. Additionally, interactions underlie a delicate control of signaling pathways, e.g. by post-translational modifications of the protein partners - hence, many diseases are caused by the perturbation of these mechanisms. Despite the high degree of cell-state specificity of PPIs, many interactions are measured under artificial conditions (e.g. yeast cells are transfected with human genes in yeast two-hybrid assays) or even if detected in a physiological context, this information is missing from the common PPI databases. To overcome these problems, we developed a method that assigns context information to PPIs inferred from various attributes of the interacting proteins: gene expression, functional and disease annotations, and inferred pathways. We demonstrate that context consistency correlates with the experimental reliability of PPIs, which allows us to generate high-confidence tissue- and function-specific subnetworks. We illustrate how these context-filtered networks are enriched in bona fide pathways and disease proteins to prove the ability of context-filters to highlight meaningful interactions with respect to various biological questions. We use this approach to study the lung-specific pathways used by the influenza virus, pointing to IRAK1, BHLHE40 and TOLLIP as potential regulators of influenza virus pathogenicity, and to study the signalling pathways that play a role in Alzheimer's disease, identifying a pathway involving the altered phosphorylation of the Tau protein. Finally, we provide the annotated human PPI network via a web frontend that allows the construction of context-specific networks in several ways.

Protein-protein-interactions (PPIs) participate in virtually all biological processes. However, the PPI map is not static but the pairs of proteins that interact depends on the type of cell, the subcellular localization and modifications of the participating proteins, among many other factors. Therefore, it is important to understand the specific conditions under which a PPI happens. Unfortunately, experimental methods often do not provide this information or, even worse, measure PPIs under artificial conditions not found in biological systems. We developed a method to infer this missing information from properties of the interacting proteins, such as in which cell types the proteins are found, which functions they fulfill and whether they are known to play a role in disease. We show that PPIs for which we can infer conditions under which they happen have a higher experimental reliability. Also, our inference agrees well with known pathways and disease proteins. Since diseases usually affect specific cell types, we study PPI networks of influenza proteins in lung tissues and of Alzheimer's disease proteins in neural tissues. In both cases, we can highlight interesting interactions potentially playing a role in disease progression.

Dietary abscisic acid ameliorates influenza-virus-associated disease and pulmonary immunopathology through a PPARγ-dependent mechanism

The anti-inflammatory phytohormone abscisic acid (ABA) modulates immune and inflammatory responses in mouse models of colitis and obesity. ABA has been identified as a ligand of lanthionine synthetase C-like 2, a novel therapeutic target upstream of the peroxisome proliferator-activated receptor γ (PPARγ) pathway. The goal of this study was to investigate the immune modulatory mechanisms underlying the anti-inflammatory efficacy of ABA against influenza-associated pulmonary inflammation. Wild-type (WT) and conditional knockout mice with defective PPARγ expression in lung epithelial and hematopoietic cells (cKO) treated orally with or without ABA (100 mg/kg diet) were challenged with influenza A/Udorn (H3N2) to assess ABA's impact in disease, lung lesions and gene expression. Dietary ABA ameliorated disease activity and lung inflammatory pathology, accelerated recovery and increased survival in WT mice. ABA suppressed leukocyte infiltration and monocyte chemotactic protein 1 mRNA expression in WT mice through PPARγ since this effect was abrogated in cKO mice. ABA ameliorated disease when administered therapeutically on the same day of the infection to WT but not mice lacking PPARγ in myeloid cells. We also show that ABA's greater impact is between days 7 and 10 postchallenge when it regulates the expression of genes involved in resolution, like 5-lipoxygenase and other members of the 5-lipoxygenase pathway. Furthermore, ABA significantly increased the expression of the immunoregulatory cytokine interleukin-10 in WT mice. Our results show that ABA, given preventively or therapeutically, ameliorates influenza-virus-induced pathology by activating PPARγ in pulmonary immune cells, suppressing initial proinflammatory responses and promoting resolution.

Epithelial cells, the "switchboard" of respiratory immune defense responses: effects of air pollutants

"Epimmunome", a term introduced recently by Swamy and colleagues, describes all molecules and pathways used by epithelial cells (ECs) to instruct immune cells. Today, we know that ECs are among the first sites within the human body to be exposed to pathogens (such as influenza viruses) and that the release of chemokine and cytokines by ECs is influenced by inhaled agents. The role of the ECs as a switchboard to initiate and regulate immune responses is altered through air pollutant exposure, such as ozone, tobacco smoke and diesel exhaust emissions. The details of the interplay between ECs and immune cells are not yet fully understood and need to be investigated further. Co-culture models, cell specific genetically-modified mice and the analysis of human biopsies provide great tools to gain knowledge about potential mechanisms. Increasing our understanding about the role of ECs in respiratory immunity may yield novel therapeutic targets to modulate downstream diseases.

Key role of regulated upon activation normal T-cell expressed and secreted, nonstructural protein1 and myeloperoxidase in cytokine storm induced by influenza virus PR-8 (A/H1N1) infection in A549 bronchial epithelial cells

Influenza virus infection causes severe respiratory disease such as that due to avian influenza (H5N1). Influenza A viruses proliferate in human epithelial cells, which produce inflammatory cytokines/chemokines as a "cytokine storm" attenuated with the viral nonstructural protein 1 (NS1). Cytokine/chemokine production in A549 epithelial cells infected with influenza A/H1N1 virus (PR-8) or nonstructural protein 1 (NS1) plasmid was examined in vitro. Because tumor necrosis factor-α (TNF-α) and regulated upon activation normal T-cell expressed and secreted (RANTES) are predominantly produced from cells infected with PR-8 virus, the effects of mRNA knockdown of these cytokines were investigated. Small interfering (si)TNF-α down-regulated RANTES expression and secretion of RANTES, interleukin (IL)-8, and monocyte chemotactic protein-1 (MCP-1). In addition, siRANTES suppressed interferon (IFN)-γ expression and secretion of RANTES, IL-8, and MCP-1, suggesting that TNF-α stimulates production of RANTES, IL-8, MCP-1, and IFN-γ, and RANTES also increased IL-8, MCP-1, and IFN-γ. Furthermore, administration of TNF-α promoted increased secretion of RANTES, IL-8, and MCP-1. Administration of RANTES enhanced IL-6, IL-8, and MCP-1 production without PR-8 infection. These results strongly suggest that, as an initial step, TNF-α regulates RANTES production, followed by increase of IL-6, IL-8, and MCP-1 and IFNs concentrations. At a later stage, cells transfected with viral NS1 plasmid showed production of a large amount of IL-8 and MCP-1 in the presence of the H(2)O(2)-myeloperoxidse (MPO) system, suggesting that NS1 of PR-8 may induce a "cytokine storm" from epithelial cells in the presence of an H(2)O(2)-MPO system.

Evaluation and management of seasonal influenza in the emergency department

Seasonal influenza causes significant morbidity and mortality, primarily due to increased complication rates among the elderly population and patients with chronic diseases. Timely diagnosis of influenza and early recognition of an influenza outbreak or epidemic are key components in preventing influenza-related complications, hospitalizations, and deaths. Emergency departments are the most frequent points of entry for most influenza cases and are well positioned to identify and manage influenza community outbreaks and epidemics. Emergency departments need specific infection control measures to curb the spread of influenza in the Emergency Department and hospital during the influenza season.

The prostanoid 15-deoxy-Δ12,14-prostaglandin-j2 reduces lung inflammation and protects mice against lethal influenza infection

BACKGROUND

Growing evidence indicates that influenza pathogenicity relates to altered immune responses and hypercytokinemia. Therefore, dampening the excessive inflammatory response induced after infection might reduce influenza morbidity and mortality.

METHODS

Considering this, we investigated the effect of the anti-inflammatory molecule 15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)) in a mouse model of lethal influenza infection.

RESULTS

Administration of 15d-PGJ(2) on day 1 after infection, but not on day 0, protected 79% of mice against lethal influenza infection. In addition, this treatment considerably reduced the morbidity associated with severe influenza infection. Our results also showed that treatment with 15d-PGJ(2) decreased influenza-induced lung inflammation, as shown by the diminished gene expression of several proinflammatory cytokines and chemokines. Unexpectedly, 15d-PGJ(2) also markedly reduced the viral load in the lungs of infected mice. This could be attributed to maintained type I interferon gene expression levels after treatment. Interestingly, pretreatment of mice with a peroxisome proliferator-activated receptor gamma (PPARγ) antagonist before 15d-PGJ(2) administration completely abrogated its protective effect against influenza infection.

CONCLUSIONS

Our results demonstrate for the first time that treatment of mice with 15d-PGJ(2) reduces influenza morbidity and mortality through activation of the PPARγ pathway. PPARγ agonists could thus represent a potential therapeutic avenue for influenza infections.

Apoptosis, cytokine and chemokine induction by non-structural 1 (NS1) proteins encoded by different influenza subtypes

Background

Influenza pandemic remains a serious threat to human health. Viruses of avian origin, H5N1, H7N7 and H9N2, have repeatedly crossed the species barrier to infect humans. Recently, a novel strain originated from swine has evolved to a pandemic. This study aims at improving our understanding on the pathogenic mechanism of influenza viruses, in particular the role of non-structural (NS1) protein in inducing pro-inflammatory and apoptotic responses.

Methods

Human lung epithelial cells (NCI-H292) was used as an in-vitro model to study cytokine/chemokine production and apoptosis induced by transfection of NS1 mRNA encoded by seven infleunza subtypes (seasonal and pandemic H1, H2, H3, H5, H7, and H9), respectively.

Results

The results showed that CXCL-10/IP10 was most prominently induced (> 1000 folds) and IL-6 was slightly induced (< 10 folds) by all subtypes. A subtype-dependent pattern was observed for CCL-2/MCP-1, CCL3/MIP-1α, CCL-5/RANTES and CXCL-9/MIG; where induction by H5N1 was much higher than all other subtypes examined. All subtypes induced a similar temporal profile of apoptosis following transfection. The level of apoptosis induced by H5N1 was remarkably higher than all others. The cytokine/chemokine and apoptosis inducing ability of the 2009 pandemic H1N1 was similar to previous seasonal strains.

Conclusions

In conclusion, the NS1 protein encoded by H5N1 carries a remarkably different property as compared to other avian and human subtypes, and is one of the keys to its high pathogenicity. NCI-H292 cells system proves to be a good in-vitro model to delineate the property of NS1 proteins.

Infection of lung epithelial cells with pandemic 2009 A(H1N1) influenza viruses reveals isolate-specific differences in infectivity and host cellular responses

To better understand the early virus-host interactions of the pandemic 2009 A(H1N1) viruses in humans, we examined early host responses following infection of human epithelial cell cultures with three 2009 A(H1N1) viruses (A/California/08/2009, A/Mexico/4108/2009, and A/Texas/15/2009), or a seasonal H1N1 vaccine strain (A/Solomon Islands/3/2006). We report here that infection with pandemic A/California/08/2009 and A/Mexico/4108/2009 viruses resulted in differences in virus infectivity compared to either pandemic A/Texas/15/2009 or the seasonal H1N1 vaccine strain. In addition, IFN-β levels were decreased in cell cultures infected with either the A/California/08/2009 or the A/Mexico/4108/2009 virus. Furthermore, infection with A/California/08/2009 and A/Mexico/4108/2009 viruses resulted in lower expression of four key proinflammatory markers (IL-6, RANTES, IP-10, and MIP-1β) compared with infection with either A/Texas/15/2009 or A/Solomon Islands/3/2006. Taken together, our results demonstrate that 2009 A(H1N1) viruses isolated during the Spring wave induced varying degrees of early host antiviral and inflammatory responses in human respiratory epithelial cells, highlighting the strain-specific nature of these responses, which play a role in clinical disease.

Evodia rutaecarpa and Three Major Alkaloids Abrogate Influenza A Virus (H1N1)-Induced Chemokines Production and Cell Migration

Evodia rutaecarpa is commonly used as an anti-inflammatory herbal remedy in traditional Chinese medicine. In this study, the ethanol extract of E. rutaecarpa (ER) and three major quinazoline alkaloids dehydroevodiamine (DeHE), evodiamine (Evo) and rutaecarpine (Rut), isolated from ER were employed to study their inhibitory effects against influenza A virus (H1N1)-induced chemokines production in A549 lung epithelial cells as well as on chemokines-evoked cell recruitment in HL-60-differentiated macrophages. The results showed that ER was a potent inhibitor of RANTES secretion by H1N1-inoculated A549 cells (IC(50): 1.9 ± 0.4 μg ml(-1)). Three alkaloids, although to differing extents, all concentration dependent, inhibited H1N1-induced RANTES production with Evo consistently being the most potent among these active components. ER also moderately and significantly inhibited H1N1-stimulated MCP-1 production in A549 cells. This was mimicked by Evo and Rut, but not DeHE. In the macrophage recruitment assay, both RANTES and MCP-1 markedly evoked cell migration and this phenomenon was significantly suppressed by ER. Evo and Rut, but not DeHE, also had the ability to inhibit cell migration toward RANTES and MCP-1, respectively. In summary, three major alkaloids displayed different potentials for inhibiting chemokines secretion and subsequently cell migration, which could partially explain the activity of ER. As an effective agent to suppress H1N1-induced chemokines production and block chemokine-attracted leukocytes recruitment, E. rutaecarpa and its active components may be useful in influenza virus infection-related inflammatory disorders.

Profiles of cytokine and chemokine gene expression in human pulmonary epithelial cells induced by human and avian influenza viruses

Influenza pandemic remains a serious threat to human health. In this study, the repertoire of host cellular cytokine and chemokine responses to infections with highly pathogenic avian influenza H5N1, low pathogenicity avian influenza H9N2 and seasonal human influenza H1N1 were compared using an in vitro system based on human pulmonary epithelial cells. The results showed that H5N1 was more potent than H9N2 and H1N1 in inducing CXCL-10/IP-10, TNF-alpha and CCL-5/RANTES. The cytokine/chemokine profiles for H9N2, in general, resembled those of H1N1. Of interest, only H1N1, but none of the avian subtypes examined could induce a persistent elevation of the immune-regulatory cytokine - TGF-β2. The differential expression of cytokines/chemokines following infection with different influenza viruses could be a key determinant for clinical outcome. The potential of using these cytokines/chemokines as prognostic markers or targets of therapy is worth exploring.

Respiratory epithelial cells in innate immunity to influenza virus infection

Infection by influenza virus leads to respiratory failure characterized by acute lung injury associated with alveolar edema, necrotizing bronchiolitis, and excessive bleeding. Severe reactions to infection that lead to hospitalizations and/or death are frequently attributed to an exuberant host response, with excessive inflammation and damage to the epithelial cells that mediate respiratory gas exchange. The respiratory mucosa serves as a physical and chemical barrier to infection, producing mucus and surfactants, anti-viral mediators, and inflammatory cytokines. The airway epithelial cell layer also serves as the first and overwhelmingly primary target for virus infection and growth. This review details immune events during influenza infection from the viewpoint of the epithelial cells, secretory host defense mechanisms, cell death, and recovery.

Host immune and apoptotic responses to avian influenza virus H9N2 in human tracheobronchial epithelial cells

The avian influenza virus H9N2 subtype has circulated in wild birds, is prevalent in domestic poultry, and has successfully crossed the species boundary to infect humans. Phylogenetic analyses showed that viruses of this subtype appear to have contributed to the generation of highly pathogenic H5N1 viruses. Little is known about the host responses to H9N2 viruses in human airway respiratory epithelium, the primary portal for viral infection. Using an apically differentiated primary human tracheobronchial epithelial (TBE) culture, we examined host immune responses to infection by an avian H9N2 virus, in comparison with a human H9N2 isolate. We found that IFN-β was the prominent antiviral component, whereas interferon gamma-induced protein 10 kDa (IP-10), chemokine (C-C motif) ligand (CCL)-5 and TNF-α may be critical in proinflammatory responses to H9N2 viruses. In contrast, proinflammatory IL-1β, IL-8, and even IL-6 may only play a minor role in pathogenicity. Apparently Toll-like receptor (TLR)-3, TLR-7, and melanoma differentiation-associated gene 5 (MDA-5) contributed to the innate immunity against the H9N2 viruses, and MDA-5 was important in the induction of IFN-β. We showed that the avian H9N2 virus induced apoptosis through the mitochondria/cytochrome c-mediated intrinsic pathway, in addition to the caspase 8-mediated extrinsic pathway, as evidenced by the cytosolic presence of active caspase 9 and cytochrome c, independent of truncated BH3 interacting domain death agonist (Bid) activation. Further, we demonstrated that FLICE-like inhibitory protein (FLIP), an apoptotic dual regulator, and the p53-dependent Bcl-2 family members, Bax and Bcl-x(s), appeared to be involved in the regulation of extrinsic and intrinsic apoptotic pathways, respectively. The findings in this study will further our understanding of host defense mechanisms and the pathogenesis of H9N2 influenza viruses in human respiratory epithelium.

Influenza H5N1 and H1N1 virus replication and innate immune responses in bronchial epithelial cells are influenced by the state of differentiation

Influenza H5N1 virus continues to be enzootic in poultry and transmits zoonotically to humans. Although a swine-origin H1N1 virus has emerged to become pandemic, its virulence for humans remains modest in comparison to that seen in zoonotic H5N1 disease. As human respiratory epithelium is the primary target cells for influenza viruses, elucidating the viral tropism and host innate immune responses of influenza H5N1 virus in human bronchial epithelium may help to understand the pathogenesis. Here we established primary culture of undifferentiated and well differentiated normal human bronchial epithelial (NHBE) cells and infected with highly pathogenic influenza H5N1 virus (A/Vietnam/3046/2004) and a seasonal influenza H1N1 virus (A/Hong Kong/54/1998), the viral replication kinetics and cytokine and chemokine responses were compared by qPCR and ELISA. We found that the in vitro culture of the well differentiated NHBE cells acquired the physiological properties of normal human bronchi tissue which express high level of α2-6-linked sialic acid receptors and human airway trypsin-like (HAT) protease, in contrast to the low expression in the non-differentiated NHBE cells. When compared to H1N1 virus, the H5N1 virus replicated more efficiently and induced a stronger type I interferon response in the undifferentiated NHBE cells. In contrast, in well differentiated cultures, H5N1 virus replication was less efficient and elicited a lower interferon-beta response in comparison with H1N1 virus. Our data suggest that the differentiation of bronchial epithelial cells has a major influence in cells' permissiveness to human H1N1 and avian H5N1 viruses and the host innate immune responses. The reduced virus replication efficiency partially accounts for the lower interferon-beta responses in influenza H5N1 virus infected well differentiated NHBE cells. Since influenza infection in the bronchial epithelium will lead to tissue damage and associate with the epithelium regeneration, the data generated from the undifferentiated NHBE cultures may also be relevant to disease pathogenesis.

Innate immune response to H3N2 and H1N1 influenza virus infection in a human lung organ culture model

We studied cytokine responses to influenza virus PR8 (H1N1) and Oklahoma/309/06 (OK/06, H3N2) in a novel human lung tissue model. Exposure of the model to influenza virus rapidly activated the mitogen-activated protein kinase signaling (MAPK) pathways ERK, p38 and JNK. In addition, RNase protection assay demonstrated the induction of several cytokine and chemokine mRNAs by virus. This finding was reflected at the translational level as IL-6, MCP-1, MIP-1 alpha/beta, IL-8 and IP-10 proteins were induced as determined by ELISA. Immunohistochemistry for IP-10 and MIP-1 alpha revealed that alveolar epithelial cells and macrophages were the source of these two cytokines. Taken together, both PR8 and OK/06 cause similar induction of cytokines in human lung, although OK/06 is less effective at inducing the chemokines MCP-1 and IL-8. This human organ culture model should thus provide a relevant platform to study the biological responses of human lung to influenza virus infection.

Influenza

OBJECTIVE

Influenza is a major concern for intensivists in all communities in the U.S. While there is considerable concern whether or not the country will be ready for a pandemic influenza, even seasonal influenza poses a major challenge to hospitals. The objective of this review is to summarize current knowledge of influenza with emphasis on the issues that intensivist will encounter.

SETTING

Intensive care unit in a 450-bed, tertiary care, teaching hospital.

METHODS

Source data were obtained from a PubMed search of the medical literature. PubMed "related articles" search strategies were likewise employed frequently.

SUMMARY AND CONCLUSIONS

Seasonal influenza causes more than 200,000 hospitalizations and 41,000 deaths in the U.S. every year, and is the seventh leading cause of death in the U.S. Despite this impact there is a shortcoming in knowledge of influenza among many health care workers, and a paucity of clinical data and studies to guide therapy. Intensivists need to recognize the importance of seasonal influenza as a cause of severe morbidity and mortality. This review summarizes current knowledge of the diagnosis, complications, therapy, and infection control measures associated with influenza.

Quantification of mRNA encoding cytokines and chemokines and assessment of ciliary function in canine tracheal epithelium during infection with canine respiratory coronavirus (CRCoV)

One of the first lines of defence against viral infection is the innate immune response and the induction of antiviral type I interferons (IFNs). However some viruses, including the group 2 coronaviruses, have evolved mechanisms to overcome or circumvent the host antiviral response. Canine respiratory coronavirus (CRCoV) has previously been shown to have a widespread international presence and has been implicated in outbreaks of canine infectious respiratory disease (CIRD). This study aimed to quantify pro-inflammatory cytokine mRNAs following infection of canine air-interface tracheal cultures with CRCoV. Within this system, immunohistochemistry identified ciliated epithelial and goblet cells as positive for CRCoV, identical to naturally infected cases, thus the data obtained would be fully transferable to the situation in vivo. An assay of ciliary function was used to assess potential effects of CRCoV on the mucociliary system. CRCoV was shown to reduce the mRNA levels of the pro-inflammatory cytokines TNF-α and IL-6 and the chemokine IL-8 during the 72 h post-inoculation. The mechanism for this is unknown, however the suppression of a key antiviral strategy during a period of physiologic and immunological stress, such as on entry to a kennel, could potentially predispose a dog to further pathogenic challenge and the development of respiratory disease.

Monocyte chemoattractant protein 1 contributes to an adequate immune response in influenza pneumonia

Monocyte chemoattractant protein 1 (MCP-1) and its receptor CCR2 have been shown to play an import role in leukocyte recruitment to sites of infection and inflammation. To investigate the role of MCP-1 during infection with influenza we inoculated wild-type (WT) and MCP-1 knockout (KO) mice with a non-lethal dose of a mouse adapted strain of influenza A. Influenza infection of WT mice resulted in a profound increase in pulmonary MCP-1 levels. MCP-1 KO mice had enhanced weight loss and did not fully regain their body weight during the 14-day observation period. In addition, MCP-1 KO mice demonstrated elevated viral loads 8 days after infection, which was accompanied by reduced leukocyte recruitment into the infected lungs, primarily caused by a diminished influx of macrophages and granulocytes. Moreover, pulmonary levels of IgA were reduced in MCP-1 KO mice. The pulmonary concentrations of tumor necrosis factor-alpha, interleukin-6, macrophage inflammatory protein 2 and interferon-gamma were higher in MCP-1 KO mice. This study shows that MCP-1 contributes to an adequate protective immune response against influenza infection in mice.

A question of self-preservation: immunopathology in influenza virus infection

Influenza A viruses that circulate normally in the human population cause a debilitating, though generally transient, illness that is sometimes fatal, particularly in the elderly. Severe complications arising from pandemic influenza or the highly pathogenic avian H5N1 viruses are often associated with rapid, massive inflammatory cell infiltration, acute respiratory distress, reactive hemophagocytosis and multiple organ involvement. Histological and pathological indicators strongly suggest a key role for an excessive host response in mediating at least some of this pathology. Here, we review the current literature on how various effector arms of the immune system can act deleteriously to initiate or exacerbate pathological damage in this viral pneumonia. Generally, the same immunological factors mediating tissue damage during the anti-influenza immune response are also critical for efficient elimination of virus, thereby posing a significant challenge in the design of harmless yet effective therapeutic strategies for tackling influenza virus.

Dual regulatory effect of plant extracts of Forsythia suspense on RANTES and MCP-1 secretion in influenza A virus-infected human bronchial epithelial cells

In this study, we investigated the effects of 95% ethanol (FS-t1), 50% ethanol (FS-t2) and water (FS-w) extracts of Forsythia suspense Vahl (Oleaceae) on the production of regulated on activation, normal T cell expressed and secreted (RANTES) and macrophage chemotactic protein-1 (MCP-1) by influenza A virus (H1N1)-infected human bronchial epithelial cell line A549. Virus infection evoked a markedly enhanced production of RANTES from basal 16 +/- 4 to 1307 +/- 294 pg/ml after 72 h inoculation. At the non-cytotoxic doses (20, 100 and 200 microg/ml), FS-t1, FS-t2 and FS-w exhibited a consistent inhibitory effect on virus-stimulated RANTES secretion in a dose-dependent manner wilh IC(50) of 42 +/- 6, 117 +/- 15 and 232 +/- 28 microg/ml, respectively. H1N1 also stimulated MCP-1 production in A549 cells, however to a less degree, from basal 133 +/- 21 to 391 +/- 98 pg/ml after 72 h viral inoculation. The effects of three extracts on MCP-1 secretion were more complex. FS-t1 displayed both positive and negative effect on virus-stimulated MCP-1 production dependent on the concentrations used. On the other hand, FS-t2 increased virus-induced MCP-1 secretion by 1.4-3.3 times while the third fraction FO-w increased by 2.6-3.7 times. These results suggested that Forsythia suspense consisted of both negative and positive regulatory components on RANTES and MCP-1 secretion in H1N1-infected A549 cells, respectively.

Proinflammatory cytokine responses induced by influenza A (H5N1) viruses in primary human alveolar and bronchial epithelial cells

Background

Fatal human respiratory disease associated with influenza A subtype H5N1 has been documented in Hong Kong, and more recently in Vietnam, Thailand and Cambodia. We previously demonstrated that patients with H5N1 disease had unusually high serum levels of IP-10 (interferon-gamma-inducible protein-10). Furthermore, when compared with human influenza virus subtype H1N1, the H5N1 viruses in 1997 (A/Hong Kong/483/97) (H5N1/97) were more potent inducers of pro-inflammatory cytokines (e.g. tumor necrosis factor-a) and chemokines (e.g. IP-10) from primary human macrophages in vitro, which suggests that cytokines dysregulation may play a role in pathogenesis of H5N1 disease. Since respiratory epithelial cells are the primary target cell for replication of influenza viruses, it is pertinent to investigate the cytokine induction profile of H5N1 viruses in these cells.

Methods

We used quantitative RT-PCR and ELISA to compare the profile of cytokine and chemokine gene expression induced by H5N1 viruses A/HK/483/97 (H5N1/97), A/Vietnam/1194/04 and A/Vietnam/3046/04 (both H5N1/04) with that of human H1N1 virus in human primary alveolar and bronchial epithelial cells in vitro.

Results

We demonstrated that in comparison to human H1N1 viruses, H5N1/97 and H5N1/04 viruses were more potent inducers of IP-10, interferon beta, RANTES (regulated on activation, normal T cell expressed and secreted) and interleukin 6 (IL-6) in primary human alveolar and bronchial epithelial cells in vitro. Recent H5N1 viruses from Vietnam (H5N1/04) appeared to be even more potent at inducing IP-10 than H5N1/97 virus.

Conclusion

The H5N1/97 and H5N1/04 subtype influenza A viruses are more potent inducers of proinflammatory cytokines and chemokines in primary human respiratory epithelial cells than subtype H1N1 virus. We suggest that this hyper-induction of cytokines may be relevant to the pathogenesis of human H5N1 disease.

TNF-alpha and IFN-alpha enhance influenza-A-virus-induced chemokine gene expression in human A549 lung epithelial cells

Lung epithelial cells are the primary cellular targets for respiratory virus pathogens such as influenza and parainfluenza viruses. Here, we have analyzed influenza A, influenza B and Sendai virus-induced chemokine response in human A549 lung epithelial cells. Influenza virus infection resulted in low CCL2/MCP-1, CCL5/RANTES, CXCL8/IL-8 and CXCL10/IP-10 production at late times of infection. However, when cells were pretreated with TNF-alpha or IFN-alpha, influenza-A-virus-induced chemokine production was greatly enhanced. Cytokine pretreatment resulted in enhanced expression of RIG-I, IKKepsilon, interferon regulatory factor (IRF)1, IRF7 and p50 proteins. Most importantly, influenza-A-virus-induced DNA binding of IRF1, IRF3, IRF7 and NF-kappaB onto CXCL10 ISRE and NF-kappaB elements, respectively, was markedly enhanced in cytokine-pretreated cells. Our results suggest that IFN-alpha and TNF-alpha have a significant role in priming epithelial cells for higher cytokine and chemokine production in influenza A virus infection.

Motorcycle exhaust particles induce IL-8 production through NF-kappaB activation in human airway epithelial cells

Motorcycle exhaust particles (MEP) are among the major air pollutants, especially in urban area of Taiwan. In our previous study, data showed that MEP induce proinflammatory and proallergic response profiles in BALB/c mice. Effects of MEP on interleukin (IL)-8 production in A549 human airway epithelial cells were further investigated in this study. It was found that MEP enhanced IL-8 protein and mRNA expression in human epithelial cells. Pretreatment with an NF-kappaB inhibitor (1 mM PDTC), extracellular signal-regulated kinase (ERK) inhibitor (50 microM PD98059), JNK inhibitor (25 microM SP600125), p38 inhibitor (2 microM SB203580), and three antioxidants (500 U/ml superoxide dismutase [SOD], 50 microM vitamin E, 10 mMN-acetylcysteine [NAC]) attenuated the MEP-induced increase in IL-8 production. Through further, direct detection of nuclear factor (NF)-kappaB activation in epithelial cells using immunoblotting of nuclear p65 and NF-kappaB reporter assay, data showed that MEP induced nuclear translocation of p65 and enhancement of NF-kappaB luciferase gene expression. MEP also induced activation of ERK, JNK, and p38 signaling pathways and produced an increase of oxidative stress in A549 cells. By using mitogen-activated protein kinase (MAPK) inhibitors and antioxidant, it was demonstrated that ERK inhibitor, JNK inhibitor, and antioxidants but not p38 inhibitor attenuated the MEP-induced increase in NF-kappaB reporter activity. In conclusion, evidence shows that filter-trapped particles emitted from unleaded gasoline-fueled, two-stroke motorcycle engines induce an increase in IL-8 production by activation of NF-kappaB in human airway epithelial cells.

Down-regulation of inducible nitric oxide synthase by lysophosphatidic acid in human respiratory epithelial cells

Viral infection generally results in the activation of inducible nitric oxide synthase (iNOS or NOS2) in respiratory epithelial cells by inflammatory cytokines. Activated NOS2 catalyzes synthesis of nitric oxide (NO), which in excess can cause cellular injury. On the other hand, lysophosphatidic acid (LPA), a lipid mediator released from epithelial cells, platelets, and fibroblasts in injured tissue, functions in repair of cell injury. However, details of the mechanism for repair by LPA remain unknown. We demonstrated one effect of LPA favoring repair, specifically inhibition by LPA of cytokine-induced NOS2 protein and mRNA expression by human respiratory epithelial cells in vitro. NO production by LPA-treated, cytokine-stimulated cells was also reduced. These decreases were prevented by Rho kinase inhibition with Y-27632. Thus, down-regulation by LPA of cytokine-induced increases in NOS2 activity is likely to involve a Rho-dependent signaling pathway. Harmful biologic effects of NO in viral respiratory infection might be modified by therapeutic manipulations involving LPA or Rho.

Diesel exhaust enhances influenza virus infections in respiratory epithelial cells

Several factors, such as age and nutritional status, can affect the susceptibility to influenza infections. Moreover, exposure to air pollutants, such as diesel exhaust (DE), has been shown to affect respiratory virus infections in rodent models. Influenza virus primarily infects and replicates in respiratory epithelial cells, which are also a major targets for inhaled DE. Using in vitro models of human respiratory epithelial cells, we determined the effects of an aqueous-trapped solution of DE (DE(as)) on influenza infections. Differentiated human nasal and bronchial epithelial cells, as well as A549 cells, were exposed to DE(as) and infected with influenza A/Bangkok/1/79. DE(as) enhanced the susceptibility to influenza virus infection in all cell models and increased the number of influenza-infected cells within 24 h post-infection. This was not caused by suppressing antiviral mediator production, since interferon (IFN) beta levels, IFN-dependent signaling, and IFN-stimulated gene expression were also enhanced by exposure to DE(as). Many of the adverse effects induced by DE exposure are mediated by oxidative stress. Exposure to DE(as) used in these studies generated oxidative stress in respiratory epithelial cells, and addition of the antioxidant glutathione-ethylester (GSH-ET) reversed the effects of DE(as) on influenza infections. Furthermore, DE(as) increased influenza virus attachment to respiratory epithelial cells within 2 h post-infection. Taken together, the results presented here suggest that in human respiratory epithelial cells oxidative stress generated by DE(as) increases the susceptibility to influenza infection and that exposure to DE(as) increases the ability of the virus to attach to and enter respiratory epithelial cells.

Influenza A mutant viruses with altered NS1 protein function provoke caspase-1 activation in primary human macrophages, resulting in fast apoptosis and release of high levels of interleukins 1beta and 18

Several NS1 mutant viruses of human influenza A/PR/8/34 (H1N1) virus were tested for their ability to induce pro-inflammatory cytokines in primary human macrophages. The findings revealed a pronounced difference in the virus-induced cytokine pattern, depending on the functionality of the NS1 protein-encoded domains. The PR8/NS1-125 mutant virus, which encodes the first 125 aa of the NS1 protein, thus lacking the C-terminal domains, induced significantly higher amounts of beta interferon, interleukin (IL) 6, tumour necrosis factor alpha and CCL3 (MIP-1alpha) when compared with the A/PR/8/34 wild-type virus. However, this mutant virus was as efficient as wild-type virus in the inhibition of IL1beta and IL18 release from infected macrophages. Another group of viral mutants either lacking or possessing non-functional RNA-binding and dimerization domains induced 10-50 times more biologically active IL1beta and five times more biologically active IL18 than the wild-type or PR8/NS1-125 viruses. The hallmark of infection with this group of mutant viruses was the induction of rapid apoptosis in infected macrophages, which correlated with the enhanced activity of caspase-1. These results indicated that the NS1 protein, through the function of its N-terminal domains, might control caspase-1 activation, thus repressing the maturation of pro-IL1beta-, pro-IL18- and caspase-1-dependent apoptosis in infected primary human macrophages.

Role of apoptosis and cytokines in influenza virus morbidity

Influenza virus is a major human pathogen that causes epidemics and pandemics with increased morbidity and, especially in the elderly and those with pre-existing medical conditions, increased mortality. Influenza is characterised by respiratory symptoms and constitutional symptoms. Whilst knowledge of the mechanisms underlying host and tissue specificity has advanced considerably of late we still know relatively little about other aspects of influenza virus virulence. In this review, we will explore what is known about the role of apoptosis in respiratory epithelial cell damage and the role of cytokines in inflammation and constitutional symptoms with particular emphasis on the link between apoptosis, inflammation, fever and cytokine production.

Inhibition of RANTES expression by indirubin in influenza virus-infected human bronchial epithelial cells

The human bronchial epithelial cells are the primary sites of influenza virus infection. In this study, the effect of indirubin on the expression of the chemokine regulated on activation, normal T cell expressed and secreted (RANTES) by the influenza virus-infected H292 human epithelial cell line was examined. The expression of RANTES mRNA was analyzed using reverse transcription polymerase chain reaction and the concentration of RANTES production was determined by the enzyme-linked immunosorbent assay. At the non-cytotoxic concentrations, indirubin was found to reduce both the expression and production of RANTES in influenza A/NWS/33-infected H292 cells. Inhibition was also observed in influenza virus B/Lee-infected cells. Significant reduction of the expression of IL-8 was not observed after the infection. Indirubin-3'-oxime, a recently developed derivative with kinase inhibitory activity, also mediates a potent inhibitory effect on the expression of RANTES. The influenza virus infection-induced phosphorylation of the nuclear transcription NF-kB regulatory molecule IkBalpha and the p38 MAP kinase were also found to be inhibited by indirubin-3'-oxime. This finding suggests that indirubin is one of the components in the Chinese medicinal herbs Isatis indigotica and Strobilanthes cusia with immunomodulatory activity on the expression of RANTES.

Influenza A virus-induced apoptosis in bronchiolar epithelial (NCI-H292) cells limits pro-inflammatory cytokine release

Infection of cells with influenza A virus results in cell death with apoptotic characteristics. Apoptosis is regarded as a non-inflammatory process. However, during influenza an inflammatory response occurs in the airway epithelium. An examination of this apparent paradox was made using influenza A virus infection of human nasal and bronchiolar epithelial cells. Some cytokine genes (IL-18, CCL2 and CCL5) were expressed constitutively in nasal cells but no cytokine was released. In bronchiolar cells, IL-1 beta, IL-6 and CXCL8 expression was constitutive, whilst CCL2 and CCL5 expression was upregulated following influenza virus infection. IL-6, CXCL8 and CCL5 were released but IL-1 beta and CCL2 were not. In bronchiolar cells, cell death was inhibited by the caspase-8 (Z-IETD-fmk) and pan-caspase (Z-VAD-fmk) inhibitors and these inhibitors enhanced expression of CCL5 and increased the levels of the three secreted cytokines significantly. Thus, the amount of each cytokine released from bronchiolar cells is reduced during cell death, implying that the observed inflammatory response in influenza would be greater if cell death did not occur. Reduced cytokine release is also associated with fragmentation of the Golgi body, as the caspase inhibitors also rescued influenza A virus-induced fragmentation of the Golgi ribbon.

Expression of cytokine and chemokine genes by human middle ear epithelial cells induced by influenza A virus and Streptococcus pneumoniae opacity variants

Real-time PCR and enzyme-linked immunosorbent assay were used to evaluate the ability of influenza A virus and Streptococcus pneumoniae opacity variants, either alone or in combination, to induce cytokine and chemokine genes in primary cultures of human middle ear epithelial (HMEE) cells. Following treatment with influenza A virus, the induction of gene expression, which occurred in a dose- and time-dependent manner, was strong for macrophage inflammatory protein 1 alpha (MIP-1 alpha) and MIP-1 beta; moderate for tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and IL-8; and weak for IL-1 beta and monocyte chemotactic peptide 1 (MCP-1). Except for TNF-alpha, all the gene products were detected in the cell culture supernatants. In contrast, infection of HMEE cells with S. pneumoniae alone induced low levels of mRNA expression of MIP-1 alpha and MIP-1 beta and did not significantly induce the transcription of the other cytokines and chemokines examined. However, both S. pneumoniae opacity variants increased mRNA expression of MIP-1 alpha, MIP-1 beta, IL-6, and MCP-1 in HMEE cells activated by a prior influenza A virus infection compared to levels in cells treated with either agent alone. Up-regulation of IL-6, IL-8, and MCP-1 mRNA expression and production by the virus in combination with opaque S. pneumoniae was two- to threefold higher than that induced by the virus combined with the transparent S. pneumoniae variant. These data indicate that the activation of HMEE cells by influenza A virus enhances the induction of cytokine and chemokine gene transcripts by S. pneumoniae and that this effect appears to be most pronounced when S. pneumoniae is in the opaque phase.

CXCR4-dependent HIV-1 infection of differentiated epithelial cells

Epithelial cells constitute a physical barrier to sexual transmission of HIV, but are also a source of cytokines that could alter infection efficiency. We studied HIV infection of the human colonic epithelial cell line HCT116, which is a model for differentiation of intestinal mucosal epithelium. Differentiated HCT116 cells had increased expression of cell surface C-X-C chemokine receptor type-4 (CXCR4) that mediated HIV entry, despite the apparent absence of cell surface CD4. HIV infection in differentiated HCT116 cells increased the levels of IL-1alpha, and IFN-alpha mRNA even though only 1% of cells had integrated provirus. The inefficient, CXCR4-mediated infection of differentiated HCT116 cells supports the view that epithelial cells are a barrier and not a portal for HIV transmission. However, low level infection of epithelial cells could trigger the release of cytokines that indirectly increase the transmission rate.

Exacerbations of Bronchitis: bronchial eosinophilia and gene expression for interleukin-4, interleukin-5, and eosinophil chemoattractants

Eosinophilia has been reported during exacerbations of bronchitis, but the mechanisms of tissue recruitment of eosinophils are unclear. We quantified eosinophils and the concurrent expression of cytokines and chemokines probably responsible for the tissue eosinophilia in bronchial biopsies obtained from three groups of nonatopic subjects: (1) healthy nonsmokers (n = 7; FEV1 % predicted = 108 +/- 4 [mean +/- SEM]); (2) nonasthmatic smokers with chronic bronchitis (CB) in a stable phase of their disease (n = 11; FEV1 % predicted: 75 +/- 5); and (3) nonasthmatic subjects with CB who sought medical advice for an exacerbation of their condition (n = 9; FEV(1) % predicted: 61 +/- 8). We applied anti-EG2 antibody and immunostaining to detect and count eosinophils. We performed in situ hybridization to visualize and enumerate cells expressing the genes for interleukin (IL)-4 and IL-5 and the eosinophil chemokines eotaxin, monocyte chemoattractant protein (MCP)-4, or regulated on activation, normal T-cell expressed and secreted (RANTES). We confirmed an increase in EG2-positive eosinophils in patients with CB in exacerbation. We found messenger RNA (mRNA) positivity for IL-4 and IL-5 in CB, but the between-group differences were not statistically significant. However, the numbers of lymphomononuclear cells expressing eotaxin mRNA were significantly greater in the smokers with CB than in the healthy nonsmokers without CB (p < 0.01). Following an exacerbation, RANTES expression was upregulated and this chemokine was strongly expressed in both the surface epithelium and in subepithelial lymphomononuclear cells: only RANTES showed a significant positive correlation with the increasing number of EG2-positive cells (r = 0.51; p < 0.03). In conclusion, an allergic profile of inflammation can also occur in CB: the marked upregulation of RANTES in the epithelium and subepithelium most likely accounts for the increased eosinophilia associated with an exacerbation of bronchitis.

Molecular pathogenesis of influenza A virus infection and virus-induced regulation of cytokine gene expression

Despite vaccines and antiviral substances influenza still causes significant morbidity and mortality world wide. Better understanding of the molecular mechanisms of influenza virus replication, pathogenesis and host immune responses is required for the development of more efficient means of prevention and treatment of influenza. Influenza A virus, which replicates in epithelial cells and leukocytes, regulates host cell transcriptional and translational systems and activates, as well as downregulates apoptotic pathways. Influenza A virus infection results in the production of chemotactic (RANTES, MIP-1 alpha, MCP-1, MCP-3, and IP-10), pro-inflammatory (IL-1 beta, IL-6, IL-18, and TNF-alpha), and antiviral (IFN-alpha/beta) cytokines. Cytokine gene expression is associated with the activation of NF-kappa B, AP-1, STAT and IRF signal transducing molecules in influenza A virus-infected cells. In addition of upregulating cytokine gene expression, influenza A virus infection activates caspase-1 enzyme, which is involved in the proteolytic processing of proIL-1 beta and proIL-18 into their biologically active forms. Influenza A virus-induced IFN-alpha/beta is essential in host's antiviral defence by activating the expression of antiviral Mx, PKR and oligoadenylate synthetase genes. IFN-alpha/beta also prolongs T cell survival, upregulates IL-12 and IL-18 receptor gene expression and together with IL-18 stimulates NK and T cell IFN-gamma production and the development of Th1-type immune response.