Respiratory syncytial virus reverses airway hyperresponsiveness to methacholine in ovalbumin-sensitized mice

MG53 attenuates nitrogen mustard-induced acute lung injury

Nitrogen mustard (NM) is an alkylating vesicant that causes severe pulmonary injury. Currently, there are no effective means to counteract vesicant‐induced lung injury. MG53 is a vital component of cell membrane repair and lung protection. Here, we show that mice with ablation of MG53 are more susceptible to NM‐induced lung injury than the wild‐type mice. Treatment of wild‐type mice with exogenous recombinant human MG53 (rhMG53) protein ameliorates NM‐induced lung injury by restoring arterial blood oxygen level, by improving dynamic lung compliance and by reducing airway resistance. Exposure of lung epithelial and endothelial cells to NM leads to intracellular oxidative stress that compromises the intrinsic cell membrane repair function of MG53. Exogenous rhMG53 protein applied to the culture medium protects lung epithelial and endothelial cells from NM‐induced membrane injury and oxidative stress, and enhances survival of the cells. Additionally, we show that loss of MG53 leads to increased vulnerability of macrophages to vesicant‐induced cell death. Overall, these findings support the therapeutic potential of rhMG53 to counteract vesicant‐induced lung injury.

Qingfei oral liquid inhibited autophagy to alleviate inflammation via mTOR signaling pathway in RSV-infected asthmatic mice

Qingfei oral liquid (QF) is a traditional Chinese medicine that has been used to treat patients with viral pneumonia and asthma for decades. Our previous study revealed that QF prevents airway inflammation and reduces airway hyperresponsiveness (AHR) in respiratory syncytial virus (RSV)-infected asthmatic mice. RSV infection can exacerbate asthma in pediatric patients and induce autophagy, which leads to the promotion of inflammatory cytokine production in the pathology of this disease. The effect of QF on regulating autophagy in RSV-infected asthma patients has not been fully elucidated. In this study, we identified compounds of QF by HPLC-DAD-Q-TOF-MS/MS. The RSV infected OVA challenged mice, we evaluated the RSV-infected asthma model. We found that treatment with QF alleviated airway inflammation and mitigated airway AHR in RSV-infected asthmatic mice. In addition, we found that QF inhibited autophagosome formation and the expression of LC3 protein by using electron and laser confocal microscopy, respectively, to assess RSV-infected asthmatic mice lung tissues. Furthermore, QF was found to reduce the quantity of autophagy and its related proteins LC3B (light chain 3B), Beclin-1, p62 and Atg5 (autophagy-related gene 5) and downstream inflammatory cytokines TNF-α, IL-4, IL-6, and IL-13 via an action in mTOR-dependent signaling in vivo and in vitro. These findings suggest that QF can alleviate the inflammation caused by RSV infection in asthmatic mice, and its mechanism may be involved in the regulation of autophagy via the mTOR signaling pathway.

Pulmonary function analysis in cotton rats after respiratory syncytial virus infection

The cotton rat (Sigmodon hispidus) is an excellent small animal model for human respiratory viral infections such as human respiratory syncytial virus (RSV) and human metapneumovirus (HMPV). These respiratory viral infections, as well as other pulmonary inflammatory diseases such as asthma, are associated with lung mechanic disturbances. So far, the pathophysiological effects of viral infection and allergy on cotton rat lungs have not been measured, although this information might be an important tool to determine the efficacy of vaccine and drug candidates. To characterize pulmonary function in the cotton rat, we established forced oscillation technique in uninfected, RSV infected and HDM sensitized cotton rats, and characterized pulmonary inflammation, mucus production, pulmonary edema, and oxygenation. There was a gender difference after RSV infection, with females demonstrating airway hyper-responsiveness while males did not. Female cotton rats 2dpi had a mild increase in pulmonary edema (wet: dry weight ratios). At day 4 post infection, female cotton rats demonstrated mild pulmonary inflammation, no increase in mucus production or reduction in oxygenation. Pulmonary function was not significantly impaired after RSV infection. In contrast, cotton rats sensitized to HDM demonstrated airway hyper-responsiveness with a significant increase in pulmonary inflammation, increase in baseline tissue damping, and a decrease in baseline pulmonary compliance. In summary, we established baseline data for forced oscillation technique and other respiratory measures in the cotton rat and used it to analyze respiratory diseases in cotton rats.

Qingfei oral liquid alleviates airway hyperresponsiveness and mucus hypersecretion via TRPV1 signaling in RSV-infected asthmatic mice

Pediatric asthma is exacerbated by Respiratory Syncytial Virus (RSV) infection, and Transient Receptor Potential Vanilloid 1 (TRPV1) promotes production of inflammatory cytokines and mucus hypersecretion in the pathology of this disease. Our previous research revealed that Qingfei oral liquid (QF) inhibited airway inflammation and mucus hypersecretion in RSV-infected asthmatic mice models and that this may be associated with the TRPV1-regulation of NF-κB and Mucin 5AC (MUC5AC) expression, but the exact mechanism is unknown. In the present study, LC-MS was used for analyzing the chemicals in QF, ovalbumin (OVA)-induced asthmatic mice inhaled RSV three consecutive times to create an RSV-infected asthmatic model. We found treatment from QF alleviated airway hyperresponsiveness (AHR) and reduced congestion, edema, and infiltration of inflammatory cells into pulmonary tissues. Additionally, QF was found to decrease expression of NF-κB and its downstream inflammatory cytokines IL-1β, IL-4, IL-5, and IL-13, as well as a decrease in MUC5AC and pro-inflammatory cytokines in PKC via a reduction in Protein Kinase C-dependent signaling. These findings suggest that QF can alleviate AHR and mucus hypersecretion caused by RSV infection in asthmatic mice, and its mechanism may be associated with the regulation of the TRPV1 signaling pathway.

Respiratory syncytial virus prevents the subsequent development of ovalbumin-induced allergic responses by inhibiting ILC2 via the IL-33/ST2 pathway

AIM

How respiratory syncytial virus (RSV) influences the development of ovalbumin (OVA)-induced asthma remains elusive. As potent T helper (Th)2 cytokine producers, group 2 innate lymphoid cells (ILC2s) are known to serve important functions in the pathogenesis of allergic inflammation. However, how RSV infection affects innate immunity, especially with regard to the function of ILC2s in OVA-induced allergic airway inflammation, is largely unknown.

MATERIALS & METHODS

RSV was used to infect adult BALB/c mice intranasally prior to sensitization and subsequent challenge with OVA. ILC2 frequencies and Th2 cytokine production by ILC2s were assessed by flow cytometry. Cytokine levels were detected both by real-time PCR and ELISA.

RESULTS

Previous infection with RSV attenuated airway inflammation and decreased Th2 cytokine production in mice sensitized and challenged with OVA. Furthermore, previous infection with RSV inhibited the influx of ILC2s into the lung, and constrained their Th2 cytokine production. Adoptive transfer of ILC2s increased asthma-associated airway inflammation in mice previously infected with RSV. These results indicate that previous infection with RSV prevents OVA-induced asthma development via inhibition of ILC2s. Previous infection with RSV attenuated IL-33 production in lung tissue and reduced relative ST2L expression in lung ILC2s, meaning that previous infection with RSV may alter ILC2 function via the IL-33/ST2 signaling pathway.

CONCLUSION

These results demonstrate that previous infection with RSV attenuates OVA-induced airway inflammation by inhibiting the recruitment and Th2 cytokine production of ILC2s via the IL-33/ST2 pathway.

Characterization of Cotton Rat (Sigmodon hispidus) Eosinophils, Including Their Response to Respiratory Syncytial Virus Infection

Eosinophils have been postulated to play a protective role against infection with respiratory syncytial virus (RSV), increase the severity of allergic asthma during respiratory viral infection, and drive vaccine-enhanced disease. To address these questions in the cotton rat model of RSV infection, we characterized cotton rat eosinophils by electron microscopy as well as by bronchoalveolar lavage and histology of lung sections. Using these methods, we demonstrated that eosinophils comprise approximately half of all cells in the bronchoalveolar lavage fluids from cotton rats. The function of these cells was comparable to that of eosinophils of other species. Ex vivo, eosinophils stimulated with calcium ionophores secreted eosinophil peroxidase. In vivo, treatment with house dust mite antigen increased eosinophil numbers in lung. Infection with Staphylococcus aureus lead to a marked increase in neutrophils without an increase in eosinophils, and eosinophil numbers were not influenced by infection with influenza virus or measles virus. Similarly, infection with RSV did not result in an increase in eosinophils. Lastly, RSV infection did not increase eosinophil recruitment into the lung after challenge with house dust mite antigen, but it did increase eosinophil recruitment into the lungs of cotton rats previously immunized with formalin-inactivated RSV vaccine, thus contributing to vaccine-enhanced disease.

The Use of Mouse Asthma Models to Successfully Discover and Develop Novel Drugs

The past 20 years have seen a proliferation of scientific data on the pathophysiology of asthma. Most of these data were generated in mice using tool reagents, gene-deficient or transgenic animals. In contrast, studies on disease pathogenesis in patients are scarce. Previously, a good novel antiasthma target for drug development was one that abrogated asthma in mice when it was knocked out, neutralized or induced asthma when it was overexpressed. This type of approach led to many drug candidates that worked in mice but unfortunately failed in patients, thereby demonstrating that the results of experiments in mice are not always predictive of clinical efficacy. Currently, there is active debate about the use of mouse models in drug discovery. In this review, we summarize the obstacles and challenges faced when using experimental mouse models of asthma in drug discovery. We propose that the initial selection of a novel drug target begins with defining the unmet medical need and specific patient population, followed by a thorough evaluation of available human data, and, only then, well-planned and executed mouse asthma experiments. Using this approach, we argue that mouse models lend support for the target when the models are tailored for the specific asthma patient population, and that targeted, reliable, and predictive mouse models can indeed improve and accelerate the drug discovery process.

The effects of melamine with or without cyanuric acid on immune function in ovalbumin-sensitized mice

Melamine is commonly used in the chemical industry, and it has been found to exist on food processing equipment and utensils. Previous investigations suggested that melamine alone or its combination with cyanuric acid appears to be toxic to immune system in animals. The objective of this study is to investigate the potential effects of melamine with or without cyanuric acid on immune function in ovalbumin- sensitized mice. Our data indicated that melamine-related administration caused a significant decreasing in the content of IL-4 in mice in comparison to negative control group. Significant increasing in the content of histamine (HIS) was recorded in almost all treated groups. The co-administration of melamine and cyanuric acid with high dose (each at 16mgkg^-12d^-1) led to a significantly lower contents of IL-10, IL-16 and monocyte chemoattractant protein-1 (MCP-1) in mouse serum in comparison to negative control group. Moreover, our data indicated that the number of Th1 and Th2 cells, and the ratio of Th1/Th2 spleen lymphocytes were significantly changed after treatment. Also, our results demonstrated that the profiles of both CD40 and CD40L were significantly altered in spleen lymphocytes after treatment.

Adipose tissue B2 cells promote insulin resistance through leukotriene LTB4/LTB4R1 signaling

Tissue inflammation is a key component of obesity-induced insulin resistance, with a variety of immune cell types accumulating in adipose tissue. Here, we have demonstrated increased numbers of B2 lymphocytes in obese adipose tissue and have shown that high-fat diet-induced (HFD-induced) insulin resistance is mitigated in B cell-deficient (Bnull) mice. Adoptive transfer of adipose tissue B2 cells (ATB2) from wild-type HFD donor mice into HFD Bnull recipients completely restored the effect of HFD to induce insulin resistance. Recruitment and activation of ATB2 cells was mediated by signaling through the chemokine leukotriene B4 (LTB4) and its receptor LTB4R1. Furthermore, the adverse effects of ATB2 cells on glucose homeostasis were partially dependent upon T cells and macrophages. These results demonstrate the importance of ATB2 cells in obesity-induced insulin resistance and suggest that inhibition of the LTB4/LTB4R1 axis might be a useful approach for developing insulin-sensitizing therapeutics.

Mouse Models of Acute Respiratory Distress Syndrome: A Review of Analytical Approaches, Pathologic Features, and Common Measurements

Acute respiratory distress syndrome (ARDS) is a severe pulmonary reaction requiring hospitalization, which is incited by many causes, including bacterial and viral pneumonia as well as near drowning, aspiration of gastric contents, pancreatitis, intravenous drug use, and abdominal trauma. In humans, ARDS is very well defined by a list of clinical parameters. However, until recently no consensus was available regarding the criteria of ARDS that should be evident in an experimental animal model. This lack was rectified by a 2011 workshop report by the American Thoracic Society, which defined the main features proposed to delineate the presence of ARDS in laboratory animals. These should include histological changes in parenchymal tissue, altered integrity of the alveolar capillary barrier, inflammation, and abnormal pulmonary function. Murine ARDS models typically are defined by such features as pulmonary edema and leukocyte infiltration in cytological preparations of bronchoalveolar lavage fluid and/or lung sections. Common pathophysiological indicators of ARDS in mice include impaired pulmonary gas exchange and histological evidence of inflammatory infiltrates into the lung. Thus, morphological endpoints remain a vital component of data sets assembled from animal ARDS models.

RSV vaccine-enhanced disease is orchestrated by the combined actions of distinct CD4 T cell subsets

There is no currently licensed vaccine for respiratory syncytial virus (RSV) despite being the leading cause of lower respiratory tract infections in children. Children previously immunized with a formalin-inactivated RSV (FI-RSV) vaccine exhibited enhanced respiratory disease following natural RSV infection. Subsequent studies in animal models have implicated roles for CD4 T cells, eosinophils and non-neutralizing antibodies in mediating enhanced respiratory disease. However, the underlying immunological mechanisms responsible for the enhanced respiratory disease and other disease manifestations associated with FI-RSV vaccine-enhanced disease remain unclear. We demonstrate for the first time that while CD4 T cells mediate all aspects of vaccine-enhanced disease, distinct CD4 T cell subsets orchestrate discrete and specific disease parameters. A Th2-biased immune response, but not eosinophils specifically, was required for airway hyperreactivity and mucus hypersecretion. In contrast, the Th1-associated cytokine TNF-α was necessary to mediate airway obstruction and weight loss. Our data demonstrate that individual disease manifestations associated with FI-RSV vaccine-enhanced disease are mediated by distinct subsets of CD4 T cells.

RSV is a significant healthcare burden and is the leading cause of bronchiolitis and pneumonia during childhood. The failure of the 1960's FI-RSV vaccine trial to not only elicit protection against RSV infection, but also provoke enhanced morbidity and mortality in vaccinees has significantly hampered development of new RSV vaccines for fear of disease potentiation. Therefore we sought to determine the specific immunological mechanisms that mediate FI-RSV VED to provide a framework to evaluate factors associated with disease exacerbation. Work presented herein demonstrate for the first time that individual disease manifestations associated with FI-RSV-immunization are mediated by distinct CD4 T cell subsets and not by eosinophils. Our results stress the need to evaluate multiple disease parameters for future RSV vaccine candidates. Failure to thoroughly assess the immune response and disease manifestations associated with new candidate vaccines may lead to undesired results in vaccine trials and further hinder future vaccine development.

Defective innate immune responses to respiratory syncytial virus infection in ovalbumin-sensitized mice

BACKGROUND/PURPOSE

Respiratory viral infections have frequently been reported to closely correlate with asthma exacerbations. Distinctive expression of cytokine/chemokine and anomalous responses of innate immunity induced by respiratory viral infections were suggested to play a key role. This study further evaluates the effects of airway sensitization on innate immunity in response to different viruses.

METHODS

Murine sensitization was established using an ovalbumin (OVA) sensitization model. Mice were subsequently infected with either respiratory syncytial virus (RSV) or human metapneumovirus (hMPV). Type I interferon (IFN), cytokines, and chemokines were measured in bronchoalveolar lavage (BAL) fluid. Pulmonary tissue samples were collected for the analysis of viral titers and type I IFN signal transcriptors.

RESULTS

Distinct expressions of cytokine/chemokine responses after viral infection were also found in mice with OVA sensitization. A significant increase of virus replication was found in lungs of RSV-infected sensitized mice. The increment of RSV titer was associated with the decreased levels of type I IFN. Although Toll-like receptor 3 (TLR3) expression was significantly increased in the lungs, the key signal transcriptor, IFN regulatory factor 3, was significantly suppressed in the RSV-infected sensitized mice.

CONCLUSION

A defective antiviral innate response was observed in the murine respiratory allergy model. Suppressed expression of IFN signal transcriptor contributes to decreased production of type I IFN. The defective innate immune response might result in acute viral exacerbations of allergic airway diseases.

Small interfering RNAs targeted to interleukin-4 and respiratory syncytial virus reduce airway inflammation in a mouse model of virus-induced asthma exacerbation

Asthma exacerbations are caused primarily by viral infections. Antisense and small interfering RNA (siRNA) technologies have gained attention as potential antiasthma and antiviral approaches. In this study we analyzed whether gene silencing of interleukin (IL)-4 expression and respiratory syncytial virus (RSV) replication by RNA interference is able to suppress allergen- and virus-induced responses in a mouse model of virus-induced asthma exacerbation. Knockdown efficacy of IL-4 siRNA molecules was analyzed in the human HEK293T cell line by cotransfection of six different siRNAs with a plasmid carrying mouse IL-4. The most potent siRNA was then used in a mouse model of RSV-induced asthma exacerbation. BALB/c mice were sensitized intraperitoneally with ovalbumin (OVA) and then infected 12 days later intranasally with RSV Long strain (1×10(6) TCID50/mouse), followed 1 day later by intranasal challenge with OVA for 3 days. Mice were pretreated intranasally three times with either siRNA to IL-4 or GFP control, 2 days before, and on the first two OVA challenge days. siRNAs to RSV or rhinovirus control were inoculated intranasally once, 3 hr before RSV infection. Combined anti-IL-4 and anti-RSV siRNAs were able to significantly reduce total cell counts and eosinophilia in bronchoalveolar lavage fluid, development of airway hyperresponsiveness, and airway inflammation and to downregulate IL-4 mRNA expression and RSV viral RNA, but to upregulate IFN-γ levels in lung tissues. We conclude that anti-helper T cells type 2 and antiviral siRNAs may constitute a new therapeutic approach for treatment of virus induced asthma exacerbations.

Respiratory syncytial virus (RSV) infection in elderly mice results in altered antiviral gene expression and enhanced pathology

Elderly persons are more susceptible to RSV-induced pneumonia than young people, but the molecular mechanism underlying this susceptibility is not well understood. In this study, we used an aged mouse model of RSV-induced pneumonia to examine how aging alters the lung pathology, modulates antiviral gene expressions, and the production of inflammatory cytokines in response to RSV infection. Young (2-3 months) and aged (19-21 months) mice were intranasally infected with mucogenic or non-mucogenic RSV strains, lung histology was examined, and gene expression was analyzed. Upon infection with mucogenic strains of RSV, leukocyte infiltration in the airways was elevated and prolonged in aged mice compared to young mice. Minitab factorial analysis identified several antiviral genes that are influenced by age, infection, and a combination of both factors. The expression of five antiviral genes, including pro-inflammatory cytokines IL-1β and osteopontin (OPN), was altered by both age and infection, while age was associated with the expression of 15 antiviral genes. Both kinetics and magnitude of antiviral gene expression were diminished as a result of older age. In addition to delays in cytokine signaling and pattern recognition receptor induction, we found TLR7/8 signaling to be impaired in alveolar macrophages in aged mice. In vivo, induction of IL-1β and OPN were delayed but prolonged in aged mice upon RSV infection compared to young. In conclusion, this study demonstrates inherent differences in response to RSV infection in young vs. aged mice, accompanied by delayed antiviral gene induction and cytokine signaling.

Elevated macrophage inflammatory protein 1α and interleukin-17 production in an experimental asthma model infected with respiratory syncytial virus

BACKGROUND

Respiratory syncytial virus (RSV) infection is associated with both the development and exacerbation of bronchial asthma. We examined eosinophil infiltration and the cytokine profiles of both airway and peripheral blood in antigen-sensitized mice infected with RSV to investigate the pathogenesis of exacerbations of asthma due to RSV infection.

METHODS

Ovalbumin (OVA)-sensitized mice were challenged by OVA inhalation 3 times and then infected with RSV [10(5) TCID50 (50% of tissue culture infectious dose)/25 g body weight] or mock infection immediately after the last challenge. Animals from each group, namely, the control (PBS instead of OVA inhalation plus mock infection), RSV (PBS plus RSV), OVA (OVA plus mock) and OVA/RSV (OVA plus RSV) were analyzed. Analysis included evaluation of airway responsiveness to methacholine, pathological findings in the airway by hematoxylin and eosin (HE) and Luna staining, bronchoalveolar fluid (BALF) and peripheral leukocytes counts, and concentrations of multiple cytokines/chemokines in both BALF and serum.

RESULTS

Airway responsiveness was significantly enhanced in the OVA and OVA/RSV groups compared with the control group. Levels of tissue and BALF eosinophils were higher in the OVA and OVA/RSV groups than in the RSV or control group. Significantly higher levels of macrophage inflammatory protein (MIP)-1α in BALF were observed in the OVA/RSV group compared with the 3 other groups. Production of serum IL-17 was also significantly elevated in the OVA/RSV group compared with the control or OVA group.

CONCLUSIONS

These findings suggest that MIP-1α and IL-17 may play important roles in acute exacerbation of asthma induced by RSV in an animal model.