Role of Dendritic Cells in Pathology of Respiratory Syncytial Virus Infection in Neonates

Respiratory syncytial virus (RSV) is one of the leading causes of bronchiolitis in children. We have shown that neonatal mice respond to primary RSV infection with T helper type 2 (Th2) biased immune responses, which are enhanced following reinfection. Dendritic cells (DCs) including myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) play important roles in driving host responses to RSV infection. mDCs present antigens to help Th cells differentiate, and pDCs protect against viral infection through type I interferons (IFNs). Despite data demonstrating importance of mDCs and pDCs in protection against RSV, it has not been studied in an age appropriate model. Using a neonatal mouse model, we have shown that downregulation of IL-4 receptor alpha (IL-4Rα) on pulmonary myeloid dendritic cells (mDCs) via antisense oligonucleotides protected against RSV induced Th2 immunopathology. Thus, we examined the role of IL-4Rα on mDCs in RSV infection. Here, we discovered that IL-4Rα is developmentally regulated such that neonates have higher levels of IL-4Rα on mDCs. To determine if this elevated expression of IL-4Rα on mDCs was responsible for RSV pathogenesis in neonatal mice, we specifically deleted it from neonatal mDCs (or overexpressed it on adult mDCs) and studied RSV pathogenesis using our neonatal mouse model of RSV infection. Deletion of IL-4Rα from mDCs in our neonatal RSV infection model resulted in reduced disease as evidenced by reduction in Th2 biased inflammation and mucus cell hyperplasia and production. This was accompanied by improved lung function and enhanced mDC maturation status after infection. Furthermore, overexpression of IL-4Rα on adult mDCs was able to induce RSV disease similar to that observed in our neonatal model of RSV infection (i.e., Th2 biased responses including mucus hyperproduction). In vitro CD4+ T cell differentiation assays using mDCs from neonatal littermate control or IL-4Rα-/- mice were also performed to determine the specificity of the in vivo response. Low levels of type I IFNs have been reported in the nasal aspirates of RSV-infected infants. Since pDCs are responsible for a significant proportion of type I IFN production, we characterized the role of type I IFNs and pDC responses in the immunopathogenesis during RSV reinfection in our neonatal mouse model. We found that neonatal pDCs, while recruited to the airways, are recruited in low numbers in the response to neonatal RSV infection. Further, those pDCs that are recruited produce insufficient quantities of type I IFNs. Supplying IFN-α or adult pDCs locally to the neonatal mouse prior to RSV infection in neonates abrogated RSV induced immunopathophysiologies and this protection remained even after reinfection. Specifically, it reduced Th2 responses and lung inflammation and improved lung function. This improvement was due to a decrease in viral load and IL-4Rα expression on Th2 cells after IFN-α treatment. The severity of RSV pathogenesis in infants stems partly from immature immune responses. Our data demonstrate that developmentally regulated IL-4Rα expression on mDCs and inefficient type I IFN production from neonatal pDCs are critical for protection against RSV induced immunopathophysiologies. This study highlights critical differences between neonatal and adult DCs in RSV infection

Crawling with virus: Translational insights from a neonatal mouse model on the pathogenesis of respiratory syncytial virus in infants

© 2015, American Society for Microbiology. The infant immune response to respiratory syncytial virus (RSV) remains incompletely understood. Here we review the use of a neonatal mouse model of RSV infection to mimic severe infection in human infants. We describe numerous age-specific responses, organized by cell type, observed in RSV-infected neonatal mice and draw comparisons (when possible) to human infants

Building a better neonatal mouse model to understand infant respiratory syncytial virus disease

© 2015 You et al. Background: Respiratory syncytial virus (RSV) is the number one cause of lower respiratory tract infection in infants; and severe RSV infection in infants is associated with asthma development. Today, there are still no vaccines or specific antiviral therapies against RSV. The mechanisms of RSV pathogenesis in infants remain elusive. This is partly due to the fact that the largely-used mouse model is semi-permissive for RSV. The present study sought to determine if a better neonatal mouse model of RSV infection could be obtained using a chimeric virus in which the F protein of A2 strain was replaced with the F protein from the line 19 clinical isolate (rA2-19F). Methods: Five-day-old pups were infected with the standard laboratory strain A2 or rA2-19F and various immunological and pathophysiological parameters were measured at different time points post infection, including lung histology, bronchoalveolar lavage fluid (BALF) cellularity and cytokines, pulmonary T cell profile, and lung viral load. A cohort of infected neonates were allowed to mature to adulthood and reinfected. Pulmonary function, BALF cellularity and cytokines, and T cell profiles were measured at 6 days post reinfection. Results: The rA2-19F strain in neonatal mice caused substantial lung pathology including interstitial inflammation and airway mucus production, while A2 caused minimal inflammation and mucus production. Pulmonary inflammation was characterized by enhanced Th2 and reduced Th1 and effector CD8+ T cells compared to A2. As with primary infection, reinfection with rA2-19F induced similar but exaggerated Th2 and reduced Th1 and effector CD8+ T cell responses. These immune responses were associated with increased airway hyperreactivity, mucus hyperproduction and eosinophilia that was greater than that observed with A2 reinfection. Pulmonary viral load during primary infection was higher with rA2-19F than A2. Conclusions: Therefore, rA2-19F caused enhanced lung pathology and Th2 and reduced effector CD8+ T cell responses compared to A2 during initial infection in neonatal mice and these responses were exacerbated upon reinfection. The exact mechanism is unknown but appears to be associated with increased pulmonary viral load in rA2-19F vs. A2 infected neonatal lungs. The rA2-19F strain represents a better neonatal mouse model of RSV infection

Limited type I interferons and plasmacytoid dendritic cells during neonatal respiratory syncytial virus infection permit immunopathogenesis upon reinfection

Respiratory syncytial virus (RSV) infection is the number one cause of bronchiolitis in infants, yet no vaccines are available because of a lack of knowledge of the infant immune system. Using a neonatal mouse model, we previously revealed that mice initially infected with RSV as neonates develop Th2-biased immunopathophysiologies during reinfection, and we demonstrated a role for enhanced interleukin-4 receptor α (IL-4Rα) expression on T helper cells in these responses. Here we show that RSV infection in neonates induced limited type I interferon (IFN) and plasmacytoid dendritic cell (pDC) responses. IFN alpha (IFN-α) treatment or adoptive transfer of adult pDCs capable of inducing IFN-α prior to neonatal RSV infection decreased Th2-biased immunopathogenesis during reinfection. A reduced viral load and downregulation of IL-4Rα on Th2 cells were observed in IFN- α-treated neonatal mice, suggesting dual mechanisms of action. © 2014, American Society for Microbiology

Exposure to combustion generated environmentally persistent free radicals enhances severity of influenza virus infection

© 2014 Lee et al. Background: Exposures to elevated levels of particulate matter (PM) enhance severity of influenza virus infection in infants. The biological mechanism responsible for this phenomenon is unknown. The recent identification of environmentally persistent free radicals (EPFRs) associated with PM from a variety of combustion sources suggests its role in the enhancement of influenza disease severity. Methods: Neonatal mice (\u3c seven days of age) were exposed to DCB230 (combustion derived PM with a chemisorbed EPFR), DCB50 (non-EPFR PM sample), or air for 30 minutes/day for seven consecutive days. Four days post-exposure, neonates were infected with influenza intranasally at 1.25 TCID50/neonate. Neonates were assessed for morbidity (% weight gain, peak pulmonary viral load, and viral clearance) and percent survival. Lungs were isolated and assessed for oxidative stress (8-isoprostanes and glutathione levels), adaptive immune response to influenza, and regulatory T cells (Tregs). The role of the EPFR was also assessed by use of transgenic mice expressing human superoxide dismutase 2. Results: Neonates exposed to EPFRs had significantly enhanced morbidity and decreased survival following influenza infection. Increased oxidative stress was also observed in EPFR exposed neonates. This correlated with increased pulmonary Tregs and dampened protective T cell responses to influenza infection. Reduction of EPFR-induced oxidative stress attenuated these effects. Conclusions: Neonatal exposure to EPFR containing PM resulted in pulmonary oxidative stress and enhanced influenza disease severity. EPFR-induced oxidative stress resulted in increased presence of Tregs in the lungs and subsequent suppression of adaptive immune response to influenza

IL-4Rα on CD4\u3csup\u3e+\u3c/sup\u3e T cells plays a pathogenic role in respiratory syncytial virus reinfection in mice infected initially as neonates

RSV is the major cause of severe bronchiolitis in infants, and severe bronchiolitis as a result of RSV is associated with subsequent asthma development. A biased Th2 immune response is thought to be responsible for neonatal RSV pathogenesis; however, molecular mechanisms remain elusive. Our data demonstrate, for the first time, that IL-4Rα is up-regulated in vitro on human CD4+ T cells from cord blood following RSV stimulation and in vivo on mouse pulmonary CD4+ T cells upon reinfection of mice, initially infected as neonates. Th cell-specific deletion of Il4ra attenuated Th2 responses and abolished the immunopathophysiology upon reinfection, including airway hyper-reactivity, eosinophilia, and mucus hyperproduction in mice infected initially as neonates. These findings support a pathogenic role for IL-4Rα on Th cells following RSV reinfection of mice initially infected as neonates; more importantly, our data from human cells suggest that the same mechanism occurs in humans

Type I Interferon Potentiates IgA Immunity to Respiratory Syncytial Virus Infection During Infancy

© 2018, The Author(s). Respiratory syncytial virus (RSV) infection is the most frequent cause of hospitalization in infants and young children worldwide. Although mucosal RSV vaccines can reduce RSV disease burden, little is known about mucosal immune response capabilities in children. Neonatal or adult mice were infected with RSV; a subset of neonatal mice received interferon alpha (IFN-α) (intranasal) prior to RSV infection. B cells, B cell activating factor (BAFF) and IgA were measured by flow cytometry. RSV specific IgA was measured in nasal washes. Nasal associated lymphoid tissue (NALT) and lungs were stained for BAFF and IgA. Herein, we show in a mouse model of RSV infection that IFN-α plays a dual role as an antiviral and immune modulator and age-related differences in IgA production upon RSV infection can be overcome by IFN-α administration. IFN-α administration before RSV infection in neonatal mice increased RSV-specific IgA production in the nasal mucosa and induced expression of the B-cell activating factor BAFF in NALT. These findings are important, as mucosal antibodies at the infection site, and not serum antibodies, have been shown to protect human adults from experimental RSV infection

IL-4Rα on dendritic cells in neonates and Th2 immunopathology in respiratory syncytial virus infection

© Society for Leukocyte Biology. Respiratory syncytial virus (RSV) is one of the leading causes of bronchiolitis in children, and severe RSV infection early in life has been associated with asthma development. Using a neonatal mouse model, we have shown that down-regulation of IL-4 receptor α (IL-4Rα) with antisense oligonucleotides in the lung during neonatal infection protected from RSV immunopathophysiology. Significant down-regulation of IL-4Rα was observed on pulmonary CD11b+ myeloid dendritic cells (mDCs) suggesting a role for IL-4Rα on mDCs in the immunopathogenesis of neonatal RSV infection. Here, we demonstrated that neonatal CD11b+ mDCs expressed higher levels of IL-4Rα than their adult counterparts. Because CD11b+ mDCs mainly present antigens to CD4+ T cells, we hypothesized that increased expression of IL- 4Rα on neonatal CD11b+ mDCs was responsible for Th2 - biased RSV immunopathophysiology. Indeed, when IL-4Rα was selectively deleted from CD11b+ mDCs, the immunopathophysiology typically observed following RSV reinfection was ablated, including Th2 inflammation, airway-mucus hyperproduction, and pulmonary dysfunction. Further, overexpression of IL-4Rα on adult CD11b+ DCs and their adoptive transfer into adult mice was able to recapitulate the Th2-biased RSV immunopathology typically observed only in neonates infected with RSV. IL-4Rα levels on CD11c+ cells were inversely correlated with maturation status of CD11b+ mDCs upon RSV infection. Our data demonstrate that developmentally regulated IL-4Rα expression is critical for the maturity of pulmonary CD11b+ mDCs and the Th2-biased immunopathogenesis of neonatal RSV infection

Designing an electrode for EDM

This thesis is about designing an electrode for an Electric Discharge Machine. EDM is one of the most used methods for machining. It is a process of eroding material from the work piece with the help of series of sparks to bring out the desired shape. It is very useful for machining hard metals. There are various kinds of EMD, like, Wire EDM, electrode EDM. This thesis is based on Electrode EDM. Graphite is one of the most suitable materials for electrode in use

Tracking the Rapid Opening and Closing of Polar Coronal Holes through IBEX ENA Observations

Fast solar wind (SW) flows outward from polar coronal holes (PCHs). The latitudinal extent of the fast SW varies during different phases of the solar cycle. The fast SW in the inner heliosheath produces a flatter proton spectrum than the slow SW that can be observed through energetic neutral atoms (ENAs) by the Interstellar Boundary Explorer (IBEX). In this study, we investigate the evolution of PCHs as reflected in the high-time resolution ENA flux measurements from IBEX-Hi, where the PCHs are identified by ENA spectral indices <1.8. The ENA spectral index over the poles shows a periodic evolution over the solar cycle 24. The surface area with flatter ENA spectra (<1.8) around the ecliptic south pole increases slightly from 2009–2011 and then decreased gradually from 2012–2014. The PCH completely disappears in 2016 and then starts to appear again starting in 2017, gradually growing until 2019. This evolution shows a clear correlation with the change in the PCH area observed at the Sun once the delay in the ENA observation time is included. In addition, the higher-cadence ENA data at the highest latitudes show a rapid evolution of the ENA spectrum near the south pole in 2014 and 2017. The rapid evolution in 2014 is related to a rapid closing of PCHs in 2012 and that in 2017 is related to a rapid opening of PCHs in late 2014. These results also agree qualitatively with the evolution of the ENA spectral index from simulations using a simple time-dependent heliospheric flow model