Acute Respiratory Syncytial Virus Infection Research Articles

Psychometric evaluation of the respiratory syncytial virus infection, intensity and impact questionnaire (RSV-iiiQ) in adults

BackgroundDespite a number of respiratory syncytial virus (RSV) vaccine candidates being tested in clinical trials, disease-specific, self-reported instruments assessing symptom severity of RSV infection from the perspective of adult patients are still needed. The RSV Infection, Intensity and Impact Questionnaire (RSV-iiiQ) was adapted from the Influenza Intensity and Impact Questionnaire (FluiiQ™). This study evaluated some measurement properties of the RSV-iiiQ.MethodsData were collected in a web-based survey over two consecutive days. Participants completed the RSV-iiiQ, the Patient Global Impression of Severity, Sheehan Disability Scale, Patient Global Impression of Change, EQ-5D-5L, and a demographic questionnaire. Test-retest reliability, internal consistency, construct validity, and responsiveness of the RSV-iiiQ scales were assessed.Results111 adults with RSV were enrolled and self-reported a variety of symptoms across the range of disease severity via a web-based platform. The RSV-iiiQ scales demonstrated satisfactory test-retest reliability, construct validity, and discriminating ability. One-factor confirmatory factor analyses confirmed that each of the four scales was sufficiently unidimensional, and internal consistencies indicated that the computation of RSV-iiiQ scale scores was plausible. Correlation-based analyses provided support for the construct validity of the RSV-iiiQ scores, and known groups analyses supported discriminating ability. Estimates of responsiveness of the scale scores were also satisfactory.ConclusionsRSV infection is highly symptomatic and causes significant disease burden, and self-report instruments assessing symptom severity and impact are important for evaluation of new treatments. This study describes the preliminary psychometric properties of the RSV-iiiQ and indicates this tool may be useful for the assessment of the severity of symptoms and impact of acute RSV infection in adults. The findings also indicated two items, Runny nose and Ear pain, may be unnecessary and should be revisited using item response theory analysis with a larger sample size.

Cost of illness due to respiratory syncytial virus acute lower respiratory tract infection among infants hospitalized in Argentina

BackgroundInformation is scarce regarding the economic burden of respiratory syncytial virus (RSV) disease in low-resource settings. This study aimed to estimate the cost per episode of hospital admissions due to RSV severe disease in Argentina.MethodsThis is a prospective cohort study that collected information regarding 256 infants under 12 months of age with acute lower respiratory tract infection (ALRTI) due to RSV in two public hospitals of Buenos Aires between 2014 and 2016. Information on healthcare resource use was collected from the patient’s report and its associated costs were estimated based on the financial database and account records of the hospitals. We estimated the total cost per hospitalization due to RSV using the health system perspective. The costs were estimated in US dollars as of December 2022 (1 US dollar = 170 Argentine pesos).ResultsThe mean costs per RSV hospitalization in infants was US$587.79 (95% confidence interval [CI] $535.24 – $640.33). The mean costs associated with pediatric intensive care unit (PICU) admission more than doubled from those at regular pediatric wards ($1,556.81 [95% CI $512.21 – $2,601.40] versus $556.53 [95% CI $514.59 – $598.48]).ConclusionsThis study shows the direct economic impact of acute severe RSV infection on the public health system in Argentina. The estimates obtained from this study could be used to inform cost-effectiveness analyses of new preventive RSV interventions being developed.

TLR7 promotes chronic airway disease in RSV-infected mice.

Respiratory syncytial virus (RSV) commonly infects the upper respiratory tract (URT) of humans, manifesting with mild cold or flu-like symptoms. However, in infants and the elderly, severe disease of the lower respiratory tract (LRT) often occurs and can develop into chronic airway disease. A better understanding of how an acute RSV infection transitions to a LRT chronic inflammatory disease is critically important to improve patient care and long-term health outcomes. To model acute and chronic phases of the disease, we infected wild-type C57BL/6 and toll-like receptor 7 knockout (TLR7 KO) mice with RSV and temporally assessed nasal, airway and lung inflammation for up to 42 days post-infection. We show that TLR7 reduced viral titers in the URT during acute infection but promoted pronounced pathogenic and chronic airway inflammation and hyperreactivity in the LRT. This study defines a hitherto unappreciated molecular mechanism of lower respiratory pathogenesis to RSV, highlighting the potential of TLR7 modulation to constrain RSV pathology to the URT.

Features of respiratory syncytial virus infection in children in the post-COVID 19 era

Respiratory syncytial virus (RSV) infection in children is a major public health problem, especially in the 0-1 year age group where clinical forms of the disease can evolve severely with life-threatening complications. In the period 2020 – 2022, as a result of epidemiological measures specific to the COVI-19 pandemic (protective mask, online teaching activity, social distancing) we have witnessed a considerable decrease in the number of cases of RSV infection in children. With the lifting of prophylactic measures and the onset of the cold season, we have seen an increase in the number of admissions with a diagnosis of respiratory virus in pediatric wards. In this article, we aim to analyze the clinical, evolutionary and epidemiological features of respiratory syncytial virus infection in children in the 2022 - 2023 season. We conducted a retrospective clinical study of RSV infection cases admitted to the Pediatric Infectious Diseases Clinical Departments of the National Institute of Infectious Diseases “Prof. Dr. Matei Bals” in the period October 2022 - March 2023. During this period, we registered 195 cases of RSV infection in children, which represents 6.47% of the total number of hospitalized virologic illnesses in children (195/3012). All pediatric RSV infection cases admitted to our wards have progressed favorably; we have not recorded any deaths. From an epidemiological point of view, the peak incidence of RSV infection in children occurred in December (98 cases). The most frequent clinical form of the disease was the medium form, but severe forms represented 31.8%. Among the complications, the most common were respiratory (acute respiratory failure, pneumonia/bronchopneumonia), hematological (intrainfectious and deficiency anemia, leukopenia, thrombocytopenia), digestive (diarrheal disease, hepatic cytolysis syndrome) and acute dehydration syndrome associated with hydro electrolytic and acid-base disturbances. Severe complications were more frequent than in previous seasons, being associated with a risk of an unfavorable outcome: acute respiratory failure and neurological complications (convulsions, encephalitis). We also observed that acute RSV infection in the 2022 - 2023 season is characterized by the association of co-infections (viral, bacterial and fungal) more frequent than in previous years (22.5%). The most frequent co-infections were bacterial (superinfections - pneumonia/bronchopneumonia) probably due to the immunosuppression of the hosts as a result of repeated recent episodes of viral infections. Of note, RSV infection associated with other coinfections evolved more severely, with prolonged hospitalization and more complications. In conclusion we can say that RSV infection in the 2022 - 2023 season evolved more severely in children compared to previous seasons because in the last 3 years during the COVID-19 pandemic there were very few cases of respiratory viroids, thus the population was not naturally immunized, especially the age group 0 - 4 years. In addition, the abandonment of specific protective measures for respiratory diseases has “exploded” the number of respiratory illnesses in the pediatric population, especially in children.

Respiratory syncytial virus with ongoing COVID-19: is it an emerging threat?

Respiratory syncytial virus with ongoing COVID-19: is it an emerging threat?

Neuromedin U Induces Pulmonary ILC2 Activation via the NMUR1 Pathway during Acute Respiratory Syncytial Virus Infection.

Activated group 2 innate lymphoid cells (ILC2s) play a crucial role in respiratory syncytial virus (RSV)-induced airway inflammation and allergy-like symptoms because of their ability to secrete large quantities of type 2 cytokines. Cytokines such as IL-33, IL-25, and thymic stromal lymphopoietin are activators of ILC2s. Besides, a regulatory effect of neurotransmitters on ILC2 activation has been reported recently. However, whether and how RSV infection induces neurotransmitter production in the lungs and regulates pulmonary ILC2 activation remains unclear. In this study, using a murine model established by intranasal infection with RSV, we found that acute RSV infection induced the production of a neurotransmitter, neuromedin U (NMU), in the lungs of RSV-infected mice and upregulated the expression of NMUR1 (neuromedin U receptor 1) on ILC2s. Moreover, invivo administration of NMU exacerbated RSV-induced airway inflammation by promoting the proliferation and activation of pulmonary ILC2s via the NMUR1 pathway, which involved PI3K, mitogen-activated protein kinase kinase, and NFAT signaling proteins. Furthermore, pulmonary neurons responded to the stimulation of RSV infection and secreted NMU in a Toll-like receptor 4- and Toll-like receptor 7-dependent manner. Collectively, our data suggest that NMU is a powerful neuropeptide to activate ILC2s, highlighting the critical regulatory effects of neurotransmitters on antiviral, inflammatory, and tissue homeostasis at the mucosal barrier during a viral respiratory infection.

Nasal-spraying Bacillus spores as an effective symptomatic treatment for children with acute respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is a leading cause of Acute Respiratory Tract Infections (ARTIs) in young children. However, there is currently no vaccine or treatment available for children. Here, we demonstrated that nasal-spraying probiotics containing 5 billion of Bacillus spores (LiveSpo Navax) is an effective symptomatic treatment in a 6-day randomized controlled clinical study for RSV-infected children (n = 40–46/group). Navax treatment resulted in 1-day faster recovery-time and 10–50% better efficacy in relieving ARTI symptoms. At day 3, RSV load and level of pro-inflammatory cytokines in nasopharyngeal samples was reduced by 630 folds and 2.7–12.7 folds respectively. This showed 53-fold and 1.8–3.6-fold more effective than those in the control-standard of care-group. In summary, nasal-spraying Bacillus spores can rapidly and effectively relieve symptoms of RSV-induced ARTIs while exhibit strong impacts in reducing viral load and inflammation. Our nasal-spraying probiotics may provide a basis for simple-to-use, low-cost, and effective treatment against viral infection in general.

Hydrophilic But Not Hydrophobic Surfactant Protein Genetic Variants Are Associated With Severe Acute Respiratory Syncytial Virus Infection in Children.

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection-related hospitalization in the first year of life. Surfactant dysfunction is central to pathophysiologic mechanisms of various pulmonary diseases including RSV. We hypothesized that RSV severity is associated with single nucleotide polymorphisms (SNPs) of surfactant proteins (SPs). We prospectively enrolled 405 RSV-positive children and divided them into moderate and severe RSV disease. DNA was extracted and genotyped for sixteen specific SP gene SNPs. SP-A1 and A2 haplotypes were assigned. The association of RSV severity with SP gene SNPs was investigated by multivariate logistic regression. A likelihood ratio test was used to test the goodness of fit between two models (one with clinical and demographic data alone and another that included genetic variants). p ≤ 0.05 denotes statistical significance. A molecular dynamics simulation was done to determine the impact of the SFTPA2 rs1965708 on the SP-A behavior under various conditions. Infants with severe disease were more likely to be younger, of lower weight, and exposed to household pets and smoking, as well as having co-infection on admission. A decreased risk of severe RSV was associated with the rs17886395_C of the SFTPA2 and rs2243639_A of the SFTPD, whereas an increased risk was associated with the rs1059047_C of the SFTPA1. RSV severity was not associated with SNPs of SFTPB and SFTPC. An increased risk of severe RSV was associated with the 1A0 genotype of SFTPA2 in its homozygous or heterozygous form with 1A3. A molecular dynamic simulation study of SP-A variants that differ in amino acid 223, an important amino acid change (Q223K) between 1A0 and 1A3, showed no major impact on the behavior of these two variants except for higher thermodynamic stability of the K223 variant. The likelihood ratio test showed that the model with multi-allelic variants along with clinical and demographic data was a better fit to predict RSV severity. In summary, RSV severity was associated with hydrophilic (but not with hydrophobic) SPs gene variants. Collectively, our findings show that SP gene variants may play a key role in RSV infection and have a potential role in prognostication.

Altered cytokine and chemokine profiles in the lungs of vitamin A deficient mice with respiratory syncytial virus infection

Abstract Human respiratory syncytial virus (RSV) is a leading cause of severe acute lower respiratory tract disease worldwide in infants and young children. Epidemiologically, low levels of vitamin A (VA) are known to increase susceptibility to severe respiratory infection. However, little is known regarding how VA impacts lung immune function, specifically during RSV infection. Here, we investigated the impact of VA deficiency (VAD) on innate immunity in the lungs following RSV infection using a BALB/c mouse model. Groups of VA sufficient (VAS) and VAD, 6 to 8-week-old mice were intranasally infected with RSV, and lung tissues were collected at 3, 4, and 8 days post-infection for evaluation of vitamin A status, flow cytometry for innate immune populations, and Luminex bead-based multiplex assays for inflammatory cytokines. Acute RSV infection negatively impacted lung VA status in vitamin-replete mice. Although no differences in morbidity were observed between treatment groups, VAD mice had more neutrophils recruited to the lungs. VAD also altered the phenotype of γδ T cell populations in the lung, resulting in significantly increased frequencies of CD27+ γδ T cells, and fewer CD27 negative γδ T cells compared to VAS mice. Moreover, cytokine and chemokine production was altered in the lung of VAD animals after RSV infection, with reduced production of IL-1β, IL-6, IL-17, and KC (CXCL1). These results suggest that VAD alters the inflammatory environment in the lung, which may contribute to disease susceptibility. Future experiments will focus on further changes to the innate and adaptive immune systems in the lungs during VAD after RSV infection. Supported by Roy J. Carver Charitable Trust Grant #20-5306

Meta-Analysis of Whole Blood Transcriptome Datasets Characterizes the Immune Response of Respiratory Syncytial Virus Infection in Children.

Respiratory syncytial virus (RSV) is the most common and critical viral pathogen causing acute lower respiratory tract infection in infants and young children and has a huge disease burden worldwide. At present, there are many studies on RSV transcriptomics exploring the mechanism of disease, but different studies show different gene expression patterns and results due to different sample collection platforms and data analysis strategies. A meta-analysis was performed on eight whole blood transcriptome datasets containing 436 children with acute RSV infection and 241 healthy children. A total of 319 differentially expressed genes (DEGs) (P value <0.0001) were identified in a meta-analysis using a random effect model. Functional enrichment analysis showed that several pathways related to immunity were significantly altered, including the “chemokine signaling pathway”, “natural killer cell mediated cytotoxicity” and “cytokine–cytokine receptor interaction”. Immune cell type analysis showed that the proportion of neutrophils in most RSV-infected children was higher than that in healthy children. These immune characteristics may help to provide new insights into RSV infection in children.

Respiratory Syncytial Virus–Associated Neurologic Complications in Children: A Systematic Review and Aggregated Case Series

To describe the features and frequency of respiratory syncytial virus (RSV)-associated severe acute neurologic disease in children. We performed a systematic review of the literature to identify reports of severe acute neurologic complications associated with acute RSV infection in children aged <15years (PROSPERO Registration CRD42019125722). Main outcomes included neurologic, clinical, and demographic features of cases and the frequency of disease. We aggregated available case data from the published literature and from the Australian Acute Childhood Encephalitis (ACE) study. We identified 87 unique studies from 26 countries describing a spectrum of RSV-associated severe acute neurologic syndromes including proven encephalitis, acute encephalopathy, complex seizures, hyponatremic seizures, and immune-mediated disorders. The frequency of RSV infection in acute childhood encephalitis/encephalopathy was 1.2%-6.5%. We aggregated data from 155 individual cases with RSV-associated severe acute neurologic complications; median age was 11.0months (IQR 2.0-21.5), most were previously healthy (71/104, 68%). Seizure was the most frequently reported neurologic feature (127/150, 85%). RSV was detected in the central nervous system of 12 cases. Most children recovered (81/122, 66%); however, some reports described partial recovery (33/122, 27%) and death (8/122, 7%). RSV-associated neurologic complications have been widely reported, but there is substantial heterogeneity in the design and quality of existing studies. The findings from our study have implications for the investigation, management, and prevention of RSV-associated neurologic complications. Further, this systematic review can inform the design of future studies aiming to quantify the burden of childhood RSV-associated neurologic disease.

Tissue-Resident Memory T Cells in the Lungs Protect against Acute Respiratory Syncytial Virus Infection.

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection in young children. The T cell response plays a critical role in facilitating clearance of an acute RSV infection, and memory T cell responses are vital for protection against secondary RSV exposures. Tissue-resident memory (TRM) T cells have been identified as a subset of memory T cells that reside in nonlymphoid tissues and are critical for providing long-term immunity. There is currently limited information regarding the establishment and longevity of TRM T cell responses elicited following an acute RSV infection as well as their role in protection against repeated RSV infections. In this study, we examined the magnitude, phenotype, and protective capacity of TRM CD4 and CD8 T cells in the lungs of BALB/c mice following an acute RSV infection. TRM CD4 and CD8 T cells were established within the lungs and waned by 149 d following RSV infection. To determine the protective capacity of TRMs, FTY720 administration was used to prevent trafficking of peripheral memory T cells into the lungs prior to challenge of RSV-immune mice, with a recombinant influenza virus expressing either an RSV-derived CD4 or CD8 T cell epitope. We observed enhanced viral clearance in RSV-immune mice, suggesting that TRM CD8 T cells can contribute to protection against a secondary RSV infection. Given the protective capacity of TRMs, future RSV vaccine candidates should focus on the generation of these cell populations within the lung to induce effective immunity against RSV infection.

Juvenile, but Not Adult, Mice Display Increased Myeloid Recruitment and Extracellular Matrix Remodeling during Respiratory Syncytial Virus Infection.

Early life respiratory syncytial virus (RSV) infection has been linked to the onset of asthma. Despite this association, our knowledge of the progression of the initial viral infection is limited, and no safe or effective vaccine currently exists. Bronchioalveolar lavage, whole-lung cellular isolation, and gene expression analysis were performed on 3-wk- (juvenile) and 8-wk-old (adult) RSV-infected C57BL/6 mice to investigate age-related differences in immunologic responses; juvenile mice displayed a sustained myeloid infiltrate (including monocytes and neutrophils) with increased RNA expression of Ccl2, Ccl3, and Ccl4, when compared with adult mice, at 72 h postinfection. Juvenile mice demonstrated αSma expression (indicative of myofibroblast activity), increased hyaluronan deposition in the lung parenchyma (attributed to asthma progression), and a lack of CD64 upregulation on the surface of monocytes (which, in conjunction with serum amyloid P, is responsible for clearing residual hyaluronan and cellular debris). RSV infection of human airway epithelial cell, human lung fibroblast, and U937 monocyte cocultures (at air-liquid interface) displayed similar CCL expression and suggested matrix metalloproteinase-7 and MMP9 as possible extracellular matrix modifiers. These mouse data, in conjunction with our findings in human monocytes, suggest that the sustained influx of myeloid cells in the lungs of juvenile mice during acute RSV infection could potentiate extracellular matrix remodeling, facilitating conditions that support the development of asthma.

Respiratory Syncytial Virus Infection Promotes Necroptosis and HMGB1 Release by Airway Epithelial Cells.

Rationale: Respiratory syncytial virus (RSV) bronchiolitis causes significant infant mortality. Bronchiolitis is characterized by airway epithelial cell (AEC) death; however, the mode of death remains unknown.Objectives: To determine whether necroptosis contributes to RSV bronchiolitis pathogenesis via HMGB1 (high mobility group box 1) release.Methods: Nasopharyngeal samples were collected from children presenting to the hospital with acute respiratory infection. Primary human AECs and neonatal mice were inoculated with RSV and murine Pneumovirus, respectively. Necroptosis was determined via viability assays and immunohistochemistry for RIPK1 (receptor-interacting protein kinase-1), MLKL (mixed lineage kinase domain-like pseudokinase) protein, and caspase-3. Necroptosis was blocked using pharmacological inhibitors and RIPK1 kinase-dead knockin mice.Measurements and Main Results: HMGB1 levels were elevated in nasopharyngeal samples of children with acute RSV infection. RSV-induced epithelial cell death was associated with increased phosphorylated RIPK1 and phosphorylated MLKL but not active caspase-3 expression. Inhibition of RIPK1 or MLKL attenuated RSV-induced HMGB1 translocation and release, and lowered viral load. MLKL inhibition increased active caspase-3 expression in a caspase-8/9-dependent manner. In susceptible mice, Pneumovirus infection upregulated RIPK1 and MLKL expression in the airway epithelium at 8 to 10 days after infection, coinciding with AEC sloughing, HMGB1 release, and neutrophilic inflammation. Genetic or pharmacological inhibition of RIPK1 or MLKL attenuated these pathologies, lowered viral load, and prevented type 2 inflammation and airway remodeling. Necroptosis inhibition in early life ameliorated asthma progression induced by viral or allergen challenge in later life.Conclusions: Pneumovirus infection induces AEC necroptosis. Inhibition of necroptosis may be a viable strategy to limit the severity of viral bronchiolitis and break its nexus with asthma.

Mast cell hyperplasia underlies respiratory syncytial virus infection-induced predisposition for asthma

Abstract Asthma is a chronic inflammatory airway disease, which affects approximately 300 million people worldwide. A growing number of epidemiological cohort studies supports an association between pediatric allergic asthma susceptibility and prior respiratory syncytial virus (RSV) infection. In this study, we aimed to experimentally test whether RSV infection promotes the subsequent development of allergic asthma. Either wild type mice or mast cell-deficient congenic KitW-sh mice were infected with RSV or sterile vehicle. After infection clearance, the mice were sensitized to Ragweed (A. artemisiifolia) pollen allergens and subsequently challenged intranasally with Ragweed to induce asthma. Disease severity was measured as airway hyperreactivity to inhaled β-methylcholine using a mechanical ventilator. RSV caused an acute and productive infection in mice, which was associated with a rapid cytokine response in the lungs. In our murine allergic asthma model, the wild type animals which had previously cleared the RSV infection developed more severe disease, when compared to mice that have not experienced RSV. We found that there was a sustained increase in the numbers of airway mast cells following the resolution of an acute RSV infection. The induction of allergic asthma disease in our animal model was dependent on mast cells, as it was strongly attenuated in mast cell-deficient KitW-sh mice. Furthermore, there was no potentiation of allergic asthma severity by a previous RSV infection in Sash mice, indicating this process is mast cell-dependent. Thus, RSV induces airway mast cell hyperplasia, which predisposes mice for more severe allergic responses.

Respiratory Syncytial Virus: Spectrum of Clinical Manifestations and Complications in Children.

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection in infants and young children. Despite its substantial disease burden, no effective vaccine is available. Clinical manifestations of RSV encompass the spectrum of acute upper and lower respiratory tract infection. Hallmarks of the virus are its propensity to progress to lower respiratory disease and to cause disproportionate disease severity at extremes of ages. Acute RSV infection may be complicated by secondary bacterial infections and respiratory failure requiring mechanical ventilation and prolonged hospitalization. In the developed world, most RSV infections are self-limited; however, globally, RSV is a significant cause of mortality in children younger than age 5 years. Severe RSV infection in infancy has also been associated with the development of childhood asthma. Thus, the extensive disease burden of RSV and its attributable mortality portend the urgency of vaccine development targeted toward populations disproportionately affected by severe disease. [Pediatr Ann. 2019;48(9):e349-e353.].

New therapies for acute RSV infections: where are we?

Respiratory syncytial virus (RSV) infection is one of the main causes of infant hospitalization and mortality. The single-stranded RNA virus codes for 11 proteins of which the F protein, a surface epitope responsible for RSV fusion, is the most targeted for developing antiviral medicines and vaccines. The peak of symptoms occurs around day 4 to 6 of illness and the airway obstruction is merely caused by the host immune inflammatory response. Risk factors for severe bronchiolitis are prematurity, comorbidity, and/or being immunocompromised. At present, there are no curative therapies available for RSV infections and treatment is supportive only. Development of new antiviral medicines is however promising. The aim of this review is to give a summary of the most important new antiviral therapies in clinical development for RSV infection and to explain their mode of action. We therefore performed a literature search on this topic.Conclusion: There are currently at least eight antivirals being investigated in clinical trials. They all use different approaches to either focus on preventing viral fusion with host cells or inhibiting virus replication. Some target RSV surface epitopes like the F protein to halt fusion, others aim for RNA chain termination, while small interfering RNAs downregulate viral protein production. What is known: • RSV bronchiolitis is a very important pediatric disease as it is one of the main causes of infant hospitalization and mortality. By the age of 2years, 95% of all the infants worldwide will have been infected. • The only recommended therapy is supportive since there are no existing curative therapies yet. What this study adds: • This review gives an overview of the current progress in the research field of RSV antivirals with background information on their mode of action.

Nasopharyngeal Lactobacillus is associated with a reduced risk of childhood wheezing illnesses following acute respiratory syncytial virus infection in infancy

Early life acute respiratory infection (ARI) with respiratory syncytial virus (RSV) has been strongly associated with the development of childhood wheezing illnesses, but the pathways underlying this association are poorly understood. To examine the role of the nasopharyngeal microbiome in the development of childhood wheezing illnesses following RSV ARI in infancy. We conducted a nested cohort study of 118 previously healthy, term infants with confirmed RSV ARI by RT-PCR. We used next-generation sequencing of the V4 region of the 16S ribosomal RNA gene to characterize the nasopharyngeal microbiome during RSV ARI. Our main outcome of interest was 2-year subsequent wheeze. Of the 118 infants, 113 (95.8%) had 2-year outcome data. Of these, 46 (40.7%) had parental report of subsequent wheeze. There was no association between the overall taxonomic composition, diversity, and richness of the nasopharyngeal microbiome during RSV ARI with the development of subsequent wheeze. However, the nasopharyngeal detection and abundance of Lactobacillus was consistently higher in infants who did not develop this outcome. Lactobacillus also ranked first among the different genera in a model distinguishing infants with and without subsequent wheeze. The nasopharyngeal detection and increased abundance of Lactobacillus during RSV ARI in infancy are associated with a reduced risk of childhood wheezing illnesses at age 2years.

RSV infection in a macrophage-cell line activates the non-canonical NF-κB pathway and induces pro-inflammatory cytokine expression

Respiratory syncytial virus (RSV) is a highly prevalent infectious agent that causes severe respiratory tract illnesses in infants and children worldwide. Children who have suffered severe RSV infections during infancy are prone to develop recurrent episodes of wheezing and asthma that may be associated with viral persistence. RSV infections in humans and animal models are characterized by extensive inflammatory responses. Epithelial cell lines acutely infected by RSV have shown activation of the NF-κB signaling through two independent pathways: the canonical pathway, mediated by RelA and p50 subunits, and the non-canonical pathway, mediated by the subunits RelB and p52. Herein, we investigated the state of activation of the canonical and non-canonical NF-κB signaling pathways in macrophages either acutely or persistently infected by RSV and examined the expression of pro-inflammatory mediators. Activation of NF-κB subunits was analyzed through Western blot assays using acutely RSV-infected epithelial cells as a control. The expression levels of two pro-inflammatory cytokines and a chemokine were determined by quantitative RT-PCR and through immunobead assays. The results showed that p52 was abundant during acute and persistent RSV infection, indicating that macrophages predominantly activate the non-canonical pathway. We also observed activation of IL-1β, TNF-α and CCL5/RANTES transcription, though at higher levels in persistently infected macrophages than in acutely infected macrophages. In contrast, the protein levels of these cytokines/chemokine did not correlate with their mRNA transcription, as quantitation displayed higher levels during acute infection than in persistent infection, suggesting post-transcriptional regulation by RSV persistence.

CD4+ T cells mediate respiratory syncytial virus (RSV)-induced airway inflammation through secreting Th2 cytokines

Objective To investigate the role of CD4+ T cells in airway inflammation induced by respiratory syncytial virus (RSV) infection. Methods Animal models of acute RSV infection were established. Lung tissues were stained with hematoxylin and eosin (HE) to observe histopathological changes. Total number of CD4+ T cells and the number of CD4+ T cells secreting Th1/Th2 cytokines (IFN-γ, IL-4, IL-5 and IL-13) in spleen were detected by flow cytometry. Adoptive transfer of CD4+ T cells was performed to identify the role of CD4+ T cells in RSV-induced airway inflammation. Results RSV infection increased the total number of splenic CD4+ T cells, particularly Th2-type CD4+ T cells. The absolute numbers of IL-4/IL-5/IL-13-secreting CD4+ T cells were increased significantly after RSV infection. Furthermore, adoptive transfer of CD4+ T cells into BALB/c mice not only promoted the infiltration of mononuclear cells in lung, but also enhanced the secretion of Th2 cytokines during RSV infection. Conclusion CD4+ T cells are involved in RSV-induced airway inflammation through secreting Th2 cytokines. Key words: Respiratory syncytial virus; CD4+ T cell; Airway inflammation