Spread Of Respiratory Syncytial Virus Research Articles

The genomic evolutionary dynamics and global circulation patterns of respiratory syncytial virus

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infection in young children and the second leading cause of infant death worldwide. While global circulation has been extensively studied for respiratory viruses such as seasonal influenza, and more recently also in great detail for SARS-CoV-2, a lack of global multi-annual sampling of complete RSV genomes limits our understanding of RSV molecular epidemiology. Here, we capitalise on the genomic surveillance by the INFORM-RSV study and apply phylodynamic approaches to uncover how selection and neutral epidemiological processes shape RSV diversity. Using complete viral genome sequences, we show similar patterns of site-specific diversifying selection among RSVA and RSVB and recover the imprint of non-neutral epidemic processes on their genealogies. Using a phylogeographic approach, we provide evidence for air travel governing the global patterns of RSVA and RSVB spread, which results in a considerable degree of phylogenetic mixing across countries. Our findings highlight the potential of systematic global RSV genomic surveillance for transforming our understanding of global RSV spread.

AN INTRODUCTION TO NIRSEVIMAB

Respiratory syncytial virus (RSV) is a dominating respiratory infection worldwide. It is responsible for infecting millions of children worldwide each winter through highly contagious droplets and secretions. Over 2.1 million of these children require some form of medical attention during illness. Due to this high disease burden, the development of new agents to prevent or reduce the spread of RSV has been a top priority. Recently, nirsevimab, a new monoclonal antibody was introduced for the 2023-2024 winter season that holds promise for limiting the spread, morbidity, and mortality associated with RSV.

Fractional Optimal Control Model and Bifurcation Analysis of Human Syncytial Respiratory Virus Transmission Dynamics

In this paper, the Caputo-based fractional derivative optimal control model is looked at to learn more about how the human respiratory syncytial virus (RSV) spreads. Model solution properties such as boundedness and non-negativity are checked and found to be true. The fundamental reproduction number is calculated by using the next-generation matrix’s spectral radius. The fractional optimal control model includes the control functions of vaccination and treatment to illustrate the impact of these interventions on the dynamics of virus transmission. In addition, the order of the derivative in the fractional optimal control problem indicates that encouraging vaccination and treatment early on can slow the spread of RSV. The overall analysis and the simulated behavior of the fractional optimum control model are in good agreement, and this is due in large part to the use of the MATLAB platform.

Safety signal identification for COVID-19 bivalent booster vaccination using tree-based scan statistics in the Vaccine Safety Datalink

BackgroundTraditional active vaccine safety monitoring involves pre-specifying health outcomes and biologically plausible outcome-specific time windows of concern, limiting the adverse events that can be evaluated. In this study, we used tree-based scan statistics to look broadly for >60,000 possible adverse events after bivalent COVID-19 vaccination. MethodsVaccine Safety Datalink enrollees aged ≥5 years receiving Moderna or Pfizer-BioNTech bivalent COVID-19 vaccine through November 2022 were followed for 56 days post-vaccination. Incident diagnoses in inpatient or emergency department settings were analyzed for clustering within the hierarchical ICD-10-CM diagnosis code “tree” and temporally within post-vaccination follow-up. The conditional self-controlled tree-temporal scan statistic was used, conditioning on total number of cases of each diagnosis and total number of cases of any diagnosis occurring during the scanning risk window across the entire tree. P = 0.01 was the pre-specified cut-off for statistical significance. ResultsAnalysis included 352,509 doses of Moderna and 979,189 doses of Pfizer-BioNTech bivalent vaccines. After Moderna vaccination, no statistically significant clusters were found. After Pfizer-BioNTech, there were clusters of unspecified adverse events (Days 1–3, p = 0.0001–0.0007), influenza (Days 35–56, p = 0.0001), cough (Days 44–55, p = 0.0002), and COVID-19 (Days 52–56, p = 0.0004). ConclusionsFor Pfizer-BioNTech only, we detected clusters of: (1) unspecified adverse effects, as have been observed in other vaccine studies using this method, and (2) respiratory disease toward the end of follow-up. The respiratory clusters were likely due to overlap of follow-up with the spread of respiratory syncytial virus, influenza, and COVID-19, i.e., confounding by seasonality. The untargeted nature of the method and its inherent adjustment for the many diagnoses and risk intervals evaluated are unique advantages. Limitations include susceptibility to time-varying confounding, lower statistical power for assessing risks of specific outcomes than in traditional studies targeting fewer outcomes, and the possibility of missing adverse events not strongly clustered in time or within the “tree.”

A Comparative Analysis of the Occurrence of Lower Respiratory Tract Infections Caused by Respiratory Syncytial Virus among Newborns in the Years before and during Covid-19 Pandemic at a Tertiary Referral Hospital in Slovenia

Objective − In this study we aimed to compare the occurrence of lower respiratory tract infections caused by respiratory syncytial virus in the neonatal population in the years before and during the COVID-19 pandemic.Methods − Cases of newborns, hospitalized due to viral lower respiratory tract infection from 2015 to 2020, were analyzed retrospectively, and compared according to cause (respiratory syncytial virus, non-respiratory syncytial virus) and treatment requirements before (2015−2019) and after (2020) the outbreak of the COVID-19 pandemic.Results − The number of newborns with lower respiratory tract infections and newborns contracting respiratory syncytial virus declined significantly during the COVID-19 pandemic. Respiratory syncytial virus was the major causative agent before the pandemic, while after the lockdown no more cases were reported. There were no significant differences between the two periods regarding the number of patients requiring treatment with oxygen (P=0.705), non-invasive (P=0.842) and invasive ventilation (P=0.574), or in terms of median hospital stay (P=0.670) and the duration of non-invasive (P=0.350) and invasive ventilation (P=0.556), while the difference in the duration of treatment with oxygen was statistically significant (P=0.048).Conclusions − A decline was found in the number of newborns hospitalized due to respiratory syncytial virus and non-respiratory syncytial virus lower respiratory tract infections during the COVID-19. Our results strongly suggest that social distancing and other lockdown strategies were effective in slowing down the spread of respiratory syncytial virus and decreasing the need for hospitalization among newborns, but may be not equally effective for all agents causing lower respiratory tract infections.

Role of Differences in Respiratory Syncytial Virus F and G Glycoproteins on Susceptibility to Inactivation by Antimicrobial Peptides LL-37 and Human Beta-Defensins.

Antimicrobial peptides are proteins that have been found to be an important factor in the natural immune response to a variety of pathogens. Respiratory syncytial virus (RSV) is a respiratory pathogen with the capability to cause serious upper and lower respiratory infections in infants and children and is a major viral cause of infant mortality. There is currently no functional vaccine for the virus, as recent efforts have been hindered by the virus's low immunogenicity, its ability to effectively mutate, and underlying instabilities of potential vaccines. Previous studies have shown that antimicrobial peptides may affect viral replication and spread of RSV. Our study evaluates the susceptibility of chimeric strains of RSV that express different fusion (F) and attachment (G) proteins to susceptibilities to inactivation by LL-37 and human beta-defensins (hBDs) hBD-1, hBD-3, and hBD-4. We show that LL-37 and hBD-3 result in dose-dependent, strain-independent inactivation of RSV, whereas treatment with either hBD-1 or hBD-4 appears more variable between strains. This suggests a potential role of the viral structural proteins in mitigating the inhibitory effects of the peptides. This study provides the first evidence of the sensitivity of RSV to several hBDs and indicates a role of LL-37 and beta-defensins in both limiting establishment of natural RSV infections and in the therapeutic treatment of severe RSV disease.

Summarizing Study Characteristics and Diagnostic Performance of Commercially Available Tests for Respiratory Syncytial Virus: A Scoping Literature Review in the COVID-19 Era.

BackgroundNonpharmaceutical interventions to prevent the spread of coronavirus disease 2019 also decreased the spread of respiratory syncytial virus (RSV) and influenza. Viral diagnostic testing in patients with respiratory tract infections (RTI) is a necessary tool for patient management; therefore, sensitive and specific tests are required. This scoping literature review aimed to summarize the study characteristics of commercially available sample-to-answer RSV tests.ContentPubMed and Embase were queried for studies reporting on the diagnostic performance of tests for RSV in patients with RTI (published January 2005–January 2021). Information on study design, patient and setting characteristics, and published diagnostic performance of RSV tests were extracted from 77 studies that met predefined inclusion criteria. A literature gap was identified for studies of RSV tests conducted in adult-only populations (5.3% of total subrecords) and in outpatient (7.5%) or household (0.8%) settings. Overall, RSV tests with analytical time >30 min had higher published sensitivity (62.5%–100%) vs RSV tests with analytical time ≤30 min (25.7%–100%); this sensitivity range could be partially attributed to the different modalities (antigen vs molecular) used. Molecular-based rapid RSV tests had higher published sensitivity (66.7%–100%) and specificity (94.3%–100%) than antigen-based RSV tests (sensitivity: 25.7%–100%; specificity:80.3%–100%).SummaryThis scoping review reveals a paucity of literature on studies of RSV tests in specific populations and settings, highlighting the need for further assessments. Considering the implications of these results in the current pandemic landscape, the authors preliminarily suggest adopting molecular-based RSV tests for first-line use in these settings.

Study Pre-protocol for "BronchStart - The Impact of the COVID-19 Pandemic on the Timing, Age and Severity of Respiratory Syncytial Virus (RSV) Emergency Presentations; a Multi-Centre Prospective Observational Cohort Study".

Background: Bronchiolitis (most frequently caused by respiratory syncytial virus; RSV) is a common winter disease predominantly affecting children under one year of age. It is a common reason for presentations to an emergency department (ED) and frequently results in hospital admission, contributing to paediatric units approaching or exceeding capacity each winter. During the SARS-CoV-2 pandemic, the circulation of RSV was dramatically reduced in the United Kingdom and Ireland. Evidence from the Southern Hemisphere and other European countries suggests that as social distancing restrictions for SARS-CoV-2 are relaxed, RSV infection returns, causing delayed or even summer epidemics, with different age distributions. Study question: The ability to track, anticipate and respond to a surge in RSV cases is critical for planning acute care delivery. There is an urgent need to understand the onset of RSV spread at the earliest opportunity. This will influence service planning, to inform clinicians whether the population at risk is a wider age range than normal, and whether there are changes in disease severity. This information is also needed to inform decision on the timing of passive immunisation of children at higher risk of hospitalisation, intensive care admission or death with RSV infection, which is a public health priority. Methods and likely impact: This multi-centre prospective observational cohort study will use a well-established research network (Paediatric Emergency Research in the UK and Ireland, PERUKI) to report in real time cases of RSV infection in children aged under two years, through the collection of essential, but non-identifying patient information. Forty-five centres will gather initial data on age, index of multiple deprivation quintile, clinical features on presentation, and co-morbidities. Each case will be followed up at seven days to identify treatment, viral diagnosis and outcome. Information be released on a weekly basis and used to support clinical decision making.

1333. A National Outbreak of Respiratory Syncytial Virus Associated with Emergence of a Genetically Distinct ON1 variant

BackgroundA national outbreak of respiratory syncytial virus (RSV) has been observed in the community since Fall 2020 in Taiwan.MethodsWe reviewed a national laboratory-based surveillance network established over 20 years by Taiwan Centers for Disease Control (TCDC) for respiratory viral positivity rate and viral pathogen in outpatient department and hospitalized patients. A retrospective study of children younger than 5 years old hospitalized with RSV infections at Chang Gung Memorial Hospital (CGMH) including Lin Kou and Kaohsiung branch between 2018 and 2020 was conducted. Samples positive for RSV A were sequenced. Patients’ clinical data was obtained from medical files and stratified by genotype and year.Results2020 showed a 4-fold surge in RSV cases in Taiwan, in which surpassed both 2011 (the appearance of ON1 strain in Taiwan) and 2013 (ON1 strain predominates in Taiwan)(Figure1,Table1). Phylogenetic analysis of G protein sequences showed that most strains in 2020 were clustered apart from 2018, 2019 seasons and other ON1 reference strains between 2011 and 2016, indicating a novel ON1 variant had been circulating in the community(Figure2). The novel ON1 variants carried six amino acid changes, of which T113I,V131D, H258Q,H266L,Y304H located in the mucin domains and N178G in central conserved domain. These changes emerged gradually in 2019 and showed a high consistency in 2020. The unique amino acid substitution E257K in the second mucin domain was noticed in 2020 exclusively. Besides, 10 substitutes in F protein were appeared between 2018 and 2020, of which R213S and N276S were in antigenic sites. Furthermore, substitutes T12I and H514N in F protein were first emerged since 2020. On multivariate analysis, age (OR 0.97; 95% CI 0.94-0.99; p 0.02) and ON1 variant in 2020 (OR 2.52; 95% CI 1.13-5.63; p 0.025) were independently associated with oxygen saturation < 94% during hospitalization (Table 2). Figure 2. The phylogenetic tree of G protein sequences including ON1 strains in our study from 2018 to 2020 and reference strains from 2011 to 2016 The phylogenetic tree showed that most strains of the 2020 season clustered apart from those of the previous seasons, which indicated there was a novel ON1 variant circulating in the community associated with 2020 RSV epidemic. Variables with p<0.1 in the univariate analysis were included in the multivariate analysis.ConclusionAn unprecedented RSV epidemic within the last 10 years caused by a novel ON1 variant has occurred in 2020 (Figure 1), suggesting the sets of mutations may confer fitness advantage. Further studies on viral replication, infectivity and virulence is needed to understand the evolution and spread of RSV. Disclosures All Authors: No reported disclosures

Risk of Transmission and Viral Shedding From the Time of Infection for Respiratory Syncytial Virus in Households.

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection worldwide, but reports of temporal changes in the risk of transmission among close contacts has been scarce. This study aimed to examine an association between the viral load trajectory and transmission risk to develop a better control strategy for the disease spread. We conducted a household-based prospective cohort study in Biliran Province, the Philippines, and enrolled 451 participants to observe the development of acute respiratory infection. Including the cases found at the health-care facility, we analyzed the data of viral loads with symptom records obtained from 172 followed participants who had household member positive for RSV with a rapid test during an RSV outbreak in 2018–2019. We developed a model estimating a temporal change in the viral shedding from the infection and evaluated transmission dynamics. We found that most transmission events occurred within approximately 7 days of the household exposure, including potential presymptomatic transmissions. The inferred risk of infection among those younger than 5 years was 3.5 times higher than that of those older than 5 years. This finding suggested that the initial week after the household exposure is particularly important for preventing RSV spread.

Study Pre-protocol for “BronchStart - The Impact of the COVID-19 Pandemic on the Timing, Age and Severity of Respiratory Syncytial Virus (RSV) Emergency Presentations; a Multi-Centre Prospective Observational Cohort Study”

Background: Bronchiolitis (most frequently caused by respiratory syncytial virus; RSV) is a common winter disease predominantly affecting children under one year of age. It is a common reason for presentations to an emergency department (ED) and frequently results in hospital admission, contributing to paediatric units approaching or exceeding capacity each winter. During the SARS-CoV-2 pandemic, the circulation of RSV was dramatically reduced in the United Kingdom and Ireland. Evidence from the Southern Hemisphere and other European countries suggests that as social distancing restrictions for SARS-CoV-2 are relaxed, RSV infection returns, causing delayed or even summer epidemics, with different age distributions. Study question: The ability to track, anticipate and respond to a surge in RSV cases is critical for planning acute care delivery. There is an urgent need to understand the onset of RSV spread at the earliest opportunity. This will influence service planning, to inform clinicians whether the population at risk is a wider age range than normal, and whether there are changes in disease severity. This information is also needed to inform decision on the timing of passive immunisation of children at higher risk of hospitalisation, intensive care admission or death with RSV infection, which is a public health priority. Methods and likely impact: This multi-centre prospective observational cohort study will use a well-established research network (Paediatric Emergency Research in the UK and Ireland, PERUKI) to report in real time cases of RSV infection in children aged under two years, through the collection of essential, but non-identifying patient information. Forty-five centres will gather initial data on age, index of multiple deprivation quintile, clinical features on presentation, and co-morbidities. Each case will be followed up at seven days to identify treatment, viral diagnosis and outcome. Information be released on a weekly basis and used to support clinical decision making.

Comparative analysis of spatial-temporal patterns of human metapneumovirus and respiratory syncytial virus in Africa using genetic data, 2011\u20132014

BackgroundHuman metapneumovirus (HMPV) and respiratory syncytial virus (RSV) are leading causes of viral severe acute respiratory illnesses in childhood. Both the two viruses belong to the Pneumoviridae family and show overlapping clinical, epidemiological and transmission features. However, it is unknown whether these two viruses have similar geographic spread patterns which may inform designing and evaluating their epidemic control measures.MethodsWe conducted comparative phylogenetic and phylogeographic analyses to explore the spatial-temporal patterns of HMPV and RSV across Africa using 232 HMPV and 842 RSV attachment (G) glycoprotein gene sequences obtained from 5 countries (The Gambia, Zambia, Mali, South Africa, and Kenya) between August 2011 and January 2014.ResultsPhylogeographic analyses found frequently similar patterns of spread of RSV and HMPV. Viral sequences commonly clustered by region, i.e., West Africa (Mali, Gambia), East Africa (Kenya) and Southern Africa (Zambia, South Africa), and similar genotype dominance patterns were observed between neighbouring countries. Both HMPV and RSV country epidemics were characterized by co-circulation of multiple genotypes. Sequences from different African sub-regions (East, West and Southern Africa) fell into separate clusters interspersed with sequences from other countries globally.ConclusionThe spatial clustering patterns of viral sequences and genotype dominance patterns observed in our analysis suggests strong regional links and predominant local transmission. The geographical clustering further suggests independent introduction of HMPV and RSV variants in Africa from the global pool, and local regional diversification.

Study Pre-protocol for "BronchStart - The Impact of the COVID-19 Pandemic on the Timing, Age and Severity of Respiratory Syncytial Virus (RSV) Emergency Presentations; a Multi-Centre Prospective Observational Cohort Study".

Background: Bronchiolitis (most frequently caused by respiratory syncytial virus; RSV) is a common winter disease predominantly affecting children under one year of age. It is a common reason for presentations to an emergency department (ED) and frequently results in hospital admission, contributing to paediatric units approaching or exceeding capacity each winter. During the SARS-CoV-2 pandemic, the circulation of RSV was dramatically reduced in the United Kingdom and Ireland. Evidence from the Southern Hemisphere and other European countries suggests that as social distancing restrictions for SARS-CoV-2 are relaxed, RSV infection returns, causing delayed or even summer epidemics, with different age distributions. Study question: The ability to track, anticipate and respond to a surge in RSV cases is critical for planning acute care delivery. There is an urgent need to understand the onset of RSV spread at the earliest opportunity. This will influence service planning, to inform clinicians whether the population at risk is a wider age range than normal, and whether there are changes in disease severity. This information is also needed to inform decision on the timing of passive immunisation of children at higher risk of hospitalisation, intensive care admission or death with RSV infection, which is a public health priority. Methods and likely impact: This multi-centre prospective observational cohort study will use a well-established research network (Paediatric Emergency Research in the UK and Ireland, PERUKI) to report in real time cases of RSV infection in children aged under two years, through the collection of essential, but non-identifying patient information. Forty-five centres will gather initial data on age, index of multiple deprivation quintile, clinical features on presentation, and co-morbidities. Each case will be followed up at seven days to identify treatment, viral diagnosis and outcome. Information be released on a weekly basis and used to support clinical decision making.

House dust mite proteins reduce the spread of Respiratory Syncytial Virus in the BEAS-2B bronchial epithelial cell line.

Abstract House dust mites (HDM) are a predominant causative agent of airway hypersensitivity and asthma. The HDM group 1 allergens include Der p 1, a cysteine protease that contributes to sensitization and symptom exacerbation. Respiratory syncytial virus (RSV) infection of infants and small children can lead to severe pneumonitis. RSV activation of TLRs and RIG-I-like receptors induces proinflammatory cytokines and chemokines, which exacerbate disease, and type I/III interferons (IFNs) which induce expression of antiviral IFN stimulated genes (ISGs). Since RSV in children is coincident with HDM exposure, we used BEAS-2B human bronchial epithelial cells to explore the effects of HDM on RSV infection BEAS2B cells were exposed to HDM extract or Der p 1 alone before, during, or after RSV infection. Surprisingly, HDM extract or Der p 1 decreased RSV infection in a dose and time-dependent manner. In a viral entry assay, HDM extract reduced the area of foci, rather than their number, suggesting that one or more HDM proteins attenuate cell to cell spread. Preliminary experiments point to a role for the cysteine protease activity of Der p 1. We also measured expression of a panel of representative proinflammatory mediators and ISGs. Compared to RSV alone, Der p 1 increased expression of some proinflammatory mediators, while HDM extract decreased expression of a panel of ISGs. In the absence of RSV, HDM extract increased proinflammatory mediators while Der p 1 did not affect gene expression. These results were unchanged following heat treatment at 65°C for 1 h. Elucidating mechanisms by which HDM proteins enhance protection against RSV may reveal novel antiviral mediators that locally control RSV infection.

New Look at RSV Infection: Tissue Clearing and 3D Imaging of the Entire Mouse Lung at Cellular Resolution.

Background: Respiratory Syncytial Virus (RSV) is the major cause of severe acute respiratory tract illness in young children worldwide and a main pathogen for the elderly and immune-compromised people. In the absence of vaccines or effective treatments, a better characterization of the pathogenesis of RSV infection is required. To date, the pathophysiology of the disease and its diagnosis has mostly relied on chest X-ray and genome detection in nasopharyngeal swabs. The development of new imaging approaches is instrumental to further the description of RSV spread, virus–host interactions and related acute respiratory disease, at the level of the entire lung. Methods: By combining tissue clearing, 3D microscopy and image processing, we developed a novel visualization tool of RSV infection in undissected mouse lungs. Results: Whole tissue analysis allowed the identification of infected cell subtypes, based on both morphological traits and position within the cellular network. Furthermore, 3D imaging was also valuable to detect the cytoplasmic viral factories, also called inclusion bodies, a hallmark of RSV infection. Conclusions: Whole lung clearing and 3D deep imaging represents an unprecedented visualization method of infected lungs to allow insight into RSV pathophysiology and improve the 2D histology analyses.

Nosocomial Infections in Patients Hospitalized with Respiratory Syncytial Virus: A Practice Review.

Viral testing is not always recommended in children with bronchiolitis due to doubts concerning its prognostic use. In this retrospective study, we investigated how the RSV testing would influence the frequency of nosocomial infections (NI). The files of 305 children, hospitalized due to the respiratory syncytial virus (RSV) infection in the period 2010-2014, were reviewed in the study. We found ten cases of NI. The RSV preventive measures did not vary in the consecutive years investigated, but the number of viral tests substantially varied. In 2010, 2012, and 2014, when ca. 2 tests per RSV(+) patient were performed, the risk of NI per patient was 1.3%, while in 2011 and 2013, when the RSV testing was less frequent, the accumulated risk per patient was 5.2%. There was a strong adverse relationship between the number of tests performed and the number of NI (rho=-0.975). The children with NI, when compared to those without NI, required a longer hospital stay, generating higher hospital costs regarding treatment, productivity loss, and indirect costs. The expenditure for RSV testing in the years of a low NI risk was higher than that in the high-risk years. Conversely, the expenditure related to NI management was lower in the years of a low NI risk. Each euro spent on RSV testing saved over 26 € from the NI management expenditure. We conclude that RSV testing is needed in the hospital setting to isolate the infected children and to prevent nosocomial RSV spread. This strategy is health advantageous and requires less resources than NI treatment.

Uncovering critical properties of the human respiratory syncytial virus by combining in vitro assays and in silico analyses.

Many aspects of the respiratory syncytial virus (RSV) are still poorly understood. Yet these knowledge gaps have had and could continue to have adverse, unintended consequences for the efficacy and safety of antivirals and vaccines developed against RSV. Mathematical modelling was used to test and evaluate hypotheses about the rate of loss of RSV infectivity and the mechanisms and kinetics of RSV infection spread in SIAT cells in vitro. While the rate of loss of RSV integrity, as measured via qRT-PCR, is well-described by an exponential decay, the latter mechanism failed to describe the rate at which RSV A Long loses infectivity over time in vitro based on the data presented herein. This is unusual given that other viruses (HIV, HCV, influenza) have been shown to lose their infectivity exponentially in vitro, and indeed an exponential rate of loss of infectivity is always assumed in mathematical modelling and experimental analyses. The infectivity profile of RSV in HEp-2 and SIAT cells remained consistent over the course of an RSV infection, over time and a large range of infectivity. However, SIAT cells were found to be ∼ 100× less sensitive to RSV infection than HEp-2 cells. In particular, we found that RSV spreads inefficiently in SIAT cells, in a manner we show is consistent with the establishment of infection resistance in uninfected cells. SIAT cells are a good in vitro model in which to study RSV in vivo dissemination, yielding similar infection timescales. However, the higher sensitivity of HEp-2 cells to RSV together with its RSV infectivity profile being similar to that of SIAT cells, makes HEp-2 cells more suitable for quantifying RSV infectivity over the course of in vitro RSV infections in SIAT cells. Our findings highlight the importance and urgency of resolving the mechanisms at play in the dissemination of RSV infections in vitro, and the processes by which this infectivity is lost.

High throughput screening to identify host-factors involved in RSV fusion

Respiratory syncytial virus (RSV) is the major cause of childhood respiratory disease; however, currently there is no licenced vaccine available and the only therapeutic, a monoclonal antibody against the viral Fusion (F) protein, is expensive and applied sparingly. RSV particles enter cells by membrane fusion, orchestrated by F – a type I integral membrane protein. This process was recently shown to involve macropinocytosis of the particle. Separately, RSV can spread through induction of direct cell-cell fusion – again orchestrated by F. Little is currently known about the host-factors involved in regulating or inhibiting RSV F-mediated fusion. Here, using two different high-throughput screening approaches, we have identified host-factors involved in regulating RSV fusion. Using quantitative mass-spectrometry analysis of isolated cell membrane fractions from mock and RSV-infected cells we have identified membrane proteins which are differentially regulated during RSV infection. Furthermore, using lentiviral libraries expressing individual interferon stimulated genes (ISGs) from different mammalian species we have investigated ISG-mediated inhibition of RSV fusion. Our data provides important insights into host-factors involved in RSV spread, furthering our understanding of the fusion process and identifying potential targets for antiviral therapy.

Whole genome analysis of local Kenyan and global sequences unravels the epidemiological and molecular evolutionary dynamics of RSV genotype ON1 strains.

The respiratory syncytial virus (RSV) group A variant with the 72-nucleotide duplication in the G gene, genotype ON1, was first detected in Kilifi in 2012 and has almost completely replaced circulating genotype GA2 strains. This replacement suggests some fitness advantage of ON1 over the GA2 viruses in Kilifi, and might be accompanied by important genomic substitutions in ON1 viruses. Close observation of such a new virus genotype introduction over time provides an opportunity to better understand the transmission and evolutionary dynamics of the pathogen. We have generated and analysed 184 RSV-A whole-genome sequences (WGSs) from Kilifi (Kenya) collected between 2011 and 2016, the first ON1 genomes from Africa and the largest collection globally from a single location. Phylogenetic analysis indicates that RSV-A circulation in this coastal Kenya location is characterized by multiple introductions of viral lineages from diverse origins but with varied success in local transmission. We identified signature amino acid substitutions between ON1 and GA2 viruses’ surface proteins (G and F), polymerase (L), and matrix M2-1 proteins, some of which were positively selected, and thereby provide an enhanced picture of RSV-A diversity. Furthermore, five of the eleven RSV open reading frames (ORFs) (G, F, L, N, and P) formed distinct phylogenetic clusters for the two genotypes. This might suggest that coding regions outside of the most frequently studied G ORF also play a role in the adaptation of RSV to host populations, with the alternative possibility that some of the substitutions are neutral and provide no selective advantage. Our analysis provides insight into the epidemiological processes that define RSV spread, highlights the genetic substitutions that characterize emerging strains, and demonstrates the utility of large-scale WGS in molecular epidemiological studies.

PM10 exposure is associated with increased hospitalizations for respiratory syncytial virus bronchiolitis among infants in Lombardy, Italy

Respiratory syncytial virus (RSV) is the primary cause of acute lower respiratory infections in children, bronchiolitis in particular. Airborne particulate matter (PM) may influence the children's immune system and foster the spread of RSV infection.We aimed to verify whether PM10 exposure is associated with hospitalization due to RSV bronchiolitis.We selected hospital discharge records (HRD) with ICD-9-CM code 466.11 of infants < 1 year of age, occurring in the epidemic seasons of two years (2012–2013) in Lombardy, Italy. Cases were assigned daily PM10 and apparent temperature levels of the capital city of their residential province. Different exposure windows were considered: single days preceding hospitalization (lag 0 to 30), their average estimates (lag 0–1 to 0–30), and the four weeks preceding hospitalization (week 1 to 4). Negative binomial regression models adjusted for apparent temperature and season were applied to the daily counts of hospitalizations in each province. Results were expressed as incidence rate ratios (IRR) and 95% confidence intervals (95%CI) per 10 µg/m3 increase in PM10 concentration. Random effects meta-analyses of province-specific IRR were performed to obtain regional estimates.2814 HRD met our inclusion criteria; males represented about 55% of the cases. A 6% increased risk of hospitalization (95%CI: 1.03–1.10) was found at lag 0 and an almost overlapping 7% increase at lag 1. IRR ranged from 1.03 to 1.05 between lags 2 and 11. No increased risk was observed from lag 12. When considering averaged daily lags, risk estimates gradually increased in the two weeks preceding hospitalization from 1.08 (1.04–1.12) at lag 0–1 to 1.15 (1.08–1.23) between lags 0–11 and 0–13. Analyses on weekly lags showed a risk increase of 6% (1.01–1.12) during week 1 and of 7% (1.02–1.13) during week 2.Our study found a clear association between short- and medium-term PM10 exposures and increased risk of hospitalization due to RSV bronchiolitis among infants.