Distribution of respiratory syncytial virus subtypes A and B among infants presenting to the emergency department with lower respiratory tract infection or apnea

RSV Risk Profile in Hospitalized Adults and Comparison with Influenza and COVID-19 Controls in Valladolid, Spain, 2010-2022

INTRODUCTION

We aimed to describe the risk profile of respiratory syncytial virus (RSV) infections among adults ≥ 60 years in Valladolid from January 2010 to August 2022, and to compare them with influenza and COVID-19 controls.

METHODS

This was a retrospective cohort study of all laboratory-confirmed RSV infections identified in centralized microbiology database during a 12-year period. We analyzed risk factors for RSV hospitalization and severity (length of stay, intensive care unit admission, in-hospital death or readmission < 30 days) and compared severity between RSV patients vs. influenza and COVID-19 controls using multivariable logistic regression models.

RESULTS

We included 706 RSV patients (635 inpatients and 71 outpatients), and 598 influenza and 60 COVID-19 hospitalized controls with comparable sociodemographic profile. Among RSV patients, 96 (15%) had a subtype identified: 56% A, 42% B, and 2% A + B. Eighty-one percent of RSV patients had cardiovascular conditions, 65% endocrine/metabolic, 46% chronic lung, and 43% immunocompromising conditions. Thirty-six percent were coinfected (vs. 21% influenza and 20% COVID-19; p =  < .0001 and 0.01). Ninety-two percent had signs of lower respiratory infection (vs. 85% influenza and 72% COVID-19, p =  < .0001) and 27% cardiovascular signs (vs. 20% influenza and 8% COVID-19, p = 0.0031 and 0.0009). Laboratory parameters of anemia, inflammation, and hypoxemia were highest in RSV. Among RSV, being a previous smoker (adjusted OR 2.81 [95% CI 1.01, 7.82]), coinfection (4.34 [2.02, 9.34]), and having cardiovascular (3.79 [2.17, 6.62]), neurologic (2.20 [1.09, 4.46]), or chronic lung (1.93 [1.11, 3.38]) diseases were risks for hospitalization. Being resident in care institutions (1.68 [1.09, 2.61]) or having a coinfection (1.91[1.36, 2.69]) were risks for higher severity, while RSV subtype was not associated with severity. Whereas RSV and influenza patients did not show differences in severity, RSV patients had 68% (38-84%) lower odds of experiencing any severe outcome compared to COVID-19.

CONCLUSIONS

RSV especially affects those with comorbidities, coinfections, and living in care institutions. RSV vaccination could have an important public health impact in this population.

Viral load in hospitalized infants with respiratory syncytial virus bronchiolitis: a three-way comparative analysis

Viral load measurement of Respiratory syncytial virus (RSV) in acute bronchiolitis depends on specimen collection, viral load quantification, and transport media. The aim of this study was to investigate viral load in three-way-comparative analyses; nasal swab versus nasal wash, quantitative real-time polymerase chain reaction (RT-PCR) versus cell tissue culture, and various transport media. A prospective cohort study of infants aged < 12 months, admitted to the Soroka Medical Center, due to acute bronchiolitis, was conducted. Two nasal swabs and two nasal wash samples (in UTM and VCM) were collected from each infant upon admission and after 48 h. Samples were immediately stored at -80 °C and tested at Viroclinics DDL (Rotterdam, Netherlands). Quantitative RT-PCR and quantitative virus culture were performed using tissue culture infective dose (TCID50). Spearman's correlation coefficient test assessed the correlation between the different methods, viral load, and clinical severity score. One hundred samples were collected from 13 infants (mean age 5.7 ± 3.8 months, 46% males). Twelve patients were RSV-A positive, and one was RSV-B positive. A high correlation was found between transport media- UTM and VCM (0.92, P < 0.001) and between nasal swabs and nasal wash samples (0.62, P = 0.02). RSV signals were higher in nasal wash than in swabs. PCR signals were lower in the second collection compared to the first. No correlation was found between viral load and clinical severity.    Conclusion: RSV viral load is comparable across nasal wash, nasal swabs, and various transport media. However, it did not correlate with clinical severity, probably due to the limited sample size. Broader analyses are warranted. What is Known: • Viral load measurement in Respiratory Syncytial Virus (RSV) bronchiolitis depends on specimen collection, viral load quantification, and transport media. • The COVID-19 pandemic underscored the paramount significance of proper specimen collection, notably through nasal swabs. What is New: • RSV viral load was investigated in three-way-comparative analyses. • RSV viral load correlated well across PCR and tissue culture, nasal wash and swabs, and various transport media. RSV viral load did not correlate with clinical severity.

Association of disease severity and genetic variation during primary Respiratory Syncytial Virus infections

BACKGROUND

Respiratory Syncytial Virus (RSV) disease in young children ranges from mild cold symptoms to severe symptoms that require hospitalization and sometimes result in death. Studies have shown a statistical association between RSV subtype or phylogenic lineage and RSV disease severity, although these results have been inconsistent. Associations between variation within RSV gene coding regions or residues and RSV disease severity has been largely unexplored.

METHODS

Nasal swabs from children (< 8 months-old) infected with RSV in Rochester, NY between 1977-1998 clinically presenting with either mild or severe disease during their first cold-season were used. Whole-genome RSV sequences were obtained using overlapping PCR and next-generation sequencing. Both whole-genome phylogenetic and non-phylogenetic statistical approaches were performed to associate RSV genotype with disease severity.

RESULTS

The RSVB subtype was statistically associated with disease severity. A significant association between phylogenetic clustering of mild/severe traits and disease severity was also found. GA1 clade sequences were associated with severe disease while GB1 was significantly associated with mild disease. Both G and M2-2 gene variation was significantly associated with disease severity. We identified 16 residues in the G gene and 3 in the M2-2 RSV gene associated with disease severity.

CONCLUSION

These results suggest that phylogenetic lineage and the genetic variability in G or M2-2 genes of RSV may contribute to disease severity in young children undergoing their first infection.

Seasonality, Clinical Characteristics, and Outcomes of Respiratory Syncytial Virus Disease by Subtype Among Children Aged <5 Years: New Vaccine Surveillance Network, United States, 2016-2020

BACKGROUND

Respiratory syncytial virus (RSV) is a leading cause of acute respiratory illnesses in children. RSV can be broadly categorized into 2 major subtypes: A and B. RSV subtypes have been known to cocirculate with variability in different regions of the world. Clinical associations with viral subtype have been studied among children with conflicting findings such that no conclusive relationships between RSV subtype and severity have been established.

METHODS

During 2016-2020, children aged <5 years were enrolled in prospective surveillance in the emergency department or inpatient settings at 7 US pediatric medical centers. Surveillance data collection included parent/guardian interviews, chart reviews, and collection of midturbinate nasal plus/minus throat swabs for RSV (RSV-A, RSV-B, and untyped) using reverse transcription polymerase chain reaction.

RESULTS

Among 6398 RSV-positive children aged <5 years, 3424 (54%) had subtype RSV-A infections, 2602 (41%) had subtype RSV-B infections, and 272 (5%) were not typed, inconclusive, or mixed infections. In both adjusted and unadjusted analyses, RSV-A-positive children were more likely to be hospitalized, as well as when restricted to <1 year. By season, RSV-A and RSV-B cocirculated in varying levels, with 1 subtype dominating proportionally.

CONCLUSIONS

Findings indicate that RSV-A and RSV-B may only be marginally clinically distinguishable, but both subtypes are associated with medically attended illness in children aged <5 years. Furthermore, circulation of RSV subtypes varies substantially each year, seasonally and geographically. With introduction of new RSV prevention products, this highlights the importance of continued monitoring of RSV-A and RSV-B subtypes.

Deviations in RSV epidemiological patterns and population structures in the United States following the COVID-19 pandemic

Respiratory Syncytial Virus (RSV) is a leading cause of acute respiratory tract infection, with the greatest impact on infants, immunocompromised individuals, and older adults. RSV prevalence decreased substantially in the United States (US) following the implementation of COVID-19-related non-pharmaceutical interventions but later rebounded with abnormal seasonality. The biological and epidemiological factors underlying this altered behavior remain poorly defined. In this retrospective cohort study from 2009 to 2023 in Chicago, Illinois, US, we examined RSV epidemiology, clinical severity, and genetic diversity. We found that changes in RSV diagnostic platforms drove increased detections in outpatient settings post-2020 and that hospitalized adults infected with RSV-A were at higher risk of intensive care admission than those with RSV-B. While population structures of RSV-A remained unchanged, RSV-B exhibited a genetic shift into geographically distinct clusters. Mutations in the antigenic regions of the fusion protein suggest convergent evolution with potential implications for vaccine and therapeutic development.

No association between disease severity and respiratory syncytial virus subtypes RSV-A and RSV-B in hospitalized young children in Norway

OBJECTIVE

There is conflicting evidence whether subtypes of Respiratory syncytial virus have different seasonality or are differentially associated with clinical severity. We aimed to explore the associations between disease severity and RSV subtypes RSV-A and RSV-B and to describe the circulation of RSV subtypes pattern by season and age.

METHODS

Active prospective hospital surveillance for RSV-A and RSV-B in children <59 months of age was conducted during 2015-2018. All febrile children 12-59 months of age were enrolled, whereas children <12 months were eligible if presenting with fever or respiratory symptoms. Risk factors and upper and lower respiratory tract infection was identified by linkage to national registry data and analyzed using penalized maximum likelihood logistic regression.

RESULTS

Both RSV-A and B were found to co-circulate throughout all three study seasons, and no clear seasonal pattern was identified. Likewise, we found no association between sex or measures of severity with RSV-A or RSV-B. There was significantly more RSV-A than RSV-B among children with comorbidities.

CONCLUSIONS

No association was found between disease severity or sex and RSV subtypes RSV-A and RSV-B in hospitalized young children in Norway.

Clinical comparison of HMPV and RSV infections in hospitalised Malaysian children: A propensity score matched study

INTRODUCTION

Human metapneumovirus (hMPV) and respiratory syncytial virus (RSV) are significant contributors to the burden of acute respiratory infections in children, but data on hMPV from Southeast Asia are limited despite its potential for serious disease. This study aimed to compare the clinical presentation, resource utilisation and outcomes between hMPV and RSV infections in hospitalised Malaysian children.

METHODS

This retrospective, observational study included children aged ≤12 years old hospitalised with hMPV or RSV, confirmed via direct fluorescent antibody (DFA) methods, between 1 July to 30 October 2022 at Hospital Tuanku Ja'afar Seremban, Malaysia. Demographic, clinical presentation, resource utilisation and outcome data were analysed. Propensity score matching was used to balance cohorts based on key demographic and clinical characteristics.

RESULTS

This study included 192 patients, comprising 112 with hMPV and 80 with RSV. hMPV patients were older (median age 20.5 vs. 9.4 months, p < 0.001) and had a higher incidence of comorbidities (24.1% vs. 7.5%, p = 0.003). Fever was more common in the hMPV group (97.3% vs. 73.8%, p < 0.001), but the other clinical manifestations were similar. Postmatching analysis showed higher corticosteroid use in the hMPV group (p = 0.01). No significant differences were observed in the use of other resources, PICU admissions, duration of hospitalisation or mortality rates between both groups.

CONCLUSION

hMPV and RSV infections in children share similar clinical manifestations and outcomes, with hMPV affecting older children and showing higher corticosteroid usage. These findings emphasise the need for equal clinical vigilance for both hMPV and RSV in paediatric respiratory infections.

Altered RSV Epidemiology and Genetic Diversity Following the COVID-19 Pandemic

Respiratory Syncytial Virus (RSV) is a leading cause of acute respiratory tract infection, with greatest impact on infants, immunocompromised individuals, and older adults. RSV prevalence decreased substantially following the implementation of non-pharmaceutical interventions to mitigate the COVID-19 pandemic but later rebounded with initially abnormal seasonality. The biological and epidemiological factors underlying this altered behavior remain poorly defined. In this retrospective cohort study, we examined RSV epidemiology, clinical severity, and genetic diversity in the years surrounding the COVID-19 pandemic. We found that changes in RSV diagnostic platforms drove increased detections in outpatient settings after 2020 and that hospitalized adults with RSV-A were at higher risk of needing intensive care than those with RSV-B. While the population structure of RSV-A remained unchanged, the population structure of RSV-B shifted in geographically distinct clusters. Mutations in the antigenic regions of the fusion protein suggest convergent evolution with potential implications for vaccine and therapeutic development.

Genetic diversity and its impact on disease severity in respiratory syncytial virus subtype-A and -B bronchiolitis before and after pandemic restrictions in Rome

OBJECTIVES

To scrutinize whether the high circulation of respiratory syncytial virus (RSV) observed in 2021-2022 and 2022-2023 was due to viral diversity, we characterized RSV-A and -B strains causing bronchiolitis in Rome, before and after the COVID-19 pandemic.

METHODS

RSV-positive samples, prospectively collected from infants hospitalized for bronchiolitis from 2017-2018 to 2022-2023, were sequenced in the G gene; phylogenetic results and amino acid substitutions were analyzed. Subtype-specific data were compared among seasons.

RESULTS

Predominance of RSV-A and -B alternated in the pre-pandemic seasons; RSV-A dominated in 2021-2022 whereas RSV-B was predominant in 2022-2023. RSV-A sequences were ON1 genotype but quite distant from the ancestor; two divergent clades included sequences from pre- and post-pandemic seasons. Nearly all RSV-B were BA10 genotype; a divergent clade included only strains from 2021-2022 to 2022-2023. RSV-A cases had lower need of O2 therapy and of intensive care during 2021-2022 with respect to all other seasons. RSV-B infected infants were more frequently admitted to intensive care units and needed O2 in 2022-2023.

CONCLUSIONS

The intense RSV peak in 2021-2022, driven by RSV-A phylogenetically related to pre-pandemic strains is attributable to the immune debt created by pandemic restrictions. The RSV-B genetic divergence observed in post-pandemic strains may have increased the RSV-B specific immune debt, being a possible contributor to bronchiolitis severity in 2022-2023.

Immunogenicity and protective efficacy of an RSV G S177Q central conserved domain nanoparticle vaccine

Introduction

Respiratory syncytial virus (RSV) can cause lower respiratory tract disease in infants and elderly populations. Despite decades of research, there remains no safe and approved RSV vaccine. Previously, we showed that an RSV G glycoprotein subunit vaccine candidate with a single point mutation within the central conserved domain (CCD), i.e. S177Q, considerably improved immunogenicity.

Methods

Here, we examine the development of nanoparticle (NP) vaccines having either an RSV G protein CCD with wild-type sequence (NPWT) or an S177Q mutation (NP-S177Q). The NP vaccine immunogens were adjuvanted with monophosphoryl lipid A (MPLA), a TLR4 agonist to improve Th1- type responses. BALB/c mice were primed with 10 μg of NP-WT vaccine, NPS177Q, or vehicle, rested, and then boosted with a high (25 μg) or low (10 μg) dose of the NP-WT or NP-S177Q homologous candidate and subsequently challenged with RSV A2.

Results

The results showed that mice boosted with NP-S177Q developed superior immunogenicity and neutralizing antibodies compared to NP-WT boosting. IgG from either NP-S177Q or NP-WT vaccinated mice did not interfere with fractalkine (CX3CL1) binding to CX3CR1 and effectively blocked G protein CX3C-CX3CR1 binding. Both NP-WT and NP-S177Q vaccination induced similar neutralizing antibodies to RSV in challenged mice compared to vehicle control. NP-S177Q boosting improved correlates of protection including reduced BAL cell infiltration following RSV challenge. However, the NP vaccine platform will require improvement due to the poor solubility and the unexpectedly weaker Th1-type IgG2a response.

Discussion

The results from this study support further NP-S177Q vaccine candidate development.

Risk Factors Associated with Severe RSV Infection in Infants: What Is the Role of Viral Co-Infections?

The respiratory syncytial virus (RSV) represents the leading cause of viral lower respiratory tract infections (LRTI) in children worldwide and is associated with significant morbidity and mortality rates. The clinical picture of an RSV infection differs substantially between patients, and the role of viral co-infections is poorly investigated. During two consecutive winter seasons from October 2018 until February 2020, we prospectively included children up to 2 years old presenting with an acute LRTI, both ambulatory and hospitalized. We collected clinical data and tested nasopharyngeal secretions for a panel of 16 different respiratory viruses with multiplex RT-qPCR. Disease severity was assessed with traditional clinical parameters and scoring systems. A total of 120 patients were included, of which 91.7% were RSV positive; 42.5% of RSV-positive patients had a co-infection with at least one other respiratory virus. We found that patients suffering from a single RSV infection had higher pediatric intensive care unit (PICU) admission rates (OR = 5.9, 95% CI = 1.53 to 22.74), longer duration of hospitalization (IRR = 1.25, 95% CI = 1.03 to 1.52), and a higher Bronchiolitis Risk of Admission Score (BRAS) (IRR = 1.31, 95% CI = 1.02 to 1.70) compared to patients with RSV co-infections. No significant difference was found in saturation on admission, O2 need, or ReSViNET-score. In our cohort, patients with a single RSV infection had increased disease severity compared to patients with RSV co-infections. This suggests that the presence of viral co-infections might influence the course of RSV bronchiolitis, but heterogeneity and small sample size in our study prevents us from drawing strong conclusions. IMPORTANCE RSV is worldwide the leading cause of serious airway infections. Up to 90% of children will be infected by the age of 2. RSV symptoms are mostly mild and typically mimic a common cold in older children and adolescents, but younger children can develop severe lower respiratory tract disease, and currently it is unclear why certain children develop severe disease while others do not. In this study, we found that children with a single RSV infection had a higher disease severity compared to patients with viral co-infections, suggesting that the presence of a viral co-infection could influence the course of an RSV bronchiolitis. As preventive and therapeutic options for RSV-associated disease are currently limited, this finding could potentially guide physicians to decide which patients might benefit from current or future treatment options early in the course of disease, and therefore, warrants further investigation.

Immunity Cell Responses to RSV and the Role of Antiviral Inhibitors: A Systematic Review

Antigen-presenting cells recognize respiratory syncytial virus antigens, and produce cytokines and chemokines that act on immune cells. Dendritic cells play the main role in inflammatory cytokine responses. Similarly, alveolar macrophages produce IFN-β, IFN-α, TNF-α, IL-6, CXCL10, and CCL3, while alternatively activated macrophages differentiate at the late phase, and require IL-13 or IL-4 cytokines. Furthermore, activated NKT cells secrete IL-13 and IL-4 that cause lung epithelial, endothelial and fibroblasts to secrete eotaxin that enhances the recruitment of eosinophil to the lung. CD8⁺ and CD4⁺T cells infection by the virus decreases the IFN-γ and IL-2 production. Despite this, both are involved in terminating virus replication. CD8⁺T cells produce a larger amount of IFN-γ than CD4⁺T cells, and CD8⁺T cells activated under type 2 conditions produce IL-4, down regulating CD8 expression, granzyme and IFN-γ production. Antiviral inhibitors inhibit biological functions of viral proteins. Some of them directly target the virus replication machinery and are effective at later stages of infection; while others inhibit F protein dependent fusion and syncytium formation. TMC353121 reduces inflammatory cytokines, TNF-α, IL-6, and IL-1β and chemokines, KC, IP-10, MCP and MIP1-α. EDP-938 inhibits viral nucleoprotein (N), while GRP-156784 blocks the activity of respiratory syncytial virus ribonucleic acid (RNA) polymerase. PC786 inhibits non-structural protein 1 (NS-1) gene, RANTES transcripts, virus-induced CCL5, IL-6, and mucin increase. In general, it is an immune reaction that is blamed for the disease severity and pathogenesis in respiratory syncytial virus infection. Anti-viral inhibitors not only inhibit viral entry and replication, but also may reduce inflammatory cytokines and chemokines. Many respiratory syncytial virus inhibitors are proposed; however, only palivizumab and ribavirin are approved for prophylaxis and treatment, respectively. Hence, this review is focused on immunity cell responses to respiratory syncytial virus and the role of antiviral inhibitors.

Clinical and Viral Factors Associated With Disease Severity and Subsequent Wheezing in Infants With Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) causes substantial morbidity and mortality in infants and young children worldwide. Here we evaluated host demographic and viral factors associated with RSV disease severity in 325 RSV-infected infants under 1 year of age from 3 European countries during 2017-2020. Younger infants had a higher clinical severity (ReSViNET) score and were more likely to require hospitalization, intensive care, respiratory support, and/or mechanical ventilation than older infants (<3 months vs 3 to <6 months and 3 to <6 months vs ≥6 months). Older age (≥6 months vs <3 months), higher viral load, and RSV-A were associated with a greater probability of fever. RSV-A and RSV-B caused similar disease severity and had similar viral dynamics. Infants with a more severe RSV infection, demonstrated by having a higher ReSViNET score, fever, and requiring hospitalization and intensive care, were more likely to have developed subsequent wheezing at 1 year of age.

CLINICAL TRIALS REGISTRATION

NCT03756766.

Rapid typing diagnosis and clinical analysis of subtypes A and B of human respiratory syncytial virus in children

Background

Human respiratory syncytial virus (HRSV) is the leading pathogens causing acute respiratory infections (ARI) in children under five years old. We aimed to investigate the distribution of HRSV subtypes and explore the relationship between viral subtypes and clinical symptoms and disease severity.

Methods

From November 2016 to April 2017, 541 children hospitalized because of ARI were included in the study. Throat swabs were collected for analysis and all samples were tested by multiplex one-step qRT-PCR for quantitative analysis and typing of HRSV. Patients’ demographics, clinical symptoms as well as laboratory and imaging results were retrieved from medical records.

Results

HRSV was detected in 19.6% of children hospitalized due to ARI. HRSV-positive children were younger (P < 0.001), had a higher frequency of wheezing and pulmonary rales (P < 0.001; P = 0.003), and were more likely to develop bronchopneumonia (P < 0.001). Interleukin (IL) 10、CD4/CD8 (below normal range) and C-reactive protein levels between subtypes A and B groups were significantly different (P = 0.037; P = 0.029; P = 0.007), and gender differences were evident. By age-stratified analysis between subtypes A and B, we found significant differences in fever frequency and lymphocyte ratio (P = 0.008; P = 0.03) in the 6–12 months age group, while the 12. 1–36 months age group showed significant differences in fever days and count of leukocytes, platelets, levels aspartate aminotransferase, IL-6, lactate dehydrogenase and proportion CD4 positive T cells(P = 0.013; P = 0.018; P = 0.016; P = 0.037; P = 0.049; P = 0.025; P = 0.04). We also found a positive correlation between viral load and wheezing days in subtype A (P < 0.05), and a negative correlation between age, monocyte percentage and LDH concentration in subtype B (P < 0.05).

Conclusions

HRSV is the main causative virus of bronchopneumonia in infants and children. The multiplex one-step qRT-PCR not only provides a rapid and effective diagnosis of HRSV infection, but also allows its typing. There were no significant differences in the severity of HRSV infection between subtypes A and B, except significant gender-specific and age-specific differences in some clinical characteristics and laboratory results. Knowing the viral load of HRSV infection can help understanding the clinical features of different subtypes of HRSV infection.

Respiratory syncytial virus infection among adults after hematopoietic stem cell transplantation

Introduction:

Respiratory syncytial virus (RSV) is a common cause of morbidity among hematopoietic stem cell transplant (HSCT) recipients, with RSV-associated lower respiratory tract infection carrying high mortality rates. There have been no large studies till date, describing the incidence, clinical features, and outcomes of RSV infection among adult HSCT recipients in India.

Methods:

A prospective cohort of 100 adults who underwent HSCT was followed up for a maximum period of 18 months starting from the date of transplantation for any episode of respiratory tract infectious disease (RTID). Respiratory samples were collected for laboratory confirmation of the presence and subtyping of RSV by real-time reverse transcriptase-polymerase chain reaction.

Results:

The study population comprised of 66% (66/100) males and 34% (34/100) females. Autologous HSCT recipients constituted 78% (78/100) and allogeneic HSCT recipients constituted 22% (22/100) of the study population. The incidence of RSV-RTID among adults after HSCT was 0.82/100 patient months. Most cases occurred during the winter season and the predominant subtype was RSV-A (9/11, 81.8%). Lower RTID was the most common clinical diagnosis made at presentation (9/11, 81.8%). Female gender was predictive of RSV-RTID (log rank P = 0.002). All the RSV-RTID episodes recovered completely without targeted therapy.

Conclusion:

RSV is a significant cause of morbidity among adult HSCT recipients in India. Prophylaxis and treatment measures need to be instituted after a proper risk-benefit assessment. Longitudinal studies with larger sample sizes are needed to confirm these results.

Respiratory syncytial virus subtype circulation and associated disease severity at an Australian paediatric referral hospital, 2014-2018

AIM

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections in children and the development of vaccines to protect at-risk groups is a global priority. The aim of this study was to describe RSV subtype circulation patterns and associated disease severity to inform on potential impact of an RSV-specific prevention strategy.

METHODS

Single-centre retrospective observational study of children aged <16 years with laboratory-confirmed RSV infection from 2014 to 2018 inclusive. We described the features and frequency of all RSV subtype detections. We selected a random sample of RSV-A and RSV-B cases from each year (n = 200), described demographic and clinical features of these cases, and compared indicators of disease severity between subtypes.

RESULTS

We identified 3591 RSV detections over a 5-year period and found consistent co-circulation of subtypes with alternating predominance. Demographic and clinical characteristics were similar between children presenting with RSV-A and RSV-B infections. There was no difference in indicators of severity between the subtypes except for paediatric intensive care unit length of stay which was longer in the RSV-B group (3 vs. 5 days, P = 0.006). Respiratory co-infections were more frequent in the RSV-B group (41.8% vs. 27.4%, P = 0.035). When these were excluded there was no longer a detectable difference in paediatric intensive care unit length of stay.

CONCLUSIONS

We found co-circulation of RSV subtypes and no convincing evidence of a difference in disease severity between subtypes. RSV-specific interventions will need to be equally effective against both RSV-A and RSV-B to have the greatest impact on reducing severe RSV disease in this population.

Seasonality, molecular epidemiology, and virulence of Respiratory Syncytial Virus (RSV): A perspective into the Brazilian Influenza Surveillance Program

Background

Respiratory Syncytial Virus (RSV) is the main cause of pediatric morbidity and mortality. The complex evolution of RSV creates a need for worldwide surveillance, which may assist in the understanding of multiple viral aspects.

Objectives

This study aimed to investigate RSV features under the Brazilian Influenza Surveillance Program, evaluating the role of viral load and genetic diversity in disease severity and the influence of climatic factors in viral seasonality.

Methodology

We have investigated the prevalence of RSV in children up to 3 years of age with severe acute respiratory infection (SARI) in the state of Espirito Santo (ES), Brazil, from 2016 to 2018. RT-qPCR allowed for viral detection and viral load quantification, to evaluate association with clinical features and mapping of local viral seasonality. Gene G sequencing and phylogenetic reconstruction demonstrated local genetic diversity.

Results

Of 632 evaluated cases, 56% were caused by RSV, with both subtypes A and B co-circulating throughout the years. A discrete inverse association between average temperature and viral circulation was observed. No correlation between viral load and disease severity was observed, but children infected with RSV-A presented a higher clinical severity score (CSS), stayed longer in the hospital, and required intensive care, and ventilatory support more frequently than those infected by RSV-B. Regarding RSV diversity, some local genetic groups were observed within the main genotypes circulation RSV-A ON1 and RSV-B BA, with strains showing modifications in the G gene amino acid chain.

Conclusion

Local RSV studies using the Brazilian Influenza Surveillance Program are relevant as they can bring useful information to the global RSV surveillance. Understanding seasonality, virulence, and genetic diversity can aid in the development and suitability of antiviral drugs, vaccines, and assist in the administration of prophylactic strategies.

Severe respiratory disease caused by human respiratory syncytial virus impairs language learning during early infancy

Human respiratory syncytial virus infection is a leading cause of pediatric morbidity and mortality. A previous murine study showed that during severe acute respiratory infections the virus invades the central nervous system, and that infected animals evolve with long-lasting learning difficulties associated with long-term potentiation impairment in their hippocampus. We hypothesized here that human infants who presented a severe episode of respiratory syncytial virus infection before 6 months of age would develop long-term learning difficulties. We measured the acquisition of the native phoneme repertoire during the first year, a milestone in early human development, comprising a reduction in the sensitivity to the irrelevant nonnative phonetic information and an increase in the sensitivity to the information relevant for the native one. We found that infants with a history of severe respiratory infection by the human respiratory syncytial virus presented poor distinction of native and nonnative phonetic contrasts at 6 months of age, and remained atypically sensitive to nonnative contrasts at 12 months, which associated with weak communicative abilities. Our results uncover previously unknown long-term language learning difficulties associated with a single episode of severe respiratory infection by the human respiratory syncytial virus, which could relate to memory impairments.

Respiratory syncytial virus infection: why does disease severity vary among individuals?

Introduction: Respiratory syncytial virus (RSV) is the most common cause of acute lower respiratory tract infections in infancy. While many infants are infected with RSV, the nature and severity of the disease vary among individuals. RSV causes bronchiolitis, pneumonia, and asthma exacerbation. However, most children infected with RSV have only mild upper airways disease and may be asymptomatic.Areas covered: Despite efforts to elucidate mechanisms for the various clinical responses to RSV infection, they remain largely unknown, suggesting that susceptibility and disease are influenced by multiple intrinsic and extrinsic factors. This article reviews the available literature on the field of RSV disease severity and discusses important factors associated to susceptibility and different disease outcome.Expert opinion: The severity of RSV-induced illness is a phenomenon that depends on a variety of graded mechanisms of interaction between the host, virus, and environment. This may lead to differences in the intensity of immune response in the lung and different courses of the disease. By characterizing, classifying, and grading the affecting factors in high-risk patients versus those who do not fall ill by RSV, we may find therapies or point to disease-limiting medications.

Contribution of Dendritic Cells in Protective Immunity against Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) is a major cause of severe respiratory disease in infants and the elderly. The socioeconomic burden of RSV infection is substantial because it leads to serious respiratory problems, subsequent hospitalization, and mortality. Despite its clinical significance, a safe and effective vaccine is not yet available to prevent RSV infection. Upon RSV infection, lung dendritic cells (DCs) detecting pathogens migrate to the lymph nodes and activate the adaptive immune response. Therefore, RSV has evolved various immunomodulatory strategies to inhibit DC function. Due to the capacity of RSV to modulate defense mechanisms in hosts, RSV infection results in inappropriate activation of immune responses resulting in immunopathology and frequent reinfection throughout life. This review discusses how DCs recognize invading RSV and induce adaptive immune responses, as well as the regulatory mechanisms mediated by RSV to disrupt DC functions and ultimately avoid host defenses.

Respiratory Syncytial Virus Seasonality, Beijing, China, 2007-2015

During July 2007-June 2015, we enrolled 4,225 hospitalized children with pneumonia in a study to determine the seasonality of respiratory syncytial virus (RSV) infection in Beijing, China. We defined season as the period during which >10% of total PCRs performed each week were RSV positive. We identified 8 distinctive RSV seasons. On average, the season onset occurred at week 41 (mid-October) and lasted 33 weeks, through week 20 of the next year (mid-May); 97% of all RSV-positive cases occurred during the season. RSV seasons occurred 3-5 weeks earlier and lasted ≈6 weeks longer in RSV subgroup A-dominant years than in RSV subgroup B-dominant years. Our analysis indicates that monitoring such RSV subgroup shifts might provide better estimates for the onset of RSV transmission. PCR-based tests could be a flexible or complementary way of determining RSV seasonality in locations where RSV surveillance is less well-established, such as local hospitals throughout China.

Crystal Structure and Immunogenicity of the DS-Cav1-Stabilized Fusion Glycoprotein From Respiratory Syncytial Virus Subtype B

Background:

Respiratory syncytial virus (RSV) subtypes, A and B, co-circulate in annual epidemics and alternate in dominance. We have shown that a subtype A RSV fusion (F) glycoprotein, stabilized in its prefusion conformation by DS-Cav1 mutations, is a promising RSV-vaccine immunogen, capable of boosting RSV-neutralizing titers in healthy adults. In both humans and vaccine-tested animals, neutralizing titers elicited by this subtype A DS-Cav1 immunogen were ~ 2- to 3-fold higher against the homologous subtype A virus than against the heterologous subtype B virus.

Methods:

To understand the molecular basis for this subtype difference, we introduced DS-Cav1 mutations into RSV strain B18537 F, determined the trimeric crystal structure, and carried out immunogenicity studies.

Results:

The B18537 DS-Cav1 F structure at 2-Å resolution afforded a precise delineation of prefusion F characteristics, including those of antigenic site Ø, a key trimer-apex site. Structural comparison with the subtype A prefusion F indicated 11% of surface residues to be different, with an alpha-carbon root-mean-square deviation (RMSD) of 1.2 Å; antigenic site Ø, however, differed in 23% of its surface residues and had an alpha-carbon RMSD of 2.2 Å. Immunization of vaccine-tested animals with DS-Cav1-stabilized B18537 F induced neutralizing responses ~100-fold higher than with postfusion B18537 F. Notably, elicited responses neutralized RSV subtypes A and B at similar levels and were directed towards both conserved equatorial and diverse apical regions.

Conclusion:

We propose that structural differences in apical and equatorial sites–coupled to differently focused immune responses–provide a molecular explanation for observed differences in elicited subtype A and B neutralizing responses.

How Respiratory Syncytial Virus Genotypes Influence the Clinical Course in Infants Hospitalized for Bronchiolitis

Background

We aimed to study respiratory syncytial virus (RSV) genotype distribution, clinical presentation, and disease severity in infants with bronchiolitis from RSV subtypes and new RSV genotypes.

Methods

We prospectively enrolled previously healthy term infants less than 1 year old hospitalized for bronchiolitis in an Italian university hospital over 12 epidemic seasons. In 312 nasopharyngeal washings positive for RSV, we sequenced the viral genotype and analyzed this according to patient data. Strain-specific RSV loads were quantified for 273 specimens.

Results

From 2005-2006 to 2011-2012, the RSV-A genotype NA1 predominated, and was replaced in 2012 by the novel ON1. All infants infected with RSV subtype B were genotype BA. Stratifying data according to genotypes NA1, ON1, and BA showed that NA1-infected infants were the youngest and had the most severe clinical course. Conversely, BA-infected infants had less severe symptoms and more frequently had eosinophilia and a family history of asthma. Infants with the ON1 genotype had a milder clinical course than those with NA1 and more risk factors for asthma, despite having the highest viral loads.

Conclusion

The disease course in infants hospitalized for acute RSV bronchiolitis may depend on the RSV genotype.

Clinical characteristics, predictors, and performance of case definition-Interim results from the WHO global respiratory syncytial virus surveillance pilot

Background

The lack of a uniform surveillance case definition poses a challenge to characterize the epidemiology, clinical features, and disease burden of the respiratory syncytial virus (RSV). Global standards for RSV surveillance will inform immunization policy when RSV vaccines become available.

Methods

The WHO RSV surveillance pilot leverages the capacities of the Global Influenza Surveillance and Response System (GISRS). Hospitalized and non‐hospitalized medically attended patients of any age were tested for RSV using standardized molecular diagnostics throughout the year in fourteen countries. An extended severe acute respiratory infection (extended SARI) or an acute respiratory infection (ARI) case definition was used that did not require fever as a criterion.

Results

Amongst 21 221 patients tested for RSV between January 2017 and September 2018, 15 428 (73%) were hospital admissions. Amongst hospitalized RSV‐positive patients, 50% were aged <6 months and 88% <2 years. The percentage of patients testing positive for RSV was 37% in children <6 months and 25% in those aged 6 months to 2 years. Patients with fever were less likely to be RSV positive compared to those without fever (OR 0.74; 95% CI: 0.63‐0.86). For infants <6 months, 29% of RSV ARI cases did not have fever.

Conclusion

Requiring fever in a case definition for RSV lowers the sensitivity to detect cases in young children. Countries should consider ways to leverage the GISRS platform to implement RSV surveillance with an augmented case definition amongst the young pediatric population.

Respiratory Syncityal Virus A and B: three bronchiolitis seasons in a third level hospital in Italy

Background

Respiratory syncytial virus (RSV) is the main cause of hospitalization for bronchiolitis among infants. RSV is classified into two subtypes, A and B, whose predominance alternates during different epidemic seasons. The clinical impact of viral factors is controversial and many evidences suggest a critical role for the immune host response. Premature children are at the highest risk for severe RSV infection. The main aim of this study is to identify the different RSV subtypes circulating in the last three epidemic seasons and to evaluate whether any of them was associated with poor prognosis in term and preterm infants.

Methods

We performed a retrospective analysis of medical records for all patients aged less than one year which were hospitalized during the winter season between November 2015 and April 2018 with clinical diagnosis of bronchiolitis and nasopharyngeal aspirates positive for RSV.

Results

We enrolled 422 children, of which 50 were born preterm. During the analysis period, we observed a significant increase in the rates of oxygen supplementation and admission to intensive care unit. The evidence shows an alternating pattern in the prevalence of RSV subtypes among term born; in each epidemic season, the prevalent serotype is the cause of the majority of the cases requiring intensive care. Conversely, RSV-A is always prevalent in preterm children and caused most of the cases requiring intensive care.

Conclusions

During the 3 seasons analyzed, we observed an alternating prevalence of RSV A and B. While there are no differences in severity between RSV A and B in term population, RSV-A is prevalent and causes most of the severe cases in the premature group. Furthermore, an increase in RSV-related oxygen therapy and PICU admission has been documented not only in the premature population. Considering the absence of appropriate therapeutic strategies, our work emphasizes the importance of implementing prophylaxis measures against RSV and highlights the urgent need to gain knowledge about immune response to the virus, also in premature children.

Electronic supplementary material

The online version of this article (10.1186/s13052-019-0704-0) contains supplementary material, which is available to authorized users.

Respiratory syncytial virus, human metapneumovirus, and influenza virus infection in Bangkok, 2016-2017

Children and adults residing in densely populated urban centers around the world are at risk of seasonal influenza-like illness caused by respiratory viruses such as influenza virus, human metapneumovirus (hMPV), and respiratory syncytial virus (RSV). In a large metropolitan of Thailand’s capital city Bangkok, most respiratory infections are rarely confirmed by molecular diagnostics. We therefore examined the frequency of RSV, hMPV, and influenza virus in 8,842 patients who presented influenza-like illness and sought medical care at a large hospital in Bangkok between 2016 and 2017. Using a multiplex real-time reverse-transcription polymerase chain reaction (RT-PCR), 30.5% (2,699/8,842) of nasopharyngeal (NP) swab samples tested positive for one or more of these viruses. Influenza virus comprised 17.3% (1,528/8,842), of which the majority were influenza A/H3N2. Such infection was most prevalent among adults and the elderly. RSV was identified in 11.4% (1,011/8,842) and were mostly ON1 and BA9 genotypes. Of the hMPV-positive samples (3.6%, 318/8,842), genotypes A2, B1, and B2 were detected. A small number of individuals experienced co-infections (1.8%, 155/8,842), most commonly between RSV and influenza A/H3N2. RSV and hMPV co-infections were also found, but mainly in young children. Viral respiratory tract infection peaked locally in the rainy season (June to September). These findings support the utility of rapid nucleic acid testing of RSV, hMPV, and influenza virus in patients with ILI.

A quantitative assessment of dynamical differences of RSV infections in vitro and in vivo

Experimental results in vitro and in animal models are used to guide researchers in testing vaccines or treatment in humans. However, viral kinetics are different in vitro, in animals, and in humans, so it is sometimes difficult to translate results from one system to another. In this study, we use a mathematical model to fit experimental data from multiple cycle respiratory syncytial virus (RSV) infections in vitro, in african green monkey (AGM), and in humans in order to quantitatively compare viral kinetics in the different systems. We find that there are differences in viral clearance rate, productively infectious cell lifespan, and eclipse phase duration between in vitro and in vivo systems and among different in vivo systems. We show that these differences in viral kinetics lead to different estimates of drug effectiveness of fusion inhibitors in vitro and in AGM than in humans.

Characterization of circulating RSV strains among subjects in the OUTSMART-RSV surveillance program during the 2016-17 winter viral season in the United States

Background

Respiratory syncytial virus (RSV) is an established cause of serious lower respiratory disease in infants, elderly and high-risk populations. The OUTSMART surveillance program aims to characterize patient populations and currently circulating RSV strains, and monitor temporal and geographic evolution of RSV F and G proteins in the U.S.

Methods

The OUTSMART 2016–17 study collected RSV-positive samples from 25 RSVAlert^® laboratories from 4 U.S. regions and Puerto Rico during November 2016 through March 2017. Frequencies of A and B subtypes and genotypes were determined for several demographic and geographic variables. To gauge the representativeness of the OUTSMART patients, results were compared to discharge data from the NEDS and NIS databases.

Results

A total of 1,041 RSV-positive samples with associated demographic data were obtained and the RSV F gene and second variable region of the G gene were sequenced. The majority of samples (76.0%) came from children under 2 years old: <1 year (48.4%), 1–2 years (27.6%). The OUTSMART patient sample was similar to NEDS and NIS for age, gender, and geographic location. Both OUTSMART and national RSV cases peaked in January. Of OUTSMART samples, 45.3% were subtype A, 53.7% were subtype B and 1.0% were mixed A and B. The percentage of RSV B cases increased with increasing age. Hospitalization (length of hospital stay, LOS, >24 hrs) occurred in 29.0% of patients of which 52.0% had RSV B. Outpatients (LOS <24 hrs) were 64.4% of total of which 73.3% were diagnosed in the ER and discharged, while only 6% were diagnosed in other outpatient settings.

Conclusions

The OUTSMART 2016–17 study was representative of the U.S. RSV experience. Geographic and temporal information from the RSV surveillance program will be used to establish a molecular baseline of RSV F and G sequence variability and to help inform development of novel agents for RSV prophylaxis and treatment.

Human respiratory syncytial virus load normalized by cell quantification as predictor of acute respiratory tract infection

Human respiratory syncytial virus (HRSV) is a common cause of respiratory infections. The main objective is to analyze the prediction ability of viral load of HRSV normalized by cell number in respiratory symptoms. A prospective, descriptive, and analytical study was performed. From 7307 respiratory samples processed between December 2014 to April 2016, 1019 HRSV-positive samples, were included in this study. Low respiratory tract infection was present in 729 patients (71.54%). Normalized HRSV load was calculated by quantification of HRSV genome and human β-globin gene and expressed as log10 copies/1000 cells. HRSV mean loads were 4.09 ± 2.08 and 4.82 ± 2.09 log10 copies/1000 cells in the 549 pharyngeal and 470 nasopharyngeal samples, respectively (P < 0.001). The viral mean load was 4.81 ± 1.98 log10 copies/1000 cells for patients under the age of 4-year-old (P < 0.001). The viral mean loads were 4.51 ± 2.04 cells in patients with low respiratory tract infection and 4.22 ± 2.28 log10 copies/1000 cells with upper respiratory tract infection or febrile syndrome (P < 0.05). A possible cut off value to predict LRTI evolution was tentatively established. Normalization of viral load by cell number in the samples is essential to ensure an optimal virological molecular diagnosis avoiding that the quality of samples affects the results. A high viral load can be a useful marker to predict disease progression.

Respiratory Syncytial Virus Genotypes, Host Immune Profiles, and Disease Severity in Young Children Hospitalized With Bronchiolitis

Background

Data on how respiratory syncytial virus (RSV) genotypes influence disease severity and host immune responses is limited. Here, we characterized the genetic variability of RSV during 5 seasons, and evaluated the role of RSV subtypes, genotypes, and viral loads in disease severity and host transcriptional profiles.

Methods

A prospective, observational study was carried out, including a convenience sample of healthy infants hospitalized with RSV bronchiolitis. Nasopharyngeal samples for viral load quantitation, typing, and genotyping, and blood samples for transcriptome analyses were obtained within 24 hours of hospitalization. Multivariate models were constructed to identify virologic and clinical variables predictive of clinical outcomes.

Results

We enrolled 253 infants (median age 2.1 [25%-75% interquartile range] months). RSV A infections predominated over RSV B and showed greater genotype variability. RSV A/GA2, A/GA5, and RSV B/BA were the most common genotypes identified. Compared to GA2 or BA, infants with GA5 infections had higher viral loads. GA5 infections were associated with longer hospital stay, and with less activation of interferon and increased overexpression of neutrophil genes.

Conclusions

RSV A infections were more frequent than RSV B, and displayed greater variability. GA5 infections were associated with enhanced disease severity and distinct host immune responses.

Respiratory Syncytial Virus: Infection, Detection, and New Options for Prevention and Treatment

Respiratory syncytial virus (RSV) infection is a significant cause of hospitalization of children in North America and one of the leading causes of death of infants less than 1 year of age worldwide, second only to malaria. Despite its global impact on human health, there are relatively few therapeutic options available to prevent or treat RSV infection. Paradoxically, there is a very large volume of information that is constantly being refined on RSV replication, the mechanisms of RSV-induced pathology, and community transmission. Compounding the burden of acute RSV infections is the exacerbation of preexisting chronic airway diseases and the chronic sequelae of RSV infection. A mechanistic link is even starting to emerge between asthma and those who suffer severe RSV infection early in childhood. In this article, we discuss developments in the understanding of RSV replication, pathogenesis, diagnostics, and therapeutics. We attempt to reconcile the large body of information on RSV and why after many clinical trials there is still no efficacious RSV vaccine and few therapeutics.

Respiratory Syncytial Virus: The Influence of Serotype and Genotype Variability on Clinical Course of Infection

Respiratory syncytial virus (RSV) belongs to the recently defined Pneumoviridae family, Orthopneumovirus genus. It is the leading cause of acute bronchiolitis and one of the most common causes of infant viral death worldwide, with infection typically occurring as recurrent seasonal epidemics. There are two major RSV subtypes, A and B, and multiple genotypes, which can coexist during RSV epidemic season every year and result in different disease severity. Recently, new RSV genomic sequences and analysis of RSV genotypes have provided important data for understanding RSV pathogenesis. Novel RSV strains do spread rapidly and widely, and a knowledge of viral strain-specific phenotypes may be important in order to include the more virulent strains in future therapeutical options and vaccine development. Here we summarize recent literature exploring genetic and molecular aspects related to RSV infection, their impact on the clinical course of the disease and their potential utility in the development of safe and effective preventive and therapeutic strategies.

Universal vaccine against respiratory syncytial virus A and B subtypes

Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract infection in infants, young children, and the elderly. Two subtypes of RSV, A and B, circulate alternately at 1-2-year intervals during epidemics. The attachment glycoprotein (G protein) of RSV is one of the major targets for immune responses. In this study, we generated a recombinant fusion protein, GcfAB, which consists of the central regions (a.a. residues 131-230) of the G proteins of both RSV A (A2 strain) and B (B1 strain) subtypes, and investigated immunogenicity, protective efficacy, and immunopathology. We immunized mice with GcfAB plus cholera toxin as a mucosal adjuvant via intranasal (IN) or sublingual (SL) routes. The IN group showed higher levels of RSV G-specific antibody responses, including serum IgG and mucosal IgA, compared with the SL group. On the contrary, more vigorous RSV G-specific CD4+ T-cell responses were elicited in the SL group than in the IN group after RSV-A but not RSV-B viral challenge. Furthermore, the SL group showed more pulmonary eosinophil recruitment and body weight loss than did the IN group after RSV-A challenge. Both IN and SL immunization with GcfAB provided potential protection against both subtypes of infections. Together, these results suggest that vaccination with GcfAB via an IN route could be a universal vaccine regimen preventing both RSV A and B infections.

Epidemiology and Clinical Presentations of Respiratory Syncytial Virus Subgroups A and B Detected with Multiplex Real-Time PCR

Respiratory syncytial virus (RSV) is one of the most important pathogenic infections of children and requires in-depth research worldwide, and especially in developing countries. We used a novel multiplex real-time PCR to test 5483 patients (≤ 14 years old) hospitalized with respiratory illness in Guangzhou, China, over a 3-year period. Of these patients, 729 were positive for RSV-A (51.2%, 373/729) or RSV-B (48.8%, 356/729), but none was infected with both viruses. Two seasonal peaks in total RSV were detected at the changes from winter to spring and from summer to autumn. RSV-B was dominant in 2013 and RSV-A in 2015, whereas RSV-A and RSV-B cocirculated in 2014. The clinical presentations of 645 RSV-positive patients were analyzed. Bronchiolitis, dyspnea, coryza, vomiting, poor appetite, and diarrhea occurred more frequently in RSV-A-positive than RSV-B-positive patients, whereas chill, headache, myalgia, debility, and rash etc. were more frequent in RSV-B-positive than RSV-A-positive patients, suggesting specific clinical characteristics for RSV-A and RSV-B. Coinfectons with other pathogens were common and diverse. Bronchiolitis, fever (≥ 38°C), and poor appetite were more frequent in patients with single RSV infections than in coinfected patients, suggesting the key pathogenic activity of RSV. Analysis of the relationships between the comparative viral load and clinical presentations showed significant differences in bronchiolitis, fever (≥ 38°C), and rash etc. among patients with different viral loads. This study provides a novel rapid method for detecting RSV subgroups, and provides new insights into the epidemiology and clinical implications of RSV.

Caffeine for the Treatment of Apnea in Bronchiolitis: A Randomized Trial

OBJECTIVE

To evaluate the efficacy and safety of caffeine citrate in the treatment of apnea in bronchiolitis.

STUDY DESIGN

Eligible infants aged ≤4 months presenting to the main pediatric emergency service with apnea associated bronchiolitis were stratified by gestational age (<34 weeks or longer) and randomized to receive a single dose of intravenous 25 mg/kg caffeine citrate or saline placebo. The primary efficacy outcome was a 24-hour apnea-free period beginning after completion of the blinded study drug infusion. Secondary outcomes were frequency of apnea by 24, 48, and 72 hours after study medication, need for noninvasive/invasive ventilation, and length of stay in the hospital's pediatric intensive care/step-down unit.

RESULTS

A total of 90 infants diagnosed with viral bronchiolitis associated with apnea (median age, 38 days) were enrolled. The rate of respiratory virus panel positivity was similar in the 2 groups (78% for the placebo group vs 84% for the caffeine group). The geometric mean duration to a 24-hour apnea-free period was 28.1 hours (95% CI, 25.6-32.3 hours) for the caffeine group and 29.1 hours (95% CI, 25.7-32.9 hours) for the placebo group (P = .88; OR, 0.99; 95% CI, 0.83-1.17). The frequency of apnea at 24 hours, 24-48 hours, and 48-72 hours after enrollment and the need for noninvasive and invasive ventilation were similar in the 2 groups. No safety issues were reported.

CONCLUSIONS

A single dose of caffeine citrate did not significantly reduce apnea episodes associated with bronchiolitis.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT01435486.

Respiratory syncytial virus outbreak on an adult stem cell transplant unit

BACKGROUND

An increase in respiratory syncytial virus type B (RSV-B) infections was detected on an adult hematology/oncology and stem cell transplant unit during March 2015. This prompted an outbreak investigation.

METHODS

Nosocomial cases were defined as RSV-B-positive patients who developed respiratory virus symptoms ≥ 7 days after admission to the unit or were readmitted with symptoms ≤ 7 days since last discharge from the unit. Strict outbreak control measures were implemented to stop the outbreak.

RESULTS

During the outbreak, 19 cases of RSV-B were detected, 14 among patients and 5 among health care workers (HCWs). Additionally, 2 HCWs tested positive for respiratory syncytial virus type A and 1 tested positive for influenza B among the 27 symptomatic HCWs evaluated. No specific antiviral therapy was given and all cases recovered without progression to lower respiratory tract infection. After no new cases were identified for 2 weeks, the outbreak was declared over.

CONCLUSIONS

High vigilance for respiratory viruses on high-risk inpatient units is required for detection and prevention of potential outbreaks. Multiple respiratory viruses with outbreak potential were identified among HCWs. HCWs with respiratory virus symptoms should not provide direct patient care. Absence of lower respiratory tract infection suggests lower virulence of RSV-B, compared with respiratory syncytial virus type A, among immunocompromised adults.

The impact of viral dynamics on the clinical severity of infants with respiratory syncytial virus bronchiolitis

The impact of dynamic respiratory syncytial virus (RSV) load on the clinical severity of hospitalized infants with bronchiolitis has not been clarified. Nasopharyngeal aspirates were obtained from 60 infants who were diagnosed with bronchiolitis within 96 hr of wheezing onset upon admission and on days 3, 5, and 7 in the hospital, and 17 respiratory viruses were detected. The RSV load was quantified by real-time qPCR for RSV subtypes A and B at different time points. Scoring criteria were used to evaluate the degree of severity. A total of 40 infants were determined to be RSV-positive, nine were identified as RSV subtype A (RSVA), and 31 were RSV subtype B (RSVB). The peak RSV load was observed upon admission, and the RSV load decreased significantly over time; in addition, this decrease began to have significant differences on day 5. There was a positive correlation between the RSV load and the clinical score (r(2)  = 0.121 and P < 0.001). According to the clinical scores, the infants in the severe group tended to have higher RSV loads than those in the moderate and mild groups. Multivariate logistic regression models revealed that the viral load on day 3 was independently associated with the degree of severity. This study elucidated that a higher mean RSV load was associated with a more severe disease and a longer duration of hospitalization and symptoms. This study also clarified RSV replication in infants and provides a theoretical basis for specifying an anti-RSV therapy strategy.

New options in the treatment of respiratory syncytial virus disease

Respiratory syncytial virus (RSV) remains a significant cause of morbidity and mortality in infants, immunocompromised patients and the elderly. Despite the high disease burden, an effective vaccine or specific therapy are lacking which is largely due to our limited understanding of the immune response to RSV and how it relates to clinical disease severity. Current treatment for RSV remains largely supportive and RSV-specific options for prophylaxis and/or treatment are limited to palivizumab and ribavirin. There are a number of promising compounds currently under development, including new monoclonal antibodies and small molecules. These newer antivirals have the potential to impact both the prevention and treatment of RSV disease in the main target populations.

Relating plaque morphology to respiratory syncytial virus subgroup, viral load, and disease severity in children

BACKGROUND

Viral culture plaque morphology in human cell lines are markers for growth capability and cytopathic effect, and have been used to assess viral fitness and select preattenuation candidates for live viral vaccines. We classified respiratory syncytial virus (RSV) plaque morphology and analyzed the relationship between plaque morphology as compared to subgroup, viral load and clinical severity of infection in infants and children.

METHODS

We obtained respiratory secretions from 149 RSV-infected children. Plaque morphology and viral load was assessed within the first culture passage in HEp-2 cells. Viral load was measured by polymerase chain reaction (PCR), as was RSV subgroup. Disease severity was determined by hospitalization, length of stay, intensive care requirement, and respiratory failure.

RESULTS

Plaque morphology varied between individual subjects; however, similar results were observed among viruses collected from upper and lower respiratory tracts of the same subject. Significant differences in plaque morphology were observed between RSV subgroups. No correlations were found among plaque morphology and viral load. Plaque morphology did not correlate with disease severity.

CONCLUSION

Plaque morphology measures parameters that are viral-specific and independent of the human host. Morphologies vary between patients and are related to RSV subgroup. In HEp-2 cells, RSV plaque morphology appears unrelated to disease severity in RSV-infected children.

Characterization of a respiratory syncytial virus L protein inhibitor

The respiratory syncytial virus (RSV) L protein is a viral RNA-dependent RNA polymerase that contains multiple enzyme activities required for RSV replication. The RSV L inhibitors described in literature are limited by their cytotoxicity or the lack of RSV B subtype coverage. Here, we characterize a new RSV L inhibitor with strong antiviral activity against both RSV A and B subtypes and no detectable cytotoxicity. This compound, AZ-27, was equally active against RSV live viruses and subgenomic replicons and demonstrated advantages over other classes of RSV inhibitors in time-of-addition and cell line dependency studies. Resistance studies identified a dominant mutation in the putative capping enzyme domain of L protein, which conferred strong resistance to the AZ-27 series but not other classes of RSV inhibitors, supporting RSV L protein as the direct target for AZ-27. This novel and broad-spectrum RSV L polymerase inhibitor may pave the way toward an efficacious RSV therapeutic and provide a new tool for interrogation of the L protein function.

Epidemiological changes of respiratory syncytial virus (RSV) infections in Israel

RSV is the leading cause of lower respiratory-tract infections in infants and therefore demands in-depth epidemiological characterization. We investigated here the distribution of RSV types in Israel between the years 2005–2012. Clinical samples were collected from 11,018 patients hospitalized due to respiratory illnesses and were evaluated for the presence of various respiratory viruses, including RSV A and RSV B. Until 2008, each year was characterized by the presence of one dominant type of RSV. However, from 2008, both RSV A and B types were detected at significant levels, particularly among infants aged 0–2 years. Furthermore, significant changes in the RSV A and RSV B subtypes circulating in Israel since 2008 were observed. Finally, we demonstrate that, irrespectively of the changes observed in RSV epidemiology, when the pandemic H1N1pdm09 influenza virus appeared in 2009, RSV infections were delayed and were detected when infection with H1N1pdm09 had declined.

Proof of principle for epitope-focused vaccine design

Vaccines prevent infectious disease largely by inducing protective neutralizing antibodies against vulnerable epitopes. Multiple major pathogens have resisted traditional vaccine development, although vulnerable epitopes targeted by neutralizing antibodies have been identified for several such cases. Hence, new vaccine design methods to induce epitope-specific neutralizing antibodies are needed. Here we show, with a neutralization epitope from respiratory syncytial virus (RSV), that computational protein design can generate small, thermally and conformationally stable protein scaffolds that accurately mimic the viral epitope structure and induce potent neutralizing antibodies. These scaffolds represent promising leads for research and development of a human RSV vaccine needed to protect infants, young children and the elderly. More generally, the results provide proof of principle for epitope-focused and scaffold-based vaccine design, and encourage the evaluation and further development of these strategies for a variety of other vaccine targets including antigenically highly variable pathogens such as HIV and influenza.

Medically attended respiratory syncytial virus infections in adults aged ≥ 50 years: clinical characteristics and outcomes

BACKGROUND

Few studies have examined respiratory syncytial virus (RSV) infections in adults. We assessed the characteristics and outcomes of RSV relative to other viral infections.

METHODS

Patients ≥ 50 years old with acute respiratory illness were recruited for studies of influenza vaccine effectiveness from 2004 through 2010. Nasopharyngeal swabs from enrollees were analyzed for the presence of RSV and other respiratory viruses by multiplex reverse transcription polymerase chain reaction. Clinical data were obtained from interview and medical records.

RESULTS

A total of 2225 samples were tested across all seasons. The mean age was 64.2 (SD, 10.7) years; the mean interval from illness onset to sample collection was 4 (SD, 2.2) days. One or more viruses were detected in 1202 (54%) participants. In a multivariable logistic regression model, RSV was associated with ages 65-79 years (vs 50-64 years), symptoms of cough, nasal congestion and wheezing, and longer interval from illness onset to clinical encounter. RSV was not associated with the presence of chronic obstructive pulmonary disease or congestive heart failure in univariate analyses. Hospital admission within 30 days after illness onset was less common among patients with RSV compared to those with influenza (unadjusted odds ratio = 0.54 [95% confidence interval, .29-1.01], P = .06).

CONCLUSIONS

RSV is a common cause of acute respiratory illness in adults aged ≥ 50 years; the risk of infection increases with age. Delays in healthcare seeking and reduced risk of hospital admission in patients with RSV suggest a milder course of illness relative to influenza.

Apnea in children hospitalized with bronchiolitis

OBJECTIVE

To identify risk factors for inpatient apnea among children hospitalized with bronchiolitis.

METHODS

We enrolled 2207 children, aged <2 years, hospitalized with bronchiolitis at 16 sites during the winters of 2007 to 2010. Nasopharyngeal aspirates (NPAs) were obtained on all subjects, and real-time polymerase chain reaction was used to test NPA samples for 16 viruses. Inpatient apnea was ascertained by daily chart review, with outcome data in 2156 children (98%). Age was corrected for birth <37 weeks. Multivariable logistic regression was performed to identify independent risk factors for inpatient apnea.

RESULTS

Inpatient apnea was identified in 108 children (5%, 95% confidence interval [CI] 4%-6%). Statistically significant, independent predictors of inpatient apnea included: corrected ages of <2 weeks (odds ratio [OR] 9.67) and 2 to 8 weeks (OR 4.72), compared with age ≥ 6 months; birth weight <2.3 kg (5 pounds; OR 2.15), compared with ≥ 3.2 kg (7 pounds); caretaker report of previous apnea during this bronchiolitis episode (OR 3.63); preadmission respiratory rates of <30 (OR 4.05), 30 to 39 (OR 2.35) and >70 (OR 2.26), compared with 40 to 49; and having a preadmission room air oxygen saturation <90% (OR 1.60). Apnea risk was similar across the major viral pathogens.

CONCLUSIONS

In this prospective, multicenter study of children hospitalized with bronchiolitis, inpatient apnea was associated with younger corrected age, lower birth weight, history of apnea, and preadmission clinical factors including low or high respiratory rates and low room air oxygen saturation. Several bronchiolitis pathogens were associated with apnea, with similar apnea risk across the major viral pathogens.