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

Integrating immunoinformatics and computational epitope prediction for a vaccine candidate against respiratory syncytial virus

Respiratory syncytial virus (RSV) poses a significant global health threat, especially affecting infants and the elderly. Addressing this, the present study proposes an innovative approach to vaccine design, utilizing immunoinformatics and computational strategies. We analyzed RSV's structural proteins across both subtypes A and B, identifying potential helper T lymphocyte, cytotoxic T lymphocyte, and linear B lymphocyte epitopes. Criteria such as antigenicity, allergenicity, toxicity, and cytokine-inducing potential were rigorously examined. Additionally, we evaluated the conservancy of these epitopes and their population coverage across various RSV strains. The comprehensive analysis identified six major histocompatibility complex class I (MHC-I) binding, five MHC-II binding, and three B-cell epitopes. These were integrated with suitable linkers and adjuvants to form the vaccine. Further, molecular docking and molecular dynamics simulations demonstrated stable interactions between the vaccine candidate and human Toll-like receptors (TLR4 and TLR5), with a notable preference for TLR4. Immune simulation analysis underscored the vaccine's potential to elicit a strong immune response. This study presents a promising RSV vaccine candidate and offers theoretical support, marking a significant advancement in vaccine development efforts. However, the promising in silico findings need to be further validated through additional in vivo studies.

Differences Between RSV A and RSV B Subgroups and Implications for Pharmaceutical Preventive Measures

INTRODUCTION

Understanding the differences between respiratory syncytial virus (RSV) subgroups A and B provides insights for the development of prevention strategies and public health interventions. We aimed to describe the structural differences of RSV subgroups, their epidemiology, and genomic diversity. The associated immune response and differences in clinical severity were also investigated.

METHODS

A literature review from PubMed and Google Scholar (1985-2023) was performed and extended using snowballing from references in captured publications.

RESULTS

RSV has two major antigenic subgroups, A and B, defined by the G glycoprotein. The RSV F fusion glycoprotein in the prefusion conformation is a major target of virus neutralizing antibodies and differs in surface exposed regions between RSV A and RSV B. The subgroups co-circulate annually, but there is considerable debate as to whether clinical severity is impacted by the subgroup of the infecting RSV strain. Large variations between the studies reporting RSV subgroup impact on clinical severity were observed. A tendency for higher disease severity may be attributed to RSV A but no consensus could be reached as to whether infection by one of the subgroup caused more severe outcomes. RSV genotype diversity decreased over the last two decades, and ON and BA have become the sole lineages detected for RSV A and RSV B, since 2014. No studies with data obtained after 2014 reported a difference in disease severity between the two subgroups. RSV F is relatively well conserved and highly similar between RSV A and B, but changes in the amino acid sequence have been observed. Some of these changes led to differences in F antigenic sites compared to reference F sequences (e.g., RSV/A Long strain), which are more pronounced in antigenic sites of the prefusion conformation of RSV B. Initial results from the second season after vaccination suggest specific RSV B efficacy wanes more rapidly than RSV A for RSV PreF-based monovalent vaccines.

CONCLUSIONS

RSV A and RSV B both contribute substantially to the global RSV burden. Both RSV subgroups cause severe disease and none of the available evidence to date suggests any differences in clinical severity between the subgroups. Therefore, it is important to implement measures effective at preventing disease due to both RSV A and RSV B to ensure impactful public health interventions. Monitoring overtime will be needed to assess the impact of waning antibody levels on subgroup-specific efficacy.

Microbiological and epidemiological features of respiratory syncytial virus

The properties of the main surface proteins and the viral cycle of the respiratory syncytial virus (RSV) make it an attractive pathogen from the perspective of microbiology. The virus gets its name from the manner it infects cells, which enables it to produce syncytia, which allow the virus' genetic material to move across cells without having to release viral offspring to the cellular exterior, reducing immune system identification. This causes a disease with a high impact in both children and adults over 60, which has sparked the development of several preventive interventions based on vaccines and monoclonal antibodies for both age groups. The epidemiological characteristics of this virus, which circulates in epidemics throughout the coldest months of the year and exhibits a marked genetic and antigenic drift due to its high mutation capability, must be taken into consideration while using these preventive methods. The most important microbiological and epidemiological elements of RSV are covered in this study, along with how they have affected the creation of preventive medications and their use in the future.

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.

Epidemiology of respiratory syncytial virus in a large pediatric hospital in Central Italy and development of a forecasting model to predict the seasonal peak

BACKGROUND

Respiratory Syncytial Virus (RSV) is responsible for the majority of acute lower respiratory infections in infants and can affect also older age groups. Restrictions linked to the emergence of the SARS-CoV-2 pandemic and their subsequent lifting caused a change in the dynamics of RSV circulation. It is therefore fundamental to monitor RSV seasonal trends and to be able to predict its seasonal peak to be prepared to the next RSV epidemics.

METHODS

We performed a retrospective descriptive study on laboratory-confirmed RSV infections from Bambino Gesù Children's Hospital in Rome from 1st January 2018 to 31st December 2022. Data on RSV-positive respiratory samples (n = 3,536) and RSV-confirmed hospitalizations (n = 1,895) on patients aged 0-18 years were analyzed. In addition to this, a SARIMA (Seasonal AutoRegressive Integrated Moving Average) forecasting model was developed to predict the next peak of RSV.

RESULTS

Findings show that, after the 2020 SARS-CoV-2 pandemic season, where RSV circulation was almost absent, RSV infections presented with an increased and anticipated peak compared to pre-pandemic seasons. While mostly targeting infants below 1 year of age, there was a proportional increase in RSV infections and hospitalizations in older age groups in the post-pandemic period. A forecasting model built using RSV weekly data from 2018 to 2022 predicted the RSV peaks of 2023, showing a reasonable level of accuracy (MAPE 33%). Additional analysis indicated that the peak of RSV cases is expected to be reached after 4-5 weeks from case doubling.

CONCLUSION

Our study provides epidemiological evidence on the dynamics of RSV circulation before and after the COVID-19 pandemic. Our findings highlight the potential of combining surveillance and forecasting to promote preparedness for the next RSV epidemics.

Development and validation of a respiratory syncytial virus multiplex immunoassay

PURPOSE

Respiratory syncytial virus (RSV) is one of the leading causes of severe respiratory disease in infants and adults. While vaccines and monoclonal therapeutic antibodies either are or will shortly become available, correlates of protection remain unclear. For this purpose, we developed an RSV multiplex immunoassay that analyses antibody titers toward the post-F, Nucleoprotein, and a diverse mix of G proteins.

METHODS

A bead-based multiplex RSV immunoassay was developed, technically validated to standard FDA bioanalytical guidelines, and clinically validated using samples from human challenge studies. RSV antibody titers were then investigated in children aged under 2 and a population-based cohort.

RESULTS

Technical and clinical validation showed outstanding performance, while methodological developments enabled identification of the subtype of previous infections through use of the diverse G proteins for approximately 50% of samples. As a proof of concept to show the suitability of the assay in serosurveillance studies, we then evaluated titer decay and age-dependent antibody responses within population cohorts.

CONCLUSION

Overall, the developed assay shows robust performance, is scalable, provides additional information on infection subtype, and is therefore ideally suited to be used in future population cohort studies.

RSV Disease Burden in Primary Care in Italy: A Multi-Region Pediatric Study, Winter Season 2022-2023

INTRODUCTION

Human respiratory syncytial virus (RSV) is one of the most frequent causes of respiratory infections in children under 5 years of age, but its socioeconomic impact and burden in primary care settings is still little studied.

METHODS

During the 2022/2023 winter season, 55 pediatricians from five Italian regions participated in our community-based study. They collected a nasal swab for RSV molecular test from 650 patients under the age of 5 with acute respiratory infections (ARIs) and performed a baseline questionnaire. The clinical and socioeconomic burden of RSV disease in primary care was evaluated by two follow-up questionnaires completed by the parents of positive children on Days 14 and 30.

RESULTS

RSV laboratory-confirmed cases were 37.8% of the total recruited ARI cases, with RSV subtype B accounting for the majority (65.4%) of RSV-positive swabs. RSV-positive children were younger than RSV-negative ones (median 12.5 vs. 16.5 months). The mean duration of symptoms for all children infected by RSV was 11.47 ± 6.27 days. We did not observe substantial differences in clinical severity between the two RSV subtypes, but RSV-A positive patients required more additional pediatric examinations than RSV-B cases. The socioeconomic impact of RSV infection was considerable, causing 53% of children to be absent from school, 46% of parents to lose working days, and 25% of families to incur extra costs.

CONCLUSIONS

Our findings describe a baseline of the RSV disease burden in primary care in Italy before the introduction of upcoming immunization strategies.

Recent advances in the prevention of respiratory syncytial virus in pediatrics

PURPOSE OF REVIEW

Respiratory syncytial virus (RSV) is a ubiquitous virus and the leading cause of pediatric hospitalization in the United States. Prevention strategies are key for reducing the burden of RSV. Several new agents aimed at preventing RSV in infants and children were FDA-approved in 2023, and many more are in the development pipeline. This review highlights new developments in RSV prevention in pediatric patients and the important safety considerations for clinical trials.

RECENT FINDINGS

Two new preventive therapies were FDA approved in 2023; a maternal vaccine (Abrysvo) and a mAb (Beyfortus) have both demonstrated reduction in medically attended lower respiratory tract infections in infants and children. Evaluation of ongoing clinical trials demonstrates that the field is expanding further to include direct immunization of infants and children utilizing a variety of delivery modalities. While these developments present the optimistic prospect of RSV prevention in a range of ages, acute and long-term risks must be carefully evaluated.

SUMMARY

Prevention of RSV is more accessible than ever, but careful consideration must be given to risks associated with new and developing prevention strategies. Rigor of clinical trials including longitudinal outcomes of agents in development and postmarketing surveillance of newly approved therapies will be of paramount importance to ensure long-term safety of new RSV prevention strategies.

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.

Respiratory syncytial virus: can we still believe that after pandemic bronchiolitis is not a critical issue for public health?

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection among infants and young children, resulting in annual epidemics worldwide. Since the beginning of the COVID-19 pandemic, non-pharmacological interventions were applied, interfering with the circulation of most respiratory viruses, including RSV. The aim of this study is to analyze the RSV infection trend among hospitalized infants during the actual epidemic season (2022-2023) in comparison with the last pre-pandemic season (2018-2019), in order to outline whether significant differences emerge due to COVID-19 pandemia. We retrospectively reviewed medical data on infants hospitalized at the Bambino Gesù Children's Hospital with diagnosis of bronchiolitis in the current epidemic season and in the last pre-pandemic season, 2018-2019. RSV remains the main etiological agent of bronchiolitis in terms of frequency and severity of infections in the ongoing epidemic season. The first RSV case of the 2022-2023 season was detected at week 42 vs week 47 in the 2018-2019 season. The length of epidemic season was of 17 weeks in 2022-2023 vs 18 weeks in 2018-2019. Comparing the two seasons, age at admission was significantly higher in the current season (median age 2022-2023 65 days vs median age 2018-2019 58 days), but the disease severity was similar.       Conclusions: The 2022-2023 bronchiolitis season in Italy started earlier than the usual pre-pandemic seasons but seasonality pattern may be going back to the pre-pandemic one. This season was not more severe than the previous ones. The impact of RSV disease on health care systems and costs remains a critical issue. What is Known: • RSV is one of the major leading causes of hospitalization among children aged less than 3 months. SarsCOV2 pandemic interfered with the seasonal circulation of most respiratory viruses, Including RSV. What is New: • The 2022-2023 bronchiolitis season in Italy started and peaked earlier than the usual pre-pandemic seasons but seasonality pattern may be realigning to the pre-pandemic one. The impact of RSV disease on health care systems and costs is concerning.

Impact of the publication of the Italian guidelines for bronchiolitis on the management of hospitalized children in Pisa, Italy

Bronchiolitis represents one of the major causes of hospitalization and mortality in children younger than 1 year, but its management continues to be heterogenous both in those who are hospitalized and in those who are not. To assess the impact of the publication of the Italian guidelines on bronchiolitis in October 2014, we analyzed data from children aged ≤12 months admitted for bronchiolitis at the University Hospital of Pisa from January 2010 to December 2019, dividing them into two groups based on whether admission was either preceding (Group 1) or following (Group 2) the publication of the guidelines. 346 patients (mean age 4.1 ± 2.8 months, 55% males) were admitted in the study period; 43.3%, 49.4%, and 7.3% of patients had mild, moderate or severe bronchiolitis, respectively. The mean length of hospital stay was 6.7 ± 2.9 days; 90.5% of the patients underwent nasal swab and 200 patients tested positive for RSV (in mono or coinfection with other viruses). We found no difference in RSV prevalence and severity distribution between the two groups, while we observed a significant reduction in the use of both chest X-rays (66.9% vs. 34.8%, p < 0.001), blood testing (93.4% vs. 58.2%, p < 0.001) and inhaled or systemic corticosteroids (93.1% vs. 47.8%, p < 0.001) in Group 2. No significant reduction in the use of antibiotics and of inhaled β2 agonists was found. Our data suggest that the publication of the Italian guidelines for bronchiolitis has contributed to improving the management of patients admitted for bronchiolitis in our Unit.

Increased RSV-A Bronchiolitis Severity in RSV-Infected Children Admitted to a Reference Center in Catalonia (Spain) Between 2014 and 2018

Between 2014 and 2018, we evaluated the severity of 687 cases of bronchiolitis caused by respiratory syncytial virus (RSV) in Catalonia, Spain. Compared to RSV-B, RSV-A cases required intensive care (adjusted relative risk (aRR) = 1.44, p < 0.01) and respiratory support (aRR = 1.07, p < 0.01) more often; hospital stay was one day longer (p < 0.01). Subgroup identification may aid clinical evaluation and seasonal healthcare planning.

Epidemiology and molecular characteristics of respiratory syncytial virus (RSV) among italian community-dwelling adults, 2021/22 season

BACKGROUND

Respiratory syncytial virus (RSV) is a leading cause of acute respiratory infections worldwide. While historically RSV research has been focused on children, data on RSV infection in adults are limited. The goal of this study was to establish the prevalence of RSV in community-dwelling Italian adults and analyze its genetic variability during the 2021/22 winter season.

METHODS

In this cross-sectional study, a random sample of naso-/oropharyngeal specimens from symptomatic adults seeking for SARS-CoV-2 molecular testing between December 2021 and March 2022 were tested for RSV and other respiratory pathogens by means of reverse-transcription polymerase chain reaction. RSV-positive samples were further molecularly characterized by sequence analysis.

RESULTS

Of 1,213 samples tested, 1.6% (95% CI: 0.9-2.4%) were positive for RSV and subgroups A (44.4%) and B (55.6%) were identified in similar proportions. The epidemic peak occurred in December 2021, when the RSV prevalence was as high as 4.6% (95% CI: 2.2-8.3%). The prevalence of RSV detection was similar (p = 0.64) to that of influenza virus (1.9%). All RSV A and B strains belonged to the ON1 and BA genotypes, respectively. Most (72.2%) RSV-positive samples were also positive for other pathogens being SARS-CoV-2, Streptococcus pneumoniae and rhinovirus the most frequent. RSV load was significantly higher among mono-detections than co-detections.

CONCLUSION

During the 2021/22 winter season, characterized by the predominant circulation of SARS-CoV-2 and some non-pharmaceutical containment measures still in place, a substantial proportion of Italian adults tested positive for genetically diversified strains of both RSV subtypes. In view of the upcoming registration of vaccines, establishment of the National RSV surveillance system is urgently needed.

Influence of Sex on Respiratory Syncytial Virus Genotype Infection Frequency and Nasopharyngeal Microbiome

Respiratory syncytial virus (RSV) has a significant health burden in children, older adults, and the immunocompromised. However, limited effort has been made to identify emergence of new RSV genotypes' frequency of infection and how the combination of nasopharyngeal microbiome and viral genotypes impact RSV disease outcomes. In an observational cohort designed to capture the first infant RSV infection, we employed multi-omics approaches to sequence 349 RSV complete genomes and matched nasopharyngeal microbiomes, during which the 2012/2013 season was dominated by RSV-A, whereas 2013 and 2014 was dominated by RSV-B. We found non-G-72nt-duplicated RSV-A strains were more frequent in male infants (P = 0.02), whereas G-72nt-duplicated genotypes (which is ON1 lineage) were seen equally in both males and females. DESeq2 testing of the nasal microbiome showed Haemophilus was significantly more abundant in infants with RSV-A infection compared to infants with RSV-B infection (adjusted P = 0.002). In addition, the broad microbial clustering of the abundant genera was significantly associated with infant sex (P = 0.03). Overall, we show sex differences in infection by RSV genotype and host nasopharyngeal microbiome, suggesting an interaction between host genetics, virus genotype, and associated nasopharyngeal microbiome. IMPORTANCE Respiratory syncytial virus (RSV) is one of the leading causes of lower respiratory tract infections in young children and is responsible for high hospitalization rates and morbidity in infants and the elderly. To understand how the emergence of RSV viral genotypes and viral-respiratory microbiome interactions contribute to infection frequency and severity, we utilized an observational cohort designed to capture the first infant RSV infection we employed multi-omics approaches to sequence 349 RSV complete genomes and matched nasopharyngeal microbiomes. We found non-G-72nt-duplicated RSV-A genotypes were more frequent in male infants, whereas G-72nt-duplicated RSV-A strains (ON1 lineage) were seen equally in both males and females. Microbiome analysis show Haemophilus was significantly more abundant in infants with RSV-A compared to infants with RSV-B infection and the microbial clustering of the abundant genera was associated with infant sex. Overall, we show sex differences in RSV genotype-nasopharyngeal microbiome, suggesting an interaction host genetics-virus-microbiome interaction.

Low Levels of RSV Testing Among Adults Hospitalized for Lower Respiratory Tract Infection in the United States

INTRODUCTION

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection (LRTI)-related hospitalizations in older adults. Without RSV-specific treatment for adults, testing is uncommon, leading to potential underestimation of RSV incidence in real-world data studies. This study aimed to quantify the frequency of RSV testing during LRTI-related hospitalizations of older adults to inform interpretation of incidence estimates.

METHODS

Administrative and billing data for hospitalizations of adults aged ≥ 65 years with a primary or secondary diagnosis of LRTI during the 2016-2019 RSV seasons (October-April) were extracted from the US all-payer Premier Healthcare Database (PHD). Billing codes identified RSV tests administered during eligible hospitalizations. The proportion of LRTI-related hospitalizations with a billed RSV test was calculated for each hospital in PHD, and summarized descriptively by hospital bed size, teaching status, and population served.

RESULTS

Most of the 937 study hospitals performed RSV testing infrequently during LRTI hospitalization; median percentage of LRTI hospitalizations with RSV testing was 4.3%, and 78.4% of hospitals performed RSV testing in less than 25% of LRTI-related hospitalizations. RSV testing varied extensively by hospital type. Median percentage tested was significantly higher for hospitals with ≥ 200 beds (9.1%) versus < 200 beds (1.6%), for teaching (11.0%) versus non-teaching (2.5%) hospitals, and in urban (7.4%) versus rural (0.7%) settings. The median percentage of RSV testing increased over time, from 0.8% to 6.3% between the 2016/17 and 2018/19 seasons.

CONCLUSION

A small proportion of older adults hospitalized with LRTI are tested for RSV in US hospitals. Large variability occurs across hospital types. Consequently, retrospective database analyses likely result in a substantial underestimation of the true RSV-related hospitalization incidence. RSV incidence studies using real-world data need to assess for RSV testing frequency and adjust their results for under ascertainment associated with limited testing.

Pre COVID-19 molecular epidemiology of respiratory syncytial virus (RSV) among children in Bangladesh

Epidemiological data of specific respiratory pathogens from the pre-COVID-19 period are essential to determine the effects of the COVID-19 pandemic on other respiratory infections. In this study, we revealed the pre-COVID-19 molecular epidemiology of respiratory syncytial virus (RSV) among children in Bangladesh. We tested 3170 samples collected from 2008 to 2012 for a panel of respiratory viruses; RSV, human metapneumovirus (hMPV), human parainfluenza viruses (hPIV) 1, 2, 3, and adenovirus. Five hundred fifty-five samples (17.5 %) were positive for RSV, including 2.5% having co-infections with other viruses. Genotypic characterization of RSV showed that RSV-A (82%) contributed more acute respiratory infections than RSV-B (18%). Clinical features were similar with RSV-A and RSV-B infections. However, children with RSV-B were more likely to have upper respiratory infections (URI) (10% vs. 29%, p = 0.03). Among RSV-A cases, hospitalization was higher for ON1 cases (25%, ON1 vs. 8%, NA1, p = 0.04), whereas the recovery without a disability was higher among the NA1 cases (56%, ON1 vs. 88%, NA1, p = 0.02). The time to the most recent common ancestor (TMRCA) for RSV in Bangladesh was 1949 for RSV-A and 1944 for RSV-B. This study revealed the genotypic diversity and evolutionary relatedness of RSV strains in Bangladesh and provided pre-COVID molecular epidemiology data to understand better the COVID-19 impact on upcoming RSV epidemiology in Bangladesh.

Controlled Human Infection Challenge Studies with RSV

Despite considerable momentum in the development of RSV vaccines and therapeutics, there remain substantial barriers to the development and licensing of effective agents, particularly in high-risk populations. The unique immunobiology of RSV and lack of clear protective immunological correlates has held back RSV vaccine development, which, therefore, depends on large and costly clinical trials to demonstrate efficacy. Studies involving the deliberate infection of human volunteers offer an intermediate step between pre-clinical and large-scale studies of natural infection. Human challenge has been used to demonstrate the potential efficacy of vaccines and antivirals while improving our understanding of the protective immunity against RSV infection. Early RSV human infection challenge studies determined the role of routes of administration and size of inoculum on the disease. However, inherent limitations, the use of highly attenuated/laboratory-adapted RSV strains and the continued evolutionary adaptation of RSV limits extrapolation of results to present-day vaccine testing. With advances in technology, it is now possible to perform more detailed investigations of human mucosal immunity against RSV in experimentally infected adults and, more recently, older adults to optimise the design of vaccines and novel therapies. These studies identified defects in RSV-induced humoral and CD8+ T cell immunity that may partly explain susceptibility to recurrent RSV infection. We discuss the insights from human infection challenge models, ethical and logistical considerations, potential benefits, and role in streamlining and accelerating novel antivirals and vaccines against RSV. Finally, we consider how human challenges might be extended to include relevant at-risk populations.

Management of Hospitalized Respiratory Syncytial Virus Bronchiolitis in the Pediatric Ward in Spain: Assessing the Impact of a New Clinical Practice Protocol

BACKGROUND

Bronchiolitis caused by the respiratory syncytial virus (RSV) is the main reason for hospitalization in infants. Supportive care is the mainstay of treatment, and tests are restricted to a few indications. During 2015, our hospital bronchiolitis protocol (2015 HBP) was updated according to the latest practice guidelines.

OBJECTIVE

The objective of this study was to assess implementation of the 2015 HBP and the clinical outcome of children aged ≤ 24 months with RSV bronchiolitis admitted to a pediatric ward.

METHODS

We compared the use of treatments and tests, hospital length of stay (LOS), and oxygen requirements before implementation of the 2015 HBP (2014-2015 and 2015-2016 seasons) and after implementation (2016-2017 and 2017-2018 seasons).

RESULTS

The study population comprised 251 children (44.90%) in the first period and 308 (55.10%) in the second (median age 99 days, interquartile range 44-233). After implementation of the 2015 HBP, a statistically significant reduction was found in the percentage of patients undergoing the following treatments or diagnostic tests: salbutamol, from 57.77 to 31.17% (p < 0.001); epinephrine, from 61.75 to 1.30% (p < 0.001); 3% hypertonic saline, from 70.12 to 6.82% (p < 0.001); antibiotics, from 33.07 to 23.05% (p = 0.008); and chest X-ray, from 43.82 to 31.17% (p = 0.001). No statistically significant reductions were observed in the use of corticosteroids and blood tests. Hospital LOS and oxygen requirements were similar in each period.

CONCLUSIONS

Appropriate implementation of the 2015 HBP in the pediatric ward improves the use of medication and chest X-ray without modifying clinical outcomes. However, further efforts are needed to reduce the use of salbutamol, corticosteroids, and blood tests.

Epidemiology and prevention of respiratory syncytial virus infections in children in Italy

Respiratory syncytial virus (RSV) is the leading global cause of respiratory infections in infants and the second most frequent cause of death during the first year of life. This highly contagious seasonal virus is responsible for approximately 3 million hospitalizations and 120,000 deaths annually among children under the age of 5 years. Bronchiolitis is the most common severe manifestation; however, RSV infections are associated with an increased long-term risk for recurring wheezing and the development of asthma. There is an unmet need for new agents and a universal strategy to prevent RSV infections starting at the time of birth. RSV is active between November and April in Italy, and prevention strategies must ensure that all neonates and infants under 1 year of age are protected during the endemic season, regardless of gestational age at birth and timing of birth relative to the epidemic season. Approaches under development include maternal vaccines to protect neonates during their first months, monoclonal antibodies to provide immediate protection lasting up to 5 months, and pediatric vaccines for longer-lasting protection. Meanwhile, improvements are needed in infection surveillance and reporting to improve case identification and better characterize seasonal trends in infections along the Italian peninsula. Rapid diagnostic tests and confirmatory laboratory testing should be used for the differential diagnosis of respiratory pathogens in children. Stakeholders and policymakers must develop access pathways once new agents are available to reduce the burden of infections and hospitalizations.

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.

Evolutionary analysis of human respiratory syncytial virus collected in Myanmar between 2015 and 2018

We studied genetic variation in the second hypervariable region (HVR) of the G gene of human respiratory syncytial virus (HRSV) from 1701 nasal swab samples collected from outpatients with acute respiratory infections at two general hospitals in the cities Yangon and Pyinmana in Myanmar from 2015 to 2018. HRSV genotypes were characterized using phylogenetic trees constructed using the maximum likelihood method. Time-scale phylogenetic tree analyses were performed using the Bayesian Markov chain Monte Carlo method. In total, 244 (14.3%) samples were HRSV-positive and were classified as HRSV-A (n = 84, 34.4%), HRSV-B (n = 158, 64.8%), and co-detection of HRSV-A/HRSV-B (n = 2, 0.8%). HRSV epidemics occurred seasonally between July (1.9%, 15/785) and August (10.5%, 108/1028), with peak infections in September (35.8%, 149/416) and October (58.2%, 89/153). HRSV infection rate was higher in children ≥1 year of age than in those <1 year of age (70.5% vs. 29.5%). The most common HRSV symptoms in children were cough (80%-90%) and rhinorrhea (70%-100%). The predominant genotypes were ON1for HRSV-A (78%) and BA9 for HRSV-B (64%). Time to the most recent common ancestor was 2014 (95% highest posterior density [HPD], 2012-2015) for HRSV-A ON1 and 2009 (95% HPD, 2004-2012) for HRSV-B BA9. The mean evolutionary rate (substitutions/site/year) for HRSV-B (2.12 × 10^-2, 95% HPD, 8.53 × 10^-3-3.63 × 10^-2) was slightly higher than that for HRSV-A (1.39 × 10^-2, 95% HPD, 6.03 × 10^-3-2.12 × 10^-2). The estimated effective population size (diversity) for HRSV-A increased from 2015 to 2016 and declined in mid-2018, whereas HRSV-B diversity was constant in 2015 and 2016 and increased in mid-2017. In conclusion, the dominant HRSV-A and HRSV-B genotypes in Myanmar were ON1 and BA9, respectively, between 2015 and 2018. HRSV-B evolved slightly faster than HRSV-A and exhibited unique phylogenetic characteristics.

Respiratory Syncytial Virus Bronchiolitis in Infancy: The Acute Hospitalization Cost

Introduction: Respiratory syncytial virus (RSV) bronchiolitis is among the leading causes of hospitalization in infants. Prophylaxis with palivizumab may reduce RSV infection, but its prescription is restricted to high-risk groups. The aim of the study is to retrospectively determine acute hospitalization costs of bronchiolitis. Materials and methods: Infants aged 1 month-1 year, admitted to Bambino Gesù Children Hospital, Rome, Italy, with a diagnosis of bronchiolitis from January 1 till December 31, 2017, were included in the study. Results: A total of 531 patients were enrolled in the study, and the mean age was 78.75 days. The main etiologic agent causing bronchiolitis was RSV, accounting for 58.38% of infections. The total cost of bronchiolitis hospitalization was 2,958,786 euros. The mean cost per patient was significantly higher in the case of RSV (5,753.43 ± 2,041.62 euros) compared to other etiology (5,395.15 ± 2,040.87 euros) (p = 0.04). Discussion: The study confirms the high hospitalization cost associated with bronchiolitis. In detail, in the case of RSV etiology, the cost was higher compared to other etiology, which is likely due to the longer hospitalization and the more frequent admission to the intensive cure department. Conclusion: This study highlights that bronchiolitis is an important cost item even in a tertiary hospital and that cost-effective interventions targeting RSV are increasingly urgent.

Respiratory Syncytial Virus in Greece, 2016-2018

Human respiratory syncytial virus (RSV) is the leading cause of acute bronchiolitis in infants and young children. Children under the age of 2 years, hospitalized for bronchiolitis in the pediatric clinic of a tertiary hospital in northern Greece, were tested for RSV infection during two RSV seasons (2016-2017 and 2017-2018). RSV was detected in 37 of 71 (52.1%) patients, most of them younger than 6 months. Both RSV subtypes were detected - RSV-A (54.1%) and RSV-B (45.9%) - with predominance of RSV-A during the 2016-2017 and RSV-B during the 2017-2018 season. RSV-A and RSV-B sequences clustered within the ON1 and BA genotypes, respectively. Compared to the prototype strains, several amino acid substitutions were observed in the duplication region of the G gene. The study provides a first insight into the molecular epidemiology of RSV in Greece.