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Background: Following the pandemic restrictions, the epidemiology of respiratory syncytial virus (RSV) has changed, leading to intense hospitalization peaks., Objectives: This study, conducted at multiple sites in Italy, aimed to describe the temporal dynamics of two post-COVID-19 RSV epidemics. Additionally, the circulating RSV-A and -B lineages were characterized and compared to those found in 2018 and 2019., Study Design: Respiratory specimens and data were collected from RSV-positive patients, both inpatients, and outpatients, of all ages at three sites in north-central Italy. To analyze these samples, roughly one-sixth were sequenced in the attachment glycoprotein G gene and subjected to phylogenetic and mutational analyses, including pre-pandemic sequences from north-central Italy., Results: The first post-pandemic surge of RSV cases was quite intense, occurring from October 2021 to early January 2022. The subsequent RSV epidemic (from November 2022 to early March 2023) also had a high impact, characterized by a rise in elderly patient cases. Post-pandemic cases of RSV-A were caused by various strains present in Italy prior to COVID-19. In contrast, a distinct RSV-B lineage, which was concurrently spreading in other countries, was identified as the main cause of the surge in 2022-2023 but remained undetected in Italy before the pandemic., Conclusions: This study describes the temporal dynamics of post-pandemic RSV subgroups and uncovers a lineage of RSV-B with high genetic divergence that may have increased the impact of decreased population immunity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Our aim was to hypothesize that the COVID-19 pandemic influenced the characteristics of viral bronchiolitis by comparing the last 3 epidemics with 3 pre-COVID-19 epidemics in infants hospitalized with bronchiolitis., Methods: We prospectively enrolled 637 consecutive infants (median age 3.0 ± 2.1 months, 58.5% males), hospitalized for bronchiolitis during 6 consecutive annual epidemic seasons from 2017 to 2023. All parents of the children were given a structured anamnestic questionnaire. A nasopharyngeal aspirate was tested for 15 respiratory viruses. As measures of severity, we evaluated the O 2 supplementation and the admission at the pediatric intensive care unit., Results: A total of 166 were hospitalized with bronchiolitis in 2017-2018, 97 in 2018-2019, 69 in 2019-2020, 0 in 2020-2021, 129 in 2021-2022 and 176 in 2022-2023. Taking together the 332 bronchiolitis cases hospitalized during the 3 prepandemic seasons, they peaked between December and January; after the flat curve in 2020-2021, the cases of bronchiolitis peaked in November 2021 and in December 2022. While the 2021-2022 season registered a less severe clinical presentation, O 2 supplementation and pediatric intensive care unit admissions increased in 2022-2023 with respect to the prepandemic seasons ( P < 0.001)., Conclusions: This study represents an important scientific demonstration of the impact of primary prevention measures on the epidemiology of viral infections; their fluctuations were related to the intensity of restrictive measures and to the changing trend of respiratory viruses. It is essential to predict the real temporal trend of bronchiolitis not to leave high-risk children uncovered and to guide hospitals to maintain a high level of readiness., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Acute bronchiolitis is a viral infection of the lower respiratory tract affecting infants aged under 12 months, variably presenting with respiratory distress, diffuse crackles and inflammatory wheezing. The main causative agent is Respiratory Syncytial Virus (RSV). The diagnosis is clinical and treatment mainly supportive. Despite the availability of more than 30 international guidelines, consistent management recommendations are lacking and considerable variability in patients' care persists among different providers., Objective: To review and describe current knowledge about epidemiology, physiopathology, clinic, diagnosis and management of acute bronchiolitis, with particular emphasis on updated evidence and future perspectives in terms of treatment and prevention., Methods and Results: We searched Cochrane for systematic reviews and PubMed for scientific articles published in the last 10 years, using a combination of the following search terms: "bronchiolitis", "respiratory syncytial virus", "epidemiology", "risk factors", "severity", "diagnosis", "clinic", "diagnostic imaging", "management", "asthma", "wheezing", "bronchodilator", "steroids", "hypertonic saline", "oxygen", "blood gas analysis", "HHHFNC", "rehydration", "enteral feeding", "parenteral hydration", "prevention", "vaccine" and "COVID-19 or SARS-CoV2". We accordingly performed a deep and extensive selection of the most updated and considerable literature on the matter, summarizing the most significant evidence concerning all aspects of acute bronchiolitis (epidemiology, clinic, diagnosis, management and prevention). Furthermore, we examined references and available guidelines from UK, USA, Canada, Italy and Spain. Results are extensively discussed below., Conclusion: Although acute bronchiolitis has been a widely known disease for decades, its therapeutic approach remained unchanged and essentially limited to respiratory and metabolic support. Despite the abundance of studies, there is no significant evidence concerning therapeutic alternatives (e.g. steroids, inhaled hypertonic solution), which are therefore not recommended. According to most recent data, "acute bronchiolitis" definition encompasses a plethora of different clinical entities related to each subject's genetic and immune predisposition. Therefore, future research should focus on the precise characterization of such subcategories in order to individualize therapeutic management and ensure the most appropriate evidence-based care., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

New technologies for the prevention of infectious diseases are emerging to address unmet medical needs, in particular, the use of long-acting monoclonal antibodies (mAb) to prevent Respiratory Syncytial Virus (RSV) lower respiratory tract disease in infants during their first RSV season. The lack of precedent for mAbs for broad population protection creates challenges in the assessment of upcoming prophylactic long-acting mAbs for RSV, with associated consequences in legislative and registration categorization, as well as in recommendation, funding, and implementation pathways. We suggest that the legislative and regulatory categorization of preventative solutions should be decided by the effect of the product in terms of its impact on the population and health-care systems rather than by the technology used or its mechanism of action. Immunization can be passive and active, both having the same objective of prevention of infectious diseases. Long-acting prophylactic mAbs work as passive immunization, as such, their recommendations for use should fall under the remit of National Immunization Technical Advisory Groups or other relevant recommending bodies for inclusion into National Immunization Programs. Current regulations, policy, and legislative frameworks need to evolve to embrace such innovative preventative technologies and acknowledge them as one of key immunization and public health tools.

Bronchiolitis is an acute respiratory illness that is the leading cause of hospitalization in young children. This document aims to update the consensus document published in 2014 to provide guidance on the current best practices for managing bronchiolitis in infants. The document addresses care in both hospitals and primary care. The diagnosis of bronchiolitis is based on the clinical history and physical examination. The mainstays of management are largely supportive, consisting of fluid management and respiratory support. Evidence suggests no benefit with the use of salbutamol, glucocorticosteroids and antibiotics with potential risk of harm. Because of the lack of effective treatment, the reduction of morbidity must rely on preventive measures. De-implementation of non-evidence-based interventions is a major goal, and educational interventions for clinicians should be carried out to promote high-value care of infants with bronchiolitis. Well-prepared implementation strategies to standardize care and improve the quality of care are needed to promote adherence to guidelines and discourage non-evidence-based attitudes. In parallel, parents' education will help reduce patient pressure and contribute to inappropriate prescriptions. Infants with pre-existing risk factors (i.e., prematurity, bronchopulmonary dysplasia, congenital heart diseases, immunodeficiency, neuromuscular diseases, cystic fibrosis, Down syndrome) present a significant risk of severe bronchiolitis and should be carefully assessed. This revised document, based on international and national scientific evidence, reinforces the current recommendations and integrates the recent advances for optimal care and prevention of acute bronchiolitis., (© 2023. The Author(s).)

Aim: Emergency room admissions have decreased globally during the COVID-19 pandemic, particularly for respiratory diseases. We evaluated hospital admissions for respiratory diseases in the first year of the Italian pandemic and compared them with the corresponding period in 2016-2017., Methods: The study was carried out at the Sapienza University in Rome, Italy, and covered 9 March to 28 February 2020-2021 and 2016-2017. We tested 85 hospitalised children who were negative for the virus that causes COVID-19 in 2020-2021 and compared them with 476 hospitalised children from 2016-2017, as we had also tested nasal washing samples for 14 respiratory viruses during that period., Results: Hospitalisations for acute respiratory tract infections were 82.2% lower in 2020-2021 than 2016-2017. The respiratory syncytial virus (RSV) and several other viruses were detected less frequently during the pandemic. An extraordinary finding was that rhinoviruses remained seasonal. In 2020-2021, we detected a virus in 54.1% of the hospitalised children: rhinoviruses in 41, RSV in 4 and other viruses in 1. This was significantly lower than the 71.6% in 2016-2017: RSV in 130, rhinoviruses in 128 and other viruses in 83., Conclusion: Pandemic measures dramatically reduced childhood respiratory infections, particularly RSV, but were less effective at reducing rhinoviruses., (©2022 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.)

Background: Bronchiolitis is the most frequent cause of hospitalization in infants younger than 1 year of age. We sought to evaluate the correlation between lymphocyte count and clinical manifestation in infants hospitalized with bronchiolitis., Materials and Methods: We performed a retrospective cohort study evaluating 1297 children hospitalized for bronchiolitis from 2004 to 2019. A nasal washing was tested for 14 respiratory viruses by PCR. A clinical severity score, ranging 0-8, was assigned at hospital admission. History and clinical course were recorded for each infant. Patients were divided in 3 groups according to lymphocyte count tertiles. Parents of enrolled patients have been phoned annually over 5 years to evaluate respiratory sequelae., Results: A total of 433 children had 2914.2 ± 745.5/mm 3 lymphocytes (Group 1), 432 had 4897.6 ± 561.5/mm 3 lymphocytes (Group 2) and 432 had 7884 ± 1903.3/mm 3 lymphocytes (Group 3). Group 1 patients were more frequently infected by RSV and presented with fever, a worse clinical severity score. They more frequently needed oxygen supplementation, underwent a prolonged hospitalization needed to be admitted to pediatric intensive care unit. Finally, they had more frequently a family history of eczema, wheezing and asthma. We found no differences between lymphocytes count and respiratory sequelae (at least two episodes of wheezing per year)., Conclusions: Infants with low lymphocyte count are more likely to have a worse clinical course of bronchiolitis., (© 2022 Wiley Periodicals LLC.)

Background: The heterogeneity of bronchiolitis may imply or reflect a different predisposition to respiratory sequelae., Objective: Our aim was to investigate whether, among infants hospitalized with bronchiolitis, different clinical profiles extracted by latent class analysis (LCA) are associated with different risks of wheezing., Methods: Over 15 consecutive epidemic seasons (2004-2019), we prospectively enrolled infants <1 year hospitalized for the first episode of bronchiolitis in a single tertiary hospital. A detailed clinical questionnaire was filled for each infant. LCA was applied to differentiate bronchiolitis phenotypes, and after hospital discharge, a phone interview was performed annually to record the presence of wheezing episodes. Adjusted multivariate regression analyses were run to investigate the risk of wheezing during 7 years follow-up according to clinical phenotypes., Results: LCA performed on 1312 infants resulted in a three-class model. Profile 1 (65.5%): moderate bronchiolitis; Profile 2 (6.1%): severe bronchiolitis; and Profile 3(28.4%): bronchiolitis infants with high eosinophils blood count. At 1 year of follow up, about 50% of children presented wheezing in each profile. Compared to Profile 1, the adjusted odds ratio (OR) of having wheezing episodes was significantly higher in Profile 2 at 2, 3, and 4 years of follow-up. At 7 years, Profile 3 had an adjusted OR = 2.58, higher than Profile 2 (adjusted OR = 2.29)., Conclusions: LCA clearly identified a "moderate", "severe," and "high eosinophils blood count" bronchiolitis. During the first 4 years after bronchiolitis, the "severe" profile showed the higher risk of wheezing, but after 7 years this risk seems higher in the "high eosinophils blood count" group., (© 2021 Wiley Periodicals LLC.)

The diffusion of the SARS-CoV-2 virus and the implementation of restrictive measures led to a drastic reduction of respiratory syncytial virus (RSV) diffusion. Few RSV cases have been detected worldwide, even after the removal of the restrictions. We review the current literature and present possible explanations on why there has been a significant reduction of RSV detection during the COVID-19 pandemic. We also hypothesize what may happen when RSV begins to circulate again. The increase of an immunologically naïve population, with infants born from mothers who have not reinforced their immunity to RSV, could lead to greater RSV epidemics in the coming seasons. It is crucial to prepare the scientific community and to keep RSV surveillance active to avoid dramatic consequences., (© 2021 Wiley Periodicals LLC.)

Background: Social distancing measures are used to reduce the spreading of COVID-19. The aim of this study was to assess the impact of local restrictions on the transmission of respiratory virus infections., Methods: we retrospectively analyzed the nasopharyngeal samples of all patients (0-18 years old) admitted with respiratory symptoms in a large Italian tertiary hospital during the last three seasons from 2018 to 2021., Results: A strong reduction in all viral respiratory infections was observed in the last season (2020-2021) compared to the two previous seasons (-79.69% and -80.66%, respectively). In particular, we found that during the epidemic period 2018-2019 and 2019-2020, the total number of Respiratory Syncytial Virus (RSV) cases was, respectively 726 and 689, while in the last season a total of five cases was detected. In the first months of 2018-2019 and 2019-2020, the total flu infections were 240 and 354, respectively, while in the last season we did not detect any influenza virus. As other viruses, the presence of Rhinovirus declined, but to a lesser extent: a total of 488 cases were assessed compared to the 1030 and 1165 cases of the two previous respective epidemic seasons., Conclusions: Public health interventions and distancing (including continuous use of face masks) settled to counter the pandemic spread of COVID-19 had a macroscopic impact on all respiratory virus transmission and related diseases, with a partial exception of Rhinovirus. The absence of viruses' circulation could result in a lack of immunity and increased susceptibility to serious infections in the next seasons.

Background: A study of respiratory syncytial virus-A (RSV A) genotype ON1 genetic variability and clinical severity in infants hospitalized with bronchiolitis over 6 epidemic seasons (2012-2013 to 2017-2018) was carried out., Methods: From prospectively enrolled term infants hospitalized for bronchiolitis, samples positive for RSV A ON1 (N = 139) were sequenced in the second half of the G gene. Patients' clinical data were obtained from medical files and each infant was assigned a clinical severity score. ANOVA comparison and adjusted multinomial logistic regression were used to evaluate clinical severity score and clinical parameters., Results: The phylogenetic analysis of 54 strains showed 3 distinct clades; sequences in the last 2 seasons differed from previous seasons. The most divergent and numerous cluster of 2017-2018 strains was characterized by a novel pattern of amino acid changes, some in antigenic sites. Several amino acid changes altered predicted glycosylation sites, with acquisition of around 10 new O-glycosylation sites. Clinical severity of bronchiolitis increased in 2016-2017 and 2017-2018 and changed according to the epidemic seasons only., Conclusions: Amino acid changes in the hypervariable part of G protein may have altered functions and/or changed its immunogenicity, leading to an impact on disease severity., (© The Author(s) 2020. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

Bronchiolitis severity is determined by a complex interaction among viral replication and antiviral immunity. The current respiratory syncytial virus (RSV)-A, genotype ON1 demonstrated a high replicative capacity but seemed to be clinically less severe than the previously circulating RSV-A, NA1. To learn insights about ON1 innate immune response, we analyzed expression levels of type I/III interferon (IFN)-related genes in the respiratory mucosa of infants with RSV bronchiolitis. We enrolled RSV-positive bronchiolitis patients over 12 epidemic seasons at a university hospital in Rome. From nasopharyngeal washings' cells (46 positive to NA1, 47 to ON1 and 28 to RSV-B, genotype BA), the mRNA copy number of the type III IFN receptor (IFNLR1 and IL10RB subunits), and of the type I/III IFN-stimulated genes, MxA and ISG56, was calculated using the threshold cycle relative quantification method with respect to an invariant gene. Expression levels of type III IFN receptor subunits genes positively correlated to each other and did not differ in infants infected with different RSV genotypes. The ISGs levels also positively correlated between them but differed among groups. MxA levels were significantly higher in NA1-infected infants than in those with ON1 and BA; ISG56 expression was slightly higher in NA1 than in the other strains. Interestingly, a moderate negative correlation existed between viral load and both ISGs values in ON1-infected infants only. The reduced ISG levels elicited during infections with ON1 (and BA) may cause a weaker control of RSV replication and/or an inadequate host immune response which may impact the risk of respiratory sequelae.

Aim: To test the hypothesis that the balance of type-1/type-2 immune response differs between infants hospitalized with respiratory syncytial virus (RSV) bronchiolitis during the peak months and those during the nonpeak months., Methods: We prospectively enrolled 90 unrelated full-term previously healthy infants hospitalized during the first year of life for RSV sole bronchiolitis over 2 epidemics (November 2016 to April 2017 and October 2017 to April 2018). We stratified infants as follows: hospitalized during the peak months (n: 71) and during the nonpeak months (n: 19). The frequencies of CD4+ producing interferon (IFN)-γ and interleukin (IL)-4 and of CD8+ producing IFN-γ T cells were measured by flow cytometry from infant peripheral whole blood. The T-helper cell (Th2) polarization index was calculated as the ratio between CD4+ T cells producing IL-4 and CD4+ T cells producing IFN-γ., Results: Infants hospitalized during nonpeak months were significantly less frequently breast-fed, had a higher eosinophils count, a significantly higher percentage of CD4+ T cells producing IL-4 and higher Th2 polarization index than infants hospitalized during the peak months., Conclusions: We elucidated the presence of different endotypes in infants with RSV sole bronchiolitis. Previously healthy full-term infants hospitalized during the nonpeak months seem to be more likely those with a possible predisposition to atopy.

Background: The only pharmacologic prophylaxis against respiratory syncytial virus (RSV) infection in preterm infants is the humanized monoclonal antibody palivizumab. After the 2014 modification of the American Academy of Pediatrics (AAP) recommendations, the Italian Medicines Agency (AIFA) limited the financial coverage for palivizumab prescriptions to otherwise healthy preterm infants with < 29 weeks of gestational age (wGA) aged < 12 months at the beginning of the 2016-2017 RSV season. However, due to the effect on disease severity and hospitalizations following this limitation, shown by several Italian clinical studies, in November 2017 AIFA reinstated the financial coverage for these infants. In this systematic review, we critically summarize the data that show the importance of palivizumab prophylaxis., Methods: Data from six Italian pediatric institutes and the Italian Network of Pediatric Intensive Care Units (TIPNet) were retrieved from the literature and considered. The epidemiologic information for infants 29-36 wGA, aged < 12 months and admitted for viral-induced acute lower respiratory tract infection were retrospectively reviewed. RSV-associated hospitalizations were compared between the season with running limitation, i.e. 2016-2017, versus 2 seasons before (2014-2015 and 2015-2016) and one season after (2017-2018) the AIFA limitation., Results: During the 2016-2017 RSV epidemic season, when the AIFA limited the financial coverage of palivizumab prophylaxis based on the 2014 AAP recommendation, the study reports on a higher incidences of RSV bronchiolitis and greater respiratory function impairment. During this season, we also found an increase in hospitalizations and admissions to the Pediatric Intensive Care Units and longer hospital stays, incurring higher healthcare costs. During the 2016-2017 epidemic season, an overall increase in the number of RSV bronchiolitis cases was also observed in infants born full term, suggesting that the decreased prophylaxis in preterm infants may have caused a wider infection diffusion in groups of infants not considered to be at risk., Conclusions: The Italian results support the use of palivizumab prophylaxis for otherwise healthy preterm (29-36 wGA) infants aged < 6 months at the beginning of the RSV season.

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.

Background: In this study we sought to evaluate the association between viral bronchiolitis, weather conditions, and air pollution in an urban area in Italy., Methods: We included infants hospitalized for acute bronchiolitis from 2004 to 2014. All infants underwent a nasal washing for virus detection. A regional agency network collected meteorological data (mean temperature, relative humidity and wind velocity) and the following air pollutants: sulfur dioxide, nitrogen oxide, carbon monoxide, ozone, benzene and suspended particulate matter measuring less than 10µm (PM 10 ) and less than 2.5µm (PM 2.5 ) in aerodynamic diameter. We obtained mean weekly concentration data for the day of admission, from the urban background monitoring sites nearest to each child's home address. Overdispersed Poisson regression model was fitted and adjusted for seasonality of the respiratory syncytial virus (RSV) infection, to evaluate the impact of individual characteristics and environmental factors on the probability of a being positive RSV., Results: Of the 723 nasal washings from the infants enrolled, 266 (68%) contained RSV, 63 (16.1%) rhinovirus, 26 (6.6%) human bocavirus, 20 (5.1%) human metapneumovirus, and 16 (2.2%) other viruses. The number of RSV-positive infants correlated negatively with temperature (p < 0.001), and positively with relative humidity (p < 0.001). Air pollutant concentrations differed significantly during the peak RSV months and the other months. Benzene concentration was independently associated with RSV incidence (p = 0.0124)., Conclusions: Seasonal weather conditions and concentration of air pollutants seem to influence RSV-related bronchiolitis epidemics in an Italian urban area., (Copyright © 2017. Published by Elsevier Inc.)

Bronchiolitis is the leading cause of hospitalization in infants under 12 months. Our aims were to analyze epidemiological characteristics of infants with bronchiolitis over 10 consecutive seasons and to evaluate whether there are any clinical differences between infants hospitalized for bronchiolitis during epidemic peak months and infants in non-peak months. We enrolled consecutive enrolled 723 previously healthy term infants hospitalized at the Paediatric Emergency Department, "Sapienza" University of Rome over the period 2004-2014. Fourteen respiratory viruses were detected from nasopharyngeal aspirates by molecular methods. Clinical and demographic data were extracted from clinical charts. Viruses were detected in 351 infants (48.5%): RSV in 234 (32.4%), RV in 44 (6.1%), hBoV in 11 (1.5%), hMPV in 12 (1.6%), co-infections in 39 (5.4%), and other viruses in 11 (1.5%). Analyzing the 10 epidemic seasons, we found higher incidence for bronchiolitis every 4 years with a peak during the months December-January. Infants hospitalized during peak months had lower family history for asthma (P = 0.003), more smoking mothers during pregnancy (P = 0.036), were slightly higher breastfed (0.056), had lower number of blood eosinophils (P = 0.015) and had a higher clinical severity score (P = 0.017). RSV was detected mostly during peak months, while RV was equally distributed during the seasons. We found some variations in bronchiolitis incidence during epidemics, and discriminative characteristics in infants hospitalized for bronchiolitis during peak months and in non-peak months, that might reflect two different populations of children. Pediatr Pulmonol. 2016;51:1330-1335. © 2016 Wiley Periodicals, Inc., (© 2016 Wiley Periodicals, Inc.)

The relationship between viral infection, host immune response in infants with respiratory syncytial virus (RSV) bronchiolitis and subsequent wheezing is discussed. We measured RSV-RNA load and interferon-λ1-3 expression in the nasopharyngeal washings from 68 infants hospitalized for RSV bronchiolitis, and wheezing was assessed 36 months after the first episode of bronchiolitis. Higher RSV-RNA load and higher interferon-λ2/3 levels were found in children with recurrent wheezing at 36-month follow-up.

Objectives: The airway expression of type III interferons (IFNs) was evaluated in infants hospitalized for respiratory syncytial virus (RSV) or rhinovirus (HRV) bronchiolitis. As an additional objective we sought to determine whether a different expression of IFN lambda 1-3 was associated with different harboring viruses, the clinical course of bronchiolitis or with the levels of well established IFN stimulated genes (ISGs), such as mixovirus resistance A (MxA) and ISG56., Methods: The analysis was undertaken in 118 infants with RSV or HRV bronchiolitis. Nasopharyngeal washes were collected for virological studies and molecular analysis of type III IFN responses., Results: RSV elicited higher levels of IFN lambda subtypes when compared with HRV. A similar expression of type III IFN was found in RSVA or RSVB infected infants and in those infected with HRVA or HRVC viruses. Results also indicate that IFN lambda 1 and IFN lambda 2-3 levels were correlated with each other and with MxA and ISG56-mRNAs. In addition, a positive correlation exists between the IFN lambda1 levels and the clinical score index during RSV infection. In particular, higher IFN lambda 1 levels are associated to an increase of respiratory rate., Conclusions: These findings show that differences in the IFN lambda 1-3 levels in infants with RSV or HRV infections are present and that the expression of IFN lambda 1 correlates with the severity of RSV bronchiolitis., (Copyright © 2014 The British Infection Association. Published by Elsevier Ltd. All rights reserved.)

The relationship between viral load, disease severity and antiviral immune activation in infants suffering from respiratory syncytial virus (RSV)-associated bronchiolitis has not been well identified. The main objective of this study was to determine the existence of a correlation between RSV load and disease severity and also between different clinical markers and mRNA levels of the interferon stimulated gene (ISG)56 in infants hospitalized for bronchiolitis. We also evaluated whether viral load tended to be persistent over the course of the RSV infection. The levels of RSV-RNA were quantified in nasopharyngeal washings, collected from 132 infants infected with RSV as a single (90.15%) or as a dual infection with other respiratory viruses (9.85%). Results indicated that viral load was positively related to the clinical severity of bronchiolitis, the length of hospital stay, the levels of glycemia and the relative gene expression of ISG56, whereas an inverse correlation was observed with the levels of hemoglobin. We also found that the RSV load significantly decreased between the first and second nasopharingeal washings sample in most subjects. These results suggest that infants with high RSV load on hospital admission are more likely to have both more severe bronchiolitis and a higher airway activation of antiviral immune response.

Given the critical role of pattern recognition receptors (PRRs) in acid nucleic recognition in the initiation of innate immunity and the orchestration of adaptive immunity, the aim of this study was to determine whether any heterogeneity of PRR expression in the airway tracts of infants with respiratory syncytial virus (RSV) infection might explain the broad clinical spectrum of RSV-associated bronchiolitis in infants. For this purpose, the levels of melanoma differentiation-associated protein-5 (MDA-5), retinoic acid inducible gene-1 (RIG-1), and Toll-like receptor 3 (TLR-3), TLR-7, TLR-8, and TLR-9 mRNAs were evaluated, using TaqMan quantitative reverse transcription-PCR, in cells from nasopharyngeal washes collected from 157 infants suffering from acute bronchiolitis whether or not they were associated with respiratory viruses. High interindividual variability was observed in both virus-positive and -negative infants; however, the relative gene expression levels of MDA-5, RIG-1, TLR-7, and TLR-8 were significantly higher in the virus-infected group, whereas the expression levels of TLR-3 and TLR-9 were not significantly different. The differences in the gene expression of MDA-5, RIG-1, TLR-7, and TLR-8 were more evident in infants with RSV infection than in those with bocavirus or rhinovirus infection. In RSV-infected infants, PRR-mRNA levels also were analyzed in relation to interferon protein levels, viral load, clinical severity, days of hospitalization, age, and body weight. A significant positive correlation was observed only between RSV viral load and RIG-1 mRNA levels. These findings provide the first direct evidence that, in infants with respiratory virus-associated bronchiolitis, especially RSV, there are substantial changes in PRR gene expression; this likely is an important determinant of the clinical outcome of bronchiolitis.

Respiratory diseases caused by respiratory syncytial virus (RSV) and human rhinovirus (HRV) are frequent causes of the hospitalization of children; nonetheless, RSV is responsible for the most severe and life-threatening illnesses. Viral infection triggers an inflammatory response, activating interferon (IFN)-mediated responses, including IFN-stimulated genes (ISG) expression with antiviral and immunomodulatory activities. In parallel, the reactive oxygen species (ROS) production activates nuclear factor erythroid 2-related factor 2 (NRF2), whose antioxidant activity can reduce inflammation by interacting with the NF-kB pathway and the IFN response. To clarify how the interplay of IFN and NRF2 may impact on clinical severity, we enrolled children hospitalized for bronchiolitis and pneumonia, and measured gene expression of type-I and III IFNs, of several ISGs, of NRF2 and antioxidant-related genes, i.e., glucose-6-phosphate dehydrogenase (G6PD), heme oxygenase 1 (HO1), and NAD(P)H dehydrogenase [Quinone] 1 (NQO1) in RSV- (RSV-A N = 33 and RSV-B N = 30) and HRV (N = 22)-positive respiratory samples. NRF2 and HO1 expression is significantly elevated in children with HRV infection compared to RSV (p = 0.012 and p = 0.007, respectively), whereas ISG15 and ISG56 expression is higher in RSV-infected children (p = 0.016 and p = 0.049, respectively). Children admitted to a pediatric intensive care unit (PICU) had reduced NRF2 expression (p = 0.002). These data suggest, for the first time, that lower activation of the NRF2 antioxidant response in RSV-infected infants may contribute to bronchiolitis severity. [ABSTRACT FROM AUTHOR]

Although recent guidelines recommend a minimalist approach to bronchiolitis, there are several issues with this posture. First, there are concerns about the definition of the disease, the quality of the guidelines, the method of administration of bronchodilators, and the availability of tools to evaluate the response to therapies. Second, for decades it has been assumed that all cases of viral bronchiolitis are the same, but recent evidence has shown that this is not the case. Distinct bronchiolitis phenotypes have been described, with heterogeneity in clinical presentation, molecular immune signatures and clinically relevant outcomes such as respiratory failure and recurrent wheezing. New research is critically needed to refine viral bronchiolitis phenotyping at the molecular and clinical levels as well as to define phenotype-specific responses to different therapeutic options. [ABSTRACT FROM AUTHOR]