Respiratory syncytial virus and parainfluenza virus

Structure switching aptamer enhance sensitivity and specificity of photonic crystal-based sensors for RSV-G protein detection

Photonic crystal-based aptasensors for viral proteins detection offer the advantage of producing visible readouts. However, they usually suffer from limited sensitivity and high non-specific background noise. A significant contributing factor to these issues is the use of fixed-conformation aptamers in these sensors. To address this challenge, we have developed an approach to transforming aptamers into molecular switches that undergo conformational changes upon target binding. This strategy enhances the performance of colorimetric aptasensors by improving sensitivity and reducing background noise without the need for post-SELEX modifications. In this study, we present an efficient aptamer screening method designed to facilitate the development of target-responsive aptamer structure switches from pre-existing aptamers with stable conformations. A novel algorithm was developed that integrates binding motif information with secondary structure data to generate three ssDNA libraries. Through virtual screening, we identified an aptamer with structure-switching properties (MSA-Apt-16) (Kd = 7.6 nM), and its structure-switching property was further validated using molecular simulations and circular dichroism spectroscopy. Further, the binding kinetics and selectivity of both aptamers were evaluated using SPR. MSA-Apt-16 displayed a kon of 1.39 × 105 Ms-1 and a koff of 1.76 × 10-4 s- 1, signifying a high binding affinity and selectivity. In contrast, Apt-H8 showed a kon of 1.22 × 10-4 Ms-1 and a koff of 1.89 × 10-3s-1, showing a low binding affinity with RSV-G. Moreover, we demonstrated the enhanced sensitivity of the newly designed molecular switching aptamer (MSA-Apt-16) compared to the parent aptamer (Apt-H8) by incorporating them into the photonic crystal-based colorimetric sensing platform for the detection of RSV-G protein. The molecular switching aptasensor successfully detected RSV-G protein, exhibiting efficient color changes, significantly reduced background noise, and a limit of detection (LOD) of 1 pg/mL with a linear range of 1-500 pg/mL (signal-to-noise ratio = 3, R2 = 0.9489), and an analytical recovery of 94.0 ± 1.5 % to 102.0 ± 1.5 % in artificial serum, saliva, and nasal swab samples. In contrast, the parent aptamer demonstrated a LOD of 1 ng/mL with a linear range of 1-500 ng/mL (R2 = 0.9129). Our pipeline offers a robust and broadly applicable technique for developing aptamer switches personalized to specific targets, significantly reducing background noise and enhancing aptasensor efficiency, thus expanding the potential applications of aptasensors in various diagnostic fields.

Risk of nosocomial respiratory syncytial virus versus influenza among adult patients in acute care hospitals

Background

While nosocomial influenza is common, the risk of transmission in acute care remains unclear in the absence of systematic surveillance. Even less is known about the risk of nosocomial respiratory syncytial virus (RSV) among immunocompetent adults.

Aim

To compare the proportions and incidences of nosocomial cases caused by these two similar respiratory infections among hospitalized adults.

Methods

A retrospective study was conducted at two tertiary care hospitals in Southern Finland. Data on all hospitalized adult patients with a positive RSV or influenza test during 2016-22 were used to detect all nosocomial and community-acquired RSV and influenza cases. The proportion of nosocomial cases of all hospitalized cases was calculated. The incidences of nosocomial cases per 1000 bed-days were calculated by season and ward type for the five seasons before the COVID-19 pandemic.

Results

Nosocomial RSV and influenza occurred in 2.8% and 8.1% of all hospitalized adult patients with a laboratory-confirmed infection. Over five seasons, 2016-20, the total incidences of nosocomial RSV and influenza cases per 1000 bed-days were 0.027 (95% confidence interval: 0.013, 0.050) and 0.32 (0.27, 0.39). Nosocomial RSV infections were especially poorly recorded with a virus-specific ICD-10 diagnosis code listed for only 16.7% of RSV and 59.8% of nosocomial influenza patients.

Conclusion

Despite preventive measures, the incidence of nosocomial influenza was more than tenfold, and the proportion of nosocomial cases was almost threefold compared with RSV among hospitalized adults in acute care. Prevention and surveillance of both nosocomial influenza and RSV should be improved also among immunocompetent adult patients.

Nirsevimab Effectiveness at Preventing RSV-Related Hospitalization in Infants

BACKGROUND

In pivotal trials, nirsevimab showed promising efficacy in reducing hospitalizations for respiratory syncytial virus-associated lower respiratory tract infections (RSV-LRTIs). Nirsevimab's real-world effectiveness needs to be assessed.

METHODS

This population-based study used the French National Health Data System. All infants born between February 6 and September 15, 2023 were eligible. Each day during the study period (September 15, 2023, to January 31, 2024), all infants newly passively immunized with nirsevimab were matched to unimmunized controls in a 1:1 ratio according to sex, birth month, gestational age, department of residence, and the French Social Deprivation Index (Fdep). Study outcomes included RSV-LRTI-related hospitalization, RSV-LRTI necessitating admission to a pediatric intensive care unit (PICU) or high dependency unit (HDU), and RSV-LRTI requiring ventilation support or oxygen therapy. We estimated nirsevimab effectiveness using propensity score-weighted conditional Cox models.

RESULTS

The study included 82,474 infants (41,237 in each group) with a median follow-up of 118 days (interquartile range, 76 to 125). The population included predominantly male infants (52.5%) born at term (94.6%), mostly between April and July 2023 (64.0%), and from more advantaged municipalities (FDep first quintile: 29.8%). In total, 342 infants (0.8%) in the nirsevimab group and 992 (2.4%) in the unimmunized group were hospitalized for RSV-LRTI. Nirsevimab's effectiveness was 65% (95% confidence interval [CI], 61 to 69) for RSV-LRTI hospitalizations; 74% (95% CI, 56 to 85) for RSV-LRTI PICU admissions; 64% (95% CI, 55 to 71) for RSV-LRTI HDU admissions; 66% (95% CI, 51 to 76) for RSV-LRTI hospitalization requiring ventilation support; and 67% (95% CI, 57 to 75) for RSV-LRTI hospitalization requiring oxygen therapy. Subgroup and sensitivity analyses yielded consistent effectiveness estimates.

CONCLUSIONS

This study in a nationwide monoclonal antibody infusion setting suggests that a single injection of nirsevimab was associated with substantial protection of infants against hospitalization for RSV-LRTI.

Recommendation for the use of respiratory syncytial virus vaccines

Respiratory syncytial virus (RSV) is the most common pathogen for young children hospitalized with bronchiolitis and pneumonia. Most infections occur below 1 year of age. RSV is also a significant viral pathogen for adults with respiratory tract infection. Vaccines targeting the pre-fusion protein of RSV, including recombinant and mRNA vaccines, are now available. A committee of experts from related fields was convened by the Taiwan Immunization Vision and Strategy to develop recommendations for RSV vaccination in the elderly and pregnant women. The recommendation is not intended as a sole source of guidance in the prevention of RSV infection in children. The provisions listed in this recommendation are comprehensive suggestions made by experts in Taiwan based on existing medical evidence. This recommendation should be subject to modification in light of additional medical research findings in the future, and these provisions should not be cited as a basis for dispute resolution.

The Epidemiology and Clinical Burdens of Human Parainfluenza Virus Infections Amongst Hospitalized Children Under 5 Years of Age in Jordan: A National Multi-Center Cross-Sectional Study

Human parainfluenza virus (HPIV) is a major cause of respiratory illnesses in children under five years, with clinical manifestations ranging from mild upper respiratory tract infections to severe lower respiratory tract diseases. This multi-center, cross-sectional study investigated the burden, clinical features, and predictors of respiratory viral infections in hospitalized children across four sites in Jordan. Nasopharyngeal specimens from 1000 eligible children were analyzed. In this article, we focused on HPIV infections. The overall HPIV positivity rate was 22.6%, with HPIV-3 accounting for 90.3% of cases. Significant geographic variability was observed, with higher positivity rates in the southern region. HPIV-positive cases frequently presented with symptoms like nasal congestion, tachypnea, and poor feeding. Co-infections with respiratory syncytial virus (RSV) or influenza were associated with worse outcomes, including an increased need for invasive ventilation. The logistic regression identified male gender, asthma, and respiratory acidosis as predictors of complications. Geographic differences in HPIV prevalence and severity were notable, emphasizing the influence of environmental and socioeconomic factors. These findings underscore the urgent need for enhanced HPIV surveillance, targeted public health interventions, and vaccine development to mitigate the disease burden. This study provides critical insights that guide healthcare strategies and improve outcomes in young children at risk of severe HPIV infections.

New Approaches to Respiratory Syncytial Virus Prevention and Treatment

There have been several recent advances in the prevention of lower respiratory tract disease (LRTD) due to respiratory syncytial virus (RSV) infection in older adults and young children. Three different vaccines are now approved for use in older adults; one of these vaccines is also approved for use in pregnant individuals for the prevention of LRTD due to RSV in their infants. In addition, a new monoclonal antibody is available to prevent RSV LRTD in infants born during or entering their first RSV season and in children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season. Despite these advances in prevention efforts, specific antiviral treatment options for RSV infection remain limited. Several promising compounds remain in development.

Trends in human parainfluenza virus in Scotland before and after the peak of the COVID-19 pandemic, January 2017 to October 2023

BackgroundHuman parainfluenza viruses (HPIV) commonly cause upper respiratory tract infections, with potential for severe lower respiratory complications. Understanding seasonal increases informs strategies to prevent HPIV spreading.AimWe examined the impact of COVID-19 on HPIV epidemiological and clinical patterns in Scotland using non-sentinel and sentinel surveillance data.MethodsInformation on HPIV swab positivity (January 2017-October 2023) and demographic data was obtained from the Electronic Communication of Surveillance in Scotland (ECOSS) non-sentinel surveillance sources (laboratory-based data from hospital and community) and the Community Acute Respiratory Infection (CARI) sentinel surveillance programme (enhanced surveillance and symptom data).ResultsIn 2020 during early COVID-19 waves, HPIV detection decreased aligning with lockdowns and preventive measures. In summer 2021, HPIV positivity increased, with HPIV-3 possibly reverting to pre-pandemic seasonality, but HPIV-1 not yet re-establishing alternate-year peaks. Most positive results from non-sentinel sources came from hospital tests. Sentinel surveillance (CARI) complemented non-sentinel data, offering community-level insights. There was no significant difference in CARI swab positivity by sex in any age group. Consistent with historical trends, children under five years exhibited highest test positivity: 9.3% (95% CI: 7.6-11.2) in females and 8.5% (95% CI 7.0-10.2) in males.ConclusionThe COVID-19 pandemic impacted HPIV detection in Scotland. The decline during the pandemic peak and subsequent partial resurgence underscores the complex interplay between viral epidemiology and public health measures. Combining diverse surveillance systems provides a comprehensive understanding of HPIV dynamics. Insights into age-specific and symptom-associated patterns contribute to understanding HPIV epidemiology and refining public health strategies.

Impact of Palivizumab in Preventing Severe Acute Lower Respiratory Infection in Moderate-to-Late Preterm Infants: A Nationwide Cohort Study

BACKGROUND

Respiratory syncytial virus (RSV) prophylaxis using palivizumab effectively reduces RSV-associated morbidity in preterm infants. In Korea, national insurance coverage for palivizumab was implemented in October 2016 for moderate-to-late preterm (MLPT) infants born during the RSV season (October-March) who have older siblings. However, no large-scale studies have investigated the changes in the incidence and risk of severe acute lower respiratory infections (ALRIs) after insurance coverage implementation for MLPT infants.

METHODS

This large-scale retrospective cohort study used data from the Korean National Health Insurance Service between October 2013 and December 2019. MLPT infants (32 0/7-35 6/7 weeks of gestation) with older siblings were stratified into pre-insurance period (PIP; October 2013-September 2016) and insurance period (IP; October 2016-March 2019) groups based on the date of birth with respect to initial insurance palivizumab implementation. Severe ALRI outcomes (hospitalization, respiratory support, and intensive care unit admission) were evaluated up to 1 year of age using multivariable logistic regression models.

RESULTS

Of the 11,722 MLPT infants included in the study, 6,716 and 5,006 infants were included in the IP and PIP groups, respectively. The incidences of ALRI-hospitalization and ALRI-respiratory support were significantly lower in the IP group than that in PIP group (24.0% vs. 26.0% and 3.1% vs. 4.0%, respectively). Additionally, ALRI-respiratory support risk was significantly lower in the IP group (adjusted odds ratio 0.771, 95% confidence interval 0.626-0.949, P = 0.014) than that in the PIP group. Among infants born during the RSV season, the risk of ALRI-hospitalization and ALRI-respiratory support were significantly lower in the IP group than that in the PIP group. However, no significant differences were observed between the IP and PIP groups for infants born during the non-RSV season.

CONCLUSION

The risks of severe ALRI outcomes decreased in Korea following the 2016 insurance implementation of palivizumab prophylaxis for MLPT infants born during the RSV season with older siblings.

Novel intercellular spread mode of respiratory syncytial virus contributes to neutralization escape

Developing widely used respiratory syncytial virus (RSV) vaccines remains a significant challenge, despite the recent authorization of two pre-F vaccines for elderly adults. Previous reports have suggested that even when vaccine-induced immunity generates high titers of potent neutralizing antibodies targeting the pre-F protein, it may not fully inhibit breakthrough of RSV infections. This incomplete inhibition of RSV breakthrough infections can lead to an increased risk of enhanced respiratory disease (ERD) in vaccinated individuals. The reasons why potent neutralizing antibodies cannot fully prevent RSV breakthrough infections are not yet clear. In an attempt to explain this phenomenon, we investigated the effect of potent neutralizing antibodies on the intercellular spread of RSV. Our findings indicated that a specific titer of potent neutralizing antibodies, such as 5C4, could block certain modes of intercellular spread, such as the diffusion of cell-free virions and the delivery of virions through filopodia. However, these antibodies did not fully inhibit the entire process of intercellular spread. Through the use of super-resolution imaging techniques, we observed a novel and efficient spread mode called the transition of viral materials through intercellular nanotubes (TVMIN), independent of virions and insensitive to the presence of antibodies. TVMIN allowed RSV-infected cells to directly transfer viral materials to neighboring cells via intercellular nanotubes that are rich in microfilaments. TVMIN began as early as 5 h post-infection (h.p.i.) and rapidly initiated infection in recipient cells. Our data provided new insights into the intercellular spread of RSV and might help explain the occurrence of breakthrough infections.

Parental knowledge about respiratory syncytial virus and attitudes toward infant immunization with monoclonal antibodies in France

BACKGROUND AND AIM

Respiratory syncytial virus (RSV) is a leading cause of hospitalization of infants with respiratory infections. A new immunization using monoclonal antibodies (mAbs) may offer protection against RSV infections. A study was conducted across eight countries to gain insight into parental awareness of RSV, their sources of child health information, and attitudes toward infant immunization against RSV using mAbs. This paper presents the findings from France.

METHODS

In 2021, a survey was conducted in eight countries among expecting and current parents with children younger than 24 months of age. Eligible respondents included parents who were open to childhood immunizations, i.e., they had given or planned to give their children "all," "most," or "some" immunizations.

RESULTS

In France, the survey respondents had high adoption rates for childhood immunizations. Key drivers behind these high rates were the desire to protect their children from severe diseases and adherence to mandatory immunizations, whereas concerns about safety were the main barriers. While general practitioners and pediatricians were key sources of advice on child health, many parents also requested information about immunizations from health authorities and nurses. Sources of advice varied with parental age, gender, educational level, and income. The majority of parents had no knowledge about mAbs or passive immunization, and the overall awareness of RSV was low. When informed about RSV and mAbs, most parents held neutral to positive attitudes toward nirsevimab for their infants if recommended by a healthcare professional and/or included in the immunization program. These findings were further confirmed by the 60 %-80 % uptake rates of nirsevimab following the introduction in September 2023.

Saline nebulizers in treatment of bronchiolitis

Introduction

This study was conducted to assess the response to treatment and compare the effects of nebulized normal saline 0.9% and hypertonic saline 3% in the management of acute bronchiolitis, a condition associated with multiple complications in pediatric patients.

Materials and Methods

In this clinical trial, a total of 60 children diagnosed with viral bronchiolitis in the autumn and winter of 2018 at Ali Asghar Children's Hospital's emergency department were enrolled. The cohort consisted of 30 children in the control group treated with normal saline 0.9% nebulization and 30 in the treatment group treated with 3% hypertonic saline nebulization. Demographic variables, symptom onset duration, and initial heart and respiratory rates were recorded. Disease severity was assessed using the Respiratory Distress Assessment Index (RDAI). Data were analyzed using SPSS software.

Results

Following treatment, both groups exhibited significant improvements in vital signs (respiratory rate, heart rate, and oxygen saturation) and RDAI scores (P value < 0.001). However, there was no statistically significant difference in the degree of improvement in vital signs and RDAI scores between the two treatment groups (P value > 0.05). The mean hospital stay duration did not significantly differ between the groups (P value = 0.16).

Conclusion

Nebulized hypertonic saline and normal saline both effectively ameliorated symptoms in children with bronchiolitis. The absence of a significant difference between these treatments suggests that either can be recommended for use in the pediatric population experiencing acute bronchiolitis symptoms.

Viral co-detection of influenza virus and other respiratory viruses in hospitalized Brazilian patients during the first three years of the coronavirus disease (COVID)-19 pandemic: an epidemiological profile

Introduction

In Brazil, few studies were performed regarding the co-detection of respiratory viruses in hospitalized patients. In this way, the study aimed to describe the epidemiological profile of hospitalized patients due to influenza virus infection that presented co-detection with another respiratory virus.

Methods

The epidemiological analysis was made by collecting data from Open-Data-SUS. The study comprised patients infected by the influenza A or B virus with positive co-detection of another respiratory virus, such as adenovirus, bocavirus, metapneumovirus, parainfluenza virus (types 1, 2, 3, and 4), rhinovirus, and respiratory syncytial virus (RSV). The markers [gender, age, clinical signs and symptoms, comorbidities, need for intensive care unit (ICU) treatment, and need for ventilatory support] were associated with the chance of death. The data was collected during the first three years of the coronavirus disease (COVID)-19 pandemic-from December 19, 2019, to April 06, 2023.

Results

A total of 477 patients were included, among them, the influenza A virus was detected in 400 (83.9%) cases. The co-detection occurred, respectively, for RSV (53.0%), rhinovirus (14.0%), adenovirus (13.4%), parainfluenza virus type 1 (10.7%), parainfluenza virus type 3 (5.2%), metapneumovirus (3.8%), parainfluenza virus type 2 (3.6%), bocavirus (3.4%), and parainfluenza virus type 4 (1.5%). The co-detection rate was higher in the male sex (50.7%), age between 0-12 years of age (65.8%), and white individuals (61.8%). The most common clinical symptoms were cough (90.6%), dyspnea (78.8%), and fever (78.6%). A total of 167 (35.0%) people had at least one comorbidity, mainly cardiopathy (14.3%), asthma (8.4%), and diabetes mellitus (7.3%). The need for ICU treatment occurred in 147 (30.8%) cases, with most of them needing ventilatory support (66.8%), mainly non-invasive ones (57.2%). A total of 33 (6.9%) patients died and the main predictors of death were bocavirus infection (OR = 14.78 [95%CI = 2.84-76.98]), metapneumovirus infection (OR = 8.50 [95%CI = 1.86-38.78]), race (other races vs. white people) (OR = 3.67 [95%CI = 1.39-9.74]), cardiopathy (OR = 3.48 [95%CI = 1.13-10.71]), and need for ICU treatment (OR = 7.64 [95%CI = 2.44-23.92]).

Conclusion

Co-detection between the influenza virus and other respiratory viruses occurred, mainly with RSV, rhinovirus, and adenovirus being more common in men, white people, and in the juvenile phase. Co-detection of influenza virus with bocavirus and metapneumovirus was associated with an increased chance of death. Other factors such as race, cardiopathy, and the need for an ICU were also associated with a higher chance of death.

Disease Burden Associated with All Infants in Their First RSV Season in the UK: A Static Model of Universal Immunization with Nirsevimab Against RSV-Related Outcomes

INTRODUCTION

Respiratory syncytial virus (RSV) leads to significant morbidity in newborn infants in the United Kingdom (UK). Nirsevimab, a long-acting monoclonal antibody, received approval from the European Medicines Agency and has been licensed by the Medicines and Healthcare products Regulatory Agency for preventing RSV lower respiratory tract disease (LRTD) in neonates and infants during their first RSV season. The objective of this study was to assess the potential impact of nirsevimab on RSV-associated LRTDs, related costs, and loss of quality-adjusted life years (QALYs) in infants experiencing their first RSV season.

METHODS

The impact of administering nirsevimab across all infant populations compared to palivizumab in the high-risk palivizumab-eligible population was assessed via a static decision-analytic model specified for a UK birth cohort experiencing their first RSV season. The RSV-related health events of interest included primary care (PC), accident and emergency (A&E) visits, hospitalizations [including hospitalizations alone and those resulting in intensive care unit (ICU) admissions], recurrent wheezing in infants who were previously hospitalized, and all-cause LRTD hospitalizations.

RESULTS

Under the current standard of practice (SoP), RSV was estimated to result in 329,425 RSV LRTDs annually, including 24,381 hospitalizations and ICU admissions, representing £117.8 million (2024 GBP) in costs. Comparatively, universal immunization of all infants with nirsevimab could avoid 198,886 RSV LRTDs, including 16,657 hospitalizations and ICU admissions, resulting in savings of £77.2 million in RSV treatment costs. Considering the impact on all-cause LRTD of a universal immunization strategy, nirsevimab could be valued between £243 and £274, assuming willingness-to-pay (WTP) thresholds of £20,000 and £30,000 per QALY saved, respectively.

CONCLUSIONS

This analysis demonstrated that the health and economic burden of RSV would be substantially reduced in all infants experiencing their first RSV season in the UK (including term, preterm, and palivizumab-eligible infants) as a result of a universal immunization strategy with nirsevimab.

Impact of respiratory tract infections on spinal muscular atrophy with focus on respiratory syncytial virus infections: a single-centre cohort study

AIMS OF THE STUDY

Spinal muscular atrophy (SMA) is a degenerative neuromuscular disorder leading to muscle hypotonia, weakness, and respiratory and bulbar impairment. Infants with SMA have an increased risk of respiratory tract infections (RTI) including severe respiratory syncytial virus (RSV) infections. Therefore, guidelines for the treatment of SMA recommend RSV prophylaxis with palivizumab for patients aged below two years who have compromised motor functions ("non-sitters"). Since palivizumab is not approved for RSV prophylaxis in SMA patients in Switzerland, payers usually do not grant cost approvals for this indication. Therefore, this study aimed to investigate the frequency of severe RTI among SMA patients focusing on RSV infections requiring hospital treatment and to determine the long-term impact of RSV infections on the natural history of SMA.

METHODS

A single-centre cohort study at the tertiary paediatric Neuromuscular Centre Zurich, Switzerland, including data of SMA patients with a genetic-based therapy initiated below two years of age between May 2019 and December 2022. All hospitalisations were analysed with a focus on severe RTI and especially RSV infections, and their impact on nutritional and respiratory function. The costs of inpatient treatment of RSV infections were determined and compared with estimated expenses for RSV prophylaxis with palivizumab.

RESULTS

12 SMA patients (median age at treatment initiation: 3.5 months, range: 0-17 months) were followed for a cumulative period of 25.75 years (7 SMA type 1; 5 SMA type 2 including one presymptomatic individual). With an incidence rate of 2.34 per patient-year, the risk of severe RTI was especially high in SMA type 1 (versus 0.1 in SMA type 2, p = 0.044). A total of 37 hospitalisations (279 hospital days) was necessary for the treatment of RTI in general; 9 of them were attributed to RSV infections (in 5 SMA type 1 patients; 84 hospital days). Only 3/12 SMA patients had received seasonal RSV prophylaxis with palivizumab. No RSV infections requiring hospital treatment occurred in patients while receiving seasonal RSV prophylaxis. During RTI, nutritional support had to be commonly initiated and continued after discharge. In 3/7 SMA type 1 patients, non-invasive ventilation was started during acute treatment for RTI and continued to the end of follow-up.

CONCLUSION

We observed a high risk of RTI, especially RSV infections, among young SMA patients. Failure to adhere to established care protocols, for example by omitting RSV prophylaxis, may be linked to a heightened risk of morbidity in these children.

Unveiling viral pathogens in acute respiratory disease: Insights from viral metagenomics in patients from the State of Alagoas, Brazil

BACKGROUND

Respiratory illness affects individuals across all age demographics on a global scale, often precipitated by viral infections. The symptomatic manifestations of these diseases bear clinical resemblance, complicating the accurate determination of their etiological origins. Furthermore, the diagnostic panels for respiratory pathogens used within local medical practices, may not encompass the full spectrum of viral agents responsible for such ailments. Consequently, a significant number of clinically important viral pathogens may remain undetected.

METHODS AND FINDINGS

In the light of this, we conducted a metagenomic examination of 66 nasopharyngeal swab specimens, obtained from patients presenting with acute respiratory conditions yet tested negative by the standard diagnostic panels available locally. These specimens were obtained from the Public Health Laboratory, Maceio, State of Alagoas. Our findings indicate a predominant diagnostic escape of rhinoviruses and notably enterovirus D68. Moreover, our study identified a substantial quantity of sequence reads attributed to human respirovirus 3 (human parainfluenza 3) along with various herpresviruses including human herpesvirus-1, Epstein-Barr virus (Human herpesvirus-4), Human herpesviruses 6 and 7 and human parvovirus B19 (B19V). Notably, the metagenomic analysis uncovered a widespread presence of the emerging human vientovirus FB in most of sample pools, though its clinical importance remains to be elucidated.

CONCLUSIONS

The obtained results in this study underscore the invaluable role of viral metagenomics in the identification of underrecognized viruses bearing clinical relevance. Furthermore, it offers insights into the dissemination of these pathogens within the studied area, thereby informing public health strategies aimed at enhancing diagnostic accuracy and improving patient care.

Cold-adapted influenza vaccine carrying three repeats of a respiratory syncytial virus (RSV) fusion glycoprotein epitope site protects BALB/c mice and cotton rats against RSV infection

Respiratory syncytial virus is the major cause of respiratory viral infections, particularly in infants, immunocompromised populations, and the elderly (over 65 years old), the prevention of RSV infection has become a priority. In this study, we generated a chimeric influenza virus, termed LAIV/RSV/HA-3F, using reverse genetics technology which contained three repeats of the RSV fusion protein neutralizing epitope site II to the N terminal in the background of the hemagglutinin (HA) gene of cold adapted influenza vaccine A/California/7/2009 ca. LAIV/RSV/HA-3F exhibited cold-adapted (ca) and attenuated (att) phenotype. BALB/c mice immunized intranasally with LAIV/RSV/HA-3F showed robust immunogenicity, inducing viral-specific antibody responses against both influenza and RSV, eliciting RSV-specific humoral, cellular and mucosal immune responses. LAIV/RSV/HA-3F also conferred protection as indicated by reduced viral titers and improved lung histopathological alterations against live RSV virus challenge. Mechanismly, single-cell RNA sequencing (scRNA-seq) and single-cell T cell antigen receptor (TCR) sequencing were employed to characterize the immune responses triggered by chimeric RSV vaccine, displaying that LAIV/RSV/HA-3F provided protection mainly via interferon-γ (IFN-γ). Moreover, we found that LAIV/RSV/HA-3F significantly inhibited viral replication in the challenged lung and protected against subsequent RSV challenge in cotton rats without causing lung disease. Taken together, our findings demonstrated that LAIV/RSV/HA-3F has potential as a promising bivalent vaccine with dual purpose candidate for the prevention of influenza and RSV, and preclinical and clinical studies warrant further investigations.

Epidemiology of Human Parainfluenza Virus Infections among Pediatric Patients in Hainan Island, China, 2021-2023

Human parainfluenza viruses (HPIVs) are the leading causes of acute respiratory tract infections (ARTIs), particularly in children. During the COVID-19 pandemic, non-pharmaceutical interventions (NPIs) significantly influenced the epidemiology of respiratory viruses. This study analyzed 19,339 respiratory specimens from pediatric patients with ARTIs to detect HPIVs using PCR or tNGS, focusing on the period from 2021 to 2023. HPIVs were identified in 1395 patients (7.21%, 1395/19,339), with annual detection rates of 6.86% (303/4419) in 2021, 6.38% (331/5188) in 2022, and 7.82% (761/9732) in 2023. Notably, both the total number of tests and HPIV-positive cases increased in 2023 compared to 2021 and 2022. Seasonal analysis revealed a shift in HPIV prevalence from winter and spring in 2021-2022 to spring and summer in 2023. Most HPIV-positive cases were in children aged 0-7 years, with fewer infections among those aged 7-18 years. Since June 2022, HPIV-3 has been the most prevalent serotype (59.55%, 524/880), whereas HPIV-2 had the lowest proportion (0.80%, 7/880). The proportions of HPIV-1 (24.89%, 219/880) and HPIV-4 (15.45%, 136/880) were similar. Additionally, the incidence of co-infections with other common respiratory pathogens has increased since 2021. This study highlights rising HPIV detection rates post-COVID-19 and underscores the need for continuous surveillance of HPIVs to inform public health strategies for future epidemic seasons.

Occurrence of Central Nervous System Complications of Respiratory Syncytial Virus Infections: A Systematic Review with Meta-Analysis

An increasing base of evidence suggests that respiratory syncytial virus (RSV) infections may be associated with neurological complications. In accord with the PRISMA statement, we performed a systematic review and meta-analysis on the occurrence of encephalitis and encephalopathy associated with documented RSV infections. PubMed, Embase, and Scopus databases were searched for eligible observational studies published up to 10 April 2024. Raw data included the occurrence of RSV infections among cases of encephalitis and/or encephalopathy and cases of encephalitis and/or encephalopathy among series of RSV infections. Data were pooled in a random effects model. Case reports were also collected, and their data pooled as a cumulative series. Heterogeneity was assessed using the I2 measure, while reporting bias was assessed by means of funnel plots and regression analysis. A total of 15 studies for a total of 7719 RSV infections and 1631 cases of encephalitis were analyzed. Moreover, 27 case reports and case series were retrieved, for a total of 84 individual cases of encephalitis/encephalopathy occurring during a documented RSV infection. A pooled prevalence of 2.20 cases of encephalitis/encephalopathy per 100 RSV cases (I2 = 99%) was calculated, while a prevalence of RSV infections among cases of encephalitis/encephalopathy was estimated to 3.53 per 100 cases for studies on respiratory specimens (I2 = 48%) and 0.37 per cases on central nervous system (CNS) specimens (I2 = 0%). Detection of RSV within the CNS was relatively rare (17.86% of pooled case reports), being associated with male gender (adjusted odds ratio [aOR] 5.021, 95% confidence interval [95%CI] 1.104 to 22.831) and recovery with long-term sequelae (aOR 5.699, 95%CI 1.152; 28.183). Case fatality ratio was estimated to be 0.43 per 100 cases on observational studies and 10.71% in case reports, a difference likely due to publication bias. In summary, RSV represented a not frequent but notable cause of encephalitis/encephalopathy in adults and children. The paucity of available studies not only recommends a cautious appraisal of our results but stresses the clinical significance of future studies on incident cases of encephalitis and/or encephalopathy.

CXCR3+ effector regulatory T cells associate with disease tolerance during lower respiratory pneumovirus infection

Lifestyle factors like poor maternal diet or antibiotic exposure disrupt early life microbiome assembly in infants, increasing the risk of severe lower respiratory infections (sLRI). Our prior studies in mice indicated that a maternal low-fibre diet (LFD) exacerbates LRI severity in infants by impairing recruitment of plasmacytoid dendritic cells (pDC) and consequently attenuating expansion of lung regulatory T (Treg) cells during pneumonia virus of mice (PVM) infection. Here, we investigated whether maternal dietary fibre intake influences Treg cell phenotypes in the mediastinal lymph nodes (mLN) and lungs of PVM-infected neonatal mice. Using high dimensional flow cytometry, we identified distinct clusters of regulatory T cells (Treg cells), which differed between lungs and mLN during infection, with notably greater effector Treg cell accumulation in the lungs. Compared to high-fibre diet (HFD)-reared pups, frequencies of various effector Treg cell subsets were decreased in the lungs of LFD-reared pups. Particularly, recruitment of chemokine receptor 3 (CXCR3+) expressing Treg cells was attenuated in LFD-reared pups, correlating with lower lung expression of CXCL9 and CXCL10 chemokines. The recruitment of this subset in response to PVM infection was similarly impaired in pDC depleted mice or following anti-CXCR3 treatment, increasing immunopathology in the lungs. In summary, PVM infection leads to the sequential recruitment and expansion of distinct Treg cell subsets to the lungs and mLN. The attenuated recruitment of the CXCR3+ subset in LFD-reared pups increases LRI severity, suggesting that strategies to enhance pDCs or CXCL9/CXCL10 expression will lower immune-mediated pathogenesis.

Acute Respiratory Tract Infections (ARTIs) in Children after COVID-19-Related Social Distancing: An Epidemiological Study in a Single Center of Southern Italy

In Sicily (Italy), respiratory syncytial virus (RSV), rhinovirus (HRV), and influenza virus triggered epidemics among children, resulting in an increase in acute respiratory tract infections (ARTIs). Our objective was to capture the epidemiology of respiratory infections in children, determining which pathogens were associated with respiratory infections following the lockdown and whether there were changes in the epidemiological landscape during the post-SARS-CoV-2 pandemic era.

MATERIALS AND METHODS

We analyzed multiplex respiratory viral PCR data (BioFire® FilmArray® Respiratory Panel 2.1 Plus) from 204 children presenting with respiratory symptoms and/or fever to our Unit of Pediatrics and Pediatric Emergency.

RESULTS

Viruses were predominantly responsible for ARTIs (99%), with RSV emerging as the most common agent involved in respiratory infections, followed by human rhinovirus/enterovirus and influenza A. RSV and rhinovirus were also the primary agents in coinfections. RSV predominated during winter months, while HRV/EV exhibited greater prevalence than RSV during the fall. Some viruses spread exclusively in coinfections (human coronavirus NL63, adenovirus, metapneumovirus, and parainfluenza viruses 1-3), while others primarily caused mono-infections (influenza A and B). SARS-CoV-2 was detected equally in both mono-infections (41%) and coinfections (59%).

CONCLUSIONS

Our analysis underlines the predominance of RSV and the importance of implementing preventive strategies for RSV.

Severe Human Parainfluenza Virus Community- and Healthcare-Acquired Pneumonia in Adults at Tertiary Hospital, Seoul, South Korea, 2010-2019

The characteristics of severe human parainfluenza virus (HPIV)-associated pneumonia in adults have not been well evaluated. We investigated epidemiologic and clinical characteristics of 143 patients with severe HPIV-associated pneumonia during 2010-2019. HPIV was the most common cause (25.2%) of severe virus-associated hospital-acquired pneumonia and the third most common cause (15.7%) of severe virus-associated community-acquired pneumonia. Hematologic malignancy (35.0%), diabetes mellitus (23.8%), and structural lung disease (21.0%) were common underlying conditions. Co-infections occurred in 54.5% of patients admitted to an intensive care unit. The 90-day mortality rate for HPIV-associated pneumonia was comparable to that for severe influenza virus-associated pneumonia (55.2% vs. 48.4%; p = 0.22). Ribavirin treatment was not associated with lower mortality rates. Fungal co-infections were associated with 82.4% of deaths. Clinicians should consider the possibility of pathogenic co-infections in patients with HPIV-associated pneumonia. Contact precautions and environmental cleaning are crucial to prevent HPIV transmission in hospital settings.

Pulmonary Infection

Pneumonia is a significant cause of morbidity and mortality in the community and hospital settings. Bacterial, viral, mycobacterial, and fungal pathogens are all potential causative agents of pulmonary infection. Chest radiographs and computed tomography are frequently utilized in the assessment of pneumonia. Learning the imaging patterns of different potential organisms allows the radiologist to formulate an appropriate differential diagnosis. An organism-based approach is used to discuss the imaging findings of different etiologies of pulmonary infection.

Association of respiratory infections and the impact of vaccinations on cardiovascular diseases

Influenza, pneumococcal, severe acute respiratory syndrome coronavirus 2, and respiratory syncytial virus infections are important causes of high morbidity and mortality in the elderly. Beyond the burden of infectious diseases, they are also associated with several non-infectious complications like cardiovascular events. A growing body of evidence in prospective studies and meta-analyses has shown the impact of influenza and pneumococcal vaccines on types of cardiovascular outcomes in the general population. Influenza vaccination showed a potential benefit for primary and secondary prevention of cardiovascular diseases across all ages. A reduced risk of cardiovascular events for individuals aged 65 years and older was associated with pneumococcal vaccination. Despite scientific evidence on the effectiveness, safety, and benefits of the vaccines and recommendations to vaccinate elderly patients and those with risk factors, vaccination rates remain sub-optimal in this population. Doubts about vaccine necessity or efficacy and concerns about possible adverse events in patients and physicians refer to delayed acceptance. Vaccination campaigns targeting increasing professional recommendations and public perceptions should be implemented in the coming years. The aim of this review paper is to summarize the effect of vaccination in the field of cardiovascular disease to achieve a higher vaccination rate in this patient population.

Prediction of hospital-acquired influenza using machine learning algorithms: a comparative study

BACKGROUND

Hospital-acquired influenza (HAI) is under-recognized despite its high morbidity and poor health outcomes. The early detection of HAI is crucial for curbing its transmission in hospital settings.

AIM

This study aimed to investigate factors related to HAI, develop predictive models, and subsequently compare them to identify the best performing machine learning algorithm for predicting the occurrence of HAI.

METHODS

This retrospective observational study was conducted in 2022 and included 111 HAI and 73,748 non-HAI patients from the 2011-2012 and 2019-2020 influenza seasons. General characteristics, comorbidities, vital signs, laboratory and chest X-ray results, and room information within the electronic medical record were analysed. Logistic Regression (LR), Random Forest (RF), Extreme Gradient Boosting (XGB), and Artificial Neural Network (ANN) techniques were used to construct the predictive models. Employing randomized allocation, 80% of the dataset constituted the training set, and the remaining 20% comprised the test set. The performance of the developed models was assessed using metrics such as the area under the receiver operating characteristic curve (AUC), the count of false negatives (FN), and the determination of feature importance.

RESULTS

Patients with HAI demonstrated notable differences in general characteristics, comorbidities, vital signs, laboratory findings, chest X-ray result, and room status compared to non-HAI patients. Among the developed models, the RF model demonstrated the best performance taking into account both the AUC (83.3%) and the occurrence of FN (four). The most influential factors for prediction were staying in double rooms, followed by vital signs and laboratory results.

CONCLUSION

This study revealed the characteristics of patients with HAI and emphasized the role of ventilation in reducing influenza incidence. These findings can aid hospitals in devising infection prevention strategies, and the application of machine learning-based predictive models especially RF can enable early intervention to mitigate the spread of influenza in healthcare settings.

The increase of bronchiolitis severity in the 2022-2023 season in an Italian tertiary children's hospital: An isolated phenomenon or a warning sign?

AIM

Recent literature has shown epidemiological changes in bronchiolitis with an increased incidence in the post-SARS-CoV-2 pandemic period but reports regarding disease severity are conflicting. We aimed to describe the epidemiology, disease severity, and microbiology of bronchiolitis during the 2022-2023 cold season compared to the previous 5 years.

METHODS

This single-center retrospective observational study at IRCCS Gaslini, Italy, included all children aged 0-2 years hospitalized for bronchiolitis from 1 September 2017 to 31 August 2023. Findings from the 2022-2023 season were compared to the previous 5 years.

RESULTS

We observed a statistically significant increase in the 2022-2023 season in the absolute number of bronchiolitis admissions. Children who required mechanical ventilation (MV) dramatically increased from a total of seven patients in the previous five seasons to 17 in the 2022-2023 season alone (p = .001). All other severity parameters significantly increased: the need for respiratory support (p = .002), the median length of stay (5 days vs. 4 days, p = .001), and the median duration of respiratory support (4 days vs. 3 days, p = .016).

CONCLUSIONS

We report a substantial increase in the severity of bronchiolitis in the season 2022-2023 with a remarkable number of previously healthy infants requiring MV. Further studies are needed to confirm whether our findings are an isolated phenomenon or part of a true global trend. Health systems need to be prepared and protective preventive measures should be implemented for all newborns.

Pre-COVID-19-pandemic RSV epidemiology and clinical burden in pediatric primary care in Italy: a comparative analysis across two regions for the 2019/2020 season

BACKGROUND

Respiratory syncytial virus (RSV) infection in children under 5 years have a significant clinical burden, also in primary care settings. This study investigates the epidemiology and burden of RSV in Italian children during the 2019/20 pre-pandemic winter season.

METHODS

A prospective cohort study was conducted in two Italian regions. Children with Acute Respiratory Infection (ARI) visiting pediatricians were eligible. Nasopharyngeal swabs were collected and analyzed via multiplex PCR for RSV detection. A follow-up questionnaire after 14 days assessed disease burden, encompassing healthcare utilization and illness duration. Statistical analyses, including regression models, explored associations between variables such as RSV subtype and regional variations.

RESULTS

Of 293 children with ARI, 41% (119) tested positive for RSV. Median illness duration for RSV-positive cases was 7 days; 6% required hospitalization (median stay: 7 days). Medication was prescribed to 95% (110/116) of RSV cases, with 31% (34/116) receiving antibiotics. RSV subtype B and regional factors predicted increased healthcare utilization. Children with shortness of breath experienced a 36% longer illness duration.

CONCLUSIONS

This study highlights a significant clinical burden and healthcare utilization associated with RSV in pre-pandemic Italian primary care settings. Identified predictors, including RSV subtype and symptomatology, indicate the need for targeted interventions and resource allocation strategies. RSV epidemiology can guide public health strategies for the implementation of preventive measures.

Resurgence of respiratory syncytial virus with dominance of RSV-B during the 2022-2023 season

Background

Respiratory syncytial virus (RSV) is a common cause of upper and lower respiratory tract infections. This study aimed to explore the prevalence of respiratory syncytial virus (RSV) and other respiratory viruses in Bulgaria, characterize the genetic diversity of RSV strains, and perform amino acid sequence analyses of RSV surface and internal proteins.

Methods

Clinical and epidemiological data and nasopharyngeal swabs were prospectively collected from patients with acute respiratory infections between October 2020 and May 2023. Real-time PCR for 13 respiratory viruses, whole-genome sequencing, phylogenetic, and amino acid analyses were performed.

Results

This study included three epidemic seasons (2020-2021, 2021-2022, and 2022-2023) from week 40 of the previous year to week 20 of the following year. Of the 3,047 patients examined, 1,813 (59.5%) tested positive for at least one viral respiratory pathogen. RSV was the second most detected virus (10.9%) after SARS-CoV-2 (22%). Coinfections between RSV and other respiratory viruses were detected in 68 cases, including 14 with SARS-CoV-2. After two seasons of low circulation, RSV activity increased significantly during the 2022-2023 season. The detection rates of RSV were 3.2, 6.6, and 13.7% in the first, second, and third seasons, respectively. RSV was the most common virus found in children under 5 years old with bronchiolitis (40%) and pneumonia (24.5%). RSV-B drove the 2022-2023 epidemic. Phylogenetic analysis indicated that the sequenced RSV-B strains belonged to the GB5.0.5a and GB5.0.6a genotypes. Amino acid substitutions in the surface and internal proteins, including the F protein antigenic sites were identified compared to the BA prototype strain.

Conclusion

This study revealed a strong resurgence of RSV in the autumn of 2022 after the lifting of anti-COVID-19 measures, the leading role of RSV as a causative agent of serious respiratory illnesses in early childhood, and relatively low genetic diversity in circulating RSV strains.

Predictors of Respiratory Syncytial Virus, Influenza Virus, and Human Metapneumovirus Carriage in Children Under 5 Years With WHO-Defined Fast-Breathing Pneumonia in Pakistan

BACKGROUND

Pneumonia is a leading cause of morbidity and mortality in children < 5 years. We describe nasopharyngeal carriage of respiratory syncytial virus (RSV), human metapneumovirus (hMPV), and influenza virus among children with fast-breathing pneumonia in Karachi, Pakistan.

METHODS

We performed a cross-sectional analysis of nasopharyngeal swabs from children aged 2-59 months with fast-breathing pneumonia, enrolled in the randomized trial of amoxicillin versus placebo for fast-breathing pneumonia (RETAPP) (NCT02372461) from 2014 to 2016. Swabs were collected using WHO standardized methods, processed at the Aga Khan University, Pakistan. Viral detection was performed using LUMINEX xTAG respiratory viral panel assay and logistic regression identified clinical and sociodemographic predictors.

FINDINGS

Of the 1000 children tested, 92.2% (n = 922) were positive for viral carriage. RSV, hMPV, and influenza virus were detected in 59 (6.4%), 56 (6.1%), and 58 (6.3%) children and co-infections in three samples (two RSV-hMPV and one influenza-hMPV). RSV carriage was common in infants (56%), we observed a higher occurrence of fever in children with hMPV and influenza virus (80% and 88%, respectively) and fast breathing in RSV (80%) carriage. RSV carriage was positively associated with a history of fast/difficulty breathing (aOR: 1.96, 95% CI 1.02-3.76) and low oxygen saturation (aOR: 2.52, 95% CI 1.32-4.82), hMPV carriage was positively associated with a complete vaccination status (aOR: 2.22, 95% CI 1.23-4.00) and body temperature ≥ 37.5°C (aOR: 2.34, 95% CI 1.35-4.04) whereas influenza viral carriage was associated with body temperature ≥ 37.5°C (aOR: 4.48, 95% CI 2.53-7.93).

CONCLUSION

We observed a high nasopharyngeal viral carriage among children with WHO-defined fast-breathing pneumonia in Pakistan. Fever, difficulty in breathing, hypoxia and vaccination status are important clinical predictors for viral nonsevere community-acquired pneumonia.

Respiratory Syncytial Virus Infections in Recipients of Bone Marrow Transplants: A Systematic Review and Meta-Analysis

Human Respiratory Syncytial Virus (RSV) is a common cause of respiratory tract infections. Usually associated with infants and children, an increasing amount of evidence suggests that RSV can cause substantial morbidity and mortality in immunocompromised individuals, including recipients of bone marrow transplantation (BMT). The present systematic review was therefore designed in accordance with the PRISMA guidelines to collect available evidence about RSV infections in BMT recipients. Three medical databases (PubMed, Embase, and MedRxiv) were therefore searched for eligible observational studies published up to 30 September 2023 and collected cases were pooled in a random-effects model. Heterogeneity was assessed using I2 statistics. Reporting bias was assessed by means of funnel plots and regression analysis. Overall, 30 studies were retrieved, including 20,067 BMT cases and 821 RSV infection episodes. Of them, 351 were lower respiratory tract infections, and a total of 78 RSV-related deaths were collected. A pooled attack rate of 5.40% (95% confidence interval [95%CI] 3.81 to 7.60) was identified, with a corresponding incidence rate of 14.77 cases per 1000 person-years (95%CI 9.43 to 20.11), and a case fatality ratio (CFR) of 7.28% (95%CI 4.94 to 10.60). Attack rates were higher in adults (8.49%, 95%CI 5.16 to 13.67) than in children (4.79%, 95%CI 3.05 to 7.45), with similar CFR (5.99%, 95%CI 2.31 to 14.63 vs. 5.85%, 95%CI 3.35 to 10.02). By assuming RSV attack rates as a reference group, influenza (RR 0.518; 95%CI 0.446 to 0.601), adenovirus (RR 0.679, 95%CI 0.553 to 0.830), and human metapneumovirus (RR 0.536, 95%CI 0.438 to 0.655) were associated with a substantially reduced risk for developing corresponding respiratory infection. Despite the heterogeneous settings and the uneven proportion of adult and pediatric cases, our study has identified high attack rates and a substantial CFR of RSV in recipients of BMT, stressing the importance of specifically tailored preventive strategies and the need for effective treatment options.

Opportunistic Infections Post-Lung Transplantation: Viral, Fungal, and Mycobacterial

Opportunistic infections are a leading cause of lung transplant recipient morbidity and mortality. Risk factors for infection include continuous exposure of the lung allograft to the external environment, high levels of immunosuppression, impaired mucociliary clearance and decreased cough reflex, and impact of the native lung microbiome in single lung transplant recipients. Infection risk is mitigated through careful pretransplant screening of recipients and donors, implementation of antimicrobial prophylaxis strategies, and routine surveillance posttransplant. This review describes common viral, fungal, and mycobacterial infectious after lung transplant and provides recommendations on prevention and treatment.

Respiratory Syncytial Virus-Associated Deaths among Children under Five before and during the COVID-19 Pandemic in Bangladesh

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory infections in young children worldwide. RSV-associated deaths in children are underreported in Bangladesh. We analyzed hospital-based surveillance data on severe acute respiratory infections (SARIs) in under-five children before (August 2009-February 2020) and during the COVID-19 pandemic (March 2020-March 2022). Using the World Health Organization definition, we identified SARI cases in 14 tertiary-level hospitals. Nasopharyngeal and oropharyngeal swabs were collected for real-time reverse-transcriptase-polymerase chain reaction (rRT-PCR) testing of six respiratory viruses, including RSV. SARI deaths during the pandemic (2.6%, 66) were higher than pre-pandemic (1.8%, 159; p < 0.001). Nearly half of pandemic deaths (47%) had underlying respiratory viruses, similar to the pre-pandemic rate (45%). RSV detection in deaths was consistent pre-pandemic (13%, 20/159) and during the pandemic (12%, 8/66). Children aged < 6 months constituted 57% (16) of RSV-related deaths. Evaluating interventions like maternal vaccination and infant monoclonal antibody prophylaxis is crucial to address RSV, a major contributor to under-five SARI deaths.

Epidemiology of Bronchiolitis and Respiratory Syncytial Virus and Analysis of Length of Stay from 2015 to 2022: Retrospective Observational Study of Hospital Discharge Records from an Italian Southern Province before and during the COVID-19 Pandemic

BACKGROUND

Severe respiratory infections, including pneumonia or bronchiolitis, caused by RSV can range from mild upper respiratory tract infections to those leading to hospitalization and serious complications such as respiratory failure in children. High-risk groups, such as premature infants and infants with underlying medical conditions, have a higher susceptibility to severe RSV disease. We conducted a retrospective study from years 2015 to 2022 in the Local Health Authority (LHA) of Pescara that counts about 320,000 inhabitants, with the aim to evaluate the burden of RSV infection, focusing on the incidence, hospitalization, and characteristics that may prolong hospital stays.

METHODS

All hospitalizations from 2015 to 2022 were extracted from the hospital discharge record. The monthly hospitalization rates were calculated and standardized by gender and age for the population resident in the Province of Pescara on 1 January 2015.

RESULTS

During the study period, 31,837 admissions were reported among patients aged less than 6 years. Of those, 520 hospitalizations were referred for bronchiolitis. Monthly admission rates highlighted the seasonality of bronchiolitis admissions, with higher rates in the months from December to March in all study years included. The winter seasons of years 2021 and 2022 reported a surge in bronchiolitis incidence, with a rate of 4.0/1000 (95% CI 2.964-5.146) in December 2021 and 4.0 (95% CI 2.891-5.020) in December 2022.

CONCLUSIONS

Bronchiolitis represents an important cause of hospitalization among patients aged less than 6 years. The incidence was particularly increased during the winter seasons in years 2021 and 2022.

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.

Non-glycosylated G protein with CpG ODN provides robust protection against respiratory syncytial virus without inducing eosinophilia

Introduction

Respiratory syncytial virus (RSV) vaccines targeting the fusion glycoprotein (F protein) are highly effective clinically in preventing RSV challenges. The attachment glycoprotein (G protein) is a potentially effective vaccine antigen candidate, as it is important for cell adhesion during infection. However, vaccine-associated enhanced diseases in mice, such as eosinophilic lung inflammation following RSV challenge, are a concern with G protein vaccines. This study aimed to design an effective G protein vaccine with enhanced safety and efficacy by evaluating the efficacy and adverse reactions of vaccines composed of different recombinant G proteins and adjuvants in mice.

Methods

Mice were subcutaneously immunized with glycosylated G protein expressed in mammalian cells (mG), non-glycosylated G protein expressed in Escherichia coli (eG), or F protein with or without aluminum salts (alum), CpG oligodeoxynucleotide (CpG ODN), or AddaVax. After vaccination, the levels of G-specific antibody and T-cell responses were measured. The immunized mice were challenged with RSV and examined for the viral load in the lungs and nasal turbinates, lung-infiltrating cells, and lung pathology.

Results

mG with any adjuvant was ineffective at inducing G-specific antibodies and had difficulty achieving both protection against RSV challenge and eosinophilia suppression. In particular, mG+CpG ODN induced G-specific T helper 1 (Th1) cells but only a few G-specific antibodies and did not protect against RSV challenge. However, eG+CpG ODN induced high levels of G-specific antibodies and Th1 cells and protected against RSV challenge without inducing pulmonary inflammation. Moreover, the combination vaccine of eG+F+CpG ODN showed greater protection against upper respiratory tract RSV challenge than using each single antigen vaccine alone.

Discussion

These results indicate that the efficacy of recombinant G protein vaccines can be enhanced without inducing adverse reactions by using appropriate antigens and adjuvants, and their efficacy is further enhanced in the combination vaccine with F protein. These data provide valuable information for the clinical application of G protein vaccines.

Respiratory syncytial virus burden and risk factors for severe disease in patients presenting to the emergency department with flu-like symptoms or acute respiratory failure

BACKGROUND

Predictors of Respiratory Syncytial Virus (RSV) infection and determinants of RSV unfavorable outcomes are still unclear. We assessed RSV burden and investigated the risk factors associated with RSV positive swab and RSV severe disease.

METHODS

A retrospective, single center, cohort study included all consecutive patients referred to the emergency department of L. Sacco University Hospital (Milan) with flu-like symptoms or acute respiratory failure (aRF) tested per protocol for SARS-CoV-2, RSV, Influenza A (InvA) during the 2022-2023 autumn/winter season. Clinical characteristics and patients' outcomes were registered. Respiratory failure, need for respiratory support, shock, sepsis or in-hospital death defined severe disease.

MAIN FINDINGS

The analysis included 717 patients (65.1% negative swab, 14.1% InvA, 8.5% RSV, 8.6% SARS-CoV-2, 3.6% other viruses). Compared with the study cohort, RSV patients had the highest occurrence of aRF (62.7%) and severe disease (70.5%); mortality was similar to InvA (6.6% vs 5.9%, p = 0.874). Compared with InvA patients, RSV patients were older (p = 0.009), had higher Charlson index (p = 0.001), higher prevalence of chronic heart failure (p = 0.001) and were more frequently on ICS (p = 0.026) and immunosuppressants (p = 0.018). Heart failure [OR (95%CI):3.286 (1.031-10.835); p = 0.041], chronic exposure to ICS [OR (95%CI):2.377 (1.254-4.505); p = 0.008] and immunosuppressants [OR (95%CI):3.661 (1.246-10.754); p = 0.018] predicted RSV infection. Glycaemia ≥120 mg/dL [OR (95%CI):5.839 (1.155-29.519); p = 0.033], leucocytes ≥8000 cells/μL [OR (95%CI):5.929 (1.090-32.268); p = 0.039], and past/active smoking [OR (95%CI):7.347 (1.301-41.500); p = 0.024] predicted severe RSV disease.

CONCLUSIONS

RSV infection is associated with significant mortality and morbidity. Preventive strategies for RSV infection such as vaccination are highly warranted, especially in older patients with cardiovascular and chronic respiratory conditions.

Clinical impact of human parainfluenza virus infections before and during the COVID-19 pandemic in Southern China

Human parainfluenza viruses (HPIVs) are a leading cause of acute respiratory tract infections (ARTIs). Non-pharmaceutical interventions (NPIs) were widely administered to combat the pandemic of the coronavirus disease 2019 (COVID-19). Respiratory specimens were obtained from 10,454 hospitalized children with ARTIs to detect HPIV. We investigated differences in epidemiological and clinical characteristics of HPIV infections before (2017-2019) and during the COVID-19 pandemic (2020-2022). HPIVs were detected in 392 (3.75%, 392/10,454) patients, of whom 70 (17.86%), 48 (12.24%), and 274 (69.90%) were positive for HPIV1, HPIV2, and HPIV3, respectively. Detection rates of HPIV3 were higher in 2020-2022 than in 2017-2019 (3.38% vs. 2.24%). The seasonal distribution of HPIV1 showed no difference, but HPIV3 peaked between September and December during the COVID-19 pandemic, which differed from previous epidemiological patterns. Compared to the period before the COVID-19 pandemic, there has been a noticeable decrease in the incidence of asthma, moist rales, and emesis in patients infected with HPIV1 and in asthma, expectoration, and severe pneumonia in patients infected with HPIV3 during 2020-2022. The detection rates of HPIV increased in Southern China during the COVID-19 outbreak, which underlines the importance of continuous surveillance of HPIV in the next epidemic season.

A fatal case of neonatal viral sepsis caused by human parainfluenza virus type 3

BACKGROUND

Sepsis is a systemic inflammatory response syndrome caused by severe infection in children, but cases of sepsis associated with human parainfluenza virus (HPIV) have been rarely reported in newborns.

CASE PRESENTATION

We report a case of HPIV-3 positive full-term newborn admitted to the Neonatal Intensive Care Unit of Beijing Children's Hospital due to hematuria, gloomy spirit, inactivity and loss of appetite for 6 h. He had septic shock when he arrived the Accident & Emergency Department requiring immediate intubation and mechanical ventilation. Intravenous antibiotics were started. He had completely negative response to all anti-shock treatments including fluid resuscitation and vasopressor supports, and died 14 h later. Viral nucleic acid detection and metagenomic next-generation sequencing (mNGS) analyses of nasopharyngeal aspirate and blood specimens verified an HPIV-3 infection, with negative bacterial culture results. The HPIV-3 strain detected in this patient was subtyped as HPIV C3a, and two unreported amino acid mutations were found in the HN protein region.

CONCLUSION

The patient had a severe infection associated with HPIV-3, which was the cause of sepsis and septic shock. This study showed the diagnostic value of mNGS in etiological diagnosis, especially in severe neonatal case.

Seasonality and risk factor analysis of respiratory syncytial virus infection in children in Taiwan-A retrospective study from 1995 to 2005

Respiratory syncytial virus (RSV) is one of the important pathogens leading to acute respiratory tract infection in infants and young children. We aimed to investigate the seasonality of RSV infection in different parts of Taiwan and to delineate the risk factors for severe RSV infections. We collected RSV-infected patients' data by retrospective chart review. A total of 1740 RSV-infected children aged under 18 years were enrolled. The infection was acquired during hospitalization in 103 (7.1%) children, while none of them required ventilator support or needed intensive care before RSV infection. The need for intensive care or ventilator support was significantly associated with congenital heart disease (CHD), chronic lung disease, and neuromuscular diseases. Age <1 year and nosocomially acquired infection are also significant predictors for the need of intensive care. Only the presence of CHD, especially acyanotic CHD, was significantly associated with a fatal outcome. RSV infection occurs all year round. Monthly distribution of RSV infections in Northern Taiwan showed a bimodal pattern, with one peak from March to May, and another from August to October. The distribution in Southern Taiwan showed a single peak from April to July. The occurrence of RSV correlates positively with temperature and rain. The bimodal seasonal distribution pattern in Northern Taiwan may be a transitional pattern shifting from a single high winter peak in temperate areas to a wider summer peak in tropical areas. Continuous surveillance is needed to explore the possible effect of global warming on the seasonality of RSV infection.

Circulation patterns and molecular epidemiology of human respiratory syncytial virus over five consecutive seasons in Morocco

Background

Respiratory syncytial virus (HRSV) is the leading cause of respiratory tract infections in infants and young children. we investigated the prevalence and characteristics of HRSV in Morocco and explored trends in circulating genotypes through partial G gene analysis of HRSV strains prevalent from 2012 to 2017.

Methods

Respiratory samples were gathered from both outpatients and inpatients meeting ILI or SARI case definitions. The patients' ages varied from 1 month to 99 years old. Nucleic acids were extracted and HRSV type/subtype was detected by RT-qPCR. A subset of positive samples was randomly selected in each epidemic year, the complete viral genome was sequenced, phylogenetic analysis was performed using the MEGA7 program and the genotypes were confirmed.

Results

The 3679 specimens were collected from 2012 to 2017, of which 726 (19.7%) were positive for HRSV. The 35% (257/726) of HRSV-positives were of the HRSV-A subtype, while the HRSV-B subtype accounted for 61% (442/726). The co-infection rate was 3.7% (27/726). The virus circulates in a periodic pattern, where epidemics occur during the fall months through early spring. HRSV genotype was confirmed in 127 specimens (56 HRSV-A and 71 HRSV-B). Based on phylogenetic analysis, all HRSV-A were ON1 genotype, and HRSV-B were mostly BA9 genotype. HRSV-B belonging to the BA10 genotype was detected in 2012 exclusively.

Conclusions

BA9, BA10, and ON1 were the only HRSV genotypes detected between 2012 and 2017. Variations in the G gene amino acid chain were identified in local strains, which suggests an increased need for continuous genomic surveillance.

Increased innate immune activation induces protective RSV-specific lung-resident memory T cells in neonatal mice

Young infants frequently experience respiratory tract infections, yet vaccines designed to provide mucosal protection are lacking. Localizing pathogen-specific cellular and humoral immune responses to the lung could provide improved immune protection. We used a well-characterized murine model of respiratory syncytial virus (RSV) to study the development of lung-resident memory T cells (TRM) in neonatal compared to adult mice. We demonstrated that priming with RSV during the neonatal period failed to retain RSV-specific clusters of differentiation (CD8) TRM 6 weeks post infection, in contrast to priming during adulthood. The reduced development of RSV-specific TRM was associated with poor acquisition of two key markers of tissue residence: CD69 and CD103. However, by augmenting both innate immune activation and antigen exposure, neonatal RSV-specific CD8 T cells increased expression of tissue-residence markers and were maintained in the lung at memory time points. Establishment of TRM correlated with more rapid control of the virus in the lungs upon reinfection. This is the first strategy to effectively establish RSV-specific TRM in neonates providing new insight into neonatal memory T cell development and vaccine strategies.

The role of vaccination in COPD: influenza, SARS-CoV-2, pneumococcus, pertussis, RSV and varicella zoster virus

Exacerbations of COPD are associated with worsening of the airflow obstruction, hospitalisation, reduced quality of life, disease progression and death. At least 70% of COPD exacerbations are infectious in origin, with respiratory viruses identified in approximately 30% of cases. Despite long-standing recommendations to vaccinate patients with COPD, vaccination rates remain suboptimal in this population.Streptococcus pneumoniae is one of the leading morbidity and mortality causes of lower respiratory tract infections. The Food and Drug Administration recently approved pneumococcal conjugate vaccines that showed strong immunogenicity against all 20 included serotypes. Influenza is the second most common virus linked to severe acute exacerbations of COPD. The variable vaccine efficacy across virus subtypes and the impaired immune response are significant drawbacks in the influenza vaccination strategy. High-dose and adjuvant vaccines are new approaches to tackle these problems. Respiratory syncytial virus is another virus known to cause acute exacerbations of COPD. The vaccine candidate RSVPreF3 is the first authorised for the prevention of RSV in adults ≥60 years and might help to reduce acute exacerbations of COPD. The 2023 Global Initiative for Chronic Lung Disease report recommends zoster vaccination to protect against shingles for people with COPD over 50 years.

Prenatal exposure to RSV season influences first-year risk of RSV lower respiratory illness and RSV-specific immune responses assessed at birth

Maternal-to-fetal transmission of respiratory syncytial virus (RSV) has been shown to occur but whether late prenatal exposure to RSV season influences offspring postnatal RSV-lower respiratory illness (LRI) risk in early life or RSV immune status at birth is unclear. In this study, the duration of third trimester RSV season exposure was determined for 1,094 newborns of the Tucson Children's Respiratory Study (TCRS) and found to show an inverse relation to risk for first RSV-LRI in the first year. Cord blood anti-RSV antibody is related to third trimester RSV season exposure but not to first year RSV-LRI risk. In a separate birth cohort (the Infant Immune Study), supernatants from cord blood mononuclear cells stimulated with the recall antigen, UV-inactivated RSV, were assayed for IFN-γ and IL-4. The frequency of detectable IFN-γ (but not IL-4) was increased for those with at least 2 mo of third trimester RSV season exposure, suggestive of a fetal immune response to RSV. IMPORTANCE Our study found that duration of third trimester exposure to RSV season related inversely to subsequent risk of postnatal RSV-LRI in the first year, thus implicating this exposure as an important factor in reducing risk of postnatal RSV-LRIs, a risk reduction that appears to be independent of maternally transferred anti-RSV antibody level. The increase in frequency of detectable IFN-γ and not IL-4 in response to UV-inactivated RSV in cord blood immune cells for infants with greater third trimester exposure to RSV season is suggestive of a Type-1 immune response to RSV occurring in utero.

Host Responses to Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) infections are a constant public health problem, especially in infants and older adults. Virtually all children will have been infected with RSV by the age of two, and reinfections are common throughout life. Since antigenic variation, which is frequently observed among other respiratory viruses such as SARS-CoV-2 or influenza viruses, can only be observed for RSV to a limited extent, reinfections may result from short-term or incomplete immunity. After decades of research, two RSV vaccines were approved to prevent lower respiratory tract infections in older adults. Recently, the FDA approved a vaccine for active vaccination of pregnant women to prevent severe RSV disease in infants during their first RSV season. This review focuses on the host response to RSV infections mediated by epithelial cells as the first physical barrier, followed by responses of the innate and adaptive immune systems. We address possible RSV-mediated immunomodulatory and pathogenic mechanisms during infections and discuss the current vaccine candidates and alternative treatment options.

Vitamin D3 protects against respiratory syncytial virus-induced barrier dysfunction in airway epithelial cells via PKA signaling pathway

Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infection in infants and young children globally and is responsible for hospitalization and mortality in the elderly population. Virus-induced airway epithelial barrier damage is a critical step during RSV infection, and emerging studies suggest that RSV disrupts the tight junctions (TJs) and adherens junctions (AJs) between epithelial cells, increasing the permeability of the airway epithelial barrier. The lack of commercially available vaccines and effective antiviral drugs for RSV emphasizes the need for new management strategies. Vitamin D3 is a promising intervention for viral infection due to its critical role in modulating innate immune responses. However, there is limited evidence on the effect of vitamin D3 on RSV pathogenies. Here, we investigated the impact of vitamin D3 on RSV-induced epithelial barrier dysfunction and the underlying mechanisms. We found that pre-incubation with 1,25(OH)2D3, the active form of vitamin D3, alleviated RSV-induced epithelial barrier disruption in a dose-dependent manner without affecting viability in 16HBE cells. 1,25(OH)2D3 induced minor changes in the protein expression level of TJ/AJ proteins in RSV-infected cells. We observed increased CREB phosphorylation at Ser133 during 1,25(OH)2D3 exposure, indicating that vitamin D3 triggered protein kinase A (PKA) activity in 16HBE. PKA inhibitors modified the restoration of barrier function by 1,25(OH)2D3 in RSV-infected cells, implying that PKA signaling is responsible for the protective effects of vitamin D3 against RSV-induced barrier dysfunction in airway epithelial cells. Our findings suggest vitamin D3 as a prophylactic intervention to protect the respiratory epithelium during RSV infections.

Pathogen Profiles in Outpatients with Non-COVID-19 during the 7th Prevalent Period of COVID-19 in Gunma, Japan

The identification of pathogens associated with respiratory symptoms other than the novel coronavirus disease 2019 (COVID-19) can be challenging. However, the diagnosis of pathogens is crucial for assessing the clinical outcome of patients. We comprehensively profiled pathogens causing non-COVID-19 respiratory symptoms during the 7th prevalent period in Gunma, Japan, using deep sequencing combined with a next-generation sequencer (NGS) and advanced bioinformatics technologies. The study included nasopharyngeal swabs from 40 patients who tested negative for severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) using immuno-chromatography and/or quantitative reverse transcription polymerase chain reaction (qRT-PCR) methods. Comprehensive pathogen sequencing was conducted through deep sequencing using NGS. Additionally, short reads obtained from NGS were analyzed for comprehensive pathogen estimation using MePIC (Metagenomic Pathogen Identification Pipeline for Clinical Specimens) and/or VirusTap. The results revealed the presence of various pathogens, including respiratory viruses and bacteria, in the present subjects. Notably, human adenovirus (HAdV) was the most frequently detected virus in 16 of the 40 cases (40.0%), followed by coryneforms, which were the most frequently detected bacteria in 21 of the 40 cases (52.5%). Seasonal human coronaviruses (NL63 type, 229E type, HKU1 type, and OC43 type), human bocaviruses, and human herpesviruses (human herpesvirus types 1-7) were not detected. Moreover, multiple pathogens were detected in 50% of the subjects. These results suggest that various respiratory pathogens may be associated with non-COVID-19 patients during the 7th prevalent period in Gunma Prefecture, Japan. Consequently, for an accurate diagnosis of pathogens causing respiratory infections, detailed pathogen analyses may be necessary. Furthermore, it is possible that various pathogens, excluding SARS-CoV-2, may be linked to fever and/or respiratory infections even during the COVID-19 pandemic.

Advances in mRNA vaccines for viral diseases

Since the onset of the pandemic caused by severe acute respiratory syndrome coronavirus 2, messenger RNA (mRNA) vaccines have demonstrated outstanding performance. mRNA vaccines offer significant advantages over conventional vaccines in production speed and cost-effectiveness, making them an attractive option against other viral diseases. This article reviewed recent advances in viral mRNA vaccines and their delivery systems to provide references and guidance for developing mRNA vaccines for new viral diseases.

Surveillance towards preventing paediatric incidence of respiratory syncytial virus attributable respiratory tract infection in primary and secondary/tertiary healthcare settings in Merseyside, Cheshire and Bristol, UK

INTRODUCTION

Respiratory syncytial virus (RSV) is a common respiratory virus, particularly affecting children, and can cause respiratory infections such as croup and bronchiolitis. The latter is a leading cause of paediatric hospitalisation within the UK. Children <3 years of age and/or with underlying health conditions are more vulnerable to severe RSV infection.There are currently limited data on the incidence of laboratory-confirmed RSV, particularly within primary care settings and outside the typical 'RSV season', which in the Northern hemisphere tends to coincide with winter months. There is also a lack of data on the health economic impact of RSV infection on families and healthcare systems.This observational surveillance study aims to collect data on the incidence of laboratory-confirmed RSV-attributable respiratory tract infection (RTI) in children aged <3 years presenting to primary, secondary or tertiary care; it also aims to estimate the health economic and quality of life impact of RSV-attributable infection in this cohort. Such data will contribute to informing public health strategies to prevent RSV-associated infection, including use of preventative medications.

METHODS AND ANALYSIS

Parents/carers of children <3 years of age with RTI symptoms will consent for a respiratory sample (nasal swab) to be taken. Laboratory PCR testing will assess for the presence of RSV and/or other pathogens. Data will be obtained from medical records on demographics, comorbidities, severity of infection and hospitalisation outcomes. Parents will complete questionnaires on the impact of ongoing infection symptoms at day 14 and 28 following enrolment. The primary outcome is incidence of laboratory-confirmed RSV in children <3 years presenting to primary, secondary or tertiary care with RTI symptoms leading to health-seeking behaviours. Recruitment will be carried out from December 2021 to March 2023, encompassing two UK winter seasons and intervening months.

ETHICS AND DISSEMINATION

Ethical approval has been granted (21/WS/0142), and study findings will be published as per International Committee of Medical Journal Editors' guidelines.

RSV-induced expanded ciliated cells contribute to bronchial wall thickening

Viral infection, particularly respiratory syncytial virus (RSV), causes inflammation in the bronchiolar airways (bronchial wall thickening, also known as bronchiolitis). This bronchial wall thickening is a common pathophysiological feature in RSV infection, but it causes more fatalities in infants than in children and adults. However, the molecular mechanism of RSV-induced bronchial wall thickening remains unknown, particularly in healthy adults. Using highly differentiated pseudostratified airway epithelium generated from primary human bronchial epithelial cells, we revealed RSV-infects primarily ciliated cells. The infected ciliated cells expanded substantially without compromising epithelial membrane integrity and ciliary functions and contributed to the increased height of the airway epithelium. Furthermore, we identified multiple factors, e.g., cytoskeletal (ARP2/3-complex-driven actin polymerization), immunological (IP10/CXCL10), and viral (NS2), contributing to RSV-induced uneven epithelium height increase in vitro. Thus, RSV-infected expanded cells contribute to a noncanonical inflammatory phenotype, which contributes to bronchial wall thickening in the airway, and is termed cytoskeletal inflammation.

RSV infection does not induce EMT

Respiratory syncytial virus (RSV) infection does not cause severe disease in most of us despite suffering from multiple RSV infections in our lives. However, infants, young children, older adults, and immunocompromised patients are unfortunately vulnerable to RSV-associated severe diseases. A recent study suggested that RSV infection causes cell expansion, resulting in bronchial wall thickening in vitro. Whether the virus-induced changes in the lung airway resemble epithelial-mesenchymal transition (EMT) is still unknown. Here, we report that RSV does not induce EMT in three different in vitro lung models: the epithelial A549 cell line, primary normal human bronchial epithelial cells, and pseudostratified airway epithelium. We found that RSV increases the cell surface area and perimeter in the infected airway epithelium, which is distinct from the effects of a potent EMT inducer, TGF-β1-driven cell elongation-indicative of cell motility. A genome-wide transcriptome analysis revealed that both RSV and TGF-β1 have distinct modulation patterns of the transcriptome, which suggests that RSV-induced changes are distinct from EMT.