Respiratory syncytial virus morbidity, premorbid factors, seasonality, and implications for prophylaxis

A First-in-Human Trial to Evaluate the Safety and Immunogenicity of a G Protein-Based Recombinant Respiratory Syncytial Virus Vaccine in Healthy Adults 18-45 Years of Age

BACKGROUND

With the enormous morbidity and mortality caused by respiratory syncytial virus (RSV) infections among infants and the elderly, vaccines against RSV infections are in large market demand.

METHODS

We conducted a first-in-human (FIH), randomized, double-blind, placebo-controlled dose escalation study to evaluate the safety and immunogenicity response of the rRSV vaccine (BARS13) in healthy adults aged 18-45. A total of 60 eligible participants were randomly assigned to receive one of four dose levels or vaccination regimens of BARS13 or placebo at a 4:1 ratio.

RESULTS

The mean age was 27.40, and 23.3% (14/60) were men. No treatment-emergent adverse events (TEAEs) led to study withdrawal within 30 days after each vaccination. No serious adverse event (SAE) was reported. Most of the treatment-emergent adverse events (TEAEs) recorded were classified as mild. The high-dose repeat group had a serum-specific antibody GMC of 885.74 IU/mL (95% CI: 406.25-1931.17) 30 days after the first dose and 1482.12 IU/mL (706.56-3108.99) 30 days after the second dose, both higher than the GMC in the low-dose repeat group (885.74 IU/mL [406.25-1931.17] and 1187.10 IU/ mL [610.01-2310.13]).

CONCLUSIONS

BARS13 had a generally good safety and tolerability profile, and no significant difference in terms of adverse reaction severity or frequency was observed between different dose groups. The immune response in repeat-dose recipients shows more potential in further study and has guiding significance for the dose selection of subsequent studies.

Respiratory Syncytial Virus is the Most Common Causative Agent of Viral Bronchiolitis in Young Children: An Updated Review

BACKGROUND

Viral bronchiolitis is a common condition and a leading cause of hospitalization in young children.

OBJECTIVE

This article provides readers with an update on the evaluation, diagnosis, and treatment of viral bronchiolitis, primarily due to RSV.

METHODS

A PubMed search was conducted in December 2021 in Clinical Queries using the key terms "acute bronchiolitis" OR "respiratory syncytial virus infection". The search included clinical trials, randomized controlled trials, case control studies, cohort studies, meta-analyses, observational studies, clinical guidelines, case reports, case series, and reviews. The search was restricted to children and English literature. The information retrieved from the above search was used in the compilation of this article.

RESULTS

Respiratory syncytial virus (RSV) is the most common viral bronchiolitis in young children. Other viruses such as human rhinovirus and coronavirus could be etiological agents. Diagnosis is based on clinical manifestation. Viral testing is useful only for cohort and quarantine purposes. Cochrane evidence-based reviews have been performed on most treatment modalities for RSV and viral bronchiolitis. Treatment for viral bronchiolitis is mainly symptomatic support. Beta-agonists are frequently used despite the lack of evidence that they reduce hospital admissions or length of stay. Nebulized racemic epinephrine, hypertonic saline and corticosteroids are generally not effective. Passive immunoprophylaxis with a monoclonal antibody against RSV, when given intramuscularly and monthly during winter, is effective in preventing severe RSV bronchiolitis in high-risk children who are born prematurely and in children under 2 years with chronic lung disease or hemodynamically significant congenital heart disease. Vaccines for RSV bronchiolitis are being developed. Children with viral bronchiolitis in early life are at increased risk of developing asthma later in childhood.

CONCLUSION

Viral bronchiolitis is common. No current pharmacologic treatment or novel therapy has been proven to improve outcomes compared to supportive treatment. Viral bronchiolitis in early life predisposes asthma development later in childhood.

Risk factors for hospitalized respiratory syncytial virus disease and its severe outcomes

Introduction

Respiratory syncytial virus (RSV) is a major cause of hospital admission for acute lower respiratory tract infection in young children.

Objectives

We aimed to identify risk factors for hospitalized RSV disease and its severe outcomes.

Methods

We conducted a retrospective cohort study analyzing data of a ICD‐10‐code‐based hospital surveillance for severe acute respiratory infections (SARI). Using univariable and multivariable logistic regression analysis, we assessed age‐group, gender, season, and underlying medical conditions as possible risk factors for RSV and its severe outcomes including ICU admission, application of ventilator support, and death, respectively.

Results

Of the 413 552 patients hospitalized with SARI in the database, 8761 were diagnosed with RSV from week 01/2009 to 20/2018 with 97% (8521) aged <5 years. Among children aged <5 years, age‐groups 0‐5 months (OR: 20.29, 95% CI: 18.37‐22.41) and 6 months‐1 year (OR: 4.59, 95% CI: 4.16‐5.06), and underlying respiratory and cardiovascular disorders specific to the perinatal period (OR: 1.32, 95% CI: 1.11‐1.57) were risk factors for being diagnosed with RSV. Age‐group 0‐5 months (OR: 2.39, 95% CI: 1.45‐3.94), low birth weight (OR: 6.77, 95% CI: 1.28‐35.71), preterm newborn (OR: 6.71, 95% CI: 2.19‐20.61), underlying respiratory and cardiovascular disorders specific to the perinatal period (OR: 4.97, 95% CI: 3.36‐7.34), congenital malformation of the heart (OR: 3.65, 95% CI: 1.90‐7.02), congenital malformation of the great vessels (OR: 3.50, 95% CI: 1.10‐11.18), congenital defect originating in perinatal period (OR: 4.07, 95% CI: 1.71‐9.70), cardiovascular disease (OR: 5.19, 95% CI: 2.77‐9.72), neurological disorders (OR: 6.48, 95% CI: 3.76‐11.18), blood disease (OR: 3.67, 95% CI: 1.98‐6.79), and liver disease (OR: 14.99, 95% CI: 1.49‐150.82) contributed to ICU admission in RSV cases.

Conclusions

Using ICD‐10‐based surveillance data allows to identify risk factors for hospitalized RSV disease and its severe outcomes, and quantify the risk in different age‐groups.

Ten years of severe respiratory syncytial virus infections in a tertiary paediatric intensive care unit

AIM

To describe the epidemiology and treatment of respiratory syncytial virus (RSV) infection in a tertiary paediatric intensive care unit (PICU), including the clinical presentations, comorbidities, respiratory support required, costs and outcomes.

METHODS

This study was an analysis of a database for all children with RSV infections admitted to the PICU in Melbourne between 2005 and 2015.

RESULTS

A total of 604 episodes of community-acquired RSV infections were analysed, and the median age of children was 4 months (interquartile range 2-14 months); 94% of cases had lower respiratory tract infection, principally bronchiolitis, and 8.9% presented with extrapulmonary features. Respiratory support included humidified high-flow nasal cannula oxygen therapy (76% of patients since its introduction in 2011), non-invasive ventilation (41%) and intubation and mechanical ventilation (32%). Almost half (n = 270; 45%) had one or more pre-existing comorbid condition. Risk factors for intubation and mechanical ventilation were presence of comorbidities (odds ratio 1.97; confidence interval 1.39-2.79, P < 0.001) and transfer from an external hospital (odds ratio 1.82; confidence interval 1.58-2.57, P < 0.001). Of the children without pre-existing comorbidities, 25% required intubation and mechanical ventilation. Following the introduction of humidified high-flow nasal cannula oxygen therapy, the number of annual PICU admissions for RSV infection doubled; however, the number of children requiring intubation remained unchanged. The median length of intensive care unit stay was 3.7 days and further hospital stay was 3.6 days, and the average cost per case was approximately AU$20000.

CONCLUSIONS

RSV infection carries a high burden in PICU, in bed-days and cost. Chronic comorbidities and transfer from a peripheral hospital were associated with a higher rate of need for mechanical ventilation.

Bacterial co-infection of the respiratory tract in ventilated children with bronchiolitis; a retrospective cohort study

Background

Viral bronchiolitis is the most common cause of respiratory failure requiring invasive ventilation in young children. Bacterial co-infections may complicate and prolong paediatric intensive care unit (PICU) stay. Data on prevalence, type of pathogens and its association with disease severity are limited though. These data are especially important as bacterial co-infections may be treated using antibiotics and could reduce disease severity and duration of PICU stay. We investigated prevalence of bacterial co-infection and its association with disease severity and PICU stay.

Methods

Retrospective cohort study of the prevalence and type of bacterial co-infections in ventilated children performed in a 14-bed tertiary care PICU in The Netherlands. Children less than 2 years of age admitted between December 2006 and November 2014 with a diagnosis of bronchiolitis and requiring invasive mechanical ventilation were included. Tracheal aspirates (TA) and broncho-alveolar lavages (BAL) were cultured and scored based on the quantity of bacteria colony forming units (CFU) as: co-infection (TA > 10^{^5}/BAL > 10^{^4} CFU), low bacterial growth (TA < 10^{^5}/BAL < 10^{^4} CFU), or negative (no growth). Duration of mechanical ventilation and PICU stay were collected using medical records and compared against the presence of co-infection using univariate and multivariate analysis.

Results

Of 167 included children 63 (37.7%) had a bacterial co-infection and 67 (40.1%) low bacterial growth. Co-infections occurred within 48 h from intubation in 52 out 63 (82.5%) co-infections. H.influenza (40.0%), S.pneumoniae (27.1%), M.catarrhalis (22.4%), and S.aureus (7.1%) were the most common pathogens. PICU stay and mechanical ventilation lasted longer in children with co-infections than children with negative cultures (9.1 vs 7.7 days, p = 0.04 and 8.1vs 6.5 days, p = 0.02).

Conclusions

In this large study, bacterial co-infections occurred in more than a third of children requiring invasive ventilation for bronchiolitis and were associated with longer PICU stay and mechanical ventilation. These findings support a clinical trial of antibiotics to test whether antibiotics can reduce duration of PICU stay.

Respiratory Syncytial Virus Prophylaxis in Neurologic and Muscular Disorders in the Canadian Respiratory Syncytial Virus Evaluation Study of Palivizumab

BACKGROUND

This study aimed to examine the risk of respiratory-related hospitalization in children with neurologic and muscular disorders (NMDs) who received respiratory syncytial virus (RSV) prophylaxis in the Canadian RSV Evaluation Study of Palivizumab.

METHODS

Canadian RSV Evaluation Study of Palivizumab is a prospective registry of children who received ≥1 palivizumab injection among 32 Canadian sites. Demographic data were collected at enrollment, and respiratory events were documented monthly. Cox proportional hazard analyses were conducted to compare respiratory illness-related hospitalization (RIH) and RSV-related hospitalization (RSVH) among children with NMD and those prophylaxed for standard indications (SI) and complex medical disorders.

RESULTS

Group differences were found in enrollment age and weight, birth weight, household crowding, neonatal stay and supplemental oxygen requirement (all P < 0.05). RIH and RSVH incidences were 19.2%, 3.3% (NMD, n = 605); 6.0%, 1.5% (SI, n = 20,335), 9.4%, 1.6% (complex medical disorders, n = 4063), respectively. Children with NMD had a higher risk of RIH (hazard ratio [HR]: 1.90; 95% confidence interval (CI): 1.41-2.56; P < 0.0005) than those with SI. RSVH risk was greater in children with NMD compared with both the SI (HR: 2.26; 95% CI: 1.38-3.72; P = 0.001) and complex medical disorders groups (HR: 2.74; 95% CI: 1.55-4.84; P = 0.001). Children with more severe infantile onset NMD had a higher risk of RIH than those with general hypotonic disorders (HR: 1.69; 95% CI: 1.06-2.68; P = 0.027) but not RSVH.

CONCLUSIONS

Children with NMD who received palivizumab had a higher risk of both RIH and RSVH. Our results imply that all children with NMD, regardless of disease severity, are at risk for respiratory-related illness and RSV infection.

The Impact of RSV-Associated Respiratory Disease on Children in Asia

Acute respiratory tract infections (ARTIs) are leading contributors to the global infectious disease burden, which is estimated to be 112,900,000 disability adjusted life years. Viruses contribute to the etiology of ARTIs in a big way compared with other microorganisms. Since the discovery of respiratory syncytial virus (RSV) 61 years ago, the virus has been recognized as a major cause of ARTI and hospitalization in children. The morbidity and mortality attributable to RSV infection appear to be higher in infants < 3 months and in those with known risk factors such as prematurity, chronic lung, and congenital heart diseases. Crowded living conditions, exposure to tobacco smoke, and industrial or other types of air pollution also increase the risk of RSV-associated ARTI. Many epidemiological studies have been conducted in developed countries to understand the seasonal patterns and risk factors associated with RSV infections. Dearth of information on RSV-associated morbidity and mortality in Asian and developing countries indicates the need for regional reviews to evaluate RSV-associated disease burden in these countries. Epidemiological studies including surveillance is the key to track the disease burden including risk factors, seasonality, morbidity, and mortality associated with RSV infection in these countries. These data will contribute to improve the clinical diagnosis and plan preventive strategies in resource-limited developing countries.

Incidence and seasonality of respiratory syncytial virus hospitalisations in young children in Denmark, 2010 to 2015

For future decisions on respiratory syncytial virus (RSV)-vaccination strategies and implementation into national immunisation-programmes, we used national registry data (hospitalisation, microbiology and vital statistics) to determine the age-specific incidence and direct medical costs of annual RSV-associated admissions in children < 5 years-old for the period of 2010–2015. We identified ca 2,500 RSV-associated hospitalisations annually amounting to total direct medical-costs of ca EUR 4.1 million per year. The incidence of RSV-associated hospitalisations peaked in infants 1–2 months of age followed by infants 2–3 months of age, and infants < 1 month of age, respectively. Infant boys were at higher risk of severe RSV infection as compared to infant girls: male-to-female ratio peaked with 1.4 at four months of age and gradually levelled out with increasing age to 1.0 at 4 years of age. Five RSV-associated deaths were identified. Our findings demonstrate that in a western country as Denmark, RSV constitutes a considerable burden on childhood health. Furthermore, the best approach to reduce the high incidence of RSV-associated hospitalisations in young infants < 3 months of age may be maternal vaccination due to general challenges in achieving sufficient and protective immune responses in young infants.

Severe Respiratory Syncytial Virus Infection in Hospitalized Children Less Than 3 Years of Age in a Temperate and Tropical Climate

BACKGROUND

Respiratory syncytial virus (RSV) infection is a frequent cause of hospitalization in infants younger than 3 years of age. We aimed to determine the factors associated with severe RSV disease.

METHODS

Retrospective medical review of children up to 3 years of age admitted for laboratory-proven RSV infection between January 1, 2013, and December 31, 2014, was conducted at the Women's and Children's Hospital, Adelaide, South Australia, and the Paediatric Department at Cairns Hospital, Cairns, North Queensland. Severity of infection was determined using the validated Brisbane RSV Infection Severity Score.

RESULTS

Four-hundred ninety-six children (383 at Women's and Children's Hospital and 113 at Cairns Hospital) were included in the study, with 76, 323 and 97 patients identified as having mild, moderate or severe disease, respectively. Decreasing age [odds ratio (OR) = 0.95; 95% confidence interval (CI) = 0.90-0.99, P = 0.020), and being Indigenous, increased (OR = 2.6; 95% CI = 1.4-4.9, P = 0.002) the risk of severe RSV infection in hospitalized children. Underlying respiratory (P = 0.029, OR = 2.5; 95% CI = 1.1-5.8) or cardiac (OR = 2.7; 95% CI = 1.1-6.4, P = 0.024) conditions, as well as the presence of tachypnoea on admission (OR = 2.2; 95% CI = 1.2-4.1, P = 0.009), were also independent predictors of severe RSV infection. Seasonal variation in hospitalization was observed between temperate and tropical climates but was not associated with disease severity.

CONCLUSIONS

Young infants, Indigenous patients and children with underlying respiratory and cardiac disease should be observed closely for signs of deterioration. Infants with tachypnoea on admission should be continuously monitored.

Analysis of genetic variability of respiratory syncytial virus groups A and B in Kuwait

Respiratory syncytial virus (RSV) is the most frequently identified viral agent in infants, children, and elderly people with acute respiratory tract infections (ARTIs). This study is the only one of its kind in Kuwait, and its purpose was to investigate the genetic variability of the G protein gene in RSV strains prevalent in Kuwait. Respiratory samples were collected from patients with ARTIs in various hospitals in Kuwait and subjected to reverse transcription PCR (RT-PCR) amplifying a fragment of the G gene of RSV. A total of 305 samples were collected between January and mid-December 2016, and 77 (25.2%) were positive for RSV. Group A viruses were predominant over group B viruses; the RSV-A group was detected in 52 (67.5%) of the positive samples, while the RSV-B group was detected in 25 (32.5%) of the positive samples. Phylogenetic analysis showed that all RSV-A strains grouped into eight clusters of identical sequences of untyped strains. Twelve RSV-B strains, on the other hand, belonged to the RSV-B/BA10 genotype, while the rest were untyped. These data suggest that new and untyped strains of RSV-A group likely predominated in Kuwait and that the BA10 genotype of the RSV-B group became the dominant genotype in the 2016 season.

Mutating the CX3C Motif in the G Protein Should Make a Live Respiratory Syncytial Virus Vaccine Safer and More Effective

Respiratory syncytial virus (RSV) belongs to the family Paramyxoviridae and is the single most important cause of serious lower respiratory tract infections in young children, yet no highly effective treatment or vaccine is available. Through a CX3C chemokine motif (182CWAIC186) in the G protein, RSV binds to the corresponding chemokine receptor, CX3CR1. Since RSV binding to CX3CR1 contributes to disease pathogenesis, we investigated whether a mutation in the CX3C motif by insertion of an alanine, A186, within the CX3C motif, mutating it to CX4C (182CWAIAC187), which is known to block binding to CX3CR1, might decrease disease. We studied the effect of the CX4C mutation in two strains of RSV (A2 and r19F) in a mouse challenge model. We included RSV r19F because it induces mucus production and airway resistance, two manifestations of RSV infection in humans, in mice. Compared to wild-type (wt) virus, mice infected with CX4C had a 0.7 to 1.2 log10-fold lower virus titer in the lung at 5 days postinfection (p.i.) and had markedly reduced weight loss, pulmonary inflammatory cell infiltration, mucus production, and airway resistance after challenge. This decrease in disease was not dependent on decrease in virus replication but did correspond to a decrease in pulmonary Th2 and inflammatory cytokines. Mice infected with CX4C viruses also had higher antibody titers and a Th1-biased T cell memory response at 75 days p.i. These results suggest that the CX4C mutation in the G protein could improve the safety and efficacy of a live attenuated RSV vaccine.IMPORTANCE RSV binds to the corresponding chemokine receptor, CX3CR1, through a CX3C chemokine motif (182CWAIC186) in the G protein. RSV binding to CX3CR1 contributes to disease pathogenesis; therefore, we investigated whether a mutation in the CX3C motif by insertion of an alanine, A186, within the CX3C motif, mutating it to CX4C (182CWAIAC187), known to block binding to CX3CR1, might decrease disease. The effect of this mutation and treatment with the F(ab')2 form of the anti-RSV G 131-2G monoclonal antibody (MAb) show that mutating the CX3C motif to CX4C blocks much of the disease and immune modulation associated with the G protein and should improve the safety and efficacy of a live attenuated RSV vaccine.

Respiratory syncytial virus hospitalization risk in the second year of life by specific congenital heart disease diagnoses

Children with hemodynamically significant congenital heart disease (CHD) are at elevated risk of morbidity and mortality due to respiratory syncytial virus (RSV) disease compared to their healthy peers. Previous studies have demonstrated lower RSV hospitalization risk among all children with CHD at 12-23 months of age versus 0-11 months of age. However, RSV hospitalization risk at 12-23 months of age by specific CHD diagnosis has not been characterized. Both case-control and cohort studies were conducted using data from the US National Inpatient Sample from 1997 to 2013 to characterize relative risk of RSV hospitalization among children 12-23 months of age with CHD. Related CHD diagnoses were combined for analysis. Hospitalizations for RSV and unspecified bronchiolitis were described by length of stay, mechanical ventilation use, mortality, and total charges. Over the 17-year period, 1,168,886 live birth hospitalizations with CHD were identified. Multiple specific CHD conditions had an elevated odds ratio or relative risk of RSV hospitalization. Mean total RSV hospitalization charges were significantly higher among children with CHD relative to those without CHD ($19,650 vs $7,939 in 2015 dollars) for this period. Compared to children without CHD, children with Ebstein's anomaly, transposition of the great arteries, aortic stenosis, heterotaxia, and aortic arch anomalies had 367-, 344-, 203-, 117- and 47-fold increased risk of inpatient RSV mortality, respectively. Unspecified bronchiolitis hospitalization odds and relative risk across CHD diagnoses were similar to those observed with RSV hospitalization; however, unspecified bronchiolitis hospitalizations were associated with shorter mean days of stay and less frequently associated with mechanical ventilation or mortality. Among children with more severe CHD diagnoses, RSV disease remains an important health risk through the second year of life. These data can help inform decisions regarding interventions to protect children with CHD from severe RSV disease during their second year of life.

Clinical and Epidemiologic Characteristics of Hospitalized Patients with Laboratory-Confirmed Respiratory Syncytial Virus Infection in Eastern China between 2009 and 2013: A Retrospective Study

Respiratory syncytial virus (RSV) is a leading cause of morbidity and mortality worldwide in children aged <5 years and older adults with acute lower respiratory infections (ALRIs). However, few studies regarding the epidemiology of hospitalizations for RSV infection have been performed previously in China. Here, we aimed to describe the clinical and epidemiologic characteristics of hospitalized patients with laboratory-confirmed RSV infection in eastern China. Active surveillance for hospitalized ALRI patients using a broad case definition based on symptoms was performed from 2009–2013 in 12 sentinel hospitals in eastern China. Clinical and epidemiologic data pertaining to hospitalized patients of all ages with laboratory-confirmed RSV infection by PCR assay were collected and analyzed in this study. From 2009 to 2013, 1046 hospitalized patients with laboratory-confirmed RSV infection were enrolled in this study, and 14.7% of patients had subtype A, 24.2% of patients had subtype B, 23.8% of patients with subtype not performed, and 37.3% of patients had RSV coinfections with other viruses. RSV and influenza coinfections (33.3%) were the most common coinfections noted in this study. Moreover, young children aged <5 years (89.1%, 932/1046), particularly young infants aged <1 year (43.3%, 453/1046), represented the highest proportion of patients with RSV infections. In contrast, older adults aged ≥60 years (1.1%, 12/1046) represented the lowest proportion of patients with RSV infections among enrolled patients. The peak RSV infection period occurred mainly during autumn and winter, and 57% and 66% of patients exhibited symptoms such as fever (body temperature ≥38°C) and cough separately. Additionally, only a small number of patients were treated with broad-spectrum antiviral drugs, and most of patients were treated with antimicrobial drugs that were not appropriate for RSV infection. RSV is a leading viral pathogen and a common cause of viral infection in young children aged <5 years with ALRIs in eastern China. Effective vaccines and antiviral agents targeting RSV are needed to mitigate its large public health impact.

Paramyxovirus Infection: Mortality and Morbidity in a Pediatric Intensive Care Unit

OBJECTIVES

We investigated mortality and morbidity of patients admitted to a pediatric intensive care unit (PICU) with paramyxovirus infection.

METHODS

A retrospective study between October 2002 and March 2015 of children with a laboratory-confirmed paramyxovirus infection was included.

RESULTS

In all, 98 (5%) PICU admissions were tested positive to have paramyxovirus infection (respiratory syncytial virus =  66, parainfluenza  =  27 and metapneumovirus  =  5). The majority of admissions were young patients (median age 1.05 years). Bacteremia and bacterial isolation in any site were present in 10% and 28%, respectively; 41% were mechanically ventilated, and 20% received inotropes. The three respiratory viruses caused similar mortality and morbidity in the PICU. Fatality (seven patients) was associated with malignancy, positive bacterial culture in blood, the use of mechanical ventilation, inotrope use, lower blood white cell count and higher C reactive protein (p  =  0.02-0.0005). Backward binary logistic regression for these variables showed bacteremia (odds ratio [OR]: 31.7; 95% CI: 2.3-427.8; p  =  0.009), malignancy (OR: 45.5; 95% CI: 1.4-1467.7; p  =  0.031) and use of inotropes (OR: 15.0; 95% CI: 1.1-196.1; p  =  0.039) were independently associated with non-survival. March and July appeared to be the two peak months for PICU hospitalizations with paramyxovirus infection.

CONCLUSIONS

Infections with paramyxoviruses account for 5% of PICU admissions and significant morbidity. Patient with premorbid history of malignancy and co-morbidity of bacteremia are associated with non-survival. March and July appeared to be the two peak months for PICU admissions with paramyxoviruses.

Risk of Respiratory Syncytial Virus Infection in Cyanotic Congenital Heart Disease in a Subtropical Area

OBJECTIVE

To compare the risk of respiratory syncytial virus (RSV)-associated hospitalization and analyze the epidemiology of RSV infection in patients with cyanotic and acyanotic congenital heart disease (CHD), we analyzed the nationwide health insurance database from 2005-2010.

STUDY DESIGN

This study included 1050 patients with cyanotic CHD and 7077 patients with acyanotic CHD. Patients with acyanotic CHD were further classified into hemodynamically significant (hs)-acyanotic and non-hs-acyanotic groups according to whether they underwent surgery or took at least 2 anticongestive medications.

RESULTS

RSV-associated hospitalization was higher in the cyanotic group than in hs-acyanotic and non-hs-acyanotic groups both before 1 year of age (4.8% vs 2.1% vs 1.5%, P < .001) and between 1 and 2 years of age (0.9% vs 0.56% vs 0.14%, P = .003). The hospitalization duration, intensive care, ventilator support prevalence, hospitalization cost, and mortality rate were significantly higher in the cyanotic group than in the other 2 groups. Logistic regression revealed that cyanotic CHD was the most significant risk factor for the ventilator support and RSV-associated mortality. In both patients with cyanotic and acyanotic CHD, RSV-associated hospitalization rate was higher in patients aged younger than 1 year and in spring and autumn in Taiwan, a subtropical country.

CONCLUSIONS

The results show that patients with cyanotic CHD have a higher risk of severe RSV infection than do those with acyanotic CHD. RSV prophylaxis is more important and may reduce costs more for patients with cyanotic CHD.

A Recombinant G Protein Plus Cyclosporine A-Based Respiratory Syncytial Virus Vaccine Elicits Humoral and Regulatory T Cell Responses against Infection without Vaccine-Enhanced Disease

Respiratory syncytial virus (RSV) infection can cause severe disease in the lower respiratory tract of infants and older people. Vaccination with a formalin-inactivated RSV vaccine (FI-RSV) and subsequent RSV infection has led to mild to severe pneumonia with two deaths among vaccinees. The vaccine-enhanced disease (VED) was recently demonstrated to be due to an elevated level of Th2 cell responses following loss of regulatory T (Treg) cells from the lungs. To induce high levels of neutralizing Abs and minimize pathogenic T cell responses, we developed a novel strategy of immunizing animals with a recombinant RSV G protein together with cyclosporine A. This novel vaccine induced not only a higher level of neutralizing Abs against RSV infection, but, most importantly, also significantly higher levels of Treg cells that suppressed VED in the lung after RSV infection. The induced responses provided protection against RSV challenge with no sign of pneumonia or bronchitis. Treg cell production of IL-10 was one of the key factors to suppress VED. These finding indicate that G protein plus cyclosporine A could be a promising vaccine against RSV infection in children and older people.

Biomarkers of respiratory syncytial virus (RSV) infection: specific neutrophil and cytokine levels provide increased accuracy in predicting disease severity

Despite fundamental advances in the research on respiratory syncytial virus (RSV) since its initial identification almost 60 years ago, recurring failures in developing vaccines and pharmacologic strategies effective in controlling the infection have allowed RSV to become a leading cause of global infant morbidity and mortality. Indeed, the burden of this infection on families and health care organizations worldwide continues to escalate and its financial costs are growing. Furthermore, strong epidemiologic evidence indicates that early-life lower respiratory tract infections caused by RSV lead to the development of recurrent wheezing and childhood asthma. While some progress has been made in the identification of reliable biomarkers for RSV bronchiolitis, a "one size fits all" biomarker capable of accurately and consistently predicting disease severity and post-acute outcomes has yet to be discovered. Therefore, it is of great importance on a global scale to identify useful biomarkers for this infection that will allow pediatricians to cost-effectively predict the clinical course of the disease, as well as monitor the efficacy of new therapeutic strategies.

Respiratory syncytial virus (RSV) and its propensity for causing bronchiolitis

Infants and young children with acute onset of wheezing and reduced respiratory airflows are often diagnosed with obstruction and inflammation of the small bronchiolar airways, ie bronchiolitis. The most common aetological agents causing bronchiolitis in young children are the respiratory viruses, and of the commonly encountered respiratory viruses, respiratory syncytial virus (RSV) has a propensity for causing bronchiolitis. Indeed, RSV bronchiolitis remains the major reason why previously healthy infants are admitted to hospital. Why RSV infection is such a predominant cause of bronchiolitis is the subject of this review. By reviewing the available histopathology of RSV bronchiolitis, both in humans and relevant animal models, we identify hallmark features of RSV infection of the distal airways and focus attention on the consequences of columnar cell cytopathology occurring in the bronchioles, which directly impacts the development of bronchiolar obstruction, inflammation and disease. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Clinical characteristics and risk factors of severe respiratory syncytial virus-associated acute lower respiratory tract infections in hospitalized infants

BACKGROUND

To investigate the clinical characteristics and analyze risk factors for severe respiratory syncytial virus (RSV) infection in hospitalized infants with acute lower respiratory tract infections (ALRIs).

METHODS

A retrospective review of the medical records of infants with RSV-associated ALRIs between March 1st, 2011 and February 29th, 2012 was conducted. Subjects were followed up over the phone or by outpatient visit six and twelve months after discharge.

RESULTS

Among 913 RSV-associated ALRIs infants, 288 (31.5%) had severe infections, which accounted for 4.2% of hospitalized children. The hospital RSV mortality rate was 1.0%. The proportions of cases with tachypnea, apnea, cyanosis, and fine rales were significantly higher in the severe ALRIs group (all P<0.001). Multivariate logistic regression showed that low-birth-weight [1.698 (1.028-2.805)], age less than 3 months old [3.385 (2.174-5.271)], congenital heart disease [1.667 (1.149-2.418)], bronchopulmonary dysplasia [8.505 (1.731-41.780)], and airway abnormalities [2.246 (1.008-5.005)] were independent risk factors for severe ALRIs. The incidence of bronchitis, pneumonia and readmission in the severe group was significantly higher than that of the non-severe group during the one-year follow-up (all P<0.001).

CONCLUSIONS

Younger age, low birth weight and underlying disease are associated with severe RSVassociated ALRIs. Furthermore, severe RSV infections may be associated with a higher frequency of subsequent bronchitis, pneumonia and re-hospitalization in the following year.

A systematic review of predictive modeling for bronchiolitis

PURPOSE

Bronchiolitis is the most common cause of illness leading to hospitalization in young children. At present, many bronchiolitis management decisions are made subjectively, leading to significant practice variation among hospitals and physicians caring for children with bronchiolitis. To standardize care for bronchiolitis, researchers have proposed various models to predict the disease course to help determine a proper management plan. This paper reviews the existing state of the art of predictive modeling for bronchiolitis. Predictive modeling for respiratory syncytial virus (RSV) infection is covered whenever appropriate, as RSV accounts for about 70% of bronchiolitis cases.

METHODS

A systematic review was conducted through a PubMed search up to April 25, 2014. The literature on predictive modeling for bronchiolitis was retrieved using a comprehensive search query, which was developed through an iterative process. Search results were limited to human subjects, the English language, and children (birth to 18 years).

RESULTS

The literature search returned 2312 references in total. After manual review, 168 of these references were determined to be relevant and are discussed in this paper. We identify several limitations and open problems in predictive modeling for bronchiolitis, and provide some preliminary thoughts on how to address them, with the hope to stimulate future research in this domain.

CONCLUSIONS

Many problems remain open in predictive modeling for bronchiolitis. Future studies will need to address them to achieve optimal predictive models.

Increased concentration of iodide in airway secretions is associated with reduced respiratory syncytial virus disease severity

Recent studies have revealed that the human and nonrodent mammalian airway mucosa contains an oxidative host defense system. This three-component system consists of the hydrogen peroxide (H2O2)-producing enzymes dual oxidase (Duox)1 and Duox2, thiocyanate (SCN(-)), and secreted lactoperoxidase (LPO). The LPO-catalyzed reaction between H2O2 and SCN(-) yields the bactericidal hypothiocyanite (OSCN(-)) in airway surface liquid (ASL). Although SCN(-) is the physiological substrate of LPO, the Duox/LPO/halide system can generate hypoiodous acid when the iodide (I(-)) concentration is elevated in ASL. Because hypoiodous acid, but not OSCN(-), inactivates respiratory syncytial virus (RSV) in cell culture, we used a lamb model of RSV to test whether potassium iodide (KI) could enhance this system in vivo. Newborn lambs received KI by intragastric gavage or were left untreated before intratracheal inoculation of RSV. KI treatment led to a 10-fold increase in ASL I(-) concentration, and this I(-) concentration was approximately 30-fold higher than that measured in the serum. Also, expiratory effort, gross lung lesions, and pulmonary expression of an RSV antigen and IL-8 were reduced in the KI-treated lambs as compared with nontreated control lambs. Inhibition of LPO activity significantly increased lesions, RSV mRNA, and antigen. Similar experiments in 3-week-old lambs demonstrated that KI administration was associated with reduced gross lesions, decreased RSV titers in bronchoalveolar lavage fluid, and reduced RSV antigen expression. Overall, these data indicate that high-dose KI supplementation can be used in vivo to lessen the severity of RSV infections, potentially through the augmentation of mucosal oxidative defenses.

Sucrose stabilization of Respiratory Syncytial Virus (RSV) during nebulization and experimental infection

BACKGROUND

Respiratory syncytial virus (RSV) is a common respiratory pathogen that can cause severe pneumonia. In vivo studies of RSV can be difficult due to variation in viral infection and disease severity in some animal models. Factors that may contribute to the variation are decreases in viral titer due to preparation and storage and method of virus administration. Nebulization is one method of RSV administration that provides even distribution of virus to all lung lobes; however, the exact quantity of the virus killed by nebulization is not defined. To test the hypothesis that sucrose enhances RSV stability and infectivity, a series of in vitro experiments were conducted with RSV strain Memphis 37 stored at varying concentrations (0%, 3%, 5%, 8%, 10%, 15%, and 20%) of sucrose as a possible cryo- and nebulization protectant. The optimal in vitro concentration was then assessed in vivo in a lamb model.

METHODS

Prior to titering the virus on HEp-2 cells, the various virus solutions were subjected to one freeze-thaw cycle and one nebulization cycle. Forty-eight hours after viral plating, infectious foci were detected and counted using immunofluorescent imaging. Titers were determined after freeze-thaw and after freeze-thaw followed by nebulization, then compared to the stock titers (before freezing) as well as to one another to determine the loss of infectivity. To further test this in vivo, lambs 2 to 3-days-old were infected via nebulization with RSV using inoculate containing either 20% sucrose or no sucrose followed by assessments of infection severity.

RESULTS

Nebulization of virus in 0% sucrose resulted in a 0.580 log reduction in infectivity while virus in 20% sucrose exhibited a 0.297 log reduction. In vivo studies demonstrated that 20% sucrose enhanced RSV lesions and antigen distribution.

CONCLUSIONS

The data suggests that both nebulization and freeze-thawing of RSV in the absence of sucrose cause unacceptable losses in viral infectivity and that sucrose acts as a RSV protectant in both regards.

Clinical and epidemiologic characteristics of respiratory syncytial virus infection among children aged <5 years, Jingzhou City, China, 2011

Severe acute respiratory illness (SARI) surveillance began in Jingzhou City, China, in 2010. A subset of 511 children aged <5 years enrolled in the SARI study during 2011 were tested for influenza and noninfluenza respiratory viral infection by real-time reverse-transcription polymerase chain reaction. Respiratory syncytial virus (RSV) was most commonly detected. Children aged 12-23 and 24-60 months were equally likely to test positive for RSV. Although cases of RSV infection could be detected throughout the year, the greatest numbers were detected from autumn to early winter.

Lamb model of respiratory syncytial virus-associated lung disease: insights to pathogenesis and novel treatments

Preterm birth is a risk factor for respiratory syncytial virus (RSV) bronchiolitis and hospitalization. The pathogenesis underlying this is not fully understood, and in vivo studies are needed to better clarify essential cellular features and molecular mechanisms. Such studies include analysis of lung tissue from affected human infants and various animal models. The preterm and newborn lamb lung has developmental, structural, cellular, physiologic, and immunologic features similar to that of human infants. Also, the lamb lung is susceptible to various strains of RSV that infect infants and cause similar bronchiolar lesions. Studies in lambs suggest that viral replication in airways (especially bronchioles) is extensive by 4 days after infection, along with bronchiolitis characterized by degeneration and necrosis of epithelial cells, syncytial cell formation, neutrophil infiltration, epithelial cell hypertrophy and hyperplasia, and innate and adaptive immune responses. RSV bronchiolitis greatly affects airflow and gaseous exchange. RSV disease severity is increased in preterm lambs compared with full-term lambs; similar to human infants. The lamb is conducive to experimental assessment of novel, mechanistic therapeutic interventions such as delivery of vascular endothelial growth factor and enhancement of airway epithelial oxidative responses, Club (Clara) cell protein 10, and synthesized compounds such as nanobodies. In contrast, exposure of the fetal ovine lung in vivo to ethanol, a risk factor for preterm birth, reduces pulmonary alveolar development and surfactant protein A expression. Because the formalin-inactivated RSV vaccination enhances some inflammatory responses to RSV infection in lambs, this model has the potential to assess mechanisms of formalin-inactivated RSV enhanced disease as well as newly developed vaccines.

Epidemiology and risk factors for severe respiratory syncytial virus infections requiring pediatric intensive care admission in Hong Kong children

PURPOSE

Respiratory syncytial virus (RSV) is a common cause of lower respiratory tract infection in young children. However, there are limited data on severe RSV infection requiring pediatric intensive care unit (PICU) admission. This retrospective study described features of RSV-associated PICU admissions in Hong Kong and investigated factors for mortality and duration of PICU stay.

METHODS

Children with laboratory-confirmed RSV infection and admitted to the PICUs of all eight government hospitals in Hong Kong between January 2009 and June 2011 were identified from computerized auditing systems and PICU databases. RSV in respiratory samples was detected by direct immunofluorescence and/or viral culture. The relationships between mortality and PICU duration and demographic and clinical factors were analyzed.

RESULTS

A total of 118 (2.4 %) PICU admissions were identified among 4,912 RSV-positive pediatric cases in all hospitals. Sixty-five (55.6 %) patients were infants. PICU admissions were higher between October and March. Eight (6.8 %) patients died, but only two were infants. RSV-associated mortality was related to prior sick contact, presence of older siblings, neurodevelopmental conditions, chromosomal and genetic diseases, and bacterial co-infections, but none was significant following logistic regression analyses (odds ratio 9.36, 95 % confidence interval 0.91-96.03 for prior sick contact, p = 0.060). Chronic lung disease was the only risk factor for the duration of PICU admission (β = 0.218, p = 0.017).

CONCLUSIONS

The majority of RSV-infected children do not require PICU support. There is winter seasonality for RSV-associated PICU admission in Hong Kong. Prior sick contact is the only risk factor for RSV-associated mortality, whereas the presence of chronic lung disease is associated with longer PICU stay. The current risk-based approach of RSV prophylaxis may not be effective in reducing severe RSV infections.

Strategies for reducing the risk of respiratory syncytial virus infection in infants and young children: a Canadian nurses' perspective

Respiratory syncytial virus (RSV) infections are prevalent globally and can cause substantial morbidity in infants and young children. The virus is easily transmitted by direct hand-to-hand contact and can lead to serious respiratory disease and hospitalization, particularly in premature infants and children with certain medical conditions. Educating families with young children, especially those in remote rural regions, regarding the potential adverse health outcomes of RSV infection and measures to reduce the risk of transmitting or acquiring RSV has been a key focus of the health care system in Canada. Geographic, cultural, and socioeconomic factors present formidable challenges to the execution of this endeavor. Therefore, it is critical to develop and systematically implement effective educational programs for both families and health care providers. In Canada, nurses play a critical role in education and counseling. In this review, we share our perspectives and suggest empirical practices that may be applicable worldwide.

Respiratory syncytial virus-associated intensive care unit admission in children in Southern China

Background

There are incomplete data on the global burden of viral lower respiratory tract infection, in particular the role of Respiratory Syncytial Virus, in children requiring health services.

Findings

In this study set in a large urban area of southern China from 1 January 2007 to 31 December 2010, children 1 month to 14 years of age with RSV-associated “severe” or “very severe pneumonia” according to World Health Organization definitions, and meeting local criteria for admission to the pediatric intensive care unit, were followed for the course of their admission. The median age was 3 months and 79% (135/171) of children with RSV were under six months of age. All children needed supplemental oxygen, and 22% required mechanical ventilatory support. The mortality rate was 3.5%. In multivariate analysis, congenital heart disease and Trisomy 21 were associated with death.

Conclusions

Children admitted to an intensive care unit with RSV-associated severe/very pneumonia in a large urban setting in southern China were most commonly ≤ six months old and almost one quarter of these had respiratory failure. The overall mortality rate was 3.5%. RSV vaccine strategies that would protect children from early infancy are urgently needed.

Respiratory syncytial virus infections in infants and children with congenital heart disease: update on the evidence of prevention with palivizumab

PURPOSE OF REVIEW

Lower respiratory tract infections multiply morbidity and mortality within patients with significant congenital heart disease (CHD). For respiratory syncytial virus (RSV), one of the most important pathogens, immunoprophylaxis with palivizumab has successfully been introduced. The question is which patients will benefit most from this costly preventive treatment.

RECENT FINDINGS

The era after the introduction of palivizumab has revealed a steep decrease in mortality. The markers of success - hospital stays, admission to the intensive care unit, days on mechanical ventilation, and death - consistently favor immunoprophylaxis. The key point of treatment success remains in all cases a careful patient selection, adherence to a time limit of 30 days between the injections and early use after cardiac surgery with cardiopulmonary bypass, as well as avoidance of nosocomial-acquired infections. Preventive therapy with palivizumab in patients with CHD has been investigated in terms of operating efficiency - with the lowest costs per quality-adjusted life years compared with preterm infants with or without bronchopulmonary dysplasia.

SUMMARY

The burden of RSV disease will decline, once a vaccine is available. Meanwhile, immunoprophylaxis with palivizumab is a useful tool for high-risk patients to reduce comorbidity and fatal outcome. Pharmacoeconomic considerations measuring quality-adjusted life years indicate important information about cost-effectiveness.

Morbidity and outcome of severe respiratory syncytial virus infection

BACKGROUND

Respiratory syncytial virus (RSV) is the main cause of severe acute respiratory infection (SARI) in infants and young children. This study aimed to identify risk factors for intensive care unit (ICU) admission, prolonged length of stay (PLOS), and mortality in patients hospitalized with SARI caused by RSV.

METHODS

This prospective cohort study included children hospitalized with SARI (according to the World Health Organization definition) and whose laboratory results proved RSV infection during the period from February 2010 to May 2011.

RESULTS

Out of 240 enrolled patients, 24 patients (10%) were admitted to the ICU, 57 patients (24.3%) had a PLOS of >9 days and 12 patients (5%) died. The presence of cyanosis (P = 0.000; OR, 351.7) and lung consolidation (P = 0.006, OR, 9.3) were independent risk factors associated with ICU admission. The need for ICU admission (P = 0.000; OR, 6.1) and lung consolidation (P = 0.008, OR, 2.46) were independent risk factors associated with PLOS. The presence of an underlying congenital heart disease (P = 0.03, OR, 18.3), thrombocytopenia (P = 0.04, OR, 32.86) and mechanical ventilation (P = 0.000; OR, 449.4) were the only independent risk factors associated with mortality in our study.

CONCLUSIONS

Early recognition of risk factors for complicated RSV disease on admission prompts early interventions and early ICU admissions for these children.

Perinatal lamb model of respiratory syncytial virus (RSV) infection

Respiratory syncytial virus (RSV) is the most frequent cause of bronchiolitis in infants and children worldwide. Many animal models are used to study RSV, but most studies investigate disease in adult animals which does not address the unique physiology and immunology that makes infants more susceptible. The perinatal (preterm and term) lamb is a useful model of infant RSV disease as lambs have similar pulmonary structure including airway branching, Clara and type II cells, submucosal glands and Duox/lactoperoxidase (LPO) oxidative system, and prenatal alveologenesis. Lambs can be born preterm (90% gestation) and survive for experimentation although both preterm and term lambs are susceptible to ovine, bovine and human strains of RSV and develop clinical symptoms including fever, tachypnea, and malaise as well as mild to moderate gross and histologic lesions including bronchiolitis with epithelial injury, neutrophil infiltration and syncytial cell formation. RSV disease in preterm lambs is more severe than in term lambs; disease is progressively less in adults and age-dependent susceptibility is a feature similar to humans. Innate and adaptive immune responses by perinatal lambs closely parallel those of infants. The model is used to test therapeutic regimens, risk factors such as maternal ethanol consumption, and formalin inactivated RSV vaccines.