Respiratory syncytial viral infection in infants with congenital heart disease

Respiratory syncytial virus prophylaxis in children with cardiac disease: a retrospective single-centre study

OBJECTIVES

To examine the characteristics of congenital heart disease patients hospitalised with respiratory syncytial virus infection after prophylaxis and determine the associated comorbidities and the incidence of breakthrough respiratory syncytial virus infections.

STUDY DESIGN

This is a retrospective, single-centre study that was conducted over a period of 7 years. Respiratory syncytial virus infection was identified by classification codes and confirmed by virological tests. Data on baseline demographics, cardiac anomalies, other underlying disease, criteria for hospitalisation, type of respiratory illness and management, complications, and palivizumab prophylaxis were analysed by standard descriptive methods and comparative statistics.

RESULTS

A total of 30 patients were enrolled. The majority were ≤ 2 years (n = 24). The mean admission age was 15.1 months (standard deviation = 18.3). In all, 90% were acyanotic, 40% had haemodynamically significant disease, and 60% had ≥ 1 underlying medical illness. Patients were admitted with: respiratory distress (86.7%), hypoxaemia (66.7%), fever (60%), inability to maintain oral intake (36.7%), and apnoea (16.7%). More than 50% required mechanical ventilation and intensive care with a median stay of 11 days (range: 1-43); the length of hospital stay for all children was 10 days (range: 1-65). Complications included: concurrent bacterial sepsis (20%), electrolyte abnormalities (16.7%), and worsening pulmonary hypertension (13.3%). Of 10 infants ≤ 2 years with haemodynamically significant heart disease, four had received prophylaxis. There was one death, which was attributed to respiratory syncytial virus infection.

CONCLUSIONS

Overall, 185 infants ≤ 2 years with haemodynamically significant cardiac disease received prophylaxis. In all, six qualifying infants missed immunisation and were hospitalised. Breakthrough respiratory syncytial virus infections occurred in 2.2%, demonstrating good efficacy of palivizumab in this population compared with the original, multi-centre, randomised trial.

Perinatal exposure to insecticide methamidophos suppressed production of proinflammatory cytokines responding to virus infection in lung tissues in mice

Methamidophos, a representative organophosphate insecticide, is regulated because of its severe neurotoxicity, but it is suspected of contaminating agricultural foods in many countries due to illicit use. To reveal unknown effects of methamidophos on human health, we evaluated the developmental immunotoxicity of methamidophos using a respiratory syncytial virus (RSV) infection mouse model. Pregnant mice were exposed to methamidophos (10 or 20 ppm) in their drinking water from gestation day 10 to weaning on postnatal day 21. Offsprings born to these dams were intranasally infected with RSV. The levels of interleukin-6 (IL-6) and interferon-gamma in the bronchoalveolar lavage fluids after infection were significantly decreased in offspring mice exposed to methamidophos. Treatment with methamidophos did not affect the pulmonary viral titers but suppressed moderately the inflammation of lung tissues of RSV-infected offspring, histopathologically. DNA microarray analysis revealed that gene expression of the cytokines in the lungs of offspring mice exposed to 20 ppm of methamidophos was apparently suppressed compared with the control. Methamidophos did not suppress IL-6 production in RSV-infected J774.1 cell cultures. Thus, exposure of the mother to methamidophos during pregnancy and nursing was suggested to cause an irregular immune response in the lung tissues in the offspring mice.

Effect of brazilian propolis on exacerbation of respiratory syncytial virus infection in mice exposed to tetrabromobisphenol a, a brominated flame retardant

Tetrabromobisphenol A (TBBPA), a brominated flame retardant, has been found to exacerbate pneumonia in respiratory syncytial virus- (RSV-) infected mice. We examined the effect of Brazilian propolis (AF-08) on the exacerbation of RSV infection by TBBPA exposure in mice. Mice were fed a powdered diet mixed with 1% TBBPA alone, 0.02% AF-08 alone, or 1% TBBPA and 0.02% AF-08 for four weeks and then intranasally infected with RSV. TBBPA exposure increased the pulmonary virus titer and level of IFN-γ, a representative marker of pneumonia due to RSV infection, in the lungs of infected mice without toxicity. AF-08 was significantly effective in reducing the virus titers and IFN-γ level increased by TBBPA exposure. Also, AF-08 significantly reduced proinflammatory cytokine (TNF-α and IL-6) levels in the lungs of RSV-infected mice with TBBPA exposure, but Th2 cytokine (IL-4 and IL-10) levels were not evidently increased. Neither TBBPA exposure nor AF-08 treatment affected the anti-RSV antibody production in RSV-infected mice. In flow cytometry analysis, AF-08 seemed to be effective in reducing the ratio of pulmonary CD8a⁺ cells in RSV-infected mice with TBBPA exposure. TBBPA and AF-08 did not exhibit anti-RSV activity in vitro. Thus, AF-08 probably ameliorated pneumonia exacerbated by TBBPA exposure in RSV-infected mice by limiting excess cellular immune responses.

Acute bronchiolitis

Bronchiolitis is the most common lower respiratory tract infection to affect infants and toddlers. High-risk patients include infants younger than 3 months, premature infants, children with immunodeficiency, children with underlying cardiopulmonary or neuromuscular disease, or infants prone to apnea, severe respiratory distress, and respiratory failure. Bronchiolitis is a self-limited disease in healthy infants and children. Treatment is usually symptomatic, and the goal of therapy is to maintain adequate oxygenation and hydration. Use of a high-flow nasal cannula is becoming common for children with severe bronchiolitis.

Extracorporeal membrane oxygenation for the treatment of acute respiratory failure due to respiratory syncytial virus after congenital heart surgery

Mechanical circulatory support using extracorporeal membrane oxygenation is a therapeutic option for intractable cardiac or respiratory failure. It has widely been used for adult and pediatric patient population with considerable success in cases with otherwise dismal prognosis. We describe the successful use of extracorporeal membrane oxygenation in a 9-month-old patient suffering from a virus-related respiratory failure after congenital cardiac surgery.

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.

Maternal milk protects infants against bronchiolitis during the first year of life. Results from an Italian cohort of newborns

OBJECTIVE

Bronchiolitis is one of the primary causes of hospitalization in infancy. We evaluated the effect of breastfeeding on the occurrence of hospitalization for bronchiolitis in the first year of life.

METHODS

In a prospective cohort study, 1,814 newborns of =33 weeks of gestational age (wGA) were enrolled in 30 Italian Neonatology Units and followed-up for 1 year to assess hospitalizations for bronchiolitis. Children were grouped as 'never breastfed' and 'ever breastfed'; these latter were further divided into those 'exclusively breastfed' and 'breastfed associated with milk formula'. The risk of hospitalization for bronchiolitis was evaluated with survival analysis, and hazard ratios (HR) with 95% confidence interval [95% CI] were calculated.

RESULTS

Among enrolled newborns 22.9% were 'never breastfed'; in the breastfed group, 65% were 'exclusively breastfed' and 35% were 'breastfed with associated milk formula'. At 12 months of age, the risk of hospitalization for bronchiolitis was significantly higher in the 'never breastfed' group (HR: 1.57; 95% CI: 1.00-2.48). 'Breastfed associated with formula milk' and 'exclusively breastfed' groups were at similar risk of hospitalization for bronchiolitis. This observed protective effect of maternal milk was not explained by the higher prevalence of conditions able to increase the risk of bronchiolitis among 'never breastfed newborns'.

CONCLUSIONS

Breastfeeding, even in association with formula milk, reduces the risk of hospitalization for bronchiolitis during the first year of life. Encouraging breastfeeding might be an effective/inexpensive measure of prevention of lower respiratory tract infections in infancy.

Medical retrieval and needs of infants with bronchiolitis: an analysis by gestational age

AIM

Viral bronchiolitis is the most common lower respiratory tract infection in children less than 12 months of age. Prematurity is an independent risk factor for disease severity. Many infected infants require hospitalisation and those living in regional centres frequently require transfer to metropolitan hospitals capable of providing assisted ventilation.

METHOD

We reviewed infants with bronchiolitis transported by the Victorian Newborn Emergency Transport Service between January 2003 and June 2007. We compared the clinical presentation and treatment required by infants born preterm with those of their term counterparts.

RESULTS

Of the 192 infants transported, 92 were born preterm. Preterm infants were younger at time of transport (mean post-menstrual age 41 weeks vs. 45 weeks) and were more likely to require invasive ventilation (60% vs. 32%, P < 0.001) and to receive a fluid bolus (47% vs. 34%, P = 0.04) when compared with infants who had been born at term. Apnoea, either as a presenting symptom or in combination with respiratory distress, was more common in the preterm group (70% vs. 36%, P < 0.001).

CONCLUSION

Higher illness severity should be anticipated in ex-preterm infants who present with bronchiolitis. Preterm infants with bronchiolitis are more likely to require invasive ventilation and fluid resuscitation than term infants, suggesting the need for a lower threshold for referral and medical retrieval.

The risk of mortality among young children hospitalized for severe respiratory syncytial virus infection

Respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) is the leading cause of childhood morbidity. Although also an important cause of childhood mortality worldwide, the impact of key risk factors has not been established. A systematic review of 34 articles reporting case fatality rates in young children hospitalized for severe RSV LRTI, according to the presence of underlying RSV risk factors, was conducted. The weighted mean case fatality rate was 1.2% (range, 0-8.3%; median, 0%; n = 10) among preterm infants; 5.2% (range, 2.0-37.0%; median, 5.9%; n = 7) among children with CHD; and 4.1% (range, 0-10.5%; median, 7.0%; n = 6) among children with BPD. Case fatality estimates among children not at high risk (n = 6) ranged from 0% to 1.5% (weighted mean, 0.2%; median, 0.0%). Fatality during hospitalization for severe RSV LRTI is rare among children not at high risk, but occurs more commonly among children at higher risk of RSV LRTI.

The cost effectiveness of palivizumab in congenital heart disease: a review of the current evidence

OBJECTIVE

To review and summarize the literature concerning the cost-effectiveness of palivizumab compared to no prophylaxis in infants and young children with congenital heart disease (CHD).

METHODS

A systematic literature search (MEDLINE to March 2012, limited to English language) identified studies that examined the cost-effectiveness of palivizumab in CHD populations. The quality of each study was assigned a quality score of 1-100 based on the Quality of Health Economic Studies (QHES) instrument.

RESULTS

Ten studies were identified through the search strategy, of which four principally addressed the research question and six additional articles examined CHD in conjunction with other high-risk indications for palivizumab in their economic analyses. QHES for the studies ranged from 58-100, with a median score of 93 (76 for principal articles, 94 for secondary analyses). Cost-utility analyses, which evaluated costs per quality-adjusted life year (QALY), showed favorable results in five analyses (range $10,329-$16,648 per QALY), while the other two suggested no cost-effectiveness ($146,061 and $169,971 per QALY). Of three cost-effectiveness analyses, which assessed costs per hospital admission prevented (HAP), two concluded that the drug was not cost-effective ($16,216/day of hospitalization prevented and $868,296/HAP), while one did not interpret the final result ($43,561/HAP).

LIMITATIONS

Significant variance exists across study characteristics, analytic models utilized, duration of RSV seasons assessed, primary outcome measures evaluated, sensitivity analyses conducted, and other model assumptions. Further, it was difficult to obtain true CHD-based quality scores for the studies that analyzed more than one indication.

CONCLUSIONS

The findings of this review currently remain inconclusive. Although a favorable trend was identified in the cost-utility analyses, additional rigorously conducted studies are necessary to better estimate the cost-effectiveness of palivizumab for CHD infants in clinical practice.

Targeting RSV with vaccines and small molecule drugs

Respiratory syncytial virus (RSV) is the most significant cause of pediatric respiratory infections. Palivizumab (Synagis®), a humanized monoclonal antibody, has been used successfully for a number of years to prevent severe RSV disease in at-risk infants. However, despite intense efforts, there is no approved vaccine or small molecule drug for RSV. As an enveloped virus, RSV must fuse its envelope with the host cell membrane, which is accomplished through the actions of the fusion (F) glycoprotein, with attachment help from the G glycoprotein. Because of their integral role in initiation of infection and their accessibility outside the lipid bilayer, these proteins have been popular targets in the discovery and development of antiviral compounds and vaccines against RSV. This review examines advances in the development of antiviral compounds and vaccine candidates.

Burden of respiratory syncytial virus infection in young children

Respiratory syncytial virus (RSV) is the most frequent and important cause of lower respiratory tract infection in infants and children. It is a seasonal virus, with peak rates of infection occurring annually in the cold season in temperate climates, and in the rainy season, as temperatures fall, in tropical climates. High risk groups for severe RSV disease include infants below six mo of age, premature infants with or without chronic lung disease, infants with hemodynamically significant congenital heart disease, infants with immunodeficiency or cystic fibrosis, and infants with neuromuscular diseases. Mortality rates associated with RSV infection are generally low in previous healthy infants (below 1%), but increase significantly in children with underlying chronic conditions and comorbidities. Following early RSV lower respiratory tract infection, some patients experience recurrent episodes of wheezing mimicking early childhood asthma with persistence of lung function abnormalities until adolescence. There is currently no RSV vaccine available, but promising candidate vaccines are in development. Palivizumab, a monoclonal RSV antibody that is the only tool for immunoprophylaxis in high-risk infants, lowers the burden of RSV infection in certain carefully selected patient groups.

Palivizumab in preventing respiratory syncytial virus-related hospitalization in high-risk infants

Respiratory syncytial virus (RSV) causes seasonal epidemics (winter or wet-season) of serious lower respiratory tract infections in young infants with subsequent increased frequency of recurrent wheezing during early childhood. Palivizumab is a humanized monoclonal antibody that provides immunoprophylaxis against RSV when administered monthly over the RSV season. It significantly reduced hospitalizations in high-risk infants including preterm infants with and without bronchopulmonary dysplasia and infants with hemodynamically significant congenital heart disease. Since its license in 1998, approximately 36 methodologically different economic studies have been performed to prove cost-effectiveness of the product. The majority of cost-effectiveness analyses revealed costs of palivizumab exceeding anticipated savings from reduced RSV hospitalizations. A minority of studies performed cost-effectiveness analyses using incremental cost-effectiveness ratios as costs per quality-adjusted life-year gained. The wide variability in the results of economic studies with estimates ranging from cost savings to incremental costs of a high order of magnitude with its use is discussed, in the light of the continuing burden of RSV disease, the limited treatment modalities, and the continuing research for a vaccine.

Early repair of large infant ventricular septal defect despite respiratory syncytial virus-induced respiratory failure with postrepair chylous pericardial effusion requiring pleuropericardial window: a case report and review of the literature

The surgical correction of congenital cardiac lesions that are complicated by intercurrent respiratory syncytial virus (RSV) pneumonitis has traditionally been deferred for at least 6 to 8 weeks. The presumption is that using cardiopulmonary bypass will increase the risk of postoperative pulmonary complications. We present an infant who developed acute respiratory failure related to RSV pneumonitis and required urgent mechanical ventilation. Cardiac evaluation revealed a large nonrestrictive ventricular septal defect (VSD), aortic arch hypoplasia, normally functioning bicuspid aortic valve, and hemodynamic instability associated with markedly increased pulmonary blood flow. Separation from mechanical ventilation was unsuccessful preoperatively. He underwent VSD repair with cardiopulmonary bypass less than 4 weeks after initial RSV infection. He was extubated successfully within 72 hours of VSD repair. Approximately 6 weeks postoperatively, he developed a circumferential chylous pericardial effusion of unclear etiology--an exceedingly rare complication of VSD repair in early infancy in a non-Down syndrome patient. The chylous effusion was initially managed unsuccessfully with Portogen/Monogen and a percutaneously placed pericardial drain. Two weeks later, he underwent creation of a pleuropericardial window with successful resolution of the chylous effusion. It is of interest to pediatricians to be able to correctly time the repair of congenital heart disease lesions after RSV infection to minimize post-bypass pulmonary complications and yet avoid morbidity from undue delays in repair. In addition, chylopericardium can occur in infants after VSD repair, and dietary modification and catheter drainage may not be adequate.

Capnometry as a predictor of admission in bronchiolitis

OBJECTIVES

Bronchiolitis is a dynamic condition, and predicting clinical deterioration can be difficult. The objective of this study was to determine whether capnometry readings among bronchiolitic children admitted to the hospital are significantly different from those discharged from the emergency department.

METHODS

We prospectively studied a convenience sample of children younger than 24 months with clinical bronchiolitis. A single end-tidal CO2 (ETCO2) reading was taken before treatment, and a clinical work of breathing score was assigned to each patient. Treating physicians and nurses were blinded to capnometry readings. The decision to admit was based on the judgment of the attending physician. Descriptive statistics and appropriate hypothesis testing were performed. A receiver operating characteristic curve was constructed for the association between admission and capnometry readings. The α was set at 0.05 for all comparisons.

RESULTS

One hundred five children with bronchiolitis were included for study. Capnometry readings for admitted (mean, 32.6 mm Hg; 95% confidence interval [CI], 30.3-34.9 mm Hg) and discharged (mean 31.4 mm Hg; 95% CI 29.8-33.0 mm Hg) bronchiolitic children were not significantly different. Capnometry readings for low (mean, 31.7 mm Hg; 95% CI, 29.5-33.8 mm Hg), intermediate (mean, 32.1 mm Hg; 95% CI, 30.1-34.1 mm Hg), and high (mean, 30.5 mm Hg; 95% CI, 19.3-41.7 mm Hg) work of breathing (score) ranges were not significantly different.

CONCLUSIONS

Capnometry readings are not useful in predicting admission for children younger than 2 years with clinical bronchiolitis. There are no significant differences in capnometry readings among bronchiolitic children with low, medium, and high work of breathing scores.

Down syndrome and hospitalizations due to respiratory syncytial virus: a population-based study

OBJECTIVE

To assess the risk estimates for respiratory syncytial virus (RSV) hospitalization in children with Down syndrome (DS) and the clinical features and severity of RSV lower respiratory tract infection (LRTI) in hospitalized children.

STUDY DESIGN

Statewide hospitalization data for children with DS for 1995 through 2006 from the Colorado Health and Hospital Association database were combined with birth data from the Colorado Department of Public Health and Environment to obtain population-based estimates of RSV LRTI hospitalization for children with DS in the first 2 years of life. RSV hospitalization data for children with DS at the Children's Hospital Colorado for 2000 through 2006 were used to compare the course and severity of hospitalization of DS LRTI admissions with those of matched control subjects.

RESULTS

There were 85 RSV LRTI hospitalizations in 630 children born with DS in Colorado, with 50 having no concurrent underlying conditions identified. Children with DS had a significantly higher risk than did those without DS for being hospitalized with RSV LRTI (OR, 5.99; 95% CI, 6.68-5.38), even in the absence of other underlying conditions (OR 3.5; 95% CI, 3.10-4.12). In the case-control study, children with DS hospitalized for RSV presented more frequently with fever (P = .005), had consolidation reported more often on chest radiography (P = .003), and were given bronchodilator therapy more often during the hospital stay (P = .002).

CONCLUSIONS

Children with DS have a higher risk of being hospitalized with RSV LRTI even in the absence of coexisting risk factors. They present more often with fever and more often have radiographic consolidation detected on chest radiography.

Respiratory syncytial virus immunoprophylaxis in high-risk infants with heart disease

AIM

Passive immunisation with palivizumab is recommended in many countries for children with haemodynamically significant cardiac disease. We trialled respiratory syncytial virus (RSV) immunoprophylaxis in such infants during 2008–2009.

METHODS

We identified all RSV admissions between 2005–2009 and examined all patients with significant cardiac disease who received palivizumab in 2008–2009.

RESULTS

Infants with symptomatic cardiac disease had a more complicated course of RSV bronchiolitis with longer hospital stay, more frequent intensive care admission, longer intensive care stay and were more likely to receive respiratory support (all P < 0.05). One hundred seventeen infants with symptomatic cardiac disease received palivizumab. Of these, two (1.7%) required admission for RSV bronchiolitis. Overall, there was a reduction in admission of infants with symptomatic cardiac disease with RSV bronchiolitis in 2008–2009 (2% per year) compared with 2005–2007 (5–9% per year; P < 0.03). The number of patients with symptomatic cardiac disease who required intensive care for RSV bronchiolitis in the same period was unchanged, as a number presented to our service with RSV infection prior to commencing immunoprophylaxis or having had their cardiac diagnosis made in other centres.

CONCLUSIONS

Compared with other infants, those with haemodynamically significant cardiac disease have a more complicated course of illness with RSV bronchiolitis. In these infants, palivizumab reduced the number of hospitalisations because of RSV. Cohorting patients for maximal palivizumab use reduced overall cost. To significantly impact on intensive care admissions overall, immunoprophylaxis should be considered at a regional level.

High risk for RSV bronchiolitis in late preterms and selected infants affected by rare disorders: a dilemma of specific prevention

Respiratory syncytial virus (RSV) is the most frequent aetiologic agent that causes bronchiolitis and lower respiratory tract infection in infants. These infections may be severe and even life-threatening in selected high-risk populations. Traditional, well-established, high-risk populations are preterm infants with or without chronic lung disease and children with congenital heart disease. For these children, RSV prophylaxis using palivizumab, a monoclonal anti-RSV humanised antibody against the F-protein of RSV, has proven safe and efficacious in preventing RSV-related hospitalisation. Recently, a number of rare medical conditions have been associated with the risk of severe RSV infections. Evidence of safety and efficacy of RSV prophylaxis in these populations is lacking. Given the low incidence of these conditions, randomised trials are not feasible. A practical, opinion-based approach to this dilemma is offered in this paper. It is proposed that these rare disorders may qualify for RSV prophylaxis if the association between a specific condition and the risk of severe RSV infection is confirmed in at least 3 independent publications, of which at least 1 includes a prospective cohort study. To facilitate pharmaco-economic analyses, at least one of the three studies must also report on the absolute risk of severe RSV infection in the specified illness. The authors believe that qualification criteria will enable caregivers to target RSV prophylaxis more effectively in children with rare conditions and the proposed approach provides direction for future epidemiological studies on the risk of severe RSV infection in children with these uncommon, medical illnesses.

Changes in cardiac output and stroke volume as measured by non-invasive CO monitoring in infants with RSV bronchiolitis

OBJECTIVES

The primary aim of the study was to determine the changes, if any, in cardiac output (CO) and stroke volume (SV) in normal infants with RSV bronchiolitis. The secondary aim was to determine whether changes in CO (ΔCO) and SV (ΔSV) are associated with changes in respiratory rate (ΔRR).

METHODS

Non-invasive CO recordings were obtained within 24 h of admission and discharge. Changes in CO, SV, and HR measurements were compared using paired t-tests. The effect of fluid boluses during the first 24 h (<60 or ≥60 cc/kg) on CO was assessed by 2 way ANOVA with time and group as main effect. The relationship between ΔRR and ΔCO or ΔSV was assessed by linear regression. Data is presented as Mean ± SEM and mean differences with 95 % confidence interval (p < 0.05 considered significant).

RESULTS

15 infants with RSV bronchiolitis were studied. CO (1.31 ± 0.13 to 1.11 ± 0.11 l/min (0.21 [0.04-0.37]) and SV (9.42 ± 1.10 to 7.75 ± 0.83 ml/beat (1.67 [0.21-3.12]) decreased significantly while HR (142.1 ± 4.0 to 145.2 ± 3.1 beats/min 3.0 [-5.3 to 11.3]) was unchanged. SV (p = 0.02) and CO (p = 0.04) significantly decreased only in the 7 infants that received ≥60 cc/kg. ΔRR correlated significantly with ΔCO (r (2) = 0.28, p = 0.04); but not with ΔSV (r (2) = 0.20, p = 0.09).

CONCLUSIONS

∆CO was related to ΔSV and not Δ HR. The ∆CO and ΔSV were affected by fluid boluses. ΔRR correlated with ΔCO. Non-invasive CO monitoring can trend CO and SV in infants with bronchiolitis during hospitalization.

Managing the morbidity associated with respiratory viral infections in children with congenital heart disease

Children with congenital heart disease (CHD) are at risk for increased morbidity from viral lower respiratory tract infections because of anatomical cardiac lesions than can worsen an already compromised respiratory status. Respiratory syncytial virus (RSV) remains an important pathogen in contributing toward the morbidity in this population. Although the acute treatment of RSV largely remains supportive, the development of monoclonal antibodies, such as palivuzumab, has reduced the RSV-related hospitalization rate in children with CHD. This review highlights the specific cardiac complications of RSV infection, the acute treatment of bronchiolitis in patients with CHD, and the search for new therapies against RSV, including an effective vaccine, because of the high cost associated with immunoprophylaxis and its lack of reducing RSV-related mortality.

Risk factors for severe respiratory syncytial virus lower respiratory tract infection

RSV infection is a leading cause of lower respiratory tract infection, especially in High-risk infants with a history of prematurity, bronchopulmonary dysplasia (BPD), congenital heart disease (CHD), neuromusculair impairment, immunodeficiency, and Down syndrome. Host related risk factors that have been identified to be associated with severe RSV related lower respiratory tract infection include young age below 6 months at the beginning of RSV season, multiple birth, male sex, low socioeconomic status and parental education, crowded living conditions, young siblings, maternal smoking and indoor smoke pollution, malnutrition/small for gestational age, family history of atopy or asthma, low cord serum RSV antibody titers, and living at altitude.Risk factors increasing the risk of acquisition of RSV have been identified to be birth before and/or during RSV season, day care attendance, presence of older siblings in school or day-care, and lack of breast feeding. Some of these risk factors are discussed controversially and some of them are found continuously throughout the literature.Given the high cost of RSV prophylaxis, especially for the large population of late preterm infants, algorithms and risk score systems have been published that could identify high-risk infants for treatment with palivizumab out of this gestational age group. Several models reported on an average sensitivity and specificity of 70 percent and, thus, are helpful to identify infants at high risk for severe RSV infection and need for prophylaxis with palivizumab.

Natural polymorphisms and resistance-associated mutations in the fusion protein of respiratory syncytial virus (RSV): effects on RSV susceptibility to palivizumab

Specific mutations in respiratory syncytial virus (RSV) fusion protein can cause palivizumab resistance. We assessed the incidence of sequence polymorphisms and palivizumab resistance in clinical RSV isolates collected from immunoprophylaxis-naive subjects. Polymorphisms were identified at low frequency, and only polymorphic mutations in antigenic site A (<1% of all polymorphisms) conferred palivizumab resistance.

Progress in understanding and controlling respiratory syncytial virus: still crazy after all these years

Human respiratory syncytial virus (RSV) is a ubiquitous pathogen that infects everyone worldwide early in life and is a leading cause of severe lower respiratory tract disease in the pediatric population as well as in the elderly and in profoundly immunosuppressed individuals. RSV is an enveloped, nonsegmented negative-sense RNA virus that is classified in Family Paramyxoviridae and is one of its more complex members. Although the replicative cycle of RSV follows the general pattern of the Paramyxoviridae, it encodes additional proteins. Two of these (NS1 and NS2) inhibit the host type I and type III interferon (IFN) responses, among other functions, and another gene encodes two novel RNA synthesis factors (M2-1 and M2-2). The attachment (G) glycoprotein also exhibits unusual features, such as high sequence variability, extensive glycosylation, cytokine mimicry, and a shed form that helps the virus evade neutralizing antibodies. RSV is notable for being able to efficiently infect early in life, with the peak of hospitalization at 2-3 months of age. It also is notable for the ability to reinfect symptomatically throughout life without need for significant antigenic change, although immunity from prior infection reduces disease. It is widely thought that re-infection is due to an ability of RSV to inhibit or subvert the host immune response. Mechanisms of viral pathogenesis remain controversial. RSV is notable for a historic, tragic pediatric vaccine failure involving a formalin-inactivated virus preparation that was evaluated in the 1960s and that was poorly protective and paradoxically primed for enhanced RSV disease. RSV also is notable for the development of a successful strategy for passive immunoprophylaxis of high-risk infants using RSV-neutralizing antibodies. Vaccines and new antiviral drugs are in pre-clinical and clinical development, but controlling RSV remains a formidable challenge.

The epidemiology of respiratory syncytial virus lower respiratory tract infections in children less than 5 years of age in Indonesia

BACKGROUND

Although the epidemiology of respiratory syncytial virus (RSV) lower respiratory tract infections (LRI) is well known in industrialized countries, the burden in developing Asian countries is not well studied.

METHODS

To define the burden of RSV disease in children <5 years of age in rural and urban Indonesia, infants and children were enrolled from peri-urban and rural subdistricts, in the following 2 cohorts: (a) a cross-sectional cohort of approximately 100 children from each of 2 subdistricts in the following 5 age groups: 3 to 5, 6 to 8, 9 to 11, 12 to 23, and 24 to 48 months; (b) a birth cohort of all newborns in both subdistricts during the 28 months of the study. All subjects were visited weekly at home. Children with World Health Organization-defined LRI or wheezing had a nasal wash for detection of RSV using an enzyme immunoassay and polymerase chain reaction.

RESULTS

Of the 2014 children studied, 1074 were in the cross-sectional and 940 in the newborn cohorts. Of the 802 episodes of LRI, 163 were caused by RSV. The RSV LRI incidence per 1000 child-years (C-Y) was higher in rural areas (57.25 vs. 38.54), P < 0.05. No RSV LRI occurred in the first 2 months of life and the peak incidence was in the 6- to 8-month-old infants (103/1000 C-Y). The rates were lowest in those <6 months, 16.5 per 1000 C-Y, compared with 83.1 per 1000 C-Y in those 6 to 11 months of age (P < 0.001), 66.99 in those 12 to 23 months of age, and 28.1 in 2- to 5-year-olds.

CONCLUSIONS

In Indonesia, the incidence of RSV LRI in the first 6 months of life is relatively low with most disease occurring in older children.

A randomized controlled trial of motavizumab versus palivizumab for the prophylaxis of serious respiratory syncytial virus disease in children with hemodynamically significant congenital heart disease

Children with hemodynamically significant congenital heart disease (CHD) are at risk for serious respiratory syncytial virus (RSV) disease. This study was designed to assess the safety and tolerability of motavizumab versus palivizumab in children with CHD and was not powered for efficacy. Patients (n = 1236) aged ≤24 mo were randomized to receive five monthly doses (15 mg/kg) of motavizumab or palivizumab during the RSV season. Adverse events (AEs) and serious AEs (SAEs) were recorded through 30 d after the last dose. RSV hospitalizations and RSV outpatient medically attended lower respiratory tract infections (MALRI; season 2) were summarized. Approximately 93 and 50% of patients reported an AE or SAE, respectively. Skin events occurred in 19.3% of motavizumab recipients and 16.2% of palivizumab recipients. Rates of hospitalizations and RSV MALRI were similar between treatment groups [relative risk (RR): 0.75; 95% CI, 0.34-1.59 and RR: 0.49; 95% CI, 0.10-1.99, respectively; both p > 0.05]. Motavizumab and palivizumab had similar safety profiles in children with hemodynamically significantly CHD; with the exception of skin events which were increased in motavizumab recipients. Safety and efficacy were consistent with another study comparing motavizumab with palivizumab in premature infants without CHD.

Pharmacological management of acute bronchiolitis

This article reviews the current knowledge base related to the pharmacological treatments for acute bronchiolitis. Bronchiolitis is a common lower respiratory illness affecting infants worldwide. The mainstays of therapy include airway support, supplemental oxygen, and support of fluids and nutrition. Frequently tried pharmacological interventions, such as ribavirin, nebulized bronchodilators, and systemic corticosteroids, have not been proven to benefit patients with bronchiolitis. Antibiotics do not improve the clinical course of patients with bronchiolitis, and should be used only in those patients with proven concurrent bacterial infection. Exogenous surfactant and heliox therapy also cannot be recommended for routine use, but surfactant replacement holds promise and should be further studied.

Economic evaluation of palivizumab in children with congenital heart disease: a Canadian perspective

BACKGROUND

Respiratory syncytial virus (RSV) is a common cause of bronchiolitis in infants. In children with congenital heart disease (CHD), it is associated with significant morbidity and mortality. Palivizumab is a monoclonal antibody that reduces the number of RSV-associated hospitalizations in children with CHD. We sought to assess cost savings and cost-effectiveness of palivizumab in children < 2 years old with hemodynamically significant CHD in a provincially administered RSV prophylaxis program.

METHODS

A cohort of children who received palivizumab (N = 292) from 2003-2007 was compared to a historical cohort of children (N = 412) from 1998-2003 who met the eligibility criteria for palivizumab prior to initiation of the prophylaxis program. Direct and indirect costs and benefits were determined.

RESULTS

The direct and indirect costs in the historical cohort were $838 per patient season compared to $9130 per patient season in the palivizumab cohort. Risk of admission was reduced by 42%, and days in hospital were reduced by 83%. The incremental cost of the RSV prophylaxis program was $8292 per patient for 1 RSV season. The incremental cost to prevent 1 day of hospitalization was $15,514. The cost of palivizumab accounted for 87.9% of the cost of prophylaxis.

CONCLUSIONS

Palivizumab is clinically effective; however, the cost was exceptionally high relative to the outcomes in this population. Given the financial constraints in a public health care setting, more strict criteria for patient selection or reduced drug costs would improve the cost-effectiveness of RSV prophylaxis.

Viral agents causing lower respiratory tract infections in hospitalized children: evaluation of the Speed-Oligo® RSV assay for the detection of respiratory syncytial virus

Respiratory syncytial virus (RSV) is the viral agent which is more frequently involved in lower respiratory tract infections (LRTIs) in infants under 1 year of age in developed countries. A new oligochromatographic assay, Speed-Oligo® RSV, was designed and optimized for the specific detection and identification of RSV subtypes A and B. The test was evaluated in 289 clinical samples from 169 hospitalized children using an immunochromatography (IC) test, virus isolation by culture, and an in-house real-time polymerase chain reaction (RT-PCR). Other viruses causing LRTIs were investigated by cell culture or PCR-based tests. Sixty-two patients were infected by RSV (36.7%). In addition, adenovirus, influenza B, parainfluenza 2, and human metapneumovirus were detected in rates ranging from 5 to 8%. A proportion of 10.1% of the patients had mixed infections. The sensitivity, specificity, and positive and negative predictive values were, respectively, 94.9, 99.4, 98.9, and 97.4% for Speed-Oligo® RSV, 92.9, 96.3, 92.9, and 96.3% for RT-PCR/RSV, and 58.4, 98.1, 93.3, and 82.6% for IC. Our rates of viral detection and co-infection were similar to those of previously reported series. Finally, we find that Speed-Oligo® RSV is a rapid and easy-to-perform technique for the detection of RSV and the identification of subtypes A and B.

Epidemiology and prevention of respiratory syncytial virus infections among infants and young children

Since its discovery in 1956, respiratory syncytial virus (RSV) has been recognized as one of the most common causes of serious lower respiratory tract infections in young children worldwide. While considered a high priority, development of a safe and effective vaccine has remained elusive. Prevention of RSV disease relies on infection control and hygiene measures, as well as providing immunoprophylaxis in select infants. The prophylaxis, however, is costly, and so targeting the recipient population and timing of administration is important for optimal effectiveness and judicious use of limited health care resources. This article reviews the epidemiology of RSV infections in infants and young children, including risk factors for severe disease, so as to inform decisions about prevention efforts.

Factors predicting prolonged hospital stay for infants with bronchiolitis

BACKGROUND

Prior prediction models for length of stay (LOS) in bronchiolitis have focused more on birth- and disease-related risk factors than on early hospital course factors, particularly common clinical markers including respiratory status and caloric intake.

OBJECTIVES

1) Study the associations of various clinical markers and LOS; and 2) develop a LOS prediction model.

DESIGN

Retrospective cohort study.

SETTING

Children's Hospital of Wisconsin.

PATIENTS

Inclusion criteria were: age < 365 days old; admission between November 1, 2004 and April 15, 2005; final diagnosis of bronchiolitis; placement on the bronchiolitis treatment protocol; and lack of concurrent condition impacting LOS.

RESULTS

During the study period, 272/347 infants admitted with bronchiolitis met inclusion criteria. On hospital day 2, infants in the prolonged LOS group (≥ 108 hours) had a significantly greater number of hours on supplemental oxygen, maximum supplemental oxygen use, minimum supplemental oxygen use, maximum respiratory rate, mean respiratory score, and number of times suctioned. They had significantly lower minimum oxygen saturation and caloric intake. Recursive partitioning demonstrated five variables (hours of supplemental oxygen, maximum respiratory rate, minimum supplemental oxygen use, gestation, and caloric intake) to predict short or prolonged LOS with an area under the receiver-operator characteristic curve of 0.89/0.72 in the learning/test trees; sensitivity, 0.85; and specificity, 0.82.

CONCLUSIONS

There are important differences between infants with bronchiolitis having short and prolonged hospital stays, including several clinical markers identifiable on hospital day 2. This model may be a useful prediction tool for targeting early interventions for high-risk infants.

Hospitalizations due to respiratory syncytial virus in children with congenital malformations

Statewide respiratory syncytial virus (RSV) lower respiratory tract infection hospitalization data of Colorado children with congenital malformations was used to estimate the population-based risk and severity of disease of RSV hospitalizations. Spina bifida without anencephaly, cleft palate, lung agenesis or dysgenesis, and biliary atresia were associated with a higher risk of being hospitalized with RSV lower respiratory tract infection and an increased severity of disease when hospitalized.

Respiratory syncytial virus infection in children with congenital heart disease: global data and interim results of Korean RSV-CHD survey

Respiratory syncytial virus (RSV) is a main cause of hospitalization for bronchiolitis and pneumonia in infants worldwide. Children with hemodynamically significant congenital heart disease (HS-CHD), as well as premature infants are at high risk for severe RSV diseases. Mortality rates for CHD patients hospitalized with RSV have been reported as about 24 times higher compared with those without RSV infection. Recently with advances in intensive care, mortality rates in CHD patients combined with RSV have decreased below 2%. The requirements of intensive care and mechanical ventilation for CHD patients with RSV infection were still higher than those without RSV infection or with non-CHD children. RSV infection has frequently threatened CHD infants with congestive heart failure, cyanosis, or with pulmonary hypertension. As a progressive RSV pneumonitis in those infants develops, the impairment of oxygen uptake, the breathing workload gradually increases and eventually causes to significant pulmonary hypertension, even after the operation. Preventing RSV infection as much as possible is very important, especially in infants with HS-CHD. A humanized monoclonal antibody, palivizumab, has effective in preventing severe RSV disease in high-risk infants, and progressive advances in supportive care including pulmonary vasodilator have dramatically decreased the mortality (<1%). Depending on the global trend, Korean Health Insurance guidelines have approved the use of palivizumab in children <1 year of age with HS-CHD since 2009. Korean data are collected for RSV prophylaxis in infants with CHD.

A decade of respiratory syncytial virus epidemiology and prophylaxis: translating evidence into everyday clinical practice

Respiratory syncytial virus (RSV) is a common infection in infancy, with nearly all children affected by two years of age. Approximately 0.5% to 2.0% of all children are hospitalized with lower respiratory tract disease, of which 50% to 90% have bronchiolitis and 5% to 40% have pneumonia. Morbidity and mortality are highest in children with nosocomial infection and in those with underlying medical illnesses such as cardiac and chronic lung disease. Aboriginal children residing in remote northern regions are specifically considered to be at high risk for hospitalization due to RSV infection. Thorough hand washing and health education are the principal strategies in primary prevention. In the absence of a vaccine, palivizumab prophylaxis is currently the best intervention to reduce the burden of illness and RSV-related hospitalization in high-risk children. Health care professionals should provide palivizumab prophylaxis cost effectively in accordance with recommendations issued by pediatric societies and national advisory bodies. The present article reviews the epidemiology of RSV infection and the short- and long-term impact of disease in high-risk infants and special populations. Prevention strategies and treatment are discussed based on the existing scientific evidence, and future challenges in the management of RSV infection are addressed.

Analysis of respiratory syncytial virus preclinical and clinical variants resistant to neutralization by monoclonal antibodies palivizumab and/or motavizumab

BACKGROUND

Palivizumab is a US Food and Drug Administration-approved monoclonal antibody for the prevention of respiratory syncytial virus (RSV) lower respiratory disease in high-risk infants. Motavizumab, derived from palivizumab with enhanced antiviral activity, has recently been tested in humans. Although palivizumab escape mutants have been generated in the laboratory, the development of resistant RSV in patients receiving palivizumab has not been reported previously.

METHODS

We generated palivizumab and motavizumab escape mutants in vitro and examined the development of resistant mutants in RSV-breakthrough patients receiving immunoprophylaxis. The effect of these mutations on neutralization by palivizumab and motavizumab and in vitro fitness was studied.

RESULTS

Antibody-resistant RSV variants selected in vitro had mutations at position 272 of the fusion protein, from lysine to asparagine, methionine, threonine, glutamine, or glutamate. Variants containing mutations at positions 272 and 275 were detected in breakthrough patients. All these variants were resistant to palivizumab, but only the glutamate variant at position 272 demonstrated resistance to motavizumab. Mixtures of wild-type and variant RSV soon lost the resistant phenotype in the absence of selection.

CONCLUSIONS

Resistant RSV variants were detected in a small subset (∼ 5%) of RSV breakthrough cases. The fitness of these variants was impaired, compared to wild-type RSV.

Prevention of serious respiratory syncytial virus-related illness. I: Disease pathogenesis and early attempts at prevention

Respiratory syncytial virus (RSV) was first described 160 years ago but was not officially recognized as a cause of serious illness in children until the late 1950s. It has been estimated that virtually all children have had at least one RSV infection by their second birthday. RSV is responsible for annual disease outbreaks, usually during a defined winter seasonal period that can vary by community and year. RSV is recognized as the leading cause of hospitalization among young children worldwide. Infants of young chronologic age and children with predisposing factors, such as premature birth, pulmonary disease, or congenital heart disease, are most susceptible to serious illness. Unlike other viruses, immunity to RSV infection is incomplete and short lived, and reinfection is common throughout life. Initial attempts to develop a vaccine in the 1960s met with unexpected and tragic results; many children vaccinated with a formalin-inactivated wild-type virus developed serious pulmonary disease upon subsequent natural infection. Numerous other vaccine technologies have since been studied, including vectored approaches, virus-like particles, DNA vaccines, and live attenuated virus vaccine. As of early 2010, only two companies or institutions had RSV vaccine candidates in early clinical trials, and no vaccine is likely to be licensed for marketing in the immediate future.

Serum SP-D levels as a biomarker of lung injury in respiratory syncytial virus bronchiolitis

To evaluate whether SP-D concentration is a useful biomarker of the severity of respiratory syncytial virus (RSV) bronchiolitis, we determined SP-D concentrations in patients with RSV bronchiolitis with or without chronic heart disease. We enrolled 52 patients who had been diagnosed with RSV bronchiolitis and required admission to the hospital at the Department of Pediatrics of Fukushima Medical University School of Medicine from 2004 through 2005. These patients were divided into two groups: Group 1 consisted of patients without any underlying disease and Group 2 consisted of patients with chronic heart disease. These patients were assigned to one of three categories. Stage A consisted of patients without oxygen dosage, Stage B of patients who required oxygen dosage, and Stage C of patients required artificial respiration. We evaluated baseline characteristics, clinical features, and serum SP-D concentration in Group 1, Group 2, and a control group (healthy infants without infection). Mean serum SP-D concentrations in patients with RSV bronchiolitis were higher than those in the control group (125.8 ± 49.3 and 44.2 ± 20.1 ng/ml, respectively). Mean serum SP-D concentration was also higher in Group 2 than in Group 1 patients (160.4 ± 56.4 and 112.3 ± 39.4 ng/ml, respectively). Mean serum SP-D concentrations were higher in Stage C than in Stages A or B patients, and mean serum SP-D concentrations were higher in Stage B than in Stage A. These findings suggest that serum SP-D is associated with the severity of RSV bronchiolitis and that it may be a useful biomarker for the severity of RSV bronchiolitis.

Community-acquired respiratory infections in young children with congenital heart diseases in the palivizumab era: the Spanish 4-season civic epidemiologic study

INTRODUCTION

To investigate the epidemiology of acute respiratory tract infections (ARIs) in children younger than 24 months old with hemodynamically significant congenital heart diseases. Primary aim: incidence of hospital admission due to ARI. Secondary aims: risk factors, etiologic agents, clinical outcomes, and usefulness of preventive measures.

PATIENTS AND METHODS

Prospective, multicenter, epidemiologic study conducted in 57 Spanish hospitals covering four 7-month seasons (2004-2008).

RESULTS

A total of 2613 patients were eligible for the study. Three hundred fifty-four patients (13.5%) (95% confidence interval: 12.3-14.9) required a total of 453 hospital admissions. Clinical diagnoses: bronchiolitis (54.1%), upper respiratory tract infection (21%), pneumonia (19.9%), and others (17.4%). Median length of hospital stay: 7.0 days. No etiologic agent was identified in two-thirds of the patients. In the remaining patients either a single agent (26.8%) or polymicrobial infection (5%) was identified. Respiratory syncytial virus (RSV) was the agent that was most commonly found (3.8% specific hospitalization rate). Children receiving adequate RSV prophylaxis (90.5%) had a 58.2% (95% confidence interval: 37.6-78.3) reduction in RSV hospitalization. Risk factors for admission included malnourishment, infant age, male gender, chromosome alterations, wheezing, inadequate RSV prophylaxis fulfillment, and siblings <11 years of age. Pediatric intensive care unit care was required in 21.8% of the admissions and 9 patients (0.34%) died.

CONCLUSIONS

Hospital admission rate and severity of ARI remain as important issues in hemodynamically significant congenital heart disease patients. The strict fulfillment of prophylactic recommendations against RSV is the only protective factor that can be modulated to decrease the ARI hospital admission rate.

The infectious march: the complex interaction between microbes and the immune system in asthma

There has been significant progress in our knowledge about the relationship between infectious disease and the immune system in relation to asthma, but many unanswered questions still remain. Respiratory tract infections such as those caused by respiratory syncytial virus and rhinovirus during the first 2 years of life are still clearly associated with later wheezing and asthma, but the mechanism has not been completely worked out. Is there an "infectious march" triggered by infection in infancy that progresses to disease pathology or are infants who contract respiratory infections predisposed to developing asthma? This review focuses on the common themes in the interaction between microbes and the immune system, and presents a critical appraisal of the evidence to date. The various mechanisms whereby microbes alter the immune response and how this might influence asthma are discussed along with new and promising clinical practices for prevention and therapy. Recent advances in using sensitive polymerase chain reaction detection methods have allowed more rigorous testing of the causality hypothesis of virus infection leading to asthma, but the evidence is still equivocal. Various exceptions and inconsistencies in the clinical trials are discussed in light of new guidelines for subject inclusion/exclusion in hopes of providing some standardization. Despite past failures in vaccination and disappointing results of some clinical trials, the new strategies for prophylaxis including RNA interference and targeted delivery of microbicides offer a large dose of hope to a world suffering from an increasing incidence of asthma as well as a huge burden of health care cost and loss of quality of life.

Disease severity and viral load are correlated in infants with primary respiratory syncytial virus infection in the community

Respiratory syncytial virus (RSV) is a major cause of respiratory tract infections in infants, with remarkable variability in disease severity. Factors determining severity of disease in previously healthy infants are still unclear. It was hypothesized that disease severity is correlated with viral load in primary RSV infection. Infants of a healthy birth cohort were included at signs of their first respiratory tract infection. Nasopharyngeal aspirate was obtained within 48-96 hr and disease severity was assessed with a previously published severity scoring model. PCR was applied to test the aspirates in a semi-quantitative way for the presence of 10 respiratory pathogens. In case of multiple infection, the pathogen with the highest load was defined as the primary pathogen. The correlation between disease severity and viral load was analyzed. A total of 82 infants were included over a period of 2 years. Median age at first respiratory tract infection was 3 months. Pathogens were detected in 77 (94%) infants; more than one pathogen was detected in 35 (43%) infants. RSV was present in aspirates of 30 infants; in 16 aspirates RSV was the primary pathogen. A negative correlation between RSV CT-value and disease severity was found in all RSV cases (rho = -0.52, P = 0.003) and in cases with RSV as the primary pathogen (rho = -0.54, P = 0.03). In conclusion, this is the first report on viral loads in previously healthy infants with RSV infection in the community. Disease severity correlated positively with viral load during primary RSV infection.

Fatality rates in published reports of RSV hospitalizations among high-risk and otherwise healthy children

OBJECTIVE

To review the fatalities among children hospitalized with respiratory syncytial virus (RSV) infection, and identify factors leading to a fatal outcome.

RESEARCH DESIGN AND METHODS

Review of literature identified from a structured search of PubMed (1966-2009) using the following Medical Subject Headings: respiratory syncytial virus infection; hospitalized; infants; and risk factors. Publications were restricted to: English language; full papers; inclusion of > or =10 subjects; children aged < or =18 years, hospitalization for RSV infection; and deaths reported. Case fatality rates were defined as number of deaths divided by number of children hospitalized for RSV and were calculated for each study.

RESULTS

Thirty-six studies met the inclusion and exclusion criteria. Case fatality rates among children hospitalized for RSV ranged from 0 to 33%. In general, studies showed that subgroups of high-risk children (chronic lung disease [CLD] 3.5-23%, congenital heart disease [CHD] 2-37%, and prematurity 0-6.1%) had higher fatality rates than older or otherwise healthy children (consistently <1%). Presence of severe underlying comorbidities such as neuromuscular disease, immunosuppression, and malignancies was associated with death among term and/or older (>1 year) children. Higher fatality rates were reported for infants receiving intensive unit care (1.1-8.6%), extracorporeal life support (33%) or for those who acquired nosocomial RSV infection (0-12.2%). The majority of studies did not report cause of death and clinical details of the fatal cases were often not provided. Other limitations of this review include our search limits, the possibility of inherent bias in our methodology that could result in an under or over estimation of case-fatality rates, and potential publication bias.

CONCLUSIONS

Children at high risk for RSV (CLD, CHD and prematurity), those with severe underlying comorbidities, or those with nosocomial RSV appear to be at increased risk for death after RSV hospitalization. More data are needed on cause of death and how much is directly attributable to RSV.

Functional disorder of primary immunity responding to respiratory syncytial virus infection in offspring mice exposed to a flame retardant, decabrominated diphenyl ether, perinatally

Perinatal exposure to a representative flame retardant, decabrominated diphenyl ether (DBDE), was shown previously to increase viral titers in the lungs of respiratory syncytial virus (RSV)-infected offspring on day 5 post-infection, resulting in exacerbation of pneumonia. In this study, the significant increase of pulmonary viral titers was confirmed even on day 1 post-infection and the effect on the primary immune response to RSV infection were examined to assess a mode of DBDE action on developmental immunotoxicity. On day 1 after infection, the secretion of both TNF-alpha and IL-6 decreased significantly in the bronchoalveolar lavage fluid prepared from RSV-infected offspring exposed to DBDE perinatally, but IL-1beta increased. However, in ex vivo lipopolysaccharide stimulation test, the productivity of TNF-alpha in the bronchoalveolar lavage cells, which are mainly primary immune cells responding to RSV infection, prepared from offspring mice exposed to DBDE perinatally was not lower than that in the control. The primary immune cells retained normally the ability of cytokine production after the DBDE exposure. Gene expressions of innate pattern recognition receptors (Toll-like receptor 3 and 4, melanoma differentiation-associated gene-5, and retinoic acid-inducible gene I) in lung tissues were not affected by DBDE exposure. Because the levels of TNF-alpha, IL-6, and IL-1beta are known to be elevated in the lungs of RSV-infected mice, these irregular productions due to perinatal DBDE exposure indicate a disorder of the primary immune response to RSV infection. Thus, perinatal exposure to DBDE was suggested to cause a functional disorder of primary immunity responding to RSV infection.

Immunoprophylaxis and immunotherapy: role in the prevention and treatment of repiratory syncytial virus

It is now apparent that neutralizing antibody may play an important role in ameliorating RSV lower repiratory tract illness. At the present time immunoprophylaxis and immunotherapy with polyclonal antibodies show the most promise in the prevention and treatment of RSV illness. Several questions remained to be answered. These include the practical application of IGIV in prevention and treatment of RSV illness. Intravenous lines are often difficult to place and maintain. With the further development of polyclonal or monoclonal antibodies it may be possible to immunize prospective donors and boost their anti RSV titers to the degree that a hyper-immune IGIV with sufficient antibody to be given intramuscularly could be produced. The role for RSV-specific monoclonal antibodies for disease prevention or treatment must be defined as well as the appropriatee viral epitopes to target. In the absence of a safe and effective vaccine, it is clear that, despite these questions passive immunotherapy and immunoprophylaxis offers the greatest hope for the prevention and treatment of RSV disease in high risk infants and children.

A phase 2, randomized, double-blind safety and pharmacokinetic assessment of respiratory syncytial virus (RSV) prophylaxis with motavizumab and palivizumab administered in the same season

Background

Respiratory syncytial virus (RSV) is an important pathogen causing annual epidemics of bronchiolitis and pneumonia among infants worldwide. High-risk infants currently receive RSV prophylaxis with palivizumab, a humanized RSV monoclonal antibody (MAb). In preclinical in vitro and in vivo (cotton-rat model) studies, motavizumab, a new RSV MAb, was shown to have greater anti-RSV activity than palivizumab. Motavizumab is currently under review for licensing approval. Since both MAbs may be available concurrently, this study evaluated their safety and tolerability when administered sequentially during the same RSV season.

Methods

Between April 2006 and May 2006, 260 high-risk infants were randomly assigned 1:1:1 to receive monthly intramuscular injections: 2 doses of motavizumab followed by 3 doses of palivizumab (M/P); 2 doses of palivizumab followed by 3 doses of motavizumab (P/M); or 5 doses of motavizumab (control). Adverse events (AEs, serious AEs [SAEs]), development of antidrug antibody (ADA), and serum drug trough concentrations were assessed.

Results

Most children received all 5 doses (246/260 [94.6%]) and completed the study (241/260 [92.7%]). While overall AE rates were similar (mostly level 1 or 2 in severity), SAEs and level 3 AEs occurred more frequently in the M/P group (SAEs: 22.9% M/P, 8.4% P/M, 11.8% motavizumab only; level 3 AEs: 15.7% M/P, 6.0% P/M, 6.5% motavizumab only). This trend in AE rates occurred before and after switching from motavizumab to palivizumab, suggesting a cause other than the combined regimen. Frequencies of AEs judged by the investigator to be related to study drug were similar among groups. Two deaths occurred on study (both in the M/P group, before palivizumab administration); neither was considered by the site investigator to be related to study drug. Mean serum drug trough concentrations were comparable among groups; ADA detection was infrequent (5.1% or less of any group).

Conclusions

The conclusions drawn from this study are limited by the small sample size per group. However, within this small study, overall AE rates, serum drug trough concentrations, and development of ADA associated with administering motavizumab and palivizumab sequentially to high-risk children appear comparable to administering motavizumab alone during the same RSV season.

Trial Registration

clinicaltrials.gov NCT00316264

Serum antibody response to respiratory syncytial virus F and N proteins in two populations at high risk of infection: children and elderly

Human respiratory syncytial virus (hRSV) is the main viral cause of severe respiratory infections in children and a common cause of morbidity in the elderly. The nucleocapsid (N) and fusion (F) proteins of hRSV were expressed in insect cells and used as antigens in two independent enzyme-linked immunosorbent assays (ELISAs) to measure the serum antibody response in two populations at high risk of hRSV infection, children and the elderly. Fifty-seven serum specimens from children aged from 1 to 10 years old and 91 sera from adults over 60 years old were tested. The ELISA results were compared with those obtained by an immunofluorescence assay (IFA) based on hRSV-infected cells, which was considered as the reference technique. Sensitivity and specificity were 94% and 85% for the N-ELISA and 86% and 81% for the F-ELISA, respectively. When the immune responses of the two groups of individuals were compared, it appeared that almost 100% of the elderly had antibodies against the N or F protein whereas only 50% of the sera from children had antibodies against either of the two viral proteins. In conclusion, the F and N ELISAs can be used successfully for detecting a specific antibody response to hRSV.

Respiratory syncytial virus outbreak defined by rapid screening in a neonatal intensive care unit

Palivizumab is currently licensed for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in infants and children with chronic lung disease, with a history of preterm birth, or with haemodynamically significant congenital heart disease, but its routine use during outbreaks in neonatal intensive care units (NICUs) is not currently recommended. Here we report an outbreak in a NICU detected during a screening trial for RSV infection using a rapid antigen test (Respi-Strip^®). Eleven preterm infants in our NICU tested positive for RSV during January 2009. Subsequent testing of the remaining infants in the NICU revealed two additional asymptomatic cases. In addition to precautions against cross-infection, palivizumab prophylaxis was administered to the remaining 37 premature infants. Two days after treatment, RSV was detected in two additional infants who had become symptomatic. To our knowledge this is the largest RSV outbreak in a NICU to be identified at an early stage by rapid testing and effectively controlled by infection control measures and palivizumab prophylaxis.

Respiratory syncytial virus infections: characteristics and treatment

In this review, we describe the history, epidemiology and clinical manifestations of infections attributed to respiratory syncytial virus (RSV) in children. At present, no cure exists for RSV infection but commonly employed palliative treatments include oxygen and inhaled β2-adrenoceptor agonists, such as salbutamol, to relieve the wheezing and increased bronchiolar smooth muscle constriction. Adrenaline (epinephrine) has been found to be superior to the selective β2-adrenoceptor agonists. Oral or inhaled corticosteroids should counteract the inflammatory response to RSV infection but their effectiveness is controversial. Inhaled ribavirin is the only licensed antiviral product approved for the treatment of RSV lower respiratory-tract infection in hospitalized children, although its use is now restricted to high-risk infants. Other treatments considered are nasopharyngeal suctioning, surfactant therapy, recombinant human deoxyribonuclease I, heliox (helium:oxygen) and inhaled nitric oxide. Prevention of infection by RSV antibodies is another strategy and, currently, palivizumab is the only safe, effective and convenient preventative treatment for RSV disease in high-risk populations of infants and young children. Its cost-effectiveness, however, has been questioned. Both live attenuated and subunit vaccines against RSV infection have been developed but so far there is no safe and effective vaccine available. Finding effective treatments and prophylactic measures remains a major challenge for the future.