Sequelae of respiratory syncytial virus infections. A role for intervention studies

Association between early viral LRTI and subsequent wheezing development, a meta-analysis and sensitivity analyses for studies comparable for confounding factors

Introduction

Consideration of confounding factors about the association between Lower Respiratory Tract Infections (LRTI) in childhood and the development of subsequent wheezing has been incompletely described. We determined the association between viral LRTI at ≤ 5 years of age and the development of wheezing in adolescence or adulthood by a meta-analysis and a sensitivity analysis including comparable studies for major confounding factors.

Methods

We performed searches through Pubmed and Global Index Medicus databases. We selected cohort studies comparing the frequency of subsequent wheezing in children with and without LRTI in childhood regardless of the associated virus. We extracted the publication data, clinical and socio-demographic characteristics of the children, and confounding factors. We analyzed data using random effect model.

Results

The meta-analysis included 18 publications (22 studies) that met the inclusion criteria. These studies showed that viral LRTI in children ≤ 3 years was associated with an increased risk of subsequent development of wheezing (OR = 3.1, 95% CI = 2.4–3.9). The risk of developing subsequent wheezing was conserved when considering studies with comparable groups for socio-demographic and clinical confounders.

Conclusions

When considering studies with comparable groups for most confounding factors, our results provided strong evidence for the association between neonatal viral LRTI and the subsequent wheezing development. Further studies, particularly from lower-middle income countries, are needed to investigate the role of non-bronchiolitis and non-HRSV LRTI in the association between viral LRTI in childhood and the wheezing development later. In addition, more studies are needed to investigate the causal effect between childhood viral LRTI and the wheezing development later.

Trial registration

Review registration: PROSPERO, CRD42018116955; https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42018116955.

Persistent recurring wheezing in the fifth year of life after laboratory-confirmed, medically attended respiratory syncytial virus infection in infancy

Background

Respiratory syncytial virus (RSV) infection in infancy is associated with subsequent recurrent wheezing.

Methods

A retrospective cohort study examined children born at ≥32 weeks gestation between 1996–2004. All children were enrolled in an integrated health care delivery system in Northern California and were followed through the fifth year of life. The primary endpoint was recurrent wheezing in the fifth year of life and its association with laboratory-confirmed, medically-attended RSV infection during the first year, prematurity, and supplemental oxygen during birth hospitalization. Other outcomes measured were recurrent wheezing quantified through outpatient visits, inpatient hospital stays, and asthma prescriptions.

Results

The study sample included 72,602 children. The rate of recurrent wheezing in the second year was 5.6% and fell to 4.7% by the fifth year. Recurrent wheezing rates varied by risk status: the rate was 12.5% among infants with RSV hospitalization, 8% among infants 32–33 weeks gestation, and 18% in infants with bronchopulmonary dysplasia. In multivariate analyses, increasing severity of respiratory syncytial virus infection was significantly associated with recurrent wheezing in year 5; compared with children without RSV infection in infancy, children who only had an outpatient RSV encounter had an adjusted odds ratio of 1.38 (95% CI,1.03–1.85), while children with a prolonged RSV hospitalization had an adjusted odds ratio of 2.59 (95% CI, 1.49–4.50).

Conclusions

Laboratory-confirmed, medically attended RSV infection, prematurity, and neonatal exposure to supplemental oxygen have independent associations with development of recurrent wheezing in the fifth year of life.

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.

Respiratory outcomes, utilization and costs 12 months following a respiratory syncytial virus diagnosis among commercially insured late-preterm infants

OBJECTIVES

To determine, among a commercially-insured population of late-preterm infants, utilization of healthcare resources and costs during the 1 year following a diagnosis of respiratory syncytial virus lower respiratory infection (RSV LRI).

METHODS

Administrative claims for non-capitated, commercially-insured infants <1 year old were used to identify infants diagnosed with RSV LRI and unspecified bronchiolitis/pneumonia (UBP). Infants were stratified by the setting of diagnosis. Infants without evidence of RSV LRI or UBP were selected as a comparison group. Economic and clinical outcomes were analyzed descriptively using propensity score weighting and logged ordinary least squares models were used to examine the relationship between RSV and costs (adjusted to 2006 USD) incurred within 1 year of RSV LRI.

RESULTS

The majority of infants were 3 months or older at the time of RSV LRI or UBP diagnosis. The rate of wheezing was significantly greater for infants in the RSV LRI and UBP cohorts relative to the comparison group (p < 0.001). Infantile asthma rates were 6-9 times higher among RSV LRI and UBP infants than the comparison group. RSV LRI and UBP infants also had significantly more emergency department visits and outpatient visits than the comparison group. The marginal healthcare costs were significantly higher for RSV LRI inpatients ($24,027) and outpatients ($2703) infants than for the comparison group (all p < 0.001).

CONCLUSION

Commercially insured late-preterm infants with RSV infection are at high risk for recurrent wheezing and infantile asthma during the 1-year period after the initial episode and impose a significant economic burden to the healthcare system.

WITHDRAWN: Inhaled corticosteroids during acute bronchiolitis in the prevention of post-bronchiolitic wheezing

BACKGROUND

Acute bronchiolitis in infants and young children is associated with long-term airway disease also known as post-bronchiolitic wheezing. Two major hypotheses have been proposed to explain the association between bronchiolitis and PBW. The first hypothesis considers bronchiolitis to be the first manifestation of recurrent wheezing in infants and children who are susceptible to obstructive airway disease. The second hypothesis suggests that the infection and concomitant inflammatory reaction in the acute phase leads to airway epithelium injury resulting in long-term obstructive airway disease. In line with the latter hypothesis, corticosteroids may have a beneficial effect on the prevention of post-bronchiolitic wheezing.

OBJECTIVES

The objective of this review was to evaluate the effect of inhaled corticosteroids, started during the acute phase of bronchiolitis, on the prevention of post-bronchiolitic wheezing.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2006, issue 3) which contains the Cochrane Acute Respiratory Infections Group's trials register, MEDLINE (1966 to September 2006), EMBASE (1980 to September 2006) and Current Contents (September 2006). Abstracts and reports of congresses (ERS 1999 to September 2005, ATS 1999 to September 2005) were obtained. We contacted experts in the field and pharmaceutical companies for ongoing or unpublished studies.

SELECTION CRITERIA

Randomised placebo-controlled trials studying the effect of inhaled corticosteroids in children younger than two years of age with the clinical diagnosis of acute bronchiolitis were included.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed trial quality using the Jadad 5-point scale.

MAIN RESULTS

Five studies matched the inclusion criteria, with a median Jadad score of 4 (Inter Quartile Range 3 to 4), involving 374 infants. Pooling of the data was limited, due to the clinical diversity of the studies. However, no effect of inhaled corticosteroids in the prevention of wheezing (diary records or GP diagnosed), hospital re-admissions or use of corticosteroids or bronchodilators could be demonstrated. Duration of therapy, length of follow up or causative agent (respiratory syncytial virus or not) did not influence the pooled effect. In the three studies that also evaluated the adverse events, none were reported.

AUTHORS' CONCLUSIONS

This review does not demonstrate an effect of inhaled corticosteroids given during the acute phase of bronchiolitis in the prevention of post-bronchiolitic wheezing. The small number of included participants and the inability to pool all clinical outcomes precludes us from making strong recommendations.

Inhaled corticosteroids during acute bronchiolitis in the prevention of post-bronchiolitic wheezing

BACKGROUND

Acute bronchiolitis in infants and young children is associated with long-term airway disease also known as post-bronchiolitic wheezing. Two major hypotheses have been proposed to explain the association between bronchiolitis and PBW. The first hypothesis considers bronchiolitis to be the first manifestation of recurrent wheezing in infants and children who are susceptible to obstructive airway disease. The second hypothesis suggests that the infection and concomitant inflammatory reaction in the acute phase leads to airway epithelium injury resulting in long-term obstructive airway disease. In line with the latter hypothesis, corticosteroids may have a beneficial effect on the prevention of post-bronchiolitic wheezing.

OBJECTIVES

The objective of this review was to evaluate the effect of inhaled corticosteroids, started during the acute phase of bronchiolitis, on the prevention of post-bronchiolitic wheezing.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2006) which contains the Cochrane Acute Respiratory Infections Group's trials register, MEDLINE (1966 to September 2006), EMBASE (1980 to September 2006) and Current Contents (September 2006). Abstracts and reports of congresses (ERS 1999 to September 2005, ATS 1999 to September 2005) were obtained. We contacted experts in the field and pharmaceutical companies for ongoing or unpublished studies.

SELECTION CRITERIA

Randomised placebo-controlled trials studying the effect of inhaled corticosteroids in children younger than two years of age with the clinical diagnosis of acute bronchiolitis were included.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data and assessed trial quality using the Jadad 5-point scale.

MAIN RESULTS

Five studies matched the inclusion criteria, with a median Jadad score of 4 (Inter Quartile Range 3 to 4), involving 374 infants. Pooling of the data was limited, due to the clinical diversity of the studies. However, no effect of inhaled corticosteroids in the prevention of wheezing (diary records or GP diagnosed), hospital re-admissions or use of corticosteroids or bronchodilators could be demonstrated. Duration of therapy, length of follow up or causative agent (respiratory syncytial virus or not) did not influence the pooled effect. In the three studies that also evaluated the adverse events, none were reported.

AUTHORS' CONCLUSIONS

This review does not demonstrate an effect of inhaled corticosteroids given during the acute phase of bronchiolitis in the prevention of post-bronchiolitic wheezing. The small number of included participants and the inability to pool all clinical outcomes precludes us from making strong recommendations.

Inhibition of respiratory syncytial virus in cultured cells by nucleocapsid gene targeted deoxyribozyme (DNAzyme)

Respiratory syncytial virus (RSV), which presents the primary cause of bronchiolitis and pneumonia among infants and causes significant morbidity and mortality in immunodeficient patients, remains a health problem worldwide. Unfortunately, an effective vaccine is currently unavailable and pharmacologic treatment needs further optimization for RSV disease. Because RSV is a non-segmented negative-strand RNA virus, it may be sensitive to the genome RNA cleaving by DNAzyme, an artificial nucleic acids molecule with high catalytic capability of cleaving complementary RNA molecules. Thus, RSV-targeted DNAzymes potentially present as a therapeutic candidate of RSV diseases. In this study, DNAzymes targeting the RSV genomic RNA or mRNA were designed and synthesized, one of which (DZn1133) did cleave RSV RNA in vitro, inhibit the transcription and expression of F viral gene, reduce the RSV yield by about 7 logs and protect more than 90% RSV-infected Hep-2 cells from a cytopathic effect at 8 microM. Moreover, 10 wild RSV strains isolated from clinic patients including both subgroups A and B were all suppressed by DZn1133 with greater anti-RSV activity than antisense DNA or ribavirin.

Nuclear heat shock response and novel nuclear domain 10 reorganization in respiratory syncytial virus-infected a549 cells identified by high-resolution two-dimensional gel electrophoresis

The pneumovirus respiratory syncytial virus (RSV) is a leading cause of epidemic respiratory tract infection. Upon entry, RSV replicates in the epithelial cytoplasm, initiating compensatory changes in cellular gene expression. In this study, we have investigated RSV-induced changes in the nuclear proteome of A549 alveolar type II-like epithelial cells by high-resolution two-dimensional gel electrophoresis (2DE). Replicate 2D gels from uninfected and RSV-infected nuclei were compared for changes in protein expression. We identified 24 different proteins by peptide mass fingerprinting after matrix-assisted laser desorption ionization-time of flight mass spectrometry (MS), whose average normalized spot intensity was statistically significant and differed by +/-2-fold. Notable among the proteins identified were the cytoskeletal cytokeratins, RNA helicases, oxidant-antioxidant enzymes, the TAR DNA binding protein (a protein that associates with nuclear domain 10 [ND10] structures), and heat shock protein 70- and 60-kDa isoforms (Hsp70 and Hsp60, respectively). The identification of Hsp70 was also validated by liquid chromatography quadropole-TOF tandem MS (LC-MS/MS). Separate experiments using immunofluorescence microscopy revealed that RSV induced cytoplasmic Hsp70 aggregation and nuclear accumulation. Data mining of a genomic database showed that RSV replication induced coordinate changes in Hsp family proteins, including the 70, 70-2, 90, 40, and 40-3 isoforms. Because the TAR DNA binding protein associates with ND10s, we examined the effect of RSV infection on ND10 organization. RSV induced a striking dissolution of ND10 structures with redistribution of the component promyelocytic leukemia (PML) and speckled 100-kDa (Sp100) proteins into the cytoplasm, as well as inducing their synthesis. Our findings suggest that cytoplasmic RSV replication induces a nuclear heat shock response, causes ND10 disruption, and redistributes PML and Sp100 to the cytoplasm. Thus, a high-resolution proteomics approach, combined with immunofluorescence localization and coupled with genomic response data, yielded unexpected novel insights into compensatory nuclear responses to RSV infection.

The role of virus-specific immunoglobulin E in airway hyperresponsiveness

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis during infancy and is associated with subsequent wheezing and asthma, but the nature of this association is not fully understood. We investigated the role of RSV-specific IgE antibodies in the pathophysiology of virus-induced airway dysfunction in a mouse model. Lung infection with RSV resulted in significant increases in mRNA expression for IgE and both of its high- and low-affinity receptors. In serum, virus-specific IgE antibodies reached peak levels by Day 21 after infection. Data from in vitro experiments show that RSV can induce mast cell degranulation, but only if these cells are sensitized with specific IgE. When passively sensitized in vivo with virus-specific IgE, mice developed exaggerated airway responsiveness to methacholine on airway infection, an effect that required the high-affinity receptor of IgE. These data suggest that RSV-specific IgE may contribute to the pathophysiology of airway dysfunction in children who develop this class of specific antibody.

Risk factors for recurrent wheezing following acute bronchiolitis: a 12-month follow-up

The objective of this study was to identify wheezing recurrences and related risk factors in two groups of infants with bronchiolitis: respiratory syncytial virus (RSV)+ and RSV- as determined by RSV enzyme immunoassay. A 1-year prospective cohort study was conducted with infants younger than 2 years old. Follow-up was made monthly, by a clinical visit and/or by telephone, checking the number of wheezing episodes per month and possible related risk factors. There were 96 subjects enrolled, of whom 77 reached complete follow-up: 36 were RSV+ (46.8%), and 41 were RSV- (53.2%). In the RSV+ group, there were 17 males (47%), vs. RSV- with 30 males (73%) (P < 0.05); 22 RSV+ (61%) were admitted to hospital, vs.14 RSV- (34%) (P < 0.05). Mean age was not significantly different in both groups. The mean number of recurrences was 3.36 episodes/infant/year in the RSV+ and 2.34 in the RSV- group (P = 0.06). Crude relative risk (RR) for a new recurrence of an obstructive episode was 1.33 (95% CI, 0.99-1.79). After adjustment for several potential confounders, the RR was 1.41 (95% CI, 1.03-1.93). Hospitalization stay was longer in the RSV+ than the RSV- group (P < 0.05). In the RSV+ group, patients who had been hospitalized showed more recurrences (4.18) than those with outpatient treatment (2.07) (P < 0.05); this difference did not exist in the RSV- group. The related risk factors for recurrent wheeze in the RSV- group were male gender, number of siblings, and daycare attendance (P < 0.05). In the RSV+ group, the risk of recurrent wheeze was only increased by admission to hospital during the acute bronchiolitis episode (P < 0.05). We speculate that there may be a higher rate of increased airway reactivity and/or preexisting diminished lung function in RSV+ infants requiring hospitalization for their initial illness. In conclusion, RSV-proven bronchiolitis, particularly in those infants who are hospitalized, is associated with a higher recurrence of wheezing episodes in the subsequent 12 months. Other factors appear to account for recurrent wheeze in the RSV- group.

Common community respiratory viruses in patients with cancer: more than just "common colds"

Community respiratory viruses long have been recognized as primary respiratory pathogens among infants and young children. More recently, it has become clear that these viruses cause a considerable disease burden throughout life. The consequences of repeated infections are most evident in elderly and immunocompromised persons. Even in otherwise healthy persons, reinfections often require medical attention but generally are undiagnosed and unrecognized. These reinfections may spread from healthy persons to those at highest risk. Control requires a multifaceted approach combining vaccination, chemoprophylaxis, and aggressive early antiviral treatment of high-risk individuals, as well as education of all populations affected by these viruses.

Ribavirin treatment up-regulates antiviral gene expression via the interferon-stimulated response element in respiratory syncytial virus-infected epithelial cells

Respiratory syncytial virus (RSV) is a mucosa-restricted virus that is a leading cause of epidemic respiratory tract infections in children. RSV replication is a potent activator of the epithelial-cell genomic response, influencing the expression of a spectrum of cellular pathways, including proinflammatory chemokines of the CC, CXC, and CX(3)C subclasses. Ribavirin (1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) is a nontoxic antiviral agent currently licensed for the treatment of severe RSV lower respiratory tract infections. Because ribavirin treatment reduces the cytopathic effect in infected cells, we used high-density microarrays to investigate the hypothesis that ribavirin modifies the virus-induced epithelial genomic response to replicating virus. Ribavirin treatment administered in concentrations of 10 to 100 micro g/ml potently inhibited RSV transcription, thereby reducing the level of RSV N transcripts to approximately 13% of levels in nontreated cells. We observed that in both the absence and the presence of ribavirin, RSV infection induced global alterations in the host epithelial cell, affecting approximately 49% of the approximately 6,650 expressed genes detectable by the microarray. Ribavirin influences the expression of only 7.5% of the RSV-inducible genes (total number of genes, 272), suggesting that the epithelial-cell genetic program initiated by viral infection is independent of high-level RSV replication. Hierarchical clustering of the ribavirin-regulated genes identified four expression patterns. In one group, ribavirin inhibited the expression of the RSV-inducible CC chemokines MIP-1 alpha and -1 beta, which are important in RSV-induced pulmonary pathology, and interferon (IFN), a cytokine important in the mucosal immune response. In a second group, ribavirin further up-regulated a set of RSV- and IFN-stimulated response genes (ISGs) encoding antiviral proteins (MxA and p56), complement products, acute-phase response factors, and the STAT and IRF transcription factors. Because IFN-beta expression itself was reduced in the ribavirin-treated cells, we further investigated the mechanism for up-regulation of the IFN-signaling pathway. Enhanced expression of IFI 6-16, IFI 9-27, MxA/p78, STAT-1 alpha, STAT-1 beta, IRF-7B, and TAP-1-LMP2 transcripts were independently reproduced by Northern blot analysis. Ribavirin-enhanced TAP-1-LMP2 expression was a transcriptional event where site mutations of the IFN-stimulated response element (ISRE) blocked RSV and ribavirin-inducible promoter activity. Furthermore, ribavirin up-regulated the transcriptional activity of a reporter gene selectively driven by the ISRE. In specific DNA pull-down assays, we observed that ribavirin enhanced RSV-induced STAT-1 binding to the ISRE. We conclude that ribavirin potentiates virus-induced ISRE signaling to enhance the expression of antiviral ISGs, suggesting a mechanism for the efficacy of combined treatment with ribavirin and IFN in other chronic viral diseases.

A randomized trial of montelukast in respiratory syncytial virus postbronchiolitis

Infants often develop reactive airway disease after respiratory syncytial virus (RSV) bronchiolitis. Cysteinyl-leukotrienes (cys-LT) are released during RSV infection and may contribute to the inflammation. We hypothesized that a cys-LT receptor antagonist would ameliorate reactive airway disease subsequent to RSV bronchiolitis. One hundred and thirty infants who were 3 to 36 months old, hospitalized with acute RSV bronchiolitis, were randomized into a double-blind, parallel comparison of 5-mg montelukast chewable tablets or matching placebo given for 28 days starting within 7 days of symptom debut. Infants with a suspected history of asthma were excluded. One hundred sixteen infants provided diary card data for the treatment period. Median age was 9 months. Infants on montelukast were free of any symptoms on 22% of the days and nights compared with 4% of the days and nights in infants on placebo (p = 0.015). Daytime cough was significantly reduced on active treatment (p = 0.04). Exacerbations were significantly delayed from montelukast compared with placebo (p < 0.05). In conclusion, cys-LT antagonist treatment reduces lung symptoms subsequent to RSV bronchiolitis.

Early ribavarin treatment of bronchiolitis: effect on long-term respiratory morbidity

BACKGROUND

The mortality rate from respiratory syncytial virus (RSV) bronchiolitis has significantly reduced over the last decade. A major concern now is the long-term respiratory morbidity following RSV bronchiolitis.

METHODS

In this prospective study, we randomly assigned 49 previously healthy infants with severe RSV bronchiolitis, early in the course of illness (< 5 days duration), to receive either conservative treatment (n = 21) or additional ribavirin treatment (n = 24). Both groups were closely matched for age and clinical characteristics.

RESULTS

During a prospective, closely monitored, 1-year follow-up period, the group treated with ribavirin had significantly fewer episodes (2.7 +/- 2.3 episodes vs 6.4 +/- 4.2 episodes per patient per year) and reduced severity of reactive airway disease (0.08 episodes vs 1.09 episodes of moderate-to-severe illness per patient per year) and respiratory illness-related hospitalization (25 hospital days vs 90 hospital days per 100 patients per year).

CONCLUSIONS

Early ribavirin treatment of RSV bronchiolitis in previously healthy infants resulted in reduction of incidence and severity of reactive airway disease as well as respiratory illness-related hospitalization.

A cohort of children hospitalised with acute RSV bronchiolitis: impact on later respiratory disease

This paper reviews the results from a cohort study in which 47 children hospitalised with respiratory syncytial virus (RSV) bronchiolitis and their 93 controls, matched for age, sex and place of living, were prospectively followed-up at the mean ages of 1, 3 and 7.5. Asthma was significantly more common in the RSV bronchiolitis group at all times. Asthma during the year prior to follow-up at age 7.5 was seen in 23% of the RSV children and in 2% of the controls (P < 0.001). Allergic sensitisation was found in 41% of the RSV children and in 22% of the controls (P = 0.039). When comparing these results with findings from other studies it is obvious that the rate of asthma and other bronchial obstructive symptoms are increased after RSV bronchiolitis but the various results concerning allergic sensitisation are not conclusive. Prospective studies are needed with some kind of randomised intervention against RSV before the mechanisms behind the post-bronchiolitic symptoms and the possibly increased risk for IgE mediated allergy can be settled.

Respiratory outcomes in high-risk children 7 to 10 years after prophylaxis with respiratory syncytial virus immune globulin

PURPOSE

Respiratory syncytial virus infections have been implicated in the development of asthma. We evaluated the long-term effects of respiratory syncytial virus immune globulin, an effective prophylactic agent for the prevention of these infections in children, on respiratory and allergic outcomes in children at high risk of chronic airway disease.

SUBJECTS AND METHODS

Thirteen children at high risk of respiratory disease (mean [+/-SD] age, 8.6 +/- 1.1 years) were evaluated using pulmonary function and allergy skin testing 7 to 10 years after they had received prophylaxis with respiratory syncytial virus immune globulin. For comparison, 26 high-risk control children (mean age, 8.5 +/- 0.9 years) were also evaluated. Health outcomes data were collected from all subjects. The children were matched for age and gestational age. There were more boys, and a lesser frequency of a lower respiratory tract infection with respiratory syncytial virus (P <0.001) in the group that had been treated prophylactically than in the controls. The ratio of the forced expiratory volume in 1 second to forced vital capacity was significantly better in children who had received immune globulin (median, 0.88; interquartile range, 0.81 to 0.91) than in the controls (median, 0.76; interquartile range, 0.67 to 0.86; P = 0.02). Children were also less atopic (2 of 13) in the respiratory syncytial virus immune globulin group than in the control group (13 of 26, P <0.04) and were less likely to have missed school (P = 0.006) or have had an asthma attack (P = 0.03).

CONCLUSION

The results suggest that prophylaxis of respiratory syncytial virus infections in infancy may have long-term effects on respiratory and immunologic parameters relevant to the development of asthma. Larger-scale studies are needed.

Clinical perspectives on the association between respiratory syncytial virus and reactive airway disease

Asthma is a leading cause of morbidity and mortality among children worldwide, as is respiratory syncytial virus (RSV). This report reviews controlled retrospective and prospective studies conducted to investigate whether there is an association between RSV bronchiolitis in infancy and subsequent development of reactive airway disease or allergic sensitization. Findings indicate that such a link to bronchial obstructive symptoms does exist and is strongest for children who experienced severe RSV illness that requires hospitalization. However, it is not yet clear what roles genetic predisposition and environmental or other risk factors may play in the interaction between RSV bronchiolitis and reactive airway disease or allergic sensitization. Randomized, prospective studies utilizing an intervention against RSV, such as a passive immunoprophylactic agent, may determine whether preventing RSV bronchiolitis reduces the incidence of asthma.

Potential therapeutic implications of new insights into respiratory syncytial virus disease

Viral bronchiolitis is the most common cause of hospitalization in infants under 6 months of age, and 70% of all cases of bronchiolitis are caused by respiratory syncytial virus (RSV). Early RSV infection is associated with respiratory problems such as asthma and wheezing later in life. RSV infection is usually spread by contaminated secretions and infects the upper then lower respiratory tracts. Infected cells release proinflammatory cytokines and chemokines, including IL-1, tumor necrosis factor-alpha, IL-6, and IL-8. These activate other cells and recruit inflammatory cells, including macrophages, neutrophils, eosinophils, and T lymphocytes, into the airway wall and surrounding tissues. The pattern of cytokine production by T lymphocytes can be biased toward 'T-helper-1' or 'T-helper-2' cytokines, depending on the local immunologic environment, infection history, and host genetics. T-helper-1 responses are generally efficient in antiviral defense, but young infants have an inherent bias toward T-helper-2 responses. The ideal intervention for RSV infection would be preventive, but the options are currently limited. Vaccines based on protein subunits, live attenuated strains of RSV, DNA vaccines, and synthetic peptides are being developed; passive antibody therapy is at present impractical in otherwise healthy children. Effective vaccines for use in neonates continue to be elusive but simply delaying infection beyond the first 6 months of life might reduce the delayed morbidity associated with infantile disease.

Detection of IgA and IgG but not IgE antibody to respiratory syncytial virus in nasal washes and sera from infants with wheezing

BACKGROUND AND OBJECTIVE

The capacity of respiratory syncytial virus (RSV) to stimulate an IgE antibody response and enhance the development of atopy and asthma remains controversial. Nasal washes and sera from 40 infants (20 with wheezing, 9 with rhinitis, and 11 without respiratory tract symptoms) were obtained to measure IgE, IgA, and IgG antibody to the immunodominant, F and G, virion proteins from RSV.

STUDY DESIGN

Children (aged 6 weeks to 2 years) were enrolled in the emergency department during the mid-winter months and seen at follow-up when they were asymptomatic. All nasal washes were tested for RSV antigen. Determinations of antibody isotypes (IgE, IgA, and IgG) to RSV antigens were done in nasal washes and sera by using an enzyme-linked immunosorbent assay. In a subset of nasal washes, IgE to RSV was also evaluated by using a monoclonal anti-F(c)E antibody-based assay.

RESULTS

Fifteen patients with wheezing, two with rhinitis, and one control subject tested positive for RSV antigen at enrollment. Thirteen patients with wheezing were <6 months old, and most (77%) were experiencing their first attack. Among the children with positive test results for RSV antigen, an increase in both nasal wash and serum IgA antibody to RSV-F(a) and G(a) was observed at the follow-up visit. However, there was no evidence for an IgE antibody response to either antigen.

CONCLUSION

Both IgA and IgG antibodies to the immunodominant RSV-F(a) and G(a) antigens were readily detected in the nasal washes and sera from patients in this study. We were unable to demonstrate specific IgE antibody to these antigens and conclude that the production of IgE as a manifestation of a T(H)2 lymphocyte response to RSV is unlikely.

Wheezing following lower respiratory tract infections with respiratory syncytial virus and influenza A in infancy

We examined the incidence of subsequent wheezing in 292 children, hospitalized for influenza A or respiratory syncytial virus (RSV) lower respiratory tract infection, during two consecutive seasons (November-December, 1993 and March-April, 1995). Questionnaires concerning episodes of wheezing and known risk factors for wheezy bronchitis were mailed to parents 1 year after hospitalization. Sixty per cent of parents reported two or more episodes of wheezing following either influenza A or RSV. Hospitalization as a result of wheezing was necessary in 15% of the patients. The severity of the primary infection, as indicated by the need for treatment in the intensive care unit (ICU), was correlated with later wheezing. No additional significant risk factors predicting later wheezing could be identified.

Influenza and respiratory syncytial virus. Update on infection, management, and prevention

This article is an overview of the epidemiology and spectrum of clinical disease attributed to influenza and respiratory syncytial virus in children. It separately discusses the pathogenesis of the two diseases and the host responses to the viruses to emphasize each infection's significance and need for a vaccine. Updates on current preventive measures and a preview of potential future vaccine developments are presented.

The environmental predictors of allergic disease

The prevalence of allergic diseases has been on the rise for the last 200 years, when hay fever, an easy and obvious-to-recognize illness, was virtually unknown in Europe and North America. Genetic factors are unlikely to explain these rapid increases. Among the potential environmental factors, exposure to ambient air pollution has been intensely debated. Besides passive smoking, which has convincingly been shown to increase the risk for asthma and bronchial hyperresponsiveness among exposed children, the evidence to suggest that outdoor pollution to sulfur dioxide, particulate matter, diesel exhaust, and ozone is causally related with the inception of allergic diseases is poor. Rather, factors associated with the lifestyle of populations or families, such as socioeconomic status, allergen exposure, sibship size, early childhood infections, dietary habits, and growing up in anthroposophic families or a farming environment, may prove to be of greater relevance. The future challenge is to tackle the complex interplay between environmental factors and genetic determinants that will eventually contribute to a better understanding and to better prevention strategies for such multifactorial conditions as asthma and allergies.

Reduced long-term respiratory morbidity after treatment of respiratory syncytial virus bronchiolitis with ribavirin in previously healthy infants: a preliminary report

Previously healthy infants less than 6 months of age with severe respiratory syncytial virus bronchiolitis who required hospitalization were identified from hospital records. Infants had been treated either conservatively (control group, n = 19) or with ribavirin added to conservative management (study group, n = 22). All infants underwent a 1-year follow-up after the initial illness. There was a significant reduction in the prevalence of reactive airway disease in the group treated with ribavirin (P < 0.05) compared with the control group, both in terms of the proportion of patients developing airway reactivity (59% vs. 89%) and the number of episodes of reactive airway disease (31 vs. 70). Our data suggest that ribavirin reduces the prevalence of airway reactivity.

Subgroup specific protection of mice from respiratory syncytial virus infection with peptides encompassing the amino acid region 174-187 from the G glycoprotein: the role of cysteinyl residues in protection

We identified subgroup specific protective epitopes represented by the amino acid regions 174-187 and 171-187 of the G glycoproteins from respiratory syncytial virus (RSV), subgroups A and B. Mice immunized with coupled synthetic peptides corresponding to either the region 174-187 containing a Cys186-->Ser substitution or to the native region 171-187 were completely resistant to RSV infection but only to the respective virus. The protective activities of the peptides 174-187 were dependent on the Cys186-->Ser substitution. In addition, a recombinant protein representing the region 125-203 of the A subgroup G glycoprotein expressed in Escherichia coli was capable without further treatment to completely protect animals against RSV subgroup A infection. We show that the combinations of cysteinyl residues (positions 173, 176, 182, and 186) retained within either synthetic peptides or the recombinant protein G125-203 greatly influenced their protective activities. This indicates that the region 171-187 is essential for the protection conferred by the G125-203 protein. Furthermore, our results strongly suggest that the peptides' and recombinant protein's potencies are a function of a loop-like structure which is stabilized by intramolecular disulfide linkages between Cys176-Cys182 and Cys173-Cys186. This is further supported by the observation that chemical blocking of the sulfidryl groups in synthetic peptides completely eliminated their protective activity.