Respiratory syncytial virus infections in children and adults

Virus Infections in Older People

Older people are more prone to viral infections, and often have worse outcomes. This was well demonstrated during the COVID-19 pandemic, where a disproportionate number of deaths occurred in the oldest and frailest people. The assessment of the older person with a viral infection is complicated by the high prevalence of multiple comorbidities and sensory or cognitive impairment. They often present with common geriatric syndromes such as falls or delirium, rather than the more typical features of a viral illness in younger people. Comprehensive geriatric assessment by a specialist multidisciplinary team is the gold standard of management, as viral illness is unlikely to present in isolation of other healthcare needs. We discuss the presentation, diagnosis, prevention, and management of common viral infections-respiratory syncytial virus, coronavirus, norovirus, influenza, hepatitis, herpes, and dengue viruses-with special consideration of infections in the older patient.

Vitamin D deficiency in children with acute bronchiolitis: a prospective cross-sectional case- control study

Background

25(OH) vitamin D levels are inversely associated with respiratory infections and childhood wheezing.

Objective

To evaluate serum 25(OH) vitamin D levels in infants and toddlers with acute bronchiolitis, compared to subjects with non-respiratory febrile illness.

Methods

A prospective cross-sectional case-control study which compared serum 25(OH) vitamin D levels between infants and toddlers diagnosed with acute bronchiolitis to subjects with non-respiratory febrile illness. Multivariate logistic regression, adjusted for age, sex, ethnicity and nutrition was performed. Correlation between serum vitamin D levels and bronchiolitis severity was assessed via Modified Tal Score and length of hospital stay (LOS).

Results

One hundred twenty-seven patients aged < 24 months were recruited; 80 diagnosed with acute bronchiolitis and 47 patients with non- respiratory febrile illnesses. Both groups had similar demographics aside from age (median [IQR] 5 [3–9] vs. 9 [5–16] months in the bronchiolitis group compared to control group (p = 0.002)). Serum 25(OH) vitamin D levels were significantly lower in the bronchiolitis group; median [IQR] 28[18–52] vs. 50[25–79] nmol/L, respectively, (p = 0.005). Deficient vitamin D levels (< 50 nmol/L) was found more frequently in the bronchiolitis group than controls; 73% vs. 51% (p = 0.028). Multivariate logistic regression showed vitamin D deficiency was more probable in bronchiolitis patients; OR [95% CI] 3.139[1.369–7.195]. No correlation was found between serum vitamin D levels and bronchiolitis severity, which was assessed via Modified Tal Score and by length of hospital stay.

Conclusion

Children with acute bronchiolitis displayed significantly lower vitamin D levels than children with non-respiratory acute febrile illnesses.

Assessment of the Effects of Active Immunisation against Respiratory Syncytial Virus (RSV) using Decision-Analytic Models: A Systematic Review with a Focus on Vaccination Strategies, Modelling Methods and Input Data

BACKGROUND

Several vaccine and antibody candidates are currently in development for the prevention of lower respiratory tract infections caused by the respiratory syncytial virus (RSV).

METHODS

We searched MEDLINE, Embase, and SCOPUS and included model-based evaluations of RSV vaccinations. Two reviewers performed the selection, data extraction, and quality evaluation with EVIDEM. Cost-effectiveness (CE) estimates were converted to $US purchasing power parity (PPP), year 2018 values. Potential economic and epidemiological outcomes were summarised for maternal, infant, children, and elderly vaccinations. The PROSPERO identifier is CRD42019122570.

RESULTS

In total, 22 model-based studies were reviewed. On average, a potential 27% reduction in RSV hospitalisations in infants was projected for maternal vaccination and 50% for direct infant immunisation. The CE of maternal vaccination was $US1766-5857 PPP 2018/disability-adjusted life-years (DALYs) for Global Alliance for Vaccines and Immunisation (Gavi)-eligible countries. For England, the maximum cost-effective price of maternal vaccination was estimated at $US81.5 PPP 2018. Infant vaccination was associated with higher CE ratios in low- and high-income settings. Vaccination of neonates born before the RSV season was the most cost effective in high-income settings. Higher values for vaccine effectiveness, duration of protection, and vaccine uptake increased the benefits. Due to indirect effects, the vaccination of school-age children and a cocooning strategy were effective alternatives to protect infants, and the vaccination of children aged < 5 years had a beneficial impact on the elderly.

CONCLUSION

RSV vaccines with anticipated characteristics may reduce a sizeable proportion of the RSV burden. The results are subject to uncertainty because of the limited epidemiological and clinical data. Data on RSV incidence and hospitalisation risk for granular age strata should be prioritised to facilitate the evaluation of RSV interventions and decision making.

Cost-analysis of Withdrawing Immunoprophylaxis for Respiratory Syncytial Virus in Infants Born at 33-35 Weeks Gestational Age in Quebec: A Multicenter Retrospective Study

BACKGROUND

In 2015, the Quebec Ministry of Health limited palivizumab prophylaxis for respiratory syncytial virus (RSV) in premature infants to those born at <33 weeks gestational age (wGA), unless other indications were present. We compared RSV-related costs for 2 seasons before the change (2013-2014, 2014-2015) and 2 seasons after (2015-2016, 2016-2017) in premature infants 33-35 wGA.

METHODS

Using payer and societal perspectives, costs associated with hospitalizations for RSV and lower respiratory tract infection (LRTI) in infants born at 33-35 wGA were estimated. Inputs were from a 2013-2017 retrospective cohort study in 25 Quebec hospitals of RSV/LRTI hospitalizations among infants <6 months old at the start of, or born during, the RSV season. Resource utilization data (hospital stay, procedures, visits, transportation, out-of-pocket expenses and work productivity) were collected from charts and parent interviews allowing estimation of direct and indirect costs. Costs, including palivizumab administration, were derived from provincial sources and adjusted to 2018 Canadian dollars. Costs were modeled for preterm infants hospitalized for RSV/LRTI pre- and postrevision of guidelines and with matched term infants hospitalized for RSV/LRTI during 2015-2017 (comparator).

RESULTS

Average total direct and indirect costs for 33-35 wGA infants were higher postrevision of guidelines ($29,208/patient, 2015-2017; n = 130) compared with prerevision ($16,976/patient, 2013-2015; n = 105). Total costs were higher in preterm infants compared with term infants (n = 234) postrevision of guidelines ($29,208/patient vs. $10,291/patient).

CONCLUSIONS

Immunoprophylaxis for RSV in infants born at 33-35 wGA held a cost advantage for hospitalizations due to RSV/LRTI.

Cost-effectiveness of Palivizumab for Respiratory Syncytial Virus: A Systematic Review

CONTEXT

Palivizumab prophylaxis is used as passive immunization for respiratory syncytial virus (RSV). However, because of its high cost, the value of this intervention is unclear.

OBJECTIVE

To systematically review the cost-effectiveness of palivizumab prophylaxis compared with no prophylaxis in infants <24 months of age.

DATA SOURCES

Medline, Embase, and Cochrane Library up to August 2018.

STUDY SELECTION

Two reviewers independently screened results to include economic evaluations conducted between 2000 and 2018 from Organization for Economic Cooperation and Development countries.

DATA EXTRACTION

Two reviewers independently extracted outcomes. Quality appraisal was completed by using the Joanna Briggs Institute checklist. Costs were adjusted to 2017 US dollars.

RESULTS

We identified 28 economic evaluations (20 cost-utility analyses and 8 cost-effectiveness analyses); most were from the United States (n = 6) and Canada (n = 5). Study quality was high; 23 studies met >80% of the Joanna Briggs Institute criteria. Palivizumab prophylaxis ranged from a dominant strategy to having an incremental cost-effectiveness ratio of $2 526 203 per quality-adjusted life-year (QALY) depending on study perspective and targeted population. From the payer perspective, the incremental cost-effectiveness ratio for preterm infants (29-35 weeks' gestational age) was between $5188 and $791 265 per QALY, with 90% of estimates <$50 000 per QALY. Influential parameters were RSV hospitalization reduction rates, palivizumab cost, and discount rate.

LIMITATIONS

Model design heterogeneity, model parameters, and study settings were barriers to definitive conclusions on palivizumab's economic value.

CONCLUSIONS

Palivizumab as RSV prophylaxis was considered cost-effective in prematurely born infants, infants with lung complications, and infants from remote communities.

Modified Tal Score: Validated score for prediction of bronchiolitis severity

OBJECTIVE

To further validate the use of the Modified Tal Score (MTS), a clinical tool for assessing bronchiolitis severity, by physicians with varying experience and training levels, and to determine the ability of the MTS to predict bronchiolitis severity.

METHODS

This prospective cohort study included infants of <12 months of age who were diagnosed with bronchiolitis and assessed via MTS. We calculated the intra-class correlation coefficient (ICC) among four groups of raters: group 1, board-certified pediatric pulmonologists; group 2, board-certified pediatricians; group 3, senior pediatric residents; and group 4, junior pediatric residents. Clinical outcomes were determined as length of oxygen support and length of stay (LOS). We assessed MTS's prediction of these outcomes. Relative risk (RR) for clinical severity was calculated via a Generalized Linear Model.

RESULTS

Twenty-four physicians recorded a total of 600 scores for 50 infants (average age 5 ± 3 months; 56% male). The ICC values with group 1 as a reference were 0.92, 0.87, and 0.83, for groups 2, 3, and 4, respectively (P < 0.001). RR for oxygen support required was; 1.33 (CI 1.12-1.57), 1.26 (1.1-1.46), 1.26 (1.06-1.5), and 1.21 (0.93-1.58) for groups 1, 2, 3, and 4, respectively. RR for LOS was; 1.15 (CI 0.97-1.37), 1.19 (1.03-1.38), 1.18 (1.0-1.39), and 1.18 (0.93-1.51) for groups 1, 2, 3, and 4, respectively.

CONCLUSION

The MTS is a simple and valid scoring system for evaluating infants with acute bronchiolitis, among different physician groups. The first score upon admission is a fair predictor of oxygen requirement at 48 h, and LOS at 72 h.

Respiratory syncytial virus prophylaxis in cystic fibrosis: the Canadian registry of palivizumab data (2005-2016)

Respiratory syncytial virus (RSV) may cause severe illness in cystic fibrosis (CF) children, but recommendations vary on prophylaxis. CARESS is a prospective registry of children who received palivizumab in 32 Canadian sites from 2005 to 2016. Demographic data were collected at enrollment and respiratory illness-related events recorded monthly. We reviewed respiratory illness hospitalization (RIH) and RSV hospitalization (RSVH) in CF children aged < 24 months versus those prophylaxed for standard indications (SI; prematurity, chronic lung disease [CLD] and congenital heart disease [CHD]), and complex medical disorders (CM). Of 23,228 children analyzed, 19,452 (83.8%) were SI, 3349 (14.4%) were CM, and 427 (1.8%) were CF. CF children were more likely to be Caucasian, heavier at birth and enrollment, and less likely to have a sibling or live in crowded conditions. CF children were similar to the other groups in daycare attendance, history of atopy, and exposure to smoking. RIH incidences were 4.3% (premature), 13.8% CLD, 11.5% CHD, 11.7% CM, and 6.8% CF. RSVH incidence in CF children was similar to that in the SI and CM groups: 1.1, 1.5, and 2.0% groups respectively. Cox regression analyses showed that compared to CF children, the HRs for RSVH in SI (HR 2.0 95% CI 0.5-8.3, p = 0.3) and CM (HR 2.4, 95% CI 0.6-9.8, p = 0.2) did not differ. CF children are equally at risk for RSVH relative to those prophylaxed for other indications. Pending robust evidence from prospective trials, palivizumab could perhaps be considered in the interim, for young CF patients born early during the RSV season with evidence of serious lung disease.

Palivizumab prophylaxis for respiratory syncytial virus in infants with cystic fibrosis: is there a need?

Respiratory syncytial virus (RSV) infection in cystic fibrosis (CF) infants is associated with significant morbidities. This study's objective is to evaluate the effectiveness and adverse events related to palivizumab (PVZ) in CF infants. Data on respiratory-related illness (RIH) and RSV hospitalizations (RSVH) were collected retrospectively in CF infants aged < 2 years in Alberta, Canada, from 2000 to 2017. Logistic regression models were used to compare the odds of RSVH or RIH in PVZ infants from the Canadian registry of palivizumab (CARESS) versus untreated (UPVZ) infants from Alberta, after adjusting for potential confounders. Illness severity was compared between cohorts using χ² and t tests. A total of 267 CF infants were included: 183 (PVZ) and 84 (UPVZ). A total of 53.3% were tested for RSV. Fifty-five infants experienced a RIH and 10 had a RSVH. The PVZ cohort experienced similar odds of RSVH but decreased odds of RIH versus UPVZ, adjusting for gestational age, birth weight, birth during RSV peak months, and presence of siblings (Exp(B) = 0.23 [0.11-0.49], p < 0.0005). In RSVH-related subjects, PVZ subjects experienced shorter length of overall stay (LOS; t = 2.39 [df = 7], p = 0.048). In those with a RIH, the PVZ group had shorter overall intensive care unit (t = 3.52 [df = 15], p = 0.003) and hospital LOS (t = 2.11 [df = 52], p = 0.04). No serious adverse events were related to PVZ. The odds of RSVH were similar between groups, but PVZ subjects had decreased odds of RIH. The low number of RSV tests performed may explain the similarity in RSVH rates. Significant differences in LOS may indicate decreased RSVH and RIH illness severity in the PVZ versus UPVZ groups.

Functional Impairment of Mononuclear Phagocyte System by the Human Respiratory Syncytial Virus

The mononuclear phagocyte system (MPS) comprises of monocytes, macrophages (MΦ), and dendritic cells (DCs). MPS is part of the first line of immune defense against a wide range of pathogens, including viruses, such as the human respiratory syncytial virus (hRSV). The hRSV is an enveloped virus that belongs to the Pneumoviridae family, Orthopneumovirus genus. This virus is the main etiological agent causing severe acute lower respiratory tract infection, especially in infants, children and the elderly. Human RSV can cause bronchiolitis and pneumonia and it has also been implicated in the development of recurrent wheezing and asthma. Monocytes, MΦ, and DCs significantly contribute to acute inflammation during hRSV-induced bronchiolitis and asthma exacerbation. Furthermore, these cells seem to be an important component for the association between hRSV and reactive airway disease. After hRSV infection, the first cells encountered by the virus are respiratory epithelial cells, alveolar macrophages (AMs), DCs, and monocytes in the airways. Because AMs constitute the predominant cell population at the alveolar space in healthy subjects, these cells work as major innate sentinels for the recognition of pathogens. Although adaptive immunity is crucial for viral clearance, AMs are required for the early immune response against hRSV, promoting viral clearance and controlling immunopathology. Furthermore, exposure to hRSV may affect the phagocytic and microbicidal capacity of monocytes and MΦs against other infectious agents. Finally, different studies have addressed the roles of different DC subsets during infection by hRSV. In this review article, we discuss the role of the lung MPS during hRSV infection and their involvement in the development of bronchiolitis.

Serious Adverse Events in the Canadian Registry of Children Receiving Palivizumab (CARESS) for Respiratory Syncytial Virus Prevention

OBJECTIVES

To evaluate the safety and tolerability of palivizumab for RSV prophylaxis in high-risk children in everyday practice.

METHODS

High-risk children prophylaxed against RSV infection were recruited into a prospective, observational, Canadian RSV Evaluation Study of Palivizumab (CARESS) registry with active, serious adverse event (SAE) monitoring from 2008 to 2013. SAE reports were systematically collected and assessed for severity and relationship to palivizumab. Data were analyzed by Chi-square or Fisher Exact Tests to examine group differences in proportions.

RESULTS

13025 infants received 57392 injections. Hospitalizations for respiratory-related illness (RIH) were reported in 915 patients, and SAEs other than RIH were reported in 52 patients. Of these, 6 (0.05%) patients had a total of 14 hypersensitivity reactions that were deemed possibly or probably related to palivizumab (incidence: 2.8 per 10,000 patient-months). The SAEs of 42 patients were assessed as not related to palivizumab. SAEs in the remaining 4 patients were not classifiable as their records were incomplete. There were no significant demographic predictors of SAE occurrence.

CONCLUSIONS

Under active surveillance, a small proportion of infants in the CARESS registry experienced SAEs that had a potential relationship with palivizumab and these appeared to be unpredictable in terms of onset. Palivizumab appears to be a safe and well-tolerated antibody for RSV prophylaxis in high-risk children in routine practice.

The eukaryotic elongation factor 1A is critical for genome replication of the paramyxovirus respiratory syncytial virus

The eukaryotic translation factor eEF1A assists replication of many RNA viruses by various mechanisms. Here we show that down-regulation of eEF1A restricts the expression of viral genomic RNA and the release of infectious virus, demonstrating a biological requirement for eEF1A in the respiratory syncytial virus (RSV) life cycle. The key proteins in the replicase/transcriptase complex of RSV; the nucleocapsid (N) protein, phosphoprotein (P) and matrix (M) protein, all associate with eEF1A in RSV infected cells, although N is the strongest binding partner. Using individually expressed proteins, N, but not P or M bound to eEF1A. This study demonstrates a novel interaction between eEF1A and the RSV replication complex, through binding to N protein, to facilitate genomic RNA synthesis and virus production.

Systematic review and meta-analysis of respiratory syncytial virus infection epidemiology in Latin America

Respiratory syncytial virus (RSV) is a frequent cause of acute respiratory infection and the most common cause of bronchiolitis in infants. The aim of this systematic review and meta-analysis was to obtain a comprehensive epidemiological picture of the data available on disease burden, surveillance, and use of resources in Latin America. Pooled estimates are useful for cross-country comparisons. Data from published studies reporting patients with probable or confirmed RSV infection in medical databases and gray literature were included from 74 studies selected from the 291 initially identified. When considering all countries, the largest pooled percentage RSV in low respiratory tract infection patients was found in the group between 0 and 11 months old, 41.5% (95% CI 32.0–51.4). In all countries, percentages were increasingly lower as older children were included in the analyses. The pooled percentage of RSV in LRTIs in the elderly people was 12.6 (95% CI 4.2–24.6). The percentage of RSV infection in hospitalized newborns was 40.9% (95% CI 28.28–54.34). The pooled case fatality ratio for RSV infection was 1.74% (95% CI 1.2–2.4) in the first 2 years of life. The average length of stay excluding intensive care unit admissions among children with risk factors for severe disease was 12.8 (95% CI 8.9–16.7) days, whereas it averaged 7.3 (95% CI 6.1/8.5) days in otherwise healthy children.We could conclude that infants in their first year of age were the most vulnerable population. To our knowledge, this is the first systematic review on RSV disease burden and use of health resources in Latin America.

Development and validation of the Liverpool infant bronchiolitis severity score: a research protocol

AIM

To develop and validate a bronchiolitis severity scoring instrument for use by nurses and other healthcare professions.

BACKGROUND

Bronchiolitis is a viral lower respiratory tract infection of infancy. In industrialized countries, admission rates have increased over the last decade with up to 3% of all infants born being admitted to hospital. A small number of these hospitalized infants will require admission to critical care for either invasive or non-invasive ventilation. During the seasonal epidemic, the number of unplanned admissions to critical care with bronchiolitis substantially increases.

DESIGN

We will use a mixed methods study design.

METHODS

We will use scale development and psychometric methods to develop a scoring instrument and to test the instrument for content, construct and criterion validity and reliability in several different clinical locations. This study protocol has been reviewed and approved by the NHS National Research Ethics Service, January 2011.

DISCUSSION

There is an urgent need to develop a valid and reliable severity scoring instrument sensitive to clinical changes in the infant, to facilitate clinical decision-making and help standardize patient care. Furthermore, a valid and reliable scoring instrument could also be used as a proxy patient-reported outcome measure to evaluate the efficacy of clinical interventions in randomized controlled trials.

Non-invasive ventilation for severe bronchiolitis: analysis and evidence

OBJECTIVES

(1) To examine whether infants with severe bronchiolitis, fulfilling criteria for further respiratory support, could be managed outside a Pediatric Intensive Care Unit (PICU) with non-invasive ventilation (NIV) alone. (2) To study the characteristics, clinical course and outcome of NIV responders and non responders to assess safety and efficacy and inform guideline construction.

HYPOTHESIS

Infants with severe bronchiolitis can be safely managed with NIV outside a PICU.

STUDY DESIGN

Retrospective case review.

PATIENT SELECTION

Cohort of infants with objective evidence of severe bronchiolitis requiring respiratory support nursed in a Pediatric High Dependency Unit (PHDU) and/or Intensive Care Unit (ICU) between 2001 and 2007.

METHODOLOGY

Analysis of patient characteristics and respiratory parameters at admission and initiation of ventilation, changes after 2 and 4 hr of NIV or invasive ventilation, complications, short and long-term outcomes were analyzed.

RESULTS

One thousand and thirty-five infants with bronchiolitis were admitted with 67 ventilation episodes identified from 65 patients. Fifty-five episodes, including 34 with apnea, were treated exclusively with NIV. Six infants failed to respond and were invasively ventilated. Six patients were invasively ventilated at presentation. Non-responders had a significantly higher rate of bacterial infection. Significant improvements in respiratory parameters in responders occurred by 2 hr and sustained at 4 hr. Duration of hospital stay, ventilation requirement and oxygen requirement were significantly shorter in responders. Short and longer-term follow up data did not identify any adverse effects related to NIV.

CONCLUSIONS

NIV was effective in 80% of infants receiving respiratory support for severe bronchiolitis.

Eicosanoids and respiratory viral infection: coordinators of inflammation and potential therapeutic targets

Viruses are frequent causes of respiratory infection, and viral respiratory infections are significant causes of hospitalization, morbidity, and sometimes mortality in a variety of patient populations. Lung inflammation induced by infection with common respiratory pathogens such as influenza and respiratory syncytial virus is accompanied by increased lung production of prostaglandins and leukotrienes, lipid mediators with a wide range of effects on host immune function. Deficiency or pharmacologic inhibition of prostaglandin and leukotriene production often results in a dampened inflammatory response to acute infection with a respiratory virus. These mediators may, therefore, serve as appealing therapeutic targets for disease caused by respiratory viral infection.

CARESS: the Canadian registry of palivizumab

BACKGROUND

Palivizumab is indicated for respiratory syncytial virus (RSV) prophylaxis in high-risk children. However, relatively little is known about the current use, compliance, and outcomes associated with this medication.

METHODS

A prospective, observational, registry based on 27 sites, with monthly follow-up of infants at high risk for RSV who received at least 1 dose of palivizumab during the 2005-2009 RSV seasons.

RESULTS

A total of 5286 children were enrolled (56.6% male; 71.7% white; average gestational age, 32.1 ± 5.5 weeks). Of them, 3741 patients (70.8%) were prophylaxed for prematurity only, 449 (8.5%) for bronchopulmonary dysplasia/chronic lung disease, 508 (9.6%) for congenital heart disease, and 588 (11.1%) for other reasons. Overall, 19,485 doses were given. On average, infants received 86.0% ± 28.4% of their expected number of injections; 71.2% of infants received their injections in the recommended time periods. Of the 5286 participants enrolled, 308 patients were hospitalized for respiratory tract illness (hospitalization rate, 5.8%). The RSV-hospitalization rate was calculated as 1.38%. Having siblings increased likelihood of hospitalization (66.9% vs. 55.7%, P < 0.005), and was significantly correlated with time to hospitalization in this cohort (P = 0.050).

CONCLUSIONS

The overall RSV-hospitalization rate in our study was within the range found in previous reports (1.3%-5.3%), although it did not mimic the declining rates of the US Palivizumab Outcomes Registry. This could be due to increased testing for RSV when hospitalized and increasing rates of prophylaxis of infants with underlying medical disorders.

Genetic variability of group A human respiratory syncytial virus strains circulating in Germany from 1998 to 2007

The variability between respiratory syncytial virus (RSV) strains is one of the features of RSV infections that might contribute to the ability of the virus to infect people repeatedly and cause yearly outbreaks. To study the molecular epidemiology of RSV, more than 1,400 RSV isolates from human nasopharyngeal aspirates or nasal or throat swabs from patients with respiratory illness were identified and differentiated by TaqMan reverse transcription-PCR into groups A and B. RSV group A was dominant in seven out of nine epidemic seasons. Phylogenetic analysis revealed that RSV group A genotypes GA2 and GA5 circulated from 1998 to 2007. Genotype GA7 was present in only two seasons (1999 to 2000 and 2002 to 2003). Comparison of the synonymous mutation/nonsynonymous mutation ratios showed greater evidence for selection pressure for genotype GA2 (1.18) than for GA5 (4.34). Partial protein sequences were predicted to encode G proteins of 298 amino acids in length and in a few cases of G proteins of 297 amino acids in length. Amino acid analysis also revealed genotype-specific amino acid substitutions: two substitutions for genotype GA2, seven for GA5, and three for GA7. Two to four putative, genotype-specific N-linked glycosylation sites were determined. Predicted O-glycosylation sites included 22 to 34 residues. This study provides for the first time data on the circulation pattern of RSV group A genotypes and their molecular characterization in Germany during nine consecutive epidemic seasons.

Viral pathogens in acute exacerbations of chronic obstructive pulmonary disease

The objective of this study is to determine the prevalence of respiratory syncytial virus (RSV) and other viral respiratory pathogens in emergency department (ED) patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD). COPD patients presenting to the ED with <10 days of AECOPD symptoms were eligible. We used PCR to test nasal swabs for common viral respiratory pathogens. We completed viral studies on 76 patients from two EDs. Patients had a mean age of 72 years, and were 68% male, 99% white, and 29% current smokers. Influenza vaccination was reported by 87%. Viruses were detected in 19 of 76 patients (25%). These included RSV A (2) and B (4); parainfluenza 1 (1), 2 (0), and 3 (2); influenza A (3) and B (0); rhinovirus (4); and human metapneumovirus (3). A putative viral etiology was identified in 25% of AECOPD presenting for emergency care, of which approximately one-third were RSV-related.

Descriptive epidemiological features of bronchiolitis in a population-based cohort

OBJECTIVE

The goal was to investigate the epidemiological features of incident bronchiolitis by using a population-based infant cohort.

METHODS

Outpatient and inpatient health records were used to identify incident bronchiolitis cases among 93,058 singleton infants born in the Georgia Air Basin between 1999 and 2002. Additional health-related databases were linked to provide data on sociodemographic variables, maternal characteristics, and birth outcome measures.

RESULTS

From 1999 to 2002, bronchiolitis accounted for 12,474 incident health care encounters (inpatient or outpatient contacts) during the first year of life (134.2 cases per 1000 person-years). A total of 1588 hospitalized bronchiolitis cases were identified (17.1 cases per 1000 person-years). Adjusted Cox proportional-hazard analyses for both case definitions indicated an increased risk of incident bronchiolitis in the first year of life (follow-up period: 2-12 months) for boys, infants of First Nations status, infants with older siblings, and infants living in neighborhoods with smaller proportions of maternal postsecondary education. The risk also was elevated for infants born to young mothers (<20 years of age) or mothers who did not initiate breastfeeding in the hospital. Infants with low (1500-2400 g) or very low (<1500 g) birth weight and those with congenital anomalies also had increased risk. Maternal smoking during pregnancy increased the risk of hospitalized bronchiolitis.

CONCLUSIONS

This population-based study of the epidemiological features of bronchiolitis provides evidence for intervening with high-risk infants and their families. Clinical and public health interventions are recommended for the modifiable risk factors of maternal breastfeeding and smoking and for modification of vulnerable environments where possible (eg, limiting exposure to other young children), during high-risk periods such as the first few months of life or the winter season.

The cost-effectiveness of palivizumab for respiratory syncytial virus prophylaxis in premature infants with a gestational age of 32-35 weeks: a Canadian-based analysis

BACKGROUND

Prophylactic therapy with palivizumab, a humanized monoclonal antibody, has been shown to reduce the number of respiratory syncytial virus (RSV)-related hospitalizations in preterm infants, including those in the 32-35 weeks' gestational age (GA) subgroup. The cost-effectiveness of this therapy in Canada is unknown.

OBJECTIVES

To evaluate the cost-effectiveness of palivizumab as respiratory syncytial virus prophylaxis in premature infants born at 32-35 weeks' GA.

DESIGN

A decision analytic model was designed to compare both direct and indirect medical costs and benefits of prophylaxis in this subgroup of premature infants. Sensitivity analyses were performed to ascertain the robustness of the model for five point estimates: mortality rate, discounting rates, health-utility values, degree of vial-sharing and administration costs. A probabilistic sensitivity analysis (PSA) was also conducted.

SETTING

Canadian publicly funded health-care system (Ministry of Health payer perspective) for base-case analysis. Societal perspective, accounting for future lost productivity, was adopted for a secondary analysis.

PARTICIPANTS

Canadian infants born at 32-35 weeks' GA without chronic lung disease.

INTERVENTIONS

Palivizumab prophylaxis versus no prophylaxis.

MAIN OUTCOME MEASURES

Expected costs and incremental cost-effectiveness ratio expressed as cost per life-year gained (LYG) and quality-adjusted life-year (QALY) using 2007 Canadian dollars.

RESULTS

The expected costs were higher for palivizumab prophylaxis as compared with no prophylaxis. The incremental cost-effectiveness ratio (ICER) for the base-case scenario was $20 924 per QALY after discounting, which is considered cost-effective in Canada. When the uncertainty of the input parameter assumptions was tested through sensitivity analyses assessing several data sources for five key parameters, no substantial differences were found from the base-case results. The PSA indicated a 0.99 probability that the ICER for palivizumab was less than $50 000/QALY. Sub-analyses that varied the number of risk factors found that for infants with two or more risk factors, or at least moderate risk, palivizumab had incremental costs per QALY that indicated moderate-to-strong evidence for adoption (range: $808-81 331, per QALY).

CONCLUSIONS

Palivizumab was cost-effective and the authors' model supports prophylaxis for infants born at 32-35 weeks' GA, particularly those with more than two risk factors or at least a moderate level of risk according to a risk scoring tool.

Role of metapneumovirus in viral respiratory infections in young children

The contribution of human metapneumovirus (hMPV) relative to that of other respiratory viruses as a cause of respiratory infections in children less than 1 year old has been evaluated. From October 2003 to April 2004, nasopharyngeal samples from 211 children less than 1 year old were analyzed to detect respiratory viruses. Respiratory syncytial virus (RSV) was the predominant virus isolated (96 children [45.5%]), followed by influenza A virus, parainfluenza virus, adenovirus, cytomegalovirus, and herpes simplex virus type 1, which were only occasionally detected. From January 2004 to April 2004, a nested retrotranscription-PCR, using in-house primers directed to the matrix protein gene of hMPV, was carried out on samples in which no other viruses were detected. hMPV was detected in 18 (16.2%) children, indicating that this virus was the second-most-frequent cause of viral respiratory infections in children less than 1 year old. The rate of hospitalization for RSV- and hMPV-infected children was higher than 75%. While RSV had a peak from December to February, hMPV was increasingly detected from January to April. The mean age of hMPV-infected children (6.44 +/- 3.64 [mean +/- standard deviation] months) was significantly higher than that of RSV-infected children (3.99 +/- 2.96 [mean +/- standard deviation] months). On the other hand, 64.3% of the RSV-infected children and 12.5% of the hMPV-infected children showed high levels of C-reactive protein. Although several authors have reported that clinical symptoms of hMPV-positive patients mirrored those of RSV-positive patients, differences between the two viruses can be found.

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.

Antisense approaches for inhibiting respiratory syncytial virus

Respiratory syncytial virus (RSV) continues as an emerging infectious disease not only among infants and children, but also for the immune-suppressed, hospitalised and the elderly. To date, ribavirin (Virazole, ICN Pharmaceuticals, Inc.) remains the only therapeutic agent approved for the treatment of RSV. However, its clinical benefits are small and occur only in a fraction of RSV-infected patients. The prophylactic administration of palivizumab (Synagis, MedImmune, Inc.) is problematic and costly and, therefore, only recommended for use in high-risk infants. Clearly, the need for an effective and safe drug remains high. This review discusses several different antisense approaches and compares them with traditional strategies, such as RSV-targeting antibodies and antivirals, as well as developments in vaccine research.

Naturally occurring parainfluenza virus 3 infection in adults induces mild exacerbation of asthma associated with increased sputum concentrations of cysteinyl leukotrienes

BACKGROUND

Viral respiratory tract infections represent the most frequent cause of asthma exacerbation in both children and adults, but the precise mechanism of such exacerbation remains unknown.

OBJECTIVES

To determine the critical mediator of naturally occurring parainfluenza virus (PIV) 3-induced mild asthma exacerbations in adults.

METHODS

The study subjects were 19 adult asthmatics with mild asthma exacerbation (peak expiratory flow = 60-80% of predicted before bronchodilator use and >80% of predicted after initial bronchodilator treatment). Differential cell counts and concentrations of inflammatory markers including eosinophil cationic protein (ECP), cysteinyl leukotrienes (cysLTs), interleukin (IL)-5, IL-10 and IL-12 were measured in the induced sputum obtained from adults with PIV3- (n = 9) and non-cold-induced (n = 10) exacerbation of asthma during both acute and convalescent phases.

RESULTS

PIV3 infection was confirmed by the presence of viral RNA in nasopharyngeal aspirates. Mild exacerbation of asthma was not associated with significant changes in sputum differential cell counts. Concentrations of sputum ECP and cytokines were comparable between PIV3 and non-cold-induced patients. In contrast, PIV3 infection was associated with a significant increase in sputum cysLTs during the acute phase of mild asthma exacerbation.

CONCLUSIONS

Our results identified cysLTs as a critical mediator of PIV3-induced acute asthma exacerbation.

Effects of primary and secondary low-grade respiratory syncytial virus infections in a murine model of asthma

BACKGROUND

Respiratory syncytial virus (RSV) infection is known to develop and exacerbate asthma in young children. In adult, RSV causes recurrent but asymptomatic infections. However, the impact of asymptomatic RSV infection on adult asthma is yet to be determined. The present study is designed to determine the effects of primary and secondary low-grade RSV infections on allergic airway inflammation in a murine model of allergic asthma.

METHODS

A low-grade RSV (2 x 10(3) plaque-forming units/mouse) was inoculated, and this caused neither pulmonary inflammation nor symptoms but induced significant IFN-gamma production in thoracic lymph nodes. To investigate interaction between low-grade virus and Dermatophagoides farinae (Df), airway hyper-responsiveness, lung inflammation and cytokine production from thoracic lymph nodes were compared after primary and secondary low-grade RSV infections in four groups of mice; control, Df allergen-sensitized, RSV-infected and Df-sensitized RSV-infected mice. A direct comparison between low- and high-grade RSV infections was also performed in primary infection. To investigate the role of IL-5 during secondary RSV infection, anti-IL-5 monoclonal antibody (anti-IL-5 mAb) was injected in mice and similar parameters were compared in four groups of mice.

RESULTS

Primary high-grade RSV infection increased allergen-induced airway inflammation, while primary low-grade RSV infection attenuated allergen-induced airway inflammation concomitant with significant IFN-gamma production in lung-draining lymph nodes. In marked contrast, secondary low-grade RSV infection increased both IFN-gamma and IL-5 production, resulting in exacerbation of allergen-induced airway inflammation. Anti-IL-5 mAb treatment in secondary low-grade RSV infection and Df allergen-sensitized mice attenuated virus and allergen-induced airway inflammation.

CONCLUSIONS

Low-grade RSV infection per se does not cause pulmonary inflammation, whereas it induces a significant immunological response in the allergen-sensitized host. These results indicate that subclinical and recurrent RSV infection may play an important role in exacerbation and maintenance of asthma in adults, wherein IL-5 is critically involved.

Viral etiology of acute respiratory tract infections in children presenting to hospital: role of polymerase chain reaction and demonstration of multiple infections

BACKGROUND

Viral lower respiratory tract infections are a leading cause of hospitalization for young children.

METHODS

We used polymerase chain reaction (PCR) and conventional methods of cell culture and antigen detection to establish the viral etiology of acute respiratory tract infections in 75 hospitalized children.

RESULTS

One or more viral pathogens were detected in 65 (87%) children, with respiratory syncytial virus being the most commonly identified virus (36 children). Other viruses identified included influenza virus types A and B, parainfluenzavirus type 3, adenovirus, enterovirus, rhinovirus, coronavirus and human metapneumovirus. PCR increased the diagnostic yield significantly compared with antigen detection and culture, with 39 (21%) diagnoses identified by this method. Multiple infections were identified in 20 (27%) children.

CONCLUSIONS

PCR-based methodologies offer increased sensitivity for the detection of most respiratory viruses in young children. The inclusion of PCR into diagnostic testing strategies is needed to broaden our understanding of the natural ecology of respiratory viruses and the significance of multiple infections.

Chapter 22. Non-HIV antiviral agents

This chapter focuses on non-HIV antiviral agents. The development of antiviral agents to treat non-HIV infections is largely focused on therapies for the treatment of chronic hepatitis infections B and C. Nucleoside analog continue to be the mainstay of Hepatitis B Virus (HBV) therapeutics. The first small molecule inhibitor of Hepatitis C Virus (HCV), the NS3 protease inhibitor BILN-2061, entered phase 2 clinical trials, producing a striking reduction in viral load in treated individuals. The development of the HCV replicon system and its application to screening for antiviral agents provided tangible benefit with the disclosure of mechanistically and structurally diverse HCV inhibitors. Adefovir dipivoxil has been approved in the United States and the European Union for the treatment of HBV, providing a second small molecule antiviral to add to lamivudine (3TC) and the injectable protein IFNα as the only approved agents for treating HBV infection. The chapter also provides details of the inhibitors of hepatitis B and C virus, the inhibitors of simplex virus and human cytomegalovirus, the inhibitors of respiratory viruses and the inhibitors of West Nile virus and Papilloma virus.

Role of monocytes and eosinophils in human respiratory syncytial virus infection in vitro

RSV infection in airway epithelial cells (EC) results in production of the chemokines RANTES and MIP1alpha and the leukocyte differentiation factor GM-CSF. The chemokines attract monocytes and eosinophils to the site of infection, where GM-CSF may influence their function and differentiation. In turn, these inflammatory cells may limit the progression of RSV infection, as well as initiate immune responses. In the present study, the effect of monocytes and eosinophils on viral replication and infection-dependent release of EC-derived cytokines was investigated. The modulation of immune cell costimulatory molecules, CD80, CD86, CD40, and HLA-DR, and the release of the CD4(+) T cell chemoattractant IL-16 were also investigated. Employing immunofluorescence techniques, monocytes and eosinophils in cocultures with infected EC were found to inhibit the spread of RSV to uninfected cells. Monocytes also had a significant effect on replication of RSV. Monocytes phagocytized the virus, while eosinophils inhibited reinfection mainly by extracellular means. The release of G-CSF and GM-CSF in the infected cultures was not significantly affected by either monocytes or eosinophils, while RANTES release was significantly decreased. The expression of CD40, CD80, CD86, and HLA-DR on monocytes, but not on eosinophils, increased in an RSV-dose-dependent manner. IL-16 release was not induced in RSV-infected EC, but was significantly increased in coculture with monocytes. These results suggest that both monocytes and eosinophils attracted to the site of RSV infection play an important role in confining infection, while RSV-exposed monocytes may be involved in promoting/polarizing immune responses to RSV.

Community-acquired pneumonia

Community-acquired pneumonia (CAP) remains an important cause of morbidity and mortality. Streptococcus pneumoniae is the most common pathogen and respiratory syncitial virus the most important viral pathogen in children. The role of urinary antigen testing and PCR for the diagnosis forS. pneumoniae infection has been an important adjunct to clinical examination, showing good sensitivity and specificity. Host-related immune responses play an important role in defining the severity of illness. Other than the use of Activated Protein C and immunization, the clinical use of therapies designed to modulate these abnormal responses remains largely experimental. The 7-valent vaccine represents a major advance in the prevention of invasive pneumococcal disease. The importance of effective triage and the deleterious effects of deviation from protocols are underscored. Continuous positive pressure ventilation and noninvasive mechanical ventilation are available as options for respiratory support in cases of severe CAP and require further evaluation.

The quest for an efficacious antiviral for respiratory syncytial virus

Respiratory syncytial virus (RSV) continues as an emerging infectious disease not only among infants and children, but also for the immune-suppressed, hospitalized and the elderly. To date, ribavirin (Virazole) remains the only therapeutic agent approved for the treatment of RSV. The prophylactic administration of palivizumab is problematic and costly. The quest for an efficacious RSV antiviral has produced a greater understanding of the viral fusion process, a new hypothesis for the mechanism of action of ribavirin, and a promising antisense strategy combining the 2'-5' oligoadenylate antisense (2-5A-antisense) approach and RSV genomics.