Respiratory syncytial virus and parainfluenza virus

Ikkepsilon regulates viral-induced interferon regulatory factor-3 activation via a redox-sensitive pathway

Respiratory syncytial virus (RSV)-induced chemokine gene expression occurs through the activation of a subset of transcription factors, including Interferon Regulatory Factor (IRF)-3. In this study, we have investigated the signaling pathway leading to RSV-induced IRF-3 activation and whether it is mediated by intracellular reactive oxygen species (ROS) generation. Our results show that RSV infection induces expression and catalytic activity of IKKepsilon, a noncanonical IKK-like kinase. Expression of a kinase-inactive IKKepsilon blocks RSV-induced IRF-3 serine phosphorylation, nuclear translocation and DNA-binding, leading to inhibition of RANTES gene transcription, mRNA expression and protein synthesis. Treatment of alveolar epithelial cells with antioxidants or with NAD(P)H oxidase inhibitors abrogates RSV-induced chemokine secretion, IRF-3 phosphorylation and IKKepsilon induction, indicating that ROS generation plays a fundamental role in the signaling pathway leading to IRF-3 activation, therefore, identifying a novel molecular target for the development of strategies aimed to modify the inflammatory response associated with RSV infection of the lung.

Parainfluenza type 3 infection post stem cell transplant: high prevalence but low mortality

Parainfluenza type 3 (PIV 3) is a well-recognized cause of respiratory illness after stem cell transplantation (SCT), with an estimated incidence of 2-7% and a high mortality rate associated with lower respiratory tract infection (LRTI). A 12-month retrospective study was undertaken in which 23 positive cases of PIV 3 occurred in SCT recipients. The frequency of infection was 36.1% in matched unrelated donor SCT recipients, 23.8% in sibling allogeneic SCT recipients and 2.3% in autologous transplant recipients. Seventeen cases were outpatient or community acquired despite standard infection control measures. Eleven patients only developed upper respiratory tract symptoms. LRTI symptoms developed in 12 patients, of whom eight had a new infiltrate on chest X-ray. Overall mortality at 30 days from PIV 3 diagnosis was 4% (one patient). Four patients died within 100 days of PIV 3 diagnosis, but PIV 3 was not believed to be the primary cause of death in any of these patients. Early ribavirin was used in eight patients and only one patient who received ribavirin died. These results suggest a higher prevalence of PIV 3 but a lower mortality than documented previously, particularly in allogeneic transplant recipients. The authors propose that the high prevalence reflects the unit's policy of active surveillance for respiratory viruses and the difficulty in preventing transmission of PIV 3, especially in the outpatient setting during an outbreak period. Ribavirin treatment may improve outcome in patients with LRTI but is not required in all patients with PIV 3.

Clinical predictors of the severity of bronchiolitis

INTRODUCTION

Bronchiolitis is the most common serious, acute viral infection in infants. Besides the diagnostic and treatment challenges, the appropriate time and the need of hospitalization remain unanswered. We wonder whether clinical predictors such as age less than 6 months, respiratory frequency more than 45 breaths per minute and oxygen saturation less than 95% could be of any help in assessing the severity of the disease and the need for admission.

MATERIALS AND METHODS

A prospective study was held in the emergency department from November 2000 to January 2002, in which each patient with positive nasopharyngeal respiratory syncytial virus was included. Other inclusion criteria were full-term birth, clinical signs of respiratory diseases, age between 2 weeks up to 24 months and no underlying illnesses such as bronchopulmonary dysplasia and chronic heart or lung diseases. The sensitivity, specificity and relative risk (RR) were calculated by statistical analyses.

RESULTS

During the study period, 378 patients were included, 117 of whom were hospitalized (31%). Age less than 6 months (sensitivity 62%, specificity 72% and RR 2.68 ), respiratory frequency more than 45 breaths per minute (sensitivity 68%, specificity 82% and RR 4.57) and oxygen saturation less than 95% (sensitivity 68%, specificity 87% and RR 4.67) predicted the severity of the pulmonary disease and the need for admission. The cumulative analysis of the three parameters showed a specificity of 91% and a sensitivity of 86%, with a relative risk of 4.54 among those admitted into the hospital. Respiratory frequency more than 45 breaths per minute (sensitivity 76%, specificity 82% and RR 2.85) and oxygen saturation less than 95% (sensitivity 84%, specificity 86% and RR 2.65) were more significant than age less than 6 months (sensitivity 60%, specificity 70% and RR 3.70) in predicting the admission into the paediatric intensive care unit.

CONCLUSION

Oxygen saturation less than 95%, respiratory frequency more than 45 breaths per minute and age less than 6 months in respiratory-distressed infants are important parameters to predict the need for admission and emphasize the severity of bronchiolitis.

Impact of human metapneumovirus and human cytomegalovirus versus other respiratory viruses on the lower respiratory tract infections of lung transplant recipients

Viral respiratory tract infections in lung transplant recipients may be severe. During three consecutive winter‐spring seasons, 49 symptomatic lung transplant recipients with suspected respiratory viral infection, and 26 asymptomatic patients were investigated for presence of respiratory viruses either in 56 nasopharyngeal aspirate or 72 bronchoalveolar lavage samples taken at different times after transplantation. On the whole, 1 asymptomatic (3.4%) and 28 symptomatic (57.1%) patients were positive for human metapneumovirus (hMPV, 4 patients), influenza virus A (3 patients), and B (2 patients), respiratory syncytial virus (2 patients), human coronavirus (2 patients), human parainfluenza virus (2 patients), rhinovirus (5 patients), while 4 patients were coinfected by 2 respiratory viruses, and 5 were infected sequentially by 2 or more respiratory viruses. In bronchoalveolar lavage samples, hMPV predominated by far over the other viruses, being responsible for 60% of positive specimens, whereas other viruses were present in nasopharyngeal aspirates at a comparable rate. RT‐PCR (detecting 43 positive samples/128 examined) was largely superior to monoclonal antibodies (detecting 17 positive samples only). In addition, HCMV was detected in association with a respiratory virus in 4/18 HCMV‐positive patients, and was found at a high concentration (>10⁵ DNA copies/ml) in 3/16 (18.7%) patients with HCMV‐positive bronchoalveolar lavage samples and pneumonia. Coinfections and sequential infections by HCMV and respiratory viruses were significantly more frequent in patients with acute rejection and steroid treatment. In conclusion: (i) about 50% of respiratory tract infections of lung transplant recipients were associated with one or more respiratory viruses; (ii) hMPV largely predominates in bronchoalveolar lavage of symptomatic lung transplant recipients, thus suggesting a causative role in lower respiratory tract infections; (iii) RT‐PCR appears to be the method of choice for detection of respiratory viruses in lung transplant recipients, (iv) a high HCMV load in bronchoalveolar lavage is a risk factor for viral pneumonia, suggesting some measure of intervention for the control of viral infection. J. Med. Virol. 78:408–416, 2006. © 2006 Wiley‐Liss, Inc.

Plasmacytoid dendritic cells inhibit pulmonary immunopathology and promote clearance of respiratory syncytial virus

Respiratory syncytial virus (RSV) infection is widely spread and is a major cause of bronchiolitis in infants and high-risk adults, often leading to hospitalization. RSV infection leads to obstruction and inflammation of the airways and induction of innate and acquired immune responses. Because dendritic cells (DCs) are essential in the elicitation of these immune responses, we investigated the presence and the role of dendritic cell subtypes upon RSV infection in the lung. Here, we report that RSV infection increased the number of both conventional and plasmacytoid dendritic cells in the lung and the lung-draining lymph nodes. In particular, the increase in plasmacytoid dendritic cell numbers was sustained and lasted until 30 d after infection. Depletion of plasmacytoid dendritic cells resulted in decreased RSV clearance. In addition, depletion of plasmacytoid dendritic cells resulted in an exacerbation of all manifestations of immune-mediated pathology caused by RSV infection. In conclusion, this study demonstrates that both conventional and plasmacytoid dendritic cells are attracted to the site of RSV infection. It is demonstrated that plasmacytoid dendritic cells play a protective role during RSV infection by modulation of local immune responses.

Alpha and lambda interferon together mediate suppression of CD4 T cells induced by respiratory syncytial virus

The mechanism by which respiratory syncytial virus (RSV) suppresses T-cell proliferation to itself and other antigens is poorly understood. We used monocyte-derived dendritic cells (MDDC) and CD4 T cells and measured [(3)H]thymidine incorporation to determine the factors responsible for RSV-induced T-cell suppression. These two cell types were sufficient for RSV-induced suppression of T-cell proliferation in response to cytomegalovirus or Staphylococcus enterotoxin B. Suppressive activity was transferable with supernatants from RSV-infected MDDC and was not due to transfer of live virus or RSV F (fusion) protein. Supernatants from RSV-infected MDDC, but not MDDC exposed to UV-killed RSV or mock conditions, contained alpha interferon (IFN-alpha; median, 43 pg/ml) and IFN-lambda (approximately 1 to 20 ng/ml). Neutralization of IFN-alpha with monoclonal antibody (MAb) against one of its receptor chains, IFNAR2, or of IFN-lambda with MAb against either of its receptor chains, IFN-lambdaR1 (interleukin 28R [IL-28R]) or IL-10R2, had a modest effect. In contrast, blocking the two receptors together markedly reduced or completely blocked the RSV-induced suppression of CD4 T-cell proliferation. Defining the mechanism of RSV-induced suppression may guide vaccine design and provide insight into previously uncharacterized human T-cell responses and activities of interferons.

T280M variation of the CX3C receptor gene is associated with increased risk for severe respiratory syncytial virus bronchiolitis

BACKGROUND

Recent data suggest that immunologic response during respiratory syncytial virus (RSV) infection is partially modified through interaction of viral G glycoprotein with the host's chemokine receptor, CX3CR1. We hypothesized that two nonsynonymous, single-nucleotide polymorphisms of the CX3CR1 gene (CX3CR1-V249I and CX3CR1-T280M) that disrupt the affinity of CX3CR1 for its natural ligand (fractalkine) could also affect the G glycoprotein-CX3CR1 pathway.

METHODS

To test the hypothesis, DNA samples were obtained from 82 children hospitalized for RSV bronchiolitis in a 1-year period. One hundred twenty sex-matched healthy adults, without a history of severe lower respiratory tract infections, formed the control group.

RESULTS

Epidemiologic data showed an increase in the RSV infection rate during the late winter season, with a peak rate in early spring. Genotyping revealed predominance of the 280M-containing genotypes (M/M or T/M) in cases compared with controls (37.8% versus 20.8%, respectively; odds ratio, 2.03; 95% confidence interval, 1.1-3.9; P = 0.025), demonstrating an association between the common CX3CR1-T280M variations and increased risk of severe RSV bronchiolitis.

CONCLUSIONS

Our findings support the hypothesis of the pivotal role of the G glycoprotein CX3CR1 pathway in the pathogenesis of RSV bronchiolitis and propose CX3CR1 as a potential therapeutic target.

Cost-effectiveness of respiratory syncytial virus prophylaxis with palivizumab

BACKGROUND

A monoclonal antibody, palivizumab, directed against respiratory syncytial virus (RSV) has been shown to decrease hospitalisation rates. Because of its expense, the cost-effectiveness of this agent should be determined for high-risk groups.

AIM

To determine characteristics of RSV infection in Townsville and the economic feasibility of palivizumab immunoprophylaxis in high-risk groups.

METHODS

Cases of RSV-positive bronchiolitis were retrospectively identified. Cases were grouped according to recognised risk factors. The hypothetical costs of palivizumab immunoprophylaxis for infants at risk were calculated.

RESULTS

The rate of hospitalisation with RSV-positive lower respiratory tract infection was 22 per 1000 live births but increased to 50 per 1000 among Indigenous babies born weighing <2500 g. The cost of preventing an admission in each of the identified high-risk groups, based on drug costs alone, ranged from AD 69,861 to AD 88,547.

CONCLUSION

Palivizumab was not cost-effective in the prophylaxis of RSV in the high-risk group of infants tested here.

Variation in the type I interferon gene cluster on 9p21 influences susceptibility to asthma and atopy

A genome-wide screen for asthma and atopy susceptibility alleles conducted in the Hutterites, a founder population of European descent, reported evidence of linkage with a short tandem repeat polymorphism (STRP) within the type I interferon (IFN) gene cluster on chromosome 9p21. The goal of this study was to identify variation within the IFN gene cluster that influences susceptibility to asthma and atopic phenotypes. We screened approximately 25 kb of sequence, including the flanking sequence of all 15 functional genes and the single coding exon in 12, in Hutterites representing different IFNA-STRP genotypes. We identified 78 polymorphisms, and genotyped 40 of these (in 14 genes) in a large Hutterite pedigree. Modest associations (0.003<P<0.05) with asthma, bronchial hyper-responsiveness (BHR), and atopy were observed with individual variants or genes, spanning the entire 400 kb region. However, pairwise combinations of haplotypes between genes showed highly significant associations with different phenotypes (P<10(-5)) that were localized to specific pairs of genes or regions of this cluster. These results suggest that variation in multiple genes in the type I IFN cluster on 9p22 contribute to asthma and atopy susceptibility, and that not all genes contribute equally to all phenotypes.

Respiratory Syncytial Virus, Airway Inflammation, and FEV1Decline in Patients with Chronic Obstructive Pulmonary Disease

BACKGROUND

Respiratory syncytial virus (RSV) is increasingly recognized as an important pathogen in adults with cardiopulmonary disease. It has been associated with acute exacerbations of chronic obstructive pulmonary disease (COPD); however, it has also been detected in the lower airway in the stable state, but the consequences of RSV in stable disease have not previously been determined. We therefore studied the consequences of RSV persistence in adults with COPD and its effect on airway inflammation and lung function decline.

METHODS

A total of 241 sputum samples from 74 patients with COPD (FEV(1)% predicted, 39.2%; interquartile range, 29.6-57.8%) were collected quarterly in the stable state over 2 yr. RSV was detected by polymerase chain reaction (PCR), quantitative microbiology was performed, and inflammatory cytokines were quantified by ELISA.

RESULTS

RSV RNA was detected in 32.8% of sputum samples. Patients in whom RSV was more frequently detected (> 50% of samples RSV PCR-positive, n=18) had higher airway inflammation and faster FEV(1) decline over the study (101.4 ml/yr [95% confidence interval, 57.1-145.8]) compared with those with less frequent detection of RSV (n=56; 51.2 ml/yr [31.7-70.8]; p=0.01). The observed relationship between RSV detection and accelerated lung function decline was independent of smoking status, exacerbation frequency, and lower airway bacterial load.

CONCLUSIONS

Persistent RSV detection in patients with COPD is associated with airway inflammation and accelerated decline in FEV(1). Chronic RSV infection may be a novel therapeutic target to alter the natural history of COPD.

Comparison of human metapneumovirus, respiratory syncytial virus and influenza A virus lower respiratory tract infections in hospitalized young children

BACKGROUND

We compared the clinical and demographic features of children with lower respiratory tract infection (LRI) caused by human metapneumovirus (HMPV), respiratory syncytial virus (RSV) and influenza A virus and sought to determine whether coinfection by HMPV and other respiratory viruses leads to increased disease severity.

METHODS

Nasal wash specimens were prospectively obtained from 516 children hospitalized for LRI during a 1-year period and tested for the presence of HMPV by reverse transcription-polymerase chain reaction and for RSV and influenza A by direct immunofluorescence.

RESULTS

HMPV was detected in 68 (13%) patients and was the third most common viral pathogen; 16 of 68 HMPV-positive children (24%) had coinfection with other respiratory viruses (HMPVco).HMPV patients were older than RSV patients (17.6 +/- 16.8 months versus 10.5 +/- 11.8 months, P = 0.02). HMPV was associated with wheezing and hypoxemia at a rate similar to that of RSV and higher than that of influenza A. Atelectasis was more common among HMPV (40%) than among RSV and influenza patients (13%, P < 0.05 for each). HMPV infection was more often associated with a diagnosis of pneumonia than RSV and influenza A and was more often associated with a diagnosis of asthma and less often associated with a diagnosis of bronchiolitis than RSV infection (P < 0.05 for each), even when corrected for age. Children with HMPVco had a higher rate of gastrointestinal symptoms but did not show a more severe respiratory picture.

CONCLUSIONS

The clinical pattern of HMPV more closely resembles that of RSV than that of influenza A LRI, yet the differences in age, radiographic findings and clinical diagnosis suggest that HMPV pathogenesis may differ from that of RSV.

Differential resistance/susceptibility patterns to pneumovirus infection among inbred mouse strains

Respiratory syncytial virus (RSV) is a prominent cause of airway morbidity in children under 1 yr of age. It is assumed that host factors influence the severity of the disease presentation and thus the need for hospitalization. As a first step toward the identification of the underlying genes involved, this study was undertaken to establish whether inbred mouse strains differ in susceptibility to pneumonia virus of mice (PVM), the murine counterpart of RSV, which has been shown to accurately mimic the RSV disease of children. With this purpose in mind, double-chamber plethysmography and carbon monoxide uptake data were collected daily for 7 days after inoculation of PVM in six inbred strains of mice. In parallel, histological examinations and lung viral titration were carried out from day 5 to day 7 after inoculation. Pulmonary structure/function values reflected the success of viral replication in the lungs and revealed a pattern of continuous variation, with resistant, intermediate, and susceptible strains. The results suggest that SJL (resistant) and 129/Sv (susceptible) strains should be used in crossing experiments aimed at identifying genes controlling pneumovirus replication by the positional cloning approach. Similarly, crossing experiments using BALB/c or C57BL/6 (resistant) and DBA/2 or 129/Sv (susceptible) will allow the identification of the genes involved in the control of pulmonary inflammation during pneumovirus infection.

High incidence of pulmonary bacterial co-infection in children with severe respiratory syncytial virus (RSV) bronchiolitis

BACKGROUND

Respiratory syncytial virus (RSV) is the most common cause of viral lower respiratory tract infections (LRTI). Viral LRTI is a risk factor for bacterial superinfection, having an escalating incidence with increasing severity of respiratory illness. A study was undertaken to determine the incidence of pulmonary bacterial co-infection in infants and children with severe RSV bronchiolitis, using paediatric intensive care unit (PICU) admission as a surrogate marker of severity, and to study the impact of the co-infection on morbidity and mortality.

METHODS

A prospective microbiological analysis was made of lower airways secretions on all RSV positive bronchiolitis patients on admission to the PICU during three consecutive RSV seasons.

RESULTS

One hundred and sixty five children (median age 1.6 months, IQR 0.5-4.6) admitted to the PICU with RSV bronchiolitis were enrolled in the study. Seventy (42.4%) had lower airway secretions positive for bacteria: 36 (21.8%) were co-infected and 34 (20.6%) had low bacterial growth/possible co-infection. All were mechanically ventilated (median 5.0 days, IQR 3.0-7.3). Those with bacterial co-infection required ventilatory support for longer than those with only RSV (p<0.01). White cell count, neutrophil count, and C-reactive protein did not differentiate between the groups. Seventy four children (45%) received antibiotics prior to intubation. Sex, co-morbidity, origin, prior antibiotics, time on preceding antibiotics, admission oxygen, and ventilation index were not predictive of positive bacterial cultures. There were 12 deaths (6.6%), five of which were related to RSV.

CONCLUSIONS

Up to 40% of children with severe RSV bronchiolitis requiring admission to the PICU were infected with bacteria in their lower airways and were at increased risk for bacterial pneumonia.

Hospitalization for respiratory syncytial virus infection in young children: development of a clinical prediction rule

BACKGROUND

Because passive immunization against respiratory syncytial virus (RSV) is costly, its use should be restricted to well-defined groups of high risk children. We aimed to develop a clinical prediction rule that estimates the individual monthly risk of hospitalization for RSV infection in young children.

METHODS

A retrospective cohort study was conducted in the southwestern part of The Netherlands. We included children born between January 1, 1996 and December 31, 1998. Children hospitalized for proven RSV infection were compared with children not hospitalized for RSV infection. The monthly risk was estimated with a logistic regression model including 5 clinical predictors (gender, gestational age, birth weight, presence of bronchopulmonary dysplasia and age) and the mean seasonal monthly pattern of RSV infections. We compared the predictive performance of the prediction rule with the guidelines of the American Academy of Pediatrics (AAP).

FINDINGS

Information was collected on 2469 hospitalized children and 140,661 children who were 1,181,790 months at risk. All predictors were statistically significant, with age and the seasonal monthly RSV pattern having the strongest effects. The clinical prediction rule that included these predictors could better discriminate between high and low risk children than the AAP guidelines and would potentially reduce the number of immunizations by 20%.

INTERPRETATION

The prediction rule reliably estimates individual monthly risks of hospitalization for RSV infection in the population studied. It provides an improved index for passive immunization but further validation in other populations is required.

Transmissibility, infectivity and immunogenicity of a live human parainfluenza type 3 virus vaccine (HPIV3cp45) among susceptible infants and toddlers

BACKGROUND

This study examined the transmissibility between young children of an intranasally administered live attenuated human parainfluenza virus type 3 (HPIV3)-cp45 vaccine candidate.

METHODS

Eighty subjects were enrolled in playgroups among whom there was at least one infected vaccinee in close contact with a seronegative placebo recipient over 21 days without a confounding infection with wtHPIV3. Following vaccination viral cultures were obtained on nine occasions to detect shedding and transmission of HPIV3cp45. Serum antibody titers were measured before and 7 weeks after vaccination.

RESULTS

No child fulfilled the criteria for transmission of HPIV3cp45 giving a risk of transmission of 0.04 (95% CI 0.01-0.19), hence establishing that HPIV3cp45 is less infectious than wtHPIV3 and risk of transmission is not a limitation to further clinical development of this vaccine candidate.

Viral pneumonia in older adults

Viruses account for a substantial portion of respiratory illnesses, including pneumonia, in the elderly population. Presently, influenza virus A H3N2 and respiratory syncytial virus are the most commonly identified viral pathogens in older adults with viral pneumonia. As diagnostic tests such as reverse-transcription polymerase chain reaction become more widely used, the relative importance of additional viruses (such as parainfluenza, rhinoviruses, coronaviruses, and human metapneumovirus) will likely increase. Influenza virus should be considered as a cause of pneumonia during the winter months, especially during periods of peak activity. Patients with high-grade fever, myalgias, and cough should arouse the highest suspicion. Respiratory syncytial virus pneumonia should also be suspected during the winter in patients with coryza, wheezing, low-grade fever, and patchy infiltrates, especially if negative for influenza on rapid testing. Because clinical features and periods of activity for many viruses overlap, laboratory confirmation of influenza is recommended for cases involving seriously ill or institutionalized patients.

Cigarette smoke suppresses Th1 cytokine production and increases RSV expression in a neonatal model

Respiratory syncytial virus (RSV) infects approximately 90% of young children by the age of 2 yr, with peak rates occurring during 2-6 mo of age. Exposure to side-stream cigarette smoke (SS) may increase the incidence or manifestation of an RSV infection. We hypothesized that exposure to SS would alter the subsequent immune response to RSV infection in neonatal mice. BALB/c mice were exposed to air or 1.5 mg/m3 of SS from day (d) 1 up to 35 d of age. A subset was intranasally infected with 4x10(4) PFU of RSV/g body wt on d 7 and rechallenged at 28 d of age. Immune responses were assessed on d 4 and 7 after RSV rechallenge. Both air- and SS-exposed mice responded to RSV rechallenge with neutrophilia and decreased Clara cell secretory protein levels within the lung. However, an increase in bronchoalveolar lavage fluid eosinophils, in addition to reduced levels of Th1 cytokines (IFN-gamma and IL-12), decreased lung tissue inflammation, and decreased mucus production was observed in SS-exposed mice compared with air-exposed mice after RSV rechallenge. Ultimately changes in cytokine and inflammatory responses due to SS exposure likely contributed to increased viral gene expression. These results suggest that SS exposure plays a significant role in shaping the neonatal response to RSV infection.

Respiratory syncytial virus infection reversed anti-asthma effect of neonatal Bacillus Calmette-Guerin vaccination in BALB/c mice

Bacillus Calmette-Guerin (BCG) vaccination can protect animals from asthma, but the effect of BCG on childhood asthma prevention is controversial in humans. To verify the hypothesis that the BCG anti-asthma effect in childhood might be reversed by a respiratory virus infection, newborn BALB/c mice were divided into five groups. Control and ovalbumin (OVA) groups were mock vaccinated and mock infected. The BCG/OVA group was BCG vaccinated and mock infected. The respiratory syncytial virus (RSV)/OVA group was mock vaccinated and RSV infected. The BCG/RSV/OVA group was BCG vaccinated and RSV infected. Except for the control group, all groups underwent OVA sensitization and challenge. Airway hyperresponsiveness (AHR) was measured after challenge and cells in bronchoalveolar lavage fluid (BALF) were counted. Cytokines in BALF and serum OVA-specific IgE were detected by ELISA and inflammatory characteristics of lung sections were scored. Mice with neonatal BCG vaccination (BCG/OVA group) were significantly protected from BALF eosinophilia, AHR to methacholine, peribronchiolitis, alveolitis, and peribronchial eosinophilia in comparison with the OVA, RSV/OVA, and BCG/RSV/OVA groups. AHR in the OVA group was greater than in the BCG/OVA group but lower than in the RSV/OVA and BCG/RSV/OVA groups. No significant differences in BALF eosinophilia, AHR, and lung inflammation were found between the RSV/OVA and BCG/RSV/OVA groups. The impact of BCG vaccination on anti-asthma in mice was not dependent on interferon-gamma, IL-4, and IL-10 levels. The results suggested that RSV infection can reverse the anti-asthma effect of neonatal BCG vaccination in BALB/c mice.

A case-crossover study of wintertime ambient air pollution and infant bronchiolitis

We examined the association of infant bronchiolitis with acute exposure to ambient air pollutants.

DESIGN

We employed a time-stratified case-crossover method and based the exposure windows on a priori, biologically based hypotheses.

PARTICIPANTS

We evaluated effects in 19,901 infants in the South Coast Air Basin of California in 1995-2000 with a hospital discharge record for bronchiolitis in the first year of life (International Classification of Diseases, 9th Revision, CM466.1).

EVALUATIONS/MEASUREMENTS

Study subjects' ZIP code was linked to ambient air pollution monitors to derive exposures. We estimated the risk of bronchiolitis hospitalization associated with increases in wintertime ambient air pollutants using conditional logistic regression.

RESULTS

We observed no increased risk after acute exposure to particulate matter < or = 2.5 microm in aerodynamic diameter (PM2.5), carbon monoxide, or nitrogen dioxide. PM2.5 exposure models suggested a 26-41% increased risk in the most premature infants born at gestational ages between 25 and 29 weeks; however, these findings were based on very small numbers.

CONCLUSIONS

We found little support for a link between acute increases in ambient air pollution and infant bronchiolitis except modestly increased risk for PM2.5 exposure among infants born very prematurely. In these infants, the periods of viral acquisition and incubation concurred with the time of increased risk. RELEVANCE TO PROFESSIONAL PRACTICE: We present novel data for the infant period and the key respiratory disease of infancy, bronchiolitis. Incompletely explained trends in rising bronchiolitis hospitalization rates and increasing number of infants born prematurely underscore the importance of evaluating the impact of ambient air pollution in this age group in other populations and studies.

Expression of select immune genes (surfactant proteins A and D, sheep beta defensin 1, and toll-like receptor 4) by respiratory epithelia is developmentally regulated in the preterm neonatal lamb

Preterm infants experience enhanced susceptibility and severity to respiratory syncytial virus (RSV) infection. Terminal airway epithelium is an important site of RSV infection and the extent of local innate immune gene expression is poorly understood. In this study, expression of surfactant proteins A and D (SP-AD), sheep beta defensin 1 (SBD1), and toll-like receptor 4 (TLR4) mRNA were determined in whole lung homogenates from lambs. SP-AD and TLR4 mRNA expression increased (p < 0.05) from late gestation to term birth. In addition, gene expression of LCM-retrieved type II pneumocytes (CD208+), adjacent epithelium (CD208-) and bronchial epithelium demonstrated that bronchiole-alveolar junction epithelium (combined CD208 +/-) had significant (p < 0.05) developmental increases in SP-AD, SBD1 and TLR4 mRNA, whereas CD208+ cells had statistically significant increases only with SP-A mRNA. Using immunofluorescence, SP-AD antigen distribution and intensity were also greater with developmental age. These studies show reduced SBD1, SP-AD, and TLR4 expression in the preterm lung and this may underlie enhanced RSV susceptibility.

Real-time PCR in clinical microbiology: applications for routine laboratory testing

Real-time PCR has revolutionized the way clinical microbiology laboratories diagnose many human microbial infections. This testing method combines PCR chemistry with fluorescent probe detection of amplified product in the same reaction vessel. In general, both PCR and amplified product detection are completed in an hour or less, which is considerably faster than conventional PCR detection methods. Real-time PCR assays provide sensitivity and specificity equivalent to that of conventional PCR combined with Southern blot analysis, and since amplification and detection steps are performed in the same closed vessel, the risk of releasing amplified nucleic acids into the environment is negligible. The combination of excellent sensitivity and specificity, low contamination risk, and speed has made real-time PCR technology an appealing alternative to culture- or immunoassay-based testing methods for diagnosing many infectious diseases. This review focuses on the application of real-time PCR in the clinical microbiology laboratory.

Steroid-responsive subacute polymyositis in an adult following respiratory syncytial virus infection

The role of viral infections in the aetiopathogenesis of polymyositis remains speculative. We report a case of profound subacute polymyositis with incipient ventilatory failure following serologically confirmed infection by respiratory syncytial virus (RSV), with a dramatic and sustained response to pulse corticosteroid therapy. We suggest a possible autoimmune mechanism to account for this sequence of events.

Human parainfluenza virus 3 neuraminidase activity contributes to dendritic cell maturation

Mechanisms of dendritic cells (DCs) immunomodulation by parainfluenza viruses have not been characterized. We analyzed whether the human parainfluenza 3 (HPF3) virus hemagglutinin-neuraminidase glycoprotein (HN) might influence DC maturation. HN possesses a receptor binding function and a neuraminidase or desialidating activity. To assess whether the neuraminidase activity of HN affects DC maturation, human myeloid DCs were exposed to either live or UV-inactivated HPF3 viruses containing wild type or a mutated form of HN with decreased neuraminidase activity. Exposure of human DCs to either UV-inactivated or live virus induced up-regulation of CD83 and CD86 surface markers, morphological changes, and a cytokine expression pattern consistent with maturation. However, the level of maturation was found to be lower in DCs infected with the neuraminidase deficient variant as compared to the wild type. These results suggest that during the course of viral infection, HN's neuraminidase activity may play an important role contributing to maturation and activation of DCs.

Peroxisome-proliferator-activated receptor-gamma agonists inhibit the release of proinflammatory cytokines from RSV-infected epithelial cells

The epithelial cells of the airways are the target cells for respiratory syncytial virus (RSV) infection and the site of the majority of the inflammation associated with the disease. Recently, peroxisome-proliferator-activated receptor gamma (PPARgamma), a member of the nuclear hormone receptor superfamily, has been shown to possess anti-inflammatory properties. Therefore, we investigated the role of PPARgamma agonists (15d-PGJ(2), ciglitazone and troglitazone) on the synthesis of RSV-induced cytokine release from RSV-infected human lung epithelial cells (A549). We observed that all PPARgamma ligands inhibited dose-dependently the release of TNF-alpha, GM-CSF, IL-1alpha, IL-6 and the chemokines CXCL8 (IL-8) and CCL5 (RANTES) from RSV-infected A549 cells. Concomitantly, the PPARgamma ligands diminished the cellular amount of mRNA encoding for IL-6, CXCL8 and CCL5 and the RSV-induced binding activity of the transcription factors NF-kappaB (p65/p50) and AP-1 (c-fos), respectively. Our data presented herein suggest a potential application of PPARgamma ligands in the anti-inflammatory treatment of RSV infection.

Impact of palivizumab on admission to the ICU for respiratory syncytial virus bronchiolitis: a national survey

STUDY OBJECTIVES

To assess the effect of palivizumab licensing for respiratory syncytial virus (RSV) prophylaxis on national pediatric ICU (PICU) admissions and on the need for mechanical ventilation due to RSV bronchiolitis in Israel.

DESIGN

Prospective national surveillance survey.

SETTING

All PICUs in Israel.

PATIENTS OR PARTICIPANTS

All patients admitted to a PICU because of acute bronchiolitis in two consecutive RSV seasons (November 2000 to April 2001 and November 2001 to April 2002).

METHODS

Data on demographic and epidemiologic factors and RSV prophylaxis status were collected for every infant with bronchiolitis who was admitted to a PICU in Israel in the year before and after issuance of the Israel Ministry of Health recommendation for palivizumab prophylaxis (January 2001).

RESULTS

One hundred five patients were admitted to a PICU because of RSV bronchiolitis in the year before the recommendations were issued, and 123 patients were admitted in the year after they were issued. Mechanical ventilation was required by 33 and 42 children, respectively. Gestational age was > 32 weeks in 92.9% and 83.9% of the admitted patients, respectively, and 89% and 91% of the patients, respectively, were free of chronic lung disease (CLD). In both periods, 83% of the children who were admitted to a PICU did not meet the American Academy of Pediatrics criteria for RSV prophylaxis.

CONCLUSIONS

Most of the children with severe RSV bronchiolitis needing PICU admission from 2000 to 2002 born at term did not have CLD and were not candidates for RSV prophylaxis according to the current recommendations.

Aerosol delivery in respiratory syncytial virus bronchiolitis: hood or face mask?

OBJECTIVES

To compare the utility of the hood versus the face mask for delivery of inhaled medications to infants hospitalized with viral bronchiolitis.

STUDY DESIGN

Randomized, double-blinded, controlled trial; 49 hospitalized infants with viral bronchiolitis, age 2.75 +/- 2.2 months (mean +/- SD), were grouped to either the hood (n = 25) or the mask (n = 24). Each subject received inhalation treatments with the use of both devices. Half of the Hood Group received the active drug treatment (1.5 mg epinephrine in 4 mL saline [3%]) via hood followed immediately by placebo treatment (normal saline) via mask, whereas the other half received the opposite order. Half of the Mask Group received the active drug treatment via mask followed immediately by placebo treatment via hood, whereas the other half received the opposite order. Therapy was repeated 3 times daily until discharge. Outcome measures included clinical scores and parental preference.

RESULTS

Percent improvement in clinical severity scores after inhalation was significant in both groups on days 1, 2, and 3 after admission (Hood Group: 15%, 15.4%, and 16.4%, respectively; Mask Group: 17.5%, 12.1%, and 12.7%, respectively; P < .001). No significant difference in clinical scores improvement between groups was observed. Eighty percent (39/49) of parents favored the hood over the mask; 18% (9/49) preferred the mask and 2% (1/49) were indifferent.

CONCLUSIONS

In infants hospitalized with viral bronchiolitis and in whom aerosol treatment is considered, aerosol delivery by hood is as effective as by mask. However, according to parents, the tolerability of the hood is significantly better than that of a mask.

Evidence of human coronavirus HKU1 and human bocavirus in Australian children

Undiagnosed cases of respiratory tract disease suspected of an infectious aetiology peak during the winter months. Since studies applying molecular diagnostic assays usually report reductions in the number of undiagnosed cases of infectious disease compared to traditional techniques, we applied PCR assays to investigate the role of two recently described viruses, namely human coronavirus (HCoV) HKU1 and human bocavirus (HBoV), in a hospital-based paediatric population. Both viruses were found among Australia children with upper or lower respiratory tract disease during the autumn and winter of 2004, contributing to 21.1% of all microbial diagnoses, with individual incidences of 3.1% (HCoV-HKU1) and 5.6% (HBoV) among 324 specimens. HBoV was found to coincide with another virus in more than half of all instances and displayed a single genetic lineage, whilst HCoV-HKU1 was more likely to occur in the absence of another microbe and strains could be divided into two genetic lineages which we propose be termed HCoV-HKU1 type A and type B. Children under the age of 2 years were most at risk of infection by these viruses which contribute significantly to the microbial burden among patients with respiratory tract disease during the colder months.

Prospective study of healthcare utilisation and respiratory morbidity due to RSV infection in prematurely born infants

BACKGROUND

A study was undertaken to determine the impact of respiratory syncytial virus (RSV) infection, both in hospital and the community, on healthcare utilisation and respiratory morbidity in prematurely born infants and to identify risk factors for symptomatic RSV infection.

METHODS

A hospital and community follow up study was undertaken of 126 infants born before 32 weeks of gestational age. Healthcare utilisation (hospital admissions and general practitioner attendances) in the first year, respiratory morbidity at follow up (wheeze and cough documented by parent completed diary cards), and RSV positive lower respiratory tract infections (LRTIs) were documented. Nasopharyngeal aspirates were obtained for immunofluorescence and culture for RSV whenever the infants had an LRTI, either in the community or in hospital.

RESULTS

Forty two infants had an RSV positive LRTI (RSV group), 50 had an RSV negative LRTI (RSV negative LRTI group), and 32 infants had no LRTI (no LRTI group). Compared with the RSV negative LRTI and the no LRTI groups, the RSV group required more admissions (p=0.392, p<0.001) and days in hospital (p=0.049, p=0.006) and had more cough (p=0.05, p=0.038) and wheeze (p=0.003, p=0.003) at follow up. Significant risk factors for symptomatic RSV LRTI were number of siblings (p=0.035) and maternal smoking in pregnancy (p=0.005), for cough were number of siblings (p=0.002) and RSV LRTI (p=0.02), and for wheeze was RSV LRTI (p=0.019).

CONCLUSION

RSV infection, even if hospital admission is not required, is associated with increased subsequent respiratory morbidity in prematurely born infants.

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.

Bench-to-bedside review: Paediatric viral lower respiratory tract disease necessitating mechanical ventilation--should we use exogenous surfactant?

Treatment of infants with viral lower respiratory tract disease (LRTD) necessitating mechanical ventilation is mainly symptomatic. The therapeutic use of surfactant seems rational because significantly lower levels of surfactant phospholipids and proteins, and impaired capacity to reduce surface tension were observed among infants and young children with viral LRTD. This article reviews the role of pulmonary surfactant in the pathogenesis of paediatric viral LRTD. Three randomized trials demonstrated improved oxygenation and reduced duration of mechanical ventilation and paediatric intensive care unit stay in young children with viral LRTD after administration of exogenous surfactant. This suggest that exogenous surfactant is the first beneficial treatment for ventilated infants with viral LRTD. Additionally, in vitro and animal studies demonstrated that surfactant associated proteins SP-A and SP-D bind to respiratory viruses, play a role in eliminating these viruses and induce an inflammatory response. Although these immunomodulating effects are promising, the available data are inconclusive and the findings are unconfirmed in humans. In summary, exogenous surfactant in ventilated infants with viral LRTD could be a useful therapeutic approach. Its beneficial role in improving oxygenation has already been established in clinical trials, whereas the immunomodulating effects are promising but remain to be elucidated.

Detection of respiratory syncytial virus genome by subgroups-A, B specific reverse transcription loop-mediated isothermal amplification (RT-LAMP)

Annual seasonal outbreaks of respiratory syncytial virus (RSV) infection occur every winter. Most patients are diagnosed clinically by a rapid detection kit for RSV protein(s) from nasopharyngeal secretion (NPS), but some problems have been reported on the specificity and sensitivity of such rapid detection kits. To ratify these issues, a sensitive, specific, simple, and rapid molecular based diagnostic method is expected to be introduced and we have developed a method to detect the RSV genome of subgroups A and B independently by reverse transcription loop-mediated isothermal amplification (RT-LAMP). We detected the genomic RNA corresponding approximately to 0.1 TCID 50 in the sample by RT-LAMP for both RSV subgroups under isothermal condition within 60 min after extraction of RNA. Specific DNA amplification was monitored by a real-time turbidimeter and the quantity of RNA was calculated. The RSV genome was detected in 47 of 50 NPS by RT-LAMP, and in 42 by nested RT-PCR, whereas virus isolation was positive for 29 and enzyme-linked immunoassay (EIA) for 34. RSV subgroup A was detected in 25 by RSV RT-LAMP A, RSV subgroup B in 23 by RSV RT-LAMP B, and dual infection with RSV subgroups A and B was identified in one case. They were confirmed with digestion with a specific restriction enzyme, Bgl II. The results showed the potential clinical feasibility of RT-LAMP as a useful diagnostic tool for the detection of RSV with high sensitivity similar to nested RT-PCR.

The cotton rat (Sigmodon hispidus) is a permissive small animal model of human metapneumovirus infection, pathogenesis, and protective immunity

Human metapneumovirus (hMPV) is a newly described paramyxovirus that is an important cause of acute respiratory tract disease. We undertook to develop a small animal model of hMPV infection, pathogenesis, and protection. Hamsters, guinea pigs, cotton rats, and nine inbred strains of mice were inoculated intranasally with hMPV. The animals were sacrificed, and nasal and lung tissue virus yields were determined by plaque titration. None of the animals exhibited respiratory symptoms. The quantity of virus present in the nasal tissue ranged from 4.6 x 10(2) PFU/gram tissue (C3H mice) to greater than 10(5) PFU/gram (hamster). The amount of virus in the lungs was considerably less than in nasal tissue in each species tested, ranging from undetectable (<5 PFU/g; guinea pigs) to 1.8 x 10(5) PFU/gram (cotton rat). The peak virus titer in cotton rat lungs occurred on day 4 postinfection. hMPV-infected cotton rat lungs examined on day 4 postinfection exhibited histopathological changes consisting of peribronchial inflammatory infiltrates. Immunohistochemical staining detected virus only at the luminal surfaces of respiratory epithelial cells throughout the respiratory tract. hMPV-infected cotton rats mounted virus-neutralizing antibody responses and were partially protected against virus shedding and lung pathology on subsequent rechallenge with hMPV. Viral antigen was undetectable in the lungs on challenge of previously infected animals. This study demonstrates that the cotton rat is a permissive small animal model of hMPV infection that exhibits lung histopathology associated with infection and that primary infection protected animals against subsequent infection. This model will allow further in vivo studies of hMPV pathogenesis and evaluation of vaccine candidates.

Human metapneumovirus in infants and young children in Thailand with lower respiratory tract infections; molecular characteristics and clinical presentations

Human metapneumovirus (hMPV) is a recently identified Paramyxovirus. The clinical features and molecular characteristics of hMPV in Asian populations have so far remained obscure.

OBJECTIVE

The present study was designed to investigate the prevalence of hMPV in infants and young children presented with acute lower respiratory tract infection (ALRI) and to identify the molecular characteristics and clinical presentations.

METHODS

There were 236 nasopharyngeal secretions (NPs) collected from infants and children presented with ALRI at King Chulalongkorn Memorial hospital between March 2001 and September 2003. Reverse transcriptase-polymerase chain reaction (RT-PCR) applying specific primers was done to identify hMPV and hRSV. Phylogenetic analysis of hMPV N, F and L genes was also performed.

RESULTS

Of the 220 (236) infants and young children tested, positive results were found in 12 specimens (5.4%). The mean age of children with hMPV infections was 22+/-11 months. They mostly presented with fever with cough (100%) and upper respiratory tract symptoms (10/12, 83%). Eleven of twelve infants (92%) were hospitalized. Additionally, phylogenetic analysis identified two distinct lineages of hMPV.

CONCLUSION

Our results demonstrated the prevalence, molecular characterization and clinical spectrum of hMPV infection in infants and young children presented with lower respiratory tract infections in Thailand.

Entry of parainfluenza virus into cells as a target for interrupting childhood respiratory disease

Human parainfluenza viruses cause several serious respiratory diseases in children for which there is no effective prevention or therapy. Parainfluenza viruses initiate infection by binding to cell surface receptors and then, via coordinated action of the 2 viral surface glycoproteins, fuse directly with the cell membrane to release the viral replication machinery into the host cell's cytoplasm. During this process, the receptor-binding molecule must trigger the viral fusion protein to mediate fusion and entry of the virus into a cell. This review explores the binding and entry into cells of parainfluenza virus type 3, focusing on how the receptor-binding molecule triggers the fusion process. There are several steps during the process of binding, triggering, and fusion that are now understood at the molecular level, and each of these steps represents potential targets for interrupting infection.

Immune responses and disease enhancement during respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is one of the commonest and most troublesome viruses of infancy. It causes most cases of bronchiolitis, which is associated with wheezing in later childhood. In primary infection, the peak of disease typically coincides with the development of specific T- and B-cell responses, which seem, in large part, to be responsible for disease. Animal models clearly show that a range of immune responses can enhance disease severity, particularly after vaccination with formalin-inactivated RSV. Prior immune sensitization leads to exuberant chemokine production, an excessive cellular influx, and an overabundance of cytokines during RSV challenge. Under different circumstances, specific mediators and T-cell subsets and antibody-antigen immune complex deposition are incriminated as major factors in disease. Animal models of immune enhancement permit a deep understanding of the role of specific immune responses in RSV disease, assist in vaccine design, and indicate which immunomodulatory therapy might be beneficial to children with bronchiolitis.

Growth of respiratory syncytial virus in primary epithelial cells from the human respiratory tract

Respiratory syncytial virus (RSV) is the most important cause of lower respiratory tract disease in infants and children. To study RSV replication, we have developed an in vitro model of human nasopharyngeal mucosa, human airway epithelium (HAE). RSV grows to moderate titers in HAE, though they are significantly lower than those in a continuous epithelial cell line, HEp-2. In HAE, RSV spreads over time to form focal collections of infected cells causing minimal cytopathic effect. Unlike HEp-2 cells, in which wild-type and live-attenuated vaccine candidate viruses grow equally well, the vaccine candidates exhibit growth in HAE that parallels their level of attenuation in children.

Real-time detection of virus particles and viral protein expression with two-color nanoparticle probes

Respiratory syncytial virus (RSV) mediates serious lower respiratory tract illness in infants and young children and is a significant pathogen of the elderly and immune compromised. Rapid and sensitive RSV diagnosis is important to infection control and efforts to develop antiviral drugs. Current RSV detection methods are limited by sensitivity and/or time required for detection. In this study, we show that antibody-conjugated nanoparticles rapidly and sensitively detect RSV and estimate relative levels of surface protein expression. A major development is use of dual-color quantum dots or fluorescence energy transfer nanobeads that can be simultaneously excited with a single light source.

Respiratory syncytial virus influences NF-kappaB-dependent gene expression through a novel pathway involving MAP3K14/NIK expression and nuclear complex formation with NF-kappaB2

A member of the Paramyxoviridae family of RNA viruses, respiratory syncytial virus (RSV), is a leading cause of epidemic respiratory tract infection in children. In children, RSV primarily replicates in the airway mucosa, a process that alters epithelial cell chemokine expression, thereby inducing airway inflammation. We investigated the role of the mitogen-activated protein kinase kinase kinase 14/NF-kappaB-inducing kinase (NIK) in the activation of NF-kappaB-dependent genes in alveolus-like A549 cells. RSV infection induces a time dependent increase of NIK mRNA and protein expression that peaks 12 to 24 h after viral exposure. Immunoprecipitation kinase assays indicate that NIK kinase activity is activated even more rapidly (within 6 h of RSV adsorption) associated with an endogenous approximately 50-kDa NF-kappaB2 substrate. Because NIK associates with IKKalpha to mediate processing of the 100-kDa NF-kappaB2 precursor into its 52-kDa DNA binding isoform ("p52"), the effects of RSV on NIK complex formation with IKKalpha and NF-kappaB2 were determined by coimmunoprecipitation assay. We find that NIK, IKKalpha, and both 100 kDa- and 52-kDa NF-kappaB2 isoforms strongly complex 15 h after exposure to RSV at times subsequent to NIK kinase activation. Western immunoblot and microaffinity DNA pull-down assays showed a parallel increase in nuclear translocation and DNA binding of the NF-kappaB2-Rel B complex. Interestingly, we make the novel observations that NIK also transiently translocates into the nucleus complexed with 52-kDa NF-kappaB2. Small interfering RNA-mediated NIK "knock-down" blocked RSV-inducible 52-kDa NF-kappaB2 processing and interfered with the early activation of a subset of NF-kappaB-dependent genes, indicating the importance of this activation pathway in the genomic NF-kappaB response to RSV. Together, these data indicate that RSV infection rapidly activates the noncanonical NF-kappaB activation pathway prior to the more potent canonical pathway activation. This appears to be through a novel mechanism involving induction of NIK kinase activity, expression, and nuclear translocation of a ternary complex with IKKalpha and processed NF-kappaB2.

Immunisation in the current management of cystic fibrosis patients

Although no special recommendations exist, clearly patients with cystic fibrosis (CF) can benefit from immunisation. We reviewed the literature regarding vaccination in CF and other chronic diseases. CF subjects should follow national immunisation programmes without delay to obtain optimal vaccination coverage. Indeed they may escape normal programmes due to frequent hospital admissions and school absenteeism and may be more at risk to get "vaccine-controlled" diseases at any age. There is no uniform European immunisation schedule for basic infant and childhood vaccines or for vaccines against hepatitis A (HAV) and B (HBV), varicella (VZ) and booster vaccinations. HAV and HBV vaccination is appropriate in CF as recommended in general for patients with chronic liver disease (CLD). Varicella (VZ) vaccination is not recommended in all European countries. There are no recent data about possible worsening of pulmonary status following VZ in CF, but it is known to cause pulmonary damage in non-CF adults and to be potentially fatal post transplantation and during steroid treatment. Therefore it is recommended at least for seronegative adolescents and transplant candidates. Influenza vaccine is recommended annually for CF patients aged > or =6 months. Pneumococcal vaccine is generally indicated for CF patients. RSV infection might play a role in the initial Pseudomonas colonization and the decline in pulmonary function. However no RSV vaccine is available at present. There are no recommendations for palivizumab in CF as an alternative but expensive prophylaxis. Anti-bacterial vaccinations protecting directly against Pseudomonas aeruginosa colonisation are promising for the future, potential candidates are currently being assessed in phase III clinical trials. More studies are needed to complete recommendations especially for CF adults and transplant candidates.

Neurologic complications associated with respiratory syncytial virus

Encephalopathy has been demonstrated to be associated with respiratory syncytial virus bronchiolitis. In this study, the data on all patients less than 14 years of age hospitalized with respiratory syncytial virus bronchiolitis over the past 4 years was reviewed. Patients who had concomitant diagnoses consistent with neurologic disease underwent detailed chart review. There were 964 patients (age 0.1 to 13.6 years) with a diagnosis of respiratory syncytial virus bronchiolitis. Thirty-six of these patients had concurrent neurologic diagnoses. Twenty-four patients were excluded because of preexistent neurologic disorders, probable simple febrile seizures, or a history of epilepsy. Twelve respiratory syncytial virus-positive patients had definite neurologic complications without another recognized cause. Seven of these patients had seizures (predominantly generalized tonic-clonic and one with status epilepticus), three had generalized encephalopathy (marked hypotonia and decreased responsiveness) of whom two also developed esotropia. Two patients developed isolated esotropia. There was an incidence of neurologic complications of 1.2% (0.7% seizures) in a total of 964 patients with respiratory syncytial virus bronchiolitis. This percentage does not include presumed simple febrile seizures or exacerbations of preexisting seizure disorder (further 1.3%). Neurologic complications occur with respiratory syncytial virus bronchiolitis, and physicians and other caregivers should be aware of this entity as well as the favorable prognosis.

Respiratory syncytial virus infection in elderly and high-risk adults

BACKGROUND

Respiratory syncytial virus (RSV) is an increasingly recognized cause of illness in adults. Data on the epidemiology and clinical effects in community-dwelling elderly persons and high-risk adults can help in assessing the need for vaccine development.

METHODS

During four consecutive winters, we evaluated all respiratory illnesses in prospective cohorts of healthy elderly patients (> or =65 years of age) and high-risk adults (those with chronic heart or lung disease) and in patients hospitalized with acute cardiopulmonary conditions. RSV infection and influenza A were diagnosed on the basis of culture, reverse-transcriptase polymerase chain reaction, and serologic studies.

RESULTS

A total of 608 healthy elderly patients and 540 high-risk adults were enrolled in prospective surveillance, and 1388 hospitalized patients were enrolled. A total of 2514 illnesses were evaluated. RSV infection was identified in 102 patients in the prospective cohorts and 142 hospitalized patients, and influenza A was diagnosed in 44 patients in the prospective cohorts and 154 hospitalized patients. RSV infection developed annually in 3 to 7 percent of healthy elderly patients and in 4 to 10 percent of high-risk adults. Among healthy elderly patients, RSV infection generated fewer office visits than influenza; however, the use of health care services by high-risk adults was similar in the two groups. In the hospitalized cohort, RSV infection and influenza A resulted in similar lengths of stay, rates of use of intensive care (15 percent and 12 percent, respectively), and mortality (8 percent and 7 percent, respectively). On the basis of the diagnostic codes of the International Classification of Diseases, 9th Revision, Clinical Modification at discharge, RSV infection accounted for 10.6 percent of hospitalizations for pneumonia, 11.4 percent for chronic obstructive pulmonary disease, 5.4 percent for congestive heart failure, and 7.2 percent for asthma.

CONCLUSIONS

RSV infection is an important illness in elderly and high-risk adults, with a disease burden similar to that of nonpandemic influenza A in a population in which the prevalence of vaccination for influenza is high. An effective RSV vaccine may offer benefits for these adults.

The Role of Viruses in the Aetiology of Community-Acquired Pneumonia in Adults

Background

The role of viruses in community-acquired pneumonia may have been previously underestimated. We aimed to study the incidence and clinical characteristics of community-acquired pneumonia (CAP) due to respiratory viruses in adults adding PCR to routine conventional laboratory tests.

Methods

Consecutive adult patients diagnosed of CAP from January 2003 to March 2004 were included. Conventional tests including cultures of blood, sputum, urine antigen detection of Streptococcus pneumoniae and Legionella pneumophila, and paired serologies were routinely performed. Nasopharyngeal swabs were processed for study of respiratory viruses through antigen detection by indirect immunofluorescence assay, isolation of viruses in cell culture and detection of nucleic acids by two independent multiplex RT-PCR assays. According to the aetiology, patients were categorized in 4 groups: group 1, only virus detected; group 2, only bacteria detected; group 3, viral and bacterial; and group 4, unkown aetiology.

Results

Of 340 patients diagnosed with CAP, 198 had nasopharyngeal swabs available and were included in this study. Aetiology was established in 112 (57%) patients: group 1, n=26 (13%); group 2, n=66 (33%); group 3, n=20 (10%). The most common aetiological agent was S. neumoniae (58 patients, 29%), followed by respiratory viruses (46 patients, 23%). Forty-eight respiratory viruses were identified: influenza virus A ( n=16), respiratory syncytial virus A ( n=5), adenovirus ( n=8), parainfluenza viruses ( n=5), enteroviruses ( n=1), rhinoviruses ( n=8) and coronavirus ( n=5). There were two patients coinfected by two respiratory viruses. Serology detected 6 viruses, immunofluorescence 8, viral culture 12, and PCR 45. For the viruses that could be diagnosed with conventional methods, the sensitivity and specificity of RT-PCR was 85% and 92%, respectively. The only clinical characteristic that significantly distinguished viral from bacterial aetiology was a lower number of leukocytes ( P=0.004).

Conclusion

PCR revealed that viruses represent a common aetiology of CAP. There is an urgent need to reconsider routine laboratory tests for an adequate diagnosis of respiratory viruses, as clinical characteristics are unable to reliably distinguish viral from bacterial aetiology.

Laboratory diagnosis and surveillance of human respiratory viruses by PCR in Victoria, Australia, 2002-2003

Respiratory viruses were identified by the polymerase chain reaction (PCR) in more than 4,200 specimens collected during 2002 and 2003 in Victoria, Australia from patients admitted to hospitals or participating in an influenza surveillance program. Influenza viruses and picornaviruses were important causes of morbidity in both years. Additional testing of picornavirus‐positive samples suggested that rhinoviruses but not enteroviruses were more likely to be associated with respiratory symptoms, irrespective of the season in which they circulated. Detection of influenza viruses was strongly associated with the clinical symptoms of cough, fever, and fatigue; but each of the other respiratory viruses occasionally caused these symptoms or was responsible for symptoms severe enough to require hospitalization. Human coronaviruses HCoV‐OC43 and HCoV‐229E circulated at low levels throughout the study period with peak activity in winter, but overall did not circulate as widely as has often been reported for these agents. Evidence for the human metapneumovirus (hMPV) was only sought in the second year of the study and revealed low‐level circulation of this virus, mainly in the cooler months among the very young and adult populations. The detection rate of all viruses declined with increasing age of the patient, particularly in hospital patients. Infection with more than one respiratory virus occurred in a small number of patients; picornaviruses were most commonly implicated in these dual infections. J. Med. Virol. 75:122–129, 2005. © 2005 Wiley‐Liss, Inc.

New human coronavirus, HCoV-NL63, associated with severe lower respiratory tract disease in Australia

A new human coronavirus, HCoV-NL63, was associated recently with bronchiolitis. The current study aimed to examine retrospectively stored specimens for the presence of HCoV-NL63 using nested RT-PCR assays targeting the 1a and 1b genes. The study population was composed of patients with acute respiratory disease warranting presentation to Queensland hospitals. HCoV-NL63 was detected in the nasopharyngeal aspirates (NPA) of 16 of 840 specimens representing 766 patients (2%). HCoV-NL63 positive individuals were diagnosed most commonly with lower respiratory tract (LRT) disease (81%). The clinical diagnosis was commonly supported by an abnormal chest X-ray (56%) together with respiratory distress (50%), wheeze (44%), and rales (25%) on first presentation with HCoV-NL63 infection. All patients positive for HCoV-NL63 required admission to hospital. Among 38% of HCoV-NL63 positive specimens a second pathogen was detected. Sequencing of amplicon from gene 1b revealed more than 99% nucleotide homology with the viral type strains while sequencing amplicon from gene 1a permitted the grouping of viral strains. It was shown that HCoV-NL63 is associated with severe LRT disease in an Australian hospital setting during the cooler months of the year. We propose that HCoV-NL63 is a global and seasonal pathogen of both children and adults associated with severe LRT illness.

Nosocomial outbreak of respiratory syncytial virus subgroup B variants with the 60 nucleotides-duplicated G protein gene

In January 2001, 20 children among 40 residents under 2 years old at a nursery home in Sapporo, Japan had respiratory symptoms and were confirmed as having respiratory syncytial virus (RSV) infection by a conventional diagnostic kit. Nasopharyngeal aspirates were collected from four RSV-positive patients and total RNA was extracted directly from the specimens for the analysis of RSV grouping and genotyping. All four RSV strains had the same G protein gene sequence of subgroup B and were assigned to identical strains. Interestingly, the G protein gene had a duplication of 60 nucleotides at the C-terminal third of the G protein gene in which three nucleotides differed each other. The predicted polypeptide is lengthened by 20 amino acids. The clinical picture of these cases was not different from those of patients with other RSV strains. These novel mutations were thought to be introduced in vivo.

Enhanced surfactant protein and defensin mRNA levels and reduced viral replication during parainfluenza virus type 3 pneumonia in neonatal lambs

Defensins and surfactant protein A (SP-A) and SP-D are antimicrobial components of the pulmonary innate immune system. The purpose of this study was to determine the extent to which parainfluenza type 3 virus infection in neonatal lambs alters expression of sheep beta-defensin 1 (SBD-1), SP-A, and SP-D, all of which are constitutively transcribed by respiratory epithelia. Parainfluenza type 3 viral antigen was detected by immunohistochemistry (IHC) in the bronchioles of all infected lambs 3 days postinoculation and at diminished levels 6 days postinoculation, but it was absent 17 days postinoculation. At all times postinoculation, lung homogenates from parainfluenza type 3 virus-inoculated animals had increased SBD-1, SP-A, and SP-D mRNA levels as detected by fluorogenic real-time reverse transcriptase PCR. Protein levels of SP-A in lung homogenates detected by quantitative-competitive enzyme-linked immunosorbent assay and protein antigen of SP-A detected by IHC were not altered. These studies demonstrate that parainfluenza type 3 virus infection results in enhanced expression of constitutively transcribed innate immune factors expressed by respiratory epithelia and that this increased expression occurs concurrently with decreased viral replication.

[Asthma and respiratory syncytial virus. New opportunities for therapeutic intervention]

Numerous studies have described an association between respiratory sincticial virus (RSV) infection in infancy and the subsequent development of airway hyperresponsiveness (AHR). Besides the exaggerated immune response and the abnormal neurogenic mechanisms induced by RSV, recent studies have correlated the "persistence" of RSV in the lower respiratory tract with the development of AHR. Several investigators have evaluated whether treatment with antiviral or immunosuppressive agents could decrease the long term respiratory abnormalities induced by RSV. The RSV murine model has allowed us to study the immunopathogenesis of RSV-induced AHR. Once the airway obstruction, typical of acute disease, is resolved and no virus is longer detected by cell cultures, mice progress into a chronic phase characterized by AHR and persistent airway inflammation. The use of polymerase chain reaction assay for RSV quantitation has demonstrated, quite unexpectedly, the presence of RSV RNA in the lower respiratory tract of mice during the chronic phase of the disease. As an example of intervention, the administration of an anti-RSV neutralizing antibody (palivizumab) was associated with a significant reduction in viral replication, pulmonary inflammation and inflammatory cytokines, as well as a significant improvement in the pulmonary function both in the acute and chronic phases of the disease. Future clinical studies to determine whether therapy with palivizumab can prevent the long-term morbidity associated with RSV in children are warranted.