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Rationale: Human rhinoviruses (HRV) are the leading cause of upper respiratory infections and have been postulated to trigger asthma exacerbations. However, whether HRV are detected during crises because upper respiratory infections often accompany asthma attacks, or because they specifically elicit exacerbations, is unclear. Moreover, although several hypotheses have been advanced to explain virus-induced exacerbations, their mechanism remains unclear. Objectives: To determine the role of HRV in pediatric asthma exacerbations and the mechanisms mediating wheezing. Methods: We prospectively studied 409 children with asthma presenting with upper respiratory infection in the presence or absence of wheezing. Candidate viral and immune mediators of illness were compared among children with asthma with different degrees of severity of acute asthma. Measurements and Main Results: HRV infections specifically associated with asthma exacerbations, even after adjusting for relevant demographic and clinical variables defined a priori (odds ratio, 1.90; 95% confidence interval, 1.21-2.99; P ¼ 0.005). No difference in virus titers, HRV species, and inflammatory or allergic molecules was observed between wheezing and nonwheezing children infected with HRV. Type III IFN-l 1 levels were higher in wheezing children infected with HRV compared with nonwheezing (P , 0.001) and increased with worsening symptoms (P , 0.001). Moreover, after adjusting for IFN-l 1 , children with asthma infected with HRV were no longer more likely to wheeze than those who were HRV-negative (odds ratio, 1.18; 95% confidence interval, 0.57-2.46; P ¼ 0.66). Conclusions: Our findings suggest that HRV infections in children with asthma are specifically associated with acute wheezing, and that type III IFN-l 1 responses mediate exacerbations caused by HRV. Modulation of IFN-l 1 should be studied as a therapeutic target for exacerbations caused by HRV.Keywords: asthma; interferon-l; rhinovirus; children; asthma exacerbation Asthma exacerbations are the main cause of hospitalization in children, and occur in association with respiratory viral infections (1, 2). Human rhinoviruses (HRV) are frequently isolated in the upper airways of children during respiratory infections and during asthma attacks, and have been postulated to trigger these crises (3, 4). However, whether HRV are detected during asthma crises because they are the most frequent cause of upper respiratory infections (URI; which accompany asthma attacks), or because they can specifically elicit asthma exacerbations is unclear. To our knowledge, no pediatric study has compared the viral etiology of URI in patients with asthma with and without wheezing to investigate the specific association between HRV URI and asthma attacks.Several hypotheses have been advanced to explain the mechanisms that trigger asthma crises during respiratory infections (4-7). Focused mainly on HRV-associated episodes, two nonexclusive theories attribute asthma attacks to direct viral injury and immune-mediated exacerbations ...

We conducted a prospective, observational study to characterize the clinical manifestations of respiratory infections caused by human metapneumovirus (hMPV) and other viruses in 194 premature infants and young children with chronic lung disease or congenital heart disease in Buenos Aires. Children had 567 episodes of respiratory illness and were monitored until they were 2 years old or until the completion of the study. hMPV elicited 12 infections (2%) year-round; 30% were of moderate or greater severity. Human parainfluenza virus type 3 caused 24 infections (4%), and 5 (25%) of 20 lung infections led to hospitalization. Respiratory syncytial virus (RSV) caused 33 episodes--17% of infections and 32% of hospitalizations during the respiratory season. None of the 10 children infected with influenza virus had severe disease. The present study of at-risk children suggests that hMPV and influenza virus are infrequent agents of severe disease and highlights the need for preventive interventions against RSV in developing countries.

The cytotoxic T-lymphocyte (CTL) response is important for the control of viral replication during respiratory syncytial virus (RSV) infection. The attachment glycoprotein (G) of RSV does not encode major histocompatibility complex class I-restricted epitopes in BALB/c mice (H-2 d ). Furthermore, studies to date have described an absence of significant CTL activity directed against this protein in humans. Therefore, G previously was not considered necessary for the generation of RSV-specific CTL responses. In this study, we demonstrate that, despite lacking H-2 d -restricted epitopes, G enhances the generation of an effective CTL response against RSV. Furthermore, we show that this stimulatory effect is independent of virus titers and RSV-induced inflammation; that it is associated primarily with the secreted form of G; and that the effect depends on the cysteine-rich region of G (GCRR), a segment conserved in wild-type isolates worldwide. These findings reveal a novel function for the GCRR with potential implications for the generation of protective cellular responses and vaccine development.

OBJECTIVE-The protective role of breastfeeding against severe acute lung disease in infants is well established, but its mechanism is unclear. Most hypotheses assume that breastfeeding confers similar passive protection to every infant; however, a few observations have suggested that the benefits of breast milk against severe lung disease may differ according to gender. The objective of this study was to determine whether the effect of breastfeeding on susceptibility to severe acute lung disease among infants at high risk is different for girls and boys.METHODS-A cohort was analyzed prospectively by use of 2 different strategies: (1) predictors of first episode of rehospitalization by univariate and multivariate analyses using robust Poisson regression and (2) mean number of rehospitalizations between groups using multiple regression negative binomial models.RESULTS-A total of 119 high-risk, very low birth weight infants were enrolled. Breast milk protected girls but not boys against severe acute lung disease. The interaction between breastfeeding and gender was clinically and statistically significant, even after adjustment for variables that can Address correspondence to Fernando P. Polack, MD, Johns Hopkins University, 615 N Wolfe St, E5202, Baltimore, MD 21205. E-mail: fpolack@jhsph.edu PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275). Drs Klein and Bergel contributed equally to this work.The authors have indicated they have no financial relationships relevant to this article to disclose. What's Known on This SubjectThe protective role of breastfeeding against severe acute lung disease in infants is well established, but its mechanism is unclear. Most hypotheses assume that breastfeeding confers similar passive protection to every infant. What This Study AddsThis study reveals an unexpected gender-related difference in the protective effects of breast milk; suggests that severity of respiratory diseases in infancy may be amenable to modulation by a nonspecific mechanism; challenges the established dogma that the protective effect of breast milk is exerted by passive transfer of IgA; and contributes to redefine the populations of premature infants at highest risk for severe lung disease, in this case nonbreastfeeding girls. The protective role of breastfeeding against severe respiratory infections in healthy term infants is well established. 8,9 In VLBW infants, a similar beneficial effect has been described. 10 For all of these populations, the mechanism of breast milk-mediated protection is unclear. A widely accepted hypothesis attributes the effect of breast milk to neutralization of infectious agents by passively transferred secretory immunoglobulin A in the respiratory tract of exposed infants. 9,11-13 Alternative theories attribute protection to the passive transfer of other molecules with anti-infective activity. 14-16 All of these hypotheses assume that breastfeeding confers similar passive protection to each and every infant; however, a few observations in recent years suggested...