IL-13 genetic polymorphism identifies children with late wheezing after respiratory syncytial virus infection

An overview on the RSV-mediated mechanisms in the onset of non-allergic asthma

Respiratory syncytial virus (RSV) infection is recognized as an important risk factor for wheezing and asthma, since it commonly affects babies during lung development. While the role of RSV in the onset of atopic asthma is widely recognized, its impact on the onset of non-atopic asthma, mediated via other and independent causal pathways, has long been also suspected, but the association is less clear. Following RSV infection, the release of local pro-inflammatory molecules, the dysfunction of neural pathways, and the compromised epithelial integrity can become chronic and influence airway development, leading to bronchial hyperreactivity and asthma, regardless of atopic status. After a brief review of the RSV structure and its interaction with the immune system and neuronal pathways, this review summarizes the current evidence about the RSV-mediated pathogenic pathways in predisposing and inducing airway dysfunction and non-allergic asthma development.

The Burden and Long-term Respiratory Morbidity Associated with Respiratory Syncytial Virus Infection in Early Childhood

INTRODUCTION

The REGAL (RSV Evidence-a Geographical Archive of the Literature) series provide a comprehensive review of the published evidence in the field of respiratory syncytial virus (RSV) in Western countries over the last 20 years. The objective of this fifth publication was to determine the long-term respiratory morbidity associated with RSV lower respiratory tract infection (RSV LRTI) in early life.

METHODS

A systematic review was undertaken for articles published between January 1, 1995 and December 31, 2015. This was supplemented by inclusion of papers published whilst drafting the manuscript. Studies reporting data on the incidence and long-term wheezing and asthma following RSV LRTI in early life were included. Study quality and strength of evidence (SOE) were graded using recognized criteria.

RESULTS

A total of 2337 studies were identified of which 74 were included. Prospective, epidemiologic studies consistently demonstrated that RSV LRTI is a significant risk factor for on-going respiratory morbidity characterized by transient early wheezing and recurrent wheezing and asthma within the first decade of life and possibly into adolescence and adulthood (high SOE). RSV LRTI was also associated with impaired lung function in these children (high SOE). Respiratory morbidity has been shown to result in reduced quality of life and increased healthcare resource use (moderate SOE). The mechanisms through which RSV contributes to wheezing/asthma development are not fully understood, but appear to relate to the viral injury, preexisting abnormal lung function and/or other factors that predispose to wheezing/asthma, including genetic susceptibility, altered immunology, eosinophilia, and associated risk factors such as exposure to environmental tobacco smoke (high SOE).

CONCLUSION

There is growing evidence that RSV LRTI in early childhood is associated with long-term wheezing and asthma and impaired lung function. Future research should aim to fully elucidate the pathophysiological mechanisms through which RSV causes recurrent wheezing/asthma.

Predictors of asthma following severe respiratory syncytial virus (RSV) bronchiolitis in early childhood

BACKGROUND

We sought to identify predictors of asthma development following severe early childhood RSV bronchiolitis. Different definitions of asthma were also compared.

METHODS

This longitudinal, observational study (N = 343) followed patients (<2 years old) from a placebo-controlled trial (N = 979) of montelukast after RSV bronchiolitis to identify clinical, demographic, or biochemical predictors of asthma, atopic disorders, and chronic asthma therapy use at 6 years of age (Clinical Trials Registry Number: NCT01140048). Asthma (primary definition) was based on parental identification of wheeze at 6 AND 12 months before 6 years of age; definitions based on physician diagnosis as well as parental identification of wheeze at 6 OR 12 months (to consider seasonal effect) were also assessed. Post-hoc analyses evaluated agreement among asthma diagnosis criteria.

RESULTS

Prevalence of asthma (primary definition by parental identification), asthma (physician diagnosis), atopic disorders, and chronic asthma therapy use (parental identification) was 6.1%, 22.4%, 36.2%, and 14.5%, respectively. Predictors for asthma (primary definition) included male gender, a relative with asthma, and RAST positive for dog dander; for physician diagnosis of asthma, high severity score for RSV bronchiolitis, high respiratory rate, and asthma diagnosis before enrollment. Predictors of atopic disorders included allergic rhinitis before enrollment, a relative with asthma, and the plasma biomarkers IL-5, IL-16, and IL-18. Predictors of chronic asthma therapy use included asthma diagnosis before enrollment and geographic region (Europe and Africa). Only 42% of patients with asthma (primary definition) also met the asthma definition by physician diagnosis and chronic asthma therapy use.

CONCLUSION

Among children with early RSV bronchiolitis, hereditary factors (i.e., having a relative with asthma) and RSV bronchiolitis severity were predictors of asthma and atopic disorders at 6 years of age. Of interest, there was poor agreement among the asthma definitions evaluated. Pediatr Pulmonol. 2016;51:1382-1392. © 2016 Wiley Periodicals, Inc.

Strategies targeting the IL-4/IL-13 axes in disease

IL-4 and IL-13 are pleiotropic Th2 cytokines produced by a wide variety of different cell types and responsible for a broad range of biology and functions. Physiologically, Th2 cytokines are known to mediate host defense against parasites but they can also trigger disease if their activities are dysregulated. In this review we discuss the rationale for targeting the IL-4/IL-13 axes in asthma, atopic dermatitis, allergic rhinitis, COPD, cancer, inflammatory bowel disease, autoimmune disease and fibrotic disease as well as evaluating the associated clinical data derived from blocking IL-4, IL-13 or IL-4 and IL-13 together.

Genes associated with RSV lower respiratory tract infection and asthma: the application of genetic epidemiological methods to understand causality

Infants with respiratory syncytial virus (RSV) lower respiratory tract infections (LRIs) are at increased risk for childhood asthma. The objectives of this article are to review the genes associated with both RSV LRI and asthma, review analytic approaches to assessing shared genetic risk and propose a future perspective on how these approaches can help us to understand the role of infant RSV infection as both an important risk factor for asthma and marker of shared genetic etiology between the two conditions. The review of shared genes and thus pathways associated with severity of response to RSV infection and asthma risk can help us to understand mechanisms of disease and ultimately propose new and novel targets for primary prevention of both diseases.

Impact of genetic polymorphisms on paediatric atopic dermatitis

In order to investigate whether polymorphisms of genes encoding some factors of innate and adaptive immunity play a role in the development of, or protection against atopic dermatitis (AD) and condition its severity, we genotyped 33 candidate genes and 47 single nucleotide polymorphisms (SNPs) using Custom TaqMan Array Microfluidic Cards and an ABI 7900HT analyser (Applied Biosystems, Foster City, CA, USA). The study involved 104 children with AD (29 with mild-to-moderate and 75 with severe disease; 42 girls; mean age ± SD, 5.8 ± 3.3 years) and 119 healthy controls (49 girls; mean age, 4.8 ± 3.0 years). IL10-rs1800872T, TG and MBL2-rs500737AG were all significantly more frequent among the children with AD ( P = 0.015, P = 0.004 and P = 0.030), whereas IL10-rs1800896C and TC were more frequent in those without AD ( P = 0.028 and P = 0.032). The VEGFA-rs2146326A and CTLA4-rs3087243AG SNPs were significantly more frequent in the children with mild/moderate AD than in those with severe AD ( P = 0.048 and P = 0.036). IL10-rs1800872T and TG were significantly more frequent in the children with AD and other allergic diseases than in the controls ( P = 0.014 and P = 0.007), whereas IL10-rs1800896TC and C were more frequent in the controls than in the children with AD and other allergic diseases ( P = 0.0055 and P = 0.0034). These findings show that some of the polymorphisms involved in the immune response are also involved in some aspects of the development and course of AD and, although not conclusive, support the immunological hypothesis of the origin of the inflammatory lesions.

Objectives, design and enrollment results from the Infant Susceptibility to Pulmonary Infections and Asthma Following RSV Exposure Study (INSPIRE)

Background

Respiratory syncytial virus (RSV) lower respiratory tract infection (LRI) during infancy has been consistently associated with an increased risk of childhood asthma. In addition, evidence supports that this relationship is causal. However, the mechanisms through which RSV contributes to asthma development are not understood. The INSPIRE (Infant Susceptibility to Pulmonary Infections and Asthma Following RSV Exposure) study objectives are to: 1) characterize the host phenotypic response to RSV infection in infancy and the risk of recurrent wheeze and asthma, 2) identify the immune response and lung injury patterns of RSV infection that are associated with the development of early childhood wheezing illness and asthma, and 3) determine the contribution of specific RSV strains to early childhood wheezing and asthma development. This article describes the INSPIRE study, including study aims, design, recruitment results, and enrolled population characteristics.

Methods/design

The cohort is a population based longitudinal birth cohort of term healthy infants enrolled during the first months of life over a two year period. Respiratory infection surveillance was conducted from November to March of the first year of life, through surveys administered every two weeks. In-person illness visits were conducted if infants met pre-specified criteria for a respiratory illness visit. Infants will be followed annually to ages 3-4 years for assessment of the primary endpoint: wheezing illness. Nasal, urine, stool and blood samples were collected at various time points throughout the study for measurements of host and viral factors that predict wheezing illness. Nested case-control studies will additionally be used to address other primary and secondary hypotheses.

Discussion

In the INSPIRE study, 1952 infants (48% female) were enrolled during the two enrollment years and follow-up will continue through 2016. The mean age of enrollment was 60 days. During winter viral season, more than 14,000 surveillance surveys were carried out resulting in 2,103 respiratory illness visits on 1189 infants. First year follow-up has been completed on over 95% percent of participants from the first year of enrollment.

With ongoing follow-up for wheezing and childhood asthma outcomes, the INSPIRE study will advance our understanding of the complex causal relationship between RSV infection and early childhood wheezing and asthma.

Genetic polymorphisms and risk of recurrent wheezing in pediatric age

Background

Wheezing during early life is a very common disorder, but the reasons underlying the different wheezing phenotypes are still unclear. The aims of this study were to analyse the potential correlations between the risk of developing recurrent wheezing and the presence of specific polymorphisms of some genes regulating immune system function, and to study the relative importance of the associations of different viruses and genetic polymorphisms in causing recurrent episodes.

Methods

The study involved 119 otherwise healthy infants admitted to hospital for a first episode of wheezing (74 of whom subsequently experienced recurrent episodes) and 119 age- and sex-matched subjects without any history of respiratory problem randomly selected from those attending our outpatient clinic during the study period. All of the study subjects were followed up for two years, and 47 single nucleotide polymorphisms (SNPs) in 33 candidate genes were genotyped on whole blood using an ABI PRISM 7900 HT Fast Real-time instrument.

Results

IL8-rs4073AT, VEGFA-rs833058CT, MBL2-rs1800450CT and IKBKB-rs3747811AT were associated with a significantly increased risk of developing wheezing (p = 0.02, p = 0.03, p = 0.05 and p = 0.0018), whereas CTLA4-rs3087243AG and NFKBIB-rs3136641TT were associated with a significantly reduced risk (p = 0.05 and p = 0.04). IL8-rs4073AT, VEGFA-rs2146323AA and NFKBIA-rs2233419AG were associated with a significantly increased risk of developing recurrent wheezing (p = 0.04, p = 0.04 and p = 0.03), whereas TLR3-rs3775291TC was associated with a significantly reduced risk (p = 0.03). Interestingly, the study of gene-environment interactions showed that rhinovirus was significantly associated with recurrent wheezing in the presence of IL4Ra-rs1801275GG and G (odds ratio [OR] 6.03, 95% confidence interval [CI]: 1.21-30.10, p = 0.03) and MAP3K1-rs702689AA (OR 4.09, 95% CI: 1.14-14.61, p = 0.03).

Conclusions

This study shows a clear relationship between the risk of wheezing and polymorphisms of some genes involved in the immune response. Although further studies are needed to confirm the results, these findings may be useful for the early identification of children at the highest risk of developing recurrent episodes and possibly subsequent asthma.

Immunity to RSV in Early-Life

Respiratory Syncytial Virus (RSV) is the commonest cause of severe respiratory infection in infants, leading to over 3 million hospitalizations and around 66,000 deaths worldwide each year. RSV bronchiolitis predominantly strikes apparently healthy infants, with age as the principal risk factor for severe disease. The differences in the immune response to RSV in the very young are likely to be key to determining the clinical outcome of this common infection. Remarkable age-related differences in innate cytokine responses follow recognition of RSV by numerous pattern recognition receptors, and the importance of this early response is supported by polymorphisms in many early innate genes, which associate with bronchiolitis. In the absence of strong, Th1 polarizing signals, infants develop T cell responses that can be biased away from protective Th1 and cytotoxic T cell immunity toward dysregulated, Th2 and Th17 polarization. This may contribute not only to the initial inflammation in bronchiolitis, but also to the long-term increased risk of developing wheeze and asthma later in life. An early-life vaccine for RSV will need to overcome the difficulties of generating a protective response in infants, and the proven risks associated with generating an inappropriate response. Infantile T follicular helper and B cell responses are immature, but maternal antibodies can afford some protection. Thus, maternal vaccination is a promising alternative approach. However, even in adults adaptive immunity following natural infection is poorly protective, allowing re-infection even with the same strain of RSV. This gives us few clues as to how effective vaccination could be achieved. Challenges remain in understanding how respiratory immunity matures with age, and the external factors influencing its development. Determining why some infants develop bronchiolitis should lead to new therapies to lessen the clinical impact of RSV and aid the rational design of protective vaccines.

Genetic predisposition of RSV infection-related respiratory morbidity in preterm infants

The aim of this study was to assess whether prematurely born infants have a genetic predisposition to respiratory syncytial virus (RSV) infection-related respiratory morbidity. One hundred and forty-six infants born at less than 36 weeks of gestation were prospectively followed. Nasopharygeal aspirates were obtained on every occasion the infants had a lower respiratory tract infection (LRTI) regardless of need for admission. DNA was tested for 11 single-nucleotide polymorphisms (SNPs). Chronic respiratory morbidity was assessed using respiratory health-related questionnaires, parent-completed diary cards at a corrected age of 1 year and review of hospital notes. Lung function was measured at a post menstrual age (PMA) of 36 weeks and corrected age of 1 year. A SNP in ADAM33 was associated with an increased risk of developing RSV LRTIs, but not with significant differences in 36-week PMA lung function results. SNPs in several genes were associated with increased chronic respiratory morbidity (interleukin 10 (IL10), nitric oxide synthase 2A (NOS2A), surfactant protein C (SFTPC), matrix metalloproteinase 16 (MMP16) and vitamin D receptor (VDR)) and reduced lung function at 1 year (MMP16, NOS2A, SFTPC and VDR) in infants who had had RSV LRTIs.

CONCLUSIONS

Our results suggest that prematurely born infants may have a genetic predisposition to RSV LRTIs and subsequent respiratory morbidity which is independent of premorbid lung function.

The relationship between respiratory syncytial virus and asthma

Asthma is a chronic inflammatory disease of the lung that is a leading cause of morbidity and mortality in children worldwide. Most infants who experience wheezing episodes also exhibit evidence of an ongoing respiratory viral infection. Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infection in children and is a common cause of wheezing in infants and young children. In the past several decades, a number of studies have demonstrated a relationship between infants with severe RSV infections and the subsequent development of asthma later during childhood. This review provides an overview of data that suggests a severe RSV infection early in childhood is linked to development of asthma later in life. In addition, the current and potential future use of various animal models to gain additional insight into the relationship between RSV and asthma is discussed.

Respiratory syncytial virus infection and recurrent wheezing in Chilean infants: a genetic background?

Respiratory syncytial virus (RSV) infection has been associated to recurrent wheezing, but pathogenic mechanisms are unclear. Interleukin-4/Interleukin-13 (IL-4/IL-13) pathway is involved in both conditions. A common host genetic susceptibility may exist in patients whom RSV will trigger severe illness and those who develop recurrent wheezing.

OBJECTIVE

To assess, by a candidate-gene approach, whether genetic polymorphisms in IL-4/IL-13 pathway are associated with RSV infection severity and its outcome in Chilean children. A cohort of 118 RSV-infected infants was analyzed and followed for one year. Severity of acute infection and later recurrent wheezing were characterized. Alleles and genotypes frequencies were determined for two SNP in each of the genes IL-4, IL-13 and IL-4Rα. Association tests and interaction analyses were performed. Enrollment included 60 moderate and 58 severe cases. Two SNP were found associated to severity during acute infection in IL-4Rα gene (Gln551Arg, Ile50Val). The follow up was completed in 71% of patients (84/118). Later recurrent wheezing was 54% in severe group, versus 31% in moderate cases (p=0.035). In relation to outcome, allele Ile50 in IL-4Rα was more frequent in patients with moderate disease and no wheezing outcome. A common protector genotype is proposed for Chilean children: IL-4Rα Ile/Ile.

CONCLUSION

Genetic variations in the host are associated to infection severity and outcome. A common genetic background might be influencing both pathologies.

Interleukin-13 signaling and its role in asthma

Asthma affects nearly 300 million people worldwide. The majority respond to inhaled corticosteroid treatment with or without beta-adrenergic agonists. However, a subset of 5 to 10% with severe asthma do not respond optimally to these medications. Different phenotypes of asthma may explain why current therapies show limited benefits in subgroups of patients. Interleukin-13 is implicated as a central regulator in IgE synthesis, mucus hypersecretion, airway hyperresponsiveness, and fibrosis. Promising research suggests that the interleukin-13 pathway may be an important target in the treatment of the different asthma phenotypes.

Elevated risk of asthma after hospitalization for respiratory syncytial virus infection in infancy

Severe respiratory syncytial virus (RSV) infection in infancy is associated with substantial morbidity worldwide; whether it is a risk factor for childhood asthma is contentious. A systematic review of 28 articles was conducted, summarizing estimates of asthma risk after RSV hospitalization during infancy. Prevalence estimates of asthma, among those hospitalized for RSV in infancy, were from 8% to 63%, 10% to 92%, and 37%, at ages <5, 5 to 11, and ≥ 12 years, respectively. These rates were higher than those among non-hospitalized comparisons. The attributable risk of asthma due to RSV ranged from 13% to 22% and from 11% to 27% among children aged ≤ 5 and aged 5 to 11, respectively, and was 32% among children ≥ 12 years of age. Overall, 59% of asthma prevalence estimates from those previously hospitalized for RSV exceeded 20%, compared to only 6% of non-hospitalized comparison estimates. Despite variability in asthma prevalence estimates after RSV-related hospitalization, available data suggest a link between severe RSV infection in infancy and childhood asthma.

Respiratory syncytial virus infection and chronic respiratory morbidity - is there a functional or genetic predisposition?

A systematic literature review has been undertaken. Respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) in infancy is associated with chronic respiratory morbidity. Premorbid abnormal lung function may predispose to RVS LRTI in prematurely born infants.

CONCLUSION

  Single-nucleotide polymorphisms in genes coding for IL-8, IL-19, IL-20, IL-13 mannose-binding lectin, IFNG and a RANTES polymorphism have been associated with subsequent wheeze following RSV LRTI in term-born infants.

IL10 family member genes IL19 and IL20 are associated with recurrent wheeze after respiratory syncytial virus bronchiolitis

Mechanisms underlying the increased risk of recurrent wheeze after respiratory syncytial virus lower respiratory tract infection (RSV LRTI) are unclear. Specifically, information about genetic determinants of recurrent wheeze after RSV LRTI is limited. We performed a candidate gene association study to identify genetic determinants of recurrent wheeze after RSV LRTI. We investigated 346 single nucleotide polymorphisms (SNPs) in 220 candidate genes in 166 Dutch infants hospitalized for RSV LRTI. Logistic regression analysis was used to study associations between genotypes and haplotypes and recurrent wheeze after RSV LRTI. We found associations with recurrent wheeze for SNPs in IL19, IL20, MUC5AC, TNFRSF1B, C3, CTLA4, CXCL9, IL4R, and IL7 genes. Haplotype analysis of the combined IL19/IL20 genotyped polymorphisms demonstrated an inverse association between the TGG haplotype and recurrent wheeze after RSV LRTI. IL19 and IL20 genes were notably associated with recurrent wheeze in infants without asthmatic parents. The association of IL20 SNP rs2981573 with recurrent wheeze was confirmed in a healthy birth cohort. We concluded that genetic variation in adaptive immunity genes and particularly in IL19/IL20 genes associates with the development of recurrent wheeze after RSV LRTI, suggesting a role for these IL10 family members in the etiology of airway disease during infancy.

Local interleukin-10 production during respiratory syncytial virus bronchiolitis is associated with post-bronchiolitis wheeze

Background

Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants. Following RSV bronchiolitis, 50% of children develop post-bronchiolitis wheeze (PBW). Animal studies have suggested that interleukin (IL)-10 plays a critical role in the pathogenesis of RSV bronchiolitis and subsequent airway hyperresponsiveness. Previously, we showed that ex vivo monocyte IL-10 production is a predictor of PBW. Additionally, heterozygosity of the single-nucleotide polymorphism (SNP) rs1800872 in the IL10 promoter region was associated with protection against RSV bronchiolitis.

Methods

This study aimed to determine the in vivo role of IL-10 in RSV pathogenesis and recurrent wheeze in a new cohort of 235 infants hospitalized for RSV bronchiolitis. IL-10 levels in nasopharyngeal aspirates (NPAs) were measured at the time of hospitalization and the IL10 SNP rs1800872 genotype was determined. Follow-up data were available for 185 children (79%).

Results

Local IL-10 levels during RSV infection turned out to be higher in infants that later developed physician diagnosed PBW as compared to infants without PBW in the first year after RSV infection (958 vs 692 pg/ml, p = 0.02). The IL10 promoter SNP rs1800872 was not associated with IL-10 concentration in NPAs.

Conclusion

The relationship between high local IL-10 levels during the initial RSV infection and physician diagnosed PBW provides further evidence of the importance of the IL-10 response during RSV bronchiolitis.

Respiratory syncytial virus interferon antagonist NS1 protein suppresses and skews the human T lymphocyte response

We recently demonstrated that the respiratory syncytial virus (RSV) NS1 protein, an antagonist of host type I interferon (IFN-I) production and signaling, has a suppressive effect on the maturation of human dendritic cells (DC) that was only partly dependent on released IFN-I. Here we investigated whether NS1 affects the ability of DC to activate CD8+ and CD4+ T cells. Human DC were infected with RSV deletion mutants lacking the NS1 and/or NS2 genes and assayed for the ability to activate autologous T cells in vitro, which were analyzed by multi-color flow cytometry. Deletion of the NS1, but not NS2, protein resulted in three major effects: (i) an increased activation and proliferation of CD8+ T cells that express CD103, a tissue homing integrin that directs CD8+ T cells to mucosal epithelial cells of the respiratory tract and triggers cytolytic activity; (ii) an increased activation and proliferation of Th17 cells, which have recently been shown to have anti-viral effects and also indirectly attract neutrophils; and (iii) decreased activation of IL-4-producing CD4+ T cells--which are associated with enhanced RSV disease--and reduced proliferation of total CD4+ T cells. Except for total CD4+ T cell proliferation, none of the T cell effects appeared to be due to increased IFN-I signaling. In the infected DC, deletion of the NS1 and NS2 genes strongly up-regulated the expression of cytokines and other molecules involved in DC maturation. This was partly IFN-I-independent, and thus might account for the T cell effects. Taken together, these data demonstrate that the NS1 protein suppresses proliferation and activation of two of the protective cell populations (CD103+ CD8+ T cells and Th17 cells), and promotes proliferation and activation of Th2 cells that can enhance RSV disease.

The role of cytokines and chemokines in severe respiratory syncytial virus infection and subsequent asthma

Respiratory syncytial virus (RSV) is the primary cause of serious lower respiratory tract illness in infants and young children worldwide. The mechanism is largely unknown. RSV stimulates airway epithelial cells and resident leukocytes to release cytokines. Cytokines and chemokines involved in host response to RSV infection are thought to play a central role in the pathogenesis. In addition, RSV infection early in life has been associated with the development of asthma in later childhood. It is likely that the persistence of cytokines and chemokines in fully recovered patients with RSV in the long term can provide a substratum for the development of subsequent asthma. This review describes the genetic factors in cytokines and chemokines associated with severity of RSV disease, cytokines and chemokines synthesis in RSV infection, and the role of these innate immune components in RSV-associated asthma.

Inefficient lymph node sensitization during respiratory viral infection promotes IL-17-mediated lung pathology

Development of bronchus-associated lymphoid tissue has been suggested to enhance local antiviral immune responses; however, ectopic lymph node formation often corresponds to chronic inflammatory diseases. These studies investigated the role of ectopic pulmonary lymph nodes upon respiratory syncytial virus (RSV) infection using CCR7-deficient mice, which develop bronchus-associated lymphoid tissue early in life. CCR7(-/-) mice exhibited impaired secondary lymph node formation, enhanced effector T cell responses and pathogenic mucus production in the lung after RSV infection. IL-17 production from CD4 T cells in CCR7(-/-) mice was most remarkably enhanced. Wild-type animals reconstituted with CCR7(-/-) bone marrow recapitulated the pathogenic lung phenotype in CCR7(-/-) mice, whereas CCR7(-/-) animals reconstituted with wild-type bone marrow had normal lymph node development, diminished IL-17 production and reduced lung pathology. Mixed bone marrow chimeras revealed an alteration of immune responses only in CCR7(-/-) T cells, suggesting that impaired trafficking promotes local effector cell generation. Lymphotoxin-α-deficient mice infected with RSV were used to further examine locally induced immune responses and demonstrated increased mucus production and amplified cytokine responses in the lung, especially IL-17. Neutralization of IL-17 in CCR7(-/-) or in lymphotoxin-α-deficient animals specifically inhibited mucus hypersecretion and reduced IL-13. Thus, immune cell trafficking to secondary lymph nodes is necessary for appropriate cytokine responses to RSV as well as modulation of the local environment.

Respiratory viral infections in infants: causes, clinical symptoms, virology, and immunology

In global terms, respiratory viral infection is a major cause of morbidity and mortality. Infancy, in particular, is a time of increased disease susceptibility and severity. Early-life viral infection causes acute illness and can be associated with the development of wheezing and asthma in later life. The most commonly detected viruses are respiratory syncytial virus (RSV), rhinovirus (RV), and influenza virus. In this review we explore the complete picture from epidemiology and virology to clinical impact and immunology. Three striking aspects emerge. The first is the degree of similarity: although the infecting viruses are all different, the clinical outcome, viral evasion strategies, immune response, and long-term sequelae share many common features. The second is the interplay between the infant immune system and viral infection: the immaturity of the infant immune system alters the outcome of viral infection, but at the same time, viral infection shapes the development of the infant immune system and its future responses. Finally, both the virus and the immune response contribute to damage to the lungs and subsequent disease, and therefore, any prevention or treatment needs to address both of these factors.

High incidence of recurrent wheeze in children with down syndrome with and without previous respiratory syncytial virus lower respiratory tract infection

BACKGROUND

Respiratory syncytial virus (RSV)-induced lower respiratory tract infection (LRTI) is associated with the subsequent development of recurrent wheeze. In a recent study, we found a high incidence (9.9%) of hospitalization for RSV-induced LRTI among children with Down syndrome (DS), indicating DS as a new risk factor for RSV-induced LRTI. In the current study we aimed to investigate the development of long-term airway morbidity in children with DS after hospitalization for RSV-induced LRTI.

METHODS

A combined retrospective cohort and prospective birth cohort of children with DS with a history of hospitalization for RSV-induced LRTI was studied (n = 53). Three control populations were included: children with DS without hospitalization for RSV-induced LRTI (n = 110), children without DS but with hospitalization for RSV-induced LRTI (n = 48), and healthy siblings of the previous 3 groups mentioned (n = 49). The primary outcome was physician-diagnosed wheeze up to 2 years of age.

RESULTS

The incidence of physician-diagnosed recurrent wheeze in children with DS with a history of hospitalization for RSV-induced LRTI was 36%. Unexpectedly, up to 30% of children with DS without a history of RSV-induced LRTI had physician-diagnosed recurrent wheeze (no significant difference). In children without DS physician-diagnosed wheeze was found more frequently in children hospitalized for RSV-induced LRTI than healthy controls (31% vs. 8%, P = 0.004).

CONCLUSIONS

In this combined retrospective/prospective cohort study RSV-induced LRTI did not significantly contribute to the risk of recurrent wheeze in children with DS. An unexpected finding was that recurrent wheeze was very common among children with DS.

Systemic T-helper and T-regulatory cell type cytokine responses in rhinovirus vs. respiratory syncytial virus induced early wheezing: an observational study

BACKGROUND

Rhinovirus (RV) associated early wheezing has been recognized as an independent risk factor for asthma. The risk is more important than that associated with respiratory syncytial virus (RSV) disease. No comparative data are available on the immune responses of these diseases.

OBJECTIVE

To compare T-helper1 (Th1), Th2 and T-regulatory (Treg) cell type cytokine responses between RV and RSV induced early wheezing.

METHODS

Systemic Th1-type (interferon [IFN] -gamma, interleukin [IL] -2, IL-12), Th2-type (IL-4, IL-5, IL-13) and Treg-type (IL-10) cytokine responses were studied from acute and convalescence phase serum samples of sole RV (n = 23) and RSV affected hospitalized wheezing children (n = 27). The pre-defined inclusion criteria were age of 3-35 months and first or second wheezing episode. Analysis was adjusted for baseline differences. Asymptomatic children with comparable demographics (n = 11) served as controls for RV-group.

RESULTS

RV-group was older and had more atopic characteristics than RSV-group. At acute phase, RV-group had higher (fold change) IL-13 (39-fold), IL-12 (7.5-fold), IFN-gamma (6.0-fold) and IL-5 (2.8-fold) concentrations than RSV-group and higher IFN-gamma (27-fold), IL-2 (8.9-fold), IL-5 (5.6-fold) and IL-10 (2.6-fold) than the controls. 2-3 weeks later, RV-group had higher IFN-gamma (>100-fold), IL-13 (33-fold) and IL-10 (6.5-fold) concentrations than RSV-group and higher IFN-gamma (15-fold) and IL-2 (9.4-fold) than the controls. IL-10 levels were higher in acute phase compared to convalescence phase in both infections (p < 0.05 for all).

CONCLUSION

Our results support a hypothesis that RV is likely to trigger wheezing mainly in children with a predisposition. IL-10 may have important regulatory function in acute viral wheeze.

The year in review

Over the last year there have been more studies determining predisposition to severe bronchiolitis and its consequences. Studies have highlighted various single-nucleotide polymorphisms (SNPs) to be significantly associated with respiratory syncytial virus (RSV) hospitalisation, and a candidate gene approach demonstrated that innate immune gene SNPs had the strongest association with bronchiolitis. The impact of 'other' viruses (RSV, influenza, adenovirus, parainfluenza, rhinovirus, human metapneumovirus [hMPV], coronavirus, boca-virus, enterovirus, paraechovirus) has been investigated. In one series only children with RSV infection experienced recurrent wheezing and in another only RSV infection was associated with respiratory complications (hypoxia correlated with prolonged hospitalisation). Others have examined the long-term outcome of viral infection in infancy. The above studies and others published in the last year will be discussed.

Immune and genetic aspects of asthma, allergy and parasitic worm infections: evolutionary links

There are important parallels in the immunobiology of allergy and asthma, and of the human host's response to parasitic worms. Th-2 immune actions with 'weep and sweep' mucosal biology are common to both - pathological in the first and protective in the second. Common up-regulating genetic variants of Th-2 immunity, notably in IL13 and STAT6, predict increased risk of asthma and allergy, but diminished intensity of infection by Ascaris and Schistosoma. Endemic exposures of humans to parasitic worms may have been one evolutionary force selecting for genetic variants that promote asthma and allergy.

Recognizing the importance of respiratory syncytial virus in chronic obstructive pulmonary disease

Acute exacerbations of chronic obstructive pulmonary disease (COPD) are responsible for a large proportion of the health care dollar expenditure, morbidity, and mortality related to COPD. Respiratory infections are the most common cause of acute exacerbations, but recent evidence indicates that the importance of respiratory syncytial virus (RSV) infection in COPD is under-appreciated. Improved detection of RSV using techniques based on the polymerase chain reaction accounts for much of the increased recognition of the importance of this virus in COPD patients. Furthermore, COPD patients may be more susceptible to RSV infection, possibly due to RSV-or immune response-induced pulmonary effects that are altered by age, environmental exposures, genetics, COPD itself, or a combination of these. However, although RSV infection occurs throughout life, viral and host factors that place COPD patients at increased risk are unclear. The complexities of RSV effects in COPD present opportunities for research with the goal of developing approaches to selectively modify damaging viral effects (e.g., altered airway function), while retaining beneficial immunity (e.g., clearance of virus) in COPD patients. This review explores the role RSV plays in acute exacerbations of COPD, the potential for RSV disease in chronic stable COPD, and newer concepts in RSV diagnosis, epidemiology, and host defense.

The effect of high dose inhaled corticosteroids on wheeze in infants after respiratory syncytial virus infection: randomised double blind placebo controlled trial

OBJECTIVE

To determine whether early initiated anti-inflammatory therapy with prolonged high dose inhaled glucocorticoids influences the occurrence and severity of recurrent wheeze after respiratory syncytial virus related lower respiratory tract infections.

DESIGN

Randomised double blind placebo controlled trial.

SETTING

Paediatric departments of 19 Dutch clinical centres.

PARTICIPANTS

243 previously healthy infants (126 boys, 117 girls) aged less than 13 months and admitted to hospital with respiratory syncytial virus infection.

INTERVENTIONS

200 mug extra fine hydrofluoroalkane (HFA) beclometasone dipropionate twice daily or matched placebo administered by a pressurised metered dose inhaler and a spacer during the first three months after hospital admission.

MAIN OUTCOME MEASURE

The primary outcome was the number of days with wheeze in the year after the three month intervention period.

RESULTS

Of the 243 eligible infants, 119 were randomised to receive beclometasone and 124 to receive placebo. No significant difference was found in the number of days with wheeze between the two groups (total days, 1761/33 568 in the beclometasone group v 2301/36 556 in the placebo group, P=0.31) and the proportion of infants with wheeze did not differ between the groups (61% in the beclometasone group v 62% in the placebo group, P=0.90). In the predefined subgroup of infants who did not need mechanical ventilation (n=221), beclometasone reduced the number of days with wheeze by 32% (relative reduction in total days, 1315/30 405 in the beclometasone group v 2120/33 149 in the placebo group, P=0.046). This reduction was most pronounced during the first six months of the follow-up year after intervention. The proportion of infants with wheeze did not differ between the groups (59% in the beclometasone group v 60% in the placebo group, P=0.89).

CONCLUSIONS

Early initiated high dose extra fine HFA beclometasone to infants during the first three months after hospital admission for respiratory syncytial virus infection has no major effect on recurrent wheeze. The general use of such treatment during lower respiratory tract infection with respiratory syncytial virus should not be advocated.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN12352714.

Novel concepts in virally induced asthma

Viruses are the predominant infectious cause of asthma exacerbations in the developed world. In addition, recent evidence strongly suggests that viral infections may also have a causal role in the development of childhood asthma. In this article, we will briefly describe the general perception of how the link between infections and asthma has changed over the last century, and then focus on very recent developments that have provided new insights into the contribution of viruses to asthma pathogenesis. Highlighted areas include the contribution of severe early life viral infections to asthma inception, genetic determinants of severe viral infections in infancy, the differences in innate and adaptive immune system cytokine responses to viral infection between asthmatic and nonasthmatic subjects, and a potential vaccine strategy to prevent severe early life virally-induced illness.

Respiratory syncytial virus persistence: evidence in the mouse model

Several studies have described a clear association between respiratory syncytial virus (RSV) lower respiratory tract infection in infancy and the subsequent development of persistent wheezing in children. Using the mouse model we demonstrated that RSV induces long-term airway disease characterized by chronic airway inflammation and airway hyperreactivity (AHR). The RSV murine model offers great advantages to study the immunopathogenesis of RSV-induced long-term airway disease. Mice can be challenged with aerosolized methylcholine to determine the presence of AHR. We can apply the reverse transcription-polymerase chain reaction assay (RT-PCR) to detect RSV RNA in the respiratory tract and we can perform lung gene expression analysis to further characterize the chronic changes induced by RSV infection. Compared with sham-inoculated controls, RSV-infected mice developed chronic airway disease characterized by AHR and persistent airway inflammation. Forty-two days after RSV infection, a time point when RSV could no longer be isolated, RT-PCR demonstrated, quite unexpectedly, the presence of RSV RNA in the lower respiratory tract of mice. The presence of genomic RNA persisted for months after inoculation. Furthermore, preliminary studies also demonstrated that on day 42 there were a number of genes differentially expressed in RSV-infected mice compared with controls. RSV-infected mice with persistent AHR exhibited presence of abnormal chronic inflammatory changes, altered gene expression profiles, and persistence of RSV RNA, which may contribute to long-term airway disease induced by RSV. Future studies are needed to define the significance of persistent RSV RNA in the mouse model, and its potential role in the pathogenesis of RSV-induced persistent wheezing in children.

Lung dendritic cells in respiratory syncytial virus bronchiolitis

Respiratory syncytial virus (RSV) bronchiolitis, an important respiratory disease in infancy, is thought to be caused by severe inflammation of the small peripheral airways and has been associated with the development of recurrent wheeze, childhood asthma, and early allergen sensitization. Both innate and adaptive immune responses are thought to contribute to the development of bronchiolitis in RSV infection. If vaccination and specific therapy for bronchiolitis, which are currently lacking, are to be developed, detailed understanding of the immune responses involved is essential. Dendritic cells (DCs) are uniquely positioned to link innate to adaptive immune responses and may therefore be central to the development of bronchiolitis. In murine models, plasmacytoid DCs are recruited to the lung early in infection, presumably from the bone marrow, whereas lung myeloid DCs increase in numbers later in infection, with the advent of inflammation, and are derived from local lung precursors. Plasmacytoid DCs limit viral replication and they may have additional regulatory properties controlling pulmonary inflammation and lung function changes during bronchiolitis. In contrast, lung myeloid DCs are likely to contribute to inflammation during and after bronchiolitis and they may also facilitate sensitization to allergens. Myeloid DCs mature upon RSV infection and become potent activators of naive T cells, whereas in healthy lungs they are mostly immature and unable to stimulate naive T cells. As central players in the induction of adaptive immune responses, lung DCs need to be considered as targets for novel therapies and vaccination approaches.

Regulation of immunity to respiratory syncytial virus by dendritic cells, toll-like receptors, and notch

The activation and maintenance of pulmonary viral disease is regulated at multiple levels and determined by the early innate response to the pathogenic stimuli. Subsequent activation events that rely directly and indirectly on the virus itself can alter the development and severity of the ensuing immunopathologic responses. In the present review we outline several interconnected mechanisms that rely on the early recognition of viral nucleic acid for the most appropriate anti-viral immune responses, including TLRs and Notch activation in DCs and T cells. Deviation or persistence of the immune response to respiratory viruses may impact significantly on the severity of the responses. While these mechanisms are likely similar in most respiratory viral infections, this review will focus on findings with respiratory syncytial virus (RSV) infections.

New perspectives on mechanisms underlying chronic allergic inflammation and asthma in 2007

This review summarizes selected articles appearing from January to December 2007 in the Journal of Allergy and Clinical Immunology. Articles were chosen that related to advances in mechanisms of chronic allergic inflammation and asthma, including those describing gene association studies, mast cells, IgE, eosinophils, cytokines, the inception of allergy, airway remodeling, preclinical therapeutic targets, and virally induced asthma.

Advances in asthma and allergy genetics in 2007

This review discusses the main advances in the genetics of asthma and allergy published in the Journal in 2007. The association studies discussed herein addressed 3 main topics: the effect of the environment and gene-environment interactions on asthma/allergy susceptibility, the contribution of T(H)2 immunity gene variants to allergic inflammation, and the role of filaggrin mutations in atopic dermatitis and associated phenotypes. Other articles revealed novel, potentially important candidate genes or confirmed known ones. Collectively, the works published in 2007 reiterate that allergy and asthma are typical complex diseases; that is, they are disorders in which intricate interactions among environmental and genetic factors modify disease susceptibility by altering the fundamental structural and functional properties of target organs at critical developmental windows.

Polymorphisms in IL13, total IgE, eosinophilia, and asthma exacerbations in childhood

BACKGROUND

It is unclear whether single nucleotide polymorphisms (SNPs) in the gene for IL-13 (IL13) influence asthma severity and/or asthma morbidity.

OBJECTIVES

To examine the relation between IL13 SNPs and asthma-related phenotypes in 2 independent populations.

METHODS

We used family-based methods to test for association between SNPs in IL13 and asthma-related phenotypes in Costa Rican children with asthma. We attempted to reproduce significant findings in white (non-Hispanic) children with asthma in the Childhood Asthma Management Program (CAMP).

RESULTS

In Costa Rica and in CAMP, the A allele (Gln) of IL13 coding SNP (rs20541) was significantly associated with increased eosinophil count (P < .011 in both studies) and increased serum total IgE (P < .054 in both studies). The T allele of IL13 promoter SNP (rs1800925) was inversely associated with asthma exacerbations in Costa Rica (P = .069). Although this SNP (rs1800925) was not associated with asthma exacerbations among all white children in CAMP, it was associated with increased risk of asthma exacerbations among children on inhaled corticosteroids (P = .02).

CONCLUSION

Polymorphisms in IL13 were significantly associated with serum total IgE and eosinophil count in 2 populations. IL13 polymorphisms may also be associated with asthma exacerbations, and this effect may be dependent on medication use. Our study is the first to report a potential negative interaction between a genetic polymorphism and response to inhaled corticosteroids.

CLINICAL IMPLICATIONS

Polymorphisms in IL13 are associated with serum total IgE and eosinophil count and may be associated with asthma exacerbations.