Effect of experimental rhinovirus 16 colds on airway hyperresponsiveness to histamine and interleukin-8 in nasal lavage in asthmatic subjects in vivo

Syk is downstream of intercellular adhesion molecule-1 and mediates human rhinovirus activation of p38 MAPK in airway epithelial cells

The airway epithelium is the primary target of inhaled pathogens such as human rhinovirus (HRV). Airway epithelial cells express ICAM-1, the major receptor for HRV. HRV binding to ICAM-1 mediates not only viral entry and replication but also a signaling cascade that leads to enhanced inflammatory mediator production. The specific signaling molecules and pathways activated by HRV-ICAM-1 interactions are not well characterized, although studies in human airway epithelia implicate a role for the p38 MAPK in HRV-induced cytokine production. In the current study, we report that Syk, an important immunoregulatory protein tyrosine kinase, is highly expressed by primary and cultured human airway epithelial cells and is activated in response to infection with HRV16. Biochemical studies revealed that ICAM-1 engagement by HRV and cross-linking Abs enhanced the coassociation of Syk with ICAM-1 and ezrin, a cytoskeletal linker protein. In polarized airway epithelial cells, Syk is diffusely distributed in the cytosol under basal conditions but, following engagement of ICAM-1 by cross-linking Abs, is recruited to the plasma membrane. The enhanced Syk-ICAM-1 association following HRV exposure is accompanied by Syk phosphorylation. ICAM-1 engagement by HRV and cross-linking Abs also induced phosphorylation of p38 in a Syk-dependent manner, and conversely, knockdown of Syk by short interfering (si)RNA substantially diminished p38 activation and IL-8 gene expression. Taken together, these observations identify Syk as an important mediator of the airway epithelial cell inflammatory response by modulating p38 phosphorylation and IL-8 gene expression following ICAM-1 engagement by HRV.

Antimicrobial strategies: an option to treat allergy?

Respiratory infections by bacteria and viruses often trigger symptoms of asthma in both adults and children. This observation and subsequent mechanistic studies have demonstrated important interactions among allergens, microbes and the atopic host. The mechanisms responsible for microbe-induced asthma exacerbations are only incompletely understood. A focal point of current research is the inflammatory response of the host following an encounter with a pathogenic microbe, including variations in chemokine and cytokine production and resulting in changes in bronchial hyper-responsiveness and lung function. Direct bronchial infection, exposure of nerves with resulting neurogenic inflammation and a deviated host immune response are among the mechanisms underlying these functional disorders. Lately, suboptimal innate immune responses, expressed as defective interferon production, have gained attention as they might be amenable to intervention. This review describes the suggested mechanisms involved in the complex interactions between 'asthmagenic' microbes, the immune system and atopy, based on in-vitro and in-vivo experimental models and epidemiological evidence. In addition, it provides a synopsis of potential therapeutic strategies either directly against the microorganisms or in respect to the associated inflammation.

Immune responses to viral infections: relevance for asthma

Severe respiratory viral infections in childhood are associated with the development of asthma later in life. Rhinovirus, respiratory syncytial virus and metapneumovirus are of particular importance as triggers of asthma. Effects of virus infection on dendritic cell function in the airways may predispose children to allergic sensitization. Asthmatic subjects may have impaired interferon responses to viral infection that also predispose to allergic sensitization. Difference in Toll-like receptor expression on airway epithelial cells is a potential mechanism for the altered immune responses of asthmatic children.

Protein kinase R, IkappaB kinase-beta and NF-kappaB are required for human rhinovirus induced pro-inflammatory cytokine production in bronchial epithelial cells

Rhinovirus infections cause the majority of acute exacerbations of airway diseases such as asthma and chronic obstructive pulmonary disease, with increased pro-inflammatory cytokine production by infected bronchial epithelial cells contributing to disease pathogenesis. Theses diseases are a huge cause of morbidity worldwide, and contribute a major economic burden to healthcare costs. Current steroid based treatments are only partially efficient at controlling virus induced inflammation, which remains an unmet therapeutic goal. Although NF-kappaB has been implicated, the precise mechanisms of rhinovirus induction of pro-inflammatory gene expression in bronchial epithelial cells are unclear. We hypothesised that rhinovirus replication and generation of dsRNA was an important process of pro-inflammatory cytokine induction. Using pharmalogical (2-aminopurine and a new small molecule inhibitor) and genetic inhibition of the dsRNA binding kinase protein kinase R, striking inhibition of dsRNA (polyrIC) and rhinovirus induced CCL5, CXCL8 and IL-6 protein was observed. Using confocal microscopy, rhinovirus induced protein kinase R phosphorylation co-located with NF-kappaB p65 nuclear translocation. Focusing on CXCL8, both rhinovirus infection and dsRNA treatment required IkappaB kinase-beta for induction of CXCL8. Analysis of cis-acting sites in the CXCL8 promoter revealed that both rhinovirus infection and dsRNA treatment upregulated CXCL8 promoter activation via NF-kappaB and NF-IL6 binding sites. Together, the results demonstrate the importance of dsRNA in induction of pro-inflammatory cytokines by rhinoviruses, and suggest that protein kinase R is involved in NF-kappaB mediated gene transcription of pro-inflammatory cytokines via IkappaB kinase-beta. These molecules regulating rhinovirus induction of inflammation represent therapeutic targets.

A critical appraisal of methods used in early clinical development of novel drugs for the treatment of asthma

Asthma is a heterogeneous disorder characterized by chronic airway inflammation, hyperresponsiveness and remodeling. Being the hallmark of asthma, airway inflammation has become the most important target for therapeutic agents. Consequently, during the past decade various semi-and non-invasive methods have been explored to sample the airway inflammation in asthma. In this review, we provide a practical overview of the current status of various sampling techniques including sputum induction, exhaled breath analysis, and bronchoprovocation tests (BPTs). We focus on their applicability for monitoring in clinical practice and in intervention trials in asthma.

The link between bronchiolitis and asthma

Bronchiolitis and asthma are common wheezing illnesses of childhood. Respiratory syncytial virus is the main causative agent of Bronchiolitis. Rhinovirus is the most common trigger of exacerbations of asthma, but also has been detected increasingly in doing children with Bronchiolitis. Reportedly, childhood asthma develops in 40% of children with a history of Bronchiolitis. No convincing link has been reported between Bronchiolitis and development of atopy, although atopy generally is regarded as the main risk factor for chronic asthma. This article focuses on the association between bronchiolitis and the development of asthma. The authors address the question how respiratory syncytial virus and rhinovirus infections in young children, together with genetics and immunologic immaturity, may contribute to the development of asthma.

Combination therapy: Synergistic suppression of virus-induced chemokines in airway epithelial cells

Viruses are associated with the majority of exacerbations of asthma and chronic obstructive pulmonary disease. Virus induction of neutrophil and lymphocyte chemokines in bronchial epithelium is important in exacerbation pathogenesis. Combined corticosteroid/beta2 agonists synergistically suppress airway smooth muscle chemokine production. Because bronchial epithelium expresses glucocorticoid and beta2 receptors, we investigated whether combination therapy can synergistically suppress rhinovirus-induced bronchial epithelial cell neutrophil (CXCL5, CXCL8) and lymphocyte (CCL5, CXCL10) chemokine production. We investigated modulation of rhinovirus- and IL-1beta-induced bronchial epithelial cell chemokine production by salmeterol and fluticasone propionate, used at therapeutic concentrations, alone and in combination. After 1 h pretreatment, combined treatment significantly inhibited rhinovirus 16, 1B, and IL-1beta-induced CCL5 and CXCL8 protein and mRNA production in BEAS-2B cells compared with fluticasone alone. When used 4 h after treatment, the combination significantly reduced virus-induced CCL5 but not CXCL8. Salmeterol alone had no effect; therefore, this inhibition was synergistic. Kinetic analysis demonstrated that combination therapy reduced by 5-fold the concentration of corticosteroid required to inhibit CXCL8 mRNA expression. In primary cells, salmeterol alone reduced rhinovirus-induced CCL5 and CXCL10 and increased CXCL5 production in a dose-dependent manner but had no effect on CXCL8. Fluticasone alone reduced CCL5, CXCL8, and CXCL10 but had no effect on CXCL5. Combination therapy augmented inhibition of CXCL8, CCL5, and CXCL10 but had no effect on CXCL5. Corticosteroids and beta2 agonists suppress rhinovirus-induced chemokines in bronchial epithelial cells through synergistic and additive mechanisms. This effect was greater for lymphocyte- than for neutrophil-related chemokines.

Phosphatidylinositol 3-kinase is required for rhinovirus-induced airway epithelial cell interleukin-8 expression

Rhinovirus (RV) is a common cause of asthma exacerbations. The signaling mechanisms regulating RV-induced airway epithelial cell responses have not been well studied. We examined the role of phosphatidylinositol (PI) 3-kinase in RV-induced interleukin (IL)-8 expression. Infection of 16HBE14o- human bronchial epithelial cells with RV39 induced rapid activation of PI 3-kinase and phosphorylation of Akt, a downstream effector of PI 3-kinase. RV39 also colocalized with cit-Akt-PH, a citrogen-tagged fluorescent fusion protein encoding the pleckstrin homology domain of Akt, indicating that 3-phosphorylated PI accumulates at the site of RV infection. Inhibition of PI 3-kinase and Akt attenuated RV39-induced NF-kappaB transactivation and IL-8 expression. Inhibition of PI 3-kinase also blocked internalization of labeled RV39 into 16HBE14o- cells, suggesting that the requirement of PI 3-kinase for RV39-induced IL-8 expression, at least in part, relates to its role in viral endocytosis.

Effects of viral respiratory infections on lung development and childhood asthma

Viral infections are closely linked to wheezing in infancy, and those children with recurrent virus-induced wheezing episodes are at great risk for chronic childhood asthma. Infancy is a time of increased susceptibility to viral infections, and this stage is also characterized by pulmonary alveolar multiplication and extensive remodeling of the airways to accommodate growth. This coincidence, together with the observation that children with asthma can have structural lung changes and functional deficits at an early age, suggests that viral infections could adversely affect lung development. Inflammatory mediators induced by viral infection are known to have effects on the remodeling process, suggesting a plausible mechanism to support this theory. Furthermore, animal models of viral infection during lung growth and development suggest that developmental factors are important in determining the consequences of infection on long-term lung function. Greater understanding of the effects of viral infections on lung development and growth in early childhood might lead to the discovery of additional strategies for the prevention of recurrent wheezing and chronic asthma.

Infectious triggers of asthma

There is abundant evidence that asthma is frequently exacerbated by infectious agents. Several viruses have been implicated in the inception and exacerbation of asthma. Recent attention has been directed at the role of infections with the atypical bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae as agents capable of triggering asthma exacerbations and potentially as inciting agents for asthma. This article examines the evidence for interaction between specific infectious agents and exacerbations of asthma, including the immunopathology of infection-triggered asthma, and the current therapeutic options for management.

Human rhinovirus infection induces airway epithelial cell production of human beta-defensin 2 both in vitro and in vivo

We hypothesized that airway epithelial cells, the primary site of human rhinovirus (HRV) infection, provide a link between the innate and specific immune response to HRV via production of human beta-defensin (HBD)-2, a potent in vitro attractant and activator of immature dendritic cells. Infection of primary cultures of human epithelial cells with several HRV serotypes induced expression of HBD-2 mRNA and protein, indicating that HBD-2 production was independent of viral receptor usage or mechanisms of viral RNA internalization. Induction of HBD-2 was dependent upon viral replication and could be mimicked by transfection of cells with synthetic dsRNA, but was not dependent upon epithelial production of IL-1. Studies with stable epithelial cell lines expressing HBD-2 promoter constructs, as well as inhibitor studies in primary cells, both demonstrated that induction of HBD-2 involves activation of the transcription factor, NF-kappaB. Other transcription factors must also be activated by HRV infection, however, as expression of HBD-3 mRNA was also induced and there is no putative NF-kappaB recognition sequence in the promoter of this gene. HBD-2 showed no direct antiviral activity against HRV. In vivo infection of normal human subjects with HRV-16 induced expression of mRNA for HBD-2 in nasal epithelial scrapings. Increases in mRNA correlated with viral titer and with increased levels of HBD-2 protein in nasal lavages. This represents the first demonstration that HRV infection induces epithelial expression of HBD-2 both in vitro and in vivo, and supports the concept that HBD-2 may play a role in host defense to HRV infection.

Exaggerated IL-8 and IL-6 responses to TNF-alpha by parainfluenza virus type 4-infected NCI-H292 cells

Respiratory viruses induce and potentiate airway inflammation, which is related to the induction of proinflammatory mediators such as interleukin (IL)-8 and IL-6. Here we report on mechanisms implicated in IL-8 and IL-6 production by airway epithelium-like NCI-H292 cells exposed to parainfluenza virus type 4a (PIV-4). PIV-4 readily infected NCI-H292 cells as reflected by intracellular PIV-4 antigen expression. PIV-4 infection triggered a biphasic IL-8 and IL-6 mRNA response. Transient transfection with truncated and mutated promoter constructs identified NF-kappaB and activator protein (AP)-1, and CCAAT-enhancer binding protein (C/EBP) as the relevant transcription factors for PIV-4-induced IL-8 and IL-6 gene transcription, respectively. An increase of DNA-binding activities for NF-kappaB and C/EBP paralleled the induction of the first and second IL-8 and IL-6 mRNA peaks, whereas the onset of AP-1 paralleled the first IL-8 mRNA peak only. The second mRNA peak, apparently dependent on viral replication, coincided also with a marked reduction of IL-8 and IL-6 mRNA degradation. Importantly, cells at the time of the reduced mRNA degradation displayed an exaggerated IL-8 and IL-6 protein production to a secondary stimulus, as exemplified by steeper dose-response curves to TNF-alpha. Thus PIV-4 infection enhances epithelial IL-8 and IL-6 production by transcriptional and posttranscriptional mechanisms. The previously unrecognized phase of reduced IL-8 and IL-6 mRNA degradation and the concurrent amplified epithelial IL-8 and IL-6 responses may play an important role in virus-induced potentiation of airway inflammation.

Role of nasal nitric oxide in the resolution of experimental rhinovirus infection

BACKGROUND

Human rhinovirus (HRV) infections are associated with exacerbations of asthma, chronic obstructive pulmonary disease, and sinusitis. Nitric oxide (NO) might play an important role in host defense through its potent antiviral properties. Previous studies have shown that HRV infection in human subjects increased nasal epithelial expression of type 2 nitric oxide synthase (NOS2), an isoform of the enzyme that produces NO.

OBJECTIVE

We sought to investigate whether increases in exhaled NO (eNO) would accompany the increased NOS2 expression and would be associated with clearance of the virus.

METHODS

Six human subjects were infected with HRV-16 intranasally. eNO from nasal and lower airways was measured by means of direct measurement at multiple controlled flow rates. eNO was monitored at baseline (day 1) and on days 2 to 5, 8, 14, and 42 after infection. Nasal lavages were performed on days 1 to 5 and 8, and nasal scrapings were performed on days 1 to 4. NOS2 mRNA expression in nasal cells was measured by using quantitative real-time RT-PCR. Viral shedding in nasal lavage fluid was monitored by using real-time RT-PCR and bioassay.

RESULTS

Peak HRV titers and symptom scores were correlated on day 3, and HRV persisted until day 5 (n=4) or day 8 (n=2). Infection was associated with transient but significant increases in lymphocytes and monocytes in nasal lavage fluid. Significant increases in both nasal and lower airway eNO concentrations accompanied HRV infection and were positively correlated. Increased nasal eNO concentrations on day 3 were associated with increased expression of NOS2 mRNA in nasal scrapings. Symptom scores on day 4 were inversely correlated with the increases in nasal eNO concentration.

CONCLUSIONS

We conclude that increased production of NO occurs as part of the host response to HRV infection and speculate that NO plays a beneficial role in viral clearance.

Viral respiratory infection and the link to asthma

BACKGROUND

Acute wheezing secondary to viral infection is common in children. Whereas many children suffer primarily mild to moderate symptoms, others develop severe coughing and wheezing.

METHODS

Review of recent medical literature regarding the correlation between viral illness and increased susceptibility to develop severe respiratory illnesses and subsequent asthma.

DISCUSSION

In infants factors that predispose to severe disease and lower respiratory airway effects include small lung size, passive smoke exposure, virus-induced immune responses, severe disease and infection at a young age. Acute asthma symptoms have been correlated with a variety of viral pathogens, most commonly respiratory syncytial virus bronchiolitis in infancy and rhinovirus in older children. Epidemiologic and biologic factors that influence development of asthma include repeated exposure to infectious disease during early childhood, early exposure to pets, a farming lifestyle, alterations in bacterial flora of the intestine and increased use of antibiotics. Thus the likelihood of asthma is related to the specific pathogen, severity of infection, cumulative number of infections and stage of immunologic development. Progress is also being made in understanding how viruses can adversely affect lung or immune development. In asthmatic children viral infections initiate bronchospasm and airway obstruction. It is hoped that research on virus-induced airway alterations and the host factors that lead to severe clinical illnesses can help clinicians to identify children whose wheezing is an early sign of asthma.

Rhinovirus 16 3C protease induces interleukin-8 and granulocyte-macrophage colony-stimulating factor expression in human bronchial epithelial cells

Rhinovirus (RV), a member of the Picornaviridae family, accounts for many virus-induced asthma exacerbations. RV induces airway cell chemokine expression both in vivo and in vitro. Because of the known interactions of proteases with cellular functions, we hypothesized that RV 3C protease is sufficient for cytokine up-regulation. A cDNA encoding RV16 3C protease was constructed by PCR amplification and transfected into 16HBE14o- human bronchial epithelial cells. 3C protease induced expression of both IL-8 and GM-CSF, as well as transcription from both the IL-8 and GM-CSF promoters. 3C expression also induced activator protein 1 and NF-kappaB transcriptional activation. Finally, mutation of IL-8 promoter AP-1 and NF-kappaB promoter sequences significantly reduced 3C-induced responses. Together, these data suggest expression of RV16 3C protease is sufficient to induce chemokine expression in human bronchial epithelial cells, and does so in an AP-1- and NF-kappaB-dependent manner.

Host defense function of the airway epithelium in health and disease: clinical background

Respiratory infection is extremely common and a major cause of morbidity and mortality worldwide. The airway epithelium has an important role in host defense against infection and this is illustrated in this review by considering infection by respiratory viruses. In patients with asthma or chronic obstructive pulmonary disease, respiratory viruses are a common trigger of exacerbations. Rhinoviruses (RV) are the most common virus type detected. Knowledge of the immunopathogenesis of such RV-induced exacerbations remains limited, but information is available from in vitro and from in vivo studies, especially of experimental infection in human volunteers. RV infects and replicates within epithelial cells (EC) of the lower respiratory tract. EC are an important component of the innate-immune response to RV infection. The interaction between virus and the intracellular signaling pathways of the host cell results in activation of potentially antiviral mechanisms, including type 1 interferons and nitric oxide, and in the production of cytokines and chemokines [interleukin (IL)-1 beta, IL-6, IL-8, IL-11, IL-16, tumor necrosis factor alpha, granulocyte macrophage-colony stimulating factor, growth-regulated oncogene-alpha, epithelial neutrophil-activating protein-78, regulated on activation, normal T expressed and secreted, eotaxin 1/2, macrophage-inflammatory protein-1 alpha], which influence the subsequent induced innate- and specific-immune response. Although this is beneficial in facilitating clearance of virus from the respiratory tract, the generation of proinflammatory mediators and the recruitment of inflammatory cells result in a degree of immunopathology and may amplify pre-existing airway inflammation. Further research will be necessary to determine whether modification of EC responses to respiratory virus infection will be of therapeutic benefit.

Interleukin-1beta and interleukin-1ra levels in nasal lavages during experimental rhinovirus infection in asthmatic and non-asthmatic subjects

BACKGROUND

Exacerbations of asthma are often associated with rhinovirus (RV)-induced common colds. During experimental RV-infection in healthy subjects, increased levels of the pro-inflammatory mediator IL-1beta and the anti-inflammatory IL-1 receptor antagonist (IL-1ra) have been found in nasal lavage.

OBJECTIVE

We postulated that the balance between nasal pro- and anti-inflammatory mediator expression is disturbed in asthma, resulting in more extensive inflammation following RV-exposure in asthma.

METHODS

We determined IL-1ra, IL-1beta, and IL-8 in nasal lavages (days -2, 3, and 6) of non-asthmatics and asthmatics (with and without pre-treatment with the inhaled steroid budesonide) before and after experimental RV16-infection (days 0 and 1).

RESULTS

Following RV16-infection, a significant increase in IL-8 was observed in the placebo- and budesonide-treated asthmatics (P=0.033 and 0.037, respectively), whereas IL-1beta only increased in the two asthma groups combined (P=0.035). A small, but significant, increase in IL-1ra was only observed in the budesonide-treated asthmatics (P=0.047). At baseline, IL-1ra levels were significantly higher in the non-asthmatics than in the placebo-treated asthmatics (P=0.017).

CONCLUSION

These results demonstrate differences between non-asthmatic and asthmatic subjects in the basal levels of nasal cytokines and their inhibitors, and in the effect of experimental RV-infection on these levels. The results indicate that RV may enhance inflammation more markedly in asthmatics, and suggest that this may in part be explained by lower IL-1ra levels. In addition, the observation that budesonide-treatment may result in higher nasal IL-1ra levels supports the hypothesis that steroids act in part by increasing the endogenous anti-inflammatory screen.

Are rhinovirus-induced airway responses in asthma aggravated by chronic allergen exposure?

Airway inflammation in asthma may represent a favorable environment for respiratory viral infections, augmenting virus-induced exacerbations in asthma. We postulated that repeated low-dose allergen exposure preceding experimental rhinovirus 16 (RV16) infection increases the severity of RV-induced airway obstruction and inflammation. Thirty-six house dust mite-allergic patients with mild to moderate asthma participated in a three-arm, parallel, placebo-controlled, double-blind study. Patients inhaled a low dose of house dust mite allergen for 10 subsequent working days (Days 1-5 and 8-12) and/or were subsequently infected with RV16 (Days 15 and 16). Allergen exposure resulted in a significant fall in FEV1 (p < 0.001) and provocative concentration of histamine causing a 20% fall in FEV1 (p < 0.001) and an increase in exhaled nitric oxide (p < 0.001) and percentage of sputum eosinophils (p < 0.001). RV16 infection led to a fall in FEV1 (p = 0.02) and increases in the percentage of sputum neutrophils (p = 0.01), sputum interleukin-8 (p = 0.04), and neutrophil elastase (p = 0.04). Successive allergen exposure and RV16 infection had no synergistic or additive effect on any of the clinical or inflammatory outcomes. In conclusion, repeated low-dose allergen exposure and RV16 infection induce distinct inflammatory profiles within the airways in asthma without apparent interaction between these two environmental triggers. This suggests that preceding allergen exposure, at the used dose and duration, is not a determinant of the severity of RV-induced exacerbations in patients with mild to moderate asthma.

Double-stranded RNA induces the synthesis of specific chemokines by bronchial epithelial cells

Virus-induced secretion of proinflammatory chemokines (e.g., regulated on activation, normal T cells expressed and secreted [RANTES], interleukin [IL]-8) by airway epithelial cells helps to initiate antiviral responses and airway inflammation by enhancing inflammatory cell recruitment. To define mechanisms for virus-induced chemokine secretion, monolayers of nontransformed bronchial epithelial cells were transfected or incubated with polydeoxyinosinic-deoxycytidylic acid (synthetic double-stranded [ds] RNA), rhinovirus dsRNA, or single-stranded RNA (ssRNA), and the secretion of selected chemokines was determined. Transfection or incubation with dsRNA, but not ssRNA, significantly enhanced secretion of RANTES and IL-8, but not eotaxin or macrophage inflammatory protein-1alpha. Mechanistically, dsRNA induced and activated dsRNA-dependent protein kinase (PKR), and activated nuclear factor-kappaB and p38 mitogen-activated protein kinase. Furthermore, the PKR inhibitor 2-aminopurine significantly blocked dsRNA-induced RANTES and IL-8 secretion, whereas the p38 mitogen-activated protein kinase inhibitor SB203580 suppressed dsRNA-induced IL-8, but not RANTES. These findings indicate that dsRNA selectively induce the secretion of chemokines such as IL-8 and RANTES, and implicate dsRNA-sensitive signaling proteins in this process. Moreover, these data suggest that this may be an important mechanism for the selective secretion of chemokines by viruses (e.g., rhinovirus, respiratory syncytial virus, influenza) that synthesize dsRNA during replication.

Infectious triggers of pediatric asthma

Respiratory infections can cause wheezing illnesses in children of all ages and also can influence the causation and disease activity of asthma. For years it has been recognized that respiratory syncytial virus infections often produce the first episode of wheezing in children who go on to develop chronic asthma. More recently, it has been proposed that repeated infections with other common childhood viral pathogens might help the immune system develop in such a way as to prevent the onset of allergic diseases and possibly asthma. In addition to the effects of viral infections, infections with certain intracellular pathogens, such as chlamydia and mycoplasma, may cause acute and chronic wheezing in some individuals, whereas common cold and acute sinus infections can trigger acute symptoms of asthma. In this article, the epidemiologic, mechanistic, and treatment implications of the association between respiratory infections and asthma are discussed.

STAT4 signal pathways regulate inflammation and airway physiology changes in allergic airway inflammation locally via alteration of chemokines

Mice homozygous for the STAT4-null mutation were sensitized to cockroach Ag, challenged intratracheally 21 days later, and compared with STAT4-competent allergic mice. The STAT4(-/-) mice showed significant decreases in airway hyperreactivity (AHR) and peribronchial eosinophils compared with wild-type controls. In addition, pulmonary levels of chemokines were decreased in the STAT4(-/-) mice, including CC chemokine ligand (CCL)5, CCL6, CCL11, and CCL17. However, levels of Th2-type cytokines, such as IL-4 and IL-13, as well as serum IgE levels were similar in the two groups. Transfer of splenic lymphocytes from sensitized wild-type mice into sensitized STAT4(-/-) mice did not restore AHR in the mutant mice. Furthermore, chemokine production and peribronchial eosinophilia were not restored during the cellular transfer experiments. Thus, it appears that STAT4 expression contributes to a type 2 process such as allergen-induced chemokine production and AHR. In additional studies, competent allergic mice were treated with anti-IL-12 locally in the airways at the time of allergen rechallenge. These latter studies also demonstrated a decrease in AHR. Altogether, these data suggest that STAT4-mediated pathways play a role locally within the airway for the exacerbation of the allergen-induced responses.

Relationships among specific viral pathogens, virus-induced interleukin-8, and respiratory symptoms in infancy

Both virus-mediated damage to airway tissues and induction of pro-inflammatory cytokines such as interleukin-8 (IL-8) could contribute to symptom severity during viral respiratory infections in children. To test the hypothesis that IL-8 contributes to the pathogenesis of respiratory symptoms during naturally acquired respiratory viral infections in children, nasal wash samples collected from infants with acute viral infections (n = 198) or from healthy uninfected infants (n = 31) were analysed for IL-8. Nasal wash IL-8 was positively related to age in uninfected children (rs = 0.36, p < 0.05). Respiratory syncytial virus (RSV) infection caused more severe respiratory symptoms compared to infections with influenza A, parainfluenza viruses, or rhinoviruses. In addition, RSV, parainfluenza and rhinovirus infections increased levels of IL-8 in nasal lavage fluid, and there were some differences in the ability of the viruses to induce IL-8 production (RSV>influenza, p < 0.05). Finally, there were significant correlations between nasal wash IL-8 levels and symptom scores during infections with rhinovirus (rs = 0.56, p < 0.001) or influenza A (rs = 0.45, p < 0.05), but not with parainfluenza virus or RSV. These findings provide evidence of a close relationship between the generation of IL-8 and symptoms during acute community-acquired infections with rhinovirus or influenza A. In contrast, for RSV and parainfluenza infections, factors in addition to IL-8 production appear to contribute to the generation of clinical symptoms.

Chemokines and inflammation in the nasal passages of infants with respiratory syncytial virus bronchiolitis

This study measured chemokines in nasal lavage fluids (NLF) from infants with respiratory syncytial virus (RSV) bronchiolitis, defined by lung hyperinflation and wheezing. Comparison was made to RSV-positive infants without bronchiolitis and RSV-negative infants with acute respiratory illnesses. RSV-positive illnesses were associated with increased epithelial shedding, increased RANTES/protein ratios, and increased IL-8/protein ratios in NLF compared to RSV-negative illnesses. Among RSV-positive infants, bronchiolitics had greater total cell counts and percentage epithelial cells in NLF than nonbronchiolitics. Bronchiolitics also had roughly twice the NLF RANTES/IL-8 ratio than nonbronchiolitics (P =.043). Semiquantitative reverse transcriptase-polymerase chain reaction of nasal epithelium suggested similar RANTES/IL-8 ratio increases among bronchiolitics. A more mildly affected, RSV-positive outpatient population showed none of these differences. We conclude that RSV bronchiolitis is associated with a shift toward relatively more RANTES in nasal secretions of infants sick enough to require hospitalization, and mucosal epithelium may contribute to this process. Similar processes in the lower airways may enhance inflammation due to RANTES-responsive cell types and affect clinical manifestations.

Interferon-gamma enhances rhinovirus-induced RANTES secretion by airway epithelial cells

Respiratory viruses, including rhinoviruses, infect respiratory epithelium and induce a variety of cytokines and chemokines that can initiate an inflammatory response. Cytokines, such as interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha, could enhance epithelial cell activation by inducing virus receptors. To test this hypothesis, effects of IFN-gamma or TNF-alpha on expression of intercellular adhesion molecule (ICAM)-1, rhinovirus binding, and virus-induced chemokine secretion on A549 and human bronchial epithelial cells (HBEC) were determined. The results varied with the type of cell. IFN-gamma was a stronger inducer of ICAM-1 and viral binding on HBEC, whereas TNF-alpha had greater effects on A549 cells. In addition, IFN-gamma, but not TNF-alpha, synergistically enhanced regulated on activation, normal T cells expressed and secreted (RANTES) mRNA expression and protein secretion induced by RV16 or RV49. To determine whether IFN-gamma could enhance RANTES secretion independent of effects on ICAM-1 and RV binding, HBEC were transfected with RV16 RNA in the presence or absence of IFN-gamma. RV16 RNA alone stimulated RANTES secretion, and this effect was enhanced by IFN-gamma. These results demonstrate that IFN-gamma can enhance rhinovirus-induced RANTES secretion by increasing viral binding, and through a second receptor-independent pathway. These findings suggest that IFN-gamma, by upregulating RANTES secretion, could be an important regulator of the initial immune response to rhinovirus infections.

Airways inflammation and COPD: epithelial-neutrophil interactions

Neutrophils are recognized as major cellular mediators of inflammation. They contain specific and highly regulated mechanisms for controlling the expression of adhesion molecules that allow for their tethering and migration into inflammatory sites. These adhesion molecules not only are activated by exogenous pollutants but are regulated by endothelial and epithelial cell signals. Lipid mediators, such as platelet-activating factor, reactive oxygen and nitrogen species, and cytokines from airway epithelial cells, further control neutrophil functions such as infiltration and activation resulting in an increase in respiratory burst activity and release of granule enzymes, such as elastase. Furthermore, virus and bacteria products affect inflammation by increasing secondary epithelial mediators. However, once the endogenous or exogenous agents are expelled, neutrophil populations are programmed to die and are cleared by macrophage phagocytosis.

Rhinovirus respiratory infections and asthma

Viral infections, particularly respiratory illnesses caused by rhinovirus, are the most common cause of asthma exacerbations in children and contribute in large part to asthma morbidity in adults. Epidemiologic studies and increasingly sophisticated viral detection methodologies have helped to define the role of rhinovirus as a potential causative agent in asthma exacerbations. Rhinovirus-induced lung disease is multifaceted and can be characterized in terms of a variety of physiologic, immunologic, and viral processes. The precise direct and indirect mechanisms of viral contribution to exacerbations must still be elucidated. Understanding them will have an impact on the design of future treatment modalities.

Nasal lavage as a tool for the assessment of upper-airway inflammation in adults and children

The prevalence of respiratory allergies has increased over the last 20 years, highlighting the need for a simple and noninvasive tool to investigate, in a clinical and epidemiological context, airway-inflammation mechanisms encountered in allergic and inflammatory processes. The nose, as the first region of the respiratory tract to come in contact with airborne pollutants, is easily explored with the use of nasal lavage (NL). We evaluated an NL method for adults and children, along with its reproducibility and capacity to separate different subgroups. NL reproducibility, assessed in 10 healthy, nonsmoking adults on three different occasions, was determined with the use of the intraclass coefficient of correlation for such inflammatory markers as total cell count, albumin, urea, neutrophil elastase, alpha(1)-antitrypsin, interleukin-6, and interleukin-8. Using this NL method, we analyzed nasal markers of 50 healthy adults (smokers and nonsmokers) and 12 healthy children. Our NL method demonstrated high reproducibility with regard to total cell count, albumin, urea, and alpha(1)-antitrypsin (intraclass correlation coefficient > 0.75). Compared with NL results in nonsmokers, NL in heavy smokers revealed significant increased concentrations of total cell counts and interleukin-8 and significant decreased concentrations of interleukin-6. These findings suggest that NL can be used as a tool in the assessment of inflammation because it has the correct reproducibility and can discriminate between heavy smokers and nonsmokers. Moreover, the use of this standardized method in children is feasible.

Relationship of viral infections to wheezing illnesses and asthma

Viral infections can influence both the development and the severity of asthma. In early life, viral infections can either increase or, remarkably, decrease the risk of subsequent asthma. In children and adults with existing asthma, viral respiratory infections frequently cause acute airway obstruction and wheezing. This article discusses the influence of viral infections on mechanisms of virus-induced airway inflammation in relationship to the development, persistence and severity of asthma.

Infections

Infection, in particular by respiratory viruses, plays an important role in triggering exacerbations and has also been implicated in the etiology of asthma and chronic obstructive pulmonary disease (COPD). This chapter reviews the epidemiological evidence that implicates infectious pathogens as triggers. The chapter also discusses the mechanisms of interaction between the host-pathogen response and preexisting airway pathology resulting in an exacerbation. Much of the treatment of infective exacerbations for both asthma and COPD is symptomatic, consisting of bronchodilators or supportive in the form of oxygen, and in severe cases it includes noninvasive or invasive ventilatory measures. The current therapy for virus-induced exacerbations of asthma and COPD relies on increased treatment of preexisting disease. Antibiotics are indicated for bacterial infections. The effective use of antiviral agents, particularly for influenza viruses, requires viral diagnosis, commencement of treatment early in the course of an exacerbation, or the targeting of high-risk groups for prophylaxis. Alternative strategies for drug development involve the identification of key factors common to exacerbations induced by a range of different viruses. Increased knowledge of the host–virus interaction can help in designing treatments that can increase virus clearance and minimize immunopathology.

Rhinovirus-induced airway inflammation in asthma: effect of treatment with inhaled corticosteroids before and during experimental infection

Asthma exacerbations are frequently linked to rhinovirus infections. However, the associated inflammatory pathways are poorly understood, and treatment of exacerbations is often unsatisfactory. In the present study we investigated whether antiinflammatory treatment with inhaled corticosteroids prevents any rhinovirus-induced worsening of lower airway inflammation. To that end, we selected 25 atopic patients with mild asthma who underwent experimental rhinovirus 16 (RV16) infection, while receiving double-blind, placebo-controlled treatment with the inhaled corticosteroid budesonide (800 microg twice a day) throughout the study period, starting 2 wk before infection. We assessed inflammatory cell numbers in the bronchial mucosa as obtained by bronchial biopsies 2 d before and 6 d after RV16 infection, and analyzed those in relation to cold symptoms, changes in blood leukocyte counts, airway obstruction, and airway hyperresponsiveness. RV16 colds induced an increase in CD3(+) cells in the lamina propria (p = 0.03) and tended to decrease the numbers of epithelial eosinophils (p = 0.06) in both groups analyzed as a whole. The T cell accumulation was positively associated with cold symptoms. Budesonide pretreatment improved airway hyperresponsiveness (p = 0.02) and eosinophilic airways inflammation (p = 0.04). Yet it did not significantly affect the RV16-associated changes in the numbers of any of the inflammatory cell types. We conclude that RV16 infection by itself induces only subtle worsening of airway inflammation in asthma, which is not improved (or worsened) by inhaled corticosteroids. The latter finding is in keeping with the limited protection of inhaled corticosteroids against acute asthma exacerbations.

Repeatability and validity of cell and fluid-phase measurements in nasal fluid: a comparison of two methods of nasal lavage

BACKGROUND

There is little information on the repeatability of cell counts and fluid-phase measurements in nasal fluid obtained by different methods of nasal lavage.

OBJECTIVE

To compare the repeatability and validity of total and differential cell counts and eosinophil cationic protein (ECP) in nasal secretions obtained by two methods of nasal lavage.

PATIENTS AND METHODS

Twelve healthy subjects and twelve subjects with clinically stable allergic rhinitis were randomly assigned to two nasal lavages (separated by 48 h), by one of two methods in the first week and by the second method in the following week. One method was a modification of the method described by Greiff et al. and Grunberg and coworkers and the other was that described by Naclerio and coworkers.

RESULTS

Both methods of nasal lavage gave poorly repeatable eosinophil counts and ECP in normal subjects but better repeatability in subjects with rhinitis. The modified Greiff/Grunberg method gave higher and more repeatable total cell count and, in subjects with rhinitis, more reproducible ECP levels compared with the Naclerio

METHOD

Both methods were able to discriminate between healthy and rhinitic subjects: mean +/- SD eosinophil percentage count and eosinophil cationic protein differences were 4.5 +/- 4% (P < 0.05) and 24.5 +/- 46.9 microg/L (P < 0.05), respectively, with the modified method and 7.0 +/- 4% (P < 0.05) and 26.9 +/- 68 microg/L (P < 0.05), respectively, with the Naclerio method.

CONCLUSION

Both methods are valid and discriminate between normal and rhinitic subjects. In subjects with rhinitis, although the repeatability of eosinophil counts is similar by both methods, the modified Greiff/Grunberg method gives more reproducible ECP measurements, compared with the Naclerio method.

IL-13-induced airway hyperreactivity during respiratory syncytial virus infection is STAT6 dependent

Airway damage and hyperreactivity induced during respiratory syncytial virus (RSV) infection can have a prolonged effect in infants and young children. These infections can alter the long-term function of the lung and may lead to severe asthma-like responses. In these studies, the role of IL-13 in inducing and maintaining a prolonged airway hyperreactivity response was examined using a mouse model of primary RSV infection. Using this model, there was evidence of significant airway epithelial cell damage and sloughing, along with mucus production. The airway hyperreactivity response was significantly increased by 8 days postinfection, peaked during days 10-12, and began to resolve by day 14. When the local production of Th1- and Th2-associated cytokines was examined, there was a significant increase, primarily in IL-13, as the viral response progressed. Treatment of RSV-infected mice with anti-IL-13 substantially inhibited airway hyperreactivity. Anti-IL-4 treatment had no effect on the RSV-induced responses. Interestingly, when IL-13 was neutralized, an early increase in IL-12 production was observed within the lungs, as was a significantly lower level of viral Ags, suggesting that IL-13 may be regulating an important antiviral pathway. The examination of RSV-induced airway hyperreactivity in STAT6(-/-) mice demonstrated a significant attenuation of the response, similar to the anti-IL-13 treatment. In addition, STAT6(-/-) mice had a significant alteration of mucus-producing cells in the airway. Altogether, these studies suggest that a primary factor leading to chronic RSV-induced airway dysfunction may be the inappropriate production of IL-13.

The treatment of rhinovirus infections: progress and potential

The common cold is an important illness both as a result of the economic impact of this common disease and because of the morbidity associated with the complications of the illness. Recent attempts to develop antiviral treatments for the common cold represent a substantial advance over previous efforts. Formidable barriers remain to be overcome, however, before any of these new products will be proven to be clinically useful. Recent advances in our understanding of the pathogenesis of common cold symptoms have provided insights into potential new targets for the treatment of this illness.

The role of viruses in the induction and progression of asthma

Viral respiratory infections have been related to asthma in several ways. It is well established that viral common colds precipitate exacerbations of asthma. Severe bronchiolitis in early life is related to subsequent wheezing and therefore may represent a marker of susceptibility to asthma; alternatively, it could be involved in the initiation of the disease. Finally, it is possible that some infections may protect from the development of asthma and allergies by promoting a type-1 host response. However, whether respiratory or other viruses could mediate such a protective effect is debated. The design and implementation of novel anti- or proviral strategies targeting asthma depends on the resolution of these questions. This review presents current evidence on the epidemiologic correlations and proposed mechanisms for the involvement of viral infections in the development and progression of asthma.

Relationship of upper and lower airway cytokines to outcome of experimental rhinovirus infection

To test the hypothesis that rhinovirus (RV)-induced immune responses influence the outcome of RV infections, we inoculated 22 subjects with allergic rhinitis or asthma with RV16. Nasal secretions and induced sputum were repeatedly sampled over the next 14 d. RV16 infection increased nasal granulocyte colony-stimulating factor (G-CSF) and interleukin (IL)-8, which was accompanied by neutrophilia in blood and nasal secretions. Nasal G-CSF correlated closely with increased blood neutrophils (r(s) = 0.69, p < 0.005), whereas nasal neutrophils correlated with both G-CSF (r(s) = 0.87, p < 0.001) and IL-8 (r(s) = 0.75, p < 0.001). Although similar relationships were present in sputum, changes in sputum neutrophils and G-CSF with RV16 infection were relatively modest. In addition, virus-induced changes in the sputum interferon-gamma-to-IL-5 messenger RNA ratio were inversely related to both peak cold symptoms (r(s) = -0.60, p < 0.005) and the time to viral clearance (undetectable picornavirus RNA). These results indicate that airway IL-8 and G-CSF are closely associated with virus-induced neutrophilic inflammation during an experimental RV infection in atopic volunteers. In addition, the balance of airway T-helper cell type 1 (Th1)- and Th2-like cytokines induced by RV infection may help determine the clinical outcome of common cold infections, raising the possibility that the individual subject's immune response, rather than atopic status per se, is important in this regard.

Role of NF-kappa B in cytokine production induced from human airway epithelial cells by rhinovirus infection

Infection of human epithelial cells with human rhinovirus (HRV)-16 induces rapid production of several proinflammatory cytokines, including IL-8, IL-6, and GM-CSF. We evaluated the role of NF-kappaB in HRV-16-induced IL-8 and IL-6 production by EMSA using oligonucleotides corresponding to the binding sites for NF-kappaB in the IL-6 and IL-8 gene promoters. Consistent with the rapid induction of mRNA for IL-8 and IL-6, maximal NF-kappaB binding to both oligonucleotides was detected at 30 min after infection. NF-kappaB complexes contained p65 and p50, but not c-Rel. The IL-8 oligonucleotide bound recombinant p50 with only about one-tenth the efficiency of the IL-6 oligonucleotide, even though epithelial cells produced more IL-8 protein than IL-6. Neither the potent glucocorticoid, budesonide (10-7 M), nor a NO donor inhibited NF-kappaB binding to either cytokine promoter or induction of mRNA for either IL-8 or IL-6. Sulfasalazine and calpain inhibitor I, inhibitors of NF-kappaB activation, blocked HRV-16-induced formation of NF-kappaB complexes with oligonucleotides from both cytokines, but did not inhibit mRNA induction for either cytokine. By contrast, sulfasalazine clearly inhibited HRV-16 induction of mRNA for GM-CSF in the same cells. Thus, HRV-16 induces epithelial expression of IL-8 and IL-6 by an NF-kappaB-independent pathway, whereas induction of GM-CSF is at least partially dependent upon NF-kappaB activation.

Chemokine concentrations in nasal washings of infants with rhinovirus illnesses

We determined RANTES (regulated on activation, normal T cell expressed and secreted) and interleukin-8 (IL-8) concentrations, and total white blood cell (WBC) and differential counts in nasal wash samples from rhinovirus-infected infants presenting with wheezing or acute upper respiratory illness alone and compared them with those from healthy infants. RANTES concentrations were significantly greater in acute samples from wheezy patients than in those from patients with acute upper respiratory illness only, or in control samples. IL-8 concentrations and WBC and neutrophil counts were significantly greater in acute samples from wheezy infants and patients with upper respiratory illness alone than in control samples, but they did not differ significantly between the 2 patient groups.

The role of viral infections in the natural history of asthma

Viral infections have been related to the inception of recurrent wheezing illnesses and asthma in infants and are probably the most frequent cause of exacerbations of established disease in older children and adults. The well-recognized clinical effects of viral infections are mainly caused by virus-induced immune responses. Clinical studies of natural and experimentally induced viral infections have led to the identification of mechanisms of inflammation that could be involved in producing airway obstruction and lower airway symptoms. In addition, host factors that are associated with more vigorous viral replication or severe clinical illness are beginning to be identified. Advances in molecular virology and our understanding of immune responses to viral infections may lead to the development of new strategies for the prevention and treatment of virus-induced respiratory disorders.

Experimental rhinovirus 16 infection increases intercellular adhesion molecule-1 expression in bronchial epithelium of asthmatics regardless of inhaled steroid treatment

BACKGROUND

Rhinovirus infections in airway epithelial cells in vitro have been shown to upregulate intercellular adhesion molecule-1 (ICAM-1) expression. Epithelial ICAM-1, in its dual role as the major rhinovirus receptor and as adhesion molecule for inflammatory cells may be involved in the pathogenesis of rhinovirus-induced exacerbations of asthma.

OBJECTIVE

We aimed to investigate the effect of experimental rhinovirus 16 (RV16) infection on ICAM-1 expression in bronchial mucosal biopsies in asthma. In addition, the effect of 2 weeks pretreatment with inhaled budesonide (800 microg b.d.) on RV16-associated changes in ICAM-1 expression was studied.

METHODS

The study had a parallel, placebo-controlled design in 25 steroid-naive nonsmoking atopic asthmatic subjects. After 2 weeks budesonide (BUD) or placebo (PLAC) pretreatment bronchoscopy was performed 2 days before (day -2) and 6 days after (day 6) RV16 inoculation (on days 0 and 1). Immunohistochemical staining for ICAM-1 was performed on snap-frozen bronchial biopsies. ICAM-1 staining intensity on the basal epithelial cells was scored semiquantitatively from 1 (weak) to 3 (intense). Similarly, epithelial intactness was noted (1 = basal cells only, 2 = basal and parabasal cells, 3 = intact epithelium).

RESULTS

ICAM-1 scores were not significantly different between the groups at day -2 (P > or = 0.08). Subsequent RV16 infection was associated with a trend towards an increase in ICAM-1 expression in the BUD-group (P = 0.07), whereas the increase was significant in the PLAC-group (P = 0.03). However, the increase was not significantly different between the groups (P = 0.74). Epithelial intactness score was not different between the groups before RV16 infection (P > or = 0.07), and no significant changes were observed in either group (P > or = 0.59). Moreover, ICAM-1 score did not correlate significantly with epithelium score in either group, at any time-point (P > or = 0.27).

CONCLUSION

We conclude that an RV16 common cold in atopic asthmatic subjects is associated with increased ICAM-1 expression in the bronchial epithelium, which is not related to epithelial intactness. Glucocorticoid treatment does not appear to prevent the RV16-associated increased ICAM-1 expression. This suggests that other treatment modalities are required to protect against the spreading of infection during rhinovirus-induced exacerbations in asthma.

The role of respiratory viruses in acute and chronic asthma

Respiratory infections can have dual effects related to asthma. First, there is increasing evidence that severe infections with RSV and PIV in infancy can alter lung development and physiology to increase the risks of subsequent wheezing and asthma. Second, infections with common cold viruses and influenza commonly precipitate wheezing symptoms in children and adults who already have established asthma, and RV appears to be the most important virus in producing exacerbations of the disease. The principal mechanisms by which this occurs appears to be viral replication in epithelial cells, triggering a cascade of inflammation involving granulocytes, macrophages, T cells, and secreted cytokines and mediators. The inflammatory process, although essential to clear the infection, augments pre-existing airway inflammation in asthma, leading to increased airway obstruction and lower respiratory tract symptoms. Greater understanding of virus-induced changes in inflammation and corresponding changes in airway physiology may lead to new therapeutic approaches to the treatment and prevention of virus-induced airway dysfunction.

The effect of an experimental rhinovirus 16 infection on bronchial lavage neutrophils

BACKGROUND

Viral respiratory tract infections are the most frequent cause of asthma exacerbations. Of the respiratory viruses associated with these exacerbations, rhinovirus (RV) is the most common. It is proposed that these RV infections may enhance airway inflammation and thus provoke asthma.

OBJECTIVE

It is our hypothesis that RV infections generate nasal proinflammatory mediators that are associated with an initial increase in circulating leukocytes and may contribute to later development of neutrophilic airway inflammation.

METHODS

To evaluate this hypothesis, subjects with a history of allergic asthma were experimentally inoculated with strain 16 RV (RV16). The effect of this experimental infection was evaluated on circulating leukocytes, nasal-derived mediators, and markers of bronchial inflammation that were obtained by bronchoscopy and lavage.

RESULTS

RV16 inoculation was associated with an initial increase in circulating neutrophils. Paralleling these acute changes in circulating neutrophils was an increase in nasal concentrations of IL-8 and granulocyte-colony-stimulating factor (G-CSF). The RV16-associated changes in circulating and nasal G-CSF correlated with increases in peripheral blood neutrophils (r(s) = 0.874, P <. 001 and r(s) = 0.898, P <.001, respectively). Bronchial lavage samples showed no increase in neutrophils 48 hours after RV16 inoculation; however, 96 hours after RV inoculation there was a significant increase in bronchial neutrophils compared with preinoculation values.

CONCLUSIONS

These results suggest that the production of nasal mediators associated with the RV infection, particularly G-CSF, may be important to the eventual development of neutrophilic bronchial inflammation and thus contribute to asthma exacerbations.

Effects of allergic inflammation of the nasal mucosa on the severity of rhinovirus 16 cold

BACKGROUND

Despite the strong association of asthma exacerbations with rhinovirus (RV) infection, inoculation of asthmatic subjects with RV only causes small changes in lower airway function, suggesting that RV infection is not itself sufficient to provoke asthma exacerbations.

OBJECTIVE

Our purpose was to test whether allergic inflammation increases the airway response to RV infection.

METHODS

We compared the severity of RV type 16-induced colds in 2 groups of 10 subjects with allergic rhinitis. One group received 3 nasal challenges with allergen and the other received challenges with placebo over the week before nasal inoculation with RV type 16 (4000 tissue culture infective dose 50% per subject). Subjects kept symptom diaries and were assessed with spirometry, methacholine challenge, nasal lavage, and sputum induction on days 2, 4, 7, 10, 15, and 30 after inoculation.

RESULTS

The 2 groups developed equal rates of infection (90%), similar cold symptoms (Jackson score median [interquartile range], 11 [6-33] vs 20.5 [6-42] for allergen and placebo groups respectively, P =.54), and similar changes in cellular profile and in IL-6 and IL-8 concentrations in nasal lavage fluid and induced sputum after RV inoculation. The incubation period was significantly longer in the allergen group (2.5 [1-5.5] vs 1 [1-1] day, P =.03) and the duration of cold symptoms was shorter (5 [4-7] vs 8.5 [6-10] days, P =.008). We also found an inverse correlation between the percent of eosinophils in nasal lavage fluid before inoculation and the severity of cold symptoms (r = -0.58, P =. 008).

CONCLUSION

In subjects with allergic rhinitis, augmented nasal allergic inflammation before inoculation with RV type 16 does not worsen the severity of cold symptoms but delays their onset and shortens their duration.

Effect of clarithromycin on experimental rhinovirus-16 colds: a randomized, double-blind, controlled trial

PURPOSE

Macrolide antibiotics are frequently prescribed to patients with symptoms of a common cold. Despite their lack of proven antiviral activity, macrolide antibiotics may have anti-inflammatory actions, such as inhibition of mucus secretion and production of interleukins 6 and 8 by epithelial cells. Because the symptoms of rhinovirus colds are attributed to the inflammatory response to infection, we studied the effects of treatment with clarithromycin on the symptomatic and inflammatory response to nasal inoculation with rhinovirus.

SUBJECTS AND METHODS

We performed a prospective, double-blind, controlled trial in 24 healthy subjects who were seronegative for antibodies to rhinovirus-16. Subjects were randomly assigned to receive either clarithromycin (500 mg) or trimethoprim-sulfamethoxazole (800/160 mg, as a control antibiotic) twice a day for 8 days, beginning 24 hours before inoculation with rhinovirus-16.

RESULTS

All 12 subjects in each group were infected and developed symptomatic colds. The groups did not differ in the intensity of cold symptoms (median [25th to 75th percentile] score in the clarithromycin group of 25 [5 to 33] versus 21 [11 to 26] in the trimethoprim-sulfamethoxazole group, P = 0.86), weight of nasal secretions (25 g [8 to 56 g] versus 12 g [5 to 28 g], P = 0.27), or decline in nasal peak flow during the 8 days following viral inoculation. In both groups, similar and significant increases from baseline were observed in the numbers of total cells and neutrophils, and in the concentrations of interleukins 6 and 8, in nasal lavage fluid during the cold. The changes that we observed did not differ from those in an untreated historical control group.

CONCLUSIONS

We conclude that clarithromycin treatment has little or no effect on the severity of cold symptoms or the intensity of neutrophilic nasal inflammation in experimental rhinovirus-16 colds.

Increased neutrophil numbers and IL-8 levels in airway secretions in acute severe asthma: Clinical and biologic significance

The inflammatory events in the airways at the time of acute respiratory failure from acute severe asthma are poorly understood. To determine the patterns of cellular inflammation in the airways in acute severe asthma, we analyzed tracheal aspirates collected within 12 h of intubation from patients intubated emergently for acute severe asthma (n = 10) and from patients intubated electively for nonpulmonary surgery (n = 14). The number of neutrophils in tracheal aspirates from asthma patients was 10 times higher than normal (4.2 [0.6 to 335.0] [median, range] versus 0.4 [0.009 to 9.4] x 10(6)/ml, p = 0.001), and there was a strong trend for a positive relationship between neutrophil number and duration of intubation (r(s) = 0.64, p = 0.06). Although eosinophil numbers were also significantly higher than normal (0.5 [0.0 to 23.3] versus 0.0 [0.0 to 0.1] x 10(6)/ml, p = 0.003), the numbers of eosinophils were 8-fold less than neutrophils, and there was no significant correlation between eosinophil number and duration of intubation (r(s) = 0.4, p = 0.26). Interleukin-8 (IL-8), a chemoattraction for neutrophils, was 19 times higher than normal in tracheal aspirates from asthmatic patients (75.0 [9.0 to 168.0] versus 4.0 [0.08 to 24.0] ng/ml, p < 0. 05) and correlated significantly with the neutrophil number (r(s) = 0.77, p = 0.03). Furthermore, the IL-8 levels correlated positively with the duration of mechanical ventilation (r(s) = 0.74, p = 0.03). Surprisingly, the number of neutrophils increased significantly during the period of intubation in the asthmatic subjects, possibly because of intravenous corticosteroid treatment. We conclude that neutrophils are the dominant inflammatory leukocyte characterizing airway inflammation in acute severe asthma that requires mechanical ventilation, and that IL-8 is an important mediator of this neutrophilia.

Viral and bacterial infections in the development and progression of asthma

Viral respiratory infections produce wheezing illnesses in patients of all ages. In infancy, infections with respiratory syncytial virus and parainfluenza virus are the major cause of bronchiolitis and croup, whereas infections with common cold viruses such as rhinoviruses are the principal triggers for wheezing in older children and adults with asthma. In addition to causing increased wheezing in asthma, there is mounting evidence that infections early in childhood can affect the development of the immune system and thereby modify the risk for the subsequent development of allergies and asthma. Both of these effects appear to be mediated by virus-induced immune responses. Early during the course of viral infection, resident cells in the airway are activated in an antigen-independent fashion, triggering antiviral responses but also activating and recruiting cells to the airway that could contribute to airway obstruction and respiratory symptoms. Virus-specific T- and B-cell responses may also have dual effects in the presence of preexisting airway inflammation. Finally, there is evidence of synergistic interactions between allergen- and virus-induced airway inflammation. It is likely that greater definition of mechanisms of virus-induced inflammation will provide therapeutic targets for the treatment and possibly the prevention of allergies and asthma.

Respiratory viruses and asthma

Viral infections have become increasingly recognized as a significant cause of asthma exacerbations, mainly because of improved viral detection techniques. Unfortunately, the ability to specifically treat viral infections and to limit the asthma morbidity associated with these agents has not kept pace with diagnostic technology. This article focuses on current concepts of the epidemiology of viruses in asthma exacerbations, investigations studying the physiologic and immunologic consequences of viral infection, and potential therapies to minimize virally-induced airway hyperresponsiveness. To impact this significant health problem, researchers must definitively ascertain the mechanisms by which viruses induce airway reactivity and must develop rational, safe approaches to prevent the consequences of viral infection in the patient with asthma.