key: cord-0888325-3zg27whi
authors: Edwards, Michael R.; Kebadze, Tatiana; Johnson, Malcolm W.; Johnston, Sebastian L.
title: New treatment regimes for virus-induced exacerbations of asthma
date: 2006-10-31
journal: Pulmonary Pharmacology & Therapeutics
DOI: 10.1016/j.pupt.2005.09.005
sha: ca8028af0a5d4530763b324515e71978d00ae99f
doc_id: 888325
cord_uid: 3zg27whi

Abstract This review will focus on the role of viruses as causes of asthma exacerbations. The article will briefly review the current literature supporting this view, with a special focus on human rhinovirus (RV), the main virus associated with exacerbations of asthma. The review will then refer to possible strategies for treatment, and will include discussion on treatment with specific anti-viral therapy and type I interferon as a treatment for RV. The review will also include a discussion on current therapies for asthma, such as glucocorticosteroid and β 2 agonist therapy alone and in combination and why this may be relevant to virus-induced exacerbations of asthma. Finally, the potential for future anti-inflammatory/immunomodulatory therapies with a focus on NF-κB inhibition will be discussed.

Asthma exacerbations, the majority of which are caused by respiratory viral infection, are a continuing problem in respiratory medicine worldwide. Most viral exacerbations are due to either respiratory syncytial viruses (RSV), coronaviruses, influenza viruses or human rhinoviruses (RV), with RV being the most frequent causative agent. In vitro and in vivo, RV infects the bronchial epithelium and upregulates a range of pro-inflammatory cytokines, chemokines, adhesion molecules, mucins and growth factors, all of which are thought to contribute to loss of lung function and lower airway inflammation [1] [2] [3] [4] . A large number of these mediators are upregulated solely, or in part, by the transcription factor NF-kB. This would suggest that inhibiting the functions of this transcription factor may alleviate symptoms associated with RV-induced exacerbations of asthma. In virusinduced asthma, bronchial biopsies and sputum have neutrophilic and lymphocytic infiltrates [4, 5] , and these cell types are therefore implicated in exacerbation pathogenesis. Due to the lack of a small animal model, there are many unclarified issues regarding the immunology of RV infection, and how this relates to exacerbations of asthma.

A recent study has estimated the economic impact of asthma in Germany to be in billions of Euros [6] . Although the actual costs of viral exacerbations are not known, it is arguable that they would contribute significantly to this cost, as viral infections account for about 80% of asthma exacerbations in children, and between 40% and 76% in adults [7] [8] [9] [10] [11] [12] . In the UK, one study has estimated the cost of asthma exacerbations to be approximately 3.5-fold higher per patient when compared to asthma patients that did not experience exacerbation [13] . Currently, the medical needs of patients suffering from viral exacerbations of asthma are largely unmet. There is no vaccine for RV or RSV, and the use of influenza vaccines in reducing virus-induced exacerbations remain controversial [14] . Steroids so far have been disappointing in their ability to control symptoms in models of experimental RV challenge of asthmatics [15] [16] [17] [18] , and high-dose steroids remain only partially effective at controlling virus-induced exacerbations of asthma [19, 20] . A range of anti-viral, anti-RV compounds and combinations of the above have been used as therapies for RV infection, these have had variable efficacies in controlling RV-associated illnesses. This review will summarise the current understanding of virus-induced exacerbations of asthma, with a special focus on RV, including the epidemiology, host defence and immunology. Studies of treatments aimed at virus-induced exacerbations will also be discussed, with an emphasis on how better understanding the process of infection and upregulation of proinflammatory mediator gene expression may be useful in aiding the design of novel therapies for virus-induced asthma exacerbations.

There is now overwhelming evidence that respiratory viruses are associated with acute exacerbations of asthma, accounting for up to 80-85% of acute exacerbations [7, 10, 21, 22] . Of the common respiratory viruses, RV have emerged as the most frequent. Other respiratory viruses such as RSV influenza viruses, parainfluenza viruses, coronaviruses, adenoviruses and the newly described metapneumoviruses, may also be associated with exacerbations of asthma. In children o2 years of age, RSV, infection is a common cause of significant morbidity in the form of wheeze or bronchiolitis [9, 10, 22, 23] . In older children and adults, RSV is still implicated in exacerbations of acute asthma, but does not appear to be as important as RV [7, 10, 21] . Influenza is an important pathogen during winter epidemics [24] , but outside these periods it is not a major contributor to exacerbations of asthma. Recent data [25] [26] [27] suggest that human metapneumovirus has a minor contribution (o12%) to virus-induced exacerbations of asthma. The relative frequency of detection of each virus type in exacerbations of children 42 years and adults as found in previous studies [10, 21, 22] are summarised in Fig. 1 , and represent approximate estimates for the most common respiratory viruses identified. 3 . Virus-induced exacerbations of asthma: similar and distinct pathology and mechanisms of action to persistent asthma Virus-induced exacerbations of asthma have both similar and distinct properties to persistent asthma. Respiratory virus-induced exacerbations of asthma may occur in patients with phenotypes that differ from the atopic phenotype characteristic of allergen-induced asthma. One [10, 21, 22] , and presented here as an average. Viral infection was measured in these studies using virus culture, RT-PCR or both.

obvious difference between allergen-induced asthma and exacerbations is that inhaled corticosteroids, which are effective for the treatment of persistent asthma, do not work with the same efficacy in asthma exacerbations [19, 20] . Evidence for similar mechanisms of action is suggested by the fact that allergen exposure and virus infection may act in a synergistic or additive manner, increasing the risk of asthma exacerbations [28] . Pollutants such as nitrogen dioxide may also increase the risk of virusinduced exacerbations of asthma [29] . Some interesting differences between asthma exacerbations and persistent asthma are highlighted by the following observations.

Virus-induced asthma exacerbations may differ from persistent or allergen-induced asthma in that neutrophils appear to play a more prominent role in exacerbations, while eosinophils predominate in the latter. T lymphocytes appear important to both. The importance of neutrophils and CD4+ and CD8+ T lymphocytes in asthma exacerbations is supported by several studies [4, 5, 11, 15, [30] [31] [32] [33] [34] [35] . In atopic asthmatics, eosinophils or eosinophil activation are also increased in virus-induced asthma. Given that a mixed aetiology is likely very common [28, 36] , it is not surprising that there is much overlap in pathogenesis. Differences also exist in the way asthmatics respond to viral infection and may affect the outcome of infection and hence disease severity. Although asthmatics have the same incidence of viral infection as normals, they have increased severity and duration of lower airway symptoms and reduction in lung function than normals [37] . A recent study has also reported persistence of RV in children suffering from exacerbations of asthma, with children showing RV persistence having more severe exacerbations [38] . Also, increased levels of RV replication have also been observed accompanied by lower levels of virus-induced interferon (IFN)-b expression and virus-induced apoptosis compared to normals [39] . In certain studies, greater levels of proinflammatory cytokine elaboration and inflammatory cell recruitment are observed [4] . Peripheral blood mononuclear cells from asthmatics when cultured with RV exhibiting lower levels of the T H 1 cytokines IFN-g and IL-12, suggesting that asthmatics may have a defective T H 1 response to viral infection [40] . These data support two important points; firstly virus exacerbations of asthma have different properties to persistent or allergen-induced asthma, and secondly, researchers are still defining the characteristics of viral exacerbations and the populations in the community that are at risk. These important points must be appreciated prior to discussing new treatments for virus-induced exacerbations of asthma. 4 . Human RV-the most common virus associated with exacerbations of asthma

RVs belong to the Picornaviridae family of viruses. These viruses have small RNA genomes (approximately 7 kb), [41, 42] , are non-enveloped and are stable in the environment. There are at least 100 serotypes, which are divided into major or minor groups depending on receptor specificity. Most RV are major group RV, and bind human ICAM-1, minor group RV bind the LDL receptor [43] . The difference in receptor specificity appears to be explained by a charge difference of the H1 loop of structural protein VP1 [44] . RV can replicate efficiently in the upper airway and can be detected in the lower airway although replication remains to be proven in vivo [45, 46] . RV infection can be readily observed in the bronchial epithelium [47] in vivo, and ex vivo, detected by sampling both the lower airway [48, 49] and upper airway [50, 51] .

RV are now well established as the major virus associated with exacerbations of asthma and also chronic obstructive pulmonary disease (COPD) [4, 8, 21, 37, [52] [53] [54] . Using virus-specific RT-PCR and virus culture techniques, epidemiological studies have observed that RV has the highest incidence of all respiratory viruses in exacerbations of asthma in adults and children42 years of age; approximately 60-65% of viral exacerbations are due to RV infection [7, 8, 10, 22, 26] , as presented in Fig. 1 . RV infection appears to be prevalent in children returning to school, leading to significant epidemics, and increased hospital admissions in the month of September in the Northern Hemisphere [55] . A thorough review of the epidemiology of RV infection of the lower respiratory tract is available elsewhere [56] .

Due to the lack of a small animal model, many aspects of immunology and host defence against RV infection remain unelucidated. Experimental and natural infections, and in vitro infection of lung epithelial cells have been useful in the study of RV-induced inflammation, in both asthma and COPD. The immunology of RV infection is a rapidly expanding field, and has been thoroughly reviewed elsewhere. This review will highlight the main findings and discuss some of the unresolved issues; interested readers are directed to the following recent reviews for more information [57] [58] [59] [60] . RV upregulate the expression of a range of pro-inflammatory mediators from lung epithelium in vitro and in vivo including the chemokines IL-8/CXCL8 [61] [62] [63] [64] [65] , ENA78/CXCL5 [66] , eotaxin/CCL10 [67, 68] RANTES/ CCL5 [67, 69] , IP-10/CXCL10 [70] , growth and differentiation factors such as IL-6 [62, 64, 71] , GM-CSF [62, 64, 65, 72, 73] , IL-11 [74, 75] and also adhesion molecules ICAM-1 and VCAM [76] [77] [78] [79] [80] , and respiratory mucins [81, 82] .

Virus-induced exacerbations of both asthma and COPD are associated with lower airway infection [47, 83] , resulting in lower airway inflammatory responses characterised by infiltration of CD4+ and CD8+ T cells, neutrophils, eosinophils and activation of local macrophages and mast cells [5, [84] [85] [86] . Experimental and natural infections of human subjects have also shown that subjects infected with RV show an increased level of the above cytokines in nasal secretions and sputum [1] [2] [3] [4] . In one study, the accumulation of inflammatory cells and molecules correlated with increased symptom scores [2] , and in another, decreased lung function of asthmatics [1] , giving support to the current hypothesis that the local inflammatory reaction contributes to exacerbations in asthmatics. Therefore, if the upregulation of inflammatory molecules and cells can be prevented, diseases may be prevented. Inhibition of RVinduced inflammatory cytokine/chemokine production therefore represents an important therapeutic target for asthma. Some inflammatory molecules induced by respiratory virus infection and the cells they attract are outlined in Fig. 2 .

A striking observation is that all the pro-inflammatory molecules and growth factors upregulated by RV so far studied in detail require the transcription factor NF-kB (discussed below). The NF-kB or Rel family of transcription factors (p65, p50, c-Rel) are implicated in the expression of over 100 pro-inflammatory genes (for a review see [87] [88] [89] ). NF-kB is sequestered in the cytoplasm by its specific inhibitor IkB, when phosphorylated by upstream kinases, IkB is ubiquitinated and degraded by the proteasome, allowing NF-kB to translocate to the nucleus. The upstream kinases responsible for relaying the signal include NF-kB inducing kinase (NIK) [90] and the IkB kinases (IKK)-aXb [91, 92] , and the more recently identified IKK-i/e [93, 94] and TANK binding kinase-1 (TBK-1) [95] [96] [97] . Once in the nucleus, NF-kB can bind to various cis-acting sites within the promoter of NF-kB responsive genes and promote transcription (depicted in Fig. 3) .

The promoters of GM-CSF, IL-6, CXCL8, CXCL10, ICAM-1 and VCAM all contain NF-kB binding sequences, and NF-kB is required for the expression of these genes following RV infection in vitro [62, 63, 70, 71, 76, 80] . We have also extended this analysis for CXCL8 and IL-6 and have shown that NF-kB cis-acting sequences are absolutely required for RV-induced promoter activation for these genes in bronchial epithelial cells, and have identified a role for IKK-b, using the specific IKK-b inhibitor AS602868 (Serono, M.R. Edwards and S.L. Johnston, submitted). The role of NF-kB signalling in RV-induced CCL5 and IL-11 gene expression is not yet known, however seems likely to be implicated as both promoters contain NF-kB sequences, and these are important for gene expression following infection with other respiratory viruses [98, 99] . The role of NF-kB in RV-induced CCL10 and CXCL5 has not yet been studied; however, both genes also have NF-kB sites within their promoter, that are required for gene expression in various systems [100] [101] [102] . Hence inhibition of NF-kB translocation, and NF-kB signalling represents a potential area of therapeutic intervention.

One unresolved question in RV biology is how NF-kB signalling is initiated by virus infection. The dsRNA binding anti-viral protein kinase (PKR) has been widely implicated in NF-kB signalling via interacting with IKK-a/ b, or by phosphorylating IkB directly [103] [104] [105] [106] . Tolllike receptor 3 (TLR3) [107] , and the recently described retinoic acid inducible gene (RIG)-I [108] also activate NF-kB in response to viral infection or dsRNA. Gern et al. [68] have demonstrated a role for PKR in RV-induced pro-inflammatory mediators from bronchial epithelial cells. PKR would thus seem a potential therapeutic target in RV exacerbations of asthma; however, PKR is also implicated in beneficial anti-viral host responses. Through its ability to phosphorylate eukaryotic initiation factor-2a, PKR causes termination of host protein synthesis following viral infection [109] , in an attempt to limit viral replication. PKR is also involved in type I IFN responses [110] . Hence, the possibility of beneficial and/or detrimental affects of PKR inhibition in RV exacerbations of asthma remains an open issue.

The late 1980s and early 1990s saw great interest in antirhinoviral treatments, directed mainly at the control of clinical colds. Compounds which interfere with viral attachment and uncoating by binding to the picornaviral capside protein VP1 were first investigated in the late 1980s [111] [112] [113] , and RV 3C protease inhibitors such as Ruprintrivir much later [114] . These drugs showed a broad inhibition to RV infection in vitro [115] . The modes of action of all treatment options discussed in this review are shown in Fig. 4 .

The viral capsid binder R61837 was first used in 1989, in a model of experimental infection with RV9. R61837 was given in a single dose (2.5 mg) intranasally either 28 or 4 h prior to challenge, and continued up to 4 or 6 days, respectively, post-challenge [112] . Clinical colds were 3 . Activation of NF-kB p65, p50 by the IKK-a/b/g complex, or an alternative IKK complex consisting of IKK-i/e, TBK-1 and TANK. Following viral infection, or dsRNA recognistion via PKR and/or TLR3, RIG-I, or cytokines, e.g. TNF-a or IL-1b (via NIK), IKK phosphorylates IkB leading to its degradation by the proteasome. Once free, NF-kB p65, p50 subunits translocate to the nucleus and upregulate NF-kB responsive genes, such as CXCL8, IL-6 and GM-CSF. defined on the basis of using 44 tissues over the baseline rate plus development of one other relevant symptom (sore throat, sneezing, etc.). When given 4 h prior to challenge, and for 6 days duration, R61837 reduced the incidence of colds, mean total symptom score and weight of nasal secretions compared to a control group given placebo. The effects of R61837 on the duration of the clinical cold, or length of time spent exhibiting symptoms were not studied.

In contrast, the oxazoline WIN54954 was tested in 1993, and showed poor efficacy in experimental models of RV39 and RV23 [111] . Dosing consisted of a 600 mg oral dose, every 8 h for 6 days. Challenge occurred on study day 2. WIN54954 did not reduce any of the parameters tested when compared to placebo, including incidence of colds, mean total symptom score and viral titre. One explanation for the poor performance of WIN54954 was the low levels of drug recovered from saliva and nasal wash after treatment. Few patients had concentrations greater than the minimum inhibitory concentration (MIC) for the test virus. Pirodavir (R77, 975) when given as an intranasal therapy (2 mg), was also disappointing in a study of natural virus infection [113] . Pirodavir reduced only viral titre when compared to control groups treated with placebo, the duration of colds and mean total symptom score were not reduced by Pirodavir.

The anti-picornaviral agent Pleconaril has been used in randomised, placebo-controlled, phase II clinical trials as a treatment of the common cold [116] . Pleconaril acts by preventing uncoating of picornaviruses, including most serotypes of RVs tested in vitro [117] . Participating volunteers commenced treatment 1-1.5 days after a clinical picornavirus infection was established. Individuals taking Pleconaril, when taken as a 400 mg dose in liquid form, or as a 400 mg tablet three times daily showed significant improvement in mean symptoms scores at days 2-5 after commencement of treatment, and decreases in mean duration of illness. Despite promising initial results, Pleconaril has not yet been tested in the setting of RVinduced exacerbations of asthma.

The RV 3C protease inhibitor Ruprintrivir (Agouron Pharmaceuticals, Inc.) has also been tested in a doubleblind, placebo-controlled phase II trial of experimental RV39 challenge [114] . RV 3C protease is required for cleavage of the rhinoviral precursor polyprotein into individual components prior to viral assembly. Furthermore, RV 3C protease is required for generation of the RNA polymerase and hence viral RNA replication. RV 3C protease has also been implicated in initiation of host cell signalling leading to pro-inflammatory cytokine production [65] . Ruprintrivir was designed using solved X-ray crystal structures of the RV 3C protease, and was designed to bind irreversibly to the RV 3C active site [118] . Ruprintrivir demonstrated a broad anti-picornaviral spectrum in vitro, with an MIC of 0.023 mM [119] . The above study utilised Ruprintrivir as either two or five times a day as prophylaxis, 6 h prior to infection, or as a treatment five times a day 24 h after infection. As a prophylaxis, Ruprintrivir reduced mean total symptom score, viral titre, nasal secretions but not the incidence or frequency of clinical colds (as assessed by the number of infected subjects that developed clinical colds). As a therapeutic treatment, Ruprintrivir also reduced symptom scores, nasal secretions and viral titre. Ruprintrivir was generally well tolerated, despite this study requiring numerous deliveries via nasal spray.

The above studies provide evidence that treatment of clinical colds with anti-rhinoviral therapies is useful. However, there are potential problems with these approaches, with respect to potential therapies for virusinduced asthma exacerbations. For example, therapy of capsid binding molecules has led to the development of escape mutants [117] . It could also be argued for the RV 3C protease inhibitors, that virus binding, uncoating and entry could be a stimulus for cell signalling events, leading to initiation of pro-inflammatory mediator gene expression [61] , and future therapies should aim at preventing the early steps of virus uncoating and entry. In support of this view, a study of Ruprintrivir to prevent RV14-induced IL-6 and CXCL8 suggested that this agent was not 100% effective at reducing mediator production, despite a high dose of 10 mM being used [120] . For therapies such as Ruprintrivir, which were administered via nasal spray, it can also be argued that delivery by this method may not be effective at treating the lower airway, where virus-induced asthma exacerbations are believed to be triggered. Furthermore, dosing regimes must also be suitable for children, as well as adults, in a setting of asthma exacerbations. Perhaps a further criticism of many of these studies is that duration of clinical colds was not affected by most treatments. Pleconaril was the only treatment successful at reducing duration of clinical cold. These therapies, although reducing symptoms may not necessarily affect duration of symptoms, and therefore may not improve the rate of general practitioner consultations, hospital admission rates, and school and work absenteeism for infected individuals with virus-induced exacerbations of asthma.

Several versions of human ICAM-1 have been used in clinical studies, including soluble ICAM-1 (Tremacamra/ BIRR 4) [121] , antibodies to ICAM-1 [122] , and fusion proteins of ICAM-1 and IgA [123] . In vitro, soluble ICAM-1 preparations have been shown to reduce titres of a large range of major group RVs [123, 124] . Tremacamra has been tested in randomised double-blind placebo-controlled studies both as a therapeutic and prophylactic intervention to RV39 challenge [121] . In these clinical studies, Tremacamra has shown promise as a therapy, reducing the proportion of clinical colds following experimental RV39 challenge, total symptom score, nasal mucus weight, and significantly lowering CXCL8 release on days 3 and 4 post-infection compared to placebo. Tremacamra also significantly reduced RV39 replication on days 2-4 postinfection. Also, Tremacamra was useful in controlling RVinduced symptoms if given prior to challenge, or after challenge but before establishment of symptoms. Tremacamra holds promise as a therapy for clinical colds, however, has not been tested in a context of exacerbations of asthma.

Type I IFNs are potent anti-viral mediators having a range of effects that limit viral infection and dissemination. Type I IFNs include the numerous IFN-as, IFN-b and the newly identified IFN-ls [125] . Type I IFNs act on virally infected cells or uninfected cells and induce a well-ordered anti-viral programme, involving the upregulation and activation of a range of IFN inducible genes, such as PKR, which phosphorylate eIF-2a and hence blocks translation, also anti-viral RNase L and Mx proteins. IFNs can induce apoptosis, or induce more IFN gene expression in an autocrine or paracrine manner. IFNs also activate NK cells and are required for NK cell survival, and may have other effects on both innate and adaptive immunity (for a review see [126, 127] ).

Type 1 IFNs-a and b have been extensively studied in the prevention of clinical colds since the 1980s. The potential of IFN-a2 attracted wide interest, culminating in several reports in the early to mid-1980s. In 1984, IFN-a2 was used as therapy for experimental RV39 infection [128] . Previous studies had suggested that effectiveness of IFN-a2 was dose dependent, with high doses (2-4.5 Â 10 7 IU per day) effective at reducing both RV infection and illness, and lower doses, 10 6 IU, effective at reducing illness (symptom scores), but not necessarily affecting the incidence of colds [129] [130] [131] . Despite the effectiveness of IFN-a2 in models of experimental RV infection at these high doses, significant side effects were observed, including blood-tinged mucus, and even mucosal histopathological abnormalities [131] . This study sought to examine the efficacy of 10 6 IU IFN-a2 delivered three times daily for 5 days via nasal spray or drops. Challenge with RV39 occurred 28 h later. IFN-a2 reduced virus shedding, with the drops having a more potent effect. IFN-a2 delivered via drops also significantly reduced nasal mucus weights, but neither treatment reduced the frequency of clinical colds.

IFN-a2 has also been tested as a prophylactic treatment in natural viral infections. In one study, twice daily IFN-a2 at 10 6 IU for 28 days demonstrated less RV-associated colds, but was not significantly different to placebo [132] . Another study utilised IFN-a2b at either 1.5 Â 10 6 units twice daily or 2.5 Â 10 6 once daily each for 4 weeks; control subjects were given dose-matched placebo [133] . During the medication period, twice daily IFN-a2b greatly reduced the number of RV-associated colds, but had no effect on parainfluenza-associated colds. The effects of IFN were slowly lost after the treatment period, with frequencies of RV-associated colds being about equal after 8 days post-treatment. At both doses, IFN-a2b exhibited side effects, mostly in the form of nasal blood-tinged mucus.

Several studies have investigated the potential of IFN-b in treatment of clinical colds. The first study of intranasally administered recombinant IFN-b (IFN-b Ser) involved 13 doses of 2 Â 10 6 IU over 4 days. This treatment showed promise in control of experimental RV9 or RV14 challenge [134] . This study involved RV challenge occurring after the fourth dose of IFN-b. There were significantly lower symptom scores, nasal secretions and virus release compared with placebo. The next study with IFN-b Ser involved both a tolerance and efficacy study against experimental RV challenge. Volunteers were pre-treated with either IFN-b Ser (12 Â 10 6 , or 3 Â 10 6 IU) 36 h before infection, and continued for 25 days [135] . The tolerance study demonstrated numerous side effects particularly with the high-dose regime, including blood-tinged mucus, and an increase in subepithelial lymphocytic infiltrates in nasal biopsies. The efficacy study also reported significant decreases in nasal mucus weights, less development or incidence of clinical colds, but not less viral shedding, and these differences were only significant with the high-dose regime.

A third study involving prophylaxis against natural infections reported quite disappointing results [136] . Two randomised placebo-controlled trials in 1986-87 utilised IFN-b Ser given either 6 days a week for 4 weeks (9 Â 10 6 IU), or a higher dose (24 Â 10 6 IU) for 24 consecutive days. Both studies failed to show a significant reduction in the incidence of clinical colds compared to placebo, and also in patients that received cold, the number of days of illness did not differ between IFN-b Ser treated groups and placebo.

These studies provide a useful background to assess the potential of IFN therapy for viral exacerbations of asthma. An advantage that type I IFN therapy has over anti-RV therapies is that all exacerbations of asthma with viral agents could be controlled. Specific RV therapies would treat 60-65% of virus-induced exacerbations; however, broad-spectrum therapies such as IFN would not have this disadvantage. In particular, the above studies suggest that IFN-a2 is effective when given prior to experimental RV infection, or as a prophylactic therapy in a context of natural RV infections. IFN-b has been less impressive, exhibiting some effect when given prior to experimental RV challenge, but no effect as a prophylactic in natural infections. It is believed that these differences are not due to differences in anti-viral activity, as both IFN-a2 and IFN-b have similar anti-rhinoviral activities in vitro [137] . The relative ineffectiveness of IFN-b has been thought to be due to instability as a nasal spray [136, 137] ; however, when used as drops, IFN-b also did not perform in a prophylactic study against natural RV infection [136] .

Delivery and dose appeared to be contentious issues in these studies, with the effectiveness of IFN-a dependent upon a high enough dose to prevent infection and clinical colds, but low enough to prevent unwanted side effects.

However, most studies reported side effects, even at lower doses of 10 6 IU given daily. It can be argued that such side effects would be even more problematic in asthmatics, particularly the increased inflammation of the nasal passage, which appeared to be a hallmark of intranasal IFN therapy. Another issue for asthmatics would be effective delivery to the upper versus lower airway. While RV when administered by nasal spray can definitely be found in the lower airway during experimental infection, it is currently unknown whether intranasally applied IFN would act at a high enough concentration in the lower airway. An alternative could be IFN delivered via oral inhalation, similar to inhaled corticosteroids, thereby ensuring delivery to the lower airway. The ultimate effectiveness of IFN therapy in RV-induced exacerbations of asthma has yet to be investigated.

IFN has also been tested in conjunction with other treatments such as non-steroidal anti-inflammatory agents. This approach is based on the belief that no single molecule therapy has proved effect for RV-associated clinical colds, as no single therapy can block viral infection and replication, and the associated host response to infection, including the cellular, and humoral inflammatory reactions [138] . These studies aimed to treat the clinical colds with a combination of treatments in the early phase of infection, with the argument that this regime at this time would be effective in not only controlling infection, but the many symptoms associated with the host inflammatory response to infection.

Intranasal IFN-a2b was used along with ipratropium and oral naproxen in a model of experimental RV infection [139] . The treatment was given 24 h post-infection, and continued for 4 days. This treatment effectively reduced days of virus shedding and virus titre compared to placebo, and decreased nasal mucus weights on days 3-4 postinfection. Intranasal IFN-a2b has also been studied with oral chlorpheniramine and ibuprofen, versus treatments consisting of intranasal placebo with oral chlorpheniramine and ibuprofen, or both oral and intranasal placebos, in experimental RV39 infection [138] . The combination reduced the total symptom score by about 22%, compared to 27% with only oral chlorpheniramine and ibuprofen, or 19% achieved with placebos. The combination also significantly reduced nasal mucus weights generated by clinical colds, and also reduced viral titres compared to the other groups on day 3 post-infection. The effects of these treatments on the duration of clinical colds were not studied however. There appeared to be significant side effects associated with the combination treatment regime. One fifth of subjects having received the combination complained of blood-tinged nasal mucus. Drowsiness and nasal dryness were also common for all groups.

Glucocorticosteroids (GC), are the mainstay of current asthma therapy. Steroids when administered topically are potent inflammatory agents, acting to help reduce proinflammatory molecule gene expression operating largely at the level of pre-transcription (for a review, see [140] ). Steroids can reduce inflammation through glucocorticoid receptor (GR)-DNA interactions, GR-transcription factor interactions, inducing histone deacetylation, and therefore reducing DNA unwinding and hence transcription of inflammatory genes, and finally by inducing anti-inflammatory agents.

Despite evidence that steroids attenuate RV-associated inflammatory responses in vitro [75, 77] , the use of steroids in virus-induced exacerbations of asthma remains controversial. Several in vivo studies report poor efficacy of steroids in preventing inflammation and reduction of lung function in models of experimental RV infection [15] [16] [17] [18] .

Farr et al. [18] examined the potential use of prednisone (30 mg twice daily), or intranasal beclomethasone (168 micrograms twice a day), given 3-4 days prior to challenge as a prophylactic treatment in a model of experimental RV infection. Treatment ceased 5 days post-challenge. Up to 48 h, this treatment appeared affective at reducing nasal obstruction, nasal mucus weights, and nasal kinin concentrations; however, this effect was lost when steroid treatment ceased. Another study also examined prednisone (20 mg) given three times daily for 5 days, with treatment commencing 11 h prior to RV infection [141] . The steroids reduced nasal kinin and mucus concentrations but had little effect on other symptoms. Virus load was higher in the steroid-treated group, with significant differences on days 3 and 4 post-infection. The data suggest that an adverse effect of steroids may be suppression of antiviral mediators that are required for the natural defence against viral infection in vivo. No support for this has yet been observed in vitro; however, the relative effects of steroids on type I IFNs, defensins (for enveloped viruses), or other anti-viral components remains largely unexplored.

Grunberg et al. [15] examined the possible benefits of inhaled budesonide (800 mg, twice daily) treatment in mild asthmatics during experimental RV infection. Treatment commenced 2 weeks prior to challenge and was maintained throughout the study period (until 2 weeks post-challenge). Budesonide improved lung function in the asthmatics, and decreased eosinophil numbers, but did not reduce total inflammatory cell numbers in the lung. The authors concluded that steroids only gave partial protection in RV-associated inflammation of asthma. In another study, it was observed that budesonide treatment caused a small but significant increase in the soluble IL-1R antagonist in nasal secretions. There was no significant difference between CXCL8 and IL-1b levels between asthmatics treated with budesonide and control asthmatics treated with placebo [16] . These data support the idea that steroids may have benefits in RV-associated exacerbations by increasing the level of anti-inflammatory mediators within the airway, rather than having a direct effect on proinflammatory mediator expression.

The use of GCs in treating virus-induced wheeze in children under 17 years of age has also been carefully examined. A meta-analysis of compiled data from several studies showed that maintenance low-dose inhaled GCs did not demonstrate any clear reduction over placebo in the proportion of hospital admissions due to viral wheeze, and this treatment did not affect the prescription rate of oral GCs as treatment when these individuals were admitted to hospital [142] . Several other studies report similar findings [143] [144] [145] . In contrast, a study investigating emergency room hospital admissions and community cases of viral infection in autumn in Canada revealed that in children, patients admitted to hospital with exacerbations are less likely to have been given prior treatment in the form of inhaled GCs or leukotriene receptor antagonists [55] . Also, two clinical studies consisting of older children (413 years) and adults have shown that GCs alone have failed to reduce asthma exacerbation rates. In these studies, increasing the GC dose did not reduce the rate of asthma exacerbations [19, 20] , Currently, there is much evidence suggesting that the use of GCs alone is only partially protective against virus-induced exacerbations of asthma, and that preventive therapy can be improved. Again these data indirectly support the idea that exacerbations of asthma may involve processes that are different to persistent asthma.

GCs may act in concert with other therapeutics, for example, long-acting b 2 agonists (LABA) in combination therapy. LABAs act via a G protein coupled receptor, activate adenylate cyclase and through the second messenger cAMP, induce intracellular signalling events affecting a broad range of physiological processes, alone and in combination with GCs, such as smooth muscle growth and differentiation [146] , inflammation [147] [148] [149] [150] [151] [152] [153] and response to bacterial infection [154, 155] . In severe or persistent asthma, several studies in vitro and in vivo have shown that the combined use of GCs and LABA has advantages over the use of GCs alone, in terms of alleviating inflammation, controlling smooth muscle remodelling and improving lung function [146, [156] [157] [158] [159] [160] .

Considering the ability of LABA to enhance the antiinflammatory properties of GCs, and exert some antiinflammatory effects themselves in vitro [147, 152, 161] , an important question is whether or not combination therapy of LABA and GCs can reduce asthma exacerbation rates. Studies completed thus far suggest a positive effect of b 2 agonists when combined with GCs, in reducing frequencies of asthma exacerbations [162, 163] ; however, further evidence is required before the use of GCs in this way is generally accepted. These studies may also be of mixed aetiology, as exacerbations in general were investigated, and not specifically virus-induced exacerbations. It is also unclear whether the enhanced effect produced by b 2 agonists in the above studies was due to bronchodilation, or by decreasing inflammation, or both.

There are yet to be clinical studies using combination therapy in models of experimental or natural RV infection in asthma. Until such studies are performed, the potential role of combination therapy in the treatment of RVinduced asthma exacerbations remains open. One caveat to this idea is the general observation that virus-induced exacerbations of asthma involve not only eosinophils, but recruitment of both neutrophils, and activated T cells into the inflamed airway, and also activation of local macrophages [5, [84] [85] [86] . The ability of combination therapy to control neutrophilic and lymphocytic-induced inflammation is yet to be investigated experimentally.

As NF-kB is involved in induction of the majority of pro-inflammatory mediators studied so far in RV infection (see section above), NF-kB signalling components represent possible therapeutic targets. In murine models of allergic asthma, there has been some success with NF-kB inhibition. The redox inhibitor MOL294 and NF-kB decoy oligodeoxynucleotides have been successful in reducing pro-inflammatory molecule expression, lung inflammation and airway hyper-responsiveness to metacholine [164, 165] .

Recent studies have shown that the RV induction of CXCL8 and IL-6 from bronchial epithelial cells is an IKKb dependent process, and is sensitive to inhibition with AS602868 (Serono International, [166] ), a selective IKK-b inhibitor (M.R. Edwards and S.L. Johnston, unpublished observations), suggesting that IKK-b inhibition may be a useful therapeutic option. A recent review has given a thorough summary of the current range of selective IKK inhibitors available, including both organic-based and small molecule inhibitors [88] ; therefore, they will not be discussed in detail here. Importantly, the current range of selective IKK inhibitors have just begun to find their way into clinical trials, after showing promise in cell-based assays and murine models of disease. Inhibitors of these types have not yet been tested in human models of experimental virus infection, or asthma.

Concerning virus exacerbations of asthma, one caveat to the idea of NF-kB inhibition is that protective, anti-viral mediators may also be induced in an NF-kB dependent manner. The obvious example of this is IFN-b, which in many systems, is made initially on viral infection in an NF-kB dependent manner [167] [168] [169] [170] . Clearly, the potential role of NF-kB in the expression of mediators that are beneficial to the host response to infection needs to be carefully considered before NF-kB intervention becomes a serious therapeutic option. With the discovery of alternate NF-kB signalling intermediates such as IKK-i/e and TBK-1, the proposition of NF-kB inhibition has become more complex (see Fig. 3 ). However, the role of individual NF-kB signalling intermediates in both harmful pro-inflammatory mediator gene expression as well as in useful anti-viral mediator gene expression, is a much understudied field, and whether distinct signalling intermediates exist for IFN expression versus pro-inflammatory cytokine expression is currently unclear. Further research efforts are required before the role of this important transcription factor and its signalling pathways can be fully understood.

Many respiratory viruses, in particular RV, cause exacerbations of asthma, and this is a healthcare concern worldwide. RVs upregulate pro-inflammatory mediators and cause local inflammation in the lower airway, and this may precipitate exacerbations of asthma in certain individuals. Individuals suffering from viral exacerbations of asthma are yet to be treated effectively, and there is wide interest in a range of treatment options for these unmet medical needs. Specific anti-rhinoviral therapy, IFN therapy, and steroid-based therapies have all been studied in the past with mixed successes. Anti-viral therapies have been classically applied in the context of clinical colds (Table 1) ; however, they have not yet been studied in exacerbations of asthma. With the link between RV and asthma exacerbations now more established, the antirhinoviral treatments Pleconaril and Tremacamra should be regarded as serious therapeutic options. The study of type I IFN therapy in clinical colds has highlighted many problems with this treatment. Dose, delivery and safety all remain important issues for viral exacerbations of asthma. As a deficiency in IFN-b expression has been recently described in asthmatics [39] , type I IFN therapy remains a candidate treatment however. One potential area of further research is combined anti-viral, anti-inflammatory therapy, which may inhibit viral replication as well as treating upper and lower airway inflammation. Another area that has yet to be tested formally is NF-kB inhibition, as many RVinduced inflammatory mediators are NF-kB dependent. The wealth of literature so far reported on RV-induced exacerbations of asthma suggests that the relationship of infection and asthma exacerbation, in particular the cellular and molecular immunological aspects of pathogenesis, is still unclear, and further experimental infection studies are required to better understand these important processes. In particular, how asthmatics may differ from normal individuals who do not suffer from lower airway disease is a priority. There is also a need for further vigorous pursuit of the molecular mechanisms of infection and pro-inflammatory mediator induction, for example, the development of small animal models that will be invaluable for testing these ideas and providing future therapeutic targets. [134] [135] [136] a Refers to the symptoms studied by the authors. O refers to successful control of the symptom being studied. p refers to unsuccessful control of that particular symptom. NS refers to the symptom not being studied. b Limitations are those as suggested by the authors in each study.

321 2. Respiratory virus infections as exacerbators of asthma

Virus-induced exacerbations of asthma: similar and distinct pathology and mechanisms of action to persistent asthma

Human RV-the most common virus associated with exacerbations of asthma

Human or recombinant soluble ICAM-1 and derivatives

Experimental rhinovirus 16 infection. Effects on cell differentials and soluble markers in sputum in asthmatic subjects

Association between interleukin-8 concentration in nasal secretions and severity of symptoms of experimental rhinovirus colds

Rhinovirus-16 colds in healthy and in asthmatic subjects: similar changes in upper and lower airways

Inflammatory indices in induced sputum: a feasibility study

Lower airways inflammation during rhinovirus colds in normal and in asthmatic subjects

Asthma: prevalence and cost of illness

Respiratory viruses and exacerbations of asthma in adults

Community study of role of viral infections in exacerbations of asthma in 9-11 year old children

Detection of respiratory syncytial virus, parainfluenzavirus 3, adenovirus and rhinovirus sequences in respiratory tract of infants by polymerase chain reaction and hybridization

Detection of viral, Chlamydia pneumoniae and Mycoplasma pneumoniae infections in exacerbations of asthma in children

Neutrophil degranulation and cell lysis is associated with clinical severity in virus-induced asthma

Use of induced sputum for the diagnosis of influenza and infections in asthma: a comparison of diagnostic techniques

Risk factors and costs associated with an asthma attack

Randomised placebo-controlled crossover trial on effect of inactivated influenza vaccine on pulmonary function in asthma

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

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

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

A randomized controlled trial of glucocorticoid prophylaxis against experimental rhinovirus infection

Doubling the dose of inhaled corticosteroid to prevent asthma exacerbations: randomised controlled trial

Doubling the dose of budesonide versus maintenance treatment in asthma exacerbations

Viruses as precipitants of asthma symptoms. III. Rhinoviruses: molecular biology and prospects for future intervention

Rhinovirus and respiratory syncytial virus in wheezing children requiring emergency care. IgE and eosinophil analyses

Association of rhinovirus infection with increased disease severity in acute bronchiolitis

The incidence of respiratory tract infection in adults requiring hospitalization for asthma

Human metapneumovirus and lower respiratory tract disease in otherwise healthy infants and children

Asthma exacerbations in children associated with rhinovirus but not human metapneumovirus infection

Metapneumovirus and acute wheezing in children

Synergism between allergens and viruses and risk of hospital admission with asthma: case-control study

Personal exposure to nitrogen dioxide and risk of airflow obstruction in asthmatic children with upper respiratory infection

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

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

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

Bronchoalveolar lavage fluid cellularity and soluble intercellular adhesion molecule-1 in children with colds

Bronchial inflammation and the common cold: a comparison of atopic and non-atopic individuals

Activated, cytotoxic CD8(+) T lymphocytes contribute to the pathology of asthma death

A study of modifiable risk factors for asthma exacerbations: virus infection and allergen exposure synergistically increase risk of asthma hospitalization in children

Frequency, severity, and duration of rhinovirus infections in asthmatic and non-asthmatic individuals: a longitudinal cohort study

Persistence of rhinovirus RNA after asthma exacerbation in children

Asthmatic bronchial epithelial cells have a deficient innate immune response to infection with rhinovirus

A defective type 1 response to rhinovirus in atopic asthma

The complete nucleotide sequence of a common cold virus: human rhinovirus 14

Human rhinovirus 2: complete nucleotide sequence and proteolytic processing signals in the capsid protein region

The cellular receptor to human rhinovirus 2 binds around the 5-fold axis and not in the canyon: a structural view

Sequence and structure of human rhinoviruses reveal the basis of receptor discrimination

Similar frequency of rhinovirusinfectible cells in upper and lower airway epithelium

Rhinoviruses replicate effectively at lower airway temperatures

Rhinoviruses as pathogens of the lower respiratory tract

Detection of rhinovirus RNA in lower airway cells during experimentally induced infection

Pathogenesis of lower respiratory tract symptoms in experimental rhinovirus infection

Detection of rhinovirus in sinus brushings of patients with acute communityacquired sinusitis by reverse transcription-PCR

Detection of rhinovirus infection of the nasal mucosa by oligonucleotide in situ hybridization

Viruses as precipitants of asthma symptoms. I. Epidemiology

Detection of rhinovirus in induced sputum at exacerbation of chronic obstructive pulmonary disease

Viral respiratory infections in elderly patients and patients with chronic obstructive pulmonary disease

The September epidemic of asthma exacerbations in children: a search for etiology

Rhinovirus and the lower respiratory tract

Mechanisms of virus-induced asthma

Viruses in asthma

Rhinovirus respiratory infections and asthma

The immunology of virus infection in asthma

Low grade rhinovirus infection induces a prolonged release of IL-8 in pulmonary epithelium

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

Rhinovirus stimulation of interleukin-8 in vivo and in vitro: role of NF-kappaB

Infection of a human respiratory epithelial cell line with rhinovirus. Induction of cytokine release and modulation of susceptibility to infection by cytokine exposure

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

Rhinovirus induction of the CXC chemokine epithelial-neutrophil activating peptide-78 in bronchial epithelium

Rhinovirus infection up-regulates eotaxin and eotaxin-2 expression in bronchial epithelial cells

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

Rhinovirus replication causes RANTES production in primary bronchial epithelial cells

Human airway epithelial cells produce Ip-10 (Cxcl10) in vitro and in vivo upon rhinovirus infection

Rhinovirus stimulation of interleukin-6 in vivo and in vitro. Evidence for nuclear factor kappa B-dependent transcriptional activation

Nitric oxide inhibits rhinovirus-induced granulocyte macrophage colony-stimulating factor production in bronchial epithelial cells

Role of p38 mitogen-activated protein kinase in rhinovirus-induced cytokine production by bronchial epithelial cells

Interleukin-11: stimulation in vivo and in vitro by respiratory viruses and induction of airways hyperresponsiveness

Dexamethasone regulation of lung epithelial cell and fibroblast interleukin-11 production

Rhinovirus infection induces expression of its own receptor intercellular adhesion molecule 1 (ICAM-1) via increased NF-kappaB-mediated transcription

Corticosteroids inhibit rhinovirus-induced intercellular adhesion molecule-1 up-regulation and promoter activation on respiratory epithelial cells

Rhinovirus infection in nonasthmatic subjects: effects on intrapulmonary airways

Expression of ICAM-1 in nasal epithelium and levels of soluble ICAM-1 in nasal lavage fluid during human experimental rhinovirus infection

Respiratory epithelial cell expression of vascular cell adhesion molecule-1 and its up-regulation by rhinovirus infection via NF-kappaB and GATA transcription factors

Induction of mucin secretion from human bronchial tissue and epithelial cells by rhinovirus and lipopolysaccharide

Rhinovirus infection induces mucus hypersecretion

Rhinoviruses infect the lower airways

Rhinovirus infection increases 5-lipoxygenase and cyclooxygenase-2 in bronchial biopsy specimens from nonatopic subjects

Biopsy neutrophilia, neutrophil chemokine and receptor gene expression in severe exacerbations of chronic obstructive pulmonary disease

Exacerbations of bronchitis: bronchial eosinophilia and gene expression for interleukin-4, interleukin-5, and eosinophil chemoattractants

Signaling to NF-kappaB

The IKK NF-kappa B system: a treasure trove for drug development

NF-kappa B: a pivotal role in asthma and a new target for therapy

Differential regulation of IkappaB kinase alpha and beta by two upstream kinases, NF-kappaB-inducing kinase and mitogenactivated protein kinase/ERK kinase kinase-1

A cytokine-responsive IkappaB kinase that activates the transcription factor NF-kappaB

Direct phosphorylation of IkappaB by IKKalpha and IKKbeta: discrimination between free and NF-kappaB-bound substrate

IKKepsilon is part of a novel PMA-inducible IkappaB kinase complex

IKK-i, a novel lipopolysaccharide-inducible kinase that is related to IkappaB kinases

IFN-regulatory factor 3-dependent gene expression is defective in Tbk1-deficient mouse embryonic fibroblasts

IKKepsilon and TBK1 are essential components of the IRF3 signaling pathway

Toll/IL-1 receptor domain-containing adaptor inducing IFN-beta (TRIF) associates with TNF receptor-associated factor 6 and TANK-binding kinase 1, and activates two distinct transcription factors, NF-kappa B and IFN-regulatory factor-3, in the Tolllike receptor signaling

Respiratory syncytial virus-induced RANTES production from human bronchial epithelial cells is dependent on nuclear factor-kappa B nuclear binding and is inhibited by adenovirus-mediated expression of inhibitor of kappa B alpha

Transcriptional induction of multiple cytokines by human respiratory syncytial virus requires activation of NF-kappa B and is inhibited by sodium salicylate and aspirin

Activation of eotaxin gene transcription by NF-kappa B and STAT6 in human airway epithelial cells

TNFalphainduced macrophage chemokine secretion is more dependent on NF-kappaB expression than lipopolysaccharides-induced macrophage chemokine secretion

Cloning and characterization of the human neutrophil-activating peptide (ENA-78) gene

NF-kappaB activation by double-stranded-RNA-activated protein kinase (PKR) is mediated through NF-kappaB-inducing kinase and IkappaB kinase

Activation of NF-kappa B by the dsRNA-dependent protein kinase, PKR involves the I kappa B kinase complex

The catalytic activity of dsRNA-dependent protein kinase, PKR, is required for NF-kappaB activation

Doublestranded RNA-dependent protein kinase activates transcription factor NF-kappa B by phosphorylating I kappa B

Recognition of double-stranded RNA and activation of NF-kappaB by Toll-like receptor 3

The RNA helicase RIG-I has an essential function in double-stranded RNA-induced innate antiviral responses

Mechanism of activation of the double-stranded-RNA-dependent protein kinase, PKR: role of dimerization and cellular localization in the stimulation of PKR phosphorylation of eukaryotic initiation factor-2 (eIF2)

Essential role for the dsRNA-dependent protein kinase PKR in innate immunity to viral infection

Efficacy of oral WIN 54954 for prophylaxis of experimental rhinovirus infection

Suppression of colds in human volunteers challenged with rhinovirus by a new synthetic drug (R61837)

Intranasal pirodavir (R77,975) treatment of rhinovirus colds

Phase II, randomized, double-blind, placebocontrolled studies of Ruprintrivir nasal spray 2-percent suspension for prevention and treatment of experimentally induced rhinovirus colds in healthy volunteers

In vitro activity of Pleconaril and AG7088 against selected serotypes and clinical isolates of human rhinoviruses

Oral Pleconaril treatment of picornavirus-associated viral respiratory illness in adults: efficacy and tolerability in phase II clinical trials

VP1 sequencing of all human rhinovirus serotypes: insights into genus phylogeny and susceptibility to antiviral capsid-binding compounds

Structure of human rhinovirus 3C protease reveals a trypsin-like polypeptide fold, RNA-binding site, and means for cleaving precursor polyprotein

In vitro antiviral activity of AG7088, a potent inhibitor of human rhinovirus 3C protease

Inhibition of human rhinovirus-induced cytokine production by AG7088, a human rhinovirus 3C protease inhibitor

Efficacy of Tremacamra, a soluble intercellular adhesion molecule 1, for experimental rhinovirus infection: a randomized clinical trial

Modification of experimental rhinovirus colds by receptor blockade

Comparative antirhinoviral activities of soluble intercellular adhesion molecule-1 (sICAM-1) and chimeric ICAM-1/immunoglobulin A molecule

In vitro studies of the antirhinovirus activity of soluble intercellular adhesion molecule-1

IFN-lambdas mediate antiviral protection through a distinct class II cytokine receptor complex

Induction and regulation of IFNs during viral infections

Type I interferons (/) in immunity and autoimmunity

Intranasal interferon-alpha 2 treatment of experimental rhinoviral colds

Prevention of rhinovirus colds by human interferon alpha-2 from Escherichia coli

Efficacy and tolerance of intranasally applied recombinant leukocyte A interferon in normal volunteers

Intranasal interferon alpha 2 for prevention of rhinovirus infection and illness

Intranasal interferon-alpha 2 prophylaxis of natural respiratory virus infection

Intranasal interferon-alpha 2b for seasonal prophylaxis of respiratory infection

Interferon-beta ser as prophylaxis against experimental rhinovirus infection in volunteers

Tolerance and efficacy of intranasal administration of recombinant beta serine interferon in healthy adults

Ineffectiveness of recombinant interferon-beta serine nasal drops for prophylaxis of natural colds

Comparative susceptibility of respiratory viruses to recombinant interferons-alpha 2b and -beta

Combined antiviral-antimediator treatment for the common cold

Combined antiviral and antimediator treatment of rhinovirus colds

Molecular mechanisms of corticosteroid actions

Oral prednisone therapy in experimental rhinovirus infections

Inhaled steroids for episodic viral wheeze of childhood. The Cochrane Database of Systematic Reviews

Efficacy of a short course of parent-initiated oral prednisolone for viral wheeze in children aged 1-5 years: randomised controlled trial

Effect of inhaled corticosteroids on episodes of wheezing associated with viral infection in school age children: randomised double blind placebo controlled trial

Effect of continuous treatment with topical corticosteroid on episodic viral wheeze in preschool children

Interaction between glucocorticoids and beta2 agonists on bronchial airway smooth muscle cells through synchronised cellular signalling

Additive anti-inflammatory effect of formoterol and budesonide on human lung fibroblasts

Effects of budesonide and formoterol on NF-kappaB, adhesion molecules, and cytokines in asthma

Cytokine release and adhesion molecule expression by stimulated human bronchial epithelial cells are downregulated by salmeterol

Possible anti-inflammatory effect of salmeterol against interleukin-8 and neutrophil activation in asthma in vivo

Anti-inflammatory, membrane-stabilizing interactions of salmeterol with human neutrophils in vitro

Regulation of TNF-alpha-induced eotaxin release from cultured human airway smooth muscle cells by beta2-agonists and corticosteroids

Synergistic inhibition by beta(2)-agonists and corticosteroids on tumor necrosis factor-alpha-induced interleukin-8 release from cultured human airway smooth-muscle cells

Effect of salmeterol on Pseudomonas aeruginosa infection of respiratory mucosa

Effect of salmeterol on Haemophilus influenzae infection of respiratory mucosa in vitro

Asthma therapy modulates primingassociated blood eosinophil responsiveness in allergic asthmatics

Effect of inhaled fluticasone with and without salmeterol on airway inflammation in asthma

Effects of fluticasone plus salmeterol versus twice the dose of fluticasone in asthmatic patients

Comparison of combination inhalers vs inhaled corticosteroids alone in moderate persistent asthma

Added salmeterol versus higher-dose corticosteroid in asthma patients with symptoms on existing inhaled corticosteroid. Allen & Hanburys Limited UK Study Group

Effects of formoterol and budesonide on GM-CSF and IL-8 secretion by triggered human bronchial epithelial cells

Effect of inhaled formoterol and budesonide on exacerbations of asthma. Formoterol and Corticosteroids Establishing Therapy (FACET) International Study Group

Budesonide/formoterol combination therapy as both maintenance and reliever medication in asthma

A small molecule inhibitor of redox-regulated NF-kappa B and activator protein-1 transcription blocks allergic airway inflammation in a mouse asthma model

Selective blockade of NF-kappa B activity in airway immune cells inhibits the effector phase of experimental asthma

AS602868, a pharmacological inhibitor of IKK2, reveals the apoptotic potential of TNF-alpha in Jurkat leukemic cells

An ATF/CREB binding site is required for virus induction of the human interferon beta gene (corrected)

Influenza A virus NS1 protein prevents activation of NF-kappaB and induction of alpha/beta interferon

Identification of the rel family members required for virus induction of the human beta interferon gene

The X-ray crystal structure of the NF-kappa B p50.p65 heterodimer bound to the interferon beta -kappa B site