Mechanisms of virus induced exacerbations of asthma

SARS-CoV-2 accessory proteins involvement in inflammatory and profibrotic processes through IL11 signaling

SARS-CoV-2, the cause of the COVID-19 pandemic, possesses eleven accessory proteins encoded in its genome. Their roles during infection are still not completely understood. In this study, transcriptomics analysis revealed that both WNT5A and IL11 were significantly up-regulated in A549 cells expressing individual accessory proteins ORF6, ORF8, ORF9b or ORF9c from SARS-CoV-2 (Wuhan-Hu-1 isolate). IL11 is a member of the IL6 family of cytokines. IL11 signaling-related genes were also differentially expressed. Bioinformatics analysis disclosed that both WNT5A and IL11 were involved in pulmonary fibrosis idiopathic disease and functional assays confirmed their association with profibrotic cell responses. Subsequently, data comparison with lung cell lines infected with SARS-CoV-2 or lung biopsies from patients with COVID-19, evidenced altered profibrotic gene expression that matched those obtained in this study. Our results show ORF6, ORF8, ORF9b and ORF9c involvement in inflammatory and profibrotic responses. Thus, these accessory proteins could be targeted by new therapies against COVID-19 disease.

Oral administration of Clostridium butyricum rescues streptomycin-exacerbated respiratory syncytial virus-induced lung inflammation in mice

Changes in the intestinal microbiota indirectly impact the health of mucosa distal to the intestine, particularly the respiratory tract. However, the effects of intestinal microbiota dysbiosis on the regulation of respiratory syncytial virus (RSV) infection are not clear. In this study, we examined the effects of altering the intestinal microbiota on the pulmonary immune response against RSV infection. BALB/c mice were treated with streptomycin before infection with RSV to study the altered immune response. The ingestion of streptomycin led to a marked alteration in the intestinal microbiota with a reduced abundance of Lactobacillus and Clostridium genera, followed by greatly aggravated pulmonary inflammation in response to RSV infection. This aggravated inflammation was associated with a dysregulated immune response against RSV infection, characterized by the increased expression of IFN-γ and IL-17 and increased pulmonary M1-like macrophage polarization, and decreased expression of IL-5. Supplementation of Clostridium butyricum (CB) prevented aggravated inflammation and the dysregulated immune response characterized by greater M2 polarization of pulmonary macrophages and decreased release of IFN-γ and IL-17 as well as increased IL-5 levels. Furthermore, in vitro and in vivo experiments identified that butyrate, the main metabolite produced by CB, promoted M2 polarization of macrophages in RSV-infected mice exposed to streptomycin. Together, these results demonstrate the mechanism by which intestinal microbiota modulate the pulmonary immune response to RSV infection.

Anti-IgE and Biologic Approaches for the Treatment of Asthma

Current asthma treatments are effective for the majority of patients with mild-to-moderate disease. However, in those with more severe refractory asthma, agents other than inhaled corticosteroids and beta-agonists are needed both to better manage this group of patients and to avoid the side effects of high-dose corticosteroids and the social and personal hardship endured. Several biological pathways have been targeted over the last 20 years, and this research has resulted in pharmacological approaches to attempt to better treat patients with severe refractory asthma. The flagship of the biologics, the anti-IgE monoclonal antibody, omalizumab, has proven efficacious in selected subgroups of asthma patients. Tailoring asthma treatments to suit specific subtypes of asthma patients is in keeping with ideals of personalized medicine. Research in the complex interplay of allergens, epithelial host defenses, cytokines, and innate and adaptive immunity interactions has allowed better understanding of the mechanics of allergy and inflammation in asthma. As a result, new biologic treatments have been developed that target several different phenotypes and endotypes in asthma. As knowledge of the efficacy of these biological agents in asthma emerges, as well as the type of patients in whom they are most beneficial, the movement toward personalized asthma treatment will follow.

Natural helper cells mediate respiratory syncytial virus-induced airway inflammation by producing type 2 cytokines in an IL-33-dependent manner

AIM

Type 2 cytokine production during respiratory virus infection is considered to be linked with asthma exacerbation. As potent Th2 cytokine producers, natural helper (NH) cells play a key role in influenza virus-induced airway hyper-responsiveness. However, it is unclear whether NH cells contribute to respiratory syncytial virus (RSV)-induced airway inflammation, and how the cytokine profile in NH cells is changed during RSV infection.

METHODS

BALB/c mice were infected intranasally with RSV. The number of NH cells in lungs was detected by flow cytometry. The expression of cytokine mRNAs was performed by real-time RT-PCR. Cytokines levels were determined by ELISA.

RESULTS

Following intranasal infection with RSV, BALB/c mice showed an increase in the expression of mRNAs for Th2-like cytokines in NH cells. Furthermore, adoptive transfer of pulmonary NH cells resulted in a massive infiltration of mononuclear cells, in particular eosinophils and neutrophils in lungs, in parallel with an augmented production of Th2-associated cytokines, such as IL-4, IL-5 and IL-10 in bronchoalveolar lavage fluids, providing convincing evidence that NH cells contribute to RSV-induced lung pathogenesis by producing type 2 cytokines. It should be noted that blocking IL-33 with antibody can diminish the absolute number of pulmonary NH cells and the relative expression of mRNAs for type 2 cytokines in pulmonary NH cells, suggesting that IL-33 is necessary for activating Th2-type NH cells.

CONCLUSION

These results reveal that pulmonary NH cells might participate in RSV-induced airway inflammation by producing large quality of type 2 cytokines in an IL-33-dependent manner.

Natural helper cells contribute to pulmonary eosinophilia by producing IL-13 via IL-33/ST2 pathway in a murine model of respiratory syncytial virus infection

It has been reported that natural helper cells, which are a non-T, non-B innate lymphoid cell type expressing c-Kit and ST2, mediate influenza-induced airway hyper-reactivity by producing substantial IL-13. However, little is known about natural helper cells for the development of RSV-induced airway inflammation, particularly eosinophilic infiltration. By using BALB/c mice that were infected intranasally with RSV, it became clear that infection with RSV can induce an increase in the absolute number of natural helper cells in the lungs of mice. It seems likely that these natural helper cells contribute to the massive eosinophilic infiltration in an IL-13-dependent manner. In fact, the number of IL-13-producing natural helper cells as well as the expression of IL-13 mRNA in natural helper cells was enhanced significantly during RSV infection, suggesting that natural helper cells might be cellular source of the Th2-type cytokine IL-13. Indeed, adoptive transfer of pulmonary natural helper cells augmented not only the production of IL-13 but also the infiltration of eosinophils in the lungs of transferred mice. Pulmonary natural helper cells can produce IL-13 following response to IL-33, which was increased markedly in the lungs of mice after intranasal RSV infection. The expression of IL-13 mRNA in pulmonary natural helper cells was up-regulated by in vitro IL-33 stimulation. Furthermore, blockade of IL-33 receptor subunit, ST2, diminished the frequency of IL-13-producing natural helper cells. Taken together, these results demonstrate that natural helper cells may play an important role in RSV-induced pulmonary eosinophilia by producing IL-13 via the IL-33/ST2 pathway.

Herpesvirus-associated acute urticaria: an age matched case-control study

Background

Acute and recurrent acute urticaria are often associated with multiple factors including infections and recent data suggest a role for herpesviruses.

Objective

To test the null hypothesis, that is, there is no association of herpesvirus infections with urticaria.

Methods

Thirty-seven patients between one month and 15 years of age were age matched to 37 controls who were healthy or had mild acute respiratory infections but without urticaria. Patients and controls were followed for 1 to 6 years. Diagnostic studies included DNA detection by real-time PCR for herpes simplex virus (HSV) types 1 and 2, Epstein-Barr virus (EBV), cytomegalovirus (CMV) and human herpesvirus-6 (HHV-6). Tests for other infections included adenovirus, parvovirus B 19, respiratory syncytial virus, influenza A, Group A streptococci, rotavirus, and parasites.

Results

Specific infections were diagnosed in 26 of 37 cases and among 9 of 37 control children (P=0.0002). Single or concomitant herpesvirus infections occurred in 24 cases and in 4 controls (65% vs 11 %, p=0.0003). Cases had 10 HHV-6 infections, 8 CMV infections, 5 EBV infections, and 4 HSV-1 infections.

Conclusion

Herpesvirus infections are associated with acute or recurrent acute urticaria.

Increased CXCL10 expression in nasal fibroblasts from patients with refractory chronic rhinosinusitis and asthma

BACKGROUND

Chronic rhinosinusitis (CRS) is characterized by local inflammation of the sinonasal tissues. CRS patients with nasal polyps and asthma often develop acute exacerbation of sinonasal symptoms after upper respiratory tract infections. However, the influence of concomitant asthma on the nasal immune response to viral infection remains unclear.

METHODS

Specimens of nasal polyp and mucosal tissues were obtained from 3 groups of CRS patients (n = 14 per group): 1) patients without asthma (CRS group), 2) patients with aspirin-tolerant asthma (ATA group), and 3) patients with aspirin-intolerant asthma (AIA group). Nasal fibroblasts isolated from the specimens were stimulated with poly I:C. CXCL10 expression was analyzed by the quantitative real-time polymerase chain reaction and enzyme-linked immunoadsorbent assay. Biopsy specimens from CRS patients without asthma were subjected to immunohistochemistry for detection of T-bet and GATA-3 expression in CD3+ T cells by double labeling.

RESULTS

Nasal fibroblasts from the ATA and AIA groups showed significantly enhanced expression of CXCL10 mRNA and protein after poly I:C stimulation compared with cells from the CRS group and the control group (normal nasal mucosa). In addition to T helper (Th)2 cells, there was more abundant infiltration of Th1 cells into tissues from the AIA and ATA groups.

CONCLUSIONS

Our findings suggest that CRS associated with asthma may become intractable through the over-production of CXCL10 in response to viral infection.

Identification of innate immune response endotypes in asthma: implications for personalized medicine

Asthma is an idiopathic disease characterized by episodic inflammation and reversible airway obstruction triggered by exposure to environmental agents. Because this disease is heterogeneous in onset, exacerbations, inflammatory states, and response to therapy, there is intense interest in developing personalized approaches to its management. Of focus in this review, the recognition that a component of the pathophysiology of asthma is mediated by inflammation has implications for understanding its etiology and individualizing its therapy. Despite understanding how Th2 polarization mediates asthma exacerbations by aeroallergen exposure, we do not yet fully understand how RNA virus infections produce asthmatic exacerbations. This review will summarize the explosion of information that has revealed how patterns produced by RNA virus infection trigger the innate immune response (IIR) in sentinel airway cells. When the IIR is triggered, these cells elaborate inflammatory cytokines and protective mucosal interferons whose actions activate long-lived adaptive immunity and limit organismal replication. Recent work has shown the multifaceted way that dysregulation of the IIR is linked to viral-induced exacerbation, steroid insensitivity, and T helper polarization of adaptive immunity. New developments in quantitative proteomics now enable accurate identification of subgroups of individuals that demonstrate activation of IIR ("innate endotype"). Potential applications to clinical research are proposed. Together, these developments open realistic prospects for how identification of the IIR endotype may inform asthma therapy in the future.

Dual role of interleukin-10 in the regulation of respiratory syncitial virus (RSV)-induced lung inflammation

RSV lower respiratory tract infections (LRTI) are among the most common diseases necessitating hospital admission in children. In addition to causing acute respiratory failure, RSV infections are associated with sequelae such as secondary bacterial infections and reactive airway disease. One characteristic host response observed in severe RSV-induced LRTI and/or subsequent development of asthma is increased expression of interleukin (IL)-10. However, contradictory results have been reported regarding whether IL-10 inhibits asthmatic responses or intensifies the disease. We aimed to reconcile these discordant observations by elucidating the role of IL-10 in regulating the host response to RSV LRTI. In this study, we used a lung-specific, inducible IL-10 over-expression (OE) transgenic mouse model to address this question. Our results showed that the presence of IL-10 at the time of RSV infection not only attenuated acute inflammatory process (i.e. 24 h post-infection), but also late inflammatory changes [characterized by T helper type 2 (Th2) cytokine and chemokine expression]. While this result appears contradictory to some clinical observations where elevated IL-10 levels are observed in asthmatic patients, we also found that delaying IL-10 OE until the late immune response to RSV infection, additive effects rather than inhibitory effects were observed. Importantly, in non-infected, IL-10 OE mice, IL-10 OE alone induced up-regulation of Th2 cytokine (IL-13 and IL-5) and Th2-related chemokine [monocyte chemoattractant protein 1 (MCP-1), chemokine (C-C motif) ligand 3 (CCL3) and regulated upon activation normal T cell expressed and secreted (RANTES)] expression. We identified a subset of CD11b(+)CD11c(+)CD49b(+)F4/80(-)Gr-1(-) myeloid cells as a prinicipal source of IL-10-induced IL-13 production. Therefore, the augmented pathological responses observed in our 'delayed' IL-10 over-expression model could be attributed to IL-10 OE alone. Taken together, our study indicated dual roles of IL-10 on RSV-induced lung inflammation which appear to depend upon the timing of when elevated IL-10 is expressed in the lung.

Intracellular RNA recognition pathway activates strong anti-viral response in human mast cells

Mast cells have been implicated in the first line of defence against parasites and bacteria, but less is known about their role in anti-viral responses. Allergic diseases often exacerbate during viral infection, suggesting an increased activation of mast cells in the process. In this study we investigated human mast cell response to double-stranded RNA and viral infection. Cultured human mast cells were incubated with poly(I:C), a synthetic RNA analogue and live Sendai virus as a model of RNA parainfluenza virus infection, and analysed for their anti-viral response. Mast cells responded to intracellular poly(I:C) by inducing type 1 and type 3 interferons and TNF-α. In contrast, extracellular Toll-like receptor 3 (TLR)-3-activating poly(I:C) failed to induce such response. Infection of mast cells with live Sendai virus induced an anti-viral response similar to that of intracellular poly(I:C). Type 1, but not type 3 interferons, up-regulated the expression of melanoma differentiation-associated gene 5 (MDA-5) and retinoic acid-inducible gene-1 (RIG-1), and TLR-3, demonstrating that human mast cells do not express functional receptors for type 3 interferons. Furthermore, virus infection induced the anti-viral proteins MxA and IFIT3 in human mast cells. In conclusion, our results support the notion that mast cells can recognize an invading virus through intracellular virus sensors and produce high amounts of type 1 and type 3 interferons and the anti-viral proteins human myxovirus resistance gene A (MxA) and interferon-induced protein with tetratricopeptide repeats 3 (IFIT3) in response to the virus infection.

Evaluation of serum immunoglobulin E levels in bronchial asthma

Background:

Immunoglobulin E and associated cellular responses are responsible for allergic airway diseases. A hypersensitivity reaction initiated by immunologic mechanisms, mediated by IgE antibodies occurs in allergic asthma

Aim:

To estimate and compare serum IgE levels in mild, moderate, and severe asthmatics and in normal subjects and to obtain a mathematical model describing the relationship between serum IgE levels and severity of asthma.

Materials and Methods:

A stratified sample of 60 patients within age group of 18-60 years and 31 male and 29 female asthmatic patients and 13 healthy controls within 18-60 years were included in this study and classified according to GINA classification. Serum IgE levels were estimated by using ELISA kit.

Results:

Mean IgE levels ranged from 151.95 IU/ml in normal subjects to 1045.32 IU/ml in severe asthmatics. The model developed was 27% efficient.

Conclusion:

Serum Immunoglobulin E levels were high in asthmatics as compared to normal subjects. On an average, the levels increased as the severity of asthma increased. However, there was no statistically significant correlation since the variability in each level of asthma was very large

FADS genetic variants and omega-6 polyunsaturated fatty acid metabolism in a homogeneous island population

Long-chain polyunsaturated fatty acids (PUFA) orchestrate immunity and inflammation through their capacity to be converted to potent inflammatory mediators. We assessed associations of FADS gene cluster polymorphisms and fasting serum PUFA concentrations in a fully ascertained, geographically isolated founder population of European descent. Concentrations of 22 PUFAs were determined by gas chromatography, of which ten fatty acids and five ratios defining FADS1 and FADS2 activity were tested for genetic association against 16 single nucleotide polymorphisms (SNP) in 224 individuals. A cluster of SNPs in tight linkage disequilibrium in the FADS1 gene (rs174537, rs174545, rs174546, rs174553, rs174556, rs174561, rs174568, and rs99780) were strongly associated with arachidonic acid (AA) (P = 5.8 x 10(-7) - 1.7 x 10(-8)) among other PUFAs, but the strongest associations were with the ratio measuring FADS1 activity in the omega-6 series (P = 2.11 x 10(-13) - 1.8 x 10(-20)). The minor allele across all SNPs was consistently associated with decreased omega-6 PUFAs, with the exception of dihomo-gamma-linoleic acid (DHGLA), where the minor allele was consistently associated with increased levels. Our findings in a geographically isolated population with a homogenous dietary environment suggest that variants in the Delta-5 desaturase enzymatic step likely regulate the efficiency of conversion of medium-chain PUFAs to potentially inflammatory PUFAs, such as AA.

Ipratropium bromide for acute asthma exacerbations in the emergency setting: a literature review of the evidence

Since the 1970s, when inhaled anticholinergic agents were first introduced as adjunct therapies for the immediate treatment of pediatric asthma exacerbations, several trials have shown varying degrees of benefit from their use as bronchodilators in combination with inhaled short-acting beta-adrenergic agonists and systemic corticosteroids. Although other anticholinergics exist, ipratropium bromide (IB) specifically has emerged as the overwhelming choice of pulmonologists and emergency physicians because of its limited systemic absorption from the lungs when given as an inhaled preparation. However, although the varying trials, predominantly in the emergency department setting, have typically shown a trend toward improved outcomes, none has set forth clear dosing protocol recommendations for use by practicing physicians. It is our goal in this review of the available literature on the use of IB, as an adjunct to inhaled short-acting beta-adrenergic agonists, to summarize practical, evidence-based recommendations for use in the pediatric emergency department setting for acute asthma exacerbations. We also hope to better delineate the most effective dosing regimen in those patients who might benefit most from the addition of IB and to explore proposed additional benefits it may have as a modulator of cholinergic-induced effects from high-dose beta-agonist therapy and viral triggers.

Acute exacerbations of asthma: epidemiology, biology and the exacerbation-prone phenotype

Asthma is a highly prevalent chronic respiratory disease affecting 300 million people world-wide. A significant fraction of the cost and morbidity of asthma derives from acute care for asthma exacerbations. In the United States alone, there are approximately 15 million outpatient visits, 2 million emergency room visits, and 500,000 hospitalizations each year for management of acute asthma. Common respiratory viruses, especially rhinoviruses, cause the majority of exacerbations in children and adults. Infection of airway epithelial cells with rhinovirus causes the release of pro-inflammatory cytokines and chemokines, as well as recruitment of inflammatory cells, particularly neutrophils, lymphocytes, and eosinophils. The host response to viral infection is likely to influence susceptibility to asthma exacerbation. Having had at least one exacerbation is an important risk factor for recurrent exacerbations suggesting an 'exacerbation-prone' subset of asthmatics. Factors underlying the 'exacerbation-prone' phenotype are incompletely understood but include extrinsic factors: cigarette smoking, medication non-compliance, psychosocial factors, and co-morbidities such as gastroesophageal reflux disease, rhinosinusitis, obesity, and intolerance to non-steroidal anti-inflammatory medications; as well as intrinsic factors such as deficient epithelial cell production of the anti-viral type I interferons (IFN-alpha and IFN-beta). A better understanding of the biologic mechanisms of host susceptibility to recurrent exacerbations will be important for developing more effective preventions and treatments aimed at reducing the significant cost and morbidity associated with this important global health problem.

Relation between inflammation and symptoms in asthma

Asthma symptoms are the main reason for healthcare utilization and are a fundamental parameter for the evaluation of asthma control. Currently, asthma is defined as a chronic inflammatory disease. A French expert group studied the association between inflammation and asthma symptoms by carrying out a critical review of the international literature. Uncontrolled asthmatics have an increased number of polynuclear eosinophils in the induced sputum and an increased production of exhaled NO. Control by anti-inflammatory treatment is accompanied by a reduction in bronchial eosinophilia and exhaled NO. Asthma symptoms are the result of complex mechanisms and many factors modify their perception. Experimental data suggest that there is a relationship between the perception of symptoms and eosinophilic inflammation and that inhaled corticoid therapy improves this perception. Although they are still not applicable in routine practice, follow-up strategies based on the evaluation of inflammation are thought to be more effective in reducing exacerbations than those usually recommended based on symptoms and sequential analysis of respiratory function. Inhaled corticosteroid therapy is the reference disease-modifying therapy for persistent asthma. Recent studies demonstrated that adjustment of anti-inflammatory treatment based on symptoms is an effective strategy to prevent exacerbations and reduce the total number of doses of inhaled corticosteroids.

[The relationship between inflammation and symptoms in asthma]

In asthma, symptoms are the main reason for recourse to healthcare and are a fundamental parameter for the evaluation of asthma control. Currently, asthma is defined as a chronic inflammatory disease. Uncontrolled asthmatics have an increased number of eosinophils in induced sputum and an increased production of exhaled NO. Control by anti-inflammatory treatment is accompanied by a reduction in bronchial eosinophilia and exhaled NO. Asthma symptoms are the result of complex mechanisms and many factors modify their perception. Experimental data suggests that there is a relationship between the perception of symptoms and eosinophilic inflammation, and that inhaled corticoid therapy improves this perception. Although they are still not applicable in routine practice, follow-up strategies based on the evaluation of inflammation are thought to be more effective in reducing exacerbations than those usually recommended based on retrospective evaluation of symptoms and sequential analysis of respiratory function. Inhaled corticosteroid therapy is the reference maintenance therapy for persistent asthma and adjustment of anti-inflammatory treatment based on symptoms is an effective strategy to prevent exacerbations and reduce the total dose of inhaled corticosteroids. A French expert group has undertaken a study of the association between inflammation and asthma symptoms by carrying out a critical review of the international literature.

Infections

This chapter reviews the epidemiological evidence implicating infectious pathogens as triggers and will discuss the mechanisms of interaction between the host–pathogen response and preexisting airway pathology that result in an exacerbation. Asthma is a multifaceted syndrome involving atopy, bronchial hyperreactivity, and IgE and non-IgE-mediated acute and chronic immune responses. The asthmatic airway is characterized by an infiltrate of eosinophils and of T-lymphocytes expressing the type 2 cytokines IL-4, IL-5, and IL-13. Trigger factors associated with acute exacerbations of asthma include exposure to environmental allergens, especially animals, molds, pollens and mites, cold, exercise, and drugs. The frequency of exacerbations is a major factor in the quality of life of patients with COPD. The typical clinical features of an exacerbation include increased dyspnea, wheezing, cough, sputum production, and worsened gas exchange. Although noninfectious causes of exacerbations such as allergy, air pollution, or inhaled irritants including cigarette smoke may be important, acute airway infections are the major precipitants. The infection and consequent host inflammatory response result in increased airway obstruction. The success of vaccination to prevent respiratory virus infections has been limited by significant variation within the major virus types causing disease. Currently much of the treatment of infective exacerbations of asthma and COPD is symptomatic, consisting of increased bronchodilators, either short-acting β 2—agonists in inhaled or intravenous form or anticholinergics or theophyllines, or supportive in the form of oxygen and in severe cases noninvasive or invasive ventilatory measures.

Randomized controlled trial of ipratropium bromide and salbutamol versus salbutamol alone in children with acute exacerbation of asthma

OBJECTIVE

To evaluate effect of addition of ipratropium to salbutamol delivered by metered dose inhaler and spacer in the beginning of treatment of mild to moderate exacerbation of asthma.

METHODS

Children between 5 to 15 years of age with mild to moderate exacerbation of asthma were randomized to receive either a combination of ipratropium bromide and salbutamol or salbutamol alone administered by metered dose inhaler and spacer. The effects on clinical asthma score and spirometric parameters were compared.

RESULTS

A total of 60 children were randomized in the study. The baseline characteristics of two groups were comparable. Children getting combination of salbutamol and ipratropium showed significantly greater improvement in percent-predicted PEFR and FEF25-75% than children receiving salbutamol alone.

CONCLUSION

There was beneficial effect of addition of ipratropium to salbutamol administered by MDI with spacer at the beginning of therapy for mild to moderate acute exacerbation of asthma in children.

Postinfectious cough: ACCP evidence-based clinical practice guidelines

BACKGROUND

Patients who complain of a persistent cough lasting >3 weeks after experiencing the acute symptoms of an upper respiratory tract infection may have a postinfectious cough. Such patients are considered to have a subacute cough because the condition lasts for no >8 weeks. The chest radiograph findings are normal, thus ruling out pneumonia, and the cough eventually resolves, usually on its own. The purpose of this review is to present the evidence for the diagnosis and treatment of postinfectious cough, including the most virulent form caused by Bordetella pertussis infection, and make recommendations that will be useful for clinical practice.

METHODS

Recommendations for this section of the guideline were obtained from data using a National Library of Medicine (PubMed) search dating back to 1950, which was performed in August 2004, of the literature published in the English language. The search was limited to human studies, using the search terms "cough," "postinfectious cough," "postviral cough," "Bordetella pertussis," "pertussis infection," and "whooping cough."

RESULTS

The pathogenesis of the postinfectious cough is not known, but it is thought to be due to the extensive inflammation and disruption of upper and/or lower airway epithelial integrity. When postinfectious cough emanates from the lower airway, this is often associated with the accumulation of an excessive amount of mucus hypersecretion and/or transient airway and cough receptor hyperresponsiveness; all may contribute to the subacute cough. In these patients, the optimal treatment is not known. Except for bacterial sinusitis or early on in a B pertussis infection, therapy with antibiotics has no role, as the cause is not bacterial infection. The use of inhaled ipratropium may be helpful. Other causes of postinfectious cough are persistent inflammation of the nose and paranasal sinuses, which leads to an upper airway cough syndrome (previously referred to as postnasal drip syndrome), and gastroesophageal reflux disease, which may be a complication of the vigorous coughing. One type of postinfectious cough that is particularly virulent is that caused by B pertussis infection. When the cough is accompanied by paroxysms of coughing, posttussive vomiting, and/or an inspiratory whooping sound, the diagnosis of a B pertussis infection should be made unless another diagnosis is proven. This infection is highly contagious but responds to antibiotic coverage with an oral macrolide when administered early in the course of the disease. A safe and effective vaccine to prevent B pertussis is now available for adults as well as children. It is recommended according to CDC guidelines.

CONCLUSIONS

In patients who have a cough lasting from 3 to 8 weeks with normal chest radiograph findings, consider the diagnosis of postinfectious cough. In most patients, a specific etiologic agent will not be identified, and empiric therapy may be helpful. A high degree of suspicion for cough due to B pertussis infection will lead to earlier diagnosis, patient isolation, and antibiotic treatment.

Formoterol attenuates neutrophilic airway inflammation in asthma

STUDY OBJECTIVES

Airway neutrophil levels are increased in patients with severe asthma and during asthma exacerbations. Long-acting beta2-agonists (LABAs), such as formoterol, reduce the number of asthma exacerbations. While beta2-agonists may affect neutrophil function in vitro, it is uncertain whether they have effects on neutrophilic inflammation in asthmatic patients in vivo.

DESIGN

In a double-blind randomized crossover study, we evaluated the effects of 4 weeks of treatment with formoterol (Turbuhaler), 24 microg bid, compared to placebo on sputum neutrophil numbers and interleukin (IL)-8 levels in asthmatic patients. Therapy with budesonide (administered via Turbuhaler), 400 microg bid for 4 weeks, was added at the end as a "gold standard" antiinflammatory effect comparison.

PATIENTS

We studied 15 steroid-naïve nonsmoking patients who ranged from 19 to 51 years of age and had mild persistent asthma.

RESULTS

Formoterol therapy significantly reduced sputum IL-8 levels and neutrophil numbers compared to placebo. There was a significant correlation between the reduction in sputum IL-8 levels and the number of neutrophils, indicating that formoterol may attenuate neutrophilic airway inflammation by inhibiting IL-8 production.

CONCLUSIONS

Our data suggest that the LABA formoterol reduces neutrophilic airway inflammation in patients with mild asthma and that this might be beneficial in preventing asthma exacerbations.

Bronchoalveolar lavage eosinophil cationic protein and interleukin-8 levels in acute asthma and acute bronchiolitis

OBJECTIVE

In this study, we measured the levels of eosinophil cationic protein (ECP) and interleukin (IL)-8 in bronchoalveolar lavage (BAL) fluid from patients with acute asthma and acute bronchiolitis, to determine any similarities or dissimilarities in the profiles of these biochemical markers in the two diseases.

METHODS

BAL fluids were obtained from children with acute asthma (n=16), infants with acute bronchiolitis caused by respiratory syncytial virus (n=18), and control subjects (n=14). Children with asthma were selected to be free of viral infection. BAL cell counts and differentials were determined, and ECP and IL-8 levels were measured by radioimmunoassay and ELISA, respectively.

RESULTS

ECP levels in BAL fluids were significantly higher in the asthma group than in the bronchiolitis (P<0.01) or control (P<0.0001) groups. However, IL-8 levels were significantly higher in the bronchiolitis group than in the asthma (P<0.01) or control (P<0.001) groups. IL-8 levels in the asthma group and ECP levels in the bronchiolitis group were similar to those of the control group.

CONCLUSION

This difference in profiles of ECP and IL-8 in acute asthma and acute bronchiolitis, together with a different inflammatory cell pattern, suggests that the nature of the inflammatory process within the lower respiratory tract may be distinctive in these two diseases.

Inflammatory events in severe acute asthma

Severe acute asthma can be induced by different triggers, allergens, irritants, viruses, etc., which induce inflammation and provoke acute bronchoconstriction. Inflammatory cells, such as activated eosinophils and neutrophils identified in sputum and bronchial lavages (BL) in severe acute asthma from children and adults are associated with increased levels of IL-5, IL-8, and of proinflammatory mediators. Viruses, but also endotoxin or allergen exposure, are able to recruit neutrophils, via an IL-8 production by activated macrophages or epithelial cells. Together, these inflammatory mediators are responsible for the diffuse bronchial inflammation, which involve large and small airways. Activated T cells may also be related to the pathogenesis of severe asthma. An aberrant CD8+ T lymphocyte response in bronchi, with a cytotoxic activity has been associated with fatal asthma. Moreover, the persistence of inflammatory cells in bronchi, particularly neutrophils, which respond poorly to corticosteroids, could be in part responsible for the epithelial damage, the extensive mucus plugging, and the abnormalities of epithelial and endothelial permeability which are associated with severe acute asthma. Further studies are necessary to better identify the implication of this increased bronchial permeability in the persistence of high levels of airway resistance, particularly in patients with status asthmaticus.

Mechanisms of rhinovirus-induced asthma

Several epidemiological studies using sensitive detection methodologies have confirmed that the majority of acute asthma exacerbations follow upper respiratory tract infections--common colds. Most of these colds are due to human rhinoviruses (RVs). RVs are able to reach and replicate in epithelial cells of the lower airways and can activate these cells to produce pro-inflammatory mediators. Under some circumstances, RVs can also become cytotoxic to the epithelium. Atopic asthmatic individuals produce less interferon-gamma and more interleukin-10 than normal subjects in response to RV infection. Symptom severity as well as viral shedding after experimental RV infection, is inversely correlated with 'atopic' status, expressed as the interferon-gamma to interleukin-5 ratio. Expression of co-stimulatory molecules on immune cells is also affected in atopic asthmatics, suggesting an aberrant immune response to RV that may lead to suboptimal viral clearance and viral persistence. Some of the above effects can be reversed in vitro by corticosteroids, second-generation antihistamines or anti-oxidants; however, the optimal strategy for treating acute asthma exacerbations requires further research at both mechanistic and clinical levels.

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.

Virus infections, wheeze and asthma

Viral infections are the most frequent triggers of wheeze and asthma and yet their role in the development of symptoms remains controversial. Pre-existing airway abnormalities contribute to early virus-induced symptoms which usually remit in early childhood, whereas an interaction with airway inflammation causes exacerbations in asthma. However, the distinction between these two groups and the reason why some but not other children wheeze with viral infections is still debated. The effect of early infections on the developing immune system is also complex. The successful maturation of the T-cell response from a predominantly type 2 (atopic predisposition) at birth to a predominantly type 1 (optimal viral immunity) response, is influenced by genetic factors and the number of infections, as both are known to affect outcome. The relative parts played by predisposition and immunomodulation by early infections in later development of asthma are still controversial. These contentions are gradually being resolved by detailed prospective studies.

Virus infections, wheeze and asthma

Viral infections are the most frequent triggers of wheeze and asthma and yet their role in the development of symptoms remains controversial. Pre-existing airway abnormalities contribute to early virus-induced symptoms which usually remit in early childhood, whereas an interaction with airway inflammation causes exacerbations in asthma. However, the distinction between these two groups and the reason why some but not other children wheeze with viral infections is still debated. The effect of early infections on the developing immune system is also complex. The successful maturation of the T-cell response from a predominantly type 2 (atopic predisposition) at birth to a predominantly type 1 (optimal viral immunity) response, is influenced by genetic factors and the number of infections, as both are known to affect outcome. The relative parts played by predisposition and immunomodulation by early infections in later development of asthma are still controversial. These contentions are gradually being resolved by detailed prospective studies.

Cell cooperation in development of eosinophil-predominant inflammation in airways

A large body of research supports a pathogenic role of Th2 cells in allergic diseases such as asthma. These disorders are characterized by recruitment to selected peripheral tissues of a mixed leukocyte inflammatory infiltrate including a predominant eosinophil component. The development of this inflammatory response is dependenton accumulation of Th2 cells in the affected tissues. Our studies aim to define the mechanisms that control the development of this tissue inflammatory response, focusing particularly on the mechanisms that recruit Th2 cells to the lung and airway. We have found that Th2 cells are on their own poorly competent for antigen-induced recruitment to the lung. By contrast, Th1 cells are avidly recruited to the lungs in response to airway antigen challenge. More important, recruitment of Th1 cells to the lung resulted in enhanced recruitment of Th2 cells to this tissue. The increased Th1 cell-induced recruitment of Th2 cells was associated with upregulation of endothelial vascular cell adhesion molecule-1 (VCAM-1) expression in airway-associated endothelial cells and could be largely blocked by systemic treatment with a monoclonal anti-VCAM-1 antibody. Systemic blocking of tumor necrosis factor (TNF) also blunted the airway inflammatory response. The prominent roles of TNF and VCAM-1 in recruitment of Th2 cells suggested that an inflammatory microenvironment was essential for the recruitment of Th2 cells. In fact, recruitment of Th2 cells to the airway could be induced in an antigen-independent fashion by proinflammatory stimuli such as intranasal instillation of endotoxin. This antigen nonspecificity of the Th2 cell recruitment suggested a model in which Th2 cell recruitment is in response to general inflammatory signals rather than to antigen itself. This model provides an explanation for the clinical observation that bacterial or viral respiratory tract infections are associated with disease exacerbations in allergic asthmatics. More generally, these data imply that Th2 cells, like other leukocytes, are recruited efficiently to sites of tissue inflammation, and that these nonspecifically recruited Th2 cells have substantial potential to modulate local inflammatory processes.

Role of viruses and atypical bacteria in exacerbations of asthma in hospitalized children: a prospective study in the Nord-Pas de Calais region (France)

We studied the role of viruses and atypical bacteria in children hospitalized with exacerbated asthma by a prospective study of children with acute asthma admitted to the Department of Pediatrics in Lille, and to 15 hospitals in the Nord-Pas de Calais region, from October 1, 1998-June 30, 1999. We included children aged 2-16 years with active asthma, defined as three or more recurrent episodes of reversible wheezing. The severity of asthma and of asthmatic exacerbations was recorded. Immunofluorescence assays (IFA) on nasopharyngeal secretions (NPS), serological tests, or both, were used for detection of influenza virus, respiratory syncytial virus (RSV), adenovirus, parainfluenza virus, and coronavirus. Polymerase chain reaction (PCR) assays on NPS were used for rhinovirus and enterovirus. Serological tests for Chlamydia pneumoniae and Mycoplasma pneumoniae were performed. A control group of asymptomatic asthmatic outpatients was examined for respiratory viruses (using IFA and PCR). Eighty-two symptomatic children (mean age, 7.9 years) were examined. Viruses were detected in 38% (enterovirus, 15.8%; rhinovirus, 12%; RSV, 7.3%). Serological tests for atypical bacteria were positive in 10% of patients (C. pneumoniae, 5%; M. pneumoniae, 5%). Among the 27 control subjects (mean age, 7.9 years), one PCR was positive for enterovirus. There was no correlation between severity of chronic asthma or asthmatic exacerbations and the diagnosis of infection. Atypical bacterial pathogen infections were linked with prolonged asthmatic symptoms. In conclusion, we confirmed the high incidence of viral infection in acute exacerbations of asthma, especially enteroviruses or rhinoviruses. Persistent clinical features were more frequently associated with atypical bacterial infections, suggesting that these infections should be investigated and treated in cases of persistent asthmatic symptoms.

Airway hyperresponsiveness: using bronchial challenge tests in research and management of asthma

Bronchial challenge tests have been standardized in detail during the past two decades. They are providing relevant pathophysiological and clinical information about patients with asthma or chronic obstructive pulmonary disease (COPD), by allowing the measurement of the degree of airway hyperresponsiveness, which includes an increased sensitivity as well as increased maximal response to bronchoconstrictor stimuli. There are various types of challenges, to which the responses are not interchangeable. Responses to so-called "indirect" challenges are largely dependent on the state of activation of inflammatory or resident cells within the airways, and the state of activation can vary rapidly, either spontaneously or through intervention. Responses to "direct" challenges are dependent on less variable, rather chronic features of airways inflammation or remodeling. Bronchoprovocation tests provide integrated information about multiple pathophysiological pathways within the airway. This is in contrast to the measurements of cells, mediators, or cytokines in biological fluids, which provide only very specific information on selected inflammatory pathways. It has recently been shown that the outcome of asthma can substantially be improved when long-term treatment is not only guided by symptoms and lung function, but also by the degree of airway hyperresponsiveness to direct stimuli. Taken together, current data warrant a broader usage of bronchoprovocation tests in the research as well as clinical management of asthma and COPD. In asthma, it allows selective, individually targeted therapy of the patient as opposed to the currently recommended regimens that are (increasingly) unselective in their approach. The potential benefits of monitoring other phenotypic disease markers is currently under investigation.

Effects of glutathione S-transferase P1, M1, and T1 on acute respiratory illness in school children

The relationships between glutathione S-transferase (GST) M1, GSTT1, and GSTP1 genotypes and acute respiratory illness were investigated in a cohort of fourth grade school children aged 9-11 years who resided in 12 southern California communities. We used respiratory illness-related absences as a measure of respiratory illness occurrence. We ascertained respiratory illness-related school absences using an active surveillance system from January 1996 through June 1996. Genotypes for GSTM1 (null versus present), GSTT1 (null versus present), and GSTP1 (Ile105Val) were determined using genomic DNA from buccal cell specimens. The effects of GST genotypes on respiratory illness were assessed using stratified absence incidence rates and Poisson regression models. GSTP1 genotype was associated with risk for respiratory illness severe enough to result in a school absence. Children who were homozygous for the Val105 variant allele had lower incidence rates of upper and lower respiratory illnesses than did children who were homozygous for the Val105 allele. Children inheriting at least one Val105 allele were protected from respiratory illnesses (relative risk, 0.80; 95% confidence interval, 0.65-0.99). GSTM1 and T1 genotypes were not associated with respiratory illness. We conclude that GSTP1 genotype influences the risk or severity of respiratory infections in school-aged children.

Expression of tachykinins in nonnociceptive vagal afferent neurons during respiratory viral infection in guinea pigs

Immunohistochemistry was combined with retrograde labeling to characterize the effect of respiratory infection with Sendai virus on the number of Substance P/Neurokinin A-containing vagal afferent neurons whose cell bodies resided in the nodose ganglia and whose receptive fields were located in guinea pig trachea. Of the neurons labeled from the trachea of vehicle-inoculated guinea pigs, few stained positively for Substance P/Neurokinin A (approximately 3% of total labeled neurons). These neurons had small diameter cell bodies (mode = 16-20 microm), a feature of nociceptive-like C-fibers. Viral infection (Day 4 after inoculation) was associated with a significantly greater number of labeled neurons containing Substance P/Neurokinin A (approximately 20% of total labeled neurons). The majority of these had a relatively large cell body diameter (mode = 36- 40 microm), a feature of nonnociceptive afferent neurons. This induction appeared to be reversible as there were significantly fewer Substance P/Neurokinin A positive neurons in nodose ganglia from virus-inoculated guinea pigs at Day 28 after inoculation, a time point when virus-induced airway inflammation had all but resolved. These findings support the hypothesis that viral infection leads to a qualitative change in the vagal afferent innervation of guinea pig airways such that both small diameter nociceptive-like neurons and large diameter nonnociceptive neurons express tachykinins.

Infection with influenza a virus leads to flu antigen-induced cutaneous anaphylaxis in mice

It is well established, that viral infections may trigger urticaria or allergic asthma; however, as viral infections induce T helper 1 polarized responses, which lead to the inhibition of T helper 2 cell development, the opposite would be plausible. We wanted to investigate how viral infections may mediate allergic symptoms in a mouse model; therefore, we infected BALB/C mice with influenza A virus intranasally. Histologic analyses of lung sections and bronchoalveolar lavages were performed. In addition, cells from the mediastinal lymph nodes were restimulated in vitro to analyze which types of cytokines were induced by the flu infection. Furthermore, flu-specific antibody titers were determined and local anaphylaxis was measured after rechallenge with flu antigen. We found that airways inflammation consisted predominately of macrophages and lymphocytes, whereas only a few eosinophils were observed. interferon-gamma but no interleukin-4 and little interleukin-5 could be detected in the culture supernatants from in vitro restimulated T cells from the draining lymph nodes. The antibody response was characterized by high levels of virus-specific IgG2a, IgG2b, and IgG1 and, surprisingly, low levels of virus-specific IgE antibodies. Interestingly, flu-infected mice developed active and passive cutaneous anaphylaxis after rechallenge with flu-antigen. As the passive cutaneous anaphylaxis reaction persisted over 48 h and was significantly lower after passive transfer of the serum, which was IgE depleted, local anaphylaxis seemed to be mediated predominately by specific IgE antibodies. Taken together, our results demonstrate that mice infected with flu virus develop virus-specific mast cell degranulation in the skin. Our results may also have implications for the pathogenesis of urticaria or other atopic disorders in humans.

Comparison of three methods for respiratory virus detection between induced sputum and nasopharyngeal aspirate specimens in acute asthma

Viral respiratory tract infections are associated frequently with acute exacerbations of asthma. Nasopharyngeal aspirates and bronchoalveolar lavage specimens are used extensively for detecting viral respiratory tract infections, but not sputum. The aim of the study was to determine the efficiency of viral detection in induced sputum versus nasopharyngeal aspirate obtained during acute exacerbations of asthma, comparing three laboratory methods of viral diagnosis. Paired samples of induced sputum and nasopharyngeal aspirate obtained from 32 adults admitted to hospital with acute asthma were subjected to reverse transcription-polymerase chain reaction (RT-PCR), viral culture, and immunofluorescence assay. The results show that RT-PCR was associated with significantly higher rates of viral detection than culture (P=0.005) or immunofluorescence (P=0.001), without significant differences in the rates of viral detection between induced sputum and nasopharyngeal aspirate. It is concluded that induced sputum specimens are feasible for detection of viral respiratory tract infections by RT-PCR during acute exacerbations 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.

Viruses in asthma

Current evidence suggests that the overall load of infectious agents, including respiratory viruses, encountered early in life is an important factor influencing maturation of the immune system from a type 2 bias at birth towards predominantly type 1 responses, thus avoiding atopic diseases. The 'hygiene hypothesis' proposes that the relatively sterile environment present in industrialised Western countries has contributed to the recent epidemic of asthma and atopy. Whether specific infections are of greater or lesser protective value is an important question if strategies are to be derived to mimic the beneficial effects of childhood infection whilst avoiding morbidity and potential mortality of the natural pathogens. Infection by respiratory viruses is a major trigger of wheezing in infants and of exacerbations of asthma in older children. Viruses are detected in up to 85% of such episodes. Rhinovirus is common in all age groups; respiratory syncytial virus (RSV) is most important in infants and young children. Knowledge of the immunopathogenetic mechanisms of virus infection in the asthmatic airway will lead to the development of new treatments for virus-induced asthma.

Hydrogen peroxide in breath condensate during a common cold

BACKGROUND

Hydrogen peroxide (H2O2) in exhaled air condensate is elevated in inflammatory disorders of the lower respiratory tract. It is unknown whether viral colds contribute to exhaled H2O2.

AIM

To assess exhaled H2O2 during and after a common cold.

METHODS

We examined H2O2 in the breath condensate of 20 normal subjects with acute symptoms of a common cold and after recovery 2 weeks later and, similarly, in 10 subjects without infection. H2O2 was measured with a fluorimetric assay.

RESULTS

At the time of infection exhaled H2O2 (median, ranges) was 0.20 microM (0.03-1.2 microM), and this decreased to 0.09 microM (< 0.01-0.40 microM) after recovery (p = 0.006). There was no significant difference in lung function (forced vital capacity and forced expiratory volume in 1 sec) during and after colds. In the controls, exhaled H2O2 did not change over a 2-week period.

CONCLUSIONS

H2O2 in exhaled air condensate is elevated during a common cold, and returns to normal within 2 weeks of recovery in healthy subjects. Hence, symptomatic upper respiratory tract infection may act as a confounder in studies of H2O2 as a marker of chronic lower airway inflammation.

Inflammation-induced plasticity of the afferent innervation of the airways

The activation of primary afferent neurons that innervate the airways leads to homeostatic and defensive reflexes. The anatomic and physiologic characteristics of these afferent fibers do not appear to be static properties but rather appear to change rapidly in response to inflammation. The threshold for activation of airway afferent neurons to various stimuli, for example, is not fixed; these fibers can be become sensitized during inflammation. A subset of nociceptive-like (C-fibers) airway afferent neurons not only participates in centrally mediated reflexes but is also thought to release neuropeptides at their peripheral terminals, leading to neurogenic inflammation. An increase in the content of tachykinins is commonly seen in inflamed tissues, and there is accumulating evidence that irritation and inflammation of the airways is associated with the induction of tachykinin synthesis in non-nociceptive airway afferent fibers that under normal conditions do not contain neuropeptides. The release of neurokinins from the peripheral terminals in the airways and their central terminals in the brain stem may contribute to the symptoms of inflammatory airway diseases. Elevated release of neurokinins from peripheral terminals may promote local inflammatory responses, and the release of neurokinins in the brainstem, together with inflammation-induced increases in the excitability of afferent fibers, may culminate in altered visceral autonomic reflex activity, changes in breathing pattern, and cough.

Respiratory syncytial virus predisposes mice to augmented allergic airway responses via IL-13-mediated mechanisms

The development of severe childhood asthma may be influenced by several factors including environmental and infectious stimuli. The causal relationship between infectious viral responses, such as respiratory syncytial virus (RSV), and severe asthma during early childhood is unclear. In these studies, the ability for an initial RSV infection to exacerbate and promote a more severe asthmatic-type response was investigated by combining established murine models of disease. We examined the ability of RSV to induce exacerbation of allergic disease over a relatively long period, leading to development of severe airway responses including airway inflammation and hyperreactivity. The preferential production of IL-13 during a primary RSV infection appears to play a critical role for the exacerbation of cockroach allergen-induced disease. The depletion of IL-13 during RSV infections inhibited the exacerbation and acceleration of severe allergen-induced airway hyperreactivity. This was indicated by decreases in airway hyperreactivity and changes in lung chemokine production. These data suggest that the airway responses during asthma can be greatly affected by a previous RSV infection, even when infection occurs before allergen sensitization. Overall, infection of the airways with RSV can induce an IL-13-dependent change in airway function and promotes an environment that contributes to the development of severe allergic asthmatic responses.

The relationship between atopic status and IL-10 nasal lavage levels in the acute and persistent inflammatory response to upper respiratory tract infection

We examined the influence of atopy on virus-induced airway inflammation by comparing the nasal response to naturally acquired upper respiratory tract infection in atopic and nonatopic subjects by measurement of cytokine, chemokine, and mediator levels in nasal lavage from 44 adults (23 atopic) taken during the acute and the convalescent phases of the common cold. Nasal aspirates were examined for the presence of upper respiratory viruses by RT-PCR. In atopic and nonatopic subjects there were increased levels of IL-1beta, IL-6, IL-8, TNF-alpha, RANTES, sICAM-1, MPO, ECP, IL-10, and IFN-gamma in nasal lavage during the acute compared with the convalescent phase (p < 0.001). During the acute phase histamine levels were significantly higher in the atopic than in the nonatopic subjects (p < 0.05), whereas IL-10 levels were significantly greater in the nonatopic than in the atopic subjects (p < 0.05). At convalescence levels of IL-1beta, IL-6, sICAM-1, ECP, RANTES and albumin were significantly higher in the atopic group (p < 0.05). An upper respiratory tract virus was found in 27 volunteers (61%) during the acute stage and in two volunteers (4%) at convalescence. We conclude that virus-induced inflammatory changes within the nose are more prolonged in atopic than in nonatopic subjects and that this is associated with reduced IL-10 levels in atopic compared with nonatopic subjects during the acute phase of upper respiratory tract infection.

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.

Respiratory syncytial virus: recent progress towards the discovery of effective prophylactic and therapeutic agents

Although respiratory syncytial virus (RSV) was discovered in 1955, the burden associated with this infectious agent on all population groups is only now beginning to be fully appreciated. The successful launch of the humanized monoclonal antibody Synagis (developed by MedImmune, Gaithersburg, MD, USA), as a prophylactic in September 1998 has helped to heighten awareness of the extent of mortality and morbidity associated with annual RSV epidemics. Small, drug-like molecules that would provide the clinician with effective and conveniently administered prophylactic and therapeutic agents for the prevention and treatment of RSV have not yet advanced into clinical studies. This review will summarize recent developments in the area of RSV drug discovery and development.

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.