| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Depts of Paediatric Allergy, 2 Paediatrics, and 3 Microbiology, Erciyes University School of Medicine, Kayseri, Turkey.
CORRESPONDENCE: F. Tahan, Dept of Paediatric Allergy, Erciyes University School of Medicine, Kayseri 38039, Turkey. Fax: 90 3524375825. E-mail: tahanfulya{at}yahoo.com
Keywords: Bronchiolitis, clarithromycin, eotaxin, interleukin-4, interleukin-8, respiratory syncytial virus
Received: February 27, 2006
Accepted August 29, 2006
 |
ABSTRACT |
|---|
 TOP ABSTRACT MATERIAL AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
In order to investigate the efficacy of clarithromycin in the treatment of RSV bronchiolitis, the present authors conducted a randomised, double-blind, placebo-controlled trial comparing clarithromycin with placebo in 21 infants with a diagnosis of RSV bronchiolitis. The infants were randomised to receive clarithromycin or placebo daily for 3 weeks. Levels of interleukin (IL)-4, IL-8, eotaxin, and interferon-
were determined in plasma, before and after treatment, using ELISA. Six months after treatment, parents were surveyed as to whether their child had experienced wheezing within the previous 6 months.
Treatment with clarithromycin was associated with a statistically significant reduction in the length of hospital stay, the duration of need for supplemental oxygen and the need for ß2-agonist treatment. There were significant decreases in plasma IL-4, IL-8 and eotaxin levels after 3 weeks of treatment with clarithromycin. Readmission to the hospital within 6 months after discharge was significantly lower in the clarithromycin group.
In conclusion, clarithromycin has statistically significant effects on the clinical and laboratory findings in respiratory syncytial virus bronchiolitis. Therefore, clarithromycin treatment may be helpful in reducing the short-term effects of respiratory syncytial virus bronchiolitis.
Respiratory syncytial virus (RSV) bronchiolitis is the most common lower respiratory tract infection in infancy, occurring in 90% of children of <2 yrs of age 1, 2. Severe RSV infection in the first 6 months of life is often followed by recurrent childhood wheezing 3.
Airway inflammation in RSV bronchiolitis is a multicellular process involving epithelial cells, eosinophils and neutrophils. Epithelial cells have always been thought of as major contributors to the inflammatory process of the airways during RSV infection. RSV causes widespread damage to bronchial epithelium and stimulates epithelial cells to secrete a wide range of pro-inflammatory cytokines and chemokines 4. The increase in virus-induced chemokines recruits leukocytes to the airway and could increase binding of neutrophils and eosinophils to epithelial cells.
Interleukin (IL)-8 is a key chemokine produced by RSV-infected airway cells and is involved in the activation and recruitment of neutrophils 5. Neutrophils play a major role in the pathophysiology of RSV bronchiolitis 6.
RSV infection can enhance the influx of eosinophils into the lungs 7. Kristjansson et al. 8 showed that RSV infection during early infancy promotes infiltration and activation of eosinophils. In vitro studies 9–12 have indicated that RSV infection results in the release of high concentrations of regulated on activation, normal T-cell expressed and secreted (RANTES) and macrophage inflammatory protein-1
.
RSV infection may influence the development of asthma by enhancing allergic sensitisation in the developing lung. The normal respiratory tract has evolved in close contact with aeroallergens. Sensitisation to aeroallergens is unlikely to occur through an intact mucosal epithelium. Disturbance of the respiratory mucosal surface during viral infection may allow allergens to gain access to the subepithelial layer and interact with antigen-presenting cells and inflammatory cells, leading to allergic sensitisation 13.
In order to break the apparent link that exists between RSV bronchiolitis and childhood asthma, an effective therapy against its short-term effects is necessary.
The treatment of infants with bronchiolitis has been largely supportive, with supplemental oxygen, minimal handling of the infant and the use of intravenous fluids and ventilatory support where necessary 14. The role of bronchodilators is controversial 14. The American Academy of Paediatrics does not recommend using corticosteroids for the treatment of RSV symptoms. Despite many attempts to find effective treatments for patients with RSV bronchiolitis, no consistently effective therapy has yet been described.
Macrolides are widely used in the treatment of infectious diseases, including respiratory infections 15. There is increasing evidence of an anti-inflammatory effect of macrolides.
Clarithromycin, one of the newer macrolides, has been shown to have immunomodulatory effects. Possible mechanisms of the anti-inflammatory effects of clarithromycin include inhibition of neutrophil migration and pro-inflammatory cytokines, increase in phagocytosis and natural killer cell activity and induction of eosinophil apoptosis 16–20. Clarithromycin suppresses the production of pro-inflammatory cytokines via inhibition of nuclear factor-
B activation 21.
As RSV infection initiates an immune inflammatory response that may produce long-lasting harmful effects, it was hypothesised that the course of the disease could be modified and wheezing after bronchiolitis prevented by administering macrolides to infants during an acute episode of RSV bronchiolitis. To investigate this, the present authors studied the use of 3 weeks of macrolide therapy in the treatment of RSV bronchiolitis in a double-blind, randomised, placebo-controlled trial. The current authors measured the levels of the eosinophilic CC chemokine eotaxin (thought to have a role in eosinophilic inflammation) and the CXC chemokine IL-8 (thought to have a central role in neutrophilic inflammation). With the knowledge that severe RSV infections during early infancy are associated with the excessive production of T-helper cell (Th) type 2 cytokines 22, 23, the present authors measured the levels of Th2 cytokine IL-4 (thought to have a central role in Th2-mediated diseases) and the Th1 cytokine interferon (IFN)-.
The present authors hypothesised that a 3-week course of clarithromycin therapy would result in a reduction in the hospital length of stay (LOS), a reduction in plasma IL-4, IL-8 and eotaxin levels and an enhanced production of IFN-.
|
MATERIAL AND METHODS |
|---|
|
TOPABSTRACTMATERIAL AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
7 months of age with documented respiratory tract infection with RSV admitted to the Dept of Paediatrics at the Erciyes University Hospital in Kayseri, Turkey, were enrolled in the present study. Infants with a first episode of wheezing requiring hospitalisation and with a clinical diagnosis of bronchiolitis were considered for entry into the study. Bronchiolitis was diagnosed based on clinical findings, including wheezing or wheezing with crackles, and respiratory distress with retractions. Infants with cardiac disease, cystic fibrosis or chronic neonatal lung disease associated with prematurity were excluded. Infants were also excluded if they had received corticosteroids within 24 h before presentation or bronchodilators within 4 h before presentation. The present study was approved by the Erciyes University Hospital ethics committee. Written informed consent was obtained from the parents before enrolment.
Bronchiolitis diagnosis and treatment
All children admitted to hospital with bronchiolitis were treated according to the same clinical pathway to minimise the variability of the results. A nasopharyngeal aspiration sample (NPA) was obtained routinely from all patients for detection of RSV. RSV infection was diagnosed by direct immunofluorescent staining of the NPA. An infant was considered ready for discharge when he/she had not received supplemental oxygen for 10 h, had minimal or no chest retractions and was feeding adequately without the need for intravenous fluids. Supplemental oxygen was administered to those cases showing oxygen saturation (Sp,O2) levels <94%, as determined by pulse oximetry (Trusat pulse oximeter; Datex-Ohmeda, Louisville, CO, USA). Supplemental oxygen was discontinued when Sp,O2 was consistently >93% or when the infant's condition had been stable for 4 h and he/she was starting to tolerate oral feeding.
Intravenous fluids were administered when supplemental oxygen was required, the respiratory rate was >60 breaths·min-1 or oral intake was inadequate. When the infant was able to tolerate oral feeding, the use of intravenous fluids was stopped.
The infants received ß2-agonist treatment based on oxygen saturation, respiratory rate and respiratory effort. In particular, the infants received ß2-agonist treatment when oxygen saturation was <94%, the respiratory rate was >60 breaths·min-1, there was the presence of wheezing on auscultation of the chest or respiratory distress with retractions.
Randomisation and investigational therapy
After written informed parental consent had been obtained and the NPA had been found to be positive for RSV, the infants were randomised by a single study nurse to receive clarithromycin (15 mg·kg-1) or placebo daily for 3 weeks. Simple randomisation was used 24. Patients, parents and investigators were kept blinded to the randomisation until completion of the study. The primary outcome was LOS. Secondary outcomes included changes in the IL-4, IL-8, eotaxin and IFN- levels, readmission rate and wheezing after discharge.
Each infant was assigned one bottle of solution containing either clarithromycin (clarithromycin, silicon dioxide, saccharose, kxantan zamk, tutti frutti aroma, potassium sorbate, citric acid, titanium dioxide, maltodextrin and water) or placebo (silicon dioxide, saccharose, kxantan zamk, tutti frutti aroma, potassium sorbate, citric acid, titanium dioxide, maltodextrin and water).
Clinical data
Detailed clinical histories, including the duration of symptoms before presentation at the hospital, the medical history, the infant's ability to feed, previous medication, parental smoking history and family history of atopy were recorded. Observations at admission included respiratory and heart rate while the infant was quiet, temperature, respiratory effort, Sp,O2 while breathing room air, presence of wheezing or crackles on auscultation of the chest, and level of hydration. Each infant's condition was classified as mild, moderate or severe according to a severity score 14 calculated from the Sp,O2, respiratory rate and respiratory effort observed at admission (table 1
). Six months following completion of clarithromycin or placebo therapy, parents were asked whether their child had experienced wheezing during the previous 6 months.
|
Peripheral blood (5 mL) was obtained from all the children pre-treatment and after 3 weeks of macrolide or placebo treatment. The samples were centrifuged at 2,000 rpm for 30 min and the serum was frozen at –20°C for storage prior to ELISA assay. The serum samples were analysed, both during the acute phase of the disease and after 3 weeks of treatment, for levels of IL-4, IL-8, eotaxin and IFN-.
Total immunoglobulin (Ig)E and eosinophil counts were obtained. Skin testing was performed with a battery of 25 antigens with appropriate histamine positive and saline/diluent negative controls on the upper back of the children at presentation. Reactions with an induration >3 mm of that of the negative control were considered positive.
IgE levels were measured with Uni-Cap technology in accordance with the specifications of the manufacturer (Pharmacia, Kalamazoo, MI, USA). Eosinophil counts were determined from Coulter Counter (Automated Haematology Analyser, XT-2000; Sysmex, Kobe, Japan) leukocyte measurements.
Chemokine measurements
The ELISA kits used to detect IL-4, IL-8, eotaxin and IFN- levels were obtained from Biosource (Camarillo, CA, USA). Their sensitivity was 2 pg·mL-1, 5 pg·mL-1, 2.2 pg·mL-1 and 4 pg·mL-1, respectively.
Statistical analyses
Chemokine levels in the plasma were compared according to Mann–Whitney U-tests or Wilcoxon tests, depending upon the distribution of the data. Sex, parental smoking, readmission to the hospital, duration of wheezing at admission, severity of the disease, requiring supplemental oxygen, skin test positivity and family history of atopy were compared according to Chi-squared tests. A p-value <0.05 was considered significant.
|
RESULTS |
|---|
|
TOPABSTRACTMATERIAL AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
). Likewise, there were no significant differences between the groups with respect to the number of eosinophils and plasma IgE levels (p>0.05, Mann–Whitney U-test; table 1).
Primary end-points
Treatment with clarithromycin was associated with a significant reduction in LOS (51 h versus 88 h (p<0.05); table 2). The duration of need for supplemental oxygen and intravenous fluids was higher in the placebo group (31 versus 72 h (p<0.05) and 26 versus 56 h (p<0.05), respectively; Mann–Whitney U-test; table 2).
|
).
Secondary end-points
Comparison of pre-treatment plasma chemokine levels revealed that there was no significant difference between the clarithromycin and placebo groups (p>0.05, Mann–Whitney U-test).
Three weeks of clarithromycin therapy was associated with significant changes in the plasma chemokine levels. There were significant decreases in the plasma IL-4, IL-8 and eotaxin levels following clarithromycin therapy (p<0.05, Wilcoxon; figs 1a, b and c). No differences in plasma eotaxin, IL-4 and IL-8 levels were observed for infants receiving placebo treatment (p>0.05, Wilcoxon; figs 1a, b and c). IFN- levels were below the limit of detection in all infants.
|
). The parents of those infants that were not readmitted to the hospital were surveyed on the phone regarding wheezing during the first 6 months post-treatment. None reported wheezing during that time. |
DISCUSSION |
|---|
|
TOPABSTRACTMATERIAL AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
were measured. It has been shown that clarithromycin, when compared with placebo, is capable of significant changes in some of these parameters. In RSV bronchiolitis, treatment with clarithromycin had a statistically significant effect on LOS, use of ß2-agonist treatment and plasma IL-4, IL-8 and eotaxin levels.
Clarithromycin is widely used in the treatment of infectious diseases and has an antibacterial effect. The question is whether the clinical improvement is related to its antibacterial effect. It is known that acute bronchiolitis is predominantly a viral disease. RSV is responsible for >50% of cases 25. Other agents include parainfluenza, adenovirus and, occasionally, other viruses. There is no evidence of a bacterial cause for bronchiolitis 25. In the present study group, bacterial infection was not investigated due to all subjects testing RSV positive, their leukocyte counts being normal and their C-reactive protein levels negative.
How could clarithromycin act in the short-term to effect changes in LOS and the use of ß2-agonist treatment in bronchiolitis? The present authors considered that suppressive effects of clarithromycin on the plasma IL-4, IL-8 and eotaxin levels may have a role in suppression of airway hyperresponsiveness or may inhibit cholinergic neuroeffector transmission in human airway smooth muscle, thereby influencing bronchial tone.
RSV is suspected to potentially cause increased airway responsiveness by enhancing parasympathetic bronchoconstrictive responses 26. The existing documentation reporting that macrolides attenuate the contractile response of human isolated bronchial strips to electrical field stimulation 18 leads to the hypothesis that macrolides might influence bronchial tone by inhibiting cholinergic neuroeffector transmission in human airway smooth muscle.
Airway hyperresponsiveness appears to be one manifestation of the airway inflammation induced by RSV. It has been shown that a correlation exists between numbers of mast cells, eosinophils and neutrophils and the degree of airway hyperresponsiveness 27. It has been further shown that enhanced IL-4, IL-8 and eotaxin levels have a role in the development of airway inflammation and hyperresponsiveness 28–30. Pitrez et al. 31 suggested that there were significant correlations between IL-4 levels in blood and airway secretions. The present authors found significant decreases in plasma IL-4 levels after 3 weeks of clarithromycin therapy. IL-4 is a critical cytokine in the mediation of allergic airway inflammation. IL-4 is critical in the switching of B-cellsto IgE production. It also promotes mucus hypersecretion and ascular cell adhesion molecule-1 expression in endothelial cells, resulting in the recruitment of eosinophils 32.
It is known that enhanced IL-4 has a critical role in the development of airway hyperresponsiveness 28. Inhalation of IL-4 causes the development of sputum eosinophilia and increased airway hyperreactivity 33. It is hypothesised that clarithromycin, by decreasing plasma IL-4 levels, may reduce the need for ß2-agonist therapy in RSV bronchiolitis. Indeed, infants in the placebo group required significantly longer duration of ß2-agonist therapy than infants in the clarithromycin group.
Neutrophil-mediated inflammation is involved in the augmentation of bronchial reactivity in RSV bronchiolitis 26, 29, 34, 35. IL-8 and leukotriene (LT)B4 are known neutrophil chemotactic factors and play an important role in neutrophilic airway inflammation 36. Previous studies 36, 37 demonstrated that one of the anti-inflammatory mechanisms of macrolides relates to the inhibition of IL-8 production. Macrolides also inhibit formation of LTB4 and neutrophil infiltration into lung tissue and reduce the formation of superoxide by neutrophils 38–42. Steroids fail to downregulate RSV-induced IL-8 secretion in infants. This may explain why steroid therapy is unsuccessful in RSV bronchiolitis 43.
The present authors found significant decreases in plasma eotaxin levels following clarithromycin therapy. Eotaxin is highly specific for eosinophil recruitment 30. Macrolides attenuate the release of eotaxin, granulocyte-macrophage colony-stimulating factor and RANTES 30. Lung fibroblasts are an important source of eosinophil chemotactic activity. Inhibitory effects of erythromycin on eosinophil chemotactic cytokine release by lung fibroblasts may be one of the mechanisms of decreased airway hyperresponsiveness and the resulting amelioration of disease activity following therapy with that agent 30. Macrolides may also protect epithelial cells at inflamed sites by inhibiting the release of reactive oxygen species from eosinophils 44.
Severe RSV infections during early infancy are associated with the excessive production of Th2 cytokines 22, 23, which has been suggessted as a risk factor for the development of asthma and allergic sensitisation 45. Macrolides may normalise the Th1/Th2 lymphocyte balance 38. They regulate immunologic activities by enhancing production of IFN- and by reducing production of IL-4 and IL-5 46. Treatment that restores the Th1/Th2 cytokine balance to the relative type 1 predominance may ameliorate short- and long-term effects of RSV disease.
The present authors have no data concerning the long-term effects of clarithromycin in RSV bronchiolitis. Further investigations will be required to understand the long-term effects of clarithromycin, especially reducing recurrent wheezing, allergic sensitisation and asthma.
Numerous studies 47, 48 have shown that 75% of patients with RSV bronchiolitis exhibit recurrent wheezing or pulmonary function abnormalities years later. As discussed previously, RSV infection may enhance allergic sensitisation in the developing lung through disruption of the respiratory epithelium. Macrolides promote the reparative process in the chronically inflamed upper and lower respiratory tract and are associated with salutary tissue reparative effects in patients with chronic inflammatory sinopulmonary diseases, such as chronic sinusitis, asthma, bronchiectasis, cystic fibrosis and diffuse panbronchiolitis 49. Suppressing IgE 49 and the tissue reparative effects of macrolides may partly protect against allergic sensitisation.
Further investigations of larger groups of children will be required to elucidate potential effects of macrolides in this area.
In conclusion, treatment with clarithromycin in respiratory syncytial virus bronchiolitis had statistically significant effects on hospital length of stay, duration of need for supplemental oxygen and rate of readmission to the hospital within 6 months after discharge. Suppressive effects of clarithromycin on the plasma interleukin-4, interleukin-8 and eotaxin levels may have a role in suppression of airway hyperresponsiveness and epithelial cell damage, leading to a reduction in post-bronchiolitic symptoms and allergic sensitisation. Effective therapy against the short-term effects of respiratory syncytial virus bronchiolitis could be important in reducing subsequent morbidity. The present study should encourage further studies to confirm the use of clarithromycin in respiratory syncytial virus bronchiolitis, especially in infants of <6 months of age.
|
REFERENCES |
|---|
|
TOPABSTRACTMATERIAL AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
This article has been cited by other articles:
|
|
 |
|
  J. L. Simpson, H. Powell, M. J. Boyle, R. J. Scott, and P. G. Gibson Clarithromycin Targets Neutrophilic Airway Inflammation in Refractory Asthma Am. J. Respir. Crit. Care Med., January 15, 2008; 177(2): 148 - 155. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. S. L. Shell, C. W. Calabria, G. L. Casoni, V. Poletti, P. Stafler, H. M. Corneli, J. J. Zorc, and N. Kuppermann Dexamethasone for Bronchiolitis N. Engl. J. Med., October 18, 2007; 357(16): 1659 - 1660. [Full Text] [PDF]
|
|
|
|
 |
|
 M. Korppi Macrolides and bronchiolitis in infants Eur. Respir. J., June 1, 2007; 29(6): 1283 - 1284. [Full Text] [PDF]
|
|
|
|
|
|
F. Tahan From the authors Eur. Respir. J., June 1, 2007; 29(6): 1284 - 1285. [Full Text] [PDF]
|
|
|
|
|
|
M. C. J. Kneyber and J. L. L. Kimpen Antibiotics in RSV bronchiolitis: still no evidence of effect Eur. Respir. J., June 1, 2007; 29(6): 1285 - 1285. [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
