Bronchiolitis obliterans syndrome remains the leading cause of morbidity and mortality in the pulmonary transplant population. Previous studies show that macrolide antibiotics may be efficacious in the treatment of panbronchiolitis and cystic fibrosis. In the latter, azithromycin decreases the number of respiratory exacerbations, improves FEV1, and improves quality of life. We hypothesized that oral azithromycin therapy may improve lung function in patients with bronchiolitis obliterans syndrome. To test this hypothesis, we conducted an open-label pilot trial using maintenance azithromycin therapy in six lung transplant recipients (250 mg orally three times per week for a mean of 13.7 weeks). In this study, five of these six individuals demonstrated significant improvement in pulmonary function, as assessed by FEV1, as compared with their baseline values at the start of azithromycin therapy. The mean increase in the percentage of predicted FEV1 values in these individuals was 17.1% (p ⩽ 0.05). In addition, the absolute FEV1 increased by 0.50 L (range −0.18 to 1.36 L). These data suggest a potential role for maintenance macrolide therapy in the treatment of bronchiolitis obliterans syndrome in lung transplant recipients.
Lung transplantation has emerged as an important therapeutic option for patients with a variety of end-stage pulmonary disorders. Although short-term survival is improved with transplantation, long-term survival is limited by the development of bronchiolitis obliterans syndrome (BOS), an inflammatory process of the airways synonymous with chronic allograft rejection, and marked by progressive obstructive lung disease (1). BOS affects from 12 to 18% of lung transplant recipients at 1 year and up to 75% of individuals by 5 years (2, 3). Although the majority of evidence suggests that obliterative bronchiolitis is immune mediated, many transplant recipients experience concurrent bacterial and nonbacterial infections that may increase lung inflammation and potentially worsen chronic rejection. Unfortunately, for those who fail standard immunosuppressive regimens, treatment options are rarely successful in reversing the progression of BOS. Thus, new therapeutic strategies are needed to improve long-term patient outcomes in lung transplantation.
The potential antiinflammatory role for macrolide antibiotics in the respiratory system was first described with troleandomycin in asthma (4). Subsequently, erythromycin therapy was found to improve survival markedly in patients with diffuse panbronchiolitis (5). More recently, two groups have reported clinical improvement in patients with cystic fibrosis on maintenance azithromycin therapy, as measured by a decrease in the number of respiratory exacerbations, improved FEV1, and improved quality of life (6, 7). We conducted an open-label pilot study using maintenance oral azithromycin therapy in six lung transplant recipients with BOS to assess whether this therapy might impact their clinical course. Some of the results of this study have been previously reported in the form of abstracts (8, 9).
Six lung transplant recipients with deteriorating allograft function were enrolled in an open-label pilot trial of maintenance oral azithromycin. The patients were selected because each had clinical BOS stage 1 or greater, which was unresponsive to augmented immunosuppression. BOS was diagnosed using the International Society for Heart and Lung Transplantation definition of at least a 20% decline in FEV1 from a patient's post-transplant maximum value, in the absence of acute infection or acute rejection (3). In our study, acute infection was defined by positive cultures (blood or sputum) in the presence of fever, a new pulmonary infiltrate, or new onset symptoms, including cough, shortness of breath, or sputum production. In addition to BOS, three patients had a documented history of lymphocytic bronchiolitis.
All six patients received oral azithromycin at a dose of 250 mg daily for 5 days, followed by 250 mg three times per week. Spirometry was performed to evaluate FEV1 at each follow-up visit (every 4 weeks) to the transplant clinic. The follow-up period began at the start of azithromycin therapy and continued to the time of this article preparation. The six patients were started on therapy at different time points; thus, the follow-up period for each patient varied, with the mean follow-up being 13.7 weeks (range 7 to 20.4 weeks). At the time of article preparation, all patients were still receiving maintenance azithromycin therapy. Each patient continued to receive baseline immunosuppression therapy, as is listed in Table 1
Underlying Disease (Type of Transplant)
BOS Stage/Most Recent Transbronchial Biopsy Results (Weeks Before Study)
Time Since Transplant (Weeks)
Upper/Lower Respiratory Cultures and (Days Before Study)
Colonization Versus Infection
|1||Cystic fibrosis (DLT)||25||BOS Stage 1a/lymphocytic bronchiolitis A0B2 (5 weeks)||185||Tacrolimus Prednisone Mycophenolate mofetil||Post transplant lymphoma, chronic sinusitis, history of adult respiratory distress syndrome, BOOP||Three strains of Pseudomonas, Staphylococcus aureus (58 days)||Chronic colonization|
|2||Cystic fibrosis (DLT)||23||BOS Stage 3a/Lymphocytic bronchiolitis, obliterative bronchiolitis A0B2C1 (1 week)||115||Tacrolimus Prednisone Mycophenolate mofetil||Recurrent pan-resistant pseudomonas, type I diabetes, intestinal obstruction||Pseudomonas (panresistant) (3 days)||Chronic colonization|
|3||Bronchiectasis (DLT)||51||BOS Stage 3a/Focal neutrophil infiltrate A0BX (2 weeks)||51||Tacrolimus Prednisone Mycophenolate mofetil||Chronic sinusitis, hypertension||Two strains of Pseudomonas (panresistant) M RSA (13 days)||Chronic colonization|
|4||Idiopathic pulmonary fibrosis (SLT)||53||BOS stage 2a/No rejection A0BX (4 weeks)||182||Tacrolimus Prednisone Mycophenolate mofetil||Pseudomonas pneumonia, bronchial malacia||Pseudomonas, Staphylococcus aureus (28 days)||Colonization|
|5||Bronchiectasis (DLT)||40||BOS Stage 3a/Lymphocytic bronchiolitis A0B1 (2 weeks)||165||Cyclosporine Prednisone Mycophenolate mofetil||Common variable immunodeficiency, osteoporosis, Nocardia pneumonia||Streptococcus pneumoniae (12 days)||Acute infection resolved|
|6||Obliterative bronchiolitis (DLT)*||46||BOS Stage 2b/Obliterative bronchiolitis A0BXC1 (1 week)||65||Cyclosporine Prednisone Sirolimus||Chronic renal insufficiency, pulmonary artery angioplasty||Normal flora
A two-tailed, paired t test was used to compare the absolute and percent of predicted FEV1 values recorded immediately before the start of azithromycin to the most recent FEV1 values recorded before the preparation of this article. An α of 0.05 or less was considered statistically significant. The statistical software packages used for these analyses included STATA 7.0 (College Station, TX) and Microsoft Excel (Redmond, WA).
The clinical data for each patient are displayed in Table 1. Two patients were transplanted for cystic fibrosis, two for bronchiectasis, one for idiopathic pulmonary fibrosis, and one retransplanted for obliterative bronchiolitis (originally transplanted for pulmonary arterial hypertension). Four of the six patients had documented Pseudomonas aeruginosa pulmonary or sinus colonization before the initiation of macrolide therapy. Three patients had a history of lymphocytic bronchiolitis (patients 1, 2, and 5), and two patients had histopathologic confirmation of obliterative bronchiolitis (patients 2 and 6), diagnosed by transbronchial biopsy.
At the time of the last follow-up, five of the six individuals demonstrated significant improvement in their pulmonary function, as assessed by serial measurements of FEV1, as compared with the baseline values at the start of azithromycin therapy. Individual serial FEV1 values for each patient are shown in Figure 1, beginning with the highest post-transplant FEV1 preceding azithromycin treatment, the initiation of azithromycin treatment, and all follow-up measurements to date. All changes in baseline immunosuppression or rescue therapy for each individual are also shown chronologically with respect to the start of azithromycin therapy. These six patients demonstrated a mean increase in their absolute FEV1 of 0.50 L (range, −0.18 to 1.36 L; p ⩽ 0.07), representing an average improvement in absolute FEV1 of 46%. The mean increase in the percent of predicted FEV1 values was 17.1% ± 6.9% (p ⩽ 0.05). Unexpectedly, one patient's FEV1 (patient 2) was dramatically restored to a level equal to her highest post-transplant value (Figure 1), representing a 108% increase from the start of azithromycin therapy. In addition, among the five patients who responded to azithromycin, the mean improvement in FEV1 was 0.63 L (p ⩽ 0.04). Similarly, among responders, the percentage of predicted FEV1 improved by a mean of 21.6% (p ⩽ 0.03). Taken together, these results demonstrate significantly improved pulmonary function in five out of six lung transplant recipients treated with maintenance oral azithromycin therapy.
To our knowledge, this is the first reported use of maintenance oral azithromycin therapy in lung transplant recipients for the treatment of BOS. In this pilot study, we found that the addition of oral azithromycin resulted in a statistically significant improvement in lung function in five of six individuals, as measured by serial FEV1. Although the factor(s) contributing to this observed clinical improvement remains unclear, we hypothesize that azithromycin therapy may improve BOS through one or several potential mechanisms described later here.
Numerous reports have suggested that macrolide antibiotics may possess antiinflammatory properties. These clinical studies have described improvement in patients with asthma or diffuse panbronchiolitis (4, 5, 10). More recently, Black and colleagues demonstrated temporary improvement in evening peak expiratory flow using roxithromycin in a cohort of asthmatics with positive serology for Chlamydia pneumoniae (11), and Kraft showed similar improvement using clarithromycin in a group of subjects with asthma with molecular evidence of Mycoplasma pneumoniae or C. pneumoniae (12). Furthermore, several human studies have demonstrated a reduction in inflammatory mediators in patients receiving macrolide therapy, including interleukin (IL)-8, tumor necrosis factor-α, and IL-1β (13, 14). Similarly, numerous animal and human in vitro studies have demonstrated that macrolides inhibit tumor necrosis factor-α, IL-6, IL-8, and nitrite (15–17). IL-8 is perhaps the best studied inflammatory mediator that appears to be inhibited by macrolide antibiotics. As a critical chemokine for neutrophil chemotaxis, IL-8 is produced by a variety of cell types, including neutrophils themselves, endothelial cells, and airway epithelial cells (14, 18, 19). Interestingly, several studies have noted bronchoalveolar lavage neutrophilia and elevated levels of certain inflammatory cytokines such as tumor necrosis factor-α, IL-1β, and IL-6 in obliterative bronchiolitis (20–23). Moreover, a possible reduction in tumor necrosis factor-α levels with macrolide therapy may have important, far reaching implications, as this cytokine is a potent inducer of the C-C chemokines macrophage-inflammatory proteins-1α, -1β, and regulated upon activation normal T cell expressed and secreted, which all act through the C-C chemokine receptor 5 (24, 25). This chemokine/chemokine receptor system is important for mononuclear cell recruitment and was recently found to be upregulated in a rat transplant model of obliterative bronchiolitis (William Baldwin, personal communication). Thus, these pluripotent antiinflammatory properties associated with macrolides may in part account for the clinical improvement in our patients with BOS.
Several reports have suggested a potential role for macrolide antibiotics in P. aeruginosa infections based on nonbactericidal antimicrobial effects demonstrated both in vitro and in vivo. This may be an important mechanism as pseudomonas infection represents a common problem in lung transplant recipients. Previous studies show that azithromycin or other macrolides can inhibit P. aeruginosa biofilm formation, flagellin expression, and adherence to tracheal epithelium (26–28). In vitro studies comparing the effects of erythromycin, clarithromycin, or azithromycin on the production of multiple virulence factors by P. aeruginosa found azithromycin to exert the broadest suppression at low concentrations, while not affecting bacterial growth (29). In addition, azithromycin has been shown to inhibit the transcription of quorum sensing genes of P. aeruginosa bacteria. This inhibition may prevent production of tissue-damaging proteins, which are potential inducers of a chronic inflammatory response (30). Finally, in a randomized trial in adult patients with cystic fibrosis, who are often infected with P. aeruginosa, the addition of daily azithromycin reduced the number of pulmonary exacerbations over a 3-month period without significantly altering respiratory microbiologic flora (6). Together, these data suggest a potential nonbactericidal, antipseudomonal role for macrolide antibiotics that may impact patients with BOS. Alternatively, azithromycin therapy may directly treat less commonly described pathogens in this patient population such as M. or C. pneumoniae that may also play a role in chronic rejection (31, 32).
Recently, gastroesophageal reflux has been increasingly recognized as a factor that may significantly contribute to BOS in lung transplant recipients (33). A role for erythromycin as a promotility agent has been well documented (34), and it is possible that azithromycin may improve lung function in BOS patients through a similar mechanism. Two of our patients who improved while receiving azithromycin had documented gastroesophageal reflux by cine esophagram and have been treated conventionally; however, no follow-up studies have been done to assess their reflux since starting azithromycin therapy. A future, randomized study of azithromycin for BOS should evaluate subjects for changes in gastroesophageal reflux in a prospective manner.
This observational pilot study clearly is limited by its lack of a placebo control group and small sample size, which can lead to an overestimation of therapeutic effect. In addition, we realize that in an uncontrolled study such as this one, selection bias can arise. Another possible explanation for our observed clinical improvement in these patients may be due to interactions between azithromycin and certain immunosuppressive medications. Indeed, azithromycin has been reported to elevate cyclosporine levels; however, we monitored calcineurin inhibitor levels closely and found that the addition of azithromycin therapy did not dramatically alter cyclosporine or tacrolimus levels (35). We are not aware of any reports of azithromycin augmenting levels or the activities of corticosteroids, sirolimus, azathioprine, or mycophenolate mofetil.
In summary, this is the first report that suggests a potential role for maintenance macrolide therapy in the treatment of BOS. Although it is unclear whether macrolide therapy directly affects the course of BOS or indirectly impacts other factors contributing to allograft dysfunction, the majority of patients in our small series had significant improvement in their obstructive lung disease. Furthermore, azithromycin therapy in this population has been safe and well tolerated. Thus, we believe these results may have immediate clinical impact, because to date, no other pharma cologic agent has improved lung function in BOS. Finally, these results warrant further investigation with a randomized, placebo-controlled clinical study to evaluate maintenance azithromycin therapy in the treatment of BOS in lung transplant recipients.
The authors thank Marvin C. Borja, Therese M. Cook, Edward F. Haponik, Susan M. Miller, and Peter B. Terry for their assistance in preparing this article.
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