Targeting allograft injury and inflammation in the management of post-lung transplant bronchiolitis obliterans syndrome

Obesity, organ failure, and transplantation: A review of the role of metabolic and bariatric surgery in transplant candidates and recipients

Obesity is a risk factor for kidney, liver, heart, and pulmonary diseases, as well as failure. Solid organ transplantation remains the definitive treatment for the end-stage presentation of these diseases. Among many criteria for organ transplant, efficient management of obesity is required for patients to acquire transplant eligibility. End-stage organ failure and obesity are 2 complex pathologies that are often entwined. Metabolic and bariatric surgery before, during, or after organ transplant has been studied to determine the long-term effect of bariatric surgery on transplant outcomes. In this review, a multidisciplinary group of surgeons from the Society of American Gastrointestinal and Endoscopic Surgeons and the American Society for Transplant Surgery presents the current published literature on metabolic and bariatric surgery as a therapeutic option for patients with obesity awaiting solid organ transplantation. This manuscript details the most recent recommendations, pharmacologic considerations, and psychological considerations for this specific cohort of patients. Since level one evidence is not available on many of the topics covered by this review, expert opinion was implemented in several instances. Additional high-quality research in this area will allow for better recommendations and, therefore, treatment strategies for these complex patients.

Obesity, organ failure, and transplantation: a review of the role of metabolic and bariatric surgery in transplant candidates and recipients

Obesity is a risk factor for kidney, liver, heart, and pulmonary diseases, as well as failure. Solid organ transplantation remains the definitive treatment for the end-stage presentation of these diseases. Among many criteria for organ transplant, efficient management of obesity is required for patients to acquire transplant eligibility. End-stage organ failure and obesity are 2 complex pathologies that are often entwined. Metabolic and bariatric surgery before, during, or after organ transplant has been studied to determine the long-term effect of bariatric surgery on transplant outcomes. In this review, a multidisciplinary group of surgeons from the Society of American Gastrointestinal and Endoscopic Surgeons and the American Society for Transplant Surgery presents the current published literature on metabolic and bariatric surgery as a therapeutic option for patients with obesity awaiting solid organ transplantation. This manuscript details the most recent recommendations, pharmacologic considerations, and psychological considerations for this specific cohort of patients. Since level one evidence is not available on many of the topics covered by this review, expert opinion was implemented in several instances. Additional high-quality research in this area will allow for better recommendations and, therefore, treatment strategies for these complex patients.

Dysphagia and medicine regimes in patients following lung transplant surgery: A retrospective review

PURPOSE

Dysphagia is reported following lung transplantation. Characteristics and trajectory for dysphagia are poorly understood. This retrospective study explored dysphagia and medicine regimes in patients following lung transplant.

METHOD

Medical records and endoscopic recordings of 101 patients (M:50yrs, range 20-67yrs, SD 13yrs) were reviewed. Standardised endoscopic swallowing measures were reported. Discharge reports were analysed for medicines known to cause dysphagia.

RESULT

All patients received bilateral sequential single-lung transplant. Prevalence of referral to speech pathology was 65% with 37 requiring more than one instrumental assessment. Twenty-nine patients were referred to otorhinolaryngology with suspected laryngeal abnormalities. Seventy-five percent of patients (n = 49/65) who received an instrumental assessment aspirated; of whom 63% aspirated silently (31/49). Diet on first day transferred from Intensive Care Unit (ICU) was significantly associated with intubation duration, ICU and hospital length of stay, tracheostomy and vocal fold paralysis (p < 0.001). In contrast, pre-operative reflux was significantly associated with diet on discharge (p < 0.05). Only three patients remained enterally fed on discharge. Polypharmacy (concurrent use of 5+ medicines) was prevalent.

CONCLUSION

Endoscopic, radiographic and/or manometric assessment of dysphagia in patients prior to, and following, lung transplant may allow for early management and prevention of secondary complications. Teams must consider pre-surgical reflux, length of stay in ICU and current medicine regimes when managing patients.

Current therapies for gastro-oesophageal reflux in the setting of chronic lung disease: state of the art review

The inter-relationship between chronic respiratory disease and reflux disease in the airway reflux paradigm is extremely complex and remains poorly characterised. Reflux disease is reported to cause or contribute to the severity of a number of respiratory tract diseases including laryngeal disorders, sinusitis, chronic cough, asthma, COPD, idiopathic pulmonary fibrosis, cystic fibrosis, bronchiectasis and bronchiolitis obliterans post lung transplant. It is now appreciated that reflux disease is not simply caused by liquid acid reflux but rather by a variety of chemical refluxates originating from the stomach and duodenum due to a number of different mechanisms. Reflux disease can be challenging to diagnose, particularly proving its role in the causation of direct respiratory epithelial damage. Significant advances in oesophageal assessment and gastric biomarkers have emerged in recent years as our understanding increases. There are a number of treatments available for reflux disease, both medical and surgical, but there is a paucity of large randomised trials to evaluate their efficacy in the setting of chronic respiratory disease. Everyday clinical practice, however, informs us that treatment failure in reflux disease is common. This clinical review summarises associations between reflux disease in the setting of chronic respiratory diseases and examines available evidence regarding potential therapeutic strategies.

Gastro-oesophageal reflux disease is prevalent among patients with chronic respiratory disease. A number of medical and surgical treatment options are available for GORD. This review examines available evidence in the setting of chronic lung disease.https://bit.ly/34TcMJS

Microbiome in the pathogenesis of cystic fibrosis and lung transplant-related disease

Significant advances in culture-independent methods have expanded our knowledge about the diversity of the lung microbial environment. Complex microorganisms and microbial communities can now be identified in the distal airways in a variety of respiratory diseases, including cystic fibrosis (CF) and the posttransplantation lung. Although there are significant methodologic concerns about sampling the lung microbiome, several studies have now shown that the microbiome of the lower respiratory tract is distinct from the upper airway. CF is a disease characterized by chronic airway infections that lead to significant morbidity and mortality. Traditional culture-dependent methods have identified a select group of pathogens that cause exacerbations in CF, but studies using bacterial 16S rRNA gene-based microarrays have shown that the CF microbiome is an intricate and dynamic bacterial ecosystem, which influences both host immune health and disease pathogenesis. These microbial communities can shift with external influences, including antibiotic exposure. In addition, there have been a number of studies suggesting a link between the gut microbiome and respiratory health in CF. Compared with CF, there is significantly less knowledge about the microbiome of the transplanted lung. Risk factors for bronchiolitis obliterans syndrome, one of the leading causes of death, include microbial infections. Lung transplant patients have a unique lung microbiome that is different than the pretransplanted microbiome and changes with time. Understanding the host-pathogen interactions in these diseases may suggest targeted therapies and improve long-term survival in these patients.

Graft Loss and CLAD-Onset Is Hastened by Viral Pneumonia After Lung Transplantation

BACKGROUND

Community-acquired respiratory virus (CARV) infections occur frequently after lung transplantation and may adversely impact outcomes. We hypothesized that while asymptomatic carriage would not increase the risk of chronic lung allograft dysfunction (CLAD) and graft loss, severe infection would.

METHODS

All lung transplant cases between January 2000 and July 2013 performed at our center were reviewed for respiratory viral samples. Each isolation of virus was classified according to clinical level of severity: asymptomatic, symptomatic without pneumonia, and viral pneumonia. Multivariate Cox modeling was used to assess the impact of CARV isolation on progression to CLAD and graft loss.

RESULTS

Four thousand four hundred eight specimens were collected from 563 total patients, with 139 patients producing 324 virus-positive specimens in 245 episodes of CARV infection. Overall, the risk of CLAD was elevated by viral infection (hazard ratio [HR], 1.64; P < 0.01). This risk, however, was due to viral pneumonia alone (HR, 3.94; P < 0.01), without significant impact from symptomatic viral infection (HR, 0.97; P = 0.94) nor from asymptomatic viral infection (HR, 0.99; P = 0.98). The risk of graft loss was not increased by asymptomatic CARV infection (HR, 0.74; P = 0.37) nor symptomatic CARV infection (HR, 1.39; P = 0.41). Viral pneumonia did, however, significantly increase the risk of graft loss (HR, 2.78; P < 0.01).

CONCLUSIONS

With respect to CARV, only viral pneumonia increased the risk of both CLAD and graft loss after lung transplantation. In the absence of pneumonia, respiratory viruses had no impact on measured outcomes.

[Small airway diseases and immune deficiency]

INTRODUCTION

Innate or acquired immune deficiency may show respiratory manifestations, often characterized by small airway involvement. The purpose of this article is to provide an overview of small airway disease across the major causes of immune deficiency.

BACKGROUND

In patients with common variable immune deficiency, recurrent lower airway infections may lead to bronchiolitis and bronchiectasis. Follicular and/or granulomatous bronchiolitis of unknown origin may also occur. Bronchiolitis obliterans is the leading cause of death after the first year in patients with lung transplantation. Bronchiolitis obliterans also occurs in patients with allogeneic haematopoietic stem cell transplantation, especially in the context of systemic graft-versus-host disease.

VIEWPOINT AND CONCLUSION

Small airway diseases have different clinical expression and pathophysiology across various causes of immune deficiency. A better understanding of small airways disease pathogenesis in these settings may lead to the development of novel targeted therapies.

Improved characterization of medically relevant fungi in the human respiratory tract using next-generation sequencing

BACKGROUND

Fungi are important pathogens but challenging to enumerate using next-generation sequencing because of low absolute abundance in many samples and high levels of fungal DNA from contaminating sources.

RESULTS

Here, we analyze fungal lineages present in the human airway using an improved method for contamination filtering. We use DNA quantification data, which are routinely acquired during DNA library preparation, to annotate output sequence data, and improve the identification and filtering of contaminants. We compare fungal communities and bacterial communities from healthy subjects, HIV+ subjects, and lung transplant recipients, providing a gradient of increasing lung impairment for comparison. We use deep sequencing to characterize ribosomal rRNA gene segments from fungi and bacteria in DNA extracted from bronchiolar lavage samples and oropharyngeal wash. Comparison to clinical culture data documents improved detection after applying the filtering procedure.

CONCLUSIONS

We find increased representation of medically relevant organisms, including Candida, Cryptococcus, and Aspergillus, in subjects with increasingly severe pulmonary and immunologic deficits. We analyze covariation of fungal and bacterial taxa, and find that oropharyngeal communities rich in Candida are also rich in mitis group Streptococci,a community pattern associated with pathogenic polymicrobial biofilms. Thus, using this approach, it is possible to characterize fungal communities in the human respiratory tract more accurately and explore their interactions with bacterial communities in health and disease.

Aspiration and allograft injury secondary to gastroesophageal reflux occur in the immediate post-lung transplantation period (prospective clinical trial)

OBJECTIVES

To provide novel pilot data to quantify reflux, aspiration, and allograft injury immediately post-lung transplantation.

BACKGROUND

Asymptomatic reflux/aspiration, associated with allograft dysfunction, occurs in lung transplant recipients. Early fundoplication has been advocated. Indications for surgery include elevated biomarkers of aspiration (bile salts) in bronchoalveolar lavage fluid (BALF). Measurements have been mostly documented after the immediate posttransplant period. We report the first prospective study of reflux/aspiration immediately posttransplantation to date.

METHODS

Lung transplant recipients were recruited over 12 months. At 1 month posttransplantation, patients completed a Reflux Symptom Index questionnaire and underwent objective assessment for reflux (manometry and pH/impedance). Testing was performed on maintenance proton pump inhibitor. BALF was assessed for pepsin, bile salts, interleukin-8 and neutrophils.

RESULTS

Eighteen lung transplant recipients, median age of 46 years (range: 22-59 years), were recruited. Eight of 18 patients had abnormal esophageal peristalsis. Five of 17 patients were positive on Reflux Symptom Index questionnaire. Twelve of 17 patients had reflux. Three patients exclusively had weakly acid reflux. Median acid exposure was 4.8% (range: 1%-79.9%) and median esophageal volume exposure was 1.6% (range: 0.7-5.5). There was a median of 72 reflux events (range: 27-147) per 24 hours. A correlation existed between Reflux Symptom Index score and proximal reflux (r = 0.533, P = 0.006). Pepsin was detected in 11 of 15 BALF samples signifying aspiration (median: 18 ng/mL; range: 0-43). Bile salts were undetectable, using spectrophotometry and rarely detectable using dual mass spectrometry (2/15) (levels 0.2 and 1.2 μmol/L). Lavage interleukin-8 and neutrophil levels were elevated. A correlation existed between proximal reflux events and neutrophilia (r = 0.52, P = 0.03).

CONCLUSIONS

Lung transplant recipients should be routinely assessed for reflux/aspiration within the first month posttransplant. Reflux/aspiration can be present early postoperatively. Pepsin was detected suggesting aspiration. Bile salts were rarely detected. Proximal reflux events correlated with neutrophilia, linked to allograft dysfunction and mortality. These results support the need for early assessment of reflux/aspiration, which may inform fundoplication.

Aspiration, localized pulmonary inflammation, and predictors of early-onset bronchiolitis obliterans syndrome after lung transplantation

BACKGROUND

We hypothesized that immune mediator concentrations in the bronchoalveolar fluid (BALF) are predictive of bronchiolitis obliterans syndrome (BOS) and demonstrate specific patterns of dysregulation, depending on the presence of acute cellular rejection, BOS, aspiration, and timing of lung transplantation.

STUDY DESIGN

We prospectively collected 257 BALF samples from 105 lung transplant recipients. The BALF samples were assessed for absolute and differential white blood cell counts and 34 proteins implicated in pulmonary immunity, inflammation, fibrosis, and aspiration.

RESULTS

There were elevated BALF concentrations of interleukin (IL)-15, IL-17, basic fibroblast growth factor, tumor necrosis factor-α, and myeloperoxidase, and reduced concentrations of α1-antitrypsin, which were predictive of early-onset BOS. Patients with BOS had an increased percentage of BALF lymphocytes and neutrophils, with a reduced percentage of macrophages (p < 0.05). The BALF concentrations of IL-1β; IL-8; interferon-γ-induced protein 10; regulated upon activation, normal T-cell expressed and secreted; neutrophil elastase; and pepsin were higher in patients with BOS (p < 0.05). Among those with BOS, BALF concentrations of IL-1RA; IL-8; eotaxin; interferon-γ-induced protein 10; regulated upon activation, normal T-cell expressed and secreted; myeloperoxidase; and neutrophil elastase were positively correlated with time since transplantation (p < 0.01). Those with worse grades of acute cellular rejection had an increased percentage of lymphocytes in their BALF (p < 0.0001) and reduced BALF concentrations of IL-1β, IL-7, IL-9, IL-12, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, interferon-γ, and vascular endothelial growth factor (p ≤ 0.001). Patients with aspiration based on detectable pepsin had increased percentage of neutrophils (p < 0.001) and reduced BALF concentrations of IL-12 (p < 0.001).

CONCLUSIONS

The BALF levels of IL-15, IL-17, basic fibroblast growth factor, tumor necrosis factor-α, myeloperoxidase, and α1-antitrypsin at 6 to 12 months after lung transplantation are predictive of early-onset BOS, and those with BOS and aspiration have an augmented chemotactic and inflammatory balance of pulmonary leukocytes and immune mediators. These data justify the surgical prevention of aspiration and argue for the refinement of antirejection regimens.

Lung-enriched organisms and aberrant bacterial and fungal respiratory microbiota after lung transplant

RATIONALE

Long-term survival after lung transplantation is limited by infectious complications and by bronchiolitis obliterans syndrome (BOS), a form of chronic rejection linked in part to microbial triggers.

OBJECTIVES

To define microbial populations in the respiratory tract of transplant patients comprehensively using unbiased high-density sequencing.

METHODS

Lung was sampled by bronchoalveolar lavage (BAL) and upper respiratory tract by oropharyngeal wash (OW). Bacterial 16S rDNA and fungal internal transcribed spacer sequencing was used to profile organisms present. Outlier analysis plots defining taxa enriched in lung relative to OW were used to identify bacteria enriched in lung against a background of oropharyngeal carryover.

MEASUREMENTS AND MAIN RESULTS

Lung transplant recipients had higher bacterial burden in BAL than control subjects, frequent appearance of dominant organisms, greater distance between communities in BAL and OW indicating more distinct populations, and decreased respiratory tract microbial richness and diversity. Fungal populations were typically dominated by Candida in both sites or by Aspergillus in BAL but not OW. 16S outlier analysis identified lung-enriched taxa indicating bacteria replicating in the lower respiratory tract. In some cases this confirmed respiratory cultures but in others revealed enrichment by anaerobic organisms or mixed outgrowth of upper respiratory flora and provided quantitative data on relative abundances of bacteria found by culture.

CONCLUSIONS

Respiratory tract microbial communities in lung transplant recipients differ in structure and composition from healthy subjects. Outlier analysis can identify specific bacteria replicating in lung. These findings provide novel approaches to address the relationship between microbial communities and transplant outcome and aid in assessing lung infections.

Conventional and novel approaches to immunosuppression

Immunosuppressive therapy has contributed significantly to improved survival after solid organ transplantation. Nevertheless, treatment-related adverse events and persistently high risk of chronic graft rejection remain major obstacles to long-term survival after lung transplantation. The development of new agents, refinements in techniques to monitor immunosuppression, and enhanced understanding of transplant immunobiology are essential for further improvements in outcome. In this article, conventional immunosuppressive regimens, novel approaches to preventing graft rejection, and investigational agents for solid organ transplantation are reviewed.

Lung transplantation in autoimmune diseases

In the last 45 years, lung transplantation has evolved from its status as a rare extreme form of surgical therapy for the treatment of advanced lung diseases to an accepted therapeutic option for select patients. Although pulmonary fibrosis and pulmonary vascular diseases are important indications for lung transplantation, only a small percentage of transplants are performed in patients with collagen vascular diseases. The reasons for this low number are multifactorial. This article reviews issues relevant to all lung transplant candidates and recipients as well as those specific to patients with autoimmune diseases.

Animal models of airway diseases

Over the past 20 years, the growing awareness that purinergic signaling events literally shape the immune and inflammatory responses to infection and allergic reactions warranted the development of animal models to assess their importance in vivo in acute lung injury and chronic airway diseases. The pioneer work conducted with the adenosine deaminase (ADA)-deficient mouse provided irrefutable evidence that excess adenosine (ADO) accumulating in the lungs of asthmatic patients, constitutes a powerful mediator of disease severity. These original studies launched the development of murine strains for the two major ectonucleotidases responsible for the generation of airway ADO from ATP release: CD39 and CD73. The dramatic acute lung injury and chronic lung complications, manifested by these knockout mice in response to allergens and endotoxin, demonstrated the critical importance of regulating the availability of ATP and ADO for their receptors. Therapeutic targets are currently evaluated using knockout mice and agonists/antagonists for each ADO receptor (A(1)R, A(2A)R, A(2B)R, and A(3)R) and the predominant ATP receptors (P2Y(2)R and P2X(7)R). This chapter provides an in-depth description of each in vivo study, and a critical view of the therapeutic potentials for the treatment of airway diseases.

[Medical complications of lung transplantation]

In 2010, lung transplantation is a valuable therapeutic option for a number of patients suffering from of end-stage non-neoplastic pulmonary diseases. The patients frequently regain a very good quality of life, however, long-term survival is often hampered by the development of complications such as the bronchiolitis obliterans syndrome, metabolic and infectious complications. As the bronchiolitis obliterans syndrome is the first cause of death in the medium and long term, an intense immunosuppressive treatment is maintained for life in order to prevent or stabilize this complication. The immunosuppression on the other hand induces a number of potentially severe complications including metabolic complications, infections and malignancies. The most frequent metabolic complications are arterial hypertension, chronic renal insufficiency, diabetes, hyperlipidemia and osteoporosis. Bacterial, viral and fungal infections are the second cause of mortality. They are to be considered as medical emergencies and require urgent assessment and targeted therapy after microbiologic specimens have been obtained. They should not, under any circumstances, be treated empirically and it has also to be kept in mind that the lung transplant recipient may present several concomitant infections. The most frequent malignancies are skin cancers, the post-transplant lymphoproliferative disorders, Kaposi's sarcoma and some types of bronchogenic carcinomas, head/neck and digestive cancers. Lung transplantation is no longer an exceptional procedure; thus, the pulmonologist will be confronted with such patients and should be able to recognize the symptoms and signs of the principal non-surgical complications. The goal of this review is to give a general overview of the most frequently encountered complications. Their assessment and treatment, though, will most often require the input of other specialists and a multidisciplinary and transversal approach.