Is Lymphocytic Bronchiolitis a Marker of Acute Rejection? An Analysis of 2,697 Transbronchial Biopsies After Lung Transplantation

Advances in lung transplantation: 60 years on

Lung transplantation is a well-established treatment for advanced lung disease, improving survival and quality of life. Over the last 60 years all aspects of lung transplantation have evolved significantly and exponential growth in transplant volume. This has been particularly evident over the last decade with a substantial increase in lung transplant numbers as a result of innovations in donor utilization procurement, including the use donation after circulatory death and ex-vivo lung perfusion organs. Donor lungs have proved to be surprisingly robust, and therefore the donor pool is actually larger than previously thought. Parallel to this, lung transplant outcomes have continued to improve with improved acute management as well as microbiological and immunological insights and innovations. The management of lung transplant recipients continues to be complex and heavily dependent on a tertiary care multidisciplinary paradigm. Whilst long term outcomes continue to be limited by chronic lung allograft dysfunction improvements in diagnostics, mechanistic understanding and evolutions in treatment paradigms have all contributed to a median survival that in some centres approaches 10 years. As ongoing studies build on developing novel approaches to diagnosis and treatment of transplant complications and improvements in donor utilization more individuals will have the opportunity to benefit from lung transplantation. As has always been the case, early referral for transplant consideration is important to achieve best results.

Acute Rejection and Chronic Lung Allograft Dysfunction: Obstructive and Restrictive Allograft Dysfunction

Lung transplantation is an established treatment of well-selected patients with end-stage respiratory diseases. However, lung transplant recipients have the highest rates of acute and chronic rejection among transplanted solid organs. Owing to ongoing alloimmune recognition and associated immune-driven airway/vascular remodeling, precipitated by multifactorial, endogenous or exogenous, post-transplant injuries to the bronchovascular axis of the secondary pulmonary lobule, most lung transplant recipients will suffer from a pathophysiological decline of their allograft, either functionally and/or structurally. This review discusses current knowledge, barriers, and gaps in acute cellular rejection and chronic lung allograft dysfunction-the greatest impediment to long-term post-transplant survival.

Elevated cell-free DNA in respiratory viral infection and associated lung allograft dysfunction

Respiratory viral infection (RVI) in lung transplant recipients (LTRs) is a risk for chronic lung allograft dysfunction (CLAD). We hypothesize that donor-derived cell-free DNA (%ddcfDNA), at the time of RVI predicts CLAD progression. We followed 39 LTRs with RVI enrolled in the Genomic Research Alliance for Transplantation for 1 year. Plasma %ddcfDNA was measured by shotgun sequencing, with high %ddcfDNA as ≥1% within 7 days of RVI. We examined %ddcfDNA, spirometry, and a composite (progression/failure) of CLAD stage progression, re-transplant, and death from respiratory failure. Fifty-nine RVI episodes, 38 low and 21 high %ddcfDNA were analyzed. High %ddcfDNA subjects had a greater median %FEV₁ decline at RVI (-13.83 vs. -1.83, p = .007), day 90 (-7.97 vs. 0.91, p = .04), and 365 (-20.05 vs. 1.09, p = .047), compared to those with low %ddcfDNA and experienced greater progression/failure within 365 days (52.4% vs. 21.6%, p = .01). Elevated %ddcfDNA at RVI was associated with an increased risk of progression/failure adjusting for symptoms and days post-transplant (HR = 1.11, p = .04). No difference in %FEV₁ decline was seen at any time point when RVIs were grouped by histopathology result at RVI. %ddcfDNA delineates LTRs with RVI who will recover lung function and who will experience sustained decline, a utility not seen with histopathology.

Impact of SLCO1B3 polymorphisms on clinical outcomes in lung allograft recipients receiving mycophenolic acid

Single-nucleotide polymorphisms (SNPs) in genes involved in mycophenolic acid (MPA) metabolism have been shown to contribute to variable MPA exposure, but their clinical effects are unclear. We aimed to determine if SNPs in key genes in MPA metabolism affect outcomes after lung transplantation. We performed a retrospective cohort study of 275 lung transplant recipients, 228 receiving mycophenolic acid and a control group of 47 receiving azathioprine. Six SNPs known to regulate MPA exposure from the SLCO, UGT and MRP2 families were genotyped. Primary outcome was 1-year survival. Secondary outcomes were 3-year survival, nonminimal (≥A2 or B2) acute rejection, and chronic lung allograft dysfunction (CLAD). Statistical analyses included time-to-event Kaplan-Meier with log-rank test and Cox regression modeling. We found that SLCO1B3 SNPs rs4149117 and rs7311358 were associated with decreased 1-year survival [rs7311358 HR 7.76 (1.37-44.04), p = 0.021; rs4149117 HR 7.28 (1.27-41.78), p = 0.026], increased risk for nonminimal acute rejection [rs4149117 TT334/T334G: OR 2.01 (1.06-3.81), p = 0.031; rs7311358 GG699/G699A: OR 2.18 (1.13-4.21) p = 0.019] and lower survival through 3 years for MPA patients but not for azathioprine patients. MPA carriers of either SLCO1B3 SNP had shorter survival after CLAD diagnosis (rs4149117 p = 0.048, rs7311358 p = 0.023). For the MPA patients, Cox regression modeling demonstrated that both SNPs remained independent risk factors for death. We conclude that hypofunctional SNPs in the SLCO1B3 gene are associated with an increased risk for acute rejection and allograft failure in lung transplant recipients treated with MPA.

Molecular assessment of rejection and injury in lung transplant biopsies

BACKGROUND

Improved understanding of lung transplant disease states is essential because failure rates are high, often due to chronic lung allograft dysfunction. However, histologic assessment of lung transplant transbronchial biopsies (TBBs) is difficult and often uninterpretable even with 10 pieces.

METHODS

We prospectively studied whether microarray assessment of single TBB pieces could identify disease states and reduce the amount of tissue required for diagnosis. By following strategies successful for heart transplants, we used expression of rejection-associated transcripts (annotated in kidney transplant biopsies) in unsupervised machine learning to identify disease states.

RESULTS

All 242 single-piece TBBs produced reliable transcript measurements. Paired TBB pieces available from 12 patients showed significant similarity but also showed some sampling variance. Alveolar content, as estimated by surfactant transcript expression, was a source of sampling variance. To offset sampling variation, for analysis, we selected 152 single-piece TBBs with high surfactant transcripts. Unsupervised archetypal analysis identified 4 idealized phenotypes (archetypes) and scored biopsies for their similarity to each: normal; T-cell‒mediated rejection (TCMR; T-cell transcripts); antibody-mediated rejection (ABMR)-like (endothelial transcripts); and injury (macrophage transcripts). Molecular TCMR correlated with histologic TCMR. The relationship of molecular scores to histologic ABMR could not be assessed because of the paucity of ABMR in this population.

CONCLUSIONS

Molecular assessment of single-piece TBBs can be used to classify lung transplant biopsies and correlated with rejection histology. Two or 3 pieces for each TBB will probably be needed to offset sampling variance.

Development of a Multivariate Prediction Model for Early-Onset Bronchiolitis Obliterans Syndrome and Restrictive Allograft Syndrome in Lung Transplantation

BACKGROUND

Chronic lung allograft dysfunction and its main phenotypes, bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS), are major causes of mortality after lung transplantation (LT). RAS and early-onset BOS, developing within 3 years after LT, are associated with particularly inferior clinical outcomes. Prediction models for early-onset BOS and RAS have not been previously described.

METHODS

LT recipients of the French and Swiss transplant cohorts were eligible for inclusion in the SysCLAD cohort if they were alive with at least 2 years of follow-up but less than 3 years, or if they died or were retransplanted at any time less than 3 years. These patients were assessed for early-onset BOS, RAS, or stable allograft function by an adjudication committee. Baseline characteristics, data on surgery, immunosuppression, and year-1 follow-up were collected. Prediction models for BOS and RAS were developed using multivariate logistic regression and multivariate multinomial analysis.

RESULTS

Among patients fulfilling the eligibility criteria, we identified 149 stable, 51 BOS, and 30 RAS subjects. The best prediction model for early-onset BOS and RAS included the underlying diagnosis, induction treatment, immunosuppression, and year-1 class II donor-specific antibodies (DSAs). Within this model, class II DSAs were associated with BOS and RAS, whereas pre-LT diagnoses of interstitial lung disease and chronic obstructive pulmonary disease were associated with RAS.

CONCLUSION

Although these findings need further validation, results indicate that specific baseline and year-1 parameters may serve as predictors of BOS or RAS by 3 years post-LT. Their identification may allow intervention or guide risk stratification, aiming for an individualized patient management approach.

Bronchoscopic procedures and lung biopsies in pediatric lung transplant recipients

Bronchoscopy remains a pivotal diagnostic and therapeutic intervention in pediatric patients undergoing lung transplantation (LTx). Whether performed as part of a surveillance protocol or if clinically indicated, fibre-optic bronchoscopy allows direct visualization of the transplanted allograft, and in particular, an assessment of the patency of the bronchial anastomosis (or tracheal anastomosis following heart-lung transplantation). Additionally, bronchoscopy facilitates differentiation of infective processes from rejection episodes through collection and subsequent assessment of bronchoalveolar lavage (BAL) and transbronchial biopsy (TBBx) samples. Indeed, the diagnostic criteria for the grading of acute cellular rejection is dependent upon the histopathological assessment of biopsy samples collected at the time of bronchoscopy. Typically, performed in an out-patient setting, bronchoscopy is generally a safe procedure, although complications related to hemorrhage and pneumothorax are occasionally seen. Airway complications, including stenosis, malacia, and dehiscence are diagnosed at bronchoscopy, and subsequent management including balloon dilatation, laser therapy and stent insertion can also be performed bronchoscopically. Finally, bronchoscopy has been and continues to be an important research tool allowing a better understanding of the immuno-biology of the lung allograft through the collection and analysis of collected BAL and TBBx samples. Whilst new investigational tools continue to evolve, the simple visualization and collection of samples within the lung allograft by bronchoscopy remains the gold standard in the evaluation of the lung allograft. This review describes the use and experience of bronchoscopy following lung transplantation in the pediatric setting.

An international ISHLT/ATS/ERS clinical practice guideline: diagnosis and management of bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS) is a major complication of lung transplantation that is associated with poor survival. The International Society for Heart and Lung Transplantation, American Thoracic Society, and European Respiratory Society convened a committee of international experts to describe and/or provide recommendations for 1) the definition of BOS, 2) the risk factors for developing BOS, 3) the diagnosis of BOS, and 4) the management and prevention of BOS. A pragmatic evidence synthesis was performed to identify all unique citations related to BOS published from 1980 through to March, 2013. The expert committee discussed the available research evidence upon which the updated definition of BOS, identified risk factors and recommendations are based. The committee followed the GRADE (Grading of Recommendation, Assessment, Development and Evaluation) approach to develop specific clinical recommendations. The term BOS should be used to describe a delayed allograft dysfunction with persistent decline in forced expiratory volume in 1 s that is not caused by other known and potentially reversible causes of post-transplant loss of lung function. The committee formulated specific recommendations about the use of systemic corticosteroids, cyclosporine, tacrolimus, azithromycin and about re-transplantation in patients with suspected and confirmed BOS. The diagnosis of BOS requires the careful exclusion of other post-transplant complications that can cause delayed lung allograft dysfunction, and several risk factors have been identified that have a significant association with the onset of BOS. Currently available therapies have not been proven to result in significant benefit in the prevention or treatment of BOS. Adequately designed and executed randomised controlled trials that properly measure and report all patient-important outcomes are needed to identify optimal therapies for established BOS and effective strategies for its prevention.

Pre-transplant impedance measures of reflux are associated with early allograft injury after lung transplantation

BACKGROUND

Acid reflux has been associated with poorer outcomes after lung transplantation. Standard pre-transplant reflux assessment has not been universally adopted. Non-acid reflux may also induce a pulmonary inflammatory cascade, leading to acute and chronic rejection. Esophageal multichannel intraluminal impedance and pH testing (MII-pH) may be valuable in standard pre-transplant evaluation. We assessed the association between pre-transplant MII-pH measures and early allograft injury in lung transplant patients.

METHODS

This was a retrospective cohort study of lung transplant recipients who underwent pre-transplant MII-pH at a tertiary center from 2007 to 2012. Results from pre-transplant MII-pH, cardiopulmonary function testing, and results of biopsy specimen analysis of the transplanted lung were recorded. Time-to-event analyses were performed using Cox proportional hazards and Kaplan-Maier methods to assess the associations between MII-pH measures and development of acute rejection or lymphocytic bronchiolitis.

RESULTS

Thirty patients (46.7% men; age, 54.2 years) met the inclusion criteria. Pre-transplant cardiopulmonary function and pulmonary diagnoses were similar between outcome groups. Prolonged bolus clearance (hazard ratio [HR], 4.11; 95% confidence interval [CI], 1.34-12.57; p = 0.01), increased total distal reflux episodes (HR, 4.80; 95% CI, 1.33-17.25; p = 0.02), and increased total proximal reflux episodes (HR, 4.43; 95% CI, 1.14-17.31; p = 0.03) were significantly associated with decreased time to early allograft injury. Kaplan-Meier curves also demonstrated differences in time to rejection by prolonged bolus clearance (p = 0.01) and increased total distal reflux episodes (p = 0.01). Sub-group analysis including only patients with MII-pH performed off proton pump inhibitors (n = 24) showed similar results.

CONCLUSIONS

Prolonged bolus clearance, increased total distal reflux episodes, and increased total proximal reflux episodes on pre-transplant MII-pH were associated with decreased time to early allograft injury after lung transplantation. Routine pre-transplant MII-pH may provide clinically relevant data regarding transplant outcomes and peri-transplant care.

SaLUTaRy: survey of lung transplant rejection

BACKGROUND

The International Society for Heart and Lung Transplantation (ISHLT) guidelines on the interpretation of lung rejection in pulmonary allograft biopsy specimens were revised most recently in 2007. The goal of our study was to determine how these revisions, along with nuances in the interpretation and application of the guidelines, affect patient care.

METHODS

A Web-based survey was e-mailed to pathologists and pulmonologists identified as being part of the lung transplant team at institutions in the United States with active lung transplant programs as determined from the Organ Procurement and Transplantation Network Web site (http://optn.transplant.hrsa.gov/members/directory.asp).

RESULTS

Grades B1 and B2 in asymptomatic patients would fall into the same treatment group under the 2007 classification, which combines B1 and B2 into B1R. Also, some pulmonologists would not interpret a pathologic diagnosis of lymphocytic bronchiolitis as grade B rejection, resulting in under-treatment of these patients. Regarding bronchiolitis obliterans, most pulmonologists would treat the patient differently if there were an active mononuclear inflammatory infiltrate, and most pathologists would comment on the presence of such an infiltrate, contrary to the 2007 guidelines, which discourage reporting this infiltrate. We also found discrepancies among pathologists in their interpretation of airway lymphocytic infiltrates, whether eosinophils can be present in bronchial-associated lymphoid tissue, and whether airway inflammation represents rejection or bacterial infection.

CONCLUSIONS

The issue of grading and treating airway inflammation in pulmonary allograft biopsy specimens continues to be problematic, despite revised ISHLT guidelines. Clarification of guidelines for pathologists and pulmonologists using evidence-based criteria could lead to improved communication and patient care.

Low CD4/CD8 Ratio in Bronchus-Associated Lymphoid Tissue Is Associated with Lung Allograft Rejection

Background. Bronchus-associated lymphoid tissue (BALT) has been associated with lung allograft rejection in rat transplant models. In human transplant recipients, BALT has not been linked to clinically significant rejection. We hypothesize that the immunohistochemical composition of BALT varies with the presence of acute lung allograft rejection. Methods. We retrospectively examined 40 human lung allograft recipients transplanted from 3/1/1999 to 6/1/2008. Patients were grouped by frequency and severity of acute rejection based on International Society of Heart Lung Transplant (ISHLT) criteria. Transbronchial biopsies were reviewed for BALT by a blinded pathologist. BALT if present was immunohistochemically stained to determine T-and B-cell subpopulations. Results. BALT presence was associated with an increased frequency of acute rejection episodes in the first year after transplantation. Patients with a lower CD4/CD8 ratio had an increased rejection rate; however, BALT size or densities of T-cell and B-cell subpopulations did not correlate with rejection rate. Conclusion. The presence of BALT is associated with an increased frequency of rejection one year after transplant. The lower the CD4/CD8 ratio, the more acute rejection episodes occur in the first year after transplantation. The immunohistochemical composition of BALT may predict patients prone to frequent episodes of acute cellular rejection.

Lymphocytic bronchiolitis after lung transplantation is associated with daily changes in air pollution

Acute rejection represents a major problem after organ transplantation, being a recognized risk for chronic rejection and mortality. Recently, it became clear that lymphocytic bronchiolitis (LB, B-grade acute rejection) is more important than previously thought, as it predisposes to chronic rejection. We aimed to verify whether daily fluctuations of air pollution, measured as particulate matter (PM) are related to histologically proven A-grade rejection and/or LB and bronchoalveolar lavage (BAL) fluid cellularity after lung transplantation. We fitted a mixed model to examine the association between daily variations in PM(10) and A-grade rejection/LB on 1276 bronchoscopic biopsies (397 patients, 416 transplantations) taken between 2001 and 2011. A difference of 10 μg/m(3) in PM(10) 3 days before diagnosis of LB was associated with an OR of 1.15 (95% CI 1.04-1.27; p = 0.0044) but not with A-grade rejection (OR = 1.05; 95% CI 0.95-1.15; p = 0.32). Variations in PM(10) at lag day 3 correlated with neutrophils (p = 0.013), lymphocytes (p = 0.0031) and total cell count (p = 0.024) in BAL. Importantly, we only found an effect of PM10 on LB in patients not taking azithromycin. LB predisposed to chronic rejection (p < 0.0001). The risk for LB after lung transplantation increased with temporal changes in particulate air pollution, and this was associated with BAL neutrophilia and lymphocytosis. Azithromycin was protective against this PM effect.

Aerosol drug delivery in lung transplant recipients

BACKGROUND

Inhaled drug delivery after lung transplantation provides a unique opportunity for direct treatment of a solid organ transplant. At present, no inhaled therapies are approved for this population though several have received some development. Primary potential applications include inhaled immunosuppressive and anti-infective drugs.

OBJECTIVES

The objective of this article is to review potential applications of inhaled medications for lung transplant recipients, the techniques used to develop inhaled drugs and the challenges of aerosol delivery in this specific population.

METHODS

The results of relevant studies are reviewed and two developmental examples are presented.

RESULTS/CONCLUSIONS

Inhaled medications may provide significant advantages for lung transplant recipients. Past studies with inhaled cyclosporine and amphotericin-B provide useful guidance for clinical development of new preparations.