Development and validation of primary graft dysfunction predictive algorithm for lung transplant candidates

BACKGROUND

Primary graft dysfunction (PGD) is the leading cause of early morbidity and mortality after lung transplantation. Accurate prediction of PGD risk could inform donor approaches and perioperative care planning. We sought to develop a clinically useful, generalizable PGD prediction model to aid in transplant decision-making.

METHODS

We derived a predictive model in a prospective cohort study of subjects from 2012 to 2018, followed by a single-center external validation. We used regularized (lasso) logistic regression to evaluate the predictive ability of clinically available PGD predictors and developed a user interface for clinical application. Using decision curve analysis, we quantified the net benefit of the model across a range of PGD risk thresholds and assessed model calibration and discrimination.

RESULTS

The PGD predictive model included distance from donor hospital to recipient transplant center, recipient age, predicted total lung capacity, lung allocation score (LAS), body mass index, pulmonary artery mean pressure, sex, and indication for transplant; donor age, sex, mechanism of death, and donor smoking status; and interaction terms for LAS and donor distance. The interface allows for real-time assessment of PGD risk for any donor/recipient combination. The model offers decision-making net benefit in the PGD risk range of 10% to 75% in the derivation centers and 2% to 10% in the validation cohort, a range incorporating the incidence in that cohort.

CONCLUSION

We developed a clinically useful PGD predictive algorithm across a range of PGD risk thresholds to support transplant decision-making, posttransplant care, and enrich samples for PGD treatment trials.

Validation of a novel donor lung scoring system based on the updated lung Composite Allocation Score

Lung transplantation (LTx) continues to have lower rates of long-term graft survival compared with other organs. Additionally, lung utilization rates from brain-dead donors remain substantially lower compared with other solid organs, despite a growing need for LTx and the significant risk of waitlist mortality. This study aims to examine the effects of using a combination of the recently described novel lung donor (LUNDON) acceptability score and the newly adopted recipient lung Composite Allocation Score (CAS) to guide transplantation. We performed a review of nearly 18 000 adult primary lung transplants from 2015-2022 across the US with retroactive calculations of the CAS value. The medium-CAS group (29.6-34.5) had superior 1-year posttransplant survival. Importantly, the combination of high-CAS (> 34.5) recipients with low LUNDON score (≤ 40) donors had the worst survival at 1 year compared with any other combination. Additionally, we constructed a model that predicts 1-year and 3-year survival using the LUNDON acceptability score and CAS values. These results suggest that caution should be exercised when using marginally acceptable donor lungs in high-priority recipients. The use of the LUNDON score with CAS value can potentially guide clinical decision-making for optimal donor-recipient matches for LTx.

Developing machine learning models to predict primary graft dysfunction after lung transplantation

Primary graft dysfunction (PGD) is the leading cause of morbidity and mortality in the first 30 days after lung transplantation. Risk factors for the development of PGD include donor and recipient characteristics, but how multiple variables interact to impact the development of PGD and how clinicians should consider these in making decisions about donor acceptance remain unclear. This was a single-center retrospective cohort study to develop and evaluate machine learning pipelines to predict the development of PGD grade 3 within the first 72 hours of transplantation using donor and recipient variables that are known at the time of donor offer acceptance. Among 576 bilateral lung recipients, 173 (30%) developed PGD grade 3. The cohort underwent a 75% to 25% train-test split, and lasso regression was used to identify 11 variables for model development. A K-nearest neighbor's model showing the best calibration and performance with relatively small confidence intervals was selected as the final predictive model with an area under the receiver operating characteristics curve of 0.65. Machine learning models can predict the risk for development of PGD grade 3 based on data available at the time of donor offer acceptance. This may improve donor-recipient matching and donor utilization in the future.

A Pilot Randomized Controlled Trial of De Novo Belatacept-based Immunosuppression After Lung Transplantation

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is the leading cause of death beyond the first year after lung transplantation. The development of donor-specific antibodies (DSA) is a recognized risk factor for CLAD. Based on experience in kidney transplantation, we hypothesized that belatacept, a selective T-cell costimulatory blocker, would reduce the incidence of DSA after lung transplantation, which may ameliorate the risk of CLAD.

METHODS

We conducted a pilot randomized controlled trial (RCT) at 2 sites to assess the feasibility and inform the design of a large-scale RCT. All participants were treated with rabbit antithymocyte globulin for induction immunosuppression. Participants in the control arm were treated with tacrolimus, mycophenolate mofetil, and prednisone, and participants in the belatacept arm were treated with tacrolimus, belatacept, and prednisone through day 89 after transplant then converted to belatacept, mycophenolate mofetil, and prednisone for the remainder of year 1.

RESULTS

After randomizing 27 participants, 3 in the belatacept arm died compared with none in the control arm. As a result, we stopped enrollment and treatment with belatacept, and all participants were treated with standard-of-care immunosuppression. Overall, 6 participants in the belatacept arm died compared with none in the control arm (log rank P  = 0.008). We did not observe any differences in the incidence of DSA, acute cellular rejection, antibody-mediated rejection, CLAD, or infections between the 2 groups.

CONCLUSIONS

We conclude that the investigational regimen used in this pilot RCT is associated with increased mortality after lung transplantation.

Smoking exposure-induced bronchus-associated lymphoid tissue in donor lungs does not prevent tolerance induction after transplantation

The presence of bronchus-associated lymphoid tissue (BALT) in donor lungs has been suggested to accelerate graft rejection after lung transplantation. Although chronic smoke exposure can induce BALT formation, the impact of donor cigarette use on alloimmune responses after lung transplantation is not well understood. Here, we show that smoking-induced BALT in mouse donor lungs contains Foxp3+ T cells and undergoes dynamic restructuring after transplantation, including recruitment of recipient-derived leukocytes to areas of pre-existing lymphoid follicles and replacement of graft-resident donor cells. Our findings from mouse and human lung transplant data support the notion that a donor's smoking history does not predispose to acute cellular rejection or prevent the establishment of allograft acceptance with comparable outcomes to nonsmoking donors. Thus, our work indicates that BALT in donor lungs is plastic in nature and may have important implications for modulating proinflammatory or tolerogenic immune responses following transplantation.

B cells mediate lung ischemia/reperfusion injury by recruiting classical monocytes via synergistic B cell receptor/TLR4 signaling

Ischemia/reperfusion injury-mediated (IRI-mediated) primary graft dysfunction (PGD) adversely affects both short- and long-term outcomes after lung transplantation, a procedure that remains the only treatment option for patients suffering from end-stage respiratory failure. While B cells are known to regulate adaptive immune responses, their role in lung IRI is not well understood. Here, we demonstrated by intravital imaging that B cells are rapidly recruited to injured lungs, where they extravasate into the parenchyma. Using hilar clamping and transplant models, we observed that lung-infiltrating B cells produce the monocyte chemokine CCL7 in a TLR4-TRIF-dependent fashion, a critical step contributing to classical monocyte (CM) recruitment and subsequent neutrophil extravasation, resulting in worse lung function. We found that synergistic BCR-TLR4 activation on B cells is required for the recruitment of CMs to the injured lung. Finally, we corroborated our findings in reperfused human lungs, in which we observed a correlation between B cell infiltration and CM recruitment after transplantation. This study describes a role for B cells as critical orchestrators of lung IRI. As B cells can be depleted with currently available agents, our study provides a rationale for clinical trials investigating B cell-targeting therapies.

Impact of Angiotensin Blockade on Development of Chronic Lung Allograft Dysfunction

Background: The renin-angiotensin-aldosterone system (RAAS) is responsible for a multitude of physiological functions, including immunological effects such as promotion of TGF-β and upregulation of IL-6 and IL-8 which are also implicated in the development of chronic lung allograft dysfunction (CLAD). Blockade of the RAAS pathway in pre-clinical models has demonstrated a decrease in these cytokines and pulmonary neutrophil recruitment. Objective: This study sought to evaluate whether use of RAAS inhibitor (RAASi) in lung transplant recipients impacted CLAD-free survival. Methods: In this retrospective, single-center study, 35 lung transplant recipients who received a RAASi post-transplant were compared to 70 lung transplant recipients not exposed to a RAASi and were followed for up to 5 years post-transplant. Results: The incidence of CLAD did not differ based on RAASi treatment (34.3% in RAASi vs 38.6%, P-value .668). This was confirmed with a multivariable Cox proportional hazards model with RAASi initiation as a time-varying covariate (RAASi hazard ratio of 1.01, P-value .986). Incidence of hyperkalemia and acute kidney injury were low in the RAASi group. Conclusions: This study demonstrated no association between post-transplant RAASi use and decreased risk of CLAD development. RAASi were also well tolerated in this patient population.

Characteristics of donor lungs declined on site and impact of lung allocation policy change

OBJECTIVE

National and institutional data suggest an increase in organ discard rate (donor lungs procured but not implanted) after a new lung allocation policy was introduced in 2017. However, this measure does not include on-site decline rate (donor lungs declined intraoperatively). The objective of this study is to examine the impact of the allocation policy change on on-site decline.

METHODS

We used a Washington University (WU) and our local organ procurement organization (Mid-America Transplant [MTS]) database to abstract data on all accepted lung offers from 2014 to 2021. An on-site decline was defined as an event in which the procuring team declined the organs intraoperatively, and the lungs were not procured. Logistic regression models were used to investigate potentially modifiable reasons for decline.

RESULTS

The overall study cohort comprised 876 accepted lung offers, of which 471 donors were at MTS with WU or others as the accepting center and 405 at other organ procurement organizations with WU as the accepting center. At MTS, the on-site decline rate increased from 4.6% to 10.8% (P = .01) after the policy change. Given the greater likelihood of non-local organ placement and longer travel distance after policy change, the estimated cost of each on-site decline increased from $5727 to $9700. In the overall group, latest partial pressure of oxygen (odds ratio [OR], 0.993; 95% confidence interval [CI], 0.989-0.997), chest trauma (OR, 2.474; CI, 1.018-6.010), chest radiograph abnormality (OR, 2.902; CI, 1.289-6.532), and bronchoscopy abnormality (OR, 3.654; CI, 1.813-7.365) were associated with on-site decline, although lung allocation policy era was unassociated (P = .22).

CONCLUSIONS

We found that nearly 8% of accepted lungs are declined on site. Several donor factors were associated with on-site decline, although lung allocation policy change did not have a consistent impact on on-site decline.

Tocilizumab for antibody-mediated rejection treatment in lung transplantation

Tocilizumab (TCZ), an IL-6 inhibitor, has shown promise in the treatment of donor-specific antibodies (DSA) and chronic antibody-mediated rejection (AMR) in renal transplant recipients. However, its use in lung transplantation has not been described. This retrospective case-control study compared AMR treatments containing TCZ in 9 bilateral lung transplant recipients to 18 patients treated for AMR without TCZ. Treatment with TCZ resulted in more clearance of DSA, lower recurrence of DSA, lower incidence of new DSA, and lower rates of graft failure when compared to those treated for AMR without TCZ. The incidence of infusion reactions, elevation in transaminases, and infections were similar between the 2 groups. These data support a role for TCZ in pulmonary AMR and establish preliminary evidence to design a randomized controlled trial of IL-6 inhibition for the management of AMR.

Development and validation of the lung donor (LUNDON) acceptability score for pulmonary transplantation

There is a chronic shortage of donor lungs for pulmonary transplantation due, in part, to low lung utilization rates in the United States. We performed a retrospective cohort study using data from the Scientific Registry of Transplant Recipients database (2006-2019) and developed the lung donor (LUNDON) acceptability score. A total of 83 219 brain-dead donors were included and were randomly divided into derivation (n = 58 314, 70%) and validation (n = 24 905, 30%) cohorts. The overall lung acceptance was 27.3% (n = 22 767). Donor factors associated with the lung acceptance were age, maximum creatinine, ratio of arterial partial pressure of oxygen to fraction of inspired oxygen, mechanism of death by asphyxiation or drowning, history of cigarette use (≥20 pack-years), history of myocardial infarction, chest x-ray appearance, bloodstream infection, and the occurrence of cardiac arrest after brain death. The prediction model had high discriminatory power (C statistic, 0.891; 95% confidence interval, 0.886-0.895) in the validation cohort. We developed a web-based, user-friendly tool (available at https://sites.wustl.edu/lundon) that provides the predicted probability of donor lung acceptance. LUNDON score was also associated with recipient survival in patients with high lung allocation scores. In conclusion, the multivariable LUNDON score uses readily available donor characteristics to reliably predict lung acceptability. Widespread adoption of this model may standardize lung donor evaluation and improve lung utilization rates.

Antibody-Mediated Rejection: Diagnosis and Treatment

Antibody-mediated rejection (AMR) is a form of lung allograft rejection that is emerging as an important risk factor for chronic lung allograft dysfunction and decreased long-term survival. In this review, we provide a brief overview of our current understanding of its pathophysiology with an emphasis on donor-specific antibodies before moving on to focus on the current diagnostic criteria and treatment strategies. Our goal is to discuss the limitations of our current knowledge and explore how novel diagnostic and therapeutic options aim to improve outcomes through earlier definitive diagnosis and preemptive targeted treatment.

Outcomes of Extracorporeal Membrane Oxygenation for Primary Graft Dysfunction After Lung Transplantation

BACKGROUND

Primary graft dysfunction (PGD) is the leading cause of death in the first 30 days after lung transplantation and is also associated with worse long-term outcomes. Outcomes of patients with PGD grade 3 requiring extracorporeal membrane oxygenation (ECMO) support after lung transplantation have yet to be well described. We sought to describe short- and long-term outcomes for patients with PGD grade 3 who required ECMO support.

METHODS

This is a single-center retrospective cohort study of patients undergoing lung transplantation. We stratified patients with PGD grade 3 into non-ECMO, venoarterial (VA) ECMO, and venovenous (VV) ECMO groups after transplantation. We then compared the outcomes between the groups.

RESULTS

Of 773 lung transplant recipients, PGD grade 3 developed in 204 (26%) at any time in the first 72 hours after lung transplantation. Of these, 13 (5%) required VA ECMO and 25 (10%) required VV ECMO support. The 30-day, 1-year, and 5-year survival in the VA ECMO group was 62%, 54%, and 43% compared with 96%, 84%, and 65% in the VV ECMO group and 99%, 94%, and 71% in the non-ECMO group. Multivariable Cox regression analysis showed that VA ECMO was associated with increased mortality (hazard ratio, 2.37; 95% CI, 1.06-5.28; P = .04).

CONCLUSIONS

Patients who required VA ECMO support for PGD grade 3 have significantly worse survival compared with those who did not require ECMO and those who required VV ECMO support. This suggests that VA ECMO treatment of patients with PGD grade 3 after lung transplantation can be a predictable risk factor for mortality.

Utilizing computed tomography volumetry for size matching prior to lung transplantation: a case series

Background

Appropriate size matching between donor and recipient is critical for successful pulmonary transplantation. Although surrogate measurements such as height and gender are often utilized to approximate predicted lung volume, these methods provide only a gross estimation with wide variability and poor predictive value.

Case Description

A single center exploratory study was conducted in which four patients underwent lung transplantation (LT) with pre-operative computed tomography (CT) volumetry obtained in both the donor and recipient to facilitate decision making regarding organ size and suitability. In four cases in which CT volumetry was used, the lung volumes calculated using surrogate measurements significantly overestimated both donor and recipient lung volumes quantified by CT volumetric analysis. All recipients underwent successful LT without necessary graft downsizing.

Conclusions

This is an initial report of prospectively utilizing CT volumetry as an adjunct to decision-making regarding suitability of donor lungs. In these cases, CT volumetry facilitated the confident acceptance of donor lungs that were initially predicted to be oversized based on other clinical measures.

A comparison of outcomes after lung transplantation between European and North American centers

BACKGROUND

With advancements in basic science and clinical medicine, lung transplantation (LT) has evolved rapidly over the last three decades. However, it is unclear if significant regional variations exist in long-term outcomes after LT.

METHODS

To investigate potential differences, we performed a retrospective, comparative cohort analysis of adult patients undergoing deceased donor single or double LT in North America (NA) or Europe between January 2006 and December 2016. Data up to April 2019 were abstracted from the International Society for Heart and Lung Transplantation (ISHLT) Thoracic Organ Registry. We compared overall survival (OS) between North American and European LT centers in a propensity score matched analysis.

RESULTS

In 3,115 well-matched pairs, though 30-day survival was similar between groups (NA 96.2% vs Europe 95.4%, p = 0.116), 5-year survival was significantly higher in European patients (NA 60.1% vs Europe 70.3%, p < 0.001).

CONCLUSIONS

This survival difference persisted in a sensitivity analysis excluding Canadian patients. Prior observations suggest that these disparities are at least partly related to better access to care via universal healthcare models prevalent in Europe. Future studies are warranted to confirm our findings and explore other causal mechanisms. It is likely that potential solutions will require concerted efforts from healthcare providers and policymakers.

A pilot randomized controlled trial of de novo belatacept-based immunosuppression following anti-thymocyte globulin induction in lung transplantation

The development of donor-specific antibodies (DSA) after lung transplantation is common and results in adverse outcomes. In kidney transplantation, Belatacept has been associated with a lower incidence of DSA, but experience with Belatacept in lung transplantation is limited. We conducted a two-center pilot randomized controlled trial of de novo immunosuppression with Belatacept after lung transplantation to assess the feasibility of conducting a pivotal trial. Twenty-seven participants were randomized to Control (Tacrolimus, Mycophenolate Mofetil, and prednisone, n = 14) or Belatacept-based immunosuppression (Tacrolimus, Belatacept, and prednisone until day 89 followed by Belatacept, Mycophenolate Mofetil, and prednisone, n = 13). All participants were treated with rabbit anti-thymocyte globulin for induction immunosuppression. We permanently stopped randomization and treatment with Belatacept after three participants in the Belatacept arm died compared to none in the Control arm. Subsequently, two additional participants in the Belatacept arm died for a total of five deaths compared to none in the Control arm (log rank p = .016). We did not detect a significant difference in DSA development, acute cellular rejection, or infection between the two groups. We conclude that the investigational regimen used in this study is associated with increased mortality after lung transplantation.

Lung Allograft Rejection

Rejection is a major complication following lung transplantation. Acute cellular rejection (ACR), and antibody-mediated rejection (AMR) are risk factors for the subsequent development of chronic lung allograft dysfunction and worse outcomes after transplantation. Although ACR has well-defined histopathologic diagnostic criteria and grading, the diagnosis of AMR requires a multidisciplinary diagnostic approach. This article reviews the identification, clinical and pathologic features of, and therapeutic options for ACR and AMR.

Coronavirus disease 2019 positivity immediately after lung transplantation: A case report

Management of COVID-19 in lung transplant recipients is challenging. We report a case of a 71-year-old male who underwent bilateral lung transplantation with an unexpected case of COVID-19. The patient had been fully vaccinated. The patient and donor tested negative for pretransplant COVID-19. On routine bronchoscopy on day 1 after transplant, the COVID-19 test was positive. Mycophenolic mofetil and the second dose of basiliximab were skipped, but tacrolimus and prednisone were continued. He was treated with casirivimab/imdevimab and remdesivir. He was discharged on day 14 and has had no episodes of acute rejection during the 3 months.

The Impact of Center Volume on Outcomes in Lung Transplantation

BACKGROUND

Studies in lung transplantation have shown variable association between hospital volume and clinical outcomes. We aimed to identify the pattern of effect of hospital volume on individual patient survival after lung transplantation.

METHODS

We performed a retrospective analysis using the United Network for Organ Sharing national thoracic organ transplantation database. Adult patients who underwent lung transplantation between January 2013 and December 2017 were included. The association between mean annual center volume and 1-year overall survival was examined using restricted cubic splines in a random effects multivariable Cox model. The volume threshold for optimal 1-year overall survival was subsequently approximated by the maximum likelihood approach using segmented linear splines in the same model.

RESULTS

The study included 10,007 patients at 71 transplant centers. Median annual center volume was 22 cases (interquartile range, 10.6 to 38). A center volume threshold was identified at 33 cases per year (95% confidence interval, 28 to 37). Higher center volume, to 33 cases per year, was associated with better 1-year survival (hazard ratio 0.989, 95% confidence interval, 0.980 to 0.999 every additional case). Further increase in center volume above 33 cases per year showed no additional benefit (hazard ratio 1.000, 95% confidence interval, 0.996 to 1.003 every additional case). Twenty-three centers (32.4%) reached the volume threshold of 33 cases per year.

CONCLUSIONS

One-year survival after lung transplantation improved with increasing center volume to as many as 33 cases per year. Low volume centers below the 33 cases per year threshold had large variations in their outcomes and had a higher risk of performing poorly, although many of them maintained good performance.

Lung transplant for pulmonary fibrosis with dendriform ossification

Dendriform pulmonary ossification (DPO) is a rare condition defined as disseminated, widespread heterotopic bone formation within the lungs. This condition is associated with restrictive pulmonary disease, such as interstitial pneumonia or fibrosis. The clinical features and pathophysiology of DPO, however, remain unclear. We report a case of a 66-year-old male with idiopathic pulmonary fibrosis accompanied by DPO who was treated with a double lung transplant. His postoperative course was uneventful without recurrence of DPO.

Management of chronic rejection after lung transplantation

Outcomes after lung transplantation are limited by chronic lung allograft dysfunction (CLAD). The incidence of CLAD is high, and its clinical course tends to be progressive over time, culminating in graft failure and death. Indeed, CLAD is the leading cause of death beyond the first year after lung transplantation. Therapy for CLAD has been limited by a lack of high-quality studies to guide management. In this review, we will discuss the diagnosis of CLAD in light of the recent changes to definitions and will discuss the current clinical evidence available for treatment. Recently, the diagnosis of CLAD has been subdivided into bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS). The current evidence for treatment of CLAD mainly revolves around treatment of BOS with more limited data existing for RAS. The best supported treatment to date for CLAD is the macrolide antibiotic azithromycin which has been associated with a small improvement in lung function in a minority of patients. Other therapies that have more limited data include switching immunosuppression from cyclosporine to tacrolimus, fundoplication for gastroesophageal reflux, montelukast, extracorporeal photopheresis (ECP), aerosolized cyclosporine, cytolytic anti-lymphocyte therapies, total lymphoid irradiation (TLI) and the antifibrotic agent pirfenidone. Most of these treatments are supported by case series and observational studies. Finally, we will discuss the role of retransplantation for CLAD.

Transplantation of Donor Lung with Partial Anomalous Pulmonary Venous Return Using a Carrel Patch

Partial anomalous pulmonary venous return is a rare congenital aberrancy which involves oxygen-rich pulmonary venous drainage into the right atrium instead of systemic circulation. Here, we report a case of isolated partial anomalous pulmonary venous return of the right upper lobe in a donor lung. Successful transplantation was performed with a Carrel patch technique for left atrial cuff reconstruction using a segment of donor vena cava. This is the third report of partial anomalous pulmonary venous return in a right donor lung, but the first to describe this reconstructive approach to restore physiologic venous drainage.

Variability in azithromycin practices among lung transplant providers in the International Society for Heart and Lung Transplantation Community

Chronic lung allograft dysfunction (CLAD) is the most important long-term complication after lung transplant (LTx), and clinical experience suggests significant variability in its management. We sought to capture azithromycin practices among LTx providers internationally. A survey was distributed via the International Society for Heart and Lung Transplantation and completed by 103 respondents (15 countries). Azithromycin indications, timing, and dosing varied significantly, and 37 (36%) reported inconsistency even within their center. Thirty (29%) reported initiating azithromycin prophylactically (during initial transplant hospitalization). Of 73 others, only 10 (14%) reported waiting until CLAD diagnosis (with persistent ≥20% pulmonary function decline). Most initiated azithromycin after a CLAD risk-factor and/or event, including 59 (81%) for a persistent ≥10% decrement in FEV₁, 32 (44%) for lymphocytic bronchiolitis, and 27 (37%) for bronchoalveolar lavage neutrophilia. Azithromycin prescribing patterns appear to vary significantly, and further study is needed to elucidate the optimal timing and indications for its initiation after LTx.

Bleeding and thrombotic complications associated with anticoagulation prior to lung transplantation: a case series

Background

Scarce data is available on therapeutic anticoagulation (AC) in patients undergoing pulmonary transplantation. We describe our institutional experience with AC-induced coagulopathy in recipients at the time of transplantation and evaluate its impact on posttransplant outcomes.

Methods

Records of adult patients on therapeutic AC at the time of lung transplantation from January 2014 to July 2021 were reviewed. Administration of preoperative pharmacologic reversal was assessed, with adequate reversal defined as international normalized ratio (INR) ≤1.5. We evaluated the incidence of major bleeding complications [delayed sternal closure, reoperation due to bleeding, chest tube output ≥1,500 cc, ≥4 units of packed red blood cells, ≥4 units of platelets, or ≥5 units of fresh frozen plasma (FFP)], major thrombotic complications [venous thromboembolism (VTE) or other major thrombosis on imaging], and inpatient mortality.

Results

Of 602 lung transplant recipients, 10 patients taking preoperative warfarin were included in the study. While most patients received pharmacologic reversal preoperatively (n=9, 90%), successful reversal was rarely achieved (n=3, 30%). Inadequate INR reversal was associated with major bleeding events (n=6, 60%). Major thrombotic complications were more frequent (n=7, 70%) than bleeding events. Notably, all fatalities within the cohort (n=2, 20%) were associated with thrombotic, but not bleeding, complications.

Conclusions

This is the first known report on the incidence and impact of AC-induced coagulopathy in patients undergoing lung transplantation. Major thrombotic events are frequent and associated with high mortality. Routine surveillance and treatment may be warranted.

Different-team procurements: A potential solution for the unintended consequences of change in lung allocation policy

The new lung allocation policy has led to an increase in distant donors and consequently enhanced logistical burden of procuring organs. Though early single-center studies noted similar outcomes between same-team transplantation (ST, procuring team from transplanting center) and different-team transplantation (DT, procuring team from different center), the efficacy of DT in the contemporary era remains unclear. In this study, we evaluated the trend of DT, rate of transplanting both donor lungs, 1-year graft survival, and risk of Grade 3 primary graft dysfunction (PGD) using the Scientific Registry of Transplant Recipient (SRTR) database from 2006 to 2018. A total of 21619 patients (DT 2085, 9.7%) with 19837 donors were included. Utilization of DT decreased from 15.9% in 2006 to 8.5% in 2018. Proportions of two-lung donors were similar between the groups, and DT had similar 1-year graft survival as ST for both double (DT, HR 1.108, 95% CI 0.894-1.374) and single lung transplants (DT, HR 1.094, 95% CI 0.931-1.286). Risk of Grade 3 PGD was also similar between ST and DT. Given our results, expanding DT may be a feasible option for improving lung procurement efficiency in the current era, particularly in light of the COVID-19 pandemic.

Lung protective ventilation based on donor size is associated with a lower risk of severe primary graft dysfunction after lung transplantation

BACKGROUND

Mechanical ventilation immediately after lung transplantation may impact the development of primary graft dysfunction (PGD), particularly in cases of donor-recipient size mismatch as ventilation is typically based on recipient rather than donor size.

METHODS

We conducted a retrospective cohort study of adult bilateral lung transplant recipients at our center between January 2010 and January 2017. We defined donor-based lung protective ventilation (dLPV) as 6 to 8 ml/kg of donor ideal body weight and plateau pressure <30 cm H₂O. We calculated the donor-recipient predicted total lung capacity (pTLC) ratio and used logistic regression to examine relationships between pTLC ratio, dLPV and PGD grade 3 at 48 to 72 hours. We used Cox proportional hazards modelling to examine the relationship between pTLC ratio, dLPV and 1-year survival.

RESULTS

The cohort included 373 recipients; 24 (6.4%) developed PGD grade 3 at 48 to 72 hours, and 213 (57.3%) received dLPV. Mean pTLC ratio was 1.04 ± 0.18. dLPV was associated with significantly lower risks of PGD grade 3 (OR = 0.44; 95% CI: 0.29-0.68, p < 0.001) and 1-year mortality (HR = 0.49; 95% CI: 0.29-0.8, p = 0.018). There was a significant association between pTLC ratio and the risk of PGD grade 3, but this was attenuated by the use of dLPV.

CONCLUSIONS

dLPV is associated with decreased risk of PGD grade 3 at 48 to 72 hours and decreased 1-year mortality. Additionally, dLPV attenuates the association between pTLC and both PGD grade 3 and 1-year mortality. Donor-based ventilation strategies may help to mitigate the risk of PGD and other adverse outcomes associated with size mismatch after lung transplantation.

Incidentally Detected Chronic Lymphocytic Leukemia in Hilar Lymph Nodes at the Time of Lung Transplantation: A Case Report

A 68-year-old man with interstitial pulmonary fibrosis underwent bilateral lung transplantation. Histopathologic examination of hilar lymph nodes in the explanted lungs showed effacement of normal nodal architecture by the proliferation of small lymphocytes, consistent with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL). Unexpectedly discovered malignancies at the time of lung transplantation is uncommon, especially in the lymph nodes. The clinical management was challenging because of attempts to balance treatment of CLL and immunosuppressive treatment to prevent graft rejection. Here, we report a case of incidentally detected CLL in hilar lymph nodes with explanted lungs and review the relevant literature.

Clinical features and outcomes of combined pulmonary fibrosis and emphysema after lung transplantation

BACKGROUND

Combined pulmonary fibrosis and emphysema (CPFE) is recognized as a characteristic syndrome of smoking-related interstitial lung disease that has a worse prognosis than idiopathic pulmonary fibrosis (IPF). However, outcomes after lung transplantation for CPFE have not been reported. The aim of this study is to describe the clinical features and outcomes of CPFE after lung transplantation.

RESEARCH QUESTION

What are the clinical features and outcomes of CPFE after lung transplantation?

STUDY DESIGN AND METHODS

This is a single-center retrospective cohort study of patients with CPFE and IPF who underwent lung transplantation at our center between January 2011 and December 2016. We defined CPFE as ≥ 10% emphysema in the upper lung fields combined with fibrosis on high-resolution computed tomography scan. We characterized the clinical features of patients with CPFE and compared their outcomes after lung transplantation to those with IPF.

RESULTS

27 of 172 (16%) patients with IPF met criteria for CPFE. Severe pulmonary hypertension was present in 16 of 27 (59%) patients with CPFE. On logistic regression analysis, CPFE was significantly associated with primary graft dysfunction (PGD) grade 3 (odds ratio: 3.14, 95% confidence interval [CI]: 1.18-8.37, p=0.02). On competing risk regression analysis, CPFE was associated with acute cellular rejection (ACR) grade ≥ A2, and chronic lung allograft dysfunction (CLAD) (hazard ratio [HR]: 1.89, 95% CI: 1.10-3.25, p=0.02, HR: 1.96, 95% CI: 1.02-3.77, p=0.04, respectively). 5-year survival was 79.0% for the CPFE group and 75.4% for the IPF group, respectively (log rank p = 0.684).

INTERPRETATION

After transplant, patients with CPFE were more likely to develop PGD, ACR, and CLAD compared to those with IPF. However, survival was not significantly different between the 2 groups.

Antibody-Mediated Rejection and Lung Transplantation

Antibody-mediated rejection (AMR) is now a widely recognized form of lung allograft rejection, with mounting evidence for AMR as an important risk factor for the development of chronic lung allograft dysfunction and markedly decreased long-term survival. Despite the recent development of the consensus diagnostic criteria, it remains a challenging diagnosis of exclusion. Furthermore, even after diagnosis, treatment directed at pulmonary AMR has been nearly exclusively derived from practices with other solid-organ transplants and other areas of medicine, such that there is a significant lack of data regarding the efficacy for these in pulmonary AMR. Lastly, outcomes after AMR remain quite poor despite aggressive treatment. In this review, we revisit the history of AMR in lung transplantation, describe our current understanding of its pathophysiology, discuss the use and limitations of the consensus diagnostic criteria, review current treatment strategies, and summarize long-term outcomes. We conclude with a synopsis of our most pressing gaps in knowledge, introduce recommendations for future directions, and highlight promising areas of active research.

One year survival worse for lung retransplants relative to primary lung transplants

BACKGROUND

Outcomes after lung re-transplantation (LRT) remain inferior compared to primary lung transplantation (PLT). We examined the impact of center volume on one-year survival after LRT.

METHODS

Using the UNOS database, we abstracted patients undergoing PLT and LRT between January 2006 and December 2017, excluding combined heart-lung transplants and multiple re-transplants. One-year survival after PLT and LRT were compared using propensity score matching. In the LRT cohort, multivariable Cox models with and without time-dependent coefficients were fitted to examine association between transplant center volume and 1-year survival. Center volume was categorized based on inspection of restricted cubic splines.

RESULTS

A total of 20,675 recipients (PLT 19853 [96.0%] vs. LRT 822 [4.0%]) were included. One-year survival was lower for LRT recipients in the matched cohort (PLT 84.8% vs LRT 76.7%). There was steady improvement in one-year survival after LRT (2006-2009 72.1% vs. 2010-2013 76.6% vs. 2014-2017 80.1%). Higher center volume was associated with better 1-year survival after LRT. This survival difference was noted in the initial 30 days after transplantation (Intermediate vs. Low volume, HR 0.282 [0.151-0.526]; High vs. Low volume HR 0.406 [0.224-0.737]) but became insignificant after 30 days.

CONCLUSIONS

Superior 1-year survival after LRT at higher volume centers is predominantly due to better 30-day outcomes. This finding suggests that LRT candidates may be referred to higher volume centers for surgery.

Bacterial products in donor airways prevent the induction of lung transplant tolerance

Although postoperative bacterial infections can trigger rejection of pulmonary allografts, the impact of bacterial colonization of donor grafts on alloimmune responses to transplanted lungs remains unknown. Here, we tested the hypothesis that bacterial products present within donor grafts at the time of implantation promote lung allograft rejection. Administration of the toll-like receptor 2 (TLR2) agonist Pam₃ Cys₄ to Balb/c wild-type grafts triggered acute cellular rejection after transplantation into B6 wild-type recipients that received perioperative costimulatory blockade. Pam₃ Cys₄ -triggered rejection was associated with an expansion of CD8⁺ T lymphocytes and CD11c⁺ CD11b^hi MHC (major histocompatibility complex) class II⁺ antigen-presenting cells within the transplanted lungs. Rejection was prevented when lungs were transplanted into TLR2-deficient recipients but not when MyD88-deficient donors were used. Adoptive transfer of B6 wild-type monocytes, but not T cells, following transplantation into B6 TLR2-deficient recipients restored the ability of Pam₃ Cys₄ to trigger acute cellular rejection. Thus, we have demonstrated that activation of TLR2 by a bacterial lipopeptide within the donor airways prevents the induction of lung allograft tolerance through a process mediated by recipient-derived monocytes. Our work suggests that donor lungs harboring bacteria may precipitate an inflammatory response that can facilitate allograft rejection.

Impact of Nighttime Lung Transplantation on Outcomes and Costs

BACKGROUND

Previous studies in the field of organ transplantation have shown a possible association between nighttime surgery and adverse outcomes. We aim to determine the impact of nighttime lung transplantation on postoperative outcomes, long-term survival, and overall cost.

METHODS

We performed a single-center retrospective cohort analysis of adult lung transplant recipients who underwent transplantation between January 2006 and December 2017. Data were extracted from our institutional Lung Transplant Registry and Mid-America Transplant services database. Patients were classified into 2 strata, daytime (5 AM to 6 PM) and nighttime (6 PM to 5 AM), based on time of incision. Major postoperative adverse events, 5-year overall survival, and 5-year bronchiolitis obliterans syndrome-free survival were examined after propensity score matching. Additionally we compared overall cost of transplantation between nighttime and daytime groups.

RESULTS

Of the 740 patients included in this study, 549 (74.2%) underwent daytime transplantation and 191 (25.8%) underwent nighttime transplantation (NT). Propensity score matching yielded 187 matched pairs. NT was associated with a higher risk of having any major postoperative adverse event (adjusted odds ratio, 1.731; 95% confidence interval, 1.093-2.741; P = .019), decreased 5-year overall survival (adjusted hazard ratio, 1.798; 95% confidence interval, 1.079-2.995; P = .024), and decreased 5-year bronchiolitis obliterans syndrome-free survival (adjusted hazard ratio, 1.556; 95% confidence interval, 1.098-2.205; P = .013) in doubly robust multivariable analyses after propensity score matching. Overall cost for NT and daytime transplantation was similar.

CONCLUSIONS

NT was associated with a higher risk of major postoperative adverse events, decreased 5-year overall survival, and decreased 5-year bronchiolitis obliterans syndrome-free survival. Our findings suggest potential benefits of delaying NT to daytime transplantation.

Economic evaluation of the specialized donor care facility for thoracic organ donor management

Background

Over the last decade two alternative models of donor care have emerged in the United States: the conventional model, whereby donors are managed at the hospital where brain death occurs, and the specialized donor care facility (SDCF), in which brain dead donors are transferred to a SDCF for medical optimization and organ procurement. Despite increasing use of the SDCF model, its cost-effectiveness in comparison to the conventional model remains unknown.

Methods

We performed an economic evaluation of the SDCF and conventional model of donor care from the perspective of U.S. transplant centers over a 2-year study period. In this analysis, we utilized nationwide data from the Scientific Registry of Transplant Recipients and controlled for donor characteristics and patterns of organ sharing across the nation’s organ procurement organizations (OPOs). Subgroup analysis was performed to determine the impact of the SDCF model on thoracic organ transplants.

Results

A total of 38,944 organ transplants were performed in the U.S. during the study period from 13,539 donors with an observed total organ cost of $1.36 billion. If every OPO assumed the cost and effectiveness of the SDCF model, a predicted 39,155 organ transplants (+211) would have been performed with a predicted total organ cost of $1.26 billion (−$100 million). Subgroup analysis of thoracic organs revealed that the SDCF model would lead to a predicted 156 additional transplants with a cost saving of $24.6 million.

Conclusions

The U.S. SDCF model may be a less costly and more effective means of multi-organ donor management, particularly for thoracic organ donors, compared to the conventional hospital-based model.

Local complement activation is associated with primary graft dysfunction after lung transplantation

BACKGROUND

The complement system plays a key role in host defense but is activated by ischemia/reperfusion injury (IRI). Primary graft dysfunction (PGD) is a form of acute lung injury occurring predominantly due to IRI, which worsens survival after lung transplantation (LTx). Local complement activation is associated with acute lung injury, but whether it is more reflective of allograft injury compared with systemic activation remains unclear. We proposed that local complement activation would help identify those who develop PGD after LTx. We also aimed to identify which complement activation pathways are associated with PGD.

METHODS

We performed a multicenter cohort study at the University of Pennsylvania and Washington University School of Medicine. Bronchoalveolar lavage (BAL) and plasma specimens were obtained from recipients within 24 hours after LTx. PGD was scored based on the consensus definition. Complement activation products and components of each arm of the complement cascade were measured using ELISA.

RESULTS

In both cohorts, sC4d and sC5b-9 levels were increased in BAL of subjects with PGD compared with those without PGD. Subjects with PGD also had higher C1q, C2, C4, and C4b, compared with subjects without PGD, suggesting classical and lectin pathway involvement. Ba levels were higher in subjects with PGD, suggesting alternative pathway activation. Among lectin pathway–specific components, MBL and FCN-3 had a moderate-to-strong correlation with the terminal complement complex in the BAL but not in the plasma.

CONCLUSION

Complement activation fragments are detected in the BAL within 24 hours after LTx. Components of all 3 pathways are locally increased in subjects with PGD. Our findings create a precedent for investigating complement-targeted therapeutics to mitigate PGD.

FUNDING

This research was supported by the NIH, American Lung Association, Children’s Discovery Institute, Robert Wood Johnson Foundation, Cystic Fibrosis Foundation, Barnes-Jewish Hospital Foundation, Danish Heart Foundation, Danish Research Foundation of Independent Research, Svend Andersen Research Foundation, and Novo Nordisk Research Foundation.

Substantial differences between local and systemic complement activation in lung transplant recipients who develop primary graft dysfunction are identified in two independent cohorts.

Local versus distant lung donor procurement does not influence short-term clinical outcomes

OBJECTIVE

The purpose of this study was to recognize clinically meaningful differences in lung transplant outcomes based on local or distant lung procurement. This could identify if the lung allocation policy change would influence patient outcomes.

METHODS

This single-center retrospective cohort study analyzed adult patients who underwent lung transplant from 2006 to 2017. Donor and recipient data were abstracted from a collaborative, prospective registry shared by our local organ procurement organization, and tertiary medical center. Short-term outcomes, 1-year survival, and hospitalization costs were compared between local and distant lung transplants defined by donor service area.

RESULTS

Of the 722 lung transplants performed, 392 (54%) had local donors and 330 (46%) had distant donors. Donors were similar in age and cause of death. Recipients were significantly different in diagnosis and local recipients had lower median lung allocation scores (local, 37.3 and distant, 44.9; P < .01). Distant lung transplants had longer total ischemic times (local, 231 ± 52 minutes and distant, 313 ± 48 minutes; P < .01). The rate of major complications, length of hospital stay, and 1-year survival were similar between groups. Distant lung transplants were associated with higher median overall cost (local, $183,542 and distant, $229,871; P < .01). Local lung transplants were more likely to be performed during daytime (local, 333 out of 392 [85%] and distant, 291 out of 330 [61%]; P < .01).

CONCLUSIONS

Local lung transplants are associated with shorter ischemic times, lower cost, and greater likelihood of daytime surgery. Short- and intermediate-term outcomes are similar for lung transplants from local and distant donors. The new lung allocation policy, with higher proportion of distant lung transplants, is likely to incur greater costs but provide similar outcomes.

Circulating exosomes with lung self-antigens as a biomarker for chronic lung allograft dysfunction: A retrospective analysis

BACKGROUND

Exosomes isolated from plasma of lung transplant recipients (LTxRs) with bronchiolitis obliterans syndrome (BOS) contain human leukocyte antigens and lung self-antigens (SAgs), K-alpha 1 tubulin (Kα1T) and collagen type V (Col-V). The aim was to determine the use of circulating exosomes with lung SAgs as a biomarker for BOS.

METHODS

Circulating exosomes were isolated retrospectively from plasma from LTxRs at diagnosis of BOS and at 6 and 12 months before the diagnosis (n = 41) and from stable time-matched controls (n = 30) at 2 transplant centers by ultracentrifugation. Exosomes were validated using Nanosight, and lung SAgs (Kα1T and Col-V) were detected by immunoblot and semiquantitated using ImageJ software.

RESULTS

Circulating exosomes from BOS and stable LTxRs demonstrated 61- to 181-nm vesicles with markers Alix and CD9. Exosomes from LTxRs with BOS (n = 21) showed increased levels of lung SAgs compared with stable (n = 10). A validation study using 2 separate cohorts of LTxRs with BOS and stable time-matched controls from 2 centers also demonstrated significantly increased lung SAgs-containing exosomes at 6 and 12 months before BOS.

CONCLUSIONS

Circulating exosomes isolated from LTxRs with BOS demonstrated increased levels of lung SAgs (Kα1T and Col-V) 12 months before the diagnosis (100% specificity and 90% sensitivity), indicating that circulating exosomes with lung SAgs can be used as a non-invasive biomarker for identifying LTxRs at risk for BOS.

Shipping Lungs Greater Distances Increases Costs Without Cutting Waitlist Mortality

BACKGROUND

On November 24, 2017, a change in lung allocation policy was initiated to replace the donor service area with a 250-nautical-mile radius circle around the donor hospital. We aim to analyze the consequences of this change, including organ acquisition cost and transplant outcomes, at the national level.

METHODS

Data on adult patients undergoing lung transplantation between April 27, 2017, and June 22, 2018 (30 weeks before to 30 weeks after allocation policy change) were extracted from the Scientific Registry of Transplant Recipients database. Patients were classified into pre-change and post-change subgroups. Six-month overall survival was evaluated by Kaplan-Meier analysis. Organ acquisition costs were compared between the pre-change and post-change groups.

RESULTS

Of the 3317 adult patients removed from the waiting list during the study period (pre-change 1637 vs post-change 1680), 2734 underwent transplantation (pre-change 1371 of 1637 [83.8%] vs post-change 1363 of 1680 [81.1%]), and 382 died or became too sick to be transplanted (pre-change 168 of 1637 [10.3%] vs post-change 214 of 1680 [12.7%], P = .077). Six-month survival rates of transplanted patients were similar between the two groups. However, average organ acquisition costs increased after policy change (pre-change $50,735 ± $10,858 vs post-change $53,440 ± $10,247, P < .001) with an increase in nonlocal donors (pre-change 44.3% vs post-change 68.9%, P < .001).

CONCLUSIONS

Organ acquisition costs and resource utilization increased with the new lung allocation policy, whereas deaths on the waiting list or after transplantation did not decrease. Further optimization of the allocation policy is necessary to balance access to transplant and proper stewardship of human and financial resources.

IL-22 is required for the induction of bronchus-associated lymphoid tissue in tolerant lung allografts

Long-term survival after lung transplantation remains profoundly limited by graft rejection. Recent work has shown that bronchus-associated lymphoid tissue (BALT), characterized by the development of peripheral nodal addressin (PNAd)-expressing high endothelial venules and enriched in B and Foxp3+ T cells, is important for the maintenance of allograft tolerance. Mechanisms underlying BALT induction in tolerant pulmonary allografts, however, remain poorly understood. Here, we show that the development of PNAd-expressing high endothelial venules within intragraft lymphoid follicles and the recruitment of B cells, but not Foxp3+ cells depends on IL-22. We identify graft-infiltrating gamma-delta (γδ) T cells and Type 3 innate lymphoid cells (ILC3s) as important producers of IL-22. Reconstitution of IL-22 at late time points through retransplantation into wildtype hosts mediates B cell recruitment into lymphoid follicles within the allograft, resulting in a significant increase in their size, but does not induce PNAd expression. Our work has identified cellular and molecular requirements for the induction of BALT in pulmonary allografts during tolerance induction and may provide a platform for the development of new therapies for lung transplant patients.

Pseudomonas aeruginosa and acute rejection independently increase the risk of donor-specific antibodies after lung transplantation

Factors contributing to donor-specific HLA antibody (DSA) development after lung transplantation have not been systematically evaluated. We hypothesized that the isolation of Pseudomonas aeruginosa in respiratory specimens would increase the risk of DSA development. Our objective was to determine the risk of DSA development associated with the isolation of Pseudomonas aeruginosa after lung transplantation. We conducted a single-center retrospective cohort study of primary lung transplant recipients and examined risk factors for DSA development using Cox regression models. Of 460 recipients, 205 (45%) developed DSA; the majority developed Class II DSA (n = 175, 85%), and 145 of 205 (71%) developed DSA to HLA-DQ alleles. Univariate time-dependent analyses revealed that isolation of Pseudomonas from respiratory specimens, acute cellular rejection, and lymphocytic bronchiolitis are associated with an increased risk of DSA development. In multivariable analyses, Pseudomonas isolation, acute cellular rejection, and lymphocytic bronchiolitis remained independent risk factors for DSA development. Additionally, there was a direct association between the number of positive Pseudomonas cultures and the risk of DSA development. Our findings suggest that pro-inflammatory events including acute cellular rejection, lymphocytic bronchiolitis, and Pseudomonas isolation after transplantation are associated with an increased risk of DSA development.

Antibody-mediated rejection after lung transplantation

Antibody-mediated rejection (AMR) has been identified as a significant form of acute allograft dysfunction in lung transplantation. The development of consensus diagnostic criteria has created a uniform definition of AMR; however, significant limitations of these criteria have been identified. Treatment modalities for AMR have been adapted from other areas of medicine and data on the effectiveness of these therapies in AMR are limited. AMR is often refractory to these therapies, and graft failure and death are common. AMR is associated with increased rates of chronic lung allograft dysfunction (CLAD) and poor long-term survival. In this review, we discuss the history of AMR and describe known mechanisms, application of the consensus diagnostic criteria, data for current treatment strategies, and long-term outcomes. In addition, we highlight current gaps in knowledge, ongoing research, and future directions to address these gaps. Promising diagnostic techniques are actively being investigated that may allow for early detection and treatment of AMR. We conclude that further investigation is required to identify and define chronic and subclinical AMR, and head-to-head comparisons of currently used treatment protocols are necessary to identify an optimal treatment approach. Gaps in knowledge regarding the epidemiology, mechanisms, diagnosis, and treatment of AMR continue to exist and future research should focus on these aspects.

Comparison of outcomes in lung and heart transplant recipients from the same multiorgan donor

BACKGROUND

Primary graft dysfunction (PGD) and acute cellular rejection (ACR) are important causes of early morbidity and mortality following lung and heart transplantation. While many studies have elucidated donor-related risk factors of PGD and ACR, these complications often occur even with "ideal" donors. Therefore, we investigated potential associations of PGD and ACR between bilateral lung and heart transplant recipients from the same multiorgan donor, respectively.

METHODS

Between 2011 and 2017, 100 donors contributed 100 bilateral lung transplants and 100 heart transplants performed. Logistic regression analysis for PGD and Cox proportional hazards regression analysis for ACR were used to estimate the relationship of heart and lung transplants.

RESULTS

The incidence of PGD was 33% among lung and 17% among heart transplant recipients. Similarly, the incidence of ACR grade ≥ A2 for lung recipients was 38% (30/80), and the incidence of ACR grade ≥ 2R for heart recipients was 19% (15/80). There was no association between the development of PGD and ACR in lung and heart transplant recipients from the same donor, respectively.

CONCLUSIONS

These findings suggest that inherent donor factors are not critical to the development of PGD and ACR after lung and heart transplantation.

Rabbit antithymocyte globulin for the treatment of chronic lung allograft dysfunction

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is the leading cause of death beyond the first year after lung transplantation. Several treatments have been used to prevent the progression or reverse the effects of CLAD. Cytolytic therapy with rabbit antithymocyte globulin (rATG) has previously shown to be a potential option. However, the effect on patients with restrictive allograft syndrome (RAS) versus bronchiolitis obliterans syndrome (BOS) and the effect of cumulative dosing are unknown.

METHODS

The charts of lung transplant patients treated with rATG at Barnes-Jewish Hospital from 2009 to 2016 were retrospectively reviewed. The primary outcome was response to rATG; patients were deemed responders if their FEV₁ improved in the 6 months after rATG treatment. Safety endpoints included incidence of serum sickness, cytokine release syndrome, malignancy, and infectious complications.

RESULTS

108 patients were included in this study; 43 (40%) patients were responders who experienced an increase in FEV₁ after rATG therapy. No predictors of response to rATG therapy were identified. Serum sickness occurred in 22% of patients, 15% experienced cytokine release syndrome, and 19% developed an infection after therapy.

CONCLUSION

40% of patients with CLAD have an improvement in lung function after treatment with rATG although the improvement was typically minimal.

The role of the immune system in lung transplantation: towards improved long-term results

Over the past 35 years, lung transplantation has evolved from an experimental treatment to the treatment of choice for patients with end-stage lung disease. Beyond the immediate period after lung transplantation, rejection and infection are the leading causes of death. The risk of rejection after lung transplantation is generally higher than after other solid organ transplants, and this necessitates more intensive immunosuppression. However, this more intensive treatment does not reduce the risk of rejection sufficiently, and rejection is one of the most common complications after transplantation. There are multiple forms of rejection including acute cellular rejection, antibody-mediated rejection, and chronic lung allograft dysfunction. These have posed a vexing problem for clinicians, patients, and the field of lung transplantation. Confounding matters is the inherent effect of more intensive immunosuppression on the risk of infections. Indeed, infections pose a direct problem resulting in morbidity and mortality and increase the risk of chronic lung allograft dysfunction in the ensuing weeks and months. There are complex interactions between microbes and the immune response that are the subject of ongoing studies. This review focuses on the role of the immune system in lung transplantation and highlights different forms of rejection and the impact of infections on outcomes.

Unintended consequences of changes to lung allocation policy

Organ allocation for transplantation aims to balance the principles of justice and medical utility to optimally utilize a scarce resource. To address practical considerations, the United States is divided into 58 donor service areas (DSA), each constituting the first unit of allocation. In November 2017, in response to a lawsuit in New York, an emergency action change to lung allocation policy replaced the DSA level of allocation for donor lungs with a 250 nautical mile circle around the donor hospital. Similar policy changes are being implemented for other organs including heart and liver. Findings from a recent US Department of Health and Human Services report, supplemented with data from our institution, suggest that the emergency policy has not resulted in a change in the type of patients undergoing lung transplantation (LT) or early postoperative outcomes. However, there has been a significant decline in local LT, where donor and recipient are in the same DSA. With procurement teams having to travel greater distances, organ ischemic time has increased and median organ cost has more than doubled. We propose potential solutions for consideration at this critical juncture in the field of transplantation. Policymakers should choose equitable and sustainable access for this lifesaving discipline.

The impact of non-HLA antibodies on outcomes after lung transplantation and implications for therapeutic approaches

The role of donor-specific antibodies (DSA) to mismatched human leukocyte antigens (HLA) in lung allograft rejection has been recognized over the past 20 years. During this time, there has been growing experience and recognition of an important role for non-HLA antibodies in lung allograft rejection. Multiple self-antigens have been identified that elicit autoimmune responses including collagen V, K-α 1 tubulin, angiotensin type 1 receptor, and endothelin type A receptor, but it is likely that other antigens elicit similar responses. The paradigm for the pathogenesis of these autoimmune responses consists of exposure of sequestered self-antigens followed by loss of peripheral tolerance, which then promotes allograft rejection. Studies have focused mainly on the impact of autoimmune responses on the development of Bronchiolitis Obliterans Syndrome or its mouse model surrogate. However, there are emerging data that illustrate that non-HLA antibodies can induce acute antibody-mediated rejection (AMR) after lung transplantation. Treatment has focused on antibody-depletion protocols, but experience is limited to cohort studies and appropriate controlled trials have not been conducted. It is noteworthy that depletion of non-HLA antibodies has been associated with favorable clinical outcomes. Clearly, additional studies are needed to identify the optimal therapeutic approaches to non-HLA antibodies in clinical practice.

Development and Optimization of an ELISA to Quantitate C3(H 2 O) as a Marker of Human Disease

Discovery of a C3(H₂O) uptake pathway has led to renewed interest in this alternative pathway triggering form of C3 in human biospecimens. Previously, a quantifiable method to measure C3(H₂O), not confounded by other complement activation products, was unavailable. Herein, we describe a sensitive and specific ELISA for C3(H₂O). We initially utilized this assay to determine baseline C3(H₂O) levels in healthy human fluids and to define optimal sample storage and handling conditions. We detected ~500 ng/ml of C3(H₂O) in fresh serum and plasma, a value substantially lower than what was predicted based on previous studies with purified C3 preparations. After a single freeze-thaw cycle, the C3(H₂O) concentration increased 3- to 4-fold (~2,000 ng/ml). Subsequent freeze-thaw cycles had a lesser impact on C3(H₂O) generation. Further, we found that storage of human sera or plasma samples at 4°C for up to 22 h did not generate additional C3(H₂O). To determine the potential use of C3(H₂O) as a biomarker, we evaluated specimens from patients with inflammatory-driven diseases. C3(H₂O) concentrations were moderately increased (1.5- to 2-fold) at baseline in sera from active systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) patients compared to healthy controls. In addition, upon challenge with multiple freeze-thaw cycles or incubation at 22 or 37°C, C3(H₂O) generation was significantly enhanced in SLE and RA patients' sera. In bronchoalveolar lavage fluid from lung-transplant recipients, we noted a substantial increase in C3(H₂O) within 3 months of acute antibody-mediated rejection. In conclusion, we have established an ELISA for assessing C3(H₂O) as a diagnostic and prognostic biomarker in human diseases.