Introduction: Lung transplant recipients are at high risk for infections unusual in their presentation as well as causative organisms. While achromobacter species infections are recognized in patients who received a lung transplant for cystic fibrosis, it is rare for this infection to occur in patients with lung disease from other causes. Here, we present an unusual case of Achromobacter xylosoxidans infection in a bilateral lung transplant recipient with pulmonary fibrosis. Description of Case: A 67-year-old woman awaiting lung transplant for hypersensitivity pneumonitis induced pulmonary fibrosis was admitted to the intensive care unit for acute on chronic hypoxic respiratory failure requiring high flow nasal cannula oxygen at 80% FiO2. She had been treated for her lung condition with mycophenolate mofetil and prednisone. One week after admission, she underwent bilateral lung transplant receiving induction with basiliximab and methylprednisone per institutional protocol. She had no evidence of primary graft dysfunction; however, bronchoscopy completed at post-transplant days 7 and 10 showed mild ischemic injury at the medial right anastomosis. She was discharged home without oxygen. At her bronchoscopy one month post-transplant, black discoloration was identified throughout the tracheobronchial tree. Broncheoalveolar lavage (BAL) resulted positive for aspergillus galactomannan, and her voriconazole dose was increased to therapeutic range. Bronchoscopy two months post-transplant showed thick grey secretions adherent to the right anastomosis partially obstructing the right mainstem. BAL was again positive for aspergillus galactomannan, and newly positive for achromobacter species. She underwent endobronchial biopsy of the lesion, which also demonstrated achromobacter xylosoxidans with areas of necrosis and abscess formation. A computed tomography (CT) scan demonstrated scattered ground glass opacities. Given radiographic changes, multiple positive histopathologic specimens, and visual evidence of infection, the patient received six weeks of treatment with ceftazidime and inhaled polymyxin E. Subsequent bronchoscopy at six months post-transplant demonstrated complete resolution of right anastomotic lesion and negative BAL cultures. Discussion:Achromobacter xylosoxidans is a non-fermenting gram negative bacterium that produces colorless bacterial colonies; it is capable of causing colonization, as was initially suspected in our patient, but can also result in infections characterized by dark discoloration in immunocompromised individuals. In a retrospective study of a 288 person lung transplant cohort, only 2 non-cystic fibrosis patients had achromobacter xylosoxidans infections; similar to this patient, both had a history of pulmonary fibrosis. This case highlights the spectrum of achromobacter infections and the role of repeat post-transplant bronchoscopies in managing opportunistic infections.

Rationale: Lung transplant recipients (LTRs) with antibody-mediated rejection (AMR) are at increased risk of chronic lung allograft dysfunction (CLAD) and early death. Currently, few methods exist to risk-stratify AMR patients for poor outcomes. We hypothesized that the degree of allograft injury at diagnosis of AMR is associated with an increased risk of CLAD/death. We tested this hypothesis using donor-derived cell-free DNA (dd-cfDNA), a sensitive molecular biomarker of allograft injury previously shown to risk-stratify LTRs in other disease states, such as acute cellular rejection. Methods: This analysis included 221 LTRs from two prospective cohort studies. Patients underwent serial plasma collection, bronchoscopy, and transbronchial biopsy at pre-specified timepoints and at times of concern for allograft dysfunction. Dd-cfDNA was measured from plasma by shotgun sequencing. AMR was diagnosed by adjudication committee according to International Society of Heart and Lung Transplantation criteria. Univariate logistic and Cox regression analyses determined the association of %dd-cfDNA levels at diagnosis of AMR with the risk of developing the primary, composite outcome of CLAD/death. Results: Fifty-six of 221 subjects had clinical AMR. Sixteen subjects were excluded due to missing %dd-cfDNA assessments or censorship, leaving 40 subjects for final analysis. Twenty-two of 40 patients had >1 episode of AMR, resulting in 71 AMR timepoints at a median of 12 months (IQR 4.7-19.9) post-transplant. Median %dd-cfDNA was 7-fold higher in AMR patients at time of their diagnosis compared with stable controls: 1.84 (0.75-6.51) versus 0.27 (0.11-0.58), p < 0.0001 (Figure 1A). Twenty-six of the 40 patients developed CLAD/death at a median of 9.5 months (4.0-23.2) from AMR diagnosis. At time of their diagnosis, median %dd-cfDNA was 0.91 (0.26-2.64) for AMR subjects that lived versus 2.24 (1.23-7.19) for those with CLAD/death, p = 0.007 (Figure 1B). In univariate analyses, higher levels of %dd-cfDNA at diagnosis of clinical AMR were associated with an increased risk of developing the composite outcome of CLAD/death with an odds ratio of 1.20 (95% CI 1.03-1.49), p = 0.048 and a hazard ratio of 1.06 (95% CI 1.004 – 1.109), p = 0.023. Conclusions: We have demonstrated that higher levels of %dd-cfDNA at the diagnosis of AMR are associated with an increased risk of CLAD and death. Ongoing studies will include multivariable analyses to adjust for confounders and further assess this association. This study adds to the growing body of literature demonstrating that dd-cfDNA is a potential clinical tool that can be used to risk-stratify post-transplant complications.

Background. Despite treatment of major risk factors such as acute rejection (AR) and organizing pneumonia (OP) in lung transplant recipients, chronic lung allograft dysfunction (CLAD) still develops at high rates, suggesting that traditional methods of assessing response to treatment and resolution remain inadequate. It is unknown whether the degree of molecular allograft injury after treatment of AR/OP modulates the risk of CLAD and death. Methods. To evaluate the association of molecular allograft injury after AR/OP with the incidence of CLAD/death, we conducted a multicenter prospective cohort study that included 93 patients who underwent lung transplantation between 2015 and 2022. The degree of molecular allograft injury after AR/OP was quantified by the mean area under the curve of longitudinal measures of plasma donor-derived cell-free DNA (dd-cfDNA).Results. Over a median follow-up of 5 y, patients who developed CLAD/death had persistently higher levels of dd-cfDNA in the months after AR/OP. In multivariable Cox regression analysis adjusting for patient and transplant risk factors, mean dd-cfDNA levels after AR/OP were independently associated with an increased risk of CLAD/death (adjusted hazard ratio, 2.84; 95% confidence interval, 1.67-4.83; P < 0.001) and remained consistent when accounting for changes in pulmonary function after AR/OP events (hazard ratio, 2.62; 95% confidence interval, 1.53-4.47; P < 0.001).Conclusions. The degree of allograft injury on the molecular level after AR/OP events in lung transplant recipients is associated with the risk of developing CLAD or death. This study demonstrates the potential of dd-cfDNA for improving risk stratification and monitoring the resolution and treatment responses of lung allograft injury.

BACKGROUND:Current International Society for Heart and Lung Transplantation (ISHLT) criteria for pulmonary antibody-mediated rejection (AMR) is predicated on a constellation of clinical, laboratory and histopathological parameters, including the presence of donor-specific antibodies (DSA). However, molecular evidence of allograft injury is not considered. The aim of this study was to investigate if allograft injury on the molecular level, as measured by donor-derived cell-free DNA (dd-cfDNA), identifies DSA positive patients experiencing a form of AMR associated with increased risk of chronic lung allograft dysfunction (CLAD) or death. METHODS:This multicenter, observational analysis included adult lung transplant recipients from 2 prospective cohort studies. Serial plasma samples were collected for dd-cfDNA measurement by shotgun sequencing. Molecular AMR was defined as the presence of DSA and dd-cfDNA level >1% occurring >30 days post-transplant. Clinical AMR was defined using ISHLT criteria. Time-dependent multivariable Cox regression models were used to determine the association of Clinical AMR or Molecular AMR with the composite outcome of CLAD or death. RESULTS:The final analysis included 209 subjects. Sixty-one subjects met criteria for molecular AMR. Molecular AMR captured 42/46 (91%) of patients who experienced Clinical AMR. Molecular AMR was associated with an increased risk of CLAD or death (HR 2.00, 95% CI: 1.18-3.38, p = 0.010). The results remained consistent analyzing Molecular AMR subjects without concomitant ISHLT Clinical AMR, acute rejection, or infection (HR 2.45, 95% CI: 1.01-5.94, p = 0.047). CONCLUSIONS:Molecular AMR identifies a population of lung transplant recipients potentially experiencing antibody-mediated rejection not captured by current ISHLT criteria.

Background:Hyperammonemia syndrome (HS) is a life-threatening complication primarily affecting lung transplant recipients (LTR). HS is strongly associated with mollicute infection. We implemented an active surveillance and prophylaxis protocol for HS in LTR. Herein, we evaluate the impact of our protocol on rates and outcomes of HS. Methods:This was a single-center retrospective cohort study of adult LTR performed from 1/1/2019 to 6/6/2024. Our surveillance and prophylaxis protocol was implemented on 8/1/2022 and included PCR testing for mollicutes on post-operative bronchoalveolar lavage samples, measurement of serum ammonia levels, and azithromycin prophylaxis. Comparisons between pre- and post-protocol implementation groups were performed. Results:151 patients received a lung transplant during the study period, 54 (35.8%) following protocol implementation. Mollicute testing was performed in 57 LTR with most tests sent after protocol implementation (87.0% vs 10.3%, p<0.0001). Ammonia levels were checked in 53.7%; however, only 24.1% had levels checked by post-operative day 3. Ten LTR (6.6%) were diagnosed with mollicute infection, six in the pre-protocol and four in the post-protocol arm, with 70% of infections due to Mycoplasma spp. All LTR received antimicrobial prophylaxis following protocol implementation. Pre-protocol, 3.1% of LTR were diagnosed with definite HS compared to 0% in the post-protocol arm, despite 4 patients being diagnosed with mollicute infection. Conclusions:Implementing a mollicute screening and prophylaxis protocol reduced cases of HS in LTR despite some LTR developing mollicute infection. Antimicrobial prophylaxis with azithromycin and doxycycline may further optimize LTR prophylaxis. Larger studies are needed to determine optimal screening and prophylaxis strategies for HS in LTR.

Background Lung transplantation offers life-saving benefits for patients with end-stage lung disease, however, long-term outcomes remain poor, with a median survival of 6.5 years. Identifying patients at risk for poor post-transplant lung function is crucial for improving outcomes. While peri-operative and demographic factors have previously been studied, the impact of donor-specific antibodies (DSA) on longitudinal post-transplant lung function remains unclear. This study examines the effects of DSA on post-transplant lung function and the risk of baseline lung allograft dysfunction (BLAD). Research question Is DSA development linked to worse longitudinal lung function, higher BLAD rates, and poorer survival compared to DSA-negative patients regardless of the development of clinical AMR? Methods This study included lung transplant recipients from two prospective cohort studies, comparing DSA+ and DSA- patients. All participants underwent serial surveillance and clinically-indicated bronchoscopy, pulmonary function tests, and DSA testing. Statistical analysis included linear mixed models for longitudinal lung function data, multivariable logistic regression for BLAD, and survival analysis using Cox Proportional Hazard models. Results We analyzed 213 patients with a median follow-up of 48.1 months. Among them, 50.7% developed DSA. DSA+ patients showed significantly lower rates of post-transplant spirometric improvement compared to DSA- patients (p=0.008 for %FVC; p=0.02 for %FEV1). After DSA detection, there was a significant decrease in the slopes of %FVC and %FEV1 (p=0.0008 and p=0.0006, respectively). DSA+ patients had a higher risk of developing BLAD (OR 2.14, 95% CI [1.45, 3.17], p=0.0001). Additionally, DSA+ patients had a higher risk of death (HR 2.98, 95% CI [1.79, 4.99], p<0.0001). These findings were consistent even when excluding patients with clinical antibody-mediated rejection (AMR). Interpretation Our study demonstrates that DSA development significantly impairs post-transplant lung function and increases the risk of BLAD even in the absence of clinical AMR. These findings suggest that DSA may serve as a biomarker of BLAD, and could potentially aid in risk stratification following lung transplantation.

Background. A prior single-center, retrospective cohort study identified baseline lung allograft dysfunction (BLAD) as a risk factor for death in bilateral lung transplant recipients. In this multicenter prospective cohort study, we test the association of BLAD with death in bilateral lung transplant recipients, identify clinical risk factors for BLAD, and assess its association with allograft injury on the molecular level. Methods. This multicenter, prospective cohort study included 173 bilateral lung transplant recipients that underwent serial pulmonary function testing and plasma collection for donor-derived cell-free DNA at prespecified time points. BLAD was defined as failure to achieve ≥80% predicted for both forced expiratory volume in 1 s and forced vital capacity after lung transplant, on 2 consecutive measurements at least 3 mo apart. Results. BLAD was associated with increased risk of death (hazard ratio, 1.97; 95% confidence interval [CI], 1.05-3.69; P = 0.03) but not chronic lung allograft dysfunction alone (hazard ratio, 1.60; 95% CI, 0.87-2.95; P = 0.13). Recipient obesity (odds ratio, 1.69; 95% CI, 1.15-2.80; P = 0.04) and donor age (odds ratio, 1.03; 95% CI, 1.02-1.05; P = 0.004) increased the risk of developing BLAD. Patients with BLAD did not demonstrate higher log10(donor-derived cell-free DNA) levels compared with no BLAD (slope [SE]: –0.0095 [0.0007] versus –0.0109 [0.0007]; P = 0.15). Conclusions. BLAD is associated with an increased risk of death following lung transplantation, representing an important posttransplant outcome with valuable prognostic significance; however, early allograft specific injury on the molecular level does not increase the risk of BLAD, supporting further mechanistic insight into disease pathophysiology.

Rationale: The association of acute cellular rejection (ACR) with chronic lung allograft dysfunction (CLAD) in lung transplant recipients has primarily been described before consensus recommendations incorporating restrictive phenotypes. Furthermore, the association of the degree of molecular allograft injury during ACR with CLAD or death remains undefined. Objectives: To investigate the association of ACR with the risk of CLAD or death and to further investigate if this risk depends on the degree of molecular allograft injury. Methods: This multicenter, prospective cohort study included 188 lung transplant recipients. Subjects underwent serial plasma collections for donor-derived cell-free DNA (dd-cfDNA) at prespecified time points and bronchoscopy. Multivariable Cox proportional-hazards analysis was conducted to analyze the association of ACR with subsequent CLAD or death as well as the association of dd-cfDNA during ACR with risk of CLAD or death. Additional outcomes analyses were performed with episodes of ACR categorized as "high risk" (dd-cfDNA ⩾ 1%) and "low risk" (dd-cfDNA < 1%). Measurements and Main Results: In multivariable analysis, ACR was associated with the composite outcome of CLAD or death (hazard ratio [HR], 2.07 [95% confidence interval (CI), 1.05-4.10]; P = 0.036). Elevated dd-cfDNA ⩾ 1% at ACR diagnosis was independently associated with increased risk of CLAD or death (HR, 3.32; 95% CI, 1.31-8.40; P = 0.012). Patients with high-risk ACR were at increased risk of CLAD or death (HR, 3.13; 95% CI, 1.41-6.93; P = 0.005), whereas patients with low-risk status ACR were not. Conclusions: Patients with ACR are at higher risk of CLAD or death, but this may depend on the degree of underlying allograft injury at the molecular level. Clinical trial registered with www.clinicaltrials.gov (NCT02423070).

BACKGROUND:Lung transplant recipients are traditionally monitored with pulmonary function testing (PFT) and lung biopsy to detect post-transplant complications and guide treatment. Plasma donor-derived cell free DNA (dd-cfDNA) is a novel molecular approach of assessing allograft injury, including subclinical allograft dysfunction. The aim of this study was to determine if episodes of extreme molecular injury (EMI) in lung transplant recipients increases the risk of chronic lung allograft dysfunction (CLAD) or death. METHODS:This multicenter prospective cohort study included 238 lung transplant recipients. Serial plasma samples were collected for dd-cfDNA measurement by shotgun sequencing. EMI was defined as a dd-cfDNA above the third quartile of levels observed for acute rejection (dd-cfDNA level of ≥5% occurring after 45 days post-transplant). EMI was categorized as Secondary if associated with co-existing acute rejection, infection or PFT decline; or Primary if not associated with these conditions. RESULTS:EMI developed in 16% of patients at a median 343.5 (IQR: 177.3-535.5) days post-transplant. Over 50% of EMI episodes were classified as Primary. EMI was associated with an increased risk of severe CLAD or death (HR: 2.78, 95% CI: 1.26-6.22, p = 0.012). The risk remained consistent for the Primary EMI subgroup (HR: 2.34, 95% CI 1.18-4.85, p = 0.015). Time to first EMI episode was a significant predictor of the likelihood of developing CLAD or death (AUC=0.856, 95% CI=0.805-0.908, p < 0.001). CONCLUSIONS:Episodes of EMI in lung transplant recipients are often isolated and may not be detectable with traditional clinical monitoring approaches. EMI is associated with an increased risk of severe CLAD or death, independent of concomitant transplant complications.

Lung transplantation is an established management strategy for advanced end-stage lung disease with the goal of restoring normal pulmonary physiology. This principle guided our management approach to the clinical challenge of a lung transplant recipient with a small chest cavity from fibrotic lung disease. Size matching should occur based on the recipient’s predicted total lung capacity, which best reflects the recipient’s normal chest cavity size. We present an instructive case that suggests that the small chest cavity size adjusts relatively quickly toward normal once the fibrotic lungs are removed, and normal allograft is implanted.

BACKGROUND:The association between organizing pneumonia (OP) after lung transplantation with the development of acute rejection (AR) remains undefined. In addition, molecular allograft injury, as measured by donor-derived cell-free DNA (dd-cfDNA), during episodes of OP and its relationship to episodes of AR, chronic lung allograft dysfunction (CLAD), or death is unknown. METHODS:This multicenter, prospective cohort study collected serial plasma samples from 188 lung transplant recipients for dd-cfDNA at the time of bronchoscopy with biopsy. Multivariable Cox regression was used to analyze the association between OP with the development of AR (antibody-mediated rejection (AMR) and acute cellular rejection (ACR)), CLAD, and death. Multivariable models were performed to test the association of dd-cfDNA at OP with the risk of AR, CLAD, or death. RESULTS:In multivariable analysis, OP was associated with increased risk of AMR (hazard ratio (HR) = 2.26, 95% confidence interval (CI) 1.04-4.92, p = 0.040) but not ACR (HR = 1.29, 95% CI: 0.66-2.5, p = 0.45) or the composite outcome of CLAD or death (HR = 0.88, 95% CI, 0.47-1.65, p = 0.69). Median levels of dd-cfDNA were higher in OP compared to stable controls (1.33% vs 0.43%, p = 0.0006). Multivariable analysis demonstrated that levels of dd-cfDNA at diagnosis of OP were associated with increased risk of both AMR (HR = 1.29, 95% CI 1.03-1.62, p = 0.030) and death (HR = 1.16, 95% CI, 1.02-1.31, p = 0.026). CONCLUSIONS:OP is independently associated with an increased risk of AMR but not CLAD or death. The degree of molecular allograft injury at the diagnosis of OP may further predict the risk of AMR and death.

BACKGROUND: Pulmonary antibody-mediated rejection (AMR) consensus criteria categorize AMR by diagnostic certainty. This study aims to define the clinical features and associated outcomes of these recently defined AMR categories.METHODS: Adjudication committees reviewed clinical data of 335 lung transplant recipients to define clinical or subclinical AMR based on the presence of allograft dysfunction, and the primary endpoints, time from transplant to allograft failure, a composite endpoint of chronic lung allograft dysfunction and/or death. Clinical AMR was subcategorized based on diagnostic certainty as definite, probable or possible AMR if 4, 3, or 2 characteristic features were present, respectively. Allograft injury was assessed via plasma donor-derived cell-free DNA (ddcfDNA). Risk of allograft failure and allograft injury was compared for AMR categories using regression models.RESULTS: Over the 38.5 months follow-up, 28.7% of subjects developed clinical AMR (n = 96), 18.5% developed subclinical AMR (n = 62) or 58.3% were no AMR (n = 177). Clinical AMR showed higher risk of allograft failure and ddcfDNA levels compared to subclinical or no AMR. Clinical AMR included definite/probable (n = 21) or possible AMR (n = 75). These subcategories showed similar clin-ical characteristics, ddcfDNA levels, and risk of allograft failure. However, definite/probable AMR showed greater measures of AMR severity, including degree of allograft dysfunction and risk of death compared to possible AMR. CONCLUSIONS: Clinical AMR showed greater risk of allograft failure than subclinical AMR or no AMR. Subcategorization of clinical AMR based on diagnostic certainty correlated with AMR severity and risk of death, but not with the risk of allograft failure. J Heart Lung Transplant 2023;42:226-235 (c) 2022 International Society for Heart and Lung Transplantation. All rights reserved.

The development of donor-specific antibodies after lung transplantation is associated with downstream acute cellular rejection, antibody-mediated rejection (AMR), chronic lung allograft dysfunction (CLAD), or death. It is unknown whether preemptive (early) treatment of de novo donor-specific antibodies (dnDSAs), in the absence of clinical signs and symptoms of allograft dysfunction, reduces the risk of subsequent CLAD or death. We performed a multicenter, retrospective cohort study to determine if early treatment of dnDSAs in lung transplant patients reduces the risk of the composite endpoint of CLAD or death. In the cohort of 445 patients, 145 patients developed dnDSAs posttransplant. Thirty patients received early targeted treatment for dnDSAs in the absence of clinical signs and symptoms of AMR. Early treatment of dnDSAs was associated with a decreased risk of CLAD or death (hazard ratio, 0.36; 95% confidence interval, 0.17-0.76; P < .01). Deferring treatment until the development of clinical AMR was associated with an increased risk of CLAD or death (hazard ratio, 3.00; 95% confidence interval, 1.46-6.18; P < .01). This study suggests that early, preemptive treatment of donor-specific antibodies in lung transplant patients may reduce the subsequent risk of CLAD or death.

Plasma donor-derived cell-free DNA (dd-cfDNA) is a sensitive biomarker for the diagnosis of acute rejection in lung transplant recipients; however, differences in dd-cfDNA levels between single and double lung transplant remains unknown. We performed an observational analysis that included 221 patients from two prospective cohort studies who had serial measurements of plasma dd-cfDNA at the time of bronchoscopy and pulmonary function testing, and compared dd-cfDNA between single and double lung transplant recipients across a range of disease states. Levels of dd-cfDNA were lower for single vs. double lung transplant in stable controls (median [IQR]: 0.15% [0.07, 0.44] vs. 0.46% [0.23, 0.74], p < .01) and acute rejection (1.06% [0.75, 2.32] vs. 1.78% [1.18, 5.73], p = .05). Doubling dd-cfDNA for single lung transplant to account for differences in lung mass eliminated this difference. The area under the receiver operating curve (AUC) for the detection of acute rejection was 0.89 and 0.86 for single and double lung transplant, respectively. The optimal dd-cfDNA threshold for the detection of acute rejection was 0.54% in single lung and 1.1% in double lung transplant. In conclusion, accounting for differences in dd-cfDNA in single versus double lung transplant is key for the interpretation of dd-cfDNA testing in research and clinical settings.

Pulmonary chronic graft-versus-host disease (PcGVHD) is a devastating complication of allogeneic hematopoietic stem cell transplant (HCT). The 2014 National Institutes of Health cGVHD consensus criteria (NIH criteria) only captures bronchiolitis obliterans syndrome (BOS). In this study, we adapted the 2019 International Society for Heart and Lung Transplantation (ISHLT) criteria of chronic lung allograft dysfunction (CLAD) to define novel phenotypes of PcGVHD and compared the performance of this criteria with the NIH criteria to identify patients with high-risk PcGVHD. We reviewed consecutive patients in a cGVHD natural history protocol (#NCT00092235) and adapted the 2019 CLAD criteria (the adapted criteria) to define PcGVHD as post-HCT forced expiratory volume at 1 second < 80% predicted value, with 4 phenotypes: obstructive, restrictive, mixed obstructive/restrictive, and undefined. An independent adjudication committee evaluated subjects for diagnosis and phenotyping. We identified 166 (47.4%) patients who met the adapted criteria, including obstruction (n = 12, 3.4%), restriction (n = 67, 19.1%), mixed obstruction/restriction (n = 47, 13.4%), and undefined (n = 40, 11.4%). In these patients, less than half (n = 78) met the NIH criteria for BOS (NIH+); the rest (n = 88) did not (NIH-). The NIH- subjects showed increased risk of death compared with those without PcGVHD (hazard ratio = 1.88, 95% confidence interval = 1.20-2.95; P = .006) that was similar to NIH+ subjects (P = .678). Our study demonstrated the potential of the adapted criteria in identifying patients with high-risk PcGVHD that have been missed by the NIH criteria. The adapted criteria could become a valuable tool to better phenotype and study lung disease in cGVHD.

Purpose Pleuroparenchymal fibroelastosis (PPFE) is a rare entity of interstitial lung disease previously reported in both lung and hematopoietic stem cell transplant (HCT) recipients. The association between PPFE and chronic Graft-versus-Host Disease (cGVHD) has not been established. Methods Patients on cGVHD protocols (NCT00092235; NCT02669251) between 10/01/2004 and 01/31/2020 were included. An independent committee of two transplant hematologists, one cardiothoracic radiologist, and three transplant pulmonologists reviewed patients' demographic and HCT information, pulmonary function tests (PFT), and thoracic CT scans. The diagnosis of PPFE was adapted from the 2013 ATS/ERS Interstitial Lung Disease Consensus Statement (Table 1). Results PPFE was diagnosed in 0.8% (3/374) of patients (Table 2). All were female with body mass index (BMI) <18.5kg/m2. Patients 2 and 3 had classical Hodgkin lymphoma (cHL) with intrathoracic involvement, received bleomycin (patient 2 and 3) and mediastinal radiation (patient 2) prior to HCT. All had severe cGVHD, requiring 1-5 lines of systemic immunosuppressive therapy. Before the development of PPFE, Patients 2 and 3 had viral pneumonia, while patient 1 had no documented pulmonary infection. Lung biopsies in all patients showed non-specific inflammation and fibrosis; of note, all were performed before the definition of PPFE as a clinical entity in 2013, and did not include the pleura or subpleural parenchyma. At data cut-off (April 2021), all patients were alive. Median time from HCT to PPFE diagnosis was 5.5 years (range, 2-6.5), and median survival post-PPFE diagnosis was 7.5 years (range, 5.5-12). Conclusion PPFE is a rare, delayed complication of HCT which can be seen with concurrent cGVHD. The pathogenesis of PPFE is unclear but may be associated with the immune-mediated lung injury in cGVHD, infection, preexisting malignancy and lung-toxic treatment. Heightened clinical awareness for PPFE among the cGVHD population warrants further study.

We appreciate the commentary by Sheshadri et al 1 regarding our manuscript entitled “ The ISHLT chronic lung allograft dysfunction consensus criteria are applicable to pulmonary chronic graft-versus-host disease. ” We concur with Sheshadri et al and highlighted in the limitations portion of our manuscript that the concept of pulmonary chronic graft-versus-host disease (pcGVHD) cannot be broadened to include all the pulmonary complications that might occur after hematopoietic stem cell transplantation (HSCT), especially restrictive lung diseases, before a clear causative and clinical relationship is success-fully established between cGVHD and the respective pulmonary disease after HSCT. The goal of our research was to propose a tool for further deciphering lung abnormalities in patients with cGVHD. We anticipated that the study would increase the awareness of pulmonary complications in HSCT recipients and trigger further investigation into the pathophysiology, diagnosis, risk strati fi cation, prevention, and treatment of different forms of lung disease in patients with cGVHD. As highlighted by Sheshadri et al and as summarized in our study limitations, our study did not aim to establish the causality between cGVHD and the proposed pcGVHD phenotypes, time of onset, pheno-typical distribution, and post-pcGVHD survival. In our study, 75% of the cohort had severe cGVHD according to a National Institutes of Health global score, and 80% of the cohort did not have pre-HSCT or longitudinal pulmonary function data. Furthermore, we lacked a non-cGVHD control group. Therefore, large-scale, multicenter longitudinal studies that enroll HSCT recipients with or without cGVHD who undergo frequent pulmonary function testing are needed to validate the results of our study and shed more light on the clinical manifestation, time of onset, phenotype distribution, and pathophysiology of the pulmonary complications we observed in patients with cGVHD. Such information is important for validat-ing the utility of the tool proposed in our study.

INTRODUCTION The clinical course of coronavirus 2019 (COVID-19) is heterogeneous, ranging from mild to severe multiorgan failure and death. In this study, we analyzed cell-free DNA (cfDNA) as a biomarker of injury to define the sources of tissue injury that contribute to such different trajectories. METHODS We conducted a multicenter prospective cohort study to enroll patients with COVID-19 and collect plasma samples. Plasma cfDNA was subject to bisulfite sequencing. A library of tissue-specific DNA methylation signatures was used to analyze sequence reads to quantitate cfDNA from different tissue types. We then determined the correlation of tissue-specific cfDNA measures to COVID-19 outcomes. Similar analyses were performed for healthy controls and a comparator group of patients with respiratory syncytial virus and influenza. RESULTS We found markedly elevated levels and divergent tissue sources of cfDNA in COVID-19 patients compared with patients who had influenza and/or respiratory syncytial virus and with healthy controls. The major sources of cfDNA in COVID-19 were hematopoietic cells, vascular endothelium, hepatocytes, adipocytes, kidney, heart, and lung. cfDNA levels positively correlated with COVID-19 disease severity, C-reactive protein, and D-dimer. cfDNA profile at admission identified patients who subsequently required intensive care or died during hospitalization. Furthermore, the increased cfDNA in COVID-19 patients generated excessive mitochondrial ROS (mtROS) in renal tubular cells in a concentration-dependent manner. This mtROS production was inhibited by a TLR9-specific antagonist. CONCLUSION cfDNA maps tissue injury that predicts COVID-19 outcomes and may mechanistically propagate COVID-19–induced tissue injury. FUNDING Intramural Targeted Anti–COVID-19 grant, NIH.

Background: Although bronchiolitis obliterans syndrome (BOS) is a well described manifestation of pulmonary involvement by chronic graft-versus-host disease (PcGvHD), additional pulmonary phenotypes of PcGvHD beyond BOS have not been well-characterized. PcGvHD and chronic lung allograft dysfunction (CLAD) in lung transplant recipients share similar pathophysiological mechanisms. We aim to use an adaptation of the International Society for Heart and Lung Transplantation (ISHLT) CLAD Consensus Criteria to describe PcGvHD phenotypes beyond BOS in order to improve the diagnosis and classification of PcGvHD.