Joe L. Hsu

Background/objectives: Transplant-related pulmonary fibrosis (TPF) occurs after allogeneic hematopoietic cell transplant and after lung transplantation. Effective therapies that prevent or reverse established transplant-related airway fibrosis remain limited. Human cell-based models are valuable for initial drug screening, but complementary in vivo models are needed to evaluate treatment responses in the presence of an allogeneic graft, an intact recipient immune system, systemic drug exposure, and multicellular tissue remodeling. This study evaluated murine orthotopic tracheal transplantation (OTT) as a practical in vivo platform for antifibrotic drug testing, using pirfenidone as a benchmark antifibrotic intervention. Methods: C57BL/6J mice underwent syngeneic or allogeneic OTT and received vehicle or pirfenidone (250 mg/kg daily) from day 21 to 30 posttransplant. Explanted grafts were analyzed for the expression of alpha-smooth muscle actin (α-SMA), fibronectin 1 (Fn1), collagen type I alpha 1 chain (Col1a1), and tenascin C (Tnc) by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Total collagen content was assessed by measuring hydroxyproline levels using a colorimetric hydroxyproline assay. Results: Pirfenidone normalized the expression of α-SMA, Fn1, Col1a1 and Tnc to levels comparable to those of syngeneic controls and significantly reduced hydroxyproline (p < 0.0001). Conclusions: Using pirfenidone as a benchmark antifibrotic, the murine OTT model detected concordant treatment-associated reductions in profibrotic gene expression and collagen content. These findings support the feasibility and pharmacodynamic responsiveness of OTT as an in vivo platform for secondary-stage antifibrotic drug testing. Additional investigational therapies will be required to establish the broader generalizability and predictive performance of the platform.

Organising pneumonia (OP) is a late, non‐infectious pulmonary complication that occurs following haematopoietic cell transplant (HCT) and may be associated with chronic graft‐versus‐host‐disease (cGVHD). Treatment typically involves protracted courses of corticosteroids that are associated with dose‐limiting adverse effects and pulmonary exacerbations upon corticosteroid tapering. Here, we describe the case of a 43‐year‐old male with OP associated with cGVHD who experienced difficulty tapering prednisone, complicated by frequent OP exacerbations. Weekly home spirometry was used to closely monitor trends in pulmonary function and help successfully guide the prednisone taper. Ultimately, prednisone dose was reduced by 80% while maintaining clinical and functional stability.

Bronchiolitis obliterans syndrome (BOS) is a severe form of chronic graft-versus-host disease (cGVHD) following allogeneic hematopoietic cell transplant (HCT), with a 5-year survival rate of 40%. Currently, there is no curative therapy for BOS. Preclinical data suggest that pirfenidone, an antifibrotic drug, may benefit small airway fibrosis in HCT-associated BOS. A single-arm, open-label, 56-week phase 1 trial with 56-month extension evaluated pirfenidone’s tolerability, safety, and efficacy in patients with BOS. Efficacy was measured using pulmonary function tests (PFTs), quantitative computed tomography (qCT) scans, patient-reported outcomes (PROs), cGVHD indices, and laboratory tests. Lung function trajectory was assessed by change in regression slopes before and during treatment. Baseline qCT metrics, including percentage normal lung, air trapping, volume change (Jacobian), and heterogeneity of volume change (Jacobian variance), were analyzed by participant response. Of 30 participants, 25 completed the 56-week trial, and 10 continued into the extension. Overall, 63% tolerated the recommended dose without safety concerns. There was significant improvement in the percent predicted forced expiratory volume in 1 second (P = .00267) when analyzing all participants, and improvement in individual PFT trend for 41.3% of participants. qCT analysis by lobe showed healthier lungs in the upper lobes of responders. Significant improvements were noted in liver function tests, PROs related to physical functioning and shortness of breath, and cGVHD skin indices. These findings indicate that pirfenidone is safe and tolerable in patients with BOS after HCT and may improve lung function and symptoms. Further trials are warranted to evaluate the efficacy of pirfenidone as a treatment for BOS after HCT. This trial was registered at www.ClinicalTrials.gov as #NCT03315741.

Rationale: Allergic bronchopulmonary aspergillosis (ABPA) is a hypersensitivity disease triggered by inhaled Aspergillus ­fumigatus (Af) spores (i.e., conidia), in persons with cystic fibrosis (CF). High iron levels have been commonly described in CF respiratory secretions. Af proteases cause a severe allergic immune response, leading to pulmonary exacerbations and progressive lung function decline. The stimuli that promote Af proteases in ABPA are poorly understood. Objectives: Determine if airway iron is a critical factor in CF-ABPA by regulating fungal protease production. Methods: We used transcriptomics and proteomics to investigate the role of iron in stimulating the production of Af proteases and evaluated the impact of these iron-induced Af proteases on the Th2 immune response in CF bronchial epithelial (CFBE) cells and in a CF-ABPA mouse model. Measurements and Main Results: Transcriptional analysis showed a significant upregulation of Af proteases with exposure to iron and a downregulation with iron chelation. This finding was validated in secretome studies showing that Af-culture filtrates (Af-cf) from iron-exposed conidia contained significantly higher levels of 14 proteases compared to controls. Exposure to iron-primed Af-cf increased the production of Th2 promoting cytokines (IL-33, IL-25 and TSLP) in CFBE cells compared to the wild type cells. In vivo, inoculation of CF mice with iron-primed Af conidia led to higher levels of serum IgE and Th2 cytokines (IL-4, IL-5, IL-9, IL-13) in lung tissue. Conclusions: These findings suggest that airway iron is a potent stimulus for Af proteases and represents a modifiable risk factor and potential therapeutic target for CF-ABPA.

Background: Bronchiolitis obliterans syndrome (BOS) is a late-onset noninfectious pulmonary complication of allogeneic hematopoietic cell transplant (HCT) that is often diagnosed at an advanced stage with severe lung impairment. Increasing use of HCT for the treatment of hematologic diseases worldwide translates to an increasing burden of BOS, particularly for the community pulmonologist. Early recognition of BOS, which offers the best opportunity to mitigate morbidity and mortality, is hampered by incomplete knowledge of the clinical course and disease process. The goal of this research statement is to survey our current understanding of BOS and to define the research agenda for the early detection of BOS. Methods: We convened a multidisciplinary panel that included community representatives for an in-depth survey of the published literature followed by an online workshop. Results: Major knowledge gaps were identified within interrelated themes of natural history and pathogenesis, risk factors, and the clinical diagnostic approach. Conclusions: This statement reflects the detailed assessment of identified knowledge gaps with associated key research questions, as well as a proposed research road map to stimulate cross-disciplinary collaborations from preclinical to clinical investigations.

Immune suppression heightens the risk for fungal infections, but the mechanisms that result in clinical disease are poorly understood. Here we demonstrate that macrophage ferroptosis, an iron-dependent form of regulated cell death, inhibits Aspergillus fumigatus ( Af ) killing. In a mouse tracheal transplant model of Af infection, we observed an increase in macrophage lipid peroxidation, a decreased expression of negative ferroptosis regulators Gpx4 and Slc7a11 , and an increase in positive regulators Ptgs2 and Nox2 , relative to syntransplants. Depletion of macrophages in transplant recipients decreased Af invasion. In vitro , iron overload reduced macrophage viability and decreased their capability to kill Af spores, through a decrease in lysosomal acidification and lysosomal loss. Treatment with ferrostatin-1, a ferroptosis inhibitor, and deferasirox (an iron chelator) restored Af killing. Ferroptotic alveolar macrophages isolated from lung transplant patients also showed a decreased ability to kill Af spores and the patients’ bronchoalveolar lavage was characterized by higher iron levels and markers of ferroptotic stress compared to non-lung transplants. These characteristics were strongly correlated with a clinical history of fungal infections, independent of immune suppressive medications. Our findings indicate that macrophage ferroptosis augments the risk of invasive aspergillosis, representing a novel mechanism for host immune dysfunction. Graphical Schematic of proposed mechanism underlying ferroptosis induced immune dysregulation and increased Af invasion in lung transplantation.

Bronchiolitis obliterans syndrome (BOS) after hematopoietic cell transplantation (HCT) is associated with substantial morbidity and mortality. Quantitative computed tomography (qCT) can help diagnose advanced BOS meeting National Institutes of Health (NIH) criteria (NIH-BOS) but has not been used to diagnose early, often asymptomatic BOS (early BOS), limiting the potential for early intervention and improved outcomes. Using pulmonary function tests (PFTs) to define NIH-BOS, early BOS, and mixed BOS (NIH-BOS with restrictive lung disease) in patients from 2 large cancer centers, we applied qCT to identify early BOS and distinguish between types of BOS. Patients with transient impairment or healthy lungs were included for comparison. PFTs were done at month 0, 6, and 12. Analysis was performed with association statistics, principal component analysis, conditional inference trees (CITs), and machine learning (ML) classifier models. Our cohort included 84 allogeneic HCT recipients, 66 with BOS (NIH-defined, early, or mixed) and 18 without BOS. All qCT metrics had moderate correlation with forced expiratory volume in 1 second, and each qCT metric differentiated BOS from those without BOS (non-BOS; P < .0001). CITs distinguished 94% of participants with BOS vs non-BOS, 85% of early BOS vs non-BOS, 92% of early BOS vs NIH-BOS. ML models diagnosed BOS with area under the curve (AUC) of 0.84 (95% confidence interval [CI], 0.74-0.94) and early BOS with AUC of 0.84 (95% CI, 0.69-0.97). qCT metrics can identify individuals with early BOS, paving the way for closer monitoring and earlier treatment in this vulnerable population.