Chronic Lung Allograft Rejection Research Articles

QuantiFERON CMV Test and CMV Serostatus in Lung Transplant: Stratification Risk for Infection, Chronic and Acute Allograft Rejection.

The QuantiFERON CMV (QCMV) test evaluates specific adaptive immune system activity against CMV by measuring IFN-γ released by activated CD8+ T lymphocytes. We aimed to evaluate the QCMV test as a predictive tool for CMV manifestations and acute or chronic lung allograft rejection (AR and CLAD) in lung transplant (LTx) patients. A total of 73 patients were divided into four groups based on donor and recipient (D/R) serology for CMV and QCMV assay: group A low-risk for CMV infection and disease (D-/R-); group B and C at intermediate-risk (R+), group B with non-reactive QCMV and group C with reactive QCMV; group D at high-risk (D+/R-). Group D patients experienced higher viral replication; no differences were observed among R+ patients of groups B and C. D+/R- patients had a higher number of AR events and group C presented a lower incidence of AR. Prevalence of CLAD at 24 months was higher in group B with a higher risk of CLAD development (OR 6.33). The QCMV test allows us to identify R+ non-reactive QCMV population as the most exposed to onset of CLAD. This population had a higher, although non-significant, susceptibility to AR compared to the R+ population with reactive QCMV.

Hepatitis C viremic lung transplantation to aviremic recipients: Comprehensive outcomes and post-transplant viremia.

Direct-acting antiviral (DAA) therapy has revolutionized solid organ transplantation by providing an opportunity to utilize organs from HCV-viremic donors. Though transplantation of HCV-viremic donor organs into aviremic recipients is safe in the short term, midterm data on survival and post-transplant complications is lacking. We provide a midterm assessment of complications of lung transplantation (LT) up to 2 years post-transplant, including patient and graft survival between HCV-viremic transplantation (D+) and HCV-aviremic transplantation (D-). This is a retrospective cohort study including 500 patients from 2018 to 2022 who underwent LT at our quaternary care institution. Outcomes of patients receiving D+ grafts were compared to those receiving D- grafts. Recipients of HCV antibody+ but PCR- grafts were treated as D- recipients. We identified 470 D- and 30 D+ patients meeting inclusion criteria. Crude mortality did not differ between groups (p=.43). Patient survival at years 1 and 2 did not differ between D+ and D- patients (p=.89, p=.87, respectively), and graft survival at years 1 and 2 did not differ between the two groups (p=.90, p=.88, respectively). No extrahepatic manifestations or fibrosing cholestatic hepatitis (FCH) occurred among D+ recipients. D+ and D- patients had similar rates of post-transplant chronic lung allograft rejection (CLAD) (p=6.7%vs. 12.8%, p=.3), acute cellular rejection (60.0%vs. 58.0%, p=.8) and antibody-mediated rejection (16.7%vs. 14.2%, p=.7). There is no difference in midterm patient or graft survival between D+ and D-LT. No extrahepatic manifestations of HCV occurred. No differences in any type of rejection including CLAD were observed, though follow-up for CLAD was limited. These results provide additional support for the use of HCV-viremic organs in selected recipients in LT.

(86) - Divergent Transcriptional Features of Obstructive and Restrictive Forms of Chronic Lung Allograft Rejection Modeled in a Single Mouse Strain Combination

(86) - Divergent Transcriptional Features of Obstructive and Restrictive Forms of Chronic Lung Allograft Rejection Modeled in a Single Mouse Strain Combination

Donor IL-17 receptor A regulates LPS-potentiated acute and chronic murine lung allograft rejection.

Chronic lung allograft dysfunction (CLAD) is a major complication after lung transplantation that results from a complex interplay of innate inflammatory and alloimmune factors, culminating in parenchymal and/or obliterative airway fibrosis. Excessive IL-17A signaling and chronic inflammation have been recognized as key factors in these pathological processes. Herein, we developed a model of repeated airway inflammation in mouse minor alloantigen-mismatched single-lung transplantation. Repeated intratracheal LPS instillations augmented pulmonary IL-17A expression. LPS also increased acute rejection, airway epithelial damage, and obliterative airway fibrosis, similar to human explanted lung allografts with antecedent episodes of airway infection. We then investigated the role of donor and recipient IL-17 receptor A (IL-17RA) in this context. Donor IL-17RA deficiency significantly attenuated acute rejection and CLAD features, whereas recipient IL-17RA deficiency only slightly reduced airway obliteration in LPS allografts. IL-17RA immunofluorescence positive staining was greater in human CLAD lungs compared with control human lung specimens, with localization to fibroblasts and myofibroblasts, which was also seen in mouse LPS allografts. Taken together, repeated airway inflammation after lung transplantation caused local airway epithelial damage, with persistent elevation of IL-17A and IL-17RA expression and particular involvement of IL-17RA on donor structural cells in development of fibrosis.

Lung Transplant Recipients and COVID-19: Report of Two Cases.

Although the WHO has declared the end of the pandemic emergency, COVID-19 still poses a threat to immunocompromised patients. The COVID-19 pandemic has spread throughout the world over the last two years, causing a significant number of deaths. After three years, SARS-CoV-2 has lost its initial lethality but has shown a significantly worse prognosis for immunocompromised patients, especially those who have undergone lung transplantation, compared with the general population. This paper presents two compelling case studies that highlight the complex challenges of COVID-19 infection in lung transplant recipients. The first case involves a patient who received a bilateral lung transplant for pulmonary artery hypertension in 2009, followed by a kidney transplant in 2022. Surprisingly, despite an initially favorable clinical course after contracting COVID-19, the patient deteriorated rapidly and died within a few days due to extensive lung involvement. This case highlights the unpredictable nature of COVID-19 and its potentially devastating impact on lung transplant recipients. The second case involves a patient who underwent bilateral lung transplantation five years earlier for chronic obstructive pulmonary disease (COPD). This individual also contracted COVID-19 and had pre-existing complications, including chronic lung allograft rejection (CLAD) and diffuse bronchial stenosis. Following viral infection, the patient's clinical condition deteriorated rapidly, with worsening bronchial stenosis. This case highlights the ability of COVID-19 to exacerbate pre-existing pulmonary complications in transplant recipients. These cases highlight the urgent need for increased vigilance and tailored management strategies when dealing with COVID-19 in lung transplant recipients. The unpredictable and detrimental course of the disease observed in these patients highlights the importance of implementing stringent preventive measures, such as vaccination and strict adherence to infection control protocols, in this vulnerable population. Further research is essential to gain a full understanding of the unique dynamics of COVID-19 in lung transplant recipients and to develop targeted interventions to improve their outcomes.

A Breath of Fresh Air - Lung Transplantation Has Come of Age

A boundless spectrum of chronic lung diseases is said to effect over 500 million persons globally. Lung transplantation is a well-established therapeutic option for patients suffering from end-stage lung diseases, however waitlist mortality and primary graft failure remain major determinants as post-transplantation 5-year survival is just above 50 percent. Recent innovations in lung transplantation have been aimed at increasing organ availability, improving allograft quality, function, and longevity. Ex-vivo Lung Perfusion (EVLP) is an exciting modality responsible for multiple paths of lung allograft reconditioning as well as significantly extending preservation times. Mechanical circulatory support (MCS), specifically extracorporeal membrane oxygenation (ECMO) has consistently gained popularity not only for its use as a bridge to transplantation, but also its intraoperative role. In tandem, EVLP and ECMO have shown promising results in increasing the number of lung transplantations performed, therefore decreasing waitlist mortality. Primary graft dysfunction (PGD) and chronic lung allograft rejection (CLAD) continue to be the most feared predictors of poor outcomes. In this review we will highlight the historical progression of lung transplantation, its encumbrance, and the most recent advancements in promising techniques for long-term allograft protection and patient survival.

Downregulation of a tumor suppressor gene LKB1 in lung transplantation as a biomarker for chronic murine lung allograft rejection.

We recently demonstrated decreased tumor suppressor gene liver kinase B1 (LKB1) level in lung transplant recipients diagnosed with bronchiolitis obliterans syndrome. STE20-related adaptor alpha (STRADα) functions as a pseudokinase that binds and regulates LKB1 activity. A murine model of chronic lung allograft rejection in which a single lung from a B6D2F1 mouse was orthotopically transplanted into a DBA/2J mouse was employed. We examined the effect of LKB1 knockdown using CRISPR-CAS9 in vitro culture system. Significant downregulation of LKB1 and STRADα expression was found in donor lung compared to recipient lung. STRADα knockdown significantly inhibited LKB1, pAMPK expression but induced phosphorylated mammalian target of rapamycin (mTOR), fibronectin, and Collagen-I, expression in BEAS-2B cells. LKB1 overexpression decreased fibronectin, Collagen-I, and phosphorylated mTOR expression in A549 cells. We demonstrated that downregulation of LKB1-STRADα pathway accompanied with increased fibrosis, results in development of chronic rejection following murine lung transplantation.

(238) Downregulation of LKB1-Stradα Pathway in Circulating Exosomes as a Biomarker for Chronic Murine Lung Allograft Rejection

(238) Downregulation of LKB1-Stradα Pathway in Circulating Exosomes as a Biomarker for Chronic Murine Lung Allograft Rejection

The mitigating effect of exogenous carbon monoxide on chronic allograft rejection and fibrosis post-lung transplantation.

Small airway inflammation and fibrosis or bronchiolitis obliterans (BO) is the predominant presentation of chronic lung allograft dysfunction (CLAD) post-lung transplantation. Carbon monoxide (CO) is a critical endogenous signaling transducer with known anti-inflammatory and anti-fibrotic effects but its therapeutic potential in CLAD remains to be fully elucidated. Here we investigate the effect of inhaled CO in modulating chronic lung allograft rejection pathology in a murine orthotopic lung transplant model of BO (B6D2F1/J→DBA/2J). Additionally, the effects of CO on the activated phenotype of mesenchymal cells isolated from human lung transplant recipients with CLAD were studied. Murine lung allografts treated with CO (250 ppm×30 minutes twice daily from days 7 to 40 post-transplantation) demonstrated decreased immune cell infiltration, fibrosis, and airway obliteration by flow cytometry, trichrome staining, and morphometric analysis, respectively. Decreased total collagen, with levels comparable to isografts, was noted in CO-treated allografts by quantitative hydroxyproline assay. In vitro, CO (250 ppm×16h) was effective in reversing the fibrotic phenotype of human CLAD mesenchymal cells with decreased collagen I and β-catenin expression as well as an inhibitory effect on ERK1/2 MAPK, and mTORC1/2 signaling. Sildenafil, a phosphodiesterase 5 inhibitor, partially mimicked the effects of CO on CLAD mesenchymal cells and was partially effective in decreasing collagen deposition in murine allografts, suggesting the contribution of cGMP-dependent and -independent mechanisms in mediating the effect of CO. These results suggest a potential role for CO in alleviating allograft fibrosis and mitigating chronic rejection pathology post-lung transplant.

Cross-Regulation of F-Box Protein FBXL2 with T-bet and TNF-α during Acute and Chronic Lung Allograft Rejection.

Chronic lung allograft dysfunction is the major barrier to long-term survival in lung transplant recipients. Evidence supports type 1 alloimmunity as the predominant response in acute/chronic lung rejection, but the immunoregulatory mechanisms remain incompletely understood. We studied the combinatorial F-box E3 ligase system: F-box protein 3 (FBXO3; proinflammatory) and F-box and leucine-rich repeat protein 2 (FBXL2; anti-inflammatory and regulates TNFR-associated factor [TRAF] protein). Using the mouse orthotopic lung transplant model, we evaluated allografts from BALB/c → C57BL/6 (acute rejection; day 10) and found significant induction of FBXO3 and diminished FBXL2 protein along with elevated T-bet, IFN-γ, and TRAF proteins 1-5 compared with isografts. In the acute model, treatment with costimulation blockade (MR1/CTLA4-Ig) resulted in attenuated FBXO3, preserved FBXL2, and substantially reduced T-bet, IFN-γ, and TRAFs 1-5, consistent with a key role for type 1 alloimmunity. Immunohistochemistry revealed significant changes in the FBXO3/FBXL2 balance in airway epithelia and infiltrating mononuclear cells during rejection compared with isografts or costimulation blockade-treated allografts. In the chronic lung rejection model, DBA/2J/C57BL/6F1 > DBA/2J (day 28), we observed persistently elevated FBXO3/FBXL2 balance and T-bet/IFN-γ protein and similar findings from lung transplant recipient lungs with chronic lung allograft dysfunction versus controls. We hypothesized that FBXL2 regulated T-bet and found FBXL2 was sufficient to polyubiquitinate T-bet and coimmunoprecipitated with T-bet on pulldown experiments and vice versa in Jurkat cells. Transfection with FBXL2 diminished T-bet protein in a dose-dependent manner in mouse lung epithelial cells. In testing type 1 cytokines, TNF-α was found to negatively regulate FBXL2 protein and mRNA levels. Together, our findings show the combinatorial E3 ligase FBXO3/FBXL2 system plays a role in the regulation of T-bet through FBXL2, with negative cross-regulation of TNF-α on FBXL2 during lung allograft rejection.

Reduction of Immunosuppression Based on Whole Blood EBV-Viral Loads in Lung Transplant Recipients

<h3>Purpose</h3> Post-transplant lymphoproliferative disorder (PTLD) is a rare but serious complication of transplantation affecting 10% of lung transplant recipients with an overall survival of 39%. Reduction of immunosuppression (RIS) for clinically suspected PTLD is included in guidelines for the treatment of PTLD. Pre-emptive RIS based on EBV DNA load is controversial with small scale studies with anecdotal evidence guiding clinical practice. We evaluated our policy of pre-emptive RIS for PTLD incidence, acute rejection, survival and CLAD in a patient control study. <h3>Methods</h3> 26 patients underwent RIS, eight of these patients received prophylactic rituximab. 52 patients were matched for age, date of transplantation, gender, and cystic fibrosis. 26 of these patients were additionally chosen for high EBV-DNA load. Risk of PTLD, acute rejection, overall survival and CLAD was analysed using Kaplan-Meier survival analysis. <h3>Results</h3> EBV DNA loads were different between the groups (p<0.001) with the RIS group having the highest level and more primary EBV infections (table 1). Acute rejection was seen 7.3 years after RIS and 11.7 and 12.3 in the matched groups (p=0,1). Overall CLAD developed earlier in the RIS group but only years after RIS (table 1). Survival and development of PTLD were not different between the groups. Time to PTLD from RIS was also not different (p=0.5, log-rank test). <h3>Conclusion</h3> Pre-emptive RIS based on EBV DNA load did not lead to a concomitant increase in acute rejection episodes, a change in overall survival or a short term increase in chronic lung allograft rejection (CLAD) diagnosis. We conclude that RIS was safe although this analysis cannot prove a reduction in the incidence of PTLD in this high risk PTLD group. A prospective randomized study for EBV DNA guided RIS possibly with pre-emptive rituximab is needed.

Transcriptional Landscape of Chronic Lung Allograft Rejection in Humans

<h3>Purpose</h3> Chronic lung allograft dysfunction (CLAD) remains the main barrier to long-term survival after lung transplant. The main phenotypes of CLAD are bronchiolitis obliterans syndrome (BOS) with small airway fibrosis, and restrictive allograft syndrome (RAS) with extensive lung parenchymal fibrosis. Mechanisms of CLAD and the pathways active in BOS/RAS remain poorly understood. We hypothesized that bulk RNA sequencing (seq) of human CLAD lungs would help uncover pro-fibrotic pathways and phenotype-specific mechanisms. <h3>Methods</h3> At time of retransplantation, we obtained CLAD lung tissue from 27 BOS and 18 RAS. Negative controls included donor lungs (18) and lobectomy samples done for suspected cancers (14); positive controls came from patients with idiopathic pulmonary fibrosis (IPF) (19). RNA was extracted and submitted for bulk RNAseq at a depth of 50 million paired-end 100-base-pair reads. Differentially expressed genes were detected using DESeq2 and NOIseq. <h3>Results</h3> Top differentially expressed genes in CLAD vs. negative controls included genes involved in cell-matrix interactions (COL10A1, ADAM9) and cell proliferation (CST, MDK). Gene Ontology analysis showed higher expression of genes associated with fibrosis and motility, whereas genes involved in defense and immunity were decreased due to immunosuppression in CLAD vs. negative controls. Analyses to compare RAS to BOS are ongoing. As we anticipated an imperfect correlation between clinical phenotypes and transcriptomic endotypes, we performed unsupervised clustering of all samples. A subset of RAS/mixed samples clustered together and in close proximity to IPF, while other distinct clusters appeared independent of clinical phenotypes: These transcriptomic endotypes will merit further exploration. <h3>Conclusion</h3> This large cohort of lung samples allows a detailed analysis of the lung allograft transcriptome in different phenotypes of CLAD, enabling identification of the top differentially expressed genes and pathways in this poorly understood condition.

MNK/eIF4E Ser209 Inhibitor eFT-508 Prevents and Therapeutically Treats Fibrosis in a Murine Model of Restrictive Chronic Lung Allograft Rejection

<h3>Purpose</h3> Lung transplant is limited by poor outcomes due to chronic lung allograft dysfunction, CLAD. A fulminant CLAD phenotype, restrictive allograft syndrome (RAS), with limited therapies underscores the need to understand underlying mechanisms. MNK1 kinase is a key translational regulator of cellular functions via eIF4E serine 209 phosphorylation. Here we investigate the role of MNK/eIF4E Ser209 in mesenchymal cell activation and the therapeutic effectiveness of eFT-508 in a murine model of RAS. <h3>Methods</h3> Human lung allograft derived MCs treated with eFT-508 (10uM x 24h) were immunoblotted for collagen I, alpha smooth muscle actin, CD44, autotaxin. A modified boyden chamber assay was utilized for migration. We recently reported a murine RAS model, B6D2F1/J into C57BL6/J. Mice were administered eFT-508 5mg/kg/daily/gavage in a preventive group days 7-28, or therapeutic group days 14-28. <h3>Results</h3> Human allograft derived MCs from CLAD patients demonstrated 4-fold increase in MNK1 (Thr197/202) and eIF4E Ser209 compared to non-fibrotic MCs. Upon eFT-508 treatment, we observed reduced eIF4E Ser209, collagen I, alpha smooth muscle actin and SPARC expression, and migration (n=7; p<0.05). CD44 and autotaxin protein expression was decreased upon eFT-508 treatment, along with secreted autotaxin activity (n=9; p=0.0005). <i>In vivo</i> preventive treatment with eFT-508 decreased airway fibrosis upon histological examination utilizing trichrome staining. Pleural thickness measurements were also reduced compared to vehicle treated controls. A significant reduction in hydroxyproline content, autotaxin secretion, and activity were also noted in eFT-508 treated transplant lung homogenates (n=7; p<0.001). Therapeutic treatment with eFT-508 reduced hydroxyproline content compared to vehicle treated allografts (n=4; p=0.0252). <h3>Conclusion</h3> MNK/eIF4E Ser209 inhibition reduced fibrotic protein expression and migration, demonstrating a role for this pathway in MC activation. <i>In vivo</i> MNK/eIF4E Ser209 inhibition reduced graft fibrosis by preventive and therapeutic treatment regimens in a murine model of RAS. This data highlights a novel therapeutic option for preventing development and progression of RAS.

Quantitative CT Correlates with Local Inflammation in Lung of Patients with Subtypes of Chronic Lung Allograft Dysfunction.

Chronic rejection of lung allografts has two major subtypes, bronchiolitis obliterans syndrome (BOS) and restrictive allograft syndrome (RAS), which present radiologically either as air trapping with small airways disease or with persistent pleuroparenchymal opacities. Parametric response mapping (PRM), a computed tomography (CT) methodology, has been demonstrated as an objective readout of BOS and RAS and bears prognostic importance, but has yet to be correlated to biological measures. Using a topological technique, we evaluate the distribution and arrangement of PRM-derived classifications of pulmonary abnormalities from lung transplant recipients undergoing redo-transplantation for end-stage BOS (N = 6) or RAS (N = 6). Topological metrics were determined from each PRM classification and compared to structural and biological markers determined from microCT and histopathology of lung core samples. Whole-lung measurements of PRM-defined functional small airways disease (fSAD), which serves as a readout of BOS, were significantly elevated in BOS versus RAS patients (p = 0.01). At the core-level, PRM-defined parenchymal disease, a potential readout of RAS, was found to correlate to neutrophil and collagen I levels (p < 0.05). We demonstrate the relationship of structural and biological markers to the CT-based distribution and arrangement of PRM-derived readouts of BOS and RAS.

A decline in club cell secretory proteins in lung transplantation is associated with release of natural killer cells exosomes leading to chronic rejection

In human lung transplant recipients, a decline in club cell secretory protein (CCSP) in bronchoalveolar lavage fluid has been associated with chronic lung allograft dysfunction (CLAD) as well as the induction of exosomes and immune responses that lead to CLAD. However, the mechanisms by which CCSP decline contributes to CLAD remain unknown. To define the mechanisms leading to CCSP decline and chronic rejection, we employed two mouse models: 1) chronic rejection after orthotopic single lung transplantation and 2) anti-major histocompatibility complex (MHC) class I-induced obliterative airway disease. In the chronic rejection mouse model, we detected circulating exosomes with donor MHC (H2b) and lung self-antigens and also development of antibodies to H2b and lung self-antigens and then a decline in CCSP. Furthermore, DBA2 mice that received injections of these exosomes developed antibodies to donor MHC and lung self-antigens. In the chronic rejection mouse model, natural killer (NK) and CD8 T cells were the predominant graft-infiltrating cells on day 14 of rejection followed by exosomes containing NK cell-associated and cytotoxic molecules on day 14 and 28. When NK cells were depleted, exosomes with NK cell-associated and cytotoxic molecules as well as fibrosis decreased. Induction of exosomes led to immune responses to donor MHC and lung self-antigens, resulting in CCSP decline, leading to NK cell infiltration and release of exosomes from NK cells. These results suggest a novel role for exosomes derived from NK cells in the pathogenesis of chronic lung allograft rejection.

Immune Checkpoints Expression in Chronic Lung Allograft Rejection.

Chronic lung allograft dysfunction (CLAD) is the main cause of poor survival and low quality of life of lung transplanted patients. Several studies have addressed the role of dendritic cells, macrophages, T cells, donor specific as well as anti-HLA antibodies, and interleukins in CLAD, but the expression and function of immune checkpoint molecules has not yet been analyzed, especially in the two CLAD subtypes: BOS (bronchiolitis obliterans syndrome) and RAS (restrictive allograft syndrome). To shed light on this topic, we conducted an observational study on eight consecutive grafts explanted from patients who received lung re-transplantation for CLAD. The expression of a panel of immune molecules (PD1/CD279, PDL1/CD274, CTLA4/CD152, CD4, CD8, hFoxp3, TIGIT, TOX, B-Cell-Specific Activator Protein) was analyzed by immunohistochemistry in these grafts and in six control lungs. Results showed that RAS compared to BOS grafts were characterized by 1) the inversion of the CD4/CD8 ratio; 2) a higher percentage of T lymphocytes expressing the PD-1, PD-L1, and CTLA4 checkpoint molecules; and 3) a significant reduction of exhausted PD-1-expressing T lymphocytes (PD-1pos/TOXpos) and of exhausted Treg (PD-1pos/FOXP3pos) T lymphocytes. Results herein, although being based on a limited number of cases, suggest a role for checkpoint molecules in the development of graft rejection and offer a possible immunological explanation for the worst prognosis of RAS. Our data, which will need to be validated in ampler cohorts of patients, raise the possibility that the evaluation of immune checkpoints during follow-up offers a prognostic advantage in monitoring the onset of rejection, and suggest that the use of compounds that modulate the function of checkpoint molecules could be evaluated in the management of chronic rejection in LTx patients.

Lung Transplantation: CT Assessment of Chronic Lung Allograft Dysfunction (CLAD).

Chronic lung allograft rejection remains one of the major causes of morbi-mortality after lung transplantation. The term Chronic Lung Allograft Dysfunction (CLAD) has been proposed to describe the different processes that lead to a significant and persistent deterioration in lung function without identifiable causes. The two main phenotypes of CLAD are Bronchiolitis Obliterans Syndrome (BOS) and Restrictive Allograft Syndrome (RAS), each of them characterized by particular functional and imaging features. These entities can be associated (mixed phenotype) or switched from one to the other. If CLAD remains a clinical diagnosis based on spirometry, computed tomography (CT) scan plays an important role in the diagnosis and follow-up of CLAD patients, to exclude identifiable causes of functional decline when CLAD is first suspected, to detect early abnormalities that can precede the diagnosis of CLAD (particularly RAS), to differentiate between the obstructive and restrictive phenotypes, and to detect exacerbations and evolution from one phenotype to the other. Recognition of early signs of rejection is crucial for better understanding of physiopathologic pathways and optimal management of patients.

IL-17 Receptor on Donor Cells Regulates Acute and Chronic Lung Allograft Rejection Potentiated by Repeated Endotoxin Inhalations

<h3>Purpose</h3> Chronic lung allograft dysfunction is a major complication after lung transplantation (LTx). Excessive IL17 receptor A (IL17RA) signaling has been recognized as a key factor; however, its precise mechanism is unclear. In a mouse minor alloantigen mismatched LTx model (C57BL/10 [B10, H-2^b] → C57BL/6 [B6. H-2^b]), we found that repeated airway endotoxin (lipopolysaccharide, LPS) challenge augments airway epithelial damage, acute and chronic rejection with airway obliteration, together with increased IL17A transcription in allografts but not isografts. We hypothesized that both donor and recipient cell responses to IL17A are important in mediating these processes. We therefore investigated the role of IL17RA on donor and recipient cells in the context of chronic rejection. <h3>Methods</h3> B10→B6 LTx and B6→B10 LTx were performed with or without intratracheal LPS administration (5 ug LPS/50 ul PBS, Day 3, 7, 10, 14, 17, 21). B6 IL17RA^−/− mice were used as donors or recipients. Grafts were assessed with micro CT scans on days 3 and 27; histological scoring and quantitative PCR were performed 28 days after LTx. <h3>Results</h3> Without LPS, neither donor nor recipient IL17RA deficiency modified histological scores or lung graft volume or density by CT scan. LPS-treated IL17RA^−/− recipients showed a similar degree of lung radiographic change and histological acute rejection compared to IL17RA^+/+ recipients; however airway obliteration was attenuated (Figure A). In contrast, recipients of IL17RA^−/− donor lungs showed reduced gain of graft density on CT, and diminished acute rejection and peri-airway fibrosis (Figure B-C). IL17RA^−/− donor grafts had fewer CXCL1 (a neutrophil chemoattractant) transcripts (Figure D). <h3>Conclusion</h3> IL17RA signaling on donor cells regulates acute and chronic rejection in LTx recipients experiencing airway inflammation.

Distinct molecular and immunological properties of circulating exosomes isolated from pediatric lung transplant recipients with bronchiolitis obliterans syndrome - a retrospective study.

Long-term success following human lung transplantation is poor due to chronic rejection. We demonstrated circulating exosomes of lung origin during acute and chronic lung allograft rejection. We analyzed plasma from pediatric lung transplant recipients (LTxRs) enrolled in the CTOT-C-03 to determine whether circulating exosomes are released into circulation during bronchiolitis obliterans syndrome (BOS). Plasma exosomes were isolated, and human leukocyte antigens (HLA) were detected. Exosomes were analyzed for lung self-antigens (SAgs), co-stimulatory molecules transcription factors, major histocompatibility complex class II (MHC-II), adhesion molecules, and 20S proteasome. Mice were immunized with exosomes from BOS or stable to determine their immunogenicity. Circulating exosomes from BOS LTxRs contained increased levels of SAgs, donor HLA class I, MHC-II, transcription factors, co-stimulatory molecules, and 20S proteasome compared with stable. Serial analysis of exosomes containing SAgs demonstrated that exosomes are detectable in the circulation before BOS. Mice immunized with exosomes from BOS, or stable, demonstrated that exosomes from BOS are distinct in inducing both humoral and cellular immune responses to SAgs. Circulating exosomes from BOS LTxRs elicit distinct humoral and cellular response. In addition, detection of SAgs on circulatory exosomes 12months before diagnosis of BOS suggest that exosomes could serve as biomarker.

Impact of Postoperative Continuous Renal Replacement Therapy in Lung Transplant Recipients

Background.Acute kidney injury (AKI) is a common complication after lung transplant (LTx), and continuous renal replacement therapy (CRRT) is increasingly of use to critically ill patients who have developed AKI. However, the optimal timing or threshold of kidney impairment for which to commence CRRT after LTx has been uncertain. There has also been limited information on the impact of CRRT among LTx recipients (LTRs) introduced in the early posttransplant period on survival, graft function, and renal function. We aimed to review LTRs who developed AKI requiring CRRT postoperatively and followed their long-term outcomes at Tohoku University Hospital (TUH).Methods.Medical records of consecutive patients who underwent LTx at TUH between 2000 and 2018 were reviewed, with follow-up to 2019 inclusive.Results.Although mortality in those who required CRRT (n = 21) was increased versus those who did not require CRRT (n = 85)(P = 0.024), conditional survival beyond 3-month posttransplant was not affected (P = 0.131). Additionally, the cumulative incidence of chronic lung allograft rejection (P = 0.160) and the development of chronic kidney disease (P = 0.757) were not significant between groups.Conclusions.The initiation of CRRT posttransplant may be a useful strategy to preserve cardiac and optimize volume management among critically ill patients.