Human telomere length is chromosome end-specific and conserved across individuals

Short telomeres cause age-related disease, and long telomeres contribute to cancer; however, the mechanisms regulating telomere length are unclear. We developed a nanopore-based method, which we call Telomere Profiling, to determine telomere length at nearly single-nucleotide resolution. Mapping telomere reads to chromosome ends showed chromosome end-specific length distributions that could differ by more than six kilobases. Examination of telomere lengths in 147 individuals revealed that certain chromosome ends were consistently longer or shorter. The same rank order was found in newborn cord blood, suggesting that telomere length is determined at birth and that chromosome end-specific telomere length differences are maintained as telomeres shorten with age. Telomere Profiling makes precision investigation of telomere length widely accessible for laboratory, clinical, and drug discovery efforts and will allow deeper insights into telomere biology.

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.

SARS-CoV-2 Accessory Protein Orf7b Induces Lung Injury via c-Myc Mediated Apoptosis and Ferroptosis

The pandemic of coronavirus disease 2019 (COVID-19) has been the foremost modern global public health challenge. The airway is the primary target in severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) infection, with substantial cell death and lung injury being signature hallmarks of exposure. The viral factors that contribute to cell death and lung injury remain incompletely understood. Thus, this study investigated the role of open reading frame 7b (Orf7b), an accessory protein of the virus, in causing lung injury. In screening viral proteins, we identified Orf7b as one of the major viral factors that mediates lung epithelial cell death. Overexpression of Orf7b leads to apoptosis and ferroptosis in lung epithelial cells, and inhibitors of apoptosis and ferroptosis ablate Orf7b-induced cell death. Orf7b upregulates the transcription regulator, c-Myc, which is integral in the activation of lung cell death pathways. Depletion of c-Myc alleviates both apoptotic and ferroptotic cell deaths and lung injury in mouse models. Our study suggests a major role of Orf7b in the cell death and lung injury attributable to COVID-19 exposure, supporting it as a potential therapeutic target.

Human telomere length is chromosome specific and conserved across individuals

Short telomeres cause age-related disease and long telomeres predispose to cancer; however, the mechanisms regulating telomere length are unclear. To probe these mechanisms, we developed a nanopore sequencing method, Telomere Profiling, that is easy to implement, precise, and cost effective with broad applications in research and the clinic. We sequenced telomeres from individuals with short telomere syndromes and found similar telomere lengths to the clinical FlowFISH assay. We mapped telomere reads to specific chromosome end and identified both chromosome end-specific and haplotype-specific telomere length distributions. In the T2T HG002 genome, where the average telomere length is 5kb, we found a remarkable 6kb difference in lengths between some telomeres. Further, we found that specific chromosome ends were consistently shorter or longer than the average length across 147 individuals. The presence of conserved chromosome end-specific telomere lengths suggests there are new paradigms in telomere biology that are yet to be explored. Understanding the mechanisms regulating length will allow deeper insights into telomere biology that can lead to new approaches to disease.

Increased expression of CXCL6 in secretory cells drives fibroblast collagen synthesis and is associated with increased mortality in idiopathic pulmonary fibrosis

RATIONALE

Recent data suggest that the localisation of airway epithelial cells in the distal lung in idiopathic pulmonary fibrosis (IPF) may drive pathology. We set out to discover whether chemokines expressed in these ectopic airway epithelial cells may contribute to the pathogenesis of IPF.

METHODS

We analysed whole lung and single-cell transcriptomic data obtained from patients with IPF. In addition, we measured chemokine levels in blood, bronchoalveolar lavage (BAL) of IPF patients and air-liquid interface cultures. We employed ex vivo donor and IPF lung fibroblasts and an animal model of pulmonary fibrosis to test the effects of chemokine signalling on fibroblast function.

RESULTS

By analysis of whole-lung transcriptomics, protein and BAL, we discovered that CXCL6 (a member of the interleukin-8 family) was increased in patients with IPF. Elevated CXCL6 levels in the BAL of two cohorts of patients with IPF were associated with poor survival (hazard ratio of death or progression 1.89, 95% CI 1.16-3.08; n=179, p=0.01). By immunostaining and single-cell RNA sequencing, CXCL6 was detected in secretory cells. Administration of mCXCL5 (LIX, murine CXCL6 homologue) to mice increased collagen synthesis with and without bleomycin. CXCL6 increased collagen I levels in donor and IPF fibroblasts 4.4-fold and 1.7-fold, respectively. Both silencing of and chemical inhibition of CXCR1/2 blocked the effects of CXCL6 on collagen, while overexpression of CXCR2 increased collagen I levels 4.5-fold in IPF fibroblasts.

CONCLUSIONS

CXCL6 is expressed in ectopic airway epithelial cells. Elevated levels of CXCL6 are associated with IPF mortality. CXCL6-driven collagen synthesis represents a functional consequence of ectopic localisation of airway epithelial cells in IPF.

The Impact of Donor Smoking on Primary Graft Dysfunction and Mortality after Lung Transplantation

Rationale: Primary graft dysfunction (PGD) is the leading cause of early morbidity and mortality after lung transplantation. Prior studies implicated proxy-defined donor smoking as a risk factor for PGD and mortality. Objectives: We aimed to more accurately assess the impact of donor smoke exposure on PGD and mortality using quantitative smoke exposure biomarkers. Methods: We performed a multicenter prospective cohort study of lung transplant recipients enrolled in the Lung Transplant Outcomes Group cohort between 2012 and 2018. PGD was defined as grade 3 at 48 or 72 hours after lung reperfusion. Donor smoking was defined using accepted thresholds of urinary biomarkers of nicotine exposure (cotinine) and tobacco-specific nitrosamine (4-[methylnitrosamino]-1-[3-pyridyl]-1-butanol [NNAL]) in addition to clinical history. The donor smoking-PGD association was assessed using logistic regression, and survival analysis was performed using inverse probability of exposure weighting according to smoking category. Measurements and Main Results: Active donor smoking prevalence varied by definition, with 34-43% based on urinary cotinine, 28% by urinary NNAL, and 37% by clinical documentation. The standardized risk of PGD associated with active donor smoking was higher across all definitions, with an absolute risk increase of 11.5% (95% confidence interval [CI], 3.8% to 19.2%) by urinary cotinine, 5.7% (95% CI, -3.4% to 14.9%) by urinary NNAL, and 6.5% (95% CI, -2.8% to 15.8%) defined clinically. Donor smoking was not associated with differential post-lung transplant survival using any definition. Conclusions: Donor smoking associates with a modest increase in PGD risk but not with increased recipient mortality. Use of lungs from smokers is likely safe and may increase lung donor availability. Clinical trial registered with www.clinicaltrials.gov (NCT00552357).

Impact of age and telomere length on circulating T cells and rejection risk after lung transplantation for idiopathic pulmonary fibrosis

BACKGROUND

Most idiopathic pulmonary fibrosis (IPF) lung transplant recipients (IPF-LTRs) have short telomere (ST) length. Inherited mutations in telomere-related genes are associated with the development of T cell immunodeficiency. Despite this, IPF-LTRs with telomere-related rare variants are not protected from acute cellular rejection (ACR). We set out to determine the impact of both age and telomere length on the circulating T cell compartment and ACR burden of IPF-LTRs.

METHODS

We identified 106 IPF-LTRs who had telomere length testing using flowFISH (57 with short telomeres and 49 with long telomeres) as well as a subset from both cohorts who had cryopreserved PBMC at least 1 time point, 6 months posttransplantation. Circulating T cells from before transplantation and at 6 and 12 months posttransplantation were analyzed using multiparameter flow cytometry to study phenotype and functional capacity, and bulk T cell receptor sequencing was performed to study repertoire diversity. Linear regression was used to study the relationship of age and telomere length on early (within 1 year) and late (between 1 and 2 years) ACR.

RESULTS

IPF-LTRs with ST were found to have premature "aging" of their circulating T cell compartment, with age-agnostic elevations in posttransplant terminal differentiation of CD8+ T cells, increased granzyme B positivity of both CD8+ and CD4+ T cells, upregulation of the exhaustion marker, CD57, and chemotactic protein CCR5, and enhanced T cell receptor clonal expansion. Additionally, we found a significant decline in early ACR burden with increasing age, but only in the ST cohort.

CONCLUSIONS

IPF-LTRs with ST have premature "aging" of their circulating T cell compartment posttransplantation and a clear age-related decline in ACR burden.

Lung transplant recipients with telomere-mediated pulmonary fibrosis have increased risk for hematologic complications

Idiopathic pulmonary fibrosis lung transplant recipients (IPF-LTRs) are enriched for short telomere length (TL) and telomere gene rare variants. A subset of patients with nontransplant short-TL are at increased risk for bone marrow (BM) dysfunction. We hypothesized that IPF-LTRs with short-TL and/or rare variants would be at increased risk for posttransplant hematologic complications. Data were extracted from a retrospective cohort of 72 IPF-LTRs and 72 age-matched non-IPF-LTR controls. Genetic assessment was done using whole genome sequencing or targeted sequence panel. TL was measured using flow cytometry and fluorescence in-situ hybridization (FlowFISH) and TelSeq software. The majority of the IPF-LTR cohort had short-TL, and 26% of IPF-LTRs had rare variants. Compared to non-IPF controls, short-TL IPF-LTRs were more likely to have immunosuppression agents discontinued due to cytopenias (P = .0375), and BM dysfunction requiring BM biopsy was more prevalent (29% vs 4%, P = .0003). IPF-LTRs with short-TL and rare variants had increased requirements for transfusion and growth factor support. Multivariable logistic regression demonstrated that short-TL, rare variants, and lower pretransplant platelet counts were associated with BM dysfunction. Pretransplant TL measurement and genetic testing for rare telomere gene variants identified IPF-LTRs at increased risk for hematologic complications. Our findings support stratification for telomere-mediated pulmonary fibrosis in lung transplant candidates.

Pseudomonas-dominant microbiome elicits sustained IL-1β upregulation in alveolar macrophages from lung transplant recipients

BACKGROUND

Isolation of Pseudomonas aeruginosa (PsA) is associated with increased BAL (bronchoalveolar lavage) inflammation and lung allograft injury in lung transplant recipients (LTR). However, the effect of PsA on macrophage responses in this population is incompletely understood. We examined human alveolar macrophage (AMΦ) responses to PsA and Pseudomonas dominant microbiome in healthy LTR.

METHODS

We stimulated THP-1 derived macrophages (THP-1MΦ) and human AMΦ from LTR with different bacteria and LTR BAL derived microbiome characterized as Pseudomonas-dominant. Macrophage responses were assessed by high dimensional flow cytometry, including their intracellular production of cytokines (TNF-α, IL-6, IL-8, IL-1β, IL-10, IL-1RA, and TGF-β). Pharmacological inhibitors were utilized to evaluate the role of the inflammasome in PsA-macrophage interaction.

RESULTS

We observed upregulation of pro-inflammatory cytokines (TNF-α, IL-6, IL-8, IL-1β) following stimulation by PsA compared to other bacteria (Staphylococcus aureus (S.Aur), Prevotella melaninogenica, Streptococcus pneumoniae) in both THP-1MΦ and LTR AMΦ, predominated by IL-1β. IL-1β production from THP-1MΦ was sustained after PsA stimulation for up to 96 hours and 48 hours in LTR AMΦ. Treatment with the inflammasome inhibitor BAY11-7082 abrogated THP-1MΦ IL-1β production after PsA exposure. BAL Pseudomonas-dominant microbiota elicited an increased IL-1β, similar to PsA, an effect abrogated by the addition of antibiotics.

CONCLUSION

PsA and PsA-dominant lung microbiota induce sustained IL-1β production in LTR AMΦ. Pharmacological targeting of the inflammasome reduces PsA-macrophage-IL-1β responses, underscoring their use in lung transplant recipients.

Rabbit Antithymocyte Globulin for Treatment of Corticosteroid Refractory Acute Cellular Rejection After Lung Transplantation

BACKGROUND

Chronic lung allograft dysfunction (CLAD) remains a major cause of death after the first year posttransplant, with acute cellular rejection (ACR) being a major risk factor for CLAD. We evaluated the use of rabbit antithymocyte globulin (rATG) for corticosteroid refractory ACR in lung transplant recipients.

METHODS

We retrospectively identified 112 adult lung transplant recipients who received rATG for refractory ACR after lung transplantation. The primary endpoint was the incidence of ACR on follow-up transbronchial biopsy. Secondary endpoints included freedom from ACR within 1 y post-rATG, CLAD progression at 1 y post-rATG, and all-cause mortality at 1 y post-rATG.

RESULTS

A complete resolution of ACR was observed in 60.2% of patients, an improvement but not complete resolution in 22.1%, and no response on follow-up biopsy in 17.8%. Mean A grade 1 y post-rATG was 0.51 in complete responders, 1.01 in partial responders, and 2.19 in nonresponders ( P  < 0.001). Complete responders had significantly less new or worsening CLAD at 1 y than partial responders (17% versus 40%; P  = 0.02). All-cause mortality rate was 14.9% in complete responders, 40% in partial responders, and 30% in nonresponders ( P  < 0.01).

CONCLUSIONS

rATG appears to be an effective treatment of refractory ACR in lung transplant recipients. Failure to respond to rATG carries an increased risk of early CLAD and death.

Incidence of Acute Cellular Rejection After Granulocyte Colony-Stimulating Factor in Lung Transplant Recipients

BackgroundNeutropenia is a common complication in lung transplant recipients (LTRs). Filgrastim may be used to treat neutropenia in LTRs, but its consequences on acute cellular rejection (ACR) remain controversial. Objective: The purpose was to examine the association between filgrastim and incidence of ACR 6 months after filgrastim administration in LTRs. Secondary outcomes included burden of ACR, infections, chronic lung allograft dysfunction (CLAD), and survival. Methods: This was a matched cohort study of patients transplanted between January 2010 and October 2019. LTRs who received filgrastim for neutropenia were compared to a cohort who did not. LTRs were matched on transplant indication, sex, age, and time post-transplant and multivariable logistic regression models were used to evaluate the likelihood of ACR. Results: 212 patients were included in the analysis (106 in each group). 50 patients (47.2%) in the filgrastim group experienced ACR compared to 37 patients (34.9%) in the no filgrastim group (P = .070). In multivariable analysis, filgrastim use was not associated with ACR at 6 months (OR 1.409, 95% CI 0.772-2.571). Time to first ACR was shorter (P = .049) and 6-month ACR score was higher in the filgrastim group (.49 vs .33, P = .047). LTRs in the filgrastim group had higher incidence of bacterial pneumonia and 1-year mortality. Conclusions: Although not associated with increased likelihood of ACR at 6 months, our study found that filgrastim is associated with increased ACR burden and decreased time to ACR. This study can help inform clinicians of ACR risk after filgrastim use in LTRs.

COVID-19 convalescent plasma boosts early antibody titer and does not influence the adaptive immune response

Multiple randomized, controlled clinical trials have yielded discordant results regarding the efficacy of convalescent plasma in outpatients, with some showing an approximately 2-fold reduction in risk and others showing no effect. We quantified binding and neutralizing antibody levels in 492 of the 511 participants from the Clinical Trial of COVID-19 Convalescent Plasma in Outpatients (C3PO) of a single unit of COVID-19 convalescent plasma (CCP) versus saline infusion. In a subset of 70 participants, peripheral blood mononuclear cells were obtained to define the evolution of B and T cell responses through day 30. Binding and neutralizing antibody responses were approximately 2-fold higher 1 hour after infusion in recipients of CCP compared with saline plus multivitamin, but levels achieved by the native immune system by day 15 were almost 10-fold higher than those seen immediately after CCP administration. Infusion of CCP did not block generation of the host antibody response or skew B or T cell phenotype or maturation. Activated CD4+ and CD8+ T cells were associated with more severe disease outcome. These data show that CCP leads to a measurable boost in anti-SARS-CoV-2 antibodies but that the boost is modest and may not be sufficient to alter disease course.

Rare surfactant-related variants in familial and sporadic pulmonary fibrosis

The role of constitutional genetic defects in idiopathic pulmonary fibrosis (IPF) is increasingly appreciated. Monogenic disorders associated with IPF affect two pathways: telomere maintenance, accounting for approximately 10% of all patients with IPF, and surfactant biology, responsible for 1%-3% of cases and often co-occurring with lung cancer. We examined the prevalence of rare variants in five surfactant-related genes, SFTPA1, SFPTA2, SFTPC, ABCA3, and NKX2-1, that were previously linked to lung disease in whole genome sequencing data from 431 patients with IPF. We identified functionally deleterious rare variants in SFTPA2 with a prevalence of 1.3% in individuals with and without a family history of IPF. All individuals had no personal history of lung cancer, but substantial bronchiolar metaplasia was noted on lung explants and biopsies. Five patients had novel missense variants in NKX2-1, but the contribution to disease is unclear. In general, patients were younger and had longer telomeres compared with the majority of patients with IPF suggesting that these features may be useful for identifying this subset of patients in the clinic. These data suggest that SFTPA2 variants may be more common in unselected IPF cohorts and may manifest in the absence of personal/family history of lung cancer or IPF.

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.

Prospective Evaluation of Coronavirus Disease 2019 (COVID-19) Vaccine Responses Across a Broad Spectrum of Immunocompromising Conditions: the COVID-19 Vaccination in the Immunocompromised Study (COVICS)

BACKGROUND

We studied humoral responses after coronavirus disease 2019 (COVID-19) vaccination across varying causes of immunodeficiency.

METHODS

Prospective study of fully vaccinated immunocompromised adults (solid organ transplant [SOT], hematologic malignancy, solid cancers, autoimmune conditions, human immunodeficiency virus [HIV]) versus nonimmunocompromised healthcare workers (HCWs). The primary outcome was the proportion with a reactive test (seropositive) for immunoglobulin G to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor-binding domain. Secondary outcomes were comparisons of antibody levels and their correlation with pseudovirus neutralization titers. Stepwise logistic regression was used to identify factors associated with seropositivity.

RESULTS

A total of 1271 participants enrolled: 1099 immunocompromised and 172 HCW. Compared with HCW (92.4% seropositive), seropositivity was lower among participants with SOT (30.7%), hematological malignancies (50.0%), autoimmune conditions (79.1%), solid tumors (78.7%), and HIV (79.8%) (P < .01). Factors associated with poor seropositivity included age, greater immunosuppression, time since vaccination, anti-CD20 monoclonal antibodies, and vaccination with BNT162b2 (Pfizer) or adenovirus vector vaccines versus messenger RNA (mRNA)-1273 (Moderna). mRNA-1273 was associated with higher antibody levels than BNT162b2 or adenovirus vector vaccines after adjusting for time since vaccination, age, and underlying condition. Antibody levels were strongly correlated with pseudovirus neutralization titers (Spearman r = 0.89, P < .0001), but in seropositive participants with intermediate antibody levels, neutralization titers were significantly lower in immunocompromised individuals versus HCW.

CONCLUSIONS

Antibody responses to COVID-19 vaccines were lowest among SOT and anti-CD20 monoclonal recipients, and recipients of vaccines other than mRNA-1273. Among those with intermediate antibody levels, pseudovirus neutralization titers were lower in immunocompromised patients than HCWs. Additional SARS-CoV-2 preventive approaches are needed for immunocompromised persons, which may need to be tailored to the cause of immunodeficiency.

Induction Strategies in Lung Transplantation: Alemtuzumab vs. Basiliximab a Single-Center Experience

Background

Induction therapy is used in about 80% of lung transplant centers and is increasing globally. Currently, there are no standards or guidelines for the use of induction therapy. At our institution, we have two induction strategies, basiliximab, and alemtuzumab. The goal of this manuscript is to share our experience and practice since this is an area of controversy.

Methods

We retrospectively reviewed 807 lung transplants performed at our institution between 2011 and 2020. Indications for the use of the basiliximab protocol were as follows: patients over the age of 70 years, history of cancer, hepatitis C virus or human immunodeficiency virus infection history, and cytomegalovirus or Epstein-Barr virus (donor positive/ recipient negative). In the absence of these clinical factors, the alemtuzumab protocol was used.

Results

453 patients underwent alemtuzumab induction and 354 patients underwent basiliximab. There were significant differences in delayed chest closure (24.7% alemtuzumab vs 31.4% basiliximab, p = 0.037), grade 3 primary graft dysfunction observed within 72 hours (19.9% alemtuzumab vs 29.9% basiliximab, p = 0.002), postoperative hepatic dysfunction (8.8% alemtuzumab vs 14.7% basiliximab, p = 0.009), acute cellular rejection in first year (39.1% alemtuzumab vs 53.4% basiliximab, p < 0.001). The overall survival rate of the patients with alemtuzumab induction was significantly higher than those of the patients with basiliximab induction (5 years survival rate: 64.1% alemtuzumab vs 52.3%, basiliximab, p < 0.001). Multivariate Cox regression analysis confirmed lower 5-year survival for basiliximab induction (HR = 1.41, p = 0.02), recipient cytomegalovirus positive (HR = 1.49, p = 0.01), postoperative hepatic dysfunction (HR = 2.20, p < 0.001), and acute kidney injury requiring renal replacement therapy (HR = 2.27, p < 0.001).

Conclusions

In this single center retrospective review, there was a significant difference in survival rates between induction strategies. This outcome may be attributable to differences in recipient characteristics between the groups. However, the Alemtuzumab group experienced less episodes of acute cellular rejection within the first year.

CD4+ T-Cell Dysfunction in Severe COVID-19 Disease Is Tumor Necrosis Factor-α/Tumor Necrosis Factor Receptor 1-Dependent

Rationale: Lymphopenia is common in severe coronavirus disease (COVID-19), yet the immune mechanisms are poorly understood. As inflammatory cytokines are increased in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, we hypothesized a role in contributing to reduced T-cell numbers. Objectives: We sought to characterize the functional SARS-CoV-2 T-cell responses in patients with severe versus recovered, mild COVID-19 to determine whether differences were detectable. Methods: Using flow cytometry and single-cell RNA sequence analyses, we assessed SARS-CoV-2-specific responses in our cohort. Measurements and Main Results: In 148 patients with severe COVID-19, we found lymphopenia was associated with worse survival. CD4⁺ lymphopenia predominated, with lower CD4⁺/CD8⁺ ratios in severe COVID-19 compared with patients with mild disease (P < 0.0001). In severe disease, immunodominant CD4⁺ T-cell responses to Spike-1 (S1) produced increased in vitro TNF-α (tumor necrosis factor-α) but demonstrated impaired S1-specific proliferation and increased susceptibility to activation-induced cell death after antigen exposure. CD4⁺TNF-α⁺ T-cell responses inversely correlated with absolute CD4⁺ counts from patients with severe COVID-19 (n = 76; R = -0.797; P < 0.0001). In vitro TNF-α blockade, including infliximab or anti-TNF receptor 1 antibodies, strikingly rescued S1-specific CD4⁺ T-cell proliferation and abrogated S1-specific activation-induced cell death in peripheral blood mononuclear cells from patients with severe COVID-19 (P < 0.001). Single-cell RNA sequencing demonstrated marked downregulation of type-1 cytokines and NFκB signaling in S1-stimulated CD4⁺ cells with infliximab treatment. We also evaluated BAL and lung explant CD4⁺ T cells recovered from patients with severe COVID-19 and observed that lung T cells produced higher TNF-α compared with peripheral blood mononuclear cells. Conclusions: Together, our findings show CD4⁺ dysfunction in severe COVID-19 is TNF-α/TNF receptor 1-dependent through immune mechanisms that may contribute to lymphopenia. TNF-α blockade may be beneficial in severe COVID-19.

Modulation of tissue resident memory T cells by glucocorticoids after acute cellular rejection in lung transplantation

Acute cellular rejection is common after lung transplantation and is associated with an increased risk of early chronic rejection. We present combined single-cell RNA and TCR sequencing on recipient-derived T cells obtained from the bronchoalveolar lavage of three lung transplant recipients with rejection and compare them with T cells obtained from the same patients after treatment of rejection with high-dose systemic glucocorticoids. At the time of rejection, we found an oligoclonal expansion of cytotoxic CD8+ T cells that all persisted as tissue resident memory T cells after successful treatment. Persisting CD8+ allograft-resident T cells have reduced gene expression for cytotoxic mediators after therapy with glucocorticoids but accumulate around airways. This clonal expansion is discordant with circulating T cell clonal expansion at the time of rejection, suggesting in situ expansion. We thus highlight the accumulation of cytotoxic, recipient-derived tissue resident memory T cells within the lung allograft that persist despite the administration of high-dose systemic glucocorticoids. The long-term clinical consequences of this persistence have yet to be characterized.

Early Convalescent Plasma for High-Risk Outpatients with Covid-19

BACKGROUND

Early administration of convalescent plasma obtained from blood donors who have recovered from coronavirus disease 2019 (Covid-19) may prevent disease progression in acutely ill, high-risk patients with Covid-19.

METHODS

In this randomized, multicenter, single-blind trial, we assigned patients who were being treated in an emergency department for Covid-19 symptoms to receive either one unit of convalescent plasma with a high titer of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or placebo. All the patients were either 50 years of age or older or had one or more risk factors for disease progression. In addition, all the patients presented to the emergency department within 7 days after symptom onset and were in stable condition for outpatient management. The primary outcome was disease progression within 15 days after randomization, which was a composite of hospital admission for any reason, seeking emergency or urgent care, or death without hospitalization. Secondary outcomes included the worst severity of illness on an 8-category ordinal scale, hospital-free days within 30 days after randomization, and death from any cause.

RESULTS

A total of 511 patients were enrolled in the trial (257 in the convalescent-plasma group and 254 in the placebo group). The median age of the patients was 54 years; the median symptom duration was 4 days. In the donor plasma samples, the median titer of SARS-CoV-2 neutralizing antibodies was 1:641. Disease progression occurred in 77 patients (30.0%) in the convalescent-plasma group and in 81 patients (31.9%) in the placebo group (risk difference, 1.9 percentage points; 95% credible interval, -6.0 to 9.8; posterior probability of superiority of convalescent plasma, 0.68). Five patients in the plasma group and 1 patient in the placebo group died. Outcomes regarding worst illness severity and hospital-free days were similar in the two groups.

CONCLUSIONS

The administration of Covid-19 convalescent plasma to high-risk outpatients within 1 week after the onset of symptoms of Covid-19 did not prevent disease progression. (SIREN-C3PO ClinicalTrials.gov number, NCT04355767.).

Lung transplantation for idiopathic pulmonary fibrosis enriches for individuals with telomere-mediated disease

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is the most common indication for lung transplantation in North America and variants in telomere-maintenance genes are the most common identifiable cause of IPF. We reasoned that younger IPF patients are more likely to undergo lung transplantation and we hypothesized that lung transplant recipients would be enriched for individuals with telomere-mediated disease due to the earlier onset and more severe disease in these patients.

METHODS

Individuals with IPF who underwent lung transplantation or were evaluated in an interstitial lung disease specialty clinic who did not undergo lung transplantation were examined. Genetic evaluation was completed via whole genome sequencing (WGS) of 426 individuals and targeted sequencing for 5 individuals. Rare variants in genes previously associated with IPF were classified using the American College of Medical Genetics guidelines. Telomere length from WGS data was measured using TelSeq software. Patient characteristics were collected via medical record review.

RESULTS

Of 431 individuals, 149 underwent lung transplantation for IPF. The median age of diagnosis of transplanted vs non-transplanted individuals was significantly younger (60 years vs 70 years, respectively, p<0.0001). IPF lung transplant recipients (IPF-LTRs) were twice as likely to have telomere-related rare variants compared to non-transplanted individuals (24% vs 12%, respectively, p=0.0013). IPF-LTRs had shorter telomeres than non-transplanted IPF patients (p=0.0028) and >85% had telomeres below the age-adjusted mean. Post-transplant survival and CLAD were similar amongst IPF-LTRs with rare variants in telomere-maintenance genes compared to those without, as well as in those with short telomeres versus longer telomeres.

CONCLUSIONS

There is an enrichment for telomere-maintenance gene variants and short telomeres among IPF-LTRs. However, transplant outcomes of survival and CLAD do not differ by gene variants or telomere length within IPF-LTRs. Our findings support individual with telomere-mediated disease should not be excluded from lung transplantation and focusing research efforts on therapies directed toward individuals with short-telomere mediated disease.

Effect of Convalescent Plasma on Organ Support-Free Days in Critically Ill Patients With COVID-19: A Randomized Clinical Trial

IMPORTANCE

The evidence for benefit of convalescent plasma for critically ill patients with COVID-19 is inconclusive.

OBJECTIVE

To determine whether convalescent plasma would improve outcomes for critically ill adults with COVID-19.

DESIGN, SETTING, AND PARTICIPANTS

The ongoing Randomized, Embedded, Multifactorial, Adaptive Platform Trial for Community-Acquired Pneumonia (REMAP-CAP) enrolled and randomized 4763 adults with suspected or confirmed COVID-19 between March 9, 2020, and January 18, 2021, within at least 1 domain; 2011 critically ill adults were randomized to open-label interventions in the immunoglobulin domain at 129 sites in 4 countries. Follow-up ended on April 19, 2021.

INTERVENTIONS

The immunoglobulin domain randomized participants to receive 2 units of high-titer, ABO-compatible convalescent plasma (total volume of 550 mL ± 150 mL) within 48 hours of randomization (n = 1084) or no convalescent plasma (n = 916).

MAIN OUTCOMES AND MEASURES

The primary ordinal end point was organ support-free days (days alive and free of intensive care unit-based organ support) up to day 21 (range, -1 to 21 days; patients who died were assigned -1 day). The primary analysis was an adjusted bayesian cumulative logistic model. Superiority was defined as the posterior probability of an odds ratio (OR) greater than 1 (threshold for trial conclusion of superiority >99%). Futility was defined as the posterior probability of an OR less than 1.2 (threshold for trial conclusion of futility >95%). An OR greater than 1 represented improved survival, more organ support-free days, or both. The prespecified secondary outcomes included in-hospital survival; 28-day survival; 90-day survival; respiratory support-free days; cardiovascular support-free days; progression to invasive mechanical ventilation, extracorporeal mechanical oxygenation, or death; intensive care unit length of stay; hospital length of stay; World Health Organization ordinal scale score at day 14; venous thromboembolic events at 90 days; and serious adverse events.

RESULTS

Among the 2011 participants who were randomized (median age, 61 [IQR, 52 to 70] years and 645/1998 [32.3%] women), 1990 (99%) completed the trial. The convalescent plasma intervention was stopped after the prespecified criterion for futility was met. The median number of organ support-free days was 0 (IQR, -1 to 16) in the convalescent plasma group and 3 (IQR, -1 to 16) in the no convalescent plasma group. The in-hospital mortality rate was 37.3% (401/1075) for the convalescent plasma group and 38.4% (347/904) for the no convalescent plasma group and the median number of days alive and free of organ support was 14 (IQR, 3 to 18) and 14 (IQR, 7 to 18), respectively. The median-adjusted OR was 0.97 (95% credible interval, 0.83 to 1.15) and the posterior probability of futility (OR <1.2) was 99.4% for the convalescent plasma group compared with the no convalescent plasma group. The treatment effects were consistent across the primary outcome and the 11 secondary outcomes. Serious adverse events were reported in 3.0% (32/1075) of participants in the convalescent plasma group and in 1.3% (12/905) of participants in the no convalescent plasma group.

CONCLUSIONS AND RELEVANCE

Among critically ill adults with confirmed COVID-19, treatment with 2 units of high-titer, ABO-compatible convalescent plasma had a low likelihood of providing improvement in the number of organ support-free days.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02735707.

Effect of Convalescent Plasma on Organ Support-Free Days in Critically Ill Patients With COVID-19: A Randomized Clinical Trial

IMPORTANCE

The evidence for benefit of convalescent plasma for critically ill patients with COVID-19 is inconclusive.

OBJECTIVE

To determine whether convalescent plasma would improve outcomes for critically ill adults with COVID-19.

DESIGN, SETTING, AND PARTICIPANTS

The ongoing Randomized, Embedded, Multifactorial, Adaptive Platform Trial for Community-Acquired Pneumonia (REMAP-CAP) enrolled and randomized 4763 adults with suspected or confirmed COVID-19 between March 9, 2020, and January 18, 2021, within at least 1 domain; 2011 critically ill adults were randomized to open-label interventions in the immunoglobulin domain at 129 sites in 4 countries. Follow-up ended on April 19, 2021.

INTERVENTIONS

The immunoglobulin domain randomized participants to receive 2 units of high-titer, ABO-compatible convalescent plasma (total volume of 550 mL ± 150 mL) within 48 hours of randomization (n = 1084) or no convalescent plasma (n = 916).

MAIN OUTCOMES AND MEASURES

The primary ordinal end point was organ support-free days (days alive and free of intensive care unit-based organ support) up to day 21 (range, -1 to 21 days; patients who died were assigned -1 day). The primary analysis was an adjusted bayesian cumulative logistic model. Superiority was defined as the posterior probability of an odds ratio (OR) greater than 1 (threshold for trial conclusion of superiority >99%). Futility was defined as the posterior probability of an OR less than 1.2 (threshold for trial conclusion of futility >95%). An OR greater than 1 represented improved survival, more organ support-free days, or both. The prespecified secondary outcomes included in-hospital survival; 28-day survival; 90-day survival; respiratory support-free days; cardiovascular support-free days; progression to invasive mechanical ventilation, extracorporeal mechanical oxygenation, or death; intensive care unit length of stay; hospital length of stay; World Health Organization ordinal scale score at day 14; venous thromboembolic events at 90 days; and serious adverse events.

RESULTS

Among the 2011 participants who were randomized (median age, 61 [IQR, 52 to 70] years and 645/1998 [32.3%] women), 1990 (99%) completed the trial. The convalescent plasma intervention was stopped after the prespecified criterion for futility was met. The median number of organ support-free days was 0 (IQR, -1 to 16) in the convalescent plasma group and 3 (IQR, -1 to 16) in the no convalescent plasma group. The in-hospital mortality rate was 37.3% (401/1075) for the convalescent plasma group and 38.4% (347/904) for the no convalescent plasma group and the median number of days alive and free of organ support was 14 (IQR, 3 to 18) and 14 (IQR, 7 to 18), respectively. The median-adjusted OR was 0.97 (95% credible interval, 0.83 to 1.15) and the posterior probability of futility (OR <1.2) was 99.4% for the convalescent plasma group compared with the no convalescent plasma group. The treatment effects were consistent across the primary outcome and the 11 secondary outcomes. Serious adverse events were reported in 3.0% (32/1075) of participants in the convalescent plasma group and in 1.3% (12/905) of participants in the no convalescent plasma group.

CONCLUSIONS AND RELEVANCE

Among critically ill adults with confirmed COVID-19, treatment with 2 units of high-titer, ABO-compatible convalescent plasma had a low likelihood of providing improvement in the number of organ support-free days.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02735707.

Renin Angiotensin Aldosterone System Antagonism in 2019 Novel Coronavirus Acute Lung Injury

It has been established that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) uses angiotensin-converting enzyme 2 (ACE2), a membrane-bound regulatory peptide, for host cell entry. Renin-angiotensin-aldosterone system (RAAS) inhibitors have been reported to increase ACE2 in type 2 pneumocyte pulmonary tissue. Controversy exists for the continuation of ACE inhibitors, angiotensin II receptor blockers, and mineralocorticoid receptor antagonists in the current pandemic. ACE2 serves as a regulatory enzyme in maintaining homeostasis between proinflammatory angiotensin II and anti-inflammatory angiotensin 1,7 peptides. Derangements in these peptides are associated with cardiovascular disease and are implicated in the progression of acute respiratory distress syndrome. Augmentation of the ACE2/Ang 1,7 axis represents a critical target in the supportive management of coronavirus disease 2019–associated lung disease. Observational data describing the use of RAAS inhibitors in the setting of SARS-CoV-2 have not borne signals of harm to date. However, equipoise persists, requiring an analysis of novel agents including recombinant human-ACE2 and existing RAAS inhibitors while balancing ongoing controversies associated with increased coronavirus infectivity and virulence.

Rapid postmortem ventilation improves donor lung viability by extending the tolerable warm ischemic time after cardiac death in mice

Uncontrolled donation after cardiac death (uDCD) contributes little to ameliorating donor lung shortage due to rapidly progressive warm ischemia after circulatory arrest. Here, we demonstrated non-hypoxia improves donor lung viability in a novel uDCD lung transplant model undergoing rapid ventilation after cardiac death and compared the evolution of ischemia-reperfusion injury in mice that underwent pulmonary artery ligation (PAL). The tolerable warm ischemia time at 37ºC was initially determined in mice using a modified PAL model. The donor lung following PAL was also transplanted into syngeneic mice and compared to those that underwent rapid ventilation or no ventilation at 37ºC prior to transplantation. Twenty-four hours following reperfusion, lung histology, PaO2/FIO2 ratio, and inflammatory mediators were measured. Four hours of PAL had little impact on PaO2/FIO2 ratio and acute lung injury score in contrast to significant injury induced by 5 hours of PAL. Four-hour PAL lungs showed an early myeloid-dominant inflammatory signature when compared to naïve lungs and substantially injured five-hour PAL lungs. In the context of transplantation, unventilated donor lungs showed severe injury after reperfusion, whereas ventilated donor lungs showed minimal changes in PaO2/FIO2 ratio, histologic score, and expression of inflammatory markers. Taken together, the tolerable warm ischemia time of murine lungs at 37^oC can be extended by maintaining alveolar ventilation for up to 4 hours. Non-hypoxic lung warm ischemia-reperfusion injury shows an early transcriptional signature of myeloid cell recruitment and extracellular matrix proteolysis prior to blood-gas barrier dysfunction and significant tissue damage.

A high-throughput screen for TMPRSS2 expression identifies FDA-approved compounds that can limit SARS-CoV-2 entry

SARS-CoV-2 (2019-nCoV) is the pathogenic coronavirus responsible for the global pandemic of COVID-19 disease. The Spike (S) protein of SARS-CoV-2 attaches to host lung epithelial cells through the cell surface receptor ACE2, a process dependent on host proteases including TMPRSS2. Here, we identify small molecules that reduce surface expression of TMPRSS2 using a library of 2,560 FDA-approved or current clinical trial compounds. We identify homoharringtonine and halofuginone as the most attractive agents, reducing endogenous TMPRSS2 expression at sub-micromolar concentrations. These effects appear to be mediated by a drug-induced alteration in TMPRSS2 protein stability. We further demonstrate that halofuginone modulates TMPRSS2 levels through proteasomal-mediated degradation that involves the E3 ubiquitin ligase component DDB1- and CUL4-associated factor 1 (DCAF1). Finally, cells exposed to homoharringtonine and halofuginone, at concentrations of drug known to be achievable in human plasma, demonstrate marked resistance to SARS-CoV-2 infection in both live and pseudoviral in vitro models. Given the safety and pharmacokinetic data already available for the compounds identified in our screen, these results should help expedite the rational design of human clinical trials designed to combat active COVID-19 infection.

Type-1 immunity and endogenous immune regulators predominate in the airway transcriptome during chronic lung allograft dysfunction

Chronic lung allograft dysfunction (CLAD) remains the major complication limiting long-term survival among lung transplant recipients (LTRs). Limited understanding of CLAD immunopathogenesis and a paucity of biomarkers remain substantial barriers for earlier detection and therapeutic interventions for CLAD. We hypothesized the airway transcriptome would reflect key immunologic changes in disease. We compared airway brush-derived transcriptomic signatures in CLAD (n = 24) versus non-CLAD (n = 21) LTRs. A targeted assessment of the proteome using concomitant bronchoalveolar lavage (BAL) fluid for 24 cytokines/chemokines and alloimmune T cell responses was performed to validate the airway transcriptome. We observed an airway transcriptomic signature of differential genes expressed (DGEs) in CLAD marked by Type-1 immunity and striking upregulation of two endogenous immune regulators: indoleamine 2, 3 dioxygenase 1 (IDO-1) and tumor necrosis factor receptor superfamily 6B (TNFRSF6B). Advanced CLAD staging was associated with a more intense airway transcriptome signature. In a validation cohort using the identified signature, we found an area under the curve (AUC) of 0.77 for CLAD LTRs. Targeted proteomic analyses revealed a predominant Type-1 profile with detection of IFN-γ, TNF-α, and IL-1β as dominant CLAD cytokines, correlating with the airway transcriptome. The airway transcriptome provides novel insights into CLAD immunopathogenesis and biomarkers that may impact diagnosis of CLAD.

Single cell RNA sequencing identifies IGFBP5 and QKI as ciliated epithelial cell genes associated with severe COPD

Background

Whole lung tissue transcriptomic profiling studies in chronic obstructive pulmonary disease (COPD) have led to the identification of several genes associated with the severity of airflow limitation and/or the presence of emphysema, however, the cell types driving these gene expression signatures remain unidentified.

Methods

To determine cell specific transcriptomic changes in severe COPD, we conducted single-cell RNA sequencing (scRNA seq) on n = 29,961 cells from the peripheral lung parenchymal tissue of nonsmoking subjects without underlying lung disease (n = 3) and patients with severe COPD (n = 3). The cell type composition and cell specific gene expression signature was assessed. Gene set enrichment analysis (GSEA) was used to identify the specific cell types contributing to the previously reported transcriptomic signatures.

Results

T-distributed stochastic neighbor embedding and clustering of scRNA seq data revealed a total of 17 distinct populations. Among them, the populations with more differentially expressed genes in cases vs. controls (log fold change >|0.4| and FDR = 0.05) were: monocytes (n = 1499); macrophages (n = 868) and ciliated epithelial cells (n = 590), respectively. Using GSEA, we found that only ciliated and cytotoxic T cells manifested a trend towards enrichment of the previously reported 127 regional emphysema gene signatures (normalized enrichment score [NES] = 1.28 and = 1.33, FDR = 0.085 and = 0.092 respectively). Among the significantly altered genes present in ciliated epithelial cells of the COPD lungs, QKI and IGFBP5 protein levels were also found to be altered in the COPD lungs.

Conclusions

scRNA seq is useful for identifying transcriptional changes and possibly individual protein levels that may contribute to the development of emphysema in a cell-type specific manner.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01675-2.

Transcriptional and Proteomic Characterization of Telomere-Induced Senescence in a Human Alveolar Epithelial Cell Line

Cellular senescence due to telomere dysfunction has been hypothesized to play a role in age-associated diseases including idiopathic pulmonary fibrosis (IPF). It has been postulated that paracrine mediators originating from senescent alveolar epithelia signal to surrounding mesenchymal cells and contribute to disease pathogenesis. However, murine models of telomere-induced alveolar epithelial senescence fail to display the canonical senescence-associated secretory phenotype (SASP) that is observed in senescent human cells. In an effort to understand human-specific responses to telomere dysfunction, we modeled telomere dysfunction-induced senescence in a human alveolar epithelial cell line. We hypothesized that this system would enable us to probe for differences in transcriptional and proteomic senescence pathways in vitro and to identify novel secreted protein (secretome) changes that potentially contribute to the pathogenesis of IPF. Following induction of telomere dysfunction, a robust senescence phenotype was observed. RNA-seq analysis of the senescent cells revealed the SASP and comparisons to previous murine data highlighted differences in response to telomere dysfunction. We conducted a proteomic analysis of the senescent cells using a novel biotin ligase capable of labeling secreted proteins. Candidate biomarkers selected from our transcriptional and secretome data were then evaluated in IPF and control patient plasma. Four novel proteins were found to be differentially expressed between the patient groups: stanniocalcin-1, contactin-1, tenascin C, and total inhibin. Our data show that human telomere-induced, alveolar epithelial senescence results in a transcriptional SASP that is distinct from that seen in analogous murine cells. Our findings suggest that studies in animal models should be carefully validated given the possibility of species-specific responses to telomere dysfunction. We also describe a pragmatic approach for the study of the consequences of telomere-induced alveolar epithelial cell senescence in humans.

Risk of primary graft dysfunction following lung transplantation in selected adults with connective tissue disease-associated interstitial lung disease

BACKGROUND

Previous studies have reported similarities in long-term outcomes following lung transplantation for connective tissue disease-associated interstitial lung disease (CTD-ILD) and idiopathic pulmonary fibrosis (IPF). However, it is unknown whether CTD-ILD patients are at increased risk of primary graft dysfunction (PGD), delays in extubation, or longer index hospitalizations following transplant compared to IPF patients.

METHODS

We performed a multicenter retrospective cohort study of CTD-ILD and IPF patients enrolled in the Lung Transplant Outcomes Group registry who underwent lung transplantation between 2012 and 2018. We utilized mixed effects logistic regression and stratified Cox proportional hazards regression to determine whether CTD-ILD was independently associated with increased risk for grade 3 PGD or delays in post-transplant extubation and hospital discharge compared to IPF.

RESULTS

A total of 32.7% (33/101) of patients with CTD-ILD and 28.9% (145/501) of patients with IPF developed grade 3 PGD 48-72 hours after transplant. There were no significant differences in odds of grade 3 PGD among patients with CTD-ILD compared to those with IPF (adjusted OR 1.12, 95% CI 0.64-1.97, p = 0.69), nor was CTD-ILD independently associated with a longer post-transplant time to extubation (adjusted HR for first extubation 0.87, 95% CI 0.66-1.13, p = 0.30). However, CTD-ILD was independently associated with a longer post-transplant hospital length of stay (median 23 days [IQR 14-35 days] vs17 days [IQR 12-28 days], adjusted HR for hospital discharge 0.68, 95% CI 0.51-0.90, p = 0.008).

CONCLUSION

Patients with CTD-ILD experienced significantly longer postoperative hospitalizations compared to IPF patients without an increased risk of grade 3 PGD.

Donor-specific antibody characteristics, including persistence and complement-binding capacity, increase risk for chronic lung allograft dysfunction

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is the major complication limiting long-term survival in lung transplant recipients (LTRs), with those developing donor-specific anti-human leukocyte antigen (HLA) antibodies (DSAs) previously found to have increased risk for CLAD. However, as DSA responses vary in timing of development, specificity, breadth, persistence, and complement-binding capacity, we hypothesized that these characteristics would impact CLAD and survival outcomes.

METHODS

We retrospectively analyzed DSA characteristics and outcomes in a single-center cohort of 582 LTRs who had serum samples collected prospectively from 2010 to 2016. Luminex-based single antigen bead assays were performed to assess DSA.

RESULTS

DSAs were detected in 247 LTRs (42%), of which 124 (21.3%) were de novo DSAs and 53 (9.1%) were complement-binding (C1q+). CLAD developed in 208 LTRs (35.7%) during the follow-up period, with 67.8% determined as bronchiolitis obliterans syndrome phenotype and 32.2% as restrictive allograft syndrome phenotype. We found a shorter time to CLAD in LTRs with persistent DSAs (p = 0.04) and HLA-DQ-specific DSAs (p = 0.03). LTRs who developed C1q+ DSAs had significantly shorter time to CLAD (p < 0.001), with 100% of C1q+ DSAs being persistent and no differences between CLAD phenotypes. CLAD-free survival was significantly reduced in LTRs who developed C1q+ DSAs (p = 0.001), HLA-DQ-specific DSAs (p = 0.03), and multiple DSAs (p = 0.02).

CONCLUSIONS

Together, our findings demonstrate that DSA characteristics of persistence, HLA-DQ specificity, and C1q+ DSAs are associated with shorter time to CLAD. Additionally, C1q+, HLA-DQ-specific, and multiple DSAs are associated with decreased CLAD-free survival. These characteristics may improve DSA risk stratification for deleterious outcomes in LTRs.

A high throughput screen for TMPRSS2 expression identifies FDA-approved and clinically advanced compounds that can limit SARS-CoV-2 entry

SARS-CoV-2 (2019-nCoV) is the pathogenic coronavirus responsible for the global pandemic of COVID-19 disease. The Spike (S) protein of SARS-CoV-2 attaches to host lung epithelial cells through the cell surface receptor ACE2, a process dependent on host proteases including TMPRSS2. Here, we identified small molecules that can reduce surface expression of TMPRSS2 using a 2,700 FDA-approved or current clinical trial compounds. Among these, homoharringtonine and halofuginone appear the most potent agents, reducing endogenous TMPRSS2 expression at sub-micromolar concentrations. These effects appear to be mediated by a drug-induced alteration in TMPRSS2 protein stability. We further demonstrate that halofuginone modulates TMPRSS2 levels through proteasomal-mediated degradation that involves the E3 ubiquitin ligase component DDB1- and CUL4-associated factor 1 (DCAF1). Finally, cells exposed to homoharringtonine and halofuginone, at concentrations of drug known to be achievable in human plasma, demonstrated marked resistance to SARS-CoV-2 pseudoviral infection. Given the safety and pharmacokinetic data already available for the compounds identified in our screen, these results should help expedite the rational design of human clinical trials designed to combat COVID-19 infection.

Aerosolization of Second-generation Triazoles: In Vitro Evaluation and Application in Therapy of Invasive Airway Aspergillosis

BACKGROUND

A lung transplant patient with invasive aspergillosis (IA) manifested symptoms of voriconazole-induced transaminitis with systemic voriconazole and progression of IA after switching to oral posaconazole. With limited options for standard triazole therapy, aerosolized delivery with one of the second-generation triazoles was considered.

METHODS

Feasibility for aerosolized delivery was evaluated using cascade impactor and analysis of physicochemical characteristics of voriconazole (10 mg/mL) and posaconazole (6, 12 mg/mL) solutions.

RESULTS

Both triazoles showed favorable characteristics for aerosol delivery with mass median aerodynamic diameter, geometric standard deviation, respirable fraction (<5.4 µm) of 2.8 µm, 2.0, 86%; 3.4 µm, 2.4, 78%; and 3.0 µm, 2.3, 79% for voriconazole and 6, 12 mg/mL of posaconazole, respectively. Aspergillus fumigatus isolate from the patient was more susceptible to voriconazole, and hence aerosolized voriconazole was introduced around the third month posttransplant at 40 mg TID for 1 week, 40 mg BID for 1 week, followed by 40 mg daily thereafter, along with IV caspofungin (50 mg/d) and liposomal amphotericin B (300 mg/d). The aerosol regimen was well tolerated by the patient with undetectable trough plasma levels of voriconazole. Bronchoscopy at the fourth month revealed improvement in anastomotic plaques with reduction in bronchoalveolar lavage galactomannan values (7.48-2.15 ng/mL). This consolidated aerosolized and intravenous regimen was maintained until 2.97 years posttransplant.

CONCLUSIONS

The intravenous solutions of both second-generation triazoles showed characteristics that were suitable for aerosol delivery. Our report further adds to the therapeutic experience with the use of aerosolized voriconazole for IA in a lung transplant patient.

Idiopathic pulmonary fibrosis lung transplant recipients are at increased risk for EBV-associated posttransplant lymphoproliferative disorder and worse survival

Epstein-Barr virus (EBV)-associated posttransplant lymphoproliferative disorder (EBV-PTLD) is a serious complication in lung transplant recipients (LTRs) associated with significant mortality. We performed a single-center retrospective study to evaluate the risks for PTLD in LTRs over a 7-year period. Of 611 evaluable LTRs, we identified 28 cases of PTLD, with an incidence of 4.6%. Kaplan-Meier analysis showed a decreased freedom from PTLD in idiopathic pulmonary fibrosis (IPF)-LTRs (P < .02). Using a multivariable Cox proportional hazards model, we found IPF (hazard ratio [HR] 3.51, 95% confidence interval [CI] 1.33-8.21, P = .01) and alemtuzumab induction therapy (HR 2.73, 95% CI 1.10-6.74, P = .03) as risk factors for PTLD, compared to EBV mismatch (HR: 34.43, 95% CI 15.57-76.09, P < .0001). Early PTLD (first year) was associated with alemtuzumab use (P = .04), whereas IPF was a predictor for late PTLD (after first year) (P = .002), after controlling for age and sex. Kaplan-Meier analysis revealed a shorter time to death from PTLD in IPF LTRs compared to other patients (P = .04). The use of alemtuzumab in EBV mismatch was found to particularly increase PTLD risk. Together, our findings identify IPF LTRs as a susceptible population for PTLD. Further studies are required to understand the mechanisms driving PTLD in IPF LTRs and develop strategies to mitigate risk.

Prolonged Cold Ischemia Induces Necroptotic Cell Death in Ischemia-Reperfusion Injury and Contributes to Primary Graft Dysfunction after Lung Transplantation

Primary graft dysfunction (PGD) is a major cause of morbidity and mortality after lung transplantation. Ischemia-reperfusion injury (IRI) is a key event that contributes to PGD, though complex interactions affect donor lungs status, such as preceding brain death (BD), hemorrhagic shock (HS), and pre-engraftment lung management, the latter recognized as important risk factors for PGD. We hypothesized that a multi-hit isogenic mouse model of lung transplantation is more closely linked to PGD than IRI alone. Left lung transplants were performed between inbred C57BL/6 mice. A one-hit model of IRI was established by inducing cold ischemia (CI) of the donor lungs at 0°C for 1, 72, or 96 hours before engraftment. Multi-hit models were established by inducing 24 hours of HS and/or 3 hours of BD before 24 hours of CI. The recipients were killed at 24 hours after transplant and lung graft samples were analyzed. In the one-hit model of IRI, up to 72-hour CI time resulted in minimal cellular infiltration near small arteries after 24-hour reperfusion. Extension of CI time to 96 hours led to increased cellular infiltration and necroptotic pathway activation, without evidence of apoptosis, after 24-hour reperfusion. In a multi-hit model of PGD, "HS + BD + IRI" demonstrated increased lung injury, cellular infiltration, and activation of necroptotic and apoptotic pathways compared with IRI alone. Treatment with an inhibitor of receptor-interacting protein kinase 1 kinase, necrostatin-1, resulted in a significant decrease of downstream necroptotic pathway activation in both single- and multi-hit models of IRI. Thus, activation of necroptosis is a central event in IRI after prolonged CI, though it may not be sufficient to cause PGD alone. Pathological evaluation of donor lungs after CI-induced IRI, in conjunction with pre-engraftment donor lung factors in our multi-hit model, demonstrated early evidence of lung injury consistent with PGD. Our findings support the premise that pre-existing donor lung status is more important than CI time alone for inflammatory pathway activation in PGD, which may have important clinical implications for donor lung retrieval.

The RNFT2/IL-3Rα axis regulates IL-3 signaling and innate immunity

Interleukin-3 (IL-3) receptor α (IL-3Rα) is the α subunit of the ligand-specific IL-3R and initiates intracellular signaling in response to IL-3. IL-3 amplifies proinflammatory signaling and cytokine storm in murine sepsis models. Here we found that RNFT2 (RING finger transmembrane-domain containing protein 2, also TMEM118), a previously uncharacterized RING finger ubiquitin E3 ligase, negatively regulated IL-3-dependent cellular responses through IL-3Rα ubiquitination and degradation in the proteasome. In vitro, IL-3 stimulation promoted IL-3Rα proteasomal degradation dependent on RNFT2, and we identified IL-3Rα lysine 357 as a ubiquitin acceptor site. We determined that LPS priming reduces RNFT2 abundance, extends IL-3Rα half-life, and sensitizes cells to the effects of IL-3, acting synergistically to increase proinflammatory signaling. In vivo, IL-3 synergized with LPS to exacerbate lung inflammation in LPS and Pseudomonas aeruginosa-challenged mice; conversely, IL-3 neutralization reduced LPS-induced lung injury. Further, RNFT2 overexpression reduced lung inflammation and injury, whereas Rnft2 knockdown exacerbated inflammatory responses in LPS-induced murine lung injury. Last, we examined RNFT2 and IL-3Rα in human lung explants from patients with cystic fibrosis and also showed that IL-3 is elevated in mechanically ventilated critically ill humans at risk for acute respiratory distress syndrome. These results identify RNFT2 as a negative regulator of IL-3Rα and show a potential role for the RNFT2/IL-3Rα/IL-3 axis in regulating innate immune responses in the lung.

Early KLRG1+ but Not CD57+CD8+ T Cells in Primary Cytomegalovirus Infection Predict Effector Function and Viral Control

CMV remains an important opportunistic pathogen in high-risk lung transplant recipients. We characterized the phenotype and function of CD8⁺ T cells from acute/primary into chronic CMV infection in 23 (donor+/recipient-; D+R-) lung transplant recipients and found rapid induction of both KLRG1⁺ and/or CD57⁺ CMV-specific CD8⁺ T cells with unexpected coexpression of CD27. These cells demonstrated maturation from an acute effector T cell (T_AEFF) to an effector memory T cell (T_EM) phenotype with progressive enrichment of KLRG1⁺CD57⁺CD27^- cells into memory. CMV-specific KLRG1⁺ T_AEFF were capable of in vitro proliferation that diminished upon acquisition of CD57, whereas only KLRG1⁺ expression correlated with T-bet expression and effector function. In contrast to blood T_AEFF, lung mucosal T_AEFF demonstrated reduced KLRG1/T-bet expression but similar CD57 levels. Additionally, increased KLRG1⁺T_AEFF were associated with early immune viral control following primary infection. To our knowledge, our findings provide new insights into the roles of KLRG1 and CD57 expression in human T cells, forming the basis for a refined model of CD8⁺ T cell differentiation during CMV infection.

GDF15 is an epithelial-derived biomarker of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is the most common and devastating of the interstitial lung diseases. Epithelial dysfunction is thought to play a prominent role in disease pathology, and we sought to characterize secreted signals that may contribute to disease pathology. Transcriptional profiling of senescent type II alveolar epithelial cells from mice with epithelial-specific telomere dysfunction identified the transforming growth factor-β family member, growth and differentiation factor 15 (Gdf15), as the most significantly upregulated secreted protein. Gdf15 expression is induced in response to telomere dysfunction and bleomycin challenge in mice. Gdf15 mRNA is expressed by lung epithelial cells, and protein can be detected in peripheral blood and bronchoalveolar lavage following bleomycin challenge in mice. In patients with IPF, GDF15 mRNA expression in lung tissue is significantly increased and correlates with pulmonary function. Single-cell RNA sequencing of human lungs identifies epithelial cells as the primary source of GDF15, and circulating concentrations of GDF15 are markedly elevated and correlate with disease severity and survival in multiple independent cohorts. Our findings suggest that GDF15 is an epithelial-derived secreted protein that may be a useful biomarker of epithelial stress and identifies IPF patients with poor outcomes.

Impaired Cytomegalovirus Immunity in Idiopathic Pulmonary Fibrosis Lung Transplant Recipients with Short Telomeres

RATIONALE

Cytomegalovirus (CMV)-related morbidities remain one of the most common complications after lung transplantation and have been linked to allograft dysfunction, but the factors that predict high risk for CMV complications and effective immunity are incompletely understood.

OBJECTIVES

To determine if short telomeres in idiopathic pulmonary fibrosis (IPF) lung transplant recipients (LTRs) predict the risk for CMV-specific T-cell immunity and viral control.

METHODS

We studied IPF-LTRs (n = 42) and age-matched non-IPF-LTRs (n = 42) and assessed CMV outcomes. We measured lymphocyte telomere length and DNA sequencing, and assessed CMV-specific T-cell immunity in LTRs at high risk for CMV events, using flow cytometry and fluorescence in situ hybridization.

MEASUREMENTS AND MAIN RESULTS

We identified a high prevalence of relapsing CMV viremia in IPF-LTRs compared with non-IPF-LTRs (69% vs. 31%; odds ratio, 4.98; 95% confidence interval, 1.95-12.50; P < 0.001). Within this subset, IPF-LTRs who had short telomeres had the highest risk of CMV complications (P < 0.01) including relapsing-viremia episodes, end-organ disease, and CMV resistance to therapy, as well as shorter time to viremia versus age-matched non-IPF control subjects (P < 0.001). The short telomere defect in IPF-LTRs was associated with significantly impaired CMV-specific proliferative responses, T-cell effector functions, and induction of the major type-1 transcription factor T-bet (T-box 21;TBX21).

CONCLUSIONS

Because the short telomere defect has been linked to the pathogenesis of IPF in some cases, our data indicate that impaired CMV immunity may be a systemic manifestation of telomere-mediated disease in these patients. Identifying this high-risk subset of LTRs has implications for risk assessment, management, and potential strategies for averting post-transplant CMV morbidities.

Jejuno-jejunal intussusception in a post-lung transplant patient from a gastrojejunostomy tube: A case report

INTRODUCTION

Gastro-jejunostomy tube is used for post-pyloric feeding for critical-ill patient who cannot tolerate oral alimentation. Jejuno-jejunal intussusception is a rare complication of gastrojejunostomy tube.

PRESENTATION OF CASE

A 39-year-old male with history of severe combined immunodeficiency, Achalasia and end-stage lung disease underwent double lung transplantation. After lung transplantation, he required gastrojejunostomy(GJ) tube placement due to his esophageal disease. Four days after gastrojejunostomy tube placement, he developed jejuno-jejunal intussusception. A 15 cm segment of thickened and enlarged bowel, which consisted of the intussusception were identified laparoscopically. Surgical reduction was performed without bowel resection.

DISCUSSION

Intussusception is uncommon in adults compared to pediatric population. In this rare case, the jejunal limb of the GJ tube placed in jejunum was the cause of jejunojejunal intussusception serving as the lead point. The GJ tube should not be placed farther down from ligaments of Treiz to prevent jejuno-jejunal intussusception.

CONCLUSIONS

A heightened index of suspicion for this rare complication should exist with a presenting patient has signs of proximal bowel obstruction and CT evidence of intussusception.

Foxp3+ T lymphocytes: immune regulators within the lung allograft

Antibody-mediated rejection (AMR) has emerged as an important cause of lung graft failure. In the current issue of the JCI, a study by Li et al. identifies a critical role of Foxp3+ T cells residing within lung allografts in the regulation of AMR. This study not only provides new insights into the nature of lung allografts as a primary site where T and B cell priming and immune regulation can occur, but also introduces the mouse orthotopic lung transplant as a model for studying the immunobiology of AMR. Because AMR can be so difficult to effectively treat in lung transplant recipients, the development of an animal model is a major advance in understanding the immunopathogenesis of AMR.

Cytokine-targeted therapy for the management of solid organ transplant recipients

INTRODUCTION

The number of solid organ transplants completed annually continues to trend upwards each year. Despite this, maintenance immunosuppression available on the market has remained relatively stagnant. Standard triple immunosuppression, composed typically of tacrolimus, mycophenolate, and steroids, lead to many side effects that limit the use of these medications. Tacrolimus, specifically, causes nephrotoxicity that can lead to renal dysfunction requiring a kidney transplant down the road. Alternative therapies for the management of immunosuppression need to be identified to try to mitigate these adverse effects. BODY: Cytokines are responsible for facilitating T cell differentiation and lead to the activation of inflammatory mediators that can contribute to graft damage and ultimately rejection. IL-4, IL-6, IL-12/23, and IL-15 are attractive targets for medications to try to ameliorate graft rejection. Various cytokine-targeted medications are currently available on the market for the treatment of inflammatory and autoimmune conditions such as rheumatoid arthritis, psoriatic arthritis, Crohn's, and multiple sclerosis.

CONCLUSION

This article reviews cytokine involvement in alloimmunity and the potential role cytokine-targeted therapy may play in prevention of allograft rejection in solid organ transplant recipients.

Detrimental Association of Hypogammaglobulinemia With Chronic Lung Allograft Dysfunction and Death Is Not Mitigated by On-Demand Immunoglobulin G Replacement After Lung Transplantation

BACKGROUND:

Hypogammaglobulinemia (HGG), immunoglobulin G (IgG) <700 mg/dL, is associated with infections, chronic lung allograft dysfunction, and death following lung transplantation. This study evaluates the use of on-demand intravenous IgG in lung transplant recipients with HGG.

MATERIALS AND METHODS:

This single-center retrospective cohort study of adult lung recipients evaluated 3 groups, no, untreated (u), or treated (t) HGG at first IgG administration or a matched time posttransplant. Primary outcome was freedom from allograft dysfunction. Secondary outcomes included development of advanced dysfunction, rejection, infection burden, and mortality.

RESULTS:

Recipients included 484 (no HGG: 76, uHGG: 192, tHGG: 216). Freedom from chronic allograph dysfunction was highest in the non-HGG group 2 years post-enrollment (no HGG 77.9% vs uHGG 56.4% vs tHGG 52.5%; P = .002). Freedom from advanced dysfunction was significantly different 2 years post-enrollment (no HGG 90.5% vs uHGG 84.7% vs tHGG 75.4%; P = .017). Patients without HGG and those with uHGG had less mortality at 2 years post-enrollment (no HGG 84.2% vs uHGG 81.3% vs tHGG 64.8%; P < .001). Gram-negative pneumonias occurred more often in the tHGG group ( P = .02).

CONCLUSIONS:

Development of chronic lung allograft dysfunction, patient survival, rejection burden, and key infectious outcomes in lung transplant recipients were still problematic in the context of on-demand IgG therapy. Prospective studies are warranted.

Belatacept for maintenance immunosuppression in cardiothoracic transplantation: The potential frontier

Current immunosuppressive regimens with calcineurin inhibitors have improved the management of patients after transplantation. However, their adverse effects are linked to increased morbidity and limit the long-term survival of heart and lung transplant recipients. Belatacept, a costimulation inhibitor interfering with the interaction between CD28 on T cells and the B7 ligands on antigen presenting cells, has shown success and is currently approved for use in renal transplant recipients. Furthermore, it lacks many of the cardiovascular, metabolic, neurologic, and renal adverse of effects of calcineurin inhibitors that have the largest impact on long-term survival in cardiothoracic transplant. Additionally, it requires no therapeutic drug monitoring and is only administered once a month. Limitations to belatacept use have been observed that must be considered when comparing immunosuppression options. Despite this, maintenance immunosuppression with belatacept has the potential to improve outcomes in cardiothoracic transplant recipients, as it has with kidney transplant recipients. However, no large clinical trials investigating belatacept for maintenance immunosuppression in heart and lung transplant recipients exist. There is a large need for focused research of belatacept in cardiothoracic transplantation. Belatacept is a viable treatment option for maintenance immunosuppression, and it is reasonable to pursue more evidence in cardiothoracic transplant recipients.

Evaluation of Direct Oral Anticoagulation Therapy in Heart and Lung Transplant Recipients

CONTEXT

Anticoagulation therapy is common in thoracic transplant recipients. Direct oral anticoagulants (DOACs) are alternatives to warfarin therapy, but characterization of their use in solid organ transplant is absent.

OBJECTIVE

The primary objective of this study was to describe a thoracic transplant patient population initiated on DOAC therapy. Secondary objectives were to assess adverse reactions, venous thromboembolism (VTE) recurrence, and drug-drug interactions during DOAC therapy.

STUDY DESIGN

Single-center retrospective cohort study.

SETTING

A tertiary care medical center including inpatient hospitalization and outpatient transplant clinic visits.

PATIENTS

Thoracic transplant recipients who were initiated on DOACs between May 1, 2011, and March 1, 2015, at the University of Pittsburgh Medical Center were included.

RESULTS

A total of 37 patients were included in the analysis. A majority of the patients were lung transplant recipients (86.4%) with a median age of 60.7 years. Twenty-eight patients had a history of VTE. The primary indication for DOAC initiation was VTE (86.5%). Rivaroxaban (78.4%) was the most commonly utilized agent. Dose reductions for major drug interactions (37.8%), renal insufficiency (10.8%), or both (8.1%) occurred within the study. Two patients had breakthrough VTE during DOAC therapy. Eight bleeding events were reported in the cohort, one of which was considered a major bleed. There was no difference in the incidence of bleeding in patients with drug-drug interactions and without drug-drug interactions during DOAC therapy (26.0% vs 7.1%, P = .154).

CONCLUSION

Direct oral anticoagulant therapy was well tolerated by thoracic transplant recipients. Drug interactions and renal dose adjustments were common.

Increasing tacrolimus time-in-therapeutic range is associated with superior one-year outcomes in lung transplant recipients

Calcineurin inhibitors (CNIs) are the backbone of traditional immunosuppressive regimens for lung transplant recipients (LTR). The CNIs are both narrow therapeutic index drugs with significant interpatient and intrapatient variability that require therapeutic drug monitoring to ensure safety and effectiveness. We hypothesized that tacrolimus time-in-therapeutic range (TTR) affects acute and chronic rejection rates in LTRs. This was a single-center, observational, cross-sectional study of 292 adult LTRs. Subjects who received tacrolimus posttransplant for the first year were included. TTR was calculated at 1 year using protocol goal ranges (12-15 mg/mL months 0-6; 10-12 mg/mL for months 7-12). The primary outcome was acute cellular rejection (ACR) burden at 1 year. Chronic lung allograft dysfunction (CLAD), mortality, and infection rate were assessed as secondary outcomes at 1 year. Primary and secondary outcomes were assessed using logistic regression. Increasing TTR by 10% was associated with a significantly lower likelihood of high-burden ACR at 1 year on univariable (OR 0.46, 95% CI 0.40-0.54, P < .001) and multivariable (OR 0.64, 95% CI 0.47-0.86, P = .003) assessment, controlling for age and induction agent. Increasing TTR by 10% was also associated with lower rates of CLAD (P < .001) and mortality (P < .001) at 1 year. Prospective studies confirming these findings appear warranted.

Systematic review and meta-analysis of post-transplant lymphoproliferative disorder in lung transplant recipients

A systematic review of papers in English on post-transplant lymphoproliferative disorder (PTLD) in lung transplant recipients (LTR) using MEDLINE, EMBASE, SCOPUS, and Cochrane databases was performed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations were strictly adhered to. Pooled odds ratios (pOR) were calculated from a random-effects model, and heterogeneity among studies was quantitated using I² values. Fourteen studies published from 2005 to 2015 were included in the meta-analysis. One hundred and sixty-four lung transplant recipients were included. LTRs who received single vs bilateral were associated with a 7.67-fold risk of death after PTLD (6 studies with 64 LTRs; pOR 7.67 95% CI 1.98-29.70; P = .003). pOR of death for early onset PTLD (<1 year post-LT) vs late onset (>1 year post-LT) was not different (3 studies with 72 LTRS; pOR 0.62, 95% CI 0.20-1.86, P = .39). Standardized mean difference (SMD) in time from transplant to PTLD onset between LTRs who died vs alive was not different (9 studies with 109 LTRs; SMD 0.03, 95% CI -0.48-0.53, P = .92). Survival in polymorphic vs monomorphic PTLD and extranodal vs nodal disease was similar (4 studies with 31 LTRs; pOR 0.44, 95% CI 0.08-2.51; P = .36. 6 studies with 81 LTRs; pOR 1.05 95% CI 0.31-3.52, P = .94). This meta-analysis demonstrates that single LTRs are at a higher risk of death vs bilateral LTRs after the development of PTLD.

Azithromycin Fails to Prevent Accelerated Airway Obliteration in T-bet-/- Mouse Lung Allograft Recipients

BACKGROUND

Cellular and molecular mechanisms of acute and chronic lung allograft rejection have yet to be clearly defined, and obliterative bronchiolitis (OB) remains the primary limitation to survival in lung transplant recipients (LTRs). We have previously shown that T-bet-deficient recipients of full major histocompatibility complex (MHC)-mismatched, orthotopic left lung transplants develop accelerated obliterative airway disease (OAD) in the setting of acute cellular rejection characterized by robust alloimmune CD8⁺ interleukin (IL)-17 and interferon (IFN)-γ responses that are attenuated with neutralization of IL-17. Azithromycin has been shown to be beneficial in some LTRs with bronchiolitis obliterans syndrome/OB. Here, we evaluated the effects of azithromycin on rejection pathology and T-cell effector responses in T-bet^-/- recipients of lung transplants.

METHODS

Orthotopic left lung transplantation was performed in BALB/c → B6 wild type or BALB/c → B6 T-bet^-/- strain combinations as previously described. Mice treated with azithromycin received 10 mg/kg or 50 mg/kg subcutaneously daily. Lung allograft histopathology was analyzed at day 10 or day 21 post-transplantation, and neutrophil staining for quantification was performed using anti-myeloperoxidase. Allograft mononuclear cells were isolated at day 10 for T-cell effector cytokine response assessment using flow cytometry.

RESULTS

We show that while azithromycin significantly decreases lung allograft neutrophilia and CXCL1 levels and attenuates allospecific CD8⁺ IL-17 responses early post-transplantation, OAD persists in T-bet-deficient mice.

CONCLUSIONS

Our results indicate that lung allograft neutrophilia is not essential for the development of OAD in this model and suggest allospecific T-cell responses that remain despite marked attenuation of CD8⁺ IL-17 are sufficient for obliterative airway inflammation and fibrosis.