Unlocking the potential of RNA-based therapeutics in the lung: current status and future directions.

Awareness of RNA-based therapies has increased after the widespread adoption of mRNA vaccines against SARS-CoV-2 during the COVID-19 pandemic. These mRNA vaccines had a significant impact on reducing lung disease and mortality. They highlighted the potential for rapid development of RNA-based therapies and advances in nanoparticle delivery systems.

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.

Robust segregation of donor and recipient cells from single-cell RNA-sequencing of transplant samples.

Background: Single-cell RNA-sequencing (scRNA-seq) technology has revealed novel cell populations in organs, uncovered regulatory relationships between genes, and allowed for tracking of cell lineage trajectory during development. It demonstrates promise as a method to better understand transplant biology; however, fundamental bioinformatic tools for its use in the context of transplantation have not been developed. One major need has been a robust method to identify cells as being either donor or recipient genotype origin, and ideally without the need to separately sequence the donor and recipient.

Donor Batf3 inhibits murine lung allograft rejection and airway fibrosis.

Chronic lung allograft dysfunction (CLAD) limits survival after lung transplantation. Noxious stimuli entering the airways foster CLAD development. Classical dendritic cells (cDCs) link innate and adaptive immunity and exhibit regional and functional specialization in the lung.

Donor and recipient human leukocyte antigen-G polymorphisms modulate the risk of adverse immunologic events following lung transplantation.

The long-term benefits of lung transplantation (LTx) are limited by pathogenic alloimmune responses that drive injury, inflammation, and chronic dysfunction. Human leukocyte antigen-G (HLA-G) plays a key role in the modulation of these pathways. This study assesses the impact of the HLA-G genotype on immunologic risk and survival following LTx.

A biomarker assay to risk-stratify patients with symptoms of respiratory tract infection.

Background: Patients who present to an emergency department (ED) with respiratory symptoms are often conservatively triaged in favour of hospitalisation. We sought to determine if an inflammatory biomarker panel that identifies the host response better predicts hospitalisation in order to improve the precision of clinical decision making in the ED.

Methods: From April 2020 to March 2021, plasma samples of 641 patients with symptoms of respiratory illness were collected from EDs in an international multicentre study: Canada (n=310), Italy (n=131) and Brazil (n=200).

Recipient bone marrow-derived IL-17 receptor A-positive cells drive allograft fibrosis in a mouse intrapulmonary tracheal transplantation model.

IL-17A is implicated in the pathogenesis of chronic lung allograft dysfunction, which limits survival after lung transplantation. While many cells express the IL-17 receptor A (IL-17RA) which is the main receptor for IL-17A, the cellular targets of IL-17A in development of post-transplant fibrosis are unknown. The purpose of this study was to determine whether IL-17RA expression by donor or recipient structural or bone marrow (BM) cells is required for the development of allograft fibrosis in a mouse intrapulmonary tracheal transplantation (IPTT) model.

delivery of regulatory T-cells for control of alloimmune priming in the donor lung.

Background: Survival after lung transplantation (LTx) is hampered by uncontrolled inflammation and alloimmunity. Regulatory T-cells (Tregs) are being studied as a cellular therapy in solid organ transplantation. Whether these systemically administered Tregs can function at the appropriate location and time is an important concern.

Lung transplantation for late-onset non-infectious chronic pulmonary complications of allogenic hematopoietic stem cell transplant.

Background: Late onset non-infectious pulmonary complications (LONIPCs) following allogenic hematopoietic stem cell transplantation (allo-HSCT) confer a significant mortality risk. Lung transplantation (LTx) has the potential to provide survival benefit but the impact of prior allo-HSCT on post-LTx outcomes is not well studied.

Methods: This retrospective, single-centre cohort study assessed the post-LTx outcomes of adults with LONIPCs of allo-HSCT.

IL-6 receptor blockade for allograft dysfunction after lung transplantation in a patient with COPA syndrome.

Objective: COPA syndrome is a genetic disorder of retrograde cis-Golgi vesicle transport that leads to upregulation of pro-inflammatory cytokines (mainly IL-1β and IL-6) and the development of interstitial lung disease (ILD). The impact of COPA syndrome on post-lung transplant (LTx) outcome is unknown but potentially detrimental. In this case report, we describe progressive allograft dysfunction following LTx for COPA-ILD.

The role of innate immunity in the long-term outcome of lung transplantation.

Long-term survival after lung transplantation remains suboptimal due to chronic lung allograft dysfunction (CLAD), a progressive scarring process affecting the graft. Although anti-donor alloimmunity is central to the pathogenesis of CLAD, its underlying mechanisms are not fully elucidated and it is neither preventable nor treatable using currently available immunosuppression. Recent evidence has shown that innate immune stimuli are fundamental to the development of CLAD.

A B cell-dependent pathway drives chronic lung allograft rejection after ischemia-reperfusion injury in mice.

Chronic lung allograft dysfunction (CLAD) limits long-term survival after lung transplant (LT). Ischemia-reperfusion injury (IRI) promotes chronic rejection (CR) and CLAD, but the underlying mechanisms are not well understood. To examine mechanisms linking IRI to CR, a mouse orthotopic LT model using a minor alloantigen strain mismatch (C57BL/10 [B10, H-2 ] → C57BL/6 [B6, H-2 ]) and isograft controls (B6→B6) was used with antecedent minimal or prolonged graft storage.

Donor human leukocyte antigen-G single nucleotide polymorphisms are associated with post-lung transplant mortality.

Human leukocyte antigen (HLA)-G is a non-classical HLA that inhibits immune responses. Its expression is modified by single nucleotide polymorphisms (SNPs), which are associated with transplant outcomes. Our aim was to investigate the association of donor and recipient HLA-G SNPs with chronic lung allograft dysfunction (CLAD) and mortality after lung transplantation.

Epithelial cell death markers in bronchoalveolar lavage correlate with chronic lung allograft dysfunction subtypes and survival in lung transplant recipients-a single-center retrospective cohort study.

Chronic lung allograft dysfunction (CLAD) remains the leading cause of late death after lung transplantation. Epithelial injury is thought to be a key event in the pathogenesis of CLAD. M30 and M65 are fragments of cytokeratin-18 released specifically during epithelial cell apoptosis and total cell death, respectively.

Innate Control of Tissue-Reparative Human Regulatory T Cells.

Regulatory T cell (Treg) therapy is a potential curative approach for a variety of immune-mediated conditions, including autoimmunity and transplantation, in which there is pathological tissue damage. In mice, IL-33R (ST2)-expressing Tregs mediate tissue repair by producing the growth factor amphiregulin, but whether similar tissue-reparative Tregs exist in humans remains unclear. We show that human Tregs in blood and multiple tissue types produced amphiregulin, but this was neither a unique feature of Tregs nor selectively upregulated in tissues.

Spectrum of chronic lung allograft pathology in a mouse minor-mismatched orthotopic lung transplant model.

Chronic lung allograft dysfunction (CLAD) is a fatal condition that limits survival after lung transplantation (LTx). The pathological hallmark of CLAD is obliterative bronchiolitis (OB). A subset of patients present with a more aggressive CLAD phenotype, called restrictive allograft syndrome (RAS), characterized by lung parenchymal fibrosis (PF).

A novel combined ex vivo and in vivo lentiviral interleukin-10 gene delivery strategy at the time of transplantation decreases chronic lung allograft rejection in mice.

Objective: Our objective was to develop a rapid-onset and durable gene-delivery strategy that is applicable at the time of transplant to determine its effects on both acute rejection and chronic lung allograft fibrosis using a mouse orthotopic lung transplant model.

Methods: C57BL/6 mice received an orthotopic left lung transplant from syngeneic donors or C57BL/10 donors. By using syngeneic lung transplantation, we established a novel gene transfer protocol with lentivirus luciferase intrabronchial administration to the donor lung ex vivo before transplantation.

Sequential broncho-alveolar lavages reflect distinct pulmonary compartments: clinical and research implications in lung transplantation.

Background: Bronchoalveolar lavage (BAL) has proven to be very useful to monitor the lung allograft after transplantation. In addition to allowing detection of infections, multiple BAL analytes have been proposed as potential biomarkers of lung allograft rejection or dysfunction. However, BAL collection is not well standardized and differences in BAL collection represent an important source of variation.

Measurement of T Cell Alloreactivity Using Imaging Flow Cytometry.

The measurement of immunological reactivity to donor antigens in transplant recipients is likely to be crucial for the successful reduction or withdrawal of immunosuppression. The mixed leukocyte reaction (MLR), limiting dilution assays, and trans-vivo delayed-type hypersensitivity (DTH) assay have all been applied to this question, but these methods have limited predictive ability and/or significant practical limitations that reduce their usefulness. Imaging flow cytometry is a technique that combines the multiparametric quantitative powers of flow cytometry with the imaging capabilities of fluorescent microscopy.

Halofuginone treatment reduces interleukin-17A and ameliorates features of chronic lung allograft dysfunction in a mouse orthotopic lung transplant model.

Background: Increasing evidence suggests that interleukin (IL)-17A plays an important role in chronic lung allograft dysfunction (CLAD), characterized by airway and lung parenchymal fibrosis, after lung transplantation. Halofuginone is a plant derivative that has been shown to inhibit Th17 differentiation. The purpose of this study was to examine the effect of halofuginone on CLAD development using a minor alloantigen‒mismatched mouse orthotopic lung transplant model.

FcRγ controls the fas-dependent regulatory function of lymphoproliferative double negative T cells.

Patients with autoimmune lymphoproliferative syndrome (ALPS) and lymphoproliferation (LPR) mice are deficient in Fas, and accumulate large numbers of αβ-TCR(+), CD4(-), CD8(-) double negative (DN) T cells. The function of these DN T cells remains largely unknown. The common γ subunit of the activating Fc receptors, FcRγ, plays an important role in mediating innate immune responses.

Rejection of tracheal allograft by intrapulmonary lymphoid neogenesis in the absence of secondary lymphoid organs.

Background: Obliterative bronchiolitis after lung transplantation is associated with intrapulmonary lymphoid neogenesis. The purpose of this study was to examine the role of lymphoid neogenesis, especially its relationship with secondary lymphoid organs (SLOs) in allograft airway rejection.

Methods: A murine intrapulmonary tracheal transplant model and a conventional subcutaneous tracheal transplant model were tested using wild-type control mice and splenectomized lymphotoxin α knockout (LT) mice deficient in SLOs as recipients.

FcRγ promotes T cell apoptosis in Fas-deficient mice.

Deficiency of Fas or its ligand leads to lymphocyte accumulation, lymphadenopathy, splenomegaly, and autoimmunity in mice and humans. Although the Fas pathway is important for limiting the number of peripheral T cells, inactivation of other pro-apoptotic molecules can also perturb T cell homeostasis independently of and/or in concert with Fas deficiency. Here, we show that combined deficiency of Fas and the Fc receptor common γ signaling chain (FcRγ) results in worsened T cell accumulation in comparison with mice lacking Fas alone, with a particularly marked increase in the number of TCRαβ(+)CD4(-)CD8(-) double negative (DN) T cells.

Autocrine IFNγ controls the regulatory function of lymphoproliferative double negative T cells.

TCRαβ(+) CD4(-)CD8(-)NK(-) double negative T cells (DN T cells) can act as regulatory T cells to inhibit allograft rejection and autoimmunity. Their role in graft-versus-host disease and mechanisms of suppression remain elusive. In this study, we demonstrate that DN T cells can inhibit CD4(+) T cell-mediated GVHD in a semi-allogeneic model of bone marrow transplantation.