Involvement of interleukin-17 during lymphocytic bronchiolitis in lung transplant patients

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

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

Immune processes in the pathogenesis of chronic lung allograft dysfunction: identifying the missing pieces of the puzzle

Lung transplantation is the optimal treatment for selected patients with end-stage chronic lung diseases. However, chronic lung allograft dysfunction remains the leading obstacle to improved long-term outcomes. Traditionally, lung allograft rejection has been considered primarily as a manifestation of cellular immune responses. However, in reality, an array of complex, interacting and multifactorial mechanisms contribute to its emergence. Alloimmune-dependent mechanisms, including T-cell-mediated rejection and antibody-mediated rejection, as well as non-alloimmune injuries, have been implicated. Moreover, a role has emerged for autoimmune responses to lung self-antigens in the development of chronic graft injury. The aim of this review is to summarise the immune processes involved in the pathogenesis of chronic lung allograft dysfunction, with advanced insights into the role of innate immune pathways and crosstalk between innate and adaptive immunity, and to identify gaps in current knowledge.

Delivering macrolide antibiotics to heal a broken heart - And other inflammatory conditions

Drug carriers to deliver macrolide antibiotics, such as azithromycin, show promise as antibacterial agents. Macrolide drug carriers have largely focused on improving the drug stability and pharmacokinetics, while reducing adverse reactions and improving antibacterial activity. Recently, macrolides have shown promise in treating inflammatory conditions by promoting a reparative effect and limiting detrimental pro-inflammatory responses, which shifts the immunologic setpoint from suppression to balance. While macrolide drug carriers have only recently been investigated for their ability to modulate immune responses, the previous strategies that deliver macrolides for antibacterial therapy provide a roadmap for repurposing the macrolide drug carriers for therapeutic interventions targeting inflammatory conditions. This review describes the antibacterial and immunomodulatory activity of macrolides, while assessing the past in vivo evaluation of drug carriers used to deliver macrolides with the intention of presenting a case for increased effort to translate macrolide drug carriers into the clinic.

Immunomodulatory Effects of Azithromycin Revisited: Potential Applications to COVID-19

The rapid advancement of the COVID-19 pandemic has prompted an accelerated pursuit to identify effective therapeutics. Stages of the disease course have been defined by viral burden, lung pathology, and progression through phases of the immune response. Immunological factors including inflammatory cell infiltration and cytokine storm have been associated with severe disease and death. Many immunomodulatory therapies for COVID-19 are currently being investigated, and preliminary results support the premise of targeting the immune response. However, because suppressing immune mechanisms could also impact the clearance of the virus in the early stages of infection, therapeutic success is likely to depend on timing with respect to the disease course. Azithromycin is an immunomodulatory drug that has been shown to have antiviral effects and potential benefit in patients with COVID-19. Multiple immunomodulatory effects have been defined for azithromycin which could provide efficacy during the late stages of the disease, including inhibition of pro-inflammatory cytokine production, inhibition of neutrophil influx, induction of regulatory functions of macrophages, and alterations in autophagy. Here we review the published evidence of these mechanisms along with the current clinical use of azithromycin as an immunomodulatory therapeutic. We then discuss the potential impact of azithromycin on the immune response to COVID-19, as well as caution against immunosuppressive and off-target effects including cardiotoxicity in these patients. While azithromycin has the potential to contribute efficacy, its impact on the COVID-19 immune response requires additional characterization so as to better define its role in individualized therapy.

Mathematical modeling of peripheral blood neutrophil kinetics to predict CLAD after lung transplantation

BACKGROUND

The presence of neutrophils in the lung was identified as a factor associated with CLAD but requires invasive samples. The aim of this study was to assess the kinetics of peripheral blood neutrophils after lung transplantation as early predictor of CLAD.

METHODS

We retrospectively included all recipients transplanted in our center between 2009 and 2014. Kinetics of blood neutrophils were evaluated to predict early CLAD by mathematical modeling using unadjusted and adjusted analyses.

RESULTS

103 patients were included, 80 in the stable group and 23 in the CLAD group. Bacterial infections at 1 year were associated with CLAD occurrence. Neutrophils demonstrated a high increase postoperatively and then a progressive decrease until normal range. Recipients with CLAD had higher neutrophil counts (mixed effect coefficient beta over 3 years = +1.36 G/L, 95% Confidence Interval [0.99-1.92], p < .001). A coefficient of celerity (S for speed) was calculated to model the kinetics of return to the norm before CLAD occurrence. After adjustment, lower values of S (slower decrease of neutrophils) were associated with CLAD (Odds Ratio = 0.26, 95% Confidence Interval [0.08-0.66], p = .01).

CONCLUSION

A slower return to the normal range of blood neutrophils was early associated with CLAD occurrence.

Early Surgical Management of Thermal Airway Injury: A Case Series

Inhalation injury is an independent risk factor in burn mortality, imparting a 20% increased risk of death. Yet there is little information on the natural history, functional outcome, or pathophysiology of thermal injury to the laryngotracheal complex, limiting treatment progress. This paper demonstrates a case series (n = 3) of significant thermal airway injuries. In all cases, the initial injury was far exceeded by the subsequent immune response and aggressive fibroinflammatory healing. Serial examination demonstrated progressive epithelial injury, mucosal inflammation, airway remodeling, and luminal compromise. Histologic findings in the first case demonstrate an early IL-17A response in the human airway following thermal injury. This is the first report implicating IL-17A in the airway mucosal immune response to thermal injury. Their second and third patients received Azithromycin targeting IL-17A and showed clinical responses. The third patient also presented with exposed tracheal cartilage and underwent mucosal reconstitution via split-thickness skin graft over an endoluminal stent in conjunction with tracheostomy. This was associated with rapid abatement of mucosal inflammation, resolution of granulation tissue, and return of laryngeal function. Patients who present with thermal inhalation injury should receive a thorough multidisciplinary airway evaluation, including early otolaryngologic evaluation. New early endoscopic approaches (scar lysis and mucosal reconstitution with autologous grafting over an endoluminal stent), when combined with targeted medical therapy aimed at components of mucosal airway inflammation (local corticosteroids and systemic Azithromycin targeting IL-17A), may have potential to limit chronic cicatricial complications.

Reducing the Fatality Rate of COVID-19 by Applying Clinical Insights From Immuno-Oncology and Lung Transplantation

There is an urgent need to identify effective strategies that can stop or reverse the inflammatory process that causes acute lung injury, ARDS, and multi-organ failure in COVID-19. Adaptive clinical trials with parallel enrollment to different arms each evaluating a rationally designed combination modality could provide the foundation for the accelerated identification of effective and safe multi-modality treatment algorithms for COVID-19 pneumonia. This article summarizes the insights and lessons learned from clinical immune-oncology trials as well as lung transplantation that are informing the clinical development of promising new strategies aimed at reducing the fatality rate in COVID-19.

IL-17A Is Critical for CD8+ T Effector Response in Airway Epithelial Injury After Transplantation

BACKGROUND

Airway epithelium is the primary target of trachea and lung transplant rejection, the degree of epithelial injury is closely correlated with obliterative bronchiolitis development. In this study, we investigated the cellular and molecular mechanisms of IL-17A-mediated airway epithelial injury after transplantation.

METHODS

Murine orthotopic allogeneic trachea or lung transplants were implemented in wild type or RORγt mice. Recipients received anti-IL-17A or anti-IFNγ for cytokine neutralization, anti-CD8 for CD8 T-cell depletion, or STAT3 inhibitor to suppress type 17 CD4+/CD8+ T cell development. Airway injury and graft inflammatory cell infiltration were examined by histopathology and immunohistochemistry. Gene expression of IL-17A, IFNγ, perforin, granzyme B, and chemokines in grafts was quantitated by real-time RT-PCR.

RESULTS

IL-17A and IFNγ were rapidly expressed and associated with epithelial injury and CD8 T-cell accumulation after allotransplantation. Depletion of CD8 T cells prevented airway epithelial injury. Neutralization of IL-17A or devoid of IL-17A production by RORγt deficiency improved airway epithelial integrity of the trachea allografts. Anti-IL-17A reduced the expression of CXCL9, CXCL10, CXCL11, and CCL20, and abolished CD8 T-cell accumulation in the trachea allografts. Inhibition of STAT3 activation significantly reduced IL-17A expression in both trachea and lung allografts; however, it increased IFNγ expression and cytotoxic activities, which resulted in the failure of airway protection.

CONCLUSIONS

Our data reveal the critical role of IL-17A in mediating CD8 T effector response that causes airway epithelial injury and lung allograft rejection, and indicate that inhibition of STAT3 signals could drive CD8 T cells from Tc17 toward Tc1 development.

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.

Chronic lung allograft dysfunction phenotypes and treatment

Chronic lung allograft dysfunction (CLAD) remains a major hurdle limiting long-term survival post lung transplantation. Given the clinical heterogeneity of CLAD, recently two phenotypes of CLAD have been defined [bronchiolitis obliterans syndrome (BOS) vs. restrictive allograft syndrome (RAS) or restrictive CLAD (rCLAD)]. BOS is characterized by an obstructive pulmonary function, air trapping on CT and obliterative bronchiolitis (OB) on histopathology, while RAS/rCLAD patients show a restrictive pulmonary function, persistent pleuro-parenchymal infiltrates on CT and pleuroparenchymal fibro-elastosis on biopsies. Importantly, the patients with RAS/rCLAD have a severely limited survival post diagnosis of 6-18 months compared to 3-5 years after BOS diagnosis. In this review, we will review historical evidence for this heterogeneity and we will highlight the clinical, radiological, histopathological characteristics of both phenotypes, as well as their risk factors. Treatment of CLAD remains troublesome, nevertheless, we will give an overview of different treatment strategies that have been tried with some success. Adequate phenotyping remains difficult but is clearly needed for both clinical and scientific purposes.

IL-17A Blockade Attenuates Obliterative Bronchiolitis and IFN-γ Cellular Immune Response in Lung Allografts

Obliterative bronchiolitis (OB), characterized by fibrous obliteration of the small airways, is a major impediment to long-term survival in lung allograft recipients. We found previously that IL-17A is produced primarily by CD4⁺ T cells and γδ T cells after lung transplant in a mouse model of orthotopic lung transplant. The absence of either subset of T cells was compensated for by expansion of the other subset, which suggested that systemic blockade of IL-17A was necessary. To determine the specific role of IL-17A in the development of OB, we treated lung allograft recipients with an IL-17A antagonistic antibody. After IL-17A blockade, the incidence of OB was significantly reduced in lung allografts. IL-17A blockade also significantly attenuated the severity of acute rejection and overall lung fibrosis. The decreased OB incidence was associated with reduced lymphocyte recruitment, particularly CD8⁺ T cells and other IFN-γ-producing lymphocytes, to the lung allograft. Interestingly, IL-17A blockade led to an increase in the frequency of IL-17A-producing T-helper cell type 17 cells and γδ T cells in lung allografts, suggesting that IL-17A is a negative regulator of these T cells. Our data suggest that blocking IL-17A after lung transplant reduces the overall IFN-γ-mediated lymphocyte response and decreases the development of OB.

Interleukin-1α induced release of interleukin-8 by human bronchial epithelial cells in vitro: assessing mechanisms and possible treatment options

Survival after lung transplantation is hampered by chronic lung allograft dysfunction (CLAD). Persistently elevated BAL-neutrophilia is observed in some patients despite treatment with azithromycin, which may be induced by IL-1α. Our aim is to establish an in vitro model, assess mechanistic pathways and test different therapeutic strategies of IL-1α-induced release of IL-8 by human bronchial epithelial cells. Bronchial epithelial cells (16HBE) were stimulated with IL-1α with or without azithromycin or dexamethasone. IL-8 protein was analyzed in cell supernatant. Different MAP kinases (p38, JNK, ERK^1/2 , Iκβ) and targets known to be involved in tumor formation (PI3K, Akt) were investigated. Finally, different treatment options were tested for their potential inhibitory effect. IL-1α induced IL-8 in bronchial epithelial cells, which was dose-dependently inhibited by dexamethasone but not by azithromycin. IL-1α induced p38 and Akt phosphorylation, but activation of these MAPK was not inhibited by dexamethasone. JNK, ERK^1/2 , Iκβ and PI3K were not activated. None of the tested drugs reduced the IL-1α induced IL-8 production. We established an in vitro model wherein steroids inhibit the IL-1α-induced IL-8 production, while azithromycin was ineffective. Despite using this simple in vitro model, we could not identify a new treatment option for azithromycin-resistant airway neutrophilia.

The role of recipient derived interleukin-17A in a murine orthotopic lung transplant model of restrictive chronic lung allograft dysfunction

The single most important cause of late mortality after lung transplantation is chronic lung allograft dysfunction (CLAD). However, the pathological development of CLAD was not as simple as previously presumed and subclassification phenotypes, bronchiolitis obliterans syndrome (BOS) and restrictive CLAD (rCLAD), have been introduced. We want to re-investigate how CLAD manifests in the murine orthotopic lung transplant model and investigate the role of interleukin 17A (IL-17A) within this model. Orthotopic LTx was performed in CB57BL/6, IL-17 WT and IL-17 KO mice. In a first experiment, CB57BL/6 mice receiving an isograft (CB57BL/6) or allograft (BALB/C) were compared. In a second experiment IL-17 WT and IL-17 KO mice (both CB57BL/6 background) received an allograft (BALB/C). Mice received daily immunosuppression with steroids and cyclosporine and were sacrificed 10weeks after transplantation for histopathological analysis by an experienced lung pathologist. After murine orthotopic lung transplantation, the allograft histopathologically presented features of human rCLAD (i.e. overt inflammation, pleural/parenchymal fibrosis and obliterative bronchiolitis). In the IL-17A KO group, less inflammation in the bronchovascular axis (p=0.03) was observed and a non-significant trend towards less bronchovascular fibrosis, pleural/septal inflammation and fibrosis, and parenchymal inflammation and fibrosis when compared to WT mice. The major mismatch orthotopic lung transplant model resembles features of human rCLAD. IL-17A mediated immunity is involved in the inflammatory component, but had little influence on the degree of fibrosis. Further mechanistic and therapeutic studies in this mouse model are needed to fully understand the mechanisms in rCLAD.

Advances in Understanding Bronchiolitis Obliterans After Lung Transplantation

Bronchiolitis obliterans syndrome (BOS) remains a major complication after lung transplantation, causing significant morbidity and mortality in a majority of recipients. BOS is believed to be the clinical correlate of chronic allograft dysfunction, and is defined as an obstructive pulmonary function defect in the absence of other identifiable causes, mostly not amenable to treatment. Recently, it has become clear that BOS is not the only form of chronic allograft dysfunction and that other clinical phenotypes exist; however, we focus exclusively on BOS. Radiologic findings typically demonstrate air trapping, mosaic attenuation, and hyperinflation. Pathologic examination reveals obliterative bronchiolitis lesions and a pure obliteration of the small airways (< 2 mm), with a relatively normal surrounding parenchyma. In this review, we highlight recent advances in diagnosis, pathologic examination, and risk factors, such as microbes, viruses, and antibodies. Although the pathophysiological mechanisms remain largely unknown, we review the role of the airway epithelium and inflammation and the various experimental animal models. We also clarify the clinical and therapeutic implications of these findings. Although significant progress has been made, the exact pathophysiological mechanisms and adequate therapy for posttransplantation BOS remain unknown, highlighting the need for further research to improve long-term posttransplantation BOS-free and overall survival.

CD26 costimulatory blockade improves lung allograft rejection and is associated with enhanced interleukin-10 expression

BACKGROUND

The ectoenzyme CD26/dipeptidyl peptidase 4 (DPP4) has costimulatory activity that contributes to T cell activation and proliferation. Here, we aimed to target this costimulatory activity for the attenuation of the alloreactive Th17-cell response during acute rejection after mouse lung transplantation.

METHODS

To test the CD26-costimulatory blockade in vitro, mixed lymphocyte reaction was performed between major histocompatibility complex class I and II fully mismatched cells (CD4(+) splenocytes, C57BL/6, responders, and antigen-presenting cells, BALB/c, stimulators) by adding the CD26 inhibitor vildagliptin (0-15 μg). Lung transplantation between BALB/c (donor) and C57BL/6 (recipient) mice was performed, including controls, CD26-inhibited (CD26-I, daily administration of vildagliptin [GLSynthesis, Worcester, MA], 10 mg/kg subcutaneous), and CD26 knockout (CD26KO) mice was performed. Analysis on Day 1 and 5 after transplant included immunohistochemistry, fluorescence-activated cell sorting, and enzyme-linked immunosorbent assay (ELISA) for immune cell detection and their key cytokines.

RESULTS

In vitro, there was a significant reduction of the Th17 cytokines interleukin (IL)-17 and IL-21. In vivo, CD26-I-treated and CD26KO mice showed significantly preserved macroscopic and histologic characteristics on Day 5 (p < 0.01), a higher partial pressure of arterial oxygen/fraction of inspired oxygen ratio (p ≤ 0.05), fewer infiltrating CD3(+) T cells (p < 0.01), but more interstitial macrophages on Day 1 (p < 0.01) compared with control. Fewer IL-17(+) cells were found in CD26-I allografts on Day 1 (p = 0.05). Higher levels of IL-10 in CD26-I and CD26KO allografts on day 5 were seen (p < 0.05). IL-10/CD206 double-staining (alternative macrophages) revealed more positive cells in CD26-I and CD26KO on Day 1 and 5 (p < 0.01).

CONCLUSIONS

CD26 costimulatory blockade promotes lung allograft acceptance via reduced T cell infiltration, less expression of IL-17, and increased expression of IL-10, likely to be derived from alternatively activated macrophages.

CD8(+)IL-17(+) T Cells Mediate Neutrophilic Airway Obliteration in T-bet-Deficient Mouse Lung Allograft Recipients

Acute cellular rejection is a known risk factor for the development of obliterative bronchiolitis, which limits the long-term survival of lung transplant recipients. However, the T cell effector mechanisms in both of these processes remain incompletely understood. Using the mouse orthotopic lung transplant model, we investigated whether C57BL/6 T-bet(-/-) recipients of major histocompatibility complex (MHC)-mismatched BALB/c lung grafts develop rejection pathology and allospecific cytokine responses that differ from wild-type mice. T-bet(-/-) recipients demonstrated vigorous allograft rejection at 10 days, characterized by neutrophilic inflammation and predominantly CD8(+) T cells producing allospecific IL-17 and/or IFN-γ, in contrast to IFN-γ-dominant responses in WT mice. CD4(+) T cells produced IL-17 but not IFN-γ responses in T-bet(-/-) recipients, in contrast to WT controls. Costimulation blockade using anti-CD154 Ab significantly reduced allospecific CD8(+)IFN-γ(+) responses in both T-bet(-/-) and WT mice but had no attenuating effect on lung rejection pathology in T-bet(-/-) recipients or on the development of obliterative airway inflammation that occurred only in T-bet(-/-) recipients. However, neutralization of IL-17A significantly attenuated costimulation blockade-resistant rejection pathology and airway inflammation in T-bet(-/-) recipients. In addition, CXCL1 (neutrophil chemokine) was increased in T-bet(-/-) allografts, and IL-17 induced CXCL1 from mouse lung epithelial cells in vitro. Taken together, our data show that T-bet-deficient recipients of complete MHC-mismatched lung allografts develop costimulation blockade-resistant rejection characterized by neutrophilia and obliterative airway inflammation that is predominantly mediated by CD8(+)IL-17(+) T cells. Our data support T-bet-deficient mouse recipients of lung allografts as a viable animal model to study the immunopathogenesis of small airway injury in lung transplantation.

Cytokine crowdsourcing: multicellular production of TH17-associated cytokines

In the 2 decades since its discovery, IL-17A has become appreciated for mounting robust, protective responses against bacterial and fungal pathogens. When improperly regulated, however, IL-17A can play a profoundly pathogenic role in perpetuating inflammation and has been linked to a wide variety of debilitating diseases. IL-17A is often present in a composite milieu that includes cytokines produced by TH17 cells (i.e., IL-17F, IL-21, IL-22, and IL-26) or associated with other T cell lineages (e.g., IFN-γ). These combinatorial effects add mechanistic complexity and more importantly, contribute differentially to disease outcome. Whereas TH17 cells are among the best-understood cell types that secrete IL-17A, they are frequently neither the earliest nor dominant producers. Indeed, non-TH17 cell sources of IL-17A can dramatically alter the course and severity of inflammatory episodes. The dissection of the temporal regulation of TH17-associated cytokines and the resulting net signaling outcomes will be critical toward understanding the increasingly intricate role of IL-17A and TH17-associated cytokines in disease, informing our therapeutic decisions. Herein, we discuss important non-TH17 cell sources of IL-17A and other TH17-associated cytokines relevant to inflammatory events in mucosal tissues.

Interleukin-17-producing CD4(+) cells home to the graft early after human heart transplantation

BACKGROUND

Interleukin-17 (IL-17) is regarded as a major effector cytokine with pro-inflammatory actions. It has pleiotropic and environment-specific functions by promoting adaptive cytotoxic T-lymphocyte responses during inflammation. Therefore, it is tempting to speculate that IL-17 plays a major role in inflammatory responses in transplant recipients. We questioned whether IL-17 is expressed in the transplanted heart during acute rejection (AR), or during immunologic quiescence, and which graft-infiltrating lymphocytes produce IL-17. In addition, we analyzed donor-specific IL-17-producing cells in peripheral blood cells in comparable periods after transplantation.

METHODS

Endomyocardial biopsies from heart transplant recipients with early or late AR or in an immunologic quiescence period were analyzed for the presence of IL-17 mRNA. In addition, the capacity of graft-infiltrating lymphocytes (GILs) to produce IL-17 was analyzed. Moreover, we determined the frequency of donor-reactive IL-17-producing peripheral blood mononuclear cells (PBMCs) using an Elispot assay.

RESULTS

Twenty-one percent (14 of 67) of the biopsies assessed were positive for IL-17 mRNA. Thirteen of 41 biopsies were observed in the early period (≤3 months) after transplantation. One (of 26) of the late biopsies expressed IL-17 (p = 0.006). Specifically, IL-17 was expressed during early AR (57%, or 8 of 14), whereas biopsies from late AR (0 of 5) did not express IL-17 mRNA (p = 0.02). During AR, IL-17 is derived from IL-17-producing CD4(+)CD161(+), and not CD8(+), GILs. In contrast to the graft findings, we detected circulating donor-reactive IL-17-producing cells mostly during immunologic quiescence.

CONCLUSIONS

Particularly early after heart transplantation, IL-17-producing CD4(+) T cells home to the graft, which contributes to the AR process.

Effects of azithromycin and tanomastat on experimental bronchiolitis obliterans

OBJECTIVE

Azithromycin has become a standard of care in therapy of bronchiolitis obliterans following lung transplantation. Matrix metalloprotease-9 broncho-alveolar lavage levels increase in airway neutrophilia and bronchiolitis obliterans. Interleukin-17 may play a role in lung allograft rejection, and interleukin-12 is downregulated in bronchiolitis obliterans. Whether these mechanisms can be targeted by azithromycin remains unclear.

METHODS

Bronchiolitis obliterans was induced by transplantation of Fischer F344 rat left lungs to Wistar Kyoto rats. Allografts with azithromycin therapy from day 1 to 28 or 56 and mono- or combination therapy with the broad-spectrum matrix metalloprotease inhibitor tanomastat from day 1 to 56 were compared to control allografts and isografts. Graft histology was assessed, and tissue cytokine expression studied using Western blotting and immunofluorescence.

RESULTS

The chronic airway rejection score in the azithromycin group did not change between 4 and 8 weeks after transplantation, whereas it significantly worsened in control allografts (P = .041). Azithromycin+tanomastat prevented complete allograft fibrosis, which occurred in 40% of control allografts. Azithromycin reduced interleukin-17 expression (P = .049) and the number of IL-17(+)/CD8(+) lymphocytes at 4 weeks, and active matrix metalloprotease-9 at 8 weeks (P = .017), and increased interleukin-12 expression (P = .025) at 8 weeks following transplantation versus control allografts.

CONCLUSIONS

The expression of interleukin-17 and matrix metalloprotease-9 in bronchiolitis obliterans may be attenuated by azithromycin, and the decrease in interleukin-12 expression was prevented by azithromycin. Combination of azithromycin with a matrix metalloprotease inhibitor is worth studying further because it prevented complete allograft fibrosis in this study.

Azithromycin and the treatment of lymphocytic airway inflammation after lung transplantation

Lymphocytic airway inflammation is a major risk factor for chronic lung allograft dysfunction, for which there is no established treatment. We investigated whether azithromycin could control lymphocytic airway inflammation and improve allograft function. Fifteen lung transplant recipients demonstrating acute allograft dysfunction due to isolated lymphocytic airway inflammation were prospectively treated with azithromycin for at least 6 months (NCT01109160). Spirometry (FVC, FEV1 , FEF25-75 , Tiffeneau index) and FeNO were assessed before and up to 12 months after initiation of azithromycin. Radiologic features, local inflammation assessed on airway biopsy (rejection score, IL-17(+)  cells/mm(2) lamina propria) and broncho-alveolar lavage fluid (total and differential cell counts, chemokine and cytokine levels); as well as systemic C-reactive protein levels were compared between baseline and after 3 months of treatment. Airflow improved and FeNO decreased to baseline levels after 1 month of azithromycin and were sustained thereafter. After 3 months of treatment, radiologic abnormalities, submucosal cellular inflammation, lavage protein levels of IL-1β, IL-8/CXCL-8, IP-10/CXCL-10, RANTES/CCL5, MIP1-α/CCL3, MIP-1β/CCL4, Eotaxin, PDGF-BB, total cell count, neutrophils and eosinophils, as well as plasma C-reactive protein levels all significantly decreased compared to baseline (p < 0.05). Administration of azithromycin was associated with suppression of posttransplant lymphocytic airway inflammation and clinical improvement in lung allograft function.

Upregulation of α-enolase in acute rejection of cardiac transplant in rat model: implications for the secretion of interleukin-17

Acute allograft rejection remains a major problem in solid organ transplantation. The enzyme α-enolase has been shown to induce an immune response in cardiac transplantation. In this study, we investigated the role of α-enolase in acute allograft rejection in a rat model of heart transplantation. Hearts from either (WF: RT1(u) ) or (Lew: RT1(1) ) rats were transplanted into (Lew: RT1(1) ) rats. No rejection occurred in the isograft group, for which the median survival time was >168 days, whereas the median survival time of the allograft group was significantly less at 10 ± 2.1 days (n = 8 per group, p < 0.001). Increased inflammation was observed in allografts, including increased α-enolase expression and increased numbers of infiltrating CD4(+) T cells (p < 0.05). By immunohistochemical staining, we confirmed that α-enolase was expressed not only in myocardial cells but also in the infiltrating lymphocytes. However, on the fifth day after transplantation, α-enolase expression was no longer observed in the lymphocytes (n = 3, p < 0.001). In contrast, no lymphocytes were found in isografts after transplantation (n = 3, p < 0.001). α-enolase expression was increased in lymphocytes, which are implicated in the acute rejection of cardiac transplants. Intragraft α-enolase inhibition may be useful as an adjuvant therapy to systemic immunosuppression in heart transplantation.

Mechanistic differences between phenotypes of chronic lung allograft dysfunction after lung transplantation

Distinct phenotypes of chronic lung allograft dysfunction (CLAD) after lung transplantation are emerging with lymphocytic bronchiolitis (LB)/azithromycin reversible allograft dysfunction (ARAD), classical or fibrotic bronchiolitis obliterans syndrome (BOS), and restrictive allograft syndrome (RAS) proposed as separate entities. We have additionally identified lung transplant recipients with prior LB, demonstrating persistent airway neutrophilia (PAN) despite azithromycin treatment. The aim of this study was to evaluate differences in the airway microenvironment in different phenotypes of CLAD. Bronchoalveolar lavage (BAL) from recipients identified as stable (control), LB/ARAD, PAN, BOS, and RAS were evaluated for differential cell counts and concentrations of IL-1α, IL-1β, IL-6, IL-8, and TNF-α. Primary human bronchial epithelial cells were exposed to BAL supernatants from different phenotypes and their viability measured. BOS and RAS showed increased BAL neutrophilia but no change in cytokine concentrations compared with prediagnosis. In both LB/ARAD and PAN, significant increases in IL-1α, IL-1β, and IL-8 were present. BAL IL-6 and TNF-α concentrations were increased in PAN and only this phenotype demonstrated decreased epithelial cell viability after exposure to BAL fluid. This study demonstrates clear differences in the airway microenvironment between different CLAD phenotypes. Systematic phenotyping of CLAD may help the development of more personalized approaches to treatment.

Receptor for advanced glycation end products (RAGE) on iNKT cells mediates lung ischemia-reperfusion injury

Activation of invariant natural killer T (iNKT) cells and signaling through receptor for advanced glycation end products (RAGE) are known to independently mediate lung ischemia-reperfusion (IR) injury. This study tests the hypothesis that activation of RAGE specifically on iNKT cells via alveolar macrophage-produced high mobility group box 1 (HMGB1) is critical for the initiation of lung IR injury. A murine in vivo hilar clamp model was utilized, which demonstrated that RAGE(-/-) mice were significantly protected from IR injury. Treatment of WT mice with soluble RAGE (a decoy receptor), or anti-HMGB1 antibody, attenuated lung IR injury and inflammation, whereas treatment with recombinant HMGB1 enhanced IR injury in WT mice but not RAGE(-/-) mice. Importantly, lung dysfunction, cytokine production and neutrophil infiltration were significantly attenuated after IR in Jα18(-/-) mice reconstituted with RAGE(-/-) iNKT cells (versus WT iNKT cells). In vitro studies demonstrated that, after hypoxia-reoxygenation, alveolar macrophage-derived HMGB1 augmented IL-17 production from iNKT cells in a RAGE-dependent manner. These results suggest that HMGB1-mediated RAGE activation on iNKT cells is critical for initiation of lung IR injury and that a crosstalk between macrophages and iNKT cells via the HMGB1/RAGE axis mediates IL-17 production by iNKT cells causing neutrophil infiltration and lung IR injury.