The common Sting1 HAQ, AQ alleles rescue CD4 T cellpenia, restore T-regs, and prevent SAVI (N153S) inflammatory disease in mice.

The significance of STING1 gene in tissue inflammation and cancer immunotherapy has been increasingly recognized. Intriguingly, common human STING1 alleles R71H-G230A-R293Q (HAQ) and G230A-R293Q (AQ) are carried by ~60% of East Asians and ~40% of Africans, respectively. Here, we examine the modulatory effects of HAQ, AQ alleles on STING-associated vasculopathy with onset in infancy (SAVI), an autosomal dominant, fatal inflammatory disease caused by gain-of-function human STING1 mutations. CD4 T cellpenia is evident in SAVI patients and mouse models. Using Sting1 knock-in mice expressing common human STING1 alleles HAQ, AQ, and Q293, we found that HAQ, AQ, and Q293 splenocytes resist STING1-mediated cell death ex vivo, establishing a critical role of STING1 residue 293 in cell death. The HAQ/SAVI(N153S) and AQ/SAVI(N153S) mice did not have CD4 T cellpenia. The HAQ/SAVI(N153S), AQ/SAVI(N153S) mice have more (~10-fold, ~20-fold, respectively) T-regs than WT/SAVI(N153S) mice. Remarkably, while they have comparable TBK1, IRF3, and NFκB activation as the WT/SAVI, the AQ/SAVI mice have no tissue inflammation, regular body weight, and normal lifespan. We propose that STING1 activation promotes tissue inflammation by depleting T-regs cells in vivo. Billions of modern humans have the dominant HAQ, AQ alleles. STING1 research and STING1-targeting immunotherapy should consider STING1 heterogeneity in humans.

MerTK-dependent efferocytosis by monocytic-MDSCs mediates resolution of post-lung transplant ischemia-reperfusion injury.

Lung transplantation (LTx) outcomes are impeded by ischemia-reperfusion injury (IRI) and subsequent chronic lung allograft dysfunction (CLAD). We examined the undefined role of MerTK (receptor Mer tyrosine kinase) on monocytic myeloid-derived suppressor cells (M-MDSCs) in efferocytosis to facilitate resolution of lung IRI. Single-cell RNA sequencing of lung tissue and bronchoalveolar lavage (BAL) from post-LTx patients were analyzed. Murine lung hilar ligation and allogeneic orthotopic LTx models of IRI were used with Balb/c (WT), Cebpb-/- (MDSC-deficient), Mertk-/- or MerTK-CR (cleavage resistant) mice. A significant downregulation in MerTK-related efferocytosis genes in M-MDSC populations of CLAD patients was observed compared to healthy subjects. In the murine IRI model, significant increase in M-MDSCs, MerTK expression, efferocytosis and attenuation of lung dysfunction was observed in WT mice during injury resolution that was absent in Cebpb-/- and Mertk-/- mice. Adoptive transfer of M-MDSCs in Cebpb-/- mice significantly attenuated lung dysfunction and inflammation. Additionally, in a murine orthotopic LTx model, increases in M-MDSCs were associated with resolution of lung IRI in the transplant recipients. In vitro studies demonstrated the ability of M-MDSCs to efferocytose apoptotic neutrophils in a MerTK-dependent manner. Our results suggest that MerTK-dependent efferocytosis by M-MDSCs can substantially contribute to the resolution of post-LTx IRI.

A rare case of spontaneous hemoperitoneum in a bone marrow transplant recipient on VV-ECMO.

A 53-year-old man with acute myeloid leukemia received an allogeneic hematopoietic cell transplant (HCT) from a matched unrelated donor. One month after his transplantation, he developed ARDS requiring initiation of VV-ECMO. He suffered from pancytopenia, managed with frequent transfusions, granulocyte-colony stimulating factor (G-CSF) and weekly thrombopoietin receptor agonist. On ECMO day 17, the patient developed severe hypotension after insertion of a chest tube for a large right-sided pneumothorax. CT angiography of the abdomen showed hemoperitoneum. Exploratory laparotomy revealed approximately 4 L of blood and a ruptured splenic hilum. A splenectomy was performed. Unfortunately, the patient continued to require multiple daily blood products and his condition continued to decline despite two reoperations. His family chose to discontinue ECMO and he passed away peacefully. Spontaneous splenic rupture after GM-CSF has never been reported in patients on VV-ECMO. This manuscript reviews the literature regarding the pathophysiology and clinical manifestation of this rare occurrence.

Venovenous ECMO for Acute Chronic Heart Failure after Bilateral Lung Transplantation.

ABSTRACT: Venovenous (VV) ECMO is rarely used during decompensated circulatory states. Although VA ECMO is the routine option, VV ECMO may be an option in selected patients. We present a case of pulmonary edema due to acute heart failure in a patient 4- and 12-year post-lung transplantation who received VV ECMO. Using a thoughtful cannulation strategy, VV ECMO, and aggressive ultrafiltration, the patient was successfully decannulated, extubated, and discharged from the hospital. In cardiogenic pulmonary edema, VV ECMO represents an additional, and likely under-utilized tool, especially in patients who are at high risk for ventilator-associated lung injury. Cannula location and size should be given additional consideration to potentially transition to V-AV ECMO configuration if necessary.

Novel Use of Ivabradine for Persistent Sinus Tachycardia in a Patient on Extracorporeal Life Support With Right Ventricular Dysfunction.

Persistent sinus tachycardia (pST) has been associated with adverse cardiovascular events in critically ill patients. Pharmacological control of heart rate with negative inotropic agents has proven to be safe but could be potentially dangerous in patients with concomitant right ventricular (RV) dysfunction. Ivabradine, a medication devoid of negative inotropy, could be a potentially safe solution for this patient population when adequate heart rate control is desired. A 17-year-old male with a history of vaping developed acute respiratory distress syndrome (ARDS) and RV dysfunction, requiring extra corporal life support (ECLS). He suffered from pST. Given his RV dysfunction, a beta-blocker was avoided, and ivabradine was used safely with improvement of his pST. This case demonstrates the efficacy of ivabradine to reduce heart rate and avoid the use of beta-blockers for patients with RV dysfunction, which could be detrimental. Ivabradine was shown to lower the heart rate without altering hemodynamic parameters.

MerTK-dependent efferocytosis by monocytic-MDSCs mediates resolution of post-lung transplant injury.

Rationale: Patients with end stage lung diseases require lung transplantation (LTx) that can be impeded by ischemia-reperfusion injury (IRI) leading to subsequent chronic lung allograft dysfunction (CLAD) and inadequate outcomes. Objectives: We examined the undefined role of MerTK (receptor Mer tyrosine kinase) on monocytic myeloid-derived suppressor cells (M-MDSCs) in efferocytosis (phagocytosis of apoptotic cells) to facilitate resolution of lung IRI. Methods: Single-cell RNA sequencing of lung tissue and BAL from post-LTx patients was analyzed. Murine lung hilar ligation and allogeneic orthotopic LTx models of IRI were used with Balb/c (WT), cebpb -/- (MDSC-deficient), Mertk -/- or MerTK-CR (cleavage resistant) mice. Lung function, IRI (inflammatory cytokine and myeloperoxidase expression, immunohistology for neutrophil infiltration), and flow cytometry of lung tissue for efferocytosis of apoptotic neutrophils were assessed in mice. Measurements and Main Results: A significant downregulation in MerTK-related efferocytosis genes in M-MDSC populations of CLAD patients compared to healthy subjects was observed. In the murine IRI model, significant increase in M-MDSCs, MerTK expression and efferocytosis was observed in WT mice during resolution phase that was absent in cebpb -/- Land Mertk -/- mice. Adoptive transfer of M-MDSCs in cebpb -/- mice significantly attenuated lung dysfunction, and inflammation leading to resolution of IRI. Additionally, in a preclinical murine orthotopic LTx model, increases in M-MDSCs were associated with resolution of lung IRI in the transplant recipients. In vitro studies demonstrated the ability of M-MDSCs to efferocytose apoptotic neutrophils in a MerTK-dependent manner. Conclusions: Our results suggest that MerTK-dependent efferocytosis by M-MDSCs can significantly contribute to the resolution of post-LTx IRI.

The common TMEM173 HAQ, AQ alleles rescue CD4 T cellpenia, restore T-regs, and prevent SAVI (N153S) inflammatory disease in mice.

The significance of STING (encoded by the TMEM173 gene), in tissue inflammation and cancer immunotherapy has been increasingly recognized. Intriguingly, common human STING alleles R71H-G230A-R293Q (HAQ) and G230A-R293Q (AQ) are carried by ~60% of East Asians and ~40% of Africans, respectively. Here, we examine the modulatory effects of HAQ, AQ alleles on STING-associated vasculopathy with onset in infancy (SAVI), an autosomal dominant, fatal inflammatory disease caused by gain-of-function human STING mutations. CD4 T cellpenia is evident in SAVI patients and mouse models. Using STING knock-in mice expressing common human STING alleles HAQ, AQ, and Q293, we found that HAQ, AQ, and Q293 splenocytes resist STING-mediated cell death ex vivo, establishing a critical role of STING residue 293 in cell death. The HAQ/SAVI(N153S) and AQ/SAVI(N153S) mice did not have CD4 T cellpenia. The HAQ/SAVI(N153S), AQ/SAVI(N153S) mice have more (~10-fold, ~20-fold, respectively) T-regs than WT/SAVI(N153S) mice. Remarkably, while they have comparable TBK1, IRF3, and NFκB activation as the WT/SAVI, the AQ/SAVI mice have no tissue inflammation, regular body weight, and normal lifespan. We propose that STING activation promotes tissue inflammation by depleting T-regs cells in vivo. Billions of modern humans have the dominant HAQ, AQ alleles. STING research and STING-targeting immunotherapy should consider TMEM173 heterogeneity in humans.

Management of nontuberculous mycobacteria in lung transplant cases: an international Delphi study.

Rationale: Nontuberculous mycobacterial (NTM) diseases are difficult-to-treat infections, especially in lung transplant (LTx) candidates. Currently, there is a paucity of recommendations on the management of NTM infections in LTx, focusing on Mycobacterium avium complex (MAC), M. abscessus and M. kansasii. Methods: Pulmonologists, infectious disease specialists, LTx surgeons and Delphi experts with expertise in NTM were recruited. A patient representative was also invited. Three questionnaires comprising questions with multiple response statements were distributed to panellists. Delphi methodology with a Likert scale of 11 points (5 to -5) was applied to define the agreement between experts. Responses from the first two questionnaires were collated to develop a final questionnaire. The consensus was described as a median rating >4 or <-4 indicating for or against the given statement. After the last round of questionnaires, a cumulative report was generated. Results: Panellists recommend performing sputum cultures and a chest computed tomography scan for NTM screening in LTx candidates. Panellists recommend against absolute contraindication to LTx even with multiple positive sputum cultures for MAC, M. abscessus or M. kansasii. Panellists recommend MAC patients on antimicrobial treatment and culture negative can be listed for LTx without further delay. Panellists recommend 6 months of culture-negative for M. kansasii, but 12 months of further treatment from the time of culture-negative for M. abscessus before listing for LTx. Conclusion: This NTM LTx study consensus statement provides essential recommendations for NTM management in LTx and can be utilised as an expert opinion while awaiting evidence-based contributions.

Resolution of post-lung transplant ischemia-reperfusion injury is modulated via Resolvin D1-FPR2 and Maresin 1-LGR6 signaling.

BACKGROUND: Dysregulation of inflammation-resolution pathways leads to postlung transplant (LTx) ischemia-reperfusion (IR) injury and allograft dysfunction. Our hypothesis is that combined treatment with specialized pro-resolving lipid mediators, that is, Resolvin D1 (RvD1) and Maresin-1 (MaR1), enhances inflammation-resolution of lung IR injury. METHODS: Expression of RvD1 and MaR1 was analyzed in bronchoalveolar lavage (BAL) fluid of patients on days 0, 1, and 7 post-LTx. Lung IR injury was evaluated in C57BL/6 (WT), FPR2-/-, and LGR6 siRNA treated mice using a hilar-ligation model with or without administration with RvD1 and/or MaR1. A donation after circulatory death and murine orthotopic lung transplantation model was used to evaluate the protection by RvD1 and MaR1 against lung IR injury. In vitro studies analyzed alveolar macrophages and type II epithelial cell activation after treatment with RvD1 or MaR1. RESULTS: RvD1 and MaR1 expressions in BAL from post-LTx patients was significantly increased on day 7 compared to days 0 and 1. Concomitant RvD1 and MaR1 treatment significantly mitigated early pulmonary inflammation and lung IR injury in WT mice, which was regulated via FPR2 and LGR6 receptors. In the murine orthotopic donation after cardiac death LTx model, RvD1 and MaR1 treatments significantly attenuated lung IR injury and increased PaO2 levels compared to saline-treated controls. Mechanistically, RvD1/FPR2 signaling on alveolar macrophages attenuated HMGB1 and TNF-α secretion and upregulated uptake of macrophage-dependent apoptotic neutrophils (efferocytosis), whereas MaR1/LGR6 signaling mitigated CXCL1 secretion by epithelial cells. CONCLUSIONS: Bioactive proresolving lipid mediator-dependent signaling that is, RvD1/FPR2 and MaR1/LGR6- offers a novel therapeutic strategy in post-LTx injury.

Hyperammonemia After Lung Transplantation: Systematic Review and a Mini Case Series.

Background: Hyperammonemia after lung transplantation (HALT) is a rare but serious complication with high mortality. This systematic review delineates possible etiologies of HALT and highlights successful strategies used to manage this fatal complication. Methods: Seven biomedical databases and grey literature sources were searched using keywords relevant to hyperammonemia and lung transplantation for publications between 1995 and 2020. Additionally, we retrospectively analyzed HALT cases managed at our institution between January 2016 and August 2018. Results: The systematic review resulted in 18 studies with 40 individual cases. The mean peak ammonia level was 769 µmol/L at a mean of 14.1 days post-transplant. The mortality due to HALT was 57.5%. In our cohort of 120 lung transplants performed, four cases of HALT were identified. The mean peak ammonia level was 180.5 µmol/L at a mean of 11 days after transplantation. HALT in all four patients was successfully treated using a multimodal approach with an overall mortality of 25%. Conclusion: The incidence of HALT (3.3%) in our institution is comparable to prior reports. Nonetheless, ammonia levels in our cohort were not as high as previously reported and peaked earlier. We attributed these significant differences to early recognition and prompt institution of multimodal treatment approach.

Macrophage activating syndrome causing decompensated right heart failure.

BACKGROUND: Macrophage activating syndrome (MAS) is a form of hemophagocytic lymphohistiocytosis (HLH), a rare complication of autoimmune disease that is characterized by cytokine storm and multiorgan failure. CASE SUMMARY: A 32-year-old male presented with acutely decompensated pulmonary arterial hypertension and right heart failure secondary to MAS. The patient was immediately started on inhaled and intravenous epoprostenol, vasopressors and dexamethasone and anakinra were administered. Despite the therapies given, the patient's condition continued to decline, and he was placed on veno-arterial extracorporeal membrane oxygenation (VA-ECMO) support. Over a few days, his clinical condition improved, and he was decannulated from VA-ECMO and later transitioned oral treprositinil and was discharged home. Due to its non-specific clinical manifestations, the diagnosis of MAS depends on high clinical suspicion and initial laboratory work up such as thrombocytopenia, transaminitis, hyperferritinemia, hypertriglyceridemia, hypofibrinogenemia, etc. In our patient, MAS led to decompensated Pulmonary Arterial Hypertension (PAH) leading to right heart failure that was refractory to inhaled and intravenous epoprostenol and vasopressors and required VA-ECMO as a bridge to recovery while his MAS was managed by anakinra and dexamethasone. CONCLUSION: MAS can result in acute decompensation of PAH and right heart failure. Besides RV failure management, immunosuppressants such as anakinra, etoposide, etc. should be utilized early in the management of MAS. In refractory right heart failure, VA-ECMO can be considered as a bridge to recovery. There is a paucity of literature supporting the utilization of VA-ECMO in the management of refractory right heart failure caused by MAS in adults and much of the data stems from pediatric studies. This case serves as a fine example of successful use of VA-ECMO in adult population.

Set Up for Failure: Pre-Existing Autoantibodies in Lung Transplant.

Lung transplant patients have the lowest long-term survival rates compared to other solid organ transplants. The complications after lung transplantation such as primary graft dysfunction (PGD) and ultimately chronic lung allograft dysfunction (CLAD) are the main reasons for this limited survival. In recent years, lung-specific autoantibodies that recognize non-HLA antigens have been hypothesized to contribute to graft injury and have been correlated with PGD, CLAD, and survival. Mounting evidence suggests that autoantibodies can develop during pulmonary disease progression before lung transplant, termed pre-existing autoantibodies, and may participate in allograft injury after transplantation. In this review, we summarize what is known about pulmonary disease autoantibodies, the relationship between pre-existing autoantibodies and lung transplantation, and potential mechanisms through which pre-existing autoantibodies contribute to graft injury and rejection.

In vivo reprogramming of pathogenic lung TNFR2+ cDC2s by IFNß inhibits HDM-induced asthma.

Asthma is a common inflammatory lung disease with no known cure. Previously, we uncovered a lung TNFR2+ conventional DC2 subset (cDC2s) that induces regulatory T cells (Tregs) maintaining lung tolerance at steady state but promotes TH2 response during house dust mite (HDM)-induced asthma. Lung IFNß is essential for TNFR2+ cDC2s-mediated lung tolerance. Here, we showed that exogenous IFNß reprogrammed TH2-promoting pathogenic TNFR2+ cDC2s back to tolerogenic DCs, alleviating eosinophilic asthma and preventing asthma exacerbation. Mechanistically, inhaled IFNß, not IFNα, activated ERK2 signaling in pathogenic lung TNFR2+ cDC2s, leading to enhanced fatty acid oxidation (FAO) and lung Treg induction. Last, human IFNß reprogrammed pathogenic human lung TNFR2+ cDC2s from patients with emphysema ex vivo. Thus, we identified an IFNß-specific ERK2-FAO pathway that might be harnessed for DC therapy.

Successful Preoperative Optimization for Lung Transplantation With Transcatheter Mitral Valve Repair.

Surgically treatable valvular heart disease is common in patients with end-stage lung disease. Nevertheless, advanced lung disease is often seen as a contraindication to cardiac surgery, and severe valvular disease is seen as a contraindication to lung transplantation. This report describes the case of a patient presenting with very severe chronic obstructive pulmonary disease and severe mitral regurgitation who was managed with transcatheter mitral valve repair and who subsequently underwent successful lung transplantation. Critical valvular heart disease in patients with chronic respiratory failure may be amenable to transcatheter therapy, which may favorably affect lung transplantation candidacy.

A novel injury site-natural antibody targeted complement inhibitor protects against lung transplant injury.

Complement is known to play a role in ischemia and reperfusion injury (IRI). A general paradigm is that complement is activated by self-reactive natural IgM antibodies (nAbs), after they engage postischemic neoepitopes. However, a role for nAbs in lung transplantation (LTx) has not been explored. Using mouse models of LTx, we investigated the role of two postischemic neoepitopes, modified annexin IV (B4) and a subset of phospholipids (C2), in LTx. Antibody deficient Rag1-/- recipient mice were protected from LTx IRI. Reconstitution with either B4 or C2nAb restored IRI, with C2 significantly more effective than B4 nAb. Based on these information, we developed/characterized a novel complement inhibitor composed of single-chain antibody (scFv) derived from the C2 nAb linked to Crry (C2scFv-Crry), a murine inhibitor of C3 activation. Using an allogeneic LTx, in which recipients contain a full nAb repertoire, C2scFv-Crry targeted to the LTx, inhibited IRI, and delayed acute rejection. Finally, we demonstrate the expression of the C2 neoepitope in human donor lungs, highlighting the translational potential of this approach.

MicroRNA-206 antagomiR‒enriched extracellular vesicles attenuate lung ischemia‒reperfusion injury through CXCL1 regulation in alveolar epithelial cells.

BACKGROUND: Our hypothesis is that the immunomodulatory capacities of mesenchymal stem cell‒derived extracellular vesicles (EVs) can be enhanced by specific microRNAs (miRNAs) to effectively attenuate post-transplant lung ischemia‒reperfusion (IR) injury. METHODS: The expression of miR-206 was analyzed in bronchoalveolar lavage (BAL) fluid of patients on Days 0 and 1 after lung transplantation. Lung IR injury was evaluated in C57BL/6 mice using a left lung hilar-ligation model with or without treatment with EVs or antagomiR-206‒enriched EVs. Murine lung tissue was used for miRNA microarray hybridization analysis, and cytokine expression, lung injury, and edema were evaluated. A donation after circulatory death and murine orthotopic lung transplantation model was used to evaluate the protection by enriched EVs against lung IR injury. In vitro studies analyzed type II epithelial cell activation after coculturing with EVs. RESULTS: A significant upregulation of miR-206 was observed in the BAL fluid of patients on Day 1 after lung transplantation compared with Day 0 and in murine lungs after IR injury compared with sham. Treatment with antagomiR-206‒enriched EVs attenuated lung dysfunction, injury, and edema compared with treatment with EVs alone after murine lung IR injury. Enriched EVs reduced lung injury and neutrophil infiltration as well as improved allograft oxygenation after murine orthotopic lung transplantation. Enriched EVs significantly decreased proinflammatory cytokines, especially epithelial cell‒dependent CXCL1 expression, in the in vivo and in vitro IR injury models. CONCLUSIONS: EVs can be used as biomimetic nanovehicles for protective immunomodulation by enriching them with antagomiR-206 to mitigate epithelial cell activation and neutrophil infiltration in the lungs after IR injury.

International Society for Heart and Lung Transplantation consensus statement for the standardization of bronchoalveolar lavage in lung transplantation.

Bronchoalveolar lavage (BAL) is a key clinical and research tool in lung transplantation (LTx). However, BAL collection and processing are not standardized across LTx centers. This International Society for Heart and Lung Transplantation-supported consensus document on BAL standardization aims to clarify definitions and propose common approaches to improve clinical and research practice standards. The following 9 areas are covered: (1) bronchoscopy procedure and BAL collection, (2) sample handling, (3) sample processing for microbiology, (4) cytology, (5) research, (6) microbiome, (7) sample inventory/tracking, (8) donor bronchoscopy, and (9) pediatric considerations. This consensus document aims to harmonize clinical and research practices for BAL collection and processing in LTx. The overarching goal is to enhance standardization and multicenter collaboration within the international LTx community and enable improvement and development of new BAL-based diagnostics.

Successful bridge to lung transplantation with transcatheter aortic valve replacement.

End-stage lung disease and advanced cardiac conditions are frequently seen together and represent a clinical dilemma. Even though both issues may be amenable to surgical management, combining lung transplant with surgical valve repair is rarely done and theoretically associated with increased morbidity and mortality risks, especially in elderly patients. Here, we describe 2 patients presenting with end-stage lung disease and significant aortic stenosis who were successfully bridged to lung transplant via transcatheter aortic valve replacement. Patient 1 was a 66-year-old man who underwent a double lung transplant 56 days after transcatheter aortic valve replacement. Patient 2 was a 70-year-old man who underwent a single right lung transplant 103 days after transcatheter aortic valve replacement. Both patients had uneventful postoperative courses and are alive at the 1-year time point with excellent performance status. This report suggests that transcatheter aortic valve replacement may favorably impact lung transplant candidacy for patients with end-stage lung disease in the setting of severe aortic stenosis, likely representing a better alternative to concomitant aortic valve replacement and lung transplant in elderly patients.

Lung IFNAR1hi TNFR2+ cDC2 promotes lung regulatory T cells induction and maintains lung mucosal tolerance at steady state.

The lung is a naturally tolerogenic organ. Lung regulatory T cells (T-regs) control lung mucosal tolerance. Here, we identified a lung IFNAR1hiTNFR2+ conventional DC2 (iR2D2) population that induces T-regs in the lung at steady state. Using conditional knockout mice, adoptive cell transfer, receptor blocking antibodies, and TNFR2 agonist, we showed that iR2D2 is a lung microenvironment-adapted dendritic cell population whose residence depends on the constitutive TNFR2 signaling. IFNß-IFNAR1 signaling in iR2D2 is necessary and sufficient for T-regs induction in the lung. The Epcam+CD45- epithelial cells are the sole lung IFNß producer at the steady state. Surprisingly, iR2D2 is plastic. In a house dust mite model of asthma, iR2D2 generates lung TH2 responses. Last, healthy human lungs have a phenotypically similar tolerogenic iR2D2 population, which became pathogenic in lung disease patients. Our findings elucidate lung epithelial cells IFNß-iR2D2-T-regs axis in controlling lung mucosal tolerance and provide new strategies for therapeutic interventions.