In type 1 diabetes (T1D), the immune system mistakenly attacks the pancreatic islet β cells resulting in the loss of insulin secretion. Insulin-replacement therapy developed more than a century ago provided means to manage the symptoms of diabetes without addressing the root cause of the disease-the faulty immune system. A healthy immune system has built-in mechanisms to limit unwanted, excessive immune activation and prevents damages to self-tissues. These immune self-tolerance mechanisms are often impaired in autoimmune patients including those with T1Ds. Understanding how immune self-tolerance is broken in patients with T1D can inform the design of new curative therapies that correct the immune defects. In this paper, we will summarize the mechanisms of immune tolerance, review their relevance to T1Ds, and discuss novel therapeutic approaches to rebalance the immune system for the treatment of T1Ds.

Chimeric antigen receptor (CAR) T cell therapy has achieved remarkable success in treating haematologic malignancies. However, the rise in clinical use has highlighted substantial challenges related to T cell- and tumour-intrinsic mechanisms. Additionally, the tumour microenvironment can render these treatments dysfunctional. Extensive attempts in the field are optimizing the key elements of CAR T cell products for therapy, including antigen specificity and affinity, metabolic fitness, phenotypic stability and manufacturing. Recent efforts in transcriptomic and epigenetic profiling, as well as high-throughput functional screening methods, have identified new classes of targets, binders and mechanisms to be exploited. Advances in gene editing and delivery offer opportunities to translate those strategies into clinical trials. Here we discuss the multifaceted exploration of CAR T cell engineering approaches and emerging directions, highlighting the available strategies that can be built on to create the next generation of cellular therapies. A summary of CAR T-cell engineering approaches, including functional screening methods, gene editing and delivery advances, and optimization of metabolic fitness.

Adoptive regulatory T cell (Treg) therapy is an emergent treatment paradigm for restoring immune tolerance in patients with autoimmune and inflammatory diseases. While preclinical models have demonstrated the remarkable efficacy of Treg cell therapy, lineage-tracing studies have also revealed that murine Tregs can lose lineage identity and adopt a proinflammatory state. Whether human Tregs exhibit a similar susceptibility to inflammatory cytokine-mediated lineage decommitment remains inconclusive. Here, we present an in vitro model of human Treg destabilization characterized by silencing of the Treg lineage-defining transcription factor, FOXP3, loss of suppressive activity, and gain of proinflammatory functions. Analysis of single-cell ATAC and transcriptomic profiles of Tregs during destabilization revealed a switch in chromatin accessibility between two elements at the IRF4 locus. Excision of the distal IRF4 element enabled Tregs to resist inflammatory cytokine-induced reprogramming, presenting a cell-engineering strategy to design more effective Treg therapies.

Adoptive regulatory T-cell (Treg) therapy is an emerging therapeutic paradigm for promoting immune tolerance in transplant and autoimmune disease settings. Prior investigations demonstrate that murine Tregs can undergo epigenetic reprogramming within chronically inflamed tissue environments, resulting in acquisition of proinflammatory functions and the capacity to exacerbate tissue damage. Despite the ramifications of Treg lineage decommitment for cell therapy applications, inflammation-induced human Treg cell fate decisions remain poorly understood. Here, we present a robust in vitromodel of IL6, IL1β, and IL23-driven Treg instability characterized by progressive FOXP3 and HELIOS downregulation, FOXP3conserved non-coding sequence (CNS)2 enhancer re-methylation, diminished in vitrosuppressive function, and elevated proinflammatory cytokine expression. To gain insight into the gene regulatory networks enabling the loss of Treg identity, we generated single-cell transcriptomic and chromatin accessibility profiles of primary human Tregs maintained in the presence or absence of IL6, IL1β, and IL23. Unsupervised clustering revealed a dysfunctional Treg population with an epigenetic signature consistent with murine Treg to “exTreg” conversion, including altered chromatin accessibility at the IFNγ, IL17A, and FOXP3CNS2 loci. Inference of transcription factor (TF)-associated changes in chromatin accessibility indicated a key role for E26 transformation-specific (ETS) family members. Ongoing experiments aim to identify specific TF modules that can be targeted to better safeguard the function and stability of Treg therapeutics.

Engineered regulatory T (T reg ) cells have emerged as precision therapeutics aimed at inducing immune tolerance while reducing the risks associated with generalized immunosuppression. This Viewpoint highlights the opportunities and challenges for engineered T reg cell therapies in treating autoimmune and other inflammatory diseases.

Background:Early data on use of catheter-directed therapies (CDT) for treatment of Intermediate or High-Risk pulmonary embolism (PE) show improvement in pulmonary artery systolic pressures (PAsP) and RV/LV ratios. Occasionally a paradoxical rise in PAsP was observed with CDT utilizing ultrasound-assisted thrombolysis (USAT). It is unclear whether this pattern is seen with CDT utilizing mechanical aspiration. Objectives:To investigate and compare the changes in PAsP between those who underwent CDT with USAT to those with mechanical aspiration. Methods:A retrospective analysis of those diagnosed with Intermediate or High-Risk PE who underwent CDT using USAT or mechanical aspiration from 7/2013 to 3/2023. The primary outcome was comparison of PAsP changes between the two modalities. Secondary outcomes include length of stay, mortality, and bleeding complications. Results:A total of 142 patients were analyzed, of which 93 underwent USAT and 49 underwent mechanical thrombectomy. The mechanical thrombectomy group had significantly lower post-intervention PAsP than the USAT group (42.2 ± 13.4 mmHg vs 54.5 ± 15.2 mmHg, p < 0.0001) and a greater adjusted mean reduction (-16.5 ± 2.7 vs. -7.7 ± 3.2 mmHg. p < 0.0001). A higher frequency of a paradoxical rise in PAsP was observed in the USAT group (22 % vs 4.1 %, p < 0.001). Conclusions:CDT utilizing mechanical thrombectomy was associated with lower post-interventional PAsP and greater mean negative change compared to USAT. Occasional paradoxical rises in PAsP were observed with both types of CDT, but they were more frequent with USAT. Hemodynamic monitoring should be considered after CDT. Condensed unstructured abstract:We report a retrospective comparison of changes to pulmonary artery systolic pressures (PAsPs) between catheter-directed ultrasound-assisted thrombolysis (USAT) and catheter-directed mechanical thrombectomy in Intermediate and High-Risk pulmonary embolism. Those treated with mechanical thrombectomy compared to USAT had significantly lower post-interventional PAsP (42.2 ± 13.4 mmHg vs 54.5 ± 15.2 mmHg, p < 0.0001) and a greater adjusted mean reduction (-16.2 ± 2.7 vs. -7.5 ± 3.2 mmHg, p < 0.0001). A paradoxical rise in PAsP was observed more frequently in the USAT group than the mechanical thrombectomy group (22 % vs 4.1 %, p < 0.001).

SESSION TITLE: Rare Cases with Masquerading Pulmonary SymptomsSESSION TYPE: Rapid Fire Case ReportsPRESENTED ON: 10/18/2022 01:35 pm - 02:35 pmINTRODUCTION: Malignant pleural mesothelioma (MPM) is a rare aggressive cancer associated with asbestos exposure. The initial presentation varies; it rarely presents with symptoms related to local invasion. We hereby present a case of MPM presenting with hemoptysis.CASE PRESENTATION: An 80-years-old male patient who is a retired brickmason presents with 2-3 days of hemoptysis. He described cough productive of blood-streaked sputum that progressed to small volume hemoptysis. Medical history is significant for atrial fibrillation on apixaban, and prior tobacco use disorder (40 pack years). He was hemodynamically stable and saturating 88% on room air. Chest CT scan showed multifocal ground glass infiltrates bilaterally with minimal pleural effusions (figure 1). Labs were significant for Hb of 11.1, elevated CRP of 107.6, ESR> 119, negative ANA/ANCAs, and SPEP/UPEP/INR/PTT that were within normal limits. His infectious workup was negative, but he did complete an empiric course of antibiotics. Symptoms were attributed to spontaneous pulmonary hemorrhage in the setting of anticoagulation use. Apixaban was discontinued, hemoptysis improved, and he was discharged home. He presented back 1 week later with exertional dyspnea, ongoing cough, and recurrence of hemoptysis despite being off anticoagulation. Repeat CT scan showed larger pleural effusions, left greater than right, and mild progression of the patchy ground glass opacities (figure 2). A left thoracocentesis was performed with 1L of bloody pleural fluid removed. Pleural studies showed an exudative pleural effusion - RBC 306k, WBC 2.7K (N: 70%, L: 30%), and the cytology was negative. Hospital stay was complicated by re-accumulation of the pleural effusion necessitating chest tube placement. Patient subsequently underwent VATS with pleural biopsies on the left. Given his worsening respiratory failure, patient decided to pursue palliative measures. Pathology revealed malignant pleural mesothelioma, sarcomatoid subtype, invading the lung parenchyma and blood vessels with hemosiderin-laden macrophages suggestive of pulmonary hemorrhage (figure 3).DISCUSSION: The incidence of MPM in the US is estimated to be approximately 3300 cases per year. The most common symptoms are breathlessness (60-90%), chest wall pain (70-90%), and constitutional symptoms such as weight loss and fatigue (30% at diagnosis—usually a late feature). Hemoptysis is a rare presenting symptom (<2%) and it is a result of local invasion of the lung parenchyma. The sarcomatoid subtype of MPM is associated with the poorest prognosis because it is the most invasive and rapidly progressive, and as such likely have a higher chance to be associated with hemoptysis as shown with this patient.CONCLUSIONS: Hemoptysis should be recognized as a rare but possible initial symptom of MPM. It may be suggestive of a more aggressive subtype.Reference #1: anes SM, Alrifai D, Fennell DA. Perspectives on the Treatment of Malignant Pleural Mesothelioma. New England Journal of Medicine. 2021;385(13):1207-18.Reference #2: Marom EM, Erasmus JJ, Pass HI, Patz EF. The role of imaging in malignant pleural mesothelioma. Seminars in Oncology. 2002;29(1):26-35.Reference #3: Murphy DC, Mount A, Starkie F, Taylor L, Aujayeb A. A review of malignant pleural mesothelioma in a large North East UK pleural centre. Pleura Peritoneum. 2020;6(1):20200144.DISCLOSURES: No relevant relationships by Farouk Al ChamiNo relevant relationships by vincenzo cioccaNo relevant relationships by Lee Greenspon, value=Grant/Research SupportRemoved 03/31/2022 by Lee GreensponNo relevant relationships by Patrick Ho SESSION TITLE: Rare Cases with Masquerading Pulmonary Symptoms SESSION TYPE: Rapid Fire Case Reports PRESENTED ON: 10/18/2022 01:35 pm - 02:35 pm INTRODUCTION: Malignant pleural mesothelioma (MPM) is a rare aggressive cancer associated with asbestos exposure. The initial presentation varies; it rarely presents with symptoms related to local invasion. We hereby present a case of MPM presenting with hemoptysis. CASE PRESENTATION: An 80-years-old male patient who is a retired brickmason presents with 2-3 days of hemoptysis. He described cough productive of blood-streaked sputum that progressed to small volume hemoptysis. Medical history is significant for atrial fibrillation on apixaban, and prior tobacco use disorder (40 pack years). He was hemodynamically stable and saturating 88% on room air. Chest CT scan showed multifocal ground glass infiltrates bilaterally with minimal pleural effusions (figure 1). Labs were significant for Hb of 11.1, elevated CRP of 107.6, ESR> 119, negative ANA/ANCAs, and SPEP/UPEP/INR/PTT that were within normal limits. His infectious workup was negative, but he did complete an empiric course of antibiotics. Symptoms were attributed to spontaneous pulmonary hemorrhage in the setting of anticoagulation use. Apixaban was discontinued, hemoptysis improved, and he was discharged home. He presented back 1 week later with exertional dyspnea, ongoing cough, and recurrence of hemoptysis despite being off anticoagulation. Repeat CT scan showed larger pleural effusions, left greater than right, and mild progression of the patchy ground glass opacities (figure 2). A left thoracocentesis was performed with 1L of bloody pleural fluid removed. Pleural studies showed an exudative pleural effusion - RBC 306k, WBC 2.7K (N: 70%, L: 30%), and the cytology was negative. Hospital stay was complicated by re-accumulation of the pleural effusion necessitating chest tube placement. Patient subsequently underwent VATS with pleural biopsies on the left. Given his worsening respiratory failure, patient decided to pursue palliative measures. Pathology revealed malignant pleural mesothelioma, sarcomatoid subtype, invading the lung parenchyma and blood vessels with hemosiderin-laden macrophages suggestive of pulmonary hemorrhage (figure 3). DISCUSSION: The incidence of MPM in the US is estimated to be approximately 3300 cases per year. The most common symptoms are breathlessness (60-90%), chest wall pain (70-90%), and constitutional symptoms such as weight loss and fatigue (30% at diagnosis—usually a late feature). Hemoptysis is a rare presenting symptom (<2%) and it is a result of local invasion of the lung parenchyma. The sarcomatoid subtype of MPM is associated with the poorest prognosis because it is the most invasive and rapidly progressive, and as such likely have a higher chance to be associated with hemoptysis as shown with this patient. CONCLUSIONS: Hemoptysis should be recognized as a rare but possible initial symptom of MPM. It may be suggestive of a more aggressive subtype. Reference #1: anes SM, Alrifai D, Fennell DA. Perspectives on the Treatment of Malignant Pleural Mesothelioma. New England Journal of Medicine. 2021;385(13):1207-18. Reference #2: Marom EM, Erasmus JJ, Pass HI, Patz EF. The role of imaging in malignant pleural mesothelioma. Seminars in Oncology. 2002;29(1):26-35. Reference #3: Murphy DC, Mount A, Starkie F, Taylor L, Aujayeb A. A review of malignant pleural mesothelioma in a large North East UK pleural centre. Pleura Peritoneum. 2020;6(1):20200144. DISCLOSURES: No relevant relationships by Farouk Al Chami No relevant relationships by vincenzo ciocca No relevant relationships by Lee Greenspon, value=Grant/Research Support Removed 03/31/2022 by Lee Greenspon No relevant relationships by Patrick Ho

Introduction: Regulatory T cells (Tregs) suppress inflammation in atherosclerosis, and therefore have the therapeutic potential to reduce the risk of MI and stroke. However, there is currently no method to generate antigen specific Tregs that target atherosclerosis. We therefore engineered Tregs that express a Chimeric Antigen Receptor (CAR) targeting malonaldehyde-modified LDL (MDA-LDL), the most common form of oxidized LDL and a key molecular component of atherosclerosis. Methods: Novel single chain variable fragments (scFv) were synthesized using sequences from antibodies targeting human MDA-LDL. Oxidized-LDL specific CARs (ox-CARs) were subsequently engineered by fusing each scFv to an IgG4 hinge, CD28 transmembrane and CD28/CD3z cytoplasmic domains. CD4 + CD25 + CD127 low/- Tregs were purified from human blood via FACS and lentivirally transduced to express the novel ox-CARs (ox-CAR-Tregs). Human atherosclerotic plaques were obtained from patients undergoing carotid endarterectomy (CEA). Autologous ox-CAR-Tregs were analyzed for activation after ex-vivo co-culture with CEA samples. Results: A rationally designed panel of 42 ox-CARs were engineered using scFv derived from 12 antibodies targeting MDA-LDL. We first assessed CAR expression and activation in Jurkat T cells to identify promising ox-CAR variants for further evaluation in human Tregs. After culture in the presence of MDA-LDL, six ox-CAR-Treg variants consistently showed significant activation, compared to controls, based on CD71 expression, cytokine expression and proliferation in the absence of CD3/28 stimulation. Human atherosclerotic samples were identified to have substantial amounts of MDA-LDL epitopes using IHC. Autologous ox-CAR-Tregs showed a dose-dependent increase in CD71 expression after ex-vivo co-culture with atherosclerotic plaque. Conclusion: An optimized CAR targeting MDA-LDL activates Tregs when cultured with human atherosclerotic plaque ex-vivo.

Alloantigen-specific regulatory T cell (Treg) therapy is a promising approach for suppressing alloimmune responses and minimizing immunosuppression after solid organ transplantation. Chimeric antigen receptor (CAR) targeting donor alloantigens can confer donor reactivity to Tregs. However, CAR Treg therapy has not been evaluated in vascularized transplant or multi-MHC mismatched models. Here, we evaluated the ability of CAR Tregs targeting HLA-A2 (A2-CAR) to prolong the survival of heterotopic heart transplants in mice. After verifying the in vitro activation, proliferation, and enhanced suppressive function of A2-CAR Tregs in the presence of A2-antigen, we analyzed the in vivo function of Tregs in C57BL/6 (B6) mice receiving A2-expressing heart allografts. A2-CAR Treg infusion increased the median survival of grafts from B6.HLA-A2 transgenic donors from 23 to 99 days, whereas median survival with polyclonal Treg infusion was 35 days. In a more stringent model of haplo-mismatched hearts from BALB/cxB6.HLA-A2 F1 donors, A2-CAR Tregs slightly increased median graft survival from 11 to 14 days, which was further extended to >100 days when combined with a 9-day course of rapamycin treatment. These findings demonstrate the efficacy of CAR Tregs, alone or in combination with immunosuppressive agents, toward protecting vascularized grafts in fully immunocompetent recipients.

TOPIC: Pulmonary Vascular Disease TYPE: Fellow Case Reports INTRODUCTION: Clot in transit (CIT) is a term associated with pulmonary embolism (PE) used to describe thrombus found in the right atrium or ventricle on echocardiography. We present a case of CIT treated in a multidisciplinary approach with catheter-directed mechanical thrombectomy. CASE PRESENTATION: A 60 year old male with a history of unprovoked PE off anticoagulation presented with dyspnea and syncope. At presentation, he was tachycardic to 130 but normotensive and not hypoxemic. Troponin-I was elevated at 0.06 ng/mL and B type-NP at 96 pg/mL. SARS-CoV-2 PCR was negative. CT angiography revealed extensive acute bilateral PE with increased RV/LV ratio of 1.9. A stat transthoracic echocardiography (TTE) found a dilated right ventricle with severely reduced systolic function, positive McConnell sign, a tricuspid annular plane systolic excursion (TAPSE) < 1cm, and a serpiginous mobile echodensity in the right atrium consistent with a CIT. A stat ultrasound of the legs also revealed extensive deep venous thrombosis in the proximal left femoral vein extending to the popliteal vein. After a multidisciplinary PE response team discussion, the patient was taken emergently to the catheterization lab. Prior to transport, VA ECMO safety lines were preemptively placed to facilitate ECMO initiation in case of decompensation. With the ECMO circuit primed and the ECMO team, cardiac anesthesiologist, and cardiothoracic surgery on standby, the patient underwent percutaneous mechanical thrombectomy utilizing the Inari Flowtriever® system. With adjunctive TTE guidance, the right atrial clot was first extracted in its entirety with no hemodynamic deterioration. This was followed by aspiration of clot from the right and left pulmonary arteries. Pulmonary artery pressures and cardiac index improved, and the procedure ended with placement of an IVC filter. The patient was transferred to the ICU and was started on enoxaparin at 1mg/kg twice a day. He was discharged on day 4 with rivaroxaban. DISCUSSION: CIT is a rare phenomenon with a prevalence rate of around 4% and is considered a medical emergency given its high mortality rate of 25-40%. While treatment guidelines are limited, anticoagulation alone has shown to be insufficient to treat CIT effectively. While there is data supporting the use of catheter directed therapies for PE, data on its use for CIT is scarce but growing. Furthermore, the preparation of advanced support prior in conjunction with the use of catheter directed therapy may be beneficial in case of life-threatening decompensation. CONCLUSIONS: Catheter-directed mechanical thrombectomy may be effective and safe as shown in this case, but requires a team capable of advanced therapies like ECMO and urgent surgical intervention if needed. REFERENCE #1: Otoupalova E, Dalal B, Renard B. Right heart thrombus in transit: a series of two cases. Crit Ultrasound J. 2017;9(1):14. doi:10.1186/s13089-017-0069-9. REFERENCE #2: Garvey S, Dudzinski DM, Giordano N, Torrey J, Zheng H, Kabrhel C. Pulmonary embolism with clot in transit: An analysis of risk factors and outcomes. Thromb Res. 2020 Mar;187:139-147. doi: 10.1016/j.thromres.2020.01.006. Epub 2020 Jan 10. PMID: 31991381. REFERENCE #3: Dhulipala V R, Fayoda B O, Kyaw H, et al. (August 04, 2020) Thrombus in Transit: Extract or Dissolve?. Cureus 12(8): e9550. doi:10.7759/cureus.9550. DISCLOSURES: No relevant relationships by Mara Caroline, source=Web Response No relevant relationships by Eliot Friedman, source=Web Response No relevant relationships by Eric Gnall, source=Web Responseresearch relationship with Inari Please note: April,2021 to presen Added 04/29/2021 by Lee Greenspon, source=Web Response, value=Grant/Research Support No relevant relationships by Patrick Ho, source=Web Response

Parkinson’s disease (PD) is an age-dependent neurodegenerative condition. Leucine-rich repeat kinase 2 (LRRK2) mutations are the most frequent cause of sporadic and autosomal dominant PD. The exact role of LRRK2 protective variants (R1398H, N551K) together with a pathogenic mutant (G2019S) in aging and neurodegeneration is unknown. We generated the following myc-tagged UAS-LRRK2 transgenic Drosophila: LRRK2 (WT), N551K, R1398H, G2019S single allele, and double-mutants (N551K/G2019S or R1398H/G2019S). The protective variants alone were able to suppress the phenotypic effects caused by the pathogenic LRRK2 mutation. Next, we conducted RNA-sequencing using mRNA isolated from dopaminergic neurons of these different groups of transgenic Drosophila. Using pathway enrichment analysis, we identified the top 10 modules (p < 0.05), with “LRRK2 in neurons in Parkinson’s disease” among the candidates. Further dissection of this pathway identified the most significantly modulated gene nodes such as eEF1A2, ACTB, eEF1A, and actin cytoskeleton reorganization. The induction of the pathway was successfully restored by the R1398H protective variant and R1398H-G2019S or N551K-G2019S rescue experiments. The oxidoreductase family of genes was also active in the pathogenic mutant and restored in protective and rescue variants. In summary, we provide in vivo evidence supporting the neuroprotective effects of LRRK2 variants. RNA sequencing of dopaminergic neurons identified upregulation of specific gene pathways in the Drosophila carrying the pathogenic variant, and this was restored in the rescue phenotypes. Using protective gene variants, our study identifies potential new targets and provides proof of principle of a new therapeutic approach that will further our understanding of aging and neurodegeneration in PD.

Infusion of regulatory T cells (Tregs) engineered with a chimeric antigen receptor (CAR) targeting donor-derived human leukocyte antigen (HLA) is a promising strategy to promote transplant tolerance. Here, we describe an anti-HLA-A2 CAR (A2-CAR) generated by grafting the complementarity-determining regions (CDRs) of a human monoclonal anti-HLA-A2 antibody into the framework regions of the Herceptin 4D5 single-chain variable fragment and fusing it with a CD28-ζ signaling domain. The CDR-grafted A2-CAR maintained the specificity of the original antibody. We then generated HLA-A2 mono-specific human CAR Tregs either by deleting the endogenous T-cell receptor (TCR) via CRISPR/Cas9 and introducing the A2-CAR using lentiviral transduction or by directly integrating the CAR construct into the TCR alpha constant locus using homology-directed repair. These A2-CAR + TCR deficient human Tregs maintained both Treg phenotype and function in vitro . Moreover, they selectively accumulated in HLA-A2-expressing islets transplanted from either HLA-A2 transgenic mice or deceased human donors. A2-CAR + TCR deficient Tregs did not impair the function of these HLA-A2 + islets, whereas similarly engineered A2-CAR + TCR deficient CD4 + conventional T cells rejected the islets in less than 2 weeks. A2-CAR + TCR deficient Tregs delayed graft- versus -host disease only in the presence of HLA-A2, expressed either by co-transferred peripheral blood mononuclear cells or by the recipient mice. Altogether, we demonstrate that genome-engineered mono-antigen-specific A2-CAR Tregs localize to HLA-A2-expressing grafts and exhibit antigen-dependent in vivo suppression, independent of TCR expression. These approaches may be applied towards developing precision Treg cell therapies for transplant tolerance.

Anti-CD19 chimeric antigen receptor (CD19-CAR)-engineered T cells are approved therapeutics for malignancies. The impact of the hinge domain (HD) and the transmembrane domain (TMD) between the extracellular antigen-targeting CARs and the intracellular signaling modalities of CARs has not been systemically studied. In this study, a series of 19-CARs differing only by their HD (CD8, CD28, or IgG4) and TMD (CD8 or CD28) was generated. CARs containing a CD28-TMD, but not a CD8-TMD, formed heterodimers with the endogenous CD28 in human T cells, as shown by co-immunoprecipitation and CAR-dependent proliferation of anti-CD28 stimulation. This dimerization was dependent on polar amino acids in the CD28-TMD and was more efficient with CARs containing CD28 or CD8 HD than IgG4-HD. The CD28-CAR heterodimers did not respond to CD80 and CD86 stimulation but had a significantly reduced CD28 cell-surface expression. These data unveiled a fundamental difference between CD28-TMD and CD8-TMD and indicated that CD28-TMD can modulate CAR T-cell activities by engaging endogenous partners.

SESSION TITLE: Disorders of the Pleura Posters SESSION TYPE: Original Investigation Posters PRESENTED ON: October 18-21, 2020 PURPOSE: To evaluate the efficacy and safety of iodopovidone pleurodesis through an indwelling pleural catheter (IPC) for the management of malignant pleural effusions (MPE), and its influence on pain, breathlessness, and quality-of-life (QoL). METHODS: Interim analysis of this Institutional Review Board-approved prospective study was conducted from November 2018 to February 2020. Inclusion criteria: 18 years or older with symptomatic and recurrent MPEs with life expectancies greater than 3 months and at least one thoracentesis with observed symptomatic benefit and complete lung reexpansion. Exclusion criteria: unexpanded lung disease, prior pleurodesis failure, transudative effusions, and an allergy to iodopovidone. In a single procedural setting, candidates received IPC insertion with subsequent complete effusion evacuation, followed by instillation of iodopovidone with a 1 hour dwell time, which was then drained. They were then instructed to perform daily drainage, record output, and call once drainage decreased to less than 150cc for 3 days, at which time pleurodesis was considered successful. The primary endpoints were pleurodesis success rate and time to pleurodesis. Secondary endpoints included complications and perceptions of pain using a 10-point scale, breathlessness using the Borg scale, and QoL index using the EQ-5D-3L survey pre-procedure and post-procedure at 2 weeks, 2 months, and 6 months. RESULTS: We identified and enrolled 17 patients. Most were female (9, 52%) and the mean age was 63 years (range: 41-82). Average preprocedural LENT score was 3, with lung cancer being the most commonly diagnosed (6, 35%). Pain was the most frequent intraprocedural complication (4, 24%). Pleurodesis success rate was 71.4% (10/17), and the mean time to pleurodesis was 45 days (range: 3-160). Mean pain scale was 3.2 prior to IPC placement, then subsequently decreased to 1.7 at 2 weeks, 1.4 at 2 months, and 1 at 6 months. Mean Borg score prior to procedure was 11.4, then 12.9 at 2 weeks, 10.3 at 2 months, and 7.5 at 6 months. Mean QoL rating prior to procedure was 3.2, which improved to 2.4 at 2 weeks, 1.7 at 2 months, and 0.5 at 6 months. Data collected at 6 months was limited due to fewer respondents. 8 patients died/entered hospice during the study period, and the median time to death/hospice after IPC placement was 101 days. CONCLUSIONS: Indwelling pleural catheter iodopovidone pleurodesis was feasible, safe, well-tolerated, and efficacious with similar success rates compared to prior studies. Perceptions of pain, breathlessness, and QoL continued to improve after patients received the procedure. CLINICAL IMPLICATIONS: Iodopovidone can be safely used as an effective sclerosant in pleurodesis for malignant pleural effusions with minimal complications and offers an ambulatory approach. Patients who undergo iodopovidone pleurodesis appear to have improvement in pain, perception of breathlessness, and QoL. DISCLOSURES: No relevant relationships by Benjamin Berg, source=Web Response No relevant relationships by Patrick Ho, source=Web Response No relevant relationships by Matt Langston, source=Web Response No relevant relationships by Ismael Matus, source=Web Response No relevant relationships by Jacqueline Pellenbarg, source=Web Response No relevant relationships by Haroon Raja, source=Web Response