Donor Characteristics Research Articles

Effects of maternal exercise on infant mesenchymal stem cell mitochondrial function, insulin action, and body composition in infancy.

Maternal exercise (ME) has been established as a useful non-pharmacological intervention to improve infant metabolic health; however, mechanistic insight behind these adaptations remains mostly confined to animal models. Infant mesenchymal stem cells (MSCs) give rise to infant tissues (e.g., skeletal muscle), and remain involved in mature tissue maintenance. Importantly, these cells maintain metabolic characteristics of an offspring donor and provide a model for the investigation of mechanisms behind infant metabolic health improvements. We used undifferentiated MSC to investigate if ME affects infant MSC mitochondrial function and insulin action, and if these adaptations are associated with lower infant adiposity. We found that infants from exercising mothers have improvements in MSC insulin signaling related to higher MSC respiration and fat oxidation, and expression and activation of energy-sensing and redox-sensitive proteins. Further, we found that infants exposed to exercise in utero were leaner at 1 month of age, with a significant inverse correlation between infant MSC respiration and infant adiposity at 6 months of age. These data suggest that infants from exercising mothers are relatively leaner, and this is associated with higher infant MSC mitochondrial respiration, fat use, and insulin action.

Interleukin-6 Levels During Normothermic Machine Perfusion Impact Postreperfusion Hemodynamics of Liver Graft Recipients: A Prospective Single-center Observational Study.

Hemodynamic instability after liver graft reperfusion increases recipient morbidity after liver transplantation. The etiologies of hemodynamic disturbances appear to be multifactorial and are poorly understood. Normothermic machine perfusion (NMP) provides an opportunity to analyze graft quality prior to transplantation. In the present study, we aim to investigate the influence of interleukin-6 (IL-6) levels during NMP on postreperfusion hemodynamics of the recipient. Consecutive NMP-liver transplants at a single-center were prospectively analyzed. Perfusate samples were collected at the beginning, after 6 h, and at the end of perfusion and analyzed for IL-6 levels. Mean arterial pressure (MAP) and catecholamine consumption during surgery were recorded. IL-6 levels at the end of NMP were correlated to donor and perfusion characteristics as well as changes in MAP and catecholamine requirements during the anhepatic and reperfusion phase. IL-6 perfusate measurements were assessed in 77 livers undergoing NMP and transplantation. Donor age, sex, cold ischemic time, and NMP time did not correlate with IL-6 levels. Perfusates of donation after circulatory death grafts showed higher IL-6 levels at the end of NMP than donation after brain death grafts. However, IL-6 levels at the end of NMP correlated with catecholamine requirements and MAP in the reperfusion phase. Per log10 increase in IL-6 levels, an increase of 42% points in administered catecholamine dose was observed, despite MAP being decreased by 3.6% points compared to baseline values. IL-6 levels may be a predictor for recipient hemodynamic instability during liver reperfusion. Larger studies are needed to confirm this finding.

Predictive value of donor kidney quality assessment and risk quantification scores on 5-year outcomes of deceased donor kidney transplantation.

Due to the excess demand for deceased donor kidneys, risk quantification scores were developed to help with kidney allocation. The kidney donor risk index (KDRI) is used in the US kidney allocation system. We currently use expanded criteria (UNOS) and Remuzzi scoring for allocation of deceased donor kidneys and the utility of KDRI in our cohort is unknown. We aim to evaluate the association of KDRI with relation to 5year graft and patient survival. Retrospective cohort study of 225 adults who received a deceased donor kidney transplant between 1 Nov 2005 and 30 June 2014. Patients were followed up for 5years or until graft-loss or death. Implant biopsies of donor kidneys were done and the Remuzzi score was calculated. The median age was 48 (IQR 42, 52.5) years and 50.7% were male. KDRI-USA, KDRI-THAI, and KDRI-AUST were found to have no correlation with 5year graft survival. Donor characteristics which define an expanded criteria donor kidney, not associated with 5year graft survival are age (p = 0.58), terminal creatinine (p = 0.71) and history of hypertension (p = 0.35). Donor cerebrovascular accident (CVA) as a cause of death (p = 0.02) and Remuzzi score were associated with graft survival at 5years, with 75.8% with Remuzzi score ≤ 3 vs 24.2% with Remuzzi score of > 3 achieving 5year graft survival (p = 0.001). The association of KDRI with graft and patient survival was not demonstrated in our cohort. Histological assessment of the transplant kidney remains the best method of predicting long-term survival during donor selection.

Development and validation of a novel nomogram model for predicting delayed graft function in deceased donor kidney transplantation based on pre-transplant biopsies

BackgroundDelayed graft function (DGF) is an important complication after kidney transplantation surgery. The present study aimed to develop and validate a nomogram for preoperative prediction of DGF on the basis of clinical and histological risk factors.MethodsThe prediction model was constructed in a development cohort comprising 492 kidney transplant recipients from May 2018 to December 2019. Data regarding donor and recipient characteristics, pre-transplantation biopsy results, and machine perfusion parameters were collected, and univariate analysis was performed. The least absolute shrinkage and selection operator regression model was used for variable selection. The prediction model was developed by multivariate logistic regression analysis and presented as a nomogram. An external validation cohort comprising 105 transplantation cases from January 2020 to April 2020 was included in the analysis.Results266 donors were included in the development cohort, 458 kidneys (93.1%) were preserved by hypothermic machine perfusion (HMP), 96 (19.51%) of 492 recipients developed DGF. Twenty-eight variables measured before transplantation surgery were included in the LASSO regression model. The nomogram consisted of 12 variables from donor characteristics, pre-transplantation biopsy results and machine perfusion parameters. Internal and external validation showed good discrimination and calibration of the nomogram, with Area Under Curve (AUC) 0.83 (95%CI, 0.78–0.88) and 0.87 (95%CI, 0.80–0.94). Decision curve analysis demonstrated that the nomogram was clinically useful.ConclusionA DGF predicting nomogram was developed that incorporated donor characteristics, pre-transplantation biopsy results, and machine perfusion parameters. This nomogram can be conveniently used for preoperative individualized prediction of DGF in kidney transplant recipients.

Pediatric donor heart utilization variability among organ procurement organizations.

Organ procurement organizations (OPOs) are responsible for the medical management of organ donors. Given the variability in pediatric donor heart utilization among OPOs, we examined factors that may explain this variability, including differences in donor medical management, organ quality, and candidate factors. The Organ Procurement and Transplant Network database was queried for pediatric (<18 years) heart donors and candidates receiving pediatric donor heart offers from 2010 to 2019. OPOs were stratified by pediatric donor heart utilization rate, and the top and bottom quintiles were compared based on donor management strategies and outcomes. A machine learning algorithm, combining 11 OPO, donor, candidate, and offer variables, was used to determine factors most predictive of whether a heart offer is accepted. There was no clinically significant difference between the top and bottom quintile OPOs in baseline donor characteristics, distance between donor and listing center, management strategies, or organ quality. Machine learning modeling suggested neither OPO donor management nor cardiac function is the primary driver of whether an organ is accepted. Instead, number of prior donor offer refusals and individual listing center receiving the offer were two of the most predictive variables of organ acceptance. OPO clinical practice variation does not seem to account for the discrepancy in pediatric donor heart utilization rates among OPOs. Listing center acceptance practice and prior number of donor refusals seem to be the important drivers of heart utilization and may at least partially account for the variation in OPO heart utilization rates given the regional association between OPOs and listing centers.

Discussion on the recruitment strategy for apheresis platelet donors in Chongqing during a public health emergency.

This study aimed to analyze the population characteristics of apheresis platelet donors in Chongqing Province and provide a scientific basis for the development of precise and efficient recruitment strategies. The ultimate goal is to increase the number of regular platelet donors in preparation for public health emergencies. This study involved 53,089 blood donors who donated apheresis platelets to the Chongqing Blood Center from 2020 to 2022. Data regarding age, sex, blood type, education level, occupation, and frequency of blood donation were collected and analyzed to identify factors influencing platelet donation. Between 2020 and 2022, the majority of apheresis platelet donors in Chongqing were aged 25-35 years, with a male-to-female ratio of 2.6:1. The ABO blood group distribution was O > A > B > AB. The apheresis platelet donors mainly consisted of college students, and the donors who had donated only once accounted for the greatest proportion. Based on the population characteristics of apheresis platelet donors in Chongqing, blood collection and supply organizations must refine emergency blood collection and supply plans during public health emergencies. This study underscores the importance of developing precise and efficient recruitment strategies for apheresis platelet donors and expanding the pool of regular apheresis platelet donors. These measures are essential to ensure the timely, safe, and effective use of clinical blood resources during public health emergencies.

COVID-19 impact on blood donor characteristics and seroprevalence of transfusion-transmitted infections in southern Thailand between 2018 and 2022

Blood safety is a critical aspect of healthcare systems worldwide involving rigorous screening, testing, and processing protocols to minimize the risk of transfusion-transmitted infections (TTIs). The present study offers a comprehensive assessment of the prevalence of hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), and syphilis among blood donors in southern Thailand. It explores the consequences of the COVID-19 pandemic on the blood transfusion service, donor characteristics, and the prevalence of TTIs. A retrospective analysis of 65,511 blood donors between 2018 and 2022 was conducted at Songklanagarind Hospital, Thailand. The socio-demographic characteristics of the donors were examined using the Chi-square test to assess the relationship between TTIs serological positivity and donor characteristics. The donors were divided into pre-COVID-19 (2018–2019) and during COVID-19 (2020–2022) groups to evaluate the impacts of COVID-19. The study found that HBV had the highest overall prevalence at 243 per hundred thousand (pht), followed by syphilis (118 pht), HCV (32 pht), and HIV (31 pht) over a five-year period of study. After COVID-19, the prevalence of HBV decreased by 21.8%; HCV decreased by 2.1%; HIV increased by 36.4%; and syphilis increased by 9.2%. The socio-demographic characteristics and TTIs prevalence were significantly altered over time. This study provides insights into blood donor characteristics and TTIs prevalence in southern Thailand, highlighting the understanding of the impact of COVID-19 on the spread of TTIs.

Better kidney allograft survival despite higher-risk donor and recipient characteristics between 1995-2014.

Advances in organ procurement, surgical techniques, immunosuppression regimens and prophylactic antibiotic therapies have dramatically improved short term kidney transplant graft failure. It is unclear how these interventions have affected longer term graft failure. It is hypothesised that graft failure has improved over the last 20 years. Data on all first kidney transplants from 1995-2014 were extracted from the Australia and New Zealand Dialysis and Transplant Registry with follow-up as of 31 December, 2021. Primary exposure was transplant era, classified into 5-year intervals. Primary outcome was all-cause 5-year graft failure. Secondary outcomes included all-cause 10-year graft failure and cause-specific graft failure. Kaplan Meier curves and multivariable Cox Proportional Hazards Regression models were used to assess trends in all-cause graft failure. Fine-Gray subdistribution hazard models verified that changes in death rates were not biasing the Cox Proportional Hazards Regression models. Cumulative incidence functions were used to assess temporal trends in cause-specific graft failure. Across 10871 kidney transplants, there was a shift towards transplanting more recipients aged over 45 years old, with more comorbidities, longer dialysis vintage, body mass index greater than 30kg/m2 and greater human leukocyte antigen mismatches. Donor age has increased but no clear shift in donor source was observed. Compared to 1995-1999 (reference), the adjusted hazard ratio for 5-year graft failure was 0.78 (95% CI 0.67-0.91), 0.70 (95% CI 0.59-0.83) and 0.60 (95% CI 0.50-0.73) for 2000-2004, 2005-2009, and 2010-2014, respectively. Ten-year graft failure similarly reduced from 0.83 (95% CI 0.74-0.93) for 2000-04 to 0.78 (95% CI 0.68-0.89) for 2010-14, compared to 1995-99. Medium and long term all-cause graft failure has improved steadily since 1995-99. Significant reductions in graft failure due to rejection and vascular causes were observed at 5 years, and due to rejection, vascular causes, death and glomerular disease at 10 years.

Donor body mass index over 30 is no barrier for pure laparoscopic donor right hepatectomy.

Challenges arise when translating pure laparoscopic donor right hepatectomy (PLDRH) results from Asian to Western donors, due to differences in body mass index (BMI). This study compares the outcomes of PLDRH and conventional open donor right hepatectomy (CDRH) in donors with BMI over 30. Medical records of live liver donors (BMI > 30) undergoing right hepatectomy (2010-2021) were compared: 25 PLDRH cases vs. 19 CDRH cases. Donor and recipient demographics, operative details, and outcomes were analyzed. PLDRH and CDRH had similar donor and recipient characteristics. PLDRH had longer liver removal and warm ischemic times, but a shorter post-liver removal duration than CDRH. Donor complication rates were comparable, with the highest complication being grade IIIa in PLDRH, necessitating needle aspiration for biloma on postoperative day 11. Fortunately, this donor fully recovered without additional treatment. No complications exceeding Clavien-Dindo grade IIIa occurred in either group. Recipient outcomes between the groups were similar. This study supports PLDRH as a viable option for donors with BMI over 30, challenging the notion that high BMI should deter considering PLDRH. The findings provide valuable insights into the safety and feasibility of PLDRH, encouraging further exploration of this technique in diverse donor populations.

Impact of donor characteristics on hepatocellular carcinoma recurrence after liver transplantation.

Impact of donor characteristics on hepatocellular carcinoma recurrence after liver transplantation.

Tissue-resident Lymphocytes Are Released During Hypothermic and Normothermic Machine Perfusion of Human Donor Kidneys.

Machine perfusion is the preferred preservation method for deceased donor kidneys. Perfusate fluid, which contains a complex mixture of components, offers potential insight into the organ's viability and function. This study explored immune cell release, particularly tissue-resident lymphocytes (TRLs), during donor kidney machine perfusion and its correlation with injury markers. Perfusate samples from hypothermic machine perfusion (HMP; n = 26) and normothermic machine perfusion (NMP; n = 16) of human donor kidneys were analyzed for TRLs using flow cytometry. Residency was defined by expressions of CD69, CD103, and CD49as. TRL release was quantified exclusively in NMP. Additionally, levels of cell-free DNA, neutrophil gelatinase-associated lipocalin, and soluble E-cadherin (sE-cadherin) were measured in NMP supernatants with quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. Both HMP and NMP samples contained a heterogeneous population of TRLs, including CD4+ tissue-resident memory T cells, CD8+ tissue-resident memory T cells, tissue-resident natural killer cells, tissue-resident natural killer T cells, and helper-like innate lymphoid cells. Median TRL proportions among total CD45+ lymphocytes were 0.89% (NMP) and 0.84% (HMP). TRL quantities in NMP did not correlate with donor characteristics, perfusion parameters, posttransplant outcomes, or cell-free DNA and neutrophil gelatinase-associated lipocalin concentrations. However, CD103+ TRL release positively correlated with the release of sE-cadherin, the ligand for the CD103 integrin. Human donor kidneys release TRLs during both HMP and NMP. The release of CD103+ TRLs was associated with the loss of their ligand sE-cadherin but not with general transplant injury biomarkers.

(428) - Characteristics of Potential Circulatory-Death Heart Donors in France

(428) - Characteristics of Potential Circulatory-Death Heart Donors in France

Origin of discrete donor–acceptor pair transitions in 2D Ruddlesden–Popper perovskites

Two-dimensional (2D) van der Waals nanomaterials have attracted considerable attention for potential use in photonic and light–matter applications at the nanoscale. Thanks to their excitonic properties, 2D perovskites are also promising active materials to be included in devices working at room temperature. In this work, we study the presence of very narrow and spatially localized optical transitions in 2D lead halide perovskites by μ-photoluminescence and time-decay measurements. These discrete optical transitions are characterized by sub-millielectronvolt linewidths (≃120μeV) and long decay times (5–8 ns). X-ray photoemission and density-functional theory calculations have been employed to investigate the chemical origin of electronic states responsible of these transitions. The association of phenethylammonium with methylammonium cations into 2D Ruddlesden–Popper perovskites, (PEA)2(MA)n−1PbnI3n+1, particularly in phases with n≥2, has been identified as a mechanism of donor–acceptor pair (DAP) formation, corresponding to the displacement of lead atoms and their replacement by methylammonium. Ionized DAP recombination is identified as the most likely physical source of the observed discrete optical emission lines. The analysis of the experimental data with a simple model, which evaluates the Coulombic interaction between ionized acceptors and donors, returns a donor in Bohr radius of the order of ≃10 nm. The analysis of the spectral and electronic characteristics of these single donor–acceptor states in 2D perovskites is of particular importance both from the point of view of fundamental research, as well as to be able to link the emission of these states with new optoelectronic applications that require long-range optically controllable interactions.

Long-Term Survival Following Primary Graft Dysfunction Development in Lung Transplantation

IntroductionPrimary graft dysfunction (PGD) is a known risk factor for early mortality following lung transplant (LT). However, the outcomes of patients who achieve long-term survival following index hospitalization are unknown. We aimed to determine the long-term association of PGD grade 3 (PGD3) in patients without in-hospital mortality. MethodsLT recipients were identified from the United Network for Organ Sharing Database. Patients were stratified based on the grade of PGD at 72 h (No PGD, Grade 1/2 or Grade 3). Groups were assessed with comparative statistics. Long-term survival was evaluated using Kaplan–Meier methods and a multivariable shared frailty model including recipient, donor, and transplant characteristics. ResultsThe PGD3 group had significantly increased length of stay, dialysis, and treated rejection post-transplant (P < 0.001). Unadjusted survival analysis revealed a significant difference in long-term survival (P < 0.001) between groups; however, following adjustment, PGD3 was not independently associated with long-term survival (hazard ratio: 0.972; 95% confidence interval: 0.862-1.096). Increased mortality was significantly associated with increased recipient age and treated rejection. Decreased mortality was significantly associated with no donor diabetes, bilateral LT as compared to single LT, transplant in 2015-2016 and 2017-2018, and no post-transplant dialysis. ConclusionsWhile PGD3 remains a challenge post LT, PGD3 at 72 h is not independently associated with decreased long-term survival, while complications such as dialysis and rejection are, in patients who survive index hospitalization. Transplant providers should be aggressive in preventing further complications in recipients with severe PGD to minimize the negative association on long-term survival.

Donor Lung Preservation at 10 °C: Clinical and Logistical Impact

IntroductionCold static donor lung preservation at 10°C appears to be a promising method to safely extend the cold ischemic time (CIT) and improve lung transplant (LTx) logistics. MethodsLTx from November 2021 to February 2023 were included in this single institution, prospective, non-randomized study comparing prolonged preservation at 10°C versus standard preservation on ice. The inclusion criteria for 10°C preservation were suitable grafts for LTx without any donor retrieval concerns. Primary endpoint: primary graft dysfunction (PGD) grade-3 at 72-h. Secondary endpoints: clinical outcomes, cytokine profile and logistical impact. ResultsThirty-three out of fifty-seven cases were preserved at 10°C. Donor and recipient characteristics were similar across the groups. Total preservation times (h:min) were longer (p<0.001) in the 10°C group [1st lung: median 12:09 (IQR 9:23–13:29); 2nd: 14:24 (12:00–16:20)] vs. standard group [1st lung: median 5:47 (IQR 5:18–6:40); 2nd: 7:15 (6:33–7:40)]. PGD grade-3 at 72-h was 9.4% in 10°C group vs. 12.5% in standard group (p=0.440). Length of mechanical ventilation (MV), ICU and hospital stays were similar in both groups. Thirty and ninety-day mortality rates were 0% in 10°C group (vs. 4.2% in standard group). IL-8 concentration was significantly higher 6-h post-LTx in the standard group (p=0.025) and IL-10 concentration was increased 72-h post-LTx in the 10°C group (p=0.045). ConclusionsPreservation at 10°C may represent a safe and feasible strategy to intentionally prolong the CIT. In our center, extending the CIT at 10°C may allow for semi-elective LTx and improve logistics with similar outcomes compared to the current standard preservation on ice.

(1350) - Using Machine Learning to Assess the Predictive Power of Donor Characteristics in Pediatric Heart Transplant Outcomes

(1350) - Using Machine Learning to Assess the Predictive Power of Donor Characteristics in Pediatric Heart Transplant Outcomes

Pediatric en bloc kidney transplant from donors

Most kidneys from small pediatric donors are transplanted to adult recipients because of the perceived risk of surgical complications and graft thrombosis. In this study, we aim to demonstrate our favorable outcomes in transplanting pediatric kidneys from donors <15 k into pediatric recipients. This study retrospectively analyzes the outcomes of seven pediatric recipients of en block kidney transplants from pediatric donors weighing <15 kg performed at King Fahad Specialist Hospital-Dammam from December 2014 to January 2018. Baseline characteristics of donors and recipients were collected. The incidences of surgical complication, immediate, and intermediate graft function were the primary outcomes. The study included seven recipients monitored for a mean duration of 6.86 ± 1.35. Donors' and recipients' mean weights were 7.4 ± 3.2 kg and 20.7 ± 9.2 kg, respectively. Ureteric stricture occurred in one patient. There was a substantial improvement of 1-year estimated glomerular filtration rate (eGFR) compared to the 1-week mark (106.7 ± 26.38 mL/min. 1.73 m2 vs. 63.7 ± 22.92 mL/min/1.73 m2, p = .0069). The observed improvement in renal function persisted at the 5-year mark and during the last follow-up, with eGFR of 70.3 ± 40.7 mL/min/1.73 m2, and 79.8 ± 30.8 mL/min/1.73 m2, respectively. There was also increase of 27.9% in the size of the en bloc kidney observed at the 6 months. In a specialized transplant center with highly skilled surgeons, the utilization of en bloc kidney transplant from donors weighing less than 15 kg is an effective strategy for expanding the donor pool and ensuring favorable graft outcomes.

Impact of the Kidney Allocation Revision on Access to Kidney Transplantation and Outcomes in the United States.

The 2014 Kidney Allocation System (KAS) revision aimed to enhance equity in organ allocation and improve patient outcomes. This study assesses the impacts of the KAS revision on renal transplantation demographics and outcomes in the United States. We conducted a retrospective study utilizing the Organ Procurement and Transplantation Network/Scientific Registry of Transplant Recipients (OPTN/SRTR) database from 1998 to 2022. We compared recipient and donor characteristics, and outcomes (graft failure and recipient survival) pre- and post-KAS revision. Post-KAS, recipients were significantly older (53 vs 48, P < .001) with an increase in Medicaid beneficiaries (7.3% vs 5.5%, P < .001). Despite increased graft survival, HR = .91 (95% CI 0.80-.92, P < .001), overall recipient survival decreased, HR = 1.06 (95% CI 1.04-1.09, P < .001). KAS revision led to greater racial diversity among recipients and donors, enhancing equity in organ allocation. However, disparities persist in graft failure rates and recipient survival across racial groups. The 2014 Kidney Allocation System revision has led to important changes in the renal transplantation landscape. While progress has been made towards increasing racial equity in organ allocation, further refinements are needed to address ongoing disparities. Recognizing the changing patient profiles and socio-economic factors will be crucial in shaping future policy modifications.

Abstract 6691: Engraftment as a determinant of response in fecal microbiome transplantation interventions for immunotherapy in melanoma

Abstract Background: Distinct gut microbiome signatures are associated with response, resistance, and toxicity to immune checkpoint blockade (ICB). Fecal microbiome transplants (FMT) have validated the importance of the gut microbiome in enhancing response and overcoming resistance to immunotherapy. However, donor selection remains a key challenge for FMT. Heterogenous responses using Healthy Donors (HD) and ICB Complete Responders (CR) as FMT donors suggest donor characteristics alone do not determine response. Here, we posit that donor-recipient relationships are critical in determining clinical responses to FMT. Methods: We studied a cohort of ICB-refractory, metastatic melanoma patients treated with combined FMT and ICB (10 recipients, 2 donors). Patient gut microbiomes were profiled using whole metagenomic sequencing (WMS) of longitudinal stool collections (baseline, day 7, day 31, and day 65 post-FMT). Immune infiltration of on-treatment tumor and colon biopsies was quantified with immunohistochemistry. mTraCX, an Earth Mover’s Distance-based algorithm, was used to evaluate taxonomic engraftment between donors and recipients. Bray-Curtis distance was used to measure functional similarities between donor and recipient gut microbiome. Clinical findings were validated in pre-clinical FMT experiments performed on BrafV600EPten−/− melanoma-bearing mice. Results: One-third of recipients (3/10) developed an objective response (R) to ICB following FMT. mTraCX demonstrated an association between clinical response to FMT and durable engraftment of donor microbiota at day 65 post-FMT (p=0.025). Taxonomic engraftment (mTraCX) correlated positively with functional engraftment (Bray-Curtis distance) (r=0.89, p&amp;lt;0.0001). Enhanced engraftment was associated with increased CD4 (r = -0.87, p=0.0045) and CD8 (r = -0.6, p=0.09) T-cell infiltration in the colon, and a trend towards increased CD8 T-cell infiltration (r = -0.5, p=0.2) in the tumor following treatment with FMT+ICB. Pre-clinical models paralleled our clinical findings as responding mice showed better donor engraftment than non-responding mice (p&amp;lt;0.0001 on day 4 and day 24 following FMT). Conclusions: Our data shows that donor engraftment is a favorable prognostic factor for ICB treatments combined with FMT. Future investigations will aim to develop donor-recipient matching criteria to enhance the feasibility and integration of FMTs into clinical practice. Citation Format: Manoj Chelvanambi, Ashish V. Damania, Sarah B. Johnson, Golnaz Morad, Rossana N. Lazcano, Beth A. Helmink, Lon W. Fong, Khalida Wani, Y David Seo, Elizabeth M. Park, Reed I. Ayabe, Bhavana Singh, Matthew C. Wong, Davis R. Ingram, Michael G. White, Alexander J. Lazar, Aditya K. Mishra, Nadim J. Ajami, Erez N. Baruch, Jennifer A. Wargo. Engraftment as a determinant of response in fecal microbiome transplantation interventions for immunotherapy in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6691.

O204: The influence of HLA matching on graft survival in lung transplant recipients is indication specific: An UNOS database analysis

Abstract Background and aims The importance of human leukocyte antigen (HLA) matching in lung transplantation remains unclear, and the influence of indication in HLA compatibility is unknown. This study aimed to determine the relationship between HLA matching and lung graft survival using a large-scale multi-center database (UNOS/OPTN) and multivariate logistic analysis. The secondary aim was to determine whether this relationship was influenced by transplant indication. Methods This retrospective observational analysis was performed using 26,312 lung transplant recipients from the UNOS/OPTN database. Patients were divided into two groups based on number of HLA mismatches (0-3 mismatches vs 4-6 mismatches) and then subcategorized by indication. Risk-adjusted outcomes were assessed by multivariate Cox analysis adjusting for donor and recipient characteristics and visualized using Kaplan-Meier survival curves. Results Increased HLA mismatch was associated with reduced allograft survival. Adjusted models found that the total HLA mismatch &amp;gt;3 increased the mortality hazard at 15 years (HR 1·05, p &amp;lt;0·05) and 20 years (HR 1·05, p&amp;lt;0·01). Pulmonary hypertension was the only indication with a statistically significant association between HLA mismatch and graft survival. Allografts in patients with 0-3 mismatches survived for 401 days longer than those with 4-6 mismatches (p=0·02). Conclusion Increased HLA mismatch reduced graft survival. When stratified by indication, this association was preserved exclusively in pulmonary hypertension. This finding is of potential clinical relevance to the management of this subsection of lung transplant recipients, impacting organ allocation, transplant surveillance and use of desensitisation and immunosuppression protocols.