Faculty Bibliography

Xenotransplantation of genetically-modified pig kidneys offers a solution to the scarcity of organs for end-stage renal disease patients.¹ We performed a 61-day alpha-Gal knock-out pig kidney and thymic autograft transplant into a nephrectomized brain-dead human using clinically approved immunosuppression, without CD40 blockade or additional genetic modification. Hemodynamic and electrolyte stability and dialysis independence were achieved. Post-operative day (POD) 10 biopsies revealed glomerular IgM and IgA deposition, activation of early complement components and mesangiolysis with stable renal function without proteinuria, a phenotype not seen in allotransplantation. On POD 33, an abrupt increase in serum creatinine was associated with antibody-mediated rejection and increased donor-specific IgG. Plasma exchange, C3/C3b inhibition and rabbit anti-thymocyte globulin (rATG), completely reversed xenograft rejection. Pre-existing donor-reactive T cell clones expanded progressively in the circulation post-transplant, acquired an effector transcriptional profile and were detected in the POD 33 rejecting xenograft prior to rATG treatment. This study provides the first long-term physiologic, immunologic, and infectious disease monitoring of a pig-to-human kidney xenotransplant and indicates that pre-existing xenoreactive T cells and induced antibodies to unknown epitope(s) present a major challenge, despite significant immunosuppression. It also demonstrates that a minimally gene-edited pig kidney can support long-term life-sustaining physiologic functions in a human.

Historically, liver transplant (LT) candidates with human immunodeficiency virus (HIV) have experienced high waitlist mortality. Since the HIV Organ Policy Equity (HOPE) Act expands access to organs from donors with HIV, we assessed the impact of HOPE on LT rate and wait time for this population. We linked data from a multicenter HOPE in Action study to Scientific Registry of Transplant Recipients (February 21, 2019 to June 1, 2024) and used Poisson regression to compare transplant rates among 99 candidates willing to accept HOPE donors (HOPE candidates) to 13 495 candidates with or without HIV not listed as willing to accept HOPE donors (non-HOPE candidates) matched on transplant center. The median time to any deceased donor liver transplant (DDLT) was 2.3 months for HOPE and 1.1 years for non-HOPE candidates. Within 2 years of listing, 90.9% of HOPE versus 58.5% of non-HOPE candidates received a DDLT (P < .001). HOPE was associated with an overall 3.11-fold higher DDLT incident rate ratio (95% CI 2.48-3.88, P < .001). Stratified by model for end-stage liver disease score categories 6 to 14, 15 to 24, 25 to 34, and 35 to 40/status 1; HOPE candidates had 10.12-fold, 5.31-fold, 1.41-fold and 2.90-fold higher DDLT rates, respectively. Willingness to accept livers from donors with HIV improves access to liver transplantation for candidates with HIV.

We sought to understand the potential impacts of a rapidly evolving donor pool on the annual recalibration of the kidney donor profile index (KDPI). Using OPTN data, we examined the kidney donor risk index (KDRI) among deceased kidney donors recovered 2011-2024. We mimicked the OPTN's annual re-mapping process to measure the KDRI-to-KDPI calibration drift and used Cox regression to translate this drift into all-cause graft failure rate differences. The 50th/75th/95th KDRI percentile among recovered donors rose from 1.19/1.47/2.0 in 2011 to 1.40/1.77/2.36 in 2024. For donors with the same KDRI, the KDPI assigned in 2024 was as much as 13 points lower than the KDPI assigned in 2012. Holding other factors constant, the KDRI-KDPI calibration shift equated to 7 years of increased age (65 vs. 58) for KDPI 86% donors. Five-year graft failure risk was 9% higher (RR: _1.0871.093_1.097) for a kidney assigned a KDPI of 86% in 2024 versus 2012. Organ recovery practices have changed. The relationship between KDPI and organ quality has become a moving target, complicating shared decision-making and altering the meaning of allocation policy thresholds. Alternative solutions to annually remapping KDPI, such as establishing a fixed reference cohort or migrating away from KDPI, could be considered.

BACKGROUND:Under the HOPE Act, transplants from donors with HIV to recipients with HIV (HIV D+/R+) have been largely limited to kidney and liver. However, recent modifications to HOPE research guidelines allow broader participation of cardiothoracic programs. METHODS:To quantify potential cardiothoracic HOPE donors, we used SRTR data (3/2016-12/2024) to identify 101,200 donors without HIV and 273 HOPE donors (with true and false positive HIV tests). Using logistic regression, we predicted the probability of having a heart or lung(s) used for transplant among donors without HIV that had a kidney or liver used. We then applied model parameters to HOPE donors that had a kidney or liver used to estimate the number of HOPE donors that might have been cardiothoracic donors if the practice were expanded. RESULTS:Among donors without HIV, cardiothoracic donation was associated with age, cause of death, hepatitis C, hypertension, diabetes, smoking, cardiovascular disease, blood gas, and circulatory death. Applying our model, an estimated 41.0% (N=111), 18.7% (N=51), and 15.2% (N=41) of HOPE donors were potential heart, any lung (single or double), or double-lung donors, as compared to 32.3%, 21.8%, and 18.2% of abdominal organ donors without HIV, respectively. This translated to an annual 13-18 potential heart and 5-8 potential lung transplants (of which 4-6 would be double-lung transplants) from HOPE donors. CONCLUSIONS:If HIV D+/R+ is more widely expanded to cardiothoracic transplantation, 41% of HOPE kidney and liver donors have potential to donate a heart and almost 20% to donate a lung to candidates with HIV.

BACKGROUND:Sarcopenia and myosteatosis are indicators of abnormal body composition (BC). Computed tomography (CT) imaging has proven to be an accurate modality for BC quantification in kidney transplantation (KT). We tested whether pre-KT CT-based BC was associated with both all-cause graft loss (ACGL) and mortality among adult recipients from two centers (Johns Hopkins Hospital [JHH] and University Medical Center Groningen [UMCG]). METHODS:Patients who underwent a KT between 2003 and 2020 were followed for a median (interquartile range) follow-up of 6.4 (4.6-8.5) years at JHH and 6.3 (5.1-7.5) years at UMCG. Cox proportional hazard models were used to estimate the associations of BC with ACGL/ mortality. Fine and Gray regression analysis was performed to assess the association between BC and death-censored graft loss. Prior to KT, 49% of recipients had sarcopenia and 66% had myosteatosis. RESULTS:In total 608 patients were included from JHH (N= 294) and UMCG (N=314). Sarcopenia was not associated with post-KT outcomes. Myosteatosis was associated with a higher risk of ACGL (adjusted hazard ratio 1.78, 95%CI:1.08 - 2.93) and mortality (adjusted hazard ratio 2.35, 95%CI: 1.27 - 4.33) at JHH, but showed no significant association at UMCG after adjusting for confounders. Myosteatosis did not show a significant association with death-censored graft loss at both centers. CONCLUSION/CONCLUSIONS:Myosteatosis ascertained from existing CT scans could help identify recipients at higher risk for ACGL who may benefit most from prehabilitation.

With U.S. Food and Drug Administration (FDA) clearance of clinical trials of kidney xenotransplantation (XTx) in living humans, understanding the recipient experience is critical. Semi-structured interviews with the three living XTx recipients identified core domains of the recipient experience, including quality of life (QoL), fears about XTx, and healthcare team communication and support. Transcribed interviews were analyzed by two qualitative researchers using an inductive thematic approach and were mapped onto the Warwick Patient Experience Model, a validated framework to assess key aspects of patient satisfaction with the healthcare experience. All three recipients (53-year-old female; 66-year-old male; 54-year old male) described a restoration of hope, contrasted with their poor quality of life on dialysis. They emphasized that access to XTx and graft survival requires mutual confidence and commitment between recipients and healthcare teams. XTx recipients use dialysis as a point of reference when describing changes in their post-transplant QoL and seemed well-situated to handle the possibility of graft failure. These insights may aid in the creation of decision aids and educational materials tailored to the specific needs of XTx recipients.

Liver transplant (LT) recipients experience a wide range of comorbidities, leading to frequent healthcare encounters. Until now, national registries, which have limited exposures and outcomes, and laborious small cohort studies have been the main data sources for LT research. Cosmos database offers electronic health record (EHR)-based insights into LT recipients at the national level with granular data. We evaluated if Cosmos data is representative of the entire US LT recipient population. Using Cosmos (N=20,235) and the national Scientific Registry of Transplant Recipients (SRTR) (N=51,281), we identified adult, first-time LT recipients between 7/2016-12/2022. We compared demographics, clinical data, and mortality across datasets, calculating Kaplan-Meier survival estimates and multi-variable Cox regressions. Recipient characteristics were highly comparable (e.g., female: Cosmos=36.5% vs. SRTR=36.4%, Black: 6.8% vs. 7.2%; BMI: 28.5 kg/m2 [24.8-32.9] vs. 28.2 [24.6-32.4]). Lab values were similar across cohorts, including MELD (24 [17-30] vs. 23 [16-30]). Transplant indications, donor characteristics, and 5-year survival (Cosmos 83.1% [82.3-83.8) vs. SRTR 80.9% [80.4-81.3]) were similar. The associations of clinical factors with survival were similar across both groups. Cosmos database demonstrated acceptable generalizability to the general US LT recipient population, which may advance LT research through a better understanding about LT recipients' experiences and outcomes.

BACKGROUND:Due to high prevalence of Kaposi Sarcoma (KS)-Associated Herpesvirus (KSHV) among people with HIV, KSHV-associated disease (KAD) may be increased after kidney transplantation from donors with HIV (HIV D+) to recipients with HIV (HIV R+). METHODS:Anti-KSHV antibodies were measured in HIV R+ and donors with and without HIV (HIV D-) using a 30-antigen multiplex assay within three multicenter kidney transplantation studies. KSHV seropositivity was defined as reactivity to conventional KSHV antigens (≥1 ORF73 or K8.1); reactivity to expanded 5-antigen and 30-antigen panels were also reported. Risk factors were identified using modified Poisson regression. Recipients were monitored for post-transplant anti-KSHV antibody changes and KAD. RESULTS:KSHV seroprevalence was 40.6% (143/352) among HIV R+, 25.2% (33/131) among HIV D+, and 7.5% (4/53) among HIV D-. In the multivariable model, only men who have sex with men (MSM) was associated with KSHV seropositivity: relative risk 1.51 (95% confidence interval [CI] 1.07-2.14) in recipients and 2.39 (95%CI 1.03-5.53) in donors. Among 418 HIV R+ (215 HIV D+/R+, 203 HIV D-/R+), there were 5 KAD cases (incidence 0.63 cases/100 person-years, 95%CI 0.26-1.52): 3 skin-only KS, 1 multicentric Castleman disease, 1 allograft KS. The allograft KS occurred in a female HIV D+/R+ and was likely donor-derived. Remaining KAD cases occurred in male HIV D-/R+ and were likely recipient KSHV reactivation or acquisition. CONCLUSIONS:In the United States, KSHV seroprevalence in donors and recipients with HIV was high, particularly among MSM. Reassuringly, KSHV-associated disease was rare, and primarily attributed to recipient rather than donor-derived KSHV.

INTRODUCTION/BACKGROUND:Predicting graft failure risk in pediatric liver transplantation (LT) recipients could identify areas for improving management. Persistent cognitive, motor, academic, and functional deficits are common in recipients and their impact on graft survival following LT helps inform risk prediction. METHODS:Using SRTR data 2008-2023, we evaluated the cognitive, motor, academic, and functional deficits of LT recipients at time of transplant to 14 years post-LT. We compared all cause graft failure (ACGF) among patients with versus without pre-LT and 1-year post-LT deficits using Cox regression, adjusting for recipient characteristics. We calculated an individual risk score for ACGF. RESULTS:In 8062 pediatric LT recipients median age 3 (IQR: 1, 10), 28.0%, 29.5%, 35.0%, and 79.8% of recipients had pre-LT deficits in cognition, motor, academic activity, and functional status respectively. This decreased to 23.0%, 18.1%, 14.2%, and 38.7% 1-year post-LT. Increased hazard of ACGF was noted in recipients with pre-LT decreased functional status (aHR = 1.13 (per 10% decrease), 95% CI: 1.10-1.15, p < 0.001), definite motor delay (aHR = 1.60, 95% CI: 1.21-2.10, p < 0.001), and inability to participate in academics (aHR = 1.49, 95% CI: 1.08-1.89, p = 0.01), but not delays in cognition (aHR = 0.91, 95% CI: 0.69-1.21, p = 0.19). Our risk score predicting ACGF demonstrated improved predictive performance compared to clinical parameters alone (C-statistic = 0.70 (0.67, 0.72) vs. 0.66 (0.64, 0.69), p < 0.001). CONCLUSIONS:Pediatric LT recipients with pre- or post-LT motor, academic, and functional deficits are at higher risk for ACGF. Care should be taken to assess deficits to identify patients who may benefit from functional intervention to potentially reduce ACGF risk.