BACKGROUND:Historically, ABO incompatibility (ABOi) has been considered a relative contraindication to liver transplant (LT) due to inferior postoperative outcomes. We seek to reassess ABOi LTs as an underused graft supply. METHODS:We retrospectively reviewed all adult and pediatric patients who underwent LT, 1987-2022. Recipients were categorized by donor blood type compatibility: incompatible (ABOi), compatible (ABOc), and identical (ABOid). Propensity scoring of 1:1:1 was performed to account for recipient age and acuity at transplant. RESULTS:Of 193,751 LTs, 2699 were ABOi (1.4%). ABOi recipients had the highest proportion of status 1 listings (22.5% versus 20.5% ABOc, 4.9% ABOid, P < 0.0001) and the highest model for end-stage liver disease (30 versus 28 ABOc, 26 ABOid, P < 0.0001) and pediatric end-stage liver disease scores at transplant (33 versus 28 ABOc, 25 ABOid, P < 0.0001). When analyzing the unmatched cohort, ABOi was associated with worse GS (HR 1.2, P < 0.001), OS (HR 1.1, P = 0.033), and increased rates of retransplantation (HR 1.35, P = 0.001). However, after performing propensity matching, there were no differences in GS, OS, or retransplantation between groups. CONCLUSIONS:There is no difference in outcomes between ABOi LT recipients and recipients of ABOc and ABOid grafts after accounting for recipient age and acuity. ABOi LT may decrease blood group disparities and improve timely LT access.

We investigated the use of robotic objective performance metrics (OPM) to predict number of cases to proficiency and independence among abdominal transplant fellows performing robot-assisted donor nephrectomy (RDN). 101 RDNs were performed by 5 transplant fellows from September 2020 to October 2023. OPM included fellow percent active control time (

Several studies have demonstrated the feasibility of robotic kidney transplant (RKT) as a safe alternative to open kidney transplant (OKT). However, significant selection bias in RKT patient selection limits meaningful comparison between the two techniques. This is a single-center retrospective review of a prospectively maintained kidney transplant database (2021–2024). Outcomes after the first 50 “non-selected” RKTs are compared with a contemporary cohort of 100 OKTs after propensity score matching for age, gender, BMI and type of donation (living vs deceased). Data pertinent to recipient demographics, intraoperative parameters, and short-term post-operative outcomes were collected and compared. Both groups were well-matched for recipient age, gender, BMI, and donation type. RKT group had significantly longer total operative time (RKT 258 min vs. OKT 183 min; p < 0.0001) and warm ischemia time (RKT 37 min vs. OKT 31 min; p < 0.0001) but significantly less blood loss (OKT 155 ml vs. RKT 93 ml). Average length of hospital stay for both groups was 5 days, with OKT group demonstrating significantly higher rates of post-operative complications (OKT 31

Brocke, Tiffany K MDa; Martens, Gregory R MD, PhDa; Awad, Michael M MD, PhD, MHPE, FACSa; Sacks, Justin M MD, MBA, FACSa; Olson, John A Jr MD, PhD, FACSa Author Information

Prolonged survival in preclinical renal xenotransplantation demonstrates that early antibody mediated rejection (AMR) can be overcome. It is now critical to evaluate and understand the pathobiology of late graft failure and devise new means to improve post xenograft outcomes. In renal allotransplantation the most common cause of late renal graft failure is transplant glomerulopathy-largely due to anti-donor MHC antibodies, particularly anti-HLA DQ antibodies. We evaluated the pig renal xenograft pathology of four long-surviving (>300 days) rhesus monkeys. We also evaluated the terminal serum for the presence of anti-SLA class I and specifically anti-SLA DQ antibodies. All four recipients had transplant glomerulopathy and expressed anti-SLA DQ antibodies. In one recipient tested for anti-SLA I antibodies, the recipient had antibodies specifically reacting with two of three SLA I alleles tested. These results suggest that similar to allotransplantation, anti-MHC antibodies, particularly anti-SLA DQ, may be a barrier to improved long-term xenograft outcomes.

BACKGROUND:An increasing number of transplant centers have adopted robot-assisted living donor nephrectomy. Thus, a transplant fellow assessment tool is needed for promoting operative independence in an objective and safe manner.METHODS:In this pilot study, data was prospectively collected on both fellow performance with focus on technique, efficiency, and communication ("overall RO-SCORE"), and operative steps ("operative steps RO-SCORE"). Robotic user performance metrics were analyzed from the da Vinci Xi system, including fellow percent active control time (ACT) and handoff counts.RESULTS:From July 2020 to February 2021, twenty-one robot-assisted donor nephrectomies were performed. In regression analysis, fellow performance (based on both RO-SCOREs and robot % ACT) was significantly associated with both time and case number, with time-to-independence modelled at 8.4-14.2 months, and case number-to-independence estimated at 15-22 cases. Robot user metrics provided valid objective measures alongside RO-SCOREs.CONCLUSIONS:This pilot study provides an effective assessment tool for promoting operative competency in robot-assisted donor nephrectomy among transplant fellows.

Abstract Background Xenotransplantation using genetically-engineered (GE) pig organs offers an unlimited supply of organs for patients with end-stage organ failure. Disrupting the porcine GGTA1/CMAH/β4GalNT2 genes (TKO) markedly reduces binding of human natural anti-pig antibodies in human to carbohydrate antigens expressed on the pig organ. However, more evident have demonstrated that T cell responses play a major role in xenogeneic rejection, and that immunosuppression alone is likely incapable of completely suppressing these responses. The object of this study is at an organ-specific level to evaluate human T cell-mediated response against GE pig renal microvascular endothelial cells (RMEC) with or without swine leukocyte antigen (SLA) class I or II. Methods Primary RMEC were isolated from the GGTA1/CMAH knockout (DKO) pigs, and immortalized using Lenti-SV40 T. The gene editing was performed to create specific TKO RMEC cell lines expressing SLA class II. Stimulation of human T cell activation or proliferation by RMEC was performed flow cytometry-based mixed lymphocyte reaction (MLR). Results The specific GE cells lacking carbohydrates or expressing SLA class I or II were confirmed. MLR data shows that human CD4+ T cell proliferation by CD31+ RMEC was higher than that by fibroblast-like renal cells (RC), and was significantly inhibited by immunosuppressive drugs. Furthermore, both of CD69+ and CD25+ T cells were significantly enhanced by RMEC with expression of SLA class I and II compared with SLA class I alone. Conclusion Porcine RMEC express SLA class I/II and known costimulatory molecules and have the ability to simulate human T cell proliferation. RMEC will be a useful reagent for the further study of xenotransplantation.

The shortage of available organs remains the greatest barrier to expanding access to transplant. Despite advances in genetic editing and immunosuppression, survival in experimental models of kidney xenotransplant has generally been limited to <100 days. We found that pretransplant selection of recipients with low titers of anti-pig antibodies significantly improved survival in a pig-to-rhesus macaque kidney transplant model (6 days vs median survival time 235 days). Immunosuppression included transient pan-T cell depletion and an anti-CD154-based maintenance regimen. Selective depletion of CD4+ T cells but not CD8+ T cells resulted in long-term survival (median survival time >400 days vs 6 days). These studies suggested that CD4+ T cells may have a more prominent role in xenograft rejection compared with CD8+ T cells. Although animals that received selective depletion of CD8+ T cells showed signs of early cellular rejection (marked CD4+ infiltrates), animals receiving selective CD4+ depletion exhibited normal biopsy results until late, when signs of chronic antibody rejection were present. In vitro study results suggested that rhesus CD4+ T cells required the presence of SLA class II to mount an effective proliferative response. The combination of low pretransplant anti-pig antibody and CD4 depletion resulted in consistent, long-term xenograft survival.

Background. Highly sensitized patients are difficult to match with suitable renal allograft donors and may benefit from xenotransplant trials. We evaluate antibody binding from sensitized patients to pig cells and engineered single allele cells to identify anti-human leukocyte antigen (HLA) antibody cross-species reactivity with swine leukocyte antigen (SLA). These novel testing strategies assess HLA/SLA epitopes and antibody-binding patterns and introduce genetic engineering of SLA epitopes. Methods. Sensitized patient sera were grouped by calculated panel reactive antibody and luminex single antigen reactivity profile and were tested with cloned GGTA1/CMAH/B4GalNT2 glycan knockout porcine cells. Pig reactivity was assessed by direct flow cytometric crossmatch and studied following elution from pig cells. To study the antigenicity of individual class I HLA and SLA alleles in cells, irrelevant sera binding to lymphoblastoid cells were minimized by CRISPR/Cas9 elimination of endogenous class I and class II HLA, B-cell receptor, and Fc receptor genes. Native HLA, SLA, and mutants of these proteins after mutating 144K to Q were assessed for antibody binding. Results. Those with predominately anti-HLA-B&C antibodies, including Bw6 and Bw4 sensitization, frequently have low pig reactivity. Conversely, antibodies eluted from porcine cells are more commonly anti-HLA-A. Single HLA/SLA expressing engineered cells shows variable antigenicity and mutation of 144K to Q reduces antibody binding for some sensitized patients. Conclusions. Anti-HLA antibodies cross-react with SLA class I in predictable patterns, which can be identified with histocompatibility strategies, and SLA class I is a possible target of genetic engineering.

Xenotransplantation of pig organs into people may help alleviate the critical shortage of donors which faces organ transplantation. Unfortunately, human antibodies vigorously attack pig tissues preventing the clinical application of xenotransplantation. The swine leukocyte antigens (SLA), homologs of human HLA molecules, can be xenoantigens. SLA molecules, encoded by genes in the pig major histocompatibility complex, contribute to protective immune responses in pig. Therefore, simply inactivating them through genome engineering could reduce the ability of the human immune system to surveil transplanted pig organs for infectious disease or the development of neoplasms. A potential solution to this problem is to identify and modify epitopes in SLA proteins to eliminate their contribution to humoral xenoantigenicity while retaining their biosynthetic competence and ability to contribute to protective immunity. We previously showed that class II SLA proteins were recognized as xenoantigens and mutating arginine at position 55 to proline, in an SLA-DQ beta chain, could reduce human antibody binding. Here, we extend these observations by creating several additional point mutants at position 55. Using a panel of monoclonal antibodies specific for class II SLA proteins, we show that these mutants remain biosynthetically competent. Examining antibody binding to these variants shows that point mutagenesis can reduce, eliminate, or increase antibody binding to class II SLA proteins. Individual mutations can have opposite effects on antibody binding when comparing samples from different people. We also performed a preliminary analysis of creating point mutants near to position 55 to demonstrate that manipulating additional residues also affects antibody reactivity.

Objective: Xenotransplantation using pig organs could end the donor organ shortage for transplantation, but humans have xenoreactive antibodies that cause early graft rejection. Genome editing can eliminate xenoantigens in donor pigs to minimize the impact of these xenoantibodies. Here we determine whether an improved cross-match and chemical immunosuppression could result in prolonged kidney xenograft survival in a pig-to-rhesus preclinical model. Methods: Double xenoantigen (Gal and Sda) knockout (DKO) pigs were created using CRISPR/Cas. Serum from rhesus monkeys (n = 43) was cross-matched with cells from the DKO pigs. Kidneys from the DKO pigs were transplanted into rhesus monkeys (n = 6) that had the least reactive cross-matches. The rhesus recipients were immunosuppressed with anti-CD4 and anti-CD8 T-cell depletion, anti-CD154, mycophenolic acid, and steroids. Results: Rhesus antibody binding to DKO cells is reduced, but all still have positive CDC and flow cross-match. Three grafts were rejected early at 5, 6, and 6 days. Longer survival was achieved in recipients with survival to 35, 100, and 435 days. Each of the 3 early graft losses was secondary to IgM antibody-mediated rejection. The 435-day graft loss occurred secondary to IgG antibody-mediated rejection. Conclusions: Reducing xenoantigens in donor pigs and chemical immunosuppression can be used to achieve prolonged renal xenograft survival in a preclinical model, suggesting that if a negative cross-match can be obtained for humans then prolonged survival could be achieved.

Martens, Gregory MD; Ladowski, Joseph M. PhD; Reyes, Luz M. MSc, PhD; Easlick, Juliet; Tector, Matt PhD; Tector, A Joseph MD, PhD, FACS Author Information