Immunosuppression withdrawal in living-donor renal transplant recipients following induction with antithymocyte globulin and rituximab: Results of a prospective clinical trial.

Durable tolerance in kidney transplant recipients remains an important but elusive goal. We hypothesized that adding B cell depletion to T cell depletion would generate an immune milieu postreconstitution dominated by immature transitional B cells, favoring tolerance. The Immune Tolerance Network ITN039ST Research Study of ATG and Rituximab in Renal Transplantation was a prospective multicenter pilot study of live donor kidney transplant recipients who received induction with rabbit antithymocyte globulin and rituximab and initiated immunosuppression (IS) withdrawal (ISW) at 26 weeks. The primary endpoint was freedom from rejection at 52 weeks post-ISW. Six of the 10 subjects successfully completed ISW. Of these 6 subjects, 4 restarted immunosuppressive medications due to acute rejection or recurrent disease, 1 remains IS-free for over 9 years, and 1 was lost to follow-up after being IS-free for 42 weeks. There were no cases of patient or graft loss. CD19+ B cell frequencies returned to predepletion levels by 26 weeks posttransplant; immunoglobulin D+CD27--naïve B cells predominated. In contrast, memory cells dominated the repopulation of the T cell compartment. A regimen of combined B and T cell depletion did not generate the tolerogenic B cell profile observed in preclinical studies and did not lead to durable tolerance in the majority of kidney transplant recipients.

Early allogeneic immune modulation after establishment of donor hematopoietic cell-induced mixed chimerism in a nonhuman primate kidney transplant model.

Background: Mixed lymphohematopoietic chimerism is a proven strategy for achieving operational transplant tolerance, though the underlying immunologic mechanisms are incompletely understood. Methods: A post-transplant, non-myeloablative, tomotherapy-based total lymphoid (TLI) irradiation protocol combined with anti-thymocyte globulin and T cell co-stimulatory blockade (belatacept) induction was applied to a 3-5 MHC antigen mismatched rhesus macaque kidney and hematopoietic cell transplant model. Mechanistic investigations of early (60 days post-transplant) allogeneic immune modulation induced by mixed chimerism were conducted. Results: Chimeric animals demonstrated expansion of circulating and graft-infiltrating CD4+CD25+Foxp3+ regulatory T cells (Tregs), as well as increased differentiation of allo-protective CD8+ T cell phenotypes compared to naïve and non-chimeric animals. In vitro mixed lymphocyte reaction (MLR) responses and donor-specific antibody production were suppressed in animals with mixed chimerism. PD-1 upregulation was observed among CD8+ T effector memory (CD28-CD95+) subsets in chimeric hosts only. PD-1 blockade in donor-specific functional assays augmented MLR and cytotoxic responses and was associated with increased intracellular granzyme B and extracellular IFN-γ production. Conclusions: These studies demonstrated that donor immune cell engraftment was associated with early immunomodulation via mechanisms of homeostatic expansion of Tregs and early PD-1 upregulation among CD8+ T effector memory cells. These responses may contribute to TLI-based mixed chimerism-induced allogenic tolerance.

Helical TomoTherapy Total Lymphoid Irradiation and Hematopoietic Cell Transplantation for Kidney Transplant Tolerance in Rhesus Macaques.

Development of a post-transplant kidney transplant tolerance induction protocol involving a novel total lymphoid irradiation (TLI) conditioning method in a rhesus macaque model is described. We examined the feasibility of acheiving tolerance to MHC 1-haplotype matched kidney transplants by establishing a mixed chimeric state with infusion of donor hematopoietic cells (HC) using TomoTherapy TLI. The chimeric state was hypothesized to permit the elimination of all immunosuppressive (IS) medications while preserving allograft function long-term without development of graft-versus-host-disease (GVHD) or rejection. An experimental group of 11 renal transplant recipients received the tolerance induction protocol and outcomes were compared to a control group (n = 7) that received the same conditioning but without donor HC infusion. Development of mixed chimerism and operational tolerance was accomplished in two recipients in the experimental group. Both recipients were withdrawn from all IS and continued to maintain normal renal allograft function for 4 years without rejection or GVHD. None of the animals in the control group achieved tolerance when IS was eliminated. This novel experimental model demonstrated the feasibility for inducing of long-term operational tolerance when mixed chimerism is achieved using a TLI post-transplant conditioning protocol in 1-haplotype matched non-human primate recipients of combined kidney and HC transplantation.

Master protocol to assess the long-term safety in kidney transplant recipients who previously received Medeor's cellular immunotherapy products: the MDR-105-SAE.

BACKGROUND: Immunosuppression in transplantation continues to be associated with a multitude of adverse effects. Induction of immune tolerance may be a viable strategy to reduce dependence on immunosuppression. Various trials are currently underway to assess the efficacy of this strategy. However, long-term safety data for these immune tolerance regimes has yet to be established. METHODS/DESIGN: At the completion of primary follow-up of various Medeor kidney transplant studies, subjects receiving cellular immunotherapy products will be followed annually as per protocolized schedule for up to an additional 84 months (7 years) to evaluate long-term safety. Long-term safety will be assessed by summarizing incidence of serious adverse events, adverse events leading to study withdrawal and hospitalization rates. DISCUSSION: This extension study will be an important step in evaluating safety issues pertaining to immune tolerance regimens, long-term effects of which are largely unknown. These data are essential for furthering an unrealized goal of kidney transplantation- graft longevity without the adverse effects from long-term immunosuppression. The study design utilizes the methodology of a master protocol, wherein multiple therapies can be assessed simultaneously with accompanied gathering of long-term safety data.

Post-pancreatic transplant enteric leaks: The role of the salvage operation.

Enteric drainage in pancreas transplantation is complicated by an enteric leak in 5%-8%, frequently necessitating pancreatectomy. Pancreatic salvage outcomes are not well studied. Risk factors for enteric leak were examined and outcomes of attempted graft salvage were compared to immediate pancreatectomy. Pancreas transplants performed between 1995 and 2018 were reviewed. Donor, recipient, and organ variables including demographics, donor type, ischemic time, kidney donor profile index, and pancreas donor risk index were analyzed. Among 1153 patients, 33 experienced enteric leaks (2.9%). Donors of allografts that developed leak were older (37.9y vs. 29.0y, p = .001), had higher KDPI (37% vs. 24%, p < .001), higher pancreas donor risk index (1.83 vs. 1.32, p < .001), and longer cold ischemic time (16.5 vs. 14.8 h, p = .03). Intra-abdominal abscess and higher blood loss decreased the chance of successful salvage. Enteric leak increased 6-month graft loss risk (HR 13.9[CI 8.5-22.9], p < .001). However, 50% (n = 12) of allografts undergoing attempted salvage survived long-term. After 6 months of pancreas graft survival, salvage and non-leak groups had similar 5-year graft survival (82.5% vs. 81.5%) and mortality (90.9% vs. 93.5%). Enteric leaks remain a challenging complication. Pancreatic allograft salvage can be attempted in suitable patients and accomplished in 50% of cases without significantly increased graft failure or mortality risk.

Robust engraftment of fetal nonhuman primate CD34-positive cells in immune-deficient mice.

Nonhuman primates (NHPs) represent one of the most important models for preclinical studies of novel biomedical interventions. In contrast with small animal models, however, widespread utilization of NHPs is restricted by cost, logistics, and availability. Therefore, we sought to develop a translational primatized mouse model, akin to a humanized mouse, to allow for high-throughput in vivo experimentation leveraged to inform large animal immunology-based studies. We found that adult rhesus macaque mobilized blood (AMb) CD34+-enriched hematopoietic stem and progenitor cells (HSPCs) engrafted at low but persistent levels in immune-deficient mice harboring transgenes for human (NHP cross-reactive) GM-CSF and IL3, but did not in mice with wild-type murine cytokines lacking NHP cross-reactivity. To enhance engraftment, fetal liver-derived HSPCs were selected as the infusion product based on an increased CD34hi fraction compared with AMb and bone marrow. Coupled with cotransplantation of rhesus fetal thymic fragments beneath the mouse kidney capsule, fetal liver-derived HSPC infusion in cytokine-transgenic mice yielded robust multilineage lymphohematopoietic engraftment. The emergent immune system recapitulated that of the fetal monkey, with similar relative frequencies of lymphocyte, granulocyte, and monocyte subsets within the thymic, secondary lymphoid, and peripheral compartments. Importantly, while exhibiting a predominantly naïve phenotype, in vitro functional assays demonstrated robust cellular activation in response to nonspecific and allogenic stimuli. This primatized mouse represents a viable and translatable model for the study of hematopoietic stem cell physiology, immune development, and functional immunology in NHPs. Summary Sentence: Engraftment of rhesus macaque hematopoietic tissues in immune-deficient mice yields a robust BLT/NeoThy-type primatized mouse model for studying nonhuman primate hematopoiesis and immune function in vivo.

Early Increases in Posttransplant Pancreatic Enzymes Are Associated With Surgical Complications But Not Graft Failure Among Pancreas Transplant Recipients.

OBJECTIVES: This study aimed to find the association between immediate postoperative increases in pancreatic enzymes and posttransplant complications among pancreas transplant recipients (PTRs). METHODS: We analyzed all PTRs transplanted at the University of Wisconsin between June 2009 and September 2018. Enzyme levels were presented as a ratio of absolute numbers to the upper limit of normal value, with value >1 considered as abnormal. We specifically evaluated bleeding, fluid collections, and thrombosis complications based on the amylase or lipase ratios on day 1 (Amylase1, Lipase1) and maximum ratios within 5 days of transplant (Amylasemax, Lipasemax). For early complications, we focused on technical complications that occurred within 90 days of transplant. For long-term outcomes, we assessed patient and graft survival, and rejections. RESULTS: There were a total of 443 PTRs, 287 were simultaneous pancreas and kidney recipients, and 156 were solitary pancreas recipients. Higher Amylase1, Liplase1, Amylasemax, and Lipasemax were associated with an increase in early complications, mainly need for pancreatectomy, fluid collections, bleeding complications, or graft thrombosis, particularly in the solitary pancreas group. CONCLUSIONS: Our finding suggests that cases of early perioperative enzyme increase merit consideration for early imaging investigation to mitigate detrimental outcomes.

Association of human leukocyte antigen mismatches between donor-recipient and donor-donor in pancreas after kidney transplant recipients.

The effects of HLA mismatching on pancreas outcomes among pancreas after kidney (PAK) recipients are undefined. Outcomes might potentially differ depending on whether there is a mismatch between pancreas donor and recipient (PD-R) or pancreas donor and kidney donor(PD-KD). All primary PAK at our centre were included in this study. Patients were divided into two groups based on the degree of HLA mismatching: low (L-MM) as 0-4 and high (H-MM) as 5-6. We analysed all (N = 73) PAK for PD-R mismatch and the subset of PAK for PD-KD mismatch (N = 71). Comparing PD-R L-MM (n = 39) and H-MM (n = 34) PAKs, we observed no difference in the rate of pancreas graft failure. There was also no difference in the rate of rejection (L-MM 33% vs. H-MM 41%) or the severity of rejection. However, we observed a significantly (P < 0.01) shorter time to acute pancreas rejection in the H-MM group (6.8 ± 8.7 mo) versus the L-MM cohort (29.0 ± 36.2 mo) (P < 0.001). Similar to the PD-R mismatched cohort, we did not observe a detrimental effect of HLA mismatching on graft outcomes in the PD-KD cohort; time to rejection was again shorter in the H-MM subset. In this study, we found no impact of HLA mismatch on either pancreas graft survival or rejection rates, though rejection occurred earlier in high mismatched PAK transplants.

Tomotherapy Applied Total Lymphoid Irradiation and Allogeneic Hematopoietic Cell Transplantation Generates Mixed Chimerism in the Rhesus Macaque Model.

Development of a new methodology to induce immunological chimerism after allogeneic hematopoietic cell (HC) transplantation in a rhesus macaque model is described. The chimeric state was achieved using a non-myeloablative, helical tomotherapy-based total lymphoid irradiation (TomoTLI) conditioning regimen followed by donor HC infusions between 1-haplotype matched donor/recipient pairs. The technique was tested as a feasibility study in an experimental group of seven rhesus macaques that received the novel TomoTLI tolerance protocol and HC allo-transplants. Two tomotherapy protocols were compared: TomoTLI (n = 5) and TomoTLI/total-body irradiation (TBI) (n = 2). Five of seven animals developed mixed chimerism. Three of five animals given the TomoTLI protocol generated transient mixed chimerism with no graft-versus-host disease (GVHD) with survival of 33, 152 and >180 days. However, the inclusion of belatacept in addition to a single fraction of TBI resulted in total chimerism and fatal GVHD in both animals, indicating an unacceptable conditioning regimen.

Belatacept for Simultaneous Calcineurin Inhibitor and Chronic Corticosteroid Immunosuppression Avoidance: Two-Year Results of a Prospective, Randomized Multicenter Trial.

BACKGROUND AND OBJECTIVES: Immunosuppressive therapy in kidney transplantation is associated with numerous toxicities. CD28-mediated T-cell costimulation blockade using belatacept may reduce long-term nephrotoxicity, compared with calcineurin inhibitor-based immunosuppression. The efficacy and safety of simultaneous calcineurin inhibitor avoidance and rapid steroid withdrawal were tested in a randomized, prospective, multicenter study. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This study reports the 2-year results of a randomized clinical trial of 316 recipients of a new kidney transplant. All kidney transplants were performed using rapid steroid withdrawal immunosuppression. Recipients were randomized in a 1:1:1 ratio to receive belatacept with alemtuzumab induction, belatacept with rabbit anti-thymocyte globulin (rATG) induction, or tacrolimus with rATG induction. The composite end point consisted of death, kidney allograft loss, or an eGFR of <45 ml/min per 1.73 m2 at 2 years. RESULTS: The composite end point was observed for 11 of 107 (10%) participants assigned to belatacept/alemtuzumab, 13 of 104 (13%) participants assigned to belatacept/rATG, and 21 of 105 (21%) participants assigned to tacrolimus/rATG (for belatacept/alemtuzumab versus tacrolimus/rATG, P=0.99; for belatacept/rATG versus tacrolimus/rATG, P=0.66). Patient and graft survival rates were similar between all groups. An eGFR of <45 ml/min per 1.73 m2 was observed for nine of 107 (8%) participants assigned to belatacept/alemtuzuab, eight of 104 (8%) participants assigned to belatacept/rATG, and 20 of 105 (19%) participants assigned to tacrolimus/rATG (P<0.05 for each belatacept group versus tacrolimus/rATG). Biopsy sample-proven acute rejection was observed for 20 of 107 (19%) participants assigned to belatacept/alemtuzuab, 26 of 104 (25%) participants assigned to belatacept/rATG, and seven of 105 (7%) participants assigned to tacrolimus/rATG (for belatacept/alemtuzumab versus tacrolimus/rATG, P=0.006; for belatacept/rATG versus tacrolimus/rATG, P<0.001). Gastrointestinal and neurologic adverse events were less frequent with belatacept versus calcineurin-based immunosuppression. CONCLUSIONS: Overall 2-year outcomes were similar when comparing maintenance immunosuppression using belatacept versus tacrolimus, and each protocol involved rapid steroid withdrawal. The incidence of an eGFR of <45 ml/min per 1.73 m2 was significantly lower with belatacept compared with tacrolimus, but the incidence of biopsy sample-proven acute rejection significantly higher. CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER: Belatacept Early Steroid Withdrawal Trial, NCT01729494.

Complex Ureteral Reconstruction in Kidney Transplantation.

OBJECTIVES: Despite advances in surgical techniques and organ preservation, transplant ureteric strictures remain a common complication in kidney transplantation. A variety of endourological and surgical techniques have been utilized; however, there is a lack of consensus on the optimal modality in dealing with these complex cases. MATERIALS AND METHODS: We present challenging ureteral reconstruction cases after failed attempts at ureteral dilatation, failed conventional open repairs, and/or with bladder dysfunction. RESULTS: All renal allografts were salvaged by successful use of bladder Boari flap and intestinal segment interpositions/diversions. CONCLUSIONS: Operative repair remains the most durable and successful approach, and minimally invasive options should be reserved for nonsurgical candidates, with consideration of a single attempt in patients with early, distal, short (<2 cm), nonischemic strictures.

Phase 3 trial of human islet-after-kidney transplantation in type 1 diabetes.

Allogeneic islet transplant offers a minimally invasive option for ß cell replacement in the treatment of type 1 diabetes (T1D). The CIT consortium trial of purified human pancreatic islets (PHPI) in patients with T1D after kidney transplant (CIT06), a National Institutes of Health-sponsored phase 3, prospective, open-label, single-arm pivotal trial of PHPI, was conducted in 24 patients with impaired awareness of hypoglycemia while receiving intensive insulin therapy. PHPI were manufactured using standardized processes. PHPI transplantation was effective with 62.5% of patients achieving the primary endpoint of freedom from severe hypoglycemic events and HbA1c  ≤ 6.5% or reduced by ≥ 1 percentage point at 1 year posttransplant. Median HbA1c declined from 8.1% before to 6.0% at 1 year and 6.3% at 2 and 3 years following transplant (P < .001 for all vs baseline), with related improvements in hypoglycemia awareness and glucose variability. The improved metabolic control was associated with better health-related and diabetes-related quality of life. The procedure was safe and kidney allograft function remained stable after 3 years. These results add to evidence establishing allogeneic islet transplant as a safe and effective treatment for patients with T1D and unstable glucose control despite intensive insulin treatment, supporting the indication for PHPI in the post-renal transplant setting.

The Fourth International Workshop on Clinical Transplant Tolerance.

The International Workshop on Clinical Transplant Tolerance is a biennial meeting that aims to provide an update on the progress of studies of immunosuppression minimization or withdrawal in solid organ transplantation. The Fourth International Workshop on Clinical Tolerance was held in Pittsburgh, Pennsylvania, September 5-6, 2019. This report is a summary of presentations on the status of clinical trials designed to minimize or withdraw immunosuppressive drugs in kidney, liver, and lung transplantation without subsequent evidence of rejection. All protocols had in common the use of donor or recipient cell therapy combined with organ transplantation. The workshop also included presentations of mechanistic studies designed to improve understanding of the cellular and molecular basis of tolerance and to identify potential predictors/biomarkers of tolerance. Strategies to enhance the safety of hematopoietic cell transplantation and to improve patient selection/risk stratification for clinical trials were also discussed.

The demise of islet allotransplantation in the United States: A call for an urgent regulatory update.

Islet allotransplantation in the United States (US) is facing an imminent demise. Despite nearly three decades of progress in the field, an archaic regulatory framework has stymied US clinical practice. Current regulations do not reflect the state-of-the-art in clinical or technical practices. In the US, islets are considered biologic drugs and "more than minimally manipulated" human cell and tissue products (HCT/Ps). In contrast, across the world, human islets are appropriately defined as "minimally manipulated tissue" and not regulated as a drug, which has led to islet allotransplantation (allo-ITx) becoming a standard-of-care procedure for selected patients with type 1 diabetes mellitus. This regulatory distinction impedes patient access to islets for transplantation in the US. As a result only 11 patients underwent allo-ITx in the US between 2016 and 2019, and all as investigational procedures in the settings of a clinical trials. Herein, we describe the current regulations pertaining to islet transplantation in the United States. We explore the progress which has been made in the field and demonstrate why the regulatory framework must be updated to both better reflect our current clinical practice and to deal with upcoming challenges. We propose specific updates to current regulations which are required for the renaissance of ethical, safe, effective, and affordable allo-ITx in the United States.

Pancreas transplants from small donors: are the outcomes acceptable? A retrospective study.

Despite good organ quality, pancreata from extremely small pediatric donors (<30 kg) are generally avoided by many centers because of concerns of reduced islet cell mass and early technical failure. Therefore, we sought to compare the outcomes of small pancreas grafts (<30 kg) to those from higher weight donors from transplants performed between 1994 and 2015 (n = 1183). A total of 33 pancreata were from donors' ≤30 kg (3%), with a mean weight of 23.8 kg and mean age of 7.8 years. Patient survival was similar at 1, 5, and 10 years between recipients of ≤30 and >30 kg donors (≤30 kg: 96.8%, 86.8%, and 78.1% vs. >30 kg: 96.8%, 89.5%, and 79.1%, P = 0.5). Pancreas graft survival at 1, 5, and 10 years was also similar, ≤30 kg: 93.9%, 73.2%, and 61.0% vs. >30 kg: 87%, 73.3%, and 58.3% (P = 0.7). This graft survival pattern was also seen when comparing pancreata from ≤20 kg donors to those from >20 to 30 kg. Cause of graft loss, and metabolic and physiologic outcomes did not differ between the groups. After assessing the impact of donor weight as a continuous variable and calculating recipient-to-donor weight ratio (RDWR), we observed no effect of donor weight on patient and graft outcomes.

Third-party vessel allografts in kidney and pancreas transplantation: Utilization, de novo DSAs, and outcomes.

Third-party vascular allografts (VAs) are an invaluable resource in kidney and pancreas transplantation when vascular reconstruction is needed and additional vessels from the organ donor are not available. We report the largest single-center experience to date on VA use, at a high-volume U.S. transplant center. Over a 7-year period, VAs were used for vascular reconstruction of 65 kidneys and 5 pancreases, in 69 recipients. The renal vein required reconstruction more often with right kidney transplantation (72.5% vs 27.5%, P < .001), and the renal artery required reconstruction more often with left kidney transplantation (67.6% vs 32.4%, P = .003). Eleven patients (15.9%) developed anti-VA de novo HLA donor-specific antibodies (dnDSAs) at a median time after transplantation of 19.0 months. Higher number of HLA mismatches between the VA donor and the recipient, and development of anti-organ allograft dnDSAs were significant predictors of anti-VA dnDSA development. Those with anti-VA dnDSAs had a higher rate of organ allograft rejection (45.4% vs 13.8%, P = .03) compared to those without, but there was no significant difference in incidence of vascular complications or graft outcomes. VAs can help circumvent challenging surgical situations. Anti-VA dnDSAs do not adversely affect organ allograft outcomes; however, they can contribute to HLA sensitization in the recipients.

Delayed kidney graft function in simultaneous pancreas-kidney transplant recipients is associated with early pancreas allograft failure.

Delayed graft function (DGF) is a common complication associated with significant untoward effects in kidney-alone transplantation. The incidence and outcomes following kidney delayed graft function (K-DGF) among patients undergoing simultaneous pancreas-kidney (SPK) transplantation are less certain. We analyzed SPK recipients transplanted at our center between January 1994 and December 2017. A total of 632 recipients fulfilled the selection criteria, including 69 (11%) with K-DGF and 563 without. The incidence of K-DGF was significantly higher in recipients of organs from older donors and donation after circulatory death (DCD). The presence of K-DGF was significantly associated with an increased risk of pancreas graft failure during the first 90 days (n = 9, incidence rate [IR] 2.45/100 person-months), but not with late pancreas failure (n = 32, IR 0.84/100 person-months), kidney graft failure, or patient death. Although DCD was associated with K-DGF, it was not associated with either pancreas (hazard ratio [HR] 0.91, 95% CI 0.58-1.44, P = .69) or kidney (HR 1.09, 95% CI 0.66-1.82, P = .74) graft failure after adjustment for potential confounders. We found K-DGF to be a significant risk factor for pancreas graft failure but not kidney graft failure, with the major risk period being early (<90 days) posttransplant, and the major donor risk factor being older donor age.

Incidence and Outcomes of Significant Weight Changes After Pancreas Transplant Alone.

BACKGROUND: Weight change, primarily weight gain, is a common problem among solid organ transplant recipients. The incidence of weight gain or loss after successful pancreas transplant alone (PTA) and the effect on graft survival is unknown. METHODS: This was a single-center observational study among PTA recipients, transplanted at our center between January 1, 2005, and July 31, 2017, who had a functional pancreas graft for at least 1 year and documented weight change at the 1-year clinic visit. RESULTS: In this cohort study of 105 PTA recipients, 28 had significant weight gain, 27 had significant weight loss, and the remaining 50 did not have significant weight change at 1-year posttransplant. When comparing the weight gain and no weight change groups, the weight gain cohort started to gain weight at 3 months posttransplant to 5 years or last follow up. Similarly, the weight loss group lost weight at 3 months posttransplant up to last follow up. Clinically significant weight gain or weight loss were not associated with uncensored or death censored graft failure in univariate regression and Kaplan-Meier survival analysis. Also, there were no significant differences between the groups in the glycated hemoglobin at last follow up. CONCLUSIONS: Approximately 50% of PTA recipients had a significant weight change at 1-year posttransplant, of which 25% gained significant weight and 25% loss. There was no significant difference in graft survival due to the significant weight changes. Further research is needed in this field.

Induction and Donor Specific Antibodies in Low Immunologic Risk Kidney Transplant Recipients.

Background: Optimal induction for patients without pretransplant donor-specific antibodies (DSAs) is poorly defined. The goal of this study was to compare the incidence of de novo DSA (dnDSA) and graft outcomes between induction therapies in patients with a negative virtual crossmatch (VXM). Methods: A retrospective chart review was performed, identifying 782 patients with a negative VXM who underwent kidney transplantation at a single, high-volume institution between January 2013 and May 2017. Kaplan-Meier analysis was used to assess the incidence of dnDSA and allograft survival between induction therapies in this group. dnDSA is defined as the development of new post-transplant DSA, at any MFI level. Results: Induction therapy included alemtuzumab (N=87, 11%), basiliximab (N=522, 67%), and anti-thymocyte globulin (ATG; N=173, 22%). One-year graft survival was similar between groups (alemtuzumab, 100%; basiliximab, 98%; ATG, 99%). Incidence of acute rejection at 1 year was <2% and not different between the three groups. Alemtuzumab was associated with the highest incidence of dnDSA at 14%, compared with 5% and 8% in basiliximab and ATG groups, respectively, at 1 year (P=0.009). In multivariate regression analyses, alemtuzumab retained its significant association with a dnDSA HR of 2.5 (95% CI, 1.51 to 4.25; P=0.0004). Conclusions: In summary, alemtuzumab was associated with a higher rate of dnDSA development in patients with a negative VXM; however, this finding was not associated with rejection or graft failure.