Kidney Transplants from HLA-Incompatible Live Donors and Survival

Current Perspectives in ABO-Incompatible Kidney Transplant

For a long time, ABO incompatible living donor kidney transplantation has been considered contraindicated, due to the presence of isohemagglutinins, natural antibodies reacting with non-self ABO antigens. However, as the demand for kidney transplantation is constantly growing, methods to expand the donor pool have become increasingly important. Thus, in the last decades, specific desensitization strategies for ABOi transplantation have been developed. Nowadays, these regimens consist of transient removal of preformed anti-A or anti-B antibodies by using plasmapheresis or immunoadsorption and B-cell immunity modulation by CD20+ cells depletion with rituximab, in association with maintenance immunosuppression including corticosteroids, tacrolimus and mycophenolate mofetil. The outcome in ABOi kidney transplantation have markedly improved over the years. In fact, although randomized trials are still lacking, recent meta analysis has revealed that there is no difference in terms of graft and patient's survival between ABOi and ABO compatible kidney transplant, even in the long term. However, many concerns still exist, because ABOi kidney transplantation is associated with an increased risk of bleeding and infectious complications, partly related to the effects of extracorporeal treatments and the strong immunosuppression. Thus, a continuous improvement in desensitization strategies, with the aim of minimize the immunosuppressive burden, on the basis of immune pathogenesis, antibodies titers and/or ABO blood group, is warranted. In this review, we discuss the main immune mechanisms involved in ABOi kidney transplantation, the pathogenesis of tolerance and the desensitization regimens, including immunoadsorption and plasmapheresis and the immunosuppressive protocol. Finally, we provide an overview on outcome and future perspectives in ABOi kidney transplant.

Immortal Time-Bias-Corrected Survival of Highly Sensitized Patients and HLA-desensitized Kidney Transplant Recipients

Introduction

In the setting of kidney transplantation (KT), we assessed the efficacy of desensitization and compared the survival of desensitized patients (HLA-incompatible KT) with similarly sensitized patients receiving HLA-compatible KT or sensitized patients still on a waiting list after adjusting for the usually unaccounted immortal time bias.

Methods

All patients in a French KT center on the waiting list between August 1994 and December 2019 with a high level of sensitization (panel-reactive antibodies [PRAs] ≥80%) were included. The primary outcome was all-cause mortality. A time-varying covariate Cox survival model was used to account for the immortal time bias. A landmark analysis was used as a sensitivity analysis.

Results

During the study period, 326 patients with high PRAs were followed, among which 147 (45%) remained on the waiting list at the time of last follow-up and 179 benefited from a KT. Thirty-six patients were desensitized, of which 30 received a kidney transplant, including eight deceased kidney donors. There were no differences in mortality rates between desensitized KT patients, nondesensitized KT patients, and waitlisted patients after adjusting for immortal time bias (hazard ratio [HR] = 0.48, P = 0.22). Death-censored graft survival was similar between desensitized and nondesensitized KT patients (HR = 0.92, P = 0.88 adjusting for donor age >65 years, donor status, and time on the waiting list). Mean estimated glomerular filtration rate at 1 year post-KT was similar for desensitized KT patients (53.3 ± 21 vs. 53.6 ± 21 ml/min per 1.73 m² for nondesensitized patients; P = 0.95).

Conclusions

HLA-desensitization was effective for highly sensitized patients and gave access to KT without detrimental effects on patient or graft survival rates.

Apheresis Efficacy and Tolerance in the Setting of HLA-Incompatible Kidney Transplantation

Nearly 18% of patients on a waiting list for kidney transplantation (KT) are highly sensitized, which make access to KT more difficult. We assessed the efficacy and tolerance of different techniques (plasma exchanges [PE], double-filtration plasmapheresis [DFPP], and immunoadsorption [IA]) to remove donor specific antibodies (DSA) in the setting of HLA-incompatible (HLAi) KT. All patients that underwent apheresis for HLAi KT within a single center were included. Intra-session and inter-session Mean Fluorescence Intensity (MFI) decrease in DSA, clinical and biological tolerances were assessed. A total of 881 sessions were performed for 45 patients: 107 DFPP, 54 PE, 720 IA. The procedures led to HLAi KT in 39 patients (87%) after 29 (15–51) days. A higher volume of treated plasma was associated with a greater decrease of inter-session class I and II DSA (p = 0.04, p = 0.02). IA, PE, and a lower maximal DSA MFI were associated with a greater decrease in intra-session class II DSA (p < 0.01). Safety was good: severe adverse events occurred in 17 sessions (1.9%), more frequently with DFPP (6.5%) p < 0.01. Hypotension occurred in 154 sessions (17.5%), more frequently with DFPP (p < 0.01). Apheresis is well tolerated (IA and PE > DFPP) and effective at removing HLA antibodies and allows HLAi KT for sensitized patients.