The impact of repeated mismatches in kidney transplantations performed after nonrenal solid organ transplantation

Donor-Specific Antibodies Targeting a Repeated Eplet Mismatch and Outcome After Kidney Retransplantation

Kidney retransplantations are associated with an increased risk of rejection and reduced graft survival compared to first transplantations, notably due to HLA sensitization. The impact of repeated eplet mismatches on retransplantation outcome has not been investigated. We retrospectively assessed the risk of antibody-mediated rejection (ABMR) and graft loss associated with preformed DSA targeting Repeated Eplet MisMatches (DREMM) in sensitized patients undergoing kidney retransplantation. We included 45 retransplanted patients with preformed DSA against the second donor. We determined HLA incompatibilities at the eplet levels, and the eplet target of the DSA using HLAMatchmaker®. Repeated mismatches were more frequent at the eplet (87%) than at the antigenic level (22%), but were not associated with the risk of ABMR. The eplet specificity of the DSA revealed that 60% of patients (n = 27) had DREMM. The presence of DREMM was associated with a higher frequency of ABMR (70% versus 28%, P = 0.005) and with a lower death-censored graft survival (log-rank test, P = 0.01). However, in multivariate Cox model, we could not show that DREMM were associated with the risk of ABMR. In conclusion, this study suggests that identifying DREMM may be an interesting clinical tool, however further larger studies are necessary to precise their exact predictive value.

Seeking Standardized Definitions for HLA-incompatible Kidney Transplants: A Systematic Review

BACKGROUND

There is no standard definition for "HLA incompatible" transplants. For the first time, we systematically assessed how HLA incompatibility was defined in contemporary peer-reviewed publications and its prognostic implication to transplant outcomes.

METHODS

We combined 2 independent searches of MEDLINE, EMBASE, and the Cochrane Library from 2015 to 2019. Content-expert reviewers screened for original research on outcomes of HLA-incompatible transplants (defined as allele or molecular mismatch and solid-phase or cell-based assays). We ascertained the completeness of reporting on a predefined set of variables assessing HLA incompatibility, therapies, and outcomes. Given significant heterogeneity, we conducted narrative synthesis and assessed risk of bias in studies examining the association between death-censored graft failure and HLA incompatibility.

RESULTS

Of 6656 screened articles, 163 evaluated transplant outcomes by HLA incompatibility. Most articles reported on cytotoxic/flow T-cell crossmatches (n = 98). Molecular genotypes were reported for selected loci at the allele-group level. Sixteen articles reported on epitope compatibility. Pretransplant donor-specific HLA antibodies were often considered (n = 143); yet there was heterogeneity in sample handling, assay procedure, and incomplete reporting on donor-specific HLA antibodies assignment. Induction (n = 129) and maintenance immunosuppression (n = 140) were frequently mentioned but less so rejection treatment (n = 72) and desensitization (n = 70). Studies assessing death-censored graft failure risk by HLA incompatibility were vulnerable to bias in the participant, predictor, and analysis domains.

CONCLUSIONS

Optimization of transplant outcomes and personalized care depends on accurate HLA compatibility assessment. Reporting on a standard set of variables will help assess generalizability of research, allow knowledge synthesis, and facilitate international collaboration in clinical trials.

Poor Patient and Graft Outcome After Induction Treatment by Antithymocyte Globulin in Recipients of a Kidney Graft After Nonrenal Organ Transplantation

Background

End-stage renal failure occurs in a substantial number of patients having received a nonrenal transplantation (NRT), for whom a kidney transplantation is needed. The medical strategy regarding the use of immunosuppression (IS) for a kidney graft in patients after an NRT is not well established. The prekidney grafts long-term IS advocates for a mild induction, such as using anti-IL-2R antibodies, whereas addition of new incompatibilities and anti-HLA preimmunization may suggest using stronger IS such as induction by polyclonal antithymocyte globulins (ATG).

Methods

We performed Cox multivariate and propensity score analysis of our validated transplant database to study the impact of the type of induction therapy on kidney graft survival of recipients of a kidney graft after NRT.

Results

We report here that kidney transplantation after NRT treated with an ATG induction has a poorer outcome (kidney and recipient survival) than that with an anti-IL-2R induction. After accounting for potential baseline differences with a multivariate Cox model, or by adjusting on a propensity score, we found that despite patients having received ATG cumulate more risk factors, ATG appears independently involved. As animal-derived biotherapeutics induce antiglycan antibodies and particularly anti-N-glycolylneuraminic acid (Neu5Gc) IgGs which may activate endothelial cells in patients and grafts, we also investigated the magnitude and the nature of the anti-Neu5Gc elicited by the induction and showed that induction was associated with a shift in anti-Neu5Gc IgG repertoire. Possible reasons and mechanisms of a deleterious ATG usage in these patients are discussed.

Conclusions

Our study suggests that ATG induction after a kidney transplantation in recipients already under maintenance IS for a NRT should be used cautiously.