Dissecting the impact of molecular T-cell HLA mismatches in kidney transplant failure: A retrospective cohort study

Introduction

Kidney transplantation is the optimal treatment in end-stage kidney disease, but de-novo donor specific antibody development continues to negatively impact patients undergoing kidney transplantation. One of the recent advances in solid organ transplantation has been the definition of molecular mismatching between donors and recipients' Human Leukocyte Antigens (HLA). While not fully integrated in standard clinical care, cumulative molecular mismatch at the level of eplets (EMM) as well as the PIRCHE-II score have shown promise in predicting transplant outcomes. In this manuscript, we sought to study whether certain T-cell molecular mismatches (TcEMM) were highly predictive of death-censored graft failure (DCGF).

Methods

We studied a retrospective cohort of kidney donor:recipient pairs from the Scientific Registry of Transplant Recipients (2000-2015). Allele level HLA-A, B, C, DRB1 and DQB1 types were imputed from serologic types using the NMDP algorithm. TcEMMs were then estimated using the PIRCHE-II algorithm. Multivariable Accelerated Failure Time (AFT) models assessed the association between each TcEMM and DCGF. To discriminate between TcEMMs most predictive of DCGF, we fit multivariable Lasso penalized regression models. We identified co-expressed TcEMMs using weighted correlation network analysis (WGCNA). Finally, we conducted sensitivity analyses to address PIRCHE and IMGT/HLA version updates.

Results

A total of 118,309 donor:recipient pairs meeting the eligibility criteria were studied. When applying the PIRCHE-II algorithm, we identified 1,935 distinct TcEMMs at the population level. A total of 218 of the observed TcEMM were independently associated with DCGF by AFT models. The Lasso penalized regression model with post selection inference identified a smaller subset of 86 TcEMMs (56 and 30 TcEMM derived from HLA Class I and II, respectively) to be highly predictive of DCGF. Of the observed TcEMM, 38.14% appeared as profiles of highly co-expressed TcEMMs. In addition, sensitivity analyses identified that the selected TcEMM were congruent across IMGT/HLA versions.

Conclusion

In this study, we identified subsets of TcEMMs highly predictive of DCGF and profiles of co-expressed mismatches. Experimental verification of these TcEMMs determining immune responses and how they may interact with EMM as predictors of transplant outcomes would justify their consideration in organ allocation schemes and for modifying immunosuppression regimens.

Incidence, risk factors, and long-term outcomes associated with antibody-mediated rejection - The long-term Deterioration of Kidney Allograft Function (DeKAF) prospective cohort study

Major gaps remain in our understanding of antibody-mediated rejection (AMR) after kidney transplant. We examined the incidence, risk factors, response to treatment, and effects on outcomes of AMR at seven transplant programs in the long-term Deterioration of Kidney Allograft Function prospective study cohort. Among 3131 kidney recipients, there were 194 observed AMR cases (6.2%) during (mean ± SD) 4.85 ± 1.86 years of follow-up. Time to AMR was 0.97 ± 1.17 (median, 0.48) years. Risk factors for AMR included younger recipient age, human leukocyte antigen DR mismatches, panel-reactive antibody >0%, positive T- or B-cell cross-match, and delayed graft function. Compared with no AMR, the adjusted time-dependent hazard ratio for death-censored graft failure is 10.1 (95% confidence interval, 6.5-15.7) for all AMR patients, 4.0 (2.5, 9.1) for early AMR (<90 days after transplant), and 24.0 (14.0-41.1) for late AMR (≥90 days after transplant). Patients were treated with different therapeutic combinations. Of 194 kidney transplant recipients with AMR, 50 (25.8%) did not respond to treatment, defined as second AMR within 100 days or no improvement in estimated glomerular filtration rate by 42 days. Long-term outcomes after AMR are poor, regardless of the initial response to treatment. Better prevention and new therapeutic strategies are needed to improve long-term allograft survival.