Project: Definition of immunogenic epitopes

Project name: Definition of immunogenic epitopes

Project leaders: Sebastiaan Heidt & Eric Spierings

 

Detailed project description:

On the population level it is clear that a higher number of epitope mismatches increases the chance of donor specific antibody (DSA) formation. However, from the same data it is clear that not all epitope mismatches result in antibody formation, leading to the hypothesis that not all epitope mismatches are equally immunogenic. For HLA epitope matching to become a clinical reality it is vital to determine the most immunogenic epitopes, which can then be avoided during future organ allocation based on epitopes. We also aim to study the outcomes that are related to transplantation with a graft containing immunogenic epitope mismatches. To this aim, large numbers of first-transplant recipients, non-immunized at time of transplantation, who either became immunized due to the transplant or not, are required.

In this project, we will determine the epitope mismatches between donor and recipient based on second-field molecular HLA typing data for the loci HLA-A, -B, -C, -DRB1, -DRB3-5, -DQB1, -DQA1, -DPB1, and -DPA1. The status of being non-immunized at time of transplant must be confirmed by a negative Luminex single antigen bead status. The transplant-induced immunization has to be reported by Luminex single antigen bead data.

 

Milestones in years:

  • 2019: Creation of a uniform way to enter second-field HLA typing data and Luminex SAB data, irrespective of vendor. Inclusion of as many laboratories worldwide as possible. Start of data collection
  • 2020: Continuation of data collection and interim analyses
  • 2021: Finalizing analyses

 

Patient description:

Inclusion criteria

  • First kidney transplant recipients: males, and females without a history of pregnancy.
  • Non-sensitized at time of transplant as defined by:
    • cPRA pre-transplant 0% based on Single Antigen Bead (SAB) analysis with all bead MFI less than 1000, or lower if a clear epitope specificity is present across many beads – all sera must have been tested in such a way that a prozone effect can be excluded.
  • Molecular HLA typing of donor and recipient
    • Class I – A, B, C
    • Class II – DRB1-3-4-5, DQA/B, DPA/B
  • Two types of patients can be considered for entry into the study:
    • Patients who develop de novo DSA(s) post-transplant either:
      • while on maintenance immunosuppression, or
      • have documented graft loss from chronic antibody mediated rejection, and are now off immunosuppression.
    • Patients who do not develop a de novo DSA post-transplant despite at least 5 years of follow up.

 Exclusion Criteria

  • Repeat transplant
  • Prior pregnancy
  • Combined renal and non-renal transplants
  • Sensitized patients at the time of transplant defined by cPRA by SAB >0%
  • Absence of molecular HLA typing for the donor and/or recipient unless DNA is available for molecular typing.
  • Patients who have no DSA but are less than 5 years post-transplant.

 

Data required:

Minimal requirements:

  • Second-field molecular HLA typing for HLA-A, -B, -C, -DRB1, -DRB3-5, -DQB1, -DQA1, -DPB1, and -DPA1 for both donor and recipient
  • Luminex SAB raw data file pre-transplant, including lot number
  • Prevention of prozone effect (specify method)
  • Induction therapy yes/no, if yes specify
  • Baseline immunosuppression at discharge
  • Baseline immunosuppression at time of de novo DSA detection
  • Baseline immunosuppression at 5 years / last follow up in non-DSA patients
  • Time post-transplant of de novo DSA detection
  • At time of first detection of de novo DSA the SAB Class I and Class II antibody testing files
  • For patients who are listed as non-DSA formers at 5 years / last follow up SAB Class I and Class II antibody testing files

Ideal requirements (in addition to minimal requirements):

  • HLA NGS typing files for all required loci on the donor and recipient
    • Alternatively DNA for donor and recipient for external NGS evaluation
  • Pre-transplant sera for additional local / core laboratory evaluation
  • Post-transplant sera at time of de novo DSA detection for additional local / core laboratory evaluation
  • Post-transplant sera for patients who are listed as non-DSA formers at 5 years / last follow up for local / core laboratory evaluation

Outcome Data requirements (optional):

  • Recipient age at time of transplant
  • Recipient sex
  • Donor age
  • Whether patient was classified as adherent or non-adherent
  • Target trough level of CNI (if used) after 6 months post-transplant
  • Acute rejection events prior to de novo DSA detection
  • Serum Creatinine at 6 months, at time of de novo DSA formation, and at last follow-up
  • Acute rejection after de novo DSA formation + type (ABMRBanff2013, TCMR, or both)
  • Graft loss + time post-transplant + cause of graft loss

In order to execute a meaningful analysis, we expect to rquire minimum of 1000 donor-patient combinations.

 

Samples required:

If no molecular typing at second field level is available for donor and/or recipient, DNA would be required for the typing to be performed. In case no Luminex SAB data is present, a serum sample from the appropriate time-point is required.

 

Reagents/additional assays required:

For a proportion of laboratories, we expect to require additional second-field molecular HLA typing, as well as Luminex SAB analysis.

 

Data infrastructure required:

A uniform way to enter second-field HLA typing data and Luminex SAB data, irrespective of vendor.

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