Determination of mismatched donor HLA in kidney transplant recipients with unknown donor HLA phenotypes

Donor HLA genotyping of ex vivo expanded urine cells from kidney transplant recipients

Antibody-mediated rejection (AMR) induced by donor-specific anti-HLA antibodies (DSA) remains a major cause of long-term graft loss after kidney transplantation. Currently, the presence of DSA cannot always be determined at a specific allele level, because existing donor HLA typing is low resolution and often incomplete, lacking HLA-DP, and occasionally HLA-C and HLA-DQ information and historical donor DNA samples are not available for HLA retyping. Here we present a novel, non-invasive technique for obtaining donor DNA from selectively expanded donor cells from urine of renal transplant recipients. Urine-derived cells were successfully expanded ex vivo from 31 of 32 enrolled renal transplant recipients, and with DNA obtained from these cells, donor HLA typing was unambiguously determined for HLA-A, -B, -C, -DRB1, -DQA1, -DQB1, -DPA1 and -DPB1 loci by next-generation sequencing. Our results showed 100% concordance of HLA typing data between donor peripheral blood and recipient urine-derived cells. In comparison, HLA typing showed that DNA derived from urine sediments mainly contained recipient-derived DNA. We also present the successful application of our novel technique in a clinical case of AMR in a renal transplant recipient. Urine-derived donor cells can be isolated from kidney transplant recipients and serve as a suitable source of donor material for reliable high-resolution HLA genotyping. Thus, this approach can aid the assessment of DSA specificity to support the diagnosis of AMR as well as the evaluation of treatment efficacy in kidney transplant recipients when complete donor HLA information and donor DNA are unavailable.

Detecting mismatched donor HLA types from allograft biopsies - An easily applicable tool for improved individualized risk assessment

Short-term allograft survival has improved among solid organ transplant (SOT) patients. An increasing number of SOT patients are prepared for re-transplantation because of chronic allograft failure. Lack of HLA typing or incomplete HLA typing of previous donors complicates pretransplant risk assessment, as repeated HLA mismatches may be missed. In addition, a complete HLA type of the donor is essential in the diagnosis of antibody-mediated rejection. We aimed to determine donor HLA types from allograft biopsies from kidney, heart and liver grafts. Graft biopsies were obtained from 13 kidney, heart and liver transplanted patients. HLA typing was performed using q-PCR. Alleles of both donor and recipient origin were detected, and donor HLA type was concluded by deducting known HLA types of the recipient. For all 13 patients, we were able to determine mismatched donor HLA alleles from graft material. These results are promising, because they enable better individualized risk assessment.

A Modified Protocol with Improved Detection Rate for Mis-Matched Donor HLA from Low Quantities of DNA in Urine Samples from Kidney Graft Recipients

Background

Urine from kidney transplant recipient has proven to be a viable source for donor DNA. However, an optimized protocol would be required to determine mis-matched donor HLA specificities in view of the scarcity of DNA obtained in some cases.

Methods

In this study, fresh early morning urine specimens were obtained from 155 kidney transplant recipients with known donor HLA phenotype. DNA was extracted and typing of HLA-A, B and DRB1 loci by polymerase chain reaction-specific sequence primers was performed using tailor-made condition according to the concentration of extracted DNA.

Results

HLA typing of DNA extracted from urine revealed both recipient and donor HLA phenotypes, allowing the deduction of the unknown donor HLA and hence the degree of HLA mis-match. By adopting the modified procedures, mis-matched donor HLA phenotypes were successfully deduced in all of 35 tested urine samples at DNA quantities spanning the range of 620–24,000 ng.

Conclusions

This urine-based method offers a promising and reliable non-invasive means for the identification of mis-matched donor HLA antigens in kidney transplant recipients with unknown donor HLA phenotype or otherwise inadequate donor information.

The Banff Conferences on renal allograft pathology – the latest 2013 report

The Banff Conference diagnostic categories and their criteria for renal biopsy interpretation were created in 1991 by a group comprising nephrologists, pathologists, transplant surgeons and immunologists. These guidelines are widely used in many countries. Every two years, participants at these meetings present and discuss research findings that have added to our knowledge of allograft pathology. From the start, features of T-cell mediated rejection were established. This was followed by discovery of C4d staining in biopsy tissue and better characterisation of antibody mediated rejection. The formation of working groups to look into problematic areas has allowed better refinements to be made to the classification scheme. The latest Banff 2013 report is significant for the inclusion of a C4d-negative category under humoral rejection. Together with the realisation that endarteritis may be antibody mediated, this latest report will greatly impact how pathologists interpret the allograft biopsy.