Introduction:
Antibody-mediated rejection (AMR), particularly Chronic AMR, significantly contributes to graft dysfunction and loss. Assessing and managing these rejections requires evaluating the recipient for HLA antibodies and typing the donor's HLA to determine which specific antibodies target the donor. However, in some cases, such as with deceased donors or older transplants, complete HLA typing may not be available or may be incomplete. In such situations, donor DNA can be extracted from the kidney biopsy, providing valuable information for assessing the current status of the donor-specific antibodies along with future risk assessment.
Methods:
To provide comprehensive transplant care, we performed HLA typing of donors using biopsy samples from grafts of four transplanted recipients, done for cause (elevated creatinine levels). In one case where typing was available, the biopsy sample was sent to assess the quality of HLA typing. In one of the patients, donor typing became available later and was included in the analysis. A tissue sample was taken in normal saline for all these patients and sent for HLA typing. The laboratory extracted DNA from the donor graft tissue using the Qiagen QIAamp DNA Mini Kit and conducted molecular HLA typing to identify the donor's HLA phenotypes. We also provided recipient HLA typing or sent a separate sample for a more comprehensive analysis.
Results:
The first donor's HLA typing was conducted using three molecular HLA typing methods: two low to intermediate-resolution rSSO techniques (HistoSpot rSSO and Luminex rSSO, respectively) and Next Generation Sequencing (NGS). The NGS technique did not help assign definitive results because of the presence of both donor and recipient DNA and also the NGS assay chemistry does not resolve the alleles.
Table 1: Representing the HLA typing of tested individuals from different sample types
R= Recipient, D= Donor, Bold font shows correctly identified Donor HLA typing, Italics showed recipient HLA captured in Kidney biopsy sample.
In the first case, allele assignment was possible for HLA typing at HLA-A, C, and DQB1. For HLA-B, DRB1, and DPB1, likely HLA typing with additional possibilities was reported (see Table 1). In the second case, HLA typing was conclusive for HLA C, DRB1, DQA, DQB1, and DPB1. However, additional possibilities were reported for HLA-A and B (Table 1) using both available rSSO typing methods. The other two cases (3 & 4) where donor typing was eventually available (Table 1) indicated the presence of both donor and recipient cells in the kidney biopsy sample, therefore, made difficult to determine the donor's HLA typing. In the case of Recipient 4, their complete HLA phenotype at all loci being homozygous likely contributed to more complexity of the situation.
Conclusions:
The feasibility of donor HLA typing from kidney biopsy has been highlighted as a potentially valuable adjunct in cases where HLA typing is either unavailable or incomplete. It is underscored that in such instances, simultaneous HLA typing of the recipient should be performed, or complete recipient HLA typing should be made available to the HLA lab, ensuring a comprehensive evaluation of donor HLA typing. Despite concerted efforts, the resolution of certain possible HLA typing combinations may remain inconclusive. However, leveraging knowledge of ethnicity, haplotype linkage disequilibrium, inheritance pattern of HLA, and population-based HLA prediction software can aid in more accurate allele assignment. The supplementary insights gained are expected to be instrumental for enhanced risk assessment, future evaluation, and improved graft outcomes. Therefore, consideration of kidney biopsy for HLA typing in these scenarios is advised.
I have no potential conflict of interest to disclose.
I did not use generative AI and AI-assisted technologies in the writing process.