Human Leukocyte Antigen Typing with Sequence Specific Oligonucleotides for Renal Transplantation in South Africa

Background: Kidney transplants are the only curative therapeutic intervention for end-stage kidney disease (ESKD). The current organ shortage in South Africa makes recipient risk assessments and effective laboratory workup crucial to assist in better organ assignment and increase the likelihood of better transplant outcomes. HLA typing is a step in the pre-transplant workup for performing virtual crossmatches and matching donors and recipients. Sequence Specific Oligonucleotide (SSO) PCR is a relatively fast and inexpensive method for determining genotypic HLA types at a 2- to 4-digit resolution. This study aimed to validate the SSO technique for achieving a 4-digit resolution when determining HLA types to improve virtual crossmatches. Methods: DNA was extracted from 33 samples. After PCR amplification, the samples were hybridized to oligonucleotide probes and the HLA A, B, C, DRB1, DQA1/B1, DRB3, DRB4, DRB5, and DPA1/B1 types were identified. These results were compared to results from external laboratories. Results: The kappa coefficient calculated for the low-resolution comparison suggested a perfect agreement between the two results (p = 0.32). Conclusions: SSO was successfully validated for HLA typing in the Johannesburg kidney transplant setting. This will improve the specificity of virtual crossmatches on an automated system by matching the resolution of the HLA typing and the HLA antibody testing. Additionally, common HLA types were identified in this donor cohort. Future research into these common HLA types and haplotypes in a South African population will inform the feasibility of reintroducing HLA matching into the pre-transplant workup.