P002 Standard duo typing of 1196 specimens revealed a strategy to use next generation sequencing as a standalone HLA typing method in clinical laboratory

Abstract

Aim Next generation sequencing (NGS) permits sequencing of the entire HLA genes and generate unambiguous phased-resolved HLA typing. NGS is increasingly used in clinical HLA laboratories for both stem cells and solid organ transplantation. Herein, we investigated if NGS can be used as a standalone HLA typing method in clinical laboratory. Methods 1196 samples were typed in parallel using NGS (Omixon) and high-definition rSSO (One Lambda) methods. In addition, SSP (Olerup) was used to type HLA-DRB4 alleles. The frequency of allelic dropout by NGS was evaluated for all nine HLA loci (A, B, C, DRB1, DRB3/4/5, DQA1, DQB1, DPA1, and DPB1). Results No allelic dropout was observed at HLA-A, - B , - C , -DRB1, -DRB5, -DQA1, -DQB1, and -DPA1 loci. However, 4.6% of the samples (55/1,196) showed allelic dropouts at one of the other three loci: HLA-DRB3, -DRB4, and -DPB1. Frequent allelic dropouts were observed at HLA-DRB4 (3.7%; 44/1,196 samples) and HLA-DPB1 (0.8%; 10/1,196 samples) loci. HLA-DRB3 allele dropout was noted in a single sample (0.1%). The table below lists the specific dropped out alleles and their associated haplotypes or other alleles. Conclusions Our results suggest that the NGS can be used as a standalone method for HLA-A, - B , - C , -DRB1, -DRB5, -DQA1, -DQB1, and -DPA1 typing. However, additional typing assays are required to confirm the homozygosity of HLA-DRB3, -DRB4, and -DPB1 loci. DRB1-DRB3/4/5 linkage can be used to identify the allelic dropouts in HLA-DRB3/4 loci for certain cases. Concurrent typing of HLA-DRB3/4 and -DPB1 by rSSO would improve the NGS workflow and turnaround time.