P189 Class II haplotypes associated with DRB1∗12 using full gene sequence analysis by next generation sequencing

• Published in: Human immunology Vol. 78; p. 197
• Main Authors: Profaizer, Tracie, Ellinger, Lori, Krishnakumar, Sujatha, Kuehn, Raquel Tamse, Delgado, Julio C., Lazar-Molnar, Eszter
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.09.2017
• ISSN: 0198-8859; 1879-1166
• DOI: 10.1016/j.humimm.2017.06.249

There is very limited information on the importance of DRB1 exon 1 variations in transplantation. Routinely, clinical laboratories do not test for exon 1 assuming it codes for the leader peptide which is cleaved off of the mature protein, and therefore not clinically important. Currently there are two CWD DRB1 alleles that differ in exon 1, DRB1∗12:01 and DRB1∗12:10, which can only be resolved by sequencing exon 1. We sought to interrogate exon 1 of DRB1 for the presence of the CWD allele, DRB1∗12:10, and to determine the HLA class II haplotypes associated with it in our local population. The Immucor Mia Fora Flex 11 HLA Typing kit was used to genotype eight HSCT recipients and their unrelated donors, as well as seven additional patients. All 23 of these individuals were previously genotyped as DRB1∗12:01 using SSOP. All 23 individuals typed as DRB1∗12:01:01. No DRB1∗12:10 was identified in this limited cohort. Two haplotypes were identified for DRB1∗12:01:01: sixteen individuals (76%) were DRB1∗12:01:01, DRB3∗02:02:01, DQA1∗05:05:01, DQB1∗03:01:01, and five individuals (24%) were DRB1∗12:01:01, DRB3∗01:01:02, DQA1∗05:05:01, DQB1∗03:01:01. Two individuals could not have their DRB3∗01:01:01 and DRB3∗02:02:01 haplotypes identified. The Immucor Mia Fora Flex 11 HLA Typing kit is unique among several commercial NGS kits in that it contains primers capable of sequencing exon 1 of DRB1. Traditionally, this region has been avoided because of the difficulty in primer design due to the very large 8000–10,000bp intron 1. The CWD allele, DRB1∗12:10 originally identified in Korean population, differs from DRB1∗12:01 by one bp in exon 1, but since exon 1 is not routinely typed, the individual frequencies of these alleles are not known. Retrospective studies in Asian populations indicated that 12% of DRB1 alleles previously typed as 12:01 were in Fact 12:10. In our study, 100% of our cohort of 23 patients typed as DRB1∗12:01, which was found to be predominantly associated with DRB3∗02:02:01 (76%) and less frequently with DRB3∗01:01:02 (23%). This is in contrast to the reported preferential association of DRB1∗12:01 with DRB3∗01:01:02 (97%), while association with DRB3∗02:02:01 was very rare (2.1%). Retrospective studies may be helpful to determine the importance of exon 1 mismatches in HSCT.