HLA-B22 diversity including a novel B54 variant (B∗5507) in the Korean population

Diversity in the HLA-B22 group was investigated in the Korean population using PCR-SSOP and DNA sequencing analyses. Allelic typing of the B22 gene was performed by gene amplification of the polymorphic exons 2 and 3 of the HLA-B genes from 91 B22 positive individuals followed by a hybridization assay using 63 digoxigenin-labelled probes. Five different SSOP patterns including an unexpected pattern were identified and correlated well with the observed serologic types and with data obtained from DNA sequencing analyses. Novel allele, B∗5507, was identified from two unrelated individuals who exhibited standard B54 serologic reactivity but an unexpected SSOP pattern. The DNA sequence of B∗5507 is identical to B∗5502 in exons 2 and 3 except for a single nucleotide substitution at codon 45 (GAG → GGG) altering glutamic acid to glycine. Among the already known B molecules, this substitution has been observed only in the B54 molecule encoded by B∗5401 allele. This is the evidence that Gly-45 is a crucial site forming the B54 serologic epitope. Interestingly, both alleles (B∗5401 and B∗5507) exhibit strong association with Cw∗0102. Along with previous data, B22 appears to be a very diverse group in the Korean population consisting of at least seven different alleles. B∗5401, B∗5502, and B∗5601 are the most frequent alleles. B∗5507, B∗5501, B∗5504, and B∗5604 appear at lower frequencies. Data obtained from this study will be useful in hematopoietic stem cell donor searches as well as in determination of a typing strategy for the HLA-B22 types in this population.