HLA-A*33-B*58: 45-DRB1*03, a deduced probable human leukocyte antigen haplotype associated with a human leukocyte antigen low-incidence allele B*58:45 in Taiwanese unrelated hematopoietic bone marrow stem cell donors

Objective: HLA-B*58:45 is a low-incidence allele in the human leukocyte antigen-B (HLA) locus. The aim of this study is to confirm the ethnicity of B*58:45 and its deduced probable HLA-associated haplotype in Taiwanese unrelated bone marrow hematopoietic stem cell donors. Materials and methods: A total of 40,000 healthy unrelated volunteer bone marrow stem cell donors (aged, 20-45 years) were tested using a sequence-based typing method. We confirmed the low-incidence allele B*58:45 in Taiwanese donors. Polymerase chain reaction was performed to amplify exon 2 and exon 3 of the HLA-A and HLA-B loci and exon 2 of the HLA-DRB1 locus using group-specific primer sets. The amplicons were sequenced in both directions with the BigDye Terminator Cycle Sequencing Ready Reaction Kit according to the manufacturer's protocols. Results: The DNA sequence of B*58:45 is identical to B*58:01:01 in exon 2 and exon 3 except for residue 595, where G is changed to A (codon 175, GGG→AGG). The nucleotide replacement causes an amino acid change at codon 175 where G (glycine) of B*58:01:01 is replaced by R (arginine). We deduced the probable HLA haplotype associated with B*58:45 in Taiwanese donors to be A*33-B*58:45-DRB1*03. Conclusion: Information on this deduced probable HLA haplotype in association with the low-incidence B*58:45 allele is of value for HLA testing laboratories for reference purposes and can help bone marrow donor registries find compatible donors for patients with this uncommon HLA allele.