Deduced probable HLA-B*40: 01:35-associated HLA haplotype (A*24-B*40:01:35-DRB1*11) found in a Taiwanese unrelated hematopoietic bone marrow stem cell donor

Objective: Human leukocyte antigen (HLA)-B*40:01:35 is a low incidence allele in the HLA-B locus. The objective of this study is to report the ethnicity of B*40:01:35 and its deduced probable HLA associated haplotype in a Taiwanese unrelated bone marrow hematopoietic stem cell donor. Materials and methods: A sequence-based typing method was employed to confirm the low incidence allele B*40:01:35. Polymerase chain reaction was performed to amplify exons 2 and 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 using the BigDye Terminator Cycle Sequencing Ready Reaction kit in both directions according to the manufacturer's protocols. Results: The DNA sequence of B*40:01:35 is identical to B*40:01:01 in exons 2 and 3, except for residue 324 where C is changed to T (codon 84, TAC→TAT). The nucleotide exchange does not cause amino acid alteration to the protein sequence of B*40:01:01 due to the silent mutation. We deduced the probable HLA haplotype in association with B*40:01:35 in Taiwanese to be A*24-B*40:01:35-DRB1*11. Conclusion: Information on the deduced probable HLA haplotype in association with the low incidence B*40:01:35 allele that we report here is of value for HLA testing laboratories for reference purposes. In addition, it can be used by stem cell transplantation donor search coordinators to determine a strategy for finding compatible donors in unrelated bone marrow donor registries when a patient has this uncommon HLA allele.