Identification of the novel allele B*4427 and a confirmatory sequence (B*44022).

This report presents a novel allele, HLA-B*4427, which was identified in a bone marrow donor of Caucasian origin, and a confirmatory sequence (B*44022). Sequence analysis revealed the new allele differs from B*44021 by a single nucleotide exchange at position 668 (C-->T), which is located in exon 4. At the protein level, it is the only B*44 variant to produce an Ala in place of a Val at codon 199. Its structure suggests that it may have originated from a point mutation in B*44021 or by gene conversion with a variety of HLA-B alleles. Cloning and sequencing of the allele B*44022 revealed a sequence identical to B*44021 and B*44 exon 4, with the codon GTC (Val) in position 199.