Sequence analysis of HLA-Bw53, a common West African allele, suggests an origin by gene conversion of HLA-B35

Abstract

In the West African population of the Gambia the class I antigen HLA-Bw53 is found at high frequency. We used the polymerase chain reaction to amplify cDNA from an individual homozygous for this allele and determined the nucleotide sequence of the polymorphic alpha 1 and alpha 2 domains. The HLA-Bw53 sequence is identical to HLA-B35 except for a short sequence at the 3' end of exon 2 (encoding the alpha 1 domain) which specifies a Bw4 rather than a Bw6 motif. This suggests an origin for HLA-Bw53 involving a gene conversion of HLA-B35 by an allele containing this Bw4 sequence. The alpha 2 domain shared by HLA-Bw53, -B35, and -Bw58 is particularly common in sub-Saharan Africans.