HLA-A*02 subtype distribution in Caucasians from northern Italy: identification of A*0220.

This study describes a comprehensive easy to perform PCR-SSOP typing approach suitable for complete genomic subtyping of HLA-A02. A single 1.6 kb PCR-amplificate spanning exons 2, 3 and 4 of the HLA-A02 gene was used for hybridization with a panel of twenty-four SSOPs. This allowed unequivocal assignment of all so far known HLA-A2 subtypes, including A0209 and A0215N which differ for nucleotide substitutions in exon 4, without the need for two separate amplifications. Using this approach, HLA-A02 subtype distribution was analyzed in 218 samples from unrelated, healthy individuals from northern Italy enrolled in the Italian Bone Marrow Registry and typed as HLA-A2 by serology or generic molecular analysis. As expected, A0201 was found in the majority (92.6%) of samples. However, a significant number (6.8%) of individuals carried A0205. Furthermore, A0202, A0208, A0209 and A0217, so far not described in Caucasians, were detected in a low number of samples (frequency ranging from 0.45% to 1.8%). Finally, a novel HLA-A02 subtype, A0220, was detected in 0.9% of the samples. As confirmed by DNA sequencing of exons 2 and 3, this allele is identical to A0201 except for a single nucleotide substitution in codon 66 which changes the predicted amino acid sequence form Lys to Asn. The findings of this study have implications for the selection of HLA-A02+ donors in unrelated bone marrow transplantation and of patients for specific immuno-therapy with HLA-A02 restricted peptide vaccines.