GENOMIC IDENTIFICATION OF THE MINOR HISTOCOMPATIBILITY ANTIGEN HA-1 LOCUS BY ALLELE-SPECIFIC PCR

Graft-versus-host disease (GvHD) can be a major complication of alloge neic bone marrow transplantation even in recipients of HLA genotype-id entical transplants. Disparities in minor histocompatibility antigens (mHags) between donor and recipient are a potential risk for the devel opment of GVHD. A mismatch for the mHag HA-1 can cause GVHD in adult r ecipients of allogeneic bone marrow from HLA-identical donors. The mHa g HAi, 1, first identified by HLA-A0201-restricted cytotoxic T cells (CTLs), was recently chemically characterized as a nonapeptide. On the cDNA level, the HA-1 locus has two alleles, HA-1(H) and HA-1(R), whic h differ in two nucleotides, resulting in a single amino acid substitu tion. Here we report on the genomic structure of the HA-1 locus. Isola tion and sequencing of cosmid DNA encoding the HA-1 peptide sequence r evealed that the HA-I alleles are encoded by two exons. Two different primer sets were designed each consisting of allele-specific primers a nd a common primer, and both sets containing intronic sequences. We pe rformed genomic DNA typing of three families consisting of 24 HLA-A02 01-positive individuals. The predicted allele-specific products correl ated in all cases with the mHag classification by CTLs and by RT-PCR. We demonstrate for the first time the genomic identification of the mH ag HA-1 locus. Prospective genomic typing for the HA-1 alleles will im prove donor selection and identify HLA-A0201-positive recipients with a high risk for HA-1-induced GvHD.