Analysis of HLA‐B*44 alleles encoded on extended HLA haplotypes by direct automated sequencing

Abstract

We developed a PCR-based approach to sequence exons 2 and 3 of HLA-B44 alleles from genomic DNA. We applied this method to determine the B44 alleles encoded on extended HLA-A, B, DRB1, DQB1 haplotypes and the degree of mismatching for B44 alleles among marrow transplant patients and their unrelated donors (URD). A total of 81 samples was studied and included 38 patients, 42 donors and the cell "FMB"; the 80 clinical samples were comprised of 8 unpaired patients, 12 unpaired donors, and 30 URD-recipient pairs. Three alleles encoding B44 were identified, B*4402 (N = 51), 4403 (N = 32) and a new allele designated B*44KB and named B*4405 (N = 4). Of the 27 patients for whom family study was available, there were 13 different B*4402, 7 different B*4403 and 2 new B*4405 haplotypes. HLA-A2, Cw*0501, B*4402, DRB1*0401, DQB1*0301 (n = 2); A2, Cw*0501, B*4402, DRB1*1501, DRB5*0101, DQB1*0602 (n = 2); and HLA-A29, Cw*1601, B*4403, DRB1*0701, DQB1*0201 (n = 5) comprised the most common patient haplotypes. Of 30 URD-recipient transplant pairs studied, 27 were HLA-A, B serologically matched and DRB1, DRB3, DRB5, DQB1 allele matched, and 3 pairs were DRB1-mismatched. All B44 allele mismatching (N = 3) occurred among the 27 matched pairs. The novel B*4402-variant sequence, HLA-B*4405, was identified in 4 individuals, and in each case was associated with an HLA-B44, Cw*02022, DRB1*0101, DQB1*0501 haplotype. HLA-B*4405 and B*4402 are identical in exon 2; in exon 3 however, B*4405 encodes T instead of G at nucleotide position 75 which translates to a substitution of tyrosine for aspartic acid at codon 116.(ABSTRACT TRUNCATED AT 250 WORDS)