High-resolution HLA typing for the DQB1 gene by sequence-based typing.

The ideal high-resolution typing strategy for polymorphic genes is sequence-based typing. SBT of genomic DNA has been developed for the HLA class II genes DRB1, DRB3/4/5 and DPB1. For the DQB1 gene the sequence-based typing method was shown to cause a number of problems. To resolve those problems, different primers to amplify and sequence exon 2 of DQB1 were designed and tested. With several primer combinations, preferential amplification was observed in individuals heterozygous for DQB1*02/*03 and DQB1*02/*04. The preference was for DQB1*02 in many instances but could also be demonstrated for DQB1*03 or *04 and resulted occasionally in allelic drop-out. The best primer combination was selected and successfully used to type individuals heterozygous for DQB1*02, *03 and *04. To distinguish DQB1*0201 and *0202, primers for amplification and sequencing of exon 3 were developed and correct subtyping was obtained. The ambiguous typing DQB1*0301/*0302 and DQB1*0303/*0304 was resolved by allele-specific amplification and sequencing. A total of 258 individuals were fully typed for their DQB1 subtypes. All samples had been previously typed by PCR-SSP and serology. Concordant typing results were obtained for all individuals tested. The DQB1 alleles detected included *0501, *0502, *0503, *0601, *0602, *0603, *0604, *0609, *0201, *0202, *0301, *0302, *0303, *0304, *0401 and *0402. Sequence-based typing of the DQB1 gene proved a reliable typing strategy for assignment of the different DQB1 alleles after intensive selection of primers and test conditions.