Rapid HLA class I DNA typing using microtiter plate-reverse hybridization assay (MRHA) by simple thermoregulation: high-resolution subtyping of the HLA-A2 and -B40 antigen groups.

We have established a precise, rapid, simple and economical subtyping method for alleles encoding the HLA-A2 and -B40 antigens using microtiter plate-reverse hybridization assay (MRHA), which is based on the general principle of HLA oligotyping by reverse dot blot hybridization. Amino-modified sequence-specific oligonucleotide (SSO) probes were immobilized covalently onto a carboxylate-modified microtiter plate. In order to perform high-resolution subtyping of the HLA-A2 and -B40 antigen groups, the alpha1 and alpha2 domain regions were amplified using a pair of group-specific primers composed of an unlabeled sense primer and a biotinylated antisense primer. PCR-amplified products were hybridized with SSO probes in hybridization buffer containing formamide for 1 hour at 37 degrees C. After washing with 2 X SSC at room temperature, the bound PCR products were detected by alkaline phosphatase-conjugated streptavidine followed by color development. All of 8 HLA-B40 suballeles, all of 2 HLA-B47 suballeles (B40 group-specific primers used in this study allowed also B47 amplification) and 17 out of 21 HLA-A2 suballeles were discriminated. The remaining four HLA-A2 suballeles were determined by analysis after exon 4 amplification. HLA-DNA typing by this method was easily and exactly performed regardless of sample number. The greatest advantages of this technique are strong positive signals obtained, reproducibility and the ease of thermoregulation for hybridization and washing as compared to previously reported microtiter plate hybridization methods.