TYPING OF THE HLA-DRB3 GENE BY TEMPERATURE-GRADIENT GEL-ELECTROPHORESIS - PREDICTION OF THE RESOLUTION OF 4 ALLELIC FRAGMENTS BY COMPUTATIONAL SIMULATION OF DNA MELTING

Four alleles are currently recognised at the HLA-DRB3 locus (DRB3*0101, DRB3*0201, DRB3*0202 and DRB3*0301). We studied whether 271 bp fragments of the polymorphic second exon, which were prepared using the polymerase chain reaction, could be typed using temperature gradient gel electrophoresis. Thermal stability curves for the allelic DNA molecules were calculated by computer simulation and the results were validated experimentally. The DRB3*0201 and DRB3*0202 derived homoduplexes were predicted to have identical thermal stability. Thus, only three denaturation and relative mobility curves were obtained for the four homoduplex fragments DRB3*0101, DRB3*0201, DRB3*0202 and DRB3*0301. Computational analysis predicted that DRB3*0201 and DRB3*0202 could be distinguished by electrophoresis of artificially generated heteroduplexes. When verified experimentally, the results of the theoretical analyses were confirmed. We conclude, that computational simulation of the melting behaviour of DNA molecules permits the resolution of allelic sequences to be predicted by temperature gradient gel electrophoresis. We also demonstrate that temperature gradient gel electrophoresis is a powerful tool for the assessment of HLA genotypes. It may have wide application in transplantation immunology and in the study of disease associations of allelic variation at the HLA loci.