TWO NOVEL ALLELES AROSE FROM THE SILENT MUTATION OF CODON 72.
YS Lin, L Li, TF Tang, J Ng, R Hartzman, and CK Hurley, C.W. Young/DOD Marrow Donor Program, Kensington MD .


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We have identified two novel alleles: DRB1*16012 and DRB5*01012 in our registry. Three of our samples showed unique SSOP patterns in intermediate level DNA based typing. These samples were then typed with DRB1*02 and DRB5* specific primers and probes as well as by direct sequencing. The sequences of primers and probes were mostly derived from the 11th International Histocompatibility Workshop. Sample GN00150, a Swiss donor, was originally typed as DRB1*13, 15; DRB3*02; DRB5*02, with an extra reaction of probe DRB7102. We performed PCR-SSOP typing on these four alleles. Probe DR7102 was only seen in the DRB1*02 group hybridization pattern. Later, direct sequencing revealed that GN00150 differs from DRB1*16011 by one nucleotide at codon 72, CGG verses CGC. This point mutation, however, does not affect the encoded polypeptide. The allele was assigned as DRB1*16012. GN00152 and GN00200 are two unrelated donors of Caucasoid origin carry a DRB1*15 and a DRB5*. Interestingly, their intermediate level PCR-SSOP patterns also contained reactivity with probe DR7102, making it difficult to define the DR type. However, allele specific PCR-SSOP typing and direct sequencing data indicated the existence of a novel DRB5* allele. This novel allele was most likely derived from a point mutation event at the third base of codon 72 (G to C), similar to DRB1*16012. The diversity of HLA DRB gene is commonly caused by sequence substitution. We are expecting to see more and more new alleles arise through this genetic variation.