5.2
TITLE: BEAD MICROARRAY FOR HLA MOLECULAR TYPING

A. X. Li,¹ L. Mao,¹ S. Wang,¹ M. Seul,¹ J. Garcia–Gomez,² S. Musa,² J. Cicciarelli,² Y. Iwaki.<sup>2

1</sup>Research, BioArray Solutions LTD, Warren, NJ; ²DNA, USC/Metic Transplantation Lab, Los Angeles, CA

We describe a novel assay design developed on BioArray Solutions (BAS) bead array platform for multiplexed HLA molecular typing. BAS uses planar bead arrays assembled on a silicon chip. Each 0.3mm square chip contains approximately 4000 beads with up to 100 probes corresponding to different colored beads. To date, we have tested 240 clinical samples by custom bead arrays incorporating the NMDP probe set in comparison to the conventional SSOP protocols with agreeing results, proving that our system reliably accommodates the high sample throughput required in bone marrow registry typing. In addition, the technology offers unique flexibility in implementing custom probe designs. We have developed a novel design that combines group specific amplifications with multiplexed detection on bead arrays. In typing HLA–DR, this design reduced the allele ambiguity by at least 10 fold comparing to conventional hybridization assay designs. The methodology allows rapid efficient DR typing eliminating many of the allele ambiguities. We are also developing a probe set for HLA–A, B with similar approach.