A study published this month in the journal Tissue Antigens reports that researchers at Roche Molecular Systems (SWX:RO) (SWX:ROG) (Pink Sheets: RHHBY) in Pleasanton, CA have used high-throughput sequencing technology from 454 Life Sciences, a Roche Company, to carry out high-resolution human leukocyte antigen (HLA) genotyping in research samples. In the study, the researchers performed ultra-deep amplicon sequencing of specific HLA class I and II gene loci with the Genome Sequencer FLX System and successfully assigned allele-level genotypes using software developed by Conexio Genomics. The results of the study have important implications for future research on a wide variety of human diseases and tissue transplantation.
HLA class I and class II genes play a critical role in the adaptive immune response. Importantly, they encode for the cell-surface proteins responsible for differentiating between self, non-self cells and other antigens. For example, accurate HLA genotyping is clinically important for hematopoetic stem cell (HSC) transplantation between unrelated donors and recipients to minimize the risk of graft rejection and graft versus host disease (GVHD). Accurate HLA genotyping is also critically important for research on many human diseases. “Specific alleles and haplotypes at the class I and class II loci are strongly associated with a variety of autoimmune disease as well as some cancers and infectious diseases,” explained Henry Erlich study author and Director of the Department of Human Genetics at Roche Molecular Systems. “High resolution, high throughput HLA typing will be very valuable in these large research association studies.”
Accurate HLA genotyping is complicated by the highly polymorphic nature of this genomic region. There are hundreds of different allele sequences at the various HLA class I and class II genes. Current methods, based on Sanger-sequencing technology, are limited in their ability to resolve “phase ambiguities” which occurs commonly when an individual is heterozygous at many positions that are very close to one another.