Office of Technology Development (OTD)

David Bick, MD
Thomas Ellis, PhD

Allogeneic hematopoietic stem cell transplant (HSCT) often involves selecting from a group of siblings the best HLA match for a patient. HSCT donors must have a tissue HLA type that matches the recipient. Matching is performed on the basis of variability at three or more loci of the HLA gene, and a perfect match at these loci is preferred. High resolution typing techniques are often used to identify the best possible donor among a group of siblings. However it is expensive and time-consuming to “high-resolution type” all possible sibling donors. Here we describe a novel method for screening HLA-related siblings for HSCT.   

Utilizing embryo genetic screening technology developed at the Medical College of Wisconsin, researchers at the Blood Center of Wisconsin have developed an assay using short tandem repeat (STR) linkage analysis to provide rapid and inexpensive method for screening for HLA-matched sibling donors in HSCT. The method uses linkage patterns of 6 polymorphic trimeric STRs located throughout the HLA complex. These 6 STRs were selected from over 200 known and newly identified STRs based on their chromosomal locations, polymorphism, and suitability for multiplex PCR amplification. The method involves initial duplex STR-specific amplification with fluorochrome-conjugated primers, followed by size analysis using capillary electrophoresis (ABI 3130). Comparison of STR analysis with HLA haplotypes in 26 family case workups showed 100% agreement. In 2 cases, HLA phenotypically-identical siblings were disparate at the STR locus centromeric to HLA-DPB1. This was due to a single mismatch at HLA-DP in one case and a class II crossover event in the second case. STR linkage analysis successfully identified all siblings who were HLA disparate. Analysis of 10 HLA-identical unrelated recipient/donor pairs gave no indication that STR alleles are conserved with specific HLA haplotypes.

STR linkage analysis provides a rapid and inexpensive method for HLA screening of potential donors for related HCST, so that confirmatory HLA typing is performed only on likely matches. The method may be used to confirm genotypic identity in families with multiple common HLA haplotypes or homozygosity, without resorting to confirmation by sequencing may be useful for defining genetic heterogeneity within HLA haplotypes.

• Screens for best candidate among sibling donors
• Provides inexpensive, PCR-based, fragment analysis assay compatible with current HLA lab techniques
• Easily incorporated into “kits”
• Reduces costs by eliminating need to type all related HSTC donor candidates
• Potential for screening non-related donors

Validated assay