Quantitative monitoring of multi-donor chimerism: a systematic, validated framework for routine analysis

Abstract

Despite therapeutic advantages, double-donor (DD) HSCTs present technical problems for molecular chimerism (CHM) monitoring. These DD chimeras contain three matched DNAs, so that the genomes of donor(s) and recipient often share the same alleles. In the STR assay, shared recipient/donor alleles are common and have identical physico-chemical properties. As a consequence of the latter, they co-migrate in the same band ('shared peak'), which prevents measuring each allele separately. Without individual allelic measurements, the direct calculation of the chimeric recipient/donor DNA ratio is precluded. This is the first study to document and systematically examine these problems. Its goal was to provide a validated framework for accurate, routine monitoring based on a stepwise analytic paradigm for approximating percent CHM (%CHM) from shared STR-alleles. Analysis of STR-DNA from DD loci showed that at least four of six alleles were typically shared. Despite such extensive allelic sharing, we show how simple arithmetic procedures can be applied for standardized calculation of %CHM based on peak measurements. Criteria for selecting loci suitable for such analysis are provided. Validation of the computational results required analyzing 18 'informative' loci with pre-established reference values for %CHM. In all cases, the results for %CHM, calculated from peak measurements, were ± 5% of the reference value. The conclusions of the study are as follows: (1) Multi-donor chimeras, with shared alleles, can be accurately and simply analyzed within the usual limits of STR measurement error; (2) by examining these various facets of DD CHM analysis, this novel study has provided a basis for standardized, routine quantitative monitoring using the STR/VNTR assay.

Heterogeneous Niche Activity of Ex-Vivo Expanded MSCs as Factor for Variable Outcomes in Hematopoietic Recovery

“…Thus various approaches have been tried to enhance the kinetics of engraftment, including ex-vivo expansion of HSCs [50] and the increase of the graft size by double cord transplantation [42, 51]. Of those approaches, clinical trials of co-transplanting MSCs and HSCs to enhance the hematopoietic recovery have been increasingly attempted, but results from multi-center trials reveal variable outcomes in hematopoietic recovery [29].…”

Larger Size of Donor Alloreactive NK Cell Repertoire Correlates with Better Response to NK Cell Immunotherapy in Elderly Acute Myeloid Leukemia Patients

“…Clones exhibiting greater than 30% lysis were scored as alloreactive. Peripheral blood and bone marrow chimerism was determined by variable number tandem repeat (VNTR) assay (23).…”

An overview of the progress on double umbilical cord blood transplantation

“…47 Algorithms are available that can provide approximations of the chimerism pattern following dUCBT. 48 Dominance reversion has rarely been reported, except for a 15-year old boy treated with dUCBT for acute lymphoblastic leukemia in whom long-term mixed donor chimerism and dominance reversion (on day 253 post transplant) were observed during follow up for more than 16 months (479 days post transplant). 49 Furthermore, in a phase I dUCBT clinical trial involving patients with hematologic malignancies undergoing a reduced intensity conditioning regimen, a patient with 95% single donor chimerism on day 65 post transplant was reported to lose single unit dominance in favor of mixed donor chimerism over time.…”