#43
CHIMERISM EVALUATION USING STR ANALYSIS IN THE ABSENCE OF DONOR SAMPLE.
Bernadette M. Senghore, MSc , George Odeleye BSc , Judith Marsh MD and Deborah A. Sage, PhD . London United Kingdom, NBS-South Thames, SW17,0RB, H&I and London United Kingdom, St George
s Hospital, SW17,0QT, Haematology .
Complications associated with haemopoietic stem cell transplantation (HSCT) are poor engraftment and graft versus host disease. There are various techniques available for monitoring engraftment. The most sensitive of these, is analysis using Short Tandem Repeats (STR).
Following HSCT samples are assessed for chimerism at regular interval. The procedure we use to monitor chimerism in post transplant patients is as follows:
Patient’s pre and post transplant and the donor peripheral blood samples are investigated using a panel of 13 STR markers located on various chromosomes. Following PCR amplification samples are multiplexed and electropheresd on the ABI Prism™ 310 Genetic Analyser (PE Biosystems). Genotyping is performed using the Genescan™ Analysis Software(PE Biosystems). Based on the peak areas, levels of chimerism are assessed using protocols described by Nollet et al (2001).
In some situations it can be very difficult to obtain donor material for the post transplant analysis, and this can delay results/therapeutic intervention. In cases of great clinical urgency, provided there are allelic differences between the patient and donor, it is possible to evaluate the level of chimerism by comparing the STR profiles of the pre and post transplant samples. The efficacy of this procedure in assessing the level of chimerism in the absence of donor material is illustrated below.
Patient A – 4 Informative loci – THO1, FES/FPS, D21S11, FGA.
90% Donor at 3 months post HSCT.
Patient B – 4 Informative loci – Amelogenin, vWA31, D21S11, FGA.
80% Donor at 1 month, and 90 % Donor at 2 months post HSCT.
These cases illustrate that in some instances, even in the absence of donor sample, STR analysis can be an effective way of monitoring engraftment.
Nollett et al (2001). BMT, 28, 511.