[Application of chimerism analysis to allogeneic hematopoietic stem cell transplantation by STR-PCR]

The aim of this study was to analyze chimerism, evaluate the status of engraftment and predict the outcome of allogeneic hematopoietic stem cell transplantation (allo-HSCT) by multiple short tandem repeat (STR) amplification using fluorescence labeling polymerase chain reaction (PCR) combined with capillary electrophoresis. Peripheral blood and bone marrow in 27 patients who received myeloablative allogenetic cell transplantation were collected before and after transplantation in different times. 10 and 7 different STR markers were co-amplified in a single reaction by using a commercial AmpF/STR Profiler Plus/Cofiler plus PCR amplification kits. Separation of the PCR products and fluorescence detection were performed by ABI prism 310 Genetic Analyzer with capillary electrophoresis. The Genescan and Genotype soft ware were used for size calling and quantification of peak areas. The formula to calculate donor chimerism values was based on the different allelic distribution type between donor and recipient. The results showed that donor chimerism was similar by the two methods. The median number of informative alleles was 6.3 (4 - 9) by Profiler Plus and 4.9 (2 - 6) by Cofiler Plus. The donor alleles appeared in 26 patients on day 28 post transplantation. One patient was not observed to appear donor alleles. 14 patients with 100% donor chimerism (DC) had stable engraftment and they still survive in free leukemia. 9 patients had unstable mixed chimerism (DC: 0% - 90.2%), and 5 of them relapsed after allo-HSCT, 6 patients died. Decrease of donor chimerism appeared prior to graft rejection and disease relapse. The incidence of GVHD was higher in group of full donor chimerism. It is concluded that dynamic monitoring donor chimerism by STR-PCR in combination with all auto-capillary electrophoresis is a valuable tool for predicting graft rejection, disease relapse and occurrence of GVHD, and provides a basis for early clinical intervention in the patients received allo-HSCT.