Chimerism monitoring following allogeneic hematopoietic stem cell transplantation

Information regarding the chimeric status of hematopoietic stem cell transplantation (HSCT) recipients is of great significance when comparing different conditioning and prophylactic therapies. In recent years, short tandem repeats/variable number tandem repeats (STRs/VNTRs) have emerged as the best tool for chimerism monitoring. However, the polymorphisms of STR/VNTR markers vary within and between ethnic groups. The issue is further complicated in a heterogeneous population such as occurs in the Indian subcontinent. In the present study, we attempted to devise a robust scheme to identify a set of polymorphic STRs/VNTRs most suitable for chimerism evaluation in north Indian HCST recipients. At first, we did genotyping of 11 STR and one VNTR in 1000 randomly chosen north Indian individuals to quantify different diversity parameters. Resulting data indicated that ApoB3'HVR, FES, VWA, D3S1358 and D16S310 were most polymorphic loci with the average heterozygosity being 0.756+/-0.17. Furthermore, all markers were genotyped in 77 HLA-matched donor-recipient pairs to evaluate the informativeness in differentiating donor's and recipient's cells. A panel of seven markers (ApoB3HVR-D3S1358-HUM-THO1-VWF-1-D16S310-FES-VWA) differentiated 98.70% of donor-recipient pairs. This set of markers also successfully monitored the graft status in 14 HSCT cases during multiple time points following HSCT. The results were compared to the commercially available AmpF/STR SGM Plus multiplex PCR kit (Applied Biosystems, Foster City, CA, USA). Our findings established that the panel of seven markers we identified was more cost-effective and informative.