Allogeneic Transplantation with Identical MHC: Clinic-Pronostic Value of Discrepances of Microsatellite DNA Regions between Recipient and Donor.

Introduction: Detection of disparity in microsatellite DNA regions (STR - Short Tandem Repeats) between recipient and donor allows for sensitive and specific monitorization of the degree of haematopoietic chimerism. It is well known that disparities between donor and recipient in various polymorphic systems (mainly MHC) are associated with an increased incidence of graft-versus-host disease (GVHD). However, it is still unknown whether or not STR disparities could have a similar biological effect.

Aim: To study the relationship between STR disparities and frequency of GVHD, overall survival and event free survival in patients who have received allogeneic transplantation.

Patients: 161 consecutive patients transplanted with peripheral blood stem cells from identical MHC sibling donor at a single center were included in the study. Their characteristics were: median age 44 (17–69); Male/Female: 94/67; Sex disparity: 46%; Diagnosis: 39 AML, 26 ALL, 24 MDS, 19 MM, 17 CML, 14 NHL, 10 CLL, 10 HD, 1 CMPD,U, and 1 Hypereosinophilic Syndrome. The conditioning regimen was reduced intensity in 81 patients and myeloablative in the remainly 80 pts. All 161 patients engrafted and were evaluable for acute GVHD (aGVHD), while 128 were included in the analysis of chronic GVHD (cGVHD), according to the available follow-up.

Methods: After genomic DNA extraction, PowerPlex®16 System kit (Promega Corporation, Madison, WI) was used to amplify 16 STR regions (15 plus gender marker, Amilogenin). The amplified products were analysed using GeneScan 2.1 (Applied Biosystems, Foster City, CA) after electrophoresis in the ABIPrism 377 (Applied Biosystems). The chi-square and y t-Student tests were used for statistical analysis. Log-rank analysis was applied for comparing differences in survival. Multivariate analysis was carried out according to the cox-regression method.

Results: The number of STR disparities between recipient and donor ranged from 4 to 15 (median: 9). Discordances in D13S317, D18S51 and TPOX were associated with higher grades of aGVHD severity (p=0.024, p=0.027 and p=0.034, respectively). Disparities in D16S539 was associated with cGVHD (p=0.043). The number of loci discrepancies was not related to any clinical parameter included in the analysis (aGVHD, cGVHD, EFS y OS). However, when patients were grouped according to STR mismatches (<11 disparities and >11, n=127 and 17, respectively), shorter OS was associated in patients with >11 disparities (p=0.021).

Conclusions: The presence of STR disparities could be associated with the development of complications during sibling allogeneic transplantation, including presentation of aGVHD. The data available only shows a marginal association and must be considered as preliminary.