GvHD and Engraftment after Haploidentical Stem Cell Transplantation. A Comparison of 3 Immunomagnetic Selection Procedures.

Profound depletion of T and B cells is a fundamental prerequisite for haploidentical transplantation. Here, we compare hematopoietic engraftment and occurrence of GvHD after two different positive selection procedures (with anti-CD34 coated or anti-CD133 coated beads) and after a direct depletion procedure with CD3/CD19 coated microbeads in children with leukemias (ALL, AML, CML) and lymphomas. Median purity of stem cells was comparable after CD34+ selection and CD133+ selection, whereas stem cells were only slightly enriched after CD3+/CD19+ depletion (97.5%, 93.4% and 1.02%). Indirect depletion of T cells was better after CD34+ selection than after CD133+ selection (4.1log vs. 3.75log, p<0.001). Direct T cell depletion with anti-CD3 coated microbeads produced results comparable to CD34+ selection. Those grafts comprised also remarkable amounts of effector cells such as NK cells (median number: 40 x10⁶/kg), dendritic cells and monocytes (median number: 120 x10⁶/kg). Recovery of stem cells was similar in all three methods (77.3%, 80.6%, and 70% respectively).

Primary engraftment occurred in 85% (44/52) of patients with CD34+ selected stem cells and in 78% (11/14) of patients with CD133+ selected cells. After reconditioning, sustained engraftment was achieved in 98% and 100%. All patients (10/10) with CD3+/CD19+ depleted grafts had primary engraftment. Recovery of platelets was rapid especially in patients with CD133+ selected grafts (median time to reach independence from substitution = 14.5 days). GvHD grade II occurred in 6%, 7% and 25%, respectively. Only one patient had severe GvHD grade III-IV (CD34+).Conclusions: CD34+ selection and CD133+ selection resulted in similar engraftment and GvHD rates. CD3+/CD19+ depletion resulted in better engraftment but produced slightly more GvHD. Thus, the methods may be individually used according to the patient’s requirements.