Effect of anti-CD52 antibody alemtuzumab on ex-vivo culture of umbilical cord blood stem cells

BACKGROUND: Excessive maturation of hematopoietic cells leads to a reduction of long-term proliferative capability during cord blood (CB) expansion. In this study, we report the effects of anit-CD52 (Alemtuzumab, Campath) on both short- and long-term ex vivo expansion of CB hematopoietic stem cells (HSC) by evaluating the potential role of Alemtuzumab in preserving the repopulating capability in CB HSC and nonlymphoid progenitors. METHODS: Ex vivo expansion experiments were carried out using freshly purified CB CD34(+ )cells in StemSpan™ SFEM medium in the presence of stem cell factor, Flt3-Ligand and thrombopoietin at 50 ng/ml. Alemtuzumab (10 μg/ml) was used to deplete CD52(+ )cells during the cultures. Flow cytometry was used to monitor CB HSC and their differentiation. Colony forming unit (CFU) assays and long term culture-initiating cell (LTC-IC) assays were performed on cells obtained from day 0 (before culture) and day 14 after cultures. Secondary cultures was performed using CD34(+ )cells isolated at 35 days from primary cultures and further cultured in StemSpan™ SFEM medium for another 14 days to confirm the long term effect of alemtuzumab in liquid cultures. RESULTS: Compared to cytokines alone, addition of alemtuzumab resulted in a significant increase in total nucleated cells, absolute CD34(+ )cells, myeloid and megakaryocytic progenitors, multi-lineage and myeloid CFU and LTC-IC. CONCLUSION: The results from current study suggested that the use of alemtuzumab for ex vivo expansion of CBHSC maybe advantageous. Our findings may improve current technologies for CBHSC expansion and increase the availability of CB units for transplantation. However, in vivo studies using animal models are likely needed in further studies to test the hematopoietic effects using such expanded CB products.