Download Previously, we demonstrated that activation of Notch receptors by

ENHANCED T CELL RECONSTITUTION BY CORD BLOOD PROGENITORS EXPANDED EXVIVO USING THE NOTCH LIGAND DELTA1
Dallas, Mari H, Bernstein, Irwin B., Fred Hutchinson Cancer Research Center, Seattle, Washington
Background: Delayed immune reconstitution (IR) after hematopoietic cell transplantation (HCT) increases
the risk of post-transplant opportunistic infections. The rate of IR is directly correlates with the no. of
hematopoietic stem cells (HSC) infused and is particularly delayed in patients undergoing cord blood
transplantation (CBT) secondary to the limited numbers of HSC. Objectives: Methods to increase the no.
of CB progenitors have the potential to accelerate IR after CBT. Our lab has developed a clinically relevant
method for ex vivo expansion of CB precursors when cultured with an engineered Notch ligand, Delta1. I
hypothesize that culture of CB with Delta1 increases the no. of progenitors that rapidly engraft in the
thymus and accelerate T cell recovery after CBT. Design: Sorted CD34+CD38- CB cells were cultured for
28d on immobilized Delta1 in serum free media with Il3, Il6, Flt3l, SCF and TPO. Sub-lethally irradiated
(275cGy) NOD/SCIDc-/- mice received 103 non-cultured (NC) CB cells or the progeny of 10 3 Delta1–
cultured (DC) or IgG-cultured (IgG) cells. We evaluated bone marrow (BM), thymus and blood samples for
human CD45+ cells by FACs at various times after HCT . Results: CB cells cultured with Delta1 increased
the total no. of cell by 103-fold. 2 and 4 wks after HCT, BM from recipients of DC cells showed an 18-and
3-fold increase, respectively, in the no. of human CD45 + cells compared to recipients of NC cells (p<0.05).
4 wk after HCT, thymuses from recipients of DC cells had a 9-fold increase in the no.of human CD45 +
cells compared to recipients of NC cells (p<0.05). 6 and 8 wks after HCT, blood samples from recipients of
DC cells contained 9- and 3-fold higher no. of CD3+ cells compared to recipients of NC cells (p<0.04).
Furthermore, data suggest that DC cells facilitated engraftment of NC cells in the BM and thymus. Mice
received 103 NC cells along with 106 DC cells (NC+DC) or103 NC cell along with 106 IgG cells (NC+IgG).
The NC+DC group had 20-and 5-fold higher no of BM and thymic cells, respectively, compared to the
NC+IgG (p<0.05). Despite injecting the same no. of NC cells, there was a 4-fold increase in the no. of
human CD45+ cells derived from the NC cells in the group that received DC cells compared to IgG cells.
Conclusions: Culturing with Delta1 increases the no. of progenitors that rapidly engraft in the thymus and
hasten T cell recovery after CBT. Furthermore, data suggest that DC CB cells facilitate BM and thymic
engraftment by NC CB cells. This report describes a novel and clinically feasible ex-vivo culture system
using Delta1 for the generation of progenitors as a means to accelerate initial T-cell recovery after HCT.