Chimeric Antigen Receptor Engineered Allogeneic Cd27-Negative T Cells For The Treatment Of Cd19+Leukemia

3046 Background: Relapsed/refractory pediatric acute lymphoblastic leukemia (ALL) has a poor prognosis. Adoptive immunotherapy with chimeric antigen receptor (CAR) engineered T cells targeted against a tumor associated antigen, such as CD19 on B-lineage leukemia, has shown immense promise in this patient population. An important aspect of CAR therapy is the source of effector cells, autologous or allogeneic. A barrier to using allogeneic T cells is that the naïve subset may lead to graft-versus-host disease (GVHD). A potential strategy to circumvent this would be to use surface markers such as CD27 to distinguish between naïve and memory T cells. CD27 is present on naïve and central memory T cells, but not on effector memory and terminal effector memory T cells. Our objectives were to determine if allogeneic CD27- cells provide superior immunologic memory against pathogens commonly encountered in patients with refractory ALL and have decreased alloreactivity potential compared to CD27+ cells. We also sought to assess the cytotoxic potential of CD27- cells transduced with an anti-CD19 CAR vector against CD19+ leukemia cells. Methods: CD27- and CD27+ cell fractions were isolated from donor PBMC using magnetic microbead separation. Lymphocyte proliferation assays were performed to determine immunologic memory to antigen and mitogen stimuli. Alloreactivity potential was tested using one-way mixed lymphocyte reactions. CD27- cells were transduced with an anti-CD19 CAR and their cytotoxicity against a CD19+ leukemia cell line was determined in vitro via BATDA assay and in vivo in NSG mice. Results: CD27- cells had stronger immunologic memory against pathogens and were less alloreactive than CD27+ cells. CD27- cells expressing an anti-CD19 CAR demonstrated potent killing of a CD19+ leukemia cell line compared to untransduced CD27- cells, both in vitro and in vivo. Conclusions: CD27- allogeneic cells provide pathogen protection, have low GVHD potential and, when transduced with an anti-CD19 CAR, have cytotoxic capability against CD19+ leukemia cells. These findings make CD27- T cells a promising population to be used as effector T cells in CAR therapy, providing dual infection and leukemia control.