Low interleukin-2 concentration favors generation of early memory T cells over effector phenotypes during chimeric antigen receptor T-cell expansion

• Background. Adoptive T-cell therapy offers new options for cancer treatment. Clinical results suggest that T-cell persistence, depending on T-cell memory, improves efficacy. The use of interleukin (IL)-2 for in vitro T-cell expansion is not straightforward because it drives effector T-cell differentiation but does not promote the formation of T-cell memory. We have developed a cost-effective expansion protocol for chimeric antigen receptor (CAR) T cells with an early memory phenotype.Methods. Lymphocytes were transduced with third-generation lentiviral vectors and expanded using CD3/CD28 microbeads. The effects of altering the IL-2 supplementation (0-300 IU/mL) and length of expansion (10-20 days) on the phenotype of the T-cell products were analyzed.Results. High IL-2 levels led to a decrease in overall generation of early memory T cells by both decreasing central memory T cells and augmenting effectors. T memory stem cells (T-SCM, CD95(+)CD45RO(-)CD45RA(+)CD27(+)) were present variably during T-cell expansion. However, their presence was not IL-2 dependent but was linked to expansion kinetics. CD19-CART cells generated in these conditions displayed in vitro antileukemic activity. In summary, production of CART cells without any cytokine supplementation yielded the highest proportion of early memory T cells, provided a 10 fold cell expansion and the cells were functionally potent.Discussion. The number of early memory T cells in a T-cell preparation can be increased by simply reducing the amount of IL-2 and limiting the length of T-cell expansion, providing cells with potentially higher in vivo performance. These findings are significant for robust and cost:effective T-cell manufacturing.

Nyckelord

chimeric antigen receptor T cells

effector function

human

interleukin-2

T-cell expansion

T-cell memory

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