Novel method for effectively amplifying human peripheral blood T cells in vitro

The use of chimeric antigen receptor-modified T cells (CAR T cells) is an effective therapy for advanced cancer, especially hematological malignancies, and this method has attracted widespread attention in the last several years. The type, number and vitality of the effector cells clearly play important roles in this approach. In this study, to expand the possibility of curing cancer through adoptive cell therapy (ACT), we developed a novel method for effectively obtaining abundant T cells in vitro. The fusion proteins of three cytokines, SA-hIL-2, SA-hIL-7 and SA-hIL-21, were anchored onto biotin magnetic beads to increase the number of cytokines on the surface of the magnetic beads, which increased the local concentration of cytokines and thus promoted the binding of cytokines to T cells. Next, we examined the effects of these modified magnetic beads on the proliferation rate of T cells and CD19 CAR T cells. In this study, we report the expression and purification of the active bifunctional fusion proteins SA-hIL-2, SA-hIL-7 and SA-hIL-21, which were bound to biotin magnetic beads to develop a platform that was employed to increase the local concentration of cytokines. When the cells had been cultured for 14 days, the proliferation rate of the CD3⁺ T cells in the group that received cytokine-coupled biotin magnetic beads (Beads-SA-CK) was higher than that of the cells in the groups that received soluble cytokines (Soluble-SA-CK) and that of the cells in the standard group (Standard-CK). We speculate that this difference may be the result of the increased expression of Bcl-2 and the increased phosphorylation of Stat5. Moreover, our results preliminarily indicate that compared with the other two treatments, Soluble-SA-CK and Standard-CK, adding cytokine-coupled biotin magnetic beads more effectively increases the proliferation rate of CD19 CAR-T cells. As expected, the CD19 CAR-T cells stimulated by Beads-SA-CK had a stronger anticancer effect than the cells stimulated by the other two treatments. An effective method of preparing abundant T cells in vitro was developed, and it may provide a novel strategy for ACT.