Assessment of in vitro and in vivo persistence of different forms of IL-15 expressed in primary human cord blood NK cells. (A) Scheme of various constructs, each containing luciferase as well as tCD19 to serve as a parental control. Of the 4 constructs, 3 contain IL-15: sIL-15, sIL-15c, and mIL-15. The transgenes are separated by a P2A or T2A sequence, as indicated. (B) The transduction efficiency of each construct in NK cells was represented by the coexpressed tCD19. (C) A scheme of validating the persistence of the transduced NK cells in vivo. Human NK cells (4 × 106 cells per dose) that carry the luciferase gene with or without the various forms of IL-15 were administered into NSG mice via tail vein injection. NK persistence was monitored by bioluminescence imaging (BLI) (n = 4 mice per group). (D) Ventral BLI was performed on days 0, 2, 4, and 8 to monitor NK cell persistence. Due to an accident in operation, 1 mouse of sIL-15c was found dead before imagining on day 8. (E) Quantification of the ventral bioluminescence images. Data are shown as mean ± SEM; ∗∗∗P < .001. TM, transmembrane.
