HA22 and BL22-derived CD22 CARs mediate similar lytic activity. (A) The lytic activity HA22 and BL22-derived CD22 CARs in the context of second and third-generation signaling constructs was compared against ALL cell lines at the indicated E:T ratios in a 4-hour 51Cr-release assay. SEM of triplicate wells is shown. The first row compares binding affinity of the scFv (BL22 versus HA22-derived) in second-generation vectors, the second row makes the comparison in the third-generation vectors, and the third row compares vectors with and without CH2CH3 domains (HA22-28z versus HASH22-28z). (B) Comparison of signaling domain structure on vector formats using REH, SEM, NALM-6, and KOPN-8 cell line targets. Lytic activity is expressed in lytic units, which corrects for transduction efficiency, at an E/T ratio of 10:1. Significant differences are noted, using an unpaired student t test. (C) Increasing concentrations of CD22-Fc, as designated on the x-axis, were added to triplicate wells in a 4-hour lytic assay using REH as the target and an E:T of 10:1. CD19-CAR, dashed line, served as a negative control. Assays were repeated 3 times with similar results.
