Redirected Activity of Human Antitumor Chimeric Immune Receptors is Governed by Antigen and Receptor Expression Levels and Affinity of Interaction

Abstract

Novel Ab-based immunotherapeutic strategies have exploited T-cell receptor-like chimeric immune receptors (CIR) expressed on the surface of transduced human peripheral blood mononuclear cell (PBMC) to redirect potent non-major histocompatibility complex-dependent cytotoxicity to tumor cells expressing a tumor-associated antigens. We transduced human PBMC with 2 fully human CIRs that trigger through the zeta-chain of CD3 and contain either one of two human scFv specific for the same epitope on the extracellular domain of HER2 but with distinctly different affinities (KD 1616 and 1 nM) for this antigen. Potent direct CIR-mediated killing and in vitro tumor growth inhibition mediated by transduced PBMC were observed against targets expressing different levels of HER2. High-affinity CIR showed stronger ability to bind Ag and retain binding than low-affinity CIR. When lytic potential of the 2 CIRs was evaluated, their efficiency was comparable under conditions of high CIR and Ag expression, whereas low-affinity CIR was more efficient than high-affinity CIR in conditions of limiting Ag and CIR expression levels. When tumor growth inhibition was evaluated, Ag and CIR levels, rather than CIR affinity appeared relevant. Ag-driven CIR activation resulted in the production of soluble factors mediating efficient bystander effect. By carefully defining CIR surface expression and increasing affinity for a specific target antigen, it may be possible to selectively exclude CIR-mediated activity against targets expressing low levels of antigen, as normal cells. On the contrary, low antigen-expressing tumor variants could be eliminated by decreasing CIR affinity. Tuning CIR expression and affinity might help in discriminating different biologic contexts.

Novel CD4-Based Bispecific Chimeric Antigen Receptor Designed for Enhanced Anti-HIV Potency and Absence of HIV Entry Receptor Activity

“…4). These results suggest that the advantages of serial engagement initially proposed for TCR-peptide/ MHC interaction can also apply to CARs, as has been proposed by others for CARs against cancer (71,72,73) as well as HIV (37).…”

Target Antigen Density Governs the Efficacy of Anti–CD20-CD28-CD3 ζ Chimeric Antigen Receptor–Modified Effector CD8+ T Cells

“…Because the threshold may be influenced by many other factors, such as affinity (42), structure (43), epitope localization of individual CAR-Ag pairs (44,45), and the expression of a coreceptor on target cells (46), the threshold may vary among mAbs and target Ags. We also could not investigate the relationship between the expression of CD20 and the ADCC activity of mAbs because NK cell activity is predominant in the CD20-CEM system, and a clear threshold has not been observed (28).…”

HER2/neu: an increasingly important therapeutic target. Part 1: basic biology & therapeutic armamentarium

“…Although this provided proof-of-principle for imparting functional capacity to T-lymphocytes enabling them to recognize and respond to the HER2/neu antigen, electroporation and the use of T-cell hybridomas was not readily translatable to the clinical arena. The development of retrovirus/lentivirus vectors provided for more efficient transduction of T-lymphocytes and NK cells [272][273][274][275][276][277][278][279][280]. Various groups have sought to refine the CAR constructs, including tuning affinity of the HER2/neu antigen-recognition domain [275], utilizing the T-cell receptor peptide recognition domain instead of an antibody-based recognition domain [281] and incorporation of costimulatory elements [282] within the construct.…”

“…The development of retrovirus/lentivirus vectors provided for more efficient transduction of T-lymphocytes and NK cells [272][273][274][275][276][277][278][279][280]. Various groups have sought to refine the CAR constructs, including tuning affinity of the HER2/neu antigen-recognition domain [275], utilizing the T-cell receptor peptide recognition domain instead of an antibody-based recognition domain [281] and incorporation of costimulatory elements [282] within the construct. With the identification of Heregulin as a ligand for heterodimers involving HER3 or HER4, including those with HER2/neu, a chimeric ligand molecule (heregulin and intracellular signaling component from the CD3 ζ-chain) was developed [283].…”