No abstract

Chimeric receptor (CR)-redirected lymphocytes (T bodies) have great potential in the eradication of tumor cells. To extend this approach to target cells that do not express surface ligands to costimulatory receptors (eg, cancer cells), we have generated an antibody-based tripartite chimeric receptor (TPCR) that contains scFv linked to the costimulatory molecule, CD28 without its ligand-binding domain, and to the cytoplasmic moiety of the FcR␥ subunit. In this study, we tested the ability of 2,4,6-trinitrophenyl (TNP)-specific TPCR to drive primary, naïve T cells derived from CR-transgenic (Tg) mice to undergo full activation. As a control, we used Tg mice expressing a similar transgene but lacking the signaling region of CD28 (Tg-TPCR⌬CD28). Only T cells from the TPCR-Tg and not the CD28-truncated TPCR-Tg mice could undergo activation following stimulation on hapten-modified target cells not expressing B7. Moreover, when stimulated with TNP protein displayed on plastic, the TPCR-Tg T cells expressing the entire TPCR gene became fully activated for proliferation, interleukin 2 production, protection from apoptosis, and killing of TNP-modified target cells. Finally, TPCR-Tg mice manifested a delayed-type hypersensitivity response following skin challenge in the absence of priming. Taken together, our results suggest that the TPCR is the receptor configuration of choice for clinical applications using primary T or stem cells. IntroductionThe chimeric receptor (CR) approach has been designed 1 to redirect the specificity of effector lymphocytes toward a variety of clinically important targets such as tumor or virally infected cells. The CR is based on an artificial immune receptor composed of an extracellular antigen-binding domain (usually in the form of single-chain variable region fragment [scFv] derived from an antibody or T-cell receptor [TCR]) linked through a transmembrane motif to a cytoplasmic lymphocyte-signaling moiety (eg, TCR/ CD3-or FcR␥ immune receptor tyrosine-based activation motifs [ITAMs]). Using an antibody-derived scFv as the recognition unit enables the nonmajor histocompatibility complex (MHC)-restricted specificity of the humoral arm of the immune system to be combined with the efficient homing, extravasation, and target rejection mediated by the cellular arm of the immune system. Indeed, such CR genes when expressed in T cells were found to be functional, and on encountering their antigens, to induce lymphokine production and cytolysis by the recipient cells. [2][3][4] As such, effector lymphocytes armed with CR hold promise for the adoptive therapy of various cancers and HIV-infected cells, and several clinical trials have been initiated to evaluate this potential. 5,6 The first configuration of single-chain CR was composed of 2 functional moieties-an extracellular recognition unit and an intracellular signaling domain. 7,8 This configuration is active when expressed in preactivated T cells or when used against target cells that express the surface B7 marker (CD80 or CD86). Because, in ad...