The T-body approach: redirecting T cells with antibody specificity.

"T-bodies" are genetically engineered T cells armed with chimeric receptors whose extracellular recognition unit is comprised of an antibody-derived recognition domain and whose intracellular region is derived from lymphocyte stimulating moiety(ies). The structure of the prototypic chimeric receptor, also known as a chimeric immune receptor, is modular, designed to accomodate various functional domains and thereby to enable choice of specificity and controlled activation of T cells. The preferred antibody-derived recognition unit is a single chain variable fragment (scFv) that combines the specificity and binding residues of both the heavy and light chain variable regions of a monoclonal antibody. The most common lymphocyte activation moieties include a T-cell costimulatory (e.g. CD28) domain in tandem with a T-cell triggering (e.g. CD3zeta) moiety. By arming effector lymphocytes (such as T cells and natural killer cells) with such chimeric receptors, the engineered cell is redirected with a predefined specificity to any desired target antigen, in a non-HLA restricted manner. Chimeric receptor (CR) constructs are introduced ex vivo into T cells from peripheral lymphocytes of a given patient using retroviral vectors. Following infusion of the resulting T-bodies back into the patient, they traffic, reach their target site, and upon interaction with their target cell or tissue, they undergo activation and perform their predefined effector function. Therapeutic targets for the T-body approach include cancer and HIV-infected cells, or autoimmune effector cells. To date, the most investigated area is cancer therapy. Here, the T-bodies are advantageous because their tumor recognition is not HLA-specific and, therefore, the same constructs can be used for a wide spectrum of patients and cancers.