A SPACER REGION BETWEEN THE SINGLE-CHAIN ANTIBODY-CHAIN AND THE CD3 ZETA-CHAIN DOMAIN OF CHIMERIC T-CELL RECEPTOR COMPONENTS IS REQUIRED FOR EFFICIENT LIGAND-BINDING AND SIGNALING ACTIVITY

The elimination of tumor cells by cytotoxic T lymphocytes (CTLs) could become the basis of a biological cancer therapy. The recognition spec ificity of cytotoxic T lymphocytes (CTLs) can be genetically modified by stable introduction of chimeric T cell receptor genes and thus be d irected towards tumor cells. We designed a recombinant T cell receptor (TCR) component consisting of a single chain Fv derivative of a monoc lonal antibody (scFv) serving as the extracellular antigen-binding dom ain and the zeta-chain of the TCR/CD3 complex serving as a signal tran sducing domain. Three chimeric receptor constructs differing in their molecular structure were derived and their functions in transduced T c ells compared. A construct in which the scFv domain, specific for the ErbB-2 receptor, was fused directly to the zeta-chain, and two constru cts containing different hinge regions between the functional domains, were made. The hinge regions serve as spacers which increase the dist ance of the scFv moiety from the plasma membrane. Only the two scFv-ze ta chimeras containing a hinge region showed ErbB-2 binding activity, when expressed in T cells. The scFv-zeta construct which lacks a space r segment did not. Consistently, only the spacer-containing chimeras t ransduced T cell receptor signals following ErbB-2 mediated crosslinki ng. An increase in intracellular Ca2+ concentrations and cytokine secr etion was observed. ErbB-2 expressing tumor cells were efficiently lys ed by CTLs which expressed th spacer-containing scFv-zeta chimeras. Ou r results will help to optimize the design of recombinant T cell recep tor components useful in the grafting of a specificity of are cognitio n on to cytotoxic T cells and possibly the gene therapy of cancer.