Anti-Idiotypic Antibody Facilitates scFv Chimeric Immune Receptor Gene Transduction and Clonal Expansion of Human Lymphocytes for Tumor Therapy

Abstract

Chimeric immune receptors (CIR) transduced into lymphocytes link target recognition by single chain antibody Fv (scFv) to activation through CD28/TCRζ signaling. As surrogate antigens, anti-idiotypic antibodies may facilitate gene-transduction and clonal expansion of human lymphocytes for in vivo tumor therapy. The murine monoclonal antibody (MAb) 8H9 reacts with a novel antigen widely expressed on solid tumors. A CIR consisting of human CD8-leader sequence, 8H9-scFv, CD28 (transmembrane and cytoplasmic domains), and TCR-ζ chain was constructed, ligated into the pMSCVneo vector, and used to transfect the packaging line GP + envAM12 bearing an amphotropic envelope. Rat anti-idiotypic MAb 2E9 (IgG2a) was used to clone retroviral producer line as well as to expand gene-modified primary human lymphocytes. Sequential enrichments using either affinity chromatography or cell sorting using anti-idiotypic MAb 2E9 significantly improved the percentage of producer clones positive for surface 8H9-scFv and the efficiency of their supernatant in transducing the indicator cell line K562. By 3 weeks of in vitro culture, >95% of transduced primary human lymphocytes were CIR-positive. Upon periodic stimulation with 2E9, these lymphocytes underwent >10⁶-fold expansion by 6 months in culture. They mediated antigen-specific non-MHC restricted cytokine release and tumor cytotoxicity, and inhibited human xenograft engraftment in SCID mice. Anti-idiotypic antibody may provide a useful tool for optimizing gene transduction of CIR fusion constructs into primary human lymphocytes and their continual expansion in vitro.