Background: Recombinant chimeric immune receptors (CIRs) with anti-CEA specificity can retarget grafted T-cells to CEA-expressing tumors in an HLA-independent manner. To reduce the immunogenicity of conventional CIR in humans, an attempt was made to generate a CIR encoded by all human genes.

Materials and methods: A single-chain variable fragmented (scFv) antibody gene was prepared from variable region genes of the C2-45 human mAb clone specific for CEA. The scFv gene was connected to a gene construct comprised of the cDNAs for the human CD8a hinge region, the human CD28 transmembrane and cytoplasmic domains, and the human CD3zeta intracellular domain. The resulting human CIR gene, designated L45scFv-CIR, was inserted into the pcDNA3.1 expression vector and transfected into human primary T-cells.

Results: Flow cytometric analysis using allophycocyanin-labeled CEA demonstrated the expression of the L45scFv-CIR protein on the T-cells and its specific antigen binding activity.

Conclusion: This L45scFv-CIR gene, consisting of four human genes, may be a useful tool for eradication of CEA-expressing but HLA-downregulated tumor cells.