Schematic representation of chimeric retroviral glycoproteins displaying an anti-CD3 scFv.

A cDNA encoding an scFv derived from the OKT3 monoclonal antibody raised against the human CD3 was fused to the amino-terminal end of the 4070A-MLV env gene, at a position corresponding to the first codon of the SU envelope subunit. A spacer, 7 amino acids long, was inserted between the scFv polypeptide and the envelope glycoprotein to minimize steric hindrances. The SU/TM cleavage site was inactivated by replacing the Lys-Tyr-Lys-Arg wild-type amino acid sequence by the IPe-Glu-Gly-Arg sequence. L indicates leader-signal peptide; ligand, anti-CD3 scFv polypeptide; SU, surface envelope subunit; TM, transmembrane envelope subunit.