A genetically engineered single-gene-encoded anti-TAG72 chimeric antibody secreted from myeloma cells.

SP2/0Ag14 murine myeloma cells transfected with the expression vector mpSV2neo-EP-FV-CH2-3-PA containing the single gene FV-CH2-3 secreted a single-gene-encoded chimeric antibody molecule FV/M4. This single-chain protein consisted of the heavy- and light-chain variable (VH and VL) domains covalently joined through a flexible linker peptide, while the carboxyl end of VL domain was connected to the amino terminus of hinge region of the ccM4 heavy-chain. Our data showed that the FV/M4 retained both its immunoreactivity for tumor-associated TAG72 antigen and its cytolytic activity to tumor cells as did the parental ccM4 antibody. Therefore, this single-gene-construct approach circumvents inefficiencies inherent in delivering two genes into a mammalian cell for assembly of a functional chimeric antibody and provides an alternative for construction of chimeric antibodies. It is particularly attractive for ex vivo transfection of cells from patients for certain gene-therapy modalities not only for cancer but also for a range of diseases in which immunotherapeutic approaches are used.