Construction, expression, and characterization of anticarcinoma sFv fused to IL-2 or GM-CSF.

ABSTRACT

Local production of cytokines by genetically engineered tumor cells decreases their tumorigenicity and elicits protective immune responses against the parental tumor cells. An alternative approach to elicit a therapeutic immune response is to use fusion proteins that can target tumor cells and simultaneously activate effector cells. Fusion proteins between human IL-2, murine or human GM-CSF, and sFv of antihuman carcinoma antibody L6 have been constructed, expressed in both COS and Chinese hamster ovary (CHO) cells, and purified by affinity chromatography. The biologic activity of L6 sFV-hIL-2, L6 sFv-mGM-CSF, and L6 sFv-hGM-CSF was tested on human T cell blasts, factor-dependent FDCP-1, and TF-1 cells, respectively. The ability of soluble L6 sFv-hIL-2, L6 sFv-mGM-CSF, and L6 sFv-hGM-CSF to stimulate the proliferation of the indicator cells was found to be comparable to that of recombinant hIL-2, mGM-CSF, or hGM-CSF. Tumor cells coated with L6 sFV-mGM-CSF or L6 sFv-hGM-CSF were also tested in this way and were found to be potent stimulators, indicating that the cytokines were functionally active when bound to the tumor cell surface. This work demonstrates the feasibility of targeting sFv-cytokine fusion proteins for the activation of effector cells as an alternative to cytokine gene therapy.