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

Local production of cytokines by genetically engineered tumor cells decreas es their tumorigenicity and elicits protective immune responses against the parental tumor cells. An alternative approach to elicit a therapeutic immu ne response is to use fusion proteins that can target tumor cells and simul taneously activate effector cells. Fusion proteins between human IL-2, muri ne or human GM-CSF, and sFv of antihuman carcinoma antibody L6 have been co nstructed, 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, fac tor-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 prolifera tion of the indicator cells was found to be comparable to that of recombina nt hIL-2, mGM-CSF, or hGM-CSF. Turner cells coated with L6 sFV-mGM-CSF or L 6 sFv-hGM-CSF were also tested in this way and were found to be potent stim ulators, indicating that the cytokines were functionally active when bound to the tumor cell surface. This work demonstrates the feasibility of target ing sFv-cytokine fusion proteins for the activation of effector cells as an alternative to cytokine gene therapy.