CONSTRUCTION OF RECOMBINANT VACCINIA VIRUS EXPRESSING GM-CSF AND ITS USE AS TUMOR VACCINE

We made several generic plasmids for construction of recombinant vacci nia virus (rvv) expressing foreign proteins in high yield. Rvvs expres sing biologically active Escherichia coli beta-galactosidase (rvv-lacZ ) and the cytokine murine GM-CSF (rvv-mGM-CSF) were constructed by usi ng these plasmids. To obtain attenuated rvv, cDNA for these proteins w as inserted in the thymidine kinase gene of vaccinia virus. Their expr ession was controlled by vaccinia early/late promoter, 7.5 K so that t hese proteins could be expressed in the infected cells throughout the life cycle of the virus. Female C57BL/6 mice were immunized subcutaneo usly with B16-F10 melanoma cells infected with rvv, and 2 weeks later challenged with viable B16 cells. Mice immunized with rvv-mGM-CSF show ed delay in tumor development, smaller tumor volumes and longer surviv al time compared with unimmunized mice, as well as mice immunized with rvv-lacZ. Mice immunized with rvv-mGM-CSF followed by a booster injec tion after 1 week responded slightly better than those immunized once, but this difference was not statistically significant. These results suggested that rvv-mGM-CSF could be a promising vaccine for cancer the rapy.