An approach to C-type virus immunoprevention of spontaneously occurring tumors in laboratory mice.

A review of our current progress in C-type virus vaccine research is presented. This includes the findings of C-type virus or its antigen expressions in every naturally occurring tumor of two strains of "low-incidence" laboratory mice, the BALB/cCr mouse and the NIH Swiss mouse. Vaccine preparation methods are described including the inactivation of C-type virus infectivity with optimal maintenance of the antigen titers of at least two of the polypeptides of the C-type virus, gp69/71 and p30. The cell-mediated immune response of the mouse to C-type virus vaccines, as measured by a footpad assay for delayed-type hypersensitivity and an in vitro lymphocyte transformation assay, is described. Studies with two murine C-type viruses (Rauscher leukemia and Gross leukemia) a simian C-type virus, and an avian C-type virus (avian myeloblastosis virus) showed that the cell-mediated immune response of the animal includes type-specific, group-specific, and interspecies-specific reactivity. The mouse gave a cell-mediated immune response to at least one of the polypeptides of the C-type virus, the gp69/71, whether this polypeptide was presented to the immune system of the mouse as whole virus, Tween-ether-treated virus, or a purified polypeptide. One measure of the effectiveness of the C-type virus vaccines was provided by immunization of the mouse with Rauscher leukemia virus preparation that induced resistance to challenge with both live Rauscher leukemia virus and a naturally occurring BALB/c leukemia virus. Evidence is presented that the C-type virus can act as an effective transplantation antigen in syngeneic tumor cell lines resulting in the immunogenicity and loss of tumorigenicity of these cell lines. An approach to the viral immunoprevention of spontaneously occurring tumors is discussed.