Protection of mice against cancer by immunization with membranes but not purified virions from virus infected cancer cells.

The life span of C57/Bl mice inoculated with Lewis lung carcinoma cells was prolonged if the mice were pre-immunized with membranes from these cells infected in vitro with influenza virus. Likewise, BALB/c mice were protected against the malignant tumour WEHI-11 by prior immunization with extracts of cultured WEHI-11 cells which had been infected with influenza virus or Semiliki Forest virus (SFV). Partially purified SFV grown in WEHI-11 cells also protected mice from cancer grafts but neither highly purified SFV nor the glycoprotein from the envelope of this virus protected the mice. It is concluded that SFV-induced immunopotentiation against cancer is not due to covalent linkage of tumour specific transplantation antigen (TSTA) to viral envelope protein but more probably is due to the apposition of viral glycoprotein and cellular TSTA in the plasma membrane of the cancer cell.