Sensitization of human tumor cells to homologous complement by vaccinia virus treatment

Although cell membranes have potent inhibitors which protect the activation of complement on the self cell membranes, some viruses have been shown to activate complement via the alternative pathway on the virus-infected cells. Tumour cells have been made reactive to homologous complement following treatment with such viruses and became highly immunogenic to syngeneic host guinea pigs and mice. Vaccinia virus (VV) made murine tumour cells highly immunogenic thus generating complement activating capacity on the infected cells. Since it has been suggested that VV can make some human tumour cells immunogenic to the cancer patients, we examined VV to see if the virus also has the capacity to make human tumour cells reactive with homologous human complement. Our present results indicate that not only is this the case but ultraviolet-treated VV also has the same effect.