Augmented immunogenicity of tumor cell membranes produced by surface budding viruses: parameters of optimal immunization.

Membranes prepared from tumor cells infected with surface budding viruses are much more immunogenic than membranes from uninfected tumor cells. Factors affecting immunization with membranes from virus-infected tumor cells were studied. Preparations made with influenza virus were clearly superior to those prepared with vesicular stomatitis virus (VSV). Membranes infected with VSV were maximally immunogenic at a dose equivalent to a 10% cell pack whereas influenza-virus-infected membranes were immunogenic at 1/100th of this dose. Subcutaneous inoculation was better than other routes of administration. Maximum protection against challenge with viable tumor cells was afforded by two inoculations of VSV-infected membranes spaced 3 days apart or a single inoculation with influenza-virus-infected membranes. Administration of membranes in complete Freund's adjuvant either had no effect of induced a slight degree of tumor enhancement. Immunization with influenza-virus-infected membranes significantly reduced tumor size and incidence even at a challenge dose of tumor cells which was 50 times the LD100.