Antitumor immunity. II. Viability, tumorigenicity, and immunogenicity of neuraminidase-treated tumor cells: effective immunization of animals with a tumor vaccine.

A dimethylbenzdithionaphthene (DBDN)-induced fibrosarcoma showed reduced transplantability if previously treated with Vibrio cholerae neuraminidase (VCN). However, the reduced transplantability of VCN-treated tumor cells was not associated with any loss of their viability or tumorigenic capability, but appeared to be due to their increase in immunogenicity. High doses of VCN-treated tumor cells could grow even in normal individuals. Lower doses, which did not induce tumor development in normal individuals, did so if injected into immunosuppressed animals. Although X-irradiation of VCN-treated tumor cells reduced their tumorigenic potential, it did not impair their increased immunogenic properties. Thus a suitable method for the preparation of a "tumor vaccine" was provided. The immunization of animals with the vaccine and a working hypothesis regarding its mechanism of action were described.