An attenuated strain of Salmonella typhimurium, SL3235, developed as a prototypic typhoid vaccine, is shown to retard growth of a murine plasmacytoma, TEPC-183, and to prolong survival of tumor-bearing mice. Live salmonella, but not acetone-killed organisms, had antitumor activity. The immunotherapeutic effect was demonstrable when the tumor was injected intralesionally or intraperitoneally. Increased survival, longer mean time to death, and retardation of tumor growth were found when the salmonella were given intralesionally as late as the sixth day post-tumor injection. Timing of salmonella inoculation, as well as the salmonella dose, had an effect on treatment efficacy. Injection of salmonella intraperitoneally exerted a strong antitumor effect when given as late as the third day post-tumor inoculation. The highest dose (2 x 10(6)) of salmonella was less effective than doses 10- or 100-fold lower. TEPC-183 plasmacytoma is rapidly growing and highly immunosuppressive, so the ability of the salmonella to exert therapeutic activity against it is a measure of the potency of the vaccine. These observations are of interest, as they show that a genetically engineered, avirulent strain of Salmonella has immunotherapeutic properties similar to those of BCG and other biological response modifiers, and might have clinical potential as an antitumor agent.

Culture supernatants of Legionella pneumophila, Philadelphia 1, were found to have proteolytic activity, as well as a nondialyzable, heat‐labile cytotoxin for Chinese hamster ovary (CHO) cells, and a factor which caused hemorrhagic dermal ulceration when injected intradermally into mice. A protease was purified from culture supernates by filtration on Sephacryl S‐200 followed by chromatography on DEAE cellulose. Proteolytic activity had a pH optimum of 5.5, and migrated as two bands in PAGE, with molecular weights of 42 and 31 kDa. CHO cell cytotoxic, dermal ulcerative, and proteolytic activities copurified. The results are consistent with the same protein being responsible for these activities.