Increased resistance to tumor graft in mice infected by vaccinal strains of Brucella abortus.

Kinetics of proliferation in vivo and the effect on murine tumors of the vaccinal strain Brucella abortus B19 and two derivatives, 19BA and B19R, were studied. Inocula of 5 x 10(6) organisms of each strain produced comparable infections peaking on day 8. Several protocols of Brucella treatment yielded favorable results in EL4 lymphoma and Lewis tumor. The treatment for EL4 lymphoma seemed optimal 8--14 days after infection with 5 x 10(6) -- 5 x 10(7) organisms. In comparison with BCG, Brucella grew faster in vivo and accumulated more in the spleen. The effects of BCG and Brucella were comparable on EL4 lymphoma, but BCG was less effective than Brucella on Lewis tumor. The results encourage trials using live Brucella vaccine as an antitumor agent in man.