The tumor recall response of antitumor immunity primed by a live, recombinant Listeria monocytogenes vaccine comprises multiple effector mechanisms

Listeria monocytogenes, a facultative intracellular bacterium, can induce a potent antitumor immune response if engineered to express a model tumor an tigen also expressed by the tumor cells. The effectiveness of this approach is dependent on L. monocytogenes-induced tumor-specific CD4(+) and CD8(+) T-cells, CD8(+) T-cells may mediate tumor eradication largely through direc t CTL activity, but the role of CD4(+) T-cells and other cells of the immun e system is less clear. Here we investigate their role and the role of the cytokines they produce in the ability of L, monocytogenes-induced antitumor immunity to protect against tumor challenge. Our results suggest that a co mplex cytokine response, involving type 2 as well as type 1 cytokines, is r esponsible for the ability of Lm-NP-immunized mice to resist tumor challeng e, potentially mediating tumor cell killing through multiple effector pathw ays. (C) 2001 Academic Press.