T CELL ACTIVATION FOR CANCER IMMUNOTHERAPY

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Our laboratory has focused on the generation of tumor reactive T cells derived from lymph nodes (LNs) primed by progressive tumors or by tumor vaccinations. Based upon extensive animal studies, we have shown that these tumor-primed LNs can be secondarily activated in vitro by anti-CD3 mAb, as a surrogate antigen, and expanded in IL-2 for subsequent adoptive immunotherapy. These anti-CD3 activated cells mediate immunologically specific tumor regression. This culture method preferentially activates CD8+ cells which have been found to mediate the antitumor responses in vivo; without the requirement of CD4+ cells. These effector cells appear to manifest their antitumor effects by the release of type 1 cytokines (ie. IFNgamma and GM-CSF) in response to tumor antigen. By contrast, effector cells which release type 2 cytokines (ie., IL-10) do not mediate tumor regression in vivo. More recently, we have found that we can further stimulate tumor- primed LN cells with the addition of anti-CD28 mAb as a co- stimulatory signal. This has resulted in enhanced cytokine release in response to tumor antigen. In addition, we have observed the preferential activation of CD4+ tumor reactive T cells utilizing this culture procedure when purified CD3+ cells are activated as opposed to the unfractionated LN population. These findings indicate at the components of the cell population and the in vitro activating conditions can have a profound effect on the subsequent cell population which is generated. Our preliminary results provide us with methods to examine the role of CD4 versus CD8+ T cells in adoptive immunotherapy; and to determine if enriched subpopulations of T cells with tumor reactivity can be selectively cultured. We propose the following specific aims: l) To examine the antitumor reactivity of tumor-primed LN cells after in vitro activation with anti-CD3 mAb and co-stimulation with anti-CD28 mAb; 2)To examine the antitumor reactivity of tumor-primed LN cells after in vitro activation with anti-Vbeta mAbs and co-stimulation with anti-CD28 mAb; 3) To examine the effect of different cytokines during the in vitro activation of tumor-primed LN cells on the maturation of pre- effector cells and; 4) To examine other co-stimulatory signals on the in vitro activation of tumor-primed LN cells (i.e. anti-CD40 or anti-41BB). The objectives of these aims are to provide us with a better understanding regarding the cellular effector mechanisms involved in the immune destruction of tumor, and to selectively activate and expand pre-existing tumor-reactive T cells present at low frequencies.