Cytokines as an adjuvant to tumor vaccines: efficacy of local methods of delivery.

BACKGROUND: We examined alternative methods of delivering cytokines as an adjunct for priming lymph node (LN) cells draining sites of vaccine inoculation for the purpose of generating immune cells for adoptive immunotherapy. METHODS: Using syngeneic murine tumors we examined the ability of IL-2, IL-4, or GM-CSF delivered locally to a site of tumor inoculum to induce antitumor reactive draining LN cells. Mice were inoculated subcutaneously with tumor cells transduced to secrete cytokine; tumor cells admixed with fibroblasts transduced to secrete cytokine; or intralesional inoculation of cytokine in established tumor to induce sensitized LN cells capable of mediating tumor regression in adoptive transfer. RESULTS: Both IL-4 and GM-CSF cytokines were effective in enhancing the antitumor reactivity of vaccine-primed LN cells compared to IL-2, which was ineffective. The local delivery of GM-CSF by autocrine or paracrine secretion of genetically engineered cells, as well as direct intratumoral delivery was capable of upregulating LN sensitization compared to systemic administration, which did not. CONCLUSIONS: The local delivery of GM-CSF as an adjuvant for tumor vaccination can be accomplished by various methods, including direct injection, which avoids the need for gene transfer.

Characteristics and in vivo homing of long-term T-cell lines and clones derived from tumor-draining lymph nodes.

Lymph nodes draining a progressively growing tumor contain T-cells which can be activated sequentially by anti-CD3 and IL-2 to differentiate into tumor-specific effector cells. In this study, long-term cultured T-cell lines were established from activated MCA 106 tumor-draining lymph node cells by periodic stimulation with irradiated tumor cells in the presence of low concentrations of IL-2 (< or = 60 International units/ml). Such long-term cultured cell lines maintained therapeutic effects when transferred to tumor-bearing mice. Although the initial anti-CD3/IL-2-activated T-cells displayed a broad distribution of T-cell antigen receptor beta chain variable region (V beta) usages, long-term cultured cells were dominated by T-cells expressing a few V beta elements. Of six cell lines, only three V beta phenotypes (V beta 5, 11, 13) were identified, and individual cell lines frequently expressed a single V beta gene product. Despite restricted V beta expression, each cell line mediated tumor-specific reactivity in adoptive immunotherapy. Many T-cell clones were isolated from long-term cell lines. Three V beta 13 T-cell clones demonstrated specific in vivo antitumor effects, whereas two V beta 11 and two V beta 5 clones revealed a significant degree of cross-reactivity against the antigenically distinct MCA 205 tumor. Although the initial anti-CD3/IL-2-activated cells lacked demonstrable cytotoxic reactivity, T-cell clones derived from them exhibited cytotoxic effects to the MCA 106 tumor cells. The specificity of the cytotoxicity mediated by each clone reflected its in vivo antitumor effects. Furthermore, studies of in vivo localization of cloned T-cells demonstrated tumor-specific infiltration of the 5A2 (V beta 13) clone to the MCA 106 tumor metastases, whereas clone 9H6 (V beta 5) revealed some accumulation in the MCA 205 tumor. Again, the in vivo antitumor effects of the 9H6 clone correlated with its in vivo infiltration into the specific MCA 106 and the nonspecific MCA 205 metastases. Taken together, the long-term culture of anti-CD3/IL-2-activated tumor-draining lymph node cells resulted in selective expansion of a few T-cells as evidenced by the limited T-cell receptor V beta expression. Our results also demonstrated that systemically administered antitumor T-cell clones gained access and accumulated at metastatic tumor sites, and the degree of infiltration correlated with the specificity of the in vivo antitumor effect as well as the in vitro cytotoxic activity.

Stimulation of tumor-draining lymph node cells with superantigenic staphylococcal toxins leads to the generation of tumor-specific effector T cells.

In animal studies, lymph nodes (LN) draining progressive tumors contain immunologically sensitized but functionally deficient T cells. These preeffector cells can differentiate into mature effector cells on stimulation in vitro with anti-CD3 and IL-2. However, anti-CD3 react with all T cells and the activated cell population expressed a broad but normal distribution of V beta phenotypes. In this study, we examined the feasibility of using bacterial superantigens to stimulate tumor-draining LN cells. Because of their TCR V beta restriction, superantigen activation may afford a means to identify T cell subsets that are important in the antitumor immune response. Stimulation of draining LN cells with staphylococcal enterotoxins A (SEA) or B (SEB) followed by culture in IL-2 resulted in selective activation and expansion of V beta 3 and V beta 11 or V beta 3 and V beta 8 T cells, respectively. However, in adoptive immunotherapy, SEB- but not SEA-activated cells mediated the regression of established pulmonary metastases. To define the relative antitumor effects of V beta 3 and V beta 8 T cells, SEB-activated cells were depleted of either V beta 3 or V beta 8 T cells with mAb and magnetic beads. The antitumor effects were demonstratably diminished after V beta 8 cell depletion but enhanced after V beta 3 cell depletion. Using antigenically distinct MCA 205 and 207 sarcomas, tumor regression mediated by the activated cells was found to be immunologically specific for the tumor that stimulated the draining LN. Furthermore, the SEB-activated cells were virtually all T cells consisting of approximately equal proportions of CD4+ and CD8+ cells and the collaboration of the two T cell subsets was required for in vivo antitumor effects. However, the helper function of CD4+ cells could be facilitated by the administration of exogenous IL-2. Despite their in vivo antitumor reactivity, SEB-activated cells did not exhibit tumor cytotoxicity in the 4-h 51Cr release assay. However, they secreted IFN-gamma on specific stimulation with tumor cells. Taken together, these results provide for the first time clear evidence of the functional significance of superantigen interactions with immunologically committed T cells and suggest a preferential V beta use that might be associated with the T cell immune response to progressively growing tumors.

Cross-reactivity of anti-CD3/IL-2 activated effector cells derived from lymph nodes draining heterologous clones of a murine tumor.

Cells from lymph nodes (LN) draining progressively growing tumors can differentiate into immune effector cells upon in vitro stimulation with anti-CD3 monoclonal antibodies followed by interleukin-2. The adoptive transfer of these activated LN cells to tumor-bearing mice mediates potent tumor-specific therapeutic effects. In this study, we sought to further characterize the antitumor efficacy and specificity mediated by the anti-CD3/IL-2 activated tumor-draining LN cells against heterologous clones derived from the murine MCA 106 sarcoma. Ten clones of divergent characteristics with regard to morphology, in vivo growth rate, ability to establish pulmonary metastases, MHC class I (H-2) antigen expression, susceptibility to lysis by allogeneic cytotoxic T-lymphocytes, as well as sensitivity to doxorubicin were selected and analyzed. In adoptive immunotherapy experiments, pulmonary metastases derived from each clone were found to be sensitive to the therapeutic effects of activated cells derived from LN draining the parental MCA 106 tumor. The antigenic cross-reactivity was evident from the observation that activated cells from LN draining each of the individual tumor clones were capable of mediating the regression of parental tumor metastases. The specificity of the antitumor reactivities mediated by LN cells draining MCA 106 clones was demonstrated by a lack of in vivo efficacy against metastases derived from the antigenically distinct MCA 205 sarcoma. Additionally, selected clones were tested for their ability to stimulate draining LN against other cloned tumors or used as targets for therapy with activated LN cells draining different clones. In all 29 adoptive immunotherapy experiments, there was complete cross-reactivity between different MCA 106 tumor clones. These findings suggest that the MCA 106 tumor-specific antigen(s) that stimulates draining LN in vivo and recognized by the anti-CD3/IL-2 activated cells is present on most if not all tumor cells. However, in the absence of a demonstrably resistant tumor clone, a very highly polymorphic antigen with many cross-reactive, but distinct epitopes might be operative and attributable to these observations.