Autologous adjuvant linked fibroblasts induce anti-glioma immunity: implications for development of a glioma vaccine

Summary Objectives: Adjuvant-linked vaccines have been shown to induce anti-tumor immunity in patients with a variety of solid tumors. In this study we describe anin vitro model of active immunotherapy using autologous fibroblasts as immunogen. Correlative results from glioma patients immunized with autologous fibroblasts are also described. Methods: Peripheral blood lymphocytes (PBLs) from normal subjects were immunizedin vitro against autologous skin fibroblasts coupled to the adjuvant muramyl dipeptide. The lymphocytes developed cell-mediated cytotoxicity that was measured with a short-term chromium release assay. Results ofin vitro experiments were compared to data derived from glioma patients immunized with subcutaneous injection of an autologous adjuvantlinked fibroblast vaccine. Glioma target cells and fibroblast immunogens were derived from early passage primary tissue culture. Results: A comparison of autologous vs. homologous immunogen indicated that major histocompatibility complex matching was required at the sensitization stage of immunity (17.2±3.4% specific lysis vs. 0.4±3.1%,P<0.01). Pre-treatment of fibroblast immunogen cells with interferon gamma (IFN-γ) was found to significantly increase immunity (42.2±10.0%,P<0.01), as did IFN-γ pre-treatment of tumor target cells (35.8±9.0%,P<0.01). The positive effect of IFN-γ was diminished by treatment of cells with IFN-α. Thesein vitro results correlated well within vivo data derived from glioma patients immunized with an autologous adjuvant-linked fibroblast vaccine. PBLs from patients developed direct cell-mediated cytotoxicity against autologous tumor cells. Lysis of tumor targets afterin vivo immunization increased over a three-week interval (from 1.2 ± 3.0% to 21.0 ± 3.4%,P < 0.01) while lysis of a non-MHC matched control cell line remained essentially unchanged. Conclusions: Specific lysis of glioma targetsin vitro was achieved afterin vivo sensitization with autologous adjuvant-linked fibroblasts. Collectively, the data indicate that biochemically modified autologous cells can stimulate anti-glioma immunity in humans. The degree of specific immunity seen in our patients compares favorably with other published series using glioma cells as an antigenic source. Accordingly, fibroblasts may represent a practical alternative to glioma cells for vaccine construction.