Autologous Adjuvant Linked Fibroblasta Induce Anti-Glioma Immunity: Implications for Development of a Glima Vaccine

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 an in vitromodel 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 immunized in vitroagainst 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 of in vitroexperiments were compared to data derived from glioma patients immunized with subcutaneous injection of an autologous adjuvant-linked 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. These in vitroresults correlated well with in vivodata 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 after in vivoimmunization 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 targets in vitrowas achieved after in vivosensitization 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.