SURVIVAL AND TOXICITY OF AN ALLOGENEIC CYTOKINE-SECRETING FIBROBLAST VACCINE IN THE CENTRAL-NERVOUS-SYSTEM

OBJECTIVE: In previous studies, we determined that C57BL/6 mice (H-2(b )) with intracerebral (i.c.) malignant glioma or melanoma treated with allogeneic fibroblasts genetically engineered to secrete interleukin (IL)-2 results in prolonged survival and a cellular antitumor response when the treatment is administered intratumorally (via i.c. injection ). For this study, we evaluated the survival and toxicity of the cytok ine-secreting cellular vaccine administered directly into the central nervous system in both syngeneic ((CH)-H-3 H-2(k)) and allogeneic (C57 BL/6 H-2(b)) mice using bioassay and polymerase chain reaction techniq ues. METHODS: First, brain sections were prepared at varying time inte rvals (2-60 d) after i.c. injection of the IL-2-secreting fibroblasts (H-2(k)) into allogeneic and syngeneic mice, and the presence of the c ells was detected by polymerase chain reaction for the neomycin gene, which was used as a selection marker for the gene transfer. As a secon d means of assessing survival of the IL-2-secreting cells, an in vitro bioassay technique was used. Brain sections were prepared at varying time intervals (2-60 d) after i.c. injection of the IL-2-secreting cel ls into allogeneic and syngeneic mice. Cells were disassociated and gr own in media containing neomycin. RESULTS: A positive signal by polyme rase chain reaction was no longer detectable 14 days after injection i nto allogeneic C57BL/6 (H-2(b)) mice. In contrast, under similar circu mstances, the IL-2-secreting cellular vaccine could be detected for mo re than 55 days in histocompatible ((CH)-H-3) syngeneic mice (H-2(k)). Allogeneic cells could be recovered from tissue culture for only 2 to 5 days after i.c. injection of the modified cells. In contrast, synge neic cells were recovered for up to 28 days after i.c. injection. At n o time did the mice exhibit signs of neurological deficit or adverse a ffects on their survival (>60 d). CONCLUSION: An allogeneic cytokine-s ecreting cellular vaccine has a limited lifespan in the central nervou s system, surviving only 14 days or less, and has no apparent adverse effects. These results indicate the advantage of using a modified allo geneic cell line as the delivery vehicle for gene therapy in the treat ment of an i.c. neoplasm.