FIG. 3.

Induction of an antitumor immune response. MC38cea cells (10⁶) were engrafted subcutaneously. When tumor volumes reached 30–50 μl, mice were treated intratumorally on four consecutive days with carrier fluid (mock), 10⁶ particles of UV-inactivated MV-GMCSF-antiCEA (UV-MV), 10⁶ particles of MV-EGFP-antiCEA, or 10⁶ particles of MV-GMCSF-antiCEA per day. Spleens were harvested aseptically 15 days after tumor implantation. (A) Lactate dehydrogenase (LDH) assay. MC38cea cells were cocultivated with prestimulated splenocytes obtained from mock-treated mice and mice treated with UV-MV, MV-EGFP-antiCEA, or MV-GMCSF-antiCEA. Mean values of n=7 (mock), n=8 (MV-EGFP-antiCEA), n=9 (MV-GMCSF-antiCEA), and n=4 (UV-MV) mice are shown, and the standard deviations. (B) ELISPOT assay for tumor-specific interferon (IFN)-γ secretion. Splenocytes isolated from treated mice were cocultivated with MC38cea tumor cells for 24 hr. Spots of IFN-γ-secreting cells were counted with an automated colony-counting device. (C) Virus-specific IFN-γ secretion. Splenocytes were cocultivated with MV-GMCSF-antiCEA or MV-EGFP-antiCEA at an MOI of 0.5 for 24 hr. Circles, mock treatment; asterisks, UV-MV; triangles, MV-EGFP-antiCEA; squares, MV-GMCSF-antiCEA. **p≤0.01; n.s., not significant.