Analysis of VACV infection in organotypic slice cultures with tumor cell implants. a Organotypic slice cultures (OSCs) from adult mice were established and implanted with 1 × 104 Gl261-RFP or U87-MG-RFP cells. 7 days after implantation, OSCs were infected with 5 × 106 pfu LIVP 1.1.1/well. b Standard plaque assay was performed 24 and 72 h after infection. Two-sided t test with unequal variances was used for statistics *p < 0.05. 72 h after infection OSCs implanted with GL261-RFP (c) and U87-MG-RFP (d) cells were stained with Hoechst and anti-VACV antibody to visualize infected tumor spheres. e, f IFN-γ-stimulated or unstimulated BV-2 cells were applied directly onto the OSCs implanted with GL261 cells. 24 h later OSCs were infected with LIVP 1.1.1 and stained after additional 24 h with FITC-IB4, Hoechst and anti-VACV antibody. Yellow arrows indicate exemplarily infected or non-infected BV-2 microglial cells.