Immunohistochemistry staining of MHC class II positive cells. Scale bars are equal to 1 mm and 10× magnification was applied. (A) 42 days after GLV-1h68 administration HT-29 (left) and GI-101A (right) xenografts were excised, sectioned and labeled for MHCII and vital DNA (Hoechst). In addition, GFP signals from VACV infected cells and transmission images are shown. (B) Overlay of MHCII and GFP signals in HT-29 tumors (left) and GI-101A tumors (right). (C) Uninfected HT-29 (left) and GI-101A (right) xenografts were excised at day 42 and treated identical to their infected counterparts. Tissue sections were stained for MHCII and vital DNA (Hoechst). As expected, no Virus-derived GFP signal could be detected.