Tumor stimulator cell modification by infection with Newcastle Disease Virus: Analysis of effects and mechanism in MLTC-CML cultures

Effects of tumor stimulator cell modification by infection with Newcastle D isease Virus (NDV) are described as analysed in vitro in mixed lymphocyte t umor cell cultures (MLTC). Direct antitumor effects were seen with human me lanoma or colon-carcinoma cells in a dose- and time-dependent manner when u sing live but not UV inactivated virus. When T cell stimulation was measure d by [H-3]-thymidine uptake, NDV infected tumor stimulator cells did not sh ow an augmentation but rather an inhibitory effect in comparison to non-inf ected stimulator cells. Virus infected tumor stimulator cells were, however , capable of augmenting the induction of tumor specific cytotoxic T cells i n MLTC-CML assays when using murine ESb lymphoma immune cells and syngeneic NDV modified ESb cells as stimulators. A CML stimulatory effect was also s hown for NDV modified third party cells and thereof derived conditioned med ium. These effects are most likely explained by interferon-beta which is in duced in tumor cells by NDV infection and by interferon-a which is induced in responder cells when stimulated with NDV infected stimulator cells.