[Alterations of Rous virus and polyoma virus during their synthesis in the cells of unnatural hosts].

The line of human embryo fibroblasts transformed by Rous sarcoma virus (strain Schmidt-Ruppin) contained and produced Rous sarcoma virus; this was shown by the complement fixation test, immunofluorescent test, electron microscopy and labelling with 3H-uridine peak in sucrose gradient. Biological properties of the new synthesized virus differed from that of the parent Schmidt-Ruppin strain; the range of the sensitive cells and the protein envelope antigens altered in particular. Analogous results by the change of the viral biological properties produced in the unnatural host tissue were obtained for polioma virus synthesized in the human embryo fibroblasts transformed by this virus.