Propagation of Mouse Polyoma Virus in a Strain of Mouse Mammary Tumor Cells in vitro

Summary 1) An established cell line originating from a spontaneous mouse mammary tumor is a convenient host in which to propagate and to assay polyoma virus in vitro. Cytopathic effects of the virus were first observed in cultures 6 days after infection and progressed to complete destruction of all cells by 12th day. Increasing cell destruction was accompanied by rise in tissue culture infectivity and hemagglutination titers. 2) Observations with electron microscope revealed presence of virus in infected cells beginning 6th day after infection. Virus particles were observed in the nucleus and occasionally in the cytoplasm. Particles averaged 30 mμ in diameter and did not show an internal structure.