APPENDIX B 
Polyoma and SV40 Virus 
Polyoma virus is a virus of mice, and infection of wild mouse 
populations is a common event, for the virus has often been isolated 
from a high proportion of healthy adult animals, both wild and 
laboratory bred, of many colonies (Gross, L., Proc. Soc. Exp. Biol. 88, 
362-368, 1955; Rowe, W. P., Bact. Rev. 25, 18-31, 1961). As far as is 
known the virus almost never causes a disease in these animals. However, 
when large quantities of the virus are inoculated into newborn or suckling 
mice or hamsters, a variety of solid tumors is induced (Gross, L., 
Oncogenic Viruses, Second Edition, Pergamon Press, NY). 
Polyoma virus grows lytically in mouse cells in tissue culture. Thus 
mouse cells probably in culture are transformed only by virus particles 
that contain certain kinds of defective genomes. Cells of other rodent 
species, however, can be transformed by polyoma virus particles that 
contain complete genomes (Folk, W., J. Virol., 11_» 424-431 , 1973). The 
virus does not replicate to a significant extent in human cells in tissue 
culture (Eddy, B.E., Virol. Monogr., 7 _, 1-114, 1969; Pollack, R. E., Salas, 
J., Wang, R., Kusano, T., and Green, H., J. Cell Physiol. 77_, 117-120, 1971 ). 
The resistance of the cells seems to be a consequence of the failure of the 
virus to absorb or uncoat. However even when naked viral DNA is introduced 
into the cells only an abortive cycle of replication ensues; early viral 
proteins are made, there is induction of cellular DNA synthesis, but no 
expression of late viral proteins is detectable (Gruen, R., Grassmann, M. 
and Grassmann, A., Virology, 58, 290-293, 1974). 
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