APPENDIX E 
human cells grown as single cells in the lab and also does not appear to infect 
humans, since humans exposed to polyoma do not produce antibodies. SV40 
does infect both human cells grown as single cells in the laboratory, and 
whole human beings, as evidenced by the active production of antibodies and 
the reports of isolation of SV40 from humans. This virus contaminated the 
early Salk polio vaccines and millions of people were inadvertently inoculated 
with it in the middle 1950s. To date, there is no indication that the recipient 
of the vaccine suffered any related difficulty. Both polyoma and SV40 are 
oncogenic, that is they cause tumor formation in newborn small laboratory 
mammals, and both can transform a variety of cells of mammalian origin. 
They are classified as low risk oncogenic viruses by the National Cancer 
Institute, and the viruses themselves must be handled under conditions 
equivalent to P2. Because SV40 infects human beings, and also because SV40 
and related viruses have been isolated in connection with several human 
disease states, the proposed guidelines assume that polyoma inherently 
affords a higher level of biological containment: therefore more stringent 
physical containment is required for SV40 than for polyoma. 
The guidelines require that the viral DNA used for recombination with 
a foreign DNA must itself be defective, that is, its propagation as a virus 
must be dependent on the presence of helper virus which supplies the genes for 
the missing functions. This helper can be another defective or an appropriate 
conditional lethal mutant virus. Alternatively the helper might be previously 
integrated into the genome of a stable line of host cells. The use of a 
non-defective genome as a helper is permissible if the alternatives are 
Appendix E — 18 
