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Dr. Donald S. Frederickson 
October 13, 1977 
indeed cause viral infection of mice and the highest infectivity was 
observed after subcutaneous injection. Impressive as this fact seems, 
this infectivity is still only 5 x 10 - ^ of the specific Infectivity 
of the virus in its native form. One interpretation of these data is 
that preparing naked DNA is quite an effective method of attenuating 
this virus. Thus, research with DNA, or recombinant DNA including 
these viral genes, seems to provide an important safe tv advantage — at 
least in this particular virus-sensitive host system. It seems probable 
that such research would provide an even greater safety advantage when 
dealing with this and other viruses in a virus-insensitive host system 
(i.e. the hypothetical situation in which an investigator somehow 
becomes infected with an Z_. coli K12 containing viral genes). 
(d) The viruses in this category are not human pathogens, and they 
represent animal model systems which are of great biomedical importance. 
The current practical moratorium on recombinant DNA research with these 
systems does not seem to be a sound balance of benefit versus risk. 
I hope that these comments will be helpful to you and that they will 
encourage the Recombinant DNA Advisory Committee to reconsider some of the 
revised classifications. 
Yours truly, 
A. M. Skalka, Ph.D. 
Department of Cell Biology 
AMS :pcp 
[Appendix A — 11] 
