Dr. Donald S. Frederickson 2 
October 18, 1977 
talnment facilities, however, and without any certified EK3 vector, 
no possible work can go forward. I hope chat you will consider the 
possibility of reducing further the containment requirements so 
that clones can be made using P3 plus EK2 if incomplete genomes are 
to be ligated into a plasmid. Except for Rous sarcoma virus, and 
possibly other sarcoma viruses, there is at present no reason to 
believe that one portion of the genome or another is reponsible 
for neoplastic transformation. Therefore, for non-sarcoma viruses, 
all fragments would fit the definition of containing "less than the 
complete potentially infectious viral genome" and would also not con- 
tain "any portion of the viral genome region that is known or sus- 
pected to be responsible for neoplastic transformation." 
Finally, the rules of "DNA transcripts for other RNA virus 
genomes" for mammals are a bit odd. It is true that segmented 
genomes would be harder to make as complete DNAs than non- 
segmented genomes but it is difficult to imagine that a reverse 
transcript of a lytic RNA virus could be hazardous under any 
condition. This is doubly true if vaccine strains of viruses 
were to be used — after all these were selected to be safe for 
the human population and are given in large quantities to people. 
Although I have suggested specific areas in which I believe 
that containment conditions could be altered, I want to support 
strongly the general tenor of the proposed revised Guidelines. 
I hope that you will find it possible to issue these as revised 
Guidelines in the near future. 
Sincerely 
DB/mts 
[Appendix A — 22] 
