MASSACHUSETTS INSTITUTE OF TECHNOLOGY 
CENTER FOR CANCER RESEARCH 
77 MASSACHUSETTS AVENUE, CAM8RI0CE. .MASSACHUSETTS 02139 
October 18, 1977 
Dr. Donald S. Frederickson 
Dir actor 
National Institutes o£ Health 
Rethesda, Maryland 20014 
Daar Don, 
I appreciated receiving a copy of the proposed revised NIK 
Guidelines on Recombinant DNA research. 
I want to strongly support the conclusion of the Recombinant 
Advisory Committee that "everything they have learned tends to 
diminish our estimate of the risk associated with recombinant 
DNA In E. coll K-12." I also support their conclusion that thi3 
does not mean we should drop our guard entirely but that we 
should begin the process of reducing the required containment 
levels for recombinant DNA research commensurately to our reduced 
estimate of risks. I would hope that with further experience with 
recombinant DNA research and further studies of bacterial patho- 
genesis, assessments of possible risks will continue to decline 
and that the containment requirements of the Guidelines will also 
continue to be relaxed. 
One important step forward is the reduction of physical 
containment level for shot gun experiments in mammals. It has 
always been my belief that the major potential hazard from such 
experiments would lie in the accidental Incorporation of endogenous 
viral nucleic acid into bacteria. The risk associated with such 
an occurrence now seems marginal and EK2 containment seems totally 
sufficient to prevent any conceivable hazard. 
I believe you should be aware that the field of retrovirus 
research has been seriously hampered by the present NIH Guidelines. 
The availability of clones containing fragments of retroviral genomes 
would have advanced the field enormously already and are still badly 
needed. I, of course, recognize Chat clones containing retroviral 
DNA may present special concerns and I'm not suggesting that they 
should be made at will. With the present non-existence of P4 con- 
[Appendix A — 21] 
