IMPERIAL CANCER RESEARCH FUND LABORATORIES 
Registered Charity No. 209631 
Dr . Paul Berg, 
Dept, of Biochemistry, 
Stanford University School of Medicine, 
STANFORD, California 94305, USA . 
P.O. ROX NO. 1 23 
LINCOLN’S INN FIELDS. 
LONDON, WC2A 3PX 
Cables : Cancerch 
Tel. : 01-242 0200 
10 March 1976 
Dear Dr. Berg, 
From the summary of the NIH committee guidelines for 
containing experiments with recombinant DNA reported in Science, 
it appears that there is no sub-classification of animal viruses with 
regard to the insertion of animal virus genes into E . coli . This is of 
concern to me since I plan to begin genetic and restriction endonuclease 
analyses on a group of insect viruses, the baculoviruses , which are 
potentially of great benefit to man and his environment. 
With the growing concern over the use of chemical 
insecticides for pest control, the baculoviruses are of great interest 
as biological pesticides. The Environmental Protection Agency has 
registered, after considerable safety evaluation tests, a baculovirus of 
the cotton bollworm (trade name Elcar). Baculoviruses specific for 
other pests are currently being developed for commercial production; 
the baculoviruses are species or occasionally genus "specific". 
Extensive safety testing on a variety of species (avian, piscian, 
mammalian, non-target invertebrates etc.) have been completed and in 
no instance were ill effects observed. The tests included potential for 
replication in mammalian cell cultures (including a variety of human lines), 
carcinogenicity and teratogenicity. The EPA has been cautious in 
registering these viruses and I know of no other viruses which have been 
so extensively studied with respect to safety. 
Although I have no immediate plans to clone baculovirus 
genes in E . coli, recombinant DNA techniques are potentially useful for 
studies on the genetic organization^ of these viruses. The baculoviruses 
have a large DNA genome (90 x 10 daltons). The nucleocapsids are 
enveloped and embedded in a crystalline protein matrix which confers 
several unique properties allowing rapid and extensive purification of the 
viruses. There are over 300 reported baculoviruses infecting species 
within five insect orders. Within two years time, I hope to begin 
experiments aimed at recombining closely related viruses of pest insects 
The purpose will be to obtain more effective pesticides with concern for 
safety. 
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