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1 could in the laboratory produce a pathogen, even if he 
2 wanted to. 
3 I see great uses for recombinant DNA with 
4 respect to preparation of certain vaccines in enteric 
5 diseases. Right now, the brightest hope for preparation 
6 of a vaccine against the E. col i that causes traveler's 
7 diarrhea is to purify the colonization factor pili, 
3 the hairy little organelles on the surface of the bacteria. 
9 This is very difficult to do. By use of recombinant DNA 
10 the possibility exists that the cloning of the appropriate 
11 genes could allow large amounts of this antigen to be 
12 produced and a vaccine prepared in a much more cost-effective 
13 manner. 
14 Similarly, now that much is known about the 
15 subunits of the enterotoxin, it is possible to separate 
16 the toxic portion from the binding portion, theoretically, 
17 and by use of cloned genes to prepare just the binding portion. 
18 So for these reasons I have attempted to point 
19 out that pathogens have had tens of thousands of years to 
2 Q develop, and it is highly, highly unlikely that man can 
21 put together a pathogen .in a cookbook fashion. Evidence 
22 in the past few years has suggested that this is so. 
23 The last point I want to make is that I am much 
24 more worried or bothered by known pathogens that are worked 
25 with in laboratories. Last week we saw that smallpox virus 
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