2 . 
Secondly, in the view of many, the NIH guidelines are 
incontestively inconsistent with regard to the cloning of 
genes from Shigella . On one hand, the cloning of genes 
from Shigella in E.coli. is exempt, as a result of the 
extremely close relationship of these two organisms and 
their natural and efficient exchange of genetic informa- 
tion. On the other hand, the cloning of the gene for Shiga 
toxin is prohibited, or must be carried out under P4 
conditions. As everyone knows, if one clones genes from 
Shigella one almost certainly clones the toxin gene. If 
the cloning of genes from Shigella is exempt, how can the 
cloning of one of its genes be prohibited? 
Thirdly, Alison O'Brien has shown that many pathogenic and 
non-pa thogenic coliforms, including the laboratory strain 
E. coli K-12 LE392 which is universally used as a host for 
gene bank construction, produce Shiga-like toxins. Thus, 
one presumes that many, many investigators which clone 
genes from various strains of E. coli and its relatives 
have constructed hybrids carrying the genes for Shiga-like 
toxins. These individuals consider their experiments to 
be exempt from the NIH guidelines, although in principle 
they should currently be carried out under P4 conditions. 
Since the onus of proof that a donor strain does not 
produce a toxin rests with the investigator who wishes 
to carry out a particular cloning experiment, the logical 
conclusion of a decision to maintain P4 containment for 
the cloning of the gene for Shiga-like toxin is the 
suspension of all cloning experiments involving DNA from 
E. coli donors, until adequate proof is furnished by 
individual investigators that their particular donor strains 
do not produce a Shiga-like toxin. I am not, of course, 
arguing for the implementation of such a suspension, but 
do consider it to be the logical and obligatory consequence 
of the P4 decision. 
In my view, and those of a number of others, the original 
decision to classify at the P4 level the cloning of the Shiga 
toxin gene was inappropriate, and reflected the establishment 
of toxicity of a toxin (in any model, regardless of 
appropriateness of the model vis -^- vis the normal infection 
process characteristic of the producer organism) as the sole 
criterion for evaluating the containment level for the 
cloning of toxin genes. The exclusivity of this system of 
evaluation flies in the face of crucial considerations, such 
as the essential requirements for disease production, the 
role of the toxin in the disease process, and the natural 
distribution of the toxin gene in related organisms. Such 
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