19 
thus, the bowel wall itself, would be one test toxin. One could also 
perform these experiments with tetanus toxin which has no direct effect 
on the bowel. These experiments would prcvide information on whether 
these proteins affect the bowel and whether they might cross the 
intestinal wall and enter the circulation. 
The ad hoc working group realized that these experiments did not address 
questions about what would happen when a bacterial clone producing a 
toxin colonized the bowel. Dr. Gill did not feel, however, that 
Dr. Murphy's preposed experiments would prcvide this type of information. 
Dr. Gill predicted two possible outcomes for Dr. Murphy's experiments: 
no effect is observed or the animal dies. The experiment is structured 
so that if no effect is observed, no information will be gained. If, 
on the other hand, the animals die, a biological weapon will have been 
constructed according to Dr. Gill. 
Dr. Gottesman said risk assessment considerations have cane up for three 
separate reasons and these reasons contradict each other. These are: 
(1) Risk assessment might be performed to determine how toxin 
genes act when cloned in Eh_ coli if they are expressed when 
the bacteria colonize the gut, or how they act _in situ in the 
gut if produced by bacteria which are not normally pathogenic; 
(2) The Guidelines specified that experiments performed as part of 
a risk assessment program can be performed at P3 in the P4 
facility; and 
(3) For the particular organism, risk assessment experiments might 
indicate how the organism is to be handled and whether it can 
be removed frem the facility. 
Dr. Gottesman said only the last argument is a valid reason for performing 
the risk assessment experiments proposed by Dr. Murphy. 
Dr. Holmes said the experiments proposed by Dr. Murphy will not provide 
good risk assessment data. Furthermore, no information which would be 
pertinent to stage II in the proposal, i.e, creating a melanocyte stimu- 
lating hormone (MSH) -diphtheria toxin hybrid gene. He asked if 
Dr. Murphy still intended to do stage I of the experiments (i.e., cloning 
of the diphtheria toxin gene in ED_ coli K-12). 
Dr. Murphy said he did. He said that in collaboration with investi- 
gators at Tufts University, a chimeric toxin composed of a portion of 
the diphtheria toxin molecule linked to a small polypeptide hormone 
(TRH) has been generated with protein chemistry. Diphtheria toxin 
toxicity can be delivered to cells that have TFH receptors, both in 
vitro in tissue culture and in vivo . However, as the chimeric protein 
is produced by protein chemistry, specific toxicity varies tremendously. 
He said his long range goal is to create a chimeric toxin at the gene 
[ 25 ] 
