24 
and obtain maximum production would not be penalized canpared to individuals 
who do not obtain maximal production. 
Dr. Gottesman moved that Shigella dysenteriae 6 OR be substituted for 933 
E. coli 0157:H7 as the standard strain in Appendix F-IV-H. Dr. Clowes 
seconded the motion. 
By a vote of seventeen in favor, none opposed, and no abstentions, the 
motion was accepted by RAC. 
VIII. REQUEST TO CLONE A HYBRID TOXIN GENE 
Dr. Gottesman said Dr. Jchn Murphy of the University Hospital of Boston 
University Medical Center requested permission (tabs 1230, 1233, 1235/11, 
1236, 1237) to construct a hybrid molecule in vhich the gene coding for 
interleukin-2 (IL-2) is joined to a segment of the gene encoding diphtheria 
toxin. The diphtheria toxin segment encodes the A subunit and portions of 
the B subunit of the toxin molecule. The hybrid gene would be cloned in 
E. coli K-12 host-vector systems. 
Dr. Gottesman said the Working Group on Toxins at the August 16, 1985, 
meeting had considered this proposal as well as a second related proposal 
dealing with a hybrid toxin composed of a -melanocyte stimulating hormone 
(a-MSH) and a diphtheria toxin segment. 
Dr. Gottesman reported the history of the a-MSH-diphtheria toxin proposal. 
The a-MSH-diphtheria toxin proposal had been reviewed and recarmended for 
approval by RAC at the October 25, 1982, meeting, and Dr. Murphy had been 
granted NIH permission (Appendix F-IV-I, 49 FR 46279) to propagate under 
BL4 containment the hybrid gene coding for the a-MSH-diphtheria toxin fusion 
protein. The permission required Dr. Murphy to submit data to the Working 
Group on Toxins for evaluation in order to obtain permission to remove the 
clcxies from BL4 containment. Dr. Murphy accordingly submitted data from 
risk assessment experiments to the Working Group on Toxins for review. 
These data described the effects on guinea pigs challenged by: (l) intraperi- 
toneal injection of the viable and boiled JL_ coli K-12 host-vector system 
(the control); (2) intraperitoneal injection of the viable and boiled E. 
coli K-12 host-vector system carrying and expressing the hybrid gene; and 
(3) injection of partially purified fusion protein at graded doses up 
to 1000 minimal lethal dose equivalents (based on 160 nanograms diphtheria 
toxin per kilogram body weight as minimal lethal dose. ) Dr. Murphy argued 
these data suggest ooli host-vector systems carrying the hybrid gene 
are not harmful to guinea pigs, and that up to 1000 equivalent diphtheria 
toxin doses of fusion protein challenges to guinea pigs cause no effect. 
After thorough discussion, the working group on August 16, 1985, recom- 
mended Dr. Murphy be permitted to proceed with experiments involving clones 
[406] 
