RAC SUBCOMMITTEE MEETING ON DEFINITIONS 
Description of Varieties of Live Bacterial Vaccines that Should be Exempt 
from Guidelines and from Restrictions on "Deliberate Release" 
The application of modern biotechnology to vaccine devlopment during 
the past five years has resulted in the appearance of many candidate 
vaccines. These include improved vaccines against diseases for which 
immunizing agents already exist as well as new vaccines against diseases 
which were heretofore without i rnmunopr ophy lactic control measures. Many 
of the vaccines reaching the point of clinical trials consist of live, 
attenuated genet i cal 1 y-eng i neer ed bacteria, modified by means of 
recombinant DNA technology. Certain of the live bacterial vaccines for 
human and veterinary use that are prepared by recombinant DNA technology 
should be exempt from the Guidelines and should not require RAC approval 
or environmental impact statements from federal agencies prior to 
initiating clinical studies. These varieties of vaccines are reviewed 
below, along with suggestions for certain characteristics that the strains 
should possess. 
1) "Self-Destructing" Bacterial Vaccines 
One method of attenuating enteric bacterial pathogens is by means of 
modifying the production of certain enzymes in the Leloir pathway. As a 
consequence, grown in the presence of certain substrates, the mutant 
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Recombinant DNA Research, Volume 1 1 
