10 
subconmittee did not feel it possessed sufficient virology expertise to 
adequately address this question and suggested the opinion of virologists 
be sought. 
Dr. Gottesman said the sixth question asked whether gene expression levels 
calculated several years ago are still relevant. Dr. Gottesnan said these 
estimates were based on the assumption that the maximum level of protein 
synthesis that could theoretically be turned over to production of a foreign 
protein had been turned over to synthesis of the product of the introduced 
gene. These original estimates are still valid. 
Dr. Gottesman said the seventh question in the ASPE memorandum asked how 
use of high copy number plasmids inight affect estimates of toxin production 
and gene transfer probability. The Risk Assessment Subcommittee agreed 
the issues involved in use of high copy number plasmids have already been 
factored into the calculations of maximum theoretical levels of protein 
synthesis . 
Dr. Gottesman said the eighth question dealt with the survival and effects 
of various bacteria in the environment. This question is very complex; 
since each proposed application will be reviewed on a case-by-case basis, 
the issues will be addressed at the time each proposal is reviewed. 
Dr. Gottesman said the ninth question in the ASPE memorandum dealt with 
shuttle vectors and retrovirus vectors. The subccrnmittee pointed out that 
the most important consideration in evaluating the potential for spread of 
a defective vector will be the availability of helper virus. 
Dr. Gottesman said the tenth question asks vh ether cos mid vectors pose any 
special risk. The subcommittee pointed out that is most cases cosmids are 
more contained than the bacterial virus from vhich they are derived. 
Dr. Gottesman said the eleventh question asks vhether nonconjugative plas- 
mids could be disseminated via transfer events involving transient survival 
of conjugative plasmids. The Risk Assessment Subcommittee said the type 
of plasmid to be used in a protocol is an important consideration in the 
review process. 
Dr. Gottesman said the twelfth question in the ASPE memorandum asks vhether 
virulence or others factors may exist vhich could affect the spread of 
plasmids. She said this question was cpen-ended and difficult to address. 
Dr. Clowes said much new information concerning plasmids, bacter icphages , 
cosmids, etc., has been accumulated in the years since the NTH Guidelines 
were first established. The Risk Assessment Subcarmittee in reviewing this 
additional information determined that earlier containment conclusions 
were still appropriate since the initial evaluations were often done on a 
"worst case" basis. In addition, the subccrnmittee did not identify any 
important general izable risk assessment experiments vhich should be done. 
[142] 
