Marking." This would mean that in animals that were transgenic, 
you would have to have an assayable test for the transgenic 
sequences. This would be for all containment levels BL1-N 
through BL4-N . 
Dr. Hughes said he would not comment on specific language but 
only the relevant changes. He said the issue with respect to 
defining whether a viral vector should be put at higher 
containment is whether or not the element being used is 
mobilizable. The intent is to distinguish mobilizable from non- 
mobilizable elements rather than to set an arbitrary size rule. 
With respect to classification levels, he said that simple 
transgenics should be classified BL1-N since there is little 
possibility of mobilizing the introduced sequences. 
He said there was language in the proposal which stated in effect 
that if you were to try to design your containment facility for a 
particular experiment, the precise structure of the containment 
should be such to contain any vector in use. He said there was 
some language at the end of the proposal which allows for the IBC 
to lower the classification if a pathogenic strain being worked 
with can be attenuated in a fashion that is not revertible. This 
has been added because many of the strains conventionally used as 
vectors with animals are derived from strains that have 
considerable pathogenic potential. However, in many cases they 
are attenuated in such a fashion that makes the classification of 
the parent strain no longer relevant. 
Dr. Richardson said he had particular interest in seeing 
consistency of proposed amendments to the NIH Guidelines with the 
publication CDC/NIH Biosafety in Microbiologic and Biomedical 
Laboratories . He said he had a brief list of some editorial 
changes and minor inconsistencies as well as some items which he 
considered major inconsistencies. 
Dr. Richardson said he was appreciative of USDA's need to address 
the issue of large animals which cannot be contained in 
conventional primary cages. He felt the concept of the entire 
facility being considered the primary containment, while being 
logical, created some operational and design problems. He said 
he would point these out as the discussion continued. 
Dr. Gottesman said she had been trying to take the summary of the 
proposal provided by Dr. Tolin and look at it in relation to the 
existing NIH Guidelines. She said she agreed that many of the 
changes were obviously housekeeping, but she was unclear as to 
how the changes related to the current NIH Guidelines. In 
relation to the issue of the two-thirds of a viral genome. 
Dr. Gottesman said she felt this was the most substantive issue 
that the proposal had raised. She said the biggest question was 
whether a class of experiments in animals should be exempted from 
the NIH Guidelines and if so which class. 
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Recombinant DNA Research, Volume 13 
