19 
Similarly, while the experiments described as Type 2 by the NAS 
committee report included linkage of total DNAs or segments of the 
DNAs from any animal virus, oncogenic (cancer-causing) or not, the 
experiments to be deferred under the Asilomar recommendations included 
only those in which the viral DNA was derived from highly pathogenic 
viruses as listed by the Center for Disease Control (classes 3, 4, 
and 5). For those viruses that the Asilomar report considered permissible 
for use in recombinant DNA experiments, the report recommended 
use of bacterial vector-host systems with demonstrably restricted growth 
capabilities outside the laboratory, together with moderate -risk physical 
containment facilities. With rigorously purified segments of DNA known 
not to contain genes for oncogenic transformation, existing host -vector 
systems --that is, not specially designed systems --were deemed 
permissible. 
From May 1975, when the Asilomar report was published, until 
the promulgation of the NIH Guidelines in June 1976, the recommenda- 
tions of the Asilomar Conference served as guidance for NIH-supported 
investigators. In general, this was on a voluntary basis. In the winter 
of 1975-76, the various Institutes of the NIH wrote to grantees involved 
in recombinant DNA and related research calling attention to the potential 
hazards of certain experiments, and the need for caution, and indicating 
that certain experiments were not to be carried out at all (see represent- 
ative letter in Appendix D to Appendix C). These prohibitions included 
those in the Asilomar recommendations, but also included experiments 
designated as Type 1 by the 1975 NAS Committee letter. Within the 
restrictions of the Asilomar guidelines, an increasing number of NIH 
grantees, contractors, and intramural scientists were utilizing the new 
procedures. Methods were improved. In addition, serious work on the 
development of safer hosts and vectors was initiated in several lab- 
oratories. 
Recombinant Advisory Committee. The NIH Recombinant Advisory 
Committee held its first meeting in San Francisco immediately after 
the Asilomar conference in February 1975. It proposed that NIH use 
the recommendations of the Asilomar conference as guidelines for 
research until the committee had an opportunity to elaborate more 
specific guidelines, and that NIH establish a newsletter for informal 
distribution of information. NIH accepted these recommendations. 
At the second meeting, held on May 12-13, 1975, in Bethesda, 
Maryland, the committee received a report on biohazard -containment 
facilities in the United States and reviewed a proposed NIH contract 
program for the construction and testing of microorganisms that would 
have very limited ability to survive in natural environments and would 
thereby limit any possible hazards. A subcommittee chaired by 
Dr. David Hogness was appointed to draft guidelines for research 
involving recombinant DNA molecules, to be discussed at the next 
meeting. 
