15 
Dr. Grodzicker said HTLV I I I/LAV possesses a trans-activator gene. The DNA 
containing adenoviruses can also contain a trans-activator gene but adenoviruses 
do not usually cause cancer in humans althought they do cause cancer in rodents. 
Dr. Gottesman asked whether adenoviruses might not cause cancer in animals 
because they rapidly kill cells rather than transform them. Dr. Grodzicker 
said rapid cytotoxicity is one explanation; the route of transmission is another 
possible cause. 
Dr. Joklik said many leukemia viruses such as Rous associated virus (Rav) II 
are very cytotoxic. The basis for the cytotoxicity of these retroviruses is 
not known although it has been shown that there is strain and envelope control 
of cytotoxicity. 
Dr. Gottesman asked why the incidence of disease caused by HTLV I is lower than 
the incidence of disease for HTLV III/LAV. Dr. Rapp said HTLV I infection 
rarely leads to disease; since neoplasia is a multistage process, it is assumed 
other cellular events in addition to HTLV I infection are needed to cause 
disease. Infection by HTLV III/IAV may be sufficient to cause disease. 
Dr. Friedman asked whether the working group should write specific language on 
viruses for the NIH Guidelines. Would this language apply to both ENA and FNA 
viruses? Would a special case have to be made for HTLV III/LAV? 
Dr. Landy thought such an approach is too simplistic, and the working group 
would not be able to write language addressed to combinations of viral genes. 
Dr. Grodzicker agreed it would be difficult to develop language applicable to 
all cases. 
Dr. Gottesman asked the working group if they thought a comprehensive listing 
of retroviruses in Appendix B should be developed or would descriptive language 
be more useful in the NIH Guidelines. She noted that oncogenic viruses are 
not currently classified in Appendix B although seme are listed. Dr. Grodzicker 
thought that some viruses currently listed in Appendix B do not present a 
hazard and should not be in Appendix B. 
Dr. Liberman suggested it might be reasonable to base a listing on host range. 
He said a number of organisms which pose no hazard to humans (e.g., mouse 
ecotrcpic retroviruses ) would then drop out of the listing. 
Dr. Liberman added that the American Type Culture Collection (ATCC) has the 
most extensive hazard listing of a retroviral collection because they must 
comply with international shipping regulations. The ATCC listing might be 
helpful to the working group should they decide to construct an Appendix B 
listing. 
Dr. Gottesman said the National Cancer Institute (NCI) has been working for 
two years to revise their listing of oncogenic viruses; she would contact 
individuals involved in this effort for a report on their progress. 
[ 454 ] 
