localizing TIL in situ and lack of means to do so. On page 3 ^ 
section b, Dr. Parkman expressed the need to look for viral 
genomic material by direct assay, rather than simply examine 
cadavers for gross tumor. He remarked that the subcommittee had 
asked for data regarding the sensitivity limits of the S+/L- 
assay for helper virus. 
Dr. Temin commented that some of his earlier concerns had been 
allayed because he felt that if the presence of virus at the 
level of <1 viral particle/cell population could be detected, 
then a major safety issue would be resolved. In his view, this 
seemed to be feasible, although not yet demonstrated. He noted 
an apparent inconsistency on page 11. Although Western blot 
analysis showed the presence of antibody to virus in 3/4 animals, 
the following statement claims that retrovirus is cleared 
rapidly. He suggested that continued detection of antibody may 
indicate persistent viral antigen. 
Dr. Kelley emphasized a commitment to the principle that animal 
models must be tested first. If, after exhaustive efforts, no 
suitable model could be developed for TIL retroviral infection, 
then an assessment of the risk/benefit ratio might shift toward 
human testing. 
Comments submitted in writing from Dr. Varmus were read to the 
subcommittee. In summary. Dr. Varmus also expressed concerns 
related to potential viral recombination and replication. He 
emphasized a philosophical imperative to seek the safest possible 
route, particularly in view of the absence of direct therapeutic 
effect resulting from the marking experiment. He also pointed 
out the lack of ability to quantitate PCR results because of the 
extreme sensitivity of the technique. 
Dr. Temin answered Dr. Varmus' proposal that alternative means 
for introduction of DNA be pursued, such as transfection and 
electroporation, by noting the superior efficiency of retroviral 
infection. However, he agreed that alternative vectors and 
helper cells would be useful, although the possibility of a gene 
conversion event could never be completely ruled out. Therefore, 
a test with greater sensitivity to detect such events is 
desirable. In his earlier written comments. Dr. Temin had noted 
the recent availability of safer systems than N2. The ideal 
situation would be to utilize the safest vector system and the 
most sensitive assay for replicating virus. 
Dr. Walters asked all subcommittee members to reflect on their 
comments and to determine the degree of consensus concerning the 
Anderson proposal. Each participant in the conference call was 
then asked individually to give his or her judgment of the 
proposal based on the additional information provided by 
Dr. Anderson and his colleagues. There was complete unanimity 
among those participating that, given the information provided in 
Recombinant DNA Research, Volume 13 
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