Development and Evaluation of Adeno-HTLV-III Hybrid Virus and Non-Cytopathic HTLV-III Mutant for Vaccine Use

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antibody which usually disappears rapidly after acute
infection (57). In contrast, Ad2 fibers are largely
responsible for type-specific neutralizing antibody (36)
which is long lasting (57) and may be of greater concern
in the development of a live Ad2 vaccine. We recommend
that the feasibility of exchanging Ad2 fiber coding
sequences with that of a less common Ad serotype be
considered. If the decision is made to continue with
the proposed exchange of hexon coding sequence, we
recommend the use of a serotype ether than "oncogenic"
Ad31 because of possible regulatory complications.
3. Simian immunodeficienc virus (SIV) and HIV-2
model system for AIDS
Proposed studies in which HIV I gpl20/Ad2 is administered to African green monkeys are designed to demonstrate that subclinical infection with the rAd is established with attendant development of humoral and cellmediated immunity. However, these animals cannot be
reproducibly infected with HIV 1 to determine if this
immune response might be protective. We recommend that
similar rAd constructs using SIV env gene sequences be
considered for use in macaques, wh.ch develop AIDS-like
disease after infection with virulent SIV strains. This
would provide 4 valid and much less expensive animal
model system in which to test the efficscy of live Ad
vaccines. Similarly, when the HIV 2 African green
monkey model Is established, rAd containing HIV 2 env
genes can be administered and the monkeys challenged
with HIV 2.

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