Friday, 25 October Conference Call on AIDS Vaccine

Research Committee 25-Oct-96 Page 11

Dr. Essex just hosted several "How to Make an HIV Vaccine" workshops.
He believes that we are ready for "proof-of-concept" trials with the existing AIDS
vaccine products. Having worked against cat retroviruses that cause leukemia and
immune suppression, he indicated that "if we had decided to wait to do proof-ofconcept efficacy trials until after we knew the "immune correlates", we never
would have had that vaccine." FeLV in cats and HIV in humans are similar in
many respects, although the rate of genetic variation is much lower in the former
than the latter. However, the ability of cat vaccines to induce neutralizing
antibodies was irrelevant, and thus too much attention on them in human vaccine
development may be misleading us now. Instead, precedent was set that retrovirus
vaccines can work. There was no cell-mediated immunity but still, upon
challenge, the vaccine was effective.
Dr. Essex advocates the novel idea of conducting vaccine efficacy trials in
newborn infants of infected mothers. These trials could be cost-effective,
conducted quickly and would be almost as efficacious in infants as in their HIV
positive mothers. In the trial, one population would receive AZT+placebo and the
other AZT+vaccine. If this population is protected against the disease (nonsterilizing), it could be more quickly learned. Also, FeLV vaccine does not
provide sterilizing immunity, it lowers viral load. Therefore, since we still have 8
percent transmission from mother to infant even when using AZT, you could see if
a vaccine could reduce that incidence even lower.
Dr. Essex agrees with the need for more basic research and endorses what
others have said about the necessity of "leadership." Someone needs to "step into
the gap" in at least a regional or bilateral, if not global, way. Also, he believes
there is a need for more regional and global collaboration; an initial vaccine that is
optional or best for the Western hemisphere would not necessarily be best for SubSaharan Africa.
Jerald C. Sadoff, MD, Executive Director, Vaccine Research, Merck Research
Laboratories was formerly Director of Communicable Diseases and
Immunology, Walter Reed Army Institute of Research. He has authored, or
co-authored, over 140 scientific publications on research and development
of vaccines for cholera, E. coli, gonorrhea, gram-negative shock, hepatitis
A, Klebsiella, malaria, Pseudomonas, Shigella, Salmonella, and typhoid.