Study Reveals Factors Associated with Prevention, Control of HIV Infection
New vaccine research in monkeys suggests
that scientists are homing in on the critical ingredients of a
protective HIV vaccine and identifies new HIV vaccine candidates to test
in human clinical trials. The research, which appears online in Nature
on Jan. 4, was co-funded by the National Institute of Allergy and
Infectious Diseases (NIAID), part of the National Institutes of Health.
In the study, scientists report that several Simian Immunodeficiency
Virus (SIV) prime-boost vaccine regimens have demonstrated partial
protection against acquisition of infection by a virulent,
tough-to-neutralize SIV strain that is different from the strain used to
make the vaccine—a scenario analogous to what people might encounter if
an HIV vaccine were available. The experimental vaccine regimens
reduced the monkeys’ likelihood of becoming infected per exposure to SIV
by 80 to 83 percent compared to a placebo vaccine regimen. Further, in
those monkeys that did become infected, the experimental vaccine
regimens substantially reduced the amount of virus in the blood compared
to controls. Now plans are underway for early-stage clinical trials of a
human-adapted version of one of the study’s prime-boost vaccine
combinations.
The best predictor of protection from SIV in the vaccinated monkeys
was the presence of antibodies that latched onto the virus surface
protein. This finding reinforces what scientists have learned so far
about why the first modestly effective HIV vaccine worked
in humans and indicates that the HIV surface protein Env is a critical
vaccine ingredient. The new research also provides strong evidence that
the immune system’s mechanism for preventing infection is significantly
different from its mechanism for controlling viral replication.
The research was led by first author Dan Barouch, M.D., Ph.D., of
Beth Israel Deaconess Medical Center at Harvard Medical School and the
Ragon Institute of Massachusetts General Hospital, Massachusetts
Institute of Technology and Harvard. The senior authors of the new paper
are Nelson Michael, M.D., Ph.D., of the U.S. Military HIV Research
Program (MHRP), and Jaap Goudsmit, M.D., Ph.D., of Crucell Holland BV.
NIAID intramural investigators Vanessa Hirsch, S.D., D.V.M., and Ilnour
Ourmanov, Ph.D., collaborated on the research. MHRP and the Ragon
Institute co-funded the studies with NIAID.
