AIDS/Smallpox Vaccine OK in Early Test
AIDS Vaccine That Protects Monkeys Looks Good in First Human Test
Feb. 9, 2007 -- An AIDS vaccine that uses a genetically engineered smallpox
virus to boost anti-HIV immunity looks promising in early tests on humans.
In animal tests, the vaccine did not protect monkeys against infection with
an AIDS virus. But vaccinated animals remained healthy -- and suffered no
immune damage from the deadly virus.
Now, nine humans have received small doses of the vaccine: about one-tenth
of the full dose. The vaccine was safe. And even at this tiny dose, it
stimulated the kind of immune responses that protected monkeys.
The vaccine is the brainchild of Harriet Robinson, MD, chief of microbiology
and immunology at Yerkes National Primate Research Center. Robinson is chief
scientific advisor to GeoVax Labs Inc. of Atlanta, spun off from Emory
University's vaccine center to market the vaccine.
"One of the big questions has been, 'Sure, you show promising immune
responses in monkeys, but will you get it in people?' Now we have this result
in humans, with just one tenth of a dose; it is very exciting," Robinson
Michael Keefer, MD, professor of medicine at the University of Rochester,
New York, helped test the vaccine through the NIH-sponsored HIV Vaccine Trials
Network, for which he is associate director for scientific administration.
"We are very encouraged with Dr. Robinson's approach," Keefer tells
WebMD. "She has some of the strongest data in her animal models as anyone.
And the results look pretty good from this, the very earliest human trial of
AIDS Vaccine From Smallpox Vaccine
It's a two-part vaccine. First, a person gets two doses of a DNA vaccine
carrying three important HIV genes called env, gag, and pol. Then a person gets
two doses of a smallpox virus genetically engineered to carry the same three
The smallpox component of the vaccine makes it unique. The virus, called the
modified Ankara virus or MVA, cannot replicate in humans and cannot cause
disease. It was used in the waning days of the successful global smallpox
eradication program to safely vaccinate some 120,000 people in Germany.
A side benefit of the GeoVax vaccine is that recipients will become immune
to smallpox, should that virus return via bioterror attack or lab accident.
But the main reason for using the smallpox virus is that it is one of the
most powerful stimulators of immunity known to man. And it seems that when the
virus carries HIV genes, those powerful immune responses transfer to HIV as
AIDS Vaccine in 4 Years?
There are two basic kinds of immunity. Cell-based immune responses depend on
killer blood cells that seek out and destroy infected cells. Antibody-based
immune responses depend on antibodies that stick to germs or infected cells,
inactivating them and marking them for destruction.