WEDNESDAY, April 4 (HealthDay News) -- A new study offers
insight into why an HIV vaccine failed to protect most people who
received it, but it also points to promising new targets for future
Scientists believe an HIV vaccine, designed to prevent infection
with the virus that causes AIDS, is still several years away. Tests
of experimental vaccines have largely been failures so far.
Nevertheless, the prospect of a vaccine remains tantalizing
because it could make a major dent in the spread of HIV and AIDS
around the world.
The new research "gives us a handle on how the immune system
deals with the virus and is affected by a vaccine," said study lead
author Dr. Barton Haynes, director at the Duke Human Vaccine
Institute at Duke University in Durham, N.C. "It gives us clues and
a firm direction to look into."
The study is based on work by more than 100 scientists from 25
institutions, and appears in the April 5 issue of the
New England Journal of Medicine.
Haynes and his colleagues examined the results of a 2009 study
of an HIV vaccine in Thailand. In a trial involving more than
16,000 people, the vaccine appeared to cut the risk of infection by
only 31 percent. That was still considered a major advance over
previous vaccines that didn't work at all, Haynes noted.
The vaccine, called RV144, wasn't ready for prime time because
it didn't protect enough people, Haynes said. "You want to get it
above 50 percent," he said, and some scientists believe the rate
should be even higher than that.
Despite the vaccine's failure, the authors of the new study were
able to use the data to learn more about how the immune system
deals with HIV and how the vaccine changes the "big picture" of the
body's response to the virus.
The new research is an "exhaustive molecular analysis," said Dr.
Lindsey Baden, an associate professor of medicine in the infectious
disease division at Brigham and Women's Hospital in Boston who
co-wrote a commentary accompanying the study.
Haynes said one surprising finding is about an antibody -- a
soldier of the immune system -- that helps protect against
influenza infection. Ironically, the antibody appears to mitigate
the effect of antibodies that might otherwise help protect against
HIV, he said.
Another finding was that higher levels of antibodies that home
in on a particular region of HIV's outer shell, called V1V2, were
associated with lower rates of infection with the virus.
This and other information in the study may help researchers
come up with theories about where to go next with vaccine
development, Baden said. Among other things, it can reveal parts of
the immune system that can be most useful in battling the
transmission of HIV.
Vaccines are available to fight other kinds of viruses, such as
measles and influenza. HIV is unique, however, because it inserts
its genetic material into the body's cells.
"When a person gets infected with HIV, that genetic material goes underground," Haynes said. "It's invisible to the body's immune system."
Another challenge is that the virus mutates, becoming a moving
"It changes so rapidly in the person who gets infected that even when the immune system does try to control it, in most people the immune system is always playing catch up," Haynes said.
There's more on HIV/AIDS at the
U.S. National Library of Medicine.
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