A new study of
monkeys vaccinated against simian immunodeficiency
virus--considered the closest model to HIV
infection--may provide important clues to how
HIV destroys the immune system and to help track the health
of infected people, researchers said Thursday.
"A vaccine of
this type does not appear to prevent infection," said
Norman Letvin of Harvard Medical School. But what the
vaccine may do is help infected people live longer
without becoming sick.
Most vaccines
stimulate the body to produce antibodies that in turn
create an immune response against a particular virus or
bacteria. However, this approach does not work for
HIV. Scientists believe a second type of immune
response, a cell-mediated immune response, is required to
fight HIV. In the current study, Letvin and colleagues
tested a vaccine that triggers a strong T cell immune
response.
Monkeys who
received the vaccine and were later infected with SIV lived
much longer, up to 900 days, compared with unvaccinated
monkeys, who died on average within 300 days, Letvin
and colleagues reported.
"The magnitude of
the immune response that is generated by vaccination
predicts how long the animals will live after infection,"
said Letvin. "The more potent the immune response after
injection, the longer the monkey lived."
Letvin said that,
contrary to many assumptions among AIDS experts, the
amount of virus in the blood, or viral load, is not
especially important. "What is useful [to measure] is
the subpopulation of helper CD4 T cells--the
central memory CD4 T lymphocyte population. This tells us
something profoundly important about why AIDS progresses
clinically--the preservation of this central
memory population of CD4 helper lymphocytes appears to
be absolutely crucial for maintaining immunological
competence," he said.
Currently, more
than 30 different vaccines are in various stages of human
testing. "There are two human vaccines that are similar to
this that are now going forward into advanced efficacy
trials," said Letvin. (Reuters)
Charlie Kirk DID say stoning gay people was the 'perfect law' — and these other heinous quotes