A vaccine for the monkey
equivalent of HIV appears to
eradicate the virus, a study
suggests.
Research published in the journal
Nature has shown that vaccinated
monkeys can clear Simian
Immunodeficiency Virus (SIV)
infection from their bodies.
It was effective in nine of the 16
monkeys that were inoculated.
The US scientists say they now want
to use a similar approach to test a
vaccine for HIV in humans.
Prof Louis Picker, from the Vaccine
and Gene Therapy Institute at
Oregon Health and Science
University, said: "It's always tough
to claim eradication - there could
always be a cell which we didn't
analyse that has the virus in it. But
for the most part, with very
stringent criteria... there was no
virus left in the body of these
monkeys."
Search and destroy
The research team looked at an
aggressive form of virus called
SIVmac239, which is up to 100
times more deadly than HIV.
Infected monkeys usually die within
two years, but in some inoculated
primates the virus did not take
hold.
The vaccine is based on another
virus called cytomegalovirus (CMV),
which belongs to the herpes family.
It used the infectious power of CMV
to sweep throughout the body. But
instead of causing disease, it has
been modified to spur the immune
system into action to fight off the
SIV molecules.
"It maintains an armed force, that
patrols all the tissues of the body,
all the time, indefinitely," explained
Prof Picker.
The researchers gave rhesus
macaque monkeys the vaccine, and
then exposed them to SIV.
They found that at first the
infection began to establish and
spread. But then the monkeys'
bodies started to respond,
searching out and destroying all
signs of the virus.
Of the monkeys that successfully
responded to the vaccine, they were
still clear of infection between one-
and-a-half and three years later.
Prof Picker said his team was still
trying to work out why the
vaccination worked in only about
half of the monkeys.
"It could be the fact that SIV is so
pathogenic that this is the best you
are ever going to get.
"There is a battle going on, and half
the time the vaccine wins and half
the time it doesn't," he said.
Human trials
The researchers are now testing the
vaccine to see if it can be used
after SIV exposure to treat and
potentially cure infected monkeys.
They also want to see if the
technique could work in humans.
Prof Picker said: "In order to make a
human version we have to make
sure it is absolutely safe.
The researchers now want to move
from monkeys to test the vaccine in
humans
"We have now engineered a CMV
virus which generates the same
immune response but has been
attenuated [modified to lose its
virulence] to the point where we
think it is unequivocally safe."
This would first have to pass
through the regulatory authorities,
but if it does, he said he hoped to
start the first clinical trials in
humans in the next two years.
Commenting on the research, Dr
Andrew Freedman, from Cardiff
University School of Medicine, said:
"This suggests that prophylactic
vaccines - vaccines designed to
prevent infection - using CMV
vectors may be a promising
approach for HIV.
"While they may not prevent the
initial infection, they might lead to
subsequent clearance, rather than
the establishment of chronic
infection."

SOURCE: mobile.bbc.co.uk/news/science-environment-24051860