Washington: In a research of how HIV
mutates in response to immune system, scientists claim to have
found evidence that the virus can take several escape routes,
not one preferred route.
The human immune system has the ability to temporarily
overpower HIV in early infection. Recent studies showed that
most newly infected patients develop neutralising antibodies.
But, the problem is HIV`s ability to mutate, disguising itself
enough to get away from the antibodies.
Now, a team has claimed that if a vaccine component is
identified which can stimulate neutralising antibodies, HIV`s
capacity for rapid mutation can still be a confounding factor.
"A single type of neutralising antibody may not
be enough to contain HIV. These neutralising antibodies work
really well -- they hit the virus fast and hard. But so far,
every time we look, the virus escapes," lead researcher Prof
Cynthia Derdeyn of Emory University School of Medicine said.
Derdeyn and her colleagues collaborated with
a public health program which provides thousands of couples
counselling and condom supplies every three months. Despite
these measures, a low level of HIV transmission still occurs.
The collaboration allowed the team to take blood
samples a few weeks after infection occurred and then later as
two participants` immune responses continued.
The scientists isolated individual viruses over
the first two years of HIV infection and tested how well the
patients` own antibodies could neutralise them.
"In one patient where we had very early samples,
there was evidence that neutralising antibody came up within
weeks, and that`s earlier than what was previously thought,"
Derdeyn said.
In both patients, some viruses mutated part of their
outer proteins so that after the mutation, an enzyme would be
likely to attach a sugar molecule to it. The sugar interferes
with antibody attack.
However this tactic, known as the "glycan shield," was
not observed in all cases. Other viruses mutated the part of
the outer protein that the neutralising antibodies stick to
directly. In both patients, many changes in the virus` genetic
code were necessary for escape.
"We need to understand early events in the immune
response if we are going to figure out what a potential
vaccine should have in it. What we can show is that even in
one patient, several escape strategies are going on.
"That means that in order to be immune to HIV
infection, someone may need to have several types of
neutralising antibodies ready to go. Seeing how the virus
mutates will allow researchers to choose the best parts to put
in a vaccinse," Derdeyn said.
The findings are to be published in the `Public
Library of Science Pathogens` journal.
Bureau Report
