Breakthrough in hunt for HIV vaccine

WASHINGTON (AFP) – US scientists seeking to
unravel the mysteries of HIV have made an
important breakthrough after capturing the
clearest image yet of a protein which allows
the deadly virus to attack human immune
cells, new research showed Tuesday.
Scientists at The Scripps Research Institute
(TSRI) and Weill Cornell Medical College have
managed to obtain a detailed view of the
atomic structure of the protein which envelops
HIV, the virus which causes AIDS.
The development could potentially pave the
way for a vaccine, according to the findings
published in the US journal Science.
"In order to develop a vaccine, you have to
understand what bits on that very important
trimeric protein can be recognizes by broadly
neutralizing antibodies," said Scripps Institute
cell biologist Bridget Carragher.
"And in order to understand that, you need to
understand what the structure of the thing
looks like.
"Then once you do, you can start designing a
vaccine that will mimic that thing and elicit an
antibody response and get the human being to
fight the real virus when it comes along."
Although sophisticated antiviral drugs have
been used to manage HIV infections in many
developed countries, a vaccine against
infection has proved elusive.
The failure to find a vaccine is often attributed
to the complex nature of HIV's envelope
protein, known as Env.
The delicate structure of Env has hampered
efforts to obtain the protein in a form that
allows for the atomic-resolution imaging
necessary to fully understand it.
"It tends to fall apart, for example, even when
it's on the surface of the virus, so to study it
we have to engineer it to be more stable," said
TSRI biologist Andrew Ward.
However the researchers were able to engineer
a version of the Env trimer, or three-
component structure, that has the stability
required for atomic-resolution imaging.
The scientists were then able to study the Env
trimer using cutting-edge imaging and electron
microscopy.
The use of X-ray crystallography allowed
researchers to examine the Env trimer in more
detail than previous attempts.
The data also shed light on the process by
which Env assembles and later shifts shape
during infection, and also allowed researchers
to make comparisons with protein envelopes
from other deadly viruses such as flu and
Ebola.