A new drug candidate is so potent against all
strains of HIV, researchers think it could work
as a new kind of vaccine.
Developed by researchers from more than a
dozen research institutions and led by a team
at the Scripps Research Institute in the US,
the drug is effective against doses of HIV-1,
HIV-2 and SIV (simian immunodeficiency
virus) that have been extracted from humans
or rhesus macaques - including what
researchers consider to be the ‘hardest-to-
stop’ variants. It worked against doses of HIV
that are way higher than what would be
transmitted between humans, and works for
at least eight months after injection.
"Our compound is the broadest and most
potent entry inhibitor described so far,” lead
researcher Michael Farzan from the Scripps
Institute said in a press release . "Unlike
antibodies, which fail to neutralise a large
fraction of HIV-1 strains, our protein has been
effective against all strains tested, raising the
possibility it could offer an effective HIV
vaccine alternative.”
While traditional vaccines work by delivering a
tiny, weakened dose of a virus to train your
immune system to thwart an actual attack,
this drug does something quite different. The
way HIV infects a person is by targeting their
T lymphocytes - a very specialised type of
white blood cell - and injecting its own genetic
material inside to transform them into HIV-
producing machines. So, quite literally, it turns
our immune systems against us.
But what Farzan’s team has discovered is
that a particular type of protein found on the
surface of white blood cells can actually bind
to the surface of the HIV virus in two different
places simultaneously, which means that not
only does the virus no longer have a chance
to change the position of its receptors to
escape, it’s also being blocked from entering
the T lymphocyte cells.
"When antibodies try to mimic the receptor,
they touch a lot of other parts of the viral
envelope that HIV can change with ease,"
said one of the team, Matthew Gardner, from
the Scripps Institute. "We've developed a
direct mimic of the receptors without
providing many avenues that the virus can
use to escape, so we catch every virus thus
far.”
According to James Gallagher at BBC News,
the vaccine would be delivered via a weak,
harmless type of virus that would introduce a
section of DNA to a patient’s healthy muscle
cells, containing instructions for how to
produce this HIV-blocking protein. The protein
would then be pumped out into the
bloodstream over and over, protecting the
patient from being infected over several
months. The team reported in Nature that the
effects of the drug lasted for at least 34
weeks in their monkey subjects, but they
think they could get it to last for years,
perhaps even decades.
"We are closer than any other approach to
universal protection, but we still have hurdles,
primarily with safety for giving it to many,
many people,” Franzen told the BBC. One
such concern is that no one really knows
what the long-term implications would be for
a person who is having an anti-HIV response
being pumped around their body non-stop.
The team will be looking into this when they
get their human trials underway.
"In the absence of a vaccine that can elicit
broadly protective immunity and prevent
infection, and given the lack of major
breakthroughs on the horizon to provide one,
the idea of conferring potent, sustained
vaccine-like protection against HIV infection
through gene therapy is certainly worth strong
consideration,” Nancy Haigwood from the
Oregon Health & Science University in the US,
who wasn’t involved in the study, told the
BBC.
source: www.sciencealert.com/potential-new-vaccine-blocks-every-strain-of-hiv