Yahoo – AFP, Mariette Le Roux, April 27, 2016
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| Exposed to simian HIV once a week, non-treated macaques contracted the virus after just three weeks on average, researchers say, whereas the trial monkeys given one shot of a lab-produced antibody remained virus-free for up to 23 weeks (AFP Photo/Jay Directo) |
Paris (AFP)
- Just one shot of a lab-produced antibody protected macaques against a sort of
monkey HIV for nearly six months, said a study Wednesday into a potential
vaccine alternative.
Exposed to
simian HIV (SHIV) once a week, non-treated monkeys contracted the virus after
just three weeks on average, the researchers said, whereas the trial monkeys
remained virus-free for up to 23 weeks.
In human
populations at high risk of contracting the AIDS-causing virus, such
protection, even temporary, "could have a profound impact on virus
transmission," the team of German and US-based researchers reported in the
journal Nature.
They had
examined "passive immunisation" as an alternative to an HIV vaccine,
which experts fear may still be years off.
A vaccine
works by priming the body to respond with germ-fighting antibodies whenever a
virus or bacteria invades. It is long-lasting, sometimes for life.
"Passive
immunisation" involves the transfer of antibodies generated by one person
directly to another to provide protection, which is shorter-lived.
Antibody
shots were used to protect travellers against Hepatitis A until a vaccine
became available in the 1990s, and some hope the technique could stave off
millions of HIV infections until a vaccine comes to the market.
Transferred
antibodies had previously been shown to protect animals against HIV-like
viruses for a day or two, but never as long as in this study.
Proof of
concept
Since the
outbreak started in the early 1980s, about 71 million people have been infected
by HIV, and some 34 million have died, according to UN estimates.
There is no
cure, and the only way of dealing with HIV is lifelong reliance on
antiretroviral drugs, invented in the 1990s, to stop the virus from
replicating.
The
treatment carries side effects and is costly.
The quest
for a vaccine has been long and frustrating, in spite of hundreds of millions
of dollars in funding.
Some of the
focus has shifted to antibodies, but this too proved complicated as each HIV
antibody tends to target a specific virus strain.
In recent
years, researchers have discovered that about 10-30 percent of HIV-infected
people have a naturally-present, "broadly-neutralising" (bNAb) type
of antibody which targets several strains at once.
Three of
these were tested in the new study.
Each
delayed infection in macaque monkeys, said the team -- the first by up to 12
weeks, the second by 20 weeks, and the third by 23 weeks.
A single
antibody shot "was protective against repeated low-dose SHIV infection for
several months," the team wrote.
This served
as "proof of concept" that periodic antibody shots may be useful as
an alternative to vaccination, they said, though further research must confirm
that the findings can be replicated in humans.
"When
considered in the context of a potential exposure to HIV-1 in regions of the
world where HIV-1 is endemic," wrote the team, such an infection barrier
"could have a profound impact on virus transmission".
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