An HIV vaccine developed by a team of international researchers has
advanced further than any other in years, raising hopes for controlling the
virus that can lead to AIDS.
Dan Barouch, an immunologist at Beth Israel Deaconess Medical Center and
Harvard Medical School, leads the team that created the vaccine, called
mosaic Ad26/ENV, or Ad26 for short.
In July, a paper in the British medical journal The Lancet detailed the
first human trials of Ad26, conducted in Africa, Thailand and the United
States. Most of the 393 adults in the trials showed strengthened immune
responses, and side effects were minimal. The vaccine also protected 67
percent of rhesus monkeys exposed to a simian virus similar to HIV,
according to the researchers.
Ad26 is currently in an efficacy trial involving 2,600 people in Africa;
the trial will determine if the vaccine can actually protect people from
the virus. Only four other potential HIV vaccines have made it to this
stage of development. The last one, tested in 2013 in the U.S., was shelved
due to a lack of results. Results of the Ad26 trial are expected in three
years.
Barouch talked to Discover about how the vaccine works and its potential.
Q: What’s the biggest challenge to creating an HIV vaccine?
A: HIV is a virus of extraordinary diversity. There are different genetic
sequences of HIV throughout the world, within each country and even within
every HIV-infected individual.
Q: How do you address HIV’s diversity?
A: Our approach to that question, and not saying it’s a complete answer but
at least a step in the right direction, is a so-called mosaic antigen. What
that means is that the HIV sequences that are put into the vaccine are not
from any single strain that was found in a virus from an individual. But
rather, [the vaccine] is a collage of virus strains that aims to provide
the best immune responses to combat the genetic diversity of HIV worldwide.
Q: How well does it work?
A: Animal data and the early phase human data look promising and have
warranted the advancement of this vaccine into a large-scale human trial to
test whether or not it will prevent HIV infection in humans.
It’s definitely a step in the right direction, and it’s a novel approach to
try and address the question of global virus diversity. Is it good enough?
We will only know that when we see the results of the efficacy trial.
If successful, it could have an incredibly important health effect in
curbing and ultimately controlling the HIV epidemic.