The Search For an HIV Vaccine May Soon Be Over

HIV is one of the deadliest viruses on the
planet, newly infecting about 1.7 million people in 2018. Since the early days of the
epidemic, the virus itself has confounded researchers, who have long been searching
for a vaccine to prevent its spread. And after years of slow progress, that search may soon
be over. The epidemic as we now know it, is thought
to have started in the mid-to late 1970s, but it wasn’t until 1983 that the HIV virus
was first identified and isolated. By that point, HIV had begun to rapidly spread around
the world—and since the epidemic began, it’s claimed the lives of over 32 million
people. To understand why this virus causes so much
harm, we first need to know how it invades the body. First off, it’s a retrovirus,
which is a type of virus that inserts a copy of its genome into the DNA of a host cell
— in HIV’s case, T-helper cells which help our immune system fight off infection.
After latching onto the cell, HIV fuses with it, integrating its genetic information with
the new host’s DNA. The infected cell then produces more HIV proteins, which are eventually
released into the bloodstream where they continue to replicate. If left untreated, HIV severely
weakens the immune system’s ability to function properly—this final stage of the infection
is AIDS. And it’s precisely the virus’ unique characteristics
which allow it to propagate inside the human body that also make it so difficult to tackle.
“HIV is a remarkably small virus. It has few genes comprised in it, regardless of how
small and simple it may be, it has very complex dynamic interactions with the human immune
system.” There’s currently a few ways to stop HIV
from progressing in its life cycle. Specific drugs have been developed that can stop the
virus from attaching to T-helper cells, while other types of drugs work to prevent the virus
from taking control of the cell’s nucleus and enter the bloodstream. Called antiretroviral
therapy, or ART, this drug combination works well, but is expensive and requires lifelong
upkeep. “In those resource constrained areas or
where the stigma of HIV is still a major problem, prevention methods that require daily pills
may still limit the number of individuals who would have access to these. It’s only
through the application of very highly effective vaccines that we’ve been able to control an
infection that spread around the globe, and eventually eradicate that.”
But that doesn’t mean developing a vaccine is easy. There aren’t many good models to
reference for research in humans, which means we don’t know what the body’s immune response
looks like when trying to protect itself. HIV’s extraordinary diversity and ability
to rapidly mutate are also huge obstacles in getting a grip on the virus. Just recently,
researchers announced that they’d ID’ed a new strain, the first in 19 years. Despite
this, there has been huge progress made in the last decade.
In 2009, researchers declared that a vaccine trial done in Thailand had protected a significant
minority of humans against the disease for the first time ever. RV144, is a combination
of two genetically engineered vaccines, neither of which had worked before in humans.
“We observed a modest level of efficacy over three and a half years—about 30%. So,
we have initiated a clinical trial in South Africa that is marching along the path to
try to confirm these findings from the Thai trial and extend those findings through a
number of approaches.” As the world’s largest publicly-funded international
collaboration focused on the development of vaccines to prevent HIV and AIDS, HVTN has
conducted all phases of clinical trials that have involved thousands of people. In addition
to two massive trials to test whether giving antibodies to patients can protect them from
HIV infection, as of this year the group has also fully enrolled two similarly ambitious
vaccine trials. Called HVTN 702 and 705, these regimes were designed to test whether patients
given a vaccine can create antibodies on their own. Both vary slightly in their approach—
702 is based off of the Thai trial, while 705 is focusing on overcoming the viruses’
genetic diversity. “What’s very exciting is that the immune
responses elicited by these three different vaccine strategies is different within each
clinical trial, but there’s similarities across them. And we’re looking for specific immune
responses that we will correlate with vaccine efficacy, with just a few dozen people that
will eventually lead us to a more globally effective vaccine that could be used across
different populations and routes of exposure.” With hopes high, and even higher stakes, the
mood of the vaccine research seems to be one of cautious optimism. But results of both
the 705 and 702 vaccine regimes won’t be in until late 2021 and 2022, when the trials
are expected to close. “They will certainly be a success and that
will get a clear answer as to whether or not these vaccines worked, but I think we also
have to be measured in our expectations. And that this is one of the most formidable biomedical
challenges we’ve ever undertaken as a society, as a global research community.”
If you want to learn more about the search for a potential HIV cure, check out this episode
of How Close Are We. If you liked this video, let us know down in the comments and
don’t forget to subscribe for more Seeker. As always, thanks for watching, and I’ll
see you next time.

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