This episode was filmed on May 29th, 2020.
If we have more recent episodes on the COVID-19
pandemic,
we’ll include them in the description.
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Researchers have been working on vaccine candidates
for COVID-19
for months now.
Some of their work looks like traditional
vaccine development,
albeit on a super sped up timeline.
But other research groups are trying some
more creative approaches
to therapy... including ones that involve
directly editing our genes.
This is known as gene therapy, and it’s
not as outlandish
as you might be thinking.
The outlandish part is that viruses are one
of our primary tools
for gene therapy -- meaning we might be able
to solve
our current virus problem… with a virus.
However, this approach comes with some uncertainty
and a significant price tag, so it’s hardly
a sure thing.
Here’s how it might work.
The goal of a vaccine is to safely expose
your immune system
to antigens derived from an infectious agent
like a virus.
After vaccination, our bodies recognize this
antigen
and know how to defend against it for a period
of time.
That might mean exposing our bodies to a weakened
or inactivated form of a virus or bacterium
so that our immune systems
can produce antibodies against it.
But there are plenty of other ways we can
end up with immunity.
For example, some doctors are already using
convalescent plasma
from recovered patients to transfer their
antibodies to patients
who are critically ill.
But that’s still in the testing stages.
Some of the vaccine candidates making swift
progress
in clinical trials are based on the nucleic
acids DNA and RNA.
The idea is to teach our cells to make viral
antigens and to show them
to our immune system -- rather than bundling
the antigens themselves in a shot.
One hurdle to this idea is getting that genetic
code into cells.
RNA, in particular, can get broken down pretty
quickly in our bodies.
But the concept is solid: teach cells to make
a specific part
of the virus -- like the spike protein, which
SARS-CoV-2
uses to invade our cells.
So rather than inject patients with just the
code,
another approach is more akin to fighting
fire with fire.
Or a virus with a virus.
After all, viruses are really efficient at
injecting genetic material
into host cells.
It’s what they do -- they’re really just
little nucleic acid
delivery packets, with instructions for making
more packets.
And we can reprogram those instructions.
So they’re actually perfect if we want to
introduce
genetic instructions into a cell.
But we need a virus that won’t also make
us sick, which is why
adeno-associated viruses, or AAVs, are the
DNA vehicle of choice.
AAVs are little viruses that don’t cause
disease,
further genetically engineered to deliver
their payload
without making more of themselves.
They’ve already been used in the past in
efforts
against other coronaviruses.
Different AAVs tend to infiltrate different
tissues,
and since COVID-19 affects the lungs, we’d
need to find an AAV
that can get to our airway.
Some of the AAVs scientists have tested were
able to get
into human respiratory cells in culture, but
they haven’t been tested
in actual humans yet.
And since an AAV is just a tiny DNA delivery
unit, we could swap out
different sequences and test them all very
quickly.
AAV-based gene therapy for other diseases
has already been approved
by the US Food and Drug Administration, which
could speed
implementation of a version of this therapy
for COVID,
at least according to some.
The potential downside is that this style
of gene therapy
permanently edits cells.
Not as permanently as you might be thinking.
It wouldn’t target our germ cells, meaning
we wouldn’t pass
this DNA down to our kids.
We don’t yet know all of the cell types
we would need to target,
but the changes probably wouldn’t stay with
us for a lifetime.
Which means any kind of AAV-based therapy
we develop for SARS-CoV-2
would only be a temporary fix.
But it might offer us some level of protection
while we’re
waiting on a more permanent vaccine.
But we can’t rule out other long-term side
effects
from directly tinkering with our DNA, even
if it seems like
it should be safe based on what we know.
On top of all that, there’s the cost.
Since the currently approved AAV-based drugs
treat extremely rare
genetic diseases, they come with an inflated
price tag.
But since an AAV for COVID-19 would be a much
larger market,
the cost would hopefully be lower.
Now, will gene therapy for the novel coronavirus
ever actually be a thing?
We have some good news on that front.
Researchers in Massachusetts recently announced
plans
for a COVID vaccine clinical trial using AAVs.
They’re in the preclinical trials right
now, and if all goes well,
they’ll move into human trials later this
year.
Which means if we do ever see AAV therapy,
it will still be a while.
But it’s definitely one of the more creative
efforts out there
-- and we need to try everything we’ve got.
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