[♩INTRO]
Antibodies deserve a ton of credit
they’re these sticky little Y-shaped proteins that our immune systems use
to spot and neutralize basically every kind of threat to us.
They’re so useful that, for more than a century, scientists have been harnessing
their powers in medicines and as molecular tools.
And we’ve gotten really good at finding a great antibody for a given job;
making it even better at binding its target, or antigen; and then mass-producing it.
But these monoclonal antibodies do have some drawbacks.
While they’re small compared to pathogens, they’re still big for proteins.
That makes them pretty fragile when it comes to high temperatures,
which can make shipping and storage tough.
Also, they can’t always fit into the nooks and crannies we want them to.
And that’s even if you can even get them into the body in the first place!
Antibody drugs are typically injected, so they have to be mixed with liquid.
But some antibodies either don’t dissolve well or will clump up together
when they do, which takes injection off the table.
All of this is why, as great as antibodies are, cutting-edge researchers
are hoping to develop smaller and more stable alternatives.
And they’re willing to try just about anything
from chopping antibodies up to creating plastic mimics.
When you have something that’s too big,
the most obvious solution is to make it smaller.
That’s easier said than done, of course.
Luckily, with antibodies, it’s actually pretty straightforward.
The proteins are already kind of modular, sort of like the IKEA furniture
you can piece together to create your dream bookshelf.
And in fact, the immune systems of some other animals take advantage of this!
Llamas and other camelids naturally produce smaller antibodies that consist
of just one part of what we’d consider a normal antibody.
Those helped scientists realize they could somewhat pick
and choose which pieces of an antibody to work with.
And those choices give them control over things like how long the designer
antibodies stick around inside you, where they’re effective,
and how they interact with their antigens.
For example, antigen-binding fragments, or Fabs,
are essentially just one complete arm of an antibody.
These fabulous mini-antibodies are already being used to diagnose
and treat cancer, prevent blood clots, and treat macular degeneration.
Or, you can use the sticky bits all by themselves
that’s essentially what single-chain variable fragments are.
They’re being used in the development of antitumor drugs,
as tracers for identifying and diagnosing cancers, as antitoxins,
and as treatments for inflammatory diseases like rheumatoid arthritis.
With both Fabs and these single-chain variable fragments, the smaller size
allows them to reach locations in the body that larger antibodies can’t.
But without the stabilizing components of antibodies,
they don’t tend to hang around very long.
Plus, on a molecular scale, they’re still pretty big,
and likely to be sensitive to high temperatures.
So some scientists are trying to take this miniaturization idea even further.
Researchers at the University of Washington are hoping to design
super mini-proteins that attack and neutralize pathogens like antibodies do.
These tiny proteins are just as stable as full-sized proteins.
And they actually occur naturally in humans and other animals.
It’s just that, until recently, our methods of detecting proteins weren’t good
at spotting ones this small.
And they are small! Between 40 and 400 times smaller than the average protein.
Rather than relying on natural ones, though,
the UW researchers are designing their own.
They’re developing machine-learning algorithms which figure out the smallest
possible proteins with the highest possible stickiness for a given antigen.
Then, they build them and test them out.
They’ve decided to call their creations mini-binders.
Because they’re mini. And bind to things.
And since these mini-binders are much smaller than regular antibodies,
they have several advantages.
They’re much less fragile and can withstand higher temperatures, for example.
Also, they could be administered by nose spray instead of injection.
And they can be designed to bind a pathogen in multiple different ways
without being too unwieldy,
which would make it less likely for a mutation to render them ineffective.
As a proof of concept, the team designed some mini-binders
to target the flu and SARS-CoV-2 viruses.
And the results were promising!
Mice who got them were just as likely to survive their infections
as mice that got full-fledged antibodies.
But mini-binders are still in the early stages of development,
which means we don’t yet know if they would even work in humans.
So a lot needs to be done before we can even consider counting on them
as a quick response to emerging pathogens.
And there are other ideas for the future of antibodies…
not all of which are biological in nature.
In 2010, scientists in California successfully made plastic antibodies.
They forced synthetic molecular subunits to grow into long, branching chains
around bee venom toxins.
Then, they dissolved the actual venom
leaving behind plastic polymers with perfect, toxin-shaped pockets.
And they worked!
When they gave these plastic antibodies to mice who had been exposed
to bee venom, about 60% of them lived, while none of the control group did.
What’s great about these plastic versions is that they’re cheap to make
and incredibly stable.
They can just sort of hang out wherever.
That means that, in addition to working inside the body, they could be used
in field sensors, point-of-care diagnostic tests, even deodorants!
Pretty much anywhere you might want the ability to grab a specific molecule.
But the current process for making them does require A LOT
of the target antigen, which could be difficult to obtain or might get expensive.
And the plastic antibodies made so far aren’t as specific as actual antibodies,
nor are they smaller.
So, there’s plenty of room for improvement.
But whether we’re talking plastics or simply smaller proteins,
it’s clear that antibody technologies have come an incredibly long way
since the horse-blood treatments of the 19th and 20th centuries.
They’ve helped us treat snake bites, cancers, inflammatory diseases,
blood clots, viruses, and blindness.
And they’ve given us a window into our bodies
from telling us what we’re sick with to letting us know if we’re pregnant.
Plus, they’ve become essential tools in the laboratory,
all thanks to their unmatched ability to stick to specific things.
And as researchers develop new kinds of antibodies
and antibody-inspired technologies, the potential applications for them,
both in and out of medicine, is only going to continue to grow.
Thanks for watching this episode of SciShow
the third and final episode in our antibodies mini-series!
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[♩OUTRO]