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We've learned a bit about how hummingbirds see motion in an unexpected way, and scientists are working on a potential new malaria vaccine by genetically manipulating the parasite that causes it!

Hosted by: Hank Green
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Hank: Hummingbirds are basically tiny stunt pilots, even flying backwards and upside down. Some species can flap their wings up to 80 times per second, and go from hovering in midair to speeding at over fifty kilometers per hour. And in a paper published last week, researchers from the University of British Columbia looked at hummingbird brains to figure out how they see the world as they pull off these stunts.

There’s a small spot in the brain called the nucleus of the optic tract in humans and the lentiformis mesencephalic or LM in birds. In most animals, it contains specialized neurons that detect things moving from back behind you forward, so that you can avoid collisions or maybe see something scary, or that’s going to eat you, coming at you. But hummingbird brains work a little differently from all these other animals.

Research has shown that a hummingbird’s LM is bigger relative to its brain size than in other birds, and these scientists wondered if it processes visual information differently, too. To find out, they put half a dozen hummingbirds under anesthesia and exposed the area of their brains where the LM is located, inserting tiny electrodes to record activity in their neurons. They did the same with ten zebra finches, another small bird, to get a comparison.

Then, they had all the birds watch computer-generated dots move across a screen in various directions and at various speeds. In the zebra finches, the LM did what they expected, responding more to dots that seemed to move from back-to-front. But when they checked out the hummingbird data, the researchers got a surprise.

Neurons in the hummingbird LMs were reacting pretty equally to motion in all different directions, rather than being focused on one kind of movement. The hummingbirds were also more attuned to faster-moving dots. This all-over awareness probably helps hummingbirds stabilize themselves and avoid obstacles while they’re zipping around flowers and slurping up nectar. So even amongst their flying cousins, hummingbirds are just super well-equipped for acrobatics – from their muscular wings, right on down to their brains.

If testing a patch of neurons in a tiny hummingbird brain sounds hard, what about disabling three specific genes out of 5000 in a parasite’s DNA? Scientists did just that to develop a new type of malaria vaccine, and recently completed the first human trial with some promising results.

Malaria is a devastating disease caused by parasites in the genus Plasmodium. These parasites need two hosts to complete their life cycle: mosquitoes and some vertebrate, human being the one we’re most concerned with.

The cycle begins (if you can say a cycle begins... it’s a circle, so we’re just going to pick an arbitrary point here) when a mosquito bites an infected human and sucks up parasite gametophytes, or sex cells, along with blood. These combine and grow to become the immature form of the parasite, called a sporozoite. Then, when that mosquito bites another human, the sporozoites are injected too, and travel to the liver to hunker down, grow, and multiply. Each sporozoite produces as many as 30,000 mature parasite cells, which are called merozoites, which spread through the bloodstream, burrow into red blood cells, and cause a full-blown infection.

Malaria starts with fever and flu-like symptoms, but if it’s not treated quickly it can cause organ failure, seizures, and death. It’s this complicated, multi-stage infection process that makes coming up with an effective vaccine so hard. Even the best vaccine developed so far, which was engineered with part of a protein produced by the most dangerous parasite, P. falciparum, only works about a third of the time and requires regular booster doses.

But this new vaccine uses something called a genetically attenuated parasite, or GAP, to let the immune system learn how to defend against the parasite without any real danger of infection.

Knocking out just three of the 5000 genes in the P. falciparum genome can prevent sporozoites from maturing and reproducing, so they can’t infect the bloodstream.

These scientists first tested their genetically-engineered dud on mice, and it didn’t make them sick. That was promising, but the real test came when the same mice were injected with the full-powered parasite, with all its genes intact. Even then, they didn’t develop an infection, because their immune systems were already pumping out antibodies after being exposed to the GAP.

Now, not every medical advance in mice actually works in us, so the researchers ran a test in ten human volunteers. They infected mosquitoes with the genetically-engineered sporozoites and let them snack on the volunteers’ forearms. And none of the people in the trial developed malaria, so that’s good! And just like in the mice, their immune systems started to produce antibodies.

Now, there’s still a ton of work to do to make sure this vaccine is safe and effective for public use. Like, the scientists need to expose vaccinated humans to the unmodified parasite to make sure it won’t cause an infection, because they didn’t test that this time. Plus, they have to figure out how to inject the GAP like any other vaccine, instead of using mosquitoes as a delivery system, because that’s the only way they know how to do it right now, which is pretty amazing! But, even right now, this new vaccine seems like it has huge potential to save some lives.

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