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Why One Man Let Mosquitoes Bite Him 200 Times

Would you turn your skin into a parasite buffet for science?

by Meghan Holohan
Jan 23 2017, 9:44pm

Mycteria/Getty Images

For 10 minutes, the mosquito colony feasted on Rafael Hernandez's arm. If Hernandez needed motivation to hang in there, he could remind himself that volunteering his body as a parasite buffet was for an undeniably good cause. Hernandez, a Seattle-based pediatrician, was one of just 10 people who participated in a recent study conducted by the Center for Infectious Disease Research in Seattle to help develop a vaccine for malaria, which poses a risk to at least half of the world's population. In 2015, 214 million people contracted malaria and 438,000 died from it, according to the World Health Organization.

Malaria is spread when a female mosquito—specifically an Anophele mosquito—becomes infected with a genus of parasite known as plasmodium, says Ashley Vaughan, a scientist at the Center for Infectious Disease Research and an author of the study. When the infected mosquito bites a human, the parasite enters the bloodstream and travels to the liver, where it forms a cell called a hepatocyte. After about a week of incubating, the hepatocyte bursts, spreading malaria throughout the body. 

Much to the relief of the researchers, Hernandez was doing just fine a week after the feeding frenzy. The mosquitos dining on his forearm had been genetically engineered to carry a weaker strain of malaria missing three crucial genes—p52, p36, and sap1—thereby preventing the virus from entering and incubating inside the liver, Vaughan says. 

Researchers created the modified parasites using transfection technology; they essentially removed those three genes and their genetic material coding from the genome. This means the genes are permanently eliminated and the parasite can't mutate and replace the genes, says Vaughan. 

"The study shows that genetically attenuated parasites are completely safe. Immunization with the parasites does not lead to blood stage disease," Vaughan says. "Because of the deleted genes, the parasite dies, the antigens develop, and you get an immune response." 

While none of the participants developed blood-stage disease, they'd likely need several "doses"—much like the Hepatitis C vaccine, for example—before they'd become completely immune to it. But blood tests indicated that participants did develop antibodies to malaria, meaning their immune systems' might be able to recognize and fight off the disease. 

Unfortunately, a vaccine for the rest of us is still probably years away, the researchers say. One reason is that the only way to develop immunity is exactly the way Hernandez did it. (It will take more time to develop a traditional, needle-based vaccine.) The researchers also still need to prove that it's effective in larger groups of people so they're starting a bigger trial in June.
Then they have to test it in people in malaria-prone areas who generally are harder to protect than people in malaria-free regions. 

Until then, we'll bring you the next closest thing: Here's what it feels like to be dinner for a swarm in the name of science. 

Okay, let's start with the obvious: Why on earth would you agree to this? 
Vaccines have been one of the great public health interventions of the last 100 years. We still don't have an effective vaccine for malaria, and after hearing about the successful trials of this vaccine strategy in animals, I thought it offered the potential to save hundreds of thousands of children a year. As a pediatrician, I also think it's my responsibility to help care for children in my community. 

But weren't you scared of the potential consequences? We're talking about a deadly disease.
Not really. I knew that the vaccine was based on a strain of malaria that was very easily treated. I also am not bothered by blood draws, so the daily blood tests were not a concern. Getting bitten doesn't bother me much, either. After a day, I almost always have a strong reaction. This time, I was a little anxious about the reaction I was going to have. Because my bites get very swollen and itchy, I feared that hundreds would be even worse. So, having said that, it was weird to then intentionally set my arm over a container full of buzzing mosquitoes. 

What did it look like?
The mosquitoes were essentially inside of what looked like a Chinese take-out container with a screen drawn across the top. We were asked to lay our arm across the screen and then cover our arm with a towel to keep the mosquitoes out of our sight. At first, the bites felt like more of a tickle. Then it transitioned into more of a stinging sensation, but it was not severe. 

Didn't it itch like hell afterwards? 
I do tend to get a little itchy, so I was anxious about that, too, but knew the effects would be temporary. I used a topical hydrocortisone cream, which provided some relief, but since I do have a strong reaction, they still itched quite a bit. Any distraction was very useful.

How bad was your arm? 
It was red and slightly swollen in the shape of the container, but the itching went away after about 10 days. I would absolutely do it again. The development of a vaccine is very important. 

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