Scientists Release Controversial Genetically Modified Mosquitoes In High-Security Lab
Scientists Release Controversial Genetically Modified
Mosquitoes In High-Security Lab
Scientists hope these mosquitoes could help eradicate
malaria.
Pierre Kattar for NPR Heard on Morning Edition February
20, 20195:00 AM ET
Scientists have launched a major new phase in the testing
of a controversial genetically modified organism: a mosquito designed to
quickly spread a genetic mutation lethal to its own species, NPR has learned.
For the first time, researchers have begun large-scale
releases of the engineered insects, into a high-security laboratory in Terni,
Italy.
"This will really be a breakthrough
experiment," says Ruth Mueller, an entomologist who runs the lab.
"It's a historic moment."
The goal is to see if the mosquitoes could eventually
provide a powerful new weapon to help eradicate malaria in Africa, where most
cases occur.
"It's very exciting," Mueller says.
NPR health correspondent Rob Stein was the only
journalist in the lab in Italy when a major new experiment testing the modified
mosquitoes began. Ruth Mueller runs the lab.
The lab was specially built to evaluate the modified
insects in as close to a natural environment as possible without the risk of
releasing them into the wild, about which there are deep concerns regarding
unforeseen effects on the environment.
"This is an experimental technology which could have
devastating impacts," says Dana Perls of Friends of the Earth, an
environmental group that's part of an international coalition fighting this new
generation of modified organisms.
To prevent any unforeseen effects on the environment,
scientists have always tried to keep genetically engineered organisms from
spreading their mutations.
But in this case, researchers want the modification to
spread. So they engineered mosquitoes with a "gene drive."
A gene drive is like a "selfish gene," Mueller
says, because it doesn't follow the normal rules of genetics. Normally, traits
are passed to only half of all offspring. With the gene drive, nearly all the
progeny inherit the modification.
"All the offspring. All the children — the mosquito
children — have this modification," Mueller says.
Researchers created the mosquitoes by using the powerful
new gene-editing technique known as CRISPR, which Mueller likens to a
"molecular scissor which can cut at a specific site in the DNA."
The cut altered a gene known as "doublesex,"
which is involved in the sexual development of the mosquitoes.
"The females become a bit more male," Mueller
says. "A kind of hermaphrodite."
While genetically female, the transformed insects have
mouths that resemble male mosquito mouths. That means they can't bite and so
can't spread the malaria parasite. In addition, the insects' reproductive
organs are deformed, which means they can't lay eggs.
As more and more female mosquitoes inherit two copies of
the modification, more and more become sterile.
The idea is that if these modified mosquitoes are
eventually shown to be safe and effective, they might someday be released in
African villages plagued by malaria. The hope is that they would spread their
mutation and eventually sterilize all the females. That would crash — or
drastically reduce — local populations of the main species of mosquito that
spreads malaria, known as Anopheles gambiae.
"Malaria is a huge problem affecting probably
two-thirds of the world's population," says Tony Nolan, who helped develop
the mosquitoes at Imperial College London. He is now at the Liverpool School of
Tropical Medicine.
Malaria sickens more than 200 million people each year
and kills more than 400,000, mostly young children.
Scientists think gene-drive organisms could help solve
many problems, including wiping out other insect-borne diseases such as Zika
and dengue. Gene-drive creatures might also save endangered ecosystems by
eradicating invasive rodents. They could help feed the world by creating more
efficient crops.
But critics fear that gene-drive organisms could run amok
and wreak havoc if they were ever released into the wild. The insects could
inadvertently have a negative effect on crops, for example, by eliminating
important pollinators, they fear. The insects' population crash could also lead
to other mosquitoes coming with other diseases, critics say.
"We can't be taking lightly this extermination
technology," Perls says. "We need to slow down. We need to hit the
pause button on gene drives."
Some activists in Africa agree.
"This is a technology where we don't know where it's
going to end. We need to stop this right where it is," says Nnimmo Bassey,
director of the Health of Mother Earth Foundation in Nigeria. "They're
trying to use Africa as a big laboratory to test risky technologies."
The experiment is a key step in the Target Malaria
project. The project's major funder is the Bill & Melinda Gates Foundation,
which also supports NPR and this blog.
Nolan and Mueller say the project is working methodically
and cautiously to assess the mosquitoes in close consultation with scientists,
government officials and local residents in Africa. In addition, the gene-drive
mosquitoes would affect just one of hundreds of mosquito species.
"There's going to be concerns with any technology.
But I don't think you should throw out a technology without having done your
best to understand what its potential is to be transformative for medicine.
And, were it to work, this would be transformative," Nolan says.
Other experts agree.
"If my kids lived in Africa, I'd say, 'Go for it as
quickly as possible,' " says Kevin Esvelt, an evolutionary engineer at the
Massachusetts Institute of Technology.
Esvelt is a gene-drive pioneer who has repeatedly warned
scientists to move cautiously with the technology because it is so powerful.
But Esvelt thinks Target Malaria has been acting responsibly.
"The known harm of malaria so outweighs the combined
harms of everything that has been postulated could go wrong ecologically,"
Esvelt says.
The project plans years of additional study to evaluate
the mosquitoes and possible environmental impacts, as well as social and
political consultations to build a consensus for when a release would be
permitted. That's probably at least five years away, Nolan says.
On the day NPR visited the Terni lab, Mueller
demonstrated several layers of security at the lab to keep any mosquitoes from
escaping. She noted that the experiment is being conducted in Italy, where this
species of mosquito could not survive the climate even if the insects did
escape.
"We really want to show that we work very, very
sound and responsible about this new technology," Mueller says.
To enter the most secure part of the facility, Mueller
punches a security code into a keypad to open a sliding glass door. As the door
seals, a powerful blower makes sure none of the genetically modified mosquitoes
inside escape. Anyone entering must don white lab coats to make it easier to
spot any mosquitoes that might try to hitch a ride out of the lab and must pass
through a second sealed door and blower.
Once inside, Mueller points to a small container made out
of white mosquito netting. Inside are dozens of mosquitoes.
"Here we have gene-drive mosquitoes — these
genetically modified mosquitoes," she says.
The insects quickly crashed populations of their natural
counterparts in small cages in a secure basement lab at Imperial College
London. The new experiment is designed to test them in a hot and humid
environment more closely resembling their natural habitat in the African
countries where this species of mosquito lives.
"This helps us understand better how a gene-drive
release would work in the real world," she says.
Mueller heads to a large, thick metal door.
"We will now enter the experimental chamber where
the release takes place today," she says.
The chamber houses six huge "cages." The
9-foot-high cage walls are made out of white mosquito netting to keep the
insects contained. The netting stretches from the floor to the ceiling. Each
cage contains hundreds of unmodified mosquitoes.
Every cage is equipped with several features designed to
replicate the conditions in which the mosquitoes live in the wild. The idea is
to encourage the mosquitoes' natural behavior.
The cages' features include stacks of moist clay hollow
cylinders for the mosquitoes to use as shelters. Also, large black boxes with
white backgrounds are inside the cages. The contrasting colors stimulate
swarming, which is when the mosquitoes mate.
A computer precisely controls the light in the chamber to
simulate sunrise and sunset and the natural changes in intensity and color
throughout the day.
"OK, we can start," Mueller says as several of
her colleagues crowd into the chamber.
After pulling on rubber gloves, lead technician Tania
Persampieri carefully picks up a tray holding glass dishes, each containing
dozens of the modified mosquitoes in the pupal stage of development. They're
squirming around in water.
Persampieri slowly walks over to the first cage, squats
down and picks up one of the dishes holding the mosquito pupae. She gently
slides the dish through an opening in the netting that prevents any insects
from escaping and places the vessel on the floor.
"The experiment has now started," Mueller says.
"It's very exciting."
Persampieri and her co-workers move quietly to avoid
unnecessarily stressing the mosquitoes.
Persampieri releases immature gene-drive mosquitoes in
four of the six cages. Two cages receive amounts equal to 25 percent of the
unmodified populations already in the cages; two cages receive amounts equal to
50 percent. The remaining two cages will be used for comparison and so don't
receive any modified insects.
Other technicians slide canisters of warm cow's blood
into each cage.
"We heat up the blood because this is attractive for
the mosquitoes. They don't like cold blood. They want to have a living animal
where they can bite in," Mueller says.
As the researchers are finishing, the lights in the cage
chamber start to dim.
"It's a slow dimming and also a specific light color
— very orange, very warm color — so that they really feel like [they're] having
a sunset," Mueller says.
That's key because sunset is when male mosquitoes start
their mating dance.
"The males make swarms — many mosquito males flying
around," Mueller says. "It looks a bit like dancing."
As the males swarm, females fly in and select a male;
then the pair flies out to mate.
"They couple and make babies," Mueller says.
Mueller and her colleagues are collecting thousands of
eggs from the cages every week to monitor how well the sterilizing mutation is
spreading.
The researchers hope to know within six months to a year
whether the modified mosquitoes dance well enough to efficiently spread their
lethal modification in the wild.
"Maybe you can see already if you go a bit
nearer," Mueller says, pointing to a few mosquitoes that have begun flying
around inside the black boxes.
Turns out, Terni is home to a shrine to St. Valentine.
And the experiment is beginning just before Valentine's Day. So the basilica's
annual Valentine's Day celebrations are just beginning as well with a church
service at his shrine.
As she watches the modified mosquitoes start their first
mating ritual in her lab, Mueller muses, with a laugh: "It's very
romantic."
Comments
Post a Comment