In recent years, biologists armed with a new gene-editing technology have proposed altering mosquitoes so they’re more resistant to diseases like malaria and dengue. Using a mechanism known as a “gene drive," the researchers say they can quickly push an alteration through an entire species.
“In less than five years, I think there’s a good chance it will be out there," Gates said in an interview with Bloomberg News before speaking at a conference of the American Society for Microbiology in Boston.
In normal reproduction, a mosquito carrying one copy of an altered gene passes it on to 50% of its offspring. In a gene drive, an engineered segment of DNA is inserted in the mosquito that causes nearly 100% of the offspring to inherit the altered gene, dramatically increasing the rate of spread.
“Gene drives, I do think, over the next three to five years will be developed in a form that will be extremely beneficial for knocking down" mosquito populations, Gates said. “Of course, that makes it a key tool to reduce malaria deaths."
Scientists have said they’ve successfully created malaria-resistant mosquitoes in a lab that passed on the trait to 99.5% of their progeny. While the technology may work, it’s controversial. Some researchers have warned that gene drives may not be safe—what if the targeted species cross-breed with another organism? What if released mosquitoes develop spontaneous, unintended mutations?—and have called for more regulation.
“My basic belief is that children dying of malaria is a bad thing, and that we should be able to meet these objections," Gates said. “But there’s still a fair bit of work to be done. Nothing is ready to be deployed today."
Through the Bill and Melinda Gates Foundation, the Microsoft Corp. co-founder has waged a lengthy battle against malaria, committing almost $2 billion in grants to combat the disease since launching the philanthropy group in 2000. There were about 214 million malaria cases and 438,000 deaths from the disease in 2015, according to the World Health Organization.
In the meantime, Gates says a different mosquito project already has been deployed—one that doesn’t involve genetic modification. The insects are infected with a bacterium called Wolbachia, which can block the transmission of dengue and the Zika virus. The Gates Foundation started funding work on the Wolbachia mosquitoes 15 years ago, and they have already been released in countries including Australia and Indonesia. A large-scale deployment of Wolbachia mosquitoes may take place in Colombia and Brazil in the next year, Gates said.
Speaking to thousands of attendees at the conference on Thursday night, Gates said the ultimate goal was to eradicate malaria, learning from previous efforts to wipe out diseases including smallpox and polio.
“The highest return ever in global health was smallpox eradication," he said. “Every year, the lack of disease cases and lack of having to think about vaccination has been a mind-blowing return."
The idea of a gene drive isn’t new, though it’s been helped by the use of Crispr-Cas9, a gene-editing technique that’s cheaper and faster than previous methods. Working like a pair of molecular scissors, Crispr can precisely cut out, and even replace, sections of DNA. It’s given researchers an unprecedented ability to direct where DNA should be edited. Crispr-based therapeutics for genetic diseases also are being developed, including by Editas Medicine Inc., a Cambridge, Massachusetts-based biotechnology firm backed by Gates.
Gates says he hopes to see gene editing used against HIV. His foundation has funded older gene-editing efforts against HIV, which were less efficient than Crispr.
“HIV is still a lifelong disease, and any type of cure approach or some sort of way that you’d protect somebody on a lifelong basis, that would be invaluable, but that’s at a very early stage."
While Editas isn’t working on HIV, “it’s fantastic that they’re starting with some eye diseases, looking at some things that have been completely insoluble that they may have solutions for," he said. Bloomberg