A female Aedes aegypti mosquito in the process of acquiring a blood meal from a human host. (James Gathany/CDC via AP)
Genetically engineered bugs to fight malaria and Zika? Not so fast, experts say
It is premature to fight malaria, Zika, Lyme and other diseases with genetically engineered insects or other animals that have been designed to spread their modified genes in the wild, according to an expert panel convened by the National Academies of Science, Engineering and Medicine.
But the group, saying such a “gene drive” offers promise in combating diseases or saving endangered species, concluded that experimental research should continue, including carefully controlled field tests.
The panel's report, released Wednesday, has no force of law but will likely be influential in the debate about how, when and whether to use gene-drive technology to suppress the spread of pathogens. It comes amid mounting concerns about the Zika virus, which can be spread by mosquitoes and is linked to a spike in birth defects in South America.
The National Academies formed the group in response to the recent development of gene-drive techniques. The field of biotechnology is in the midst of a revolution, in part due to a new gene-editing tool known as CRISPR, which mimics a system invented by bacteria to defend themselves against viruses. With CRISPR, scientists can easily manipulate the genetic code of almost any organism.
An earlier National Academies report, released last month, gave what could be described as a nuanced endorsement of genetically engineered (GE) crops. This new report is a close cousin, focusing on a subset of GE animals, including disease-carrying insects, in which the modified genes are designed to spread like wildfire through nature and have the potential to reduce populations or even, in theory, to drive a species to extinction. It can also protect species that are assaulted by invasive pathogens.
The new report has a more cautious tone than the crop study — more akin to a flashing red light (stop and proceed if all is clear) rather than a flashing yellow. The panel did not object to gene-drive technology in theory but said there are too many uncertainties in how it would play out. Its report states:
"There is insufficient evidence available at this time to support the release of gene-drive modified organisms into the environment. However, the potential of gene drives for basic and applied research are significant and justify proceeding with laboratory research and highly-controlled field trials."
The report said the accelerated pace of innovation in genetic engineering is both a positive and a negative. Gene-modified organisms could help eradicate vector-borne diseases and could help boost populations of endangered species (by targeting diseases that are driving down their numbers). But society should resist the temptation to deploy gene-drive organisms in a crisis, the report states:
"The presumed efficiency of gene-drive modified organisms may lead to calls for their release in perceived crisis situations before there is adequate knowledge of ecological effects, and before mitigation plans for unintended harmful consequences are in place."
That's a recurring theme in the 202-page report: This is a new science with a lot of unknowns.
It also has "many, many promising features," said James Collins, co-chair of the panel and a professor of natural history at Arizona State University. But he raised the possibility that a gene-drive effort targeting a pathogen carried by one species might ultimately fail if the pathogen adapted and became endemic in a different species.
And there might be other anticipated changes to ecosystems, the group warned.
"We have proof of concept in four species in highly controlled, narrowly defined laboratory environments," said Elizabeth Heitman, associate professor of medical ethics at Vanderbilt University Medical Center and co-chair of the panel. "Much of what we talk about as benefit and harm is speculative.”
Gene-drive technology is distinct from more conventional forms of genetic engineering, because the goal is to let the new genes drift through a broader population, propagated by sexual reproduction, rather than have them remain confined to, say, a patch of corn or soybeans. In laboratory experiments, gene drives have been successful in fruit flies, yeast and mosquitoes.
There have already been attempts to use genetic engineering as a form of pest control, but these did not constitute gene drives because they didn't endure through multiple future generations. For example, in Brazil, authorities have approved a plan to fight the Zika virus using genetically engineered mosquitoes that carry a self-destruct gene. These mosquitoes have been raised with nutrients that deactivate the lethal gene. When the males are released into the wild, their offspring carry the self-destruct gene and die before maturity.
The panel, echoing other recent reviews of CRISPR and associated technologies, urges a broad societal discussion about how genetic engineering proceeds.
"The question of how human beings manipulate nature, whether that’s a moral action or not, is not a new question," Heitman said. "We’ve not answered that question successfully in any other technology."
The biotech watchdog ETC Group called the new report "disappointing" in a release headlined "Stop the Gene Bomb!" The organization said the new report failed to address many of the potential hazards and societal implications of the new technology, including possible use of gene drives for military purposes. For example, the organization said, gene drives could be a biological weapon targeting the human microbiome.
The organization also fears that the technology will be patented and exploited for commercial purposes by large biotech corporations, including Monsanto, the frequent target of activists who oppose biotech generally.
"Historians may come to see last year's invention of a working Gene Drive as biology’s ‘nuclear’ moment. Like the first nuclear chain reaction three quarters of a century ago, the ‘mutagenic chain reaction’ denotes awesome power, potential widespread destruction and has significant geopolitical ramifications," ETC Group spokesman Jim Thomas said in the release.
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