An Oxfordshire based company is at the centre of planned controversial use of GM modified mosquitoes in Florida to combat diseases mosquito-related diseases. Dermot Martin looks into the facts of this “Jurassic Park experiment” that may have flown under the radar during these unusual times…
Oxitec has developed a GM version of Aedes aegypti a species of mosquito which causes spread of the Zika virus dengue and other arboviruses. An estimated 50,000 lives are lost every year globally because of these viruses.
The company, an arm of the US company Intrexon, has been given the green light by Floridian authorities to release 750 million genetically modified mosquitoes into the Florida Keys next year. It is part of a plan to “crash” the population of the insects and reduce - even eradicate - diseases in that area.
The bioscience behind the project is simple. The company used the CRISPR gene editing technique to make a modified version of the male Ae aegypti which expresses a genetic flaw.
The ‘new’ mosquito even has its own trademark and associated patents.
Once released into the environment, it breeds with the wild female mosquitoes blending in a gene sequence which prevents female offspring developing into adulthood. Only females bite human beings in their quest for human blood to support their eggs.
The male-female sex balance of the population, in the areas where the GM mosquitoes are released, ought to be significantly disrupted. Oxitec has already tried the system with its first generation QX 513A specimen with some evidence of success in Brazil claiming an 80 per cent reduction in the Ae aegypti population. However, the company stated that GM modified insects, released in the Brazil’s Jacobina area, eventually died out and the mosquito population recovered.
This use of CRISPR Cas9 in insect control has taken some years to develop and masses of technical skill. But the decision to go ahead in Florida with the use of its second generation OX5034 has failed to dispel concerns.
Underpinning the Oxitec method of insect control is a self-limiting gene.
When GM male insects (OX3054) are released into the wild and mate with the local female population, the offspring inherit a copy of this gene. The gene disrupts the normal functioning of the insects’ cells by over-producing a protein which cuts their ability to produce other essential proteins needed for development. Normal growth is disrupted, and the insect fails to survive to maturity.
There is outrage among environmentalists who have described it as a Jurassic Park experiment - a reference to the film in which dinosaur DNA is extracted in “fossilised insects” is used to resurrect dinosaur species.
Oxitec argues that extensive research points to the fact that its so-called gene drive system does zero harm to the environment or ecosystems.
“The self-limiting gene works by using the insect’s own biology against itself. Our control method provides a solution that only affects that particular species of pest without introducing harmful toxins,” said Derric Nimmo, (correct spelling) Product Development Manager at Oxitec.
The company says the self-limiting gene can even be turned off with an “antidote” – in this case the antibiotic tetracycline.
In the lab, Oxitec doses genetically modified mosquitoes with tetracycline so they can survive and reproduce under controlled conditions.
For pest control purposes, mature males carrying the self-destruct gene are gathered up and released into the wild to mate with females. Offspring which inherit the gene, will die without the tetracycline antidote.
Another modification which Oxitec has introduced in advance of the Florida release is a patented marker gene, which produces a fluorescent protein called dsRed2 recognition.
This protein will be found throughout the body of the larvae, pupae and adults. It glows red under light of a specific wavelength, but Oxitec say dsRed2 is non-toxic and non-allergenic.
The marker gene is a vital element for a control program, as it allows scientists to easily identify the offspring of our insects and enables track-and-trace in the wild.
Nimmo says: “By examining larvae from the field, we can see how many of the offspring are our own self-limiting insects and how many are wild ones. It is a valuable tool for quality control in production and for effective monitoring in the field. We then use that data to tailor our releases and ensure we achieve optimal pest suppression.”
Oxitec’s work has attracted financial support from the Bill and Melinda Gates Foundation which granted nearly $6m in funding in June 2018.
However, the built-in recognition technique and confidence in the science, is unlikely to placate concerns of environmentalists in the USA.
In a blistering attack Jaydee Hanson, policy director for the US International Centre for Technology Assessment and Centre for Food Safety said:
“With all the urgent crises facing our nation and the State of Florida — the COVID-19 pandemic, racial injustice, climate change — the administration has used tax dollars and government resources for a Jurassic Park experiment.
“Now the Monroe County Mosquito Control District has given the final permission needed. What could possibly go wrong? We don’t know, because the EPA unlawfully refused to seriously analyse environmental risks.
“Now without further review of the risks, the experiment can proceed,” she added.
More than 233, 000 people have also signed a petition against the proposal. There will doubtless be more protests and controversy before the project, scheduled for next year, goes ahead.
https://www.fda.gov/files/animal & veterinary/published/Oxitec-Mosquito---Draft-Environmental-Assessment.pdf
Author: Dermot Martin is a science journalist with a special interest in the life sciences and techniques for analytical chemistry.