Tuesday, June 7, 2016

Fighting Lyme Disease in the Genes of Nantucket’s Mice

(C) NY Times

Fighting Lyme Disease in the Genes of Nantucket's Mice

White-footed mice carry the pathogen that causes Lyme disease. A M.I.T. scientist is proposing to create mice that are genetically engineered to break the cycle of transmission. Yousur Al-Hlou/The New York Times 

Can genetically engineered mice save Nantucket from the scourge of Lyme disease?

If the 10,000 residents of the island off Massachusetts didn't have such a soft spot for deer, they might not be entertaining the prospect, which could provide the groundwork for an even more exotic approach to controlling tick-borne diseases on the mainland.

But popular opinion has long opposed public health officials' recommendation of radically reducing the population of deer serving both as a food source for tickscarrying the Lyme pathogen and a convenient place for adult females to lay their eggs.

"The people who get sick yell and scream at me for not doing anything about it,'' said Malcolm MacNab, chairman of the Nantucket Board of Health, "and the others yell and scream at me because I want to kill the deer." Dr. MacNab said nearly 40 percent of Nantucket residents have had Lyme disease.

So when he heard that Kevin Esvelt, an evolutionary biologist at the Massachusetts Institute of Technology, wanted to gauge the island's interest in a new approach, he invited the scientist to present it at a public meeting on Monday.

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Although deer help spread ticks that carry Lyme, Dr. Esvelt explained to about two dozen residents at yesterday's meeting, the disease can also be controlled earlier in the tick's food chain. Ticks typically contract the pathogen from white-footed mice, which they often feed on while still larvae, passing it on to humans and other mice when they bite again.

Using new genome-engineering tools, he proposes to create mice that are either immune to the Lyme-causing pathogen, or to a protein in the tick's saliva, or both, to break the cycle of transmission.

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If that works — and there is reason to think it will — he would then apply for permission to release thousands of the mice on a smaller, uninhabited island. If the number of infected ticks proved to be sufficiently reduced after two years, Nantucket could be next. The release of a few hundred thousand engineered mice over the course of about a year, Dr. Esvelt said, would ensure a stable population of resistant mice.

There is no company behind the project, which Dr. Esvelt estimated could take as long as a decade to complete. But he said he thought he could get government and philanthropic funding because it would provide evidence that might justify the use of another technology he has helped to pioneer, called "gene drive," to attack Lyme disease elsewhere.

In the Northeast and upper Midwest, the areas of the United States where Lyme is most prevalent, it would not be feasible to release enough engineered mice to spread the genes for Lyme immunity through the native mouse population.

An effort on that scale would require the addition of a gene drive, which assures that a given gene is passed to all of an organism's offspring rather than the usual half.

Gene drive technology is complicated because it has the capacity to alter an entire population of a given species, without any sure means of being canceled out if it has unforeseen consequences. It has so far only been used in laboratory experiments.

Dr. Esvelt said he wanted some indication of community support even before he starts looking for Lyme immunity genes in laboratory mice, both because he believes any effort to alter an ecosystem should not go forward without it — and because it would cost tens of millions of dollars. Ultimately, the proposal would need approval from federal and state regulators, as well as a majority of Nantucket's citizens.

"Is this a project you might wish to pursue?'' he asked on Monday. Dr. MacNab, who had anticipated some opposition to the idea, braced himself as Danica Connor, who identified herself as an herbalist, took the microphone.

"I'm the first person to say if you go tinker with Mother Nature we're going to break it,'' she said. "But you know what? Even I want to see where you go with this.''

Nantucket may have competition. Dr. Esvelt said he is scheduled to make a similar presentation on nearby Martha's Vineyard in July.

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