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Health

To Reduce Lyme Disease In Humans, Fort Collins Researcher Wants To Vaccinate Mice

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Division of Vector-borne Diseases, CDC
Laboratory mice eating oral vaccine that protects them from Lyme disease bacteria.

It begins with a rash – red, and expanding. Then, exhaustion. Joints ache as if with arthritis. There may be a headache, fever, chills. If it goes untreated, the arthritis can last years. Even worse, the brain may be affected, leading to shooting pains and tingling limbs, or even memory loss.

These are the symptoms of Lyme disease, a tick-borne illness that affects around 300,000 Americans each year, according to the Centers for Disease Control and Prevention. There is no human vaccine for Lyme, but now a CDC researcher has developed a new way to fight the troublesome disease: by vaccinating the mice that carry it. 

"Our dream is to reduce the incidence of Lyme disease in people," said Barbara Johnson, a researcher at the CDC's Fort Collins-based Division of Vector Borne Diseases.

Johnson led the development of a new animal-focused vaccine, in collaboration with a local company, Ventria Biosciences. It will start field trials in New England in 2015, and if shown to work, may scale up for widespread use. Her work on this project was recently recognized with a Governor's Award for High-Impact Research from the CO-LABS science consortium.

When Lyme disease is caught early, it is treated with antibiotics. Most patients recovery fairly quickly. But symptoms of disease, which is concentrated in the mid-Atlantic, Northeast, and Great Lakes region, can linger for years. Ten to 20 percent of people suffer symptoms long after treatment, and for some they are debilitating.

Researchers have been working on ways to curb the negative impacts of Lyme. There once was a vaccine for humans, but it was pulled from the market in 2002, after controversy about its side effects.

Johnson's mice-centric approach is slightly different.

"We call it a reservoir-targeted vaccine. It means that it immunizes the small animals in nature that keep the infection going."

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Credit Center for Vector-borne Diseases, CDC.
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Center for Vector-borne Diseases, CDC.
The CDC uses ticks in the nymph phase for its testing. They are about the size of a sesame seed.

The "reservoir," in this case, is the population of mice and other rodents that carry Lyme. When ticks feed on them, they pick up the bacteria that causes Lyme and spread it – in some cases, to people.

Johnson's vaccine, by keeping mice from getting Lyme, cuts the disease off at its source. In laboratory trials with mice, the vaccine has kept the animals from getting Lyme disease. Now, she's ready to test it in the field.

While most people think of vaccines as being given through injection, the researchers do not plan to capture a bunch of mice and shoot them up with the new vaccine. That's where the work of partner Ventria Biosciences, comes in.

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Credit Ventria Biosciences
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Rice grain used to make oral vaccine flour.

 Johnson worked with Ventria's Ning Huang, an expert at producing vaccine molecules in plants. They grew a modified rice that has the vaccine inside of it. They turn that rice flour into mouse food.

"We vaccinate the animals orally. That's one of the novel features of our vaccine. We don't require shots," she said.

When mice eat bait made from the rice flour, they make antibodies against Lyme disease. If they don't get Lyme, the ticks that bite them don't either.

Johnson's first papers on her experiments are in the works, and she said the field trials will determine the vaccine's success.

 Researchers will set out plots in areas where scientists know small rodents are highly infected and there are a certain number of ticks. Entomologists will then monitor those plots and control plots to see if the number of ticks with Lyme disease changes as a result. Right now, said Johnson, they believe the vaccine bait would have to be used every year to be effective.

If the vaccine works, it wouldn't mean the end of Lyme, but it could greatly reduce its spread, by being placed in bait boxes around houses or in places like public parks --  areas where people and animals are at high risk for contracting Lyme, said Johnson.

"We don't expect to vaccinate all the rodents in nature or all the North Woods of the United States," she said. 

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