MISSOULA – Researchers identified the bacterium behind the debilitating Lyme disease decades ago.
They have understood its life cycle requires an interaction between infected deer and the specific species of ticks that feeds on them.
And they’ve known while there are many different strains of the Lyme disease-causing bacterium, reinfection of people by the same strain of the bacteria is rare.
Up until recently, scientists had presumed the antibodies produced to neutralize the bacteria did their work inside a person’s body.
A recent study completed by a team of Rocky Mountain Laboratory researchers in Hamilton led by Dr. Patti Rosa discovered that wasn’t the case.
Instead, the antibodies in blood somehow found their way into the tick’s midgut and neutralized the bacteria there.
The research team’s findings could be used to eventually help verify the effectiveness of any new vaccine for the disease.
Like so many discoveries in science, serendipity came into play.
“It was a complete accident,” Rosa said. “We were looking for something different.
For the last 30 years, Rosa has studied the long, coiled microorganisms called spirochetes that carry the name of the Rocky Mountain Laboratory scientist who first isolated them.
Lyme disease was recognized as a serious health concern in 1975 after numerous children developed juvenile rheumatoid arthritis near the small town of Lyme, Connecticut. Seven years later, Willy Burgdorfer was looking for the cause of a totally different tick-borne disease when he identified the spirochetes that proved to be the cause of Lyme disease in 1982.
Lyme disease is a growing threat back east where cleared fields once used for agriculture have been allowed to reforest. That’s created the perfect environment for the bacterium to flourish with a deer population that serves as a reservoir and ticks that survive that thrive in the moist habitat.
“We don’t have Lyme disease or the ticks that transmit it here in Montana because it’s too arid,” Rosa said.
A molecular biologist by training, Rosa was fascinated by the bacterium’s complexity. Where most bacteria have a circular chromosome with one or two small pieces of DNA, the Borrelia burgdorferi spirochetes had more than 20 pieces of DNA.
“Their shape absolutely fascinated me,” Rosa said.
Rosa and her team of researchers were working to understand what the bacterium does to survive when it goes from a tick to a mammalian host when they made their discovery about how antibodies interact with the spirochetes.
Before their research, scientists believed the tick somehow regurgitated the spirochetes from its midgut and the bacterium entered the host through the tick’s salivary glands. Scientists assume that antibodies created following an infection waited in a host’s body to provide immunity for specific strains of the bacterium.
“If you try to give them the same thing again, they are immune to it,” Rosa said. “It’s as if they had been naturally vaccinated by their first infection.”
“We assumed that was happening in the host,” she said. “Spirochetes get transmitted, antibodies recognize them. what we were seeing happening in tick midgut that somehow the antibody component that was coming in and recognizing the spirochete and therefore blocking their ability to infect without killing them.”
At this point, scientists don’t know if any other vector-born pathogens, whether parasite, virus or bacteria, were being exposed to blood in the gut of an insect. Since that’s been isolated in this case, scientists know for certain the host’s blood with its protective antibodies can block the bacteria’s ability to infect.
That discovery could open the door for a new way scientists could check for the effectiveness of new vaccines.
“What that means for a vaccine trial is that you can vaccinate people and take their blood and then go back to lab and see if they have neutralizing immunity,” she said. “That’s really what you need to say that this vaccine will work without the addition to statistics of 100,000 people being vaccinated to see if they get the disease or not.”
Even after 30 years of studying the same bacterium, Rosa knows there is still lot to learn.
She is spending the next year on sabbatical from the Rocky Mountain Laboratory to work alongside researchers at Yale University hoping to unlock even more secrets.
“We still have questions,” Rosa said. “The more we know, the more we realize we don’t know. You see a little thing and then you can see through it and see what’s on the other side.”
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