Researchers Develop Lyme Disease Vaccine That Targets Tick Saliva, Prevents Feeding

Yale University researchers have developed an mRNA vaccine that provides partial protection against Lyme disease—the most common Tick-borne human illness in the United States.

First published on November 17 in the journal Science Translational Medicine, the novel vaccine developed and tested in guinea pigs offers protection against infection by the bacterium that causes Lyme disease. It may also combat other tick-borne diseases.

Specific ticks studied included Ixodes scapulari—more commonly known as a deer tick—which carries a Lyme-disease-causing bacteria called Borrelia burgdorferi.

Rather than target specific viruses or bacteria that can cause disease, this new vaccine is designed to target tick salivary proteins that are released through open wounds. So instead of triggering an immune response against a particular pathogen, this vaccine limits the amount of time that ticks have to feed upon and infect a host.

Researchers said the vaccine mirrors the same mRNA technology that has proved effective against COVID-19.

"Our vaccine is unique in that we don't actually target the pathogen, we target the vector," Jacqueline Mathias dos Santos, a co-first author on the paper and a postdoctoral associate at the Yale School of Medicine, told the Yale Daily News. "This strategy can work for Borrelia because it takes around 24 hours of tick feeding for the pathogen to be transmitted. This offers a unique opportunity to disrupt transmission. Additionally, by targeting the vector, we don't expect this to drive resistance by the pathogen."

While a minimum of 40,000 Lyme disease cases exist across the United States, researchers believe the actual infection rate could be 10 times greater. Meanwhile, other tick-borne diseases have also spread domestically.

"There are multiple tick-borne diseases, and this approach potentially offers more broad-based protection than a vaccine that targets a specific pathogen," said the study's senior author Erol Fikrig, the Waldemar Von Zedtwitz Professor of Medicine (infectious diseases) and of microbial pathogenesis at the Yale School of Medicine, and professor of epidemiology (microbial diseases) at the Yale School of Public Health. "It could also be used in conjunction with more traditional, pathogen-based vaccines to increase their efficacy."

Yale researchers collaborated with the University of Pennsylvania to analyze mRNA bits that produce all 19 of the saliva proteins.

A caveat in the research indicated that the same vaccine that aids guinea pigs did not aid mice. Researchers speculated that it is due to the inability of mice to acquire natural tick resistance after infection, or that ticks may have evolved to develop ways to specifically feed repeatedly on mice.

Another theory is that guinea pig skin, like human skin, is more layered than mice skin.

Fikrig said more study is necessary to discover how proteins in saliva can prevent infection. That eventually could include human trials to understand levels of the vaccine's efficacy.