Lyme disease vaccine provides promising protection against harmful tick bites

NEW HAVEN, Conn. — A vaccine for Lyme disease may soon provide groundbreaking protection against the tick-borne illness. Researchers from Yale University say the new formula is very similar to the vaccine for COVID-19 and successfully defended guinea pigs bitten by a Lyme-carrying tick.

Instead of causing the immune system to spring into action to fight Lyme disease, the vaccine actually attacks the root of the problem — the tick’s saliva. Study authors say the new vaccine immediately creates a response in the bite victim’s skin, limiting the amount of time a tick has to feed and infect the host. This vaccine also uses the same mRNA technology the COVID vaccines use to protect patients.

What is Lyme?

Lyme disease is a bacterial infection which enters the body once a tick latches on and bites into the skin. The most recognizable sign of the disease is the bullseye-shaped rash that forms around the bite a few days or weeks later.

At first, Lyme typically causes symptoms such as a rash, fever, headache, and severe fatigue. However, if someone with the disease doesn’t get treatment soon enough, the infection can spread to the joints, heart, and nervous system — causing severe complications. There are around 40,000 new cases of Lyme disease each year in the United States, but study authors say this number could actually be up to 10 times higher due to lack of reporting. Additionally, Lyme disease is not the only illness these insects can carry.

“There are multiple tick-borne diseases, and this approach potentially offers more broad-based protection than a vaccine that targets a specific pathogen,” explains senior author Erol Fikrig, a professor from the Yale School of Medicine and Yale School of Public Health, in a university release. “It could also be used in conjunction with more traditional, pathogen-based vaccines to increase their efficacy.”

Stopping the saliva, preventing the disease

Researchers explain that the black-legged tick species Ixodes scapularis transmits the Lyme disease pathogen Borrelia burgdorferi. This disease contains several proteins and the team focused their research on 19 different types.

Working with the University of Pennsylvania, they analyzed pieces of mRNA which produce all 19 of these tick saliva proteins. Scientists who created the COVID-19 vaccine used the same strategy to develop a formula that protects against the SARS-Cov-2 virus.

Using guinea pigs, the team discovered that vaccinated animals quickly developed redness at the bite site after encountering a disease-carrying tick. As long as researchers removed the ticks right after the redness started, none of the guinea pigs developed Lyme disease. Conversely, around half of the unvaccinated group of guinea pigs were infected with B. burgdorferi bacteria despite researchers removing the ticks.

Interestingly, the vaccine successfully protected immunized guinea pigs from a single tick bite, even if researchers left the tick on the animal’s skin. On the other hand, a single tick bite led to Lyme disease in 60 percent of the unvaccinated guinea pigs. The vaccine also prevented ticks from feeding aggressively on their hosts and caused them to dislodge from their skin quicker.

The vaccine does have its limits. Results show protection against Lyme disease dropped off when leaving three ticks attached to the vaccinated guinea pigs.

The vaccine enhances the ability to recognize a tick bite, partially turning a tick bite into a mosquito bite,” Fikrig says. “When you feel a mosquito bite, you swat it. With the vaccine, there is redness and likely an itch so you can recognize that you have been bitten and can pull the tick off quickly, before it has the ability to transmit B. burgdorferi.”

So, will the vaccine work on humans?

The Yale team cautions that this vaccine is not a finished product and they need to conduct more tests to see if it will protect people.

Similar experiments using mice revealed that the vaccine did not lead to tick infection resistance. Study authors believe part of this is due to guinea pig and human skin having more layers than mice. Ticks may have also evolved new ways of feeding off of mice, who scientists say are a natural host of I. scapularis ticks.

The study appears in the journal Science Translational Medicine.