Yale University researchers reported in the journal Science Translational Medicine on November 17 that Yale University researchers have developed a new vaccine that can provide protection in guinea pigs against bacterial infections that cause Lyme disease. Can fight other tick-borne diseases.

Studies have shown that the new vaccine does not trigger an immune response against specific pathogens, but prompts the skin to respond quickly to the components of tick saliva, thereby limiting the time the ticks must eat and infect the host.

The vaccine is provided by the same mRNA technology, which has been proven to be very effective against COVID-19.

Researchers say that in the United States, at least 40,000 cases of Lyme disease are reported each year, but the actual number of infections may be 10 times that. In addition, other tick-borne diseases have spread in many parts of the United States

"There are multiple tick-borne diseases, and this approach may provide broader protection compared to vaccines against specific pathogens," said senior author Erol Fikrig, professor of medicine (infectious diseases) and microbial pathogenesis at Yale University. School of Medicine, Professor of Epidemiology (Microbial Diseases) at Yale School of Public Health. "It can also be combined with more traditional pathogen-based vaccines to improve its efficacy."

The saliva of the black-legged tick Ixodes scapularis, which transmits the Lyme disease pathogen Borrelia burgdorferi, contains many proteins. The researchers focused on 19 different proteins.

In order to find the basis for the vaccine, Yale University researchers worked with a team led by Drew Weissman of the University of Pennsylvania to analyze the mRNA fragments that produced all 19 salivary proteins. A similar strategy is used in a vaccine effective against the SARS-Cov-2 virus. In a series of experiments, they tested this vaccine on guinea pigs, which can be infected with the Lyme disease pathogen and also used as a model for studying tick resistance.

Unlike unimmunized guinea pigs, vaccinated animals exposed to an infected tick will rapidly redden at the site of the tick bite. As long as the ticks are removed when redness occurs, all immunized animals will not develop Lyme disease. In contrast, after removing the ticks, about half of the control group was infected with Borrelia burgdorferi. When an infected tick attached to the immunized guinea pig without being removed, none of them were infected, and 60% of the control animals were indeed infected. However, if the three ticks are still attached to the guinea pig, the protective effect will be weakened even in the immunized animal.

In addition, compared to guinea pigs in the control group, ticks attached to immunized animals cannot actively eat and fall off faster.

"The vaccine enhances the ability to recognize tick bites, partially turning tick bites into mosquito bites," Fikrig said. "When you feel a mosquito bite, you slap it. After vaccination, there will be redness and possibly itching, so you can recognize that you have been bitten and can transmit Borrelia burgdorferi in the tick. Before the ability to quickly unplug it."

The researchers did notice a warning in their results: In similar experiments, mice that did not acquire natural tick resistance after infection were not able to resist Lyme disease after being vaccinated. In fact, compared with guinea pigs, mice are the natural host of scapular ticks, which suggests that ticks may have evolved a method of feeding mice repeatedly. Another possibility may be that the skin of guinea pigs, like human skin, is more layered than that of mice.

Fikrig said more research is needed to discover how the protein in saliva can prevent infection. Ultimately, human trials are needed to evaluate its efficacy on the human body.

Andaleeb Sajid, Jaqueline Matias, and Gunjan Arora of Yale University are the co-first authors of the study. Weissman of the University of Pennsylvania is also a co-author. The research was mainly funded by the Cohen Foundation and the National Institutes of Health.

Beth Connolly: elizabeth.connolly@yale.edu,

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