A new study published in the journal Science Translational Medicine is reporting the development of a novel mRNA-based vaccine designed to help resist tick bites. Preclinical tests in guinea pigs indicate the vaccine aids the immune system in recognizing tick bites, resulting in the parasites being dislodged before they can transmit any pathogenic disease.
Over a dozen diseases can be transmitted by tick bites. The most well-known is Lyme disease, caused by a bacterium called Borrelia burgdorferi. In the past, vaccines have successfully been developed to specifically target this Lyme disease bacterium. However, this new vaccine candidate takes a different approach, using mRNA technology to target the tick itself.
The vaccine is based on the same mRNA technology that led to the extraordinarily successful rapid development of COVID-19 vaccines in 2020. But instead of directing cells in the body to produce spike proteins to train the body to attack SARS-CoV-2, this particular vaccine directs cells to produce a number of proteins found in the saliva of the black-legged tick Ixodes scapularis.
Dubbed 19ISP, the mRNA vaccine contains instructions for 19 different proteins found in the tick saliva. The preclinical research successfully demonstrated the mRNA vaccine on a number of guinea pigs.
“We found that guinea pigs vaccinated with 19ISP developed skin redness after they were bitten, indicating that their immune system was activated and recruited inflammatory cells to the site to fight off infection,” explains Andaleeb Sajid, co-first author on the study. “Like other animals that developed tick immunity after repeated bites, the ticks were unable to feed on the guinea pigs and quickly detached.”
As well as demonstrating the vaccine inducing an immune response rapidly at the site of a tick bite, the researchers found the vaccinated guinea pigs also resisted infection with the Lyme disease bacterium when confronted with ticks carrying the pathogen. Sajid says this indicates a vaccine aimed at resisting tick bites could be sufficient to prevent most tick-borne diseases.
Human clinical trials testing this novel vaccine may still be a few years off as this preliminary research offered some curious caveats. While the vaccine proved effective in guinea pigs the researchers found the vaccine was not effective at inducing tick immunity in mice.
It is unclear exactly why this may be the case but mice are a natural reservoir for ticks so the researchers speculate the parasites could have evolved unique ways to co-exist with the animals. Further studies in other animals will be needed to better understand how tick immunity can be generated in different hosts.
Senior author on the new study Erol Fikrig says this vaccine is unique in the way it targets a carrier of a pathogen rather than the pathogen itself. This means it should offer a broad-based protection from all kinds of tick-induced disease and not just a single pathogen.
Fikrig speculates the way the vaccine could work in humans is by offering signals to a person they have been bitten by a tick soon after the tick has taken residence. This allows a person to quickly remove the tick before it can transmit any disease-causing bacteria or virus.
“The vaccine enhances tick recognition, partially turning a tick bite into a mosquito bite,” says Fikrig. “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.”
The new study was published in the journal Science Translational Medicine.
Source: Yale University