mRNA vaccine opens up a whole new sector in the fight against tick-borne diseases
Ticks are a significant vector for human-animal disease transfer. Ticks, which are purely blood-sucking arthropods, may bite practically all terrestrial animals and have a long lifespan, strong blood-sucking capability, and complicated life history. Ticks can carry a wide range of pathogens, including viruses, bacteria, fungi, and parasites, and can transmit more than 40 diseases, including Lyme disease, forest encephalitis, Crimean-Congo hemorrhagic fever, fever with reduced syndrome, rickettsial disease, anaplasmosis, and babesiosis, all of which can cause death or chronic sequelae and have a significant impact on life quality.
Lyme disease, a naturally epidemic disease caused by Burkholderia spirochetes infection, is usually transmitted by the black-legged tick (I. scapularis) as a vector. Each year, more than 40,000 cases of Lyme disease are documented in the United States alone, with the real number of infections probably ten times higher. Lyme disease can harm the neural system and have catastrophic effects; stage I Lyme illness can be treated with antibiotics, but drugs will not assist if the disease progresses to stage II or III, and the damage to the nervous system will be irreversible.
The COVID-19 outbreak has prompted the speedy licensing of mRNA vaccines, and the widespread usage of mRNA vaccines against COVID-19 has demonstrated their effectiveness. As a result, some scientists started looking at the possibility of mRNA vaccines in the prevention of tick-borne diseases.
On November 17, 2021, researchers from Yale University School of Medicine published a paper in Translational Medicine titled: mRNA vaccination induces tick resistance and prevents transmission of the Lyme disease agent, which was also chosen as the cover paper for the issue.
Instead of targeting specific tick-borne disease pathogens, this study targeted ticks with lipid nanoparticles (LNPs) delivering mRNA for 19 proteins (19ISP) found in the saliva of the blacklegged tick, prompting a rapid skin response to tick bites, limiting the time it takes for the tick to feed on blood and infect the host, and also allowing the host to quickly detect tick bites, preventing Lyme disease transmission.
In guinea pigs, this mRNA vaccine protects against Lyme disease infection induced by blacklegged tick bites, and because the vaccine directs towards blacklegged ticks rather than specific pathogens, it can also protect against other tick-borne diseases.
Tick bites can transmit various diseases due to the enormous number of pathogens carried by ticks. Consequently, rather than targeting specific tick-borne pathogens, the research team is developing tick vaccines.
Erol Fikrig’s team at Yale University School of Medicine, in collaboration with mRNA vaccine founder Drew Weissman’s team at the University of Pennsylvania, studied the blacklegged tick that transmits Lyme disease. The saliva of the blacklegged tick contains multiple types of proteins, and the team focused on 19 of these proteins (19ISP). The mRNA fragments that produce these proteins were used as the basis for the vaccine, the same strategy that was adopted in the COVID-19 mRNA vaccine. The team then tested the protective effect of this mRNA vaccine on guinea pigs that are likely to be bitten by ticks and infected with Lyme disease and are often used as a model for tick-borne disease research.
Vaccinated guinea pigs experienced quick redness at the site of a tick bite compared to non-mRNA vaccinated guinea pigs, and if the tick was removed at this point, none of the vaccinated guinea pigs would have contracted Lyme disease, whereas nearly half of the unvaccinated guinea pigs would have.
None of the vaccinated guinea pigs were infected with Lyme disease when one tick bite was not removed, while 60% of the unvaccinated guinea pigs were.
The vaccine’s protection was reduced when three tick bites were not removed, although the ticks attached to the vaccinated guinea pigs were unable to feed actively and shed more quickly.
The mRNA vaccine, according to the researchers, will not only help the immune system to recognize the tick, preventing Lyme disease infection. Furthermore, the vaccination causes the tick bite to turn red and itchy immediately, making the tick bite as noticeable as a mosquito bite, aiding in the removal of the pathogen before it is transferred.
According to the researchers, the mRNA vaccine could provide broader protection than a vaccine against a single pathogen, and it could also be used in conjunction with a regular pathogen-based vaccine to boost protection.
Additional studies will be undertaken to establish the proteins in tick saliva that can be utilized to prevent tick-borne infections, according to Erol Fikrig, the paper’s corresponding author. Human trials will next be conducted to determine the vaccine’s efficacy.