Ixodes scapularis, or more commonly known as the deer tick, can act as a vector for several different diseases. However, it is probably most known as the main vector for Lyme Disease, which is currently the most common vector-borne disease in the United States.~ Deer ticks obtain and spread diseases by feeding on the blood of several different vertebrates across the course of their lifetimes, including mammals, birds, and reptiles.  Their feeding habits, along with the dramatic expansion of their distribution across the eastern half of North America in the past 50 years, make deer ticks a top concern as a public health pest.* 

 

When these ticks feed, they release a series of molecules in their salivary glands that assist them in feeding. These molecules are proteins that are known as tick salivary proteins, and assist the tick in feeding by hindering the immune system of the host. However, some of these tick salivary proteins instead do the opposite in some vertebrate hosts, and create an immune response in the host called Acquired Tick Resistance. Ticks that feed on a host with Acquired Tick Resistance have diminished feeding and often detach from their hosts earlier than expected, which can have a huge effect on their ability to survive and reproduce. The hosts also often experience more redness and skin irritation at the bite site when they have Acquired Tick Resistance. A recent study revealed that a lipid nanoparticle which codes for 19 of these tick salivary proteins is responsible for inducing this Acquired Tick Resistance.  

 

Previous work had examined the potential of a vaccine created from this lipid nanoparticle in guinea pigs. While the study appeared promising in the terms of the potential of the vaccine, guinea pigs are unfortunately a poor model for understanding how the vaccine may impact the deer tick’s full life cycle.^ This study took the same lipid nanoparticle that coded for these 19 tick salivary proteins, and created an mRNA vaccine for rabbits. One group of rabbits received three doses of the vaccine, given at four week intervals. Another group of rabbits received a control version of the mRNA vaccine. After two weeks, the rabbits were checked for antibodies. This was to ensure that the vaccine worked as it should, and induced the correct immune response that would lead to Acquired Tick Resistance.  

A week following the antibody check, the rabbits were then exposed to 50 adult deer ticks. The researchers did so in perhaps my favorite line ever from a science article “all the rabbits wore Elizabethan collars and the ear that received the tick was isolated with an adapted sock, which prevented the ticks from moving to another location.” Fashion aside, the rabbits were monitored daily for any signs of host rejection by the tick and time of tick detachment. Once detached, the ticks were weighed as a measure of how well they were able to feed on a host. Female deer ticks were further monitored for their egg masses, where the researchers examined the size of the egg mass as well as how many of those eggs ended up hatching. 

Overall, researchers found there was no difference in the ways that ticks fed based on whether a rabbit was vaccinated. Both time of attachment and tick weight did not differ between the vaccinated rabbits and the control rabbits. Similarly, there wasn’t a difference in the number of eggs laid when comparing ticks that fed on vaccinated rabbits versus the control rabbits. However, there was a significant difference in the percent of eggs that hatched from the vaccinated rabbits versus the control rabbits. These results suggest that the vaccine for the tick salivary proteins in rabbits can significantly impair how well deer ticks are able to reproduce.  

While this is just one experiment, with one species, it is important to note that every new methodology for management of a pest starts somewhere. This study is extremely promising for its potential for reducing tick populations by simply giving a host a vaccine over the course of a few short weeks. In addition, Acquired Tick Resistance has been documented in several animals including guinea pigs, dogs and cattle. Eventually, it could be just as easy as having your livestock or pet vaccinated by your veterinarian to help reduce tick populations in your area.  

Article by Laura Rosenwald, BCE

References

Matias J, Cui Y, Lynn GE, DePonte K, Mesquita E, Muramatsu H, Alameh MG, Dwivedi G, Tam YK, Pardi N, Weissman D, Fikrig E. mRNA vaccination of rabbits alters the fecundity, but not the attachment, of adult Ixodes scapularis. Sci Rep. 2024 Jan 4;14(1):496. doi: 10.1038/s41598-023-50389-6. PMID: 38177212; PMCID: PMC10766947.

1. List

~ Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), Division of Vector-Borne Diseases (DVBD) (https://www.cdc.gov/lyme/index.html)  

* Lars Eisen, Rebecca J. Eisen. Changes in the geographic distribution of the blacklegged tick, Ixodes scapularis, in the United States, Ticks and Tick-borne Diseases,. Volume 14. Issue 6. 2023. https://doi.org/10.1016/j.ttbdis.2023.102233 

^ Andaleeb Sajid et al. mRNA vaccination induces tick resistance and prevents transmission of the Lyme disease agent. Sci. Transl

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