Lyme disease is caused by bacteria of the genus Borrelia, which are carried and transmitted by ticks, mainly Ixodes ricinus in Europe and Ixodes spacularis in the United States and Canada. Despite extensive research, no vaccine is available against this disease. For this reason, researchers at INRAE, in collaboration with ANSES and the Alfort National Veterinary School, are proposing a new form of indirect vaccination to combat Lyme disease, by targeting ticks.
The concept is based on a vaccine that disrupts the tick's microbiota1. For their experiments, the researchers injected mice with the vaccine. Specifically, they used another bacterium, harmless in this context, as a Trojan horse.
Once in the body, this harmless bacterium2 causes mice to produce antibodies. If the mouse is then bitten by a tick, these antibodies interact with and alter the tick's microbiota.
Analysis of post-bite ticks showed that they carried much less Borrelia than ticks that had bitten unvaccinated animals. When administered to a mouse, therefore, this vaccine "protects" the tick from colonisation by Borrelia (but does not protect the mouse from the disease).
The work concluded with a twofold advance: new knowledge on the importance of the microbiota in the infection of ticks by Borrelia, and a potential innovative vaccination strategy. The results confirm that the tick microbiota is a key factor in the development of Borrelia in ticks. This essential information raises the possibility of developing an innovative vaccination strategy aimed at disrupting the microbiota of vectors of the agent responsible for Lyme disease.
1 The Borrelia bacterium lives in the tick's microbiota.
2 A harmless strain of Escherichia coli was used in the experiment. This bacterium has many varieties, some of which can be harmful.
A global issue
Ticks are not the only vectors of disease. There are also mosquitoes, which transmit numerous diseases such as dengue fever, Zika and malaria. Controlling and protecting against these vectors, and the diseases they carry, is therefore a global public health issue. There are currently no vaccines able to protect humans from contracting these diseases, only treatments designed to cure or relieve patients. Anti-microbiota vaccines represent an opportunity to develop innovative vaccines against vector-borne pathogens.
Reference: Wu-Chuang A./ Mateos-Hernandez L./ Maitre A. et al. (2023). Microbiota perturbation by anti-microbiota vaccine reduces the colonization of Borrelia afzelii in Ixodes ricinus. Microbiome. DOi: 10.1186/s40168-023- 01599-7