Ticks transmit viruses and bacteria that infect people, livestock, wildlife, and pets every year around the world. Scientists at the University of Tennessee College of Veterinary Medicine have identified a specific protein in tick saliva that appears to play a central role in how that transmission happens.
The study was published in The EMBO Journal. It was led by professor Hameeda Sultana and alumni postdoctoral fellow Waqas Ahmed, with contributions from several current and former graduate students and faculty collaborators.
The protein in question is found inside exosomes, which are tiny particles that ticks release through their saliva when feeding on a host. According to Phys.org, Sultana's laboratory was the first to identify exosomes derived from tick saliva between 2018 and 2020.
"Exosomes are tiny bubble-like vesicles with messages in them," Sultana explains. "They are tiny membrane-bound particles that transport proteins and other biological signals between cells and tissues."
When a tick bites, those exosomes carry a range of molecules that help the tick feed without being detected and without triggering the host's immune defenses. The protein identified in this study is a glycine-rich protein that the researchers found plays a specific role in helping the tick feed and in moving pathogens between tick and host.
"They contain several arthropod proteins that could facilitate tick feeding, pathogen acquisition from infected hosts to naïve ticks, and transmission of pathogens from infected ticks to naïve hosts," Sultana said.
To test the protein's role, the researchers used genetic tools to silence the gene responsible for producing it. The results were significant. Ticks without the protein had trouble feeding effectively and showed reduced body weight after feeding. Virus levels were also substantially lower in those ticks.
That finding points to the protein as a potential target for a vaccine. Rather than treating a tick-borne illness after infection, a vaccine targeting this protein could potentially block transmission before it fully occurs.
Faculty collaborator Girish Neelakanta said the work connects tick biology to a broader understanding of disease risk. "Ticks transmit several pathogens," Neelakanta said. "Studies like this provide evidence about tick molecules that play an important role not only in tick biology but also in the interactions with pathogens."
Tick-borne diseases have become a growing public health concern in many parts of the world, partly due to expanding tick populations and shifting habitats. Most current prevention strategies focus on repellents, protective clothing, and early removal of ticks after outdoor exposure. A vaccine that interferes with transmission at the tick saliva level would represent a different kind of approach, one that targets the mechanism of spread rather than the pathogen itself.
The researchers believe exosomes could become an important target for disease prevention strategies going forward. Further research will be needed to determine whether a vaccine based on this protein could be developed and tested in humans or animals.
