How Bacteria Survive and Spread in Ticks

Washington State University researchers have discovered how the bacteria that cause anaplasmosis and Lyme disease hijack cellular processes in ticks to ensure their survival and spread to new hosts, including humans.

Specifically, the team found that the bacteria can manipulate a protein known as ATF6, which helps cells detect and respond to infection, to support its own growth and survival inside the tick. The findings, published in Proceedings of the National Academy of Sciences, could serve as a launching point for developing methods to eliminate the bacteria in ticks before they are transmitted to humans and other animals. 

“Most research has looked at how these bacteria interact with humans and animals and not how they survive and spread in ticks,” said Kaylee Vosbigian, lead author on the study. “What we have found could open the door to targeting these pathogens in ticks, before they are ever a threat to people.”

The researchers focused their study on Ixodes scapularis, also known as the blacklegged tick, which is responsible for spreading both Anaplasma phagocytophilum and Borrelia burgdorferi, the causative agents of anaplasmosis and Lyme disease.

They discovered that when ATF6 is activated in tick cells, it triggers the production of stomatin, a protein that helps move cholesterol through cells as part of a normal cellular processes. The bacteria exploit this process against their tick hosts, using the cholesterol, which they need to grow and build their own cell membranes but cannot produce themselves, to support their own survival and success.

When the researchers blocked the production of stomatin, restricting the availability of cholesterol, bacterial growth is significantly reduced. The researchers believe this shows targeting the ATF6-stomatin pathway could lead to new methods for interrupting the disease cycle in ticks before transmission occurs.

As part of the study, Vosbigian also developed a new research tool called ArthroQuest, a free, web-based platform hosted by WSU that allows scientists to search the genomes of ticks, mosquitoes, lice, sand flies, mites, fleas and other arthropod vectors for transcription factor binding sites.