Finding a way to interrupt the life cycle of disease carrying ticks


By RUDI HEMPE
CELS News Editor & Reporter

For the past three years, Sudha Pichu, PhD, has been exploring the function of genes in disease-carrying ticks.

And according to the principal investigator on the project, Dr. Thomas N. Mather, director of the Center for Vector-Borne Disease, her research has made great progress toward a vaccine against tick-borne diseases.

The research is centered on tick saliva and while that may sound simple, it isn’t—there are more than 8,000 genes in tick salivary gland cells, and understanding how they function in tick blood feeding will be critical in developing anti-tick vaccines.

Assistant Research Professor Shahid Karim started the work on this project by identifying a convenient means for silencing tick salivary genes using inhibitory RNA. By knocking down a specific gene, he reasoned that he would be able to determine if the tick needed the protein coded for by that gene in stealing blood or transmitting pathogens. But when his postdoc status expired, Pichu took the project over.

“Dr. Mather hired me because of my work in proteomics,” said Pichu who worked on kidney stones in her native India.

Mather says that Pichu, who has since returned to India for an unspecified time, started looking at the problem from another direction—evaluating the functional role of specific molecules deduced from an extensive salivary gland gene library. One group of proteins that she studied has the potential for modifying dopamine and other neurotransmitters which help ticks regulate their salivary secretions. One of these molecules, named Sult 1 (short for sulfatransferase) has the potential to take dopamine and make it inactive so the tick can stop drooling—“Otherwise the tick could drool to death,” says Pichu.

Still another molecule that Pichu found in tick saliva, a serine protease, likely acts as an important anticoagulant. “Ticks have many types of anticoagulants which they use to steal blood, but the specific properties of this serine protease have never been reported before in blood feeding arthropods”, says Pichu.

The USDA earmark grant advanced and greatly accelerated development of using inhibitory RNA (RNAi) in ticks, which will be an important tool in anti-tick vaccine development,” explained Mather. One next step for the team will be to use RNAi to knock down the genes responsible for Pichu’s newly identified proteins and evaluate their role in tick blood feeding.

“If we can keep ticks from stealing blood, then it should be possible to greatly suppress the tick population,” says Mather, noting that ticks need a blood meal to reproduce.

“Right now, white tail deer are the most important reproductive hosts for deer ticks, but one strategy would be to turn them into tick killers using an anti-tick vaccine,” says Mather, referring to the relationship between ticks and deer. “It would be one way to interrupt the tick life cycle, and that should reduce the incidence of diseases like Lyme disease,” he added.

Mather is hoping Pichu will be able to return and rejoin the research even though the earmark funding for her postdoc training has expired.

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