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Researchers at Old Dominion University are hoping to find ways to use a tick's own immune system as a way to control the transmission of infectious microbes.

In a study funded by a $440,000 grant from the National Science Foundation, Wayne Hynes, associate professor, and Daniel Sonenshine, eminent professor emeritus, both in the Department of Biological Sciences, are investigating mechanisms to prevent transmission of microbes that cause Lyme Disease and other conditions from the tick to its hosts.

They also hope to learn how to control the spread of infectious diseases transmitted by these vectors and/or control the microorganisms themselves.

Ticks are vectors of a number of important diseases, and with current mechanisms for controlling ticks often less effective than those for controlling insects, these arachnids may be more of a health problem for humans and wildlife than insects, Hynes said.

"This study addresses the fundamental issue of the tick response to bacterial infection and also addresses the question of why some microbes have been able to successfully colonize blood-feeding arthropods and become the agents of vector-borne diseases," he said.

The project examines the hypothesis that the American dog tick expresses a stronger antimicrobial response following bacterial infection when compared to the deer tick and the Lone Star tick. The study will provide information on how and why these ticks respond differently to assorted microbes.

The project will concentrate on a fundamental mechanism by which these blood-feeding arthropods resist infection by invading microbes through the use of antimicrobial peptides, a key component of an organism's innate immune response.
The project uses ticks because they harbor and transmit a greater variety of microbes than any other arthropod group.

Many arthropods possess a well-developed immune system that rejects most invading microbes. However, little is known about the immune system in ticks. More precise knowledge is needed to understand the limitations in the tick's immune system that have encouraged its ability to harbor a variety of microorganisms, Hynes said.

Ticks of the same genus as the deer tick tolerate a greater diversity of microbial species than other tick types. Most ticks of that genus that are microbe-tolerant feed on a diverse array of hosts ranging from cold-blooded vertebrates to almost any type of bird or mammal.

"It is proposed that these tick generalists have a less efficient immune system that facilitates colonization by a diverse array of invading microbes," Hynes said. "It is hypothesized that differences in ticks' innate immune mechanisms are important determinants of their ability to function as vectors of pathogenic agents."

By using Lyme disease-causing bacteria, and non-pathogenic bacteria and comparing the response to these microbes in the deer tick, the role of internal antimicrobial agents will be examined, he said.

This article was posted on: September 27, 2002

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