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Gnat's Proteins May Help Humans / March 27, 1998 / News from the USDA Agricultural Research Service

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Gnat's Proteins May Help Humans

By Marcia Wood
March 27, 1998

Proteins that a pesky gnat secretes when biting sheep or cattle might someday be used in new vaccines and other drugs to help animals or humans.

In nature, the proteins help a tiny gnat enhance blood flow to the bite area. At the same time, the gnat may be transmitting particles of viruses that cause bluetongue, a livestock disease, according to scientists with USDA's Agricultural Research Service in Laramie, Wyo.

The gnat, grayish-black and about one-sixteenth-inch long, is known as Culicoides variipennis (KOO-lee-COY-deez vary-uh-PENN-uss). The virus gets its name from one of its symptoms-- a bluish, swollen tongue. The virus does not cause disease in humans.

Gnat salivary-gland proteins forestall blood clotting, dilate the victim's blood vessels and inhibit immune system cells that would fight off the virus. The proteins may be of use to medical researchers seeking, for example, new compounds to fight clotting that can lead to heart disease and strokes. The proteins may also be useful in blocking immune system responses in patients with arthritis or other disorders caused by an overactive immune system.

Researchers elsewhere have shown that the saliva of several other biting insects and ticks has similar specialized proteins. The ARS team was the first to find that C. variipennis gnats also secrete them.

The gnat proteins may make a suitable target for future vaccines to protect animals from viruses. This approach would differ from today's conventional vaccines that target a disease- causing virus itself. The U.S. has no generally approved bluetongue vaccine.

Bluetongue can kill sheep and, rarely, cattle. It costs the U.S. livestock industry an estimated $120 million in lost trade annually. Countries without the disease won't accept some U.S. livestock exports.

An article in the current issue of the agency's Agricultural Research magazine tells more. View it on the World Wide Web at:

Scientific contact: Walter J. Tabachnick, USDA-ARS Arthropod-borne Animal Diseases Research Laboratory, P.O. Box 3965, University Station, Laramie, WY 82071-3945. Phone: (307) 766-3600, Fax (307) 766-3500, e-mail

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