RNA Research May Solve Sick Snake Mystery: Previously Unknown Viruses Could Date to Dinosaur Days

Article excerpt

Newly discovered viruses maybe at fault in a disease that causes snakes to regurgitate their food, behave strangely and even twist themselves into knots.

Researchers at the University of California, San Francisco found three new viruses in captive snakes with inclusion body disease, a fatal illness that strikes boa constrictors and pythons and causes clumps of proteins to build up in the snakes' cells. Scientists hope to glean clues to virus evolution stretching back to the age of the dinosaurs by examining the trio's unusual genetic makeup.

"It is so different from anything out there, it's almost unrecognizable. It's way out there," says Joseph DeRisi, a Howard Hughes Medical Institute investigator at UCSF who led the work, which appears online August 14 in mBio.

DeRisi's lab tracks down elusive infectious organisms by sequencing RNA in the cells of a sick animal. RNA, or ribonucleic acid, is a genetic molecule that is a chemical cousin to DNA. Cells store instructions for building proteins in DNA, then make RNA copies of those instructions to send to cellular protein-building machinery.

Many viruses don't bother with DNA at all, instead storing their genetic information in RNA. So examining RNA gives researchers a better shot at finding viruses than deciphering DNA would. The method could also identify hitchhiking parasites or bacteria.

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An outbreak of inclusion body disease at the CaliforniaAcademy of Sciences in San Francisco allowed DeRisi's group to assemble a collection of RNA from both sick and well snakes. The trick was to isolate odd bits of viral RNA in the samples from the vastly more abundant snake RNA. It was a bit like trying to work a billion-piece jigsaw puzzle with no picture to use as a guide, DeRisi says.

A red-tailed boa named Balthazar provided just the picture the scientists needed. Balthazar is an 11-year-old, 8-foot-long snake who lives at the academy and is used in education programs. The snake is completely healthy and has never had contact with snakes infected with inclusion body disease, says Freeland Dunker, a veterinarian at the academy.

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Assembling Balthazar's complete genetic blueprint let the researchers eliminate snake RNA from their sample of sick and well snakes. What was left behind yielded three previously unknown viruses. The California Academy of Sciences virus, CASV, came from an annulated tree boa at the academy. …