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Hepatitis agents defined, cultured.

Hepatitis Agents Defined, Cultured

A mysterious particle that piggybacks onto the hepatitis B virus has been characterized, and the hepatitis B virus itself has now been grown in the laboratory. These two advances, reported last week, promise to accelerate greatly the speed of hepatitis research, scientists say.

The discoveries relate to the blood-borne hepatitis B virus, which infects as many as a million people in the United States and hundreds of millions worldwide. While some people, though infectious, carry the virus with no ill effects to themselves, others are chronically ill and may also develop liver cancer. Hepatitis B infection, for which there is no treatment, can be complicated by something called the delta agent--a "defective' virus that exists only in conjunction with the hepatitis B virus. Delta infection, believed to be on the rise worldwide, can make chronic hepatitis B infection lethal.

Myron Essex and his colleagues at the Harvard School of Public Health have grown the hepatitis B virus in the test tube. They inserted hepatitis B genetic material into cells from human liver cancer and were able to isolate cells that produced particles immunologically and structurally identical to the hepatitis B virus.

With the virus in hand, researchers will be able to screen a wide variety of drugs against the virus in an in vitro setup, says Cammille Sureau, one of the investigators. The same group previously had inserted the virus's genetic material into bone marrow cells, but the production of virus particles was transient. The newly reported cell line has been producing viruses for a year, Sureau told SCIENCE NEWS.

Researchers have been racing to develop a hepatitis B culturing procedure. Several other laboratories along with Essex's reported at an August meeting that they had produced the virus in culture. Essex's lab was the first to get its results in print; the work is described in the Oct. 10 CELL.

The ability to culture hepatitis B virus is also expected to speed research on the delta agent. Knowledge of the "satellite' virus, as researchers call it, was boosted last week when two laboratories described its structure, sequence and function in the Oct. 9 NATURE.

In papers from the Netherlands and a consortium of researchers from Chiron Corp. in Emeryville, Calif., the University of California at San Francisco and a Georgetown University laboratory in Rockville, Md., delta's genetic material was described as a single-stranded circle of RNA similar in size and shape to certain agents that infect plants. In addition, the U.S. group determined the agent's genetic sequence and discovered antibodies to a protein encoded by the RNA in the blood of patients with delta infections.

These new findings, says Michael Houghton of Chiron Corp., will someday enable researchers to develop a blood test for diagnosing delta infection-- which currently must be diagnosed through liver biopsy--and will allow researchers to conduct experimental vaccine research.

John Taylor of the Fox Chase Cancer Center in Philadelphia, whose own description of the delta infectious agent is scheduled for publication in the PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES, says the similarities with the plant infectious agents, about which a good deal is known, may shed some light on the delta agent. In addition, he says, using what is now known of delta and the hepatitis B culturing system, researchers should be able to determine how the two interact.
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Author:Silberner, Joanne
Publication:Science News
Date:Oct 18, 1986
Words:559
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