Old Viruses Resurrected Through DNA

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November 7, 2006 New York Times

 

Old Viruses Resurrected Through DNA

By _CARL ZIMMER_ (http://query.nytimes.com/search/query?ppds=bylL & v1=CARL

ZIMMER & fdq=19960101 & td=sysdate & sort=newest & ac=CARL ZIMMER & inline=nyt-per)

 

Thanks to advances in _DNA_

(http://topics.nytimes.com/top/news/health/diseasesconditionsandhealthtopics/gen\

eticsandheredity/index.html?inline=nyt-classifie

r) technology, scientists can now reconstruct new copies of old viruses.

Last year United States government scientists reconstructed the virus that

caused the _influenza_

(http://topics.nytimes.com/top/news/health/diseasesconditionsandhealthtopics/inf\

luenza/index.html?inline=nyt-classifier) epidemic of

1918. Now a team of French scientists has rebuilt a virus that infected our

apelike ancestors several million years ago.

The scientists did not isolate a virus from a fossil. Instead, they examined

vestiges of the virus that survive today within the human genome.

About 100,000 segments of human DNA are remarkably similar to retroviruses, a

class of viruses that includes _HIV_

(http://topics.nytimes.com/top/news/health/diseasesconditionsandhealthtopics/aid\

s/index.html?inline=nyt-classifier) .

Retroviruses insert a copy of their genes into the genome of their host

cell. Scientists estimate that 8 percent of the human genome is made up of this

viral DNA, known as human endogenous retroviruses, or HERVs.

“Our genome is filled with retroviruses,†said Dr. Thierry Heidmann, an

expert on HERVs at the Gustave Roussy Institute in Villejuif, France. “It’s

a

hard idea to understand, but they are part of our genome.â€

Many HERVs found in the human genome have counterparts in the genomes of

other species. They infected our distant ancestors millions of years ago, and

were passed down from generation to generation. They also produced new copies

that could reinfect egg or sperm cells, adding more HERVs to the genome. Over

time HERVs were crippled by mutations. Until now, scientists have never found

a HERV that acts like a fully functional virus.

Dr. Heidmann reasoned that disabled HERVs must descend from working

ancestors. He and his colleagues compared the DNA of HERVs from a family found

only

in humans, deducing the ancestor’s genetic makeup from the differences. They

built a corresponding piece of DNA and inserted it into human cells. Some of

the cells produced new HERVs that could infect other cells.

The scientists named the reconstructed virus Phoenix. The journal Genome

Research _published_ (http://www.genome.org/cgi/content/abstract/gr.5565706v1)

the experiment on its Web site last week.

Dr. Heidmann plans to use Phoenix to study the role of HERVs in _cancer_

(http://topics.nytimes.com/top/news/health/diseasesconditionsandhealthtopics/can\

cer

/index.html?inline=nyt-classifier) .

“The procedure is ingenious,†said Robert Belshaw, an expert on HERV

evolution at _Oxford University_

(http://topics.nytimes.com/top/reference/timestopics/organizations/o/oxford_univ\

ersity/index.html?inline=nyt-org) , who was not

involved in the study. He speculates that some people still carry working

versions of Phoenix. “It’s possible it’s also still moving between

individuals,â€

he said.