By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - Using only a genetic map as a guide, U.S. researchers said on Thursday they had built a polio ( news - web sites) virus from scratch and used it to infect and paralyze lab mice.

It is the closest anyone has yet come to creating life in a test tube -- although scientists deny a virus, which is not a living cell but which can replicate itself, is alive in the same way a bacterium, a plant, or a human being is.

Nonetheless, it has genetic material like all other life.

"If the ability to replicate is one of life's attributes, then poliovirus is a chemical with a life cycle," the researchers at the State University of New York in Stony Brook wrote in their report, published in the journal Science.

Eckard Wimmer, who led the study, denies that he has created life.

"No, I would not say I created life in a test tube," Wimmer said in a telephone interview. "We created a chemical in a test tube that, when put into cells, begins to behave a little bit like something alive. Some people say viruses are chemicals and I belong to that group."

Wimmer said once the right genetic parts were in place, the virus virtually self-assembled in a lab dish.

Polio virus does not have DNA like many organisms, but starts out with RNA, which is the working version of DNA. DNA carries the genetic code in cells, and is transcribed into RNA, which controls the production of individual proteins.

To make a virus, Wimmer and colleagues Jeronimo Cello and Aniko Paul had to first take a step backward.

"You cannot synthesize RNA," Wimmer said. "So we converted the sequence from RNA into DNA. And DNA you can synthesize. Then we had to go back to RNA. That was very simple -- by using an enzyme which can read DNA and synthesize RNA, called a transcriptase," he added.

"Now you have the RNA. That RNA we put into a cell-free juice that we developed in 1991 ... and lo and behold out came the virus. It built itself."

The "cell-free juice" is made by taking the virus's favorite home -- a human cell -- shredding it up and removing the big pieces such as the nucleus.

A JUICE FULL OF GOODIES

"The remaining juice that is there contains all the goodies that you need for the process," Wimmer, whose team first sequenced the polio genome in 1991, said.

There were not too many ingredients to throw into the broth. Polio virus has a single, long gene that produces what is called a polyprotein.

But the virus can cut this long protein into smaller pieces that can be used for its few functions.

The virus acted like polio in the test tube and also paralyzed mice genetically engineered to be susceptible to polio -- which in nature prefers to infect human beings. Polio once paralyzed tens of thousands of children a year, before vaccination made it a rare disease.

The process did cause some mutation in the genetic code which seemed to weaken the effects of the virus, Wimmer said.

There are two good vaccines for polio, but Wimmer hopes his team's process might be used to create genetically weakened versions of other viruses for use as vaccines. His team is also working with the hepatitis C virus.

This is a standard vaccine technique -- using a non-dangerous form of a virus to stimulate the immune system without causing disease.

Wimmer raised the specter of bioterrorism, noting that the aim of the current polio vaccination campaign is to wipe the virus off the face of the Earth. Only a few pockets of polio remain, notably in Africa and South Asia.

But Wimmer said if deadly viruses can be made in the lab, they may always be at least a theoretical threat -- which means vaccination may have to continue even when a disease no longer naturally exists.

"It is a wake-up call for everybody to say that what is in the public domain can be used for the betterment of mankind -- namely to combat disease -- and it can be misused. You could argue that it could be misused for bioterrorism," he said.

It is feared something similar has happened with smallpox, which was declared eradicated in 1980 after a global vaccination campaign. But samples of the virus were kept in laboratories and used to make biological weapons, which, many experts fear, remain in the hands of some governments and perhaps of extremist groups.

More from > Science
Next Story:		Research Council Urges NASA to Go to Pluto Thu Jul 11,12:21 PM ET - (Reuters)

Archived Stories by Date:

Tue Jul 09 Mon Jul 08 Sun Jul 07 Sat Jul 06 Fri Jul 05 Thu Jul 04 Wed Jul 03 Tue Jul 02 Mon Jul 01 Sun Jun 30 Sat Jun 29 Fri Jun 28 Thu Jun 27 Wed Jun 26 Tue Jun 25 Mon Jun 24 Sun Jun 23 Sat Jun 22 Fri Jun 21 Thu Jun 20 Wed Jun 19 Tue Jun 18 Mon Jun 17 Sun Jun 16 Sat Jun 15 Fri Jun 14 Thu Jun 13 Wed Jun 12 Tue Jun 11 Mon Jun 10

News Resources Message Boards: Post/Read Msgs (11 msg Jul 11, 5:00 PM ET) My Yahoo!: Add Science - Reuters to My Yahoo! News Alerts: polio