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|Science | Reuters | Space.com | AP|
Thu Jul 11, 2:36 PM ET
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.
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.
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