Wednesday, June 22, 2005

Common virus kills cancer, study finds

WASHINGTON (Reuters) - A common virus that is harmless to people can destroy cancerous cells in the body and might be developed into a new cancer therapy, U.S. researchers said on Tuesday.

The virus, called adeno-associated virus type 2, or AAV-2, infects an estimated 80 percent of the population.

"Our results suggest that adeno-associated virus type 2, which infects the majority of the population but has no known ill effects, kills multiple types of cancer cells yet has no effect on healthy cells," said Craig Meyers, a professor of microbiology and immunology at the Penn State College of Medicine in Pennsylvania.

"We believe that AAV-2 recognizes that the cancer cells are abnormal and destroys them. This suggests that AAV-2 has great potential to be developed as an anti-cancer agent," Meyers said in a statement.

He said at a meeting of the American Society for Virology that studies have shown women infected with AAV-2 who are also infected with a cancer-causing wart virus called HPV develop cervical cancer less frequently than uninfected women do.

AAV-2 is a small virus that cannot replicate itself without the help of another virus. But with the help of a second virus it kills cells.

For their study, Meyers and colleagues first infected a batch of human cells with HPV, some strains of which cause cervical cancer.

They then infected these cells and normal cells with AAV-2.

After six days, all the HPV-infected cells died.

The same thing happened with cervical, breast, prostate and squamous cell tumor cells.

All are cancers of the epithelial cells, which include skin cells and other cells that line the insides and outsides of organs.

"One of the most compelling findings is that AAV-2 appears to have no pathologic effects on healthy cells," Meyers said.

"So many cancer therapies are as poisonous to healthy cells as they are to cancer cells. A therapy that is able to distinguish between healthy and cancer cells could be less difficult to endure for those with cancer."

AAV-2 is being studied intensively as a gene therapy vector -- a virus modified to carry disease-correcting genes into the body. Gene therapy researchers favor it because it does not seem to cause disease or immune system reaction on its own.

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