Most gene therapy trials depend on viruses to deliver corrective genes to human cells.

Retroviruses are only one of several types of viruses used to deliver genes into cells.

In delivering new genes to a precisely designated site, the new method, if it works, would be safer and more effective.

Little by little, researchers say, they are finding new and better ways to deliver genes to their target cells.

Such a crippled virus, they say, could be used to deliver genes into human cells for gene therapy.

Other viral vectors have features that may be useful for delivering genes in particular circumstances.

This process requires vectors to deliver genes to the target cells.

The researchers have developed a method of delivering healthy genes directly into the brain.

At the time, the researchers were using Parkinson's disease to investigate ways to deliver genes into brain cells of rats.

It wasn't a question of whether they could deliver genes to the cells.