7 February 2007

A few good viruses

By
Cosmos Online
Viruses generally get a bad rap, but in laboratories around the world, these miniscule hijackers are themselves being hijacked to treat some of humanity’s most feared diseases.
A T4 bacteriophage injecting DNA into a cell. Providing an effective mechanism for delivering human genetic therapy is one of the ways these stigmatised parasites are proving their true value to humanity.
A few good viruses

A T4 bacteriophage injecting DNA into a cell. Providing an effective mechanism for delivering human genetic therapy is one of the ways these stigmatised parasites are proving their true value to humanity. Credit: Wikimedia

As far as words with negative connotations go, it’s hard to top ‘virus’. AIDS, bird flu, Dengue fever, Ebola – and that’s just in the first few letters of the alphabet. And when Agent Smith tells Morpheus in The Matrix that he considers the human race a virus, it’s widely understood that he’s not paying a compliment.

But for a rising number of scientists, viruses aren’t sinister at all. Instead, they are at the forefront of the latest advances in genetic technology, bringing hope to those with previously incurable diseases.

Hitchhikers, hijackers & hosts
Martha Chase and Alfred Hershey used viruses to help establish that DNA, rather than protein, forms the basis of heredity. Cheap, quick to produce, and easy to modify, a core group of viruses has filled out the toolboxes of many a biologist ever since.

Their ability to entwine themselves with the host’s genome has made viruses the darlings of the field of gene therapy. The once outlandish scenario of going into a person’s cells and correcting genetic ‘typos’ is now an earnest aim of researchers, who hope intentional viral infections will one day help sufferers of diseases such as Parkinson’s and Severe Combined Immunodeficiency (SCID), also known as ‘bubble boy syndrome’, a mutation in the genome that prevents the body’s immune system from functioning.

Researchers plan to ‘hijack the hijackers’ – swapping the virus’ harmful genes for a corrected version of the patient’s defective genes and using the virus’ unique abilities to insert the gene into patient’s genome. In reality, the procedure is fraught with difficulties, not least getting the right amount of gene in the right location without side effects.

Pavel Osten from Northwestern University in Chicago, Illinois, recently co-authored a paper on the use of viruses as DNA delivery systems, or vectors. “In my view, it is most likely that this work [gene therapy] will become a mainstream treatment of some of the devastating brain disorders for which there is currently no treatment,” he wrote.

But how would you feel about being injected with a virus to cure a disease? According to Osten, the risks are low and decreasing. “The viral vectors … are in most cases stripped down to the most basic elements that are required for gene delivery, and thus in no possible way pose any risk with respect to the original disease.”

Viruses don’t attack only animal cells, however. The vast majority of viruses actually target bacteria, including the bacteria that infect humans; they are called bacteriophages, or phages for short (from the Greek phagein, to consume). “For years researchers have been looking at using this targeted bacterial killing as an alternative to antibiotics,” says Jason Clark from Moredun Research Institute in Scotland. While this might seem a bit like inviting in the barbarians, it’s also sound science; in August of last year, the U.S. Food and Drug Administration (FDA) approved a bacteriophage food spray designed to reduce the amount of illness-causing bacteria on ready-to-eat meals.

It’s a virus’ world
Hamish Clarke is a Sydney-based science writer and a regular contributor to COSMOS and Cosmos Online.

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