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Researchers Are Using Viruses to Make Superbugs Commit Suicide

Such sweet irony.

MIKE MCRAE
22 JUN 2017
 

The gene-editing technology called CRISPR has its origins as a bacterial immune system against viruses, a feature which could be turned against them in the future.

By arming bacteriophage viruses with the tools to force bacteria into falling on their own swords, scientists hope we will be able to develop powerful new ways to defeat antibiotic resistant pathogens and perhaps even shape our body's microflora.

 

Research presented at the CRISPR 2017 conference in the US described the progress that has been made in modifying viruses that target specific bacteria with genes that make the host's enzymes cut into its own DNA.

Clustered regularly interspaced short palindromic repeats – CRISPR for short – are sequences of DNA made of a repeating codes that form a long palindrome.

Bacteria produce them as a kind of immune system against viruses called bacteriophages, slipping bits of the virus's genes scavenged out of the environment into the repeating codes.

With the viral DNA stored away in CRISPR sequences, any future infections can be detected quickly and a CRISPR-associated system (or cas) enzyme can then use the sequence as a beacon, latching onto the infecting virus genes and either snipping them selectively or tearing them to shreds.

About 25 years ago, researchers realised this cut-and-paste system of CRISPR sequences and cas enzymes could be used in the lab to edit sequences artificially, and a new engineering toolkit was born.

The technology has been in the news quite a bit in recent years as advances have been made in applying it to cancer treatments and even eliminating HIV infections.

 

While it might not be without certain risks, CRISPR gene editing has sparked a something of a minor revolution.

Bringing it back to its roots and turning it into a weapon against its creators has a sense of serendipity about it.

"I see some irony now in using phages to kill bacteria," said the chief scientific officer of Locus Biosciences, Rodolphe Barrangou, at the CRISPR 2017 conference.

Using bacteriophages as a form of therapy to treat infection isn't all that new, with trials dating as far back as the 1920s.

The use of phages is appealing because they are far more specific than antibiotics, targeting only specific types of bacteria and therefore posing no risk to our own health. The viruses can also penetrate the coatings of sticky film bacteria produce for protection and adherence.

Russia experienced a fair degree of success with phage therapy behind its Iron Curtain during the Cold War, but unable to patent the naturally occurring viruses and with the bacteria quickly adapting, red tape and limitations in technology have made it far easier to focus on antibiotics in the west.

 

With looming epidemics of superbugs on the horizon, attention is returning to bacteriophages as ways to kill bacteria, and CRISPR has put a new spin on the old idea.

A spin-off company from North Carolina State University, Locus Biosciences is testing the limits of CRISPR technology, including giving bacteriophages CRISPR sequences containing codes for antibiotic resistance genes.

Targeting bacteria with the genes, the CRISPR sequence would form a target for the bacteria's own cas enzymes, effectively blocking resistance or even prompting the bacteria into chewing up its own DNA and self-destructing.

In recent years our eyes have been opened to how complex our relationship is with bacteria in our environment, and how dull our tools are for dealing with them.

Variations in our gut microflora has been linked with everything from Parkinson's disease to autism to obesity, suggesting the species of bacteria we harbour could have major ramifications on many aspects of our health.

With its razor-honed surgical precision, it's possible the technology could one day be used to select specific strains of bacteria in our gut, deleting them from the ecosystem and allowing us to edit our microbiomes.

Given we're practically at the dawn of both CRISPR technology and our grasp on the complexity behind our body's bacterial ecosystems, we can only speculate for the time being.

As antibiotics slowly lose their shine it's probably worth paying close attention to radical new solutions such as these.

 

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