Viruses are remarkably good at destroying cells, and for the most part, this makes them fairly threatening. When it comes to cancer though, viruses may be the key to a remarkably effective cure.

Just recently, a team of researchers used custom-made viruses to sneak into cancer cells and unleash a gene-editing tool that fiddled around with their “command centers”, causing them to self-destruct. Now, a group from the Universities of Basel and Geneva have come up with their own set of cancer-killing viruses, but these little critters act quite differently.

Instead of directly targeting the cancerous cells, these stimulate the patient’s immune system, getting it to do the heavy-lifting.

As pointed out in the team's Nature Communications study, a type of meningitis virus known as lymphocytic choriomeningitis (LCMV), when inside a living creature, has long been known to trigger the release of T cells, a type of white blood cell that consumes and destroys cancerous cells, as well as viral-infected cells and cells that are otherwise damaged in some way.

This is a good cancer-killing mechanism, but there’s an obvious problem that cannot be overlooked – you cannot give someone a powerful virus in the hope it will cure their cancer at the same time.

So, in order to circumvent this, the team made artificial LCMVs, ones that would behave like regular viruses to some extent but that would not cause any harm to the patients, which in this case were laboratory rodents. Importantly, the LCMVs were also customized to contain genetic markers of the tumors – the equivalent of a red flag for the mice’s immune systems.

When infected with these artificial LCMVs, the immune system saw these viruses and the flagged tumor cells as a considerable, overwhelming threat, and it responded by ejecting hordes of killer T cells into the bloodstream. Overall, the treatment killed off enough of the tumors to push the mice into remission.

This, indubitably, is a pioneering cancer-killing method. It belongs in the relatively new category of “immunotherapy”, where instead of using drugs or radiation to kill off the cancer cells, it uses the body’s own defense mechanisms to do the job instead. Traditional chemotherapy has plenty of damaging side-effects, but immunotherapy tends to be more surgically precise – it kills cancer cells and leaves other cells intact.

The success of this trial means that human equivalents are just a couple of years down the line. For now, though, we cannot be sure how effective the treatment will be.

Nevertheless, the fact that the team has managed to turn an ancient foe into an effective ally is a testament to the power of scientific progress – and a marker of how quickly the tide is turning against cancer.