Oncolytic viruses infect tumour cells, where they can either kill the cell directly or act as a flag to the immune system.
What is an oncolytic virus?
Viruses can infect and kill cells. Some naturally occurring viruses, as well as viruses that have been altered in the lab, infect and kill cancer cells. These are known as oncolytic viruses.
Along with killing the cells directly, the viruses can also alert the immune system to attack the cancer cells.
The reovirus is an example of an oncolytic virus.
The reovirus is a naturally occurring and mostly harmless virus, which has previously been shown to effectively home in on cancer cells, while often leaving healthy cells alone. The reovirus also has the ability to cross the blood-brain barrier.
In an early study, the reovirus was injected via a drip into the bloodstreams of nine people before surgery for a brain tumour. Samples taken during their operations showed evidence that the virus had reached the tumour.
The samples also showed that those who received reovirus had higher levels of interferons - proteins that 'switch on' the body's immune system.
Our immune systems aren't very good at 'seeing' cancers – partly because cancer cells look like our body's own normal cells, and partly because cancers are good at telling immune cells to turn a blind eye. But the immune system is very good at seeing viruses, therefore more effective at seeking out tumour cells that contain a virus.
The reovirus is being studied for use on high grade gliomas, including glioblastoma.