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From viral red alert to new breed of cancer vaccine

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by Cancer Research UK | News

22 June 2003

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Cancer Research UK scientists have discovered a key element of the body’s red alert system against viruses, opening the way for a new breed of vaccine against cancer and other non-viral diseases.

The discovery – published on the website of the journal Nature – helps to explain how the immune system reacts so violently against viral infections like the common cold.

Researchers hope to develop vaccines that trick the body into confusing a cancer cell for a viral particle, in order to unleash a powerful anti-cancer immune response.

The body reacts to viral infection by producing large numbers of molecules called interferons, which work by preventing viruses from multiplying and calling in other elements of the immune system to destroy the invaders.

Scientists had thought that only certain, specialist immune cells called plasmacytoid dendritic cells were capable of producing large numbers of interferons. But in the new study, they tested other, more common types of immune cell and found that these were also able to react to viral infection, producing just as many molecules of interferon.

Interestingly, these non plasmacytoid dendritic cells reacted not just to infectious viral particles but also to fragments of double-stranded RNA (from which many viruses are made), raising the possibility of designing vaccines made from the chemical.

Lead researcher Dr Caetano Reis e Sousa, of the Cancer Research UK London Research Institute, says: “The body is primed to act ferociously against incoming viruses, but we’ve never been quite sure how it is able to recognise viral particles and to leap into action so quickly.

“Our study has revealed a new mechanism for identifying viruses and triggering their destruction. If we could apply the immune system’s zest for attacking viruses to the problem of cancer, we might be able to design much more effective anti-cancer vaccines and immunotherapies than those currently being developed.”

Previous studies on the body’s response to viruses have focused on certain molecules on the surface of immune cells which seem to act as ‘on’ switches for the immune system.

But in the new study, scientists bypassed the normal ‘on’ switches by introducing molecules of double-stranded RNA directly into the interior of non plasmacytoid dendritic cells, and found that they were still able to activate a massive anti-viral response. Researchers believe there must be a second ‘on’ switch inside certain immune cells, which could be exploited in the design of future vaccines.

Dr Lesley Walker, Cancer Research UK’s Director of Cancer Information, says: “The immune system is highly effective at recognising and destroying infectious agents, which are clearly alien, but less so when it comes to cancer, which is made up of the body’s own cells.

“But by understanding how the body can recognise viruses and react against them, it should be possible to design vaccines which elicit the same level of response against cancer.”


Note to editors:

Researchers believe that the immune response to viruses is partly dependent on a molecule called Protein Kinase R, which lies within immune cells and may be acting as an ‘on’ switch.