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How viral immunotherapies can help us treat cancer

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Professor Kevin Harrington

Professor of Biological Cancer Therapies at The Institute of Cancer Research, London

Professor Kevin Harrington specialises on viral immunotherapies, which use modified viruses to kill cancer cells and spark the immune system into action.


Viruses come in many shapes and sizes. Some, like the new coronavirus, can cause large-scale epidemics – others can be much milder, like the common cold or seasonal flu. However, the one thing all viruses have in common is their ability to infiltrate cells and kill them from the inside out. At The Institute of Cancer Research, London, scientists are using this property of viruses for good – by making them infect and kill cancer cells.

Identifying cancer cells

Oncolytic, or cancer-killing, viruses selectively infect cancer cells while leaving healthy cells alone. They deliver a one-two punch against cancer. Firstly, the virus kills cancer cells directly by infecting them and multiplying until the cancer cells burst from the inside out.

But importantly, the infection also helps flag cancer cells – which are normally good at hiding from the body’s own defences – to the immune system, which can then join the fight. In this way, oncolytic immunotherapies can help educate the immune system – teaching it to single out cancer cells so that they can be destroyed.

Genetically modified viruses

A successful example of a viral immunotherapy that was pioneered by scientists at The Institute of Cancer Research (ICR) can now be used to treat melanoma skin cancer that has spread to other areas of the skin, soft tissue or the lymph nodes. The immunotherapy was based on a genetically modified virus and was the world’s first oncolytic immunotherapy to be approved for use in the clinic.

Viral immunotherapies often use modified versions of a virus, such as the herpes simplex virus, which causes cold sores. They are genetically engineered to selectively infect cancer cells and stimulate an immune response. At the ICR, a number of new herpes simplex virus therapies are currently being developed and tested in the lab and in clinical trials across the UK.

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