The Cross-Border Biotech Blog

Biotechnology, Health and Business in Canada, the United States and Worldwide

Friday Science Review: January 27, 2012

An Evolving Concept of Oncolytic Viruses

University of Ottawa ♦ Ottawa Hospital Research Institute ♦ Ontario Cancer Institute ♦ University of Toronto ♦ University of Otago

Published in Molecular Therapy (npg), January 24, 2012

Oncolytic viruses were originally engineered to impose direct damage to tumour cells through infection, replication, and subsequent destruction of cancer cells via cell rupture. Many of today’s oncolytic viruses aim to do this, however it has become apparent that ‘next generation’ oncolytic viruses, those with the greatest efficacy, will be the viruses that not only destroy cancer cells physically but stimulate a strong innate immune response against cancer cells to continue the onslaught following initial infection.

This concept of inducing immune response is not novel. By their nature, oncolytic viruses offer the opportunity to deliver therapeutic genes at the time of infection. Indeed, previous studies have shown that viruses can be engineered to deliver cytokine genes into tumour cells. These cancerous cells then act as factories creating a protein product that leads to their own immune destruction. Suicide.

But researchers have now discovered that it may not be necessary to engineer viruses to do this. Certain viruses are capable of generating such an immune response simply through the presence of the viral particle itself. One example of such a virus is Parapoxvirus ovis, or ORFV. Researchers at the University of Ottawa found that injecting the virus into mice led to a significant upregulation of T cell response, including both CD4+ and CD8+, and an accumulation of B cells, natural killer cells, and various cytokines with anti-tumoural activity.

But there’s more to the story. ORFV infection does not lead to disease in animals, making it an excellent candidate for an oncolytic therapeutic. The real beauty though — the differentiative aspect of this virus — is that ORFV, even in the presence of antibody against the virus, continues to reinfect cancer cells. Animals seem to have a very short-lived immunity against the virus, allowing for an attenuated therapeutic activity unlike any found so far in this field.

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