Save the Virus, Kill the Cancer: Selective Inhibition of Anti-Viral Immune Response to Establish Anti-Tumor Immunity and Complete Cancer Regression

According to the Cancer Statistics Canada 2008 Report, last year 24,700 new cases and 4300 deaths were attributed to prostate cancer in Canada. Unfortunately, currently available treatment options fail to manage this disease. Such unavailability of effective treatment options have led to the development of a novel class of anti-cancer therapeutic therapies as reovirus-based virotherapy. Reovirus is a benign, naturally occurring virus has an ability to specifically target cancer cells of various origins including prostate cancer, while leaving healthy, non-cancerous cells unaffected. Additionally, reovirus virotherapy educates the patient's immune system to mount attack on cancer cells. Unfortunately, the implementation of this novel treatment has not been completely successful due to the hindrance caused by patients' immune system. During the administration of reovirus, immune system identifies reovirus as a pathogen and promptly removes it from the body. Such an anti-reoviral immune response purges reovirus before it can spread and kill enough cancer. So far, this problem has only been partially addressed by shutting down the patient's immune system using immuno-suppressive drugs. However, these harsh immuno-suppressive drugs have non-specific effects on immune system that render patients susceptible to infections, and more importantly avoid the development of reovirus-mediated initiation of beneficial anti-prostate cancer immunity. Therefore, it is believed that the success of the reovirus cancer treatment will ultimately depend on acquiring an exclusive inhibition of anti-reovirus immune response, without affecting immunity against prostate cancer. In this study, we propose a safe, practical, least invasive and clinically applicable immuno-modulatorynovel approach that will exclusively shut down anti-reovirus immunity temporarily and thus allow reovirus to persist longer and induce complete cancer regression.