Potentiating oncolytic viral therapy through an understanding of the initial immune responses to oncolytic viral infection

•Oncolytic viral therapy triggers a number of host responses including anti-viral and anti-tumor responses.•Increasing evidence suggests that both facets of the immune response must be considered and modulated.•Immune modulation is achieved with novel viral vectors and through combinatorial approaches.•Clinical trials are incorporating data to track the immune response and monitor for clinical success.

Despite the challenge of implementing oncolytic viral therapy into mainstream clinical use, the obstacles of early clinical trials have outlined numerous areas requiring additional investigation. In particular, the role of innate and adaptive immunity has received significant attention in this context. It is increasingly clear that a one-sided approach of either immune suppression or robust immune cell activation is not the answer for clinical success. Rather, recent studies are increasingly demonstrating the delicate balance between both anti-viral immune suppression and immune mediated tumor killing. In this review we focus on aspects of innate immune cell activation following oncolytic viral infection and how this response has the potential of bridging to the broader goal of viral mediated immunotherapy.