TKI-conditioned immunotherapy using uv-inactivated reovirus promotes survival in hepatocellular carcinoma, mediated by cytotoxic CD4+ T-cells

Hepatocellular carcinoma (HCC) is the third most common cause of cancer deaths worldwide. Combination immunotherapy is now standard of care for advanced HCC, improving patient outcomes. However, a considerable number of patients remain unresponsive, or are unable to tolerate therapy. Tyrosine kinase inhibitors (TKIs), such as the former first-line agent sorafenib, remain an option for such patients, yet provide only marginal efficacy. We hypothesised that a clinically advanced immunogenic "oncolytic" virus, namely, human Orthoreovirus, might improve TKI mediated therapy. Surprisingly, uv-inactivated, replication-deficient reovirus, but not live virus, significantly extended survival when combined with sorafenib in preclinical immunocompetent HCC models. Favourable responses were dependent upon adaptive immunity, mediated by IFNB-induced skewing of the infiltrating T-cell ratio in favour of cytotoxic CD4+ T-cells expressing granzyme B and perforin. Interestingly, this subset effectively killed tumours via both contact juxtacrine and paracrine processes, the former being MHCII independent. Moreover, efficacy correlated with more rapid and robust IFN production by inactivated virus due to the absence of innate viral antagonists. Thus, we reveal a means to improve TKI-HCC outcomes through an alternative virus-driven immunotherapy, underpinned by non-classical immunological mechanisms. IMPACT AND IMPLICATIONSImmune checkpoint immunotherapy is revolutionising cancer treatment, yet considerable numbers of patients still fail to respond and must resort to older, more toxic and less effective therapies, including Sorafenib for the management of HCC. We demonstrate that burgeoning virus-driven immunotherapy can be successfully combined with Sorafenib to extend preclinical HCC survival, but only when the virus is uv-inactivated to prevent already attenuated innate immune antagonism, specifically increasing the magnitude of tumour IFNB responses. IFNB was essential to promote tumour infiltration of cytotoxic CD4+ cells during therapy, which was a hallmark of long-term survival mediated by ensuing adaptive responses. We anticipate this work will be of interest to clinicians and cancer immunology researchers, promoting closer inspection of the immune microenvironment and cancer-specific responses to OV therapy, specifically those driven by non-canonical anti-cancer mechanisms involving IFNB and cytotoxic CD4+ T-cells.