Oncolytic virus treatment differentially affects the CD56dimand CD56brightNK cell subsetsin vivoand regulates a spectrum of human NK cell activity

Natural killer (NK) cells protect against intracellular infection and cancer. These properties are exploited in oncolytic virus (OV) therapy, where anti-viral responses enhance anti-tumour immunity. We have analysed the mechanism by which reovirus, an oncolytic dsRNA virus, modulates human NK cell activity. Reovirus activates NK cells in a type I interferon (IFN-I) dependent manner, resulting in STAT1 and STAT4 signalling in both CD56dimand CD56brightNK cell subsets. Gene expression profiling revealed the dominance of IFN-I responses and identified induction of genes associated with NK cell cytotoxicity and cell cycle progression, with distinct responses in the CD56dimand CD56brightsubsets. However, reovirus treatment, acting via IFN-I, inhibited NK cell proliferative responses to IL-15 and was associated with reduced AKT signalling.In vivo, human CD56dimand CD56brightNK cells responded with similar kinetics to reovirus treatment, but CD56brightNK cells were transiently lost from the peripheral circulation at the peak of the IFN-I response, suggestive of their redistribution to secondary lymphoid tissue. These results show that reovirus modulates a spectrum of NK cell activityin vivo, encompassing direct action on tumour cells and the regulation of adaptive immunity. Such activity is likely to mirror NK cell responses to natural viral infection.