Decreasing the susceptibility of malignant cells to infection does not impact the overall efficacy of myxoma virus-based oncolytic virotherapy

Abstract Oncolytic virotherapy relies on the induction of anti-tumor immune responses to achieve therapeutic efficacy. The factors which influence the induction of these responses, however, are not well understood. To begin to address this lack of knowledge we asked how decreasing the susceptibility of malignant cells to direct viral infection would impact the induction of immune responses and therapeutic efficacy caused by oncolytic myxoma virus treatment. To accomplish this, we used CRISPR/Cas9 genome editing to remove the essential sulfation enzyme N-deacetylase/N-sulfotransferase-1 from B16/F10 murine melanoma cells. This eliminates the negative cell surface charges associated with glycosaminoglycan sulfation which reduces a cell’s susceptibility to infection with myxoma virus by ∼3-10-fold. Using these cells as a model of reduced susceptibility to oncolytic infection, our data demonstrates that 3-10-fold reductions in in vivo infection do not hinder the ability of oncolytic myxoma virus to induce anti-tumor immunity and do not lower the overall efficacy of localized treatment. Additionally, our data shows that in mice bearing multiple distinct tumor masses, the choice to treat a less susceptible tumor mass does not reduce the overall therapeutic impact against either the injected or non-injected lesion. Taken together, these data suggest that minor changes in the susceptibility of malignant cells to direct oncolytic infection do not necessarily influence the overall outcomes of treatment.