Most humans are infected with Epstein-Barr virus (EBV), a cancer-causing virus. While EBV generally persists silently in B lymphocytes, periodic lytic (re-)activation of latent virus is central to its life cycle and to most EBV-related diseases. However, a substantial fraction of EBV-infected B cells and tumor cells in a population is refractory to lytic activation. This resistance to lytic activation directly and profoundly impacts viral persistence and effectiveness of oncolytic therapy for EBV+ cancers. To identify the mechanisms that underlie susceptibility to EBV-lytic activation, we used host protein-expression profiling of separated-lytic and -refractory cells.