The effective multiplicity of infection for HCMV depends on the activity of the cellular 20S proteasome

Human cytomegalovirus (HCMV) infection and reactivation continues to contribute to morbidity and mortality around the world. Antiviral compounds are available but have limitations. Here, we have defined the impact of the proteasome inhibitor bortezomib on HCMV replication. Proteasomal activities play a critical role in temporal changes required for replication. We demonstrate that disrupting these activities inhibits viral replication while likely supporting increased antiviral activity of the anti-HCMV agent, maribavir. Using a combination of live-cell imaging and computational tools, we discover that a subset of infected cells progresses to fulminant infection, which we define as the effective multiplicity of infection, and this subset would otherwise be missed when analyzing the average of the population.