HCMV infected monolayers were trypsinized and pooled at the termination of the PRA. DNA was extracted from the pooled monolayers using the Blood gDNA kit (Promega, Madison, WI). HCMV DNA was quantitated using a validated in-house assay, which targets the DNA polymerase30. Reactions were performed on an Applied Biosystems 7500 (Thermo Fisher Scientific).