CD34 and disease arising from reactivation of latent virus: To determine whether UL78 has a role in the establishment of latent infection or the capacity of the virus to reactivate, we infected human embryonic stem cell (hESC)-derived CD34+ HPCs with either WT-HCMV (TB40/E-GFP) or UL78–2XSTOP (TB40/E-GFP-UL78-2XSTOP) viruses.