PB-CD34 cell culture model for the establishment of HCMV latent infection. (A) CD34⁺ cells isolated from healthy PBMCs were cultured for up to 30 days and the phenotype of cell subsets were assessed by flow cytometry over time (n = 7). (B) Digital PCR analysis of HCMV UL55 and UL123ex4 viral genes for DNA copy number from known cell inputs determined by CCR5 qPCR from mock or HCMV strain Towne- or Merlin-infected PB-CD34 cells in a time course experiment (n ≥ 3). (C) Real-time qPCR analysis (log₁₀) of latency-associated transcripts UL111.5A, LUNA, and UL138 at day 5 PI from mock- or HCMV-infected PB-CD34 cells (n = 6) or productive infection genes UL54, UL55, UL86, UL99, and US3 (n = 4) (D). MRC5 infection served as positive control (n = 3). Data show mean ± SEM. *P < .05, **P < .01, ***P < .001. (E) Plaque assay of mock or HCMV-infected PB-CD34 cells, or supernatant from infected cultures, was applied to fibroblast monolayers and observed for CPE over time. Representative bright field microscope images are shown. Original magnification ×40, except rightmost panels (expanded insets) ×100. CMP, common myeloid progenitor; MEP, megakaryocyte-erythrocyte progenitor; MLP, multilymphoid progenitor.