HCMV differentially inhibits hematopoietic colony formation. CD34⁺-enriched cells were infected with TLsubUL21.5 at a multiply of infection (MOI) of 5 PFU/cell. Cells expressing the (A) CD34⁺/c-kit⁺ or (B) CD34⁺/CD38^– cell surface phenotypes were purified and sorted into GFP⁺ (infected) and GFP^– populations. Mock-infected cells expressing these phenotypes were also purified. Purified cells were plated in cytokine-rich methylcellulose. Erythroid and myeloid colonies were scored microscopically 10 to 14 days after infection. The frequency of colony formation is expressed as colonies formed per 1000 cells plated. The experiment shown is representative of 5 independent experiments. Error bars represent the standard deviation of 10 replicates within the experiment. Decreases in the formation of colonies that are significant are identified by associated P values that are derived from the 2-tailed Student t test. All other comparisons between GFP^– and GFP⁺ populations were not significantly different, with P > .05.