Growth of different HCMV strains (Toledo, Towne, and TowneBAC) in cultured cells (A) and cultured gingival tissues (B). In (A), human foreskin fibroblasts (HFFs) (1 × 106 cells) were infected with each virus at a MOI of 0.05. At 0, 2, 4, 7, 10, and 14 days post infection, cells and culture media were harvested and sonicated. In (B), the tissues were infected with 2 × 104 PFU of each virus at the apical surface of the tissue. At 0, 3, 6, and 10 days post infection, the tissues were harvested, suspended in a small volume of 10% milk, and sonicated. The viral titers were determined by plaque assays on HFFs. The limit of detection was 10 PFU/ml of the tissue homogenate. The values of the viral titer represent the average obtained from triplicate experiments. The standard deviation is indicated by the error bars.