FIG. 4.
Titration of infectious virus from infected tissues over time. Mice were infected with each PRV strain, and tissues were processed as described in Materials and Methods. Three mice per strain per time point were inoculated. Mice were sacrificed, and tissues were collected from mice inoculated with each virus at 36 and 72 h. At 96 h, mice inoculated with PRV-160 (US9 null), PRV-98 (gI null), PRV-91 (gE null), and PRV-Bartha were sacrificed, and tissues were harvested for virus isolation. Tissues from four mice in two separate experiments were collected from PRV-Bartha-infected mice at 168 h and 210 to 236 h, respectively. Strains at time points exceeding the time until death postinoculation were necessarily omitted.