For flow cytometry analysis, NIH 3T3 cells were infected with the indicated virus and, 18 hpi, cells were washed with PBS and harvested via trypsin digestion. Cells were fixed in a 4% formaldehyde solution, permeabilized in 1% Triton X-100 and 0.1% sodium citrate in PBS, and incubated with anti-muSOX antibodies at a 1:12.5 dilution in 1% Triton X-100, 0.5% Tween, and 3% BSA in PBS. Stained cells were then washed in PBS and incubated with goat anti-rabbit antibodies conjugated to PE-Cy5.5 (Invitrogen) at a dilution of 1:150. Data were collected on an EPICS XL cytometer (Beckman-Coulter) and analyzed using FlowJo software (Tree Star).