Wild-type, Bid-deficient, or TRAIL-R-deficient MEFs (2610 5 ) in 24-well plates were adsorbed with reovirus at room temperature for 1 h in serum-free medium, washed once with PBS, and incubated in serum-containing medium for various intervals. Cells were frozen and thawed twice prior to determination of viral titer by plaque assay using L929 cells [89] .