To generate recombinant virus in various mammalian cells, cells were infected with the * G-complemented VSVΔG-Env at an MOI of 5 for 2 h at 37˚C and then extensively washed four times or more with serum-free DMEM. After 24 h of incubation at 37˚C, the culture supernatants were collected and stored at −80˚C. The infectious titers of the viruses were determined by evaluation of each reporter assay or a focus-forming assay. Further details of the protocol can be found in a recent paper (Whitt, 2010) .