Replication of MYXA8 P0 and P10 clones. Triplicate BS-C-1 cell monolayers were infected for 6, 12, and 24 h with 5 PFU/cell of WT virus, and MYXA8 P0 and P10 clones from passages A, B, and C. Virus titers were determined in duplicate by plaque assay in BS-C-1 cells. Bars represent standard errors of the means. *, P < 0.05; **, P < 0.01.