Figure 8.

MHV68 mutant deficient in pre-miRNA-15 and pre-miRNA-9 replicates normally in vitro but demonstrates increased lytic replication in vivo. (A) Lytic replication in fibroblast cells in vitro was determined using multi-step growth curve. NIH 3T12 fibroblasts were infected with MHV68 or MHV68∆15.9 at MOI 0.05. Samples were then harvested at 12 to 24 hr increments and subjected to plaque assay to determine viral titer. Values represent the mean titer ± standard deviation (SD) (n = 3). (B) In vivo replication in lungs of wild-type mice was quantified by plaque assay. Eight mice per sample group were inoculated intranasally (i.n.) with 10⁴ PFU wild-type MHV68 (WT) or MHV68∆15.9 (∆15.9). At 5 dpi lungs were harvested and virus titers were determined by plaque assay. Values represent mean titer ± SD. ** p < 0.01 using an unpaired t-test.