FIG 6.

Viral replication and apoptosis in cultured cells and murine intestine following infection with M gene reassortant viruses. (A) T1L × T3D-RV M gene reassortant viruses used to define genes that segregate with the apoptosis-inducing capacity of reovirus. Gene segments labeled “1” in red represent those derived from T1L; gene segments labeled “3” in blue represent those derived from T3D. (B) L cells were adsorbed with T1L, T3D-RV, or one of six T1L × T3D-RV M gene reassortants at an MOI of 1 PFU/cell, and viral titers were determined at 24 hpi by plaque assay. Viral titers are expressed as PFU per milliliter of cell homogenate. (C) L cells were adsorbed with T1L, T3D-RV, or one of six T1L × T3D-RV M gene reassortants at an MOI of 100 PFU/cell. Cells were evaluated by AO assay at 38 hpi. The results are expressed as fold change in apoptosis compared with the value for T1L. Data from two experiments performed in triplicate are presented. (D and E) Mice were inoculated perorally with 10⁸ PFU of T1L, T3D-RV, or one of six T1L × T3D-RV M gene reassortants. The proximal half of the intestine was processed for viral titer, and the distal half was flushed, Swiss rolled, and processed for histology. (D) Titers of reovirus in the intestine were determined at 72 hpi by plaque assay (n ≥ 10 mice per virus). (E) At 24 hpi, histological sections were stained with an antibody against cleaved caspase-3. Cells positive for cleaved caspase-3 were enumerated manually and normalized per villus (n ≥ 8 mice per virus). Error bars indicate SEMs. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001. P values in panels C to E were determined by one-way ANOVA and Dunnett's multiple-comparison test (compared with the parental strain).