Fig 6. FAST protein is a determinant of pteropine orthoreovirus (PRV) pathogenicity.
(A, B) C3H mice (male, 3-week-old, n = 10/group) were intranasally infected with 4 × 105 plaque-forming units (PFU) of wild-type (rsMB) or FAST protein-deficient (rsMB-ΔFAST) PRV. The mice were monitored for (A) bodyweight changes and (B) survival rate for 14 days following virus inoculation. Survival curves were statistically compared with that in the control group using the log rank test. (C) Replication of PRV in mouse lungs. C3H mice (male, 3-week-old, n = 5) were intranasally infected with 4 × 105 PFU of rsMB or rsMB-ΔFAST. Animals were euthanized at 5 days post infection. Infectious virus titers in lung homogenates were determined by plaque-formation assay. Virus infectious titers were statistically compared between the two groups using the t-test. (D) Histopathological examination of C3H mice infected with PRV. Lungs of C3H mice 7 days after infection with rsMB or rsMB-ΔFAST were subjected to histopathological examination by hematoxylin–eosin (HE) staining and immunohistochemistry (IHC) with anti-sigmaC serum. Arrowheads indicate sigmaC-positive cells in IHC. Original magnifications: 200× (HE) and 400× (IHC). Scale bars indicate 100 μm (HE) or 20 μm (IHC).