FIG 4.
High-dose infection in NSG mice indicates that the ΔM33 virus can reach the salivary gland but fails to replicate efficiently once in the gland. NSG mice were infected intraperitoneally with 1 × 106 PFU of the indicated viruses. At 4, 8, and 12 days postinfection, spleens (A), livers (B), and salivary glands (C, D) were harvested and homogenized with a tissue grinder. (D) Replication of a revertant virus was assessed for salivary gland growth. (E) Virus harvested from the salivary glands at day 12 postinfection was reintroduced into animals via i.p. injection (105 PFU per animal). Dilutions of the organ homogenates were used for viral titer determination via plaque assay on NIH 3T3 cell monolayers. Each symbol represents one animal. Dashed lines, the limit of detection. Statistical analyses were performed using an unpaired t test. *, P < 0.05; ***, P < 0.001.