FIG 7.

Effect of ORF63 deficiency on replication of MuHV-4 in vivo. (A) BALB/c mice were infected intranasally with WT, ORF63 STOP, and ORF63 Rev MuHV-4 strains (1 × 10⁴ PFU). At the indicated times p.i., the infectious virus titers in lungs were determined by plaque assay. (B) Individual sera collected at the different time points were analyzed for MuHV-4-specific IgG by ELISA. Pooled naive sera provided the negative control. The data are averages from 5 mice ± SEMs and were analyzed by 2-way ANOVA and Bonferroni posttests. ***, P < 0.001; **, P < 0.01. (C) Lung histology. Seven days after infection with the different strains of MuHV-4, lungs were removed and fixed in formaldehyde before hematoxylin-eosin staining. Rectangles identify regions that are highlighted in higher-magnification pictures. Arrows indicate perivascular and peribronchial lymphocyte accumulation. The images are representative of data from at least 5 animals. (D) Spleens from the same mice were analyzed individually by infectious-center assay. (E) DNA was extracted from individual spleens. The viral genome copy number was then determined by real-time PCR.