FIG. 5.

Viral-antigen-positive cells in the hippocampus, cingulate gyrus, and basal forebrain of mice infected with recombinant viruses. Mice were infected as for Fig. 3 and sacrificed at 5 days postinfection. Brains were removed, fixed, and sectioned, and MHV proteins were detected by immunolabeling with rabbit anti-MHV-A59 serum. All sections were blinded, and the numbers of viral-antigen-positive cells per square millimeter of tissue in the basal forebrain (BF), cingulate gyrus (CG), and hippocampus (Hippo) were determined by averaging the number of positive cells per square millimeter in three sagittal sections from each of four animals per virus. Error bars indicate the standard error of the mean. The S4R22 virus-infected mice (closed bars) exhibited significantly more antigen-positive cells than did the wtR13 virus-infected mice (open bars). ∗, P < 0.05; ∗∗, P < 0.01; ∗∗∗, P < 0.001 (two-sided t test).