FIG. 4.
Histological findings for SJL/J mice after inoculation with 105 PFU of wt and mutant viruses. Longitudinal sections of the spinal cords of the infected animals were prepared on day 5 for GDVII (A) on day 6 for mutants 63 (B), 64 (C), and 43 (D), and on day 22 for mutant 43 (E and F). Viral antigens were detected by the immunoperoxidase assay with a polyclonal anti-TMEV rabbit serum (brown clusters). Virus-infected cells were localized in the gray matter and were more abundant in the GDVII- and mutant 63-infected animals than in the mutant 43 and 64 infections. In the case of mutants 43 and 64 (but not in the case of GDVII and mutant 63), there were marked signs of inflammation in the white matter (arrows) even at day 22 p.i., when no viral antigen was detectable (E and F). Magnification, ×312.