FIG. 2.

Viral titers of brains from neonatal (A) and young adult mice (B) after intracerebral infection with 5 × 10² and 5 × 10⁵ PFU of RM461, respectively. Half a gram of brain tissue was minced in 0.5 ml of MEM and centrifuged at 4°C. The viral titer in the supernatant was quantified by the plaque assay method (60). The area below the horizontal line indicates the limit of detection of virus.