Recombinant rabies virus vaccine strain SAD-l16 inoculated intracerebrally in young mice produces a severe encephalitis with extensive neuronal apoptosis.

Seven-day-old ICR mice were infected by intracerebral inoculation with recombinant rabies virus vaccine strain SAD-L16. Infected mice developed severe and fatal encephalitis with rabies virus-infected neurons in widespread regions of the brain. There was extensive neuronal death with predominant features of apoptosis, as assessed by light and electron microscopy, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining, and immunohistochemical staining for activated caspase-3. Although SAD-L16 is a neuroattenuated rabies virus, it is fully capable of spreading efficiently and inducing widespread neuronal apoptosis in the immature mouse brain.