Virulence analysis in BALB/c mouse.

<p>(A) Groups of 6 BALB/c mice were infected intranasally with 10⁵ pfu of indicated viruses or mock infected with the same volume of PBS. The mice were then monitored daily for their body weights. For each group, the average and standard deviation of the percent of body weight change are shown. (B) 3 week-old mice were inoculated intracranially with 3×10⁴ pfu viruses, and deaths were recorded daily. The virulence in nervous system decreased when K1L gene was deleted. (C) 3 week-old mice were inoculated intracranially with 3×10⁴ pfu viruses. The brains were ground and supernatant used in plaque assays, which revealed reduced virulence in VTT△C7LK1L.