FIG 2.

DTMUV exhibits high neurovirulence and age-dependent neuroinvasiveness in mice. (A) Neurovirulence test in adult mice. Groups of 3-week-old female BALB/c mice (n = 5 to 6) were inoculated i.c. with various concentrations of DTMUV. Mock-infected mice received PBS. Animals were monitored daily for the appearance of symptoms during the 21-day period of observation. (B) Viral load in the mouse brain. Three-week-old female BALB/c mice were infected i.c. with 100 PFU of DTMUV. Two or three animals were euthanized on days 2, 4, and 6 p.i. Brains were collected and homogenized in DMEM. The viral titer in each supernatant was determined by plaque assay on BHK-21 cells. (C) Neuroinvasiveness tests in mice at different ages. Groups of 1-day-old, 11-day-old, and 21-day-old female BALB/c mice were inoculated i.p. with 100 μl of dilutions containing the indicated dose of DTMUV. Animals were monitored daily for the appearance of symptoms during the 21-day period of observation. (D) Viral loads in the serum and brain of mice determined by plaque assay. Dotted and dashed lines, limits of detection of the respective assays. Statistically significant differences are indicated. *, P < 0.05.