Mice infected intracranially with SFV4-miRT124 show increased survival compared to SFV4-miRT122 or wild-type SFV4. (A) Survival and symptoms witnessed in groups of BALB/c mice infected intracranially with 100 (n = 6), 10,000 (n = 5), or 100,000 (n = 6) PFU of SFV4-miRT122 (A), 100 (n = 6), 10,000 (n = 6), or 100,000 (n = 6) PFU of SFV4-miRT124 (B), and 100 (n = 6) or 10,000 (n = 5) PFU of SFV4 (C) and graded as follows: 0, no symptoms; 1, ruffled fur, hunched back, weakness of limbs, and optic neuritis; 2, partial paralysis of hind limbs; 3, paralysis of hind or front limbs; 4, severe paralysis, tetraplegia; and 5, moribund/dead.