(a), Vector-related toxicity in neonatal mice assessed by body weight gain (BW) (a–e) and survival (f). (a–e) Ten microlitres of PBS solution containing 2.5 × 106 CIU of either wild SeV (Z-strain) (b), additive rSeV expressing enhanced green fluorescent protein (rSeV-EGFP: c), ts-rSeV/dF-EGFP (d), or rSeV/dFdMdHN-EGFP (e) was intranasally inoculated to newborn ICR mice on day 0, and body weight (BW) was measured daily. The blue line indicates the time course of each live animal, and the red line that of each dead animal. (f) The survival curves of these mice are also shown. The curves were analyzed using Kaplan–Mayer's method. The statistical significance of the survival was determined using the log–rank test.