FIG. 1.

Recombinant virus replication and cytokine production in primary neonatal infection. Four-day-old BALB/c mice were infected with 8 × 10⁴ FFU of RSV/wt, RSV/IFN-γ, or RSV/IL-4 i.n. or left naïve. (A) Weight was monitored daily, and the weight change compared to weight prior to infection was plotted. (B) TaqMan PCR for RSV L RNA was carried out with RNA from lungs collected on days 2, 4, 7, and 14 postinfection. (C and D) Lung supernatants were taken on days 2 and 4 postinfection, and the concentrations of IFN-γ (C) and IL-4 (D) were determined by ELISA. Data are representative of three experiments, and points represent data for five mice per group ± SEM. *, P < 0.05; **, P < 0.01.