Figure 1.

Lung virus titers at 1, 3, and 5 days after H1N1 virus inoculation. Female BALB/c mice, of 4-week, 6-month, and 1-year old, (n = 9 for each age group) were inoculated intranasally with a 10LD50 dose (10^4.3, 10^5.2, and 10^5.5 TCID₅₀, respectively) dose of A/Beijing/501/09 H1N1 virus. At indicated time, the tissues were taken (n = 3 mice from each age group) and virus titer was determined. ***indicate P < 0.001 relative to the corresponding the different age group mice with 4 week age group mice. Mean ± SEM.