Figure 1

Mouse Morbidity and Lung Virus Titer. Following infection with a sublethal dose of PR8 virus, mice were evaluated daily for weight loss (A) and increase in sickness score (B). Adult mice initial weight was significantly lower than aged animals (21.27 ± 0.2785 vs 24.93 ± 0.5157; P < 0.01). Aged animals (white squares) lost weight quicker, had a higher sickness score and recovered slower than adult mice (black circles). Mock infected animals (white circles -- adults; black squares - aged) did not lost weight or showed signs of disease. Influenza virus titer was evaluated in lung supernatants of adult (black bars) and aged (white bars) mice by plaquing on MDCK cells (C). Aged and adult mice had high virus titer in the lungs. Virus was recovered for a longer period of time in aged animals (C), which correlated with the delayed weight recovery (A) from aged animals and delayed reduction in sickness score (B). This suggested alterations in the immune system of elderly animals. Panels A and B are composites of three different experiments and panel C of 2 experiments. In each graph, the arithmetic mean ± SEM are displayed. The number of animals (N) used to generate each graph is displayed at the bottom of each panel. Stars indicate statistical difference between aged and naïve animals. *P < 0.05. **P < 0.01. ***P < 0.001.