FIG. 5.

att viruses provide homologous protection against influenza A/swine/Iowa/15/30 (H1N1) virus in BALB/c- and DBA/2-vaccinated mice. (A) Body weight in vaccinated/challenged BALB/c mice. Mice were vaccinated with Sw-att, Sw-ts, WF-att, WF-ts, or mock vaccinated and challenged with 100 MLD₅₀ of Sw30. Body weight was monitored daily. (B) Lung viral titers in vaccinated/challenged BALB/c mice. After challenge with Sw30, two mice in each group were sacrificed at days 3 and 6 postchallenge. Lungs were homogenized in 1 ml of PBS, and viral titers were determined by plaque assay. (C) Body weight in vaccinated/challenged DBA/2 mice. Mice were vaccinated with Sw-att or mock vaccinated and challenged with 100 MLD₅₀ of Sw30. Body weight was monitored daily. (D) Lung viral titers in vaccinated/challenged DBA/2 mice. After challenge with Sw30, two mice in each group were sacrificed at days 3 and 6 postchallenge. Lungs were homogenized in 1 ml of PBS, and viral titers were determined by plaque assay.