Influenza A virus/immunology; Lactobacillus plantarum/immunology; Orthomyxoviridae Infections/immunology; Probiotics/administration & dosage; Th1 Cells/immunology; Animals; Antibodies, Neutralizing/blood; Bronchoalveolar Lavage Fluid/immunology; Bronchoalveolar Lavage Fluid/virology; Cell Proliferation; Feces/microbiology; Immunoglobulin A/biosynthesis; Immunoglobulin A/immunology; Immunoglobulin E/blood; Interferon-gamma/biosynthesis; Interferon-gamma/immunology; Interleukin-12/biosynthesis; Interleukin-12/immunology; Killer Cells, Natural/immunology; Killer Cells, Natural/metabolism; Killer Cells, Natural/microbiology; Lung/immunology; Lung/virology; Macrophages, Peritoneal/immunology; Macrophages, Peritoneal/metabolism; Macrophages, Peritoneal/microbiology; Male; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Orthomyxoviridae Infections/microbiology; Peyer's Patches/immunology; Peyer's Patches/metabolism; Peyer's Patches/microbiology; Spleen/immunology; Spleen/metabolism; Spleen/microbiology; Th1 Cells/microbiology; Toll-Like Receptor 2/immunology; Treatment Outcome