Protection against influenza virus infection of mice fed Bifidobacterium breve YIT4064

Mice fed Bifidobacterium breve YIT4064 and immunized orally with influenza virus were more strongly protected against influenza virus infection of the lower respiratory tract than ones immunized with influenza virus only. The number of mice with enhanced anti-influenza virus immunoglobulin G (IgG) i n serum upon oral administration of B, breve YIT4064 and oral immunization with influenza virus was significantly greater than that upon oral immuniza tion with influenza virus only. These findings demonstrated that the oral a dministration of B, breve YIT4064 increased anti-influenza virus Ige antibo dies in serum and protected against influenza virus infection. The oral adm inistration of B, breve YIT4064 may enhance antigen-specific IgG against va rious pathogenic antigens taken orally and induce protection against variou s virus infections.