1. Introduction
Influenza virus infection is a significant cause of morbidity and
mortality all over the world. In particular, elderly individuals and
young children are at increased risk due to poor or weakened immune
function. Vaccination can help protect against the prevalent
subtypes of influenza, but new subtypes represent a global pandemic
threat. Furthermore, emerging resistance to neuraminidase
inhibitors is a serious concern. Therefore, enhancing natural defense
mechanisms by triggering nonspecific cell-mediated immunity
in a host might be a practical effective method for managing
influenza virus infections.
Lactobacilli are reported to have beneficial effects on host
homeostasis and to be effective in activating the immune system
(Fernandes and Shahani, 1990; Gilliland, 1989). In previous
studies, Lactobacilli were found to be effective in the prevention
or treatment of influenza virus infection in mice (Kobayashi
et al., 2011; Maeda et al., 2009; Yasui et al., 2004). In particular,