Oral administration of Lactobacillus gasseri SBT2055 is effective for preventing influenza in mice

The Lactobacillus gasseri SBT2055 (LG2055) is a probiotic lactic acid bacterium with properties such as bile tolerance and ability to improve the intestinal environment. In this study, we established that the oral administration of LG2055 exhibits efficacy to protect mice infected with the influenza virus A/PR8. The body weight losses were lower with the LG2055 administration after the PR8 virus infection. At 5 days after the infection, the virus titer was significantly decreased as was the amount of produced IL-6 in the lung tissue, the number of total cells in the bronchoalveolar lavage fluid was reduced by the LG2055 administration. The expression of the Mx1 and Oas1a genes, critical for the viral clearance in the lung tissues was increased by the pre-treatment with LG2055. These findings suggest that the LG2055 administration is effective for the protection against influenza A virus infection by the down-regulation of viral replication through the induction of antiviral genes expression.