Oral administration of milk fermented with Lactococcus lactis subsp. cremoris FC protects mice against influenza virus infection

Aims: To evaluate the protective effects of oral administration of milk fermented with a Lactococcus strain against influenza virus (IFV) infection in a mouse model. Methods and Results: Milk fermented with exopolysaccharide‐producing Lactococcus lactis subsp. cremoris (L. cremoris) FC was orally administered to BALB/c mice for 12 days. Mice were intranasally infected with IFV A/New Caledonia/20/99 (H1N1) on day 8, and survival was determined for 14 days after IFV infection. Survival rate and body weight loss after IFV infection in the L. cremoris FC fermented milk‐administered group were significantly improved compared with those in the control group. In the unfermented milk‐administered group, survival rate was not improved, whereas body weight loss was slightly improved compared with that in the control group. The mean virus titre in the lung of the L. cremoris FC fermented milk‐administered group 3 days after infection was significantly decreased compared with that in the control group. Conclusions: These results suggest that oral administration of milk fermented with L. cremoris FC protects mice against IFV infection. Significance and Impact of the Study: These results demonstrate that oral administration of milk fermented with exopolysaccharide‐producing Lactococcus strains might protect host animals against IFV infection.