Oral administration of Bifidobacterium longum ameliorates influenza virus infection in mice.

We investigated whether the oral administration of Bifidobacterium longum BB536 could ameliorate influenza virus (IFV) infection in a mice model. Mice were orally administrated BB536 or saline for 2 weeks and then infected with IFV. Orally administered BB536 significantly alleviated symptoms, reduced the loss of body weight, and inhibited viral proliferation in the lungs relative to the control group findings. Histopathological findings in the lungs were improved in the BB536 group compared to control group findings. There was no significant difference in the levels of interleukin-6 (IL-6), interferon-γ (IFN-γ), IL-10 and IL-12p40 in the lungs between the groups, but the levels of IL-6 and IFN-γ were lower (p=0.076, 0.103, respectively) in the BB536 group compared with those of control group. The levels of IL-6 and IL-10 correlated significantly with the values of weight loss, and the levels of IFN-γ correlated with the virus titers in the lungs. These results suggested the potential of the oral administration of BB536 in ameliorating IFV infection and the possible involvement of anti-inflammatory effects of BB536 in the anti-infection effects against IFV.