Fig. 1: Nasal microbiota might be critical for the suppression of IAV-caused lung infection.

A Schematic of the mouse model experimental design with depletion of the nasal microbiome. The mice (N = 20, group 1 (n = 5): abx (−) IAV (−), group2 (n = 5): abx (+) IAV (−), group 3 (n = 5): abx (−) IAV(+), group 4 (n = 5): abx (+) IAV (+)) were used in these experiments and ten mice were infected with IAV (2,130 pfu) at the indicated time points. The change in B the mean body weight (analyzed by repeated measure two-way ANOVA), and C survival rate of IAV-infected mice (analyzed by Kaplan–Meier with log-rank test) was compared according to the inoculation of intranasal antibiotics. Ten mice were used and five (abx (+), IAV (+)) were infected with IAV (2,130 pfu). The B6 mice with depletion of the nasal microbiota before IAV infection exhibited over 10% of weight loss than IAV-infected mice without abx administration, resulting in the death of all the mice at 8 days after IAV infection. Lung samples from uninfected mice (abx (+), IAV (−)) and IAV-infected mice that survived up to 7 dpi were collected. D IAV PA mRNA levels in the mice lung tissue (red dot: abx (+), IAV (–), black dot: abx (+) IAV (+)) and E viral titers from the BAL fluid of IAV-infected mice (red dot: abx (+), IAV (−), black dot: abx (+) IAV (+)) were assessed at 7 dpi. F H&E-stained micrographs were also generated from lung sections obtained at 7 dpi. Micrographs shown are representative of lung sections from five mice (red dot: abx (+), IAV (−), black dot: abx (+) IAV (+)) (Scale bar 10 uM). The micrographs were used to assess inflammation and tissue damage and to calculate a histological score. Real-time PCR and plaque assay results are analyzed by Mann–Whitney U-test and presented as mean ± SD values from three independent experiments. *p < 0.05 vs. mice without antibiotics treatment. (Abx antibiotics).