Fig. 3: Epithelial CD47 and bacterial FnBP directly interacts.

a, b Influenza virus-infected HBECs (IAV) infected with live S. aureus or S. aureus-derived samples (S, supernatant of S. aureus-cultured media; U, UV-killed S. aureus; H, heat-killed S. aureus). Paracellular FITC-dextran permeability (a) and trans-epithelial electrical resistance (b) of 7 groups: i) Mock (n = 3), ii) Virus only (n = 3), iii) Bacteria only (n = 3), iv) Super-infection (n = 3), v) Virus with S (n = 3), vi) Virus with U (n = 3), and vii) Virus with H (n = 3). c Whole mount image of CD47 (red) and S. aureus (green) in the influenza virus-infected HBECs at 1 dpi. An open arrow head indicates CD47⁺ cell without S. aureus and closed arrow heads indicate CD47⁺ cells with S. aureus. Co-localization of CD47⁺ cells and S. aureus are presented as violin plots (Mock, n = 6; + IAV, n = 6). d–g Bacterial adhesion assay. Colonization of S. aureus was assessed in HBECs inoculated with the virus (MOI 1) for 2 h before treatment with IgG1 control antibodies or α-hCD47 neutralizing antibodies (2 h), followed by S. aureus (MOI 3) infection for 3 h (IgG1 + S. aureus, n = 4; α-hCD47 Ab + S. aureus, n = 4; IgG1 + Super-infection, n = 4; α-hCD47 Ab+ Super-infection, n = 4) (d). Adherence of S. aureus WT (FnBP A+/B+, n = 4) and three mutant strains (FnBP A+/B–, n = 4; FnBP A–/B+, n = 4; FnBP A–/B–, n = 4) was assessed in HBECs inoculated with the virus (MOI 1) for 2 h, followed by S. aureus (MOI 3) infection for 3 h (e). Colonization of S. aureus WT (FnBP A+/B+) (f) and double deletion mutant (FnBP A–/B–) (g) was assessed in HBECs inoculated with the virus (MOI 1) for 2 h before treatment with IgG1 control antibodies (n = 4) or α-hCD47 neutralizing antibodies (1, 5, and 10 μg/mL for FnBP A+/B+, and 10 μg/mL for FnBP A–/B–, n = 4 each) for 2 h, followed by S. aureus (MOI 3) infection for 3 h. h Pull-down assay using His-tagged hCD47 recombinant protein. Bacterial plating [FnBP A+/B+ and FnBP A–/B– (n = 3 each in the absence or in the presence of His-tagged hCD47)] and immunoblot analysis were performed using supernatants and pellets after separation with α-His-Dynabeads™/DynaMag™−2 system. The graphs present the percentage of colony numbers grown in the culture of the supernatants or the pellets. Data are presented as mean values ± SEM. Significance was determined by one-way ANOVA with Tukey’s multiple comparisons test or unpaired two-tailed Student’s t test. n.s. not significant. Source data are provided as a Source Data file.