Figure 1. Characterization of the rPF4-S. aureus and rPF4-host cell interaction.

Transmission electron micrographs of representative micrographs of nonencapsulated (A) and encapsulated (C) S. aureus stained with uranyl acetate. Arrowheads indicate the bacterial capsule in (C). The scale bar is 500 nm. (B and D) Confocal images showing the binding of rPF4 to S. aureus. After incubation with rPF4, bacteria were incubated with rabbit polyclonal anti-PF4 antibody (1:250) for 30 min at 22 °C, followed by Alexa Fluor 488-conjugated secondary antibody. The scale bars are 10 μm (left panels) and 1 μm (right panels). (E) Effect of rPF4 on the growth of nonencapsulated S. aureus. Bacteria were grown overnight in LB media and diluted in fresh LB media to OD600 of 0.03. Bacterial suspensions (0.8 ml) were incubated with different concentrations of rPF4 (25, 50, and 100 μg/ml) for 1–3 h at 37 °C, and OD 600 was measured. Data are means ± S.D. from three individual experiments; ns, no significant difference. (F) Bacteria grown for 3 h in the absence or presence of rPF4 were diluted 1:400,000 and cultured on LB agar plates for 24 h at 37 °C. Colonies were enumerated, and data are expressed as CFU/ml and are means ± S.D. from three individual experiments.