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Fig. 4 | BMC Microbiology

Fig. 4

From: Novel human monoclonal antibodies targeting the F subunit of leukocidins reduce disease progression and mortality caused by Staphylococcus aureus

Fig. 4

Neutralization ability of YG8–1, YG8–2, and YG8–3 in vitro. (a, b) YG8–1, YG8–2, and YG8–3 inhibited the hemolysis of rabbit red blood cells (rRBCs) in a concentration-dependent manner. YG8–1, YG8–2, and YG8–3 were serially diluted in PBS and mixed with recombinant HlgAB (a) or HlgBC (b). Pre-incubation was carried out at room temperature for 30 min, and the mAbs were then incubated with erythrocytes at 37 °C for 1 h. The samples were centrifuged, and the absorbance of the supernatants was measured at 405 nm. Percent inhibition of toxin activity was calculated using the following formula: percent inhibition = ([normal activity – inhibited activity] / [normal activity]) × 100. (c) YG8–2 inhibited the interaction between HlgA and HlgB. His-HlgA (1 μg/well) was coated onto 96-well plates, and YG8–2 was added at various concentrations after pre-incubation with GST-HlgB. Bound GST-HlgB was detected using an anti-GST antibody. Data are representative of three independent experiments and shown as the mean ± SD. (d–h) YG8–2 inhibited the lysis of neutrophils and monocytes in a concentration-dependent manner. YG8–2 was pre-incubated with HlgAB (d, e), HlgBC (f), LukSF (g), and LukED (h) at various concentrations at room temperature for 30 min, and the mixture was then incubated with leukocytes at room temperature for 1 h, followed by gating for CD14 and CD11b positivity. The percentages of human neutrophils and monocytes were determined by FCM. Representative results (d) and statistical analysis (e–h) of three independent experiments are presented. Data are shown as the mean ± SD. Significant differences between groups were evaluated using two-tailed Student’s t tests

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