FIG 4.

TLR2 activation by triacylated synthetic peptides (P3C) enhanced S. aureus invasion. (A) Rate of invasion of HEK-0 cells by S. aureus with IL-8 stimulation. A total of 10⁶ HEK-0 cells were stimulated with 10 ng IL-8 for 45 min before infection with USA300 or its Δlpl mutant at an MOI of 30 and the performance of the bacterial invasion assay. (B) Rate of invasion of HEK-TLR2 cells by S. aureus with P3C stimulation. Before infection with USA300 or its Δlpl mutant, 10⁶ HEK-TLR2 cells were stimulated with 100 ng P3C. (C) Rate of invasion of HEK-0 and HEK-TLR2 cells by the S. aureus Δlgt mutant. A total of 10⁶ HEK-0 or HEK-TLR2 cells were infected with USA300Δlgt at an MOI of 30 with or without supplementation with 100 ng of P3C. The host cells were infected for 1.5 h, followed by lysostaphin treatment for another 1.5 h to kill adherent S. aureus cells. All experiments were performed at least in triplicate in three independent replications. Error bars indicate standard deviations. Statistical significance was calculated by using Student's t test (ns, no statistical difference; *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001).