S. aureus injury of human alveolar epithelial cells is reduced by antagonism of Hla. Live (green)/dead (red) imaging of human A549 cells was captured by fluorescence microscopy 4 h after infection. A549 cells were left uninfected (A) or co-cultured with S. aureus Newman in media treated with PBS (1:1,000; B), NRS (1:1,000; C), anti-Hla rabbit sera (α-Hla; 1:1,000; D), or purified HlaH35L (10 μg/ml; E). Infections were also performed with the Newman isogenic hla insertion mutant, hla∷erm, transformed with vector (F) or phla (G). Bars, 20 μm. (H) Assessment of LDH release by A549 cells that were lysed during S. aureus infection. A significant reduction in LDH release was observed compared with PBS-treated cultures upon addition of anti-Hla sera or HlaH35L, whereas an increase in LDH release was observed upon co-culture with S. aureus hla∷erm phla. Error bars indicate mean ± SD.
