FIG 4.

Lipid A structural change in a chronic-infection B. pseudomallei strain series decreases LPS recognition. (A) In comparison to lipid A from 1026b (blue scan), lipid A from MSHR1043 (orange scan) has fewer penta-acylated (5 + 2P and 5 + 1P) structures and hydroxylation (–OH) appears minimal. (B) MSHR1655 (black scan) shows more arabinose-substituted (Ara) tetra-acylated lipid A (1,494 m/z) than strain MSHR1043 collected 3 years earlier. (C) MSHR3042 (red scan) had nearly no detectable levels of penta-acylated lipid A compared to strain MSHR1655 collected 5 years earlier. (D) TNF-α release from RAW264.7 monolayers 24 h after treatment with 10 ng/ml of the indicated endotoxin-normalized LPS. (E) Cytotoxicity measurements following LPS transfection into Salmonella LPS-primed A549 human lung epithelial cells. (F) Cytotoxicity measurements following LPS transfection into Salmonella LPS-primed RAW264.7 murine macrophages. White bars represent no-Lipofectamine controls, and gray bars represent exactly the same treatment but with Lipofectamine. Data are the mean and standard deviation of the results of one representative experiment carried out in triplicate. Significance was determined by one-way ANOVA to 1026b. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, not significant.