Differential Stimulatory Activities of Smooth and Rough Brucella abortus Lipopolysaccharide in Murine Macrophages

Brucella abortus lipopolysaccharide (LPS) was isolated and purified from rough (RB51) and smooth (S2308) strains of Brucella. The LPS preparations were used to treat murine (RAW 264.7) macrophages in order to study their differential effects. Treated macrophages were tested by lysozyme release test (LRT), nitroblue tetrazolium test (NBT) and nitric oxide (NO) assay, respectively. Rough Brucella LPS induced significantly higher levels of lysozyme release, oxidative stress, and nitric oxide in murine macrophages than smooth Brucella LPS or combined LPS (rough + smooth LPS). These responses were dose-dependent. Macrophages treated with rough LPS were more Brucellacidal than those treated with smooth LPS. The minimal stimulation of murine macrophages by Brucella smooth LPS may provide basis for less active immune responses against smooth strains.