Size, charge and structural heterogeneity of Brucella abortus lipopolysaccharides demonstrated by two‐dimensional gel electrophoresis

Phenol extracted, alkali‐treated lipopolysaccharide (aLPS) from vaccine strain (S19) Brucella abortus was demonstrated by two‐dimensional gel electrophoresis to consist of at least ten silver staining, polydisperse analogues having different pIs. When tested on nitrocellulose immunoblots, all ten were antigenically reactive with bovine anti‐B. abortus polyclonal sera, but only six reacted with anti‐B. abortus O‐antigen murine monoclonal antibody. Analogues focusing at different pIs were concluded to arise from differences in either core or O‐antigen side chain structure or because of covalently bound protein. While not qualitatively different, aLPS from pathogenic B. abortus strain 2308 had lesser amounts of analogues 1, 2, 5, 6, and 8 than did aLPS from strain 19 (vaccine). The 2‐D gel electrophoresis method was demonstrated to be of value in the analysis of aLPS from B. abortus and may be useful in the study of lipopolysaccharides from other sources.