Lipopolysaccharide heterogeneity in Brucella strains isolated from marine mammals

Smooth lipopolysaccharides (S-LPSs) from Brucella strains isolated from seals, dolphins, porpoises, an otter and a minke whale were characterized by ELISA using monoclonal antibodies (mAbs) directed against seven previously defined O-polysaccharide (O-PS) epitopes and by Western blot after SDS-PAGE. All strains studied were A-dominant as shown by specific polyclonal sera and this was also confirmed by the mAbs. However, binding patterns in ELISA of mAbs to the specific common (C) epitopes were rather heterogeneous, and for some strains, such as those isolated from striped dolphins, binding of these mAbs was much reduced or negative as had previously been shown for Brucella suis biovar 2 strains. Western blot after SDS-PAGE showed the typical A-dominant strain banding pattern for all marine mammal Brucella isolates, but the average S-LPS size was shorter in many of these compared to reference Brucella abortus strain 544. Thus, S-LPSs of the marine mammal isolates show heterogeneity with regard to their O-PS C epitope content and their average size.