Structural features and immunological perception of the cell surface glycans of Lactobacillus plantarum: a novel rhamnose-rich polysaccharide and teichoic acids

Abstract

The capsular material from Lactobacillus plantarum IMB19, an isolate from fermented vegetables, has been analyzed and our results demonstrate that most of the coat of this bacterium consists of glycerol- and ribitol-type teichoic acids, further decorated with other substituents (a-glucose and alanine), and of a capsular polysaccharide (CPS) with a linear nonasaccharide repeating unit, rich in rhamnose, interconnected to the next via a phosphodiester bridge. Stimulation of immune cells with the total capsular material resulted in the enhancement of immunostimulatory (IFN gamma, TNF-alpha, IL-6 and IL-12) or immuno-regulatory (IL-10) cytokines in an in vitro splenocyte culture system. The capsular polysaccharide, and not the teichoic acids mixture, was responsible for the IFN gamma production. Indeed, a significant increase of IFN gamma along with other inflammatory cytokines, and a dose response in IFN. expression with an EC50 of 3.16 mu M was found for CPS, disclosing that this polysaccharide is a potent immunostimulatory molecule.