Antiviral and immunomodulatory effects of a novel bacterial exopolysaccharide of shallow-marine vent origin

Aims: To evaluate a novel exopolysaccharide (EPS1) from the recently described haloalkaliphilic, thermophilic Bacillus licheniformis strain T14, isolated from a shallow hydrothermal vent of Panarea Island (Italy), for its antiviral and immunomodulatory effects against herpes simplex virus type 2 (HSV-2). Methods and Results: EPS1-T14 hindered the HSV-2 replication in human peripheral blood mononuclear cells (PBMC) but not in WISH cells, indicating that cell-mediated immunity was involved in the antiviral activity. High levels of Th1-type cytokines were detected in supernatants of EPS1-treated PBMC, while Th2-type cytokines were not induced. Conclusions: The novel EPS1-T14 is a water-soluble, noncytotoxic exopolymer able to stimulate the immune response and thus contribute to the antiviral immune defence, acting as immunomodulator. Significance and Impact of the Study: The exopolysaccharide produced by B. licheniformis strain T14, stimulator of Th1 cell-mediated immunity, could be used as therapy in immunocompromised host.