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.