Antiviral and immunoregulatory effect of a novel exopolysaccharide from a marine thermotolerant Bacillus licheniformis

EPS-1 is a novel extracellular polysaccharide produced by a strain of thermotolerant Bacillus licheniformis, isolated from a shallow marine hot spring of Vulcano Island (Italy). In this paper, antiviral and immunomodulatory effects of EPS-1 were evaluated. It was found that EPS-1 treatment impaired HSV-2 replication in human peripheral blood mononuclear cells (PBMC) but not in WISH cells. Since several cytokines modulate the immune response to viruses, Th1- and Th2-type cytokines were assayed in supernatants of PBMC in different experimental conditions. EPS-1 induced IL-12, IFN-γ, IFN-α, TNF-α and IL-18, but not IL-4. Thus, the antiviral effect of EPS-1 on PBMC seems to be related to the pattern of cytokines induced.