Poly-gamma-Glutamic Acid from Bacillus Horneckiae Strain APA of Shallow Marine Vent Origin with Antiviral and Immunomodulatory Effects against Herpes Simplex Virus Type-2

The shallow vents of the Eolian Islands (Italy) are sources of almost unexplored microorganisms able to produce biomolecules with promising pharmaceutical applications. This work describes the characterization of an extracellular poly-γ-glutamic acid (γ-PGA) from the new Bacillus horneckiae strain APA, and its antiviral and immunomodulatory effects against Herpes simplex virus type 2 (HSV-2). The γ-PGA-APA was able to hinder HSV-2 replication in human peripheral blood mononuclear cells (PBMC), involving the cell-mediated immunity. The exopolymer induced the expression of high levels of Th1–type cytokines in PBMC, while it had no effects on Th2-type cytokines production. This is the first report on a γ-PGA produced by a marine thermotolerant B. horneckiae strain with antiviral and immunomodulator activities. As stimulator of Th1 cell-mediated immunity, this biopolymer could be potentially used in the treatment of immunocompromised hosts as well as in patients affected by herpes virus infections.