Inactivated Actinobacillus suis in Synergy with Interferon-α Protects Mice against Herpes Simplex Virus-2 Infection

A single intraperitoneal administration of heat-killed and lyophilized cells ofActinobacillus suis ATCC 15557 (AS preparation) into 5-week-old female BALB/c mice led to potent, but not statistically significant, nonspecific resistance to intravenous challenge with a lethal dose of herpes simplex virus, type 2 (HSV-2). A combination treatment with the intraperitoneal AS preparation and intravenous interferon (IFN)-α markedly elevated the survival rates of the mice. The production of endogenous IFN-γ was also enhanced by the combination treatment but the production of other endogenous cytokines such as tumor necrosis factor α and interleukin-12 was minimal. The focus of in vitro formation of HSV-2 was markedly inhibited by the peritoneal exudate cells induced by AS preparation in combination with IFN-α. The antiviral activity of peritoneal exudate cells induced by the combined agents was transferrable to syngeneic recipient mice. These results suggest the possibility that the AS preparation in combination with IFN-α may play an important role in controlling intracellular HSV-2 infection through the activation of immunocompetent cells and the production of endogenous IFN-γ in BALB/c mice.