Valacyclovir combined with artesunate or rapamycin improves the outcome of herpes simplex virus encephalitis in mice compared to antiviral therapy alone

• The effect of combining artesunate or rapamycin with valacyclovir against herpes simplex virus encephalitis was evaluated.
• Both combined regimens improved survival rate in a murine model of herpes simplex virus encephalitis.
• The improved survival rate with combined therapies was not due to an effect on viral replication in the brain.
• Artesunate could act by decreasing the production of cytokines and chemokines in the brain.
• The effect of rapamycin could be related to its immunosuppressive potency on T lymphocytes.

Despite antiviral therapy, the mortality rate of herpes simplex virus encephalitis (HSE) remains high and many surviving patients harbor neurological sequelae. Although viral replication is responsible for substantial neurological damages, an exaggerated inflammatory response could also contribute to this process. Artesunate (ART) and rapamycin (RAPA) have shown some benefits in the treatment of herpes simplex virus infections. Herein, we evaluated the benefit of combining ART or RAPA with valacyclovir (VACV) in a murine model of HSE. Infected mice were treated with VACV (1 mg/mL in drinking water) from day 3 post-infection (p.i.) combined or not with daily intraperitoneal administration of ART (30 mg/kg) or RAPA (20 mg/kg) from days 4 to 13 p.i. Viral load, infectious titers, cytokine and chemokine levels were measured in brain homogenates on days 5, 7 and 9. The survival rates of mice treated with VACV and ART or RAPA were higher than with VACV alone (71.9% versus 43.2% for ART and 66.7% versus 43.2% for RAPA; both P ⩽ 0.05) but no significant difference was seen in the brain viral loads. Levels of IL-1β, IL-2 (both P ⩽ 0.05), IL-6, IFN-γ (both P ⩽ 0.01), CCL2 (P ⩽ 0.01), CCL3 and CCL4 (both P ⩽ 0.05) were reduced in mice treated with VACV combined with ART versus VACV alone. Levels of IL-6, IL-1β and IFN-γ slightly increased on day 7 in mice treated with VACV combined with RAPA compared to VACV alone and then decreased on day 9. Our results suggest that immunomodulatory compounds such as ART or RAPA could benefit antiviral therapy in HSE.