Evaluation of Preventive Effects of Brazilian Green Propolis on Equine Herpes Virus 9-Induced Acute Encephalitis

In this study, we aimed to evaluate the preventive effects of Brazilian green propolis on equine herpes virus (EHV)-induced encephalitis in a hamster model. We first investigated the antiviral activity of Brazilian green propolis against EHV-9, and then, examined the effects of propolis on the kinetics and production of cytokines. Sixtyfive male, Syrian hamsters were divided into two treatment groups and control group. The 1st group is a control. The second group was infected intranasally with 50 μl of EHV-9 [3 × 104 plaque-forming units (pfu)] without propolis treatment. The third group received propolis at 500 mg/kg of ethanol extract of Brazilian green propolis by a gavage for 7 days, followed by intranasal inoculation with 50 μl of EHV-9 (3 × 104 pfu). Pre-treatment with propolis was not effective in preventing EHV-9-induced encephalitis via intranasal route. This speculation is supported by similar clinical signs and similar immunohistochemistry based on viral antigen distribution in the brain of infected hamsters in groups 2 and 3 from 3rd day post inoculation (dpi). There were significant increases in cerebral mRNA levels of IL-2, IL-10, and IFN-𝛾 after propolis administration in the propolis-treated group before and after EHV-9 challenge compared with the control non-treated group. In conclusion, Brazilian green propolis showed no obvious effect on the prevention of acute EHV-9-induced acute encephalitis in a hamster model, despite its immune-enhancing activity.