BALB/c mice (6 weeks old, n = 10 per group) were orally administered with γ-PGA in 100-µl saline once a day for 1, 3, or 5 days at a dose of 50 mg/kg body weight. Four hours after the last γ-PGA administration, total blood was collected from the abdominal vein of mice for cytokine analyses using ELISA. To test the antiviral efficacy of γ-PGA, BALB/c mice (6 weeks old, n = 7 per group) were orally administered with γ-PGA (50 mg/kg body weight) in 100 µl saline once a day for 5 days. This was followed by peroral inoculation with MNV (1 × 107 PFU/100 µL saline) 12 h after the last γ-PGA administration at day 5. γ-PGA was given once daily for another two days. Two days after inoculation, the distal ileum and MLNs were retrieved from mice for analyses of intracellular viral RNA and infectious virus titers. Homogenized tissues were subjected to centrifugation at 3,000 × g for 10 min to recover supernatants, which were then passed through a 0.20-µm pore-size membrane filter. The filtrates were used for quantification of virus titers using a plaque-forming assay.