Oral administration of Euglena gracilis Z and its carbohydrate storage substance provides survival protection against influenza virus infection in mice.

Euglena gracilis Z is a micro-algae that is used as a food or nutritional supplement. Paramylon, the carbohydrate storage substance of Euglena gracilis Z has β-1, 3-glucan structure. Euglena gracilis Z and paramylon are reported to affect the immune system. In this study, we investigated the protective effects of Euglena gracilis Z and paramylon against influenza virus infection in mice. Euglena gracilis Z and paramylon were administered to mice as a 2% dietary mixture ad libitum. At 2 weeks after initiation of dietary administration, mice were infected intranasally with influenza virus A/PR/8/34 (H1N1). Survival rate was monitored 10 days after infection. In addition, we performed virus titer and cytokine profiles in the lung. High survival rates were observed for Euglena gracilis Z and paramylon-treated groups compared to the control group. Significantly lower virus titer in the lung was observed in the Euglena gracilis Z and paramylon-treated groups compared to the control group from day 1 after infection. Higher amount of IL-1β, IL-6, IL-12 (p70), IFN-γ, and IL-10 was observed in the paramylon groups compared to the control group. Our data therefore reveals a novel immunoregulatory role of the Euglena gracilis Z and paramylon which provides protection against influenza virus infection.