Phellinus linteus Mycelia Extracts Show Potent Antiviral and Immunomodulatory Effects in H1N1 Influenza Virus-Infected Mice

<i>Phellinus linteus</i>, a medicinal mushroom with an ancient history in traditional medicine, serves as a valuable raw material for functional foods. While previous studies have shown promising antiviral effects, the present work is the most comprehensive investigation of <i>P. linteus</i> mycelial extracts and active compounds thereof against the H1N1 influenza virus infection in in vitro and animal models. Antiviral activity was evaluated using three treatment approaches (preventive, co-treatment, and therapeutic) in MDCK cells infected with H1N1 virus. In vivo studies employed male BALB/c mice exposed to aerosolized H1N1 virus (1.6 × 10⁶ PFU/mL). In the animal experiment, mice received either <i>P. linteus</i> mycelia powder (PL) at 1000 mg/kg/day or PLw/PLe at 350 mg/kg/day for 7 days before and after infection. Ethanol extracts (PLe) demonstrated superior antiviral properties compared to water extracts (PLw) in cell survival and viral inhibition tests. Animal studies revealed that both PL and PLe significantly improved recovery after H1N1 infection, with survival rates of 60% and 40%, respectively, versus 25% in controls. The treatments effectively restored depleted immune cell populations, indicating broad immunomodulatory effects. These findings highlight the potential of <i>P. linteus</i> as a functional food ingredient with promising therapeutic applications against viral infections through its action on both innate and adaptive immune responses.