Fei-Yan-Qing-Hua decoction attenuates influenza virus infection by enhancing host antiviral response through microbiota-derived acetate.

Background: Fei-Yan-Qing-Hua decoction (FYQHD) is derived from the well-known Ma Xing Shi Gan decoction, which was documented in Zhang Zhong Jing's "Treatise on Exogenous Febrile Disease" during the Han Dynasty. Although FYQHD has been used in the treatment of pneumonia and has demonstrated clinical efficacy for decades, the underlying mechanism by which FYQHD protects against influenza virus infection through modulation of gut flora remains unclear. Here, we examined the regulatory impacts of FYQHD on an influenza virus-infected mouse model and explored the mechanisms involved. Methods: An infectious mouse model was created by intranasal instillation of influenza A virus (IAV). The effectiveness of FYQHD was assessed through various measures, including weight loss, lung wet/dry ratio, oxidative stress levels, viral load in lung tissues, and intestinal injuries. Changes in gut microbiota and SCFA production were also examined. Results: The results showed that FYQHD significantly reduced viral load, increased the production of type I interferon (IFN-I), and restored the integrity of the intestinal barrier following IAV challenge. Additionally, FYQHD significantly corrected the dysbiosis of gut microbiota induced by influenza virus infection, enhancing the abundance of SCFA-producing bacteria and acetate production. However, the depletion of gut microbiota significantly attenuated the protective effects of FYQHD against influenza virus infection. Conclusion: FYQHD attenuates influenza virus-induced lung and intestinal injuries by boosting the host antiviral response through increasing the abundance of