Antiviral effects and mechanism of Qi pi pill against influenza viruses.

Background: Qi pi pill (QPP), which contains Renshen, Baizhu, Fuling, Gancao, Chenpi, Shanyao, Lianzi, Shanzha, Liushenqu, Maiya, and Zexie, was recommended for preventing and treating COVID-19 in Shandong Province (China). However, the mechanism by which QPP treats infectious diseases remains unclear. This study aims to investigate the therapeutic effect of QPP in vitro and on acute influenza infection in mice, exploring its mechanism of action against influenza A virus (IAV).

Methods: The in vitro activity of QPP was assessed using dose-response curve analysis and titer reduction assay, and its antiviral mechanism was identified in vitro by real-time polymerase chain reaction (PCR), time-of-addition, and enzymatic assays. The antiviral efficacy of QPP was further evaluated in vivo using BALB/c mice infected with IAV. At the same time, each single Chinese herbal medicine in QPP was evaluated to preliminarily identify those with antiviral effects.

Results: In vitro results showed that QPP exhibited a higher potency antiviral effect against both influenza A and B viruses, inhibiting viral RNA replication and release by targeting RNA-dependent RNA polymerase and neuraminidase. Additionally, QPP significantly decreased the expression of inflammatory cytokines in A549 cells. In vivo study revealed that QPP significantly reduced the lung index and viral load in lung tissue of mice infected with IAV. Renshen, Gancao, Zexie, and Lianzi were the Chinese herbal medicines from QPP that showed anti-IAV activity.

Conclusion: The antiviral activity of QPP targets IAV replication and release, cytokine modulation in host cells, and provides protection in mice with acute influenza infection.