Antiviral and immunomodulatory effects of Chaihu Guizhi decoction in an acute depression‐like mouse model infected with influenza A virus

Background Chaihu Guizhi Decoction (CGD) is a classical prescription in traditional Chinese medicine (TCM) that has been shown to be effective against infection and depression. However, the mechanisms of action of CGD in treating patients with depression who are also infected with a virus remain unknown. This study investigated the pharmacological mechanisms of CGD in treating depression‐like mice infected with influenza A virus (IAV). Methods The acute depression‐like mouse model infected with IAV was established. The effects of CGD on alleviating depression‐like symptoms were observed using the sucrose preference test and monoamine neurotransmitter expression. Additionally, the effectiveness of CGD against infection was assessed by examining the relative expression of the M gene and pathological changes. To evaluate the anti‐inflammatory effects of CGD, the levels of cytokines were measured, and the Th17/Treg ratio was analyzed to evaluate the immunomodulatory effects of CGD. Results The study results show that CGD enhanced the rates of sucrose preference and raised the contents of neurotransmitters dopamine (DA) and norepinephrine (NE). CGD treatment led to a reduction in lung index and the relative expression of the M gene, along with improvements in pathological changes caused by IAV. Furthermore, the levels of cytokines were decreased after treatment with CGD, and the imbalance in the ratio of Th17/Treg was corrected via a reduction in the number of Th17 cells after treatment. Conclusions CGD has a therapeutic effect in mice with depression‐like symptoms infected with IAV, increasing the levels of DA and NE, downregulating M gene expression, calming the cytokine storm, and preserving the homeostasis of Th17/Treg cells.