Protective effects of Prunella vulgaris polysaccharides against herpes simplex virus type 1 infection through the STING-TBK1-IRF3 pathway

Abstract

Objective Enhancing innate immunity through interferons (IFNs) and IFN-stimulated genes (ISGs) offers a promising strategy for preventing herpes simplex virus type 1 (HSV-1) infection. Prunella vulgaris L., a medicinal herb, has demonstrated significant anti-HSV activity; in particular, its derived polysaccharide complex (PVE30) effectively inhibits viral replication. In this study, we investigate whether PVE30 exerts an anti-HSV-1 activity through activation of the innate immune response. Methods To determine the primary stage at which PVE30 exerts its effects during the HSV-1 life cycle, plaque reduction assays were conducted. Viral infection was further assessed by investigating the DNA copies, mRNA levels and protein expression of HSV-1 in infected cells using real-time polymerase chain reaction (RT-PCR) and Western blotting. The activation of the innate immune response was evaluated by detecting mRNA levels of ISGs, including MX dynamin-like GTPase 1 (Mx1), Mx2, 2'-5'-oligoadenylate synthetase 1 (OAS1), ISG15 and IFN regulatory factor 7 (IRF7) using RT-PCR, and levels of TANK-binding kinase 1 (TBK1) and IRF3 proteins using Western blotting. The translocation of phosphorylated IRF3 and stimulator of IFN genes (STING) was observed through fluorescence microscopy. Results PVE30 pre-treatment exerted protective effects against HSV-1 infection in human immortalized keratinocytes by enhancing the innate immune response. This was shown by increased transcriptional levels of IFN-β and antiviral ISGs, along with a significant reduction in HSV-1 DNA copies, mRNA expression and protein levels. Mechanistically, PVE30 promoted TBK1 phosphorylation, leading to nuclear translocation of IRF3 and subsequent IFN-β transcription; these effects were diminished by TBK1 inhibitor GSK8612. Additionally, STING was identified as a key mediator in PVE30-activated TBK1 signaling, as its inhibition induced by C-176 reduced PVE30's efficacy. Conclusion This study elucidated the molecular mechanisms underlying the protective effects of PVE30 against HSV-1 infection. PVE30 exerted its protective role by enhancing STING-TBK1-IRF3 pathway-mediated innate immune response. Please cite this article as: Zhang YB, Xu L, Yuan M, Liu MF, Li Y, Zhong XL, Lin ZX, Xian YF, Lu P, Xi ZC, Xu HX. Protective effects of Prunella vulgaris polysaccharides against herpes simplex virus type 1 infection through the STING-TBK1-IRF3 pathway. J Integr Med. 2026; 24(3):454-465.