Cnidium monnieri Polysaccharides Exhibit Inhibitory Effect on Airborne Transmission of Influenza A Virus

Influenza A virus (IAV) continues to present a threat to public health, highlighting the need for safe and multi-target antivirals. In this study, anti-influenza activity, airborne transmission blocking capacity, and immunomodulatory effects of <i>Cnidium monnieri</i> polysaccharides (CMP) were evaluated. Cytotoxicity in A549 cells was assessed by CCK-8 (CC₅₀ = 8.49 mg/mL), antiviral efficacy against A/California/04/2009 (CA04) by dose-response (EC₅₀ = 1.63 mg/mL), and the stage of action by time-of-addition assays (pre-, co-, post-treatment). A guinea pig model infected with CA04 was used for testing the effect of pre-exposure CMP on transmission, with readouts including nasal-wash titers, seroconversion, lung index, and tissue titers (EID₅₀). RT-qPCR was employed to quantify the mRNA expression levels of proinflammatory cytokines, including TNF-α, IL-1β, and IL-6, in lung tissue, while Western blot analysis was performed to assess the expression and phosphorylation status of key proteins involved in the NF-κB signaling pathway. CMP suppressed viral replication in vitro within non-cytotoxic ranges, and pre-treatment-rather than co- or post-treatment-significantly reduced titers and cytopathic effect, consistent with effects at pre-entry steps and/or host priming. In vivo, pre-exposure CMP lowered nasal shedding, reduced aerosol transmission (3/6 seroconverted vs. 6/6 controls), decreased lung indices, and diminished tissue viral loads; IAV was undetectable in trachea at 7 days post-infection in pre-exposed animals, and nasal-turbinate titers declined relative to infection controls. Moreover, during in vivo treatment in mice, CMP significantly suppressed the levels of inflammatory cytokines (TNF-α, IL-1β, and IL-6) in lung tissue. This effect was mechanistically associated with CMP-mediated regulation of the NF-κB signaling pathway, leading to attenuation of inflammatory responses. These data indicate that CMP combines a favorable in vitro safety and efficacy profile with inhibition of airborne spread in vivo, supporting further mechanistic, pharmacokinetic, and fractionation studies toward translational development.