The mechanism of Isatis Root Polysaccharides inhibiting the proliferation of PRRSV.

Porcine Reproductive and Respiratory Syndrome (PRRS) is a severe infectious disease caused by the Porcine Reproductive and Respiratory Syndrome Virus (PRRSV). The prevalence of PRRSV worldwide significantly impacts the development of the swine industry, exerting a considerable adverse effect. PRRSV infection typically induces a substantial increase in pro-inflammatory factors within the host organism, such as IL-1β, IL-6, and TNF-α, resulting in an "inflammatory factor storm" that leads to lung lesions and severe viremia in pigs. Currently, there is no effective treatment available for this disease. Recent research indicates that Chinese herbal medicine demonstrates notable antiviral effects. In this study, we found that Isatis Root Polysaccharides (IRPS) can significantly inhibit PRRSV proliferation in vitro. To investigate the underlying cause of this phenomenon, modified porcine alveolar macrophage 3D4/21/CD163 cells were used as the target cells to study the inhibitory effect of IRPS on PRRSV-BJ4. This study demonstrates that IRPS exhibits direct virucidal activity against PRRSV and significantly inhibits the invasion of the PRRSV-BJ4 strain. IFA, ELISA, or Western blot techniques were employed to evaluate and confirm PRRSV proliferation, cytokine secretion, or TLR4 transcript and protein levels. The studies have revealed that IRPS affects cytokine secretion by influencing TLR4 and its downstream inflammatory signaling pathways, thereby preventing the development of the inflammatory factor storm and the subsequent infection of PRRSV. In this experiment, we observed a significant inhibitory effect of IRPS on the proliferation of PRRSV in vitro. This finding establishes a theoretical foundation for further research on the antiviral properties of traditional Chinese medicine.