Lysimachia christinae polysaccharides dampen pseudorabies viral infection by downregulating adsorption and exert antioxidant activity.

Pseudorabies virus (PRV) is an alpha herpes virus that causes pseudorabies. Pigs are the only natural hosts of the virus. This disease has caused considerable economic losses to the global pig industry. Since 2011, the effectiveness of vaccines has decreased greatly because of the emergence of various PRV varieties. Additionally, some people are infected with PRV. Therefore, the development of new anti-PRV agents is highly important. Lysimachia christinae is a traditional Chinese herbal medicine that has favorable effects on urine, detoxification, and swelling. In this study, the in vitro and in vivo anti-PRV activities of Lysimachia christinae polysaccharide (LCP) were investigated. Our results revealed that 200 μg/mL LCP significantly attenuated the infection of PK-15 B6 cells by PRV XJ5 and that 100 mg/kg LCP significantly reduced PRV XJ5 infection in mice. Mechanistic studies revealed that the main target of the anti-PRV effect of LCP was in the virus adsorption stage. In addition, our study revealed that LCP can reduce reactive oxygen species (ROS) and malondialdehyde (MDA) levels in PRV XJ5-infected PK-15 B6 cells and increase the activity of superoxide dismutase (SOD). These results showed that LCP can reduce the oxidative stress caused by PRV infection. In summary, LCP may be used as an antiviral drug to fight new PRV mutant strains.