Inhibition of the canonical Wnt/β-catenin pathway interferes with macropinocytosis to suppress pseudorabies virus proliferation.

Pseudorabies virus (PRV) is one of the highly contagious pathogens causing significant economic losses to the swine industry worldwide. More importantly, PRV is becoming a potential "life-threatening zoonosis" since the human-originated PRV strain was first isolated in 2019. Previously we found that the canonical Wnt/β-catenin pathway facilitates PRV proliferation, while the underlying mechanism remains unknown. In this study, the antiviral activities of the Wnt inhibitors (Adavivint, CCT251545, FH535, and iCRT14) were identified. Applying these inhibitors significantly inhibited PRV proliferation in different cell lines. Among them, CCT251545 presented the strongest anti-PRV activity with IC50 values less than 200 nM. Our in vivo studies showed that treatment with CCT251545 remarkedly decreased the viral loads and protected mice challenged with PRV. Further study found that CCT251545 neither had a virucidal effect nor affected viral adsorption while mainly interfering with the entry process of the PRV life cycle. Using the FITC-dextran uptake assay, we found that CCT251545 inhibited macropinocytosis. The formation of membrane protrusions, which is important for macropinocytosis, was also inhibited by CCT251545. Consistent with this, knockout of β-catenin suppressed the PRV macropinocytosis and the formation of protrusions. On the contrary, LiCl treatment significantly stimulated the protrusion formation and the PRV entry. Together, these findings suggest that suppression of the Wnt/β-catenin pathway inhibits the macropinocytosis-dependent entry of PRV, thereby providing potential targets for developing antiviral agents against PRV.