Pseudorabies virus (PRV) causes Aujeszky’s disease characterized by neurological disorders and reproductive failure, resulting in significant economic losses to the global pig industry. Various PRV variants in China have compromised the efficacy of existing vaccines, necessitating for the development of alternative control measures. Chloroquine (CQ), originally developed for malaria treatment, exhibits broad-spectrum antiviral activity. Aim of the present study was to evaluate anti-PRV efficacy of CQ in vitro and in vivo. PRV-infected PK-15 cells were treated with CQ at various treatment timepoints (pre-, co-, post-infection), and the impact of CQ on viral adsorption, internalization and replication in vitro was assessed via Western blot, qPCR, and immunofluorescence analysis. To assess in vivo anti-PRV efficacy of CQ, 6-8 weeks old female SPF C57BL/6 mice (n=32) were divided into three groups: Mock (n=10; mice received neither PRV infection nor CQ); PRV (n=11; PRV-infected mice without CQ treatment), and PRV+CQ (n=11; PRV-infected mice received CQ treatment at 100mg/kg body weight, i.p.). The results demonstrated that CQ (50 and 100μM) significantly suppressed PRV infection in PK-15 cells. Notably, 100μM CQ exhibited antiviral activity whether it was added co-, post-, or pre-PRV infection. Mechanistically, viral adsorption assay revealed that co-incubation or pre-treatment with CQ impeded viral adsorption, while immunofluorescence results of the early endosome marker Rab5 showed that post-treatment with CQ blocked viral internalization. In vivo experiments showed that CQ failed to improve survival rate or extend mean survival duration in PRV-infected mice, although it provided limited symptomatic relief in PRV-infected mice. Collectively, these findings indicated that CQ effectively suppressed PRV infection in vitro, which provided a theoretical foundation for development of agents against PRV.

To Cite This Article: Dai Y, Liu Y, Jiang L, Niu J, Li H, Tang J, Fang R and Ye C 2025. Antiviral activity of chloroquine against pseudorabies virus in vitro and in vivo. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.216