Deletion of pseudorabies virus US2 gene enhances viral titers in a porcine cerebral cortex primary culture system
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Pseudorabies virus (PRV) is a neurotropic virus with the ability to infect peripheral sensory ganglia. The transport of PRV from the peripheral to the central nervous system can cause lethal encephalitis in young piglets. However, the pathogenicity of PRV in the cerebral cortex remains poorly understood. In the present study, we developed a porcine cerebral cortex primary culture system (PCCS) using cerebral cortex tissue dissected from a 3-day-old piglet to investigate the pathogenicity of wild-type (WT) and US2 deleted (ΔUS2) PRV in the CNS in vitro. Immunofluorescence assays revealed cell bodies and neurites as the cellular locations infected by PRV. Growth kinetic analysis showed a persistent increase in WT and ΔUS2 viral titers in PCCS from 4 to 24 h post infection (hpi), thus indicating that US2 deletion did not disrupt viral growth. However, the mean plaque size was significantly higher in ΔUS2 PRV than in WT PRV in infected Vero cells. The viral titers and DNA levels of ΔUS2 PRV were significantly higher at 8 hpi than at 4 hpi, whereas those of WT showed no significant difference between the two time points in PCCS. Morphological investigation revealed induction of massive amounts of bouton-like swellings (varicosities) along the axon shaft in both WT and ΔUS2 PRV-infected neurons in the PCCS. Our data suggest that PRV US2 gene deletion enhances viral titers in PCCS but does not affect the varicosities induced by the viral infection.
KeywordsPseudorabies virus Genotype II Varicosities US2 Neuronal pathogenicity
We thank Dr. Shu-Jie Wang for generously providing mouse anti-PRV gE antiserum.
Chuang Lyu, Shuwen Wang, and Mingxia Sun performed the experiments. Yandong Tang, Jinmei Peng, and Zhijun Tian supplied the WT and ΔUS2 PRV strains. Chuang Lyu and Xuehui Cai designed the experiments and wrote manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
Animal experiments were approved by the Animal Ethics Committee of the Harbin Veterinary Research Institute (HVRI) and were performed in accordance with animal use ethical guidelines.