Tk-deleted Pseudorabies Virus Retains High Pathogenicity in Rats

INTRODUCTION: The pseudorabies virus (PRV) gene encoding thymidine kinase (tk) is an important virulence-associated factor. Attenuation of PRV in susceptible animals is a frequent result of tk deletion. The aim of the study was to assess the pathogenicity of tk-deleted PRV in rats. MATERIAL AND METHODS: Sprague Dawley rats were infected with the tk-deleted PRV strain SuHV-1 ΔTK:247via intranasal or intramuscular inoculation. PRV loads in ten tissues from dead and euthanised rats were determined using real-time PCR. RESULTS: Infection with SuHV-1 ΔTK:247 could cause death in rats. The 50% lethal dose (LD(50)) of SuHV-1 ΔTK:247 via intranasal inoculation was 10(3.16) TCID(50) in rats. Intramuscular inoculation required a higher dose of SuHV-1 ΔTK:247 (10(5.0) TCID(50)). A high SuHV-1 ΔTK:247 titre was observed in the trigeminal ganglia or spinal cord of dead rats. CONCLUSION: The results of this study show that rats are highly susceptible to PRV infection, and tk deletion did not completely diminish the pathogenicity of PRV in rats.