Role of the UL41 Protein of Pseudorabies Virus in Host Shutoff, Pathogenesis and Induction of TNF-α Expression

The vhs (virion host shutoff) is highly conserved in alphaherpesvirus, including pseudorabies virus (PRV). In an attempt to explore the function of vhs of PRV, we constructed and characterized a mutant virus (Delta 41). In the absence of vhs activity, Delta 41 mutant is highly attenuated in mice model and the lethality is correlated with the virus dissemination in neural tissues. As with herpes simplex virus type 1 (HSV-1), the prototype virus or alphaherpesvirus, the pronounced decrease in cellular protein synthesis triggered by wild type PRV was largely restored in cells infected with Delta 41 virus. Furthermore, tumor necrosis factor-alpha (TNF-alpha) protein expression was elevated significantly in spleen of mice infected with vhs mutant virus. Since TNF-alpha has been indicated to be an important cytokine in the innate immune response against various infections, our results implicate vhs may contribute to the protection against PRV lethality via the action of TNF-alpha. Overall, we confirm the shutoff function of vhs protein in PRV, and demonstrate the role that vhs protein plays in virulence, and regulation of cytokine production.