Characterization of the Replication Incompetent IE180 Null Pseudorabies Virus

Abstract

Pseudorabies virus (PRV) is an economically significant porcine alphaherpesvirus that traverses the nervous system via synaptically connected neurons, causing ataxia, pruritus, and seizures before host death. The master transcriptional regulator gene IE180 was removed from the PRV genome, thus producing a replication-incompetent strain. Epithelial cells and neurons infected with IE180 null PRV survived significantly longer than those infected with wild-type PRV. Survival times exceeded a month post-infection and were dependent on the multiplicity of infection. In neurons, viral entry at the axons dramatically increased survival time relative to viral entry at the cell body. IE180 null PRV could only spread in epithelial cells when trans- complemented with the IE180 gene. IE180 null PRV was transported from the axon terminal to the cell body and could not spread to neighboring neurons. The NF-κB immune response pathway was activated only in cells that were heavily infected by IE180 null PRV. Epithelial cells, neurons, and fibroblasts infected with IE180 null PRV permitted entry of a secondary virus and therefore do not exhibit super-infection exclusion. IE180 trans-complementation restored super-infection exclusion. Fluorescently-labeled IE180 null PRV strains can serve as efficient long range and long-term neuronal tracers controlled by IE180 trans-complementation.