Neuron-to-cell spread of pseudorabies virus in a compartmented neuronal culture system

Alphaherpesviruses are parasites of the peripheral nervous system in their natural hosts. After the initial infection of peripheral tissues such as mucosal cells, these neurotropic viruses will invade the peripheral nervous system that innervates the site of infection via long-distance axonal transport of the viral genome. In natural hosts, a latent and a nonproductive infection is usually established in the neuronal cell bodies. Upon reactivation, the newly replicated genome will be assembled into capsids and transported back to the site of entry, where a localized infection of the epithelial or mucosal cells will produce infectious virions that can infect naïve hosts. In this paper, we describe an in vitro method for studying neuron-to-cell spread of alphaherpesviruses using a compartmented culture system. Using pseudorabies virus as a model, we infected neuron cell bodies grown in Teflon chambers and observed spread of infection to nonneuronal cells plated in a different compartment. The cells are in contact with the neurons via axons that penetrate the Teflon barrier. We demonstrate that wild-type neuron-to-cell spread requires intact axons and the presence of gE, gI, and Us9 proteins, but does not require gD. We also provide ultrastructural evidence showing that capsids enclosed within vesicles can be found along the entire length of the axon during viral egress.