Higher resistance of porcine trigeminal ganglion neurons towards pseudorabies virus-induced cell death compared with other porcine cell types in vitro

Trigeminal ganglion (TG) neurons are important target cells for many alphaherpesviruses, constituting major sites for latency/reactivation events. Here, the in vitro kinetics of productive infection of the swine alphaherpesvirus pseudorabies virus (PRV) and resulting cell death in primary porcine TG neurons were determined, and these were compared with similar kinetics in many other porcine cell types. Confocal microscopy showed that all TG neurons expressed late genes such as viral glycoproteins, and that these glycoproteins were processed through the Golgi and reached the cell surface as in other cell types, albeit with a delay of +/- 2-6 h. However, TG neurons were much more resistant towards PRV-induced cell death compared with all other porcine cell types tested (non-neuronal TG cells, superior cervical ganglion neurons, epithelial kidney cells, arterial endothelial cells, dermal fibroblasts and cells derived from a porcine swine kidney cell line). About half of the TG neurons survived up to 96 h post-inoculation (end of experiment), whereas all other cell types almost completely succumbed within 2 days post-inoculation. In addition, infection with a strongly pro-apoptotic PRV strain that misses the anti-apoptotic US3 protein did not lead to substantial apoptosis in TG neurons, even at 72 h post-inoculation. Thus, primary porcine TG neurons can be infected with PRV in vitro, and are remarkably more resistant to PRV-induced cell death compared with other porcine cell types, suggesting a cell type-specific resistance to alphaherpesvirus-induced cell death that may have important implications for different aspects of the virus life cycle, including latency/reactivation events.