Differential Sensitivity of HSV-1 and PRV to IFN-λ Reveals a Neuron-Specific Antiviral Role for RSAD2

Alpha herpesviruses (α-HV) initially infect mucosal epithelial cells and subsequently establish lifelong latency in the peripheral nervous system (PNS). Herpes simplex virus-1 (HSV-1), a human pathogen persisting in the majority of the adult population, shares neuroinvasive properties with Pseudorabies virus (PRV), a swine α-HV, commonly used as a model α-HV. Utilizing primary peripheral neuronal cultures, we previously showed that IFN-λ pre-treatment significantly reduced PRV yield. In this paper, we further characterized the early and late neuronal responses to IFN-λ by RNA-seq, and the antiviral potential of this response against HSV-1. Notably, HSV-1 exhibited neuron-specific resistance to IFN-λ mediated antiviral responses both in murine primary neurons and human neuronal cells. An ICP34.5-deficient HSV-1 (Δ34.5) mutant showed IFN-λ sensitivity in neurons, while replicating normally in untreated neurons showing that ICP34.5 is responsible for the neuron specific IFN-λ resistance of HSV-1. Our results further demonstrate that RSAD2 is strongly induced by IFN-λ in neurons, localizing to ER-associated membranes, and effectively restricting α-HV protein synthesis in the absence of ICP34.5. siRNA-mediated RSAD2 knockdown in IFN-λ-primed primary neurons largely restored replication of Δ34.5 HSV-1, highlighting the role of this IFN-λ induced host factor in neuronal infections. Together, neuronal IFN-λ-induced RSAD2 and HSV-1 ICP34.5 define a neuron-specific antagonistic mechanism that collectively determines the replication efficiency of HSV-1 in the PNS.