Study of interferon-β antiviral activity against Herpes simplex virus type 1 in neuron-enriched trigeminal ganglia cultures

Abstract

Herpes simplex virus type 1 (HSV-1) causes a lytic infection in epithelial cells before being captured and moved via retrograde axonal transport to the nuclei of the sensory neurons of the trigeminal ganglion or dorsal root, where it establishes a latent infection. HSV-1 infection induces an antiviral response through the production of Beta Interferon (IFN-β) in infected trigeminal ganglia. The aim of this work was to characterize the response induced by IFN-β in neuron-enriched trigeminal ganglia primary cultures infected with HSV-1. An antiviral effect of IFN-β in these cultures was observed, including reduced viral production and increased cell survival. In contrast, viral infection significantly decreased both double stranded RNA dependent protein kinase (Pkr) transcription and Jak-1 and Stat-1 phosphorylation, suggesting a possible HSV-1 immune evasion mechanism in trigeminal cells. Additionally, HSV-1 infection upregulated Suppressor of Cytokine Signaling-3 (Socs3) mRNA; upregulation of socs3 was inhibited in IFN-β treated cultures. HSV-1 infection increased the number of Socs3 positive cells and modified the intracellular distribution of Socs3 protein, in infected cells. This neuron-enriched trigeminal ganglia culture model could be used to elucidate the HSV-1 viral cycle in sensory neurons and to study cellular antiviral responses and possible viral evasion mechanisms that underlie the choice between viral replication and latency.

Immune Escape via a Transient Gene Expression Program Enables Productive Replication of a Latent Pathogen

“…Indeed, IFNs are detected in sensory ganglia from latently-infected mice (Cantin et al, 1995; Chen et al, 2000; Halford et al, 1996, 1997; Shimeld et al, 1997) and promote latency establishment in dissociated ganglia cultures (De Regge et al, 2010; Wigdahl et al, 1982). As neurons reportedly lack an intrinsic response to HSV-1, they rely on and respond to extrinsic IFN sources (Liu et al, 2001; Low-Calle et al, 2014; Rosato & Leib, 2014; Van Opdenbosch et al, 2011). CD8 + T-cells within latently-infected ganglia suppress reactivation in part by producing IFNγ (Liu et al, 2001).…”

Neurons Versus Herpes Simplex Virus: The Innate Immune Interactions that Contribute to a Host–Pathogen Standoff

“…Additionally, studies demonstrate upregulation of ISGs in neurons in response to IFN [4,107]. Similarly, there is in vitro evidence suggesting that exogenous IFN can restrict HSV replication in primary neurons under certain conditions such as high IFN concentrations [108,109], or upon axonal infection [11,110]. Contrasting studies, however, have found that IFN signaling in primary DRG and TG neurons results in little to no restriction of HSV replication in vitro [97,104].…”

“…Levine and colleagues have shown that HSV-induced autophagy is dependent on PKR and the eIF2α pathway [124,125]. Additionally, PKR is upregulated upon IFN signaling in HSV-infected neurons [108], and it is required to restrict HSV infection in TG cultures treated with IFN [126]. Given the muted intrinsic responses to viral infection in sensory neurons [97], these studies taken together suggest that paracrine IFN signaling may be important in upregulating PKR thereby increasing xenophagy in addition to transcriptional arrest.…”

“…It has additionally been demonstrated that neuronal autophagy can aid in mediating viral clearance, particularly in the context of HSV infection [104]. In addition to autophagy, there is strong evidence from our group and others that paracrine IFN signaling is important in mediating neuronal control of HSV infection in vitro and in vivo [11,108–109, R osato P, L eib D, U npublished D ata ]. While autophagy and IFN signaling are often studied independently of each other, there is evidence suggesting that neuronal IFN signaling may upregulate autophagy through PKR signaling, and thus these two antiviral strategies may synergize to control neuronal HSV infection [97,108,125].…”

Neuronal IFN signaling is dispensable for the establishment of HSV-1 latency

“…IFNβ is required for long-term neuronal homeostasis even in the absence of infection (Ejlerskov et al, 2015), and can promote viability of neuron cultures after virus infection (Low-Calle et al, 2013; Samuel and Diamond, 2005). We therefore hypothesized that IFN signaling prevents neuronal loss during the initial infection, thereby sustaining the population of neurons that harbors latent HSV-1 genome and reactivation events.…”