Investigating cell-dependent immune responses to herpes simplex virus 1 (HSV-1) infection

Yang, Zhousiyu (2026) Investigating cell-dependent immune responses to herpes simplex virus 1 (HSV-1) infection. PhD thesis, University of Glasgow.

Abstract

Herpes simplex virus type 1 (HSV-1) establishes lytic infection in epithelial tissues and relies on a lifelong latent reservoir in sensory neurons, causing recurrent disease and significant clinical burden worldwide. Previous studies in our lab have used fibroblast cells as a model system for HSV-1 research. First, we investigated the role of PML by employing an ectopic expression system to visualize its colocalization to the vDNA. Our confocal microscopy data confirm that PML is rapidly recruited to incoming vDNA, a process significantly enhanced during infection with an ICP0-null mutant virus (dl1403 HSV-1), which is consistent with PML’s established role in intrinsic immunity. However, we acknowledge that this experimental system, which relies on doxycycline (DOX)-induced expression in the presence of endogenous PML or interferon-responsive PML, complicates the precise delineation between a baseline intrinsic defence and a subsequent innate immune response. We also investigated the role of histone chaperone ASF1a during HSV-1 infection. Here, we identified ASF1a as a potential restrictive factor to HSV-1 infection. Confocal microscopy data revealed that ASF1a colocalizes with incoming vDNA. Genetic ablation of ASF1a in knockout (KO) cells resulted in a significant promotion of viral replication. These data suggested ASF1a plays a direct role in restricting HSV-1 replication, likely through mediating viral chromatin assembly or transcription.
However, the tropism target during natural infection is skin epithelial cells, principally keratinocyte cells. The extent to which different keratinocyte subtypes deploy intrinsic and innate immune mechanisms to HSV-1 infection remains poorly defined. HSV-1 must counteract these host-cell defences to initiate productive infection. To investigate which host-cell responses were induced in response to HSV-1 infection, we compared four keratinocyte cell lines (HaCaT, TIGK, NOK and N-TERT cells). Baseline transcriptomic profiling of keratinocyte lines demonstrates marked heterogeneity in immune-related gene expression, including variation in interferon-stimulated genes (ISGs, including MX1, IFIT1, IFIT2, IFIT3 and IFIT5) and cytokine-responsive pathways. Upon HSV-1 infection or cytokine stimulation, these intrinsic differences translate into divergent antiviral and inflammatory transcriptional programmes, indicating that keratinocyte subtype and tissue origin strongly shapes antiviral competence. Our findings highlight a striking divergence in the ability of these cells to restrict dl1403 HSV-1 infection. Specifically, NOK cells, which we identified as having a notably attenuated ISGs signature, proved to be significantly more permissive to dl1403 HSV-1 infection relative to HaCaT, TIGK and N-TERT cells. In contrast, cell lines such as TIGK and N-TERT mounted a more robust antiviral transcriptional response upon dl1403 HSV-1 infection, characterized by the strong upregulation of pathways related to innate immunity and inflammation, which correlated with a potent restriction of viral proliferation. Our plaque assay data revealed NOK cells exhibited significantly higher permissiveness to dl1403 HSV-1 (approximately 10-fold increase in plaque number relative to other keratinocyte cells). Crucially, these data provide clear functional evidence for the broad antagonistic role of ICP0. The potent restriction of the dl1403 mutant by both basal defenses and pre-treatment with key cytokines demonstrates that multiple innate immune pathways are key targets suppressed by ICP0 during a wild-type infection. Pre-treatment with IFNβ uniformly established a near-impenetrable antiviral state in all cell lines, confirming it as a primary target for ICP0 evasion. Furthermore, the more modest, yet significant, restriction induced by pro-inflammatory cytokines IL-6 and IL-1β indicated that ICP0's suppressive functions extend beyond the canonical interferon response. Together, these findings provide mechanistic insight into cell-type-specific intrinsic and innate immunity in human fibroblast and keratinocytes and identify suitable cellular platforms for the development of stratified, physiologically relevant 3D skin culture models of HSV-1 infection.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QR Microbiology > QR355 Virology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity > Centre for Virus Research
• Supervisor's Name: Boutell, Dr. Chris and Fletcher, Dr. Adam
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-86204
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 31 Aug 2026 08:31
• Last Modified: 31 Aug 2026 08:35
• Thesis DOI: 10.5525/gla.thesis.86204
• URI: https://theses.gla.ac.uk/id/eprint/86204