METABOLIC AND EPIGENETIC REGULATION OF HERPESVIRUS INFECTION IN ORAL EPITHELIAL CELLS

Abstract

Kaposi’s sarcoma-associated herpesvirus (KSHV) is an oncogenic double-stranded DNA virus. There are no vaccines or antiviral therapies for KSHV. KSHV establishes a lifelong infection via a biphasic life cycle comprising a latent and a lytic phase. Although KSHV establishes long-term latency in most infected cell types, oral epithelial cells support sustained lytic infection, contributing to viral shedding and transmission. Lytic infection and viral replication place high energetic and biosynthetic demands on host cells, promoting extensive reprogramming of host metabolic and regulatory pathways. However, the host metabolic adaptations that support KSHV lytic infection in oral epithelial cells remain incompletely defined. In this dissertation, we investigated the metabolic and epigenetic mechanisms that facilitate KSHV lytic infection in telomerase-immortalized gingival keratinocyte (TIGK) cells by performing untargeted metabolomic profiling using liquid chromatography–high-resolution mass spectrometry (LC-MS). We characterized early metabolic alterations following KSHV infection. At 4 hours post-infection, KSHV induced rapid reprogramming of the cellular metabolism by dysregulating metabolites involved in the urea cycle, polyamine biosynthesis, dimethylarginine metabolism, and de novo pyrimidine synthesis. These early metabolic changes suggest that KSHV rapidly hijacks host metabolic pathways to support viral gene expression and replication. Furthermore, we assess the metabolic changes at 24 post-infections to complement our previous study. Combined untargeted metabolomic and lipidomic analyses were performed at 24 14 hours post-infection. At this point, KSHV infection led to pathway-specific alterations in lipid and amino acid metabolism, including increased triglyceride accumulation and depletion of several amino acids. Triglyceride enrichment is known to induce lipid droplet biogenesis, which may serve as an energy reservoir to support the elevated energetic and biosynthetic demands of viral replication. Concurrent depletion of amino acids likely reflects increased utilization to support viral protein synthesis and central carbon metabolism, indicating sustained host metabolic reprogramming during early lytic infection. In addition to metabolic remodeling, we examined the role of the host epigenetic regulator lysine-specific demethylase 1 (LSD1) during KSHV infection. KSHV infection was associated with reduced LSD1 protein levels in TIGK cells, and both LSD1 knockdown and pharmacological inhibition enhanced KSHV lytic gene expression and viral protein accumulation. Mechanistically, LSD1 inhibition increased the enrichment of the activating histone modification H3K4 dimethylation at viral lytic gene promoters. These results show that host metabolic reprogramming events and epigenetic regulation support KSHV lytic infection in oral epithelial cells. Our work increases understanding of the interaction between KSHV and its host and highlights host metabolic and chromatin-modifying pathways as crucial regulators that support lytic infection. Identifying the cellular metabolic pathways that KSHV manipulates can broaden the knowledge of how these pathways contribute to sustaining lytic infection, which can be targeted in future therapies to prevent viral spread.