Metabolomic Analysis of Lytic KSHV Infection: Induced Host Nucleotide Metabolism Is Required for Infectious Virus...

Kaposi's Sarcoma Herpesvirus (KSHV) is the etiological agent of Kaposi's Sarcoma (KS), which induces metabolic stress in infected host cells. KSHV reprograms host metabolic pathways for efficient viral replication and infectious virion production. Here, we report a time-course global metabolomics study conducted in iSLK.BAC16 cells to compare latent and lytic KSHV infection. Our data show that amino acid, central carbon, and nucleotide metabolic pathways are highly dysregulated upon reactivation. During lytic KSHV infection, pathway enrichment analysis identifies purine and pyrimidine metabolism as the top two most significantly impacted and dysregulated pathways. Further experiments have shown that nucleotide metabolism is required during lytic KSHV infection to produce maximal infectious virus. Treatment with the FDA-approved drug, methotrexate (MTX), a folate antagonist that decreases nucleotide metabolism by reducing tetrahydrofolate cofactors, significantly reduced KSHV copy number and late lytic viral gene expression upon reactivation compared to controls. Additionally, titers of cell-free supernatants from MTX-treated lytic samples showed a significant reduction in infectious virion production. Furthermore, MTX significantly decreased the viral titer of murine herpesvirus 68 (MHV-68), a model virus to study gammaherpesvirus. Overall, our study demonstrates that metabolic inhibition during lytic gammaherpesvirus infection decreases productive infection and hence serves as a potential therapeutic antiviral target.