Inhibiting pyrimidine biosynthesis impairs Ebola virus replication through depletion of nucleoside pools and activation of innate immune responses

• Published in: Antiviral research 2018-10, Vol.158, p.288-302
• Main Authors: Luthra, Priya, Naidoo, Jacinth, Pietzsch, Colette A., De, Sampriti, Khadka, Sudip, Anantpadma, Manu, Williams, Caroline G., Edwards, Megan R., Davey, Robert A., Bukreyev, Alexander, Ready, Joseph M., Basler, Christopher F.
• Format: Article
• Language: English
• Subjects: A549 Cells; Antiviral Agents - pharmacology; Biphenyl Compounds - chemistry; Biphenyl Compounds - pharmacology; Carbazoles - chemistry; Carbazoles - pharmacology; DNA Damage; Ebolavirus - drug effects; HEK293 Cells; Hemorrhagic Fever, Ebola - drug therapy; Hemorrhagic Fever, Ebola - virology; Host-Pathogen Interactions - drug effects; Humans; Immune Evasion; Immunity, Innate - drug effects; Immunity, Innate - genetics; Interferon Regulatory Factor-1 - metabolism; Interferon Regulatory Factor-1 - pharmacology; Interferon-alpha - metabolism; Interferon-beta - metabolism; Nucleosides - pharmacology; Oxidoreductases Acting on CH-CH Group Donors - antagonists & inhibitors; Pyrimidines - antagonists & inhibitors; Pyrimidines - biosynthesis; RNA Viruses - drug effects; Signal Transduction - drug effects; Vesiculovirus - drug effects; Virus Replication - drug effects; Zika Virus - drug effects
• ISSN: 0166-3542; 1872-9096
• DOI: 10.1016/j.antiviral.2018.08.012

Specific host pathways that may be targeted therapeutically to inhibit the replication of Ebola virus (EBOV) and other emerging viruses remain incompletely defined. A screen of 200,000 compounds for inhibition of an EBOV minigenome (MG) assay that measures the function of the viral polymerase complex identified as hits several compounds with an amino-tetrahydrocarbazole scaffold. This scaffold was structurally similar to GSK983, a compound previously described as having broad-spectrum antiviral activity due to its impairing de novo pyrimidine biosynthesis through inhibition of dihydroorotate dehydrogenase (DHODH). We generated compound SW835, the racemic version of GSK983 and demonstrated that SW835 and brequinar, another DHODH inhibitor, potently inhibit the MG assay and the replication of EBOV, vesicular stomatitis virus (VSV) and Zika (ZIKV) in vitro. Nucleoside and deoxynucleoside supplementation studies demonstrated that depletion of pyrimidine pools contributes to antiviral activity of these compounds. As reported for other DHODH inhibitors, SW835 and brequinar also induced expression of interferon stimulated genes (ISGs). ISG induction was demonstrated to occur without production of IFNα/β and independently of the IFNα receptor and was not blocked by EBOV-encoded suppressors of IFN signaling pathways. Furthermore, we demonstrated that transcription factor IRF1 is required for this ISG induction, and that IRF1 induction requires the DNA damage response kinase ATM. Therefore, de novo pyrimidine biosynthesis is critical for the replication of EBOV and other RNA viruses and inhibition of this pathway activates an ATM and IRF1-dependent innate immune response that subverts EBOV immune evasion functions. •An amino-tetrahydrocarbazole compound SW835 inhibits Ebola virus, vesicular stomatitis virus and Zika virus replication.•SW835 is the racemic form of GSK983.•SW835 depletes pyrimidines and induces interferon stimulated genes (ISGs).•ISG induction occurs through activation of kinase ATM and transcription factor IRF-1.•SW835 induction of ISGs subverts Ebola virus innate immune evasion mechanisms.