2′-O Methylation of the Viral mRNA Cap by West Nile Virus Evades Ifit1-Dependent and -Independent Mechanisms of Host Restriction In Vivo

PLoS Pathogens

Brian P. Daniels¹  Herbert W. Virgin²  Maria D. Gainey³  Wayne M. Yokoyama³  Michael S. Diamond³  Kristy J. Szretter³  Hyelim Cho⁴  Robyn S. Klein⁴  Ganes C. Sen⁵  Michael Gale Jr.⁵ 

[1] Department of Anatomy & Neurobiology, Washington University School of Medicine, St. Louis, Missouri, United Stated of America;Department of Immunology, University of Washington School of Medicine, Seattle, Washington, United States of America;Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United Stated of America;Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United Stated of America;Department of Pathology & Immunology, Washington University School of Medicine, St. Louis, Missouri, United Stated of America

关键词: West Nile virus;    Viral replication;    Neuronal tuning;    Central nervous system;    T cells;    Methylation;    Cytotoxic T cells;    Neurons;   

DOI  :  10.1371/journal.ppat.1002698

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Prior studies have shown that 2′-O methyltransferase activity of flaviviruses, coronaviruses, and poxviruses promotes viral evasion of Ifit1, an interferon-stimulated innate immune effector protein. Viruses lacking 2′-O methyltransferase activity exhibited attenuation in primary macrophages that was rescued in cells lacking Ifit1 gene expression. Here, we examined the role of Ifit1 in restricting pathogenesis in vivo of wild type WNV (WNV-WT) and a mutant in the NS5 gene (WNV-E218A) lacking 2′-O methylation of the 5′ viral RNA cap. While deletion of Ifit1 had marginal effects on WNV-WT pathogenesis, WNV-E218A showed increased replication in peripheral tissues of Ifit1−/− mice after subcutaneous infection, yet this failed to correlate with enhanced infection in the brain or lethality. In comparison, WNV-E218A was virulent after intracranial infection as judged by increased infection in different regions of the central nervous system (CNS) and a greater than 16,000-fold decrease in LD50 values in Ifit1−/− compared to wild type mice. Ex vivo infection experiments revealed cell-type specific differences in the ability of an Ifit1 deficiency to complement the replication defect of WNV-E218A. In particular, WNV-E218A infection was impaired in both wild type and Ifit1−/− brain microvascular endothelial cells, which are believed to participate in blood-brain barrier (BBB) regulation of virus entry into the CNS. A deficiency of Ifit1 also was associated with increased neuronal death in vivo, which was both cell-intrinsic and mediated by immunopathogenic CD8+ T cells. Our results suggest that virulent strains of WNV have largely evaded the antiviral effects of Ifit1, and viral mutants lacking 2′-O methylation are controlled in vivo by Ifit1-dependent and -independent mechanisms in different cell types.

【 授权许可】

CC BY