Characterization Of Flavivirus Disease Resistance In Mice And Comparative Analysis Of Infections With Pathogenic And Non-Pathogenic Strains Of West Nile Virus In Pluripotent Stem Cell-Derived Central Nervous System Cells

Flaviviruses are arboviruses that can cause neurological disease in mammals. Mice demonstrate variable susceptibility to flavivirus disease due to inheritance of a single allele, Flvr. Infected mice that possess Flvr exhibit no symptoms and produce less infectious virus compared to mice with the susceptible allele Flvs. The product of the Flvr allele, full length 2′-5′ oligoadenylate synthetase 1b (Oas1b), is part of the host innate immune response and a Type 1 interferon (IFN) stimulated gene (ISG). The Flvr allele encodes a truncated protein due to a premature stop codon. Cells encode multiple OAS proteins that exert their antiviral activity by synthesizing short 2′-5′-linked oligoadenylates that activate RNase L. Oas1b lacks synthetase activity and function as a dominant negative for the active synthetase Oas1a. However, RNase L was shown to have anti-flavivirus activity. A line of Oas1b+/+/RNase L-/- mice was generated to analyze the contribution of RNase L to the Oas1b-mediated flavivirus disease resistance phenotype in vivo. The results indicated that RNase L is a component of the antiviral response to flaviviruses in mice but is not needed for the full expression of the Oas1b flavivirus resistance phenotype. West Nile Virus (WNV) is a neurotropic virus with strains exhibiting varying degrees of pathogenesis in infected humans. The factors involved in this differential pathogenicity are not well understood. Using human induced pluripotent stem cells (hiPSCs) differentiated into four types of CNS cells, infections with pathogenic WNV NY99 or non-pathogenic WNV MAD78 were characterized using traditional virology techniques and also by comparative transcriptome analysis of infected neural progenitor cells (NPCs) by next generation sequencing. NY99 replicated efficiently in all four CNS cell types and induced cell cycle arrest in NPCs. Transcriptome analysis of astrocytes infected by NY99 revealed robust activation of inflammatory response in these cells. MAD78 infected NPCs as efficiently as NY99 but infected astrocytes less efficiently than WNV NY99. Infection of astrocytes by both viruses induced secretion of pro-inflammatory cytokines. Transcriptome analysis of infected NPCs revealed that infections with both viruses induced the expression of viral defense genes, ER stress genes, and inhibited neuronal development