Regional astrocyte IFN signaling restricts pathogenesis during neurotropic viral infection
Brian P. Daniels, Harsha Jujjavarapu, Douglas M. Durrant, Jessica L. Williams, Richard R. Green, James P. White, Helen M. Lazear, Michael Gale Jr., Michael S. Diamond, Robyn S. Klein
Brian P. Daniels, Harsha Jujjavarapu, Douglas M. Durrant, Jessica L. Williams, Richard R. Green, James P. White, Helen M. Lazear, Michael Gale Jr., Michael S. Diamond, Robyn S. Klein
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Research Article Infectious disease

Regional astrocyte IFN signaling restricts pathogenesis during neurotropic viral infection

Abstract

Type I IFNs promote cellular responses to viruses, and IFN receptor (IFNAR) signaling regulates the responses of endothelial cells of the blood-brain barrier (BBB) during neurotropic viral infection. However, the role of astrocytes in innate immune responses of the BBB during viral infection of the CNS remains to be fully elucidated. Here, we have demonstrated that type I IFNAR signaling in astrocytes regulates BBB permeability and protects the cerebellum from infection and immunopathology. Mice with astrocyte-specific loss of IFNAR signaling showed decreased survival after West Nile virus infection. Accelerated mortality was not due to expanded viral tropism or increased replication. Rather, viral entry increased specifically in the hindbrain of IFNAR-deficient mice, suggesting that IFNAR signaling critically regulates BBB permeability in this brain region. Pattern recognition receptors and IFN-stimulated genes had higher basal and IFN-induced expression in human and mouse cerebellar astrocytes than did cerebral cortical astrocytes, suggesting that IFNAR signaling has brain region–specific roles in CNS immune responses. Taken together, our data identify cerebellar astrocytes as key responders to viral infection and highlight the existence of distinct innate immune programs in astrocytes from evolutionarily disparate regions of the CNS.

Authors

Brian P. Daniels, Harsha Jujjavarapu, Douglas M. Durrant, Jessica L. Williams, Richard R. Green, James P. White, Helen M. Lazear, Michael Gale Jr., Michael S. Diamond, Robyn S. Klein

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Figure 7

Type I IFN responses in astrocytes in vitro.

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Type I IFN responses in astrocytes in vitro. (A and B) In vitro BBB Tran...
(A and B) In vitro BBB Transwell cultures were generated with either cerebral cortical or cerebellar astrocytes. (A) TEER recordings in cultures treated with saline vehicle or 10 U/ml recombinant IFN-β. (B) Cultures were generated with cerebral cortical or cerebellar astrocytes (x axis) derived from either WT (black bars) or Ifnar–/– mice (orange bars) and treated overnight with either saline vehicle or 10 U/ml recombinant IFN-β. Following pretreatment, WNV (0.01 MOI) was added to the top chamber of cultures and allowed to migrate for 6 hours. Data represent combined WNV genome copy numbers detected in the astrocyte monolayer and bottom chamber supernatant. (C–H) Primary human cerebral cortical or cerebellar astrocytes were treated with 10 U/ml recombinant IFN-β and analyzed for transcript expression of the indicated genes 4 and 24 hours after treatment. Ct values for all genes were normalized to Ct values of the housekeeping gene GAPDH. (I) Primary human cerebral cortical or cerebellar astrocytes were treated for 4 hours with PBS or 10U/ml recombinant IFN-β and subjected to RNA-seq. Heatmap and histogram of global gene expression across regions and treatment groups were generated from all statistically significant genes. Data in A–H represent the mean ± SEM of 5 to 6 replicates from 2 to 3 independent experiments and were analyzed by 2-way ANOVA. Data in I were derived from 3 independent samples per group and were analyzed as described in the Methods. *P < 0.05 , **P < 0.01, and ***P < 0.001. Cbl, cerebellum; Ctx, cortex.