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Hsp70 and a Novel Axis of Type 1 Interferon-Dependent Antiviral Immunity in the Measles Virus-Infected Brain

ABSTRACT: The major inducible 70 kDa heat shock protein (hsp70) is host protective in a mouse model of measles virus (MeV) brain infection. Transgenic constitutive expression of hsp70 in neurons, the primary target of MeV infection, abrogates neurovirulence in neonatal H-2d congenic C57BL/6 mice. A significant level of protection is retained after depletion of T lymphocytes, implicating innate immune mechanisms. Focus of the present work was to elucidate the basis for hsp70-dependent innate immunity using this model. Transcriptome analysis of brains from transgenic (TG) and non-transgenic (NT) mice 5 days after infection identified type 1 interferon (IFN) signaling and macrophage activation/antigen presentation as the main differences linked to survival. The pivotal role for type 1 IFN in hsp70-mediated protection was demonstrated in mice with a genetically disrupted type 1 IFN receptor (IFNAR-/-), where IFNAR-/- eliminated the difference in survival between TG and NT mice. Brain macrophages, not neurons, are the predominant source of type 1 IFN in the virus-infected brain, and in vitro studies provided a mechanistic basis by which MeV-infected neurons can induce IFN-β in uninfected microglia in an hsp70-dependent manner. MeV infection induced extracellular release of hsp70 from mouse neuronal cells that constitutively express hsp70, and extracellular hsp70 induced IFN-β transcription in mouse microglial cells through Toll-like receptors 2 and 4. Collectively, results support a novel axis of type 1 IFN-dependent antiviral immunity in the virus-infected brain that is driven by hsp70.

ORGANISM(S): Mus musculus

PROVIDER: GSE42264 | GEO | 2012/11/14

SECONDARY ACCESSION(S): PRJNA179489

REPOSITORIES: GEO

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Project description:The major inducible 70 kDa heat shock protein (hsp70) is host protective in a mouse model of measles virus (MeV) brain infection. Transgenic constitutive expression of hsp70 in neurons, the primary target of MeV infection, abrogates neurovirulence in neonatal H-2d congenic C57BL/6 mice. A significant level of protection is retained after depletion of T lymphocytes, implicating innate immune mechanisms. Focus of the present work was to elucidate the basis for hsp70-dependent innate immunity using this model. Transcriptome analysis of brains from transgenic (TG) and non-transgenic (NT) mice 5 days after infection identified type 1 interferon (IFN) signaling and macrophage activation/antigen presentation as the main differences linked to survival. The pivotal role for type 1 IFN in hsp70-mediated protection was demonstrated in mice with a genetically disrupted type 1 IFN receptor (IFNAR-/-), where IFNAR-/- eliminated the difference in survival between TG and NT mice. Brain macrophages, not neurons, are the predominant source of type 1 IFN in the virus-infected brain, and in vitro studies provided a mechanistic basis by which MeV-infected neurons can induce IFN-β in uninfected microglia in an hsp70-dependent manner. MeV infection induced extracellular release of hsp70 from mouse neuronal cells that constitutively express hsp70, and extracellular hsp70 induced IFN-β transcription in mouse microglial cells through Toll-like receptors 2 and 4. Collectively, results support a novel axis of type 1 IFN-dependent antiviral immunity in the virus-infected brain that is driven by hsp70. Hsp70 expression in mice enhances gene expression related to antiviral immune response against MeV neurovirulence. We performed microarrays on whole brain tissues in mice to obtain an unbiased picture of how hsp70 alters host innate responses to viral infection. Hsp70-overexpressing transgenic (TG) and non-transgenic (NT) mice were infected with MeV intracranially, and total brain mRNA harvested at 5 and 10 days post infection (d.p.i.) was analyzed, sampling the hemisphere opposite the side of viral inoculation. Analysis includes 6 groups: infected TG at 5 d.p.i. (n=4), infected TG at 10 d.p.i. (n=5), infected NT at 5 d.p.i. (n=4), infected NT at 10 d.p.i. (n=5), uninfected TG at 5 d.p.i. (n=4), and uninfected NT at 5 d.p.i. (n=4).

Project description:Purpose: Virus infections of the CNS cause important diseases of humans and animals. As in other tissues, innate antiviral responses mediated by type I interferons (IFN) are crucially important in controlling CNS virus infections. Semliki Forest virus (SFV) infection of the mouse provides a well-characterised and tractable model to study the pathogenesis of virus encephalitis. The maturity of neuronal populations is an established critical factor determining the outcome of CNS virus infection. Using primary cultures of mouse cortical neurons, we investigated the relationships between neuronal maturation, type I IFN responses and the outcome of SFV infection. Methods: mRNA profiles of immature and mature of primary mouse cortical neurons that were mock or iFNβ treated and mock or SFV infected were generated by deep sequencing, in triplicate, using Illumina HiSeq 2500. All 100-base-pair single-end reads were mapped to the reference mouse genome (GRCm38/mm10) using Salmon ultrafast aligner. Mapped reads were quantitated to the gene level estimates and genecount data was imported using the tximport package and differential expression analysis of RNA sequencing data was carried out using the edgeR and limma-voom packages in Bioconductor. Results: Using an optimized data analysis workflow, we mapped the 100 bp single end reads to the mouse genome (build mm10) and identified 14,933 genes in the immature and mature primary neurons with different treatments. Transcriptomic profiling revealed 3,666 genes differentially expressed between resting immature and mature cells. Multidimensional scaling plots revealed key differences between immature and mature neurons with different treatments. Immature neurons pre-treated with type I IFN and mock-infected or infected without prior IFN, clustered close to the basal (resting) control samples,indicating limited changes in gene expression under either condition. This was also the case for mature neurons treated with IFNβ. Whereas, immature neurons pre-treated with IFN and then infected, as well as mature neurons pre-treated or not with IFN and then infected underwent more dynamic changes in gene expression Conclusions: Complete transcriptome analysis demonstrated that resting immature neurons lacked the transcriptional competence to mount antiviral responses. They had no detectable transcription of the genes Ddx58 and Ifih1 which encode the key RNA virus cytoplasmic sensors RIG-I and MDA5 and no, or very low, expression of genes encoding key regulators of downstream and associated signalling pathways. Upon infection, immature neurons failed to mount an antiviral response as evidenced by their failure to produce chemokines, IFNs and other cytokines. Treatment of immature neurons with exogenous IFNb prior to infection resulted in antiviral responses and lower levels of virus replication and infectious virus production. In contrast, resting mature neurons expressed Ddx58 and Ifih1 and upon infection generated a robust antiviral response. This was augmented by pre-treatment with IFNb. Infection of mature neurons derived from IFNAR-/- mice did not make an antiviral response and replicated virus to high levels.

Project description:To investigate the early host response triggered by three different strains of Trypanosoma cruzi at a local infection site, changes in host gene expression were monitored in a murine intradermal infection model using Affymetrix oligonucleotide arrays. Robust induction of IFN-stimulated genes (ISGs) was observed in excised skin 24 hours post-infection where the level of ISG induction was parasite strain-dependent with the least virulent strain triggering a muted IFN response. Infection of mice immunodepleted of IFNÎ³-producing cells or infection of IFNÎ³-deficient mice had minimal impact on the IFN response generated in T. cruzi infected mice. In contrast, infection of mice lacking the type I IFN receptor demonstrated that type I IFNs are largely responsible for the IFN response generated at the site of infection. These data highlight type I IFNs as important components of the innate immune response to T. cruzi the site of inoculation and their role in shaping the early transcriptional response to this pathogen. We used microarrays to detail the local host transcriptional response to intradermal T. cruzi infection in WT mice and mice depleted of NK cells, or deficient in IFN-gamma or type I IFN responses. Additionally we compared the local host-transcriptional response generated to infection with 3 different strains of Trypanosoma cruzi (Y, Brazil, and G). Experiment Overall Design: Mice were infected by intradermal injection of 10^6 T. cruzi trypomastigotes in 100uL of saline split between 2 adjacent sites on the shaved side flank. Control mice were injected with an equal volume of saline. 24 hours post-injection approximately 75mm^2 of skin immediately surrounding the injection site was excised and RNA was isolated from the tissue. Balb/c mice were used for most experiments and IFN-gamma KO mice were on the Balb/c background. WT 129 mice were also used as IFNAR-/- mice were on the 129 background. In total 33 arrays were performed. 7 WT (Balb/c) control, 3 Y strain infected, 3 Brazil strain infected, 3 G strain infected, 2 IFN-gamma KO control, 2 IFN-gamma KO infected, 1 NK cell depleted control, 1 NK cell depleted infected, 3 WT (129) control, 3 WT (129) infected, 3 IFNAR KO control, 3 IFNAR KO infected

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Hsp70 and a Novel Axis of Type 1 Interferon-Dependent Antiviral Immunity in the Measles Virus-Infected Brain

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