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Astrocyte gp130-expression is critical for the control of Toxoplasma encephalitis

Toxoplasma (T.) gondii infects astrocytes, neurons and microglia cells in the CNS and, after acute encephalitis, persists within neurons. Robust astrocyte activation is a hallmark of Toxoplasma encephalitis (TE); however, the in vivo function of astrocytes is largely unknown. To study their role in TE, we generated C57BL/6 GFAP-Cre gp130fl/fl mice, which lack gp130, the signal transducing receptor for IL-6 family cytokines, in their astrocytes. In TE of wildtype mice, the gp130 ligands IL-6, IL-11, IL-27, LIF, oncostatin M, ciliary neurotrophic factor, B cell stimulating factor, and cardiotrophin-1 were upregulated. In addition, GFAP+ astrocytes of gp130fl/fl control mice were activated, increased in number, and efficiently restricted inflammatory lesions and parasites, thereby, contributing to survival from TE. In contrast, T. gondii-infected GFAP-Cre gp130fl/fl mice lost GFAP+ astrocytes in inflammatory lesions resulting in an inefficient containment of inflammatory lesions, impaired parasite control and, ultimately, a lethal necrotizing TE. Production of IFN-gamma and IGTP, which mediate parasite control in astrocytes, were even increased in GFAP-Cre gp130fl/fl mice indicating that instead of the direct anti-parasitic effect the immunoregulatory function of GFAP-Cre gp130fl/fl astrocytes was disturbed. Correspondingly, in vitro infected GFAP-Cre gp130fl/fl astrocytes inhibited growth of T. gondii efficiently after stimulation with IFN-gamma, whereas neighbouring non-infected and TNF-stimulated GFAP-Cre gp130fl/fl astrocytes became apoptotic. Collectively, these are the first experiments demonstrating a crucial function of astrocytes in CNS infection.

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Correspondence to Dirk Schlüter.

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Keywords

  • Microglia Cell
  • Inflammatory Lesion
  • Astrocyte Activation
  • Wildtype Mouse
  • Family Cytokine