Pivotal Roles of cGAS-cGAMP Signaling in Antiviral Defense and Immune Adjuvant Effects

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Science  20 Sep 2013:
Vol. 341, Issue 6152, pp. 1390-1394
DOI: 10.1126/science.1244040

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Alarm Bells

The presence of DNA in the cytosol of mammalian cells is a danger signal, indicating, for example, that a DNA-containing virus has infected the cell. This signal triggers an innate immune response, which involves the expression of type I interferons, and is critical for antiviral immunity and responses to DNA vaccines. Cyclic GMP-AMP synthase (cGAS) was recently identified as a sensor of cytosolic DNA. Li et al. (p. 1390, published online 29 August) now use knockout mice to provide genetic evidence that, in multiple cell types, cGAS is the primary DNA sensor required for the type I interferon response in vivo.


Invasion of microbial DNA into the cytoplasm of animal cells triggers a cascade of host immune reactions that help clear the infection; however, self DNA in the cytoplasm can cause autoimmune diseases. Biochemical approaches led to the identification of cyclic guanosine monophosphate–adenosine monophosphate (cGAMP) synthase (cGAS) as a cytosolic DNA sensor that triggers innate immune responses. Here, we show that cells from cGAS-deficient (cGas−/−) mice, including fibroblasts, macrophages, and dendritic cells, failed to produce type I interferons and other cytokines in response to DNA transfection or DNA virus infection. cGas−/− mice were more susceptible to lethal infection with herpes simplex virus 1 (HSV1) than wild-type mice. We also show that cGAMP is an adjuvant that boosts antigen-specific T cell activation and antibody production in mice.

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