CGAS and viral infectious disease: In vertebrates, during various viral infections, virus-associated PAMPs are recognized by pathogen recognition receptors (PRRs) such as Toll-like receptors (TLRs), retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), NOD-like receptors (12), interferon-γ-inducible protein 16 (IFI16), AIM2 (absent in melanoma 2) and cyclic GMP-AMP synthase (cGAS) that subsequently lead to the activation of inflammatory cytokines and chemokines as well as interferon (IFN) and ISG production through a cascade reaction (106).