Activation of host pattern recognition receptors by viruses

Viral recognition by the host innate immune system has become an exciting and growing area of research focus in recent years. It is now apparent that multiple pattern recognition receptor (PRR) families, including Toll-like receptors (TLRs), RIG-I-like receptors (RLRs) and NOD-like receptors (NLRs), contribute significantly to viral detection by sensing viral proteins and nucleic acids, leading to induction of cytokines and type I interferons (IFNs). Of particular current interest is the sensing of viral DNA within infected cells, since the PRRs responsible for this are only partially defined. Recently RNA polymerase III (Pol III) was shown to transcribe some viral DNAs into RNA for detection by RIG-I, leading to IFN induction. Another novel mechanism of viral DNA recognition unveiled, leading to proinflammatory cytokine production, involves the PYHIN family member AIM2.