A systematic analysis of host factors reveals a med23-interferon-? regulatory axis against herpes simplex virus type 1 replication

Herpes simplex virus type 1 (HSV-1) infects the vast majority of the global population. Whilst most people experience the relatively mild symptoms of cold sores, some individuals suffer more serious diseases like viral meningitis and encephalitis. HSV-1 is also becoming more common as a cause of genital herpes, traditionally associated with HSV-2 infection. Co-infection with HSV-2 is a major contributor to HIV transmission, so a better understanding of HSV-1/HSV-2 disease has wide implications for global healthcare. After initial infection, all herpesviruses have the ability to remain dormant, and can awaken to cause a symptomatic infection at any stage. Whether the virus remains dormant or active is the result of a finely tuned balance between our immune system and evasion techniques developed by the virus. In this study we have found a new method by which the replication of the virus is counteracted. The cellular protein Med23 was found to actively induce an innate anti-viral immune response in the form of the Type III interferons (IFN-lambda), by binding IRF7, a key regulator of interferons, and modulating its activity. Interferon lambda is well known to be important in the control of Hepatitis C infection, and a genetic mutation correlating to an increase in interferon lambda levels is strongly linked to clearance of infection. Here we find the same association between this genetic mutation and the clinical severity of recurrent cases of HSV-1 infection (coldsores). These data identify a Med23-interferon lambda regulatory axis of innate immunity, show that interferon lambda plays a significant role in HSV-1 infection, and contribute to the expanding evidence for interferon lambda in disease control.