CD4 and infection: Type I interferon (IFN) plays a dichotomous role in chronic viral infections such as Human Immunodeficiency Virus-1 (HIV), contributing to the control of viral replication during the earliest stages of infection, yet fueling disease progression by activating target cells for infection, decreasing antiviral gene expression, enabling infection with increased reservoir size, and accelerating CD4 T-cell loss [1–8].