PPM1A and viral infectious disease: Given the finding that regulation of PPM1A expression plays a critical role in the host response to HIV-1 infections, the documented ability of HIV-1 to up-regulate PPM1A expression is the first report that viral infections can affect PPM1A expression levels, and also suggests that viruses, and certainly HIV-1, may have developed the ability to escape the cellular innate antiviral response in macrophages by up-regulating PPM1A.