CD4 and HIV infectious disease: Budhiraja et al. previously showed that CycT1 and activated P-TEFb are present at low levels in human resting memory CD4 T cells, and that following HIV infections of activated CD4 T cells (which had high levels of CycT1 and P-TEFb), the subsequent establishment of viral latency was associated with downregulation of CycT1 and P-TEFb as cells returned to resting states [25, 47].