The PE/PPE multigene family codes for virulence factors and is a possible source of mycobacterial antigenic variation: Perhaps more?

► We present progress made in the field of PE/PPE proteins from Mycobacterium tuberculosis. ► They potentially provide virulence and antigenic variation. ► Many of them are secretory or cell surface localized. ► Several are thought to be vaccine and serodiagnostic marker candidates. ► Their genes are scattered but mostly exist in operons or together with Esx gene clusters.