Nef (Negative Regulatory Factor) is a protein expressed by primate lentiviruses. These include human immunodeficiency viruses (HIV-1 and HIV-2) and simian immunodeficiency virus (SIV). Nef is one of many pathogen-expressed proteins, known as virulence factors, which function to manipulate the host's cellular machinery and thus allow infection, survival or replication of the pathogen. Nef stands for Negative Factor. Alternative Names: VAN protein , HIV-1 nef, C terminal core protein protein, HIV 1 nef, Negative factor protein, HIV-1 nef protein, ABIN1 protein, HIV-1 Nef protein, ABIN protein, 3'ORF protein, F protein protein, HIV1 nef, Nef protein, HIV 1 nef protein, p27 protein