The importance of innate restriction factors to infection is highlighted by the fact that lentiviruses contain genes encoding for accessory proteins specifically to antagonize restriction - Vif that inhibits APOBEC3-mediated cytidine deamination of viral transcripts, and in the case of HIV-1 Vpu that overcomes tetherin-mediated inhibition of nascent particle release from the plasma membrane of virus-producing cells (Fig. 1). The gene discussed is BST2; the disease is infection.