Of the two types of Human immunodeficiency virus (HIV) which have been characterized, HIV-1 is more infective and is prevalent globally. The HIV virion is encapsulated by a viral envelope that contains complexes of surface proteins including glycoprotein 120 (gp120), which are important for the virus to attach and fuse to infect target cells. The glycoprotein CD4 (cluster of differentiation 4), found on the surface of T-cells, interacts with gp120 and cytokine receptors to mediate the entry of the virus into cells. This antibody, 654-30D, has been shown to neutralize HIV-1.