Cover photograph (Copyright © 2004, American Society for Microbiology. All Rights Reserved.): The picture shows the crystal structure of 2F5 (blue), a broadly neutralizing anti-human immunodeficiency virus type 1 (HIV-1) antibody, in complex with its epitope (red) in the membrane-proximal heel of the HIV-1 spike ectodomain. The indole side chain (red spheres) of the final residue of the epitope (Trp₆₇₀) is coplanar with a hydrophobic patch (blue spheres) on the 2F5 heavy chain. This patch appears to interact with the viral membrane (schematically depicted in gray), an association that substantially enhances antibody affinity for HIV-1. (See related article in October 2004: vol. 78, no. 19, p. 10724.)