Antibody Domain Exchange Is an Immunological Solution to Carbohydrate Cluster Recognition

Human antibody 2G12 neutralizes a broad range of human immunodeficiency virus type 1 (HIV-1) isolates by binding an unusually dense cluster of carbohydrate moieties on the "silent" face of the gp120 envelope glycoprotein. Crystal structures of Fab 2G12 and its complexes with the disaccharide Manalpha1-2Man and with the oligosaccharide Man9GlcNAc2 revealed that two Fabs assemble into an interlocked VH domain-swapped dimer. Further biochemical,...