Neutralizing capacity of camelid antibodies. (A) The ability of llama-derived (heavy-chain-only) antibodies (listed on the right) to neutralize HIV-1, SIVcpz, and SIVgor strains (bottom) is shown. Numbers indicate IC50s (in micrograms per milliliter) from TZM-bl cells, averaged from three different experiments, with a heat map indicating the relative neutralization potency. The highest antibody concentration used was 10 µg/ml. (B to D) Conservation of antibody binding epitopes shown in panel A. Alignments of HIV-1, SIVcpz, and SIVgor Env protein sequences are depicted, with residues identical to the HXB2 reference shown in gray. Logo plots denote the conservation of individual amino acids within each epitope, with the height of each letter indicating the proportion of sequences that contain the residue at that site. The letter “X” indicates residues within the 2H10 epitope that do not impact neutralization. JM4 contact residues are indicated on top of the alignment. Sequences are numbered according to the HXB2 reference.