Characterization of the DH475 cooperating antibody and its interaction with the HIV-1 spike

HIV evolves very quickly, so approaches to design an effective vaccine that elicits protective antibodies have thus far been unsuccessful. Current HIV vaccine design efforts seek to elicit broadly neutralizing antibodies, unique antibodies that target many viral variants, by first eliciting their precursors through prime-boost regimens. This requires an understanding of the co-evolution between viruses and antibodies. Towards this goal, we are analyzing a cooperating antibody, called DH475, which exerted pressure on HIV to evolve in such a way that it became sensitive to the DH270 broadly neutralizing antibody lineage. This study aims to elucidate how DH475 binds to the HIV viral spike and identify how DH475 facilitated the development of DH270 broadly neutralizing antibodies. We obtained a 2.90Å crystal structure of DH475 in complex with Man9 glycan, and used site-directed mutagenesis coupled with biolayer interferometry (BLI) and protein-protein docking to characterize how DH475 interacts with Env. These investigations revealed a glycan-dependent epitope, and docking analyses identified an unorthodox binding mode in which the DH475 framework and constant regions participate in binding. While further confirmation of DH475's binding mode is required, our findings indicate an overlapping epitope between the DH270 lineage and DH475, consistent with its cooperative neutralization ability. © FASEB.