Lutje Hulsik, DavidLiu, Ying-yingStrokappe, Nika M.Battella, SimoneEl Khattabi, MohamedMcCoy, Laura E.Sabin, CharlesHinz, AndreasHock, MiriamMacheboeuf, PaulineBonvin, Alexandre M. J. J.Langedijk, Johannes P. M.Davis, DavidForsman Quigley, AnnaAasa-Chapman, Marlén M. I.Seaman, MichaelRamos, AlejandraPoignard, PascalFavier, AdrienSimorre, Jean-PierreWeiss, Robin A.Verrips, C. TheoWeissenhorn, WinfriedRutten, Lucy2013-05-072013Lutje Hulsik, David, Ying-ying Liu, Nika M. Strokappe, Simone Battella, Mohamed El Khattabi, Laura E. McCoy, Charles Sabin, et al. 2013. A gp41 MPER-specific llama vhh requires a hydrophobic CDR3 for neutralization but not for antigen recognition. PLoS Pathogens 9(3): e1003202.1553-7366http://nrs.harvard.edu/urn-3:HUL.InstRepos:10611671The membrane proximal external region (MPER) of the HIV-1 glycoprotein gp41 is targeted by the broadly neutralizing antibodies 2F5 and 4E10. To date, no immunization regimen in animals or humans has produced HIV-1 neutralizing MPER-specific antibodies. We immunized llamas with gp41-MPER proteoliposomes and selected a MPER-specific single chain antibody (VHH), 2H10, whose epitope overlaps with that of mAb 2F5. Bi-2H10, a bivalent form of 2H10, which displayed an approximately 20-fold increased affinity compared to the monovalent 2H10, neutralized various sensitive and resistant HIV-1 strains, as well as SHIV strains in TZM-bl cells. X-ray and NMR analyses combined with mutagenesis and modeling revealed that 2H10 recognizes its gp41 epitope in a helical conformation. Notably, tryptophan 100 at the tip of the long CDR3 is not required for gp41 interaction but essential for neutralization. Thus bi-2H10 is an anti-MPER antibody generated by immunization that requires hydrophobic CDR3 determinants in addition to epitope recognition for neutralization similar to the mode of neutralization employed by mAbs 2F5 and 4E10.en-USBiologyBiophysicsBiomacromolecule-Ligand InteractionsMacromolecular AssembliesMicrobiologyImmunityAdaptive ImmunityImmunizationsVirologyViral StructureViral EnvelopeAntiviralsImmunodeficiency VirusesViral VaccinesMicrobial PathogensJournal Article2013-05-0710.1371/journal.ppat.1003202