PLoS Pathogens (Mar 2013)

A gp41 MPER-specific llama VHH requires a hydrophobic CDR3 for neutralization but not for antigen recognition.

  • David Lutje Hulsik,
  • Ying-ying Liu,
  • Nika M Strokappe,
  • Simone Battella,
  • Mohamed El Khattabi,
  • Laura E McCoy,
  • Charles Sabin,
  • Andreas Hinz,
  • Miriam Hock,
  • Pauline Macheboeuf,
  • Alexandre M J J Bonvin,
  • Johannes P M Langedijk,
  • David Davis,
  • Anna Forsman Quigley,
  • Marlén M I Aasa-Chapman,
  • Michael S Seaman,
  • Alejandra Ramos,
  • Pascal Poignard,
  • Adrien Favier,
  • Jean-Pierre Simorre,
  • Robin A Weiss,
  • C Theo Verrips,
  • Winfried Weissenhorn,
  • Lucy Rutten

DOI
https://doi.org/10.1371/journal.ppat.1003202
Journal volume & issue
Vol. 9, no. 3
p. e1003202

Abstract

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The 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.