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

W Weissenhorn,Tc Verrips,Mm Aasa-Chapman,Ra Weiss,Me Khattabi,A Forsman-Quigley,D Lutje Hulsik,Nm Strokappe,Le Mccoy,L Rutten,M Hock,Jp Langedijk,Yy Liu

doi:10.1186/1742-4690-9-s2-p317

Abstract

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.

Highlights

The membrane proximal external region (MPER) of the HIV-1 glycoprotein gp41 is targeted by broadly neutralizing antibodies such as 2F5, 4E10 and Z13, which recognize antigen and membrane components
We further present structural data from crystallographic and NMR analyses together with mutagenesis data that allowed to map the interaction site on gp41. This revealed that 2H10 has a long CDR3 whose tip exposes a tryptophan residue that is not required for gp41 interaction, but crucial for neutralization
ConclusionOur data indicate that 2H10 induced by immunization classifies as a functional membrane proximal external region (MPER) antibody as a bihead that requires both antigen recognition and membrane interaction for neutralization

Summary

Open Access

A gp MPER-specific llama VHH requires a hydrophobic CDR3 determinant for neutralization but not for antigen recognition. W Weissenhorn1*, D Lutje Hulsik, M Hock, YY Liu, NM Strokappe, ME Khattabi, JP Langedijk, LE McCoy, A Forsman-Quigley, MM Aasa-Chapman, RA Weiss, TC Verrips, L Rutten

Background

Methods

Conclusion