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 trimeric HIV-1 envelope glycoprotein (Env), composed of its receptor binding subunit gp120 and the fusion protein gp41, is the main target for neutralizing antibodies
Due to the absence of an effective vaccine or cure for acquired immunodeficiency syndrome (AIDS), HIV-1 infections still result in high mortality
We showed that a unit of two VHH, named bi-2H10, was capable of preventing HIV-1 from infecting cells
Summary
The trimeric HIV-1 envelope glycoprotein (Env), composed of its receptor binding subunit gp120 and the fusion protein gp, is the main target for neutralizing antibodies. Recent studies have demonstrated the potential of the human immune system to produce broadly neutralizing antibodies (bnAbs) directed against gp120 [1,2,3,4,5,6,7,8,9,10], generation of antibodies with broad crossclade neutralization activity via recombinant Env immunization has been rare [11,12,13,14].
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