Trimerization of the HIV Transmembrane Domain in Lipid Bilayers Modulates Broadly Neutralizing Antibody Binding

Abstract

The membrane-proximal external region (MPER) of HIV gp41 is an established target of antibodies that neutralize a broad range of HIV isolates. To evaluate the role of the transmembrane (TM) domain, synthetic MPER-derived peptides were incorporated into lipid nanoparticles using natural and designed TM domains, and antibody affinity was measured using immobilized and solution-based techniques. Peptides incorporating the native HIV TM domain exhibit significantly stronger interactions with neutralizing antibodies than peptides with a monomeric TM domain. Furthermore, a peptide with a trimeric, three-helix bundle TM domain recapitulates the binding profile of the native sequence. These studies suggest that neutralizing antibodies can bind the MPER when the TM domain is a three-helix bundle and this presentation could influence the binding of neutralizing antibodies to the virus. Lipid-bilayer presentation of viral antigens in Nanodiscs is a new platform for evaluating neutralizing antibodies.

Proteoliposomal formulations of an HIV-1 gp41-based miniprotein elicit a lipid-dependent immunodominant response overlapping the 2F5 binding motif

“…This structure contrasts with previously reported rigid alpha-helix structures of the MPER-TM joining region74. Finally, the inclusion of a native-like trimeric transmembrane domain, that may better control for the extent of immunogen oligomerization, should also be considered as it might favor better interactions with anti-MPER bNAbs75. Therefore, understanding the role of TM in MPER immunogenicity is probably a key issue to develop new MPER-based immunogens.…”

HIV-1 Env gp41 Transmembrane Domain Dynamics are Modulated by Lipid, Water, and Ion Interactions

“…The highly conserved gp41 TMD transmembrane domain (TMD) of Env ( Figure 1) is anchored in a cholesterol-rich lipid bilayer (22) that is flanked by the membrane proximal external region (MPER) on the exofacial leaflet and the cytoplasmic tail (CT) on the cytofacial leaflet. In the prefusion state, either one (23) or three (21,24,25) single-pass α-helices span the membrane ( Figure 1A). Previous studies have proposed that either oligomeric contacts (21,24) or head group snorkeling (23) stabilizes an internal arginine, R696, which is buried in the membrane (21).…”

“…Prior TMD MD models were either derived by homology modeling using the HIV transmembrane viral protein U (Vpu) as template (28)(29)(30) or from a 20amino acid transmembrane de novo model (31) rather than the recently published trimeric NMR TMD structure (21) which was used in this study. Previous simulations that used monomeric transmembrane models (28)(29)(30) lack quaternary contacts that are believed to stabilize the internal arginine (R696) (21,24,25). Furthermore, previous MD simulations were limited in sampling and membrane composition and were therefore unable to reveal the complex properties of the membrane components and their effect on TMD dynamics (28)(29)(30)(31).…”

Tilted, Uninterrupted, Monomeric HIV-1 gp41 Transmembrane Helix from Residual Dipolar Couplings

“…It is widely believed that TM adopts a trimeric helical bundle arrangement in the membrane bilayer. 7,8 However, a recent cryo-EM study of Env, lacking CT but including MPER and TM, did not show electron density for TM, 5 and analytical centrifugation studies of a construct containing MPER and TM (residues 666–715) at pH 7 in dodecylphosphocholine (DPC) micelles showed the peptide to be monomeric. 9 On the other hand, weak trimerization propensity was demonstrated for the TM of the analogous paramyxovirus fusion protein.…”