Mutations in gp120 Contribute to the Resistance of Human Immunodeficiency Virus Type 1 to Membrane-Anchored C-Peptide maC46

Abstract

Binding of the human immunodeficiency virus (HIV) envelope glycoprotein (Env) to the cellular CD4 receptor and a chemokine coreceptor initiates a series of conformational changes in the Env subunits gp120 and gp41. Eventually, the trimeric gp41 folds into a six-helix bundle, thereby inducing fusion of the viral and cellular membranes. C peptides derived from the C-terminal heptad repeat (CHR) of gp41 are efficient entry inhibitors as they block the six-helix bundle formation. Previously, we developed a membrane-anchored C peptide (maC46) expressed from a retroviral vector that also shows high activity against virus strains resistant to enfuvirtide (T-20), an antiviral C peptide approved for clinical use. Here, we present a systematic analysis of mutations in Env that confer resistance of HIV type 1 (HIV-1) to maC46. We selected an HIV-1 BaL strain with 10-fold reduced sensitivity to maC46 (BaL_C46) by passaging virus for nearly 200 days in the presence of gradually increasing concentrations of maC46. In comparison to wild-type BaL, BaL_C46 had five mutations at highly conserved positions in Env, three in gp120, one in the N-terminal heptad-repeat (NHR), and one in the CHR of gp41. No mutations were found in the NHR domain around the GIV motif that are known to cause resistance to enfuvirtide. Instead, maC46 resistance was found to depend on complementary mutations in the NHR and CHR that considerably favor binding of the mutated NHR to the mutated CHR over binding to maC46. In addition, resistance was highly dependent on mutations in gp120 that accelerated entry. Taken together, resistance to maC46 did not develop readily and required multiple cooperating mutations at conserved positions of the viral envelope glycoproteins gp120 and gp41.

Residues in the gp41 Ectodomain Regulate HIV-1 Envelope Glycoprotein Conformational Transitions Induced by gp120-Directed Inhibitors

“…These observations suggest that the A582T and L587A mutants bind CD4 but do not undergo CD4-induced conformational changes as efficiently as the wild-type Env. Of note, a previous study showed that in the context of the development of resistance to a C-peptide fusion inhibitor, the A582T change in HIV-1 Env affects C-peptide binding (42). This observation underscores the importance of this gp41 residue in modulating Env conformational transitions.…”

“…Changes in the gp41 ectodomain can influence HIV-1 sensitivity to gp120 ligands, even when the gp120 epitope for those inhibitory ligands is apparently intact (32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42). The mechanisms underlying these examples of HIV-1 neutralization escape are unknown.…”

ADS-J1 Inhibits HIV-1 Entry by Interacting with gp120 and Does Not Block Fusion-Active gp41 Core Formation

“…Therefore, mutations arise in the gp41 of CCR5-resistant agents (2) or the gp120 of gp41-targeting agents (27) or, as we reported, in gp41 of ADS-J1-resistant virus (3). However, taken together, our results strongly suggest that ADS-J1 is not a virus fusion inhibitor through interaction with gp41 but a gp-120 interacting compound.…”

“…Mutations in the highly conserved amino acid motif 36 to 45 in the HR1 domain confer resistance to T20 (35), providing strong evidence that HR1 is the site of interaction of T20. However, mutations in other regions of HIV-1 envelope (Env) have been also associated with T20 resistance (26,27).…”

Gene Therapy for HIV-1 Infection

“…The protein binds to the HIV-1 gp41 heptad repeat 1 region thereby interfering with six-helix bundle formation during the viral and cellular membrane fusion process. MaC46 expressing T cells are almost completely protected from HIV-1 entry and have a strong selective survival advantage compared to unmodified cells in vitro and in mouse models of HIV-1 infection (Egelhofer et al, 2004;Hermann et al, 2009a;Kimpel et al, 2010). Likewise, maC46 has been shown to be one of the most potent anti-HIV gene products currently available (Kimpel et al, 2010).…”