HIV-1 Fusion Is Blocked through Binding of GB Virus C E2D Peptides to the HIV-1 gp41 Disulfide Loop

Abstract

A strategy for antiviral drug discovery is the elucidation and imitation of viral interference mechanisms. HIV-1 patients benefit from a coinfection with GB Virus C (GBV-C), since HIV-positive individuals with long-term GBV-C viraemia show better survival rates than HIV-1 patients without persisting GBV-C. A direct influence of GBV-C on HIV-1 replication has been shown in coinfection experiments. GBV-C is a human non-pathogenic member of the flaviviridae family that can replicate in T and B cells. Therefore, GBV-C shares partly the same ecological niche with HIV-1. In earlier work we have demonstrated that recombinant glycoprotein E2 of GBV-C and peptides derived from the E2 N-terminus interfere with HIV entry. In this study we investigated the underlying mechanism. Performing a virus-cell fusion assay and temperature-arrested HIV-infection kinetics, we provide evidence that the HIV-inhibitory E2 peptides interfere with late HIV-1 entry steps after the engagement of gp120 with CD4 receptor and coreceptor. Binding and competition experiments revealed that the N-terminal E2 peptides bind to the disulfide loop region of HIV-1 transmembrane protein gp41. In conjunction with computational analyses, we identified sequence similarities between the N-termini of GBV-C E2 and the HIV-1 glycoprotein gp120. This similarity appears to enable the GBV-C E2 N-terminus to interact with the HIV-1 gp41 disulfide loop, a crucial domain involved in the gp120-gp41 interface. Furthermore, the results of the present study provide initial proof of concept that peptides targeted to the gp41 disulfide loop are able to inhibit HIV fusion and should inspire the development of this new class of HIV-1 entry inhibitors.

Peptide entry inhibitors of enveloped viruses: The importance of interfacial hydrophobicity

“…Reil and colleagues [116,117] hypothesized that the long recognized inhibition of HIV in patients co-infected with the common, asymptomatic GB virus C, which is related to hepatitis C, was due to a direct interaction between the surface glycoprotein E2 of the GB virus C and gp41, the Class I fusion protein of HIV. These authors examined peptides from the E2 protein and identified two overlapping E2 peptides, WDRGNV TLLCDCPNGPWVWV, (WWIHS = 6.5, iHHM = 3.5) and LCDCPNGP WVWVPAFCQAVG (WWIHS = 5.4, iHHM = 2.9) that inhibit HIV in vitro.…”

Disulfide Sensitivity in the Env Protein Underlies Lytic Inactivation of HIV-1 by Peptide Triazole Thiols

“…These findings show that in the HIV-1 lytic inactivation process, the PTT thiol takes advantage of the sensitivity of Env disulfides to thiol–disulfide exchange, a property that has been reported to play a role in the infection processes of HIV-1 and other enveloped viruses. 11,15,16,25–28 …”

Penetration of polymeric nanoparticles loaded with an HIV-1 inhibitor peptide derived from GB virus C in a vaginal mucosa model

“…E2 is a 20-mer peptide [LCDCPNGPWVWVPAFCQAVG], with a MW of 2165, characterized by its high hydrophobic content and the presence of three cysteine residues [11]. These properties enable it to interact with the sequence in the disulphide-loop region in gp41 and to block HIV-1 fusion to the cells.…”

“…E2 contains three cysteine residues, which may interfere with the oxidation state of the cysteine in the gp41 disulphide region. [11,12].…”