Efficacy of Fusion Peptide Homologs in Blocking Cell Lysis and HIV-Induced Fusion

Abstract

Contrary to earlier reports, we have found that tri- and hexapeptides analogous or homologous with segments of the 23-residue N-terminal fusion sequence (FS) of the viral transmembrane glycoprotein gp41 (residues 517-539) did not significantly inhibit HIV-1-induced syncytium formation, using an uninfected cell-infected cell fusion assay. In contrast, we found that the high molecular weight apolipoprotein A-1 and a 23-residue analog of the FS, with the phenylalanine residues at positions 524 and 527 replaced with alanine residues, were effective inhibitors. Although the tripeptides were ineffective as inhibitors of syncytium formation, we found a number of them inhibited red cell lysis induced by the synthetic peptide AVGIGALFLGFLGAAGSTMGARS (based on the HIV-1 gp41 FS). This effect was also seen with apolipoprotein A-1. The Ala524,527 analog of the fusion sequence could not be tested in this system because it was hemolytic. We concluded that the smaller peptides were effective inhibitors of hemolysis because they interfered with pore formation by the fusion sequence peptide, either by disrupting the pores or by preventing the peptide from adopting the alpha-helical conformation found in the pores. On the other hand, membrane fusion, which is a prelude to syncytium formation, has been shown to require the fusion sequence in the beta-strand conformation. We argue that small peptides would be unable to block interaction between such strands, although larger molecules, such as apolipoprotein A-1 and the Ala524,527 analog, would be able to do so and thus inhibit fusion. It seems, therefore, that a successful drug directed against the FS-cell membrane interaction stage of syncytium formation would need to be of relatively high molecular weight and complexity.

Inhibition of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) infectivity by peptides analogous to the viral spike protein

“…SARS WW-I and SARS WW-II have been independently identified as putative fusion peptides of the SARS-CoV S protein using biophysical approaches (Sainz et al, 2005b). Peptides analogous to class I fusion peptides often have antiviral activity (Gallaher et al, 1992;Owens et al, 1990;Silburn et al, 1998). The observation that WW-I and/or WW-II sequences inhibit infection ( Fig.…”

“…While current models of viral:cell membrane fusion are hypothetical in most aspects, the importance of several of the structural/functional motifs of class I viral fusion proteins as drug development targets has been established. For example, analogs of the orthomyxovirus, paramyxovirus (Richardson et al, 1980) and HIV-1 fusion peptide domains (Gallaher et al, 1992;Owens et al, 1990;Silburn et al, 1998) block viral infection, presumably by forming inactive heteroaggregates. Likewise, peptides analogous to the HR regions of the HIV-1 (Gallaher et al, 1992;Qureshi et al, 1990;Wild et al, 1992Wild et al, , 1993, paramyxovirus (Lambert et al, 1996;Young et al, 1999) or Ebola virus (EboV) (Watanabe et al, 2000) class I viral fusion proteins block virion infectivity by preventing the transition of the fusion protein into the six-helix bundle state.…”

Analysis of a Membrane Interacting Region of Herpes Simplex Virus Type 1 Glycoprotein H

“…InfectivitySeveral reports in the literature (62)(63)(64) describe the potential of fusion peptide analogues of orthomyxoviruses, paramyxoviruses, and human immunodeficiency virus as virus entry inhibitors. The accepted view is that the infectivity inhibition may be due to the formation of inactive aggregates between the fusogenic stretches present in the viral protein and the synthetic peptides.…”

Peptides containing membrane-interacting motifs inhibit herpes simplex virus type 1 infectivity

“…For example, analogs of the orthomyxovirus, paramyxovirus, and HIV fusion peptides [27,43,45] block viral infection, presumably by forming inactive heteroaggregates. A second target for viral inhibition has proved to be the region forming coiled-coils through heptad repeat domains.…”