Different from the HIV Fusion Inhibitor C34, the Anti-HIV Drug Fuzeon (T-20) Inhibits HIV-1 Entry by Targeting Multiple Sites in gp41 and gp120

Abstract

Fuzeon (also known as T-20 or enfuvirtide), one of the C-peptides derived from the HIV-1 envelope glycoprotein transmembrane subunit gp41 C-terminal heptad repeat (CHR) region, is the first member of a new class of anti-HIV drugs known as HIV fusion inhibitors. It has been widely believed that T-20 shares the same mechanism of action with C34, another C-peptide. The C34 is known to compete with the CHR of gp41 to form a stable 6-helix bundle (6-HB) with the gp41 N-terminal heptad repeat (NHR) and prevent the formation of the fusogenic gp41 core between viral gp41 NHR and CHR, thereby inhibiting fusion between viral and target cell membranes. Here we present data to demonstrate that, contrary to this belief, T-20 cannot form stable 6-HB with N-peptides derived from the NHR region, nor can it inhibit the 6-HB formation of the fusogenic core. Instead, it may interact with N-peptides to form unstable or insoluble complexes. Our data suggest that T-20 has a different mechanism of action from C34. The interaction of T-20 with viral NHR region alone may not prevent the formation of the fusion active gp41 core. We also demonstrate that the T-20-mediated anti-HIV activity can be significantly abrogated by peptides derived from the membrane-spanning domain in gp41 and coreceptor binding site in gp120. These new findings imply that T-20 inhibits HIV-1 entry by targeting multiple sites in gp41 and gp120. Further elucidation of the mechanism of action of T-20 will provide new target(s) for development of novel HIV entry inhibitors.

Novel Recombinant Engineered gp41 N-terminal Heptad Repeat Trimers and Their Potential as Anti-HIV-1 Therapeutics or Microbicides

“…33,000°cm 2 dmol Ϫ1 ) according to previous studies (4,20). Thermal denaturation of the samples was monitored at 222 nm by applying a temperature gradient from 20°C to 98°C with a 2-degree interval, an equilibration time of 1.5 min, and an averaging time of 60 s. The midpoint of the thermal unfolding transition (T m ) values was calculated using Jasco software utilities as described previously (21).…”

Human domain antibodies to conserved sterically restricted regions on gp120 as exceptionally potent cross-reactive HIV-1 neutralizers

“…M36 and scFv m9 did not neutralize the clade E isolate GXE at concentrations up to 667 nM. M36 was also on average more potent than the peptide C34 (Table 1); C34 (10) is a gp41-derived peptide that exhibits HIV-1 entry inhibitory activity comparable to or higher than that of the FDA approved peptide entry inhibitor T20 (DP178, brand name Fuzeon), which shares significant sequence homology with C34 although inhibits entry by a somewhat different mechanism involving binding to multiple sites (11). The inhibitory activity of m36 was dose dependent (Fig.…”

Examination of a Fusogenic Hexameric Core from Human Metapneumovirus and Identification of a Potent Synthetic Peptide Inhibitor from the Heptad Repeat 1 Region

“…While previous research concluded that HR-1 peptides could be effective inhibitors of type I integral membrane fusion proteins when constrained and presented as trimeric helical bundles (8,28), our data suggest that individual HR-1 peptides can lead to effective viral inhibition. Furthermore, recent studies of HR-2 peptides suggest the potential for multiple viral targets for inhibitory peptides (20). The prophylactic nature of the HR-1 peptide could be explained by interaction with additional targets or strong binding to the metastable prefusion state of the F protein, possibly preventing stalk extension.…”