Severe acute respiratory syndrome coronavirus (SARS-CoV) infection inhibition using spike protein heptad repeat-derived peptides

Abstract

The coronavirus SARS-CoV is the primary cause of the life-threatening severe acute respiratory syndrome (SARS). With the aim of developing therapeutic agents, we have tested peptides derived from the membrane-proximal (HR2) and membrane-distal (HR1) heptad repeat region of the spike protein as inhibitors of SARS-CoV infection of Vero cells. It appeared that HR2 peptides, but not HR1 peptides, were inhibitory. Their efficacy was, however, significantly lower than that of corresponding HR2 peptides of the murine coronavirus mouse hepatitis virus (MHV) in inhibiting MHV infection. Biochemical and electron microscopical analyses showed that, when mixed, SARS-CoV HR1 and HR2 peptides assemble into a six-helix bundle consisting of HR1 as a central triple-stranded coiled coil in association with three HR2 ␣-helices oriented in an antiparallel manner. The stability of this complex, as measured by its resistance to heat dissociation, appeared to be much lower than that of the corresponding MHV complex, which may explain the different inhibitory potencies of the HR2 peptides. Analogous to other class I viral fusion proteins, the six-helix complex supposedly represents a postfusion conformation that is formed after insertion of the fusion peptide, proposed here for coronaviruses to be located immediately upstream of HR1, into the target membrane. The resulting close apposition of fusion peptide and spike transmembrane domain facilitates membrane fusion. The inhibitory potency of the SARS-CoV HR2-peptides provides an attractive basis for the development of a therapeutic drug for SARS.

Structure of a proteolytically resistant core from the severe acute respiratory syndrome coronavirus S2 fusion protein

“…1B and 4A). Mutation of Phe with the smaller Leu generates a void inside the coiled coil that may contribute to the lower thermal stability of the SARS-CoV HR1-HR2 complex relative to MHV (19).…”

“…For the murine CoV mouse hepatitis virus (MHV), HR2 peptides have also been shown to inhibit entry at nanomolar concentrations (18). However, the corresponding peptides from SARS-CoV inhibited viral entry in Vero cells with an IC 50 in the micromolar range (19,20). This difference in inhibition could be due to a weaker interaction between the HR1 and HR2 regions of SARS-CoV S2 (19), but it cannot be excluded that other factors such as the kinetics of membrane fusion or differences in the entry pathway of these two viruses could also affect the inhibitory properties of HR2 peptides.…”

The search for a structural basis for therapeutic intervention against the SARS coronavirus

“…The CoV S protein fusion core has a stable post-fusion structure similar to HIV-1 gp41 (Eckert & Kim, 2001). In the case of SARS-CoV, several peptides derived from HR1 and HR2 regions of SARS-CoV spike proteins block viral entry by targeting the putative pre-hairpin intermediate (Bosch et al, 2004;Liu et al, 2004;Yuan et al, 2004). Peptides derived from HR2 are sufficient to inhibit SARSCoV infection Bosch et al, 2004).…”

“…In the case of SARS-CoV, several peptides derived from HR1 and HR2 regions of SARS-CoV spike proteins block viral entry by targeting the putative pre-hairpin intermediate (Bosch et al, 2004;Liu et al, 2004;Yuan et al, 2004). Peptides derived from HR2 are sufficient to inhibit SARSCoV infection Bosch et al, 2004). Interestingly, the efficacy of HR2 peptides derived from the SARSCoV spike protein is lower than those of corresponding HR2 peptides of MHV in inhibiting MHV infection (Bosch et al, 2004), which may be explained by the larger surface area buried in the HR1-HR2 interface of MHV S2 compared with that in SARS-CoV S2 Supekar et al, 2004).…”

“…Peptides derived from HR2 are sufficient to inhibit SARSCoV infection Bosch et al, 2004). Interestingly, the efficacy of HR2 peptides derived from the SARSCoV spike protein is lower than those of corresponding HR2 peptides of MHV in inhibiting MHV infection (Bosch et al, 2004), which may be explained by the larger surface area buried in the HR1-HR2 interface of MHV S2 compared with that in SARS-CoV S2 Supekar et al, 2004).…”