Stapled peptides may block HSV-1 infection in primary corneal epithelial cells

A group of stapled peptides was designed to disrupt viral DNA synthesis by mimicking a structure of the herpes simplex virus-1 (HSV-1) polymerase. African green monkey kidney epithelial cells were cultured and treated with unstapled and stapled peptides, and blocking of HSV-1 DNA synthesis and infection was assessed.

Study design

Hydrocarbon stapling consists of conformationally locking an α-helical peptide by cross-linking two adjacent sidechains. A group of stapled peptides was designed to disrupt viral DNA synthesis by mimicking the structure of the extreme C-terminal α-helix of UL30, the herpes simplex virus-1 (HSV-1) polymerase that is tethered by the processivity factor protein UL42. African green monkey kidney epithelial cells were cultured and treated with unstapled and stapled peptides, and blocking of HSV-1 DNA synthesis and infection were assessed. The most promising peptide was tested in primary human corneal epithelial cells after its negative N-terminus was replaced with two hydrophobic valine residues.

Outcomes

While the unstapled peptide failed to inhibit DNA synthesis or infection, stapled peptides were effective at both to varying degrees. Stapled peptides also blocked HSV plaque formation in the monkey cell line. The specificity of the stapled α-helical peptides was ascertained by its inability to block in vitro processive DNA synthesis by vaccinia virus proteins and vaccinia virus infection. Furthermore, the modified di-valine stapled peptide proved effective in blocking HSV-1 infection of human primary corneal epithelial cells to the same degree as in monkey cells.

Limitations

While stapled peptides blocked HSV-1 DNA synthesis and infection, the viral phenotype that has developed Acyclovir resistance due to thymidine kinase mutation was not specifically tested. Further validation with in vivo viral challenge to mouse models will be needed to thoroughly assess the clinical promise of this class of molecules in preventing or combating HSV-1 infection.

Clinical significance

Because processivity factors function only with their cognate polymerases, they present attractive targets for antivirals. As compounds that permeate effectively through cell membranes and exhibit highly specific binding, stapled peptides share important characteristics of both small- and large-molecule drugs. Such innovative peptide engineering approaches will become increasingly relevant as viruses continue to develop resistance against traditional biologics like acyclovir.