bChronic infection by hepatitis C virus (HCV) is a cause of the global burden of liver diseases. HCV entry into hepatocytes is a complicated and multistep process that represents a promising target for antiviral intervention. The recently reported amphipathic ␣-helical virucidal peptide (C5A) from the HCV NS5A protein suggests a new category of antiviral drug candidates. In this study, to identify C5A-like HCV inhibitors, synthetic peptides derived from the C5A-corresponding NS5 protein region of selected Flaviviridae viruses were evaluated for their anti-HCV activities. A peptide from GB virus A (GBV-A), but not other flaviviruses, demonstrated an inhibitory effect on HCV infection. Through a series of sequence optimizations and modifications of the peptide helicity and hydrophobicity, we obtained a peptide designated GBVA10-9 with highly potent anti-HCV activity. GBVA10-9 suppressed infection with both cell culture-derived and pseudotyped HCV in vitro, and the 50% cell culture inhibitory concentration ranged from 20 nM to 160 nM, depending on the genotypic origin of the envelope proteins. GBVA10-9 had no detectable effects on either HCV attachment to Huh7.5.1 cells or viral RNA replication. No virucidal activity was found with GBVA10-9, suggesting an action mechanism distinct from that of C5A. The inhibitory effect of GBVA10-9 appeared to occur at the postbinding step during viral entry. Taken together, the results with GBVA10-9 demonstrated a potent activity for blocking HCV entry that might be used in combination with other antivirals directly targeting virus-encoded enzymes. Furthermore, GBVA10-9 also provides a novel tool to dissect the detailed mechanisms of HCV entry. H epatitis C virus (HCV) infects an estimated 170 million people worldwide. Failure to clear circulating HCV leads to a chronic infection that is frequently associated with the development of liver cirrhosis and hepatocellular carcinoma. The current standard-of-care therapy regimen for chronic HCV infection is based on a combination of PEGylated interferon (IFN) and ribavirin. However, the significant adverse effects and the limited efficacy in specific genotypes lead to poor tolerance and virus relapse (1). Recently, the FDA approved two direct-acting antiviral drugs (DAAs) that target HCV NS3/4A protease with an increased and sustained virological response (2-5). However, a monotarget antiviral strategy greatly increases the risk of rapidly emerging resistant mutations because of the high genetic heterogeneity of HCV. Successful treatment will probably require a combination therapy with multiple inhibitors directed at diverse viral targets. Therefore, development of more effective antiviral drugs is urgently needed.HCV entry is the first step of the viral life cycle and is a promising target for inhibiting viral infection. The HCV genome encodes two envelope glycoproteins, E1 and E2, which associate as a noncovalent heterodimer and constitute the majority of the viral membrane-integrated proteins. HCV glycoproteins play pivotal roles duri...
An α-helical model peptide (Ac-EAEKAAKE-X-EKAAKEAEK-amide) was used as a template to examine the efficacy of conventional reversed-phase high-performance liquid chromatography (RP-HPLC) in separating peptide analogs with single substitutions (at position X) of diasteromeric amino acids Ile, allo-Ile, D-Ile and D-allo-Ile. We compared differences of peptide retention behavior on a C8 column and a C18 column at different temperatures. We demonstrated how subtle differences in peptide secondary structure affected by the different substitutions of amino acids with identical overall hydrophobicity enabled effective resolution of these peptide analogs. We also demonstrated the ability of RP-HPLC to separate Ile- and allo-Ile-substituted analogs of a 26-residue α-helical antimicrobial peptide (AMP), with the substitution site towards the C-terminus of the α-helix. These peptides show different values of antibacterial activity and hemolytic activity, and different selectivity against bacteria and human cells. Our results underline the ability of RP-HPLC to resolve even difficult diasteromeric peptide mixtures as well as its value in monitoring very subtle hydrophobicity changes in de novo-designed AMP.
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