Structural Basis of HIV-1 gp41 N-trimer for Designing Bifunctional Peptide-based Fusion Inhibitors.

BACKGROUND: Pathogenic viruses that cause large-scale global or regional outbreaks almost always contain class I fusion proteins. Although the viruses differ in morphology, they all require fusion protein-mediated virus-host cell membranes during the early stages of host cell invasion. METHOD: The CHR region and NHR region of fusion proteins can form the 6-HB structure to drive the fusion pore formation between viruses and host cells through metastable interactions. Here, we obtained bifunctional N-peptides with inhibitory activities against two viruses, HIV-1 and MERS-CoV, based on the sequences in the HIV-1 NHR region by constructing N-trimer conformation interacting with the CHR region. RESULT: This study demonstrates that N-peptides with the coiled triple helix structure obtained from the NHR region in 6-HB are able to target the CHR region and exhibit inhibitory activity against a variety of viruses. CONCLUSION: Moreover, this strategy can be used to investigate antivirals against unknown viruses for future outbreaks.

Research Strategy for Short-Peptide Fusion Inhibitors Based on 6-HB Core Structure against HIV-1: A Review.

Acquired Immune Deficiency Syndrome (AIDS) is a devastating infectious disease caused by the Human Immunodeficiency Virus type 1 (HIV-1). Enfuvirtide(T20) is the first HIV-1 fusion inhibitor for marketing, which plays an important role in AIDS treatment. However, in the clinical application process, T20 has several drawbacks, such as a high level of development of drug resistance, a short half-life in vivo, and rapid renal clearance, which severely limits the clinical application. Therefore, the development of novel fusion inhibitors to address T20 shortcomings has long been the research hotspot. Short peptides have a long half-life through modification and a high barrier to drug resistance, which is expected to solve the current fusion inhibitors dilemma. In this paper, we summarized six emerging R&D strategies for short peptide-based fusion inhibitors against HIV-1. We hope that this review will provide fresh insights into the development of novel fusion inhibitors, as well as ideas for other viral fusion inhibitor discoveries based on the common membrane fusion 6-HB core structure.

Structure and Function of the SARS-CoV-2 6-HB Fusion Core and Peptide-Based Fusion Inhibitors: A Review.

SARS-CoV-2 has swept the world in recent years, triggering a global COVID-19 with a tremendous impact on human health and public safety. Similar to other coronaviruses, the six-helix bundle(6-HB) is not only a core structure driving the fusion of the SARS-CoV-2 envelope with the host cell membrane, but also the target of fusion inhibitors. The sequences from the HR1 or HR2 regions composing 6-HB are thus the original primary structures for the development of peptide-based fusion inhibitors. This review summarized the structure-activity relationship of the SARS-CoV-2 6- HB, analyzed the design methods and functional characteristics of peptide-based fusion inhibitors that contain different regions of HRs, and provided an outlook on the cutting- edge approaches for optimal modification of lead compounds (pan-coronavirization, chemical modification, superhelical construction, etc). We hope that this review will provide researchers with a comprehensive understanding of the state-of-art research progress on both 6-HB and peptide-based fusion inhibitors of SARS-CoV-2, and provide some new insights for the development of antiviral drugs.

Isopeptide Bond Bundling Superhelix for Designing Antivirals against Enveloped Viruses with Class I Fusion Proteins: A Review.

Viral infection has become one of the worst human lethal diseases. In recent years, major gains have been made in the research of peptide-based antiviral agents on account of the mechanism of viral membrane fusion, among which the peptide Enfuvirtide has been listed for the treatment of AIDS. This paper reviewed a new way to design peptide-based antiviral agents by "bundling" superhelix with isopeptide bonds to construct the active advanced structure. It can solve the problem that peptide precursor compounds derived from the natural sequence of viral envelope protein tend to aggregate and precipitate under physiological conditions and low activity and endow the peptide agents with the feature of thermal stability, protease stability and in vitro metabolic stability. This approach is also providing a new way of thinking for the research and development of broad-spectrum peptide-based antiviral agents.

One step synthesis of antimicrobial peptide protected silver nanoparticles: The core-shell mutual enhancement of antibacterial activity.

Over the past few decades, the overuse of antibiotics has led to the emergence of resistant bacteria and environmental issues. Both silver nanoparticles (AgNPs) and antimicrobial peptides (AMPs) hold potential to replace antibiotics. Combining both AMPs and AgNPs into a composite material may create novel properties such as enhanced antibacterial activity, lower cytotoxicity and favorable stability in aqueous solution. We designed a 13 amino acid peptide (in short, P-13) with two functional regions: one is for antibacterial activity, and the other for reducing and stabilizing AgNPs with containing cysteine (C) residues in its C-terminus. With a single step reaction, we have successfully synthesized P-13 protected AgNPs (P-13@AgNPs) with a hydrodynamic diameter of about 11 nm. In the preliminary antibacterial activity assay, the minimum inhibitory concentrations (MICs) of P-13@AgNPs were up to 7.8 µg/mL against E. coli, S. aureus and B. pumilus, and 15.6 µg/mL against P. aeruginosa. Moreover, Flow cytometry analysis of E. coli, S. aureus, P. aeruginosa and B. pumilus show that the mortality of the strains reached 96 %, 96 %, 91 % and 90 %, respectively. The cytotoxicity of AgNPs was reduced dramatically after protected by P-13, and P-13 was favorable for the stability of the AgNPs solution. We believe this work could set up an example to make the best use of the individual material's properties to produce novel nanocomposites with better antibacterial activity.

Triterpene sapogenin-polyarginine conjugates exhibit promising antibacterial activity against Gram-positive strains.

Triterpene sapogenins are a group of biologically active compounds with antibacterial activity. However, the limited solubility and poor bioavailability of triterpene sapogenins restrict their therapeutic application. Polyarginine peptides are small cationic peptides with high affinities for multiple negatively charged cell membranes and possess moderate antibacterial activities. In this study, we designed and synthesized a series of sapogenin-polyarginine conjugates in which the triterpene sapogenin moiety was covalently appended to the positively charged polyarginine via click chemistry. A clear synergistic effect was found, and the conjugates exhibited potent and selective antibacterial activity against Gram-positive strains. Among them, BAc-R3 was the most promising compound, which was also proven to be nontoxic toward mammalian cells as well as stable in plasma. The mechanism of BAc-R3 primarily involves an interaction with the bacterial membrane, similar to that of antimicrobial peptides (AMPs). This scaffold design opens an avenue for the further development of novel antibiotics comprised of the combination of a peptide and a natural product.