Lipophilicity is a key factor to increase the antiviral activity of HIV neutralizing antibodies

The pH-sensitive action of cholesterol-conjugated peptide inhibitors of influenza virus

Influenza viruses are major human pathogens, responsible for respiratory diseases affecting millions of people worldwide, with high morbidity and significant mortality. Infections by influenza can be controlled by vaccines and antiviral drugs. However, this virus is constantly under mutations, limiting the effectiveness of these clinical antiviral strategies. It is therefore urgent to develop new ones. Influenza hemagglutinin (HA) is involved in receptor binding and promotes the pH-dependent fusion of viral and cell endocytic membranes. HA-targeted peptides may emerge as a novel antiviral option to block this viral entry step. In this study, we evaluated three HA-derived (lipo)peptides using fluorescence spectroscopy. Peptide membrane interaction assays were performed at neutral and acidic pH to better resemble the natural conditions in which influenza fusion occurs. We found that peptide affinity towards membranes decreases upon the acidification of the environment. Therefore, the released peptides would be able to bind their complementary domain and interfere with the six-helix bundle formation necessary for viral fusion, and thus for the infection of the target cell. Our results provide new insight into molecular interactions between HA-derived peptides and cell membranes, which may contribute to the development of new influenza virus inhibitors.

Dual Inhibition of Human Parainfluenza Type 3 and Respiratory Syncytial Virus Infectivity with a Single Agent

Human parainfluenza virus 3 (HPIV3) and respiratory syncytial virus (RSV) cause lower respiratory infection in infants and young children. There are no vaccines for these pathogens, and existing treatments have limited or questionable efficacy. Infection by HPIV3 or RSV requires fusion of the viral and cell membranes, a process mediated by a trimeric fusion glycoprotein (F) displayed on the viral envelope. Once triggered, the pre-fusion form of F undergoes a series of conformational changes that first extend the molecule to allow for insertion of the hydrophobic fusion peptide into the target cell membrane and then refold the trimeric assembly into an energetically stable post-fusion state, a process that drives the merger of the viral and host cell membranes. Peptides derived from defined regions of HPIV3 F inhibit infection by HPIV3 by interfering with the structural transitions of the trimeric F assembly. Here we describe lipopeptides derived from the C-terminal heptad repeat (HRC) domain of HPIV3 F that potently inhibit infection by both HPIV3 and RSV. The lead peptide inhibits RSV infection as effectively as does a peptide corresponding to the RSV HRC domain itself. We show that the inhibitors bind to the N-terminal heptad repeat (HRN) domains of both HPIV3 and RSV F with high affinity. Co-crystal structures of inhibitors bound to the HRN domains of HPIV3 or RSV F reveal remarkably different modes of binding in the N-terminal segment of the inhibitor.

Development of Protein- and Peptide-Based HIV Entry Inhibitors Targeting gp120 or gp41

Application of highly active antiretroviral drugs (ARDs) effectively reduces morbidity and mortality in HIV-infected individuals. However, the emergence of multiple drug-resistant strains has led to the increased failure of ARDs, thus calling for the development of anti-HIV drugs with targets or mechanisms of action different from those of the current ARDs. The first peptide-based HIV entry inhibitor, enfuvirtide, was approved by the U.S. FDA in 2003 for treatment of HIV/AIDS patients who have failed to respond to the current ARDs, which has stimulated the development of several series of protein- and peptide-based HIV entry inhibitors in preclinical and clinical studies. In this review, we highlighted the properties and mechanisms of action for those promising protein- and peptide-based HIV entry inhibitors targeting the HIV-1 gp120 or gp41 and discussed their advantages and disadvantages, compared with the current ARDs.

Trilobatin as an HIV-1 entry inhibitor targeting the HIV-1 Gp41 envelope

HIV-1 transmembrane protein gp41 plays a crucial role by forming a stable six-helix bundle during HIV entry. Due to highly conserved sequence of gp41, the development of an effective and safe small-molecule compound targeting gp41 is a good choice. Currently, natural polyanionic ingredients with anti-HIV activities have aroused concern. Here, we first discovered that a glycosylated dihydrochalcone, trilobatin, exhibited broad anti-HIV-1 activity and low cytotoxicity in vitro. Site-directed mutagenesis analysis suggested that the hydrophobic residue (I564) located in gp41 pocket-forming site is pivotal for anti-HIV activity of trilobatin. Furthermore, trilobatin displayed synergistic anti-HIV activities combined with other antiretroviral agents. Trilobatin has a good potential to be developed as a small-molecule HIV-1 entry inhibitor for clinical combination therapy.

Exploring Molecular-Biomembrane Interactions with Surface Plasmon Resonance and Dual Polarization Interferometry Technology: Expanding the Spotlight onto Biomembrane Structure

The molecular analysis of biomolecular-membrane interactions is central to understanding most cellular systems but has emerged as a complex technical challenge given the complexities of membrane structure and composition across all living cells. We present a review of the application of surface plasmon resonance and dual polarization interferometry-based biosensors to the study of biomembrane-based systems using both planar mono- or bilayers or liposomes. We first describe the optical principals and instrumentation of surface plasmon resonance, including both linear and extraordinary transmission modes and dual polarization interferometry. We then describe the wide range of model membrane systems that have been developed for deposition on the chips surfaces that include planar, polymer cushioned, tethered bilayers, and liposomes. This is followed by a description of the different chemical immobilization or physisorption techniques. The application of this broad range of engineered membrane surfaces to biomolecular-membrane interactions is then overviewed and how the information obtained using these techniques enhance our molecular understanding of membrane-mediated peptide and protein function. We first discuss experiments where SPR alone has been used to characterize membrane binding and describe how these studies yielded novel insight into the molecular events associated with membrane interactions and how they provided a significant impetus to more recent studies that focus on coincident membrane structure changes during binding of peptides and proteins. We then discuss the emerging limitations of not monitoring the effects on membrane structure and how SPR data can be combined with DPI to provide significant new information on how a membrane responds to the binding of peptides and proteins.

Designing improved active peptides for therapeutic approaches against infectious diseases

Infectious diseases are one of the main causes of human morbidity and mortality. In the last few decades, pathogenic microorganisms' resistance to conventional drugs has been increasing, and it is now pinpointed as a major worldwide health concern. The need to search for new therapeutic options, as well as improved treatment outcomes, has therefore increased significantly, with biologically active peptides representing a new alternative. A substantial research effort is being dedicated towards their development, especially due to improved biocompatibility and target selectivity. However, the inherent limitations of peptide drugs are restricting their application. In this review, we summarize the current status of peptide drug development, focusing on antiviral and antimicrobial peptide activities, highlighting the design improvements needed, and those already being used, to overcome the drawbacks of the therapeutic application of biologically active peptides.