Perturbations induced by synthetic peptides from hepatitis G virus structural proteins in lipid model membranes: a fluorescent approach

Design, Characterization, and Biopharmaceutical Behavior of Nanoparticles Loaded with an HIV-1 Fusion Inhibitor Peptide

New therapeutic alternatives to fight against the spread of HIV-1 are based on peptides designed to inhibit the early steps of HIV-1 fusion in target cells. However, drawbacks, such as bioavailability, short half-life, rapid clearance, and poor ability to cross the physiological barriers, make such peptides unattractive for the pharmaceutical industry. Here we developed, optimized, and characterized polymeric nanoparticles (NPs) coated with glycol chitosan to incorporate and release an HIV-1 fusion inhibitor peptide (E1) inside the vaginal mucosa. The NPs were prepared by a modified double emulsion method, and optimization was carried out by a factorial design. In vitro, ex vivo, and in vivo studies were carried out to evaluate the optimized formulation. The results indicate that the physicochemical features of these NPs enable them to incorporate and release HIV fusion inhibitor peptides to the vaginal mucosa before the fusion step takes place.

The structural dynamics of the flavivirus fusion peptide-membrane interaction

Membrane fusion is a crucial step in flavivirus infections and a potential target for antiviral strategies. Lipids and proteins play cooperative roles in the fusion process, which is triggered by the acidic pH inside the endosome. This acidic environment induces many changes in glycoprotein conformation and allows the action of a highly conserved hydrophobic sequence, the fusion peptide (FP). Despite the large volume of information available on the virus-triggered fusion process, little is known regarding the mechanisms behind flavivirus-cell membrane fusion. Here, we evaluated the contribution of a natural single amino acid difference on two flavivirus FPs, FLA(G) ((98)DRGWGNGCGLFGK(110)) and FLA(H) ((98)DRGWGNHCGLFGK(110)), and investigated the role of the charge of the target membrane on the fusion process. We used an in silico approach to simulate the interaction of the FPs with a lipid bilayer in a complementary way and used spectroscopic approaches to collect conformation information. We found that both peptides interact with neutral and anionic micelles, and molecular dynamics (MD) simulations showed the interaction of the FPs with the lipid bilayer. The participation of the indole ring of Trp appeared to be important for the anchoring of both peptides in the membrane model, as indicated by MD simulations and spectroscopic analyses. Mild differences between FLA(G) and FLA(H) were observed according to the pH and the charge of the target membrane model. The MD simulations of the membrane showed that both peptides adopted a bend structure, and an interaction between the aromatic residues was strongly suggested, which was also observed by circular dichroism in the presence of micelles. As the FPs of viral fusion proteins play a key role in the mechanism of viral fusion, understanding the interactions between peptides and membranes is crucial for medical science and biology and may contribute to the design of new antiviral drugs.

A novel genotype of GB virus C: its identification and predominance among injecting drug users in Yunnan, China

GB virus C (GBV-C) is prevalent globally and particularly among individuals at risk of parental exposures. Based on genetic diversity, this virus is now classified into six genotypes and many subtypes with distinct geographical distribution. In this study, 120 Injecting Drug Users (IDUs) were recruited from Yunnan province, China. Among them, 43 (35.8%) were positive for GBV-C RNA, 70 (58.3%) and 103 (85.8%) sero-positive for HIV-1 and HCV respectively. This revealed 18.3% of IDUs having GBV-C/HIV/HCV triple infection, which is significantly higher than 7.5% of GBV-C/HIV-1 and 10% of GBV-C/HCV dual infection rates (P<0.05). Based on 5′UTR sequences, the identified 43 viral isolates can be classified into three phylogenetic groups: one (2.3%) and two (4.7%) belonged to genotype 3 and 4, respectively, and the remaining 40 (93%) formed a new group with 97% of bootstrap support. This new GBV-C group was further confirmed by characterizing the E2 region and full-length genome sequences. Analysis of 187 nt 5′UTR sequence showed three previous reported isolates from Southeast Asia were re-classified into this new group. It implies they have the same origin with strains from Yunnan. Although we provisionally assigned this new group as GBV-C genotype 7, a simpler five groups of GBV-C nomenclature is recommended. Genotype 4, 6 and the newly designated genotype 7 could be reclassified as one group, which may represent a single GBV-C genotype. The classification of the other four groups was corresponding to that of previous reported genotype 1, 2, 3 and 5. Furthermore, the diversity of amino acid sequence in the E2 region was analyzed. The inhibitory effect of GBV-C genotype 7 on HIV-1 cell entry could be deduced. Since GBV-C may have a beneficial effect on AIDS disease progression and interact with HCV during co-infection, this finding may raise interests in future studies on this virus that was previously thought to be a “non-pathogenic virus”.

GB virus type C envelope protein E2 elicits antibodies that react with a cellular antigen on HIV-1 particles and neutralize diverse HIV-1 isolates

Broadly neutralizing Abs to HIV-1 are well described; however, identification of Ags that elicit these Abs has proven difficult. Persistent infection with GB virus type C (GBV-C) is associated with prolonged survival in HIV-1-infected individuals, and among those without HIV-1 viremia, the presence of Ab to GBV-C glycoprotein E2 is also associated with survival. GBV-C E2 protein inhibits HIV-1 entry, and an antigenic peptide within E2 interferes with gp41-induced membrane perturbations in vitro, suggesting the possibility of structural mimicry between GBV-C E2 protein and HIV-1 particles. Naturally occurring human and experimentally induced GBV-C E2 Abs were examined for their ability to neutralize infectious HIV-1 particles and HIV-1-enveloped pseudovirus particles. All GBV-C E2 Abs neutralized diverse isolates of HIV-1 with the exception of rabbit anti-peptide Abs raised against a synthetic GBV-C E2 peptide. Rabbit anti-GBV-C E2 Abs neutralized HIV-1-pseudotyped retrovirus particles but not HIV-1-pseudotyped vesicular stomatitis virus particles, and E2 Abs immune-precipitated HIV-1 gag particles containing the vesicular stomatitis virus type G envelope, HIV-1 envelope, GBV-C envelope, or no viral envelope. The Abs did not neutralize or immune-precipitate mumps or yellow fever viruses. Rabbit GBV-C E2 Abs inhibited HIV attachment to cells but did not inhibit entry following attachment. Taken together, these data indicate that the GBV-C E2 protein has a structural motif that elicits Abs that cross-react with a cellular Ag present on retrovirus particles, independent of HIV-1 envelope glycoproteins. The data provide evidence that a heterologous viral protein can induce HIV-1-neutralizing Abs.

GB virus type C interactions with HIV: the role of envelope glycoproteins

GB virus C/hepatitis G virus (GBV-C/HGV) is the most closely related human virus to hepatitis C virus (HCV). GBV-C is lymphotropic and not associated with any known disease, although it is associated with improved survival in HIV-infected individuals. In peripheral blood mononuclear cells, GBV-C induces the release of soluble ligands for HIV entry receptors (RANTES, MIP-1a, MIP-1b and SDF-1), suggesting that GBV-C may interact with lymphocytes to induce a chemokine and/or cytokine milieu that is inhibitory to HIV infection. Expression of GBV-C envelope glycoprotein E2 in CD4+ T cells or addition of recombinant E2 to CD4 cells recapitulates the HIV inhibition seen with GBV-C infection. Like HCV E2, GBV-C E2 is predicted to be post-translationally processed in the endoplasmic reticulum and is involved with cell binding. The C-termini of GBV-C E1 and E2 proteins contain predicted transmembrane domains sharing features with HCV TM domains. To date, cellular receptor(s) for GBV-C E2 have not been identified. GBV-C E2-mediated HIV inhibition is dose-dependent and HIV replication is blocked at the binding and/or entry step. In addition, a putative GBV-C E2 fusion peptide interferes with HIV gp41 peptide oligomerization required for HIV-1 fusion, further suggesting that GBV-C E2 may inhibit HIV entry. Additional work is needed to identify the GBV-C E2 cellular receptor, characterize GBV-C E2 domains responsible for HIV inhibition, and to examine GBV-C E2-mediated fusion in the context of the entire envelope protein or viral-particles. Understanding the mechanisms of action may identify novel approaches to HIV therapy.

3D-Structure of the interior fusion peptide of HGV/GBV-C by 1H NMR, CD and molecular dynamics studies

In this work, we present a structural characterization of the putative fusion peptide E2(279-298) corresponding to the E2 envelope protein of the HGV/GBV-C virus by (1)H NMR, CD and MD studies performed in H(2)O/TFE and in lipid model membranes. The peptide is largely unstructured in water, whereas in H(2)O/TFE and in model membranes it adopts an helical structure (approximately 65-70%). The partitioning free energy DeltaG ranges from -6 to -7.5 kcal mol(-1). OCD measurements on peptide-containing hydrated and oriented lipid multilayers showed that the peptide adopts a predominantly surface orientation. The (1)H NMR data (observed NOEs, deuterium exchange rates, Halpha chemical shift index and vicinal coupling constants) and the molecular dynamics calculations support the conclusions that the peptide adopts a stable helix in the C-terminal 9-18 residues slightly inserted into the lipid bilayer and a major mobility in the amino terminus of the sequence (1-8 residues).