Synthesis and photocatalytic efficiency of sol-gel Al 3+ -doped TiO 2 thin films: correlation between the structural, morphological and optical properties

International audienc

The amino-terminus of the hepatitis C virus (HCV) p7 viroporin and its cleavage from glycoprotein E2-p7 precursor determine specific infectivity and secretion levels of HCV particle types.

Viroporins are small transmembrane proteins with ion channel activities modulating properties of intracellular membranes that have diverse proviral functions. Hepatitis C virus (HCV) encodes a viroporin, p7, acting during assembly, envelopment and secretion of viral particles (VP). HCV p7 is released from the viral polyprotein through cleavage at E2-p7 and p7-NS2 junctions by signal peptidase, but also exists as an E2p7 precursor, of poorly defined properties. Here, we found that ectopic p7 expression in HCVcc-infected cells reduced secretion of particle-associated E2 glycoproteins. Using biochemical assays, we show that p7 dose-dependently slows down the ER-to-Golgi traffic, leading to intracellular retention of E2, which suggested that timely E2p7 cleavage and p7 liberation are critical events to control E2 levels. By studying HCV mutants with accelerated E2p7 processing, we demonstrate that E2p7 cleavage controls E2 intracellular expression and secretion levels of nucleocapsid-free subviral particles and infectious virions. In addition, our imaging data reveal that, following p7 liberation, the amino-terminus of p7 is exposed towards the cytosol and coordinates the encounter between NS5A and NS2-based assembly sites loaded with E1E2 glycoproteins, which subsequently leads to nucleocapsid envelopment. We identify punctual mutants at p7 membrane interface that, by abrogating NS2/NS5A interaction, are defective for transmission of infectivity owing to decreased secretion of core and RNA and to increased secretion of non/partially-enveloped particles. Altogether, our results indicate that the retarded E2p7 precursor cleavage is essential to regulate the intracellular and secreted levels of E2 through p7-mediated modulation of the cell secretory pathway and to unmask critical novel assembly functions located at p7 amino-terminus

Enveloped viruses distinct from HBV induce dissemination of hepatitis D virus in vivo

Hepatitis D virus (HDV) relies on a helper virus to package and transmit its ribonucleoprotein (RNP). Here, Perez-Vargas et al. show that HDV can use envelope proteins from HBV-unrelated viruses, including HCV and flaviviruses, to propagate in vitro and in humanized mice

Preliminary Evidence for Hepatitis Delta Virus Exposure in Patients Who Are Apparently Not Infected With Hepatitis B Virus

International audienceHepatitis delta virus (HDV) is a defective human virus that lacks the ability to produce its own envelope proteins and is thus dependent on the presence of a helper virus, which causes its surface proteins to produce infectious particles. Hepatitis B virus (HBV) was so far thought to be the only helper virus described to be associated to HDV. However, recent studies showed that divergent HDV-like viruses can be detected in fishes, birds, amphibians, and invertebrates without evidence of any HBV-like agent supporting infection (reviewed in Maya and Ploss(1)). Another recent study demonstrated that HDV can be transmitted and propagated in experimental infections ex vivo and in vivo by different enveloped viruses unrelated to HBV, including hepatitis C virus (HCV), flaviviruses like dengue and West Nile virus, and vesiculovirus.(2) Altogether, these results suggested that hepatitis D infection may, in theory, occur in patients carrying either virus.(2) These observations prompted us to search for HDV infection among patients who are HCV infected and in geographical regions with high HDV endemicity.The exact prevalence of HDV infection in Venezuela is unknown, but outbreaks of fulminant HDV infections have been reported in indigenous populations from the Amazon basin and Western Venezuela.(3) The high prevalence of HDV infection among these indigenous populations might have favored dissemination of HDV infection among other inhabitants in the country. Here, we investigated the possible HDV exposure in a cohort of Venezuelan patients infected with HCV

A novel lentiviral vector targets gene transfer into human hematopoietic stem cells in marrow from patients with bone marrow failure syndrome and in vivo in humanized mice

In vivo lentiviral vector (LV)-mediated gene delivery would represent a great step forward in the field of gene therapy. Therefore, we have engineered a novel LV displaying SCF and a mutant cat endogenous retroviral glycoprotein, RDTR. These RDTR/SCF-LVs outperformed RDTR-LVs for transduction of human CD34(+) cells (hCD34(+)). For in vivo gene therapy, these novel RDTR/SCF-displaying LVs can distinguish between the target hCD34(+) cells of interest and nontarget cells. Indeed, they selectively targeted transduction to 30%-40% of the hCD34(+) cells in cord blood mononuclear cells and in the unfractionated BM of healthy and Fanconi anemia donors, resulting in the correction of CD34(+) cells in the patients. Moreover, RDTR/SCF-LVs targeted transduction to CD34(+) cells with 95-fold selectivity compared with T cells in total cord blood. Remarkably, in vivo injection of the RDTR/SCF-LVs into the BM cavity of humanized mice resulted in the highly selective transduction of candidate hCD34(+)Lin(-) HSCs. In conclusion, this new LV will facilitate HSC-based gene therapy by directly targeting these primitive cells in BM aspirates or total cord blood. Most importantly, in the future, RDTR/SCF-LVs might completely obviate ex vivo handling and simplify gene therapy for many hematopoietic defects because of their applicability to direct in vivo inoculation

Baboon envelope pseudotyped lentiviral vectors outperform VSV-G pseudotyped lentiviral vectors for gene transfer into cytokine-stimulated and resting hematopoietic stem cells.

Affiliation ECOFECTInternational audience: Hematopoietic stem cell (HSC)-based gene therapy holds promise for the cure of many diseases. The field is now moving towards the use of lentiviral vectors (LVs) as evidenced by four successful clinical trials. These trials employed vesicular-stomatitis-virus-G protein (VSV-G)-LVs at high doses combined with strong cytokine-cocktail stimulation to obtain therapeutically relevant transduction levels but which might compromise the 'HSC' character. Summarizing all these disadvantages, alternatives to VSV-G-LVs are urgently needed. We generated here high-titer LVs pseudotyped with a baboon retroviral envelope glycoprotein (BaEV-LVs), resistant to human complement. Under mild cytokine-prestimulation to preserve the 'HSC' characteristics, a single BaEV-LV application at low dose, resulted in up to 90 % of hCD34(+)-cell transduction. Even more striking was that these new BaEV-LVs allowed at low doses efficient transduction of up to 30% of quiescent hCD34(+)-cells whereas high-dose VSV-G-LVs were insufficient. Importantly, reconstitution of NOD/Lt-SCID/γc(-/-)(NSG) mice with BaEV-LV transduced hCD34(+)-cells maintained these high transduction levels in all myeloid and lymphoid lineages including early progenitors. This transduction pattern was confirmed or even increased in secondary NSG recipient mice. This suggests that BaEV-LVs efficiently transduce true HSCs and could improve HSC-based gene therapy, for which high-level HSC correction is needed for life-long cure

Mystery solved: VSV-G-LVs do not allow efficient gene transfer into unstimulated T cells, B cells, and HSCs because they lack the LDL receptor

International audienc

A fusion peptide in preS1 and the human protein-disulfide isomerase ERp57 are involved in HBV membrane fusion process

International audienceCell entry of enveloped viruses relies on the fusion between the viral and plasma or endosomal membranes, through a mechanism that is triggered by a cellular signal. Here we used a combination of computational and experimental approaches to unravel the main determinants of hepatitis B virus (HBV) membrane fusion process. We discovered that ERp57 is a host factor critically involved in triggering HBV fusion and infection. Then, through modelling approaches, we uncovered a putative allosteric cross-strand disulfide (CSD) bond in the HBV S glycoprotein and we demonstrate that its stabilization could prevent membrane fusion. Finally, we identified and characterized a potential fusion peptide in the preS1 domain of the HBV L glycoprotein. These results underscore a membrane fusion mechanism that could be triggered by ERp57, allowing a thiol/disulfide exchange reaction to occur and regulate isomerization of a critical CSD, which ultimately leads to the exposition of the fusion peptide