The Experts below are selected from a list of 14259 Experts worldwide ranked by ideXlab platform
Yongyuan Zhang - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH ARTICLE Duck Hepatitis B Virus cccDNA Amplification Efficiency in Natural Infection Is Regulated by Virus Secretion Efficiency
2016Co-Authors: Yongyuan ZhangAbstract:Previous mutation based studies showed that ablating synthesis of Viral Envelope Proteins led to elevated hepadnaViral covalently closed circular DNA (cccDNA) amplification, but it remains unknown how cccDNA amplification is regulated in natural hepadnaViral infection because of a lack of research system. In this study we report a simple procedure to prepare two identical duck hepatitis B virus inocula, but they possess 10-100-fold difference in cccDNA amplification in infected cell culture. We demonstrate that the infected cells with higher cccDNA amplification significantly reduce the virus secretion efficiency that results in higher accumulation of relaxed circular DNA (rcDNA) and DHBsAg in the cells. The infected cells with lower cccDNA amplification significantly increase the virus secretion efficiency that leads to lower intracellular rcDNA and DHBsAg accumulation. In contrast with the findings generated in the mutation based experimental system, the regulation of cccDNA amplification in natural hepadnaViral infection bypasses direct regulation of the cellular Envelope Proteins concentration, instead it modulates virus secretion efficiency that ulti-mately impacts the intracellular rcDNA concentration, an important factor determining the destination of the synthesized rcDNA in infected cells
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duck hepatitis b virus cccdna amplification efficiency in natural infection is regulated by virus secretion efficiency
PLOS ONE, 2015Co-Authors: Yongyuan ZhangAbstract:Previous mutation based studies showed that ablating synthesis of Viral Envelope Proteins led to elevated hepadnaViral covalently closed circular DNA (cccDNA) amplification, but it remains unknown how cccDNA amplification is regulated in natural hepadnaViral infection because of a lack of research system. In this study we report a simple procedure to prepare two identical duck hepatitis B virus inocula, but they possess 10-100-fold difference in cccDNA amplification in infected cell culture. We demonstrate that the infected cells with higher cccDNA amplification significantly reduce the virus secretion efficiency that results in higher accumulation of relaxed circular DNA (rcDNA) and DHBsAg in the cells. The infected cells with lower cccDNA amplification significantly increase the virus secretion efficiency that leads to lower intracellular rcDNA and DHBsAg accumulation. In contrast with the findings generated in the mutation based experimental system, the regulation of cccDNA amplification in natural hepadnaViral infection bypasses direct regulation of the cellular Envelope Proteins concentration, instead it modulates virus secretion efficiency that ultimately impacts the intracellular rcDNA concentration, an important factor determining the destination of the synthesized rcDNA in infected cells.
Mansun Law - One of the best experts on this subject based on the ideXlab platform.
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the neutralizing face of hepatitis c virus e2 Envelope glycoprotein
Frontiers in Immunology, 2018Co-Authors: Netanel Tzarum, Ian A Wilson, Mansun LawAbstract:The high genetic variability of hepatitis C virus, together with the high level of glycosylation on the Viral Envelope Proteins shielding potential neutralizing epitopes, pose a difficult challenge for vaccine development. An effective HCV vaccine must target conserved epitopes and the HCV E2 glycoprotein is the main target for such neutralizing antibodies (NAbs). Recent structural investigations highlight the presence of a highly conserved and accessible surface on E2 that is devoid of N-linked glycans and known as the E2 neutralizing face. This face is defined as a hydrophobic surface comprising the front layer (FL) and the CD81 binding loop (CD81bl) that overlap with the CD81 receptor binding site on E2. The neutralizing face consists of highly conserved residues for recognition by cross-NAbs, yet it appears to be high conformationally flexible thereby presenting a moving target for NAbs. Three main overlapping neutralizing sites have been identified in the neutralizing face: antigenic site 412 (AS412), antigenic site 434 (AS434), and antigenic region 3 (AR3). Here, we review the structural analyses of these neutralizing sites, either as recombinant E2 or epitope-derived linear peptides in complex with bNAbs, to understand the functional and preferred conformations for neutralization, and for Viral escape. Collectively, these studies provide a foundation and molecular templates to facilitate structure-based approaches for HCV vaccine development.
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the neutralizing face of hepatitis c virus e2 Envelope glycoprotein
Frontiers in Immunology, 2018Co-Authors: Netanel Tzarum, Ian A Wilson, Mansun LawAbstract:The high genetic variability of hepatitis C virus, together with the high level of glycosylation on the Viral Envelope Proteins shielding potential neutralizing epitopes, pose a difficult challenge for vaccine development. An effective hepatitis C virus (HCV) vaccine must target conserved epitopes and the HCV E2 glycoprotein is the main target for such neutralizing antibodies (NAbs). Recent structural investigations highlight the presence of a highly conserved and accessible surface on E2 that is devoid of N-linked glycans and known as the E2 neutralizing face. This face is defined as a hydrophobic surface comprising the front layer (FL) and the CD81 binding loop (CD81bl) that overlap with the CD81 receptor binding site on E2. The neutralizing face consists of highly conserved residues for recognition by cross-NAbs, yet it appears to be high conformationally flexible, thereby presenting a moving target for NAbs. Three main overlapping neutralizing sites have been identified in the neutralizing face: antigenic site 412 (AS412), antigenic site 434 (AS434), and antigenic region 3 (AR3). Here, we review the structural analyses of these neutralizing sites, either as recombinant E2 or epitope-derived linear peptides in complex with bNAbs, to understand the functional and preferred conformations for neutralization, and for Viral escape. Collectively, these studies provide a foundation and molecular templates to facilitate structure-based approaches for HCV vaccine development.
Joseph Sodroski - One of the best experts on this subject based on the ideXlab platform.
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subunit organization of the membrane bound hiv 1 Envelope glycoprotein trimer
Nature Structural & Molecular Biology, 2012Co-Authors: Youdong Mao, Joseph Sodroski, Alon Herschhorn, Shi Hua Xiang, Xinzhen Yang, Liping Wang, Hillel HaimAbstract:The trimeric human immunodeficiency virus type 1 (HIV-1) Envelope glycoprotein (Env) spike is a molecular machine that mediates virus entry into host cells and is the sole target for virusneutralizing antibodies. The mature Env spike results from cleavage of a trimeric gp160 precursor into three gp120 and three gp41 subunits. Here we describe an ~11-A cryo-EM structure of the trimeric HIV-1 Env precursor in its unliganded state. The three gp120 and three gp41 subunits form a cage-like structure with an interior void surrounding the trimer axis. Interprotomer contacts are limited to the gp41 transmembrane region, the torus-like gp41 ectodomain, and a gp120 trimer association domain composed of the V1/V2 and V3 variable regions. The cage-like architecture, which is unique among characterized Viral Envelope Proteins, restricts antibody access, reflecting requirements imposed by HIV-1 persistence in the host.
Yorgo Modis - One of the best experts on this subject based on the ideXlab platform.
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structural models of the membrane anchors of Envelope glycoProteins e1 and e2 from pestiviruses
Virology, 2014Co-Authors: Jimin Wang, Yorgo ModisAbstract:The membrane anchors of Viral Envelope Proteins play essential roles in cell entry. Recent crystal structures of the ectodomain of Envelope protein E2 from a pestivirus suggest that E2 belongs to a novel structural class of membrane fusion machinery. Based on geometric constraints from the E2 structures, we generated atomic models of the E1 and E2 membrane anchors using computational approaches. The E1 anchor contains two amphipathic perimembrane helices and one transmembrane helix; the E2 anchor contains a short helical hairpin stabilized in the membrane by an arginine residue, similar to flaviviruses. A pair of histidine residues in the E2 ectodomain may participate in pH sensing. The proposed atomic models point to Cys987 in E2 as the site of disulfide bond linkage with E1 to form E1–E2 heterodimers. The membrane anchor models provide structural constraints for the disulfide bonding pattern and overall backbone conformation of the E1 ectodomain.
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Relating structure to evolution in class II Viral membrane fusion Proteins
Current opinion in virology, 2014Co-Authors: Yorgo ModisAbstract:Enveloped viruses must fuse their lipid membrane to a cellular membrane to deliver the Viral genome into the cytoplasm for replication. Viral Envelope Proteins catalyze this critical membrane fusion event. They fall into at least three distinct structural classes. Class II fusion Proteins have a conserved three-domain architecture and are found in many important Viral pathogens. Until 2013, class II Proteins had only been found in flaviviruses and alphaviruses. However, in 2013 a class II fusion protein was discovered in the unrelated phlebovirus genus, and two unexpectedly divergent Envelope Proteins were identified in families that also contain prototypical class II Proteins. The structural relationships of newly identified class II Proteins, reviewed herein, shift the paradigm for how these Proteins evolved.
Dimiter S Dimitrov - One of the best experts on this subject based on the ideXlab platform.
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Highly efficient selection of epitope specific antibody through competitive yeast display library sorting
mAbs, 2013Co-Authors: Vinita Puri, Emily Streaker, Zhongyu Zhu, Ponraj Prabakaran, Dimiter S DimitrovAbstract:Combinatory antibody library display technologies have been invented and successfully implemented for the selection and engineering of therapeutic antibodies. Precise targeting of important epitopes on the protein of interest is essential for such isolated antibodies to serve as effective modulators of molecular interactions. We developed a strategy to efficiently isolate antibodies against a specific epitope on a target protein from a yeast display antibody library using dengue virus Envelope protein domain III as a model target. A domain III mutant protein with a key mutation inside a cross-reactive neutralizing epitope was designed, expressed, and used in the competitive panning of a yeast display naïve antibody library. All the yeast display antibodies that bound to the wild type domain III but not to the mutant were selectively sorted and characterized. Two unique clones were identified and showed cross-reactive binding to Envelope protein domain IIIs from different serotypes. Epitope mapping of one of the antibodies confirmed that its epitope overlapped with the intended neutralizing epitope. This novel approach has implications for many areas of research where the isolation of epitope-specific antibodies is desired, such as selecting antibodies against conserved epitope(s) of Viral Envelope Proteins from a library containing high titer, high affinity non-neutralizing antibodies, and targeting unique epitopes on cancer-related Proteins.
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a new approach to measure fusion activity of cloned Viral Envelope Proteins fluorescence dequenching of octadecylrhodamine labeled plasma membrane vesicles fusing with cells expressing vesicular stomatitis virus glycoprotein
Virology, 1993Co-Authors: Anu Puri, Dimiter S Dimitrov, M Krumbiegel, Robert BlumenthalAbstract:Fusion between fluorescently labeled plasma membrane vesicles (PMV) and cells expressing vesicular stomatitis virus (VSV) glycoprotein (G-protein) was investigated by utilizing a lipid mixing assay based on fluorescence dequenching of octadecyl rhodamine (R18). The PMVs were prepared from Vero cells by hypotonic lysis. The G-protein was expressed on the cell surface either following infection with intact VSV or with an adenovirus vector (AdG12) containing the gene for the G-protein. Fusion was temperature and pH dependent and was inhibited by VSV G-antiserum. The pH dependence of PMV fusion paralleled that observed for VSV-cell fusion and VSV-induced syncytia formation. The kinetics of fusion followed an exponential dependence on time without an observable time lag after lowering pH. These findings indicate that dequenching R18-labeled PMV reliably represents the basic features of fusion of VSV with cells and can be used as a new tool in the study of fusion activity of virus Envelope Proteins expressed in cells.
