Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Capsid”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,333 records · Page 74Linked to original sources
PubMed1988

Identification of an immunodominant antigenic site involving the capsid protein VP3 of hepatitis A virus.

Hepatitis A virus, an hepatotropic picornavirus, is a common cause of acute hepatitis in man for which there is no available vaccine. Competitive binding studies carried out in solid phase suggest that neutralizing monoclonal antibodies to hepatitis A virus recognize a limited number of epitopes on the capsid surface, although the polypeptide locations of these epitopes are not well defined. Neutralization-escape mutants, selected for resistance to monoclonal antibodies, demonstrate broad cross-resistance to other monoclonal antibodies. Sequencing of virion RNA from several of these mutants demonstrated that replacement of aspartic acid residue 70 of capsid protein VP3 (residue 3070) with histidine or alanine confers resistance to neutralization by monoclonal antibody K2-4F2 and prevents binding of this antibody and other antibodies with similar solid-phase competition profiles. These results indicate that residue 3070 contributes to an immunodominant antigenic site. Mutation at residue 102 of VP1 (residue 1102) confers partial resistance against antibody B5-B3 and several other antibodies but does not prevent antibody attachment. Both VP3 and VP1 sites align closely in the linear peptide sequences with sites of neutralization-escape mutations in poliovirus and human rhinovirus, suggesting conservation of structure among these diverse picornaviruses. However, because partial neutralization resistance to several monoclonal antibodies (2D2, 3E1, and B5-B3) was associated with mutation at either residue 3070 or residue 1102, these sites appear more closely related functionally in hepatitis A virus than in these other picornaviruses.

Alanine↗
PubMed1988

Addition of a foreign oligopeptide to the major capsid protein of poliovirus.

Insertion mutants of type 3 poliovirus (Sabin strain) were constructed that encode additional amino acid sequences at the level of residue 100 of the capsid polypeptide VP1 within the neutralization site 1, corresponding to a loop on the capsid surface. The addition of a tri- or hexapeptide did not hamper virus viability. The antigenic pattern of insertion mutants was only modified locally: all mutants lost reactivity of neutralization site 1 with the corresponding monoclonal antibodies, while the reactivity of sites 2 and 3 was unaffected by the insertion. We have shown for one of the mutants--vFG68--that the antigenic specificity of the neutralization site 1 was replaced by a new one. Although vFG68 differs from its parental Sabin strain only by the addition of three amino acids within VP1, neutralizing antibodies specific for vFG68 were induced by the native virion as well as by the heat-denatured mutated virions. Our results demonstrate that an oligopeptide of three or six amino acids can lengthen VP1 at the level of antigenic site 1 without affecting virus multiplication and that this foreign peptide is exposed on the virion surface.

Amino Acid Sequence↗
PubMed1991

Improved serodiagnosis of hepatitis C virus infection with synthetic peptide antigen from capsid protein.

Cloning and expression of hepatitis C virus have allowed the development of immunoassays to detect hepatitis C virus infection. However, currently available recombinant fusion protein C100-3 assays, based on a nonstructural protein of the virus, are limited in sensitivity, particularly for detecting acute infection. In this report seroconversion panels showed that an assay based on synthetic peptides, derived from immunodominant regions of both capsid and nonstructural proteins, accelerated hepatitis C virus antibody detection by 4-10 weeks. In screening, this enzyme immunoassay increased detection from 47% to 64% in plasmapheresis donors with elevated alanine aminotransferase levels (greater than 100 international units per liter), from 15% to 24% in anti-hepatitis B core antigen-positive blood donors, and from 28% to 42% in renal dialysis patients when compared with nonstructural peptide-based assays. The screening assay was repeatedly reactive for 27 of 2902 volunteer blood donor samples (0.93%); four sera reacted only with the capsid antigen. The peptide test distinguished true from false positive results in agreement with recombinant immunoblot assay in 96% of blood donor samples repeatably reactive on a recombinant hepatitis C virus enzyme immunoassay.

Animals↗
PubMed1992

Transient immunoglobulin M antibody response to hepatitis C virus capsid antigen in posttransfusion hepatitis C: putative serological marker for acute viral infection.

The development of serological assays for hepatitis C virus (HCV) has made specific diagnosis possible. However, markers useful in indicating acute-phase HCV infection have not been identified. By an immunoblotting method, we characterized the IgM and IgG antibody response against HCV capsid antigen in patients with HCV infection. Among 88% of patients with acute posttransfusion hepatitis C recruited in a prospective study, there was a transient IgM antibody response. The IgM antibody appeared shortly after onset of hepatitis (average 3.7 weeks), persisted for several months (average 18 weeks), and then disappeared. In contrast, the IgG antibody persisted long-term once it appeared. Among patients with chronic hepatitis C with milder disease activities (serum aminotransferase increase above normal levels of less than 4-fold), the IgM antibody was negative in the majority (72%). In those with acute exacerbations (aminotransferase increase of greater than 10-fold), about 55% were negative for the IgM antibody. The reactivity of the IgM antibody in the rest was weaker or became negative upon further dilution of serum. The results suggest that IgM anti-capsid antibody may serve as a marker indicating acute or active HCV infection.

Acute Disease↗
PubMed1995

Targeting of a nuclease to murine leukemia virus capsids inhibits viral multiplication.

Capsid-targeted viral inactivation is an antiviral strategy in which toxic fusion proteins are targeted to virions, where they inhibit viral multiplication by destroying viral components. These fusion proteins consist of a virion structural protein moiety and an enzymatic moiety such as a nuclease. Such fusion proteins can severely inhibit transposition of yeast retrotransposon Ty1, an element whose transposition mechanistically resembles retroviral multiplication. We demonstrate that expression of a murine retrovirus capsid-staphylococcal nuclease fusion protein inhibits multiplication of the corresponding murine leukemia virus by 30- to 100-fold. Staphylococcal nuclease is apparently inactive intracellularly and hence nontoxic to the host cell, but it is active extracellularly because of its requirement for high concentrations of Ca2+ ions. Virions assembled in and shed from cells expressing the fusion protein contain very small amounts of intact viral RNA, as would be predicted for nuclease-mediated inhibition of viral multiplication.

3T3 Cells↗
PubMed1998

Organization of HIV-1 capsid proteins on a lipid monolayer.

In an in vitro system that mimics the assembly of immature human immunodeficiency virus (HIV) particles, ordered arrays of HIV-1 capsid (CA) proteins encoded by the viral gag gene have been obtained by incubation of histidine-tagged capsid proteins (His-HIVCA) beneath lipid monolayers containing the nickel-chelating lipid, 1,2-di-O-hexadecyl-sn-glycero-3-(1'-2"-R-hydroxy-3'-N-(5-amino-1- carboxypentyl)iminodiacetic acid)propyl ether. The membrane-bound His-HIVCA proteins formed small crystalline arrays of primitive (p1) unit cells with dimensions of a = 74.2 A, b = 126.2 A, gamma = 89.3 degrees. The image-analyzed two-dimensional projection of His-HIVCA assemblies shows a cage-like lattice, consisting of hexamer and trimer units, surrounding protein-free cage holes. The hexamer-coordinated cage holes of 26.3-A diameter are spaced at 74. 2-A intervals: these distances, and the hexamer-trimer arrangement, are consistent with previous, lower resolution studies on immature HIV-1 virus particles produced in vivo. Additionally, HIV-1 matrix protein trimer unit structures align to the His-HIVCA trimer units such that residues previously shown to interact with the HIV-1 gp120/gp41 envelope protein complex are oriented toward the hexamer cage holes. Our results form a bridge between results from conventional methods for the analysis of HIV particle structure.

Capsid↗
PubMed2002

The phosphorylated form of the ORF3 protein of hepatitis E virus interacts with its non-glycosylated form of the major capsid protein, ORF2.

Hepatitis E virus (HEV) is a human RNA virus containing three open reading frames. Of these, ORF1 encodes the viral nonstructural polyprotein; ORF2 encodes the major capsid protein, which exists in a glycosylated and non-glycosylated form; and ORF3 codes for a phosphoprotein of undefined function. Using fluorescence-based colocalization, yeast two-hybrid experiments, transiently transfected COS-1 cell co-immunoprecipitation, and cell-free coupled transcription-translation techniques, we have shown that the ORF3 protein interacts with the ORF2 protein. The domains involved in this ORF2-ORF3 association have been identified and mapped. Our deletion analysis showed that a 25-amino acid region (residues 57-81) of the ORF3 protein is required for this interaction. Using a Mexican HEV isolate, site-directed mutagenesis of ORF3, and a phosphatase digestion assay, we showed that the ORF2-ORF3 interaction is dependent upon the phosphorylation at Ser(80) of ORF3. Finally, using COS-1 cell immunoprecipitation experiments, we found that the phosphorylated ORF3 protein preferentially interacts with the non-glycosylated ORF2 protein. These findings were confirmed using tunicamycin inhibition, point mutants, and deletion mutants expressing only non-glycosylated ORF2. ORF3 maps in the structural region of the HEV genome and now interacts with the major capsid protein, ORF2, in a post-translational modification-dependent manner. Such an interaction of ORF2 with ORF3 suggests a possible well regulated role for ORF3 in HEV structural assembly.

Amino Acid Sequence↗
PubMed2006

Jab1 mediates cytoplasmic localization and degradation of West Nile virus capsid protein.

The clinical manifestations of West Nile virus (WNV), a member of the Flavivirus family, include febrile illness, sporadic encephalitis, and paralysis. The capsid (Cp) of WNV is thought to participate in these processes by inducing apoptosis through mitochondrial dysfunction and activation of caspase-9 and caspase-3. To further identify the molecular mechanism of the WNV capsid protein (WNVCp), yeast two-hybrid assays were employed using WNV-Cp as bait. Jab1, the fifth subunit of the COP9 signalosome, was subsequently identified as a molecule that interacts with WNVCp. Immunoprecipitation and glutathione S-transferase pulldown assays confirmed that direct interaction could occur between WNVCp and Jab1. Immunofluorescence microscopy demonstrated that the overexpressed WNVCp, which localized to the nucleolus, was translocated to the cytoplasm upon its co-expression with Jab1. When treated with leptomycin B, Jab1-facilitated nuclear exclusion of WNVCp was prevented, which indicated that the CRM1 complex is required for Jab1-facilitated nuclear export of WNVCp. Moreover, Jab1 promoted the degradation of WNVCp in a proteasome-dependent way. Consistent with this, WNVCp-mediated cell cycle arrest at the G(2) phase in H1299 was prevented by exogenous Jab1. Finally, an analysis of WNVCp deletion mutants indicated that the first 15 amino acids were required for interaction with Jab1. Furthermore, the double-point mutant of the WNVCp, P5A/P8A, was incapable of binding to Jab1. These results indicate that Jab1 has a potential protective effect against pathogenic WNVCp and might provide a novel target site for the treatment of disease caused by WNV.

Active Transport, Cell Nucleus↗
PubMed2000

Virus maturation targets the protein capsid to concerted disassembly and unfolding.

Many animal viruses undergo post-assembly proteolytic cleavage that is required for infectivity. The role of maturation cleavage on Flock House virus was evaluated by comparing wild type (wt) and cleavage-defective mutant (D75N) Flock House virus virus-like particles. A concerted dissociation and unfolding of the mature wt particle was observed under treatment by urea, whereas the cleavage-defective mutant dissociated to folded subunits as determined by steady-state and dynamic fluorescence spectroscopy, circular dichroism, and nuclear magnetic resonance. The folded D75N alpha subunit could reassemble into capsids, whereas the yield of reassembly from unfolded cleaved wt subunits was very low. Overall, our results demonstrate that the maturation/cleavage process targets the particle for an "off pathway" disassembly, because dissociation is coupled to unfolding. The increased motions in the cleaved capsid, revealed by fluorescence and NMR, and the concerted nature of dissociation/unfolding may be crucial to make the mature particle infectious.

Animals↗
PubMed2002

The adenovirus capsid protein hexon contains a highly conserved human CD4+ T-cell epitope.

The immunogenicity of adenovirus vectors remains a major obstacle to their safe and efficacious use for gene therapy. In order to identify T-cell epitopes directly from adenoviruses, four viral protein sequences were screened for the well-characterized 9-mer HLA-A2 binding motif. Peripheral blood mononuclear cells (PBMC) from healthy adults were tested for responses to 17 selected viral peptides using a short-term interferon-gamma ELISPOT assay. Memory T-cell responses were identified to a single peptide derived from the major capsid protein hexon in 5 of 6 HLA-A2-positive donors. Unexpectedly, responses to this hexon peptide were also detected in 4 of 6 HLA-A2-negative donors, and responder cells were identified as CD4(+) T cells by immunomagnetic depletion experiments. A longer 15-mer peptide, H910-924, was identified as the optimal CD4(+) T-cell epitope. This hexon epitope induces strong proliferative T-cell responses that can be blocked by a monoclonal antibody against HLA-DR, and molecular HLA typing of donors suggests that the peptide response is restricted by multiple HLA-DR alleles. Additionally, quantitative analysis of responses to H910-924 and whole adenovirus reveals that the frequency of circulating CD4(+) T cells specific for this single hexon epitope (mean = 61 per 10(6) PBMC) represents up to one third of the total adenovirus-specific T-cell response. Finally, comparison of hexon sequences from over 20 different human adenovirus serotypes indicates that H910-924 is highly conserved. In most individuals, therefore, T-cell responses to this hexon epitope will be induced by all adenovirus vectors, including "gutted" vectors packaged with capsid proteins and vectors based on different serotypes.

Adenoviridae↗
PubMed1999

Specific binding of the adenovirus capsid to the nuclear envelope.

Adenovirus (Ad) vectors used for gene therapy are efficient in entering the infected cell and targeting their genome to the nucleus. To study the mechanism of the interaction between Ad and the nuclear envelope we have established an in vitro assay using rat liver nuclei incubated with serotype 5 Ad vector. Binding of either fluorophore (Cy3)-labeled Ad5 (Cy3-AdGFP) or [3H]Ad5 was blocked by excess unlabeled Ad5, indicating that the interaction was specific. Binding reached equilibrium within 30 min, exhibited temperature dependence with more binding occurring at 37 degrees C than at 4 degrees C and appeared to be irreversible. Prior treatment of nuclei with glutaraldehyde or proteolysis of nuclei with trypsin inhibited the Cy3-AdGFP association with nuclei, and pretreatment of Cy3-AdGFP with human anti-Ad5 serum, but not naive human serum, inhibited Cy3-AdGFP, suggesting a requirement for direct interaction between Ad5 and nuclei. Addition of excess unlabeled Ad serotype 2 or Ad serotype 7 competed for binding with Cy3-AdGFP, indicating that the capsid determinant of nuclear binding was conserved among group B and C Ad serotypes. These data suggest that the Ad capsid and nuclear envelope contain specific domains that mediate binding of the two entities and that binding mechanisms to the nuclear envelope might be a common final pathway of different Ad serotypes.

Adenoviridae↗
PubMed1988

Expression of coxsackievirus B3 capsid proteins in Escherichia coli and generation of virus-specific antisera.

Subgenomic fragments of cloned infectious coxsackievirus B3 (CVB3) cDNA up to the size of the complete coding sequence of the viral polyprotein were inserted into the prokaryotic expression vector pPLc24 and expressed in Escherichia coli. Fusion proteins, containing 54 amino acids of MS2 replicase at their amino terminus followed by different parts of the CVB3 structural proteins, were expressed from several constructs. The expression product of a plasmid encoding the capsid proteins VP4, VP2, and the amino-terminal part of VP3 was obtained in high amounts. However, primary expression products containing the complete viral capsid precursor VP4-VP1 were completely degraded, indicating the presence of domains downstream from VP3 that are accessible to E. coli proteases. This finding is consistent with the observation that the structural intact expression product of the separately subcloned VP1 gene is also extremely unstable and consequently obtained only in low amounts. Two fusion proteins of non-overlapping parts of the viral structural proteins containing VP4, VP2, and VP3 or VP1, respectively, were isolated and used for the generation of antisera in rabbits. The antisera obtained recognize distinct CVB3 structural proteins in infected cell cultures as well as from purified CVB3 preparations. In addition, significant cross-reactivity of the described antisera with the corresponding structural proteins of other enteroviruses was observed, indicating that these antisera provide a valuable tool for an improved broad spectrum diagnosis of enteroviral infections.

Capsid↗
PubMed2004

Rapid construction of capsid-modified adenoviral vectors through bacteriophage lambda Red recombination.

There are extensive efforts to develop cell-targeting adenoviral vectors for gene therapy wherein endogenous cell-binding ligands are ablated and exogenous ligands are introduced by genetic means. Although current approaches can genetically manipulate the capsid genes of adenoviral vectors, these approaches can be time-consuming and require multiple steps to produce a modified viral genome. We present here the use of the bacteriophage lambda Red recombination system as a valuable tool for the easy and rapid construction of capsid-modified adenoviral genomes.

Adenoviridae↗
PubMed2005

Custom adeno-associated virus capsids: the next generation of recombinant vectors with novel tropism.

Recombinant gene delivery vehicles based on adeno-associated virus (rAAV) have emerged as promising vectors for the correction of genetic and acquired human disease states. These vectors possess many characteristics, including low pathogenicity and immunogenicity, and long-term gene expression after a single administered dose, that make them leading candidates for clinical gene therapy applications. Yet, the broad tissue tropism of the available AAV serotypes remains a disadvantage for the safest, most effective in vivo delivery of transgenes to target tissues. In addition, clinically relevant cell types exist that are poorly transduced by current rAAV vectors. As a result, increased efforts are now being made to tailor the tropism of rAAV to improve their transduction and selectivity profiles. Flexible, diverse methodologies have emerged that allow more control over the cell surface receptors rAAV employs for cell entry. These novel rAAV production strategies have resulted in unique vectors characterized by unique capsid protein sequences that employ alternative receptors, and have provided a better understanding of many basic aspects of the rAAV life cycle. This review aims to summarize the genetic methods currently being employed to customize rAAV capsids.

Animals↗
PubMed2004

Development of cell lines stably expressing staphylococcal nuclease fused to dengue 2 virus capsid protein for CTVI.

To explore the potential application of capsid-targeted viral inactivation (CTVI) strategy in prophylactic model against dengue virus (DV) infection, here we fused a Ca(2+)-dependent nuclease, staphylococcal nuclease (SN), to the capsid protein of dengue 2 virus (D2C) at the carboxyl terminal, and constructed the desired expression plasmid pc/D2C-SN and control plasmids pc/D2C-SN* and pc/D2C. A mammalian cell line BHK-21 was transfected by electroporation with those plasmids and thereafter selected by 5mgr;/ml blasticidin. The resistant cell clones were then expanding cultured and screened by RT-PCR and Western Blot assays. The nuclease activity of the expressed fusion protein D2C-SN was analyzed by in vitro DNA digestion assay. It was confirmed cell lines stably expressing D2C-SN and control constructs were obtained. The intracellular expressed fusion protein D2C-SN had ideal nuclease activity and no cytotoxicity on mammalian cells. Those engineered cell lines provided the experimental system for CTVI application in prophylactic model and paved the new road for combating DV infection with CTVI.

Amino Acid Sequence↗
PubMed2001

Cell-to-cell movement and assembly of a plant closterovirus: roles for the capsid proteins and Hsp70 homolog.

Diverse animal and plant viruses are able to translocate their virions between neighboring cells via intercellular connections. In this work, we analyze the virion assembly and cell-to-cell movement of a plant closterovirus and reveal a strong correlation between these two processes. The filamentous virions of a closterovirus possess a long body formed by the major capsid protein (CP) and a short tail formed by the minor capsid protein (CPm). Genetic and biochemical analyses show that the functions of these virion components are distinct. A virion body is required primarily for genome protection, whereas a tail represents a specialized device for cell-to-cell movement. Furthermore, tail assembly is mediated by the viral Hsp70 homolog (Hsp70h) that becomes an integral part of the virion. Inactivation of the ATPase domain of Hsp70h results in assembly of tailless virions that are incapable of translocation. A dual role for the viral molecular chaperone Hsp70h in virion assembly and transport, combined with the previous finding of this protein in intercellular channels, allowed us to propose a model of closteroviral movement from cell to cell.

Amino Acid Sequence↗
PubMed2003

Switch from capsid protein import to adenovirus assembly by cleavage of nuclear transport signals.

Replication and assembly of adenovirus occurs in the nucleus of infected cells, requiring the nuclear import of all viral structural proteins. In this report we show that nuclear import of the major capsid protein, hexon, is mediated by protein VI, a structural protein located underneath the 12 vertices of the adenoviral capsid. Our data indicate that protein VI shuttles between the nucleus and the cytoplasm and that it links hexon to the nuclear import machinery via an importin alpha/beta-dependent mechanism. Key nuclear import and export signals of protein VI are located in a short C-terminal segment, which is proteolytically removed during virus maturation. The removal of these C-terminal transport signals appears to trigger a functional transition in protein VI, from a role in supporting hexon nuclear import to a structural role in virus assembly.

Animals↗
PubMed1995

Use of human papillomavirus type 6 capsids to detect antibodies in people with genital warts.

Human papillomavirus (HPV) type 6 capsids were produced by recombinant vaccinia viruses and used in a capture ELISA to screen 901 human sera from three studies of genital HPVs. The highest seroprevalence was observed among subjects with recurrent genital warts. In a population-based case-control study of genital warts, 26 (58%) of 45 women with recurrent genital warts were seropositive compared with 19 (19%) of 101 control women with no history of genital warts (odds ratio, 6.5; 95% confidence interval, 3.0, 14.1). Among a cohort of pregnant women, 7 (88%) of 8 with recurrent warts were seropositive compared with 24 (30%) of 79 pregnant women with no such history. A significant association between seropositivity to HPV-6 capsids and the detection of HPV-6/11 DNA from genital specimens by polymerase chain reaction was also observed. Men with genital warts were less likely to be seropositive than were women with genital warts, and a positive association between the number of sex partners and seropositivity was observed among only the female university students.

Adult↗