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Results for “Viral Structures”

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At least 667 records · Page 37Linked to original sources

PubMed1980

The effects of octylglucoside on the Semliki forest virus membrane. Evidence for a spike-protein--nucleocapsid interaction.

Evidence is presented for a non-covalent interaction between the spike glycoprotein and the nucleocapsid of Semliki Forest virus. When isolated viruses were treated with the non-ionic detergent beta-D-octylglucoside at neutral pH and low ionic strength the lipid bilayer membrane could be removed leaving most of the spike glycoproteins attached to the nucleocapsids. The interaction between capsids and membrane protein was sensitive to elevated pH and ionic strength, but at least partially reversible at neutral pH and low ionic strength. The possible role of this interaction in the viral structure and in the mechanism of budding of the virus from the host cell is discussed.

Animals↗

PubMedDate not supplied

CD4(+) T-cell responses against the VP1-unique region in individuals with recent and persistent parvovirus B19 infection.

To date cellular immune responses against parvovirus B19 (B19) have not been studied extensively. The aim of this study was to examine the T-cell response against the VP1-unique region as the immunodominant part of the viral structural protein VP1 in individuals with different courses of B19 infection. Therefore, a group of 13 parvovirus-positive probands was separated into subgroups characterized for recent or acute, past or persistent infection by means of the presence of specific immunoglobulin (Ig)M and IgG isotypes and of viral DNA in blood and tissue. Transiently transfected B-cells expressing VP1-unique region were used in ELISpot assays to investigate T-cell responses directed against the VP1-unique region in peripheral blood mononuclear cells (PBMC) of individual donors. Significant numbers of interferon-gamma (IFN-gamma) secreting lymphocytes were detectable in PBMC of all individuals with recent, acute or persistent B19 infection, but not in PBMC of donors with past B19 infection and seronegative individuals. A more detailed analysis of IFN-gamma producing cells by intracellular cytokine staining by flow cytometry revealed, that CD4(+) T cells but not CD8(+) cytotoxic lymphocytes (CTL) were the major subpopulation of IFN-gamma producing cells. These data strongly suggest the need of virus protein production for the maintenance of VP1-unique region-specific CD4(+) T-helper cell responses in B19-infected individuals.

Antibodies, Viral↗

PubMed1980

Translation of genomic avian myeloblastosis virus RNA in a cell-free protein synthesis system from rabbit reticulocytes.

Reaction conditions suitable for translation of genomic avian myeloblastosis virus RNA in micrococcal nuclease-pretreated reticulocyte lysates are described. The products of translation were characterized by immunoprecipitation and gel electrophoresis and compared with virus-specific products formed in host cells. Genomic viral RNA directed in a cell-free system the synthesis of precursors to viral structural proteins, namely Pr76gag and Pr180gag,pol.

Animals↗

PubMed1971

Serological and structural properties of Mason-Pfizer monkey virus isolated from the mammary tumor of a Rhesus monkey.

We describe here serological and structural properties of a virus, Mason-Pfizer Monkey Virus (M-PMV), isolated from a simian mammary tumor. This virus is morphologically similar to the known oncogenic RNA viruses (oncornaviruses). It has a 60-70S RNA, and its replication is inhibited by actinomycin. Antisera prepared against the virus isolated by density-gradient centrifugation identify at least two viral structural antigens. Immunodiffusion studies show that this virus is serologically unrelated to three types of simian foamy viruses, visna virus, and the known oncornaviruses. Immunofluorescence reveals that the structural proteins of the virus are synthesized cytoplasmically. Although M-PMV productively infects human cells in vitro, serological analysis does not show the presence of M-PMV antigens in human neoplasia.

Adult↗

PubMed1979

Feline sarcoma virus-coded polyprotein: enzymatic cleavage by a type C virus-coded structural protein.

A purified 15,000-molecular-weight (Mr) Prague strain Rous sarcoma virus gag gene-coded structural protein, p15, was shown to enzymatically cleave the previously described 130,000 Mr feline sarcoma virus-coded polyprotein, Pr130. Cleavage products included proteins ranging in molecular weight from 12,000 to 110,000. The specificity of this cleavage reactivity was indicated by the fact that, under similar conditions, neither purified type C viral structural proteins nor nonviral proteins such as bovine serum albumin were cleaved to significant extents. Moreover, feline leukemia virus Pr65gag was efficiently cleaved, resulting in the generations of proteins of 30,000 (p30), 15,000 (p15), 12,000 (p12), and 10,000 (p10) Mr. Using enzymatically (p15) treated feline sarcoma virus Pr130 as starting material, we were able to purify a major 72,000 Mr cleavage product and to show it to contain the previously described feline sarcoma virus-coded nonstructural component.

Animals↗

PubMed1993

The humoral response to Puumala virus infection (nephropathia epidemica) investigated by viral protein specific immunoassays.

Enzyme-linked immunosorbent assays for determination of antibodies directed to the nucleocapsid protein (N) or to either of the two envelope glycoproteins (G1 and G2) of Puumala virus were designed and evaluated. The assays were proven to be entirely restricted for each viral structural protein by biotin-labelled monoclonal antibodies. Sera from sequentially bled nephropathia epidemica patients (acute, convalescent, and 2-year sera) and sera from 10-20 year convalescents were examined for antibody specificity. All but one (n = 19) acute phase sera were shown to contain IgM antibodies directed to all three viral proteins. In the convalescent specimens the proportions of IgM to the different viral components were similar, but lower, when compared to the acute samples. Low levels of IgM against N and G2 were found in two out of ten 2-year sera. No virus-specific IgM were detected in sera drawn 10-20 years after infection. IgG antibodies to all three viral proteins were detected in all except one acute phase serum. The IgG response initially increased more rapidly to N, as compared to the anti-glycoprotein responses. The levels of glycoprotein-specific IgG were considerably increased 2 years after the disease, when compared to the levels detected in the convalescent specimens. The levels and specificities of IgG in very late convalescent sera (drawn 10-20 years after disease) resembled those detected 2 years after infection.

Animals↗

PubMed2001

Expression of hepatitis C virus proteins does not interfere with major histocompatibility complex class I processing and presentation in vitro.

Hepatitis C virus (HCV) infection takes a chronic course in the majority of patients. The mechanisms underlying the evasion of the host immune response and viral persistence are poorly understood. In this context, we investigated interactions of HCV proteins with major histocompatibility complex (MHC) class I processing and presentation pathways using cell lines that allow the tetracycline-regulated expression of viral structural and nonstructural proteins. These well-characterized inducible cell lines were found to efficiently process and present endogenously synthesized HCV proteins via MHC class I. Functional MHC class I cell-surface expression and intracellular proteasome activity were not affected by the expression of HCV proteins. These results suggest that viral evasion of the host immune response does not involve interactions of HCV with MHC class I processing and presentation. Other mechanisms, such as interference with the interferon system, may be operative in HCV infection, leading to viral persistence.

Cell Membrane↗

PubMed1982

U.V.-enhanced reactivation of capsid protein synthesis and infectious centre formation in mouse cells infected with U.V.-irradiated Minute-Virus-of-Mice.

The effect of U.V.-irradiation of mouse A9 cells on their ability to replicate unirradiated and U.V.-irradiated Minute-Virus-of-Mice was studied. The survival of two viral functions was measured in primary infected cells: the synthesis of viral structural proteins, as detected in situ using an immunoenzymatic assay, and the production of infectious centres, as detected by plaque formation onto appropriate indicator cells. Cell irradiation prior to infection enhanced virus survival over that in control cells (U.V.-enhanced reactivation phenomenon). The magnitude of this effect was similar for both viral functions, suggesting that the step(s) of the virus cycle sensitive to the reactivation process precede(s) the release of the primary burst and secondary infection.

Animals↗

PubMed1984

Nucleotide sequence of v-fps in the PRCII strain of avian sarcoma virus.

PRCII is an avian retrovirus whose oncogene (v-fps) induces fibrosarcomas in birds. The viral gene v-fps arose by transduction of an undetermined portion of a cellular gene known as c-fps. PRCII is weakly oncogenic when compared with Fujinami sarcoma virus, another transforming virus containing v-fps. As a first step in the elucidation of the molecular basis for the decreased virulence of PRCII, we have determined the entire nucleotide sequence of v-fps in the PRCII genome. The v-fps domain in PRCII encodes a polypeptide with a molecular weight of ca. 60,500 fused to a portion of the polyprotein encoded by the viral structural gene gag. The hybrid gag-fps polyprotein of PRCII would have a molecular weight of ca. 98,100, in accord with results of previous studies of the protein encoded by the PRCII genome. The leftward junctions between fps and gag in Fujinami sarcoma virus and PRCII are located at the same position in fps, but at different positions in gag. A sequence of 1,020 nucleotides, bounded by direct repeats of 6 nucleotides, is present in v-fps of Fujinami sarcoma virus but absent from PRCII. Our data should permit further explorations of the relationship between structure and function in the transforming protein encoded by v-fps.

Amino Acid Sequence↗

PubMed1994

Trans-suppression of gene expression by hepatitis C viral core protein.

We have demonstrated that the truncated hepatitis C (HCV) core protein with its C-terminal hydrophobic domains deleted is translocated to the nucleus of transfected cells (22). In this study, intact and truncated core proteins of HCV were transiently expressed in a human hepatoblastoma cell line, HepG2, and their effects on the expression of the chloramphenycol acethyl transferase (CAT) gene driven by viral and cellular promoters were examined. The intact core protein of 22 kDa which is localized in the cytoplasm of the transfected cells suppressed the expression in all of the promoters tested. They were promoters of the SV40 early region, the c-fos oncogene, the retinoblastoma susceptibility gene, the beta-interferon gene and the beta-actin gene. In contrast, the truncated HCV core protein located in the nucleus did not show such a suppressive activity. The HCV core protein appears to function not only as a viral structural protein but as a regulator of gene expression and it might act as a suppressive factor for the cellular gene expression.

Antibodies, Viral↗

PubMed1980

Restricted initiation of protein synthesis on the potentially polycistronic Sindbis virus 42 S RNA.

Sindbis 42 S genome RNA was isolated from virions and translated in vitro before and after purification by oligo(dT)-cellulose chromatography and sucrose density gradient centrifugation under denaturing conditions. In intact 42 S RNA, only the 5'-proximal initiation site for the synthesis of nonstructural proteins was used. The internally located start site for viral structural protein formation was active in broken genome RNA molecules where, as a consequence of fragmentation, it was closer to a 5' end. The results of several kinds of experiments indicate that the fragmentation-dependent synthesis of structural proteins directed by virion RNA was not due to the presence of 26 S subgenomic messenger RNA.

Animals↗

PubMed1991

Expression of human immunodeficiency virus type 1 vif and vpr mRNAs is Rev-dependent and regulated by splicing.

We have analyzed the structure and expression of the HIV-1 vif and vpr mRNAs. The results revealed that the predominant vif and vpr mRNAs belong to the intermediate size class of HIV-1 mRNAs and that their expression is dependent on the presence of Rev protein. In addition, low levels of a small multiply spliced vpr mRNA were produced by HIV-1. cDNA cloning and expression of vpr cDNAs in eucaryotic cells revealed that high levels of Vpr were produced only from the intermediate-size mRNA in the presence of Rev. Thus, as demonstrated for the viral structural proteins, expression of Vif and Vpr is regulated by Rev. The arrangement of the splice sites and the Rev-RRE interaction are responsible for the regulation of viral expression, and especially for the switching from an early stage, producing only or primarily Tat, Rev, and Nef from multiply spliced mRNAs, to a late stage, leading to the production of Gag, Pol, Env, Vpu, Vif, and Vpr from unspliced and partially spliced mRNAs.

Base Sequence↗

PubMed1991

Hepatitis C virus.

HepCV is the major cause of NANB PT hepatitis and is also implicated as the cause in a large proportion of sporadic cases of NANBH. Chronic infection with HepCV has also been linked to the development of hepatocellular carcinoma. Chimpanzees and marmosets are the only animals found to be experimentally infectable and the virus has not been propagated in any cell culture system. HepCV is an enveloped virus with a diameter of 30-60 nm and a 10-kb positive-stranded RNA genome. Its genome organization resembles that of the flaviviruses and pestiviruses. A 5'-untranslated segment of 341 nucleotides precedes a continuous ORF of 9030/9033 nucleotides which is followed by a 54 nucleotides long 3'-non-coding segment. Further work is required to resolve the question of whether the genomic RNA possesses a 3'-poly(U) or poly(A) tail. The genome also carries an internal poly(A) segment towards the 5'-end of its ORF. Genomic RNA is probably translated into a single polyprotein of 3010/3011 amino acids which is processed into functional proteins. The viral proteins have not been identified, but on the basis of the predicted amino acid sequences, hydrophobicity plots, location of potential glycosylation sites and similarities of these properties to those of pesti- and flaviviruses, the following genome organization has been predicted. The predicted viral structural proteins, a nucleocapsid protein and two envelope glycoproteins are located at the amino-terminal end of the polyprotein. They are followed by a highly hydrophobic protein and proteins that exhibit proteinase, helicase and replicase domains and thus are probably involved in RNA replication and protein processing. The replicase domain is located close to the carboxy terminus of the polyprotein. Although the overall nucleotide and amino acid homologies between HepCV and pestiviruses are low, a number of similarities exist that point to a closer ancestral relationship to the latter than the flaviviruses. First, the 5'-untranslated segment of the HepCV genome resembles that of the pestivirus genomes in size and presence of several short ORFs and it contains several segments with high nucleotide homology. Second, the two putative envelope glycoproteins of HepCV resemble two of the three putative envelope glycoproteins of the pestiviruses. Because its genome organization and predicted virion structure closely resemble those of the flaviviruses and pestiviruses, HepCV has been proposed to be placed in the family Flaviviridae.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1985

Molecular cloning and partial sequencing of hepatitis A viral cDNA.

Hepatitis A virus was purified from infected monkey kidney cell cultures, and the viral RNA was used to synthesize double-stranded cDNA. This cDNA was cloned either after insertion into a plasmid-primed synthesis system or after insertion into the PstI site of pBR322. The resulting clones were mapped by restriction endonuclease analysis and by cross hybridization of the viral inserts to generate a composite map which represented at least 97% of the viral genome, lacking ca. 220 bases from the 5' end of the genome. The clones were verified to be hepatitis A virus specific based on their positive hybridization to viral RNA and to total hepatitis A virus-infected cellular RNA from a heterologous marmoset host system. The nucleotide sequence of 3,054 base pairs of cDNA homologous to the 5' half of the viral genome was determined, and an open reading frame of 854 consecutive coding triplets was identified. In addition, sequences which encode the VP-1 and VP-3 viral structural proteins were located in the nucleotide sequence.

Amino Acid Sequence↗

PubMed1983

The synthesis of polypeptides in influenza C virus-infected cells.

The synthesis of virus-specific polypeptides was analyzed in MDCK cells infected with the JJ/50 strain of influenza C virus. In addition to three major structural proteins gp88, NP, and M, the synthesis of five polypeptides with molecular weights of 29,500 (C1), 27,500 (C2), 24,000 (C3), 19,000 (C4), and 14,000 (C5) was found in infected cells. None of these polypeptides were detected either in virions or in immunoprecipitates obtained after treatment of infected cell lysates with antiviral serum, suggesting that they are not viral structural proteins. Polypeptides C1-C5 were found to be synthesized in MDCK cells infected with different influenza C virus strains as well as in different host cell types infected with C/JJ/50. Further, it was observed that cellular protein synthesis was greatly reduced under hypertonic conditions, whereas the synthesis of C1-C5 was relatively unaffected. These results suggest that polypeptides C1-C5 are virus coded rather than host cell coded. Peptide mapping studies showed that each of polypeptides C3, C4, and C5 had a peptide composition similar to the M protein. The amount of C2 synthesized in infected cells was insufficient for mapping. This polypeptide was, however, found to rapidly disappear in pulse-chase experiments, suggesting that C2 is probably not unique but biosynthetically related to one of the other proteins. In contrast to these polypeptides, polypeptide C1 showed a map which is largely different from any major structural polypeptide. It therefore appears likely that C1 is a nonstructural protein of influenza C virus similar to the NS1 protein of influenza A and B viruses.

Animals↗

PubMed2025

A pan-beta-coronavirus vaccine bearing conserved and asymptomatic B- and T-cell epitopes protects against highly pathogenic Delta and highly transmissible Omicron SARS-CoV-2 variants.

Over the last five years of the COVID-19 pandemic, the repetitive mutations and deletions in the SARS-CoV-2 genome, primarily targeting the Spike gene, resulted in the emergence of multiple viral variants and sub-variants. The non-updated mismatched Spike-based sub-unit vaccines are less effective due to the ability of these SARS-CoV-2 variants and sub-variants to evade vaccine-induced humoral immunity. To reduce reliance on neutralizing antibodies and prevent potential mismatches between circulating variants, sub-variants, and the vaccines, we have identified highly conserved Spike and non-Spike viral epitopes associated with protective asymptomatic B- and T-cell immune responses, respectively. We demonstrated that unvaccinated asymptomatic patients with COVID-19 recognized these conserved B- and T-cell epitopes. Using the mRNA-LNP-based antigen delivery system, we developed a multi-epitope vaccine that incorporates the conserved B-cell epitopes, CD4+ T-cell epitopes, and CD8+ T-cell epitopes. To assess the efficacy of this "asymptomatic" multi-epitope vaccine, we used the HLA-A*02:01/HLA-DRB1* 01:01-hACE-2 triple transgenic mouse model. We demonstrated that this "asymptomatic" multi-epitope vaccine conferred robust protection against infection and disease caused by the SARS-CoV-2 Delta (B.1.617.2) and Omicron (XBB.1.5) variants as assessed by: (i) prevention of weight loss, (ii) reduction of virus replication, and (iii) lung pathology. This protection was associated with: (i) strong antibody responses; and (ii) high frequency of anti-viral IFN-γ-producing CD4+ and CD8+ T-cells. These findings illustrate the possibility of developing a pan-beta-coronavirus vaccine to induce broad-spectrum protective immunity against SARS-CoV-2 variants and sub-variants by targeting highly conserved "asymptomatic" B- and T-cell epitopes identified from both structural and non-structural viral proteins.

Epitopes, T-Lymphocyte↗

PubMed1984

Avian myeloblastosis virus and E26 virus oncogene products are nuclear proteins.

The defective acute leukemia viruses avian myeloblastosis virus (AMV) and E26 virus each contain an inserted cellular sequence related to the same highly conserved cellular gene, proto-amv. The oncogenes of these two retroviruses differ from this cellular proto-oncogene in gene structure, transcript structure, and gene product. The product of the AMV oncogene (myb) is a 48,000 Mr protein, p48myb, encoded by a transduced segment (amv) of proto-amv flanked by short helper-virus-derived terminal sequences. The E26 virus oncogene product is a 135,000 Mr protein, p135gag-amve-ets, encoded by significant portions of a viral structural gene (gag), sequences related to proto-amv (amve), and additional E26-specific sequences (ets) transduced from cellular proto-ets. Both p48myb and p135gag-amve-ets transforming proteins are located in the nucleus of cells transformed by these viruses. A protein of 110,000 Mr which is specifically immunoprecipitated by antisera to amv peptides and may be the product of the normal cellular gene (proto-amv) has been located in the cytoplasm of cells that express proto-amv mRNA.

Animals↗

PubMed2001

Maturation of IgG avidity to individual rubella virus structural proteins.

BACKGROUND: the structural proteins of rubella virus, the capsid protein C and the envelope glycoproteins E1 and E2 were produced in lepidopteran insect cells using baculovirus expression vectors. The C-terminal ends of the corresponding proteins were fused to a polyhistidine tag for easy and gentle purification by metal ion affinity chromatography. OBJECTIVES: to investigate the maturation of natural and vaccinal IgG avidity against individual authentic and recombinant rubella virus (RV) structural proteins. STUDY DESIGN: the analysis was carried out using a modified immunoblotting technique where the purified baculovirus-expressed proteins were compared with authentic rubella virus proteins. Altogether, 47 well-characterised serum samples from both naturally infected patients and vaccines were studied. RESULTS: after natural RV infection, IgG antibodies specific for the E1 protein were predominant not only in terms of levels, but also in terms of rate and magnitude of avidity maturation. The avidity development of the IgG antibodies was much slower in vaccines than in patients after a natural RV infection. CONCLUSIONS: together, our results indicate that IgG avidity determination in conjunction with immunoblot analysis is useful in the diagnosis of a RV infection. The recombinant proteins showed similar reactivity patterns in the immunoblot analyses as compared with the authentic viral structural proteins, suggesting suitability for serodiagnostics.

Antibodies, Viral↗