Expression of the Japanese encephalitis virus NS3 and NS2b proteins as glutathione S-transferase fusions

Flaviviruses generate their structural and nonstructural proteins by proteolytic processing of a single large polyprotein precursor. These proteolytic events are brought about both by host cell signalase and a virally encoded protease. The virally encoded proteolytic activity has been shown to reside within the nonstructural protein 3 (NS3) and requires the product of the nonstructural 2b (NS2b) gene. In order to obtain sufficient quantities of pure NS2b and NS3 proteins for kinetic analysis, we have expressed both these proteins in recombinant systems as fusions to glutathione S-transferase (GST). The fusion constructs were driven by the strong bacteriophage T7 promoter. Transfection of these constructs into the African green monkey kidney cell line CV-1 previously infected with a recombinant vaccinia virus expressing the T7 RNA polymerase resulted in synthesis of the fusion proteins. Both the fusion proteins could be purified to homogeneity in a single step using a glutathione agarose affinity matrix.     

Analysis of hepatitis C virus capsid, E1, and E2/NS1 proteins expressed in insect cells

The baculovirus/insect cell expression system was used to express the capsid protein and glycoproteins (e1 and e2/NS1) of the hepatitis C virus (HCV). Each polypeptide domain was expressed individually using two different constructs varying at their carboxy termini in order to retain or delete hydrophobic domains that may be involved in membrane association. The capsid proteins were transported to the nucleus where they formed a single large crystal-like inclusion. The capsid proteins were phosphorylated in insect cells. The e1 and e2 polypeptides were present in both the soluble and insoluble cellular fractions. Deletion of a hydrophobic domain in the carboxy terminus of e2 resulted in the polypeptide becoming soluble but not secreted. Deletion of the carboxy terminus of e1 had no effect on solubility. Both e1 and e2 were glycosylated, with variable glycosylation of e1 giving rise to a series of polypeptides varying in apparent molecular weight. Co-infection of insect cells with viruses expressing e1 and e2 resulted in a complex that permitted the coimmunoprecipitation of e1 with antibodies to e2 and vice versa. Immunofluorescence staining of insect cells expressing e1 and e2 indicated that reactivity to e2 was more prevalent in anti-HCV positive human sera.     

Association of influenza virus NP and M1 proteins with cellular cytoskeletal elements in influenza virus-infected cells

We have investigated the association of the influenza virus matrix (M1) and nucleoprotein (NP) with the host cell cytoskeletal elements in influenza virus-infected MDCK and MDBK cells. At 6.5 h postinfection, the newly synthesized M1 was Triton X-100 (TX-100) extractable but became resistant to TX-100 extraction during the chase with a t1/2 of 20 min. NP, on the other hand, acquired TX-100 resistance immediately after synthesis. Significant fractions of both M1 and NP remained resistant to differential detergent (Triton X-114, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate [CHAPS], octylglucoside) extraction, suggesting that M1 and NP were interacting with the cytoskeletal elements. However, the high-molecular-weight form of the viral transmembrane protein hemagglutinin (HA), which had undergone complex glycosylation, also became resistant to TX-100 extraction but was sensitive to octylglucoside detergent extraction, indicating that HA, unlike M1 or NP, was interacting with TX-100-insoluble lipids and not with cytoskeletal elements. Morphological analysis with cytoskeletal disrupting agents demonstrated that M1 and NP were associated with microfilaments in virus-infected cells. However, M1, expressed alone in MDCK or HeLa cells from cloned cDNA or coexpressed with NP, did not become resistant to TX-100 extraction even after a long chase. NP, on the other hand, became TX-100 insoluble as in the virus-infected cells. M1 also did not acquire TX-100 insolubility in ts 56 (a temperature-sensitive mutant with a defect in NP protein)-infected cells at the nonpermissive temperature. Furthermore, early in the infectious cycle in WSN-infected cells, M1 acquired TX-100 resistance very slowly after a long chase and did not acquire TX-100 resistance at all when chased in the presence of cycloheximide. On the other hand, late in the infectious cycle, M1 acquired TX-100 resistance when chased in either the presence or absence of cycloheximide. Taken together, these results demonstrate that M1 and NP interact with host microfilaments in virus-infected cells and that M1 requires other viral proteins or subviral components (possibly viral ribonucleoprotein) for interaction with host cytoskeletal components. The implication of these results for viral morphogenesis is discussed.     

Recognition of synthetic oligopeptides from nonstructural proteins NS1 and NS3 of dengue-4 virus by sera from dengue virus-infected children

OBJECTIVE: To investigate the correlation between soluble forms of the intercellular adhesion molecule (sICAM-1) and vascular cell adhesion molecule (sVCAM-1) and the severity of pre-eclampsia or its possible consequences for fetal growth. DESIGN: Prospective observational study. SETTING: Institute of Medical Genetics, University of Oslo, Department of Medical Genetics and Haematological Research Laboratory, Ullev?l University Hospital; and the Department of Obstetrics and Gynaecology, The National Hospital, Oslo, Norway. PARTICIPANTS: Seventy-six women with normotensive pregnancies and 157 women with pre-eclampsia divided into three subgroups: mild, severe and pre-eclampsia with fetal growth retardation. METHODS: ELISA-measurements of plasma sICAM-1 and sVCAM-1 were performed in a group of healthy pregnant normotensive women and three groups of women with varying degrees of pre-eclampsia. RESULTS: sICAM-1 concentrations were higher in the pre-eclampsia group compared with the control group, but this difference was not statistically significant. Plasma concentrations of sVCAM-1 were significantly greater (P < 0.0001) in all pre-eclampsia subgroups (835.34, 855.25 and 964.05 ng/mL) compared with the control group (667.62 ng/mL). Within the pre-eclampsia group, plasma concentration of sVCAM-1 was significantly higher in the subgroup exhibiting fetal growth retardation (P = 0.03) compared with mild pre-eclampsia. CONCLUSION: The observed increases in plasma concentrations of sVCAM-1 suggest that measurements of this adhesion molecule may be useful in monitoring pregnancies with respect to the development of pre-eclampsia or fetal growth retardation.     

NS1-Binding protein (NS1-BP): a novel human protein that interacts with the influenza A virus nonstructural NS1 protein is relocalized in the nuclei of infected cells

We used the yeast interaction trap system to identify a novel human 70-kDa protein, termed NS1-binding protein (NS1-BP), which interacts with the nonstructural NS1 protein of the influenza A virus. The genetic interaction was confirmed by the specific coprecipitation of the NS1 protein from solution by a glutathione S-transferase-NS1-BP fusion protein and glutathione-Sepharose. NS1-BP contains an N-terminal BTB/POZ domain and five kelch-like tandem repeat elements of approximately 50 amino acids. In noninfected cells, affinity-purified antibodies localized NS1-BP in nuclear regions enriched with the spliceosome assembly factor SC35, suggesting an association of NS1-BP with the cellular splicing apparatus. In influenza A virus-infected cells, NS1-BP relocalized throughout the nucleoplasm and appeared distinct from the SC35 domains, which suggests that NS1-BP function may be disturbed or altered. The addition of a truncated NS1-BP mutant protein to a HeLa cell nuclear extract efficiently inhibited pre-mRNA splicing but not spliceosome assembly. This result could be explained by a possible dominant-negative effect of the NS1-BP mutant protein and suggests a role of the wild-type NS1-BP in promoting pre-mRNA splicing. These data suggest that the inhibition of splicing by the NS1 protein may be mediated by binding to NS1-BP.     

Structure of the haemagglutinin-esterase-fusion glycoprotein of influenza C virus

The spike glycoproteins of the lipid-enveloped orthomyxoviruses and paramyxoviruses have three functions: to recognize the receptor on the cell surface, to mediate viral fusion with the cell membrane, and to destroy the receptor. In influenza C virus, a single glycoprotein, the haemagglutinin-esterase-fusion (HEF) protein, possesses all three functions. In influenza A and B, the first two activities are mediated by haemagglutinin and the third by a second glycoprotein, neuraminidase. Here we report the crystal structure of the HEF envelope glycoprotein of influenza C virus. We have identified the receptor-binding site and the receptor-destroying enzyme (9-O-acetylesterase) sites, by using receptor analogues. The receptor-binding domain is structurally similar to the sialic acid-binding domain of influenza A haemagglutinin, but binds 9-O-acetylsialic acid. The esterase domain has a structure similar to the esterase from Streptomyces scabies and a brain acetylhydrolase. The receptor domain is inserted into a surface loop of the esterase domain and the esterase domain is inserted into a surface loop of the stem. The stem domain is similar to that of influenza A haemagglutinin, except that the triple-stranded, alpha-helical bundle diverges at both of its ends, and the amino terminus of HEF2, the fusion peptide, is partially exposed. The segregation of HEF's three functions into structurally distinct domains suggests that the entire stem region, including sequences at the amino and carboxy termini of HEF1 which precede the post-translational cleavage site between HEF1 and HEF2, forms an independent fusion domain which is probably derived from an ancestral membrane fusion protein.     

The hepatitis C virus NS2 protein generated by NS2-3 autocleavage is required for NS5A phosphorylation

Protein kinase C (PKC) is implicated in the regulation of a variety of important functions in small cell lung cancer (SCLC) cell lines, but the downstream signaling targets stimulated by PKCs in these cells remain poorly characterized. Here we report that treatment of the SCLC cell lines H 69, H 345, and H 510 with phorbol-12,13-dibutyrate (PDB) led to a rapid and striking activation of protein kinase D (PKD), a novel serine/threonine protein kinase distinct from all PKC isoforms. PKD activation induced by PDB in these SCLC cell lines was completely abrogated by treatment of the cells with the PKC inhibitor GF 109203X (GF I) at concentrations (0.5-2.5 microM) that did not inhibit PKD activity when added directly to the in vitro kinase assays. Treatment with the biologically active phorbol ester 12-O-tetradecanoylphorbol-13-acetate or with membrane-permeable diacylglycerols also stimulated PKD activation, which was also completely prevented by prior exposure of the cells to GF I. The PKC inhibitors Ro 31-8220 and Go 7874 also blocked PKD activation in response to PDB. Addition of the autocrine growth factor bombesin to cultures of H 345 cells induced significant PKD activation that also was prevented by GF I. Our results demonstrate, for the first time, the existence of a PKC/PKD pathway in SCLC cells and raise the possibility that PKD may be an important mediator of some of the biological responses elicited by PKC activation in SCLC cells.     

The N-terminal half of the influenza virus NS1 protein is sufficient for nuclear retention of mRNA and enhancement of viral mRNA translation

A collection of C-terminal deletion mutants of the influenza A virus NS1 gene has been used to define the regions of the NS1 protein involved in its functionality. Immunofluorescence analyses showed that the NS1 protein sequences downstream from position 81 are not required for nuclear transport. The capacity of these mutants to bind RNA was studied by in vitro binding tests using a model vRNA probe. These experiments showed that the N-terminal 81 amino acids of NS1 protein are sufficient for RNA binding activity. The collection of mutants also served to map the NS1 sequences required for nuclear retention of mRNA and for stimulation of viral mRNA translation, using the NP gene as reporter. The results obtained indicated that the N-terminal 113 amino acids of NS1 protein are sufficient for nuclear retention of mRNA and stimulation of viral mRNA translation. The possibility that this region of the protein may be sufficient for virus viability is discussed in relation to the sequences of NS1 genes of field isolates and to the phenotype of known viral mutants affected in the NS1 gene.     

Immunization with the N-terminal region of the nonstructural protein NS1 promotes survival after challenge with lethal influenza A virus dose

We investigated the utilization patterns of autologous blood donation for radical retropubic prostatectomy (RRP) during a 6-year period. A total of 225 patients electing RRP with blood donation were identified for analysis. Group 1 consisted of 113 men who had an RRP from 1990 to 1993. Group 2 consisted of 112 men who had an RRP from 1993 to 1995. Charts were reviewed for the number of units transfused, number of autologous units donated, and operative blood loss. More patients autodonated blood in the later group (84% vs. 75%). Technical improvements and experience have significantly decreased blood loss and the need for transfusions (69% vs. 96% in the early group). In the more current series, only 14% of patients who autodonated blood required homologous transfusion vs. 42% in the earlier group. An increase in the amount of wasted blood (42% vs. 16% in the early group) also was noted. The 4-unit donors had the lowest homologous transfusion rate in both series (group 1 = 21%, group 2 = 5%); the 2-unit donors had the lowest units wasted per person (0.74). In addition, the 2-unit donors maintained a low homologous transfusion rate of 16%. These data suggest that 2 units of autologous blood donation has a reduced risk of homologous blood transfusion while the amount of autologous blood wasted is minimized.     

Subcellular localization and some biochemical properties of the flavivirus Kunjin nonstructural proteins NS2A and NS4A

1. The mean incidence of deaths from ascites in the UK in 1993 was 1.4% (0.7% in 1991 and 0.9% in 1992) and 0.8% from sudden death syndrome (SDS). In total, the economic loss to the UK Broiler Industry in 1993 as a result of these 2 conditions was 24 Pounds M. 2. Clear geographical differences emerged in the occurrence of ascites, with, not only the lowest incidences being observed in Northern Ireland, but also the peak of the mortality from ascites occurring much later in the rearing cycle than in other regions on the mainland. 3. In all regions the incidence of SDS was lower than that of ascites but the reason for this disparity remains to be established. 4. Some of the variables associated with the road transportation of day-old chicks from the hatchery to the farm appeared to influence the incidence of ascites. These included distance or time travelled, stocking density, internal lorry temperature and the length of time the lorry was heated before transport as well as the time the shed was heated before chick arrival. Temperature was also an important factor during growth (brooding and finishing). 5. Negative pressure-powered ventilation was preferred in most organisations but more ascites was seen with positive pressure ventilation. However, the lowest incidence of ascites occurred with natural ventilation. There was more ascites relative to shed orientation when the wind direction was from the west compared to the east. 6. This survey identifies the extent of the problem of broiler ascites in the UK and also highlights the importance of good management control of day-old chicks, not only following placement, but even before their arrival on the farm.     

The effect of mutation in the NS gene on the biological properties of the influenza virus

The biological properties of influenza virus strain A/PR/8/34, virulent from mice, and its variant 25A-1, obtained by hybridization with avirulent strain A/Leningrad. This reassortant 25A-1 included 7 genes of its virulent parent strain and only gene NS of the avirulent one, which contained a single mutation in position 798 (ATG=>ATA), inducing amino acid change MET=>IIe in position 100 of the polypeptide chain of protein NS2. The loss of pathogenic properties by strain A/PR/8/34 was achieved by replacing the single gene NS with an analogous mutant gene of the variant strain A/Leningrad, adapted to low temperatures. The single-gene reassortant 25A-1 thus obtained possessed, besides decreased capacity for multiplication in the lungs of mice, ts phenotype on MDCK cells, but exhibited no thermal sensitivity in cell systems of avian origin. The above-mentioned phenotypic changes in reassortant 25A-1 were due to disturbances in virus-specific protein synthesis at early and late stages, as detected in vivo and in vitro.     

Partial nucleotide sequence of Japanese encephalitis virus ling strain genome and comparison of the encoded structural proteins and nonstructural protein NS1 among Japanese encephalitis virus strains

Approximately 4000 nucleotides of the 5'-terminal portion of Japanese encephalitis virus (JEV) Ling strain genome were cloned and sequenced. This nucleotide sequence and its encoded C-PrM-E-NS1 polyprotein sequences were also compared with the corresponding sequences of other JE virus strains. Results demonstrated that the nucleotide sequence homology varied from 97.1 to 99.3% and the amino acid homology 98.6 to 98.9%. Based on homology, the Ling strain was closer to the Beijing-1 strain than to the SA14 and JaOArS982 strains. However, only on comparison of the E sequence, which neutralization, hemagglutination-inhibition and complement fixation antigenic determinants are located, between Ling and other JEV strains demonstrated that nucleotide sequence homology varied from 97.1% to 99.3% and amino acid homology from 98.6% to 99.2%. The Ling strain JEV is more closely related to the Beijing-1 strain than to the Nakayama NIH, SA14 and JaOArS982 strains in that order. Based on this analysis, the Taiwanese JEV strain appears to be more closely related to the Chinese strain than to the Japanese strain. Also, JEV strains isolated in humans are more closely related to each other than to JEV strains of mosquito isolates.     

Peptide mapping of 125I-labelled influenza virus proteins. Matrix proteins as markers in recombination

We have examined the matrix proteins of A/Okuda/57, A/Finland/4/74 and A/New Jersey/8/76 viruses and several recombinant strains by radioiodination of the purified polypeptides followed by tryptic peptide mapping. The method is rapid and requires only small amounts of material. Reproducible differences were detected between the matrix proteins of the above parents and allowed origin of the matrix proteins of the recombinant viruses to be determined. The possible use of matrix protein identity as a marker in recombination work is discussed.     

The structure and function of the HE protein of influenza C virus

The hemagglutinin-esterase (HE) glycoprotein is an integral membrane protein and the major surface antigen of influenza C virion. It displays three biological activities: receptor-binding activity for N-acetyl-9-O-acetylneuraminic acid, fusion with the host cell membrane, and receptor-destroying activity which is a neuraminate-O-acetylesterase. This protein undergoes four kinds of posttranslational processing: proteolytic cleavage, N-glycosylation, fatty acid acylation, and phosphorylation. We summarize here the data concerning the sites on the HE molecule responsible for the biological activities including antigenic epitopes as well as those concerning the role of posttranslational modifications in virus replication.     

Mutagenesis of the NS3 protease of dengue virus type 2

The flavivirus protease is composed of two viral proteins, NS2B and NS3. The amino-terminal portion of NS3 contains sequence and structural motifs characteristic of bacterial and cellular trypsin-like proteases. We have undertaken a mutational analysis of the region of NS3 which contains the catalytic serine, five putative substrate binding residues, and several residues that are highly conserved among flavivirus proteases and among all serine proteases. In all, 46 single-amino-acid substitutions were created in a cloned NS2B-NS3 cDNA fragment of dengue virus type 2, and the effect of each mutation on the extent of self-cleavage of the NS2B-NS3 precursor at the NS2B-NS3 junction was assayed in vivo. Twelve mutations almost completely or completely inhibited protease activity, 9 significantly reduced it, 14 decreased cleavage, and 11 yielded wild-type levels of activity. Substitution of alanine at ultraconserved residues abolished NS3 protease activity. Cleavage was also inhibited by substituting some residues that are conserved among flavivirus NS3 proteins. Two (Y150 and G153) of the five putative substrate binding residues could not be replaced by alanine, and only Y150 and N152 could be replaced by a conservative change. The two other putative substrate binding residues, D129 and F130, were more freely substitutable. By analogy with the trypsin model, it was proposed that D129 is located at the bottom of the substrate binding pocket so as to directly interact with the basic amino acid at the substrate cleavage site. Interestingly, we found that significant cleavage activity was displayed by mutants in which D129 was replaced by E, S, or A and that low but detectable protease activity was exhibited by mutants in which D129 was replaced by K, R, or L. Contrary to the proposed model, these results indicate that D129 is not a major determinant of substrate binding and that its interaction with the substrate, if it occurs at all, is not essential. This mutagenesis study provided us with an array of mutations that alter the cleavage efficiency of the dengue virus protease. Mutations that decrease protease activity without abolishing it are candidates for introduction into the dengue virus infectious full-length cDNA clone with the aim of creating potentially attenuated virus stocks.     

The ORF, regulated synthesis, and persistence-specific variation of influenza C viral NS1 protein

The open reading frame (ORF) and the regulated synthesis of the influenza C viral NS1 protein were analyzed in view of viruses possessing different biological activities. We provide evidence for a 246-amino-acid NS1-ORF, encoded by five viral strains and variants. Prokaryotic expression of the prototype NS1-ORF resulted in a product of 27 kDa, confirming the predicted molecular weight. Using an antiserum raised against recombinant NS1 protein, nonstructural proteins of wild-type virus were detected in infected cells for a limited course of time, whereas a persistent virus variant was characterized by a long-term nonstructural gene expression. As examined by infection experiments, the intracellular distribution of nonstructural protein was nuclear and cytoplasmic, whereas in NS1 gene-transfected cells, the cytoplasmic localization occurred in a fine-grained structure, suggesting an analogy to influenza A viral NS1 protein. Concerning persistent infection, NS1 protein species differing in sizes and posttranslational modifications were observed for a persistent virus variant, as particularly illustrated by a high degree of NS1 phosphorylation. Virus reassortant analyses proved the importance of the NS-coding genomic segment: the minimal viral properties required for the establishment of persistence were transferred with this segment to a monoreassortant virus. Thus the influenza C viral NS1 protein is a 246-amino-acid nuclear-cytoplasmic phosphoprotein that can be subject to specific variations being functionally linked to a persistent virus phenotype.