Isolation of the nucleic acid of Newcastle disease virus (NDV)

Evaluation of Japanese encephalitis virus E and NS1 proteins immunogenicity using a recombinant Newcastle disease virus in mice

Japanese encephalitis (JE) is the most important cause of acute encephalitis syndrome (AES). Japanese encephalitis virus (JEV), the prototype member of the JE serocomplex, belongs to the genus Flavivirus. The immunogenic proteins envelope (E) and non-structural protein 1 (NS1) of JEV are widely explored for the development of vaccines and diagnostics against JEV. However, there are underlying concerns such as the risk of reversion of live-attenuated vaccines to high virulence, the incomplete inactivation of pathogens in inactivated vaccines and partial vaccine coverage. Newcastle disease virus (NDV) is an efficient viral vaccine vector to express several human and animal immunogenic proteins. In the present study, we have developed a recombinant NDV (rNDV), individually expressing the E and NS1 proteins of JEV (rNDV-Ejev and rNDV-NS1jev). The recovered rNDV-Ejev and rNDV-NS1jev were characterized in 9-day-old SPF embryonated chicken eggs and in cell culture. The vaccination of rNDV-Ejev and rNDV-NS1jev showed effective immunity against JEV upon intranasal immunization in BALB/c mice. The rNDVs vaccination produced effective neutralization antibody titers against both NDV and JEV. The cytokine profiling of the vaccinated mice showed an effective Th1 and Th2 mediated immune response. The study also provided an insight that E, when used in combination with NS1 could reduce the efficacy of only E based immunization in mice. Our results suggested rNDV-Ejev to be a promising live viral vectored vaccine against JEV. This study implies an alternative and economical strategy for the development of a recombinant vaccine against JEV.

Newcastle disease virus vector producing human norovirus-like particles induces serum, cellular, and mucosal immune responses in mice

Human norovirus infection is the most common cause of viral gastroenteritis worldwide. Development of an effective vaccine is required for reducing norovirus outbreaks. The inability to grow human norovirus in cell culture has hindered the development of live-attenuated vaccines. To overcome this obstacle, we generated a recombinant Newcastle disease virus (rNDV)-vectored experimental norovirus vaccine by expressing the capsid protein (VP1) of norovirus strain VA387. We compared two different NDV vectors, a conventional rNDV vector and a modified rNDV vector, for their efficiencies in expressing VP1 protein. Our results showed that the modified vector replicated to higher titers and expressed higher levels of VP1 protein in DF1 cells and in allantoic fluid of embryonated chicken eggs than did the conventional vector. We further demonstrated that the VP1 protein produced by rNDVs was able to self-assemble into virus-like particles (VLPs) that are morphologically similar to baculovirus-expressed VLPs. Evaluation of their immunogenicity in mice showed that the modified rNDV vector induced a higher level of IgG response than those induced by the conventional vector and by the baculovirus-expressed VLPs. The rNDV vectors predominantly induced IgG2a subclass antibody for the Th1 response, and specifically, high levels of gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), and interleukin-2 (IL-2) were detected in splenocytes. In addition, the modified rNDV vector induced a higher level of fecal IgA response in mice than did baculovirus-expressed VLPs. Our findings suggest that the rNDV vector is an efficient system to produce cost-effective VLPs in embryonated chicken eggs and has the potential to be used as a live-attenuated vaccine in humans.

IMPORTANCE

Noroviruses are the major cause of viral gastroenteritis worldwide. Currently, effective vaccines against norovirus infection are not available. In this study, we have evaluated Newcastle disease virus (NDV) as a vaccine vector for norovirus. Our results suggest that NDV can be used not only as a cost-effective method for large-scale production of norovirus-like particle vaccines but also as a live-attenuated vectored vaccine.

Newcastle disease virus fusion protein is the major contributor to protective immunity of genotype-matched vaccine

Virulent strains of Newcastle disease virus (NDV) can cause devastating disease in chickens worldwide. Although the current vaccines are substantially effective, they do not completely prevent infection, virus shedding and disease. To produce genotype-matched vaccines, a full-genome reverse genetics system has been used to generate a recombinant virus in which the F protein cleavage site has been changed to that of avirulent vaccine virus. In the other strategy, the vaccines have been generated by replacing the F and HN genes of a commercial vaccine strain with those from a genotype-matched virus. However, the protective efficacy of a chimeric virus vaccine has not been directly compared with that of a full-genome virus vaccine developed by reverse genetics. Therefore, in this study, we evaluated the protective efficacy of genotype VII matched chimeric vaccines by generating three recombinant viruses based on avirulent LaSota (genotype II) strain in which the open reading frames (ORFs) encoding the F and HN proteins were replaced, individually or together, with those of the circulating and highly virulent Indonesian NDV strain Ban/010. The cleavage site of the Ban/010 F protein was mutated to the avirulent motif found in strain LaSota. In vitro growth characteristics and a pathogenicity test indicated that all three chimeric viruses retained the highly attenuated phenotype of the parental viruses. Immunization of chickens with chimeric and full-length genome VII vaccines followed by challenge with virulent Ban/010 or Texas GB (genotype II) virus demonstrated protection against clinical disease and death. However, only those chickens immunized with chimeric rLaSota expressing the F or F plus HN proteins of the Indonesian strain were efficiently protected against shedding of Ban/010 virus. Our findings showed that genotype-matched vaccines can provide protection to chickens by efficiently preventing spread of virus, primarily due to the F protein.

Mutations in the fusion protein cleavage site of avian paramyxovirus serotype 4 confer increased replication and syncytium formation in vitro but not increased replication and pathogenicity in chickens and ducks

To evaluate the role of the F protein cleavage site in the replication and pathogenicity of avian paramyxoviruses (APMVs), we constructed a reverse genetics system for recovery of infectious recombinant APMV-4 from cloned cDNA. The recovered recombinant APMV-4 resembled the biological virus in growth characteristics in vitro and in pathogenicity in vivo. The F cleavage site sequence of APMV-4 (DIQPR↓F) contains a single basic amino acid, at the -1 position. Six mutant APMV-4 viruses were recovered in which the F protein cleavage site was mutated to contain increased numbers of basic amino acids or to mimic the naturally occurring cleavage sites of several paramyxoviruses, including neurovirulent and avirulent strains of NDV. The presence of a glutamine residue at the -3 position was found to be important for mutant virus recovery. In addition, cleavage sites containing the furin protease motif conferred increased replication and syncytium formation in vitro. However, analysis of viral pathogenicity in 9-day-old embryonated chicken eggs, 1-day-old and 2-week-old chickens, and 3-week-old ducks showed that none the F protein cleavage site mutations altered the replication, tropism, and pathogenicity of APMV-4, and no significant differences were observed among the parental and mutant APMV-4 viruses in vivo. Although parental and mutant viruses replicated somewhat better in ducks than in chickens, they all were highly restricted and avirulent in both species. These results suggested that the cleavage site sequence of the F protein is not a limiting determinant of APMV-4 pathogenicity in chickens and ducks.

Newcastle disease virus: macromolecules and opportunities

Over the past two decades, enormous advances have occurred in the structural and biological characterization of Newcastle disease virus (NDV). As a result, not only the complete sequence of the viral genome has been fully determined, but also a clearer understanding of the viral proteins and their respective roles in the life cycle has been achieved. This article reviews the progress in the molecular biology of NDV with emphasis on the new technologies. It also identifies the fundamental problems that need to be addressed and attempts to predict some research opportunities in NDV that can be realized in the near future for the diagnosis, prevention and treatment of disease(s).

Roles of the fusion and hemagglutinin-neuraminidase proteins in replication, tropism, and pathogenicity of avian paramyxoviruses

Virulent and moderately virulent strains of Newcastle disease virus (NDV), representing avian paramyxovirus serotype 1 (APMV-1), cause respiratory and neurological disease in chickens and other species of birds. In contrast, APMV-2 is avirulent in chickens. We investigated the role of the fusion (F) and hemagglutinin-neuraminidase (HN) envelope glycoproteins in these contrasting phenotypes by designing chimeric viruses in which the F and HN glycoproteins or their ectodomains were exchanged individually or together between the moderately virulent, neurotropic NDV strain Beaudette C (BC) and the avirulent APMV-2 strain Yucaipa. When we attempted to exchange the complete F and HN glycoproteins individually and together between the two viruses, the only construct that could be recovered was recombinant APMV-2 strain Yucaipa (rAPMV-2), containing the NDV F glycoprotein in place of its own. This substitution of NDV F into APMV-2 was sufficient to confer the neurotropic, neuroinvasive, and neurovirulent phenotypes, in spite of all being at reduced levels compared to what was seen for NDV-BC. When the ectodomains of F and HN were exchanged individually and together, two constructs could be recovered: NDV, containing both the F and HN ectodomains of APMV-2; and APMV-2, containing both ectodomains of NDV. This supported the idea that homologous cytoplasmic tails and matched F and HN ectodomains are important for virus replication. Analysis of these viruses for replication in vitro, syncytium formation, mean embryo death time, intracerebral pathogenicity index, and replication and tropism in 1-day-old chicks and 2-week-old chickens showed that the two contrasting phenotypes of NDV and APMV-2 could largely be transferred between the two backbones by transfer of homotypic F and HN ectodomains. Further analysis provided evidence that the homologous stalk domain of NDV HN is essential for virus replication, while the globular head domain of NDV HN could be replaced with that of APMV-2 with only a minimal attenuating effect. These results demonstrate that the F and HN ectodomains together determine the cell fusion, tropism, and virulence phenotypes of NDV and APMV-2 and that the regions of HN that are critical to replication and the species-specific phenotypes include the cytoplasmic tail and stalk domain but not the globular head domain.

Role of untranslated regions of the hemagglutinin-neuraminidase gene in replication and pathogenicity of newcastle disease virus

To determine the role of untranslated regions (UTRs) in replication and pathogenesis of Newcastle disease virus (NDV), we generated recombinant viruses with deletions in 5' and 3' UTRs of the HN mRNA. Deletion of any HN UTR did not noticeably affect in vitro replication of these viruses. However, complete deletion of the 5' UTR of the HN gene decreased the HN mRNA levels and HN protein contents in virus particles, resulting in attenuation of the virus in chickens. This indicates that the 5' UTR of HN mRNA plays an important role in replication and pathogenicity of NDV in vivo.

Adherence of human peripheral blood lymphocytes to measles-virus infected cells: modulation by solubilized rhesus erythrocyte membranes and carbohydrates

The adherence of human peripheral blood lymphocytes to HeLa cells persistently infected with measles virus (HeLa-K11) was studied. The following data were observed. (i) The proportion of HeLa-K11 cells with adherent human peripheral blood lymphocytes of rhesus monkey erythrocytes was similar over a wide range of ratios of HeLa-K11 cells to lymphocytes or erythrocytes. (ii) The great majority of human peripheral blood lymphocytes and erythrocytes reacted with the same HeLa-K11 cell (iii). The adherence of lymphocytes or erythrocytes to HeLa-K11 cells was blocked by rabbit anti-measles virus antibody or solubilized monkey erythrocyte membranes. The pretreatment of erythrocytes or lymphocytes with receptor-destroying enzyme did not alter their adherence properties. (iv) The pattern of inhibition observed with several carbohydrates was similar in both the erythrocyte and the lymphocyte adherence assays. These data are consistent with the possibility that the receptor present on both rhesus monkey erythrocytes and human lymphocytes has similar specificities and biochemical composition.

Isolation and characterization of defective interfering particle of Newcastle disease virus

Newcastle disease virus grown in embryonated eggs was separated and purified by sucrose density gradient centrifugation into two distinct type of particles, B and T, the former being normal virus particles with high activities of hemagglutination, hemolysis, neuraminidase and infectivity, the latter being non-infectious virus particles with low activities of hemolysis and neuraminidase but high hemagglutination activity. B and T particles were shown to share a common antigen by immunodiffusion test. T particles were deficient in viral RNA, since they contained only 13s RNA in a small amount, whereas B particles possessed a large amount of 57s RNA and a small amount of 13s RNA. T particles interfered with the multiplication of normal Newcastle disease virus in primary cultures of chick embryo cells.

Preparation of projection-less particles from influenza virus and their messenger activities in prokaryotic and eukaryotic systems

A fraction of projection-less particles was prepared from influenza A/Dunedin/4/73 and A/Victoria/3/75 (X-47) (H3N2) by detergent treatment and extraction into ether at 0 degrees C. The activity of this material in stimulating protein synthesis in vitro was studied and compared with that of isolated virion RNA using a) an RNA-dependent E. coli system, and b) a wheat germ system. In the bacterial system the purified RNA had the highest template activity, while in the eukaryotic system the disrupted particle preparation was by far the most active. Translation products were formed with immunological and electrophoretic properties similar to those of several influenza virion proteins. The experiments indicate that, when added in the form of disrupted projection-less particles, RNA from influenza A2 virus is utilized as a template by eukaryotic ribosomes.

Genome of infectious bronchitis virus

Techniques are described for the growth and rapid purification of the avian coronavirus infectious bronchitis virus (IBV). Purified IBV has a sedimentation coefficient of 320S and a buoyant density of 1.22 g/ml in sucrose-deuterium oxide equilibrium gradients. IBV RNA extracted by proteinase K in the presence of sodium dodecyl sulfate and further purified by phenol extraction and gradient centrifugation is single stranded and has a sedimentation coefficient of 64S, as determined by isokinetic gradient centrifugation. Analysis on sucrose gradients under both aqueous and denaturing conditions together with agarose gel electrophoresis in the presence of the chaotropic agent methylmercuric hydroxide gave a value of 8 X 10(6) for the moleclar weight of IBV RNA. This value was confirmed by RNase T1 fingerprinting, which also indicated that IBV RNA is haploid. No evidence was found of subunit structure in IBV RNA. From these results together with the recently reported observation that IBV RNA is infectious and contains a tract of polyadenylic acid (Lomniczi, J. Gen. Virol., in press), we conclude that the genome of the coronaviruses is a single continuous chain of about 23,000 mononucleotides that is of messenger polarity.

Combined antiviral effects of interferon, adenine, arabinoside, hypoxanthine arabinoside, and adenine arabinoside-5'-monophosphate in human fibroblast cultures

Adenine arabinoside and human interferon are currently being evaluated in clinical trials against herpes- and poxvirus infections. Interferon production is also a normal antiviral response. It is therefore important to examine the combined actions of interferon and antiviral arabinosides for possible synergy or antagonism. We have examined the antiviral activities of human fibroblast interferon, adenine arabinoside, hypoxanthine arabinoside, and adenine arabinoside 5'-monophosphate individually, using plaque inhibition of vaccinia and herpes simplex type 2 viruses in human skin fibroblast cultures. By combining doses of interferon and arabinosides that, acting alone, give intermediate degrees of plaque inhibition, we were able to compare the combined antiviral activity with that calculated from the activity of each inhibitor alone, assuming that the activities are statistically independent. Our results show that the plaque-inhibitory activities of interferon and the arabinosides tested are statistically independent. The results also show that the arabinosides do not destabilize the antiviral state previously induced by interferon, and that interferon pretreatment does not interfere with subsequent arabinoside action in infected cells. We have also found that arabinosides do not affect the induction of interferon synthesis by either Newcastle disease virus or double-stranded ribonucleic acid, and are not themselves interferon inducers.

Isolation of a transcriptive complex from Newcastle disease virions

An active transcriptive complex was isolated from purified virions of Newcastle disease virus. After disruption with Triton X-100 and high salt, soluble and particulate fractions were separated by density gradient centrifugation. The transcriptive complex, recovered at a density of 1.275 g/cm3, appeared as a nucleocapsid structure by electron microscopy. When analyzed by polyacryl-amide gel electrophoresis, the nucleocapsids consisted of the nucleocapsid protein, a minor protein of 53,000 molecular weight, and the large L protein. Nucleocapsids possessed less than 1% of the hemagglutinating and neuraminidase activities originally associated with virions. The active complex synthesized predominantly 11 to 20S RNA in vitro and approximately one-fourth of the RNA molecules contained polyadenylic acid segments. In the presence of S-adenosyl-L-methionine, the RNA molecules were capped and methylated at the 5' termini. The transcriptive complex was also capable of methylating exogenous Escherichia coli RNA in the absence of viral RNA synthesis.

Isolation and preliminary characterization of temperature-sensitive mutants of Newcastle disease virus

Temperature-sensitive (ts) mutants of Newcastle disease virus have been isolated and characterized genetically (complementation), biochemically (RNA synthesis) and biologically (fusion from within and hemadsorption). Fifteen of these mutants have been divided into five complementation groups. Groups A (five mutants) and E (one mutant) are ts for RNA synthesis (RNA-) as well as for the other functions. Group B contains four RNA+ mutants of which one is ts for fusion, one for hemadsorption and two for neither function. Group C contains one RNA+ mutant which is a poor cell fuser. Group D contains two RNA+ mutants which are ts for fusion. In addition, two noncomplementing mutants (group BC) fail to complement both group B and group C mutants while exhibiting complementation with mutants in groups A, D, and E.

Ultrastructure of tubular inclusions in endothelial cells of pituitary tumors associated with acromegaly

Tubular inclusions were present in 13 out of 43 pituitary adenomas of acromegalic patients and in a single chromophobe pituitary adenoma. There were none in 76 other pituitary adenomas with differing endocrinological symptomatology. The arrays were usually located in the perinuclear cistern of capillary endothelial cells. The tubule diameter in osmium fixed material measured 19-26 nm and the light core averaged 6-11 nm. A longitudinal period of about 4.5 nm could be demonstrated with PTA block staining. Fixation with glutaraldehyde and block staining with ethidium bromide as well as permanganate fixation followed by RNAse treatment showed only the core of the tubules consisting of globular subunits. Several histochemical reactions (perchloric acid extraction, methenamine-silver staining, trypsin and DNAse digestion of frozen sections) suggested that the particles consist of a core of DNA coated with protein. No virus multiplication could be detected in cell cultures or in mice innoculated with fresh tumor material. No significant antibody titers against several virus antigens could be demonstrated.

RNAs of influenza A, B, and C viruses

The nucleic acids of influenza A, B, and C viruses were compared. Susceptibility to nucleases demonstrates that influenza C virus, just as influenza A and B viruses, possesses single-stranded RNA as its genome. The base compositions of the RNAs of influenza A, B, and influenza C virus are almost identical and comparative analysis on polyacrylamide gels shows that the genome of influenza C/GL/1167/54 virus, like that of the RNAs of influenza A and B viruses, is segmented. Eight distinct RNA bands were found for influenza A/PR/8/34 virus and for influenza B/Lee/40 virus. The RNA of influenza C/GL/1167/54 virus separated into at least four segments. The total molecular weights of the RNA of influenza A/PR/8/34 and B/Lee/40 virus were calculated to be 5.29 X 10(6) and 6.43 X 10(6), respectively. A minimum value of 4.67 X 10(6) daltons was obtained for influenza C/GL/1167/54 virus RNA. The data suggest that influenza C viruses are true members of the influenza virus group.

Message activity of influenza viral RNA

The message activity of influenza virion RNA in the wheat germ cell-free protein-synthesizing system was investigated. RNA extracted from purified virions was found to direct the synthesis of a polypeptide that had the mobility of viral nucleocapsid protein on sodium dodecyl sulfate-polyacrylamide gels. Further characterization of the protein indicated it was not the nucleocapsid protein. No other polypeptides were detected. We conclude that influenza virion RNA is inactive as a template for the synthesis of virus-specific proteins.

Comparison of RNA polymerase associated with Newcastle disease virus and a temperature-sensitive mutant of Newcastle disease virus isolated from persistently infected L cells

An in vitro comparison was made of the RNA polymerase activity associated with Newcastle disease virus (NDVo) and three clones of the temperature-sensitive mutant (NDVpi) isolated from persistently infected L cells. Less polymerase activity was associated with the NDVpi clones. Also, compared to NDVo, an increase in incubation temperature from 32 to 37 or 42 C resulted in a marked decrease in polymerase activity for the temperature-sensitive mutants which coincided with their inability to replicate at 42 C.

Properties of feline leukemia virus. III. Analysis of the RNA

The kinetics of virus labeling was used to study the maturation of viral RNA in the Rickard strain of feline leukemia virus. Viral RNA labeled over differing intervals was characterized by gel electrophoresis and velocity sedimentation in sucrose gradients made up in aqueous buffer and 99% dimethyl sulfoxide. Labeled virus was found within 30 min after adding radioactive uridine to the cells and production of labeled virus reached a maximum at 4 to 5 h after pulse labeling. Native RNA from feline leukemia virus resolved into three size classes when analyzed by electrophoresis on 2.0% polyacrylamide-0.5% agarose gels: a 6.2 x 10(6) to 7.1 x 10(6) mol wt (50 to 60S) class, an 8.7 x 10(4) mol wt (approximately 8S) class, and a 2.5 x 10(4) mol wt (4 to 5S) class. From two experiments during which RNA degradation appeared minimal, these made up to 57 to 76%, 2 to 5%, and 6 to 12%, respectively, of the total RNA. The 8S RNA in feline leukemia virus has not previously been reported. The 50 to 60S RNA from virus harvested after 4 h of labeling electrophoretically migrated faster and sedimented more slowly in sucrose gradients than did the same RNA species harvested after 20 h of labeling. This argues for an intravirion modification of the high-molecular-weight RNA. The large subunits of denatured viral RNA from both 4- and 20-h labeled-viral RNA electrophoretically migrated with an estimated molecular weight of 3.2 x 10(6) but sedimented with 28S ribosomal RNA (1.8 X 10(6) mol wt) when analyzed by velocity sedimentation through 99% dimethyl sulfoxide.

Characterization of inactivation of myxoviruses and paramyxoviruses by hydroxylamine, N-methylhydroxylamine and O-methylhydroxylamine

A study of the mechanism of myxovirus and paramyxovirus inactivattion by hydroxylamine, O-methylhydroxylamine and N-methylhydroxylamine was conducted. Influenza A (WSN) was used as the sensitive myxovirus and Newcastle disease virus (NDV-L) was used as the relatively resistant paramyxovirus in certain experiments. Inactivation was found to be rapid (15 minutes) and mose effective at high concentrations (2M). All three compounds significantly decreased the hemagglutination titer of WSN treated at pH smaller than or equal to 5.0. There was no detectable change in NDV hemagglutination titer. Adsorption of hydroxylamine (pH 7.0) inactivated WSN appeared normal; however, the rate of adsorption was decreased when virus was inactivated by (pH 5.0) O-methylhydroxylamine. Equilibrium density gradient centrifugation in potassium tartrate showed no density changes in inactivated virus. WSN inactivated virus. WSN inactivated with 14C-O-methylhydroxylamine and subjected to RNA extraction showed greater than or equal to 35 percent of the 14C in the phenol phases and 21 per cent in the RNA. The 14C-O-methylhydroxylamine associated with the RNA of insensitive NDV was about 3 per cent of that associated with sensitive WSN-RNA. Hydroxylamine has no apparent effect on paramyxovirus (NDV) hemagglutination titer and less 14C-O-methylhydroxylamine is associated with the RNA of this virus. The results suggest these compounds may affect both the RNA and the envelope portion of myxoviruses (WSN) to produce inactivation.

Polyadenylate sequences on Newcastle disease virus mRNA synthesized in vivo and in vitro

Polyadenylate [poly(A)] sequences are associated with the 35 and 50S Newcastle disease virus (NDV)-specific RNAs as well as all six to seven of the 18-22S NDV-specific messenger RNAs extracted from infected chicken embryo cells. The poly(A) associated with the 18-22S RNA has an average size of 120 to 130 nucleotides. The 18-22S RNA synthesized in vitro by NDV's virion-bound polymerase contains six to seven species of the same size and relative proportions as its intracellular counterpart. This in vitro synthesized 18-22S RNA also contains covalently linked poly(A) sequences which, although variable in size, are usually larger and more heterogeneous than those from the infected cell. In vitro RNA synthesis is supported not only by magnesium (at an optimal concentration of mM) but by manganese (at an optimal concentration of 0.5 to 1.0 mM) as well. However, the major product made in the presence of manganese, although sedimenting at 18 to 22S, differs somewhat from the product made in the presence of magnesium.

Electron microscopy of viral RNA: molecular weight determination of bacterial and animal virus RNAs

A method for preparation of single-stranded RNA for electron microscopy determination of molecular weight is reported. The method uses treatment with formaldehyde at elevated temperatures to remove secondary structure and spreading in a protein monolayer from 50% formamide onto a 50% formamide hypophase. Molecular weights were determined for some bacterial and animal viruses, for which conflicting values had been reported earlier. Molecular weights determined by the method, using Escherichia coli large subunit rRNA for a standard (1.1 x 10(6)), are as follows: E. coli small subunit rRNA, 0.53 x 10(6); coliphage f2-RNA, 1.3 x 10(6); Qbeta-RNA, 1.55 x 10(6); and Newcastle disease virus RNA, 5.78 x 10(6).

Relationship between the RNA polymerase activities from influenza virions and influenza virus-infected cells

Two RNA polymerase activities were characterized in the cytoplasm of influenza Ao/NWS infected cells. Their relationship to the virion-associated RNA polymerase was studied.

Characterization of virus-specific RNAs from subacute sclerosing panencephalitis virus-infected CV-1 cells

CV-1 cells infected with subacute sclerosing panencephalitis (SSPE) virus incorporated uridine-(3)H into at least four virus-specific RNA components in the presence of actinomycin D. The component sedimenting fastest had a sedimentation coefficient of 50s corresponding to a molecular weight of 6 x 10(6). The other three RNA components have sedimentation constants of 35s, 22s, and 18s corresponding to molecular weights of 2.5 x 10(6), 1.0 x 10(6), and 0.75 x 10(6), respectively. The base composition of the 50s RNA is distinct from that of cellular RNA and comparable with base compositions of viral RNAs of other paramyxoviruses. The base composition of the 18s RNA shows approximate complementarity with the 50s RNA. RNA-RNA annealing experiments using unlabeled 50s SSPE RNA with labeled 18s RNA from cells infected with SSPE virus or measles virus show 100% annealing with 18s SSPE RNA but only 60% annealing with 18s measles RNA. These experiments suggest some differences between the 18s RNAs of SSPE virus-infected cells and measles virus-infected cells.

Separation of the messenger RNAs of Newcastle disease virus by gel electrophoresis

We have separated the 18-22S putative messenger RNA of Newcastle disease virus into seven species ranging in molecular weight from 0.55 to 1.53 x 10(6) using sodium dodecyl sulfate-acrylamide-gel electrophoresis at relatively high concentrations of acrylamide and for a relatively long time. Studies of the number and molecular weights of the proteins and the 18-22S RNAs of the virus suggests that these RNAs are in the right molecular weight range to code for the known proteins of Newcastle disease virus. In preliminary studies using this separation technique, we have demonstrated that: (a) there is no difference between the 18-22S RNA made during a normal infection and when genome replication is blocked; and (b) there is a strain-specific difference between the RNAs of Newcastle disease virus-AV and Newcastle disease virus-HP.

RNA-dependent DNA polymerase activity in preparations of a mutant of Newcastle disease virus arising from persistently infected L cells

RNA-dependent DNA polymerase activity was found in peparations of a mutant of Newcastle disease virus. The enzyme activity was not found in wild-type virus preparations.

Persistent infection of cells in culture by measles virus. 3. Comparison of virus-specific RNA synthesized in primary persistent infection in HeLa cells

The pattern of actinomycin D-resistant RNA synthesis was examined during primary infection of HeLa cells by virulent Edmonston measles virus and in two HeLa clones persistently infected by the same strain of virus. One of these clones, K11, produces infectious virus of low virulence for HeLa cells, and the other, K11A-HG-1, has thus far failed to yield infectious virus. The patterns of virus-specific RNA synthesized in these three types of infection are qualitatively similar to each other and to the patterns of virus-specific RNA synthesis in other paramyxovirus infections. There were, however, quantitative differences. In addition, virions of the virulent Edmonston strain of measles virus were found to contain high-molecular-weight RNA with a sedimentation constant identical to that of Newcastle disease virus.

Molecular weight determination of Sendai RNA by dimethyl sulfoxide gradient sedimentation

The molecular weight of the large RNA of Sendai virus has been determined by sedimentation analysis in sucrose gradients containing 99% dimethyl sulfoxide (DMSO) to be 2.3 x 10(6). Sendai RNA recovered from 99% DMSO was found to cosediment with nondenatured Sendai RNA at 46 to 48s in ordinary sucrose gradients. The molecular weight value of 2.3 x 10(6) is considerably smaller than the estimates of 6 x 10(6) to 7 x 10(6) determined under nondenaturing conditions, suggesting a unique structure for Sendai RNA.

Minor base composition of "70S-associated" 4S RNA from avian myeloblastosis virus

Using a chemical isotope derivative method, we have determined the minor base composition of the "70S-associated" 4S RNA isolated from avian myeloblastosis virus. The minor base composition of this "70S-associated" 4S RNA is strikingly similar to that of the corresponding "free" 4S RNA of the virion. This minor base content, plus the capacity to esterify amino acids, establishes that both of these virion 4S RNA fractions contain transfer RNA. The percentage of minor bases in virion "70S-associated" 4S RNA is, however, much lower than in "free" 4S virion RNA and in myeloblast 4S RNA. The implication is that the "70S-associated" 4S RNA fraction as isolated herein also contains RNA that is not transfer RNA. This latter RNA may represent either degradation products of high molecular weight RNA or indigenous 4S RNA of undetermined function.

Thermal inactivation of Newcastle disease virus. I. Coupled inactivation rates of hemagglutinating and neuraminidase activities

The thermal stability of Newcastle disease virus has been characterized in terms of the rate constants for inactivation of hemagglutinating activity (HA), neuraminidase activity (NA), and infectivity. Inactivation of HA results in the concomitant loss of NA. Infectivity, however, is much more thermolabile. Disintegration of the virus particle is not responsible for the identical rate constants for inactivation of HA and NA, nor is their parallel inactivation uncoupled in envelope fragments produced by pretreating the virus with phospholipase-C. The data indicate that a common envelope factor(s) can influence the thermal stability of both activities.

The nucleic acid of infectious bronchitis virus

The nucleic acid of infectious bronchitis virus (IBV), like that of other enveloped viruses, consists of discontinuous single stranded RNA. However, unlike many other viruses, there is extreme heterogeneity in the sizes of the RNA fragments, as revealed by centrifugation in sucrose gradients or electrophoresis in polyacrylamide gels. Two principal classes of RNA fragments are present:

A larger class comprising 74.9–85.4 per cent of total RNA and consisting of fragments having molecular weights ranging from 0.5×10⁶ to considerably greater than 3.0×10⁶ daltons and,

A smaller class comprising 9.1–19.7 per cent of total RNA with the size approximately that of ribosomal 4S RNA.

All IBV RNA's were fully susceptible to ribonuclease and had a buoyant density in caesium sulphate identical to that of tobacco mosaic virus RNA. No difference in the RNA profile for IBV was observed from the use of different methods of virus purification. The single-stranded RNA's of poliovirus and tobacco mosaic virus remained undegraded after preparation in the presence of IBV.

The 3'-terminal nucleosides of the high molecular weight RNA of avian myeloblastosis virus

The RNA isolated from avian myeloblastosis virus was fractionated by sucrose density gradient centrifugation. The 3'-OH terminal nucleosides of various fractions were determined by periodate oxidation followed by tritiated borohydride reduction. The 60-70S fraction and the 35S RNA derived from it by heating both have adenosine as the major terminal nucleoside, with cytidine as the next most frequent terminal. Control samples of tRNA(met) (f. coli) and 28S ribosomal RNA from mouse ascites tumor cells gave the expected terminal residues and molecular weights.

Viral ribonuclei acid synthesis by Newcastle disease virus mutants isolated from persistently infected L cells: effect of interferon

The synthesis of different viral ribonucleic acid (RNA) species was studied in chick embryo (CE) and mouse L-cell cultures infected with the Herts strain of Newcastle disease virus (NDV(o)) and a mutant isolated from persistently infected L cells (NDV(pi)). In CE cell cultures, both viruses synthesized significant amounts of 54, 36, and 18S RNA. However, in L cells, synthesis of 54S virion RNA was markedly reduced. From these results, it seems likely that the low yield of infective virus in L cells is due to a deficient synthesis of 54S RNA in this host. On this basis, however, it is apparent that the "covert" replication of NDV(o) in L cells is due to factors other than viral RNA synthesis. When low concentrations of interferon were used to pretreat CE cells, a differential effect on the synthesis of various RNA species was observed. The 18S RNA of NDV(o) was more sensitive to interferon action than the 36 and the 54S RNA species. In contrast, the 18S RNA of NDV(pi) was less sensitive than the 36S and the 54S RNA. The inhibition of 54S RNA synthesis correlated with the reduction of viral yield and explained the greater sensitivity of NDV(pi) to interferon.

RNA-dependent DNA polymerase activity of RNA tumor viruses. I. Directing influence of DNA in the reaction

The template requirements and deoxyribonucleic acid (DNA) products of the DNA polymerases isolated from Rauscher leukemia and avian myeloblastosis viruses have been examined. All DNA preparations or synthetic polydeoxynucleotides which are active as primers possess a duplex structure containing single-stranded regions with a 3'-hydroxyl terminus. Native DNA and fully single-stranded DNA are inactive; moreover, their activity is not enhanced by sonic oscillation or treatment with micrococcal nuclease, Neurospora nuclease, or low levels of deoxyribonuclease I. Poor DNA templates are activated by treatment with exonuclease III, large amounts of deoxyribonuclease I, or an endonuclease isolated from Rauscher viral preparations. In reactions primed with deoxyadenylate-deoxythymidylate copolymer, the product formed is covalently attached to primer strands, indicating that no new strands are initiated. DNA polymerase products formed with exonuclease III- or deoxyribonuclase I-treated DNA are duplex structures. Short single-stranded regions are completely filled in, whereas long single-stranded regions are only partly repaired. DNA preparations containing extensive single-stranded regions are poorly utilized as templates.

Relationship between the ribonucleic acid synthesizing capacity of ultraviolet-irradiated Newcastle disease virus and its ability to induce interferon

Ultraviolet (UV)-irradiated Newcastle disease virus which has lost its infectivity but has the capacity to induce interferon also has the capacity to induce ribonucleic acid (RNA) synthesis both in vitro and early in infection in vivo. With large doses of UV irradiation, RNA-synthesizing capacity and interferon-inducing capacity are lost in parallel. Limited amounts of base-paired RNA associated with a transcriptive intermediate are involved in this RNA synthesis. These findings suggest the possibility that the single-stranded RNA of the UV-irradiated virus induces interferon by serving as a template for the synthesis of base-paired RNA. UV irradiation of the virus breaks down viral RNA but at a rate which is too slow to be a major cause of the loss of RNA-synthesizing capacity. Evidence is presented which suggests that less of the template RNA of the UV-irradiated virus is copied and that the product which is synthesized is smaller than that synthesized by nonirradiated virus.

Electron microscope study of ribonucleic acid of myxoviruses

Intact ribonucleic acid (RNA) molecules in an extended form were extracted from purified influenza virus and observed in the electron microscope. For this study, the RNA extraction procedure and the Kleinschmidt protein monolayer technique were modified. The mean lengths of RNA from X7, X7-F1, and WSN strains of influenza virus were found to be 2.69, 2.55, and 2.37 mum, respectively. From these measurements, the corresponding estimated molecular weights would be 2.9, 2.8, and 2.5 x 10(6) daltons. X7 and WSN RNA preparations were exposed to pH 3 to disrupt intact molecules. Histograms of length measurements showed five peaks, which were interpreted to represent the five pieces of RNA reported to exist in the influenza virion. X7 RNA appeared to be more stable than WSN RNA when stored at 4 C. The profiles of histograms of incomplete virus RNA suggest that the high molecular-weight component is missing. In preliminary experiments on Newcastle disease virus RNA, molecules of various lengths were observed.

Ribonucleic acid polymerase in virions of Newcastle disease virus: comparison with the vesicular stomatitis virus polymerase

The virions of Newcastle disease virus (NDV) contained an enzyme that catalyzed the incorporation of ribonucleotides into ribonucleic acid (RNA). Optimal conditions for this polymerase activity were identical to the conditions for the vesicular stomatitis virus (VSV) polymerase, and both enzymes were active for longer times at 32 C than at 37 C. However, the specific activity of the NDV polymerase was less than 3% that of the VSV polymerase. Product RNA species from the NDV and VSV polymerase reactions annealed specifically to the homologous virion RNA species. Transcriptive intermediates containing product RNA attached to the respective virion RNA could be identified in both systems.

Proteins and glycoproteins of paramyxoviruses: a comparison of simian virus 5, Newcastle disease virus, and Sendai virus

The polypeptides of three paramyxoviruses (simian virus 5, Newcastle disease virus, and Sendai virus) were separated by polyacrylamide gel electrophoresis. Glycoproteins were identified by the use of radioactive glucosamine as a carbohydrate precursor. The protein patterns reveal similarities among the three viruses. Each virus contains at least five or six proteins, two of which are glycoproteins. Four of the proteins found in each virus share common features with corresponding proteins in the other two viruses, including similar molecular weights. These four proteins are the nucleocapsid protein (molecular weight 56,000 to 61,000), a larger glycoprotein (molecular weight 65,000 to 74,000), a smaller glycoprotein (molecular weight 53,000 to 56,000), and a major protein which is the smallest protein in each virion (molecular weight 38,000 to 41,000).

Nucleocapsid protein subunits of simian virus 5, Newcastle disease virus, and Sendai virus

Helical nucleocapsids of each of the paramyxoviruses simian virus 5 (SV5), Newcastle disease virus (NDV), and Sendai virus have been isolated in two different forms. One form contains larger protein subunits and is obtained from mature virions or infected cells dispersed by ethylenediaminetetraacetic acid. The other form possesses smaller subunits and is obtained from infected cells dispersed by trypsin. The estimated molecular weights of the larger subunits in the three viruses are similar: SV5, 61,000; Sendai virus, 60,000; NDV, 56,000. The smaller nucleocapsid subunits are also very similar: SV5, 43,000; Sendai virus, 46,000; NDV, 47,000. The helical nucleocapsid composed of the smaller subunit appears to be less flexible and more stable than that formed by the larger subunit. There is suggestive evidence that conversion of the larger subunit to the smaller by proteolytic cleavage may occur intracellularly. The possibility that such a mechanism could be involved in the accumulation of nucleocapsid in cells persistently infected with paramyxoviruses is discussed.