Newcastle disease virus RNA. I. Isolation and preliminary characterization of RNA from virus particles

Some properties of influenza virus nucleocapsids

Nucleocapsids released from influenza virions by sodium deoxycholate sedimented heterogeneously in sucrose gradients. Highly infectious virus (complete) preparations yielded nucleocapsids with peak distributions at 64 and 56S; von Magnus type virus (incomplete) lacked 64S nucleocapsids. Treatment of influenza virus nucleocapsids with pancreatic ribonuclease rendered the associated viral ribonucleic acid (RNA) molecules acid-soluble, indicating that capsid proteins do not completely surround the viral RNA's. However, the capsid proteins remained associated after enzymatic hydrolysis of the RNA, as judged by persistently high sedimentation rates. Sedimentation rates of viral nucleocapsids reflected the sedimentation rates of the associated RNA's: 64S nucleocapsids contained 18S RNA, whereas 56S nucleocapsids contained 15S RNA, although in both cases RNA's sedimenting at 4 to 13S were also recovered. Furthermore, just as incomplete virions lacked 64S nucleocapsids, they also lacked 18S RNA. These findings support the hypothesis that the influenza virus genome is divided among several distinct pieces of RNA.

High-level expression of a foreign gene from the most 3'-proximal locus of a recombinant Newcastle disease virus

A previous report showed that insertion of a foreign gene encoding chloramphenicol acetyltransferase (CAT) between the HN and L genes of the full-length cDNA of a virulent Newcastle disease virus (NDV) yielded virus with growth retardation and attenuation. The NDV vector used in that study was pathogenic to chickens; it is therefore not suitable for use as a vaccine vector. In the present study, an avirulent NDV vector was generated and its potential to express CAT protein was evaluated. The CAT gene was under the control of NDV transcriptional start and stop signals and was inserted immediately before the open reading frame of the viral 3'-proximal nucleocapsid protein gene. A recombinant NDV expressing CAT activity at a high level was recovered. The replication and pathogenesis of the CAT-expressing recombinant NDV were not modified significantly. These results indicate the potential utility of an avirulent NDV as a vaccine vector.

Recovery of a virulent strain of newcastle disease virus from cloned cDNA: expression of a foreign gene results in growth retardation and attenuation

A recombinant mesogenic NDV strain, Beaudette C, and an engineered recombinant NDV expressing an additional gene were generated entirely from cloned cDNAs. For this purpose, a full-length cDNA clone of the virus genome, represented in eight different subgenomic fragments, was assembled in a transcription plasmid between a T7 RNA polymerase promoter and a hepatitis delta virus ribozyme sequence. Infectious NDV could be generated in the cells infected with recombinant vaccinia virus, which expressed T7 RNA polymerase, by simultaneous expression of antigenome-sense NDV RNA from the full-length plasmid and NDV NP, P, and L proteins from cotransfected plasmids. Recombinant virus was then amplified and recovered, either after inoculation of transfection supernatant into the allantoic cavity of embryonated specific-pathogen-free eggs or after further passage in cell culture. Characterization of the recombinant NDV showed similarities in growth and pathogenicity to that of the parental wild-type virus. By using this system, a recombinant NDV containing a foreign gene encoding chloramphenicol acetyltransferase (CAT) was generated. To do this, the CAT transcription cassette containing the CAT open reading frame, flanked by NDV gene start and gene end sequence motifs, was inserted into the region between the HN and L genes of the full-length cDNA. This construct was then used in the generation of a recombinant NDV expressing CAT protein. The CAT gene was maintained stably for at least eight passages without any detectable loss of the gene from the recombinant. Generation of the recombinant virus, however, was associated with reduced plaque size, slower replication kinetics, and more than 100-fold decrease in yield. In addition, the virus showed an increase in mean death time for eggs and a lower intracerebral pathogenicity index in day-old chicks, implicating attenuation of the recombinant virus. Thus, introduction of an additional gene into the NDV genome represents a method to achieve growth retardation and attenuation. These results also indicate that NDV can be engineered to express foreign protein stably and can be manipulated in the future for use as a vaccine vector.

Characterization of paramyxoviruses isolated from three snakes

Multiple epizootics of pneumonia in captive snakes have been attributed to viruses which have been tentatively placed in the family Paramyxoviridae. Viruses isolated from an ill Neotropical rattlesnake (Crotalus durissus terrificus), from an Aruba Island rattlesnake (Crotalus unicolor), and from a bush viper (Atheris sp.) were propagated in Vero cells and characterized. Viral particles produced in Vero cells were pleomorphic, enveloped, and contained helical nucleocapsids. The viruses were sensitive to ether and to acidic and basic pH. Moreover, they had neuraminidase activity and were able to agglutinate erythrocytes from chicken and a variety of species of mammals. Hemagglutination was inhibited with rabbit antiserum raised against each virus. The buoyant densities of the three isolates ranged from 1.13/cm3 to 1.18/cm3, values consistent with that for an enveloped virus. The nucleic acid in the virion was determined to be RNA by [3H]uridine incorporation. Viral proteins characteristic of paramyxoviruses were immunoprecipitated from cells infected with each of the three isolates using rabbit anti-Neotropical virus serum. The morphologic appearance, physico- and biochemical properties, and cytopathologic effects of these snake viruses were consistent with those of certain members of the family Paramyxoviridae.

A model for the study of the mechanism of a low pH-induced interaction of the virus fusion proteins and cell membranes

A model is proposed for the study of molecular mechanisms of a low pH-induced interaction of fusion proteins of enveloped viruses and cell membranes. The model consists of large monolamellar liposomes containing ionophore nigericin in their membranes and ectodomains of fusion protein in their inner space. The process of interaction of the protein with the lipid bilayer is triggered by acidification of the liposomal constituents to the pH of fusion with the help of nigericin by adding citric acid to the outer medium. To visualize the protein structural reorganization, the tritium planigraphy was used. Comparison of the values of specific labelling of the proteins and distribution of radioactivity in individual amino acids in control (at neutral pH) and experimental liposome samples (at the pH of fusion) permits to realise the character of protein-membrane interaction. We have obtained the first results in the study of interaction of the bromelain-released soluble ectodomain of the HAXX molecule (BHA)--with the lipid membrane. The observed increase in the protein specific activity and selective increase in the specific activity of hydrophobic amino acids Ile, Phe and Tyr in experimental liposome samples as compared with the controls did not contradict to the conventional concept, that a hydrophobic N-terminus of HA2 subunit of hemagglutinin is responsible for its interaction with lipid membranes.

Transfer of condensed viral DNA into eukaryotic cells using proteoliposomes

High-molecular-weight viral DNAs have been packed into proteoliposomes prepared by reverse-phase evaporation followed by phospholipid membrane targeting by influenza virus glycoprotein bound to hydrophobic 'anchors'. DNA has been encapsulated in the form of spermine condensates--toroidal structures sized approx. 0.1 micron, resistant to ultrasound. The efficiency of entrapping into liposomes reached 30% for condensed DNA of Mr up to 3 X 10(7). Specific infectivity of simian virus 40 DNA and simian adenovirus DNA packed into such proteoliposomes was 50- to 100-fold higher than that shown by free DNA preparations under Ca.phosphate-precipitation conditions.

Influence of membrane (M) protein on influenza A virus virion transcriptase activity in vitro and its susceptibility to rimantadine

The transcriptase activity of influenza A virus ribonucleoproteins was inhibited by 42 to 49% in vitro in the presence of membrane (M) protein. The addition of M protein to the system of ribonucleoprotein preparations isolated from rimantadine-sensitive or rimantadine-resistant influenza virus strains, as well as the addition of M protein isolated from a sensitive strain, in the presence of rimantadine further inhibited the transcriptase activity of such complexes by approximately 40%. In the system containing the same ribonucleoprotein preparations, but with M protein isolated from a rimantadine-resistant influenza virus strain, the transcriptase activity was not sensitive to rimantadine. The data show that M protein can influence the activity of influenza A virus virion transcriptase and that the susceptibility of influenza virus to rimantadine may be due to the peculiarities of M protein.

The rapid isolation of ribonuclease-free immunoglobulin G by protein A-sepharose affinity chromatography

A rapid method is described for the simultaneous removal of contaminant ribonuclease activity and isolation of immunoglobulin G from fractionated or whole serum using insolubilized protein A. Protein A, isolated from the Cowan I strain of Staphylococcus aureus, was covalently attached to Sepharose CL-4B resin and used as a specific affinity absorbent for immunoglobulin G. Affinity column-purified immunoglobulin G preparations were examined for the presence of contaminating serum proteins, retention of antibody activity, and retention of antigenic properties. Following chromatography on protein A-Sepharose, immunoglobulin G preparations were devoid of contaminating serum proteins, in particular ribonuclease activity, that are not normally removed using conventional techniques of salt precipitation in combination with ion-exchange chromatography. There was no significant alteration of either antibody activity or antigenic properties of protein A-Sepharose purified immunoglobulin G.

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.

Comparative study of the electrophoretic mobility of the RNA of influenza parent and recombinant strains

The electrophoretic mobility of the RNA of Influenza viruses A/WSN, A/Singapore and their antigenic recombinants X-7 and X-9 was investigated. The genome of each virus studied consisted of seven pieces of RNA. The electrophoretic profile of the influenza virus A/WSN RNA differed from that of A/Singapore but resumbled that of the recombinant X-9 genome. The essential differences were connected with the properties of the fifth fragment of the RNA. The molecular weight of this RNA species of influenza virus A/WSN and X-9 was 5.4 X 10(5) AND 5.3 X 10(5) daltons (d) respectively. The molecular weight of the corresponding component of the influenza viruses A/Sinapore and X-7 RNA was 6.2 X 10(5) and 6.3 X 10(5)d respectively.

Methylation of messenger RNA of Newcastle disease virus in vitro by a virion-associated enzyme

Purified Newcastle disease virus contains an enzyme that incorporates the methyl group from S-adenosyl-L-methionine into RNA synthesized in vitro by the virion-associated RNA polymerase (RNA nucleotidyltransferase). Incorporation of radioactivity from S-adenosyl-L-[methyl-3H]methionine was totally dependent upon RNA synthesis. The methylation reaction was completely inhibited by S-adenosyl-L-homocysteine, suggesting the transfer of only the methyl group of S-adenosyl-methionine to RNA products. Velocity sedimentation and hybridization of the in vitro product RNA indicated that both [3H]methyl and [32P]GMP labels resided in single-stranded 18S RNA molecules which were virus specific. Approximately 1 to 2 methyl groups were incorporated per RNA molecule. DEAE-cellulose chromatography of product RNA after alkaline hydrolysis suggested that the 5' terminus was the site of methylation.

Strain-specific degradation of a viral glycoprotein in Newcastle disease virus-infected cells

In cells infected with mesogenic or lentogenic strain of Newcastle disease virus the level of neuraminidase and hemagglutinin activities sharply decreased after the addition of cycloheximide. With two velogenic strains such decreases did not occur. The infected cells were labelled with 14C-amino acids (leucine or valine) and further incubated with an excess of unlabelled precursor. Polyacrylamide gel analysis revealed a decrease of the peak correspondig to the "large" glycoprotein after the chase in cells infected with meso- or lentogenic strain (Beaudette, B1). In the cells infected with velogenic strains (Italia, Herts) no such decrease was observed. The degradation of the "large" glycoprotein as the cause of the decrease of hemagglutinin and neuraminidase activities in cycloheximide-treated cells and its possible relation to virulence is discussed.

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.

The ribonucleic acid of infectious bronchitis virus

Analysis of the nucleic acid of infectious bronchitis virus by SDS polyacrylamide gel electrophoresis revealed an RNA of molecular weight 9.0 times 10-6 Daltons. The RNA was shown to have a sedimentation coefficient of 50.

Self-annealing of Sendai virus RNA

Both complementary strands are found in 50S Sendai virion RNA. 50S Sendai virion RNA has been shown to consist of unequal amounts of a single population of plus and minus strands by annealing studies.

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.

Structural characteristics and nucleotide sequence analysis of genomic RNA from RD-114 virus and feline RNA tumor viruses

The results of molecular hybridization experiments have demonstrated that the RNA genome of RD-114 virus has extensive nucleotide sequence homology with the RNA genome of Crandell virus, an endogenous type C virus of cats, but only limited homology with the RNA genomes of feline sarcoma virus and feline leukemia virus. The genomic RNAs of RD-114 virus and Crandell virus also had identical sedimentation coefficients of 50S. A structural rearrangement of genomic RNA did not exist within released RD-114 virions, whereas a structural rearrangement of genomic RNA did occur within feline sarcoma virions and feline leukemia virions after release from virus-producing cells.

Cell-free translation of paramyxovirus messenger RNA

Polypeptides corresponding in electrophoretic mobility to virion polypeptides 1, 3, and 5 were made in a reticulocyte cell-free system to which 18S RNA from Sendai virus-infected cells was added. Immune precipitation was used to select relevant polypeptides from endogenous products. The cell-free product corresponding to virion polypeptide 3 (the nucleocapsid structure unit) was the most abundant; its tryptic peptides comigrated electrophoretically with tryptic peptides of polypeptide 3 isolated from virions. Other sedimenting classes of RNA from infected cells were tested; only the 28S fraction showed slight activity. Virion 50S RNA was inactive. These findings support the hypothesis that complementary RNA transcripts of paramyxovirion RNA are the templates for viral proteins.

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.

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.

Structural rearrangement and subunit composition of RNA from released Soehner-Dmochowski murine sarcoma virions

Two types of genomic, high-molecular-weight RNA species were found in Soehner-Dmochowski murine sarcoma virions released from virus-induced rat tumor cells grown in tissue culture. The type of RNA species observed depended on the length of exposure of the tumor cells to radioactive precursor. Early RNA of virions labeled up to 4 h with radioactive uridine had a sedimentation coefficient of 50S, and late RNA of virions labeled for 24 h had a sedimentation coefficient of 58S. Thermal transitions of early and late RNA indicated a difference in the configuration or structure of these two types of RNA. The late RNA may represent either a different configurational state of the early RNA or an aggregate molecule of two early RNA components joined together. Heat dissociation revealed that the major subunit of both RNA types was a 28S species, which was not susceptible to degradation by the addition of micrococcal nuclease to virions. A transitional, intermediate RNA species with a sedimentation coefficient of 37 to 40S was detected when early RNA was dissociated by dimethyl sulfoxide or heat at temperatures suboptimal for complete conversion. No free RNA subunit components were detected in virions harvested at intervals as short as 30 s or 5 min. A model for the assembly of genomic RNA from 28S RNA subunits is proposed.

Mumps virus replication in chick embryo lung cells: properties of ribonucleic acids in virions and infected cells

Ribonucleic acid (RNA) species in mumps virions and in infected cells were compared. The predominant RNA species in virions labeled with (3)H-uridine sedimented at 50S; RNA species sedimenting at 28, 18, and about 10S were also present. The virion-associated RNA species sedimenting slower than 50S contained some nucleotide sequences similar to 50S virion RNA. Although mumps virus replication was severely inhibited by high concentrations of actinomycin D, some virus was made, and virus-specific RNA species accumulated in infected cells. Mumps virus resembled other paramyxoviruses in inducing, in infected cells, synthesis not only of 50S RNA but also of slower sedimenting RNA species with a peak distribution at about 18S, complementary in base sequences to 50S virion RNA. In addition, base sequences of the parental type were relatively abundant in the RNA species sedimenting slower than 50S; these may represent precursors of the slowly sedimenting RNA species associated with virions. Ribonuclease-resistant RNA was detected in infected cells; this may represent replicative or transcriptive intermediates. Inhibition of protein synthesis with cycloheximide severely depressed accumulation of labeled 50S RNA in infected cells but did not interfere with accumulation of RNA species sedimenting slower than 50S. Actinomycin D treatment had a similar effect. Annealing of genomes and virus-induced complementary RNA species of Newcastle disease virus, Sendai virus, and mumps virus did not reveal any base sequence homologies.

Ribonucleic acid polymerase activity in Sendai virions and nucleocapsid

After dissociation of purified Sendai virus with the neutral detergent Nonidet P-40 and 2-mercaptoethanol, it catalyzed the incorporation of ribonucleoside triphosphates into an acid-insoluble product. The enzyme activity was associated with viral nucleocapsid as well as whole virions. The reaction product was ribonucleic acid (RNA) which annealed specifically with virion RNA. Sedimentation of the (3)H-RNA reaction product revealed two components, a 45S component with properties of double-stranded RNA and 4 to 6S component which appeared to be mostly single-stranded RNA.

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.