BEHAVIOR OF VIRUS-SPECIFIC ACTIVITIES IN TISSUE CULTURES INFECTED WITH MYXOVIRUSES AFTER CHEMICAL CHANGES OF THE VIRAL RIBONUCLEIC ACID

Persistent infections with Sendai virus and Newcastle disease viruses

Persistent infections (Pi) were established in two host-cell systems [Madin-Darby bovine kidney (MDBK) and Madin-Darby canine kidney (MDCK)] with Sendai virus and three strains of NDV, to test the influence of different viruses and host-cell systems. Virus was recovered from the persistently infected cells. An RNA- ts mutant was recovered from a Pi of MDBK cells, but no Pi could be established in MDCK cells with the three strains of NDV. Additionally, the Pi was established exclusively by a virulent strain, NDV-Milano. On the other hand, Sendai virus could establish Pi in MDBK and MDCK cell-systems. Several ts mutants were recovered from "late" passages of Pi, and from an accidental infection, a ts mutant with an altered P polypeptide. Ten other ts mutants were tested, however, the specific ts lesion could not be identified. From three Pi in MDCK cells, host range mutants (ts-f1, ts-f2, and ts-f3) were recovered. One of the mutants (ts-f1) has an altered M (matrix) protein. The host range mutants undergo a productive infection in MDBK and MDCK cells, which are nonpermissive for wild type Sendai virus. The possible significance of the results are discussed.

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.

Effect of inactivation by hydroxylamine on early functions of poliovirus

Evidence is presented that poliovirus particles with a single lethal hit by hydroxylamine do not induce in host cells either inhibition of cellular protein synthesis or viral ribonucleic acid (RNA) replication. The RNA of these viruses is not replicated even if the cells are simultaneously infected with both active and inactivated viruses. The damaged viral RNA seems to have lost both its template function and its function in the translation of normal viral proteins.

Marker rescue with ultraviolet-inactivated influenza virus

Influenza Al/CAM virus undergoes abortive growth in FL cells, whereas X-3311, a recombinant virus clone from the cross between CAM and NWS, is capable of complete replication in FL cells and plaque formation on FL monolayers (FL-marker). Clone 1-5C-4 cells are permissive for both viruses. When either clone 1-5C-4 or FL cells, which were mixedly infected with both ultraviolet-irradiated X-3311 and active CAM viruses, were plated on FL monolayers, infective centers far exceeding in number those expected from the surviving X-3311 virus were observed, i.e., the FL-marker of the irradiated parent was rescued. The significantly lower radiation sensitivity of FL-marker than that of infectivity indicates that only part of the genome is responsible for the FL-marker. The capability of X-3311 virus to produce NP antigen and its infectivity were lost at the same time when the former was assayed under the condition of low multiplicity of infection. This suggests that only infectious virus is capable of producing NP antigen and that no stepwise inactivation of the viral genome occurs. It is also suggested that any lethal ultraviolet damage inflicted upon the viral genome prevents the expression of the portion of the genome coding for NP antigen.

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.

Quantitative determination of neuraminidase-active foci in cell monolayer cultures infected with influenza or newcastle disease virus

A synthetic neuraminidase substrate [2-(3'-methoxyphenyl)-N-acetyl-alpha-neuraminic acid] was used to detect myxo- and paramyxovirus replication in tissue culture. This method allowed estimation of viral growth even in the absence of cytopathogenic effects.

Method for increasing the regularity of isolation of infectious ribonucleic acid from influenza virus

A more effective method of isolating infectious ribonucleic acid (RNA) from influenza virus was evaluated based on the enzymatic disintegration of the viral coat by Pronase, followed by phenol-detergent extraction of the RNA from susceptible and from resistant cells.

Ribonucleic Acid and Protein Synthesis in Chick Embryo Cells Infected with Fowl Plague Virus

Fowl plague virus comprised four major protein components and several minor ones, two strains of the virus giving similar results. One of the components was identified as the nucleocapsid protein. Synthesis of the virion proteins could readily be detected in infected cells 3 hr after infection. The two subcellular fractions associated with viral ribonucleic acid (RNA) polymerase activity (nuclei and ribosomal pellet) were associated with the protein of the nucleocapsid and a second virion protein of unidentified function. Measurement of viral RNA and protein synthesis in cells infected with preparations of ultraviolet irradiated virus showed that the capacity to synthesise the RNA and protein species of highest molecular weight was lost most quickly, suggesting that the pieces of viral RNA function independently.

Functional significance of sialidase during influenza virus multiplication: an electron microscope study

Morphological evidence has been obtained by electron microscopy in support of previous findings that one of the most important functions of sialidase is associated with the release of virus from infected host cells. Highly specific antiserum against fowl plague virus enzyme and specific antiserum against X7 recombinant influenza virus enzyme were shown to influence the morphology of cells infected with their homologous virus. In the presence of enzyme antiserum, an accumulation and aggregation of virus particles were evident on the cell surface and in the extracellular space of infected host cells. The aggregation of virus particles was interpreted to result from the inhibition of the release of virus.