Interferon production in L cells persistently infected with hemagglutinating virus of Japan (HVJ)

Characterization of Sendai virus persistently infected L929 cells and Sendai virus pi strain: recombinant Sendai viruses having Mpi protein shows lower cytotoxicity and are incapable of establishing persistent infection

It is commonly accepted that the temperature-sensitive phenotype of Sendai virus (SeV) persistently infected cells is caused by the M and/or HN proteins. Expression level of the L, M, HN, and V proteins is extremely low in L929 cells persistently infected with SeVpi (L929/SeVpi cells) incubated at 38 degrees C. The HN protein quickly disappears in L929/SeVpi cells following a temperature shift up to 38 degrees C, and pulse-chase experiments show that the Lpi, HNpi, and Mpi proteins are unstable at 38 degrees C. Following a temperature shift either upward or downward, M protein is translocated into the nucleus and then localizes to the perinuclear region. None of virus-specific polypeptides are detected in the cells primarily infected with SeVpi and incubated at 38 degrees C and virus proteins are not pulse-labeled at 38 degrees C, indicating that temperature-sensitive step is at an early stage of infection. The Mpi protein is transiently located in the nucleus of the SeVpi primarily infected cells. Recombinant SeVs possessing the HNpi or/and Mpi proteins are not temperature-sensitive. The HN protein is expressed at very low levels and the F protein localizes to the perinuclear region in rSeV(Mpi)-infected cells incubated at 38 degrees C for 18 h. rSeVs having the Mpi protein exhibit lower cytotoxicity and are incapable of establishing persistent infection. Amino acid 116 of the Mpi protein is related to the nuclear translocation and lower cytopathogenesis, whereas aa183 is involved in the interaction between M protein and viral glycoproteins.

High resistance of human parainfluenza type 2 virus protein-expressing cells to the antiviral and anti-cell proliferative activities of alpha/beta interferons: cysteine-rich V-specific domain is required for high resistance to the interferons

Human parainfluenza type 2 virus (hPIV-2)-infected HeLa (HeLa-CA) cells and hPIV-2 V-expressing HeLa (HeLa-V) cells show high resistance to alpha/beta interferons (IFN-alpha/beta) irrespective of whether vesicular stomatitis virus or Sindbis virus is used as a challenge virus. When Sindbis virus is used, these cells show high susceptibility to human IFN-gamma. Furthermore, the multiplication of HeLa-V cells is not inhibited by IFN-alpha/beta. HeLa cells expressing the N-terminally truncated V protein show resistance to IFN-alpha/beta, showing that the IFN resistance determinant maps to the cysteine-rich V-specific domain. A complete defect of Stat2 is found in HeLa-CA and HeLa-V cells, whereas the levels of Stat1 expression are not significantly different among HeLa, HeLa-CA, HeLa-P, and HeLa-V cells, indicating that IFN-alpha/beta resistance of HeLa-CA and HeLa-V cells is due to a defect of Stat2. HeLa-SV41V cells show high resistance to all IFNs, and no expression of Stat1 can be detected. Stat2 mRNA is fully detected in HeLa-V cells. Stat2 was scarcely pulse-labeled in the HeLa-V cells, indicating that synthesis of Stat2 is suppressed or Stat2 is very rapidly degraded in HeLa-V cells. The V protein suppresses the in vitro translation of Stat2 mRNA more extensively than that of Stat1 mRNA. An extremely small amount of Stat2 can be detected in HeLa-V cells treated with proteasome inhibitors. The half-life of Stat2 is approximately 3.5 and 2 h in uninfected and hPIV-2-infected HeLa cells, respectively. This study shows that synthesis of Stat2 may be suppressed and Stat2 degradation is also enhanced in hPIV-2-infected HeLa and HeLa-V cells.

Effect of interferon on Vero cells persistently infected with Sendai virus compared to Vero cells persistently infected with SSPE virus

Persistent infections with Sendai and SSPE virus were established in Vero cells. Sequential passages of these cells were monitored by immunofluorescence and for their sensitivity to the antiviral and antiproliferative effects of interferon (IFN). The cells rapidly developed resistance to the antiviral effect of IFN as judged by the inability of IFN to inhibit the replication of exogenous Sindbis virus. This decrease was accompanied by a reduction in the induction of the 2'-5' oligo A synthetase. Both cell lines were resistant to the antiproliferative effect of IFN. A decrease or absence of IFN receptors on the surface of the cells was not found to be the cause of their resistance to IFN.

Effects of exogenous interferon on L cells persistently infected with Sendai virus

A carrier culture of L cells persistently infected with Sendai virus (steady state) designated as L-Sendaits cells was established with a temperature-sensitive strain of the virus. When interferon was added to culture fluids from the start of the cultures at permissive (35 degrees C) or non-permissive temperature (38 degrees C), cell-associated infectivity was unaffected at 35 degrees C, while it was unexpectedly enhanced at 38 degrees C, although the cell-associated infectivity was titrated after further incubation at 32 degrees C for 2 days. The titer of cell-associated infectivity was increased by subculturing in the continuous presence of interferon at 38 degrees C. The effect of interferon on the paradoxical enhancement of cell-associated infectivity was shown to be dose dependent. When L-Sendaits cells were successively subcultured 6 times at 38 degrees C in the continuous presence or absence of interferon, more than 95 per cent of the cells contained a detectable amount of nucleocapsid (NP) antigen in the presence of interferon, whereas the antigen could be detected in only 30-40 per cent of the cells subcultured in the absence of interferon. Only when the cells subcultured at 38 degrees C in the presence of interferon were transferred to permissive temperature, could the distinct hemadsorbing and cell-associated hemagglutinating activities and the release of virus particles, as measured by hemagglutinating activity in the culture fluids, be detected. Cells subcultured in the presence of interferon accumulated more virus polypeptides than in the absence of interferon. Accumulation of virus specific RNA in the cells subcultured in the presence of interferon was about twice as much as that in the absence of interferon. Larger sized RNA (probably 50S) was the major species and two smaller RNAs could be detected in both the treated and untreated cells. When L-Sendaits cells were cultured at 38 degrees C in the presence of interferon, their multiplication was clearly inhibited. However, the cells which were subcultured twice at 38 degrees C in the continuous presence of interferon acquired resistance to the anti-cell proliferative action of interferon. Interestingly, the conversion of the sensitive state to resistant state of the cells was reversible.

Establishment and preliminary characterization of a cell line persistently infected with Newcastle disease virus

A murine osteosarcoma (OGS) cell line was permanently infected with Newcastle disease virus (NDV). The presence of NDV in the subsequent passages was demonstrated by haemadsorption and by immunofluorescence. Compared to the uninfected OGS line the persistently infected cells had a slightly reduced growth rate and they had a reduced sensitivity to several viruses, shown by several different methods. Interferon sensitivity was considerably reduced in the OGS-NDV cells, both the antiviral activity and the cell multiplication inhibitory activity.

Search for Sendai 6/94 viral RNA in the antigen-free cell line Cl-C-2 isolated from human multiple sclerosis brain tissue

The viral antigen-free cell line Cl-C-2, obtained from multiple sclerosis brain tissue by cell fusion with CV-1 cells, was examined for the presence of intracellular virus-specific RNA sequences of the persistent Sendai 6/94 virus by nucleic acid hybridization. As a specific probe for this assay, an in vitro synthesized cDNA was used. Oligodeoxyguanidylic acid served as a primer for the initiation of cDNA synthesis. The 6/94 RNA was detectable as expected in the viral antigen-expressing cell lines Cl-E-8 and Cl-F-2, which were used as a reference of the same source. In the viral antigen-free cell line Cl-C-2, however, no viral RNA sequences have been found by hybridization experiments. Corresponding superinfection studies confirmed the conclusion that in cell line Cl-C-2 no viral components are present. The lack of expression of viral proteins and of protection against superinfection seems to be correlated with the lack of viral RNA in Cl-C-2 cells, which may eliminate the persistent virus by a cellular defense mechanism.

Interferon production and response to exogenous interferon in two cell lines of mouse brain origin persistently infected with Sendai virus

Two persistently infected cell lines established from C3H mouse brain cells infected in vivo with Sendai virus were shown to differ with respect to interferon (IF) production and response to exogenous IF. MB/Sen carrier cells contained 1-5 per cent antigen positive cells when examined by immunofluorescence, and virus was occasionally recovered from the culture medium. MB/SenAS carrier cells were maintained with 0.16 per cent Sendai antiserum in the supernatant medium. All MB/SenAS cells contained viral antigen and infectious virus was present in the culture medium. MB/Sen released IF spontaneously into the culture medium. Further IF production could be stimulated in MB/Sen by superinfection with Newcastle disease virus (NDV) or vesicular stomatitis virus (VSV). Exogenous IF provided good protection against VSV challenge. In contrast, MB/SenAS produced no IF spontaneously but could be stimulated by NDV and VSV to produce IF. Exogenous IF failed to reduce the amount of VSV released into the supernatant fluid. Replication of VSV was restricted in MB/SenAS as shown by a 2.3 log10 lower virus yield compared to MB/Sen.