Effect of hyperthermia on the antiproliferative activities of murine alpha-, beta-, and gamma-interferon: differential enhancement of murine gamma-interferon.
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Fever is frequently an important side effect of interferon (IFN) therapy. Studies have shown that culturing interferon-treated cells at elevated temperature heightens the antiproliferative activity of IFN-alpha and IFN-beta. Since IFN-gamma has also been shown to be a potent antiproliferative agent, the effect of elevated temperature on IFN-gamma activity was compared to its effect on IFN-alpha and IFN-beta. Mouse B-16 melanoma cells were simultaneously cultured under cloning conditions at a range of temperatures (37.3, 38.1, 38.6, and 39.4 degrees C) in the presence of MuIFN-alpha, MuIFN-beta, and MuIFN-gamma. The antiproliferative activities of all three interferons were enhanced by incubation at the elevated temperatures. However, the elevated temperatures had a more dramatic enhancing effect on the antiproliferative activity of MuIFN-gamma (10-fold enhancement) than of either MuIFN-alpha or MuIFN-beta (2.9- and 3.4-fold enhancement, respectively). Next, the enhancing effect of elevated temperature (39.4 degrees C) was examined for a range of interferon concentrations. The degree of the enhancing effect increased with increasing concentrations of MuIFN-gamma but not with increasing concentrations of MuIFN-alpha or MuIFN-beta. Enhancing effects of temperature as high as 14-fold were observed for 100 units of MuIFN-gamma/ml. This dramatic enhancement was observed for both natural and recombinant MuIFN-gamma and was neither a function of greater relative perception of MuIFN-gamma titer at elevated temperature nor a function of greater relative stability of MuIFN-gamma at the elevated temperature. The differential enhancement of MuIFN-gamma activity by elevated temperature appeared to be specific for the antiproliferative activity, since the antiviral activity of MuIFN-gamma was not relatively more enhanced at 39.4 degrees C than were the antiviral activities of MuIFN-alpha and MuIFN-beta. These results suggest that fever may be an important factor in maximizing the antitumor effects of MuIFN-gamma and perhaps of human IFN-gamma. They also raise the possibility that a combination treatment regimen of hyperthermia and interferon therapy, particularly IFN-gamma therapy, may provide a significant antitumor effect. (+info)
Cytotoxic T lymphocytes and natural killer cell activity in the course of mengo virus infection of mice.
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Inbred C57BL/6 mice were inoculated intraperitoneally (i.p.) with mengo virus. The activity of cytotoxic T lymphocytes (CTL) and natural killer (NK) cells were measured during the first 22 days following infection. The CTL response began 7 days after virus inoculation, persisted for at least 22 days and was related to the dose of the virus inoculated. NK cell activity was elevated within 24 hr, reached its peak level on the fourth day and declined to normal levels on the eleventh day after exposure to the virus. These results suggest that NK cells represent the first cellular immune response to restrict mengo virus spread while specific CTL appear later and are probably responsible for further restriction, elimination and prevention of the viral disease. (+info)
Toward an in vitro system for picornavirus assembly: purification of mengovirus 14S capsid precursor particles.
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Mengovirus 14S subviral protein particles generated in infected L cells and in a cell-free translation system primed with mengovirus RNA were purified by sucrose gradient centrifugation and immunoaffinity chromatography. The preparations from both sources contained essentially pure proteins epsilon, alpha, and gamma, as was demonstrated in terms of virus-specific proteins (by autoradiography) and total protein content (by silver staining of sodium dodecyl sulfate-polyacrylamide electrophoresis gels). These purified proteins sedimented as discrete particles at the 14S position when recentrifuged in sucrose gradients. Although their assembly properties have not yet been studied in detail, preliminary results indicate that during incubation with virion RNA the 14S particles purified from infected cells can form a structure cosedimenting with mature mengovirus. (+info)
Regulation of interferon-induced antiviral states: contrasting profiles of decay in response to the removal of MuIFN-alpha, MuIFN-beta and MuIFN-gamma.
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The stabilities of the antiviral states induced by different types of murine interferons (IFNs) were compared to gain insight into possible differences in the modes of regulation of their respective antiviral states. Both type I (MuIFN-alpha and MuIFN-beta) and type II (MuIFN-gamma) IFNs were employed to establish antiviral states against mengovirus in mouse L-929 cells. At various times after IFN treatment, the IFNs were removed and the stability of the antiviral states was determined by single cycle mengovirus yield reduction experiments. The antiviral states induced by the two type I IFNs decayed significantly by 12 h following IFN removal. The rate of this decay was an exponential function of the level of the antiviral state induced. A transcriptional block effectively delayed the decay of the antiviral state, suggesting the involvement of a positive feedback mechanism of regulation. In contrast, the profile of the antiviral state induced by type II IFN showed a significant enhancement upon MuIFN-gamma removal. This enhancement was not dependent upon de novo transcriptional and translational activity of the cells. These data suggest that the modes of regulation of the antiviral states against mengovirus induced by type I and type II IFNs are distinctly different. (+info)
Independent regulation of the antiviral states induced by MuIFN-alpha/beta and by MuIFN-gamma.
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The stability profiles of the antiviral states induced in L-929 cells against mengovirus by murine interferons MuIFN-alpha/beta and by MuIFN-gamma were shown to be different. Treatment of cells with combinations of IFN-alpha/beta and IFN-gamma have previously been shown to result in a potentiated expression of the antiviral state. Here we report studies of the stabilities of the antiviral states induced by various combinations of IFN-alpha/beta and IFN-gamma and that the regulation of the antiviral states induced by IFN-alpha/beta and IFN-gamma were independent of each other. (+info)
Selection and characterization of an interferon-responsive clonal cell line of HeLa cells.
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HeLa cells generally do not respond well to interferon (IFN). We have used is-1, an IFN-sensitive mutant of mengovirus, to select a clone of IFN-responsive HeLa cells (F-H12). At moderate levels of human alpha/beta IFN, is-1 yields were fivefold lower in these cells than in similarly protected control cells. In contrast, wild-type mengovirus, vesicular stomatitis virus and a wild-type and thymidine kinase-negative strains of herpes simplex virus type 1 grew equally well in both cell lines. By a cell survival assay, the F-H12 line was up to 100 times more responsive to IFN than the parental line when challenged by is-1. 2'-5'-Oligo(A)-dependent endonuclease activity was the same in both lines. These observations cannot be accounted for by enhanced induction of IFN following infection. (+info)
A kinase able to phosphorylate exogenous protein synthesis initiation factor eIF-2 alpha is present in lysates of mengovirus-infected L cells.
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Infection of mouse L929 cells by mengovirus resulted in the expression of a kinase activity that selectively phosphorylated the small, 38,000-molecular-weight subunit of eucaryotic initiation factor 2 and histone H2. This kinase activity was independent of host cell RNA synthesis and was located in the postribosomal supernatant (S-100 fraction) early after infection (up to 3 h). At later times after infection (5 h), kinase activity was also associated with the polysome fraction. The kinase present in the S-100 fraction bound strongly to DEAE-cellulose, its peak activity eluting at 0.5 M KCl. Kinase activity was independent of the presence of exogenous double-stranded RNA, and KCl at concentrations greater than 0.1 M inhibited eucaryotic initiation factor 2 phosphorylation. The 67,000-molecular-weight phosphoprotein activated in interferon-treated cells by double-stranded RNA was not detected by standard phosphorylation assays in lysates from mengovirus-infected cells. Labeling of this protein in vivo during 5 h of infection was also not detected. The DEAE-cellulose-purified mengovirus kinase inhibited protein synthesis in reticulocyte lysates, and the inhibition was not reversible by high concentrations of poly(I).poly(C). (+info)
Single amino acid changes that render human IFN-alpha 2 biologically active on mouse cells.
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Human IFN-alpha 1 and IFN-alpha 2 differ in 28 of 166 amino acids and show very different specific antiviral activities on human and murine cells. We have identified, by hybrid scanning and site-directed mutagenesis, three residues in IFN-alpha 2, in positions 121, 125 and 132 which, when replaced individually or jointly by their IFN-alpha 1 counterparts, modify its activity on mouse cells by up to 400-fold. We argue that these residues are involved in direct contacts with the mouse interferon receptor. (+info)