Modulation of natural killer cell activity in mice after interferon induction: depression of activity and depression of in vitro enhancement by interferon.

Splenic natural killer (NK) cell activity of BALB/c and C3H mice was assayed after administration of the interferon inducers Escherichia coli endotoxin or Newcastle disease virus (NDV). As expected, the NK cell activity rose early in response to the interferon inducers. At 1 to 3 days after an injection of endotoxin, NK activity was hyperesponsive to interferon stimulation. At 5 to 9 days after injection of either endotoxin or NDV, splenic NK activity was depressed, and the spleen cells showed a relative refractoriness to in vitro interferon stimulation. It is postulated that this phenomenon may be related to hyporeactivity, the inability to reinduce interferon after an initial period of interferon production.     

Effect of bacteriocins on interferon production.

The level of interferon induced with NDV in human diploid cell cultures treated with pyocins was decreased compared with the control culture. This effect was maximal when pyocins were given simultaneously with interferon inducers. In experiments in vivo it was shown that pyocin itself induced very small amount if any of interferon, but administered together with NDV inhibited production of circulating interferone in mice. Similar decrease of interferon production was found when other bacteriocins, namely pneumocin 114 or E-47 aerocin, were used.     

Suppression of interferon production in mouse spleen cells by cytochalasin D.

Cytochalasin D is thought to impair microfilament function. The present study has investigated its effects on four different systems in which interferon is formed, namely (1) mouse fibroblasts induced with virus (2) mouse spleen cells induced with virus, or (3) with endotoxin or (4) by allogeneic stimulation. Cytochalasin D did not suppress formation of interferon by fibroblasts (L cells) or spleen cells stimulated with either HVJ or NDV. However it did suppress production of interferon by spleen cells in response to endotoxin or an allogeneic stimulation; here its action was apparently not on the secretion of interferon, but on some earlier event. It also suppressed the production of interferon by mouse spleen cells induced with HVJ if this had been u.v. irradiated for more than 15 min: this suggests that cytochalasin D sensitive structures do play some role in interferon production by mouse spleen cells when stimulated with HVJ, as well as when they are stimulated with endotoxin or an allogeneic stimulus.     

Interferon induction by viruses and polynucleotides: a differential effect of comptothecin.

The plant alkaloid comptothecin inhibits interferon production induced by Newcastle disease virus (NDV) or ultraviolet-irradiated NDV in chick and human cells, and by Sindbis virus in chick cells. It has no effect on interferon production induced by poly (rI).poly(rC) in chick and human cells. No effect of comptothecin could be detected on the multiplication of NDV, and it is concluded that the inhibition reflects a difference between interferon induction by viruses and by polynucleotides.     

Effect of measles-virus infection and interferon treatment on invasiveness of Shigella flexneri in HEp2-cell cultures

The influence of measles-virus infection on the invasiveness of Shigella flexneri in HEp2-cell cultures was studied. Bacterial invasiveness was significantly enhanced in cell cultures incubated with virus before bacterial inoculation. This effect was a function of time after introduction of virus to the cell cultures and of the concentration of virus. The increase in bacterial invasiveness was observed before production of infectious virus particles and before a cytopathic effect was evident. A similar enhancement of invasiveness was demonstrated when cell cultures were pretreated with UV-inactivated measles virus. Pretreatment of cells with interferon did not influence invasiveness, although it reduced the effect of measles-virus infection.     

Effect of verapamil on interferon production, mastocyte degranulation and histamine release--studies in mice sensitized with ovalbumin

The effect of verapamil, calcium antagonist, on the IFN production, the histamine release and degranulation of mastocytes were studied. The mastocytes were harvested from mice sensitized with ovalbumin, treated with verapamil and induced with Newcastle virus (NDV) to the interferon production (IFN). It has been shown that the percentage of degranulation was lower in mastocytes of the mice treated with verapamil, both induced with NDV and non-induced ones. The titer of interferon was lower when the mice induced with virus were injected with verapamil. The inhibitory effect of this drug on histamine release has only been found on the 8th day after the sensitization.     

The influence of immunization on the production of interferon in vivo and in vitro.

The present study was undertaken to compare the production of interferon by immunized mice in response to different viral inducers. Porton mice were immunized with NDV or A/Wr11/57 virus by injecting 6-week-old animals with virus on days 1, 7, and 14. The interferon response was investigated 3 weeks later. Compared with controls, the A-immunized mice after stimulation in vivo, produced more interferon when NDV was used as inducer. It was shown in sera as well as in washings of peritoneal cells. In experiments in vitro induction of interferon with NDV or A/Wr11/57 virus in macrophages of immunized mice resulted in significant rise in interferon levels. These results are in agreement with earlier investigation of others and support the role of immune recognition in the interferon response.     

Induction and properties of guinea pig serum interferon. Preliminary report

Guinea pigs, 250-350 g body weight, both sexes, were injected with 5X10(8.5) EID50 NDV (Radom strain) intracardially and intraperitoneally simultaneously. The animals were bled by cardiac puncture 0, 3, 6, 12, 24 and 48 hours after injection. After virus inactivation, serum interferon titration was performed in cultures of guinea pig embryo kidney cells with 50 percent plaque inhibition test using VSV. The highest interferon titer (64 u./ml) was found after 6 hours of inductor injection. Interferon titer decreased quickly and after 12 hours it was lower than 16 u./ml. Guinea pig serum interferon induced by NDV was resistant to pH 2 and 56 degrees C during 1 hour. Interferon was inactivated by trypsin. The decribed interferon did not protect heterologous species cells (swine) against Teschen Disease Virus infection. Other properties of this interferon are being studied.     

Murine cytomegalovirus: induction of and sensitivity to interferon in vitro.

Moderate amounts of viral inhibitor were produced by mouse embryo (ME) cultures infected with two strains of plaque-purified murine cytomegalovirus (MCV). This inhibitor was shown to be interferon, based on the possession of similar properties. The growth studies of MCV in ME cells showed that interferon was produced as early as 4 h after infection, infectious virus was produced between 12 to 16 h, and cytopathic effect was produced between 16 to 18 h. Since MCV-induced interferon production and the subsequent development of antiviral state occurred early, the long eclipse period may be due to an interferon-mediated delay of virus replication. Pretreatment of ME cells with varying concentrations of interferon before infection with MCV did not result in increased interferon production, but at high pretreatment doses a slight inhibitory effect on interferon production was observed. In vitro sensitivity studies showed that small doses of MCV were highly sensitive to the antiviral action of interferon, but higher viral doses proved to be markedly resistant. Although the available evidence does not permit a definitive interpretation of the mechanism by which MCV may show differing sensitivities to interferon action, the presence of a small interferon-resistant fraction of virus-infected cells may account for the observations.     

Distinguishing characteristics of interferon induction with poly(I)-poly(C) and Newcastle disease virus in human cells.

Exposure of a human diploid foreskin cell strain (FS-4) to polyinosinate-polycytidylate [poly(I)·poly(C)] resulted in an early rise of interferon production that peaked at about 4 hr after induction and decreased rapidly thereafter. Irradiation of cells with low to moderate doses of ultraviolet (uv) light immediately before induction with poly(I)·poly(C) increased the amount of interferon produced up to about tenfold. This enhancement was apparently due to interference with the shut-off process which in unirradiated cells leads to early termination of interferon production; in irradiated cells interferon production continued for much longer.Inoculation of FS-4 cells with Newcastle disease virus (NDV) resulted in interferon production that showed a slower rise and peaked only at about 10–15 hr after inoculation. Irradiation of cells at the time of induction with NDV resulted in a dose-dependent decrease of interferon production. However, a small fraction of the total amount of interferon produced in response to NDV, which appeared by about 5 hr after virus inoculation, was resistant to uv. This uv-resistant early peak of NDV-induced interferon was greatly enhanced in cells which 6 hr before virus inoculation had either been induced with poly(I)·poly(C) or incubated with interferon, while the appearance of the major, uv-sensitive peak of NDV-induced interferon was inhibited or delayed after the same treatments. In its characteristics the early peak of NDV-induced interferon resembled the poly(I)·poly(C)-induced interferon response. Poly(I)·poly(C)-induced, as well as the early and late NDV-induced interferons were all neutralized by an antiserum raised against poly(I)·poly(C)-induced interferon, suggesting that they represent products of the same structural gene(s). It is concluded that there may be more than one mechanism of interferon induction by a single virus.     

Differences in the response of normal and transformed BHK21 cells to dual virus infection. Conditions affecting synergism between vesicular stomatitis virus and newcastle disease virus

Polyoma-transformed BHK21 cells were less sensitive than untransformed BHK21 cells to plaque production by vesicular stomatitis virus (VSV) although neither the adsorption of the input virus to transformed cells nor the burst size were found to be reduced. Infection of either cell type with an avirulent strain (BI) of Newcastle disease virus (NDV) resulted in only a single cycle of noninfectious NDV hemagglutinin production. Neither BHK21 cells nor a polyoma-transformed clonal derivative (Cl-I) produced detectable interferon in response to NDV infection. On the contrary, dual infection with NDV and VSV resulted in a paradoxical enhancement of VSV plaque number and size in Cl-I but not in BHK21 cells. The degree of synergism was affected by the density of Cl-I cell cultures, by NDV multiplicity, and by the time interval between NDV and VSV infection. These findings suggest that alteration of cell functions affecting cellular sensitivity to single (VSV) and also dual (NDV-VSV) infection may be associated with the virus-transformed state.     

Participation of cytophilic antibody in enhancement of interferon production in macrophages by under-neutralized NDV

Summary Enhancement of interferon production in mouse peritoneal macrophages by Newcastle disease virus (NDV) under-neutralized with whole antiserum or its IgG fraction was inhibited in cells pretreated with iodoacetamide, sodium nitrite or formaldehyde, which blocked adsorption of cytophilic antibody to macrophages. Mouse embryo primary culture cells had no receptor for cytophilic antibody, and in such a cell culture, under-neutralized NDV did not enhance interferon production. Antiserum enhanced interferon production by NDV which had adsorbed to cell surfaces, but did not affect NDV that had penetrated the cells.     

Influence of acute and fractional X-irradiation on induction of interferon in vivo

Summary Acute X-irradiation with 350 R increased the synthesis of interferons induced by poly IC and endotoxin in individual sera of BALB/c mice. Fractional irradiation with 4.7 or 9.4 R daily up to total dose levels of 728, 977 and 1828 R in three different experiments had no influence on serum interferon levels induced by Semliki Forest Virus (SFV), poly IC or endotoxin. The Newcastle Disease Virus (NDV) induced interferon synthesis decreased in comparison to the non-irradiated control at a total dose of 400 R and attained the control level on further elevation of the total dose. The anti-NDV antibody production fell to one quarter of the control value after exposure to a total dose of 1828 R.     

Interferon induction with Newcastle disease virus in FS-4 cells: Effect of 5,6-dichloro-1-β-D-ribofuranosylbenzimidazole (DRB)

Summary DRB is an inhibitor of heterogeneous nuclear RNA (hnRNA) and messenger RNA (mRNA) synthesis. The effect of DRB on interferon production stimulated by Newcastle disease virus (NDV) in the human FS-4 cells was studied. Interferon production in cells primed by treatment with interferon was markedly enhanced (superinduced) in the presence of DRB. This superinduction was essentially due to an inhibition of the rapid decline (shutoff) of interferon production observed in primed cells not treated with DRB. Continuous presence of DRB was required for maximal superinduction. In this and other respects the interferon response induced by NDV in primed cells resembled poly(I) · poly(C)-induced interferon production. In contrast interferon production in cells not primed with interferon was virtually abolished by DRB treatment. Since neither virus specific RNA synthesis nor virus replication were significantly affected by DRB, the inhibition of interferon production is likely to result from the inhibitory action of DRB on a cellular, rather than viral, function. Apparently some differences exist in the synthesis or processing of the mRNAs for interferons in primed and unprimed cells and these determine the different sensitivities of these two responses to DRB.With 2 Figures     

Blocking of interferon synthesis in murine macrophages by pretreatment with interferon

The influence of pretreatment with interferon (IFN) on subsequent IFN synthesis was investigated in macrophage cultures of DBA/2 and C57BL/6 mice. The doses of IFN alpha/beta for pretreatment ranged from 10,000 U/ml to 100 U/ml and the incubation time was between 18 and 2 h. No blocking effect was observed for chemical induction with poly I:poly C or CMA. However, for viral infection with NDV, blocking was observed. This inhibition of IFN synthesis was dependent on the dose and time of IFN pretreatment and of the titer of the inducing virus. Similarly in mouse fibroblast cultures no blocking activity was observed for induction with poly I:poly C/DEAE-dextran. Again, with NDV as inducer, pretreatment with IFN resulted in inhibition of interferon synthesis. Thus, our data show that blocking occurs only with a viral inducer and suggest that it is caused by an antiviral effect.     

Effect of thymosin on interferon production and antiviral resistance in mice

The 5th and 6th fractions of thymosin, a hormone of the thymus gland, stimulated interferon production both in vivo (experiments in white and CBA mice) and in vitro in CBA mouse splenocytes when different interferon inducers were used (phage dsRNA, poly(G): poly(C), NDV, and mitogens). The highest stimulating effect in vivo was observed with interferon induction 6-8 hours after thymosin administration. An increase in production of both alpha/beta and gamma interferons under the influence of thymosin was observed. Thymosin alone induced no interferon synthesis.     

Influence and production of interferon in Rauscher virus infected mice

Summary The inoculation, during an eleven day period, of interferon did not protect NMRI mice against the splenomegalic response to the Rauscher leukemia virus. Nor was there any protection recorded by the endogenous production of interferon induced by heterologous viruses (ND or Sindbis virus) or by endotoxin, although the leukemia virus was given at the time high amounts of interferon were produced. The implications of these observations are discussed.Mice infected with the Rauscher virus were shown to loose their interferon producing ability for a heterologous virus (Sindbis) injected intravenously. This effect reached its maximum 40 hours after infection with the Rauscher virus. Thereafter, a gradual but incomplete recovery of the Interferon producing ability was recorded. However, the interferon production induced by endotoxin was not lowered in mice previously inoculated with the Rauscher virus.This work was supported by a grant from the Nationaal Fonds voor Wetenschappelijk Onderzoek.     

Interferon synthesis by peripheral blood leukocytes of patients with bronchial asthma

Interferon production by leukocytes of 28 bronchial asthma patients and 27 normal subjects was examined using whole blood technique. Interferon production in blood samples was induced by classical inducers and the obtained interferons were tested in A549 cells using EMC virus as challenge. Leukocytes from both atopic and infectious asthma patients showed decreased ability to interferon production in comparison to healthy donors. In atopic asthma statistically significant differences in interferon production induced by NDV, PHA + PMA and LPS were observed. In the case of infectious asthma lower amounts of interferon were noted after stimulation with LPS and PHA + PMA. A decrease in spontaneous interferon production was also observed.     

Potentiating Effect of Freund's Adjuvant on Interferon Production by Endotoxin or Poly rI*Poly rC

Intraperitoneal injection of mice with mineral oil, incomplete (IFA) or complete Freund's adjuvant (CFA) increased the interferon response to endotoxin or (poly rI)•(poly rC) administered intravenously 2 days later. After endotoxin administration, circulating interferon titers were increased at several different times of sampling and with a variety of endotoxin dosages. When injection of endotoxin was delayed until 6 to 8 days after the administration of IFA or CFA, interferon production was markedly decreased. Mice treated with CFA and injected with endotoxin 2 days later became more resistant to intranasal vesicular stomatitis virus challenge than mice injected with endotoxin alone. Hyporeactivity to the interferon-inducing capacity of a second injection of endotoxin 2 days after the first injection could not be overcome by administering CFA simultaneously with the first dose. CFA treatment not only raised the serum interferon titers produced by endotoxin, but also increased the number of interferon-forming cells in the spleen after administration of endotoxin in vivo. In addition, CFA enhanced the intravascular clearance of (poly rI)•(poly rC). The possibility that Freund's adjuvant increased the interferon response to endotoxin and (poly rI)•(poly rC) by stimulating the uptake and processing of the interferon inducer by lymphoreticular cells is discussed.