Role of interferon in the pathogenesis of virus diseases in mice as demonstrated by the use of anti-interferon serum. II. Studies with herpes simplex, Moloney sarcoma, vesicular stomatitis, Newcastle disease, and influenza viruses.

The effect of potent sheep anti-mouse interferon globulin was investigated in several different experimental virus diseases of mice. In anti-interferon globulin-treated mice infected intraperitoneally with herpes simplex virus (HSV) type I, the latent period was shortened, and the overall LD50 was increased several hundredfold compared to virus-infected control mice. When HSV was inoculated subcutaneously all anti-interferon globulin-treated mice died, whereas only 5% of virus-infected control mice died. Subsequent treatment with anti-interferon globulin of previously HSV-infected mice did not result in reactivation of HSV. Treatment of adult mice with anti-interferon globulin resulted in an earlier appearance of MSV-induced tumors, a greater number of mice bearing tumors, an increase in tumor size, and an increase in the duration of tumors. All tumors eventually regressed despite reinjection of anti-interferon globulin. Anti-interferon globulin treatment resulted in a rapid onset of disease and death in adult mice inoculated (intranasal) with VSV and in newborn mice infected with NDV. Anti-interferon globulin exerted no effect on the course of influenza virus infection of mice. We conclude that the early production of interferon is an importane element in the response of the mouse to several viruses exhibiting different pathogeneses.

Severity of lymphocytic choriomeningitis virus disease in different strains of suckling mice correlates with increasing amounts of endogenous interferon.

A marked difference was observed in the severity of disease in lymphocytic choriomeningitis (LCM) virus-infected suckling BALB/c, Swiss, and C3H mice. BALB/c mice had minimal liver lesions and none died, whereas C3H mice had extensive liver lesions and all mice died. An intermediate pattern was oberved for Swiss mice (36% mortality). Although there was no difference in the titers of LCM virus in the plasma or liver between these three strains of mice, there was a marked difference in the amount of interferon produced and the duration of interferonemia. C3H mice produced more interferon than Swiss mice which produced more interferon than BALB/c mice, indicating a direct correlation between the amount of interferon induced by LCM virus and the extent of disease. Inoculation of a potent anti-mouse interferon globulin markedly reduced the incidence of mortality in virus-infected C3H mice. BALB/c mice were as sensitive to the effects of interferon as C3H mice because daily administration of potent interferon preparations did induce disease in this strain. This ensemble of results supports our contention that endogenous interferon is in large part responsible for the manifestaions of acute LCM virus disease in suckling mice.

Specific binding of high-mobility-group I (HMGI) protein and histone H1 to the upstream AT-rich region of the murine beta interferon promoter: HMGI protein acts as a potential antirepressor of the promoter.

The high-mobility-group I (HMGI) protein is a nonhistone component of active chromatin. In this work, we demonstrate that HMGI protein specifically binds to the AT-rich region of the murine beta interferon (IFN-beta) promoter localized upstream of the murine virus-responsive element (VRE). Contrary to what has been described for the human promoter, HMGI protein did not specifically bind to the VRE of the murine IFN-beta promoter. Stably transfected promoters carrying mutations on this HMGI binding site displayed delayed virus-induced kinetics of transcription. When integrated into chromatin, the mutated promoter remained repressed and never reached normal transcriptional activity. Such a phenomenon was not observed with transiently transfected promoters upon which chromatin was only partially reconstituted. Using UV footprinting, we show that the upstream AT-rich sequences of the murine IFN-beta promoter constitute a preferential binding region for histone H1. Transfection with a plasmid carrying scaffold attachment regions as well as incubation with distamycin led to the derepression of the IFN-beta promoter stably integrated into chromatin. In vitro, HMGI protein was able to displace histone H1 from the upstream AT-rich region of the wild-type promoter but not from the promoter carrying mutations on the upstream high-affinity HMGI binding site. Our results suggest that the binding of histone H1 to the upstream AT-rich region of the promoter might be partly responsible for the constitutive repression of the promoter. The displacement by HMGI protein of histone H1 could help to convert the IFN-beta promoter from a repressed to an active state.

Repression of virus-induced interferon A promoters by homeodomain transcription factor Ptx1.

Interferon A (IFN-A) genes are differentially expressed after virus induction. The differential expression of individual IFN-A genes is modulated by substitutions in the proximal positive virus responsive element A (VRE-A) of their promoters and by the presence or absence of a distal negative regulatory element (DNRE). The functional feature of the DNRE is to specifically act by repression of VRE-A activity. With the use of the yeast one-hybrid system, we describe here the identification of a specific DNRE-binding protein, the pituitary homeobox 1 (Ptx1 or Pitx1). Ptx1 is detectable in different cell types that differentially express IFN-A genes, and the endogenous Ptx1 protein binds specifically to the DNRE. Upon virus induction, Ptx1 negatively regulates the transcription of DNRE-containing IFN-A promoters, and the C-terminal region, as well as the homeodomain of the Ptx1 protein, is required for this repression. After virus induction, the expression of the Ptx1 antisense RNA leads to a significant increase of endogenous IFN-A gene transcription and is able to modify the pattern of differential expression of individual IFN-A genes. These studies suggest that Ptx1 contributes to the differential transcriptional strength of the promoters of different IFN-A genes and that these genes may provide new targets for transcriptional regulation by a homeodomain transcription factor.

Domains of interaction between alpha interferon and its receptor components.

We describe how constraints on the binding of human interferons (IFNs), alpha1 and alpha2 and alpha8 on mouse cells are partially relieved by the expression of the bovine (Bo) or human (Hu) IFN alpha/beta receptor (IFNAR) component in these cells. We show that, while the binding of all three is substantially increased by the transfection of Bo IFNAR, it is accompanied by an increase in activity only in the case of alpha2 and alpha8 (IFNs that otherwise have little activity on mouse cells). IFN alpha1, which shows some partial activity on mouse cells, responds to the presence of Bo IFNAR by acting, at low concentrations, as a competitive antagonist to IFNs alpha2 and alpha8. A review of published results on IFN hybrid scanning and on the effects of expressing Bo IFNAR in human cells led us to propose that an N-terminal segment of the IFN molecule interacts directly with IFNAR. Applying site-directed mutagenesis to an IFN hybrid; alpha8[60]alpha1[92]alpha8, we show that the point mutations K84 to E84 and Y90 to D90 act synergistically to cause the hybrid to behave as the parental IFN alpha8, switching the preference from Mu to Hu IFNAR in transfected mouse cells. The published structural models for IFN reveal that positions 84 and 90 span the exposed residues of the alpha-helix C of the IFN molecule. We derive a model of IFN-receptor interaction in which the A helix and the C helix of IFN interact with IFNAR and in which a binding phase can be distinguished from a binding/activity phase. We propose that the so-called "hot" domains of the IFN molecule (the AB loop and the D helix) are presented by IFNAR to interact with an additional component of the functional receptor.

Murine interferon-alpha1 gene-transduced ESb tumor cells are rejected by host-mediated mechanisms despite resistance of the parental tumor to interferon-alpha/beta therapy.

The highly metastatic ESb tumor is totally resistant to murine interferon-alpha/beta (IFN-alpha/beta) therapy, regardless of the number of cells injected or the route of inoculation. In contrast, as we show herein, mouse IFN-alpha1-transduced ESb tumor cells were inhibited markedly when injected subcutaneously into immunocompetent mice. IFN-producing ESb tumor rejection was mediated by the immune system, because these tumor cells grew normally in immunosuppressed mice. Tumor regression was accompanied by extensive necrosis and cellular infiltrates in the tumor area. These results further support the use of IFN-alpha in cytokine gene therapy of cancer and suggest the advantage of using gene transfer rather than cytokine administration to enhance an antitumor immune response.

Kinetic evidence for an activation step following binding of human interferon alpha 2 to the membrane receptors of Daudi cells.

A single species of human interferon alpha (IFN alpha) was labelled with 125I to high incorporation for binding studies on the B-lymphoblastoid cell line, Daudi, whose growth is inhibited by low doses of IFN, the effect being saturated at about 100 U/ml (25 pM). The radiolabelled IFN was shown to be fully active and the binding affinity to cellular sites was shown to be unchanged by iodination. Experimental conditions were standardized such that binding and cell growth experiments could be performed on the same initial culture of cells. 125I-labelled IFN alpha 2 (IFN alpha prepared from Escherichia coli carrying human alpha 2 gene) was added to exponentially growing cultures (mean specific growth rate 0.77 +/- 0.07 days-1) at a mean concentration of 235000 +/- 20000 cells ml-1. Two types of binding could be discerned on growing cultures: the first with a transient peak followed by a loss or discharge of available sites, the second reaching equilibrium some 3 h after the addition of IFN. Large differences in the apparent dissociation constants were evident. The affinity of binding at the 'steady-state', appeared to be much higher. An analysis of the displacement rates for bound IFN suggested that the two reactions were occurring consecutively over the whole of the dose range studied (1-100 U/ml; 0.25-25 pM IFN). In this dose range we found that Daudi cells would eventually stop growing at all doses and that the rates of deceleration of cellular growth were linearly proportional to the dose of IFN in a double-reciprocal plot (i.e. in analogy to Michaelis-Menten kinetics). A good congruence was found between the equilibrium constants for binding and for growth inhibition (2.65 pM and 2.39 pM, respectively). The amount of IFN bound at steady state thus determines the rate at which growth is inhibited. We propose that the first reaction represents binding of IFN to surface receptors, and the second transfer of IFN to an activation complex on the cell membrane. Appropriate models and their general applicability to IFN action are discussed.

Importance of interferon alpha in the resistance of allogeneic C57B1/6 mice to the multiplication of Friend erythroleukemia cells in the liver.

Friend erythroleukemia cells (FLC) (H-2d) injected intravenously multiply extensively in the livers of syngeneic DBA/2 mice and not at all in the livers of allogeneic C57B1/6 mice. Our results indicate that interferon alpha (IFN-alpha) is an important factor in the resistance of allogeneic mice to the multiplication of FLC in the liver. (a) After i.v. inoculation of FLC there was an inverse correlation between the presence of IFN-alpha in the serum and the capacity of FLC to multiply in the liver. Thus, all 44 FLC-injected adult C57B1/6 mice had circulating IFN-alpha and FLC did not multiply in the liver of any of the mice. Interferon was not detected in the serum of 83% of 41 FLC-injected DBA/2 mice (and was found only at a low titer in 17% of the mice) and FLC multiplied in the liver of all mice. (b) FLC did multiply in the livers of newborn C57B1/6 mice and in the livers of irradiated adult C57B1/6 mice, and IFN-alpha was not detected in their sera. In contrast, after i.v. inoculation of FLC, IFN-alpha was detected in the sera of 3-week-old and athymic nu/nu adult C57B1/6 mice while FLC failed to multiply in the liver. (c) FLC also induced IFN-alpha in congenic B10.D2 (H-2d) mice and FLC did not multiply in the liver. We suggest that, depending on the site of tumor implantation, different host mechanisms have various degrees of importance in controlling the growth and/or rejection of allogeneic tumor cells, and that IFN-alpha is particularly important when FLC are injected i.v.

Inhibition of histone deacetylation induces constitutive derepression of the beta interferon promoter and confers antiviral activity.

The induction of alpha/beta interferon (IFN-alpha/beta) genes constitutes one of the first responses of the cell to virus infection. The IFN-beta gene is constitutively repressed in uninfected cells and is transiently activated after virus infection. In this work we demonstrate that histone deacetylation regulates the silent state of the murine IFN-beta gene. Using chromatin immunoprecipitation (ChIP) assays, we show a direct in vivo correlation between the transcriptionally silent state and a state of hypoacetylation of histone H4 on the IFN-beta promoter region. Trichostatin A (TSA), a specific inhibitor of histone deacetylases, induced strong, constitutive derepression of the murine IFN-beta promoter stably integrated into a chromatin context, as well as the hyperacetylation of histone H4, without requiring de novo protein synthesis. We also show in this work that TSA treatment strongly enhances the endogenous IFN level and confers an antiviral state to murine fibroblastic L929 cells. Inhibition of histone deacetylation with TSA protected the cells against the lost of viability induced by vesicular stomatitis virus (VSV) and inhibited VSV multiplication. Using antibodies neutralizing IFN-alpha/beta, we show that the antiviral state induced by TSA is due to TSA-induced IFN production. The demonstration of the predominant role of histone deacetylation during the regulation of the constitutive repressed state of the IFN-beta promoter constitutes an interesting advance on the understanding of the negative regulation of this gene and opens up the possibility of new therapeutic perspectives.

Stability of the phenotypic reversion of x-ray transformed C3H/10T1/2 cells depends on cellular proliferation after subcultivation at low cell density.

Reversion from the transformed to the non-transformed phenotype could be obtained by seeding X-ray transformed C3H/10T1/2 cells at low cell density. Cloned revertant cells of varying degrees of reversion were obtained depending on the time they were isolated after on subculture at low cell density. Most of the revertants isolated 7 and 10 days after seeding at very low cell density eventually returned to the transformed phenotype when passaged serially at high cell density. In contrast, 25-35% of the revertants isolated 17-20 days after seeding at low cell density maintained the non-transformed phenotype despite subsequent serial passages at high cell density. The finding that there was a direct relationship between the time during which transformed cells seeded at low cell density multiplied and the number of stable revertant clones obtained, suggests that possibility that reversion from the transformed to the non-transformed phenotype may be a multistep process. Revertant cells displayed a chromosomal pattern characteristic of the transformed cells rather than that of the parental non-transformed 10T1/2 cells.

Role of endogenous interferon in the anti-tumor effect of poly I-C and statolon as demonstrated by the use of anti-mouse interferon serum.

We have determined the effect of sheep anti-mouse interferon globulin on the anti-tumor effects of poly I-C, statolon, tilorone, pyran copolymer and BCG in mice inoculated with Ehrlich ascites or L 1210 lymphoma cells. Whereas the anti-tumor effects of poly I-C and statolon were nulified when mice were injected with immunoglobulins, the anti-tumor effects of pyran copolymer and BCG were not modified by this treatment. We conclude that interferon mediates the anti-tumor activity of poly I-C and statolon in these experimental systems. It is suggested that anti-interferon serum provides a direct method of determining whether other biologic effects attributed to viruses, poly I-C, statolon, tilorone, pyran copolymer (and possibly other interferon inducers) are mediated or not by interferon.

Antiviral activity of bovine interferons on primate cells.

Potent preparations of bovine leucocyte and fibroblast interferons had substantial antiviral activity on monkey cells and low activity on human cells. Thus, interferon from a 'lower' phylogenetic species can have considerable antiviral activity in primate cells, but not all primate cells are equally sensitive.

Role of interferon in the pathogenesis of herpes simplex virus disease in mice.

The use of a potent antiinterferon serum has demonstrated the importance of the interferon response in host resistance to infection with herpes simplex virus (HSV). Inoculation of mice with potent antiinterferon globulin was associated with a very marked effect on the evolution of HSV disease, as shown by an acclerated appearance of signs of disease and death. In a total of seven experiments, i.v. administration of a sheep antimouse interferon globulin (titre 4 x 10(5)) resulted in the early appearance of disease and death, and increased the overall mortality due to HSV-1 strain F injected either i.p. or s.c. Comparable results were obtained with strain B-12. Twenty-five mice that had survived HSV inoculation (s.c. or i.p.) were injected with antiinterferon globulin 18 days after viral inoculation. In no instance did this treatment induce signs of HSV disease.

Binding of 125I-labelled human alpha interferon to human lymphoid cells.

To investigate the binding of interferon to human lymphoid cells, we purified human alpha interferon and radio-labelled it with iodine-125. Binding at 4 degrees C could be saturated and was inhibited by unlabelled interferon; it was specific for cells of human origin. Dissociation constants for the complex of interferon and receptor site were of the order 10(-9)-10(-11) M. All human cells tested showed such binding. Occupation of these high-affinity sites, at 37 degrees C, was compared with the inhibition of cellular growth due to interferon. The most sensitive cell line (Daudi) gave a complete biological response with only a fraction of its sites occupied. Evidence of two sites was found for a line (P3HRI) showing intermediate sensitivity. A relatively insensitive line (Raji) showed no response when all its high-affinity sites were occupied.

Interferon enhances the expression of Fc gamma receptors.

Murine T2D4 cells derived from a T cell hybrid line were incubated with partially purified or electrophoretically pure mouse interferon and tested for the expression of Fc gamma R as assessed by a) counting the number of cells forming rosettes with IgG-sensitized sheep erythrocytes, and b) incubating the cells with heat-aggregated rabbit IgG and then determining either the number of cells stained with fluorescein conjugated goat anti-rabbit IgG or the extent of labeling by using radioactive iodinated staphylococcus protein A. Although interferon induced a rapid increase in Fc gamma R expression on the Fc gamma R-positive T2D4 cells, it did not induce either Fc gamma R on the Fc gamma R negative BW5147 cells or Fc gamma R on either cell line. Human leukocyte interferon enhanced the expression of Fc gamma R on human Burkitt cells (Daudi) but did not affect the expression of Fc gamma R on mouse cells. We suggest that interferon may influence several effector functions of the immune system by modulating Fc receptor expression.

IFN-alpha 1 gene transfection completely abolishes the tumorigenicity of murine B16 melanoma cells in allogeneic DBA/2 mice and decreases their tumorigenicity in syngeneic C57BL/6 mice.

The murine B16 melanoma (H-2b) was transfected with a retroviral vector containing the mouse IFN-alpha 1 gene. IFN-alpha 1-transfected cells produced IFN-alpha in vitro and exhibited an altered phenotype characterized by a decreased rate of multiplication, enhanced expression of H-2 antigens, an antiviral state to VSV, and decreased pigmentation. Control and IFN-alpha 1-transfected cells were tested for their ability to grow in syngeneic (H-2b) C57Bl/6 and allogeneic (H-2d) DBA/2 mice. IFN-alpha 1-producing B16 clones were less tumorigenic after s.c., i.p., and i.v. routes of injection than IFN-non-producer B16 clones in syngeneic C57Bl/6 mice. IFN-alpha 1-producing B16 cells were, however, totally rejected by allogeneic DBA/2 mice regardless of the routes and inocula tested, while control B16 cells grew in and killed DBA/2 mice. The total rejection of IFN-alpha 1-transfected B16 cells in allogeneic mice appeared to be dependent on T cells as these cells grew in DBA/2 nude mice. Incubation of IFN-alpha-producing clones with anti-mouse IFN-alpha/beta prior to injection into C57Bl/6 mice did not enhance their tumorigenicity. Likewise, injection of C57Bl/6 and DBA/2 mice with antibody to IFN-alpha/beta did not enhance the tumorigenicity of IFN-alpha 1-transfected cells. C57Bl/6 mice immunized with irradiated IFN-alpha 1 cells were only slightly protected against a subsequent challenge with parental B16 cells. In contrast, DBA/2 mice immunized with irradiated IFN-alpha 1 cells exhibited tumor-specific, long-lasting immunity to subsequent challenge with parental B16 cells.

Interferon removes its own receptors as it blocks the division of Daudi cells.

The Burkitt-derived line, Daudi, whose proliferation is inhibited by human alpha-interferon (IFN-alpha), was treated with 125I-labelled recombinant human IFN-alpha A. After separation from unbound ligand, cell-bound IFN was extracted with the detergent digitonin yielding soluble and insoluble complexes of IFN and receptor, together with a certain amount of uncomplexed IFN. 1. Soluble complexes were stable enough to be separated from uncomplexed IFN by permeation chromatography. Treatment of soluble complexes with the bifunctional reagent, disuccinimidyl suberate, yielded a radioactive product separating with an Mr of 130,000 on electrophoresis in sodium dodecyl sulphate. Similar complexes could be recovered with sodium dodecyl sulphate from the digitonin-insoluble residue, treated with the bi-functional reagent. 2. The total (soluble and insoluble) of complexed IFN obtained after digitonin extraction was a constant fraction (0.62) of the total cell-bound radioactivity, being independent of the concentration of IFN added to the cells (less than pM to greater than nM), and of the time of incubation (1 min to 20 h). However, between 30 min and 3 h of incubation, the insoluble complex increased, at the expense of the soluble complex, and there appeared a cellular pool of degraded ligand. From 3 h to 20 h the distribution of ligand-derived radioactivity remained constant while the total amount decreased to less than 10% of its value at 30 min. This decrease in binding was matched by the appearance of an equivalent quantity of radiolabelled fragments in the culture medium. 3. The inhibition of cellular division due to IFN was shown to be coincident with the disappearance of cellular binding and with the cell-mediated degradation of receptor-complexed IFN. We propose that IFN removes its own receptor and, in doing so, blocks a linked function necessary for the stimulated growth of Daudi cells.

Electrostatic interactions in the cellular dynamics of the interferon-receptor complex.

Using membrane preparations of the interferon receptor, prepared from cells of the Burkitt line, Daudi, we have examined the binding of three human recombinant alpha-interferons. 1. We discovered a binding titration of the interferons IFN-alpha A and IFN-alpha D in the pH range 6-9. Receptor binding, negligible at pH 6, rises to a maximum close to pH 9. We have shown that binding of IFN-alpha A at basic pH is to the same receptors as at neutrality and that IFN-receptor complexes extracted with digitonin are more stable at basic pH than they are at neutrality. 2. The recombinant interferon, IFN-alpha B, shows little change of binding in the pH range 6-9. At its basic optimum the binding of IFN-alpha A approaches that of IFN-alpha B, while at neutral pH the binding of IFN-alpha A is 3-4 times less. This difference at neutral pH is seen on intact cells as well as on membrane preparations. The specific activity of IFN-alpha B is close to that of IFN-alpha A, both of which are 10-20 times more active than IFN-alpha D; and the binding titration is, therefore, independent of the initial binding affinities. 3. Using hybrid IFNs constructed from the DNA sequences of alpha D and alpha B, we have isolated the sequence responsible for the binding titration to the segment comprising amino acids 61-92. Examination of these sequences reveals that Lys-84 is present in all the IFN-alpha except IFN-alpha B where it is replaced by Glu; and Tyr-90, present in most of the common IFN-alpha including alpha A and alpha D, is replaced by Asp in IFN-alpha B. Lys and Tyr would normally titrate in the pH range 6-9. We conclude that the binding titration is due to an electrostatic interaction and we propose that the interaction is between IFN-receptor complexes. The role of the interaction in the binding losses that accompany the antiproliferative effects of IFN is discussed.

Behavior of a cloned murine interferon alpha/beta receptor expressed in homospecific or heterospecific background.

A murine interferon (IFN) alpha/beta receptor was cloned from the IFN-sensitive L1210 cell line on the basis of its homology with the human receptor. A combination of methods that includes the screening of random-primed and oligo(dT)-primed cDNA libraries and polymerase chain reactions with a single-side specificity was used. At the amino acid level, the murine IFN-alpha/beta shows 46% identity with its human counterpart. Both human WISH cells presenting a low sensitivity to mouse IFN and a murine L1210 mutant subline that does not express the receptor have been stably transfected with the murine IFN-alpha/beta receptor. Whereas transfected human cells became sensitive to a limited number of mouse IFN-alpha/beta subtypes, the transfected murine L1210 mutant was found to be fully complemented and became sensitive to all mouse IFN-alpha/beta subtypes tested, including those that were not active on transfected human cells. These results strongly suggest that the receptor described here is implicated in the mediation of the activities of all murine IFN-alpha/beta subtypes.