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Comparison of the in vitro host range of recombinant met-interferon-con1, interferon-alpha 2b, and interferon-beta [corrected].

The antiviral activity of human r-metIFN-con1 was compared with that of IFN-alpha 2b and IFN-beta on a number of human, other primate, rodent, feline, and canine cell lines. Although the specific activities of r-metIFN-con1 and IFN-alpha 2b differed 10-fold, the host range was very similar. The host range of IFN-beta differed from that of r-metIFN-con1 and IFN-alpha 2b in that Vero cells were 100-fold better protected by IFN-beta and MDBK protected at a 100-fold less efficiency. In general, there were only minor differences between the host ranges of the three interferons, human and primate cells being better protected than those of other species. However, the tissue of origin of the cell appears to be more important than the species of origin in defining host range [corrected].

Animals↗

Interferon-tau and interferon-alpha interact with the same receptors in bovine endometrium. Use of a readily iodinatable form of recombinant interferon-tau for binding studies.

Trophoblasts of ruminant species secrete multiple forms of a novel Type I interferon (IFN-tau) for a few days preceding implantation. These IFN-tau are structurally distinct from IFN-alpha, -beta, and -omega, but it remains unclear whether they have any distinguishing biological properties. It has been of interest, therefore, to study their interaction with Type I IFN receptors. However, a recombinant bovine IFN-tau (boIFN-tau 1) prepared for such use is rapidly inactivated during chemical iodination with 125I, presumably because a critical tyrosine becomes modified. Here we describe the synthesis of a novel IFN-tau 1 in which Leu169 and Leu171 in the carboxyl terminus have been replaced by 2 tyrosine residues. The recombinant product (rboIFN-tau 1Y2) can be readily iodinated without significant loss of antiviral and antiproliferative activities, provided that reaction time with 125I is minimized. Both rboIFN-tau 1Y2 and rboIFN-alpha 1 compete with each other for binding to bovine endometrial cell membranes and Madin-Darby bovine kidney cells. Dissociation constants of both IFN are quite similar (Kd = 3.7 x 10(-10) and 3.5 x 10(-10) M, respectively). Cross-linking studies reveal a single size class of receptor polypeptide on endometrium and Madin-Darby canine kidney cells whose molecular weight is reduced from approximately 130,000 to approximately 70,000 by treatment with N-glycosidase. These studies with a single recombinant form of boIFN-tau avoid the difficulties that arise from use of a mixture of naturally occurring isoforms. They provide further evidence for the presence of a receptor common to both IFN-tau and IFN-alpha in bovine tissues and no indication for a unique IFN-tau-binding polypeptide in endometrium.

Animals↗

Porcine leukocyte interferon exhibits close antigenic relatedness to human interferon alpha 2, but not to human interferon alpha 1.

As reported by others using polyclonal antisera, natural human and porcine interferons (IFN)-alpha are antigenically related. Using monoclonal antibodies (mAb) in neutralization and ELISA experiments, we found differences in the subtype/antigenic composition between virus-induced porcine and human leukocyte preparations. Human leukocyte IFN-alpha contains two major antigenically distinct subtypes, IFN-alpha 1 and IFN-alpha 2. However, swine leukocytes produced only a single predominant species of IFN-alpha with high antigenic homology to human IFN-alpha 2. Moreover, we were unable to detect close antigenic relatedness between recombinant porcine and human IFN-alpha 1 subtypes.

Animals↗

Delivery of interferon to intracellular pathways by encapsulation of interferon into multilamellar liposomes is independent of the status of interferon receptors.

The antiproliferative effect of interferon alpha (IFN-alpha) against cultured 253J human bladder tumour cells was enhanced when IFN-alpha was encapsulated into multilamellar phospholipid liposomes (MLV). Moreover, significant cytostasis of a variant 253J subline (253J alpha R, resistant to the antiproliferative effect of IFN-alpha), could be achieved by delivery of IFN-alpha contained in liposomes. Although the two cell lines have the same number and affinity of cell receptors for IFN-alpha, the 253J alpha R cells did not down-regulate receptors as observed for the IFN-sensitive 253J cells. The IFN-response genes, 2'-5' oligosynthetase and gene 6-16 were equally induced in both cell lines following incubation of the cells with either free IFN-alpha or liposome-encapsulated IFN-alpha. Incorporation of radiolabelled IFN-alpha into cells by liposomes was independent of the status of IFN-receptors (the receptors being either occupied or down-regulated). These observations are consistent with the hypothesis that the antiproliferative effects of IFN-alpha against 253J and 253J alpha R cells may be mediated by internalization of IFN-alpha.

2',5'-Oligoadenylate Synthetase↗

Identification of a member of the interferon regulatory factor family that binds to the interferon-stimulated response element and activates expression of interferon-induced genes.

A family of interferon (IFN) regulatory factors (IRFs) have been shown to play a role in transcription of IFN genes as well as IFN-stimulated genes. We report the identification of a member of the IRF family which we have named IRF-3. The IRF-3 gene is present in a single copy in human genomic DNA. It is expressed constitutively in a variety of tissues and no increase in the relative steady-state levels of IRF-3 mRNA was observed in virus-infected or IFN-treated cells. The IRF-3 gene encodes a 50-kDa protein that binds specifically to the IFN-stimulated response element (ISRE) but not to the IRF-1 binding site PRD-I. Overexpression of IRF-3 stimulates expression of the IFN-stimulated gene 15 (ISG15) promoter, an ISRE-containing promoter. The murine IFNA4 promoter, which can be induced by IRF-1 or viral infection, is not induced by IRF-3. Expression of IRF-3 as a Gal4 fusion protein does not activate expression of a chloramphenicol acetyltransferase reporter gene containing repeats of the Gal4 binding sites, indicating that this protein does not contain the transcription transactivation domain. The high amino acid homology between IRF-3 and ISG factor 3 gamma polypeptide (ISGF3 gamma) and their similar binding properties indicate that, like ISGF3 gamma, IRF-3 may activate transcription by complex formation with other transcriptional factors, possibly members of the Stat family. Identification of this ISRE-binding protein may help us to understand the specificity in the various Stat pathways.

Amino Acid Sequence↗

The heparan sulfate binding sequence of interferon-gamma increased the on rate of the interferon-gamma-interferon-gamma receptor complex formation.

Interferon-gamma (IFNgamma), in common with a number of growth factors, binds both to heparan sulfate or heparin-related molecules and to a specific high affinity receptor (IFNgammaR). Using surface plasmon resonance technology, kinetic analysis of the IFNgamma. IFNgammaR complex formation was performed with the extracellular part of IFNgammaR immobilized on a sensor chip. At the sensor chip surface, IFNgamma was bound by two IFNgammaR molecules with an affinity in the nanomolar range (0.68 nM). This binding was characterized by an important on rate, kon = 7.3 x 10(6) M-1.s-1, and an off rate, koff = 5 x 10(-3).s-1. This binding assay was used to investigate a possible role of heparin in the IFNgamma.IFNgammaR complex formation. In contrast to growth factors for which binding to heparin is usually required for high affinity receptor interaction, we found in this study that IFNgamma bound to heparin displayed a strongly reduced affinity for its receptor. This is consistent with the fact that a cluster of basic amino acids (KTGKRKR, called the C1 domain) in the carboxyl-terminal sequence of the cytokine was involved both in heparin and receptor recognition. To understand how a single domain of IFNgamma could be implicated in two discrete functions (i.e. binding to heparin and to IFNgammaR), we also analyzed in a detailed manner the role of the IFNgamma carboxyl-terminal sequence in receptor binding. Using forms of IFNgamma, with carboxyl terminus truncations of defined regions of the heparin binding sequence, we found that the C1 domain functioned by increasing the on rate of the IFNgamma.IFNgammaR binding reaction but was not otherwise required for the stability of the complex. Interactions between the IFNgamma carboxyl-terminal domain and IFNgammaR could increased the association rate of the reaction either by increasing the number of encounters between the two molecules or by favoring productive collisions. The mechanisms by which heparan sulfate regulates IFNgamma activity may thus include both control of selective protease cleavage events, which directly affect the cytokine activity, and also an ability to modulate the interaction of IFNgamma with the IFNgammaR via competitive binding to the C1 domain.

Amino Acid Sequence↗

Isolation of cDNA clones for the interferon-induced 67,000-dalton protein: direct induction of a family of mRNAs by human interferon-alpha and interferon-gamma.

A partial cDNA clone for the interferon (IFN)-induced 67,000-dalton (67K) protein was isolated by immunological screening and used as a probe to study the expression of mRNAs encoding this protein. Northern blot analyses of RNA from IFN-treated GM2767 cells revealed the presence of two major 67K-specific RNA species, 2.7 and 4.3 kb in length, and two minor RNA species, 5.7 and 7.2 kb long. All of these 67K-specific RNAs were polyadenylated. Multiple 67K-specific mRNAs were observed to be induced in several cell lines. IFN-gamma was more effective at inducing these mRNAs than was IFN-alpha. In IFN-alpha-treated GM2767 cells, the 67K-specific mRNAs were detectable 6 h following IFN treatment, but not 12, 18, or 24 h following treatment. In IFN-gamma-treated cells, these mRNAs were detectable 6 h after treatment and continued to be present 24 h after treatment. The induction of the 67K-specific mRNAs in GM2767 cells did not require protein synthesis as the RNAs were induced by IFN-alpha or IFN-gamma in the presence of cycloheximide (CHX, 50 micrograms/ml). Treatment of cells with the combination of CHX and IFN-alpha mediated an enhanced accumulation of the 67K-specific mRNAs, suggesting that ongoing protein synthesis may downregulate the induction or accumulation of the IFN-alpha-induced 67K-specific mRNAs. Western blot analysis employing a monoclonal antibody to the 67K protein revealed that several distinctly sized but immunologically related proteins were induced in IFN-treated cells.

Cell Line↗

Potentiation of interferon-alpha in vitro antiviral activity by interferon-gamma is not abrogated by antibody to interferon-gamma.

The addition of minute amounts of recombinant interferon-gamma (IFN-gamma) to recombinant IFN-alpha 2 significantly enhances its antiviral activity. Although this potentiating action of IFN-gamma is destroyed by treatment with acid, it is not significantly affected by treatment with antibodies to IFN-gamma, suggesting that IFN-gamma molecules can interact with cells to potentiate IFN-alpha activity, even in the presence of neutralizing antibodies. Implications of this phenomenon are multifaceted, including the possibility that other IFN activities can be altered synergistically by combinations of different IFN types, even in the presence of specific antibodies, which have been described to occur in vivo in several pathological conditions.

Antibodies↗

Antigenic structure of human interferon omega 1 (interferon alpha II1): comparison with other human interferons.

Recombinant human interferon (IFN) omega 1 (IFN-alpha II1) was compared with other human IFNs with regard to antigenic structure, using polyclonal and monoclonal antibodies. Antisera to recombinant IFN-alpha 1 or IFN-alpha 2c cross-neutralized the antiviral activity of other species of IFN-alpha, but not that of IFN-omega 1. Antisera to IFN-beta or IFN-gamma likewise had no effect on IFN-omega 1. Conversely, antiserum to IFN-omega 1 did not neutralize any of the other IFNs examined (IFN-alpha 1, -alpha 2c, -alpha 10, -alpha B, -alpha F, -beta, -gamma). None of four monoclonal antibodies to IFN-alpha, including a broad-spectrum antibody that neutralized all five recombinant species of IFN-alpha tested, had any effect on the biological activity of IFN-omega 1. Various immunoassays for IFN-alpha did not recognize IFN-omega 1. In immunoprecipitation experiments, radiolabelled IFN-alpha 2c was not precipitated by antiserum to IFN-omega 1. In contrast, antisera to human leukocyte IFN or 'lymphoblastoid' IFN did neutralize IFN-omega 1, although with titres significantly lower than those towards the immunogen or recombinant species of IFN-alpha. In conclusion, human IFN-omega 1 is antigenically different from human IFN-alpha, IFN-beta or IFN-gamma, but is a component of 'natural' mixtures of IFN species produced by virus-induced leukocytes or Burkitt's lymphoma cells.

Amino Acid Sequence↗

Protein binding to the interferon response enhancer correlates with interferon induction of 2'-5'-oligoadenylate synthetase in normal and interferon-resistant Friend cells.

The induction of transcription of the 2'-5'-oligoadenylate (2-5A) synthetase gene by type I (alpha/beta) and type II (gamma) interferons (IFNs) has been studied in wild-type (w.t.) and IFN-resistant Friend leukemia cells (FLC). Following IFN treatment, new complexes are formed in vitro between the IFN-responsive sequence (IRS) of the 2-5A synthetase gene and cellular proteins. Within minutes after IFN-alpha/beta addition to w.t. FLC, an IRS-protein complex, designated F1, is detected, as already observed in several human cell lines. In response to IFN-gamma, a novel complex, designated Fg, is observed in w.t. FLC. The Fg complex appears within 3 h, while an F1-like complex is faintly visible 10 to 24 h later. In the IFN-alpha/beta-resistant FLC, IFN-gamma induces only the Fg complex and fails to induce F1. Fg formation is correlated with the IFN-gamma-induced transcription of the 2-5A synthetase gene and the appearance of the corresponding enzymatic activity in both w.t. and IFN-alpha/beta-resistant FLC. These findings suggest that F1 and Fg represent two distinct effector complexes by which type I and type II IFNs, respectively, induce 2-5A synthetase.

2',5'-Oligoadenylate Synthetase↗

Selective impairment of alpha-interferon-mediated natural killer augmentation in Sjögren's syndrome: differential effects of alpha-interferon, gamma-interferon, and interleukin 2 on cytolytic activity.

Natural killer (NK) function has been shown to be impaired in several autoimmune diseases including Sjögren's syndrome (SS). In the present study, in vitro effects of alpha-interferon (alpha-IFN), gamma-IFN and interleukin 2 (IL-2) on the NK cell activity were examined to analyse the regulatory system of NK-augmentation in patients with SS. The responsiveness of NK cell activity to alpha-IFN was markedly depressed in SS patients compared with normal controls, whereas the responsiveness to gamma-IFN was within normal limits. This is the first demonstration of the selective hyporesponsiveness of NK cell activity to one type of IFN in a certain disease. In addition, the kinetics study of NK-augmentation in normal donors revealed that alpha-IFN enhanced NK cell activity with a faster profile than gamma-IFN. These findings imply substantial differences between the two types of IFN in their mechanisms for enhancing NK cell activity, which deserve attention in evaluating the effects of IFNs. The present study also demonstrated that IL-2 could induce significantly higher levels of NK cell activity than alpha-IFN or gamma-IFN in SS and that this enhancing effect was almost comparable to that in normal controls. Thus, there seem to be multiple regulatory mechanisms for enhancement of NK cell activity, and a portion of the mechanisms may be selectively impaired in certain human diseases such as SS. The selective hyporesponsiveness to alpha-IFN could be relevant to the idea of viral participation in pathogenesis of SS.

Cytotoxicity, Immunologic↗

Complementation of the interferon alpha response in resistant cells by expression of the cloned subunit of the interferon alpha receptor. A central role of this subunit in interferon alpha signaling.

A subunit of the interferon alpha receptor (IFN alpha R) that confers biologic response to and specific "binding" for IFN alpha 8 has recently been cloned. We have explored the biological consequences of expressing the cloned IFN alpha R subunit in human cells resistant to IFN alpha and in mouse cell lines nonresponsive to human IFN alpha. The expression of the cloned IFN alpha R subunit in the human IFN alpha-resistant K-562 cell line restored sensitivity to the antiviral effect of not only IFN alpha 8 but also IFN alpha 2 and IFN alpha Con1. In mouse L-929 cells the expression of the cloned receptor subunit markedly increased antiviral sensitivity to human type I IFNs. In either human K-562 or mouse L-929 cells these effects were observed without a detectable increase in the binding for any of the subtypes of IFN alpha tested. We propose that the cloned IFN alpha R subunit functions as a transducer subunit for the IFN alpha R. This concept is supported by the finding that the cloned receptor protein, when it is expressed in Cos cells, has an M(r) of 75 kDa, which is different from the main IFN alpha-binding proteins, the alpha and beta subunits of the IFN alpha R. This report also suggests that alterations at the receptor level could be involved in IFN alpha resistance in some cell lines.

Animals↗

Interferon receptors on the surface of interferon-sensitive and interferon-resistant urothelial carcinomas.

In previous investigations, it was demonstrated that interferons (IFN) have antiproliferative effects in human urothelial carcinomas. However, appreciable differences were found in the sensitivity of the individual tumors investigated. We therefore examined whether this might be due to a different receptor status of the cells. The IFN-sensitive cell lines RT4 and SD as well as the IFN-resistant cell line 639V were investigated with regard to their IFN receptor status. It was demonstrated that IFN receptors were present on the cell surface in all three urothelial carcinomas investigated. The number of IFN receptors calculated for the IFN-resistant cell line 639V was 4.661 per cell, whereas the IFN-sensitive cell line SD had 4.391 receptors and RT4 had 3.307 receptors. The IFN affinity of the three cell lines tested differed only slightly. Therefore IFN affinity is unlikely to account for their marked differences in IFN sensitivity.

Cell Line↗

In situ hybridization of the mRNA for interferon-gamma, interferon-alpha E, interferon-beta, interleukin-1 beta and interleukin-6 and characterization of infiltrating cells in thyroid tissues.

Cytokine mRNA production in the thyroid tissues of patients with various thyroid diseases was analysed by in situ hybridization. In addition, infiltrating leukocytes were characterized by immunohistologic studies using the alkaline phosphatase anti-alkaline phosphatase (APAAP) staining technique. The following clinical material was investigated: two cases of Graves' disease, one with high and the other with a low amount of infiltrating leukocytes as well as two cases of non-toxic goitre also showing considerable quantities of infiltrating cells. The hybridization was performed on tissue sections with antisense probes for interferon-gamma (IFN-gamma), IFN-alpha E, IFN-beta, interleukin-6 (IL-6) and IL-1 beta. A small number of individual cells were found to express high levels of mRNA for IFN-gamma, IL-1 beta and measurable amounts of IL-6 throughout the tissue sections. However, IFN-alpha E or IFN-beta were not detected. Cytokine expressing cells were noted in the tissue of one patient with Graves' disease and in two cases with non-toxic goitre. In these samples a high amount of infiltrating leukocytes (CD45+) was detected, especially CD3+, CD8+, CD4+ and CD45RA+ T cells, in addition to B cells and macrophages. In one case an unusually large amount of T cell receptor gamma/delta+ (TcR gamma/delta+) cells was found. However, one sample of thyroid tissue derived from a patient with Graves' disease was poorly infiltrated and showed few cells expressing cytokines. In conclusion, using thyroid tissue as an example, our data suggest that the application of in situ hybridization with antisense RNA permits the study of cytokine production in tissues of both autoimmune and non-autoimmune origin.

Adult↗

2-5A synthetase activity does not increase in interferon-resistant Friend leukemia cell variants treated with alpha/beta interferon despite the presence of high-affinity interferon receptor sites.

The presence of interferon (IFN) receptors on mouse Friend leukemia cells (FLC) has been investigated in binding experiments with highly purified 125I-labeled mouse alpha/beta IFN. Both IFN-resistant clones and wild-type IFN-sensitive FLC showed a specific saturable binding site for mouse IFN with a similar affinity constant. In contrast to IFN-sensitive FLC, IFN-resistant FLC variants were not inducible by IFN for double-stranded RNA-dependent 2-5A synthetase activity.

2',5'-Oligoadenylate Synthetase↗

Retreatment with interferon and ribavirin vs interferon alone according to viraemia in interferon responder-relapser hepatitis C patients: a prospective multicentre randomized controlled study.

Low pretreatment viral load has consistently been shown to be an independent predictor of sustained response (SR) in patients with chronic hepatitis C infection. We assessed the efficacy of interferon (IFN) plus ribavirin vs IFN alone in low viraemic patients (<2 millions copies/mL) who had relapsed to a previous course of IFN and the efficacy of 24 vs 48 week combination therapy in high viraemic patients. Two hundred and ninety-seven patients were randomly assigned to one of the four regimens after stratification on pretreatment viral load. All patients received IFN-alpha2b (6 million units thrice weekly for 24 weeks and 3 million units thrice weekly for 24 weeks). Patients with low viraemia received either IFN-alpha2b alone for 48 weeks (R1: 42 patients) or IFN-alpha2b plus ribavirin (600 mg/day) for 24 weeks and IFN-alpha2b alone for the next 24 weeks (R2: 48 patients). Patients with high viral load received either IFN-alpha2b plus ribavirin for 24 weeks and then IFN-alpha2b alone for the next 24 weeks (R3: 104 patients) or IFN-alpha2b plus ribavirin for 48 weeks (R4: 103 patients). In low viraemic patients the rate of SR was 37.7% in group R1 and 59.6% in group R2 (P < 0.05). In high viraemic patients, the rate of SR was 44.7% in group R3 and 51.4% in group R4 (P: NS). Thirty-one patients discontinued treatment (10.4%) without difference regarding treatment regimen. In the regimen using ribavirin we found no difference in terms of SR between patients receiving a dose of ribavirin below 10.6 mg/kg/day (55%) or over 10.6 mg/kg/day (58%). Histological improvement occurred in 70.2% of patients regardless of the regimen. Logistic regression showed that genotype 2 and 3, Knodell score <6 and alanine aminotransferase pretreatment level >3 x upper limit of normal were significantly and independently correlated with SR. In low viraemic patients who relapsed to a previous IFN treatment, combination therapy using high-dose IFN and low-dose ribavirin is better than high-dose IFN alone. In high viraemic patients there was no benefit in increasing the duration of combination therapy from 24 to 48 weeks. In this study, it was found that low dose of ribavirin can be used safely and there is no effect of ribavirin dose on SR.

Adult↗

Primary activation of interferon A and interferon B gene transcription by interferon regulatory factor 3.

The family of interferon (IFN) regulatory factors (IRFs) encodes DNA-binding transcription factors, some of which function as modulators of virus-induced signaling. The IRF-3 gene is constitutively expressed in many tissues and cell types, and neither virus infection nor IFN treatment enhances its transcription. In infected cells, however, IRF-3 protein is phosphorylated at the carboxyl terminus, which facilitates its binding to the CBP/p300 coactivator. In the present study, we demonstrate that overexpression of IRF-3 significantly enhances virus-mediated transcription of the IFNA and IFNB genes in infected cells as well as IFN synthesis. IRF-3-mediated activation of IFN genes depends in part on carboxyl-terminal phosphorylation of a cluster of Ser/Thr residues, because a mutant with Ser/Thr to Ala substitutions activates the IFN promoter less efficiently. However, overexpression of IRF-3 in human 2FTGH cells alone results in the induction of an antiviral state, which depends on functional IFN signaling, because IRF-3 does not induce an antiviral state in mutant 2FTGH cells defective in either JAK-1 or p48 functions; also no antiviral effect of IRF-3 could be demonstrated in Vero cells that lack the IFNA and IFNB genes. This finding indicates that the observed antiviral activity of IRF-3 in 2FTGH cells results mainly from the induction of IFNs. Furthermore, E1A protein inhibited IRF-3-mediated stimulation of the IFNA4 promoter in transient expression assays; this inhibition could be reversed partially by overexpression of CBP/p300 and was not demonstrated with the mutant of E1A that does not bind p300. These results identify IRF-3 and CBP/p300 as integral components of the virus-induced complex that stimulates type 1 IFN gene transcription. The observation that adenovirus E1A antagonizes IRF-3 mediated activation suggests that E1A and IRF-3 may compete for binding to CBP/p300 and implicates a novel mechanism by which adenovirus may overcome the antiviral effects of the IFN pathway.

Adenoviridae↗

Interferon-induced 2'-5' adenylate synthetase in vivo and interferon production in vitro by lymphocytes from systemic lupus erythematosus patients with and without circulating interferon.

The interferon (IFN)-induced enzyme 2-5A synthetase was elevated in mononuclear cells from both serum IFN-positive and -negative systemic lupus erythematosus (SLE) patients. This suggests that a much higher percentage of patients than previously thought produce endogenous IFN. These results may partly explain findings that mononuclear cells from SLE patients are deficient in IFN production in vitro in response to certain IFN inducers. Although normal lymphocytes can produce an acid-labile alpha IFN after stimulation with C. parvum in vitro, the reason for endogenous production of this unusual alpha IFN by SLE patients remains unknown.

2',5'-Oligoadenylate Synthetase↗