High and low potency interferon-alpha subtypes induce (2'-5') oligoadenylate synthetase with similar efficiency

Gene modulatory effects, pharmacokinetics, and clinical tolerance of interferon-alpha1b: a second member of the interferon-alpha family

Interferon-alpha1 (IFN-alpha1), which may have a primary role in innate immunity, differs significantly in amino-acid sequence from IFN-alpha2, the only recombinant IFN-alpha with substantial clinical evaluation. Patients with metastatic malignancies received daily subcutaneous doses of 1.5-270 mug/m(2) of recombinant IFN-alpha1b. Gene modulation, pharmacokinetics, tolerability, and disease response were determined. Significant (P<0.01) dose and gene-dependent increases of 2-10 fold occurred in IFN-stimulated genes, including four (tumor necrosis factor-related apoptosis-inducing ligand, cig 5, p56, GEM) never previously identified as increased in patients; significant increases (P<0.01) resulted at the lowest dose (1.5 microg/m(2); 1.5 x 10(4) human antiviral units/m(2)). Increases (P<0.01) were sustainable for >4 weeks. Peak levels of IFN-alpha1b were at 3 h; an increase of approximately eightfold in both C(max) and AUC occurred between 15 microg/m(2) and 270 microg/m(2). Chronic toxicities of anorexia, weight loss, and fatigue were relatively uncommon. Eighteen patients were treated for >8 weeks; none experienced >grade 1 weight loss. Three patients at the highest dose developed grade 3 fatigue after > or =3 months, which required dose reduction or discontinuation. Patient acceptability of fatigue defined a dose for initiation of Phase II trials, 270 microg/m(2). Six patients (five with renal cell carcinoma) had progression-free survival for >1 year, including two who had partial responses. IFN-alpha1b resulted in potent stimulation of IFN-regulated genes and tumor regressions in renal cell carcinoma. Unique gene modulatory effects, when coupled with the moderate severity of side effects and a potentially central role in innate immunity, provide rationale for further clinical evaluation of IFN-alpha1 in virus infections and cancer.

Chemiluminescent imaging analysis of interferon alpha in serum samples

Enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase (HRP)-catalyzed fluorescent reaction, and oxalate chemiluminescence imaging analysis have been combined to develop a sensitive, simple, and rapid method for analysis of interferon alpha (alpha-IFN) in human serum samples. A typical "sandwich type" immunoassay was used. Reaction of o-phenylenediamine (OPD) with hydrogen peroxide (H(2)O(2)), catalyzed by HRP, produced 2,3-diaminophenazine (PDA), which was detected by chemiluminescence imaging analysis with the bis(2,4,6-trichlorophenyl)oxalate (TCPO)-H(2)O(2)-glyoxaline-PDA chemiluminescent system. The TCPO chemiluminescent imaging system is more sensitive and the chemiluminescence quantum yield is at least five times higher than for the luminol-H(2)O(2)-HRP-PIP (p-iodophenol) chemiluminescent imaging system. The results showed there was a very good linear correlation between response and amount of alpha-IFN in the range 1.3-156.0 pg mL(-1) (R = 0.9991) and the detection limit was 0.8 pg mL(-1) (S/N=3). The relative standard deviation (n = 9) was 4.7%. The proposed method has been used for successful analysis of the amount of alpha-IFN in human serum. The results obtained compared well with those obtained by conventional colorimetric ELISA and luminol chemiluminescent ELISA.

Correlation between the anti-virus-induced cytopathic effect activity of interferon-alpha subtypes and induction of MxA protein in vitro

There are several interferon-alpha (IFN-alpha) subtypes. Mechanism of disparity in biological effects among members of IFN-alpha subtypes remains unexplained. Biological activity of IFN-alpha is mediated in part by induction of intracellular antiviral proteins. We studied whether differences in biologic effects of IFN-alpha subtypes may rely on their antiviral protein inducing effect. Intracellular induction of MxA protein and anti-virus-induced cytopathic effect (CPE) activity of 11 IFN-alpha subtypes in human amnion WISH cells have been studied. MxA protein quantitation in cell lysates was performed by immunochemiluminescence assay and anti-virus-induced CPE activity was assessed by protection against vesicular stomatitis virus (VSV)-induced CPE. Range of MxA values was high when cells were treated with 10 and 100 IU/ml of each IFN-alpha subtype. Levels of MxA correlated with anti-VSV-induced CPE obtained with 10 IU/ml IFN-alpha subtype. Together our data show a disparity in MxA-inducing activity of IFN-alpha subtypes and suggest that differences in anti-VSV-induced CPE of IFN-alpha subtypes in WISH cells can be related to their different ability to induce MxA.

Activation of mast cells by double-stranded RNA: evidence for activation through Toll-like receptor 3

BACKGROUND

Although mast cells (MCs) have been clearly implicated in innate immune responses involving bacteria, their ability to respond to viral infection is less clear.

OBJECTIVE

Given that MCs increase at sites of inflammation and are located at surfaces where exposure to invading viruses may occur, we explored the ability of MCs to produce cytokines including type I IFNs after exposure to viruses and to polyinosine-polycytidylic acid (polyI:C), a synthetic mimic of viral double-stranded RNA, and characterized the receptors involved, if any.

METHODS

Human peripheral blood-derived cultured MCs and 2 MC lines, Laboratory of Allergic Disease MC line and human MC line 1, were stimulated with viruses and polyI:C, and cytokine production, degranulation, and signaling pathway activation were examined. Because polyI:C is a ligand for Toll-like receptor (TLR)-3, human MCs were also analyzed for TLR expression.

RESULTS

Viruses and polyI:C induced IFN-alpha and IFN-beta production. PolyI:C did not induce TNF, IL-1beta, IL-5, or GM-CSF production, in contrast with other TLR ligands (LPS, peptidoglycan, CpG-A, or flagellin). IFN-alpha production involved nuclear factor-kappaB, p38, and C-Jun NH2-terminal kinase and mitogen-activated protein kinase. RT-PCR and Western blot analysis confirmed expression of TLR-3 by all MCs. Human cultured MCs also expressed TLR-1, TLR-2, TLR-4, TLR-5, TLR-6, TLR-7 and TLR-9. Antibodies to TLR-3 significantly decreased IFN-alpha production. Bone marrow-derived MCs from TLR-3 knockout mice showed an ablated response to polyI:C.

CONCLUSIONS

Murine and human MCs produce type I IFNs after exposure to double-stranded RNA and/or virus, the former via specific interactions with TLR-3. These data suggest that MCs contribute to innate immune responses to viral infection via the production of type I IFNs.

Detection of differential expression of mouse interferon-alpha subtypes by polymerase chain reaction using specific primers

Specific primers for nine mouse interferon-alpha (IFN-alpha) subtypes, namely, IFN-alpha1, IFN-alpha1-9, IFN-alpha2, IFN-alpha4, IFN-alpha5, IFN-alpha7, IFN-alpha6/8, IFN-alpha11, and IFN-alphaB, were designed and evaluated on Poly(I).Poly(C)-induced and influenza virus-infected L929 cells. Specificity of the primers was confirmed in a cross-polymerase chain reaction (cross-PCR). IFN-alpha1, IFN-alpha1-9, IFN-alpha4, IFN-alpha6/8, IFN-alpha11, and IFN-alphaB were found to be induced in L929 cells 6-9 h after Poly(I).Poly(C) treatment. The amplification of a particular subtype was not biased in the presence of excess of other templates. Differential expression of the IFN-alpha subtypes was observed in influenza A/NWS/33- and B/Lee/40-infected L929 cells. A/NWS/33 virus was found to upregulate the gene expression of IFN-alpha1, IFN-alpha4, IFN-alpha6/8, IFN-alpha11, and IFN-alphaB in L929 cells as early as 6 h after infection. In B/Lee/40-infected L929 cells, only IFN-alpha4 was upregulated. Our results suggest that the designed primers will serve as a useful tool in analyzing the expression of IFN-alpha subtypes in various systems and hence for the evaluation of their function.

Increased oxidative stress in dimethylnitrosamine-induced liver fibrosis in the rat: effect of N-acetylcysteine and interferon-alpha

Oxidative stress may represent a common link between chronic liver damage and hepatic fibrosis. Antioxidants and interferon seem to protect against hepatic stellate cell (HSC) activation and liver fibrosis. This study evaluated (1) the effect of the profibrotic agent dimethylnitrosamine (DMN) on the hepatic oxidative balance in the rat; (2) the role played by the antioxidant agent N-acetylcysteine (NAC); and (3) the antifibrotic effects of two different types of interferon-alpha: recombinant alpha-2b (rIFN-alpha) and leukocyte alpha (LeIFN-alpha). Five groups of rats received: (1) saline; (2) DMN; (3) DMN + NAC; (4) DMN + rIFN-alpha; and (5) DMN + LeIFN-alpha. Oxidative balance was evaluated by hepatic glutathione, TBARs, protein carbonyl, and sulfhydryl determination. Fibrosis was determined by hepatic hydroxyproline content and fibronectin (FN) staining (immunohistochemistry). DMN rats showed a diffuse FN deposition, an impaired oxidative balance, and higher hepatic hydroxyproline levels compared to that of controls. NAC administration significantly reduced FN deposition, increased hepatic glutathione, and decreased TBARs and protein carbonyls. Administration of IFN-alpha exerted different effects according to the type used. Both IFNs decreased FN deposition; however, LeIFN-alpha significantly improved histology and oxidative parameters compared to those of untreated DMN and rats treated with rIFN-alpha. This study shows the role of free radicals in this model of hepatic fibrosis; the protective effect of NAC against liver fibrosis; and the antifibrotic effect exerted by IFN-alpha (particularly LeIFN-alpha) independent of its antiviral activity.

Biologic and binding activities of IFN-alpha subtypes in ACHN human renal cell carcinoma cells and Daudi Burkitt's lymphoma cells

Nine interferon-alpha subtypes, IFN-alpha1, IFN-alpha2, IFN-alpha5, IFN-alpha7, IFN-alpha8, IFN-alpha10, IFN-alpha14, IFN-alpha17, and IFN-alpha21, were separated from purified human lymphoblastoid IFN. We tested their inhibitory effects on cell growth and replication of Semliki Forest virus (SFV) and vesicular stomatitis virus (VSV) and their induction of 2',5'-oligoadenylate synthetase (2', 5'-OAS) in ACHN renal cell carcinoma cells. In terms of all three activities, the nine subtypes had similar relative activities, with IFN-alpha10 the most active and IFN-alpha1 the least. Their relative effects on cell growth were similar in two other human cell lines, SK-LU-1 lung cancer cells and KU-2 renal cell carcinoma cells, whereas cells of the Daudi Burkitt lymphoma line behaved quite differently, being highly sensitive to all the nine subtypes. The relative effects with ACHN cells correlated well with their relative binding affinities. However, each of the subtypes bound to both ACHN and Daudi cells to almost the same extent. This suggests that their profound inhibitory effects on the growth of Daudi cells are amplified at some stage in the signal transduction pathway or in the expression of genes that results from binding to the IFN-alpha receptor.

Stimulation of interferon and cytokine gene expression by imiquimod and stimulation by Sendai virus utilize similar signal transduction pathways

The imidazoquinolineamine derivative 1-(2-methyl propyl)-1H-imidazole [4,5-c]quinoline-4-amine (imiquimod) has been shown to induce alpha interferon (IFN-alpha) synthesis both in vivo and in peripheral blood mononuclear cells in vitro. In this study, we show that, in these cells, imiquimod induces expression of several IFNA genes (IFNA1, IFNA2, IFNA5, IFNA6, and IFNA8) as well as the IFNB gene. Imiquimod also induced the expression of interleukin (IL)-6, IL-8, and tumor necrosis factor alpha genes. Expression of all these genes was transient, independent of cellular protein synthesis, and inhibited in the presence of tyrosine kinase and protein kinase C inhibitors. Infection with Sendai virus led to expression of a similar set of cytokine genes and several of the IFNA genes. Imiquimod stimulates binding of several induction-specific nuclear complexes: (i) the NF-kappa B-specific complexes binding to the kappa B enhancer present in the promoters of all cytokine genes, but not in IFNA genes, and (ii) the complex(es) binding to the A4F1 site, 5'-GTAAAGAAAGT-3', conserved in the inducible element of IFNA genes. These results indicate that imiquimod, similar to viral infection, stimulates expression of a large number of cytokine genes, including IFN-alpha/beta, and that the signal transduction pathway induced by both of these stimuli requires tyrosine kinase and protein kinase activity.

The human interferon alpha-receptor protein confers differential responses to human interferon-beta versus interferon-alpha subtypes in mouse and hamster cell transfectants

The human interferon alpha-receptor (IFNAR gene product or IFN alpha R protein) was expressed in hamster CHO cells and in mouse A9 cells. The response of the IFN alpha R cDNA transfectants to human IFNs was studied by measuring induction of (2'-5') A synthetase (2'-5' AS). In the murine cells, the IFN alpha R protein conferred response to the human IFN-alpha-8 (alpha-B) subtype, but not to huIFN-alpha-2 (alpha-A) or to huIFN-beta. In murine huIFN alpha R cDNA transfectants, containing a hygromycin B resistance gene placed under the control of the 2'-5' AS gene Interferon Response Sequence (IRS), survival and growth of the cells in the presence of hygromycin B was induced by huIFN-alpha-8 but not by huIFN-alpha-2, indicating that the effect of huIFN alpha R is transcriptional. In hamster CHO cells, the huIFN alpha R protein conferred a completely different pattern of response to human IFN subtypes. Thus, the CHO-IFN alpha R transfectants responded to huIFN-beta by 2'-5' AS induction as well as by activation of the ISGF3 and IRF-1 transcription factors. In contrast, the CHO-IFN alpha R cells showed no response to huIFN-alpha-8. The differential response conferred by the huIFN alpha R protein in the two types of rodent cells, indicates that IFN subtype recognition is influenced by another component contributed by the rodent host cell. The ability of human cells, and of human-mouse hybrid cells containing human chromosome 21, to respond to all IFN subtypes is likely to depend also on interactions of the IFN alpha R protein with additional receptor components.

Differential inactivation of interferons by a protease from human granulocytes

Human leukocyte suspensions produced interferon-alpha (IFN-alpha) without induction during incubation at 37 degrees C. The highest titers were obtained at about 30 million cells/ml. The best yields, approximately 2 IU per 10(6) cells, were achieved in medium with or without albumin; serum inhibited the production. The uninduced IFN-alpha peaked at 24 h. The titers dropped on further incubation due to release of a protease from polymorphonuclear cells. The protease inactivated all tested human class I IFNs, but recombinant IFN-alpha 1 was clearly more resistant to the enzyme than rIFN-alpha 2. Human IFNs-gamma from different sources exhibited striking differences in their sensitivity to the protease. Glycosylated natural IFN-gamma from human leukocytes and glycosylated rIFN-gamma from CHO cells were relatively resistant, whereas unglycosylated rIFN-gamma from Escherichia coli was rapidly degraded by the protease. The protease was inhibited by PMSF and by greater than or equal to 1% human or fetal bovine serum but not by EDTA or less than or equal to 1% human albumin. Its optimum pH was between 7 and 8. It was resistant to treatment for 30 min at 56 degrees C.

A comparison of interferon-Con1 with natural recombinant interferons-alpha: antiviral, antiproliferative, and natural killer-inducing activities

The antiviral, antiproliferative, and natural killer (NK) cell activation by recombinant human interferon-consensus (IFN-Con1) has been compared with that of two other type I IFNs: IFN-alpha 2a (Roferon) and IFN-alpha 2b (Intron A). The specific activity (antiviral units/mg) of IFN-Con1 was 10-fold higher than that of the other two IFNs in the vesicular stomatitis virus (VSV)-HeLa antiviral assay. The antiproliferative activity on a molar basis of IFN-Con1 on Daudi cells and Eskol (a human leukemic hairy cell-like cell line) was significantly greater than that of IFN-alpha 2a and IFN-alpha 2b. IFN-Con1 also enhanced or induced NK cell killing of target cells to a greater extent than that of IFN-alpha 2a and IFN-alpha 2b. However, on antiviral unit basis, the activities were similar. These results would suggest that IFN-Con1 may be more effective at lower protein concentrations in clinical applications than other available IFNs.

Multiple interferon subtypes: the phenomenon and its relevance

Over the last 10 years the structure of various human interferon-alpha (IFN-alpha) and interferon-gamma (IFN-gamma) subtypes was elucidated by combining protein chemistry and molecular biology. In this article some key studies related to the interferon structure are reviewed. The significance of the multiplicity of IFN-alpha and IFN-gamma subtypes is discussed in view of some current results.

Cloned human interferons alpha: differential affinities for polyinosinic acid and relationship between molecular structure and species specificity

The HuIFN-alpha A and HuIFN-alpha D interferons, produced by two independent recombinant bacterial clones, have different affinities for polyinosinic acid (poly I). The monomeric form HuIFN-alpha A (FMM), but not the HuIFN-alpha D, binds to poly (I)-agarose and is protected by poly (I) from thermal inactivation. Other subtypes of HuIFN-alpha A including the monomer SMM and oligomers have no affinity for this polynucleotide. In addition, these interferons show different target cell preferences in agreement with our previous suggestion (23) that the polynucleotide binding domain may be responsible for species specificity. Two significant observations are 1) the fractions of HuIFN-alpha D and HuIFN-alpha A unbound on poly (I)-agarose show higher antiviral inducing activity on heterologous (MDBK) than on homologous (WISH) cells, whereas they induce about the same activity of 2'5' oligoadenylate synthetase in these two cell lines. These fractions are also active on L929 cells. 2) The bound fraction of HuIFN-alpha A induces almost the same antiviral and 2'5' oligoadenylate synthetase activities in MDBK and in WISH cells but neither activity in L929 cells.

Multiple molecular forms of interferon display different specific activities in the induction of the antiviral state and 2'5' oligoadenylate synthetase

Both Hu IFN-alpha A and Hu IFN-alpha D, produced by two independent recombinant bacterial clones, are mixtures of monomers, dimers and trimers. These forms, when assayed individually in heterologous MDBK cells, induced different degree of antiviral and 2'5' oligoadenylate synthetase (2'5' A synthetase) activities: the antiviral activity of the monomer is greater than that of the dimer and the trimer, whereas the activity of 2'5' A synthetase induction is lower with the monomer than with the dimer or the trimer. Similar differences are also observed on human cells. Compared to the mononeric form, the dimeric and the trimeric forms of Hu IFN-alpha A show higher antiviral inducing activity on heterologous MDBK cells than on homologous WISH cells, whereas the 2'5' A synthetase inducing activity in these two cell lines is about the same. Thus for the same antiviral activity, the trimer or the dimer compared to the monomer are much better inducers of the 2'5' A synthetase on human than on MDBK cells.

Antiviral and antiproliferative activities of interferon-alpha 1: the role of cysteine residues

Site-specific in vitro mutagenesis was used to direct serine for cysteine substitutions within the sequence of human interferon-alpha 1 (IFN-alpha 1). Antiviral specific activities and antiproliferative activities of IFN-alpha 1 analogs, expressed in M13 as fusion proteins, were assessed following purification by monoclonal antibody affinity chromatography. Based on analysis of IFN-alpha 2, IFN-alpha 1 contains two disulfide bridges between cysteine residues 29 and 139 and cysteine residues 1 and 99. IFN-alpha 1 also contains a fifth cysteine residue at position 86. The series of serine for cysteine substitutions performed indicated that IFN-alpha 1 molecules unable to form the residue 29 to residue 139 disulfide bridge have substantially reduced antiviral and antiproliferative activities, IFN-alpha 1 molecules unable to form the residue 1 to residue 99 disulfide bridge have only marginally altered antiviral and antiproliferative activities, the low antiviral activity of IFN-alpha 1 compared with other human IFN-alpha subtypes is not due to the formation of nonnative disulfide bridges involving the fifth cysteine residue at position 86, which the other subtypes lack, and (iv) the reduced biological activities of certain analogs may be due to the formation of nonnative disulfide bridges.

Epitope localization of a monoclonal antibody, LO-22, with broad specificity for interferon-alpha subtypes

A murine monoclonal antibody, LO-22, with broad cross-reactivity to human interferon-alpha (HuIFN-alpha) subtypes and some animal IFN-alpha species was found to bind less efficiently to IFN-alpha A (IFN-alpha 2a). In contrast, LO-22 bound strongly to IFN-alpha 2 (IFN-alpha 2b) and IFN-alpha 2C (IFN-alpha 2c) which differ by one or two amino acids, respectively, from IFN-alpha A; the latter has lysine at position 23 whereas the other closely related IFNs have arginine. LO-22 also bound efficiently to IFN-alpha D which is only 83% related to IFN-alpha A, but which also has arginine at position 23. These results strongly suggest that LO-22 recognizes a conserved epitope among IFN-alpha subtypes in which arginine at position 23 is involved. The specificity of a second monoclonal antibody, MT4/E4, is also reported and compared to that of LO-22.

Structure and expression of cDNA and genes for human interferon-beta-2, a distinct species inducible by growth-stimulatory cytokines

Induced human fibroblasts produce several mRNAs encoding interferon (IFN) activity. We previously cloned cDNA for a 1.3-kb RNA designated IFN-beta 2 and distinct from the 0.9-kb IFN-beta 1 mRNA. In vitro transcription--translation mapping of the full-length IFN-beta 2 cDNA sequence, shows that it encodes a 23.7-kd protein of 212 amino acids. This cDNA, fused to the SV40 early gene promoter, was transfected and amplified in Chinese hamster ovary cells and clones were obtained which constitutively produce human interferon activity. Two IFN-beta 2 genomic clones were isolated and their expression in hamster and mouse cells also produces biologically active rIFN-beta 2. Specific immunoassays show that IFN-beta 2 secreted by DNA-transformed rodent cells is a processed 21-kd protein, whose activity is cross-neutralized by antibodies to human IFN-beta 1 but not to IFN-alpha or gamma. The immunoassay also demonstrates the induction of IFN-beta 2 secretion by fibroblasts in response to growth-regulatory cytokines, such as interleukin-1 and tumor necrosis factor. The function of this IFN-beta 2 as an autoregulatory inhibitor of cell growth is discussed.

Human monocytes and lymphocytes produce different mixtures of alpha-interferon subtypes

alpha-Interferon (IFN-alpha) was produced by either peripheral blood lymphocytes or by monocytes and purified by an anti-IFN-alpha affinity column. When these preparations were analyzed by reversed-phase HPLC, a difference in the distribution of IFN-alpha subtypes from the two cell types was found. While the two major subtypes of IFN from induced lymphocytes had apparent molecular weights of 20K and 21K, monocytes produce an additional subtype of molecular weight 26K in large quantities (50%). This subtype had greater activity on human cells than on bovine cells in comparison to other IFN-alpha subtypes.

Priming of leukocytes selectively increases the level of some interferon-alpha subtypes and not others

The effect of pretreatment with interferon (IFN) ('priming') on the production of individual IFN subtypes was studied in subpopulations of human peripheral blood mononuclear cells and in the myeloid cell line KG-1. It was found that priming had a selective enhancing effect on the production of certain IFN-alpha subtypes (IFN-alpha 20K and IFN-alpha 21K) and not on others. KG-1 cells produce both IFN-alpha and -beta; however, only the production of IFN-alpha was enhanced by priming with either IFN-alpha, beta or gamma.

Nasal interferon responses in leukaemia

Nasal concentrations of leucocyte interferon measured immunoradiometrically were appreciably higher in children infected with influenza viruses than those infected with paramyxoviruses. Regardless of the infecting virus, leukaemic children produced normal amounts of interferon, but this appeared to have little effect on the duration of excretion of virus.