Murine tumor cells expressing the gene for the human interferon alpha beta receptor elicit antibodies in syngeneic mice to the active form of the receptor

Persistent effect of IFNAR-1 genetic polymorphism on the long-term pathogenesis of chronic HBV infection

Genetic polymorphism of IFNAR-1 plays a large role in determining the clearance or chronicity after hepatitis B virus (HBV) exposure. However, it is not clear whether type I interferon receptor-1 (IFNAR-1) variations continuously exert their effects to influence the final outcomes following HBV chronicity, including acute-on-chronic hepatitis B liver failure (ACLF-HBV), chronic hepatitis B (CHB), liver cirrhosis (LC), and hepatocellular carcinoma (HCC). Here we report that these four potential outcomes of chronic HBV infection are strongly associated with IFNAR-1 polymorphisms through a hospital-based case-control study of 663 cases. ACLF-HBV and HCC were each compared with CHB+LC. In comparison with the G/G genotype, the C/G and C/C genotypes at both single-nucleotide polymorphism (SNP) sites (rs1012335 and rs2257167) showed significant susceptibility to ACLF-HBV (the highest odds ratio [OR] reached 2.374; 95% CI = 1.488, 3.788; p < 0.001 for the C/G genotype at rs2257167), as well as HCC (OR = 2.475; 95% CI = 1.435, 4.426; p < 0.001 for the C/C genotype at rs1012335). The C allele at both loci was a susceptibility allele for ACLF-HBV and HCC, with the highest ORs reaching 1.653 (95% CI = 1.233, 2.216; p < 0.01 at rs1012335) in the ACLF-HBV group, and 1.659 (95% CI = 1.274, 2.159; p < 0.01 at rs1012335) in the HCC group. A strongly linked disequilibrium was also found within these two alleles (p < 0.001). Our research indicates that genetic polymorphisms of IFNAR-1 not only contribute to the determination of clearance or chronicity in the early stages of HBV exposure, but they also persistently influence pathogenesis over the long-term process of chronic HBV infection.

Polymorphisms of type I interferon receptor 1 promoter and their effects on chronic hepatitis B virus infection

BACKGROUND/AIMS

Exposure to HBV leads to a distinct clinical course which is partially pertained to host genetic variability. We aimed to study polymorphisms of type I interferon receptor 1 (IFNAR1) promoter and their potential effects on chronic HBV infection.

METHODS

Polymorphisms of IFNAR1 promoter were identified in 320 chronic hepatitis B patients, 148 spontaneously recovered individuals, 148 healthy Chinese donors and 114 Caucasians. Their functional capability in driving reporter gene expression was analyzed.

RESULTS

Four polymorphic alleles were identified at loci -568, -408, -77 and -3. Association analysis revealed that carriers of alleles -568G, -408C and their related haplotype I were less susceptible to chronic HBV infection whereas those of alleles -568C, -408T and related haplotype III were significantly associated with higher risk to chronic hepatitis B (P<0.01). In a reporter-driven system, the promoter variants with alleles -408C and -3C could drive higher expression of the reporter gene than those with alleles -408T and -3T (P<0.01). Interestingly, an allele with 9 GT repeats at -77 that was rarely found in Chinese but prevalent in Caucasian exhibited the highest transcriptional ability.

CONCLUSIONS

Our results showed that polymorphisms of IFNAR1 promoter may affect, at least in part, the outcomes of HBV infection.

Expression and biological activity of two recombinant polypeptides related to subunit 1 of the interferon-alpha receptor

Abnormal production of interferon alpha (IFN-alpha) has been found in certain autoimmune diseases and can be also observed after prolonged therapy with IFN-alpha. IFN-alpha can contribute to the pathogenesis of allograft rejection in bone marrow transplants. Therefore, the development of IFN-alpha inhibitors as a soluble receptor protein may be valuable for the therapeutic control of these diseases. We have expressed two polypeptides encoding amino acids 93-260 (P1) and 261-410 (P2) of the extracellular domain of subunit 1 of the interferon-alpha receptor (IFNAR 1-EC) in E. coli. The activities of the recombinant polypeptides and of their respective antibodies were evaluated using antiproliferative and antiviral assays. Expression of P1 and P2 polypeptides was achieved by transformation of cloned plasmid pRSET A into E. coli BL21(DE3)pLysS and by IPTG induction. P1 and P2 were purified by serial sonication steps and by gel filtration chromatography with 8 M urea and refolded by dialysis. Under reducing SDS-PAGE conditions, the molecular weight of P1 and P2 was 22 and 17 kDa, respectively. Polyclonal anti-P1 and anti-P2 antibodies were produced in mice. P1 and P2 and their respective polyclonal antibodies were able to block the antiproliferative activity of 6.25 nM IFN-alphaB on Daudi cells, but did not block IFN-alphaB activity at higher concentrations (>6. 25 nM). On the other hand, the polypeptides and their respective antibodies did not inhibit the antiviral activity of IFN-alphaB on Hep 2/c cells challenged with encephalomyocarditis virus.

The human interferon alpha species and receptors

Interferon (IFN) was approved by the U.S. Food and Drug Administration on June 5, 1986. As the first biotherapeutic approved, IFN-alpha paved the way for development of many other cytokines and growth factors. Nevertheless, we have just touched the surface of understanding the multitude of human IFNs. This paper reviews the history of the purification of human leukocyte IFN and key aspects of our current state of knowledge of human interferon alpha genes, proteins, and receptors.

The type I interferon receptor: structure, function, and evolution of a family business

Recent results indicate that coherent models of how multiple interferons (IFN) are recognized and signal selectively through a common receptor are now feasible. A proposal is made that the IFN receptor, with its subunits IFNAR-1 and IFNAR-2, presents two separate ligand binding sites, and this double structure is both necessary and sufficient to ensure that the different IFN are recognized and can act selectively. The key feature is the duplication of the extracellular domain of the IFNAR-1 subunit and the configurational geometry that this imposes on the intracellular domains of the receptor subunits and their associated tyrosine kinases.

Shared receptor components but distinct complexes for alpha and beta interferons

The type I interferon family includes 13 alpha, one omega and one beta subtypes recognized by a complex containing the receptor subunits ifnar1 and ifnar2 and their associated Janus tyrosine kinases, Tyk2 and Jak1. To investigate the reported differences in the way that alpha and beta interferons signal through the receptor, we introduced alanine-substitutions in the ifnar2 extracellular domain, and expressed the mutants in U5A cells, lacking endogenous ifnar2. A selection, designed to recover mutants that responded preferentially to alpha or beta interferon yielded three groups: I, neutral; II, sensitive to alpha interferon, partially resistant to beta interferon; III, resistant to alpha interferon, partially sensitive to beta interferon. A mutant clone, TMK, fully resistant to alpha interferon with good sensitivity to beta interferon, was characterized in detail and compared with U5A cells complemented with wild-type ifnar2 and also with Tyk2-deficient 11.1 cells, which exhibit a similar alpha-unresponsive phenotype with a partial beta interferon response. Using anti-receptor antibodies and mutant forms of beta interferon, three distinct modes of ligand interaction could be discerned: (i) alpha interferon with ifnar1 and ifnar2; (ii) beta interferon with ifnar1 and ifnar2; (iii) beta interferon with ifnar2 alone. We conclude that alpha and beta interferons signal differently through their receptors because the two ligand subtypes interact with the receptor subunits ifnar 1 and ifnar2 in entirely different ways.

Interferons Alpha, Beta, and Omega

Interferon alpha (IFN-α) is a mixture of closely related proteins, termed “subtypes,” expressed from distinct chromosomal genes. Interferon β (IFN-β) is a single protein species and is molecularly related to IFN-α subtypes, although it is antigenically distinct from them. IFN omega (IFN-ω) is antigenically distinct from IFN-α and IFN-β but is molecularly related to both. The genes of three IFN subtypes are tandemly arranged on the short arm of chromosome 9. They are transiently expressed following induction by various exogenous stimuli, including viruses. They are synthesized from their respective mRNAs for relatively short periods following gene activation and are secreted to act, via specific cell surface receptors, on other cells. IFN-α subtypes are secreted proteins and as such are transcribed from mRNAs as precursor proteins, pre-IFN-α, containing N-terminal signal polypeptides of 23 hydrophobic amino acids (aa) mainly. Pre-IFN-β contains 187 aa, of which 21 comprise the N-terminal signal polypeptide and 166 comprise the mature IFN-β protein. IFN-ω contains 195 aa—the N-terminal 23 comprising the signal sequence and the remaining 172, the mature IFN-ω protein. At the C-terminus, the aa sequence of IFN-ω is six residues longer than that of IFN-α or IFN-β proteins. IFN-α, as a mixture of subtypes, and IFN-ω may be produced together following viral infection of null lymphocytes or monocytes/macrophages. The biological activities of IFNs are mostly dependent upon protein synthesis with selective subsets of proteins mediating individual activities. IFNs can also stimulate indirect antiviral and antitumor mechanisms, depending upon cellular differentiation and the induction of cytotoxic activity.

The amino-terminal region of Tyk2 sustains the level of interferon alpha receptor 1, a component of the interferon alpha/beta receptor

Tyk2 belongs to the Janus kinase (JAK) family of receptor associated tyrosine kinases, characterized by a large N-terminal region, a kinase-like domain and a tyrosine kinase domain. It was previously shown that Tyk2 contributes to interferon-alpha (IFN-alpha) signaling not only catalytically, but also as an essential intracellular component of the receptor complex, being required for high affinity binding of IFN-alpha. For this function the tyrosine kinase domain was found to be dispensable. Here, it is shown that mutant cells lacking Tyk2 have significantly reduced IFN-alpha receptor 1 (IFNAR1) protein level, whereas the mRNA level is unaltered. Expression of the N-terminal region of Tyk2 in these cells reconstituted wild-type IFNAR1 level, but did not restore the binding activity of the receptor. Studies of mutant Tyk2 forms deleted at the N terminus indicated that the integrity of the N-terminal region is required to sustain IFNAR1. These studies also showed that the N-terminal region does not directly modulate the basal autophosphorylation activity of Tyk2, but it is required for efficient in vitro IFNAR1 phosphorylation and for rendering the enzyme activatable by IFN-alpha. Overall, these results indicate that distinct Tyk2 domains provide different functions to the receptor complex: the N-terminal region sustains IFNAR1 level, whereas the kinase-like domain provides a function toward high affinity ligand binding.

Post-translational up-regulation of the cell surface-associated alpha component of the human type I interferon receptor during differentiation of peripheral blood monocytes: role in the biological response to type I interferon

Human peripheral blood monocytes cultured in vitro exhibit a greater sensitivity to the antiviral effect of type I interferon (IFN) compared to freshly isolated monocytes. We evaluated the effect of macrophage differentiation on the expression of type I IFN receptors (IFN-R). Binding studies with iodinated IFN-alpha 2 and Scatchard plot analysis revealed that a single class of high-affinity receptors was present in freshly isolated monocytes. Monocyte differentiation to macrophages resulted in a three- to fourfold increase in the number of cell surface receptors with no change in their affinity. Polymerase chain reaction analysis of RNA revealed that comparable levels of mRNA for the IFN-R alpha (IFNAR1) and IFNAR2 components were expressed in freshly isolated monocytes and 7-day cultured macrophages. Likewise, the levels of IFNAR1 protein remained constant over time in culture. Immunofluorescence studies revealed that IFNAR1 was localized in intracellular compartments of freshly isolated monocytes, whereas it was predominantly detected on the cell surface in 7-day cultured macrophages. The increased expression of IFN-R on the plasma membrane of cultured macrophages may, at least in part, account for the increased antiviral effect of type I IFN in these cells. These modifications represent one of the events occurring during monocyte differentiation that may play a role in the regulation of macrophage functions.

Human interferon-alpha receptor: identification of the region involved in binding to interferon-alpha B

Three polypeptides comprising amino acids 1-102, 93-260, and 261-410 of the extracellular domain of the human interferon-alpha receptor HuIFN-alpha R (Uzé, G., Lutfalla, G., and Gresser, I. Cell 1990; 60:225-234) have been expressed in Escherichia coli. The polypeptides were sequestered within bacterial inclusion bodies. Inclusion body material was solubilized by 8 M urea, and the polypeptides were purified by gel filtration or histidine tag-based affinity chromatography. Overall recovery of each purified and refolded polypeptide was approximately 0.5-0.8 mg/liter of cell culture. The polypeptides migrated as homogeneous monomers of 12 kDa, 22 kDa, and 17 kDa, respectively on reduced sodium dodecylsulfate polyacrylamide gel electrophoresis. The polypeptide fragments corresponding to amino acids 1-102, and 93-260 of the extracellular domain of HuIFN-alpha R lacked the ability to bind to IFN-alpha B and to inhibit its biologic activities. The polypeptide fragment corresponding to amino acids 261-410 of the receptor molecule inhibited the antiproliferative activity of IFN-alpha B and competed with the Daudi cell surface receptor for binding to this IFN-alpha species.

Isolation of a biologically active soluble human interferon-alpha receptor-GST fusion protein expressed in Escherichia coli

The cDNA encoding the extracellular domain of the human interferon-alpha (IFN-alpha) receptor (Uzé, G., Lutfalla, G., and Gresser, I. Cell 1990;60:225-234) lacking the signal peptide has been expressed in Escherichia coli as a fusion protein with glutathione S-transferase. The fusion protein represented 12% of total bacterial proteins and was found exclusively within cytoplasmic inclusion bodies. Inclusion body material was completely solubilized by 8 M urea; 20% solubilization was achieved by cell lysis in the presence of 0.45% cholamidopropyl dimethylammoniol-propane sulfonate and 1% Triton X-100. The soluble fusion protein was purified by gel filtration and affinity chromatography. Overall recovery of affinity purified fusion protein was approximately 100-200 micrograms/liter of cell culture. The affinity purified and refolded fusion protein exhibited the expected amino terminal sequence and M(r) of 68,000 on reduced sodium dodecylsulfate gel electrophoresis. The protein reacted with antibodies specific for the cloned IFN-alpha receptor and inhibited the antiviral and antiproliferative activities of recombinant IFN-alpha B. We have demonstrated that the fusion protein binds to IFN-alpha B and competes with the cell surface receptor for binding to this IFN-alpha species.

Binding of interferon-alpha and -beta to a component of the human type I interferon receptor expressed in simian cells

The type I interferons (IFNs) are a family of homologous cytokines that compete for receptor binding. Past experiments with a cloned human IFN-alpha receptor component (designated herein as HuIFNAR-1) transfected into different cell backgrounds have given contradictory results in terms of binding and signalling after exposure of cells to different human type I IFNs. In order to investigate the binding specificity of human type I IFN subtypes to HuIFNAR-1, a cDNA encoding HuIFNAR-1 was transfected into simian COS cells. HuIFNAR-1 expression in COS cells, which was confirmed by Northern blot analysis, resulted in increased binding of 125I-labelled HuIFN-alpha 2 and -beta. These data support the participation of this receptor component in ligand binding, probably in association with other receptor components.

Configuration of the interferon-alpha/beta receptor complex determines the context of the biological response

Constituents of the Type 1 interferon (IFN) receptor (IFNABR) identified to date include the alpha and beta transmembrane subunits and the associated intracellular kinases, Jak 1 and Tyk 2. In this report, we demonstrate that a human cell type that expresses both subunits of IFNABR, together with Jak 1 and Tyk 2, exhibits a limited binding capacity for and is only partially sensitive to the effects of IFN-alpha/beta, despite adequate levels of the cytoplasmic transcription factors Stat1, Stat2, and Stat3. Specifically, a low affinity interaction between IFN-alpha/beta and cell surface receptors results in ISGF3 (Stat1:2) activation and an antiviral response, yet no IFN-inducible growth inhibition. Using a panel of murine cells that are variably configured with respect to the human IFNABR-alpha/beta subunits, we provide evidence that an additional component(s) encoded on human chromosome 21 is required to confer high affinity binding and IFN-inducible growth inhibition to cells that express the alpha and beta subunits of the IFNABR. The data indicate that transcriptional activation that leads to an antiviral response is mediated by IFN-alpha/beta activation of IFNABR-alpha and IFNABR-beta in the context of a low affinity interaction, yet a high affinity interaction is necessary for signal transducing events that mediate growth inhibition. We provide evidence that the extent of ISGF3 activation correlates directly with the magnitude of an antiviral but not a growth inhibitory response.

Intrinsic ligand binding properties of the human and bovine alpha-interferon receptors

The Type I interferon receptor (IFN-alpha R) interacts with all IFN-alpha s, IFN-beta and IFN-omega, and seems to be a multisubunit receptor. To investigate the role of a cloned receptor subunit (IFN-alpha R1), we have examined the intrinsic ligand binding properties of the bovine and human IFN-alpha R1 polypeptides expressed in Xenopus laevis oocytes. Albeit with different efficiencies, Xenopus oocytes expressing either the human or bovine IFN-alpha R1 polypeptide exhibit significant binding and formation of crosslinked complexes with human IFN-alpha A and IFN-alpha B. Thus, the IFN-alpha R1 polypeptide most likely plays a direct role in ligand binding.

Transcription termination/polyadenylation occurs at multiple sites in the human type I interferon receptor gene

Based on the previously reported sequence, we isolated an independent cDNA clone encoding a binding component of the human type I interferon receptor (IFN-R). This cDNA is identical to the published sequence except that it lacks 62 bases of 5' untranslated sequence and terminates at the first of two potential polyadenylation sites. In Northern blot analyses of poly(A)+RNAs from both IFN-sensitive and IFN-resistant Daudi cells, this cloned cDNA hybridized to a predominant mRNA of 2.4 kb, as well as to mRNAs of 1.8, 4.8, and 5.6 kb, and occasionally 6.9 kb. These various transcripts, which were also observed at similar levels in Raji B cells and two T-cell lines, Jurkat and MOLT-4, were detected after high-stringency washes, and by alternate probes corresponding to subfragments of the cDNA. In contrast, only the 4.8- and 5.6-kb transcripts hybridized to a polymerase chain reaction (PCR)-derived probe that corresponded to genomic sequences immediately down-stream from the second polyadenylation site. These results indicate that the latter transcripts arise from the same gene as the predominant 2.4-kb mRNA due to incomplete transcription termination at either of the known polyadenylation sites. Finally, Northern blot analysis of total RNAs revealed the presence of the predominant 2.4-kb type I IFN-R transcript in numerous tissues from second trimester human fetuses, suggesting that the type I IFN-R gene is constitutively expressed in multiple cell types.

Generation and characterization of anti-idiotypic antibodies recognizing the interferon-alpha receptor: implications for ligand-receptor interactions

Monoclonal antibodies LI-1 and LI-8 against interferon-alpha A (IFN-alpha A) block IFN-alpha A activity and binding to its receptor, but they recognize distinct epitopes. Surprisingly, anti-idiotypic antibodies to both LI-1 and LI-8 have properties consistent with recognition of the receptor: anti-LI-1 and anti-LI-8 antibodies inhibit the binding of IFN-alpha A to its receptor. However, anti-LI-1 is an antagonist of IFN-alpha A, while anti-LI-8 is an agonist. Thus, at least some part of the epitopes on IFN-alpha A recognized by LI-1 and LI-8 are directly involved in receptor binding. Because these epitopes are spatially distinct, the implication is that the receptor binding site on IFN-alpha A must be extensive, or there are minimally two regions of IFN-alpha A involved in receptor interactions.

Cloning and characterization of a bovine alpha interferon receptor

A bovine interferon alpha receptor (BoIFN-alpha R1) cDNA, homologous to the human cDNA, was isolated. Transfection of the BoIFN-alpha R1 cDNA into monkey COS cells results in a large increase in high-affinity binding sites for human IFN-alpha A and IFN-alpha B. Covalent crosslinking of radiolabeled HuIFN-alpha A and -alpha B demonstrates that the complex of [32P]HuIFN with the BoIFN-alpha R1 protein (predicted mass, 61,375) expressed in COS cells migrates as a 140-150 kDa band.

Specific antiviral activities of the human alpha interferons are determined at the level of receptor (IFNAR) structure

Differences in activity among the family of human IFNs alpha are much reduced if these ligands are assayed on bovine cells. In particular, the activity of IFN alpha D is much higher on bovine than on human cells. To examine these differences, the bovine counterpart of the human IFNAR has been cloned and expressed in a human cell line. The transfected cell line now recognizes the human IFN alpha D as a high-specific-activity IFN subtype, indicating that the differences in sensitivity between the bovine and human cells to the human IFN alpha lie in the structure of the IFNAR chain rather than in the other components of the functional receptor.

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.