Production of high levels of human leukocyte interferon from a continuous human myeloblast cell culture

Murine B cell response to TLR7 ligands depends on an IFN-beta feedback loop

Type I IFNs play an important, yet poorly characterized, role in systemic lupus erythematosus. To better understand the interplay between type I IFNs and the activation of autoreactive B cells, we evaluated the effect of type I IFN receptor (IFNAR) deficiency in murine B cell responses to common TLR ligands. In comparison to wild-type B cells, TLR7-stimulated IFNAR(-/-) B cells proliferated significantly less well and did not up-regulate costimulatory molecules. By contrast, IFNAR1(-/-) B cells did not produce cytokines, but did proliferate and up-regulate activation markers in response to other TLR ligands. These defects were not due to a difference in the distribution of B cell populations or a failure to produce a soluble factor other than a type I IFN. Instead, the compromised response pattern reflected the disruption of an IFN-beta feedback loop and constitutively low expression of TLR7 in the IFNAR1(-/-) B cells. These results highlight subtle differences in the IFN dependence of TLR7 responses compared with other TLR-mediated B cell responses.

Detection of Differential Expression of Porcine IFN-αSubtypes by Reverse Transcription Polymerase Chain Reaction

The porcine interferon-alpha (IFN-alpha) multigene family is a new IFN-alpha system in recent research. Characterization of the PoIFN-alpha multigene family has been described in our previous work, and 14 functional PoIFN-alpha genes were detected in the porcine genome. In this study, we designed subtype-specific primers and consensus primers for PoIFN-alpha. The expression of PoIFN-alpha was detected using the two PCR strategies in three systems, namely, poly(I).poly(C)-DEAE-dextran-induced PK15 cells, pseudorabies virus-infected PK15 cells, and infected PK15 cells with an attenuated strain of swine fever virus, respectively. In poly(I).poly(C)-DEAE-dextran-induced PK15 cells, the expression of IFN-alpha2, -alpha3, -alpha4, -alpha8, and -alpha9 after 6-h/24-h inducement in PK15 cells were observed. In pseudorabies virus-infected PK15 cells, the expression of PoIFN-alpha2, -alpha3, -alpha8, -alpha9, -alpha10, and -alpha13 was observed after 6-h/24-h infection, and in the attenuated strain of swine fever virus-infected PK15 cells, upregulation of PoIFN-alpha2, -alpha3, -alpha4, -alpha8, -alpha9, and -alpha10 was detected. The results of realtime quantitative PCR analysis suggested that the expression was time-dependent in pseudorabies virus/poly(I).poly(C)-DEAE-dextran-induced PK15 cells, but in the attenuated swine fever virus-infected PK15 system, the expression level of IFN-alpha subtypes was not obviously time dependent.

The interferons: 50 years after their discovery, there is much more to learn

The interferons (IFNs) and their receptors represent a subset of the class 2 alpha-helical cytokines that have been in chordates for millions of years. This brief review focuses on the discovery and purification of interferons, cloning of human IFN-alpha and IFN-beta, interferon receptors, activities and therapeutic uses of interferons, and the side effects of interferons.

Characterization of the porcine alpha interferon multigene family

The availability of data on the pig genome sequence prompted us to characterize the porcine IFN-alpha (PoIFN-alpha) multigene family. Fourteen functional PoIFN-alpha genes and two PoIFN-alpha pseudogenes were detected in the porcine genome. Multiple sequence alignment revealed a C-terminal deletion of eight residues in six subtypes. A phylogenetic tree of the porcine IFN-alpha gene family defined the evolutionary relationship of the various subtypes. In addition, analysis of the evolutionary rate and the effect of positive selection suggested that the C-terminal deletion is a strategy for preservation in the genome. Eight PoIFN-alpha subtypes were isolated from the porcine liver genome and expressed in BHK-21 cells line. We detected the level of transcription by real-time quantitative RT-PCR analysis. The antiviral activities of the products were determined by WISH cells/Vesicular Stomatitis Virus (VSV) and PK 15 cells/Pseudorabies Virus (PRV) respectively. We found the antiviral activities of intact PoIFN-alpha genes are approximately 2-50 times higher than those of the subtypes with C-terminal deletions in WISH cells and 15-55 times higher in PK 15 cells. There was no obvious difference between the subtypes with and without C-terminal deletion on acid susceptibility.

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.

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.

Review of recent developments in the molecular characterization of recombinant alfa interferons on the 40th anniversary of the discovery of interferon

Recombinant alfa interferons (IFN-alpha s) are approved worldwide for the treatment of a variety of cancers and diseases of virologic origin. A series of recent advances in the molecular characterization of recombinant IFN-alpha s have allowed the determination of the three-dimensional IFN-alpha 2b structure by high-resolution x-ray crystallography. We review here recent developments in our understanding of the molecular and physicochemical properties of recombinant IFN-alpha, including our current state of knowledge of the IFN-alpha gene family and the multiple species of human leukocyte IFN. Based on the reported three-dimensional structure of IFN-alpha 2b, we propose a molecular model for the IFN-alpha 2b receptor complex and predict models for the naturally occurring subtypes IFN-alpha 1 and IFN-alpha 8, as well as the synthetic, non-naturally occurring consensus IFN. Such models provide molecular insights into the mechanism of action of IFN-alpha.

Identification of nine interferon-alpha subtypes produced by Sendai virus-induced human peripheral blood leucocytes

The human interferon-alpha (IFN-alpha) family is encoded by 13 different functional genes, and including all cloned sequence variants there are 28 potential IFN-alpha proteins. To find out which of the described sequences are expressed in normal human leucocytes, we have isolated and partly characterized the components of a highly purified IFN-alpha preparation produced by Sendai virus-induced human peripheral blood leucocytes. The identification protocol consisted of N-terminal sequencing and mass mapping of the proteins separated by reverse-phase HPLC and/or SDS/PAGE. The highly purified leucocyte IFN-alpha preparation was found to contain at least nine different IFN-alpha species: IFN-alpha1a, IFN-alpha2b, IFN-alpha4b, IFN-alpha7a, IFN-alpha8b, IFN-alpha10a, IFN-alpha14c, IFN-alpha17b and IFN-alpha21b. IFN-alpha1a was the major subtype, comprising approx. 30% of total leucocyte IFN-alpha. IFN-alpha14c, the only subtype containing potential N-glycosylation sites, was shown to be glycosylated at Asn-72. Molecular mass determination of the intact proteins by electrospray ionization MS showed that there are no other post-translational modifications in the IFN-alpha subtypes than the glycosylation of IFN-alpha2b and IFN-alpha14c. Only one sequence variant was found for each subtype, suggesting that the other described gene sequences represent allelic variants or mutations that are more rarely found in the general population.

Both variant forms of interferon-alpha4 gene (IFNA4a and IFNA4b) are present in the human population

Alpha interferons (IFN-alpha) are a class of cytokines with various activities that are used as therapeutic agents for treatment of cancer and viral and immune disorder diseases. At least 13 IFN-alpha genes and 1 IFN-alpha pseudogene have been identified, which are clustered on human chromosome 9. Among the known IFN-alpha species, a number of allelic variants have been reported. Two variants of IFN-alpha4 (IFN-alpha4a and IFN-alpha4b) are known, which differ from each other by changes in their coding regions at nucleotide positions 220 and 410 and can be distinguished by selective restriction enzyme analysis. We have developed oligonucleotide primers for specific amplification of IFN-alpha4 gene fragments using the polymerase chain reaction (PCR). Genomic DNA obtained from over 28,000 normal healthy individuals and six human cell lines were used in this study. The resulting PCR products were analyzed by restriction endonuclease digestion and DNA sequencing to identify the presence of variant sequences. The results show that the DNA sequences for both variants of IFN-alpha4 are found in the population in nearly equal proportion. Individuals with either homozygous (e.g., alpha4a/alpha4a or alpha4b/alpha4b) or heterozygous (i.e., alpha4a/alpha4b) IFN-alpha4 genes were detected. Among the cell lines, KG-1, EB-3, and HTB-10 cells contain the genes for IFN-alpha4a only, whereas U-937, Namalwa, and Daudi cells contain the genes for both IFN-alpha4a and IFN-alpha4b.

Unusual effect of clusters of rare arginine (AGG) codons on the expression of human interferon alpha 1 gene in Escherichia coli

The human interferon (hIFN alpha 1) gene contains 11 arginine (Arg) codons AGG or AGA, which are extremely rare for bacteria, four of which are organized in tandems. The two AGG tandems (corresponding to Arg12 Arg13 and Arg163 Arg164) are known to inhibit the translation of hIFN alpha 1 mRNA and therefore they are considered to be responsible for the poor expression of hIFN alpha 1 gene in bacterial cells. To study the effect of these two tandems on the expression of hIFN alpha 1 in E. coli, four new gene variants were designed to contain preferential Arg codons (CGT) substituted for the rare AGG codons in either the first, the second or both AGG tandems. We found that, whereas the yield of hIFN alpha 1 protein per cell remained unchanged, the level of hIFN alpha 1 mRNA decreased gradually (by a factor of two) with the consecutive substitution of the first, second and both AGG tandems. These results indicated, first, that the AGG clusters might have a stabilizing effect on the mRNA, and second, that mRNAs devoid of such clusters were translated at a higher rate in vivo. The protein products of the four genes (having the same amino acid sequence) showed different specific antiviral activity. The most active was the product of gene hIFN alpha 1(c) in which the second AGG tandem (corresponding to Arg163, Arg164) was preserved while the least active was the protein of gene hIFN alpha 1(d) (devoid of both AGG clusters). The role of the AGG tandems in folding of the gene product is discussed.

Identification of interferon-alpha 7, -alpha 14, and -alpha 21 variants in the genome of a large human population

The genes for type I interferon (IFN), which include 14 IFN-alpha genes, 1 IFN-beta gene, 1 IFN-omega gene, and a number of IFN-omega pseudogenes, are clustered on human chromosome 9. Among IFN-alpha genes, a number of variants have been reported. Three variants of IFN-alpha 7 (IFN-alpha 7a, IFN-alpha 7b, and IFN-alpha 7c) and IFN-alpha 14 (IFN-alpha 14a, IFN-alpha 14b, and IFN-alpha 14c) and two variants of IFN-alpha 21 (IFN-alpha 21a and IFN-alpha 21b) are identified. The variants differ from each other by base changes in the coding region and can be distinguished by selective restriction enzyme analysis and DNA sequencing. We have used polymerase chain reaction (PCR) with IFN species-specific oligonucleotide primers for amplification of IFN-alpha 7, IFN-alpha 14, and IFN-alpha 21 gene sequences. Genomic DNA obtained from over 28,000 normal healthy individuals were collected in six pools for PCR amplification. To identify the presence of variant sequences, the resulting PCR products of specific IFN-alpha genes were analyzed by restriction endonuclease digestion and DNA sequencing, with a limit of detection of minor components to 1% and 10%, respectively. The results show that only one variant form for each of IFN-alpha 7, IFN-alpha 14, and IFN-alpha 21, namely, IFN-alpha 7a, IFN-alpha 14c, and IFN-alpha 21b, is detectable in the genomic DNA of the population examined. Similar results were obtained from the analysis of a human myeloblastoid cell line, KG-1.

Human natural interferon-alpha producing cells

Interferons (IFNs) are critical components of the host immune system, serving as antiviral agents, immunomodulators and inhibitors of cell growth. Among peripheral blood mononuclear cells, the primary IFN-alpha-producing cell is a light density, HLA-DR+ cell negative for cell surface markers typical for T cells, B cells, monocytes, natural-killer or progenitor cells and has been tentatively termed the 'natural IFN-producing cell' or NIPC. Although present in very low frequency (approximately 1:1000 among peripheral blood mononuclear cells), the NIPC are very potent, with an individual cell able to produce 1-2 IU of IFN. In this review, the characteristics, phenotype, regulation and relationship of NIPC to human disease are discussed.

Detection of human leukocyte interferon-alpha A and -alpha 2 genes in genomic DNAs by the use of deoxyoctadecyloligonucleotide probes

Two deoxyoctadecyloligonucleotides complementary to the sequence spanning a single base substitution between human leukocyte interferon (HuIFN) alpha A and alpha 2 genes were efficiently used as probes to distinguish between HuIFN-alpha A and -alpha 2 genes. At 37 degrees C or 42 degrees C under aqueous conditions (0.9 M NaCl), hybridization between both probes and the alpha A and alpha 2 genes without any mismatch was strong, whereas the hybridization with one base mismatch (alpha A probe-alpha 2 gene and alpha 2 probe-alpha A gene) was very weak or negligible. Because the single base substitution of G in the alpha 2 gene for A in the alpha A gene provides an extra HinfI site in the alpha 2 gene at the center of the sequence hybridizing to the alpha 2 probe, digestion with HinfI restriction endonuclease caused complete loss of the hybridization between the alpha 2 probe and the alpha 2 gene. PvuII digestion provides 298-bp fragments hybridizing to the probes only from the alpha A and alpha 2 genes among the known HuIFN-alpha genes. Thus, with the use of these oligonucleotide probes in combination with PvuII and PvuII-HinfI restriction endonuclease digestion, the existence of the sequences corresponding to both IFN-alpha A and IFN-alpha 2 genes in human genomic DNAs was demonstrated. The results also surprisingly indicate that these genes, formerly considered alleles because of their essential identity (1 base pair difference in the coding sequence), are not likely to be alleles, but represent closely related distinct genes.

[Interferon sensitivity of various cell lines]

An economic assay to determine the yield of interferon is necessary for the induction, production and purification of interferon. Using the inhibition of cytopathic effect of vesicular stomatitis virus in a microtitre system, we compared the susceptibility of different cell lines against an internal IFN alpha standard obtained from Sendai virus-induced human leukocytes. Human fibroblasts carrying trisomy G 21 and bovine MDBK cells showed the highest sensitivity followed by normal human fibroblasts. Human RH kidney cells exhibited a susceptibility similar to that of human WISH amnion cells frequently used by others. The human amnion cell line FL and monkey Vero kidney cells, as described here, were unsuitable for the determination of IFN yields.

Purification, bacterial expression, and biological activities of the human interferons

The structural and functional complexity of the human interferon system has become increasingly evident. More than eight different alpha (leukocyte) interferons are expressed in induced human cells in culture. Many of these have been purified by a combination of methods, including high-performance liquid chromatography. Moreover, at least 12 different human leukocyte interferons have been cloned, and several have been efficiently expressed in Escherichia coli and other organisms. The availability of purified species of leukocyte interferon, both natural and recombinant, has allowed structural work to be done, including amino acid sequence determinations, chemical modification studies, and the crystallization of one species. The purified material has also been used for the production of monoclonal antibodies with various specificities that are proving invaluable in rapid assays and purification techniques. Testing of the purified species for their relative potency in antiviral, antiproliferative, and immunomodulatory assays has begun to demonstrate the functional uniqueness and diversity of the purified alpha interferons. Hybrid interferon genes have been synthesized by splicing together parts of various cloned interferon genes. The resulting hybrid proteins have been valuable in establishing structure/function relationships. In several cases, the functional properties of the hybrid protein were novel and unpredicted from the properties of the parental molecules.

MOlecular cloning of human alpha and beta interferon genes from Namalwa cells

A cDNA library constructed from poly(A)+RNA of Sendai virus-induced human lymphoblastoid (Namalwa) cells was screened with a synthetic oligonucleotide specific for interferon genes. Recombinant plasmids containing sequences derived from alpha and beta interferon (IFN) mRNAs were obtained. The clones were characterized by RNA transfer hybridization, translation of hybrid-isolated RNA, and DNA sequencing. One alpha interferon (IFN-alpha) clone obtained is a variant differing from previously described clones in the location of its polyadenylation site.

Cell cultures producing human interferon

Most of 27 B-lymphoblast and 5 other cell lines derived from human leukocytes were found to produce human interferon either constitutively or after induction with Newcastle disease virus. Several produced relatively high levels of interferon after induction.