Bacterial synthesis of a novel human leukocyte interferon

A novel solid-phase test to study the binding of IFN-gamma to its receptor

A novel solid phase assay for interferon-gamma (IFN-gamma) binding to the human IFN-gamma receptor was developed. The receptor binding assay is carried out using a soluble form of the recombinant IFN-gamma receptor protein corresponding to the extracellular portion of the IFN-gamma receptor. Using different IFN molecules and anti-IFN monoclonal antibodies, we show that the specificity of the soluble IFN-gamma receptor coated to the plastic surface is not altered. In consequence, this new generation binding test can be used to characterize the interactions with the specific ligand under controlled conditions. In comparison with ELISA or RIA tests using antibodies specific for IFN-gamma, the solid-phase binding assay has the advantage of detecting only the active molecules. Finally, since the test has a large capacity, it is being applied for the screening of agents that are able to neutralize the IFN-gamma activity either by blocking the active site of the lymphokine or the binding site of the specific receptor.

Modulation of expression of the human gamma interferon gene in E. coli by site-directed mutagenesis

Plasmids expressing 2 forms of human immune interferon (IFN-gamma) in E. coli have been constructed: 1) pIFNTacI which expresses IFN-gamma with an N-terminal amino acid sequence of met-cys-tyr-cys-gln-, and 2) pIFNTacII which is a derivative of pIFNTacI from which the 9 base pairs (bp) coding for the cys-tyr-cys have been deleted. Quantitation of Western blots showed that approximately 10-fold more IFN-gamma was produced in cells harboring pIFNTacII (7.5% of total cellular protein) as compared to pIFNTacI. The IFN-gamma expressed in E. coli pIFNTacII is biologically active and routinely recoverable at 10(9) units per liter. When examined microscopically, IPTG induced E. coli harboring either plasmid construction contains prominent cytoplasmic inclusion bodies.

Sequence-directed mutagenesis: evidence from a phylogenetic history of human alpha-interferon genes

We have studied the potential contribution of template-dependent events to genetic variation in mammals by examining the sequence alterations that have occurred in the recent evolution of human interferon genes. Fifteen members of the human alpha-interferon gene family were aligned, and a phylogenetic history was inferred. Many multiple events are inferred to have occurred in the evolution of the interferon genes and for the majority of these local DNA sequences were present that were capable of serving as templates for their occurrence. We conclude that the DNA sequence has the potential to explain many of the inferred spontaneous events and to explain complex alterations to sequences--i.e., the joint occurrence of base substitutions and insertions/deletions. Thus, such a mechanism would often cause multiple sequence changes as a result of a single mutational event and would provide additional genetic variation for evolution. Sequence-directed mutations would depend upon the local DNA sequences and, hence, would not be random at the DNA level.

Cloning with tandem gene systems for high level gene expression

A method has been devised for increasing the copy number of a gene (or genes) cloned into a plasmid while minimizing the size of the plasmid. If n copies of a transcriptional unit are cloned, including the promoter, coding region and terminator, the size of the plasmid will increase by n times the total size of the unit. However, if we borrow the concept of polycistronic operon and sandwich n structural genes, each with its own ribosome binding-site, between a promoter and a transcription terminator, there will be a space saving equivalent to n-1 promoters and n-1 transcription terminators. We have constructed plasmids in which an E. coli lipoprotein promoter is followed by 1 to 4 human leukocyte interferon genes and a transcription terminator. The applications of this method in genetic engineering are discussed.

High-level expression of a chemically synthesized gene for human interferon-gamma using a prokaryotic expression vector

A chemically synthesized gene for human interferon-gamma has been cloned into a prokaryotic expression vector under the regulation of a synthetic constitutive transcriptional-translational control unit that contains a strong bacteriophage T5 early promoter and a strong ribosome-binding site. Cells harboring the recombinant plasmid express high levels (4 X 10(9) units per liter of culture) of antiviral activity specific for interferon-gamma. Analysis of total cell lysates on NaDodSO4/polyacrylamide gels revealed a 17,200-dalton protein, expected for the nonglycosylated form of human interferon-gamma, that constitutes greater than 15% of total cell protein.

Monoclonal antibodies to a recombinant human leukocyte interferon (rIFN-alpha B)

Recombinant human leukocyte B interferon (rIFN-alpha B) was purified to approximately 60% on a column of monoclonal antibody to IFN-alpha. This partially purified rIFN-alpha B was in turn used as immunogen in obtaining four monoclonal antibodies to this recombinant interferon. All four antibodies, while showing varying degrees of cross-reactivity to some other rIFN-alpha subtypes, showed specificity to monomeric and dimeric forms of rIFN-alpha B only and not to the contaminants in the partially purified preparation as demonstrated in the Western blot immunoassay.

Recognition of messenger RNA during translational initiation in Escherichia coli

The structural aspects of recognition by E. coli ribosomes of translational initiation regions on homologous messenger RNAs have been reviewed. Also discussed is the location of initiation region on mRNA, its confines, typical nucleotide sequences responsible for initiation signal, and the influence of RNA macrostructure on protein synthesis initiation. Most of the published DNA nucleotide sequences surrounding the start of various E. coli genes and those of its phages have been collected.

Purified recombinant human leukocyte interferons IFLrA and IFLrD induce human lupus inclusions in Raji and Daudi cells

Raji and Daudi are human B lymphoblastoid cell lines that readily form lupus inclusions (LIs; TRS) when grown in medium supplemented with leukocyte-, or fibroblast-derived interferon (IFN-alpha, -beta, respectively). WISH, MDBK, and GM2504 are three cell lines commonly used to measure antiviral activities. None of them form LIs in their antiviral response to alpha or immune (gamma)IFN. This distinguishes between the abilities of a cell to develop an antiviral state and to form LIs in response to IFN. Human (Hu) lymphoblastoid IFN and the two pure and homogeneous recombinant human IFN-alpha proteins IFLrA and IFLrD induce LIs in Raji cells and Daudi cells. In Daudi, a simultaneous inhibition of cell growth occurs. When compared by antiviral activities, IFLrA inhibits the growth of Daudi cells more, while IFLrD induces the greater frequency of LIs. According to molecular concentration, IFLrA and IFLrD at 133 X 10(-13) M induce LIs in Daudi cells to their maximum frequency. Growth inhibition for these same cell samples is also at maximum for IFLrA, but only 25% of maximum for IFLrD. Our results with Raji and Daudi cells provide evidence against a cause-and-effect relationship between these two biologic responses to IFN by Daudi cells. They also provide evidence for distinct, but interacting, intracellular pathways. This phenomenon is a new explanation for some of the biologic diversity shown for the HuIFNs-alpha.

Computer-assisted analysis demonstrates that polypeptides induced by natural and recombinant human interferon-alpha are the same and that some have related primary structures

The biological effects on diploid and trisomy 21 human fibroblasts of pure human interferon IFLrA, a single IFN-alpha species produced from cloned DNA, were compared with those of partially purified natural IFN-alpha. Twelve interferon-induced polypeptides were visualized by two-dimensional gel electrophoresis and autoradiography. Seven of these were shown to have related primary structures and are therefore products of related genes or are related through post-translational modification. Qualitative visual comparisons and computer-aided quantitation of autoradiograms revealed no differences in the patterns of polypeptide induction following treatment with the two types of IFN-alpha, and the two interferons also induced (2'-5') oligoisoadenylate synthetase equally. By these criteria, the activities of the two interferons are qualitatively and quantitatively indistinguishable. In addition, the effects of trisomy 21 on IFLrA-induced polypeptide synthesis and on antiviral response were similar to those previously demonstrated with natural IFN-alpha.

Mechanism of interferon action: human leukocyte and immune interferons regulate the expression of different genes and induce different antiviral states in human amnion U cells

The inhibition of virus replication and the induction of protein phosphorylation were examined in human amnion U and human fibroblast GM2767A cells treated with highly purified cloned human leukocyte and immune interferons synthesized in Escherichia coli. Both leukocyte interferon (IFN-alpha A) and immune interferon (IFN-gamma) possessed antiviral activity as measured by the single cycle yield reduction of vesicular stomatitis virus (VSV) in the human U and GM2767A cell lines. By contrast, only IFN-gamma and not IFN-alpha A inhibited the single cycle replication of reovirus in U and GM2767A cells. IFN-alpha A, but not IFN-gamma, efficiently induced the double-stranded RNA-dependent phosphorylation of the ribosome-associated protein P1 and the alpha subunit of protein synthesis initiation factor eIF-2 in U cells. However, neither IFN-alpha A nor IFN-gamma induced the phosphorylation of P1 and eIF-2 alpha in GM2767A cells. The antiviral activities of IFN-alpha A and IFN-gamma were synergistic for the inhibition of VSV but not for the inhibition of reovirus or the induction of protein phosphorylation. These results suggest that human leukocyte and immune interferons differentially regulate the expression of certain genes and induce mechanistically distinct antiviral states in human cells.

Expression of human interferon genes using the recA promoter of Escherichia coli

Interferon beta 1 and three alpha-interferon genes were cloned on Eco RI fragments isolated from a human genomic library into the Eco RI site of a plasmid containing the recA promoter of E. coli. Expression of interferon activity from cells carrying these plasmids was nalidixic acid inducible. The alpha-interferon genes were expressed only when in the same transcriptional orientation as the recA promoter while the beta 1 interferon gene was expressed in either orientation. Interferon activity was also inducibly expressed from the recA promoter in cells containing a plasmid carrying a fusion of the recA gene with the beta 1 interferon gene. This interferon activity was thirty-fold less sensitive to neutralization by polyclonal antibodies than authentic interferon, implying that the change near the amino terminus affects either antibody recognition or specific activity or both.

Secretion of interferon by Bacillus subtilis

Bacillus subtilis was transformed with a hybrid gene in which the sequence encoding the alpha-amylase signal peptide was joined by a linker to the sequence encoding mature human interferon alpha 2(IFN-alpha 2). The hybrid preprotein was cleaved precisely following the last amino acid of the alpha-amylase signal sequence and was secreted at 0.5--1 mg per liter. IFN-alpha 2, preceded by either one or six amino acids, has the same specific antiviral activity as IFN-alpha 2 itself.

Expression in Escherichia coli of chemically synthesized gene for the human immune interferon

A 454 base pair fragment of double stranded DNA consisting of a gene for a human immune interferon (hIFN-gamma), initiation and termination signals plus appropriate restriction endonuclease sites, was totally synthesized. The synthesis involved preparation of 62 oligodeoxyribonucleotides by rapid, solid phase procedures, and enzymatic ligation of the oligonucleotides. This synthetic gene was expressed in E. coli under the control of the lac UV5 promoter. The product has antiviral activity which was acid labile and completely neutralized by antiserum to hIFN-gamma but not by antiserum to hIFN-alpha or hIFN-beta. Molecular weight of hIFN-gamma produced by E. coli was estimated to be about 32,000 and 17,000 by gel filtration and SDS-polyacrylamide gel electrophoresis respectively.

The complete DNA sequence of minute virus of mice, an autonomous parvovirus

We have determined the complete nucleotide sequence of the genome of Minute Virus of Mice, an autonomous parvovirus. This single-stranded DNA is 5081 nucleotides long. The 3'-and 5'-ends of the viral strand contain imperfect palindromic sequences which consist, respectively, of 115 and 206 nucleotides. The 3'-terminal palindrome is composed of a unique sequence, whereas the 5'-terminal palindrome contains two sequences in equimolar amounts; these are related in that one is the inverted complement of the other. The DNA strand complementary to that which is encapsidated into virions contains two large open reading frames which together span almost the entire genome. Transcriptional and translational signals within the sequence have been identified and related to the known map coordinates of the viral transcripts. In this report we summarize some of the salient structural and organizational features of the MVM genome.

Antibodies that react with predetermined sites on proteins

Contrary to previous predictions, relatively short synthetic peptides that mimic part of a protein sequence are routinely capable of eliciting an antiserum that reacts with the partially mimicked protein. Peptides capable of eliciting protein-reactive serums are frequently represented in the primary sequence of a protein, can be characterized by a set of simple chemical rules, and are confined neither to immunodominant regions of intact proteins nor to the amino or carboxyl terminals. As such, synthetic peptide immunogens are valuable for eliciting reagents with predetermined specificity that can be used for basic research. In addition, some synthetic peptides are capable of mimicking regions of virus proteins and eliciting immune responses in animals that are protective against the viral agents. Such peptides may thus serve as the basis for safe, chemically defined synthetic vaccines.

Biological properties of human interferon beta 1 synthesized in recombinant bacteria

Human fibroblast interferon, designated IFN-beta 1, has been produced in E. coli by direct expression of the cloned cDNA coding for the mature polypeptide. Bacterial lysates from recombinant cultures contain a polypeptide with an apparent molecular weight of 17,500 that corresponds in size to the unglycosylated IFN-beta 1 molecule. The latter could be specifically immunoprecipitated by antibodies to purified natural IFN-beta and could inhibit the replication of Herpes simplex virus types 1 and 2 in many different cell lines. Like the natural fibroblast IFN-beta, the bacterial IFN-beta 1 was active in many human cell lines, less active in a monkey cell line and inactive in rabbit and mouse fibroblasts. The antibody titre required to neutralise the anti-herpes activity of both IFN preparations was similar suggesting that they have the same specific activities. Similarly, the bacterial IFN-beta 1 was equally active in inhibiting the proliferation of Daudi cells grown in culture. Bacterial IFN-beta 1 was also capable of enhancing natural killer cell activity and antibody-dependent cellular cytotoxicity in vitro. Thus, IFN-beta 1 produced in recombinant bacteria displays a large range of biological properties ascribed to the natural fibroblast IFN-beta molecule.

High-level expression of an interferon alpha 2 gene cloned in phage M13mp7 and subsequent purification with a monoclonal antibody

A cloned interferon alpha 2 (IFN-alpha 2) gene was partially digestd with Pvu II to give a fragment that was inserted into the HincII site of the lacZ gene of bacteriophage M13mp7. Two recombinant phages containing the IFN-alpha 2 sequences in the correct orientation for expression from the lac promoter were characterized in detail. DNA sequence analysis showed that the inserted IFN-alpha 2 gene was in phase with the initiation codon of the lacZ gene. The polypeptide product has an additional 19 amino amino acids at the amino terminus of the mature IFN-alpha 2. The first 11 amino acids originate from the amino terminus of beta-galactosidase, and the remaining 8 amino acids are part of the signal sequence of pre-IFN-alpha 2. Infection of Escherichia coli with these phage followed by induction of the lac promoter with isopropyl thiogalactoside gives high yields (up to 10(9) units/liter with an average of 1.5 X 10(8) units/liter) of the modified IFN-alpha 2. This was purified to homogeneity in a single step by immunochromatography using the monoclonal antibody NK2. The nonreduced product had an apparent molecular weight of 20,500 and was shown by immunoradiometric assay to have the same specific activity as IFN made in Namalwa cells. It exhibited the characteristic cross-species antiviral activity of IFN-alpha 2.

Expression of a chemically synthesized human alpha 1 interferon gene

Cells of Escherichia coli containing a chemically synthesized human alpha 1 interferon (IFN-alpha 1) gene, under control of the lac promoter, make a product with biological properties indistinguishable from those of the natural IFN-alpha 1 [antiviral activity, acid stability, species crossreactivity, inactivation by antisera directed against leukocyte or Namalwa cell interferon, and stimulation of (2'-5')oligoadenylate synthetase activity]. Similar levels of IFN synthesis were obtained when the expression unit (lac promoter plus synthetic IFN-alpha 1 gene) was transplanted into the obligate methylotroph Methylophilus methylotrophus.

Human interferon gamma is encoded by a single class of mRNA

Polyadenylated RNA from human peripheral blood lymphocytes and spleen cells, treated with different inducers for IFN-gamma production, was fractionated on denaturing sucrose gradients. Two IFN-gamma mRNA peaks at 12S and 16S were consistently observed. Nucleotide sequence analysis of cDNA clones showed that the 12S IFN-gamma mRNA from the different sources is identical to the gel fractionated 18S IFN-gamma mRNA which gave rise to the IFN-gamma cDNA clone p69 (1). Nucleotide sequence analysis of several IFN-gamma cDNA clones showed the presence of a CGA (Arg) codon at position 140 of mature IFN-gamma in contrast with the CAA (Gln) codon, which is found in p69 (1). Specifically primed cDNA extension on total induced polyadenylated RNA revealed the presence of a single mRNA species having a 5' untranslated region of 125-130 nucleotides. The nucleotide sequence of this region has been obtained. These data suggest that a single human IFN-gamma gene, which has very little polymorphism, gives rise to a single size class of mRNA.

Systemic lupus erythematosus: presence in human serum of an unusual acid-labile leukocyte interferon

A previously undescribed species of human leukocyte, or alpha, interferon is present in the serum of many patients with systemic lupus erythematosus. It was shown to be alpha-interferon by neutralization with specific antiserums, affinity column chromatography, and antiviral activity on bovine cells. However, 23 of 30 interferon samples tested were inactivated by incubation at pH 2, a characteristic of human "immune," or gamma, interferon. Multiple samples of interferon from the same patient had similar biological properties, but samples from different patients were not all identical, suggesting that several variants of this species of human alpha-interferon may exist.

Antiviral activity of bacteria-derived human alpha interferons against encephalomyocarditis virus infection of mice

Bacteria-derived human leukocyte interferon (IFN) subtypes, IFN-alpha A, -alpha B, and -alpha D, and two hybrid IFNs, IFN-alpha AD and -alpha DA, were examined for both in vitro and in vivo antiviral activity. Two of these materials in highly purified form (IFN-alpha D and -alpha D) protect mice against lethal doses of encephalomyocarditis virus infection. A single dose of 1 microgram of protein of IFN-alpha D 3 h before infection conferred protection in both BDF1 and CD-1 mice against encephalomyocarditis virus infection, and multiple treatments with IFN-alpha D or IFN-alpha AD extend the mean survival time of infected mice. On a weight basis, IFN-alpha AD was approximately 100-fold more effective than IFN-alpha D. There is a direct correlation between the antiviral activity of the various human IFN species in L-929 cells and in mice for both single and multiple treatments before infection, but none of the cloned human IFN subtypes were effective when administered 24 h after infection. Mixtures of the two parental materials, IFN-alpha A and -alpha D, were not as protective as the hybrid molecule IFN-alpha AD, suggesting that IFNs with unique and altered species specificity can be produced by recombinant DNA methods.

Carboxyterminal region of hybrid leukocyte interferons affects antiviral specificity

Four hybrid human leukocyte interferon (IFN-alpha) genes have been constructed and expressed in Escherichia coli using molecular cloning methods. Plasmids containing genes encoding human interferons, IFN-alpha A, IFN-alpha D, IFN-alpha I and several hybrids of the different IFN-alpha genes (formed by in vitro recombination at common restriction endonuclease sites located within the DNA sequence encoding mature polypeptides) joined identically to an E. coli trp promoter gave rise to bacterial-produced interferons with distinctly different antiviral activities. The expression plasmid which directs the synthesis of IFN-alpha I was constructed using a gene isolated from a human genomic library in a manner similar to the previous expression of IFN-alpha A and IFN-alpha D cDNA clones. The use of a cell-free transcription-translation system has allowed the calculation of the specific activities of IFN-alpha made from isolated DNA fragments containing these hybrid IFN-alpha genes. These bacterially-derived interferons vary considerably in their ability to inhibit vesicular stomatitis virus (VSV) in different mammalian cells. The results show that the cloned hybrid interferons have unique antiviral activities when compared with the parent interferons, and they demonstrate that more active IFN-alpha s can be made using recombinant DNA techniques.

Antiviral activities of hybrids of two major human leukocyte interferons

Four hybrid human leukocyte interferon (LeIF or IFN-alpha) genes have been constructed by in vitro recombination of LeIF-A (IFN-alpha 2) and LeIF-D (IFN-alpha 1) genes at common restriction endonuclease sites located within their coding regions. These hybrid genes have been expressed in E. coli under trp promoter control. The interferons produced [LeIF-AD (BglII), -AD (PvuII), -DA (BglII), -DA (PvuII)] have antiviral properties distinct from the parental molecules LeIF-A and -D, varying considerably in their abilities to inhibit plaque formation by different viruses in a range of mammalian cells. All six of the cloned LeIFs exhibit the heat stability, pH 2 stability and antigenic specificity of natural leukocyte interferons.

DNA sequence of a major human leukocyte interferon gene

The gene for human leukocyte interferon alpha 2 (designated either LeIF A or HuIFN-alpha 2) has been isolated from a human genome library. The DNA sequence of this gene demonstrates that it lacks introns. The 3' noncoding sequences of the IFN-alpha 2 gene correspond to two types of IFN-alpha 2 cDNA clones we have isolated that have alternate sites of polyadenylylation. A comparison of seven human IFN-alpha sequences shows that they are homologous in the 5' flanking region and contain identical "TATA box" sequences. The recombinant lambda clone containing the IFN-alpha 2 gene also contains two copies of the "Alu family" repeat sequence.

Total synthesis of a human leukocyte interferon gene

A 514-base pair fragment of double-stranded DNA coding for human interferon-alpha 1 (166 amino acid residues), and containing initiation and termination signals plus appropriate restriction enzyme sites for plasmid insertion, has been totally synthesized. The synthesis involved preparation of 66 oligodeoxyribonucleotides, ranging in size from 14 to 21 residues, plus 1 deoxydecanucleotide, by rapid, solid phase procedures, and enzymatic ligation of the oligonucleotides. After ligation of the synthetic gene to a plasmid vector and transformation of Escherichia coli, clones containing the anticipated gene sequence were obtained.