Synthesis of human fibroblast interferon by E. coli

Implications of glycosylation for the development of selected cytokines and their derivatives for medical use

Cytokines are important regulators of immune responses, making them attractive targets for autoimmune diseases and cancer therapeutics. Yet, the significance of cytokine glycosylation remains underestimated. Many cytokines carry N- and O-glycans and some even undergo C-mannosylation. Recombinant cytokines produced in heterologous host cells may lack glycans or exhibit a different glycosylation pattern such as varying levels of galactosylation, sialylation, fucosylation or xylose addition compared to their human counterparts, potentially impacting critical immune interactions. We focused on cytokines that are currently utilized or designed in advanced therapeutic formats, including immunocytokines, fusokines, engager cytokines, and genetically engineered 'supercytokines.' Despite the innovative designs of these cytokine derivatives, their glycosylation patterns have not been extensively studied. By examining the glycosylation of the human native cytokines, G-CSF and GM-CSF, interferons β and γ, TNF-α and interleukins-2, -3 -4, -6, -7, -9, -12, -13, -15, -17A, -21, and - 22, we aim to assess its potential impact on their therapeutic derivatives. Understanding the glycosylation of the native cytokines could provide critical insights into the safety, efficacy, and functionality of these next-generation cytokine therapies, affecting factors such as stability, bioactivity, antigenicity, and half-life. This knowledge can guide the choice of optimal expression hosts for production and advance the development of effective cytokine-based therapeutics and synthetic immunology drugs.

Standing on Shoulders: Interferon Research From Viral Interference to Lupus Pathogenesis and Treatment

The discovery of interferon in the 1950s represents much more than the identification of the first cytokine and the key mediator of antiviral host defense. Defining the molecular nature and complexity of the type I interferon family, as well as its inducers and molecular mechanisms of action, was the work of investigators working at the highest level and producing insights of great consequence. Current knowledge of receptor-ligand interactions, cell signaling, and transcriptional regulation derives from studies of type I interferon. It is on the shoulders of the giants who produced that knowledge that others stand and have revealed critical mechanisms of the pathogenesis of systemic lupus erythematosus and other autoimmune diseases. The design of novel therapeutics is informed by the advances in investigation of type I interferon, with the potential for important impact on patient management.

Engineering for an HPV 9-valent vaccine candidate using genomic constitutive over-expression and low lipopolysaccharide levels in Escherichia coli cells

Background

The various advantages associated with the growth properties of Escherichia coli have justified their use in the production of genetically engineered vaccines. However, endotoxin contamination, plasmid vector instability, and the requirement for antibiotic supplementation are frequent bottlenecks in the successful production of recombinant proteins that are safe for industrial-scaled applications. To overcome these drawbacks, we focused on interrupting the expression of several key genes involved in the synthesis of lipopolysaccharide (LPS), an endotoxin frequently responsible for toxicity in recombinant proteins, to eliminate endotoxin contamination and produce better recombinant proteins with E. coli.

Results

Of 8 potential target genes associated with LPS synthesis, we successfully constructed 7 LPS biosynthesis-defective recombinant strains to reduce the production of LPS. The endotoxin residue in the protein products from these modified E. coli strains were about two orders of magnitude lower than that produced by the wild-type strain. Further, we found that 6 loci—lpxM, lpxP, lpxL, eptA, gutQ and kdsD—were suitable for chromosomal integrated expression of HPV L1 protein. We found that a single copy of the expression cassette conferred stable expression during long-term antibiotic-free cultivation as compared with the more variable protein production from plasmid-based expression. In large-scale fermentation, we found that recombinant strains bearing 3 to 5 copies of the expression cassette had 1.5- to 2-fold higher overall expression along with lower endotoxin levels as compared with the parental ER2566 strain. Finally, we engineered and constructed 9 recombinant E. coli strains for the later production of an HPV 9-valent capsid protein with desirable purity, VLP morphology, and antigenicity.

Conclusions

Reengineering the LPS synthesis loci in the E. coli ER2566 strain through chromosomal integration of expression cassettes has potential uses for the production of a 9-valent HPV vaccine candidate, with markedly reduced residual endotoxin levels. Our results offer a new strategy for recombinant E. coli strain construction, engineering, and the development of suitable recombinant protein drugs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-021-01719-8.

Twenty-five years of type I interferon-based treatment: a critical analysis of its therapeutic use

The clinical exploitation of type I interferon (IFN) as an antiviral and antineoplastic agent is based on the properties originally attributed to this cytokine family, with schedules reflecting only their antiviral and antiproliferative activities. Nevertheless, type I IFN has emerged as a central activator of the innate immunity. As current schedules of treatment for chronic hepatitis C and for hematological and solid tumors, based on the continuous administration of recombinant type I IFN or pegylated formulations, disregard viral resistance, host genetic variants predicting treatment outcome and mechanisms of refractoriness, new administration schedules, the combination of type I IFN with new drugs and the increased monitoring of patients' susceptibility to type I IFN are expected to provide a new life to this valuable cytokine.

Structure of a chromosomal gene for human interferon beta

We have cloned and analyzed a chromosomal DNA segment containing the human interferon beta(1) gene from a human gene library. The nucleotide sequence of the protein-coding and the noncoding regions of the chromosomal gene was identical to the cDNA sequence reported previously. In the region upstream from the putative transcription initiation site, significant nucleotide sequence homology was observed between interferon beta(1) and alpha(1) genes. This region thus may play a role in expression of the interferon genes. From the sequence data and the result of nuclease S1 mapping experiments, we conclude that, like the interferon alpha(1) gene, the interferon beta(1) gene is devoid of intervening sequences.

Translating molecular insights in autoimmunity into effective therapy

Autoimmunity and the pathogenesis of autoimmune diseases were a major focus of the Walter and Eliza Hall Institute, where I started my research career. After my initial studies on immune cell culture and immune regulation, I returned to an analysis of the pathogenesis of human autoimmunity in London. Linking upregulated antigen presentation to autoimmunity led to an investigation of the role of cytokines in rheumatoid arthritis (RA), in collaboration with Ravinder Maini. These experiments defined the concept of a TNF-dependent cytokine cascade driving the manifestations of RA, which led to successful clinical trials of anti-TNF monoclonal antibody in RA patients, heralding a major change in medical practice. This success was made possible by enthusiastic support from many laboratory and clinical colleagues and taught us that cytokines are important rate-limiting steps and hence good therapeutic targets. My current scientific challenge is exploring the hypothesis of whether all major medical needs can be approached via cytokine blockade.

Many cytokines are very useful therapeutic targets in disease

Cytokines are a large family of more than 100 small proteins that function as short-range mediators involved in essentially all biological processes. They have been found to be important rate-limiting signals, and it is now known that blocking some cytokines, e.g., TNF-alpha, and cytokine receptors, such as human EGFR 1 (HER1) or HER2, yields effective therapeutics that address unmet needs. This Review Series surveys three chronic inflammatory disease areas and two forms of cancer and discusses the important role of cytokines and their receptors in these disease processes. Their role as potential therapeutic targets is also highlighted.

Cloning, high expression and purification of recombinant human intereferon-beta-1b in Escherichia coli

Sequential evaluation and process control strategy were employed for impurity profile and high recovery with quality of rhIFN-beta-1b expressed in Escherichia coli. The high-level expression was achieved by using codon substitution (AT content of 52.6% at N-terminal region) and optimization of culture conditions. The addition of rifampicin at a concentration of 200 microg/ml has increased the specific product yield of 66 mg optical density(-1) l(-1) (43.5% of total cellular protein). Eighty-three percent of lipopolysaccharides, 32% of host deoxyribonucleic acid (DNA), and 78% of host cell proteins were removed by 0.75% Triton X-100 and 2 M urea wash. Eleven percent of lipopolysaccharides, 39% of host DNA, and 12% of host cell proteins were removed at the solubilization step. Ninety-two percent of protein refolding was achieved by high-pressure diafiltration method. Refolding by high-pressure diafiltration, bed height, and height equivalent to the theoretical plate value in chromatography column were identified as key parameters for high recovery with purity. Finally, the established process yielded 34% of purified protein with greater than 99% purity and is acceptable for preclinical toxicological studies. The purified rhIFN-beta-1b obtained in this study is the highest that has been reported so far.

Optimization of culture conditions for a synthetic gene expression in Escherichia coli using response surface methodology: The case of human interferon beta

A human interferon beta (hINF-beta) synthetic gene was optimized and expressed in Escherichia coli BL21-SI using a vector with the T7 promoter. To determine the best culture conditions such as culture medium, temperature, cell density and inducer concentration, we used the response surface methodology and a Box-Behnken design to get the highest hINF-beta production. The maximum hINF-beta production of 61 mg l(-1) was attained using minimum medium and the following predicted optimal conditions: temperature of 32.5 degrees C, cell density of 0.64, and inducer concentration of 0.30 M NaCl. This is the first report showing the successful performance of the BL21-SI system in a minimum medium. The response surface methodology is effective for the optimization of recombinant protein production using synthetic genes.

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.

Interferon: The pathways of discovery

This historical account covers 50 years of seminal research work on interferon done since its discovery in 1957. Topics related to molecular structure, production and action of interferons are considered from the viewpoint of how our insights have expanded and deepened within the context of evolving tools and general knowledge in cellular and molecular biology. Lines of thought that linked each discovery to the next are expounded.

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.

Gene cloning, nucleotide sequence, and expression of a cephalosporin-C deacetylase from Bacillus subtilis

The gene encoding a cephalosporin-C deacetylase (CAH) from Bacillus subtilis SHS 0133 was cloned and sequenced. The nucleotide sequence contained an open reading frame encoding a polypeptide consisting of 318 amino acids, the molecular weight of which was in good agreement with the value obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The deduced amino acid sequence contained the common sequence Gly-X-Ser-X-Gly found in many esterases, lipases, and serine proteases. This indicates that CAH is a serine enzyme. A possible promoter sequence which is very similar to the consensus sequences of -35 and -10 regions recognized by B. subtilis RNA polymerase utilizing sigma factor H was found in the 5'-flanking region of the CAH structural gene. Two repeated A+T-rich blocks consisting of 24 bp were also found in the upstream region of the initiation codon. We constructed a series of expression plasmids by inserting the CAH gene into Escherichia coli ATG vectors. The degree of CAH gene expression depended on promoters and vector plasmids, which have different replication origins. The expressed CAH protein was an active form in the soluble fraction obtained after cell disruption. The highest expression level was accomplished with an expression plasmid, pCAH400, which has the trp promoter and the replication origin derived from pAT153. In the fermentation using a 30-liter jar fermentor, the transformant E. coli JM103(pCAH400) produced 440 U of CAH per ml of culture during a 24-h incubation. This value corresponded to 2.1 g of CAH protein in 1 liter of culture broth.

Peripheral-acting benzodiazepines inhibit the growth of human melanoma cells and potentiate the antiproliferative activity of recombinant human interferons

In this study, we evaluated the effect of a series of peripheral-acting benzodiazepines (BZDs), alone and in combination with recombinant human leukocyte (IFN-alpha A), fibroblast (IFN-beta), or immune (IFN-gamma) interferon (IFN), on the growth of human melanoma cells. Specific peripheral-acting BZDs caused a marked suppression in the proliferation of human melanoma cells. The effect on melanoma cell growth required 72 h exposure to the peripheral-acting BZDs and was not observed if the compounds were removed by 48 h. The relative potency of antiproliferative activity of a series of peripheral-acting BZDs on human melanoma cell growth did not correlate with the reported ability of these agents to bind to peripheral sites on the cell membrane of Friend erythroleukemia cells (FELC), nor did they correlate with the ability of these agents to inhibit [3H]thymidine incorporation in FELC, induce differentiation in FELC, or inhibit neurite outgrowth in nerve growth factor-treated rat pheochromocytoma (PC12) cells. The growth of human melanoma cells was also inhibited by various recombinant human IFNs, with IFN-beta displaying greater antiproliferative activity than IFN-alpha A or IFN-gamma. When the peripheral-acting BZD Ro7-3351, which displays growth inhibitory properties when used alone, was combined with IFN, the antiproliferative activity of the combination was greater than either individual compound exerted independently. The combination of IFN-beta plus Ro7-3351 was more active in suppressing HO-1 melanoma cell growth than other IFN preparations in combination with this peripheral-type BZD. Even when combined with a peripheral-acting BZD, such as Ro5-4608, which displayed only marginal antiproliferative activity against human melanoma cells when applied alone, growth suppression of the combination of this peripheral-type BZD with all three types of IFNs was more than additive. These studies suggest that specific peripheral-acting BZDs, both alone and in combination with recombinant IFNs, display novel antiproliferative activity toward human melanoma cells which may involve a different genetic locus than previously observed in other model cell culture systems.

Conformation and activity of recombinant human fibroblast interferon-beta

Conformation of highly purified recombinant human fibroblast interferon-beta (rHuIFN-beta) was correlated with its biological activity. The extent of ordered secondary structure was determined by circular dichroic (CD) spectroscopy in various buffer conditions to establish conditions of protein stability and its potential for helix formation. The highest "helicity" (about 50 +/- 5% of alpha-helices) and the highest antiviral activities (4-10 x 10(7) units/mg) were found in 50% ethylene glycol, 1 M NaCl and 0.05 M Na3PO4, pH 7.2 (Buffer I); 80 mM citric acid, 20 mM Na2HPO4, pH 2.9 (Buffer II); and 25 mM NH4OAc, 125 mM NaCl, pH 5.1 (Buffer III). Both helicity and antiviral activity of the IFN-beta decrease in parallel with denaturation by urea, heat, and/or by repeated cycles of freezing and thawing. Low pH (pH 2.9 Buffer II) exhibits a distinct stabilizing effect on the structure and antiviral activity of IFN-beta against heat denaturation.

Tryptophan promoter derivatives on multicopy plasmids: a comparative analysis of expression potentials in Escherichia coli

A collection of variant plasmids expressing either Escherichia coli galactokinase or human serum albumin under the control of several E. coli trp promoter derivatives were constructed and studied for both efficiency of expression and regulation by tryptophan. Several variables, including the length of the upstream region, tandem duplications of a core promoter, and the insertion of the trp repressor trpR gene onto the expression vector, were studied. It is shown that derivatives containing sequences upstream from the -35 region or multiple copies of the trp promoter produce twofold higher levels of protein than plasmids with a minimal trp promoter truncated at -40. We show that the expression of a heterologous protein such as albumin can be significantly improved (13% vs. 7% of total proteins) if both the upstream trp promoter region, which enhances promoter strength, and an intact trpR gene, are included on the plasmids.

Expression of human erythropoietin cDNA in human lymphoblastoid Namalwa cells: the inconsistency of a stable expression level with transient expression efficiency

Recombinant plasmids for the expression of human erythropoietin (EPO) cDNA in Namalwa cells were constructed. From the results of the EPO expression efficiency in transiently transfected cells, it was found that the simian virus 40 (SV40) early promoter directs EPO synthesis more efficiently in Namalwa cells than does the long terminal repeat promoter of Rous sarcoma virus and that the 3'-noncoding sequence including splice junction and polyadenylation site derived from the rabbit beta-globin gene are more effective than those of the SV40 early gene. However, in stable transformants, no simple relationship was found between the expression level of EPO cDNA and the structure of the introduced expression vectors.

Epstein-Barr virus shuttle vector for stable episomal replication of cDNA expression libraries in human cells

Efficient transfection and expression of cDNA libraries in human cells has been achieved with an Epstein-Barr virus-based subcloning vector (EBO-pcD). The plasmid vector contains a resistance marker for hygromycin B to permit selection for transformed cells. The Epstein-Barr virus origin for plasmid replication (oriP) and the Epstein-Barr virus nuclear antigen gene have also been incorporated into the vector to ensure that the plasmids are maintained stably and extrachromosomally. Human lymphoblastoid cells can be stably transformed at high efficiency (10 to 15%) by such plasmids, thereby permitting the ready isolation of 10(6) to 10(7) independent transformants. Consequently, entire high-complexity EBO-pcD expression libraries can be introduced into these cells. Furthermore, since EBO-pcD plasmids are maintained as episomes at two to eight copies per cell, intact cDNA clones can be readily isolated from transformants and recovered by propagation in Escherichia coli. By using such vectors, human cells have been stably transformed with EBO-pcD-hprt to express hypoxanthine-guanine phosphoribosyltransferase and with EBO-pcD-Leu-2 to express the human T-cell surface marker Leu-2 (CD8). Reconstruction experiments with mixtures of EBO-pcD plasmids demonstrated that one clone of EBO-pcD-hprt per 10(6) total clones or one clone of EBO-pcD-Leu-2 per 2 x 10(4) total clones can be recovered intact from the transformed cells. The ability to directly select for expression of very rare EBO-pcD clones and to then recover these episomes should make it possible to clone certain genes where hybridization and immunological screening methods are not applicable but where a phenotype can be scored or selected in human cell lines.

Human pancreatic secretory trypsin inhibitor (PSTI) produced in active form and secreted from Escherichia coli

As a basis for a protein design project, we decided to produce the human pancreatic secretory trypsin inhibitor (PSTI) in its active form. Total gene synthesis was carried out efficiently by (i) computer design of the gene fragments, (ii) synthesis of the oligodeoxynucleotides by the segmental support method, and (iii) assembly of double strands under optimized ligation conditions. Fusion to the ompA gene signal peptide led to secretion of processed PSTI in various constructions, with or without additional amino acids (aa) at the N-terminus. The secreted proteins (56 to 63 aa) were biologically active, suggesting that the three cysteine bridges were correctly formed. Surprisingly, after induction the product was found almost exclusively in the culture medium. Variants of PSTI with Asp or Asn at aa positions 21 and 29 [sequences published by Greene et al., Methods Enzymol. (1976) 813-825, and by Yamamoto et al., Biochem. Biophys. Res. Commun. (1985) 605-612] showed the same Ki for both human and porcine trypsin.

Epstein-Barr virus shuttle vector for stable episomal replication of cDNA expression libraries in human cells

Efficient transfection and expression of cDNA libraries in human cells has been achieved with an Epstein-Barr virus-based subcloning vector (EBO-pcD). The plasmid vector contains a resistance marker for hygromycin B to permit selection for transformed cells. The Epstein-Barr virus origin for plasmid replication (oriP) and the Epstein-Barr virus nuclear antigen gene have also been incorporated into the vector to ensure that the plasmids are maintained stably and extrachromosomally. Human lymphoblastoid cells can be stably transformed at high efficiency (10 to 15%) by such plasmids, thereby permitting the ready isolation of 10(6) to 10(7) independent transformants. Consequently, entire high-complexity EBO-pcD expression libraries can be introduced into these cells. Furthermore, since EBO-pcD plasmids are maintained as episomes at two to eight copies per cell, intact cDNA clones can be readily isolated from transformants and recovered by propagation in Escherichia coli. By using such vectors, human cells have been stably transformed with EBO-pcD-hprt to express hypoxanthine-guanine phosphoribosyltransferase and with EBO-pcD-Leu-2 to express the human T-cell surface marker Leu-2 (CD8). Reconstruction experiments with mixtures of EBO-pcD plasmids demonstrated that one clone of EBO-pcD-hprt per 10(6) total clones or one clone of EBO-pcD-Leu-2 per 2 x 10(4) total clones can be recovered intact from the transformed cells. The ability to directly select for expression of very rare EBO-pcD clones and to then recover these episomes should make it possible to clone certain genes where hybridization and immunological screening methods are not applicable but where a phenotype can be scored or selected in human cell lines.

Expression of tobacco mosaic virus RNA in transgenic plants

Tobacco mosaic virus (TMV) is a message-sense, single-stranded RNA virus that infects many Solanaceae plants. A full-length cDNA copy of TMV genomic RNA was constructed and introduced into the genomic DNA of tobacco plants using a disarmed Ti plasmid vector. Transformed plants showed typical symptoms of TMV infection, and their leaves contained infectious TMV particles. This is the first example of the expression of RNA virus genomic RNAs in plants.

Recombinant interferon-gamma inhibits the mitogenic effect of platelet-derived growth factor at a level distal to the growth factor receptor

Highly purified preparations of recombinant human interferons (rIFNs)-alpha A, -beta, and -gamma all inhibited platelet-derived growth factor (PDGF)-induced DNA synthesis in normal human dermal fibroblasts, as monitored by incorporation of [3H]-thymidine into trichloroacetic acid (TCA)-insoluble material. rIFN-gamma was the most potent, since it blocked the PDGF response by 50% at about 10 U/ml or 0.3 ng/ml, whereas with rIFN-alpha A and rIFN-beta 4000 U/ml and 600 U/ml, respectively (10 ng/ml in both cases), were required to achieve the same effect. There was a close parallelism between the ability of these rIFNs to inhibit PDGF mitogenic activity and their capacity to inhibit cell proliferation in serum-containing medium. None of the rIFNs inhibited specific binding of 125I-PDGF to fibroblasts, and none interfered with receptor internalization. The mechanism of action of rIFN-gamma was analyzed further. rIFN-gamma did not inhibit uptake of [3H]-thymidine into these cells. However, it shifted if the time point of initiation of DNA synthesis from about 14 h after stimulation with PDGF to about 18 to 21 h and decreased significantly the rate of the DNA synthesis. rIFN-gamma could be added up to 6 h following stimulation with PDGF with no loss of its inhibitory effect. rIFN-gamma also blocked the mitogenic activity of epidermal growth factor and basic fibroblast growth factor. Taken together these results implicate that rIFN-gamma exerts its antimitogenic effect by inhibiting a process that occurs late in the PDGF signaling pathway and onto which the activity pathways of other mitogens converge. In view of the important role PDGF may play in wound-healing and in the pathogenesis of the proliferative lesions of arteriosclerosis, these data point to a possible role IFN-gamma may play as a regulator of these processes in vivo.

Codon replacement in the PGK1 gene of Saccharomyces cerevisiae: experimental approach to study the role of biased codon usage in gene expression

The coding sequences of genes in the yeast Saccharomyces cerevisiae show a preference for 25 of the 61 possible coding triplets. The degree of this biased codon usage in each gene is positively correlated to its expression level. Highly expressed genes use these 25 major codons almost exclusively. As an experimental approach to studying biased codon usage and its possible role in modulating gene expression, systematic codon replacements were carried out in the highly expressed PGK1 gene. The expression of phosphoglycerate kinase (PGK) was studied both on a high-copy-number plasmid and as a single copy gene integrated into the chromosome. Replacing an increasing number (up to 39% of all codons) of major codons with synonymous minor ones at the 5' end of the coding sequence caused a dramatic decline of the expression level. The PGK protein levels dropped 10-fold. The steady-state mRNA levels also declined, but to a lesser extent (threefold). Our data indicate that this reduction in mRNA levels was due to destabilization caused by impaired translation elongation at the minor codons. By preventing translation of the PGK mRNAs by the introduction of a stop codon 3' and adjacent to the start codon, the steady-state mRNA levels decreased dramatically. We conclude that efficient mRNA translation is required for maintaining mRNA stability in S. cerevisiae. These findings have important implications for the study of the expression of heterologous genes in yeast cells.

Codon replacement in the PGK1 gene of Saccharomyces cerevisiae: experimental approach to study the role of biased codon usage in gene expression

The coding sequences of genes in the yeast Saccharomyces cerevisiae show a preference for 25 of the 61 possible coding triplets. The degree of this biased codon usage in each gene is positively correlated to its expression level. Highly expressed genes use these 25 major codons almost exclusively. As an experimental approach to studying biased codon usage and its possible role in modulating gene expression, systematic codon replacements were carried out in the highly expressed PGK1 gene. The expression of phosphoglycerate kinase (PGK) was studied both on a high-copy-number plasmid and as a single copy gene integrated into the chromosome. Replacing an increasing number (up to 39% of all codons) of major codons with synonymous minor ones at the 5' end of the coding sequence caused a dramatic decline of the expression level. The PGK protein levels dropped 10-fold. The steady-state mRNA levels also declined, but to a lesser extent (threefold). Our data indicate that this reduction in mRNA levels was due to destabilization caused by impaired translation elongation at the minor codons. By preventing translation of the PGK mRNAs by the introduction of a stop codon 3' and adjacent to the start codon, the steady-state mRNA levels decreased dramatically. We conclude that efficient mRNA translation is required for maintaining mRNA stability in S. cerevisiae. These findings have important implications for the study of the expression of heterologous genes in yeast cells.

Avian sarcoma and leukosis virus pol-endonuclease recognition of the tandem long terminal repeat junction: minimum site required for cleavage is also required for viral growth

Integration of retroviral DNA is a site-specific reaction involving an endonuclease encoded by the viral pol gene (pol-endo). In vitro the pol-endo from avian sarcoma and leukosis viruses (ASLVs) cleaves both DNA strands near the U5-U3 junction of tandem long terminal repeats (LTR-LTR junction) in single-stranded and replicative form (RF)-I substrates. We have reported previously that the sequences that are required for cleavage of single-stranded substrates by the alpha beta form of the pol-endo differ for the plus and minus strands (G. Duyk, M. Longiaru, D. Cobrinik, R. Kowal, P. deHaseth, A. M. Skalka, and J. Leis, J. Virol. 56:589-599, 1985). This is not the case with RF-I substrates, in which a maximum of 22 base pairs of U5 and 8 base pairs of U3 were required for alpha beta pol-endo cleavage in each strand. Insertion of a palindromic octanucleotide (CATCGATG) at the LTR-LTR junction abolished cleavage in RF-I but not in single-stranded DNA substrates. Deletion of the four nucleotides (TTAA) at the junction prevented cleavage in the plus strand of RF-I DNA, but did not affect cleavage of single-stranded DNA. Furthermore, the alpha beta form of ASLV pol-endo did not recognize heterologous LTR-LTR junction sequences from the reticuloendotheliosis virus or Moloney murine leukemia virus in either substrate form, despite their sequence and structural similarities to the ASLV junction. These results support a role for a sequence-specific interaction between the ASLV pol-endo and the LTR-LTR junction domains that are required for cleavage. By using the infectious Rous sarcoma virus clone pATV8-K, we introduced a set of deletions into the U5 region that would be incorporated into the LTR-LTR junction on viral replication. In the unintegrated provirus, the deletions started 43 base pairs from the LTR-LTR junction and extended various lengths toward the junction. Results of transfection studies with these clones indicated that the U5 sequences that are required for virus production in vivo correspond to those that are required for cleavage of RF-I DNA in vitro.

trp operon induction during the expression in E. coli of two IFN-gamma sequences

Two nucleotide sequences coding for mature human immune interferon (IFN-gamma) and differing from each other by nine N-terminal nucleotides were expressed in E. coli under the control of a trp promoter. The longer gene variant after the ATG initiatory codon contained a TGT TAC TGC sequence, which was absent in the shorter gene. When expressed in E. coli under the direction of identical transcription and translation regulatory elements, these genes showed different susceptibility to induction.

Tumour necrosis factors alpha and beta inhibit virus replication and synergize with interferons

Tumour necrosis factor (TNF) and lymphotoxin were initially described as tumoricidal proteins that are produced by activated macrophages and lymphocytes, respectively. Since TNF and lymphotoxin are structurally related, bind to the same cell surface receptor and have indistinguishable biological activities, they have been designated as TNF-alpha and TNF-beta, respectively. The multiple activities of these molecules indicate their importance in immunoregulative responses. Here we report that both TNF-alpha and TNF-beta have antiviral activity and synergize with interferons (IFNs) in the induction of resistance to both RNA and DNA virus infection in diverse cell types. These effects of TNFs are not due to the induction of IFN synthesis. Virus-infected cells are selectively killed by TNFs and this activity is accelerated by IFN-gamma. The production of TNFs is induced by viruses, further suggesting the importance of TNFs in the physiological antiviral response.

Regulatory effects on macrophages of human recombinant interferons-alpha

The regulatory effects of human recombinant and hybrid interferons-alpha (IFN-alpha) on macrophage-mediated tumoricidal activity were examined. Recombinant hybrid IFN-alpha-A/D suppressed the capacity of murine interferon-gamma (IFN-gamma) to activate mouse peritoneal macrophages to a tumorilytic state, and blocked the killing of syngeneic syngeneic melanoma target cells by macrophages previously committed to the cytotoxic phenotype with a 4-h pretreatment with IFN-gamma. This suppressive activity was limited to IFN-alpha-A/D, as IFN-alpha-A and IFN-alpha-D were not effective. In contrast, IFN-alpha-A, -D, and -A/D were all capable of activating human peripheral blood monocytes to lyse human tumor cells. When encapsulated in liposomes, only IFN-alpha-A/D maintained its monocyte activating efficacy. These findings suggest that the immunomodulatory effects of IFN-alpha subtypes and hybrid molecules are dependent on species of monocytes/macrophages, subtype, and nature of presentation to effector cells.

Production of recombinant mouse beta-interferon

A plasmid was constructed to express a mouse beta-interferon (IFN-beta) in Escherichia coli under the control of the modified tryptophan (trp) promoter. E. coli carrying the plasmid were cultivated in a minijar fermentor and synthesized up to 2.7 X 10(6) IU/ml of antiviral activity. At the end of the cultivation the cells became elongated and curved.

Safety and tolerance of recombinant interferon alfa-2a (Roferon-A) in cancer patients

Recombinant interferon alfa-2a (Roferon-A, Hoffmann-La Roche Inc., Nutley, NJ) has been evaluated in clinical trials of more than 1300 patients with a broad spectrum of oncologic disease. Patients with either solid tumors or hematologic malignancies were treated with daily or three-times-weekly intramuscular injections for induction periods ranging from 8 to 16 weeks. Doses ranged from 1 X 10(6) units to 124 X 10(6) units per injection. When administered in low daily doses (approximately 3 X 10(6) units), Roferon-A was well tolerated, and dose attenuation was rarely required. Change to three-times-weekly treatment regimen at the same dose was usually sufficient to control toxicity when it occurred in this group of low-dose patients. Those patients receiving higher doses frequently required dose attenuation to 50% of the starting dose to improve clinical tolerance. Virtually all patients treated with Roferon-A experienced some degree of acute toxicity manifested as fever, chills, myalgia, and/or headache. These reactions usually occurred with initial dosing and frequently improved spontaneously with continued administration of the drug. Acetaminophen pretreatment was generally useful in ameliorating these symptoms. Common adverse experiences occurring after repeated dosing included fatigue, anorexia, and weight loss. Serious adverse reactions including cardiovascular and neurologic toxicity have occurred infrequently, primarily at higher doses. Hematologic toxicity and elevations in liver function parameters were also observed, but rarely required dose attenuation. Adverse effects were usually reversible after dose reduction or discontinuation of therapy. Approximately 27% of all patients developed antibodies to rHuIFN-alpha 2A during treatment. No adverse clinical sequelae have been associated with antibody development to date.

Expression and secretion of hepatitis B viral surface antigen in E. coli

Hepatitis B viral surface antigen (HBsAg) gene was subcloned into the BglII site of Bacillus licheniformis penicillinase (penP) gene of secretory vector pJP104. Expression and secretion of HBsAg protein was achieved by the E. coli CS412 carrying the plasmid pJPS2 in which the penP:HBsAg hybrid gene was under the control of two promoters, lipoprotein (lpp) and penP, spaced 450 bases apart. The secreted form of HBsAg encoded by the hybrid penP: HBsAg gene of plasmid pJPS2 was purified by immunoaffinity chromatography and found to be a 25 kilodalton protein.

Differential antiproliferative effects of combinations of recombinant interferons alpha and gamma on two murine tumor cell lines

The in vitro antiproliferative effects of recombinant interferons (IFNs) alpha and gamma against the murine reticulum-cell sarcoma M5076 and the malignant melanoma B16 F10 were evaluated using the human hybrid IFN-alpha A/D (rHuIFN-alpha A/D), which is active on murine cells, and recombinant murine IFN gamma (rMuIFN-gamma). An isobologram analysis was used to evaluate the interactive antiproliferative effects of the recombinant IFNs on these two tumor cell lines. The data, in contrast to prior reports, indicate that rHuIFN-alpha A/D and rMuIFN-gamma interact in an additive rather than a synergistic manner against M5076 cells. When a similar analysis was performed on B16 F10 cells, synergy was obtained. Thus, either a synergistic or an additive antiproliferative effect can be obtained by combining IFN-alpha and IFN-gamma, depending upon the cell line used in the assay.

An improved Escherichia coli expression vector for the construction and identification of full-length cDNA clones

An Escherichia coli expression vector designed for the efficient synthesis and identification of a full-length cDNA clone is constructed. The vector allows the synthesis of double-stranded cDNAs downstream from the tandem lac control regions employing the vector-primer and linker procedure of Okayama and Berg [Mol. Cell Biol. 2 (1982) 161-170]. Full-length cDNA clones carrying the 5'-noncoding region in addition to the entire coding and 3'-noncoding regions can be expressed in E. coli cells without fusing their coding region to that of E. coli proteins; these clones are identified by colony immunoassay. The entire cDNA insert can be easily excised from the plasmid, since the multiple cloning sites in the vector are duplicated at both ends of the cDNA insert during its synthesis.

Chemical modifications of human and murine interferons

Methods that modify the carbohydrate and peptide portions of human and murine interferons have been described. Such work has helped considerably in our understanding of these fascinating substances. The most powerful of the methods relies on gene manipulation: it has already led, and will lead in the future, to further species with altered biological activities. Some of them may prove clinically advantageous, but one will have to be aware of the fact that some of these "unnatural" interferons could lead to immunological complications.