A type I ovine interferon with limited similarity to IFN-alpha, IFN-omega and IFN-tau: gene structure, biological properties and unusual species specificity

Interferon-Based Biopharmaceuticals: Overview on the Production, Purification, and Formulation

The advent of biopharmaceuticals in modern medicine brought enormous benefits to the treatment of numerous human diseases and improved the well-being of many people worldwide. First introduced in the market in the early 1980s, the number of approved biopharmaceutical products has been steadily increasing, with therapeutic proteins, antibodies, and their derivatives accounting for most of the generated revenues. The success of pharmaceutical biotechnology is closely linked with remarkable developments in DNA recombinant technology, which has enabled the production of proteins with high specificity. Among promising biopharmaceuticals are interferons, first described by Isaacs and Lindenmann in 1957 and approved for clinical use in humans nearly thirty years later. Interferons are secreted autocrine and paracrine proteins, which by regulating several biochemical pathways have a spectrum of clinical effectiveness against viral infections, malignant diseases, and multiple sclerosis. Given their relevance and sustained market share, this review provides an overview on the evolution of interferon manufacture, comprising their production, purification, and formulation stages. Remarkable developments achieved in the last decades are herein discussed in three main sections: (i) an upstream stage, including genetically engineered genes, vectors, and hosts, and optimization of culture conditions (culture media, induction temperature, type and concentration of inducer, induction regimens, and scale); (ii) a downstream stage, focusing on single- and multiple-step chromatography, and emerging alternatives (e.g., aqueous two-phase systems); and (iii) formulation and delivery, providing an overview of improved bioactivities and extended half-lives and targeted delivery to the site of action. This review ends with an outlook and foreseeable prospects for underdeveloped aspects of biopharma research involving human interferons.

Interferon-omega: Current status in clinical applications

Since 1985, interferon (IFN)-ω, a type I IFN, has been identified in many animals, but not canines and mice. It has been demonstrated to have antiviral, anti-proliferation, and antitumor activities that are similar to those of IFN-α. To date, IFN-ω has been explored as a treatment option for some diseases or viral infections in humans and other animals. Studies have revealed that human IFN-ω displays antitumor activities in some models of human cancer cells and that it can be used to diagnose some diseases. While recombinant feline IFN-ω has been licensed in several countries for treating canine parvovirus, feline leukemia virus, and feline immunodeficiency virus infections, it also exhibits a certain efficacy when used to treat other viral infections or diseases. This review examines the known biological activity of IFN-ω and its clinical applications. We expect that the information provided in this review will stimulate further studies of IFN-ω as a therapeutic agent.

Generation of recombinant bovine interferon tau in the human embryonic kidney cell line and its biological activity

The objective of this study was to generate recombinant bovine interferon tau (rbIFNT) in mammalian hosts. The complementary DNA encoding bovine IFNT2 was cloned for the construction of pRcRSV-bIFNT2 expression vector. The expression vector was transfected to 293 cells. Transfected cells harboring expression vector were selected with G418. Highly expressing clonal line was adapted to serum-free suspension culture in a spinner flask. The recombinant protein had 24 kDa apparent molecular mass, suggesting being expressed as a glycoprotein, and was purified from serum-free conditioned medium by the combination of Diethylaminoethanol Sepharose ion exchange and Sephacryl S-200 HR gel filtration. A total of 7.3 mg rbIFNT was obtained from 13.5 L conditioned medium. Generated rbIFNT was biologically active in terms of antiviral activity measured by the plaque inhibition assay with Madin-Darby bovine kidney cells and the vesicular stomatitis virus. The recombinant protein was also utilized for immunization to raise antibodies in the rabbit. The generated antibody was capable of use in both Western blotting and the binding assay. The results in the present study suggest that a certain amount of rbIFNT is raised in mammalian hosts by using conventional plasmid vector and its antibody provides useful tools for studies in the biology of bovine IFNT.

Inhibition of virus replication and induction of human tetherin gene expression by equine IFN-α1

Type I interferons (IFNs) play important roles in the defense of host cells against viral infection by inducing the expression of a diverse range of antiviral factors. IFNs from different animals likely share similar features with human IFNs, and some of them have cross-species activities. Equine IFN-α was proved effective in both equine and human cells. However, the previous studies mostly focused on the inhibition of virus induced cytopathic effects. In this study, we used virus-specific assays to demonstrate the antiviral activities of equine IFN-α1 in both equine and human cells. Equine IFN-α1 inhibited the expression of viral structural proteins and the production of virions of equine infectious anemia virus (EIAV) and equine arteritis virus (EAV) in equine cells. In addition, equine IFN-α1 inhibited the production of EIAV virus-like particles (VLP) from human 293T cells. An IFN-inducible human gene, tetherin, was induced in 293T cells by equine IFN-α1. Its induction correlated with the inhibition of VLP release from the cell membrane. This result indicates that equine IFN-α1 shares a similar mechanism of action with human IFN-α in regulating antiviral genes expression in human cells.

Effect of Extremely Low Frequency Electromagnetic Fields (EMF) on Phospholipase Activity in the Cultured Cells

This study was conducted to investigate the effects of extremely low frequency electromagnetic fields (EMF) on signal pathway in plasma membrane of cultured cells (RAW 264.7 cells and RBL 2H3 cells), by measuring the activity of phospholipase A(2) (PLA(2)), phospholipase C (PLC) and phospholipase D (PLD). The cells were exposed to the EMF (60 Hz, 0.1 or 1 mT) for 4 or 16 h. The basal and 0.5 µM melittin-induced arachidonic acid release was not affected by EMF in both cells. In cell-free PLA(2) assay, we failed to observe the change of cPLA(2) and sPLA(2) activity. Also both PLC and PLD activities did not show any change in the two cell lines exposed to EMF. This study suggests that the exposure condition of EMF (60 Hz, 0.1 or 1 mT) which is 2.4 fold higher than the limit of occupational exposure does not induce phospholipases-associated signal pathway in RAW 264.7 cells and RBL 2H3 cells.

[Anti-HIV effects of IFN-tau in human macrophages: role of cellular antiviral factors and interleukin-6]

Tau interferon (IFN-tau) was shown to inhibit human immunodeficiency virus (HIV) replication in vitro more strongly than human IFN-alpha, particularly in human macrophages. IFN-tau efficiently inhibited the early steps of HIV biological cycle, decreasing intracellular HIV RNA and inhibiting the initiation of the reverse transcription of viral RNA into proviral DNA. In this study, the in vitro immunomodulatory effects of IFN-tau were explored in human macrophages. We found that IFN-tau increased the synthesis of the cellular antiviral factors, such as 2',5'-oligoadenylate synthetase/RNase L and MxA protein. These results suggested that IFN-tau induces the same antiviral pathways in macrophages as other type I IFNs. We found that IFN-tau increased the production of interleukins (IL)-10 and IL-6, but not of IL-1ss or TNF-alpha, in not infected and in in vitro HIV-1/Ba-L-infected macrophages. We also found that the neutralization of IL-6 biological activity in the cell culture supernatants of IFN-tau-treated macrophages led to a decrease in the antiretroviral effects of IFN-tau towards HIV RNA. In conclusion, anti-HIV effects of IFN-tau are mediated by several modes of action, mediated either directly by IFN-tau or via other cytokines, such as IL-6, also known to be induced by IFN-alpha.

Lack of IFN-γ Production in Response to Antigenic Stimulation in Human IFN-τ-Treated Lymphocytes

Interferon-tau (IFN-tau) is a type I IFN responsible for maternal recognition of the fetus in ruminants. In addition to its physiologic role, IFN-tau also inhibits HIV replication in human lymphocytes and macrophages and displays immunomodulatory effects but lacks the toxicity associated with other type I IFNs. Human IFN-alpha promotes a Th1 response, whereas IFN-tau has anti-inflammatory properties, inducing the production of Th2 cytokines in murine models of experimental autoimmune encephalitis (EAE) or fetal loss. We compared the effects of ovine IFN-tau (OvIFN-tau) and human IFN-alpha (HuIFN-alpha) on cytokine mRNA and protein production in human peripheral blood mononuclear cells (PBMCs) activated with a recall antigen, such as purified protein derivative (PPD) of tuberculin or with a proinflammatory stimulus, such as lipopolysaccharide (LPS). In both cases, IFN-alpha increased IFN-gamma production, whereas IFN-tau did not and thereby promoted Th2 cytokine production. This original property renders IFN-tau a potential candidate for therapeutic applications in immune disorders, such as multiple sclerosis (MS), but its therapeutic use in the treatment of HIV infection should be considered with caution.

Expression of feline interferon-alpha subtypes in Esherichia coli, and their antiviral activity and animal species specificity

Two kinds of FeIFN-alpha consisting of 166 amino acids (aa) and 171 aa were expressed in Escherichia coli, and the purified proteins were tested for antiviral activity on homologous and heterologous animal cells. Crude FeIFN induced in feline cells revealed antiviral activity on both homologous and heterologous animal cells. In contrast, both types of recombinant FeIFN-alpha revealed antiviral activity only on the feline cells. All of the FeIFN-alpha subtypes showed high activity to vesicular stomatitis virus, and the three species of feline viruses belonging to different families.

Involvement of IL-6 in the anti-human immunodeficiency virus activity of IFN-tau in human macrophages

IFN-tau is a non-cytotoxic type I IFN responsible for maternal recognition of the foetus in ruminants. IFN-tau has been found to inhibit HIV replication more strongly than human IFN-alpha, particularly in human monocyte-derived macrophages, without associated toxicity. Ovine IFN-tau uses the same anti-viral cellular pathways as human IFN-alpha in human macrophages, principally inhibiting the early steps of the biological cycle of HIV, preventing the integration of HIV DNA into the host-cell genome. In this study, we investigated the immunomodulatory properties of IFN-tau in human macrophages. We found that IFN-tau increased the production of IL-10 and IL-6, but not of IL-1beta or tumour necrosis factor alpha, in unstimulated, LPS-stimulated and HIV-1/Ba-L-infected macrophages. We also found that treatment with IL-6 inhibited HIV replication. Moreover, the neutralization of IL-6 activity in the cell culture supernatants of IFN-tau-treated macrophages led to a decrease in the anti-retroviral effects of IFN-tau, suggesting that IL-6 was involved in the anti-viral activity induced by IFN-tau. By focusing on the very early steps of the biological cycle of HIV, we showed that IL-6 co-operated with IFN-tau to decrease intracellular HIV RNA levels 2 h after infection.

Involvement of phospholipase A2 and lipoxygenase in lipopolysaccharide-induced inducible nitric oxide synthase expression in glial cells

The present study underlines the importance of phospholipase A2 (PLA2)- and lipoxygenase (LO)-mediated signaling processes in the regulation of inducible nitric oxide synthase (iNOS) gene expression. In glial cells, lipopolysaccharide (LPS) induced the activities of PLA2 (calcium-independent PLA2; iPLA2 and cytosolic PLA2; cPLA2) as well as gene expression of iNOS. The inhibition of cPLA2 by methyl arachidonyl fluorophosphates (MAFP) or antisense oligomer against cPLA2 and inhibition of iPLA2 by bromoenol lactone reduced the LPS-induced iNOS gene expression and NFkappaB activation. In addition, the inhibition of LO by nordihydroguaiaretic acid (NDGA; general LO inhibitor) or MK886 (5-LO inhibitor), but not baicalein (12-LO inhibitor), completely abrogated the LPS-induced iNOS expression. Because NDGA could abrogate the LPS-induced activation of NFkappaB, while MK886 had no effect on it, LO-mediated inhibition of iNOS gene induction by LPS may involve an NFkappaB-dependent or -independent (by 5-LO) pathway. In contrast to LO, however, the cyclooxygenase (COX) may not be involved in the regulation of LPS-mediated induction of iNOS gene because COX inhibition by indomethacin (general COX inhibitor), SC560 (COX-1 inhibitor), and NS398 (COX-2 inhibitor) affected neither the LPS-induced iNOS expression nor activation of NFkappaB. These results indicate a role for cPLA2 and iPLA2 in LPS-mediated iNOS gene induction in glial cells and the involvement of LO in these reactions.

Anti-human immunodeficiency virus activity of tau interferon in human macrophages: involvement of cellular factors and beta-chemokines

Tau interferon (IFN-tau) is a noncytotoxic type I IFN responsible for maternal recognition of the fetus in ruminants. IFN-tau inhibits human immunodeficiency virus (HIV) replication more strongly than human IFN-alpha, particularly in human monocyte-derived macrophages. In this study performed in human macrophages, IFN-tau efficiently inhibited the early steps of the biological cycle of HIV, decreasing intracellular HIV RNA and inhibiting the initiation of the reverse transcription of viral RNA into proviral DNA. Two mechanisms induced by IFN-tau treatment in macrophages may account for this inhibition: (i) the synthesis of the cellular antiviral factors such as 2',5'-oligoadenylate synthetase/RNase L and MxA protein and (ii) an increased production of MIP-1alpha, MIP-1beta, and RANTES, which are natural ligands of CCR5, the principal coreceptor of HIV on macrophages. Our results suggest that IFN-tau induces the same antiviral pathways in macrophages as other type I IFNs but without associated toxicity.

Controlled intra- or extracellular production of staphylococcal nuclease and ovine omega interferon in Lactococcus lactis

A system for controlled targeting of heterologous protein was developed in the food-grade bacterium Lactococcus lactis. It is composed of the L. lactis strain NZ9000 and of two broad host range expression vectors pCYT:Nuc and pSEC:Nuc for, respectively, cytoplasmic and secreted staphylococcal nuclease (Nuc) nisin-inducible production. The level of intracellular production of Nuc measured with pCYT:Nuc (3 mg x l(-1)) is significantly lower than the one obtained with pSEC:Nuc ( approximately 20 mg x l(-1)). The secretion efficiency (SE) of Nuc is estimated to be approximately 70%, corresponding to approximately 15 mg of secreted Nuc x l(-1). Furthermore, we established that Nuc production continued in L. lactis 10 h after a 1-h nisin-pulse induction. This system was then used for intra- and extracellular production of a protein of therapeutical interest in L. lactis, the ovine interferon-omega (IFN-omega). The SE and the quantity of secreted active IFN-omega were evaluated respectively to be approximately 70% and approximately 1 mg x l(-1) ( approximately two-fold higher than the cytoplasmic form).

Regulation and inhibition of phospholipase A2

In recent years, there has been great interest in the study of phospholipid metabolism in intact cell systems. Such an interest arises mainly from the discovery that cellular membrane phospholipids serve not only in structural roles, but are also reservoirs of preformed second messenger molecules with key roles in cellular signaling. These second messenger molecules are generated by agonist-induced activation and secretion of intracellular and extracellular phospholipases, respectively, i.e. enzymes that cleave ester bonds within phospholipids. Prominent members of the large collection of signal-activated phospholipases are the phospholipase A2s. These enzymes hydrolyze the sn-2 ester bond of phospholipids, releasing a free fatty acid and a lysophospholipid, both of which may alter cell function. In addition to its role in cellular signaling, phospholipase A2 has recently been recognized to be involved in a wide number of pathophysiological situations, ranging from systemic and acute inflammatory conditions to cancer. A growing number of pharmacologic inhibitors will help define the role of particular phospholipase A2s in signaling cascades.

The evolution of the type I interferons

There are five recognized subtypes within the type I interferons (IFN), IFN-alpha, IFN-beta, IFN-delta, IFN-omega, and IFN-tau, although others may remain to be described, and the IFN-omega may have to be subdivided further because of their evident structural complexity. Together, they constitute an ancient family of intronless genes, possibly present in all vertebrates. THe IFNA/IFNB genes originated by duplication of a progenitor after the divergence of birds, most probably about 250 million years ago (MYA). The avian gene itself proceeded to duplicate to form a series of independent subtypes. The IFND, to date described only in the pig, arose from the IFNA lineage before the emergence of mammals about 180 MYA and might, therefore, be generally distributed in present day species. The IFNB, which occurs as a single gene in primates and rodents, have been duplicated in some other orders. Recent events have produced 10 or more genes in bovid species. The IFNA, which are clustered with the IFNW in humans and cattle, exist as multiple genes in all mammals so far examined as a result of a series of duplication events, some of which occurred recently and, therefore, independently in separate mammalian lineages. The IFNW diverged from the IFNA approximately 130 MYA, just prior to the emergence of mammals, and have continued to duplicate since then. The IFNT, which play a role in reproduction of ruminants, arose from an IFNW within the Artiodactyla suborder about 36 MYA and are found only in the suborder Ruminantia. These genes have also continued to duplicate to form an extensive family. Consequently, their involvement in early pregnancy is a feature of ruminants and not of other mammalian species.

Interfacial activation, lysophospholipase and transacylase activity of group VI Ca2+-independent phospholipase A2

The Group VI 80-kDa Ca2+-independent phospholipase A2 (iPLA2) has been purified from murine P388D1 macrophages and Chinese hamster ovary (CHO) cells. The amino acid sequence of the iPLA2 has been determined and shown to contain a lipase consensus sequence and eight ankyrin repeats, which makes it distinct from Group I-V PLA2s. This enzyme appears to play a key role in mediating basal phospholipid remodeling. We now report that the Group VI iPLA2 displays interfacial activation toward short chain phospholipids, 1-octanoyl-2-heptanoyl-sn-glycero-3-phosphocholine, 1,2-diheptanoyl-sn-glycero-3-phosphocholine, and 1,2-dihexanoyl-sn-glycero-3-phosphocholine micelles. ATP protects the iPLA2 from a loss in activity as a result of prolonged incubation during the assay. Hence higher enzyme activity is observed in the presence than in the absence of ATP. Similar protection was obtained with glycerol. In addition, the iPLA2 exhibits multiple activities which are strongly dependent on substrate presentation. The lysophospholipase activity of this enzyme was diminished by Triton X-100 and stimulated by glycerol. With the combination of 50 microM Triton X-100 and 50% glycerol, the enzyme's lysophospholipase activity achieved equivalent activity to its PLA2 activity. The iPLA2 displayed both lysophospholipid/transacylase and phospholipid/transacylase activity, supporting the conclusion that the mechanism of action of iPLA2 proceeds through an acyl-enzyme intermediate as proposed for the Group IV cPLA2.

Cloning and expression of a group IV cytosolic Ca2+-dependent phospholipase A2 from rat pancreatic islets. Comparison of the expressed activity with that of an islet group VI cytosolic Ca2+-independent phospholipase A2

Stimulation of pancreatic islets with glucose induces phospholipid hydrolysis and accumulation of nonesterified arachidonic acid, which may play signaling or effector roles in insulin secretion. Of enzymes that catalyze phospholipid hydrolysis, islet beta-cells express low molecular weight secretory phospholipases A2 (PLA2) and a Group VI, Ca2+-independent PLA2 (iPLA2). Previous studies indicate that islets also express a protein recognized by antibodies against a Group IV, cytosolic, Ca2+-dependent PLA2 (cPLA2). To further examine the possible expression of cPLA2 by islets, we screened a rat islet cDNA library with a probe that recognizes cPLA2 sequence, and isolated a full-length cPLA2 cDNA. The rat islet cPLA2-deduced amino acid sequence is 96% identical to those of human and mouse cPLA2. Transfection of COS-7 cells with cPLA2 cDNA in an expression vector induced expression of Ca2+-dependent PLA2 activity and of a protein recognized by anti-cPLA2 antibody. Comparison of recombinant islet cPLA2 and iPLA2 activities expressed in transfected COS-7 cells indicated that iPLA2 but not cPLA2 is stimulated by ATP. Both activities are similarly sensitive to inhibition by arachidonyltrifluoromethyl ketone, but iPLA2 is more effectively inhibited by a haloenol lactone suicide substrate than cPLA2. RT-PCR experiments with RNA from purified islet beta-cells and from an alpha-cell-enriched population prepared by fluorescence-activated cell-sorting indicated that cPLA2 mRNA is more abundant in the beta-cell population. Immunoblotting analyses indicate that islets express cPLA2-immunoreactive protein, and that interleukin-1 does not affect its expression. The cPLA2 is thus one of at least three classes of PLA2 enzymes with distinct properties expressed in beta-cells.

The interferon-tau genes of the giraffe, a nonbovid species

Genes for interferon-tau (IFNT) have been cloned from several Bovidae, and the IFNT lineage has been predicted to have arisen from the IFNW, as the divergence of the Ruminantia from other artiodactyls. Southern genomic blotting with probes specific for IFNT identified a gene in the giraffe, a nonbovid member of the Ruminantia. Here this gene has been cloned, sequenced, and expressed. It encodes a 172-amino acid mature protein with antiviral activity on bovine cells. Giraffe IFN-tau lacks the normally conserved Cys99 but has a pair of other cysteines (Cys64 and Cys86) that could provide a disulfide bridge. The giraffe IFNT gene possesses the highly conserved promoter region that distinguishes IFNT from IFNW. It seems likely that IFNT emerged before the divergence of the Giraffidae and Bovidae, which occurred some 24 million years ago.