The cross-species antiviral activities of different IFN-tau subtypes on bovine, murine, and human cells: contradictory evidence for therapeutic potential

Uterine Tissue Metabonomics Combined with 16S rRNA Gene Sequencing To Analyze the Changes of Gut Microbiota in Mice with Endometritis and the Intervention Effect of Tau Interferon

Endometritis is a common cow disease characterized by inflammation of endometrium, which leads to infertility or low fertility of cows and brings huge economic losses to the dairy industry. Tau interferon (IFN-τ) has many important biological functions, including an anti-inflammatory effect. The present study aimed to survey the effects of IFN-τ administration on gut microflora and body metabolism in mice with endometritis and to explore the potential relationship. The results indicated that IFN-τ obviously alleviated the damage and ultrastructural changes of mouse endometrium induced by Escherichia coli and enhanced tight junction protein's expression level. Through analysis by 16S rRNA gene sequencing, we found that IFN-τ, especially at 12 h, could regulate the composition of gut microbiota associated with Pediococcus, Staphylococcus, and Enterorhabdus in E. coli-induced mouse endometritis. Through histometabonomics, it was found that endometritis was related to 11 different metabolites and 4 potential metabolic pathways. These metabolites and metabolic pathways were major participants in metabolic pathways, cysteine and methionine metabolism, arachidonic acid metabolism, and pyrimidine metabolism. Correlation analysis of gut microbiota with uterine tissue metabolomics showed that changes in metabolic pathways might be affected by gut microbiota, such as Enterorhabdus in mouse endometritis. The above results indicated that the anti-inflammatory mechanism of IFN-τ might be reduction of the abundance of Enterorhabdus in the gut microbiota, affecting the expression level of important metabolites in uterine tissue and thus playing an anti-inflammatory role. IMPORTANCE The change in intestinal flora has been the focus of many disease studies in recent years, but the pathogenetic effect of interferon on endometritis is still unclear. The results of this study showed that IFN-τ alleviated the damage in mouse endometritis induced by E. coli and improved the endometrial tissue barrier. Its functional mechanism may be reduction of the abundance of Enterorhabdus in the intestinal microbiota, affecting the expression level of important metabolites in uterine tissue and thus playing an anti-inflammatory role.

Expression, Purification, and Bioactivity of a Soluble Recombinant Ovine Interferon-tau in Escherichia Coli

INTRODUCTION

Ovine interferon-tau (oIFN-τ) is a newly discovered type I interferon. This study used biochemical techniques to transform the oIFN-τ gene into Escherichia coli to obtain the mass and soluble expression of the recombinant protein.

MATERIAL AND METHODS

First, total RNA was extracted from fresh sheep embryonic tissues with TRIzol reagent and then used as a template to reverse transcribe and amplify the mature oIFN-τ gene with RT-PCR. The amplified product was next digested with the HindIII and XhoI restriction enzymes and inserted into the pET-32a(+) vector to construct the prokaryotic expression plasmid. The corrected in-frame recombinant plasmid, pET-32a(+)-oIFN-τ, was transformed into E. coli Rosetta (DE3) competent cells. After induction with isopropyl-beta-D-thiogalactopyranoside (IPTG), the recombinant protein was detected in bacteria. Finally, the bacteria were lysed by sonication, and the recombinant protein was purified by nickel affinity chromatography and DEAE anion exchange chromatography.

RESULTS

The protein was confirmed to be oIFN-τ, which mainly existed in the soluble lysate fraction, as proven by SDS-PAGE and Western blot assays.

CONCLUSION

Purified IFN-τ exists mostly in a soluble form, and its anti-vesicular stomatitis virus (VSV) activity reached 7.08×10(6)IU/mL.

The evolution of interferon-tau

Thirty years ago, a novel type I interferon (IFN) was identified by molecular cloning of cDNA libraries constructed from RNA extracted from ovine and bovine pre-implantation embryos. This protein was eventually designated as IFN-tau (IFNT) to highlight its trophoblast-dependent expression. IFNT function is not immune related. Instead, it interacts with the maternal system to initiate the establishment and maintenance of pregnancy. This activity is indispensable for the continuation of pregnancy. Our review will describe how IFNT evolved from other type I IFNs to function in this new capacity. IFNT genes have only been identified in pecoran ruminants within the Artiodactyla order (e.g. cattle, sheep, goats, deer, antelope, giraffe). The ancestral IFNT gene emerged approximately 36 million years ago most likely from rearrangement and/or insertion events that combined an ancestral IFN-omega (IFNW) gene with a trophoblast-specifying promoter/enhancer. Since then, IFNT genes have duplicated, likely through conversion events, and mutations have allowed them to adapt to their new function in concert with the emergence of different species. Multiple IFNT polymorphisms have been identified in cattle, sheep and goats. These genes and gene alleles encode proteins that do not display identical antiviral, antiproliferative and antiluteolytic activities. The need for multiple IFNT genes, numerous alleles and distinct activities remains debatable, but the consensus is that this complexity in IFNT expression and biological activity must be needed to provide the best opportunity for pregnancy to be recognized by the maternal system so that gestation may continue.

Protective Effects of Interferon-tau Against Lipopolysaccharide-Induced Embryo Implantation Failure in Pregnant Mice

Interferon-tau (IFN-τ), a novel type I interferon, is produced by trophoblast cells in ruminants. Previous studies have confirmed that IFN-τ could induce immunological tolerance in humans and other species. However, there are few reports on whether IFN-τ has a protective effect on embryo implantation failure caused by excessive inflammation at the maternal-fetal interface. In our study, a mouse model of lipopolysaccharide (LPS)-induced implantation failure was successfully established, and we investigated the protective effects of IFN-τ. First, we showed that IFN-τ increased the number of implanted embryos in LPS-treated pregnant mice. Subsequently, quantitative real-time polymerase chain reaction (qPCR) and ELISA results showed that several inflammatory cytokines [IL-1β and tumor necrosis factor-alpha (TNF-α)] whose expression was upregulated by LPS were reversed by IFN-τ treatment. Furthermore, we performed Western blotting and found that IFN-τ restrained the LPS-induced phosphorylation of IκBα and NF-κB p65. Moreover, qPCR and immunohistochemistry analyses showed that IFN-τ decreased the LPS-induced expression of mouse major histocompatibility complex (MHC) class I genes (H-2K and H-2D) in LPS-treated pregnant mice. Taken together, these results suggest that IFN-τ has a protective effect in LPS-induced implantation failure by downregulating MHC class I genes expression and inhibiting the production of inflammatory cytokines.

Interferon-τ increases BoLA-I for implantation during early pregnancy in dairy cows

Interferon-τ (IFN-τ) signals pregnancy recognition in ruminants. We investigated the effects of IFN-τ produced by embryo trophoblastic cells (ETCs) on expression of bovine leukocyte antigen-I (BoLA-I), a bovine analogue of human MHC-I, in endometrial luminal epithelial cells (EECs) during early pregnancy in dairy cows. Expression of IFN-τ and BoLA-I was increased in endometrial tissues during early pregnancy. Expression of the anti-inflammatory cytokine IL-10 was increased in endometrial tissues, while expression of the pro-inflammatory cytokine IL-6 was decreased, indicating immunosuppression. Progesterone increased IFN-τ expression in EECs. IFN-τ increased p-STAT1 and p-STAT3 levels in EECs, but reduced TRAF3 levels. In addition, IFN-τ increased expression of BoLA-I and IL-10, but decreased expression of IL-6 in EECs. These results indicate that IFN-τ enables stable implantation in dairy cows by increasing expression of BoLA-I, and by immunosuppression mediated by increased IL-10 and decreased IL-6 expression.

IFN-τ Alleviates Lipopolysaccharide-Induced Inflammation by Suppressing NF-κB and MAPKs Pathway Activation in Mice

IFN-τ, which is a type I interferon with low cytotoxicity, is defined as a pregnancy recognition signal in ruminants. Type I interferons have been used as anti-inflammatory agents, but their side effects limit their clinical application. The present study aimed to determine the anti-inflammatory effects of IFN-τ in a lipopolysaccharide-stimulated acute lung injury (ALI) model and in RAW264.7 cells and to confirm the mechanism of action involved. The methods used included histopathology, measuring the lung wet/dry ratio, determining the myeloperoxidase activity, ELISA, qPCR, and western blot. The results revealed that IFN-τ greatly ameliorated the infiltration of inflammatory cells and the expression of TNF-α, IL-1β, and IL-6. Further analysis revealed that IFN-τ down-regulated the expression of TLR-2 and TLR-4 mRNA and the activity of the NF-κB and MAPK pathways both in a lipopolysaccharide-induced ALI model and in RAW264.7 cells. The results demonstrated that IFN-τ suppressed the levels of pro-inflammatory cytokines by inhibiting the phosphorylation of the NF-κB and MAPK pathways. Thus, IFN-τ may be an optimal target for the treatment of inflammatory diseases.

IFN-τ Displays Anti-Inflammatory Effects on Staphylococcus aureus Endometritis via Inhibiting the Activation of the NF-κB and MAPK Pathways in Mice

The aim of the present study was to determine the anti-inflammatory effect of IFN-τ on endometritis using a mouse model of S. aureus-induced endometritis and to elucidate the mechanism of action underlying these effects. In the present study, the effect of IFN-τ on S. aureus growth was monitored by turbidimeter at 600 nm. IFN-τ did not affect S. aureus growth. The histopathological changes indicated that IFN-τ had a protective effect on uterus tissues with S. aureus infection. The ELISA and qPCR results showed the production of the proinflammatory cytokines TNF-α, IL-1β, and IL-6 was decreased with IFN-τ treatment. In contrast, the level of the anti-inflammatory cytokine IL-10 was increased. We further studied the signaling pathway associated with these observations, and the qPCR results showed that the expression of TLR2 was repressed by IFN-τ. Furthermore, the western blotting results showed the phosphorylation of IκB, NF-κB p65, and MAPKs (p38, JNK, and ERK) was inhibited by IFN-τ treatment. The results suggested that IFN-τ may be a potential drug for the treatment of uterine infection due to S. aureus or other infectious inflammatory diseases.

Antiviral activity of ovine interferon tau 4 against foot-and-mouth disease virus

Foot-and-mouth disease (FMD) is an economically important disease in most parts of the world and new therapeutic agents are needed to protect the animals before vaccination can trigger the host immune response. Although several interferons have been used for their antiviral activities against Foot-and-mouth disease virus (FMDV), ovine interferon tau 4 (OvIFN-τ4), with a broad-spectrum of action, cross-species antiviral activity, and lower incidence of toxicity in comparison to other type І interferons, has not yet been evaluated for this indication. This is the first study to evaluate the antiviral activity of OvIFN-τ4 against various strains of FMDV. The effective anti-cytopathic concentration of OvIFN-τ4 and its effectiveness pre- and post-infection with FMDV were tested in vitro in LFBK cells. In vivo activity of OvIFN-τ4 was then confirmed in a mouse model of infection. OvIFN-τ4 at a concentration of 500 ng, protected mice until 5days post-FMDV challenge and provided 90% protection for 10 days following FMDV challenge. These results suggest that OvIFN-τ4 could be used as an alternative to other interferons or antiviral agents at the time of FMD outbreak.

Interferon Tau Affects Mouse Intestinal Microbiota and Expression of IL-17

This study was conducted to explore the effects of interferon tau (IFNT) on the intestinal microbiota and expression of interleukin 17 (IL-17) in the intestine of mice. IFNT supplementation increased microbial diversity in the jejunum and ileum but decreased microbial diversity in the feces. IFNT supplementation influenced the composition of the intestinal microbiota as follows: (1) decreasing the percentage of Firmicutes and increasing Bacteroidetes in the jejunum and ileum; (2) enhancing the percentage of Firmicutes but decreasing Bacteroidetes in the colon and feces; (3) decreasing Lactobacillus in the jejunum and ileum; (4) increasing the percentage of Blautia, Bacteroides, Alloprevotella, and Lactobacillus in the colon; and (5) increasing the percentage of Lactobacillus, Bacteroides, and Allobaculum, while decreasing Blautia in the feces. Also, IFNT supplementation decreased the expression of IL-17 in the intestines of normal mice and of an intestinal pathogen infected mice. In conclusion, IFNT supplementation modulates the intestinal microbiota and intestinal IL-17 expression, indicating the applicability of IFNT to treat the intestinal diseases involving IL-17 expression and microbiota.

The Anti-Inflammatory Effects of Interferon Tau by Suppressing NF-κB/MMP9 in Macrophages Stimulated with Staphylococcus aureus

Previous studies have reported that interferon tau (IFNT) significantly mitigates tissue inflammation. However, this effect and its regulating pathways have not been reported for Staphylococcus aureus-induced inflammation. In this study, RAW 264.7 cells stimulated with S. aureus were used to identify the anti-inflammatory effects and mechanism of IFNT. First, IFNT was found to be noncytotoxic to macrophages treated with the high dose of 200 ng/mL IFNT. ELISA and qPCR revealed that IFNT decreased the expression of proinflammatory cytokines such as TNF-α, IL-1β, and IL-6. TLR2, which is involved in the immune response during S. aureus infection, directly affected NF-κB pathway activation and was also downregulated by IFNT. Subsequent Western blotting showed that the phosphorylation of IκBα and NF-κB p65 was inhibited by IFNT. Therefore, although the MMP9 levels were significantly downregulated in a dose-dependent manner by IFNT, little change in MMP2 was observed in S. aureus-stimulated RAW 264.7 cells. Furthermore, PDTC, an inhibitor of NF-κB, also significantly decreased MMP9 levels by inhibiting NF-κB p65 activation. All of these findings strongly suggested that IFNT suppresses the NF-κB/MMP9 signal transduction pathway and subsequently exerts its anti-inflammatory effects in S. aureus-stimulated RAW 264.7 cells.

Interferon-tau attenuates uptake of nanoparticles and secretion of interleukin-1β in macrophages

BACKGROUND

Type I interferons (IFNs), including IFN-alpha (IFNA) and IFN-beta (IFNB), have anti-inflammatory properties and are used to treat patients with autoimmune and inflammatory disorders. However, little is known of the role of IFN-tau (IFNT), a type I IFN produced by ruminant animals for inflammation. Because IFNB has recently been shown to inhibit nucleotide-binding oligomerization domain-like receptor, pyrin domain-containing 3 (NLRP3) inflammasome activation and subsequent secretion of the potent inflammatory cytokine interleukin (IL)-1β, we examined the effects of ruminant IFNT on NLRP3 inflammasome-mediated IL-1β secretion in human THP-1 macrophages.

METHODS AND RESULTS

IFNT dose-dependently inhibited IL-1β secretion induced by nano-silica, a well-known activators of NLRP3 inflammasomes, in human macrophages primed with lipopolysaccharide (LPS, TLR4 agonist) and Pam3CSK4 (TLR1/2 agonist). IFNT also suppressed phagocytosis of nano-silica and reactive oxygen species (ROS) generation. Western blot analysis showed that IFNT inhibited both pro-IL-1β and mature IL-1β. In addition, real-time RT-PCR analysis showed that IFNT suppressed IL-1β mRNA expression induced by LPS and Pam3CSK4. Although nano-silica particles did not induce IL-10 secretion, IFNT induced IL-10 secretion in a dose-dependent manner. Furthermore, IFNT-suppressed IL-1β secretion was restored by anti-IL-10 neutralizing antibody.

CONCLUSIONS

Ruminant IFNT inhibits NLRP3 inflammasome-driven IL-1β secretion in human macrophages via multiple pathways, including the uptake of nano-silica particles, generation of ROS, and IL-10-mediated inhibition of pro-IL-1β induction. It may be a therapeutic alternative to IFNA and IFNB.

Validation of an interferon stimulatory response element reporter gene assay for quantifying type I interferons

The goal of this work was to develop a virus-free, cell-based interferon (IFN) bioassay and determine the utility of this assay on biological samples that contained IFN-τ, the trophoblast-secreted maternal recognition of pregnancy factor in ruminants. Madin-Darby bovine kidney cells were transduced with lentiviral particles that contained a firefly luciferase reporter construct driven by an IFN stimulatory response element (ISRE). Stably transduced cells were selected with the use of puromycin resistance. A linear, dose-responsive response was detected with human IFN-α and ovine IFN-τ. Interferon activity was detected in conditioned media from bovine trophoblast cells and uterine flushes collected from sheep and cattle. Activity also was detected in media collected after individual or small group culture of in vitro-produced bovine blastocysts at day 8 to 10 after fertilization. In summary, this IFN stimulatory response element-reporter assay may be used as an alternative to virus-dependent, cytopathic assays. It contains a similar sensitivity to IFNs and can be completed in a shorter time than cytopathic assays and does not require heightened biosafety conditions after cell transduction.

Interferon-β sensitivity of tumor cells correlates with poor response to VA7 virotherapy in mouse glioma models

In our recent study, replicative alphaviral vector VA7 was found to be effective against orthotopic human U87-glioma xenografts in an athymic mouse model eradicating the tumors with single intravenous (i.v.) injection. Here, we tested the efficacy of VA7 in immunocompetent orthotopic GL261 and CT-2A glioma models of C57BL/6 mouse in vivo. The cell lines were susceptible to VA7 infection in vitro, but GL261 infection was highly restricted in confluent cell cultures, and mouse interferon-β (IFNβ) pretreatment prevented the replication of VA7 in both cell lines. When mice bearing orthotopic GL261 or CT-2A tumors were administered neurotropic VA7, either i.v. or intracranially (i.c.), the vector was unable to infect the tumor and no survival benefit was achieved. Pretreatments with immunosuppressive cyclophosphamide (CPA) and rapamycin markedly lowered serum-neutralizing antibodies (NAbs) but had no effect on tumor infection or survival. Intracranial GL261 tumors were refractory also in athymic C57BL/6 mice, which have serious defects in their adaptive immunity. Implanted VA7-infected GL261 cells formed tumors with only slightly delayed kinetics and without improving survival thus excluding the participation of physical barriers and indicating robust host IFN action. Mouse and human IFNβ do not seem be species cross-reactive, which might limit the translational relevance of xenograft models in oncolytic virotherapy.

Interferon-tau: current applications and potential in antiviral therapy

Interferon-tau (IFN-tau) was initially identified as an ovine pregnancy protein. Produced by the trophoblast, it is important in preventing degradation of the corpus luteum and has been used as an early marker for ovine pregnancy. As a member of the family of type I interferons, IFN-tau has demonstrated promising antiviral activity against human viral infections in vitro. Additionally, it displays high species cross-reactivity despite its absence in humans. To date, IFN-tau has shown efficacy in reducing replication of human immunodeficiency virus, feline immunodeficiency virus, and human papillomavirus. While IFN-tau shares similar antiviral activity to IFN-alpha, the current interferon of choice for treatment of viral infections, it lacks the associated toxicity. This may make IFN-tau an attractive alternative to IFN-alpha for the treatment of viral infections.

A microarray analysis for genes regulated by interferon-tau in ovine luminal epithelial cells

Interferon-tau (IFNT) is released by preimplantation conceptuses of ruminant species and prepares the mother for pregnancy. Although one important function is to protect the corpus luteum from the luteolytic activity of prostaglandin-F 2alpha, IFNT most likely regulates a range of other physiological processes in endometrium. Here, an immortalized cell line from ovine uterine luminal epithelial cells was treated with IFNT for either 8 or 24 h. RNA was subjected to cDNA microarray analysis, with RNA from untreated cells as the reference standard. Of 15 634 genes, 1274 (8%) were IFNT responsive at P<0.01 and 585 at P<0.001 to at least one treatment. Of the latter, 356 were up-regulated and 229 down-regulated. Increasing IFNT concentrations from 10 ng/ml to 10 microg/ml had minor effects, and most genes up- or down-regulated at 8 h were regulated similarly at 24 h. Although IFNT influences many genes implicated in antiviral activity and apoptosis, its action also likely regulates prostaglandin metabolism, growth factors and their receptors, apoptosis and the nuclear factor (NF)-kappaB cascade, extracellular matrix accretion, angiogenesis, blood coagulation, and inflammation. In particular, it increased mRNA concentrations of genes related to the vascular endothelial growth factor R2 pathway of angiogenesis and down-regulated ones associated with hypoxia. Two genes implicated in the antiluteolytic actions of IFNT (encoding cyclooxygenase-2 and the oxytocin receptor respectively) were down-regulated in response to all treatments. IFNT targets a complex range of physiological processes during the establishment of pregnancy.

In vitro and in vivo effects of recombinant bovine interferon-tau on bovine leukemia virus

The antiviral effects of recombinant bovine interferon-tau (rboIFN-tau) on bovine leukemia virus (BLV) were examined in vitro and in vivo. In the in vitro experiments, BLV titers decreased in FLK-BLV cells and in peripheral blood mononuclear cells of BLV-infected cattle treated with rboIFN-tau at a concentration higher than 10(2) U/ml. In order to examine the in vivo effects of rboIFN-tau, 10 BLV-infected cattle were subcutaneously injected with rboIFN-tau. In the first experiment, 6 cows were administrated with 10(5) U/kg body weight of rboIFN-tau 3 times per week for 4 weeks, while in the second experiment 4 cows were administrated with 10(6) U/kg body weight of rboIFN-tau 3 times per week for 3 weeks. No adverse effects were observed after the administration of rboIFN-tau. In experiment No. 1, the mean BLV titers in cattle decreased in the post-rboIFN-tau administration period compared to the pre-rboIFN-tau administration period. In experiment No. 2, the mean BLV titers in cattle decreased in the rboIFN-tau administration period. These results suggest that rboIFN-tau decreases BLV titers in vitro and in vivo and that rboIFN-tau possibly reduces the degree of BLV titer in cattle without severe side effects.

Effect of inclusion of serum and granulocyte-macrophage colony stimulating factor on secretion of interferon-tau during the in vitro culture of ovine embryos

In each of three experiments, in vitro-matured and -fertilised zygotes were cultured to Day 7 post insemination in synthetic oviductal fluid (SOF). In Experiment 1, zygotes were cultured in groups in either SOF plus albumin (SOFA) or serum (SOFS) and then blastocysts were cultured individually for a further 24 h without a change of media. In Experiment 2, zygotes were cultured in groups using a 2 x 2 factorial design in SOFA or SOFS, with or without recombinant ovine granulocyte-macrophage colony stimulating factor (GM-CSF; 5 ng mL(-1)). Blastocysts were then cultured individually using a split-plot design in SOFA or SOFS with or without GM-CSF. In Experiment 3, zygotes were cultured in SOFA in which GM-CSF was absent (A) or present (P) during Days 1-3, Days 3-5 or Days 5-7 of IVC in six combinations as follows: AAA, AAP, APP, PPP, PPA and PAA. Serum or GM-CSF increased secretion of interferon (IFN)-tau in Experiments 1 and 2 both between Days 5 and 7 of group culture and during individual culture. Secretion of IFN-tau during individual culture was determined by the medium in which embryos were group cultured and the effects of GM-CSF and serum were not additive. In Experiment 3, the presence of GM-CSF between Days 1 and 3 of culture was responsible for stimulation of secretion of IFN-tau between Days 5 and 7; IFN-tau secretion was detected as early as Day 3 post insemination.

VSV replication in neurons is inhibited by type I IFN at multiple stages of infection

Vesicular stomatitis virus (VSV) is a rhabdovirus which causes acute encephalitis in mice after intranasal infection. Because type I interferon (IFN) has been shown to be a potent inhibitor of VSV, we investigated the role of type I IFN in viral replication in neurons in culture. Pre-treatment of NB41A3 neuroblastoma cells or primary neuron cultures with IFN-beta or IFN-alpha strongly inhibits virus replication, with 1000-fold inhibition of infectious virus release occurring at 7 h post-infection, and maximum inhibition of 14,000-fold occurring at 14 h. Type I IFN inhibited both viral protein and RNA synthesis, but not enough to account for the inhibition of infectious virus yield. The influenza virus protein NS1 binds dsRNA and antagonizes induction of PKR activity, an IFN-inducible antiviral protein which phosphorylates and inactivates the elongation factor eIF-2alpha, resulting in cessation of translation. In NS1-expressing neuroblastoma cells, VSV replication was inhibited by IFN-beta as well as in control NB41A3 cells, and eIF-2alpha phosphorylation was blocked, suggesting that PKR activity was not involved in inhibition of viral protein synthesis. Similarly, inhibition of VSV by IFN-beta was not affected by addition of inhibitors of nitric oxide synthase, indicating that IFN-beta activity is not mediated by nitric oxide or superoxide. This contrasts with the essential role of NOS-1 in inhibition of VSV replication when neurons are treated with IFN-gamma. Analysis of cell culture supernatants revealed suppression of release of VSV particles from both NB41A3 cells and primary neurons treated with IFN. The inhibition of virion release closely matched the overall suppression of infectious VSV particle release, suggesting that type I IFN plays a role in inhibition of VSV assembly.

No effect of bovine interferon-tau for control of calf diarrhea and immunomodulation in calves

Newborn calves received a low dose of bovine interferon-tau (boIFN-tau) orally for 4 weeks and calves that had developed diarrhea received a low dose of boIFN-tau orally for 5 days. No effects of boIFN-tau were seen in the duration of the diarrhea, or in daily weight gain. Calves received a high dose of boIFN-tau subcutaneously 3 times and they were then stimulated with bovine herpesvirus type 1 vaccine. No adverse effects were observed after the administration of boIFN-tau and lymphocyte subsets from calves did not change after the stimulation. Our results suggest that boIFN-tau does not seem protecting for preventing calves from diarrhea, recovering the health of calves with diarrhea or immunomodulation, although the treatment itself is not toxic.

Characterization of N-terminal interferon tau mutants: P26L affords enhanced activity and lack of toxicity

Interferon (IFN)-tau is a type I IFN that is responsible for the maternal recognition of pregnancy in ruminants. This protein also has classic IFN-like properties, including antiviral, antiproliferative, and immunomodulatory functions. Using IFN-tau as a model, we examined the structural basis for the activity of type I IFNs, focusing on amino acids within helix A and the first section of the AB loop, which have been proposed as a site for receptor interaction. Six amino-acid substitutions were made that replaced a residue in ovine IFN-tau1mod with the corresponding residue in human IFN-alphaA. Receptor binding was enhanced by a P26L mutation and was reduced by a conservative lysine-to-histidine substitution at residue 34. Alterations in the antiviral and antiproliferative activities of the IFN-tau mutants were not always correlated, but both functions were maintained or enhanced relative to the wild-type IFN-tau by the proline-to-leucine mutation at residue 26. In contrast, this mutation did not affect the low in vitro cytotoxicity that is characteristic of ovine IFN-tau1mod. Thus, the IFN-tau P26L mutant may have potential as an improved IFN-based therapeutic.

BVDV and innate immunity

Infection with bovine viral diarrhea virus (BVDV) is prevalent in the cattle population worldwide. The virus exists in two biotypes, cytopathic and non-cytopathic, depending on the effect of the viruses on cultured cells. BVDV may cause transient and persistent infections which differ fundamentally in the host's antiviral immune response. Transient infection may be due to both cytopathic and non-cytopathic biotypes of BVDV and leads to a specific immune response. In contrast, only non-cytopathic BVD viruses can establish persistent infection as a result of infection of the embryo early in its development. Persistent infection is characterized by immunotolerance specific for the infecting viral strain. In this paper we discuss the role of innate immune responses in the two types of infection. In general, both transient and persistent infections are associated with an increased frequency of secondary infections. Associated with the increased risk of such infections are, among others, impaired bacteria killing and decreased chemotaxis. Interestingly, non-cytopathic BVDV fails to induce interferon type I in cultured bovine macrophages whereas cytopathic biotypes readily trigger this response. Cells infected with non-cytopathic BVDV are also resistant to induction of interferon by double stranded RNA, a potent interferon inducer signalling the presence of viral replication in the cell. Thus, non-cytopathic BVDV may dispose of a mechanism suppressing a key element of the antiviral defence of the innate immune system. Since interferon is also important in the activation of the adaptive immune response, suppression of this signal may be essential for the establishment of persistent infection and immunotolerance.

Influence of different isoforms of recombinant trophoblastic interferons on prostaglandin production in cultured bovine endometrial cells

In ruminants, interferon produced by the trophectoderm (IFN-tau) is recognized as the embryonic signal responsible for maternal recognition of pregnancy. IFN-tau is believed to act by down-regulating estrogen receptors, thus preventing appearance of oxytocin receptors responsible for the release of prostaglandin F(2alpha) (PGF(2alpha)) by the endometrium. The present study was undertaken to determine in vitro the biological activities of different IFN-tau isoforms and document putative alternate luteotrophic mechanisms. Endometrial cells in primary cultures were treated with five different rIFN-tau isoforms: two ovine isoforms (ro-4 and ro-11) and three bovine isoforms (rb-1a, rb-2b and rb-3b). Their effect was quantified by measurement of PGE(2) and PGF(2alpha) production by ELISA and induction of cyclooxygenase (COX-2) by Western and Northern analysis and correlated with antiviral activity previously reported. The overall pattern of response to the IFNs tested suggests that low concentrations (<1 microg/ml) reduced the production of both PGs and higher concentrations (>1 microg/ml) stimulated preferentially PGE(2); however, exceptions were noted. Isoform rb-2b with high antiviral activity inhibited PG production in both cell types at all concentrations tested. IFNs rb-1a and ro-11 had similar antiviral activities, inhibiting PG at low concentrations and stimulating them at high concentrations. Isoform rb-3b stands out relative to the other IFNs tested because it induced a variable non-dose-dependent effect on PG production and low antiviral activity. An increase in COX-2 protein expression and messenger was correlated with increased PG production. The results showing two distinct responses to IFN-tau depending on its concentration and/or isoform and the absence of correlation with antiviral activity suggest that complex transduction mechanisms are involved.

Induction of blood 2',5'-oligoadenylate synthetase activity in mice by gastric administration of ovine IFN-tau

Interferon-tau (IFN-tau) is a member of the type I IFN family. Although its distribution is restricted to ruminants, IFN-tau is active against cells of humans and mice. It has been reported that oral administration of ovine IFN-tau (OvIFN-tau) prevents both acute and chronic relapsing forms of murine experimental allergic encephalomyelitis (EAE). Here, we examined the effect in mice of peroral gastric administration of OvIFN-tau on the induction of 2',5'-oligoadenylate synthetase (OAS) activity in whole blood. Before administration, mice were deprived of food and drink for 6 h, and IFN was given by either intraperitoneal (i.p.) injection or per-oral gastric administration. When administered gastrically, IFN was introduced directly into the upper part of the stomach using an oral feeding needle. OAS activity in whole blood increased dependent on dose (0-105 U) and time (0-24 h), with no significant difference in the level of activity between the two routes. An increase in the activity of OAS in blood following administration of OvIFN-tau was observed in ICR, BALB/c, C57BL/6, NZW/N, and SJL/J mice, although the extent of the increase varied with the strain. Blood OAS levels also increased on administration of murine IFN-alpha (MuIFN-alpha). However, higher levels were detected after i.p. injection than after gastric administration.

Ovine IFN-tau modulates the expression of MHC antigens on murine cerebrovascular endothelial cells and inhibits replication of Theiler's virus

Interferon-beta (IFN-beta) has been used successfully to treat patients with relapsing-remitting multiple sclerosis (MS). IFN-tau is a new class of type I IFN that is secreted by the trophoblast and is the signal for maternal recognition of pregnancy in sheep. IFN-tau has potent immunosuppressive and antiviral activities similar to other type I IFN but is less cytotoxic than IFN-alpha/beta. The current investigation concerns the effect of recombinant ovine IFN-tau (rOvIFN-tau) on the modulation of MHC class I and II expression on cloned mouse cerebrovascular endothelial (CVE) cells. IFN-tau induced tyrosine phosphorylation of Stat1 and upregulated the expression of MHC class I on CVE. One proposed action by which type I IFN reduce the relapse rate in MS is via interference with IFN-gamma-induced MHC class II expression. IFN-tau was shown to downregulate IFN-gamma-induced MHC class II expression on CVE and, hence, may be of potential therapeutic value in downregulating inflammation in the central nervous system (CNS). IFN-tau did not upregulate the expression of MHC class II on CVE. IFN-tau also inhibited the replication of Theiler's virus in CVE. These in vitro results suggest that IFN-tau may be of therapeutic value in the treatment of virus-induced demyelinating disease.

Antiviral activities of the soluble extracellular domains of type I interferon receptors

Alternative splicing leads to the expression of multiple isoforms of the subunits (IFNAR1 and IFNAR2) of the type I IFN receptor. Here we describe two transcripts representing extracellular forms of ovine IFNAR1 and show that soluble extracellular forms of both IFNAR2 and IFNAR1, prepared in recombinant form in Escherichia coli, have antiviral (AV) activity in the absence of IFN. Exposure of Madin-Darby bovine kidney cells to the extracellular domain (R2E) of IFNAR2 at concentrations as low as 10 nM afforded complete protection against vesicular stomatitis virus and led to the rapid activation of the transcription factors ISGF3 and GAF. Although R2E can bind IFN (K(d) approximately 70 nM), activity was observed irrespective of whether or not ligand was present. R2E was inactive on mouse L929 cells but active on L929 cells expressing a membraneanchored, ovine/human chimeric IFNAR2 with an ovine extracellular domain. The data suggest that AV activity is conferred by the ability of soluble R2E to associate with the transfected IFNAR2 subunit rather than resident murine IFNAR1. Soluble extracellular forms of IFNAR1 have lower AV activity than R2E on Madin-Darby bovine kidney cells but are less species-specific and protect wild-type L929 cells as efficiently as the transfected cell line, presumably by interacting with one of the murine receptor subunits.

Differences in lymphocyte-regulatory activity among variants of ovine IFN-tau

Interferon-tau (IFN-tau) is secreted from trophectoderm of the ruminant preimplantation conceptus and functions during pregnancy to prevent luteolysis. In addition, IFN-tau can inhibit proliferation of peripheral blood lymphocytes (PBL) and other cells. Several distinct ovine IFN-tau (OvIFN-tau) gene variants exist; three of these (IFN-tau4, IFN-tau6d, IFN-tau11) differ in their ability to prevent luteolysis (IFN-tau4 > IFN-tau6d > IFN-tau11), inhibit growth of Daudi cells (IFN-tau4 > IFN-tau6d > IFN-tau11), and induce an antiviral state (IFN-tau4 > IFN-tau6d = IFN-tau11). The present objective was to compare variants for differences in ability to inhibit proliferation of phytohemagglutinin-stimulated PBL. At equal concentrations, IFN-tau4 was more inhibitory than IFN-tau6d, IFN-tau11, or an IFN-omega control. Similar differences in potency were seen when IFN-tau variants were tested at equal antiviral concentrations. Thus, the sheep trophectoderm secretes variants of IFN-tau that differ in ability to regulate lymphocyte function. The nature of the effect of the trophectoderm on endometrial lymphocytes may depend on the relative amount of each variant produced.

A classification for the interferon-tau

An attempt has been made to provide a rational organization for the many interferon-tau (IFN-tau) sequences entered in GenBank based on phylogenetic analysis and common amino acid substitutions, which might form the basis for a universal nomenclature scheme. Over the 13 years since these genes were first discovered, large numbers of cDNA and gene sequences have been reported, and there is reason to suspect that representatives of all the major ovine and bovine forms have now been described. The data are consistent with the presence of many genes and also allelic variants in sheep and cattle analogous to what has been observed for the IFN-alpha in the human. Future variants should be easily accommodated into the scheme outlined here. A flexible system of nomenclature, based on that used for HuIFN, is needed to provide a common base for comparison between research done in different laboratories and to assign relative biologic potencies to these molecules.