Cloning and expression in Saccharomyces cerevisiae of a synthetic gene for the type-I trophoblast interferon ovine trophoblast protein-1: purification and antiviral activity

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.

Mechanisms for the establishment and maintenance of pregnancy: synergies from scientific collaborations

Research on the functions of interferon tau (IFNT) led to the theory of pregnancy recognition signaling in ruminant species. But IFNT does much more as it induces expression of interferon regulatory factor 2 (IRF2) in uterine luminal (LE), superficial glandular (sGE), but not glandular (GE) epithelia. First, IRF2 silences transcription of the estrogen receptor alpha gene and, indirectly, transcription of the oxytocin receptor gene to abrogate development of the luteolytic mechanism to prevent regression of the corpus luteum and its production of progesterone for establishing and maintaining pregnancy. Second, IRF2 silences expression of classical interferon-stimulated genes in uterine LE and sGE; however, uterine LE and sGE respond to progesterone (P4) and IFNT to increase expression of genes for transport of nutrients into the uterine lumen such as amino acids and glucose. Other genes expressed by uterine LE and sGE encode for adhesion molecules such as galectin 15, cathepsins, and cystatins for tissue remodeling, and hypoxia-inducible factor relevant to angiogenesis and survival of blastocysts in a hypoxic environment. IFNT is also key to a servomechanism that allows uterine epithelia, particularly GE, to proliferate and to express genes in response to placental lactogen and placental growth hormone in sheep. The roles of secreted phosphoprotein 1 are also discussed regarding its role in implantation in sheep and pigs, as well as its stimulation of expression of mechanistic target of rapamycin mRNA and protein which is central to proliferation, migration, and gene expression in the trophectoderm cells.

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.

Chronicling the discovery of interferon tau

It has been 38 years since a protein, now known as interferon tau (IFNT), was discovered in ovine conceptus-conditioned culture medium. After 1979, purification and testing of native IFNT revealed its unique antiluteolyic activity to prevent the regression of corpora lutea on ovaries of nonpregnant ewes. Antiviral, antiproliferative and immunomodulatory properties of native and recombinant IFNT were demonstrated later. In addition, progesterone and IFNT were found to act cooperatively to silence expression of classical interferon stimulated genes in a cell-specific manner in ovine uterine luminal and superficial glandular epithelia. But, IFNT signaling through a STAT1/STAT2-independent pathway stimulates expression of genes, such as those for transport of glucose and amino acids, which are required for growth and development of the conceptus. Further, undefined mechanisms of action of IFNT are key to a servomechanism that allows ovine placental lactogen and placental growth hormone to affect the development of uterine glands and their expression of genes throughout gestation. IFNT also acts systemically to induce the expression of interferon stimulated genes that influence secretion of progesterone by the corpus luteum. Finally, IFNT has great potential as a therapeutic agent due to its low cytotoxicity, anti-inflammatory properties and effects to mitigate diabetes, obesity-associated syndromes and various autoimmune diseases.

Expression and purification of buffalo interferon-tau and efficacy of recombinant buffalo interferon-tau for in vitro embryo development

The aim of our study was to optimize growth and induction parameters, for expression and large scale purification of functionally active buffalo interferon tau, and to study its possible impact on in vitro blastocyst development. The buffalo interferon-tau gene (BuIFN-T1) bearing gene bank accession No. JX481984, with signal sequence, was obtained through polymerase chain reaction (PCR) from bovine early embryos and was cloned into pJET vector. After being verified, the fragments without signal sequence, were inserted into the expression vector pET-22b and the recombinant plasmid was induced to express the recombinant protein in a prokaryotic expression system. The recombinant BuIFN-T was confirmed by SDS-PAGE and Western blot and subjected to three steps of large scale purification using His Affinity chromatography, Anion Exchange chromatography and Gel Filtration chromatography. The purified recombinant BuIFN-T protein was validated by mass spectroscopy analysis. To examine the effect of recombinant BuIFN-T protein on developmental competency of buffalo embryos, purified recombinant BuIFN-T protein was added to in vitro embryo culture medium (at concentration of 0, 1μg/ml, 2μg/ml, 4μg/ml) for 9days. Addition of recombinant BuIFN-T (2μg/ml) significantly improved the rate of blastocyst production, 45.55% against 31.1% control (p<0.01). Here we conclude that the recombinant BuIFN-T was successfully purified to homogeneity from a prokaryotic expression system and it significantly increased the blastocyst production rate in buffalo. These findings suggest a potential impact of IFN-T in promoting embryonic growth and development.

History of Maternal Recognition of Pregnancy

The mechanism for signaling pregnancy recognition is highly variable among species, and the signaling molecule itself varies between estrogens in pigs to chorionic gonadotrophin in primates. This chapter provides insight into the menstrual cycle of women and estrous cycles of rodents, dog, cat, pigs, sheep, rabbits, and marsupials, as well as the hormones required for pregnancy recognition. Pregnancy recognition involves specific hormones such as prolactin in rodents or interferons in ruminants and estrogens in pigs that in their own way ensure the maintenance of the corpus luteum and its secretion of progesterone which is the hormone of pregnancy. However, these pregnancy recognition signals may also modify gene expression in a cell-specific and temporal manner to ensure the growth and development of the conceptus. This chapter provides some historical aspects of the development of understanding of mechanisms for the establishment and maintenance of pregnancy in several species of mammals.

Short peptide type I interferon mimetics: therapeutics for experimental allergic encephalomyelitis, melanoma, and viral infections

The classical canonical model of interferon (IFN) signaling focuses solely on the activation of STAT transcription factors, which limits the model in terms of specific gene activation, associated epigenetic events, and IFN mimetic development. Accordingly, we have developed a noncanonical model of IFN signaling and report the development of short type I IFN peptide mimetic peptides based on the model. The mimetics, human IFNα1(152-189), human IFNβ(150-187), and ovine IFNτ(156-195) are derived from the C-terminus of the parent IFNs and function intracellularly based on the noncanonical model. Vaccinia virus produces a decoy IFN receptor (B18R) that inhibits type I IFN, but the IFN mimetics bypass B18R for effective antiviral activity. By contrast, both parent IFNs and mimetics inhibited vesicular stomatitis virus. The mimetics also possessed anti-tumor activity against murine melanoma B16 tumor cells in culture and in mice, including synergizing with suppressor of cytokine signaling 1 antagonist. Finally, the mimetics were potent therapeutics against experimental allergic encephalomyelitis, a mouse model of multiple sclerosis. The mimetics lack toxic side effects of the parent IFNs and, thus, are a potent therapeutic replacement of IFNs as therapeutics.

Biological activity of recombinant bovine interferon τ produced by a silkworm-baculovirus gene expression system

Bovine interferon (bIFN) τ plays a crucial role in maternal-fetal recognition and was expressed using a Bombyx mori (Bm) nuclear polyhedrosis virus (silkworm baculovirus) gene expression system. The biological effects of Bm-recombinant bIFNτ (rbIFNτ) on prostaglandin (PG) F_2α synthesis were investigated in cultured bovine endometrial epithelial cells with oxytocin (OT, 100 nM) and on the in vitro development of bovine embryos. Bm-rbIFNτ and OT were shown to suppress PGF_2α production in a dose-dependent manner. When in vitro produced morula stage embryos were cultured for 72 hr in modified CR1aa medium supplemented with or without rbIFNτ, Bm-rbIFNτ (10 ng/ml) significantly promoted development to the expanded blastocyst stage. In conclusion, Bm-rbIFNτ was suggested to have the same bioactivity as native IFNτ.

Pregnancy recognition signaling mechanisms in ruminants and pigs

Maternal recognition of pregnancy refers to the requirement for the conceptus (embryo and its associated extra-embryonic membranes) to produce a hormone that acts on the uterus and/or corpus luteum (CL) to ensure maintenance of a functional CL for production of progesterone; the hormone required for pregnancy in most mammals. The pregnancy recognition signal in primates is chorionic gonadotrophin which acts directly on the CL via luteinizing hormone receptors to ensure maintenance of functional CL during pregnancy. In ruminants, interferon tau (IFNT) is the pregnancy recognition signal. IFNT is secreted during the peri-implantation period of pregnancy and acts on uterine epithelia to silence expression of estrogen receptor alpha and oxytocin receptor which abrogates the oxytocin-dependent release of luteolytic pulses of prostaglandin F2-alpha (PGF) by uterine epithelia; therefore, the CL continues to produce progesterone required for pregnancy. Pig conceptuses secrete interferon delta and interferon gamma during the peri-implantation period of pregnancy, but there is no evidence that they are involved in pregnancy recognition signaling. Rather, pig conceptuses secrete abundant amounts of estrogens between Days 11 to 15 of pregnancy required for maternal recognition of pregnancy. Estrogen, likely in concert with prolactin, prevents secretion of PGF into the uterine venous drainage (endocrine secretion), but maintains secretion of PGF into the uterine lumen (exocrine secretion) where it is metabolized to a form that is not luteolytic. Since PGF is sequestered within the uterine lumen and unavailable to induce luteolysis, functional CL are maintained for production of progesterone. In addition to effects of chorionic gonadotrophin, IFNT and estrogens to signal pregnancy recognition, these hormones act on uterine epithelia to enhance expression of genes critical for growth and development of the conceptus.

Contributions of an animal scientist to understanding the biology of the uterus and pregnancy

I developed a passion for reproductive biology when taking a course in Physiology of Reproduction at Louisiana State University while preparing to apply for Veterinary School at Texas A&M University. My career path changed. I entered graduate school, obtained a Ph.D. and have enjoyed an academic career conducting research in uterine biology and pregnancy in animal science departments at the University of Florida and at Texas A&M University. My contributions to science include: (1) identification of molecules secreted by or transported by uterine epithelia into the uterine lumen that are critical to successful establishment and maintenance of pregnancy, (2) discovery of steroids and proteins required for pregnancy-recognition signalling and their mechanisms of action in pigs and ruminants, (3) patterns of fetal–placental development and placental transport of nutrients, (4) identification of links between nutrients and components of histotroph that affect fetal–placental development, (5) characterising aspects of the endocrinology of pregnancy and (6) contributing to efforts to exploit the therapeutic value of interferon tau, particularly for treatment of autoimmune and inflammatory diseases. Current research focuses on select nutrients in the uterine lumen, specifically amino acids, glucose and fructose, that affect conceptus development, the therapeutic potential for interferon tau, stromal–epithelial cell signalling whereby progesterone and oestrogen act via steroid receptors in uterine stromal cells to stimulate secretion of growth factors (e.g. fibroblast growth factors and hepatocyte growth factor) that regulate uterine epithelial cells and conceptus trophectoderm, and roles of toll-like receptors expressed by uterine epithelia and conceptus trophectoderm in pregnancy.

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.

High periconceptional protein intake modifies uterine and embryonic relationships increasing early pregnancy losses and embryo growth retardation in sheep

The effects of supplemented protein level (PL) during the periconceptional period and their interaction with body condition were evaluated in sheep. Multiparous Rambouillet ewes (n = 12) received two PL of rumen undegradable protein (UIP) during a 30-day pre-mating and 15-day post-mating period: low [LPL, 24% crude protein (CP), 14 g UIP and 36 g/CP animal/day] and high [HPL, 44% CP, 30 g UIP and 50 g/CP animal/day]. While ovulation rate (OR) did not differ between treatments (1.6 +/- 0.5, mean +/- SEM), a lower fertility rate, a decreased embryo number and a reduced uterine pH (UpH) was observed in the HPL group (p < 0.05), irrespective of BC. Luteal tissue weight, volume and progesterone secretion did not differ among treatments. Sheep with lower UpH also had lower conceptus weight (Cwt; p < 0.05, r = 0.65) and conceptuses with lower mass tended to secrete less INF-tau and IGF-1, and the correspondent endometrial explants had a higher basal PGF(2alpha) release. Current study indicates that high protein diets during the periconceptional period in sheep modify uterine and embryonic relationships, increasing early pregnancy losses and inducing embryo growth retardation. Surviving embryos were affected by weight reductions, which could compromise later foetal growth and birth weight. Results evidence the key role of a balanced diet in reproductive success and indicate that the quality and nutrient composition of the maternal diet are essential for an adequate establishment of pregnancy, having paramount effects on the interplay of the embryo and the uterus.

Differential effect of IFN-tau on proliferation and distribution of lymphocyte subsets in one-way mixed lymphocyte reaction in cows and heifers

IFN-tau is a signaling protein secreted by the bovine conceptus during the peri-implantation period and responsible for pregnancy recognition. Its main role is the prevention of pulsatile release of luteolytic PGF2alpha, but it also exerts immunomodulatory activities characteristic for other type I interferons. The aim of the study was to examine the effect of IFN-tau on the proliferation and distribution of peripheral blood lymphocyte subsets during one-way mixed lymphocyte reaction (MLR) in cows and heifers. IFN-tau inhibited the proliferative response of lymphocytes in MLR both in cows and heifers in a dose-dependent manner, but cow lymphocytes were less susceptible than those ones from heifers. It was also showed that IFN-tau differentially changed lymphocyte subsets distribution in MLR in cows and heifers. In cows, the relative percentage of CD8(+) cells after MRL in the presence of IFN-tau was significantly lower than in heifers. Differential effect of rIFN-tau on proliferation and lymphocyte subsets distribution in a one-way MRL in cows and heifers indicated that the age of the mother is an important factor in immunomodulatory effect towards developing bovine embryo.

Establishment of a Large-Scale Purification Procedure for Purified Recombinant Bovine Interferon-.TAU. Produced by a Silkworm-Baculovirus Gene Expression System

We developed a procedure for the large-scale purification of bovine interferon-tau (boIFN-tau) by means of a silkworm-baculovirus gene expression system. Recombinant boIFN-tau (rboIFN-tau) was efficiently produced in the silkworm infected with boIFN-tau cDNA recombinant baculovirus and accumulated in the haemolymph. To establish a purification method suitable for mass production, we tried three crude purification methods, namely, an acidification and neutralization treatment (ANT), silica gel column chromatography (SGCC), and Blue sepharose column chromatography (BSCC) with a combination of Q-sepharose (QSC) and chelating sepharose column chromatographies (CSCC). As a result, the acidification and neutralization treatment was found to be the most efficient and cost effective. With this combination, we obtained 91% pure products. To confirm the applicability of the procedure for mass production, we inoculated 100 silkworms with the recombinant virus, and recovered about 4.55 mg (1.26 x 10(8)U/mg) of 91% pure rboIFN-tau by means of a combination of the ANT, followed by QSC and CSCC.

Expression of Cyclooxygenase-2 and Granulocyte-Macrophage Colony-Stimulating Factor in the Endometrial Epithelium of the Cow Is Up-Regulated During Early Pregnancy and in Response to Intrauterine Infusions of Interferon-τ1

On the basis of results obtained in vitro, we previously proposed a model in which signals from the conceptus, namely interferon-tau (IFN-tau) and prostaglandin E2, increase the expression of cyclooxygenase (COX)-2 or granulocyte-macrophage colony-stimulating factor (GM-CSF) in immune and nonimmune cells of the bovine endometrium. Two experiments were conducted to verify the validity of this hypothesis in vivo. In experiment 1, the in vivo expression of COX-2 and GM-CSF during early pregnancy was monitored. Uteri from heifers were collected at different days (d) of the estrous cycle and pregnancy (P). In experiment 2, the effects of intrauterine infusions of IFN-tau on the expression of COX-2 and GM-CSF were analyzed. Immunohistochemistry was performed on uterine sections, and image analysis was used to evaluate the staining intensity in the conceptus, the luminal epithelium (LE), and the subepithelial stroma. In experiment 1, staining for COX-2 was maximal between d18P and d24P, both in the LE and in the conceptus, whereas staining for GM-CSF reached a plateau between d18P and d30P in the LE. In experiment 2, in response to IFN-tau, COX-2 was up-regulated in the LE of the ipsilateral horn, whereas GM-CSF was enhanced in both uterine horns. The current report supports the view that the conceptus, through its secretion of IFN-tau, stimulates maternal epithelial expression of COX-2 and GM-CSF during the peri-attachment period in the cow.

Ovine placental lactogen specifically binds to endometrial glands of the ovine uterus

A hormonal servomechanism has been proposed to regulate differentiation and function of the endometrial glandular epithelium (GE) in the ovine uterus during pregnancy. This mechanism involves sequential actions of estrogen, progesterone, ovine interferon tau (IFNtau), placental lactogen (oPL), and placental growth hormone (oGH). The biological actions of oPL in vitro are mediated by homodimerization of the prolactin receptor (oPRLR) and heterodimerization of the oPRLR and oGH receptor. The objectives of the study were to determine the effects of intrauterine oPL, oGH, and their combination on endometrial histoarchitecture and gene expression and to localize and characterize binding sites for oPL in the ovine uterus in vivo using an in situ ligand binding assay. Intrauterine infusion of oPL and/or oGH following IFNtau into ovariectomized ewes treated with progesterone daily differentially affected endometrial gland number and expression of uterine milk proteins and osteopontin. However, neither hormone affected PRLR, insulin-like growth factor (IGF)-I, or IGF-II mRNA levels in the endometrium. A chimeric protein of placental secretory alkaline phosphatase (SEAP) and oPL was used to identify and characterize binding sites for oPL in frozen sections of interplacentomal endometrium from pregnant ewes. Specific binding of SEAP-oPL was detected in the endometrial GE on Days 30, 60, 90, and 120 of pregnancy. In Day 90 endometrium, SEAP-oPL binding to the endometrial GE was displaced completely by oPL and prolactin (oPRL) but only partially by oGH. Binding experiments using the extracellular domain of the oPRLR also showed that iodinated oPL binding sites could be competed for by oPRL and oPL but not by oGH. Collectively, results indicate that oPL binds to receptors in the endometrial glands and that oPRL is more effective than oGH in competing for these binding sites. Thus, effects of oPL on the endometrial glands may be mediated by receptors for oPRL and oGH.

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.

Possible Role of Interferon-.TAU. on In Vitro Development of Bovine Embryos

The effect of interferon-tau on in vitro development of bovine embryos was investigated. After in vitro fertilization, embryos developed to the morula stage were cultured for 3 days in TCM-199 or CR1 medium containing BSA or FCS supplemented with or without recombinant IFN-tau produced by a baculovirus expression system. Addition of baculovirus-expressed IFN-tau (100 ng/ml) significantly promoted development to the blastocyst stage in both culture media. Addition of E. coli expressed IFN-tau (2 microg/ml) also significantly promoted the embryonic development. Supplementation of BSA or FCS did not affect the growth-promoting effect of IFN-tau. To determine whether the growth-promoting effect of IFN-tau is related to the interferon type I receptors that bind to type I interferon such as IFN-alpha, embryos were cultured with IFN-alpha. Although IFN-alpha significantly promoted the development, a much higher concentration (25 microg/ml) was required than IFN-tau. A reverse transcription polymerase chain reaction analysis revealed the expression of mRNA encoded type-I IFN receptor subunit from morula to blastocyst stage embryos. The overall results suggest a novel function for IFNs in promoting embryonic development and the effect may be related to type-I IFN receptor expressed in the early stages of preimplantation embryos.

Phenotypic and ultrastructural characteristics of bronchoalveolar lavage cells of lentivirus-infected lambs treated with recombinant ovine IFN-tau

Ovine lentivirus (OvLV) belongs to the family Retroviridae and closely resembles the human immunodeficiency virus (HIV). Pulmonary lesions in OvLV-infected sheep consist of lymphoid interstitial pneumonia (LIP) and lymphocytic alveolitis. Similar pulmonary lesions occur in up to 40% of HIV-infected children and in some adults with AIDS. Interferon-tau (IFN-tau), a type I IFN, is produced by trophectoderm of ruminant conceptuses and is the pregnancy recognition signal in these species. To evaluate changes in phenotypes of bronchoalveolar lavage (BAL) cells of OvLV-infected lambs treated with recombinant ovine IFN-tau (rOvIFN-tau), 24 lambs were randomly allocated to one of four groups (n = 6 per group): 1, no virus + placebo (NVP); 2, no virus + rOvIFN-tau (NVI); 3, virus + placebo (VP); 4, virus + rOvIFN-tau (VI). The BAL cells from 3 lambs in each group were labeled with monoclonal antibodies (mAb) to cell surface markers at 16 weeks of treatment, and cells from the remaining 3 lambs in each group were labeled with mAb at 34 weeks of treatment. After labeling, BAL cells were analyzed by flow cytometry. The morphology of BAL cells from all experimental lambs was examined by transmission electron microscopy (TEM). At week 16, no differences in the relative proportions of BAL cell phenotypes were detected among the experimental groups. At week 34, VI lambs had higher proportions of CD8(+), gammadelta(+), MHC class II(+), and L-selectin (LS(+)) BAL cells compared with VP lambs. Higher proportions of CD14(+) and CD44(+) cells were found in VP lambs compared with NVP lambs at 34 weeks. OvLV-like particles were detected only in bronchoalveolar macrophages of VP lambs. In this study, rOvIFN-tau increased the proportions of primary antiviral gammadelta(+) and CD8(+) immune cells in OvLV-infected lambs. This may represent a cellular mechanism to explain the antiviral and therapeutic efficacy of this cytokine, in addition to its direct antiviral effect. However, because the actual number of cells labeled with mAb CD8 was low and some subsets of gammadelta cells may coexpress the CD8 marker, further studies are necessary to better define the role of rOvIFN-tau in the modulation of these cells in vivo.

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.

Interferon-tau stimulates granulocyte-macrophage colony-stimulating factor gene expression in bovine lymphocytes and endometrial stromal cells

Interferon-tau (IFN-tau), the antiluteolytic signal produced by the trophoblast prior to implantation in ruminants, exhibits immunomodulatory properties. It stimulates the production of prostaglandin (PG) E(2) in bovine endometrial cells via the induction of cyclooxygenase-2 (COX-2). We previously demonstrated that preconditioning lymphocytes with PGE(2) increases the expression of granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine that promotes conceptus growth and survival. Our goal in the present study was to evaluate the impact of IFN-tau on the expression of GM-CSF in bovine peripheral blood lymphocytes (PBL) and endometrial epithelial and stromal cells. Changes in PGE(2) production and mRNA levels of COX-2 were also studied in PBL in response to IFN-tau. Gene expression was estimated by semiquantitative reverse transcription-polymerase chain reaction and Northern analysis. The expression of GM-CSF in PBL was stimulated by treatment with IFN-tau. Furthermore, GM-CSF mRNA levels were increased after preconditioning PBL for 3 days with IFN-tau, followed by a 12-h restimulation without IFN-tau. Inhibition rather than stimulation of PGE(2) production and COX-2 expression in PBL during treatment with IFN-tau suggests a direct effect on GM-CSF expression. Moreover, GM-CSF expression was stimulated in uterine stromal cells in response to IFN-tau. This study provides the first evidence for stimulation of GM-CSF expression by IFN-tau in both leukocytes and endometrial stromal cells. In view of the role of GM-CSF on fetal growth and survival, these results support the hypothesis that the conceptus mediates accommodation mechanisms in the uterus during early pregnancy by modulating the expression of beneficial cytokines at the fetomaternal interface.

Interferon tau-induced hepatocyte apoptosis in sheep

Clinical applications of Type I interferon (IFN) are limited by adverse side effects mediated largely by unknown mechanisms. This study examined the mechanisms of acute hepatic injury in lambs treated with systemic administration of IFN-tau, a Type I IFN. Liver tissues were collected at 24, 48, or 96 hours after treatment with either IFN-tau or saline. Histopathology revealed acute hepatopathy including cellular swelling, cytoplasmic aggregates, and apoptosis in all IFN-tau-treated lambs, which were accompanied by elevation of aspartate transaminase (AST) (P <.01). The number of apoptotic hepatocytes in IFN-tau-treated lambs was higher than for control lambs (P <.001). Immunohistochemistry for proliferating cell nuclear antigen (PCNA) revealed that IFN-tau induced hepatocyte growth arrest at the G0/G1 phase of the cell cycle and that the majority of hepatocytes in S or G2 phase were eliminated by apoptosis. We investigated expression of bax-alpha and bcl-2, acting as pro- and antiapoptotic molecules, in IFN-tau-induced apoptosis. Northern blot analysis revealed increased expression of bax-alpha messenger RNA (mRNA) in IFN-tau-treated lambs (P <.01) compared with control lambs, consistent with the expression pattern for bax-alpha protein. However, there was no detectable difference in expression of bcl-2 proteins between control and IFN-tau-treated lambs. The levels of bax-alpha associated with the mitochondria also increased during IFN-tau treatment. Bax-alpha immunostaining showed scattered immunoreactive hepatocytes with morphological hallmarks of apoptosis. These results suggest that IFN-tau induces growth arrest as well as apoptosis by regulating bax-alpha expression. These pathological effects of IFN-tau on sheep liver indicate potential mechanisms of Type 1 IFN-induced hepatotoxicity in animals and humans.

Effects of recombinant ovine interferon-tau on ovine lentivirus replication and progression of disease

The antiviral effects of recombinant ovine interferon-tau (roIFN-tau) were studied in 26 lambs inoculated with ovine lentivirus (OvLV) or mock-infected. Six of the OvLV-infected lambs and three of the mock-infected lambs were treated with 10(6) antiviral units (AVU) per kg roIFN-tau daily for 30 days starting at day 0 post-inoculation (p.i.) and twice a week thereafter (early treatment). Six of the OvLV-infected lambs and three of the mock-infected lambs were treated with 10(6) AVU/kg roIFN-tau daily for 30 days starting at day 150 p.i. and twice a week thereafter (late treatment). Six OvLV-infected and two mock-infected lambs were treated either early or late with placebo. Cell-associated viraemia was quantified by an end-point dilution method. The weekly antibody response against OvLV proteins was studied by ELISA. All experimental animals were killed at 27 weeks p.i. and histological sections of lung were scored for the degree of lymphoid interstitial pneumonia (LIP). A 90% reduction in OvLV titres was detected at 4 weeks post-treatment in lambs that received early roIFN-tau treatment (P<0.01). Differences in virus titres were also found at weeks 2 and 6 (P<0.05). Scores for LIP degree were higher in infected lambs treated with placebo or late roIFN-tau than in the mock-infected lambs or in the infected lambs that received early roIFN-tau (P<0.05). LIP scores were not different between mock-infected lambs and infected lambs that received early roIFN-tau. These results indicate that roIFN-tau curtails OvLV replication in vivo and reduces the likelihood of development of lentivirus-induced LIP when infected lambs are treated during the initial phases of OvLV infection.

Detection and regulation of the messenger for a putative bovine endometrial 9-keto-prostaglandin E(2) reductase: effect of oxytocin and interferon-tau

During reproductive processes, prostaglandin (PG) E(2) (PGE(2)) and PGF(2alpha) play important roles in which they often exert opposite effects. At the time of recognition of pregnancy in vivo, PGF(2alpha) is recognized as the luteolytic factor in ruminants and in most species including human, whereas PGE(2) may exert a luteoprotective action. We have previously demonstrated that recombinant interferon-tau (rIFN-tau), the embryonic signal responsible for recognition of pregnancy in ruminants, stimulated in vitro the production of PGE(2) and prostaglandin-endoperoxide synthase 2 (Ptgs2; also called cyclooxygenase-2) gene expression in both epithelial and stromal endometrial cells. Since PGE(2) is the major prostaglandin produced by stromal cells, the effect on Ptgs2 could explain the increase in PGE(2) output. At high concentrations, however, recombinant ovine (ro) IFN-tau acts on epithelial cells by changing the primary PG produced from PGF(2alpha) to PGE(2). This change in the primary PG produced could be explained by a decrease in PGF synthase (PGFS) activity or an increase in PGE synthase activity, or by modulation of a putative PGE(2)-9-ketoreductase, which converts PGE(2) into PGF(2alpha). Therefore, we have investigated the regulation of the mRNAs for PGFS and PGE(2)-9-ketoreductase (9K-PGR), two enzymes that lead to the production of PGF(2alpha). Others have described 9K-PGR activity in uterus, ovaries, kidney, and liver of different species and have established that this enzyme could possess both 9K-PGR and 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) activity. Some have concluded that 9K-PGR and 20alpha-HSD are identical enzymes. Using primers sequences chosen from homologous nucleotide sequences of published rabbit 20alpha-HSD/9K-PGR and rat 20alpha-HSD cDNAs, a 317-base pair (bp) fragment was amplified by reverse transcription-polymerase chain reaction (RT-PCR), cloned, and sequenced. Homologies of 83% and 78% were found with rabbit and rat 20alpha-HSD, respectively. The presence of 20alpha-HSD/9K-PGR and prostaglandin F synthase (PGFS) mRNA expression was studied semiquantitatively in cultured epithelial cells using RT-PCR. Stimulation of cells with roIFN-t resulted in a biphasic response, an inhibition of PGF(2alpha) production at low dose (1 ng/ml) and a stimulation of PGE(2) at high dose (10 microg/ml). The increase of PGE(2) was accompanied by reduced 9K-PGR and PGFS mRNA gene expression. The effect of oxytocin (OT) was also studied, and the presence of OT had no effect on either 9K-PGR or PGFS gene expression. The 20alpha-HSD/9K-PGR transcript was also detected in other bovine tissues at different intensity (liver > kidney > testis > ovaries). We believe that the 9K-PGR and PGFS can be key enzymes in the regulation of specific PGs in the endometrium during the periimplantation period.

Acute-phase proteins and hematologic values in ovine lentivirus-infected lambs treated with recombinant ovine IFN-tau

To evaluate changes in complete blood cell (CBC) counts, haptoglobin and fibrinogen in ovine lentivirus (OvLV)-infected lambs treated with recombinant ovine interferon-tau (rOVIFN-tau), 24 lambs were allocated to one of four groups (n = 6 per group): (1) virus + rOvIFN-tau, VI, (2) virus + placebo, VP, (3) no virus + rOVIFN-tau, NVI, and (4) no virus + placebo, NVP. Three lambs in each group were treated once a day for 12 weeks, and the remaining 3 lambs were treated for 33 weeks. Blood was collected at days 0, 7, and 10 and at weeks 2-10, 12, 32, and 33 to determine CBC counts, as well as haptoglobin and fibrinogen levels. Hematologic values remained within normal limits in all groups. However, hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), and packed cell volume (PCV) values decreased (p < 0.05) in the two rOvIFN-tau-treated groups (VI and NVI) compared with the placebo-treated (VP and NVP) groups. Both rOvIFN-upsilon and OvLV had a mild negative effect on neutrophil numbers. Although Hb, MCV, MCHC, PCV, and neutrophil values declined in the rOvIFN-tau-treated lambs compared with the placebo-treated lambs, these values remained within the reference range for sheep. Experimental lambs did not show adverse clinical signs associated with OvLV infection or as a result of rOvIFN-tau treatment. The lack of significant side effects of high-dose rOvIFN-tau in sheep and previous reports of broad-spectrum and cross-species antiviral activity suggest that rOvIFN-tau warrants further investigation as an antiviral therapeutic agent.

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

It is claimed that interferon-tau (IFN-tau) has broad cross-species reactivity and less cytotoxicity than other type I IFN when used at high concentration either in vitro or in living animals. It can also amelioriate the development of experimental allergic encephalomyelitis (EAE) without the usual side effects of IFN therapy in mice autoimmunized with myelin basic protein. For these reasons, IFN-tau may have therapeutic potential in humans. Here, the antiviral (AV) activities of eight different recombinant IFN-tau were compared with those of several bovine, human, and murine type I IFN on bovine MDBK cells, murine L929 cells, and human WISH cells. The data show that only one of the IFN-tau, OvIFN-tau4, has broad cross-species reactivity. It was comparable in this respect to HuIFN-omega1 and HuIFN-alpha1. The other IFN-tau, including the variant form (OvIFN-tau1mod) tested by others in cytotoxicity experiments and for its ability to protect mice against EAE, had relatively weak AV activity on mouse and human cells. It is possibly because this particular bioengineered form of IFN-tau binds the common type I receptor of these two species with such low affinity that it lacks cytotoxic effects. The basis for its potent anti-EAE activity is unclear, but it seems possible that it does not involve the type I IFN receptor.

Effects of recombinant ovine interferon tau, placental lactogen, and growth hormone on the ovine uterus

Studies were conducted to determine effects of intrauterine administration of recombinant ovine interferon tau (IFNtau), placental lactogen (PL), and growth hormone (GH) on endometrial function. In the first study, administration of IFNtau to cyclic ewes for one period (Days 11-15) resulted in an interestrous interval (IEI) of approximately 30 days, whereas administration for two periods (Days 11-15 and Days 21-25) extended the IEI to greater than 50 days. Administration of IFNtau from Days 11 to 15 and of PL or GH from Days 21 to 25 failed to extend the IEI more than for IFNtau alone. In the second study, effects of IFNtau, PL, and GH on endometrial differentiation and function were determined in ovariectomized ewes receiving ovarian steroid replacement therapy. Endometrial expression of mRNAs for estrogen receptor (ER), progesterone receptor (PR), and oxytocin receptor (OTR) were not affected by PL or GH treatment; however, uterine milk protein mRNA levels and stratum spongiosum gland density were increased by both PL and GH treatments. Collectively, results indicated that 1) PL and GH do not regulate endometrial PR, ER, and OTR expression or affect corpus luteum life span; 2) down-regulation of epithelial PR expression is requisite for progesterone induction of secretory gene expression in uterine glandular epithelium; 3) effects of PL and GH on endometrial function require IFNtau; and 4) PL and GH regulate endometrial gland proliferation and perhaps differentiated function.

Identification of the expressed forms of ovine interferon-tau in the periimplantation conceptus: sequence relationships and comparative biological activities

Interferon-tau (IFN-tau) is secreted from trophectoderm of periimplantation ruminant conceptuses and is a critical component of pregnancy recognition. Multiple genes encode IFN-tau. The objectives of this study were to identify expressed forms of ovine IFN-tau and to compare their biological activities. Sequences analyzed after cloning 36 reverse transcription-polymerase chain reaction products of ovine conceptus RNA provided seven new cDNA that were similar in sequence to previously cloned forms (p3, p6, and p8 cDNA). Phylogenetic analysis of amino acid sequence for all new and previously reported forms showed that ovine IFN-tau forms can be divided into three main groups. Equivalent amounts of mRNA for p3, p6, and p8 forms were detected in conceptuses following RNase protection. Recombinant p3 and p8 protein had similar antiviral activity on ovine and bovine cells whereas p6 protein was less active. The p3 form was the most potent of the three in its ability to extend estrous cycle length in nonpregnant ewes. In summary, there appeared to be three main groups of ovine IFN-tau, each containing several variant forms. Antiviral activity was not particularly well correlated with ability to prevent luteolysis, suggesting that distinct intracellular mechanisms are used to exert the various actions of IFN-tau.

IFN-tau exhibits potent suppression of human papillomavirus E6/E7 oncoprotein expression

The effects of interferon-tau (IFN-tau) on tumor suppressor factors and virus oncoprotein expression were compared with two other type I IFN in human papillomavirus (HPV-16)-transformed cells. Nontumorigenic human keratinocytes, HuKc/HPV-16d-2C (d-2C), treated with recombinant human IFN-alpha2a (Roferon), a human recombinant alpha IFN hybrid, alpha B/D (IFN-alphaB/D), or ovine IFN-tau were evaluated for their effects on the levels of E6 and E7 expression. IFN-tau was comparable to IFN-alpha2a in decreasing intracellular levels of E6 and E7, and IFN-alphaB/D was more effective than IFN-a2a in suppressing E7 levels. All three IFN were capable of increasing the cellular concentration of wild-type p53 tumor suppressor with the magnitude IFN-tau > IFN-alpha2a > IFN-alphaB/D. Increases in p53 concentrations correlated with the observed decreases in E6 mRNA and protein levels. The antiviral effects observed in this study reveal that IFN-tau has potent antipapillomavirus activity. Sequences/structures unique to IFN-tau could allow for alternative IFN/receptor interactions and may explain the differences in biologic function.

Differential effects of intrauterine and subcutaneous administration of recombinant ovine interferon tau on the endometrium of cyclic ewes

Interferon tau (IFNtau) is the antiluteolytic signal produced by the conceptus of ruminants. Intrauterine administration of recombinant ovine IFNtau suppresses expression of endometrial estrogen receptor (ER) and oxytocin receptor (OTR) in the luminal and superficial glandular epithelia to abrogate the production of luteolytic prostaglandin F(2alpha) (PGF(2alpha)) pulses. Subcutaneous (s.c.) injections of recombinant ovine (o) IFNtau appear to extend the interestrous interval by altering uterine PGF(2alpha) response to oxytocin. The present study tested the hypothesis that antiluteolytic effects of roIFNtau injected into the uterine lumen (paracrine) or s.c. (endocrine) are equivalent in suppressing expression of endometrial ER and OTR and inducing uterine expression of type I IFN-regulated Mx and ubiquitin cross-reactive proteins (UCRP). Sixteen cyclic ewes were fitted with uterine catheters on Day 5 (Day 0 = estrus), were assigned randomly to receive treatment with control proteins or roIFNtau (2 x 10(7) antiviral units/day) by either intrauterine or s.c. injections from Days 11 to 15, and were ovariohysterectomized on Day 16. Results indicated that expression of ER and OTR mRNAs in endometrial epithelium was suppressed by intrauterine but not by s.c. injections of roIFNtau. Intrauterine injections of roIFNtau increased expression of Mx and UCRP mRNA in the endometrium. Subcutaneous injections of roIFNtau increased endometrial Mx mRNA levels but not UCRP mRNA. Unexpectedly, intrauterine and s.c. injections of roIFNtau were equally effective in inducing expression of Mx and UCRP mRNA in the corpus luteum. Although s.c. injections of roIFNtau induced Mx mRNA in the endometrial epithelium, s.c. injections of roIFNtau did not abrogate activation of the uterine luteolytic mechanism by suppressing epithelial ER and OTR expression. Therefore, results of this study failed to support the assumption that endocrine roIFNtau mimics antiluteolytic effects of paracrine IFNtau to improve pregnancy rates in sheep.

Expression of the interferon tau inducible ubiquitin cross-reactive protein in the ovine uterus

Ubiquitin cross-reactive protein (UCRP) is a 17-kDa protein that shows cross-reactivity with ubiquitin antisera and retains the carboxyl-terminal Leu-Arg-Gly-Gly amino acid sequence of ubiquitin that ligates to, and directs degradation of, cytosolic proteins. It has been reported that bovine endometrial UCRP is synthesized and secreted in response to conceptus-derived interferon-tau (IFNtau). In the present studies, UCRP mRNA and protein were detected in ovine endometrium. Ovine UCRP mRNA was detectable on Day 13, peaked at Day 15, and remained high through Day 19 of pregnancy. The UCRP mRNA was localized to the luminal epithelium (LE), stromal cells (ST) immediately beneath the LE, and shallow glandular epithelium (GE) on Day 13, but it extended to the deep GE, deep ST, and myometrium of uterine tissues by Day 15 of pregnancy. Western blotting revealed induction of UCRP in the endometrial extracts from pregnant, but not cyclic, ewes. Ovine UCRP was also detected in uterine flushings from Days 15 and 17 of pregnancy and immunoprecipitated from Day 17 pregnant endometrial explant-conditioned medium. Treatment of immortalized ovine LE cells with recombinant ovine (ro) IFNtau induced cytosolic expression of UCRP, and intrauterine injection of roIFNtau into ovariectomized cyclic ewes induced endometrial expression of UCRP mRNA. These results are the first to describe temporal and spatial alterations in the cellular localization of UCRP in the ruminant uterus. Collectively, UCRP is synthesized and secreted by the ovine endometrium in response to IFNtau during early pregnancy. Because UCRP is present in the uterus and uterine flushings, it may regulate endometrial proteins associated with establishment and maintenance of early pregnancy in ruminants.

Platelet-activating factor may act as an endogenous pulse generator for sheep of luteolytic PGF2alpha release

Pulsatile release of uterine prostaglandin F2alpha (PGF2alpha) induces luteolysis in ruminants. However, the mechanism(s) that initiates and maintains luteolysis has not been defined. The present study tested the hypothesis that the endogenous PGF2alpha pulse generator is uterine-derived platelet-activating factor (PAF). Ovariectomized ewes were given exogenous progesterone (P), estradiol (E), or both (P+E, mimicking the normal luteal phase). Only ewes treated with steroids released PAF into the uterine lumen and had increased PAF:acetylhydrolase activity in the uterine lumen. Steroid treatment also influenced the capacity of the uterus to release PGF2alpha in response to exogenous PAF. PAF infusion did not affect plasma PGF2alpha metabolite (PGFM) levels in control (no steroid treatment) ewes but increased plasma PGFM levels in P+E ewes (P < 0.001) and ewes treated with P or E alone (P < 0.05). Infusion of PAF followed by or coincident with oxytocin (OT) acted in a synergistic manner to increase plasma PGFM levels. Repeated infusion of PAF into the uterus at 1-h intervals induced tachyphylaxis of the PGFM response to PAF; however, sensitivity of the uterus to PAF returned spontaneously by the 6th h. Interferon-tau (IFN-tau) inhibits pulsatile release of PGF2alpha during pregnancy to prevent luteolysis. Exogenous recombinant ovine IFN-tau (50 microgram) inhibited the uterine response to PAF alone or the combined effects of PAF and OT. These results indicate that uterine PAF fulfills many of the criteria for an endogenous PGF2alpha pulse-generator: steroid induction of PAF production and uterine responsiveness to PAF-induced release of PGF; synergistic stimulation of PAF-induced PGF release by OT; inhibition of PAF effects by IFN-tau; and PAF's ability to induce pulses of PGF with a periodicity during a period of chronic exposure of the uterus to PAF.

Crystal structure of ovine interferon-tau at 2.1 A resolution

Ovine interferon-tau (ovIFN-tau) is a pregnancy recognition hormone required for normal embryonic development in sheep. In addition to its novel role in reproductive physiology, ovIFN-tau displays antiviral and antiproliferative activities similar to the IFN-alpha subtypes. To probe the structural basis for its unique activity profile, the crystal structure of ovIFN-tau has been determined at 2.1 A resolution. The fold of ovIFN-tau is similar to the previously determined crystal structures of human IFN-alpha2b and human and murine IFN-beta, which each contain five alpha-helices. Comparison of ovIFN-tau with huIFN-alpha2b, huIFN-beta, and muIFN-beta reveals unexpected structural differences that occur in regions of considerable sequence identity. Specifically, main-chain differences up to 11 A occur for residues in helix A, the AB loop, helix B, and the BC loop. Furthermore, these regions are known to be important for receptor binding and biological activity. Of particular interest, a buried ion pair is observed in ovIFN-tau between Glu71 and Arg145 which displaces a conserved tryptophan residue (Trp77) from the helical bundle core. This ion pair represents a major change in the core of ovIFN-tau compared to huIFN-alpha2b. Based on amino acid sequence comparisons, these ovIFN-tau structural features may be conserved in several human IFN-alpha subtypes and IFN-omega. The structure identifies potential problems in interpreting site-directed mutagenesis data on the human IFN-alpha family that consists of 12 proteins.

Upregulation of interleukin-4 and IFN-gamma expression by IFN-tau, a member of the type I IFN family

Trophoblast interferon-tau (IFN-tau) is a new member of the type I IFN family that is produced in large quantities by the ruminant conceptus. Like other type I IFN, IFN-tau inhibits viral replication and activates natural killer (NK)-mediated cytotoxicity. In mice and humans, type I IFN enhances type 1 T helper (Th) cell responses, but the effects of type I IFN, including IFN-tau, on cytokine expression by bovine Th cells have not been described. The present study determined the effects of IFN-tau on interleukin-4 (IL-4), IFN-gamma, and IL-10 expression by antigen-specific, CD4+ T cell lines derived from cattle immune to either Babesia bovis, Babesia bigemina rhoptry-associated protein-1, or Anaplasma marginale. IFN-tau upregulated IFN-gamma secretion and steady-state levels of IFN-gamma and IL-4 mRNA by cell lines cultured for 3-6 weeks. In contrast, the steady-state levels of IL-10 mRNA were either not changed or inhibited at these times. Similar effects were obtained with human IFN-alpha. Comparison of the quantities of IFN-gamma, IL-4, and IL-10 transcripts in IFN-tau-treated or IFN-alpha-treated cultures revealed that even though IFN-gamma was the predominant cytokine expressed by all T cell lines, both IFN-gamma and IL-4 steady-state transcript levels were upregulated by a comparable degree. Thus, these studies demonstrate that IFN-tau is an immunomodulatory cytokine that promotes enhanced IL-4 and IFN-gamma responses by effector T cells but not, strictly speaking, Thl-biased responses in cattle. These results indicate the potential use of this cytokine as an adjuvant in ruminants to boost cell-mediated immune responses.

Differential Effects of Type I IFNs on the Growth of WC1− CD8+ γδ T Cells and WC1+ CD8− γδ T Cells In Vitro

Type I IFNs have a broad array of immunoregulatory functions that include up-regulation of type 1 immune responses through enhancing differentiation and activation of CD8+ T cells and CD4+ Th1 cells. Ovine trophoblast IFN-τ is a recently described type I IFN with the potential for therapeutic use, based on its potent antiviral activity yet low toxicity. Studies were designed to determine the immunoregulatory effects of IFN-τ on Ag-stimulated T cells, and a novel effect of type I IFNs on γδ T cells was observed. In cultures of parasite Ag-stimulated bovine T cells that contained a mixture of αβ and γδ T cells, both IFN-τ and IFN-α suppressed the expansion of WC1+ CD2− CD6− CD8− γδ T cells, yet stimulated the growth of WC1− CD2+ CD6+ CD8+ γδ T cells and CD8+ αβ T cells. The CD8+ γδ T cell subset expressed high levels of the IL-2R α-chain. Furthermore, we showed that type I IFN enhanced IL-2 production by these Ag-stimulated T cell lines. In short term cultures of PBMC, IL-2 stimulated an expansion of WC1− CD6+ CD8+ γδ T cells, which was significantly increased by IFN-τ, even though IFN-τ alone did not support cell survival. These studies demonstrate for the first time that type I IFNs differentially modulate the proliferation of different subsets of γδ T cells, which appears to act in part via IL-2.

Trophoblast IFN-tau differentially induces lymphopenia and neutropenia in lambs

Type I interferons (IFN), including IFN-alpha and IFN-beta, cause severe lymphopenia, resulting from altered lymphocyte recirculation and redistribution. IFN-tau, a product of trophectoderm of ruminant conceptuses and new member of the type I IFN family has not been examined for its effect on leukocyte recirculation. Additionally, differential effects of type I IFNs on the redistribution and recirculation of subsets of T cells have not been reported. The present study determined the effects of IFN-tau on the redistribution and recirculation of ovine leukocytes and T cell subsets. Total peripheral blood leukocytes, lymphocytes, and segmented neutrophils were reduced (p < 0.05) following treatment of lambs with IFN-tau. Furthermore, administration of IFN-tau caused an acute, differential reduction in peripheral blood CD4+ T cells (p < 0.05), CD5+ cells (p < 0.05), and gammadelta TCR+ (p < 0.01) T cells but had no effect on CD8+ T cells (p > 0.05). IFN-tau reduced the percentage of gammadelta T cells by 8-fold and that of CD4+ T cells and CD5+ cells by <2-fold in peripheral blood when compared with control lambs. The reduction in leukocytes, lymphocytes, and neutrophils was observed as early as 6-12 h after administration of IFN-tau, but levels returned to control values within 48 h. These results indicate that IFN-tau, like other members of the type I IFN family, can have immediate effects on leukocyte recirculation and redistribution. The present study is the first to demonstrate that IFN-tau differentially regulates T cell recirculation with the greatest effect on gammadelta TcR+ T cells.

Structural responses of pulmonary intravascular macrophages in lentivirus-infected and/or recombinant ovine interferon-tau-treated lambs

Ovine lentivirus (OvLV), a retrovirus, infects and disseminates to various tissue organs via monocytes. The differentiation of infected monocytes into macrophages is a prerequisite for viral replication, and the presence of infected macrophages in tissue organs induces chronic immunopathology such as lymphoid interstitial pneumonia. The pulmonary intravascular macrophage (PIM) is a recently identified mononuclear phagocyte in domestic animal species, including sheep. Recombinant ovine interferon-tau (roIFN-tau), a type I IFN originally named as the ovine trophoblast protein, has potent antiviral activity against OvLV and human immunodeficiency virus and prevents the development of OvLV-associated lung pathology. We investigated and compared the structural features of PIMs in OvLV-infected and/or roIFN-tau-treated 1-month-old lambs using transmission electron microscopy. The PIMs' numerical counts were performed in toluidine blue-stained sections of Epoxy-embedded lung tissues. A reduction in the number of PIMs was observed with OvLV infection and/or roIFN-tau treatment of lambs as compared to the control group (P < or = 0.05). The majority of the PIMs in OvLV-infected and/or roIFN-tau-treated groups were devoid of their surface coat. The PIMs of OvLV-infected lambs exhibited signs of biosynthetic activation such as expanded rough endoplasmic reticulum, prominent Golgi complexes, and accumulation of secretory vesicles. A few PIMs contained OvLV-like structures. In roIFN-tau-treated OvLV-infected lambs, the lymphocytes had ruffled plasma membranes and were in intimate contact with the PIMs, as is observed during cytotoxic cell-mediated killing of target cells. Most of the PIMs in roIFN-tau-treated OvLV-infected lambs appeared smaller in size. Ovine lentivirus and roIFN-tau, individually or in combination, alter the integrity of the surface coat of PIMs and cause their disappearance from the lungs. Ovine lentivirus infection induces morphological changes that correlate with cytotoxic cell behavior between lymphocytes and PIMs in roIFN-tau-treated or placebo-treated lambs. The loss of PIMs, probably infected with OvLV, either through direct killing by roIFN-tau or indirectly by roIFN-tau-activated cytotoxic T lymphocytes may represent different aspects of therapeutic actions of this cytokine.

Clinical effects of the recombinant feline interferon-omega on experimental parvovirus infection in beagle dogs

The clinical effects of recombinant feline interferon-omega (rFeIFN-omega), produced in silkworm by recombinant baculovirus, were examined in 3-4 month-old beagle dogs given an experimental canine parvovirus type-2 (CPV-2) infection. Clinical symptoms, such as pyrexia, vomiting, anorexia and diarrhea, were observed on day 4 after oral inoculation of 10(7) TCID50 of CPV-2 (cc 238 strain) in almost all the inoculated dogs. From day 4, rFeIFN-omega (1 mega units/kg/day) or physiological saline was administered intravenously to infected dogs for 3 consecutive days. Seven out of 17 dogs treated with physiological saline showed hemorrhagic diarrhea and continuously expressed severe clinical enteritis; one dog died with a large amount of hemorrhagic rice-water stool on day 6 after viral exposure. In contrast, 4 out of 12 dogs treated with rFeIFN-omega showed severe clinical enteritis associated with intermittent diarrhea. Scoring of fecal condition revealed that treatment with rFeIFN-omega significantly shifted the enteritis from a severe to mild form. Furthermore, rFeIFN-omega administered in the morning decreased the number of dogs expressing clinical enteritis in the evening suggesting a rapid effect. Vomiting and anorexia were also improved by treatment with rFeIFN-omega. These results suggest that rFeIFN-omega can reduce severe enteritis caused by CPV-2 infection in dogs.

In vitro response to oxytocin and interferon-Tau in bovine endometrial cells from caruncular and inter-caruncular areas

Caruncules are differentiated sites of the endometrium in which placentation occurs in ruminants. We investigated whether the response to agents involved at the time of recognition of pregnancy differed in the caruncular (CAR) and inter-caruncular (ICAR) areas of the endometrium in vitro. The specialization in prostaglandin (PG) production previously described in cells from whole endometrium was reproduced in the CAR and ICAR areas: PGF2alpha and PGE2 were produced in greater proportions, respectively, in epithelial and stromal cells. The relative production of PGE2 was equivalent in epithelial cells from CAR and ICAR regions, but the production of PGF2alpha was higher (p < 0.05) in the ICAR region (2.2 +/- 0.5 vs. 4.0 +/- 0.2 ng/ microg DNA, respectively). In stromal cells, the ICAR area produced more PGE2 than did the CAR area (3.4 +/- 0.4 vs. 2.1 +/- 0.4 ng/ microg DNA, p < 0.05), and the respective PGE2:PGF2alpha ratio was significantly higher in the ICAR area (p < 0.05). The production of PGs was measured first in response to oxytocin (OT, 10(-9) to 10(-5) M) and then to recombinant ovine interferon-tau (roIFN-tau, 0.02 to 20 microg/ml) in a separate set of experiments. In epithelial cells, OT stimulated the production of PGF2alpha 6.3-fold in the CAR area and more than 33.0-fold in the ICAR area (7.1 +/- 3.2 vs. 36.3 +/- 9.8 ng/ microg DNA, respectively, p < 0.05). Production of PGE2 was also increased in both regions and reached a plateau at 4.1 +/- 0.4 ng/ microg DNA. In epithelial cells from the ICAR but not the CAR region, the PGE2:PGF2alpha ratio was decreased in the presence of OT (p < 0.05). In separate experiments, addition of roIFN-tau stimulated PGE2 production significantly (p < 0.05), and no difference (p > 0.8) was observed between CAR and ICAR regions. An increase in PGE2:PGF2alpha ratio was observed in epithelial cells from both CAR and ICAR regions, but it was significant only in the CAR region (p < 0.05). In stromal cells, roIFN-tau stimulated PGE2 production significantly in cells from the CAR and ICAR regions (35.6 +/- 2.9 vs. 24.1 +/- 3.8 ng/ microg DNA, respectively, p < 0.05). In summary, the ICAR region seems to be the privileged site for regulation of PGF2alpha production by OT, but the caruncules may be a preferred site for recognition of the embryonic IFN-tau signal. Endometrial cells from the CAR and ICAR areas appear to exhibit specialized responses, with cells from the ICAR region more responsive to OT and those from the CAR region more sensitive to roIFN-tau.

Cellular mechanisms involved during oxytocin-induced prostaglandin F2alpha production in endometrial epithelial cells in vitro: role of cyclooxygenase-2

PGs are important regulators of reproductive processes. At the time ofluteolysis in vivo, PGF2alpha is produced by endometrial cells, in response to oxytocin (OT). The mechanism by which OT induces the release of PGF2alpha remains to be defined. We have used 13 different cultures of bovine epithelial endometrial cells to study the effect of OT on the regulation of PGF2alpha and to identify the possible involvement of cyclooxygenases (COXs). OT induced a dose-dependent increase of both inositol phosphates (IPs) and [Ca2+]i concentration in epithelial cells labeled with [3H]-myoinositol or loaded with fura-2 (using a fluorescent microscope imaging system), respectively. OT induced a dose-dependent increase of both PGF2alpha production and COX-2 gene expression (as demonstrated by RT-PCR and Northern blots). PGF2alpha production was increased from 13.3 +/- 2.0 to 166.8 +/- 22.5 ng/ml (P < 0.0001). On the other hand, COX-2/beta-actin mRNA gene expression (as determined by densitometric analysis) was increased 5.1 +/- 0.7-fold (P < 0.001) with OT (10[-7] M) treatment, compared with control. Addition of indomethacin (1 microM) and a specific COX-2 inhibitor (NS-398, 1 microM) blocked the OT-induced PGF2alpha production. COX-1 and phospholipase A2 mRNA were expressed at steady-state levels, but no effect of OT was detected on their regulation. Combined to OT, 10 microq/ml of recombinant ovine interferon-tau (roIFN-tau) was able to decrease significantly (P < 0.0001) the dose-dependent increase of PGF2alpha production. Furthermore, partial bovine COX-1 (777 pb) and COX-2 (449 bp) cDNAs were cloned and sequenced. An homology of 83% and 97% was found in relation with rat and sheep, for COX-1, respectively. COX-2 was found to bear 84%, 86%, and 87% of homology in relation to rat, guinea pig, and human, respectively. Collectively, these results demonstrate, for the first time, that COX-2 is involved in the mechanism by which OT regulates PGF2alpha production in the endometrium.

IFN-tau increases PGE2 production and COX-2 gene expression in the bovine endometrium in vitro

Prostaglandins (PGs) are well known for their role in reproductive processes. At the time of pregnancy recognition, PGF2alpha is luteolytic and PGE2 may be antiluteolytic and luteotropic. During the preimplantation period, interferon-tau (IFN-tau) is produced by the conceptus and plays a crucial role in maternal recognition of pregnancy in domestic ruminants. We have demonstrated previously that recombinant bovine and ovine interferon-tau (rbIFN-tau and roIFN-tau) stimulate PGE2 production in epithelial cells, changing the primary PG produced by these cells from F2alpha to E2. In stromal cells, where PGE2 is the major PG produced, roIFN-tau induced an increase of both types of PGs. The aim of this paper is to identify the possible involvement of cyclooxygenases (COXs) in the modulation of PG production by trophoblastic interferons. Epithelial and stromal cells cultured in vitro were isolated from bovine endometrium and stimulated with increasing doses (1, 10 and 20 microg/ml) of roIFN-tau. PG levels in the culture media were measured by enzyme immunoassays (EIA) and total RNA was extracted from the cells. Northern blot analysis was performed to quantify cyclooxygenase COX-1 (constitutive), COX-2 (inducible) and phospholipase A2 (PLA2) messenger RNA (mRNA) production in response to treatment. The results indicate that roIFN-tau treatment did not affect COX-1 and PLA2 mRNA production in either cell type, whereas COX-2 expression was upregulated in both. The up-regulation of COX-2 transcript was greater in stromal than in epithelial cells. The increase in COX-2 mRNA levels was concurrent with increased production of PGE2 and PGF2alpha in stromal cells and principally PGE2 in epithelial cells. Furthermore, addition of indomethacin (1 microM) and a specific COX-2 inhibitor (NS-398, 1 microM) blocked the roIFN-tau-stimulation of PG production in both cell types. The mechanism whereby elevated COX-2 expression results in a selective increase of PGE2 in epithelial cells remains to be elucidated. In stromal cells, an increase in COX-2 mRNA levels may explain increased PG production. The overall effect of roIFN-tau in the two cell types is a net increase in PGE2 output.

Lack of effect of granulocyte-macrophage colony-stimulating factor on secretion of interferon-tau, other proteins, and prostaglandin E2 by the bovine and ovine conceptus

Three experiments tested the effects of recombinant bovine granulocyte-macrophage colony-stimulating factor (rbGM-CSF) on the preimplantation bovine and ovine conceptus. There was no effect of rbGM-CSF on the secretion of total radiolabeled protein in conditioned medium, immunoreactive interferon-tau (IFN tau), antiviral activity, or prostaglandin E2 from Day 16-18 bovine conceptuses cultured for 24 hr with, [3H]leucine and +/- 10 ng/ml rbGM-CSF. Similarly, there was no effect of 1 ng/ml rbGM-CSF on the secretion of total radiolabeled protein. IFN tau, or antiviral activity from Day 17 ovine conceptuses. There was also no beneficial effect of 1 or 10 ng/ml rbGM-CSF on the presence of immunoreactive IFN tau in conditioned medium from in vitro-produced bovine blastocysts at Day 7-8 after fertilization. Results indicate that IFN tau secretion from bovine and ovine conceptuses are unresponsive to rbGM-CSF at the concentrations tested.

Effects of recombinant interferon-tau on ovine lentivirus replication

As a pregnancy recognition signal, sheep trophoblast cells secrete a type I interferon, ovine interferon-tau (OvIFN-tau), which has potent antiviral activity. We studied the effects of a recombinant protein (rOv-IFN-tau) on the replication of ovine lentivirus (OvLV) in goat synovial membrane cells. The amount of provirus DNA, as measured by polymerase chain reaction (PCR), the virus titers, and the number of OvLV-induced syncytia were 76.5%, 82%, and 95%, respectively, lower in cultures treated with rOv-IFN-tau than in placebo-treated controls (p < 0.01). rOv-IFN-tau also reduced OvLV reverse transcriptase activity and protected cells from OvLV-induced cell lysis, but the effect was less dramatic. The antiviral activity increased with the concentration up to a maximum with 256 antiviral units of rOv-IFN-tau per ml.

Biochemical and immunological properties of related small ruminant trophoblast interferons

The objectives of this study were 1) to evaluate the biochemical and immunological properties of caprine interferon tau (cIFNtau), 2) to determine if intrauterine injection of recombinant ovine interferon tau (roIFNtau) extends CL life span in goats, and 3) to evaluate potential side effects of intramuscular (i.m.) administration roIFNtau. Caprine IFNtau was purified, and its effects on lymphocyte proliferation were evaluated. Incorporation of 3H-thymidine into newly synthesized DNA was suppressed (P<0.05) by cIFNtau. Spanish goats were also fitted with bilateral uterine catheters at Day 7 or 8 postestrus. The goats received twice-daily intrauterine injections of 100 microg roIFNtau (n = 4) or caprine serum proteins (n = 4) from Days 14 to 18 postestrus. Intrauterine injection of roIFNtau extended CL life span compared with that of control goats (26.4 +/- 1.7 vs 17.8 +/- 1.9 d, respectively; P<0.01). Potential side effects of intramuscular injections of roIFNtau were also evaluated. Goats received 0, 1, 2 or 4 mg of roIFNt on Days 10, 13, 16 or 19 of the estrous cycle. Treatment of goats with roIFN resulted in hyperthermia (P<0.01), with rectal temperatures of 40.5 degrees C recorded after 4 h and returning to normal (38.5 degrees C) after 24 h. Concomitant with the increase in rectal temperatures was a decrease (P<0.01) in plasma progesterone concentrations. Therefore, the tau interferons of goats and sheep have similar biological properties and roIFNtau has side effects associated with other classes of interferons.

Placental interferons

Trophectoderm of ruminant conceptuses (embryo and associated membranes) secrete tau interferons (IFN tau) as the pregnancy recognition signal. Secretion of IFN tau on gestational days 12-13 for sheep and gestation days 14-17 for cows and goats is critical for pregnancy recognition. IFN tau acts on uterine epithelium to suppress estrogen receptor and oxytocin receptor gene expression, which prevents uterine release of luteolytic pulses of prostaglandin F2 alpha (PGF). Expression of the progesterone receptor (PR) gene in uterine endometrium is not affected by oIFN tau. Maintenance of progesterone secretion by the corpus luteum (CL) ensures establishment of pregnancy. Pig conceptuses secrete both IFN alpha and IFN gamma between days 15-21 of gestation, but their role(s) in early pregnancy is unknown. Estrogen secreted by pig trophoblast between gestational days 11-13 and 15-25 increases endometrial receptors for prolactin and causes exocrine secretion of PGF into the uterine lumen to prevent luteolysis. Shared cell-signaling mechanisms by IFNs and lactogenic hormones through Janus kinases (JAK) 1 and 2 may provide a common pathway to abrogate luteolytic mechanisms to ensure establishment of pregnancy. The role(s) of IFNs produced by human and rodent placentae is not known.

High yield expression and secretion of the ovine pregnancy recognition hormone interferon-tau by Pichia pastoris

The early conceptus (embryo and associated membranes) of domestic ruminats signals its presence to the maternal uterus through production of interferon-tau (IFN-tau). Production of IFN-tau ensures continued production of progesterone, the hormone of pregnancy, by the ovarian corpus luteum. This paper reports the high-level expression and efficient secretion of biologically active recombinant ovine IFN-tau (rOvIFN-tau) by Pichia pastoris. The developed method produces more than 80% pure recombinant ovine IFN-tau, obviating the need for further purification for many purposes. Initial fermentation studies produced IFN-tau at 280 mg/liter and demonstrate the potential of this system for large-scale production of IFN-tau.