CD4 T suppressor cells mediate interferon tau protection against experimental allergic encephalomyelitis

Symposium review: Immunological detection of the bovine conceptus during early pregnancy

Infertility and subfertility reduce the economic viability of dairy production. Inflammation reduces conception rates in dairy cattle, but surprisingly little information exists about the populations and the functions of immune cells at the conceptus-maternal interface during the periattachment period in dairy cattle. Early pregnancy is accompanied by immune stimulation at insemination and conceptus secretion of IFN-τ, pregnancy-associated glycoproteins, prostaglandins, and other molecules whose effects on immune function during early pregnancy have not been determined. Our working hypothesis is that pregnancy induces changes in immune cell populations and functions that are biased toward immunological tolerance, tissue remodeling, and angiogenesis. This review summarizes current knowledge, starting with insemination and proceeding through early pregnancy, as this is the period of maximal embryo loss. Results indicated that early pregnancy is accompanied by a marked increase in the proportion of endometrial immune cells expressing markers for natural killer (CD335) cells and cytotoxic T cells (CD8) along with an increase in cells expressing major histocompatibility class II antigens (macrophages and dendritic cells). This is accompanied by increased abundance of mRNA for IL-15, a natural killer growth factor, and IL-10 in the endometrium during early pregnancy. Furthermore, expression of indoleamine 2,3 dioxygenase was 15-fold greater in pregnant compared with cyclic heifers at d 17, but then declined by d 20. This enzyme converts tryptophan to kynurenine, which alters immune function by creating a localized tryptophan deficiency and by activation of the aryl hydrocarbon receptor and induction of downstream tolerogenic mediators. Expression of the aryl hydrocarbon receptor is abundant in the bovine uterus, but its temporal and spatial regulation during early pregnancy have not been characterized. Pregnancy is also associated with increased expression of proteins known to inhibit immune activation, including programed cell death ligand-1 (CD274), lymphocyte activation gene-3 (CD223), and cytotoxic T-lymphocyte associated protein-4 (CD152). These molecules interact with receptors on antigen-presenting cells and induce lymphocyte tolerance. Current results support the hypothesis that early pregnancy signaling in dairy heifers involves changes in the proportions of immune cells in the endometrium as well as induction of molecules known to mediate tolerance. These changes are likely essential for uterine wall remodeling, placentation, and successful pregnancy.

Superantigens: The Good, the Bad, and the Ugly

Increasing evidence suggests that superantigens play a role in Immune-mediated diseases. Superantigens are potent activators of CD4* T cells, causing rapid and massive proliferation of cells and cytokine production. This characteristic of superantigens can be exploited in diseases where strong immunologic responses are required, such as in the B16F10 animal model of melanoma. Superantigen administration is able to significantly enhance Ineffective anti-tumor Immune responses, resulting in potent and long-lived protective anti-tumor immunity. However, superantigens are more well-known for the role they play in diseases. Studies using an animal model for neurologic demy-elinatlng diseases such as multiple sclerosis show that superantigens can induce severe relapses and activate auto-reactive T cells not involved in the Initial bout of disease. This may also involve epitope spreading of disease. Superantigens have also been implicated in acute diseases such as food poisoning and TSS, and in chronic diseases such as psoriasis and rheumatoid arthritis. Viral superantigens are also involved in the disease process, including superantigens derived from human Immunodeficiency virus and mouse mammary tumor virus. Finally, immunotherapies that ameliorate the role played by superantigens in disease are discussed.

A Recombinant Adenovirus Expressing Ovine Interferon Tau Prevents Influenza Virus-Induced Lethality in Mice

Ovine interferon tau (IFN-τ) is a unique type I interferon with low toxicity and a broad host range in vivo. We report the generation of a nonreplicative recombinant adenovirus expressing biologically active IFN-τ. Using the B6.A2G-Mx1 mouse model, we showed that single-dose intranasal administration of recombinant Ad5-IFN-τ can effectively prevent lethality and disease induced by highly virulent hv-PR8 influenza virus by activating the interferon response and preventing viral replication.

Crosstalk between neutrophils, B-1a cells and plasmacytoid dendritic cells initiates autoimmune diabetes

Type 1 diabetes develops over many years and is characterized ultimately by the destruction of insulin-producing pancreatic beta cells by autoreactive T cells. Nonetheless, the role of innate cells in the initiation of this disease remains poorly understood. Here, we show that in young female nonobese diabetic mice, physiological beta cell death induces the recruitment and activation of B-1a cells, neutrophils and plasmacytoid dendritic cells (pDCs) to the pancreas. Activated B-1a cells secrete IgGs specific for double-stranded DNA. IgGs activate neutrophils to release DNA-binding cathelicidin-related antimicrobial peptide (CRAMP), which binds self DNA. Then, self DNA, DNA-specific IgG and CRAMP peptide activate pDCs through the Toll-like receptor 9-myeloid differentiation factor 88 pathway, leading to interferon-α production in pancreatic islets. We further demonstrate through the use of depleting treatments that B-1a cells, neutrophils and IFN-α-producing pDCs are required for the initiation of the diabetogenic T cell response and type 1 diabetes development. These findings reveal that an innate immune cell crosstalk takes place in the pancreas of young NOD mice and leads to the initiation of T1D.

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.

Interferon-tau inhibits the development of diabetes in NOD mice

Interferon-alpha (IFN-alpha) inhibits the development of diabetes in animal models of autoimmune diabetes. However, the mechanism of the action is not fully understood and drug toxicity could limit its potential clinical utility. Interferon-tau (IFN-tau) is another type 1 interferon, which has less toxicity but may have different biologic activity than IFN-alpha. This study explores the effect of IFN-tau on the diabetic process in non-obese diabetic (NOD) mice. IFN-tau by intraperitoneal, subcutaneous, or oral routes of administration decreased the development of spontaneous diabetes in NOD mice. Islet inflammation was decreased 50%. IFN-tau administration to recipient mice prevented the development of passively transferred and cyclophosphamide accelerated diabetes. IFN-tau treatment also decreased anti-islet effector activity of NOD splenic cells. Immunoregulatory activity of splenic cells was augmented by IFN-tau administration as was the number of splenic CD25+CD4+ cells. Concanavalin A (Con A)-induced release of IFN-gamma was decreased in spleen cells from IFN-tau treated mice. In conclusion, IFN-tau inhibits spontaneous autoimmune diabetes and passively transferred diabetes in the NOD mouse. This diabetes sparing activity may be due to an induction of regulatory cells, possibly CD25+CD4+ T cells, which in turn inhibit anti-islet effector cell activity and the development of insulitis and diabetes. Due to the lower drug toxicity, IFN-tau could be a better drug candidate than IFN-alpha for experimental clinical trials.

Treatment of Mice with the Suppressor of Cytokine Signaling-1 Mimetic Peptide, Tyrosine Kinase Inhibitor Peptide, Prevents Development of the Acute Form of Experimental Allergic Encephalomyelitis and Induces Stable Remission in the Chronic Relapsing/Remitting Form

We have previously characterized a novel tyrosine kinase inhibitor peptide (Tkip) that is a mimetic of suppressor of cytokine signaling 1 (SOCS-1) and inhibits JAK2 phosphorylation of the transcription factor STAT1alpha. We show in this study that Tkip protects mice against experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis. Mice are immunized with myelin basic protein (MBP) for induction of disease. Tkip (63 mug) administered every other day suppressed the development of acute EAE in 75% of New Zealand White (NZW) mice. Furthermore, Tkip completely protected SJL/J mice, which where induced to get the relapsing/remitting form of EAE, against relapses compared with control groups in which >70% of the mice relapsed after primary incidence of disease. Protection of mice by Tkip was similar to that seen with the type I IFN, IFN-tau. Protection of mice correlated with lower MBP Ab titers in Tkip-treated groups as well as suppression of MBP-induced proliferation of splenocytes taken from EAE-afflicted mice. Cessation of Tkip and IFN-tau administration resulted in SJL/J mice relapsing back into disease. Prolonged treatment of mice with Tkip produced no evidence of cellular toxicity or weight loss. Consistent with its JAK2 inhibitory function, Tkip also inhibited the activity of the inflammatory cytokine TNF-alpha, which uses the STAT1alpha transcription factor. The data presented in this study show that Tkip, like the type I IFN, IFN-tau, inhibits both the autoreactive cellular and humoral responses in EAE and ameliorates both the acute and chronic relapsing/remitting forms of EAE.

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

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

CD4+CD25- T cells that express latency-associated peptide on the surface suppress CD4+CD45RBhigh-induced colitis by a TGF-beta-dependent mechanism

Murine CD4(+)CD25(+) regulatory cells have been reported to express latency-associated peptide (LAP) and TGF-beta on the surface after activation, and exert regulatory function by the membrane-bound TGF-beta in vitro. We have now found that a small population of CD4(+) T cells, both CD25(+) and CD25(-), can be stained with a goat anti-LAP polyclonal Ab without being stimulated. Virtually all these LAP(+) cells are also positive for thrombospondin, which has the ability to convert latent TGF-beta to the active form. In the CD4(+)CD45RB(high)-induced colitis model of SCID mice, regulatory activity was exhibited not only by CD25(+)LAP(+) and CD25(+)LAP(-) cells, but also by CD25(-)LAP(+) cells. CD4(+)CD25(-)LAP(+) T cells were part of the CD45RB(low) cell fraction. CD4(+)CD25(-)LAP(-)CD45RB(low) cells had minimal, if any, regulatory activity in the colitis model. The regulatory function of CD25(-)LAP(+) cells was abrogated in vivo by anti-TGF-beta mAb. These results identify a new TGF-beta-dependent regulatory CD4(+) T cell phenotype that is CD25(-) and LAP(+).

Ingested type I interferon: a potential treatment for autoimmunity

We have proposed a unifying hypothesis of the etiopathogenesis of autoimmunity that defines autoimmunity as a type I interferon (IFN) immunodeficiency syndrome. We have examined toxicity and potential efficacy in three phase I (type 1 diabetes, rheumatoid arthritis, multiple sclerosis) and one phase II clinical trials in multiple sclerosis (MS). In a phase I open-label trial in type 1 diabetes, ingested IFN-alpha preserved residual beta cell function in recent onset patients. In a second phase I trial, treatment of rheumatoid arthritis (RA) with ingested IFN-alpha reduced the secretion of interleukin-1 (IL-1), a proinflammatory cytokine. In a third phase I trial in MS, there was a significant decrease in peripheral blood mononuclear cell (PBMC) IL-2 and IFN-gamma production after ingesting IFN-alpha. In a phase II randomized, placebo-controlled, double-blind trial in MS, 10,000 IU ingested IFN-alpha significantly decreased gadolinium enhancements compared with the placebo group at month 5. Tumor necrosis factor-alpha (TNF-alpha) and IFN-gamma cytokine secretion in the 10,000 IU group at month 5 showed a significant decrease that corresponded with the effect of ingested IFN-alpha on decreasing gadolinium enhancements. Ingested IFN-alpha was not toxic in any of these clinical trials. These studies suggest that ingested IFN-alpha may have a potential role in the treatment of autoimmunity.

Superantigen enhancement of specific immunity: antibody production and signaling pathways

Superantigens are microbial proteins that induce massive activation, proliferation, and cytokine production by CD4+ T cells via specific Vbeta elements on the TCR. In this study we examine superantigen enhancement of Ag-specific CD4+ T cell activity for humoral B cell responses to T-dependent Ags BSA and HIV gp120 envelope, type I T-independent Ag LPS, and type II T-independent Ag pneumococcal polysaccharides. Injection of BSA followed by a combination of superantigens staphylococcal enterotoxin A and staphylococcal enterotoxin B (SEB) 7 days later enhanced the anti-BSA Ab response in mice approximately 4-fold as compared with mice given BSA alone. The anti-gp120 response was enhanced approximately 3-fold by superantigens. The type II T-independent Ag pneumococcal polysaccharide response was enhanced approximately 2.3-fold by superantigens, whereas no effect was observed on the response to the type I T-independent Ag LPS. The superantigen effect was completely blocked by the CD4+ T cell inhibitory cytokine IL-10. SEB-stimulated human CD4+ T cells were examined to determine the role of the mitogen-activated protein (MAP) kinase signal transduction pathway in superantigen activation of T cells. Inhibitors of the mitogen pathway of MAP kinase blocked SEB-induced proliferation and IFN-gamma production, while an inhibitor of the p38 stress pathway had no effect. Consistent with this, SEB activated extracellular signal-regulated kinase/MAP kinase as well as MAP kinase-interacting kinase, a kinase that phosphorylates eIF4E, which is an important component of the eukaryotic protein synthesis initiation complex. Both kinases were inhibited by IL-10. Thus, superantigens enhance humoral immunity via Ag-specific CD4+ T cells involving the stress-independent pathway of MAP kinase.

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.

The inhibitory effects of transforming growth factor-beta-1 (TGF-beta1) in autoimmune diseases

The importance of transforming growth factor-beta-1 (TGF-beta1) in immunoregulation and tolerance has been increasingly recognized. It is now proposed that there are populations of regulatory T cells (T-reg), some designated T-helper type 3 (Th3), that exert their action primarily by secreting this cytokine. Here, we emphasize the following concepts: (1) TGF-beta1 has multiple suppressive actions on T cells, B cells, macrophages, and other cells, and increased TGF-beta1 production correlates with protection and/or recovery from autoimmune diseases; (2) TGF-beta1 and CTLA-4 are molecules that work together to terminate immune responses; (3) Th0, Th1 and Th2 clones can all secrete TGF-beta1 upon cross-linking of CTLA-4 (the functional significance of this in autoimmune diseases has not been reported, but TGF-beta1-producing regulatory T-cell clones can produce type 1 inflammatory cytokines); (4) TGF-beta1 may play a role in the passage from effector to memory T cells; (5) TGF-beta1 acts with some other inhibitory molecules to maintain a state of tolerance, which is most evident in immunologically privileged sites, but may also be important in other organs; (6) TGF-beta1 is produced by many cell types, is always present in the plasma (in its latent form) and permeates all organs, binding to matrix components and creating a reservoir of this immunosuppressive molecule; and (7) TGF-beta1 downregulates adhesion molecules and inhibits adhesion of leukocytes to endothelial cells. We propose that rather than being passive targets of autoimmunity, tissues and organs actively suppress autoreactive lymphocytes. We review the beneficial effects of administering TGF-beta1 in several autoimmune diseases, and show that it can be effectively administered by a somatic gene therapy approach, which results in depressed inflammatory cytokine production and increased endogenous regulatory cytokine production.

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.

Oral use of interferon

Interferon-alpha (IFN-alpha) given orally has biological activity in humans and other animals. The dose providing the most benefit delivers IFN-alpha to the oral mucosa in a concentration (10(2)-10(3) IU), similar to that naturally produced in the nasal secretions during respiratory infections. In contrast, conventional IFN therapy employs parenteral doses of > 10(6) IU and, for this reason, orally administered IFN therapies have been called low-dose treatments. Efficacy in both animal disease models and human studies has been reported, and the mechanisms whereby oral administration has a systemic effect are under active study in a number of laboratories.

Expression, purification, and characterization of interferon-tau produced in Pichia pastoris grown in a minimal medium

Interferon-tau (IFN-tau) is a novel type I IFN that was originally identified as a pregnancy recognition hormone. IFN-tau shares all of the biological properties of other type I IFNs including antiviral activity and antiproliferative activity through induction of the cell cycle inhibitor gene product p21WAF1. It is a promising therapy for cancers, viral infections, and for autoimmune disorders such as multiple sclerosis, without the adverse side effects associated with IFN-alpha and IFN-beta. Here, we describe novel growth and induction conditions for the expression of functionally active and uniformly 15N-labeled IFN-tau from Pichia pastoris in a minimal media for use in initial 2D- and 3D-NMR studies in solution. Purified 15N-IFN-tau was homogenous, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and MALDI-TOF mass spectrometer (MS), and retained full biological activity. MS analysis confirmed uniform isotopic labeling of IFN-tau with 15N incorporation exceeding 99%. Circular dichroism (CD) as well as 1D-NMR and 15N-1H heteronuclear single quantum coherence (HSQC) spectra confirmed that purified 15N-labeled IFN-tau has a stable secondary structure. Besides providing a route for isotope labeling of IFN-tau, our procedure may be useful for the expression and purification of other proteins that are difficult to obtain in Pichia pastoris grown in minimal media.

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.

Early pregnancy factor: an extracellular chaperonin 10 homologue

Early pregnancy factor (EPF) has been identified as a homologue of chaperonin 10 (cpn10) with immunosuppressive and growth factor properties. As a homologue of cpn10, it belongs to the heat shock family of proteins (hsp) but, unlike other members of this family, EPF is detected extracellularly. Early pregnancy factor was first discovered in pregnancy serum by the rosette inhibition test, and the novelty of its discovery was that its presence could diagnose pregnancy within 6-24 h of a fertile mating. As well as being a monitor of the presence of a viable embryo, it is necessary for embryonic survival. In this capacity it acts as both an immunosuppressant and growth factor. Early pregnancy factor is also a product of proliferating primary and neoplastic cells and functions as an autocrine growth factor both in vivo and in vitro. It has a modifying effect on the outcome of experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. Early pregnancy factor is considered to be one of the major factors involved in the modification of multiple sclerosis observed during pregnancy.

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.

IFN-tau: a novel subtype I IFN1. Structural characteristics, non-ubiquitous expression, structure-function relationships, a pregnancy hormonal embryonic signal and cross-species therapeutic potentialities

IFN-tau (IFN-tau) constitutes a new class of type I IFN which is not virus-inducible, unlike IFN-alpha and IFN-beta, but is constitutively produced by the trophectoderm of the ruminant conceptus during a very short period in early pregnancy. It plays a pivotal role in the mechanisms of maternal recognition of pregnancy in ruminants and it displays high antiviral and antiproliferative activities across species with a prominent lack of cytotoxicity at high concentrations in vitro in cell culture and possibly in vivo. It exhibits high antiretroviral activity against HIV and exhibits immunosuppressive activity in a multiple sclerosis model and reduces embryo and fetal mortality by stimulation of IL-10 production. In this review all the biochemical and para-hormonal properties of this novel IFN-tau are described in detail: structural characteristics of proteins and genes, trophoblast expression, regulation of its expression, structure of its gene promoter, its absence in human species and in non-ruminant animals, the evolution of the IFN-tau genes, its structure-function relationships with its three-dimensional structure, structural localization of biological activities, its lack of cytotoxicity and its receptor. Surprisingly, for an IFN, IFN-tau is also a pregnancy-embryonic signal with paracrine antiluteolytic activity. In order to maintain luteal progesterone secretion, IFN-tau inhibits PGF-2alpha pulsatile secretion and oxytocin uterine receptivity in early pregnancy. It is believed to suppress pulsatile release of endometrial PGF-2alpha by preventing oxytocin and estrogen receptor expression. Additionally, it directly regulates prostaglandin metabolism and possibly the PGE:PGF-2alpha ratio.

IFN-tau suppresses both the autoreactive humoral and cellular immune responses and induces stable remission in mice with chronic experimental allergic encephalomyelitis

We have previously shown that interferon-tau (IFN-tau) pretreatment inhibits the development of both acute and chronic mouse experimental allergic encephalomyelitis (EAE), an animal model for the human demyelinating disease multiple sclerosis (MS). IFN-tau is a type I IFN that has pregnancy recognition hormone activity in ruminants. Here we show that IFN-tau induced remission in SJL/J mice that had ongoing chronic active EAE disease and protected mice against secondary relapses. IFN-tau treatment reversed lymphocyte infiltration and microglial activation in the central nervous system. Mice that were treated with IFN-tau had lower levels of anti-MBP antibodies than untreated mice in both chronic and acute forms of EAE. MBP induced proliferation in B cells from EAE mice, but treatment with IFN-tau either in vivo or in vitro blocked activation. Furthermore, IFN-tau inhibited MBP activation of T cells from EAE mice. Thus, IFN-tau inhibits the humoral arm as well as the cellular arm of the autoimmune disease EAE. The data presented here show that IFN-tau inhibits both B cell and T cell responses in EAE as well as active, chronic EAE, and this may help explain the effectiveness of type I IFNs in treatment of MS.

Immunomodulating functions of recombinant ovine interferon tau: potential for therapy in multiple sclerosis and autoimmune disorders

The interferons (IFN) are a family of complex proteins possessing antiviral, antiproliferative, and immunomodulatory activities. Two type I recombinant human IFN have been recently approved for the treatment of multiple sclerosis (MS). However, use of high dose type I IFN treatment in MS patients has been limited by dose-related toxicity. Ovine IFN tau is a unique type I interferon discovered for its role in the animal reproductive cycle. It differs from other type I IFNs in that it is remarkably less toxic even at high concentrations, is able to cross species barriers, and is not inducible by viral infection. Ovine IFN tau has been shown to be very effective in the treatment of animal models of MS. In this study, we examined the toxicity of OvIFN tau on human T-cells at high doses and its immunregulatory properties at equivalent doses. Our experiments confirmed the remarkably non-toxic nature of OvIFN tau on human cells at high concentrations as well as immunomodulating properties consistent with other type I IFNs including an antilymphoproliferative effect and inhibition of IFN gamma-induced HLA class II expression. These results suggest that OvIFN tau could be developed into a potentially less toxic therapeutic option for immune-mediated disorders including MS.

Oral feeding of interferon tau can prevent the acute and chronic relapsing forms of experimental allergic encephalomyelitis

IFN tau is a member of the type I IFN family but unlike IFN alpha and IFN beta, IFN tau lacks toxicity at high concentrations. Recently, ovine IFN tau was shown to prevent acute induction and superantigen reactivation of experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS). In this report, we examined the ability of IFN tau when administered by oral feeding to block development of EAE. Oral feeding of INF tau prevented paralysis in the acute form of EAE in NZW mice and chronic-relapsing EAE in SJL/J mice. In addition, oral feeding of IFN tau at 10(5) U/dose was as effective as intraperitoneal (i.p.) injection in preventing chronic-relapsing EAE, and both forms of IFN tau administration resulted in IL10 production. Histological examination revealed no inflammatory lymphocytic infiltration to the CNS in IFN tau treated animals as compared to controls. Prolonged treatment of IFN tau was shown to be necessary for chronic-relapsing EAE since removal of IFN tau treatment by either oral feeding or i.p. injection resulted in onset of disease. Lastly, sera from SJL/J mice which received prolonged IFN tau treatment by oral feeding exhibited little to no development of anti-IFN tau antibodies. Thus, oral feeding of ovine IFN tau may be a successful form of IFN tau administration for treatment of autoimmune diseases such as MS and may circumvent potentially debilitative antibody responses.