Tolerizing agents

Described herein is the development of fusion proteins useful for inducing tolerance in a subject. In particular embodiments, the tolerizing agents are useful for influence autoimmune, inflammatory, and/or allergic reactions. Example tolerizing fusion proteins contain a targeting portion (which delivers the fusion protein) and a toleragen or allergen or other antigen to which tolerance is desired in a subject. In particular examples, it is demonstrated that a p1 fusion protein, when administered orally, facilitates systemic and mucosal tolerance. Also described is the nasal delivery of fusion proteins, for instance for restoring immunogenicity.

1. A tolerizing fusion protein comprising a targeting portion and an antigen or allergen to which tolerance is desired, wherein the targeting portion comprises a reovirus protein σ1 (pσ1), and wherein administration of the fusion protein to a subject induces tolerance in the subject to the antigen or allergen.

2. The fusion protein of claim 1, wherein the antigen is an autoantigen or therapeutically active biological.

3. A method to induce tolerance in a subject to an antigen or allergen, comprising administering to the subject the fusion protein of claim 1.

4. A method of inducing tolerance in a subject to an antigen, comprising:

administering to the subject a single dose of a tolerizing fusion protein, wherein the tolerizing fusion protein comprises (1) a targeting portion comprising a reovirus protein σ1 (pσ1), and (2) the antigen, thereby inducing tolerance in the subject to the antigen.

5. The method of claim 4, wherein the single dose of the tolerizing fusion protein comprises 1 mg or less of the antigen.

6. The method of claim 5, wherein the single dose of the tolerizing fusion protein comprises 500 μg or less of the antigen.

7. The method of claim 6, wherein the single dose of the tolerizing fusion protein comprises 250 μg or less of the antigen.

8. The method of claim 7, wherein the single dose of the tolerizing fusion protein comprises 100 μg or less of the antigen.

9. A method of inducing antigen specific immune tolerance in a subject, comprising: administering an effective dose of a tolerizing fusion protein comprising a targeting portion and at least one epitope from the antigen to the subject, wherein the tolerizing fusion protein comprises a reovirus protein σ1 (pσ1), thereby inducing tolerance in the subject to the antigen.

10. The method of claim 4, comprising administering more than one tolerizing fusion protein to the subject.

11. The method of claim 4, wherein the tolerizing fusion protein is administered orally or nasally.

12. The method of claim 9, comprising administering more than one tolerizing fusion protein to the subject.

13. The method of claim 9, wherein the tolerizing fusion protein is administered orally or nasally.

14. The method of claim 3, comprising administering more than one fusion protein to the subject.

15. The method of claim 3, wherein the tolerizing fusion protein is administered orally or nasally.

This is the U.S. National Stage of International Application No. PCT/US2007/065278, filed Mar. 27, 2007, which was published in English under PCT Article 21(2), which in turn claims the benefit of U.S. provisional application No. 60/786,446, filed Mar. 27, 2006. Both applications are hereby incorporated by reference in their entirety.

This invention was made with government support under contracts AI018958, DE012242, AI043197, DC004976, and DE013812 awarded by the National Institutes of Health. The government has certain rights in the invention.

This disclosure relates to agents and compositions useful in stimulating tolerance to an immunogen. In particular, it relates to mucosal targeted fusion proteins that can be applied, for instance, through oral and/or nasal routes to tolerize a subject.

Oral administration of a single high dose or repeated low doses of protein has been shown to induce systemic unresponsiveness, presumably in the presence of mucosal IgA antibody responses (Challacombe et al., J. Exp. Med. 152:1459-1472, 1980; Mestecky et al., “The mucosal immune system.” In Fundamental Immunology. Paul, ed. Lippincott Williams & Wilkins, Philadelphia, Pa., 965-1020, 2003). In earlier studies, this type of immune response was dubbed oral tolerance and the concept was used to refer specifically to immune responses elicited in mucosa-associated as opposed to systemic lymphoid tissues (Tomasi, Transplantation 29:353-356, 1980). However, previous studies showed that tolerance induction occurred in the mucosal effector lymphoid tissues (Kato et al., J. Immunol. 166:3114-3121, 2001). Thus, mice fed large amounts of ovalbumin (OVA) prior to oral challenge with OVA plus native cholera toxin (CT) as mucosal adjuvant exhibited antigen (Ag)-specific unresponsiveness in both systemic and mucosal compartments, while those fed PBS showed high levels of secretory (S)-IgA Ab responses (Kato et al., J. Immunol. 166:3114-3121, 2001).

This unique response is an important natural physiological mechanism whereby the host presumably avoids development of hypersensitivity reactions to many ingested food proteins and other antigens (Garside et al, Gut 44:137-142, 1999). Thus, tolerance (or systemic unresponsiveness) represents the most common response of the host to the environment. In addition to showing tolerance to several thousand different food proteins, the host tolerates indigenous microflora which colonize the large intestine. Further, the development of mucosal tolerance against pollen and dust antigens could also be essential for the inhibition of allergic reactions, including IgE-mediated hypersensitivity. Indeed, tolerance is so strong that oral immunization only succeeds in inducing mucosal and systemic immunity when potent mucosal adjuvants, vectors or other special delivery systems are employed (Fujihashi et al, Acta. Odontol Scand. 59:301-308, 2001).

It is now generally agreed that oral tolerance is established and maintained at the level of T cells (Holt, Allergy 53:16-19, 1998; MacDonald, Curr. Opin. Immunol. 10:620-627, 1998; Mayer, Clin. Immunol. 94:1-8, 2000; Strobel & Mowat, Immunol Today 19:173-181, 1998; Strober et al., J. Clin. Immunol. 18:1-30, 1998; Wardrop & Whitacre, Inflamm. Res. 48:106-119, 1999; Weiner et al., Annu. Rev. Immunol. 12:809-837, 1994). Recent studies have identified dendritic cells as key players in the direct or indirect (via T cells) induction of oral tolerance (Mowat, Nat. Rev. Immunol. 3:331-341, 2003; Kato et al., Int. Immunol. 15:145-158, 2003; Nagler-Anderson & Shi, Crit. Rev. Immunol. 21:121-131. 2001; Viney et al., J. Immunol. 160:5815-5825, 1998; Williamson, J. Immunol. 163:3668-3675, 1999; Weiner, Immunol Rev. 182:207-214, 2001). Though the precise mechanisms by which oral delivery of Ag elicits a state of systemic unresponsiveness are not fully understood, the dosage of Ag has been shown to be an important factor (Friedman & Weiner, Proc. Natl. Acad. Sci. (USA) 91:6688-6692, 1994). For example, a high oral Ag dose leads to T cell clonal deletion or anergy, which is characterized by inhibition of both Ab- and cell-mediated immune (CMI) responses (Melamed & Friedman, Eur. J. Immunol. 25 23:935-942, 1993; Whitacre et al., J. Immunol 147:2155-2163, 1991; Chen et al., Nature 376:177-180, 1995). On the other hand, repeated delivery of low doses of protein induces cytokine-mediated active immune suppression characterized by the presence of regulatory T cells, which include TGF-β-producing Th3 cells and IL-10-producing T regulatory one (Tr1) cells or CD4⁺ CD25⁺ T regulatory (Treg) cells (Chen et al., Science 265:1237-1240, 1994; Groux et al., Nature 389:737-742, 1997; Nagler-Anderson et al., Nat. Immunol. 5:119-122, 2004). Regulatory-type T cells were first rediscovered as acquired-type Tr1 cells playing a central role in suppressing inflammatory bowel disease development (Groux et al., Nature 389:737-742, 1997). Acquired-type Treg cells, which differentiate from naïve T cells, regulate tolerance to food Ags, bacterial flora and pathogens by producing suppressive cytokines such as TGF-β1 and IL-10 (Cottrez & Groux, Transplantation 77:S12-15, 2004). In contrast, naturally occurring CD4⁺ CD25⁺ T cells or innate-type Treg cells, which are also suppressive, control the proliferation, expansion and differentiation of naïve T cells in a direct cell contact manner (Dieckmann et al., J. Exp. Med. 196:247-253, 2002) and migrate preferentially to lymphoid tissues, mainly the spleen (Cottrez & Groux, Transplantation 77:S12-15, 2004).

In addition to CD4⁺ T cell function, gut-associated lymphoreticular tissues (GALT) play critical roles in the induction of oral tolerance. In this regard, our previous studies showed that Peyer's patch (PP)-deficient (PP-null) mice generated by in utero treatment of mothers with lymphotoxin beta-receptor (LTβR)-immunoglobulin (Ig) fusion protein failed to exhibit systemic unresponsiveness to oral protein antigens (Ag) such as OVA (Fujihashi et al., Proc. Natl. Acad. Sci. (USA) 98:3310-3315, 2001). In contrast, others reported that PPs were not required for the induction of systemic tolerance (Spahn et al., Eur. J. Immunol 32:1109-1113, 2002). Recent studies have shown the importance of Ag-specific CD4⁺ CD25⁺ Treg cell clones from PPs in oral tolerance induction. Thus, Treg cells from PP of mice given a high dose of β-lactoglobulin produced high levels of TGF-β1, and adoptive transfer of these clones reduced Ag-specific plasma IgG Ab responses (Tsuji et al., Int. Immunol. 15:525-534, 2003). Despite these compelling studies, the precise cellular and molecular mechanisms and the role of PPs in the induction of systemic and mucosal unresponsiveness still remain to be elucidated.

Adenoviruses enter the host via attachment to the mucosal epithelia by its protein known as “fiber protein”. Likewise, reoviruses infect the host by attaching to M cells via a protein called “protein Gσ1” (pσ1; Wu et al., Proc. Natl. Acad. Sci. (USA) 98:9318-9323, 2001; Rubas et al., J. Microencapsul 7:385-395, 1990). These attachment proteins of adenovirus ssp. and reovirus ssp. are well known, and share a strikingly structural similarity despite lack of homology at the primary structure level. Both proteins are composed of a N-terminal shaft followed by a C-terminal globular domain, sometimes referred to as “head” or “knob”. The shaft inserts into the viral capsids, while the globular domains contain the cell-specific targeting regions. For both of these viruses, the shaft contains a domain that causes the protein to form homotrimers, the active form of the protein.

Incorporation of pσ1 into liposomes allows the latter to bind to mouse L cells and rat Peyer's patches (Rubas et al., J. Microencapsul 7:385-395, 1990), and the recombinant pσ1 is also known to bind to NALT M cells (Wu et al., Gene Ther. 7:61-69, 2000; Wu et al., Proc. Natl. Acad. Sci. (USA) 98:9318-9323, 2001). In marked contrast to results seen when DNA is given alone, immunization with DNA complexed to poly-L-lysine-conjugated pσ1 leads to elevated S-IgA and plasma IgG Ab responses (Wu et al., Proc. Natl. Acad. Sci. (USA) 98:9318-9323, 2001).

There exists a need to develop agents that can stimulate or cause tolerance in a subject to an immunogen. It is to such agents, and compositions comprising such, that this disclosure is drawn.

Described herein is the development of M cell-targeting Ag delivery systems using recombinant reovirus pσ1. Recombinant pσ1 of reovirus has been genetically fused to OVA (OVA-pσ1). It is demonstrated that this fusion protein, when administered orally, facilitates systemic and mucosal tolerance induction by innate- and/or acquired-types of Treg cells. Also described is the nasal delivery of a OVA-pσ1(m) or OVA-pσ1(Δ) fusion protein for restoring OVA immunogenicity.

Thus, there is provided herein a new approach to delivering highly virulent and antigen-specific tolerizing agents, which uses a ligand (such as a mucosal targeting ligand) fused to a specific antigen to induce host unresponsiveness solely to that antigen. The ligand portion of the protein can be fused a broad range of antigens (toleragens), enabling the generation of tolerance to a number of autoimmune disease antigens, inflammatory disease antigens, allergens, and biological therapeutic molecules (e.g., botulinum toxin), for instance. The fusion proteins are capable of regulating peripheral tolerance subsequent to nasal or oral application.

The tolerizing fusion proteins provided herein can be used in various tolerance applications, including but not limited to treatment or amelioration of autoimmune diseases, inflammatory diseases, allergic reactions, graft or transplant rejection, and so forth. In addition, the provided proteins and methods of their use permit continuous or on-going treatment of a subject with a biological therapeutic agent. For example, tolerance has been demonstrated in mice challenged with ovalbumin or myelin proteins, the latter being useful for treatment against multiple sclerosis.

The foregoing and other features and advantages will become more apparent from the following detailed description of several embodiments, which proceeds with reference to the accompanying figures.

The nucleic and amino acid sequences listed in the accompanying sequence listing are shown using standard letter abbreviations for nucleotide bases, and three-letter code for amino acids, as defined in 37 C.F.R. §1.822. Only one strand of each nucleic acid sequence is shown, but as appropriate in context the complementary strand is understood as included by any reference to the displayed strand. In the accompanying sequence listing:

SEQ ID NO: 1 shows the nucleic acid sequence encoding adenovirus 2 fiber protein (HAD278923).

SEQ ID NO: 2 shows the protein sequence of adenovirus 2 fiber protein.

SEQ ID NO: 3 shows the nucleic acid sequence encoding reovirus type 3 sigma 1 (haemagglutinin) (RET3S1).

SEQ ID NO: 4 shows the amino acid sequence of reovirus type 3 sigma 1 (haemagglutinin).

SEQ ID NO: 5 shows the nucleic acid sequence encoding adenovirus 16 fiber protein (AX034843).

SEQ ID NO: 6 shows the amino acid sequence of adenovirus 16 fiber protein.

SEQ ID NO: 7 shows the nucleic acid sequence encoding adenovirus 35 fiber (fiber) protein (30827 to 31798 of BK005236).

SEQ ID NO: 8 shows the amino acid sequence of adenovirus 35 fiber protein (30827 to 31798 of BK005236).

SEQ ID NO: 9 shows the nucleic acid sequence encoding adenovirus 37 fiber protein (x94484).

SEQ ID NO: 10 shows the amino acid sequence of adenovirus 37 fiber protein (x94484).

SEQ ID NO: 11 shows the nucleic acid sequence (V00383) encoding ovalbumin.

SEQ ID NO: 12 shows the amino acid sequence of ovalbumin.

All publications and patent applications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference (including those so indicated). The provided description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed embodiments, or that any publication specifically or implicitly referenced is prior art. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, example methods and materials are described.

I. Abbreviations

Ab, antibody

AFC, Ab forming cells

Ag, antigen

CT, native cholera toxin

GALT, gut-associated lymphoreticular tissues

iLP, small intestinal lamina propria

MLNs, mesenteric lymph nodes

OVA, ovalbumin

OVA-pσ1, OVA genetically fused to protein sigma one of reovirus

PPs, Peyer's patches

S-IgA, secretory-IgA

Treg, regulatory T

II. Terms

Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which this disclosure belongs. Definitions of common terms in molecular biology may be found in Benjamin Lewin, Genes V, published by Oxford University Press, 1994 (ISBN 0-19-854287-9); Kendrew et al. (eds.), The Encyclopedia of Molecular Biology, published by Blackwell Science Ltd., 1994 (ISBN 0-632-02182-9); and Robert A. Meyers (ed.), Molecular Biology and Biotechnology: a Comprehensive Desk Reference, published by VCH Publishers, Inc., 1995 (ISBN 1-56081-569-8).

In order to facilitate review of the various embodiments, the following explanations of specific terms are provided:

As used herein, the term “adjuvant” refers to a substance sometimes included in a vaccine formulation to enhance or modify the immune-stimulating properties of a vaccine.

As used herein, the term “antibody” refers to a large Y shaped protein molecule made by B-cells of the immune system which very selectively binds to other specific protein molecules called antigens.

As used herein, the term “antigen” refers to a foreign substance that that when introduced into the body triggers an immune system response, resulting in production of an antibody as part of the body's defense against disease.

As used herein, the term “DNA vaccine” refers to a eukaryotic expression system encoding the molecular machinery for the expression of the subunit vaccine encoded in plasmid nucleic acids.

As used herein, the term “expression” refers to the vaccine vector which is responsible for producing the vaccine.

As used herein, the term “immunization” refers to a process by which a person or animal becomes protected against a disease; the process of inducing immunity by administering an antigen (vaccine) to allow the immune system to prevent infection or illness when it subsequently encounters the infectious agent.

As used herein, the term “mucosal” means any membrane surface covered by mucous.

As used herein, “mucosal targeting ligand” refers to a viral protein or adhesins that specifically bind to the epithelia to enable uptake of the vaccine. These MTLs are not restricted to proteins, but can a protein derivatized or not with carbohydrates and/or lipids. Likewise, carbohydrate, lipid, or nucleic acids found to bind to the epithelia can also be included as mucosal targeting ligands. Methods for making MTLs and additional examples thereof are described in PCT/US2006/001346 (published as WO 2006/078567), which is incorporated herein by reference in its entirety.

As used herein, the term “toleragen” means any antigen (such as a protein, nucleic acid, carbohydrate, lipid, or combination of any thereof) that mediates host unresponsiveness. By way of example, a toleragen works by inducing the tolerized host not to produce antibodies or cell-mediated immune responses specific for the toleragen. Additional discussion of toleragens may be found, for instance, in PCT publication WO 2006/052668, which is incorporated herein in its entirety.

III. Tolerizing Agents

One of the problems for conventional tolerization regimens is the requirement to use high doses, or repeated dosing, of antigen (toleragen or allergen). This disclosure provides evidence that the addition of a targeting molecule (or tolerizing agent), represented in various embodiments by protein sigma 1 (pσ1), mediates tolerance after a single oral dose or with minimal dosing. This enables use of far less toleragen when it is genetically fused to pσ1. As an example, typically, 25 mg of toleragen (for instance, the test antigen used in this case, ovalbumin (OVA)) is required to be given twice orally in order to induce tolerance as measured by lack of proliferative T-cell responses to OVA, reduced anti-OVA antibody responses, and reduced delayed type hypersensitivity reactions. In contrast, a single, low oral dose (100 μg) of OVA-pσ1 fusion protein was sufficient to elicit tolerance. This indicates the fusion is at least 500-fold more effective than convention.

Given this finding, the addition of a targeting molecule that directs (targets) a toleragen to the host M cells and/or mucosal epithelium and/or host dendritic cells, mediates tolerance induction via binding to host sialic acid, specific host receptors, or via a combination of these or other mechanisms. Such binding events contribute in part or in whole to the eventual development of tolerance.

In addition to pσ1, other ligands that contribute to binding to M cells, dendritic cells, and/or mucosal epithelium and thereby mediate tolerance to a passenger molecule are included. As example, adenovirus 35 fiber protein or adenovirus 37 fiber protein, the latter of which has sialic acid binding activity and can also be used to elicit tolerance to a molecule fused or attached thereto. Any toleragen that can be fused to such (targeting) ligands, or adaption of such ligands for delivery of particles (e.g., nanoparticles, microspheres, liposomes, or virus-like particles), can be used to induce tolerance and thereby, for instance, prevent or treat autoimmune diseases, allergies, food allergies, or allow for tolerization to permit continued treatment with biologicals, e.g., botulinum neurotoxins (BoNTs).

Representative targeting molecules (or domains of molecules) that contribute to binding (e.g., to M cells, dendritic cells, and/or mucosal epithelium) include but are not limited to known viral proteins. Sequences of such proteins, and the nucleic acids encoding them, can be found in public databases, such as GenBank. For instance, in addition to specific sequences discussed herein in detail, another nucleotide sequence encoding a human adenovirus 2 fiber protein is found under Accession No. AJ278923. Similarly, an example reovirus 3 sigma 1 is found under Accession No. X01161.

By way of example, the fusion of the pσ1 or like (tolerizing) molecule to the heavy and/or light chain(s) of a BoNT allows the adaption of the resultant fusion protein as a prophylactic or therapeutic vaccine to prevent or treat immune reactivity against BoNT. BoNTs are currently used for a variety of treatments including tremor disorders. Consequently, repeated exposure to native BoNTs can result in the development of neutralizing antibodies to the BoNTs. Such exposure can prevent BoNT treatments. However, the use of a tolerizing molecule as described, in conjunction with BoNT light and/or heavy chains, can prevent or treat this immune reactivity. Thus, this disclosure describes the addition of mucosal targeting molecule(s) that enhance tolerance induction.

One embodiment of this present disclosure is that certain molecules that bind the mucosal epithelium can elicit tolerance in a subject. Thus, for example, using the reovirus protein σ1, a subject can be “vaccinated” for instance nasally, orally, or peripherally for tolerance induction, thereby preventing the host (subject) from reacting against the passenger antigen fused thereto. Evidence provided here shows that OVA-σ1, when given orally or nasally, makes the host unresponsive to OVA. In a similar fashion, when other protein or peptides are genetically engineered onto OVA-σ1 or pσ1, tolerance to autoimmune epitopes can also be induced. For example, peptides from mouse proteolipid protein or from myelin oligodendrocyte glycoprotein genetically engineered onto OVA-pσ1, when given, can reduce a multiple sclerosis-like disease. Thus, any components that induce human or animal autoimmune disease when fused to pσ1, and given to induce tolerance, should prevent or treat autoimmune diseases, such as multiple sclerosis, arthritis, diabetes, Hashimoto's disease, Graves' disease, Sjögren syndrome, etc.

Another embodiment is that compounds described herein can be used to induce tolerance to botulinum neurotoxins or other biological therapeutic agents. Currently, botulinum neurotoxins are used to treat tremor disorders as well as for cosmetic applications. However, one side-effect is that the individual can develop neutralizing antibodies resulting in the therapeutic loss of these treatments. Thus, an MTL fused to the β-trefoil vaccine, heavy chain, or the light chain to botulinum neurotoxins. Thus, this shows that drugs or therapeutics can be applied to pσ1, to limit the host response. These can also include host inflammatory mediators, e.g., cytokines or soluble cytokine receptors, such that the individual shows unregulated or elevated expression of these inflammatory mediators that need to be suppressed.

Also particularly contemplated are fusion proteins that contain a tolerizing ligand (or its sialic acid binding domain component) that targets the fusion protein to host M cells and/or mucosal epithelium and/or host dendritic cells, and a component or fragment of at least one botulinum neurotoxin from serotype A, B, C, D, E, F, or G that will induce tolerance to botulinum. In some specific examples, the fusion protein contains a component or fragment, or domain, from two or more serotypes, or in some instances from all of serotypes A through G.

Tolerizing antigens include, but are not limited to, autoimmune antigens (“autoantigens”), therapeutically active biological agents, allergens, inflammatory antigens, and so forth. By way of example, therapeutically active biological agents maybe any immunologically active (that is, immune stimulatory) proteins or peptides that have a therapeutic function, such as growth factors, hormones (e.g., insulin), clotting factors (e.g., Factor VIII), metabolic enzymes, therapeutic antibodies (e.g., HERCEPTIN® or Trastuzumab), toxins (e.g., botulinum toxin), and so forth. Additional specific antigens that could usefully be fused to a targeting portion in the described fusion proteins will be known to those of ordinary skill in the art. For instance, WO 2006/052668 describes a number of representative antigens and categories thereof that can be used for tolerization.

The fusion proteins described herein are useful as therapeutic compounds for treatment of subjects, including human and veterinary subjects. As demonstrated, routes of administration include oral and nasal application, though other routs are contemplated. The dosage form of a pharmaceutical composition comprising one or more of the provided tolerizing fusion proteins will be influenced by the mode of administration chosen. For instance, in addition to injectable fluids, inhalational, topical, opthalmic, peritoneal, and oral formulations can be employed. Inhalational preparations can include aerosols, particulates, and the like. In general, the goal for particle size for inhalation is about 1 μm or less in order that the pharmaceutical reach the alveolar region of the lung for absorption. Oral formulations may be liquid (for example, syrups, solutions, or suspensions), or solid (for example, powders, pills, tablets, or capsules). For solid compositions, conventional non-toxic solid carriers can include pharmaceutical grades of mannitol, lactose, starch, or magnesium stearate. Actual methods of preparing such dosage forms are known, or will be apparent, to those of ordinary skill in the art.

For oral administration, the pharmaceutical compositions can take the form of, for example, tablets or capsules prepared by conventional means with pharmaceutically acceptable excipients such as binding agents (for example, pregelatinised maize starch, polyvinylpyrrolidone or hydroxypropyl methylcellulose); fillers (for example, lactose, microcrystalline cellulose or calcium hydrogen phosphate); lubricants (for example, magnesium stearate, talc or silica); disintegrants (for example, potato starch or sodium starch glycolate); or wetting agents (for example, sodium lauryl sulphate). The tablets can be coated by methods well known in the art. Liquid preparations for oral administration can take the form of, for example, solutions, syrups or suspensions, or they can be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations can be prepared by conventional means with pharmaceutically acceptable additives such as suspending agents (for example, sorbitol syrup, cellulose derivatives or hydrogenated edible fats); emulsifying agents (for example, lecithin or acacia); non-aqueous vehicles (for example, almond oil, oily esters, ethyl alcohol or fractionated vegetable oils); and preservatives (for example, methyl or propyl-p-hydroxybenzoates or sorbic acid). The preparations can also contain buffer salts, flavoring, coloring, and sweetening agents as appropriate.

For administration by inhalation, the compounds for use according to the present disclosure are conveniently delivered in the form of an aerosol spray presentation from pressurized packs or a nebulizer, with the use of a suitable propellant, for example, dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide or other suitable gas. In the case of a pressurized aerosol, the dosage unit can be determined by providing a valve to deliver a metered amount. Capsules and cartridges for use in an inhaler or insufflator can be formulated containing a powder mix of the compound and a suitable powder base such as lactose or starch.

The pharmaceutical compositions that comprise at least one therapeutic agent, in some embodiments, will be formulated in unit dosage form, suitable for individual administration of precise dosages. The amount of active compound(s) administered will be dependent on the subject being treated, the severity of the affliction, and the manner of administration, and is best left to the judgment of the prescribing clinician. Within these bounds, the formulation to be administered will contain a quantity of the active component(s) in amounts effective to achieve the desired effect in the subject being treated.

The therapeutically effective amount of therapeutic agent, and specifically a tolerizing fusion protein, will be dependent on the specific fusion protein utilized, the subject being treated, the severity and type of the affliction, and the manner of administration. The exact dose is readily determined by one of skill in the art based on the teachings herein, along with the potency of the specific compound, the age, weight, sex and physiological condition of the subject. By way of example, in various embodiments the dosage of a tolerizing fusion protein required to achieve (or maintain) tolerance in a subject is low relative to traditional tolerization regimens. For instance, as few as one or a few doses (e.g., fewer than about three, or fewer than about five doses) of agent may be sufficient to induce tolerance. Similarly, a relatively low amount of antigen is required per dose, compared to previously known tolerance approaches). By way of example, as little as 1 mg or less of antigen in a dose (or total, in a series of doses) will be effective with some fusion proteins. In other instances, as little as 500 μg, 300 μg, 250 μg, or less in a dose, or total in a series of doses, or even as little as 200 μg, 150 μg, 100 μg, or less will be effective. Based on, and the skill of practitioners who engage in tolerance induction, specific dosages and dosage regimens can readily be worked out for any particular tolerizing fusion protein using the teachings herein.

Ovalbumin-Protein σ1 M Cell Targeting Enhances Oral Tolerance with Loss of OVA-Specific CD4⁺ T Cells

In this example, facilitated induction of oral tolerance using an M cell-targeting protein antigen delivery system was examined. Mice were fed different doses of (1) a recombinant protein sigma one (pσ1) of reovirus genetically conjugated to ovalbumin (OVA-pσ1) described herein or (2) PBS prior to oral challenge with OVA plus cholera toxin as mucosal adjuvant. A low dose of OVA-pσ1 reduced anti-OVA antibody and CD4-positive (CD4⁺) T cell responses in both mucosal and systemic lymphoid tissues. OVA/MHC II-A^dtetramer staining revealed that the numbers of OVA-specific CD4⁺ T cells were significantly more reduced in the small intestinal lamina propria (iLP) of mice fed OVA-pσ1 than of those fed PBS, while no significant difference was seen for the spleen. The spleen of orally tolerized mice showed an increased frequency of CD25⁺, CD4⁺ T cells with TGF-β1 production. These results show that mucosal and systemic unresponsiveness are regulated by distinct T cell subsets.

Mice

BALB/c mice were purchased from the Frederick Cancer Research facility (Frederick, Md.). Mice were housed in microisolators, maintained in horizontal laminar flow cabinets, and provided sterile food and water as part of a specific-pathogen-free facility in the Immunobiology Vaccine Center at the University of Alabama at Birmingham. The health of the mice was monitored by both serology for bacterial and viral pathogens and immunohistology. All of the mice used in these experiments were free of bacterial and viral pathogens.

Construction of OVA-pσ1 for M Cell Targeting

PCR was used to obtain the cloned pσ1 cDNA from reovirus serotype 3 strain Dearing as previously described (Wu et al., Gene Ther. 7:61-69, 2000). Ovalbumin (OVA) was genetically fused to pσ1's N-terminus and is referred to as OVA-pσ1. The OVA-pσ1 was produced using a Pichia pastoris yeast expression system as a his-tag labeled protein.

Oral Immunization

Mice were gastrically intubated with different doses of OVA-pσ1 dissolved in 0.25 ml of PBS. Control mice received PBS only. Seven days later, mice were orally immunized with 1 mg of OVA plus 15 μg of CT three times at weekly intervals (Kato et al., J. Immunol. 166:3114-3121, 2001). OVA-specific T and B cell responses were determined seven days after the last immunization (Kato et al., J. Immunol. 166:3114-3121, 2001).

OVA-specific Antibody Assays

OVA-specific antibody (Ab) levels in plasma and mucosal secretions were determined by an ELISA as previously described (Kato et al., J. Immunol. 166:3114-3121, 2001; Kato et al., Int. Immunol. 15:145-158, 2003; Fujihashi et al., Proc. Natl. Acad. Sci. (USA) 98:3310-3315, 2001; Hagiwara et al., J. Immunol. 170:1754-1762, 2003; Kataoka et al., J. Immunol. 172:3612-3619, 2004). Briefly, 96-well FALCON™ microtest assay plates (BD BioSciences, Oxnard, Calif.) were coated with one mg/ml of OVA in PBS. After blocking with 1% BSA in PBS, two-fold serial dilutions of samples were added to each well. Following incubation overnight at 4° C., horseradish peroxidase (HRP)-labeled goat anti-mouse μ, γ or α heavy chain-specific Abs (Southern Biotechnology Associates (SBA), Birmingham, Ala.) were added to wells. The color reaction was developed for fifteen min at room temperature with 100 μl of 1.1 mM 2, 2′-azino bis (3-ethylbenz-thiazoline-6-sulfonic acid) in 0.1 M citrate phosphate buffer (pH 4.2) containing 0.01% H₂O₂. Endpoint titers were expressed as the reciprocal log₂of the last dilution that gave an optical density at 415 nm of 0.1 greater than background.

Lymphoid Cell Isolation and Enumeration of Ab-forming Cells

The spleen and MLNs were removed aseptically and single-cell suspensions prepared in RPMI 1640 (Cellgro Mediatech, Washington, D.C.) containing HEPES buffer, non-essential amino acids, sodium pyruvate, L-glutamine, penicillin, streptomycin and gentamycin (incomplete medium) by passage through sterile wire mesh screens as described previously (Kato et al., J. Immunol. 166:3114-3121, 2001; Fujihashi et al., Proc. Natl. Acad. Sci. (USA) 98:3310-3315, 2001). Peyer's patches (PPs) were carefully excised from the small intestinal wall and dissociated using the neutral protease enzyme collagenase type IV (Sigma) in incomplete RPMI 1640 to obtain single-cell preparations (Kato et al., J. Immunol. 166:3114-3121, 2001, Kato et al., Int. Immunol. 15:145-158, 2003). Mononuclear cells in the iLP were isolated after removal of PP and intraepithelial lymphocytes from the small intestine using a combination of enzymatic dissociation and discontinuous PERCOLL™ density gradients (Pharmacia Fine Chemicals, Uppsala, Sweden). Mononuclear cells in the interface between the 40% and 75% layers were removed, washed and resuspended in RPMI 1640 containing 10% FCS (complete RPMI 1640) (Kato et al., J. Immunol. 166:3114-3121, 2001; Fujihashi et al., Proc. Natl. Acad. Sci. (USA) 98:3310-3315, 2001). Mononuclear cells obtained from mucosal and systemic lymphoid tissues were subjected to an ELISPOT assay in order to detect numbers of OVA-specific Ab-forming cells (AFCs) (Kato et al., J. Immunol. 166:3114-3121, 2001; Kato et al., Int. Immunol. 15:145-158, 2003; Fujihashi et al., Proc. Natl. Acad. Sci. (USA) 98:3310-3315, 2001; Fujihashi et al., J. Exp. Med. 183:1929-1935, 1996; Hagiwara et al., J. Immunol. 170:1754-1762, 2003; Kataoka et al., J. Immunol. 172:3612-3619, 2004). Briefly, 96-well nitrocellulose plates (Millititer HA; Millipore, Bedford, Mass.) were coated with one mg/ml of OVA for analysis of anti-OVA-specific AFCs. The numbers of OVA-specific AFCs were quantified using an IMMUNOSPOT® spot analyzer Analyzer (Cellular Technology Ltd., Cleveland, Ohio) (Hagiwara et al., J. Immunol. 170:1754-1762, 2003; Kataoka et al., J. Immunol. 172:3612-3619, 2004).

Delayed Type Hypersensitivity (DTH) Responses

OVA-specific DTH responses were measured 7 days after the last oral challenge with OVA plus CT, as described above. Briefly, PBS (20 μl) containing 10 μg of OVA was injected into the left ear pinna of mice while the right ear pinna received a PBS control injection (Kato et al., J. Immunol. 166:3114-3121, 2001; Fujihashi et al., Acta. Odontol. Scand. 59:301-308, 2001; Kato et al., Int. Immunol. 15:145-158, 2003). Ear swelling was measured 24 hours later with a dial thickness gauge (Ozaki Manufacturing Co., Ltd., Tokyo, Japan). The DTH response was expressed as the increase in ear swelling after OVA injection minus the swelling in the PBS-injected control site.

Ag-specific T Cell Responses

CD4⁺ T cells from spleen, MLNs, and PPs were purified by use of an automated magnetic activated cell sorter (AUTOMACS™) system (Miltenyi Biotec, Auburn, Calif.), as described previously (Hagiwara et al., J. Immunol. 170:1754-1762, 2003; Kataoka et al., J. Immunol. 172:3612-3619, 2004). Briefly, a nylon wool column of an enriched T cell fraction was incubated with biotinylated anti-CD4 mAb (GK 1.5) (BD PharMingen) followed by streptavidin-conjugated microbeads and sorted to purity with the AUTOMACS™. This purified T cell fraction was >97% CD4⁺ and the cells were >99% viable. The purified CD4⁺ T cell fraction was then resuspended in complete RPMI 1640 (4×10⁶cells/ml) and cultured in the presence of one mg/ml OVA of cultures of T cell-depleted, irradiated (3000 rad) splenic antigen-presenting cells taken from non-immunized, normal mice. To assess OVA-specific T cell proliferative responses, an aliquot of 0.5 μCi of tritiated [³H]-TdR (Amersham Biosciences, Arlington Heights, Ill.) was added during the final 18 hour of incubation, and the amount of [³H]-TdR incorporation was determined by scintillation counting. The supernatants of identically treated T cell cultures not incubated with [³H]-TdR were then subjected to a cytokine-specific ELISA as described below.

Cytokine-Specific ELISA

Levels of cytokines in culture supernatants were measured by an ELISA. The details of the ELISA for IFN-β, IL-2, IL-4, IL-5, IL-6 and IL-10 have been described previously (Kato et al., J. Immunol. 166:3114-3121, 2001; Kato et al., Int. Immunol. 15:145-158, 2003; Fujihashi et al., Proc. Natl. Acad. Sci. (USA) 98:3310-3315, 2001; Hagiwara et al., J. Immunol. 170:1754-1762, 2003; Kataoka et al., J. Immunol. 172:3612-3619, 2004). The following were used as coating and detection mAbs, respectively: anti-IFN-β: R4-6A2 and XMG 1.2 mAbs; anti-IL-2: JES6-1A12 and JES6-5H4 mAbs; anti-IL-4: BVD4-1D11 and BVD6-24G2 mAbs; anti-IL-5: TRFK-5 and TRFK-4 mAbs; anti-IL-6: MP5-20F3 and MP5-32C11 mAbs; and anti-IL-10: JES5-2A5 and JES5-16E3 mAbs. A mouse TGF-β1 immunoassay kit, QUANTIKINE™(R & D systems, Minneapolis, Minn.), was used to detect TGF-β1 in the culture supernatants. The levels of Ag-specific cytokine production were calculated by subtracting the results of control cultures (e.g., without Ag stimulation) from those of Ag-stimulated cultures. This ELISA was capable of detecting 0.8 ng/ml of IFN-β; 0.4 U/ml of IL-2; 25 pg/ml of IL-4; 0.8 U/ml of IL-5; 200 pg/ml of IL-6; 4 pg/ml of IL-10; and 4 pg/ml of TGF-β1.

Flow Cytometry Sorting and Analysis

In order to determine the frequencies of OVA-specific CD4⁺ T cells, mononuclear cells from spleen, MLNs, PPs and iLP were stained with FITC-conjugated anti-CD4 (GK1.5), biotinylated anti-CD25 (7D4) mAb and PE-labeled OVA/MHC II-A^dtetramer followed by Cy5.5-streptavidin before being subjected to flow cytometric analysis. For intracellular IL-10 analysis, cells were incubated with ionomycin (1 μg/ml, SIGMA, St. Louis, Mo.) and phorbol 12-myristate 13-acetate (PMA, 25 ng/ml, SIGMA) for 6 hours and then stained with PE-labeled anti-CD4, biotinylated anti-CD25 mAbs followed by Cy5.5-streptavidin. These samples were further stained intra-cellularly with ALEXA FLUOR® 488 labeled anti-IL-10 mAb (JES5-16E3). In some experiments, cells were stained with FITC-labeled anti-CD4 and biotinylated anti-CD25 mAb followed by PE-streptavidin. CD4⁺ CD25⁺ T cells were purified by flow cytometry and their TGF-β1 production was determined as described above.

Statistics

The significance of the difference (e.g., p values) among groups was evaluated by the Mann Whitney U test using a Statview II program designed for Macintosh computers.

Optimization of Oral Doses of OVA-pσ1

Since it has been shown that pσ1 can bind to mucosal M cells (Wu et al., Proc. Natl. Acad. Sci. (USA) 98:9318-9323, 2001), it can be hypothesized that oral tolerance can be effectively achieved by OVA-pσ1. To test this notion, mice were gastrically intubated with different doses of OVA-pσ1. Mice were fed one dose of either 100 μg, 500 μg or 1000 μg of OVA-pσ1. An additional group of mice was given three daily doses of 100 μg of oral OVA-pσ1. Seven days later, all groups of mice were challenged once a week for three weeks with oral OVA plus CT. OVA-specific plasma IgG Ab titers were not markedly reduced in mice given three weekly doses of 100 μg of OVA-pσ1 (FIG. 1). On the other hand, they were significantly more reduced in all other single OVA-pσ1 treatment groups than in mice fed PBS (FIG. 1). Further, OVA-specific plasma IgA and mucosal S-IgA Ab responses in mouse groups receiving one feeding of OVA-pσ1 were markedly lower than in the positive control group (PBS-fed mice) (FIG. 1). These results show that a single oral dose of OVA-pσ1 effectively induces both systemic and mucosal unresponsiveness to OVA. Based upon these results, we next employed a single oral dose of 100 μg of OVA-pσ1 for further experiments.

Oral OVA-pσ1 Facilitates Both Systemic and Mucosal Unresponsiveness

To further confirm these findings at the cellular level, the numbers of OVA-specific Ab-forming cells (AFCs) were examined in various lymphoid tissues of mice given oral OVA-pσ1 or PBS. Numbers of OVA-specific IgG and IgA AFCs in spleen and mesenteric lymph nodes (MLNs) were reduced significantly (p<0.05) in the oral pσ1-group but not in the oral PBS-Group (FIG. 2), showing that oral tolerance is indeed induced by feeding 100 μg of OVA-pσ1. In order to assess induction of unresponsiveness in mucosal effector sites, the numbers of OVA-specific AFCs in iLP were compared in groups fed PVA-pσ1 or PBS. The number of anti-OVA IgA AFCs was reduced in the pσ1—but not the PBS-fed group (FIG. 2). These results suggest that M cell targeting by OVA-pσ1 effectively induces mucosal tolerance and may contribute to the maintenance of mucosal homeostasis.

DTH and CD4⁺ T Cell Proliferative Responses

Whether tolerance was induced at the T cell level after a single oral dose of OVA-pσ1 was next determined. OVA-specific delayed-type hypersensitivity (DTH) responses were assessed in mice given either OVA-pσ1 or PBS orally. OVA-specific DTH responses were much more pronounced in the pσ1-group than in the PBS group (FIG. 3A), showing that OVA-specific T cell responses were tolerized by a single low dose of OVA-pσ1. Using the described oral challenge system, which allows examination of CD4⁺ T cell responses in mucosal lymphoid tissues, CD4⁺ T cell proliferative responses were next examined in both mucosal (MLNs and PPs) and systemic (spleen) compartments of mice given oral OVA-pσ1. The CD4⁺ T cells from spleen, PPs, and MLNs were purified by use of an automated magnetic-activated cell sorter (AUTOMACS™) system. These purified CD4⁺ T cell fractions were cultured with or without one mg/ml of OVA in the presence of T cell-depleted, irradiated splenic APCs taken from non-immunized, normal mice. Significant reductions in T cell proliferative responses were seen in the spleen, MLNs and PPs of the OVA-pσ1—but not the PBS-fed group (FIG. 3B). These results show that T cell unresponsiveness was initiated in mucosal inductive tissues such as the PPs, by M cell targeting of OVA-pσ1. Subsequently, these tolerized CD4⁺ T cells migrated into the spleen via the MLNs.

Cytokine Production by OVA-Stimulated CD4⁺ T Cells

Since T cell unresponsiveness was induced in both systemic and mucosal lymphoid tissues by a single oral dose of OVA-pσ1, Th1- and Th2-type cytokine production by OVA-stimulated CD4⁺ T cells was examined. Purified CD4⁺ T cells from the spleen and PPs of mice fed OVA or PBS were incubated with or without 1 mg of OVA in the presence of autologous APCs for five days. When the culture supernatants were harvested and examined by cytokine-specific ELISA, OVA-pσ1-fed mice showed reduced CD4⁺ Th1 (IFN-γ and IL-2) and Th2 (IL-4, IL-5, IL-6 and IL-10) cytokine responses, while mice fed oral PBS showed high levels of Th2-type cytokines, especially IL-4 and IL-10 (Table 1). A virtually identical profile of up-regulation of Th2-type cytokine synthesis was seen in the spleen of mice following oral administration of PBS. On the other hand, a hyporesponsive Th1- and Th2-type cytokine profile was noted in both PPs and spleen of mice fed OVA-pσ1 before being orally challenged with OVA plus CT (Table 1). Taken together, these results indicate that CD4⁺ T cell unresponsiveness was induced in both spleen and PPs by a single oral dose of OVA-pσ1.

In order to examine the role of OVA-specific CD4⁺ T cells in oral tolerance, mononuclear cells from spleen, PPs, MLNs and iLP were isolated one week after the last immunization and stained with FITC-conjugated anti-CD4, biotin-conjugated anti-CD25 mAbs and PE-labeled OVA/II-A^dtetramer followed by Cy5.5-streptavidin. This analysis revealed a lower frequency of tetramer⁺ OVA-specific CD4⁺ T cells in iLPs of mice given OVA-pσ1 prior to oral challenge with OVA plus CT than in mice given oral PBS (FIG. 4 and Table 2). Numbers of OVA-specific CD4⁺ T cells were reduced in PPs and MLNs of mice given oral PVA-pσ1 (Table 2), but remained essentially the same in the spleen of orally tolerized mice and of those exhibiting high OVA-specific Ab titers (Table 2). When CD25 expression on tetramer⁺ OVA-specific CD4⁺ T cells was examined, the frequency of CD4⁺ CD25⁺ T cells was found to be significantly decreased in iLP of orally tolerized mice (Table 2). In addition, the numbers of tetramer⁺ OVA-specific CD4⁺ CD25⁻ T cells in spleen, MLNs, PPs and iLP were also significantly reduced. Among these lymphoid tissues, marked reductions in OVA-specific CD4⁺ CD25⁻ T cells were seen in the iLP of orally tolerized mice (Table 2). On the other hand, increased numbers of CD4⁺ CD25⁺ T cells, especially of the OVA/II-A^dtetramer negative subset, were noted in spleen and MLNs of mice give oral PVA-pσ1 before mucosal challenge with OVA plus CT (Table 2). These results suggest that mucosal unresponsiveness to orally delivered Ag is most likely due to the reduced numbers of OVA-specific CD4⁺ T cells in the iLP (clonal deletion), a mechanism that is entirely distinct from the systemic unresponsiveness induced by active suppression by CD4⁺ CD25⁺ Treg cells.

The increased frequency of CD4⁺ CD25⁺ T cells in spleen and MLNs suggested the possibility that CD4⁺ Treg cells are induced when mice are fed OVA-pσ1 and then mucosally challenged with OVA plus CT as mucosal adjuvant. To test this possibility, we examined the production of IL-10 and TGF-β1 by CD4⁺ CD25⁺ T cells. Flow cytometry-purified CD4⁺ CD25⁺ T cells from PPs, spleen and MLNs of mice fed OVA-pσ1 or PBS were stimulated with OVA for 5 days. The culture supernatants of CD4⁺ CD25⁺ T cells from orally tolerized mice contained higher levels of TGF-β1 than did those from PBS-fed mice (FIG. 5A). Intracellular IL-10 analysis was performed to determine the extent of IL-10 production by CD4⁺ CD25⁺ Treg cells in spleen and MLNs of orally tolerized mice. Flow cytometric analysis revealed fewer IL-10-producing CD4⁺ CD25⁺ T cells in mice fed OVA-pσ1 than in mice fed PBS (FIG. 5B). These results demonstrate that TGFβ1-producing CD4⁺ Treg cells were induced in the MLNs and spleen of mice fed OVA-pσ1.

The current study shows that the OVA-pσ1 M cell-targeting delivery system facilitates the induction of oral tolerance. Mucosal and systemic unresponsiveness can be induced with a single oral dose of 100 μg of OVA-pσ1 instead of the repeated low doses of oral OVA that would otherwise be required. OVA-specific mucosal S-IgA and plasma IgG Ab responses as well as DTH and T cell proliferative responses were all reduced significantly in OVA-pσ1—but not in PBS-fed mice. Further, OVA-stimulated CD4⁺ T cells from spleen and PPs of orally tolerized mice showed much more marked reduction in the levels of both Th1- and Th2-type cytokine production than did those fed PBS before being orally challenged with OVA plus CT as adjuvant. The use of OVA/MHC II-A^dtetramer staining revealed significantly reduced numbers of OVA-specific CD4⁺ T cells in iLP of mice fed OVA-pσ1. On the other hand, the numbers of TGF-β1-producing CD4⁺ CD25⁺ T cells were higher in the MLNs and spleen of orally tolerized mice than in the control group. These results show that the M cell-targeting Ag delivery by OVA-pσ1 feeding effectively induces mucosal and systemic unresponsiveness. Of key importance is the finding that the mechanisms regulating tolerance in mucosal and peripheral lymphoid tissues are distinct.

The M cells are known to take up and transport lumenal Ags, including proteins, viruses, bacteria, small parasites, and microspheres (Ermak et al., Cell Tissue Res. 279:433-436, 1995; Neutra et al., Cell 86:345-348, 1996; Gebert et al., Int. Rev. Cytol. 167:91-159, 1996; Wolf & Bye, Annu. Rev. Med. 35:95-112, 1984). M cells have then been shown to deliver the intact Ag into underlying lymphoid tissue of the GALT (Gebert et al., Int. Rev. Cytol. 167:91-159, 1996; Wolf & Bye, Annu. Rev. Med. 35:95-112, 1984). M cells are also thought to be involved in Ag processing and presentation, since the GALT M cells express MHC class II molecules and acidic endosomal-lysosomal compartments (Allan et al., Gastroenterology 104:698-708, 1993). In addition to serving as a means of transport for lumenal Ags, the M cells also provide an entryway for pathogens. For example, invasive strains of Salmonella typhimurium initiate murine infection by invading the M cells of the PPs (Jones et al., J. Exp. Med. 180:15-23, 1994). Based upon these findings, M cell-targeting Ag delivery could be assumed to be the normal pathway for induction of Ag-specific immune responses. Indeed, NALT M cell targeting a DNA vaccine constructed with pσ1 elicited Ag-specific IgG and S-IgA Ab responses (Wu et al., Proc. Natl. Acad. Sci. (USA) 98:9318-9323, 2001). However, our current study has now shown that oral administration of OVA-pσ1 facilitates unresponsiveness to OVA in both systemic and mucosal lymphoid tissues instead of inducting OVA-specific immunity. These opposite outcomes can be partially explained by the nature of the Ag. Ovalbumin is only weakly immunogenic and always requires an adjuvant for induction of immune responses. In contrast, cytomegalovirus plasmid DNA (pCMV), a known ligand for toll-like receptor 9, is recognized by IFN-γ producing cells and dendritic cells (Krug et al., Immunity 21:107-119, 2004) and most likely induces innate and acquired immunity. Indeed, although M cells are able to transport lumenal Ags, noninvasive strains of S. typhimurium cannot penetrate M cells and are avirulent (Jones et al., J. Exp. Med. 180:15-23, 1994). An antigen's immunogenicity and pathogenicity in the GI tract could be the most critical factors in determining whether mucosal immunity or tolerance is induced.

Mucosal tolerance may be the most common immune response because it is necessary to maintain homeostasis. The normal host would readily establish unresponsiveness to commensal bacteria, food Ag and allergens. Taken together, we conclude that our OVA-pσ1 system, M cell targeting of a non-pathogenic protein Ag is an efficient strategy for the establishment of oral tolerance.

Results provided herein clearly show that M cell targeting Ag delivery system reduced the doses of feeding Ag in order to establish oral tolerance. Similar findings were reported using Ag conjugated with B subunit of CT (CT-B) (Sun et al., Proc. Natl. Acad. Sci. (USA) 91:10795-10799, 1994). That study showed that a single oral administration of relatively small amounts of particulate or soluble antigen coupled to the CT-B markedly suppressed systemic immune responses (Sun et al., Proc. Natl Acad. Sci. (USA) 91:10795-10799, 1994). Since CT-B specifically bind to GM-1 ganglioside which abundantly expressed by intestinal epithelial cells (iECs) including M cells, it still remained unclear which of iECs or M cells play a significant role in the induction of oral tolerance. The findings reported herein showed that induction of oral tolerance can be easily achieved by M cell targeting Ag delivery system most likely without Ag uptake from iECs. Recent studies showed that M cells are present in the small intestine of isolated lymphoid follicles (ILFs) as well as intestinal villi (villous M cells) (Hamada et al., J. Immunol 168:57-64, 2002; Jang et al., Proc. Natl. Acad. Sci. (USA) 101:6110-6115, 2004). Role(s) of M cells in these newly identified GALT in the induction of oral tolerance are being investigated.

Flow cytometric analysis revealed increased numbers of CD4⁺ CD25⁺ T cells in MLNs and spleen of orally tolerized mice, suggesting feeding with OVA-pσ1 induced production of Treg cells. Along this line, a recent study reported that PP-derived Treg clones produce high levels of TGF-β1 and suppressed Ag-specific Ab responses in spleen (Tsuji et al., Int. Immunol. 15:525-534, 2003). Based upon these findings, our group examined TGF-pβ1 and IL-10 production by OVA-specific CD4⁺ T cells from mice fed OVA-pσ1 prior to oral challenge with OVA plus CT. Our results clearly show that CD4⁺ CD25⁺ T cells in PPs, MLNs and spleen from orally tolerized mice produce higher levels of TGF-β1 after OVA stimulation than do those from mice fed PBS. On the other hand, intracellular IL-10 production by CD4⁺ CD25⁺ T cells from mice fed OVA-pσ1 was significantly reduced. Taken together with the observation that acquired-type CD4⁺ Treg cells are Ag-specific and produce inhibitory cytokines including TGF-β1 and IL-10 (Cottrez & Groux, Transplantation 77:S12-15, 2004), our results indicate that acquired-type CD4⁺ Treg cells are induced by oral administration of OVA-pσ1.

OVA-specific CD4⁺ T cells were significantly more reduced in the iLP of orally tolerized mice than in PBS-fed mice challenged with oral OVA plus CT, but no such reduction was seen in spleen or MLNs of either group. Similarly, others showed that a reduction of Ag-specific T cells occurred in mice given repeated low doses of cytochrome c protein (Gutgemann et al., Immunity 8:667-673, 1998). In contrast, the spleen of orally tolerized mice exhibited increased numbers of CD4⁺ CD25⁺ T cells and the presence of TGF-β1-producing CD4⁺ CD25⁺ T cells. Based upon these findings, it appears likely that mechanisms for the induction of mucosal and systemic unresponsiveness differ. Thus, mucosal unresponsiveness is clearly associated with clonal deletion of OVA-specific effector CD4⁺ T cells while systemic unresponsiveness may be achieved by active suppression of an acquired type of Treg cells. These findings are the first to show that two separate mechanisms underlie mucosal unresponsiveness and that they are entirely distinct from those which underlie systemic unresponsiveness.

It still remains unclear how this clonal deletion of OVA-specific CD4⁺ T cells actually occurs since CD4⁺ CD25⁺ T cells are also reduced significantly in the iLP of orally tolerized mice. However, one can hypothesize that the numbers of OVA-specific CD4⁺ T cells and AFC in iLP are reduced simply because OVA-specific CD4⁺ T cell migration into the iLP has been interrupted. Thus, effector CD4⁺ Th cells could be suppressed by PP-derived TGF-β1-producing CD25⁺ Treg cells in the MLNs and spleen before reaching the iLP. To support this view, our previous results showed that induction of Ag-specific Ab responses in the iLPs required three consecutive weekly oral immunizations (Kato et al., J Immunol. 166:3114-3121, 2001; Fujihashi et al., J. Exp. Med. 183:1929-1935, 1996). We are currently testing this notion using a nasal challenge system in order to better distinguish between OVA-specific CD4⁺ effector T cell and CD4⁺ Treg cell activities.

In summary, this example provides the first evidence that M cell targeting of a non-pathogenic Ag OVA-pσ1 can induce mucosal unresponsiveness via a mechanism distinct from that underlying systemic tolerance. This M cell-targeting system allowed us to elucidate the immunoregulatory mechanisms of the PP-mediated oral tolerance pathway from other potential mechanisms. Thus, these findings show that regulatory-type CD4⁺ T cells are induced in the PP and then migrate into MLNs and spleen. These CD4⁺ Treg cells contribute to the successful systemic unresponsive state that ensues. Further, these results clearly show that mucosal unresponsiveness to orally administered Ag can be attributed to a lack of Ag-specific CD4⁺ T helper cells in the iLP.

Nasal Tolerance

From the literature, it has been shown that reovirus type 3 protein sigma 1 (pσ1) is a highly structured protein featuring several domains, which mediate a multi-step interaction between the virus and the host cell (Barton et al., J. Biol. Chem. 276:2200-2211, 2000; FIG. 6). It has been shown that type 3 pσ1 interacts with at least two host receptors via separate binding domains. The head domain binds with a component of tight junctions, JAM-1 molecule, whereas sequences contained within the fibrous tail domain binds terminal α-linked sialic acid residues on host cells (Barton et al., J. Biol. Chem. 276:2200-2211, 2000; Chappell et al., J. Virol. 71:1834, 1997). To determine the relevant binding components of our recombinant pσ1 and OVA-σ1, additional constructs or variants were made and expressed in yeast (FIG. 6).

To determine the role of pσ1's sialic binding domain (SABD), a pσ1(m) construct was made in which the mutations N198→D198 and R202→G202 were introduced to interrupt the SABD's binding activity. In addition, OVA was genetically fused to pσ1(m) and called OVA-pσ1(m). Genetic fusions of OVA are all placed at the N-terminus of pσ1 so as to not interfere with the host receptor binding domains located in the pσ1's C-terminus. Thus, if sialic acid binding dictates mediation of tolerance by pad, then the loss of sialic acid binding should confer immunization. In a similar fashion, the complete removal of pσ1's SABD should do the same, and this variant, OVA-pσ1(Δ), which encompasses the OVA gene fused to the last 207 amino acids of pσ1 renders only a functional trimerizing domain and head (FIG. 6). Each of the OVA fusion proteins featured a flexible linker between the fusion partners.

Siatic Acid Binding is Important For Tolerance Induction by Pσ1

To determine the functional consequence of sialic acid binding by OVA-pσ1, groups of C57BL/6 mice were given three nasal immunizations on days 0, 7, and 14 in combination with the mucosal adjuvant, cholera toxin (CT), and one of three antigens, OVA-σ1, OVA-pσ1(Δ), or OVA or given OVA without CT. Again, OVA-pσ1(Δ) is a truncated OVA-σ1 lacking its SABD and shaft (FIG. 6). To test for a delayed-type hypersensitivity (DTH) reaction, mice were challenged after 42 days with OVA into one ear pinna and PBS into the other ear pinna. Mice immunized with OVA alone or OVA-σ1+CT failed to show swelling in the OVA-challenged ear when compared to mice immunized with OVA+CT (P<0.001) or OVA-pσ1(Δ)+CT (P=0.002) (FIG. 7). Thus, the OVA-pσ1(Δ), which lacked the SABD, behaved more as an immunogen in contrast to OVA-pσ1, which behaved as a toleragen. This collective evidence suggested that the presence of the SABD on pσ1 was required for tolerance induction, whereas, in its absence, clearly immunization occurred.

Adoptive Transfer of CD4⁺ T Cells into Naive Mice Are Unresponsive to OVA Challenge

To test whether nasal exposure to OVA-σ1 could make CD4⁺ T cells unresponsive to OVA and effectively adoptively transfer these T cells, the transgenic DO 11.10 CD4⁺ T cells were isolated from spleen and lymph nodes by cell-sorting, and adoptively transferred into naive BALB/c mice. After 24 hours, groups of mice were dosed nasally with PBS, 80 μg OVA-σ1, or 400 μg OVA, or given a single i.m. OVA immunization. Three days later, cervical lymph nodes (CLN) were removed and CD4⁺ T cells were isolated by cell-sorting. These CLN CD4⁺ T cells (2×10⁶/mouse) were adoptively transferred into naive mice, and after 24 hrs, they were challenged s.c. with OVA in incomplete Freund's adjuvant. Five days later, CD4⁺ T cells from the head and neck LN (HNLN) were isolated by cell-sorting and cultured with mitomycin C-treated feeder cells without and with 1.0 mg OVA for 5 days.³H-TdR was used to measure T cell proliferation. Mice were made unresponsive by the nasal 400 μg OVA or the 80 μg OVA-σ1 since these did not proliferate (FIG. 8). In contrast, the CD4⁺ T cells isolated from the i.m. OVA-dosed mice were responsive. Thus, dosing i.n. with OVA-σ1 can make mice unresponsive to OVA, and this unresponsiveness is mediated by CD4⁺ T cells specific for OVA. Moreover, this unresponsiveness can be adoptively transferred with CD4⁺ T cells.

OVA-pσ1 Can Be Modified With Encephalitogenic Peptides to Render Protection Against Experimental Autoimmune Encephalitis (EAE) Challenge

Thus far, we showed the feasibility of inducing tolerance against OVA, a familiar antigen frequently used in experimental systems. To forward efforts to treating autoimmune diseases, we adapted the OVA-σ1 fusion protein with peptides known to cause autoimmune disease. We hypothesized that genetic fusion of encephalitogenic peptides to OVA-σ1 should induce tolerance as shown with our studies using OVA as a test antigen. OVA-σ1 was modified because we could then follow unresponsiveness to OVA as an internal control for our studies. Thus, this modified OVA-σ1 construct, termed AR1, was made with two copies of the encephalitogenic peptide from proteolipid protein (PLP), PLP_139-151, separated by an irrelevant peptide (MOG_35-55) (FIG. 9A). C57BL/6 mice were dosed thrice with AR1, and they did not generate IgG or IgA anti-OVA Abs when compared to OVA+CT-dosed mice (FIG. 9B-D). Subsequent to i.n. challenge with OVA+CT and then tested for a DTH response, no DTH reactions were detected when compared to OVA+CT-dosed mice (FIG. 9E). A separate group of mice also was orally fed AR1 and peripherally challenged with OVA+CT, and these too were unresponsive in this DTH assay. Thus, the modification of OVA-σ1 with encephalitogenic peptides did not interfere with its ability to elicit OVA tolerance.

To test whether tolerance to the fused encephalitogenic peptides was induced by evaluating the efficacy of AR1 against PLP_139-151challenge, SJL/J mice were nasally given AR1 as described in FIG. 9. For a positive oral tolerance control group, myelin basic protein was given seven times every 2 days over a 2-wk course. As a negative control group, mice were dosed with PBS. Three wks after the onset of treatments, mice were challenged s.c. with emulsified PLP_139-151following standard protocols, and pertussis toxin (PT) was given i.p. A second PT dose was given two days later. Following this challenge protocol, mice typically show clinical disease beginning ˜9 days. The AR1 protected against EAE as evidenced by reduced clinical disease (FIG. 10A).

In addition, C57BL/6 mice were nasally dosed with 50 μg myelin oligodendrocyte glycoprotein_29-146genetically fused to pσ1 (MOG-pσ1) or to OVA-σ1 (MOG:OVA-pσ1) three times at weekly intervals, and then one week after the last i.n. dose, mice were challenged s.c. with 150 μg MOG_35-33on day 0 and 7 of challenge, and given i.v. PT on days 0 and 2. Both the MOG-pσ1 (n=5) and MOG;OVA-σ1 (n=5) protected mice (p<0.001) when compared to PBS-dosed mice (n=5) (FIG. 10B).

Protection against PLP_139-151challenge is attributed to the stimulation of the regulatory cytokines, IL-4, IL-10, and TGF-β. SJL mice were dosed with Ar1, OVA-σ1, or PBS as described for FIG. 9. Mice were then challenged with PLP_139-151peptide as described for FIG. 10. HNLN, spleens, and MLN were harvested at peak of disease (day 14) and purified CD4⁺ T cells were restimulated with PLP_139-151peptide for two days, and evaluated in a cytokine ELISPOT. PBS- and OVA-pσ1-dosed (unprotected mice) showed elevated (FIG. 11A) IFN-γ and (FIG. 11B) IL-17 cytokine-forming cells (CFC), and no (FIG. 11C) IL-4, (FIG. 11D) IL-10, or (FIG. 11E) TGF-β CFC. In contrast, AR1-dosed (tolerized) mice showed elevated IL-4, IL-10, and TGF-β CFC and no IFN-γ or IL-17 CFC. Thus, only AR1 mice were protected against challenge, and tolerance induced to irrelevant protein (OVA-pσ1) did confer protection.

It was also determined that single nasal or oral dose with MOG-pσ1 protects C57BL/6 mice against challenge with MOG_35-55. Mice (5/group) were dosed once (FIG. 12A) nasally or (FIG. 12B) orally with 10, 50, or 100 μg of MOG_29-146-pσ1 (MOG-pσ1) or with PBS, and 10 days later challenged with MOG_35-55per description for FIG. 10. In a dose-dependent fashion, protection against autoimmune challenge showed protection, but the 50 μg dose conferred the best protection with no disease, while minimal disease was observed at the 10 or 100 μg doses. Thus, pσ1 delivery in the form of a fusion protein is an effective means to deliver auto-antigens to the mucosa for the development of tolerance to self antigens.

To test whether pσ1-mediated treatment could be therapeutic, a study was performed using MOG-pσ1 to stop further development of EAE. Four groups (5/group) of mice were induced with EAE as described in FIG. 10B. Then, groups were treated with MOG-pσ1 or PBS on day 7 or groups were treated with MOG-pσ1 or PBS on day 10 and 17. Results are shown in FIG. 13. Treatment with MOG-pσ1 demonstrated that protection against further disease development can be conferred suggesting that pσ1-delivered toleragens can treat autoimmune diseases.

Studies to date have mostly relied upon oral exposure to induce tolerance (Fujihashi et al., Acta. Odontol Scand. 59:301-308, 2001; Mowat, Nature Rev. Immunol. 3:331-341, 2003; Weiner, Microbes & Infection 3:947-954, 2001) whereas most recently, studies have addressed the potential of adapting i.n. delivery (Collins et al., Infect. Immun. 70:2282-2287, 2002; Monfardini et al., J. Neuroimmunol. 123:123-134, 2002; Winkler et al., Clin. Exp. Allergy. 32:30-36, 2002). The i.n. route clearly has a number of advantages, including less antigen dose required, not subjecting the toleragen to alteration by the GI tract, and ease of delivery. In addition to considering route of delivery, efficient targeting of toleragens to mucosal inductive tissues could reduce the amount of material needed for stimulation of tolerance regardless the route of delivery.

A particular strength of the system described herein is that it can be applied to any number of toleragens that could be successfully fused to pσ1, or another mucosal binding molecule as provided herein. Without meaning to be limited to a single explanation, we propose that pσ1 can circumvent the mucosal barrier and promote the uptake of toleragens by the mucosal immune system, whether mediated via M cells, host epithelial cells, or their combination. Ultimately, T cell responsiveness will occur in the mucosal inductive sites or draining mucosal LN. This toleragen delivery platform has promise in that a single oral administration, and in some instances a single nasal application, can elicit tolerance.

In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. We therefore claim as our invention all that comes within the scope and spirit of the description, embodiments of which are described specifically in the following claims.