Patent Publication Number: US-2022211827-A1

Title: Regulatory t cell epitopes, compositions and uses thereof

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/530,104 filed Aug. 2, 2019, which is a continuation of U.S. patent application Ser. No. 14/857,693 (now U.S. Pat. No. 10,213,496) filed Sep. 17, 2015, which is a continuation of U.S. patent application Ser. No. 12/981,098 filed Dec. 29, 2010, which is a divisional of U.S. patent application Ser. No. 12/021,832 filed Jan. 29, 2008, and which claims priority to U.S. Application Ser. No. 60/898,347, filed Jan. 30, 2007, the entirety of each of which is incorporated herein by reference. 
    
    
     SEQUENCE LISTING 
     This application contains a Sequence Listing, which has been submitted in ASCII format via EFS-Web and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Jan. 14, 2022, is named SEQUENCE_LISTING_ST25.txt and is 69,198 bytes in size. 
     FIELD OF THE INVENTION 
     The invention relates generally to a novel class of T cell epitope compositions (termed “Tregitopes”). The invention provides Tregitope compositions, methods for their preparation and use. 
     BACKGROUND 
     Artificial induction of tolerance to self or to foreign antigens is the goal of therapy for autoimmunity, transplantation allergy and other diseases, and is also desirable in the context of therapy with autologous proteins and non-autologous proteins. Until recently, therapeutic tolerance induction relied on broad-based approaches that resulted in cellular depletion and cytokine profile alteration. These broad-based approaches weaken the immune system in general and leave many subjects vulnerable to opportunistic infections, autoimmune attack and cancer. There is a need in the art for less aggressive and more targeted approaches to the induction of immune tolerance. 
     Immune tolerance is regulated by a complex interplay between T cells, B cells, cytokines and surface receptors. Initial self/non-self discrimination occurs in the thymus during neonatal development where medullary epithelial cells express specific self protein epitopes to immature T cells. T cells recognizing self antigens with high affinity are deleted, but autoreactive T cells with moderate affinity sometimes avoid deletion and can be converted to so called ‘natural’ regulatory T cells (T Reg ) cells. These natural T Reg  cells are exported to the periphery and provide for constant suppression of autoimmunity. 
     A second form of tolerance occurs in the periphery where mature T cells are converted to an ‘adaptive’ TR eg  phenotype upon activation via their T cell receptor in the presence of IL-10 and TGF-fl. The possible roles for these ‘adaptive’ T Reg  cells include dampening immune response following the successful clearance of an invading pathogen as a means of controlling excessive inflammation as might be caused by an allergic reaction or low level chronic infection, or possibly to facilitate co-existence with beneficial symbiotic bacteria and viruses. ‘Adaptive’ T Reg  may also play a role in managing the life cycle of human antibodies that have undergone somatic hypermutation. 
     Natural regulatory T cells are a critical component of immune regulation in the periphery. Upon activation through their TCR natural Tregs are capable of suppressing bystander effector T cell responses to unrelated antigens through contact dependent and independent mechanisms. In addition the cytokines released by these cells including IL-10 and TGF-I3, are capable of inducing antigen-specific adaptive Tregs. Despite extensive efforts, with few exceptions, the antigen specificity of natural Tregs, and more importantly natural Tregs circulating in clinically significant volumes, is still unknown. 
     There is need in the art for the identification of regulatory T cell epitopes contained in common autologous proteins such as IgG (“Tregitopes”) and for methods for related to their preparation and of use. 
     SUMMARY 
     The present invention harnesses the functions of regulatory T cells (TRe g ), particularly those cells that already regulate immune responses to foreign and self proteins in the periphery (pre-existing or natural T Reg ). In one aspect, the invention provides T-cell epitope polypeptide compositions. 
     The selective engagement and activation of pre-existing natural Treg through the use of Tregitopes and Tregitope-antigen fusions, is therapeutically valuable as a means of treatment for any disease or condition marked by the presence of an unwanted immune response. Examples include the following: Autoimmune disease such as type 1 diabetes, MS, Lupus, and RA; Transplant related disorders such as Graft vs. Host disease (GVHD); Allergic reactions; Immune rejection of biologic medicines such as monoclonal antibodies, replacement proteins such as FVIII or Insulin, the use of therapeutic toxins such as Botulinum toxin; and the management of immune response to infectious disease whether acute or chronic. 
     In one embodiment, the present invention is directed to a T-cell epitope polypeptide composition comprising at least one polypeptide selected from the group consisting of: SEQ ID NOS:4-58. In a particular embodiment, the invention is directed to a pharmaceutical composition comprising a polypeptide of the invention and a pharmaceutically acceptable carrier. 
     In one embodiment, the present invention is directed to a nucleic acid encoding at least one T-cell epitope polypeptide selected from the group consisting of: SEQ ID NOS:4-58. In a particular embodiment, the invention is directed to a vector comprising a nucleic acid of the invention. In another embodiment, the invention is directed to a cell comprising a vector of the invention. 
     In one embodiment, the invention is directed to a method of treating or preventing a medical condition in a subject in need thereof comprising administering a therapeutically effective amount of a T-cell epitope polypeptide selected from the group consisting of: SEQ ID NOS:4-58. In a particular embodiment, the medical condition is selected from the group consisting of: an allergy, an autoimmune disease, a transplant related disorder, graft versus host disease, an enzyme or protein deficiency disorder, a hemostatic disorder, cancer, infertility; and a viral, bacterial or parasitic infection. 
     In one embodiment, the invention is directed to a kit for preventing or treating a medical condition in a subject, wherein the kit comprises at least one T-cell epitope polypeptide selected from the group consisting of: SEQ ID NOS:4-58. 
     In one embodiment, the present invention is directed to a method for expanding a population of regulatory T cells, comprising: (a) providing a biological sample from a subject; and (b) isolating regulatory T-cells from the biological sample; and contacting the isolated regulatory T-cells with an effective amount of a Tregitope composition of the invention under conditions wherein the T-regulatory cells increase in number to yield an expanded regulatory T-cell composition, thereby expanding the regulatory T-cells in the biological sample. 
     In one embodiment, the present invention is directed to a method for stimulating regulatory T cells in a biological sample, comprising: (a) providing a biological sample from a subject; (b) isolating regulatory T-cells from the biological sample; and contacting the isolated regulatory T-cells with an effective amount of a Tregitope composition of the invention under conditions wherein the T-regulatory cells are stimulated to alter one or more biological function, thereby stimulating the regulatory T-cells in the biological sample. 
     In one embodiment, the present invention is directed to a method for repressing immune response in a subject, comprising administering a composition comprising a therapeutically effective amount of a peptide comprising a Tregitope to the subject, wherein the peptide represses the immune response. In a particular embodiment, the peptide suppresses effector T cell response. In a particular embodiment, the peptide suppresses helper T cell response. In another embodiment, the peptide suppresses B cell response. 
     In one embodiment, the present invention is directed to a method of suppressing antigen specific immune response in a subject through the administration of a therapeutically effective amount of a composition comprising one or more Tregitopes, wherein the one or more Tregitopes are either covalently bound, non-covalently bound or in admixture with a specific target antigen resulting in the diminution of immune response against the target antigen. In a particular embodiment, the suppressive effect is mediated by natural Treg. In another embodiment, the suppressive effect is mediated by adaptive Treg. In another embodiment, the peptide suppresses effector T cell response. In another embodiment, the peptide suppresses helper T cell response. In another embodiment, the peptide suppresses B cell response. In a particular embodiment, the peptide comprises a sequence selected from the group consisting of: SEQ ID NOS:4-58. 
     In one embodiment, the present invention is directed to a method for enhancing the immunogenicity of a vaccine delivery vector, comprising identification and removal of regulatory T cell epitopes. In a particular embodiment, the T cell epitopes are selected from the group consisting of: SEQ ID NOS:4-58. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. 
         FIG. 1  is a schematic diagram of immunoglobulin G (IgG). 
         FIG. 2  is a series of graphical representations comparing capped and uncapped peptides. PBMC were stimulated in culture for 8 days with either CEF (positive control peptide pool) alone (top panels), CEF+ Tregitope 289-amide (middle panels), or CEF+Tregitope-289-uncapped (bottom panels). As compared to incubation with CEF alone, co-incubation of CEF with Tregitope-289-amide 1) resulted in a higher percentage of cells that had a regulatory phenotype (left panel) and 2) resulted in an associated significant (p&lt;0.0005) decrease in the interferon gamma secretion in response to CEF restimulation (right panel). By contrast, co-incubation with Tregitope 289-uncapped (bottom panels) resulted in no significant difference relative to incubation with CEF alone (top panels). 
         FIG. 3  shows activation of natural Tregs in the presence of Tregitope. Human PBMCs were stimulated directly in vitro for four days in the presence of tetanus toxin peptide  (TT830-844) , Tregitope or no stimulus. Cells were stained extracellularly with anti-CD4 and anti-CD25 and then intracellularly with FoxP3, and analyzed by flow cytometry. Incubation with Tregitope increased the percentage of CD4+CD25+Foxp3+ T cells (53.6% of 644 cells) as compared to  TT830-844  (12.5% of 745 cells) or no stimulus (19.5% of 497 cells). 
         FIG. 4  is a series of bar graphs showing Tregitope induces an up-regulation of T-regulatory cytokines and chemokines and down-regulation of T-effector cytokines and chemokines. Responses to C3d restimulation following initial stimulation with a) a pool of immunogenic peptides derived from C3d protein (black bars); b) C3d peptides+Tregitope-167 (light grey bars) or c) C3d peptides+ Tregitope 134 (medium grey bars). Responses are shown as fold increase over background, which was no stimulus (control) in the secondary incubation. The respective baseline (background) values in pg/ml are indicated within the x-axis labels. There was no significant difference in levels of IL-4, TNFa or TGF(31 
         FIG. 5  is a series of bar graphs showing responses to C3d peptide restimulation following initial stimulation with a) a pool of immunogenic peptides derived from C3d protein (black bars) or b) C3d peptides+ Tregitope-289 (light grey bars). Responses are shown as fold increase over background, which was no stimulus (control) in the secondary incubation. For each cytokine, baseline (no re-stimulus, background) values are shown within the x-axis labels. 
         FIG. 6  is a bar graph showing co-stimulation with epitopes derived from TSHR, the target antigen of Graves&#39; disease, suppresses immune response to the epitopes in PBMC from a patient with Graves&#39; disease. PBMC from a patient with Graves&#39; disease were first incubated for 8 days with either 1) a pool of TSHR peptides alone or 2) a pool of TSHR peptides and a pool of Tregitope-134, Tregitope-167, and Tregitope-289. Cells were then harvested, washed and incubated (in IL-4 ELISpot plates as described) with 1) individual TSHR peptides and the Tregitope pool or 2) the pool of TSHR peptides and the Tregitope pool. A “no restimulus” control was also plated. Responses are shown relative to restimulation with no antigen. Black bars correspond to incubations and restimulations done with antigen alone, grey bars correspond to incubations and restimulations with antigen+the Tregitope pool. In this experiment the Tregitope co-incubation suppressed response to individual TSHR peptides by 35% to 67% and suppressed the response to the pool of TSHR peptides by 65%. P values for pairwise comparisons are shown. 
         FIG. 7  is a bar graph showing average response of three subjects in response to a commercially available pool of positive control peptides (CEF) following an eight day incubation with one of the following: CEF alone, CEF+ Tregitope-289, CEF+ Tregitope 294, CEF+ Tregitope-029, CEF+ Tregitope-074, or CEF+ Tregitope-009. Responses to CEF are suppressed by 29 to 48% depending on the individual Tregitope used. Baseline responses to CEF (in the samples previously incubated to CEF alone) ranged from 1404 to 10139 IFN-y SFC/million PBMC over background (background is no restimulus). P values for pairwise comparisons are shown. 
         FIG. 8  is a bar graph showing co-incubation with Tregitope suppresses immune response to peptide epitopes derived from Botulinum neurotoxin. Peripheral blood was drawn from a subject with evidence of anti-BoNT/A antibodies. PBMC were first incubated for eight days with either a pool of BoNT/A peptides alone or pool of BoNT/A peptides+a pool of Tregitopes (Tregitope-134, Tregitope-167, and Tregitope-289). Cells were then harvested, washed and then incubated (in IFN-7 ELISpot plates) with BoNT/A peptides individually in triplicate and in a pool in triplicate. Responses are shown relative to re-stimulation with no antigen. Black bars correspond to incubations with antigen alone, grey bars correspond to incubations with antigen+the pool of Tregitopes. The response to BoNT/A was suppressed by 26% to 73%; the response to the pool of BoNT/A peptides was suppressed by 59%. P values for pairwise comparisons are shown. 
         FIG. 9  is a series of graphs showing Tregitope-289 and Tregitope-134 down-regulate proliferation in response to co-administered immunodominant antigens in vitro. PBMCs were isolated from a blood bank donor and stimulated for eight days with CEF alone, CEF+ Tregitope-134 or CEF+ Tregitope-289. Co-incubation with either of the two Tregitopes lead to a decrease in response to CEF as measured by IFN-y ELISA (left panel) and to a decrease in proliferation as measured by CFSE Fluorescence (right panel) (grey shaded refers to the suppressed responses with antigen-Tregitope co-incubation; the black refers to baseline responses following incubation with antigen alone). 
         FIG. 10  is a plot showing response to vaccinia peptide. PBMCs were isolated from a blood bank donor and stimulated for eight days with CEF alone, CEF+ Tregitope-134 or CEF+ Tregitope-289. Co-incubation with either of the two Tregitopes led to a decrease in response to CEF as measured by IFN-y ELISA (left panel) and to a decrease in proliferation as measured by CFSE Fluorescence (right panel). Grey shaded refers to the suppressed responses with antigen-Tregitope co-incubation; the black refers to baseline responses following incubation with antigen alone. 
         FIG. 11  is a series of graphs showing Tregitope suppression is mediated by cells with a regulatory phenotype. Tregitope suppression is dependent on CD4+CD25Hi T cells. Left panel: PBMC from allergic individuals were stained with anti-CD4 and anti-CD25 antibodies and analyzed by flow cytometry. The CD4+CD25Hi subset (gate) was depleted from the remaining PBMC. Center panel: CD4+CD25Hi depleted and non-depleted PBMC were co-stimulated HDM lysate with or without Tregitope-289. CD4+CD25Hi depleted PBMC were less able to suppress IFN-y than non-depleted PBMC. Right panel: co-incubation of HDM lysate and Tregitope-289 leads to decreased proliferation of CD4+ cells in response to HDM lysate stimulus. 
         FIG. 12  is a plot and graph showing expansion of TReg (CD4/CD25 Hi) correlates with IL-10 secretion. The expansion of CD4 CD25hi T cells following co-incubation with Tregitope-289 and HDM; and the amount of IL-10 secreted by the co-incubated cells following restimulation with HDM alone. Results for co-incubation with Tregitope-167 are similar: increase from 1.67% to 7.5% CD4/CD25hi cells and a five-fold increase in IL-10 secretion. 
         FIG. 13  is a series of graphs and plots showing Tregitope co-incubation causes suppression of antigen-specific allergic Th2 response. Co-culture with Tregitope and Bet v 1141-155 allergen causes a shift from Th2 effector to Th1/T Reg . PBMC from three birch-tree—pollen-allergic subjects were co-stimulated with Bet v 1141-155 peptide with or without Tregitope-167. Ten day Tregitope co-stimulation led to a decrease in IL-5 secretion (lower left panel) and to a decrease in Th2-associated surface markers (top panel) by Bet v 1144-155 tetramer positive CD4+ cells. Prolonged culture (30 days, lower right panel) led to a significant shift from Th2 (IL-5) to Th1 (IFN-y) in Bet v 1144155-specific cells. 
         FIG. 14  is a graph showing Tregitope co-administration causes suppression of effector responses to co-administered protein therapeutic in vivo. ANTIGEN-XX (see Example 5A) immunization alone (black bars) provokes a robust response by both IL-4 (left bars in pair, left axis) and anti-ANTIGEN-XX antibody titers (right bars in pair, right axis). These responses are both halved (grey bars) when ANTIGEN-XX is co-administered with the murine homologues of Tregitope-167 and Tregitope-106. Responses to ANTIGEN-XX in sham-immunized animals are negative as expected. Responses by Antibody (right bars in pair) and IL-4 ELISpot (left bars in pair) are correlated. 
         FIG. 15  is a graph showing IL-4 and antibody responses to house mite lysate (HDML) and dust mite antigen. HDML immunization (black bars) provokes a robust response by both IL-4 (Left bars in pair, left axis) and anti HDM Antigen antibody titers (Right bars in each pair, right axis). These responses are both halved (grey bars) when HDML is co-administered with the murine homologue of Tregitope-289. Responses to HDML in sham-immunized animals are negative as expected. Responses by Antibody (right bars in pair) and IL-4 ELISpot (left bars in pair) are correlated. These graphs show 38% suppression in vivo in DM naïve mice and 84% percent in the case of pre-sensitized mice. See Example 5B. 
         FIG. 16  is a bar graph showing in vivo suppression of T effector response to immunogenic peptide therapeutic (“IPT”) by Tregitope co-administration. HLA DR4 Tg mice were dosed three times subcutaneously with IPT alone or IPT+murine FC, or IPT+ Tregitope-289 (murine homologue). One week following the last dose, the mice were sacrificed and splenocytes were stimulated with the immunogenic peptide therapeutic in a 48 hr IL-4 ELISpot assy. Co-administration of immunogenic protein therapeutic with either Fc or Tregitope-289 lead to a significant reduction in IL-4 spot-forming cells. See Example 5C. 
         FIG. 17  depicts an example of an immunogenic influenza HA peptide that contains an EpiBar and the EpiMartix analysis of the promiscuous influenza epitope. The influenza HA peptide scores extremely high for all eight alleles in EpiMatrix and has a cluster score of 18. Cluster scores of 10 are considered significant. The band-like EpiBar pattern is characteristic of promiscuous epitopes. Results are shown for PRYVKQNTL (SEQ ID NO:59), RYVKQNTLK (SEQ ID NO:60), YVKQNTLKL (SEQ ID NO:61), VKQNTLKLA (SEQ ID NO:62) and KQNTLKLAT (SEQ ID NO:63). Z score indicates the potential of a 9-mer frame to bind to a given HLA allele. All scores in the top 5% are considered “hits”, while non hits (*) beow 10% are masked in  FIG. 17  for simplicity. 
         FIG. 18A  depicts the Tregitopes on the instant-disclosure and their EpiMatrix Scores. 
         FIG. 18B  depicts the Tregitopes on the instant-disclosure and their EpiMatrix Scores. 
         FIG. 19  illustrates an exemplary BLAST report of Tregitope-289 (SEQ ID NO: 4) showing homology of Tregitope-289 to other organisms. Homology analysis of the IgG derived Tregitopes to non-human species was performed by uploading the sequences into the Basic Local Alignment Search Tool (BLAST) via the NCBI website (ncbi.nlm.nih.gov/blast). The BLAST program compares protein sequences to sequence databases and calculates the statistical significance of matches in order to find regions of local similarity between sequences. The IgG-derived Tregitopes were found to be conserved across non-human species such as mouse, rat, cat, camel, cow and nonhuman primates. 
         FIG. 20  illustrates the binding of affinity of the Tregitopes of the instant disclosure to each of 4 common HLA, showing that the instant Tregitopes indentified by in silico analysis bound to human MHC molecules. Soluble MHC binding assays were performed on the synthetic IgG Tregitopes of the instant disclosure according to the methods described below in the EXEMPLIFICATION section. IC50 values (μM) were derived by a six point inhibition curve of a strong binding control peptide. 
         FIG. 21  depicts the results of interferon-g ELISpot responses to Botulinum Toxin Antigen stimulus following incubation with or without Tregitopes (spot forming cells over no-restimulus background). The results demonstrate that a pool of Tregitopes downregulates in vitro effector responses to co-administered peptide epitopes derived from Botulinum neurotoxin, a protein used to treat dystonia. PBMCs from a subject with evidence of inhibitors (anti-BoNT antibodies) were cultured for 8 days with or without a pool of Tregitope peptides (Tregitope-167, Tregitope-134, Tregitope-289). Cells were harvested and washed with PBS. 2.5×105 cells were re-stimulated in an IFN-g ELISpot plate with individual BoNT peptides, a pool of BoNT peptides, PHA positive control (not shown) or no-stimulus control. Peptides for which there was no significant baseline response are not shown. Response to positive control PHA was robust following both culture conditions. 
         FIG. 22  illustrates one embodiment of a chimeric protein where a pseudo-protein of interest is a string of immunogenic T cell epitopes derived from the Epstein Barr Virus (EBV) fused to a modified Fc protein in which the Tregitope has been modified to no longer bind MHC class II molecules and cannot stimulate natural regulatory T cells. EBV-Tregitope modified Fc SEQUENCE (Kb SIGNAL SEQUENCE) is designated as underlined text. The Tregitope is designated as bold text. The Tregitope modified amino acids are designated as shaded text. The human Fc region is designated as italicized text. 
     
    
    
     DETAILED DESCRIPTION 
     General 
     The adaptive immune cascade begins when soluble protein antigens are taken up by Antigen Presenting Cells (APCs) and processed through the Class II antigen presentation pathway. Protein antigens in the Class II presentation pathway are degraded by various proteases found in the Endoplasmic Reticulum. Some of the resulting protein fragments are bound to Class II MHC molecules. Peptide-loaded MHC molecules are trafficked to the cell surface where they are interrogated by CD4+ T cells. Peptide fragments that are capable of binding to an MHC molecule and mediating the cell to cell interaction between APC and circulating T cells are referred to as T cell epitopes. Recognition of these peptide-MHC complexes by CD4+ T cells can lead to either an immune activating or immune suppressive response based on the phenotype of the responding T cells and the local cytokine/chemokine milieu. In general, engagement between the MHC/peptide complex and the T cell receptor (TCR) of T effector cells leads to activation and the secretion of pro-inflammatory cytokines such as IL-4, and IFN-y. On the other hand the activation of natural T regulatory cells (TReg) leads to the expression of the immune suppressive cytokines IL-10 and TGF-6, among others (Shevach, E.,  Nat. Rev. Immunol.,  2:389-400, 2002). These cytokines act directly on nearby effector T cells leading in some cases to anergy or apoptosis. In other cases regulatory cytokines and chemokines convert effector T cells to T regulatory phenotypes; this process is referred here as “induced” or “adaptive” tolerance. T cell epitopes that are capable of binding to MHC molecules and engaging and activating circulating Treg are referred to as Tregitopes. 
     Initial self/non-self discrimination occurs in the thymus during neonatal development where medullary epithelial cells express specific self protein epitopes to immature T cells. T cells recognizing self antigens with high affinity are deleted, but autoreactive T cells with moderate affinity sometimes avoid deletion and can be converted to so called natural regulatory T cells (TReg) cells. These natural TReg cells are exported to the periphery and provide for constant suppression of autoimmunity. Natural regulatory T cells are a critical component of immune regulation and self tolerance. 
     Self tolerance is regulated by a complex interplay between T cells, B cells, cytokines and surface receptors. T regulatory immune responses counterbalance T effector immune response to protein antigens (whether self or foreign). A tilt of the balance toward the autoreactive side, either by increasing the number or function of autoreactive T effector cells or by diminishing the number or function of T regulatory cells, is manifested as autoimmunity. 
     A second form of tolerance occurs in the periphery where mature T cells are converted to an ‘adaptive’ TReg phenotype upon activation via their T cell receptor in the presence of IL-10 and TGF-f3, usually supplied by bystander T regulatory cells. The possible roles for these ‘adaptive’ TReg cells include dampening immune response following the successful clearance of an invading pathogen as a means of controlling excessive inflammation as might be caused by an allergic reaction or low level chronic infection, or possibly to facilitate co-existence with beneficial symbiotic bacteria and viruses. ‘Adaptive’ TReg may also play a role in managing the life cycle of human antibodies that have undergone somatic hypermutation. 
     It is thought the constant region of immunoglobulin contains several important Tregitopes whose primary function is to suppress immune response to hypermutated CDRs. Due to the high volumes of circulating IgG it is likely that there are also high volumes of T regulatory cells corresponding to the Tregitopes contained in IgG. As a partial proof of this assertion consider that chimeric proteins comprising an Fc portion of an immunoglobulin bestow several desirable properties on a chimeric protein including increased stability, increased serum half life, binding to Fc receptors, and reduced immunogenicity (Lei, T. et al.,  Cell. Immunol.,  235:12-20, 2005, Baxevanis, C. et al.,  Eur. J. Immunol.,  16:1013-1016, 1986). 
     TReg cells are also instrumental in B cell tolerance. B cells express a single low affinity Fc receptor, FcyRIIB on their cell surface (Ravetch, J. et al.,  Science,  234:718725, 1986). This receptor contains the immunoreceptor tyrosine-based inhibition motif sequence (ITIM) in its cytoplasmic domain. Co-ligation of FCyRIIB and the BCR by immune complexes act to trigger the tyrosine phosphorylation of the ITIM leading to the recruitment of the inositol phosphatase, SHIP, which inhibits BCR-triggered proliferation by interfering with the activation of MAP kinases and blocks phagocytosis by the dissociation of Burton&#39;s tyrosine kinase (Btk) from the cell membrane, which inhibits calcium influx into the cell. FcyRIIB can also induce apoptosis independent of the ITIM. Upon homo-aggregation of FcRIIB by ICs, the association of Btk with the cell membrane is enhanced triggering an apoptotic response (Pearse, R. et al.,  Immunity,  10:753-760, 1999). Expression of FcyRIIB is highly variable and cytokine dependent. IL-4 and IL-10, which are expressed by activated Th2 and TReg cells, have been shown to act synergistically to enhance FcyRIIB expression (Joshi, T. et al.,  MoL Immunol.,  43:839850, 2006) thus aiding in the suppression of a humoral response. 
     It is possible to exploit Tregitope specific TReg cells to suppress unwanted immune responses and to induce adaptive TReg to co-delivered proteins. This discovery has implications for the design of therapeutic regimens and antigen-specific therapies for transplantation, protein therapeutics, allergy, chronic infection, autoimmunity and vaccine design. Administration of a drug, a protein, or an allergen in conjunction with Tregitope can suppress effector immune response. Tregitope can be used to deliberately manipulate the immune system toward tolerance. 
     The peptides of the current invention are useful in the selective engagement and activation of regulatory T cells. It is demonstrated herein that certain pre-existing populations of regulatory T cells can be engaged, activated and applied to the suppression of unwanted immune responses in both systemic and limited, disease specific, contexts. 
     Despite extensive efforts, with few exceptions, the antigen specificity of natural Tregs, and more importantly natural Tregs circulating in clinically significant volumes, is unknown. Presented herein is a demonstration that certain human proteins circulating in the blood steam, such as immunoglobulins or the serum protein Albumin, contain T cell epitopes that relate to naturally occurring populations of regulatory T cells. In the course of normal immune surveillance these proteins are taken up by professional APC such as dendritic cells or macrophages and degraded. During the degradation process some of the epitopes contained in these proteins are bound to MHC molecules, transported to the cell surface presented to regulatory T cells. Those cells, once activated by the APC, release cytokines and chemokines help to suppress autoimmune responses that would otherwise hinder the function of the extra cellular proteins. 
     By using the peptides of the invention to selectively activate these pre-existing regulatory T cells, it is herein shown that the peptides of the invention can be used to suppress a variety of unwanted immune responses. In its simplest form systemic application of the peptides of the invention can be used as a generalized immune suppressant useful for controlling severe autoimmune reactions such as, for example, MS flare-ups, allergic reactions, transplant reactions, or uncontrolled response to infection. In a more controlled application, topically applied to joints affected by rheumatoid arthritis (RA) for example, the peptide of the invention can be used to suppress localized autoimmune responses. In a targeted application, such as might be achieved through the fusion or bonding of the peptides to certain other T cell epitopes, the peptides can suppress highly specific immune reactions while leaving the balance of the immune system intact. For example, through the delivery of a regulatory peptide fused to an autoimmune antigen such as insulin, or an allergen such as Brazil nut antigen, the immune system can be trained to “tolerate” the co-delivered antigen by converting the phenotype of responding effector T cells to that of adaptive regulatory T cells. 
     As stated above the peptides of the current invention are derived from circulating extracellular proteins. To be useful these peptides must be true T cell epitopes (i.e., capable of binding to both MHC molecules and TCRs), and be related to a pre-existing population of regulatory T cells that is sufficiently large to have a therapeutic affect. T cell epitope clusters, epitopes capable of binding to multiple MHC alleles and multiple TCRs, are key to satisfying this latter qualification. 
     Definitions 
     To further facilitate an understanding of the present invention, a number of terms and phrases are defined below. 
     As used herein, the term “biological sample” as refers to any sample of tissue, cells or secretions from an organism. 
     As used herein, the term “transplantation” refers to the process of taking a cell, tissue, or organ, called a “transplant” or “graft” from one subject and placing it or them into a (usually) different subject. The subject who provides the transplant is called the “donor”, and the subject who received the transplant is called the “recipient”. An organ or graft transplanted between two genetically different subjects of the same species is called an “allograft”. A graft transplanted between subjects of different species is called a “xenograft”. 
     As used herein, the term “medical condition” includes, but is not limited to, any condition or disease manifested as one or more physical and/or psychological symptoms for which treatment and/or prevention is desirable, and includes previously and newly identified diseases and other disorders. 
     As used herein, the term “immune response” refers to the concerted action of lymphocytes, antigen presenting cells, phagocytic cells, granulocytes, and soluble macromolecules produced by the above cells or the liver (including antibodies, cytokines, and complement) that results in selective damage to, destruction of, or elimination from the human body of cancerous cells, metastatic tumor cells, malignant melanoma, invading pathogens, cells or tissues infected with pathogens, or, in cases of autoimmunity or pathological inflammation, normal human cells or tissues. 
     As used herein, the term “effective amount” of a composition, is a quantity sufficient to achieve a desired therapeutic and/or prophylactic effect, e.g., an amount that results in the prevention of, or a decrease in, the symptoms associated with a disease that is being treated. The amount of a composition of the invention administered to the subject will depend on the type and severity of the disease and on the characteristics of the individual, such as general health, age, sex, body weight and tolerance to drugs. It will also depend on the degree, severity and type of disease. The skilled artisan will be able to determine appropriate dosages depending on these and other factors. The compositions of the present invention can also be administered in combination with each other or with one or more additional therapeutic compounds. 
     As used herein, the term “T cell epitope” means a protein determinant, 7 to 30 amino acids in length, and capable of specific binding to HLA molecules and interacting with specific TCRs. Generally, T cell epitopes are linear and do not express specific three dimensional characteristics. T cell epitopes are not affected by the presence of denaturing solvents. 
     As used herein, the term “B cell epitope” means a protein determinant capable of specific binding to an antibody. Epitopes usually consist of chemically active surface groupings of molecules such as amino acids or sugar side chains and usually have specific three dimensional structural characteristics, as well as specific charge characteristics. Conformational and non-conformational epitopes are distinguished in that the binding to the former but not the latter is lost in the presence of denaturing solvents. 
     The term “subject” as used herein refers to any living organism in which an immune response is elicited. The term subject includes, but is not limited to, humans, nonhuman primates such as chimpanzees and other apes and monkey species; farm animals such as cattle, sheep, pigs, goats and horses; domestic mammals such as dogs and cats; laboratory animals including rodents such as mice, rats and guinea pigs, and the like. The term does not denote a particular age or sex. Thus, adult and newborn subjects, as well as fetuses, whether male or female, are intended to be covered. 
     As used herein, the term MHC complex refers to a protein complex capable of binding with a specific repertoire of polypeptides known as HLA ligands and transporting said ligands to the cell surface. 
     As used herein, the term “MHC Ligand” means a polypeptide capable of binding to one or more specific MHC alleles. The term “HLA ligand” is interchangeable with the term MHC Ligand. Cells expressing MHC/Ligand complexes on their surface are referred to as “Antigen Presenting Cells” (APCs). 
     As used herein, the term T Cell Receptor or TCR refers to a protein complex expressed by T cells that is capable of engaging a specific repertoire of MHC/Ligand complexes as presented on the surface of APCs. 
     As used herein, the term “T cell epitope” means an MHC ligand capable of interacting with specific T cell receptors (TCRs). T cell epitopes can be predicted by in silico methods (De Groot, A. et al.,  AIDS Res. Hum. Retroviruses,  13:539-541, 1997; Schafer, J. et al.,  Vaccine,  16:1880-1884, 1998; De Groot, A. et al.,  Vaccine,  19:438595, 2001; De Groot, A. et al.,  Vaccine,  21:4486-504, 2003). 
     As used herein, the term “MHC Binding Motif” refers to a pattern of amino acids in a protein sequence that predicts binding to a particular MHC allele. 
     As used herein, the term “T-cell epitope cluster” refers to polypeptide that contains between about 4 to about 40 MHC binding motifs. In particular embodiments, the T-cell epitope cluster contains between about 5 to about 35 MHC binding motifs, between about 8 and about 30 MHC binding motifs; and between about 10 and 20 MHC binding motifs. 
     As used herein, the term “EpiBar” refers to a single 9-mer frame that is predicted to be reactive to at least four different HLA alleles. Sequences of known immunogens that contain EpiBars include Influenza Hemagglutinin 307-319, Tetanus Toxin 825-850, and GAD65 557-567. An example of an immunogenic peptide that contains an EpiBar is shown in  FIG. 17 .  FIG. 17  depicts an example of an EpiBar and the EpiMatrix analysis of a pormiscous influenza epitope. Consider the influenza HA peptide, an epitope known to be promiscuously immunogenic. It scores extremely high for all eight alleles in EpiMatrix. Its cluster score is 18. Cluster scores higher than 10 are considered to be significant. The band-like EpiBar pattern is characteristic of promiscuous epitopes. Results are shown in  FIG. 17  for PRYVKQNTL (SEQ ID NO:59), RYVKQNTLK (SEQ ID NO:60), YVKQNTLKL (SEQ ID NO:61), VKQNTLKLA (SEQ ID NO:62) and KQNTLKLAT (SEQ ID NO:63). Z score indicates the potential of a 9-mer frame to bind to a given HLA allele. All scores in the top 5% are considered “hits”, while non hits (*) below 10% are masked in  FIG. 17  for simplicity. As used herein, the term “Immune Synapse” means the protein complex formed by the simultaneous engagement of a given T cell Epitope to both a cell surface MHC complex and TCR. 
     As used herein, the term “regulatory T cell” means a subset of naturally occurring T cells characterized by the presence of certain cell surface markers including but not limited to CD4, CD25, and FoxP3. Upon activation regulatory T cells secrete immune suppressive cytokines and chemokines including but not limited to IL-10, TGF-p and TNF-a. 
     The term “polypeptide” refers to a polymer of amino acids, and not to a specific length; thus, peptides, oligopeptides and proteins are included within the definition of a polypeptide. As used herein, a polypeptide is said to be “isolated” or “purified” when it is substantially free of cellular material when it is isolated from recombinant and non-recombinant cells, or free of chemical precursors or other chemicals when it is chemically synthesized. A polypeptide, however, can be joined to another polypeptide with which it is not normally associated in a cell and still be “isolated” or “purified.” When a polypeptide is recombinantly produced, it can also be substantially free of culture medium, for example, culture medium represents less than about 20%, less than about 10%, or less than about 5% of the volume of the polypeptide preparation. 
     A variant polypeptide can differ in amino acid sequence by one or more substitutions, deletions, insertions, inversions, fusions, and truncations or a combination of any of these. 
     The invention also includes polypeptide fragments of the polypeptides of the invention. The invention also encompasses fragments of the variants of the polypeptides described herein. The invention also provides chimeric or fusion polypeptides. These comprise a polypeptide of the invention operatively linked to a heterologous protein or polypeptide having an amino acid sequence not substantially homologous to the polypeptide. “Operatively linked” indicates that the polypeptide and the heterologous protein are fused in-frame. 
     The isolated polypeptide can be purified from cells that naturally express it, purified from cells that have been altered to express it (recombinant), or synthesized using known protein synthesis methods. In one embodiment, the polypeptide is produced by recombinant DNA techniques. For example, a nucleic acid molecule encoding the polypeptide is cloned into an expression vector, the expression vector introduced into a host cell and the polypeptide expressed in the host cell. The polypeptide can then be isolated from the cells by an appropriate purification scheme using standard protein purification techniques. 
     For the purposes of the present invention, polypeptides can include, for example, modified forms of naturally occurring amino acids such as D-stereoisomers, non-naturally occurring amino acids; amino acid analogs; and mimetics. 
     Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described. Other features, objects, and advantages of the invention will be apparent from the description and the Claims. In the Specification and the appended Claims, the singular forms include plural referents unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. All references cited herein are incorporated herein by reference in their entirety and for all purposes to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference in its entirety for all purposes. 
     Compositions 
     In one aspect, the invention provides a novel class of T cell epitopes compositions, termed Tregitopes&#39;, which comprise a peptide or polypeptide chain with one or more defined characteristics listed below. That is, the Tregitopes of the invention include, but are not limited to, possessing one or more of the following characteristics: 
     (1) Tregitopes of the invention are derived from common human proteins. 
     (2) Tregitopes of the invention are highly conserved among known variants of their source proteins (e.g., present in more than 50% of known variants). 
     (3) Tregitopes of the invention comprise at least one putative T cell epitope as identified by EpiMatrix analysis. EpiMatrix is a proprietary computer algorithm developed by EpiVax, which is used to screen protein sequences for the presence of putative T cell epitopes. Input sequences are parsed into overlapping 9-mer frames where each frame overlaps the last by 8 amino acids. Each of the resulting frames is then scored for predicted binding affinity with respect to a panel of eight common Class II HLA alleles (DRB1*0101, DRB1*0301, DRB1*0401, DRB1*0701, DRB1*0801, DRB1*1101, DRB1*1301, and DRB1*1501). Raw scores are normalized against the scores of a large sample of randomly generated peptides. The resulting “Z” score is reported. Any 9-mer peptide with an allele-specific EpiMatrix Z-score in excess of 1.64, theoretically the top 5% of any given sample, is considered a putative T cell epitope. 
     In a preferred embodiment the Tregitopes of the invention contain several putative T cell epitopes forming a pattern known as a T cell epitope cluster. Putative T-cell epitopes are not randomly distributed throughout protein sequences but instead tend to “cluster” in specific regions. In addition, peptides containing clusters of putative T cell epitopes are more likely to test positive in validating in vitro and in vivo assays. The results of the initial EpiMatrix analysis are further screened for the presence of putative T cell epitope “clusters” using a second proprietary algorithm known as Clustimer. The Clustimer algorithm identifies sub-regions contained within any given amino acid sequence that contains a statistically unusually high number of putative T cell epitopes. Typical T-cell epitope “clusters” range from about 9 to roughly 30 amino acids in length and, considering their affinity to multiple alleles and across multiple 9-mer frames, can contain anywhere from about 4 to about 40 putative T cell epitopes. For each epitope cluster identified an aggregate EpiMatrix score is calculated by summing the scores of the putative T cell epitopes and subtracting a correcting factor based on the length of the candidate epitope cluster and the expected score of a randomly generated cluster of the same length. EpiMatrix cluster scores in excess of +10 are considered significant. 
     Many of the most reactive T cell epitope clusters contain a feature referred to as an “EpiBar”. An EpiBar is a single 9-mer frame that is predicted to be reactive to at least four different HLA alleles. Sequences that contain EpiBars include Influenza Hemagglutinin 307-319 (Cluster score of 18), Tetanus Toxin 825-850 (Cluster score of 16), and GAD65 557-567 (Cluster score of 19). In another embodiment, the peptides of the invention can comprise one or more EpiBars. 
     (4) Tregitopes of the invention bind to at least one and preferably two or more common HLA class II molecules with at least a moderate affinity (e.g., &lt;200 ILLM IC 50  in HLA binding assays based on soluble HLA molecules). 
     (4) Tregitopes of the invention are capable of being presented at the cell surface by APCs in the context of at least one and, in a preferred embodiment, two or more alleles of the HLA. 
     (5) In this context, the Tregitope-HLA complex can be recognized by pre-existing populations of regulatory T cells having TCRs that are specific for the Tregitope-HLA complex and circulating in normal control subjects. The recognition of the Tregitope-HLA complex can cause the matching regulatory T cell to be activated and to secrete regulatory cytokines and chemokines. 
     (6) Stimulating regulatory T cells with Tregitope(s) of the invention results in increased secretion of one or more of the following cytokines and chemokines: IL-10, TGF-fl, TNF-α and MCP1. This increased secretion of regulatory cytokines and chemokines is a hallmark of regulatory T cells. 
     (7) Regulatory T cells activated by the Tregitope(s) of the invention express a CD4+CD25+FOXP3 phenotype. 
     (8) Regulatory T cells activated by the Tregitope(s) directly suppress T-effector immune responses ex vivo as measured by decreased antigen-specific Th1- or Th2-associated cytokine levels, principally INF-y, IL-4, and IL-5, and by decreased proliferation of antigen-specific T effector cells as measured by CFSE dilution. 
     (10) Regulatory T cells activated by the Tregitope(s) directly suppress T effector immune responses in vivo as measured by decreased antigen-specific Th1- or Th2-associated cytokine levels (as measured by Elisa assay), decreased antigen-specific T effector cell levels (as measured by EliSpot assay) and decreased antibody titers for protein antigens. 
     (1) Natural regulatory T cells activated by the Tregitopes of the invention stimulate the development of adaptive T Reg  cells. Co-incubating peripheral T cells with the Tregitopes of the invention in the presence of antigen results in the expansion of antigen-specific CD4+/CD25+ T cells, upregulates the expression of FOXP3+ on those cells and suppresses the activation of antigen-specific T effector cells in vitro. 
     The Tregitopes of the invention are useful for regulating immune response to monoclonal antibodies, protein therapeutics, self antigens promoting autoimmune response, allergens, transplanted tissues and in other applications where tolerance is the desired outcome. Select embodiments of the Tregitopes of the invention are summarized in  FIGS. 18A and 18B  in Example 1. 
     In one embodiment, the Tregitope of the invention is a T cell epitope isolated as described in  FIGS. 18A and 18B . The Tregitopes of  FIGS. 18A and 18B  (SEQ ID NOs: 4 through 58) can bind MHC class II molecules, engage TCR in context of MHC class II molecules and activate natural regulatory T cells. 
     The polypeptides of the invention can be purified to homogeneity or partially purified. It is understood, however, that preparations in which the polypeptide is not purified to homogeneity are useful. The critical feature is that the preparation allows for the desired function of the polypeptide, even in the presence of considerable amounts of other components. Thus, the invention encompasses various degrees of purity. In one embodiment, the language “substantially free of cellular material” includes preparations of the polypeptide having less than about 30% (by dry weight) other proteins (e.g., contaminating protein), less than about 20% other proteins, less than about 10% other proteins, or less than about 5% other proteins. 
     When a polypeptide is recombinantly produced, it can also be substantially free of culture medium, for example, culture medium represents less than about 20%, less than about 10%, or less than about 5% of the volume of the polypeptide preparation. The language “substantially free of chemical precursors or other chemicals” includes preparations of the polypeptide in which it is separated from chemical precursors or other chemicals that are involved in its synthesis. The language “substantially free of chemical precursors or other chemicals” can include, for example, preparations of the polypeptide having less than about 30% (by dry weight) chemical precursors or other chemicals, less than about 20% chemical precursors or other chemicals, less than about 10% chemical precursors or other chemicals, or less than about 5% chemical precursors or other chemicals. 
     As used herein, two polypeptides (or a region of the polypeptides) are substantially homologous or identical when the amino acid sequences are at least about 45-55%, typically at least about 70-75%, more typically at least about 80-85%, and more typically greater than about 90% or more homologous or identical. To determine the percent homology or identity of two amino acid sequences, or of two nucleic acid sequences, the sequences are aligned for optimal comparison purposes (e.g., gaps can be introduced in the sequence of one polypeptide or nucleic acid molecule for optimal alignment with the other polypeptide or nucleic acid molecule). The amino acid residues or nucleotides at corresponding amino acid positions or nucleotide positions are then compared. When a position in one sequence is occupied by the same amino acid residue or nucleotide as the corresponding position in the other sequence, then the molecules are homologous at that position. As used herein, amino acid or nucleic acid “homology” is equivalent to amino acid or nucleic acid “identity”. The percent homology between the two sequences is a function of the number of identical positions shared by the sequences (e.g., percent homology equals the number of identical positions/total number of positions ×100). 
     The invention also encompasses polypeptides having a lower degree of identity but having sufficient similarity so as to perform one or more of the same functions performed by a polypeptide encoded by a nucleic acid molecule of the invention. Similarity is determined by conserved amino acid substitution. Such substitutions are those that substitute a given amino acid in a polypeptide by another amino acid of like characteristics. Conservative substitutions are likely to be phenotypically silent. Typically seen as conservative substitutions are the replacements, one for another, among the aliphatic amino acids Ala, Val, Leu and Ile; interchange of the hydroxyl residues Ser and Thr, exchange of the acidic residues Asp and Glu, substitution between the amide residues Asn and Gln, exchange of the basic residues Lys and Arg and replacements among the aromatic residues Phe and Tyr. Guidance concerning which amino acid changes are likely to be phenotypically silent are found, for example, in Bowie, J. et al.,  Science,  247:1306-1310, 1990. 
     A variant polypeptide can differ in amino acid sequence by one or more substitutions, deletions, insertions, inversions, fusions, and truncations or a combination of any of these. Variant polypeptides can be fully functional or can lack function in one or more activities. Fully functional variants typically contain only conservative variation or variation in non-critical residues or in non-critical regions. Functional variants can also contain substitution of similar amino acids that result in no change or an insignificant change in function. Alternatively, such substitutions can positively or negatively affect function to some degree. Non-functional variants typically contain one or more non-conservative amino acid substitutions, deletions, insertions, inversions, or truncation or a substitution, insertion, inversion, or deletion in a critical residue or critical region. Several examples of variant polypeptides are included in  FIGS. 18A and 18B . 
     The invention also includes polypeptide fragments of the polypeptides of the invention. The invention also encompasses fragments of the variants of the polypeptides described herein. As used herein, a fragment comprises at least about five contiguous amino acids. Useful fragments include those that retain one or more of the biological activities of the polypeptide as well as fragments that can be used as an immunogen to generate polypeptide-specific antibodies. Biologically active fragments are, for example, about 6, 9, 12, 15, 16, 20 or 30 or more amino acids in length. Fragments can be discrete (not fused to other amino acids or polypeptides) or can be within a larger polypeptide. Several fragments can be comprised within a single larger polypeptide. In one embodiment a fragment designed for expression in a host can have heterologous pre- and pro-polypeptide regions fused to the amino terminus of the polypeptide fragment and an additional region fused to the carboxyl terminus of the fragment. 
     The invention also provides chimeric or fusion polypeptides. These comprise a polypeptide of the invention operatively linked to a heterologous protein or polypeptide having an amino acid sequence not substantially homologous to the polypeptide. “Operatively linked” indicates that the polypeptide and the heterologous protein are fused in-frame. The heterologous protein can be fused to the N-terminus or C-terminus of the polypeptide. In one embodiment the fusion polypeptide does not affect function of the polypeptide per se. For example, the fusion polypeptide can be a GST-fusion polypeptide in which the polypeptide sequences are fused to the C-terminus of the GST sequences. Other types of fusion polypeptides include, but are not limited to, enzymatic fusion polypeptides, for example beta-galactosidase fusions, yeast two-hybrid GAL fusions, poly-His fusions and Ig fusions. Such fusion polypeptides, particularly poly-His fusions or affinity tag fusions, can facilitate the purification of recombinant polypeptide. In certain host cells (e.g., mammalian host cells), expression and/or secretion of a polypeptide can be increased by using a heterologous signal sequence. Therefore, in another embodiment, the fusion polypeptide contains a heterologous signal sequence at its N-terminus. 
     A chimeric or fusion polypeptide can be produced by standard recombinant DNA techniques. For example, DNA fragments coding for the different polypeptide sequences are ligated together in-frame in accordance with conventional techniques. In another embodiment, the fusion gene can be synthesized by conventional techniques including automated DNA synthesizers. Alternatively, PCR amplification of nucleic acid fragments can be carried out using anchor primers which give rise to complementary overhangs between two consecutive nucleic acid fragments which can subsequently be annealed and re-amplified to generate a chimeric nucleic acid sequence (Ausubel et al., Current Protocols in Molecular Biology, 1992). Moreover, many expression vectors are commercially available that already encode a fusion moiety (e.g., a GST protein). A nucleic acid molecule encoding a polypeptide of the invention can be cloned into such an expression vector such that the fusion moiety is linked in-frame to the polypeptide. The isolated polypeptide can be purified from cells that naturally express it, purified from cells that have been altered to express it (recombinant), or synthesized using known protein synthesis methods. In one embodiment, the polypeptide is produced by recombinant DNA techniques. For example, a nucleic acid molecule encoding the polypeptide is cloned into an expression vector, the expression vector introduced into a host cell and the polypeptide expressed in the host cell. The polypeptide can then be isolated from the cells by an appropriate purification scheme using standard protein purification techniques. 
     The invention also provides for nucleic acids that encode in whole or in part the polypeptides of the invention. The nucleic acid molecules of the invention can be inserted into vectors and used, for example, as expression vectors or gene therapy vectors. Gene therapy vectors can be delivered to a subject by, e.g., intravenous injection, local administration (U.S. Pat. No. 5,328,470) or by stereotactic injection (Chen, et al.,  Proc. Natl. Acad. Sci. USA,  91:3054-3057, 1994). The pharmaceutical preparation of the gene therapy vector can include the gene therapy vector in an acceptable diluent, or can comprise a slow release matrix in which the gene delivery vehicle is imbedded. Alternatively, where the complete gene delivery vector can be produced intact from recombinant cells, e.g., retroviral vectors, the pharmaceutical preparation can include one or more cells that produce the gene delivery system. The pharmaceutical compositions can be included in a container, pack, or dispenser together with instructions for administration. 
     Tregitopes of the invention can include allelic or sequence variants (“mutants”) or analogs thereof, or can include chemical modifications (e.g., pegylation, gycosylation). In one instance, a mutant can provide for enhanced binding to MHC molecules. In another instance, a mutant can lead to enhanced binding to TCRs. In another instance, a mutant can lead to a decrease in binding to MHC molecules and/or TCRs. Also contemplated is a mutant that binds but does not allow signaling via the TCR. 
     The invention provides for Tregitope compositions that are chimeric protein compositions. In one embodiment, the Tregitope composition comprises a first and a second polypeptide chain linked together, wherein the first chain comprises sequence numbers 4 through 58 or any combination thereof, and said second chain comprises a biologically active molecule. In one embodiment, the biologically active molecule is selected from the group consisting of: an immunogenic molecule; a T cell epitope; viral protein; bacterial protein. In one embodiment, the Tregitope composition of the invention comprises a first and a second polypeptide chain linked together, wherein said first chain comprises a Fc region wherein the amino acids in region 289-309 has been altered so as not to bind to MHC class II molecules, and said second chain comprises a immunogenic molecule. 
     In one aspect, the invention provides methods to produce a regulatory T cell line recognizing at least a portion of SEQ ID NOS:4-58. In one embodiment, one or more peptides selected from the group consisting of SEQ ID NOS:4-58 are combined in admixture with an appropriate excipient. Such compositions are useful in methods of preventing or treating inflammation in a subject in need thereof, wherein local delivery of the admixture with an appropriate excipient results in decreased inflammation in the subject. 
     In one embodiment, one or more peptides selected from the group consisting of SEQ ID NOS:4-58 are combined in admixture with a antigen or allergen. Such compositions are useful in methods of inducing tolerance to the antigen or allergen in a subject in need thereof, wherein local delivery of the admixture with a antigen or allergen results in increased tolerance to the antigen or allergen in the subject, and delivered with an appropriate excipient resulting in induced tolerance to the antigen or allergen. 
     In one embodiment, the invention provides a nucleic acid encoding comprising one or more of the Tregitope polypeptides selected from the group consisting of SEQ ID NOS:4-58. In one embodiment, the invention provides a vector comprising a nucleic acid encoding comprising one or more of the Tregitope polypeptides selected from the group consisting of SEQ ID NOS:4-58. In one embodiment, the invention provides a cell comprising a vector of the invention. The cell can be a mammalian cell, bacterial cell, insect cell, or yeast cell. 
     Cloning of Tregitope Specific T cells Cloning of Tregitope specific T cells can be conducted by techniques known to one of skill in the art. For example, isolated PBMCs are stimulated with Tregitopes at 10 pg/ml RPMI media containing 20% HSA. IL-2 is added (10 U/ml final concentration) every other day starting on day 5. T cells are stained with tetramer pools on day 11 or 12. For each pool, 2-3×10 5  cells are incubated with 0.5 mg of PE-labeled tetramer in 50 ml of culture medium (10 mg/ml) at 37° C. for 1 to 2 h, and then stained with anti-CD4-FITC (BD PharMingen, San Diego, Calif.) for 15 min at room temperature. Cells are washed and analyzed with a Becton Dickinson FACSCalibur flow cytometer (Becton Dickinson, San Jose, Calif.). Tetramers loaded with the corresponding single peptides are generated for those pools that give positive staining, and analysis is done on day 14 or 15. Cells that are positive for a particular tetramer are single-cell sorted into 96-well U-bottom plates by using a Becton Dickinson FACSVantage (San Jose, Calif.) on the same or following day. Sorted cells are expanded with 1.5-3×10 5  unmatched, irradiated (5000 rad) PBMC per well as feeders with 2.5 mg/ml PHA and 10 U/ml IL-2 added 24 h later. Specificity of cloned T cells is confirmed by staining with tetramers (loaded with cognate peptide or control peptide, HA307-319) and T cell proliferation assays with 10 mg/ml of specific peptide (Novak, E. et al.,  J. Immunol.,  166:6665-6670, 2001). 
     Methods of Use of Tregitope Compositions 
     In one aspect, the invention provides methods of using Tregitopes for the purpose of designing small molecules. In one method of the invention, Tregitope-specific T cells are stimulated three times with pools of small molecule mixtures at a concentration of 1 pg/ml and autologous dendritic cells (DC) at 2-week intervals, followed by stimulation with heterologous DC and antigens. T cells (1.25×10 5 ) and DC (0.25×10 5 ) are added per well in round-bottom, 96-well plates. T cell medium is made by supplementing 500 ml of RPMI medium 1640 with 50 ml of FCS (HyClone), penicillin, and streptomycin (GIBCO); 20 mM Hepes (GIBCO); and 4 ml 1 N NaOH solution. The IL-2 concentration is initially 0.1 nM and gradually is increased to 1 nM during subsequent rounds of stimulation. T cell clones are derived by limiting dilution by using 0.6×10 5  Epstein-Barr virus-transformed B cells (100 Gray) and 1.3×10 5  heterologous peripheral blood mononuclear cells (33 Gray) as feeder cells and 1 pg/ml phytohemagglutinin (Difco) in medium containing 2 nM IL-2. Small molecules pools that stimulate the Tregitope specific T cells are then tested as individual molecules. 
     In one aspect, the invention provides methods of using Tregitopes for the purpose of cloning T cell receptors. Total RNA is extracted with an RNeasy Mini Kit (Qiagene) from the Tregitope specific T cell lines generated as described above. One microgram of total RNA is used to clone the TCR cDNAs by a rapid amplification of cDNA end (RACE) method (GeneRacer Kit, Invitrogen). Before synthesizing the single-strand cDNA, the RNA is dephosphorylated, decapped, and ligated with an RNA oligonucleotide according to the instruction manual of 5′ RACE GeneRacer Kit. SuperScript II RT and GeneRacer Oligo-dT are used for reverse transcription of the RNA Oligo-ligated mRNA to single-strand cDNAs. 5′ RACE is performed by using GeneRacer 5′ (GeneRacer Kit) as 5′ primer and gene-specific primer TCRCAR (5′-GTT AAC TAG TTC AGC TGG ACC ACA GCC GCA GC-3′; SEQ ID NO:64) or TCRCB1R (5′-CGG GTT AAC TAG TTC AGA AAT CCT TTC TCT TGA CCA TGG C-3′; SEQ ID NO:65), or TCRCBR2 (5′-CTA GCC TCT GGA ATC CTT TCT CTT G-3′; SEQ ID NO:66) as 3′ primers for TCR a, fl1, or fl2 chains, respectively. The polymerase chain reaction (PCR) products are cloned into pCR2.1 TOPO vector (Invitrogen) and then transformed into One Shot TOP10 Competent  Escherichia coli  (Invitrogen). Plasmid DNAs are prepared from 96 individual clones from each construct for TCRa, p 1, and 132 chains. Full-length insert of all the plasmids is sequenced to determine the va/vfl usage (Zhao, Y. et al.,  J. Immunother.,  29:398-406, 2006). 
     Pharmaceutical Formulations 
     The invention provides methods of treating a subject with a medical condition comprising administering a therapeutically effective amount of a Tregitope in a pharmaceutically acceptable carrier or excipient. The Tregitopes of the present invention can be incorporated into pharmaceutical compositions suitable for administration. The pharmaceutical compositions generally comprise at least one Tregitope and a pharmaceutically-acceptable carrier in a form suitable for administration to a subject. Pharmaceutically-acceptable carriers are determined in part by the particular composition being administered, as well as by the particular method used to administer the composition. Accordingly, there is a wide variety of suitable formulations of pharmaceutical compositions for administering the Tregitope compositions (see, e.g., Remington&#39;s Pharmaceutical Sciences, Mack Publishing Co., Easton, Pa. 18th ed., 1990). The pharmaceutical compositions are generally formulated as sterile, substantially isotonic and in full compliance with all Good Manufacturing Practice (GMP) regulations of the U.S. Food and Drug Administration. 
     The terms “pharmaceutically-acceptable,” “physiologically-tolerable,” and grammatical variations thereof, as they refer to compositions, carriers, diluents and reagents, are used interchangeably and represent that the materials are capable of administration to or upon a subject without the production of undesirable physiological effects to a degree that would prohibit administration of the composition. “Pharmaceutically-acceptable excipient” means, for example, an excipient that is useful in preparing a pharmaceutical composition that is generally safe, non-toxic, and desirable, and includes excipients that are acceptable for veterinary use as well as for human pharmaceutical use. Such excipients can be solid, liquid, semisolid, or, in the case of an aerosol composition, gaseous. A person of ordinary skill in the art would be able to determine the appropriate timing, sequence and dosages of administration for particular drugs and compositions of the present invention. 
     Preferred examples of such carriers or diluents include, but are not limited to, water, saline, Ringer&#39;s solutions, dextrose solution, and 5% human serum albumin. Liposomes and non-aqueous vehicles such as fixed oils can also be used. The use of such media and compounds for pharmaceutically active substances is well known in the art. Except insofar as any conventional media or compound is incompatible with the Tregitope, use thereof in the compositions is contemplated. Supplementary active compounds can also be incorporated into the compositions. 
     A pharmaceutical composition of the invention is formulated to be compatible with its intended route of administration. The Tregitope compositions of the present invention can be administered by parenteral, topical, intravenous, oral, subcutaneous, intraarterial, intradermal, transdermal, rectal, intracranial, intraperitoneal, intranasal; vaginally; intramuscular route or as inhalants. In some embodiments of the invention, agents are injected directly into a particular tissue where deposits have accumulated, e.g., intracranial injection. Intramuscular injection or intravenous infusion are preferred for administration of the Tregitope. In some methods, particular Tregitopes of the invention are injected directly into the cranium. In some methods, the Tregitopes of the invention are administered as a sustained release composition or device, such as a Medipad™ device. 
     The Tregitope of the invention can optionally be administered in combination with other agents that are at least partly effective in treating various medical conditions as described herein. In the case of administration into the central nervous system of a subject, the Tregitope of the invention can also be administered in conjunction with other agents that increase passage of the agents of the invention across the blood-brain barrier. 
     Solutions or suspensions used for parenteral, intradermal, or subcutaneous application can include the following components: a sterile diluent such as water for injection, saline solution, fixed oils, polyethylene glycols, glycerine, propylene glycol or other synthetic solvents; antibacterial compounds such as benzyl alcohol or methyl parabens; antioxidants such as ascorbic acid or sodium bisulfite; chelating compounds such as ethylenediaminetetraacetic acid (EDTA); buffers such as acetates, citrates or phosphates, and compounds for the adjustment of tonicity such as sodium chloride or dextrose. The pH can be adjusted with acids or bases, such as hydrochloric acid or sodium hydroxide. Examples of excipients can include starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, water, ethanol, DMSO, glycol, propylene, dried skim milk, and the like. The composition can also contain pH buffering reagents, and wetting or emulsifying agents. 
     The parenteral preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic. 
     Pharmaceutical compositions suitable for injectable use include sterile aqueous solutions (where water soluble) or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersion. For intravenous administration, suitable carriers include physiological saline, bacteriostatic water, Cremophor ELTM (BASF, Parsippany, N.J.) or phosphate buffered saline (PBS). In all cases, the composition is sterile and should be fluid to the extent that easy syringeability exists. It is stable under the conditions of manufacture and storage and is preserved against the contaminating action of microorganisms such as bacteria and fungi. The carrier can be a solvent or dispersion medium containing, e.g., water, ethanol, polyol (e.g., glycerol, propylene glycol, and liquid polyethylene glycol, and the like), and suitable mixtures thereof. The proper fluidity can be maintained, e.g., by the use of a coating such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. Prevention of the action of microorganisms can be achieved by various antibacterial and antifungal compounds, e.g., parabens, chlorobutanol, phenol, ascorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic compounds, e.g., sugars, polyalcohols such as manitol, sorbitol, sodium chloride in the composition. Prolonged absorption of the injectable compositions can be brought about by including in the composition a compound that delays absorption, e.g., aluminum monostearate and gelatin. 
     Sterile injectable solutions can be prepared by incorporating the Tregitope in the required amount in an appropriate solvent with one or a combination of ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the binding agent into a sterile vehicle that contains a basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, methods of preparation are vacuum drying and freeze-drying that yields a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof. The agents of this invention can be administered in the form of a depot injection or implant preparation that can be formulated in such a manner as to permit a sustained or pulsatile release of the active ingredient. 
     Oral compositions generally include an inert diluent or an edible carrier. They can be enclosed in gelatin capsules or compressed into tablets. For the purpose of oral therapeutic administration, the binding agent can be incorporated with excipients and used in the form of tablets, troches, or capsules. Oral compositions can also be prepared using a fluid carrier for use as a mouthwash, wherein the compound in the fluid carrier is applied orally and swished and expectorated or swallowed. Pharmaceutically compatible binding compounds, and/or adjuvant materials can be included as part of the composition. The tablets, pills, capsules, troches and the like can contain any of the following ingredients, or compounds of a similar nature: a binder such as microcrystalline cellulose, gum tragacanth or gelatin; an excipient such as starch or lactose, a disintegrating compound such as alginic acid, Primogel or corn starch; a lubricant such as magnesium stearate or Sterotes; a glidant such as colloidal silicon dioxide; a sweetening compound such as sucrose or saccharin; or a flavoring compound such as peppermint, methyl salicylate or orange flavoring. 
     For administration by inhalation, the Tregitope(s) are delivered in the form of an aerosol spray from pressured container or dispenser that contains a suitable propellant, e.g., a gas such as carbon dioxide, or a nebulizer. 
     Systemic administration can also be by transmucosal or transdermal means. For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are generally known in the art, and include, e.g., for transmucosal administration, detergents, bile salts, and fusidic acid derivatives. Transmucosal administration can be accomplished through the use of nasal sprays or suppositories. For transdermal administration, the Tregitope is formulated into ointments, salves, gels, or creams and applied either topically or through transdermal patch technology as generally known in the art. 
     The Tregitope can also be prepared as pharmaceutical compositions in the form of suppositories (e.g., with conventional suppository bases such as cocoa butter and other glycerides) or retention enemas for rectal delivery. 
     In one embodiment, the Tregitope is prepared with carriers that protect the Tregitope against rapid elimination from the body, such as a controlled-release formulation, including implants and microencapsulated delivery systems. 
     Biodegradable, biocompatible polymers can be used, such as, for example, ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and polylactic acid. Methods for preparation of such formulations will be apparent to those skilled in the art. The materials can also be obtained commercially from Alza Corporation and Nova Pharmaceuticals, Inc. Liposomal suspensions (including liposomes targeted to infected cells with monoclonal antibodies to viral antigens) can also be used as pharmaceutically-acceptable carriers. These can be prepared according to methods known to those skilled in the art (U.S. Pat. No. 4,522,811). The Tregitopes or chimeric proteins can be implanted within or linked to a biopolymer solid support that allows for the slow release of the Tregitopes or chimeric proteins to the desired site. 
     It is especially advantageous to formulate oral or parenteral compositions in dosage unit form for ease of administration and uniformity of dosage. Dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the subject to be treated; each unit containing a predetermined quantity of binding agent calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier. The specification for the dosage unit forms of the invention are dictated by and directly dependent on the unique characteristics of the binding agent and the particular therapeutic effect to be achieved, and the limitations inherent in the art of compounding such Tregitope for the treatment of a subject. 
     Methods of Preventing or Treating a Medical Condition 
     The present invention is directed to, for example methods of treating one or more medical conditions comprising administering a Tregitope or chimeric protein of the invention, thereby treating the medical condition. The medical condition can be, for example, primary immunodeficiencies; immune-mediated thrombocytopenia, Kawasaki disease, hematopoietic stem cell transplantation in patients older than 20 years, chronic B-cell lymphocytic leukemia and pediatric HIV type 1 infections. Specific examples include: (Hematology) aplastic anemia, pure red cell aplasia, Diamond-Blackfan anemia, autoimmune hemolytic anemia, hemolytic disease of the newborn, acquired factor VIII inhibitors, acquired von Willebrand disease, immune-mediated neutropenia, refractoriness to platelet transfusion, neonatal alloimmune/autoimmune thrombocytopenia, posttransfusion purpura, thrombotic thrombocytopenia purpura/hemolytic uremic syndrome; (Infectious diseases) conditions in which acquiring an infectious disease could be deleterious include low birth weight (e.g., &lt;1500 g), solid organ transplantation, surgery, trauma, burns, and HIV infection; (Neurology) epilepsy and pediatric intractable Guillain-Barre syndrome, chronic inflammatory demyelinating polyneuropathy, myasthenia gravis, Lambert-Eaton myasthenic syndrome, multifocal motor neuropathy, multiple sclerosis; (Obstetrics) recurrent pregnancy loss; (Pulmonology) asthma, chronic chest symptoms, rheumatology, rheumatoid arthritis (adult and juvenile), systemic lupus erythematosus, systemic vasculitides, dermatomyositis, polymyositis, inclusion-body myositis, wegener granulomatosis; (Miscellaneous) adrenoleukodystrophy, amyotrophic lateral sclerosis, Behcet syndrome, acute cardiomyopathy, chronic fatigue syndrome, congential heart block, cystic fibrosis, autoimmune blistering dermatosis, diabetes mellitus, acute idiopathic dysautonomia, acute disseminated encephalomyelitis, endotoxemia, hemolytic transfusion reaction, hemophagocytic syndrome, acute lymphoblastic leukemia, lower motor neuron syndrome, multiple myeloma, human T-cell lymphotrophic virus-1-associated myelopathy, nephritic syndrome, membranous nephropathy, nephrotic syndrome, euthyroid ophthalmopathy, opsoclonus-myoclonus, recurrent otitis media, paraneoplastic cerebellar degeneration, paraproteinemic neuropathy, parvovirus infection (general), polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes (POEMS) syndrome, progressive lumbosacral plexopathy, lyme radiculoneuritis, Rasmussen syndrome, Reiter syndrome, acute renal failure, thrombocytopenia (nonimmune), streptococcal toxic shock syndrome, uveitis and Vogt-Koyanagi-Harada syndrome. 
     In particular embodiment, the present invention is directed to, for example, methods of treating allergy, autoimmune disease, transplant-related disorders such as graft versus host disease, enzyme or protein deficiency disorders, hemostatic disorders, cancers, infertility, or infections (viral, bacterial, or parasitic). The Tregitopes or chimeric proteins of the invention can be used with in conjunction with other proteins or compounds used for treating a subject with a medical condition in order to reduce adverse events or enhance the efficacy of the co-administered compound. 
     Application to Allergy. Allergen-specific regulatory T cells play an important role in controlling the development of allergy and asthma. Both naturally occurring CD4/CD25 regulatory T cells and secondary T Regs  (antigen-specific regulatory T cells), both expressing the transcription factor FOXp3, have been shown to inhibit the inappropriate immune responses involved in allergic diseases. A number of recent studies indicate that regulatory T cells play an important role in controlling the overdevelopment of T-helper type 2 biased immune responses in susceptible individuals, not only in animal models, but in humans as well. Recent studies indicate that T regulatory cells also suppress T cell costimulation by the secretion of TGF-p and IL-10, suggesting an important role of T regulatory cells in the regulation of allergic disorders. Impaired expansion of natural or adaptive regulatory T cells leads to the development of allergy, and treatment to induce allergen-specific regulatory T cells would provide curative therapies for allergy and asthma. 
     One strategy both for the prevention and therapy of asthma is the induction of regulatory T cells. Animals can be protected from developing asthma by immune stimulation leading to Th1 or Tr responses. 
     Application to Transplantation. The Tregitopes of the invention are useful to induce tolerance during the transplantation process, by promoting the development of cells that specifically down regulate immune responses against donor cells. Induction of Ag-specific T Reg  cells for treating organ-specific autoimmunity is an important therapeutic development, avoiding generalized immune suppression. In murine models of bone marrow transplantation, T Regs  promote donor bone marrow engraftment and decrease the incidence and severity of graft versus host disease without abrogating the beneficial graft versus tumor immunologic effect. These findings, in concert with observations that T Regs  in mice and humans share phenotypic and functional characteristics, have led to active investigations into the use of these cells to decrease complications associated with human hematopoietic cell transplantation. An imbalance of  TRegs  and effector T cells contributes to the development of graft versus host disease. However, the mechanisms of immunoregulation, in particular the allorecognition properties of TRe g s, their effects on and interaction with other immune cells, and their sites of suppressive activity, are not well understood. 
     Accumulating evidence from both humans and experimental animal models has implicated the involvement of T Regs  in the development of graft versus host disease (GVHD). The demonstration that T Reg s can separate GVHD from graft versus tumor (GVT) activity suggests that their immunosuppressive potential could be manipulated to reduce GVHD without detrimental consequence on GVT effect. Although a variety of T lymphocytes with suppressive capabilities have been reported, the two best-characterized subsets are the naturally arising, intrathymic-generated T Regs  (natural TRe g s) and the peripherally generated, inducible T Regs  (inducible TRe g s). 
     Application to Autoimmunity. Tregitopes can be used as a tolerizing agents for immunogenic compounds (protein therapeutics). This discovery has implications for the design of protein therapeutics. Thus, administration of a monoclonal antibody, autologous cytokine, or foreign protein in conjunction with Tregitopes suppresses adverse T effector immune responses. In vivo, TRegs act through dendritic cells to limit autoreactive T-cell activation, thus preventing their differentiation and acquisition of effector functions. By limiting the supply of activated pathogenic cells, T Regs  prevent or slow down the progression of autoimmune diseases. This protective mechanism appears, however, insufficient in autoimmune individuals, likely because of a shortage of T Regs  cells and/or the development and accumulation of T Reg -resistant pathogenic T cells over the long disease course. Thus, restoration of self-tolerance in these patients may require purging of pathogenic T cells along with infusion of T Regs  with increased ability to control ongoing tissue injury. Organ-specific autoimmune conditions, such as thyroiditis and insulin-dependent diabetes mellitus have been attributed to a breakdown of this tolerance mechanism. 
     Application to Diabetes. Type 1 (juvenile) diabetes is an organ-specific autoimmune disease resulting from destruction of insulin-producing pancreatic beta-cells. In non-diabetics, islet cell antigen-specific T cells are either deleted in thymic development or are converted to T regulatory cells that actively suppress effector responses to islet cell antigens. In juvenile diabetics and in the NOD mouse model of juvenile diabetes, these tolerance mechanisms are missing. In their absence, islet cell antigens are presented by human leukocyte antigen (HLA) class I and II molecules and are recognized by CD8(+) and CD4(+) auto-reactive T cells. Destruction of islet cells by these auto-reactive cells eventually leads to glucose intolerance. Co-administration of Tregitopes and islet cell antigens leads to the activation of natural T regulatory cells and the conversion of existing antigen specific effector T cell to a regulatory phenotype. In this way deleterious autoimmune response is redirected leading to the induction of antigen-specific adaptive tolerance. Modulation of auto-immune responses to autologous epitopes by induction of antigen-specific tolerance can prevent ongoing beta-cell destruction. Accordingly, a Tregitope of the invention is useful in methods for the prevention or treatment of diabetes. 
     Application to Hepatitus B (HBV) infection. Chronic HBV is usually either acquired (by maternal fetal transmission) or can be a rare outcome of acute HBV infection in adults. Acute exacerbations of chronic hepatitis B (CH-B) are accompanied by increased cytotoxic T cell responses to hepatitis B core and e antigens (HBcAg/HBeAg). In a recent study, the SYFPEITHI T cell epitope mapping system was used to predict MHC class II-restricted epitope peptides from the HBcAg and HbeAg. MHC class II tetramers using the high scoring peptides were constructed and used to measure T Reg  and CTL frequencies. The results showed that T Reg  cells specific for HBcAg declined during exacerbations accompanied by an increase in HBcAg peptide-specific cytotoxic T cells. During the tolerance phase, FOXp3-expressing T Reg  cell clones were identified. These data suggest that the decline of HbcAg T Reg  T cells accounts for the spontaneous exacerbations on the natural history of chronic hepatitis B virus infection. Accordingly, a Tregitope of the invention is useful in methods for the prevention or treatment of viral infection, e.g., HBV infection. 
     Application to SLE. A TReg epitope that plays a role in Systemic Lupus Erythematosis (SLE) or Sjogren&#39;s syndrome has been defined. This peptide encompasses residues 131-151 (RIHMVYSKRSGKPRGYAFIEY; SEQ ID NO:67) of the spliceosome protein. Binding assays with soluble HLA class II molecules and molecular modeling experiments indicated that the epitope behaves as promiscuous epitope and binds to a large panel of human DR molecules. In contrast to normal T cells and T cells from non-lupus autoimmune patients, PBMCs from 40% of randomly selected lupus patients contain T cells that proliferate in response to peptide 131-151. Alteration of the ligand modified the T cell response, suggesting that several populations of T cells responding to this peptide exist, among which may be TReg cells. T regulatory epitopes have also been defined in Sjogren&#39;s syndrome. Accordingly, a Tregitope of the invention co-administered in combination with the epitope from above is useful in methods for the prevention or treatment of SLE. 
     Application to Graves&#39; Disease. Graves&#39; disease is an autoimmune disorder that is characterized by antibodies to self-thyroid stimulating hormone receptor (TSHR) leading to leading to hyperthyroidism, or an abnormally strong release of hormones from the thyroid gland. Several genetic factors can influence susceptibility to Graves&#39; disease. Females are much more likely to contract the disease than males; White and Asian populations are at higher risk than black populations and HLA DRB1-0301 is closely associated with the disease. Accordingly, co-administration of Tregitope(s) of the invention with TSHR or other Graves&#39; disease antigens or portions thereof is useful in methods for the prevention or treatment of Graves&#39; disease. 
     Application to Autoimmune Thyroiditis. Autoimmune Thyroiditis is a condition that occurs when antibodies arise to self thyroid peroxidase and/or thyroglobulin, which cause the gradual destruction of follicles in the thyroid gland. HLA DR5 is closely associated with the disease. Accordingly, co-administration of Tregitope of the invention with thyroid peroxidase and/or thyroglobulin TSHR or portions thereof are useful in methods for the prevention or treatment of autoimmune thyroiditis. 
     Application to the Design of Vaccine Vectors. A monoclonal antibody targeting the dendritic cell surface receptor DEC-205 has shown promise as a vaccine vector capable of targeting vaccine antigens to dendritic cells. The success of anti-DEC-205 as a stimulator of strong inflammatory immune responses, however, depends on co-administration of non-specific dendritic cell maturation factors. In their absence, anti-DEC-205 induces antigen-specific tolerance rather than immunity. Therefore, regulatory T-cell epitopes contained in anti-DEC-205 promote a tolerogenic reaction that is only overcome through the co-administration of non-specific immuno-stimulators. This point has been verified experimentally, namely, that the Tregitopes contained in the anti-DEC-205 vector cause antigen-specific expansion of regulatory T cells and suppress inflammatory immune responses. Modifying those Tregitopes such that they no longer bind to MHC molecules will significantly diminish tolerogenicity, enabling use of anti-DEC-205 as an effective stand alone antigen delivery system that obviates the dangers associated with non-specific activation of the immune system. 
     KITS 
     The methods described herein can be performed, e.g., by utilizing pre-packaged kits comprising at least one Tregitope composition of the invention, which can be conveniently used, e.g., in clinical settings to treat subjects exhibiting symptoms or family history of a medical condition described herein. In one embodiment, the kit further comprises instructions for use of the at least one Tregitope composition of the invention to treat subjects exhibiting symptoms or family history of a medical condition described herein. 
     Ex Vivo Expansion of T-Regulatory Cells Using Tregitopes 
     In another aspect, the invention provides ex vivo methods for the expansion of regulatory T-cells. In one embodiment, the invention provides a method of expanding regulatory T-cells in a biological sample, the method comprising: (a) providing a biological sample from a subject; (b) isolating regulatory T-cells from the biological sample; and contacting the isolated regulatory T-cells with an effective amount of a Tregitope composition of the invention under conditions wherein the T-regulatory cells increase in number to yield an expanded regulatory T-cell composition, thereby expanding the regulatory T-cells in the biological sample. In one embodiment, the method further comprises the step of administration of the expanded regulatory T-cell composition to a subject. In one embodiment, the subject administered the expanded regulatory T-cell composition is the same individual from which the original biological sample was obtained, e.g., by autologous transplantation of the expanded regulatory T-cell composition (Ruitenberg, J. et al.,  BMC Immunol.,  7:11, 2006). 
     In Vitro Uses of Tregitope Compositions 
     In another aspect, the invention provides the use of the Tregitope compositions of the invention as reagents in the study of regulatory T-cell function in in vitro experimental models. In one embodiment, the invention provides in vitro methods for stimulation of regulatory T-cells in a biological sample, the method comprising: (a) providing a biological sample from a subject; (b) isolating regulatory T-cells from the biological sample; and contacting the isolated regulatory T-cells with an effective amount of a Tregitope composition of the invention under conditions wherein the T-regulatory cells are stimulated to alter one or more biological function, thereby stimulating the regulatory T-cells in the biological sample. In one embodiment, the invention provides in vitro methods for the measurement of binding Tregitope to a regulatory T-cells or fragment thereof. 
     The examples that follow are not to be construed as limiting the scope of the invention in any manner. In light of the present disclosure, numerous embodiments within the scope of the claims will be apparent to those of ordinary skill in the art. 
     EXEMPLIFICATION 
     Tregitopes were (1) identified using the T cell epitope mapping algorithm EpiMatrix, (2) confirmed to bind to soluble HLA, (3) proven to engage natural regulatory T cells, (4) proven to suppress the immune response to co-delivered antigens ex vivo (in human PBMC) and (3) proven to suppress the immune response to co-delivered antigens in vivo (in mice). The methods for these discoveries are outlined below followed by the corresponding results. 
     (1) Methods for the identification of T cell epitopes and T cell epitope clusters T cells specifically recognize epitopes presented by antigen presenting cells (APCs) in the context of MHC (Major Histocompatibility Complex) Class II molecules. These T-helper epitopes can be represented as linear sequences comprising 7 to 30 contiguous amino acids that fit into the MHC Class II binding groove. A number of computer algorithms have been developed and used for detecting Class II epitopes within protein molecules of various origins (De Groot, A. et al.,  AIDS Res. Hum. Retroviruses,  13: 539-541, 1997; Schafer, J. et al.,  Vaccine,  16:1880-1884, 1998; De Groot, A. et al.,  Vaccine,  19:4385-95, 2001; De Groot, A. et al.,  Vaccine,  21:4486-504, 2003). These “in silico” predictions of T-helper epitopes have been successfully applied to the design of vaccines and the deimmunization of therapeutic proteins. 
     The EpiMatrix system is a tool for predicting class I and class II epitopes. The algorithm uses matrices for prediction of 9- and 10-mer peptides binding to HLA molecules. Each matrix is based on position-specific coefficients related to amino acid binding affinities that are elucidated by a method similar to, but not identical to, the pocket profile method (Sturniolo, T. et al.,  Nat. Biotechnol.,  17:555-561, 1999). The EpiMatrix system has been used to prospectively predict a large number of epitopes that have been confirmed in vitro and in vivo. The entire amino acid of any given sequence is first parsed into overlapping 9-mer frames where each frame overlaps the last by eight amino acids. Each frame is then scored for predicted affinity to each of eight common Class II HLA haplotypes (DRB1*0101, DRB1*0301, DRB1*0401, DRB1*0701, DRB1*0801, DRB1*1101, DRB1*1301, and DRB1*1501). Due to their prevalence and their difference from each other, these eight alleles cover around 97% of human populations worldwide. EpiMatrix raw scores are then normalized with respect to a score distribution derived from a very large set of randomly generated peptide sequences. The resulting “Z” scores are normally distributed and directly comparable across alleles. 
     EpiMatrix peptide scoring. It was determined that any peptide scoring above 1.64 on the EpiMatrix “Z” scale (approximately the top 5% of any given peptide set) has a significant chance of binding to the MHC molecule for which it was predicted. Peptides scoring above 2.32 on the scale (the top 1%) are extremely likely to bind; most published T cell epitopes fall within this range of scores. Previous studies have also demonstrated that EpiMatrix accurately predicts published MHC ligands and T cell epitopes. 
     Identification of promiscuous T cell Epitope Clusters. Following epitope mapping, the result set produced by the EpiMatrix algorithm is screened for the presence of T cell epitope clusters and EpiBars. Potential T cell epitopes are not randomly distributed throughout protein sequences but instead tend to “cluster.” T cell epitope “clusters” range from 9 to roughly 30 amino acids in length and, considering their affinity to multiple alleles and across multiple frames, contain anywhere from 4 to 40 binding motifs. Using a proprietary algorithm known as ClustiMer, putative T cell epitope clusters are identified. Briefly, the EpiMatrix scores of each 9-mer peptide analyzed are aggregated and checked against a statistically derived threshold value. High scoring 9-mers are then extended one amino acid at a time. The scores of the extended sequences are then re-aggregated and compared to a revised threshold value. The process is repeated until the proposed extension no longer improves the overall score of the cluster. Tregitope(s) identified in the present studies were identified by the ClustiMer algorithm as T cell epitope clusters. They contain significant numbers of putative T cell epitopes and EpiBars indicating a high potential for MHC binding and T cell reactivity. (2) Methods for the assessment of peptide synthesis and binding to soluble MHC. 
     Synthesis of peptides. Tregitopes can be produced by direct chemical synthesis or by recombinant methods (Sambrook et al., Molecular Cloning: A Laboratory Manual, 2  ed ., Cold Spring Harbor Laboratory Press, (1989)). Peptides corresponding to the Tregitopes of the invention were prepared by 9-fluoronylmethoxycarbonyl (Fmoc) synthesis at New England peptide and on an automated Rainen Symphony/Protein Technologies synthesizer (Synpep, Dublin, Calif.). The peptides were delivered &gt;80% pure as ascertained by HPLC, mass spectrometry and UV scan (ensuring purity, mass and spectrum, respectively). 
     Binding of produced peptides. Non-biotinylated test peptide is suspended in a 96-well polypropylene plate in final concentrations ranging from 0.1 μM-400 μM in triplicate wells. Purified recombinant HLA Class II molecules in a solution containing 1 mM PefaBloc, 0.75% n-octyl-B-D-glucopyranoside in 150 mM citrate-phosphate buffer (pH 5.4), were then added to these wells at a final concentration of 200 ng/well. The 96-well plates are incubated at 37° C. in 6% CO 2  for 45 minutes. Following the incubation, biotinylated Flu HA peptide 307-319 (or another suitable control peptide) is added to a final concentration of 0.1 μM per well and incubated at 37° C. for 20 hours. The contents of each well are then added to a 96-well high binding ELISA plate previously coated with the anti-human HLA-DR L243 capture antibody (Becton Dickenson) and incubated at 4° C. for 20 hours. The plate was then developed by the addition of 100 μl (10 μg/ml) of Europium-labeled Streptavidin (Perkin-Elmer) and 100 μl Enhancement Buffer (Perkin-Elmer) to each well. The reaction was incubated in the dark at room temperature for 1530 minutes and then fluorescence was measured on a Wallac Victor 3-V time-resolved fluourometer. 10 50  values were then calculated by non-linear regression analysis using the SigmaPlot analysis program. Based on comparisons with known peptides, an IC 50  of 250 μM or more is indicative of weak binding and an IC 50  of 400 μM or more is indicative of a non-binding interaction. 
     (3) Methods for Assessing the Ability of Peptides to Engage Natural Regulatory T Cells. 
     T-cell isolation. This research program involves donated blood obtained from the Rhode Island Blood Bank in Providence, blood from volunteers recruited at Clinical Partners, Johnston, R.I., blood obtained from volunteers recruited by Stallergenes, Paris, France, and samples obtained from a commercial supplier. Donor blood was obtained in accordance with all federal guidelines and in accordance with Stallergenes and EpiVax institutional policies. The protocol for obtaining donor blood was approved by the respective institutional review boards. Peripheral blood mononuclear cells (PBMC) were isolated according to the Accuspin protocol (Sigma-Aldrich, St. Louis, Mo.). Cryopreserved PBMC from dust-mite-allergic individuals were obtained from Cellular Technologies Ltd. (Cleveland, Ohio). 
     Natural T reg assay. Human PBMCS are stimulated directly ex vivo for 4 days in the presence of tetanus toxin peptide  17830-844  alone, Tregitope alone, phytohemagglutinin alone (a mitogenic positive control) or no stimulus. 1×10 6  cells were stained with anti-CD4-FITC (clone RPA-T4; eBioscience) and anti-CD25-APC (clone BC96; eBioscience) antibodies for 30 minutes on ice in Flow Staining Buffer (eBioscience) and washed twice with buffer. Following cell surface staining, cells are fixed and permeabilized (eBioscience) and stained intracellulary for FOXp3 (clone PCH101; eBioscience) following manufacturer&#39;s protocol. The frequency of FOXp3 positive CD4+/CD25+ T cells under various culture conditions is enumerated by the Flowjo analysis software. T cell activation is indicated by increases in CD4+CD25+ expression, which, when accompanied by an increase in FOXp3 expression, is indicative that the activated cells are regulatory. 
     (4) Methods for Assessing the Ability of Peptides to Suppress the Response to Co-Administered Antigens Ex Vivo. 
     Bystander suppression assay. Isolated PBMCs were cultured for 8 days at 37° C. 5% CO 2  in presence of either an immunogenic antigen alone or that antigen in the presence of Tregitope peptide. Test antigens were added at 10 vig/mland include 1) classic antigens such as, for example, tetanus toxin peptide  TT830-844 , influenza hemagglutinin peptide 307-319, vaccinia peptide epitopes and the CEF positive control peptide pool (NIH AIDS Research &amp; Reference Reagent Program at the website aidsreagent.org; Currier, J. et al.,  J. Immunol. Methods,  260:157-72, 2002; Mwau, M. et al.,  AIDS Res. Hum. Retroviruses,  18:611-8, 2002), 2) protein therapeutics such as Botulinum Neurotoxin A, autologous autoantigens such as Thyroid Hormone Stimulating hormone and complement component C3d. Test antigens also included allergens: birch tree pollen antigen Betv1, House dust mite lysate and the purified house dust mite antigen, Der P2. Recombinant IL-2 (10 IU/ml) and IL-7 (20 ng/ml) were added to PBMC cultures on day 2. After 8 days of stimulation, cells were harvested and washed several times with PBS and assayed according to the human cytokine release assays described below. 
     Human IFN-y ELISpot. IFN-y ELISpot assays are performed using Human IFN-y ELISpot kits purchased from Mabtech. Target peptides are added at 10 pg/ml to triplicate wells containing 250,000 human peripheral blood mononuclear cells in RPMI1640 with 10% human serum and incubated for eighteen to twenty-two hours at 37° C. under a 5% CO 2  atmosphere. Triplicate wells are plated with PHA at 10 iug/mL. Six wells with no peptide are used for background determination. A response is considered positive if the number of spots in the peptide test wells is statistically different (p&lt;0.05) from that of the control wells by the Mann-Whitney U test. In general, responses are considered positive if the number of spots is at least four times background and greater than 50 spots per one million cells over background (1 response over background per 20,000 splenocytes). Results are recorded as the average number of spots over background and adjusted to spots per one million cells seeded. Suppression rates of 10% or greater, when determined to be statistically significant, are considered statistically significant. 
     Human IFN-y ELISpot IFN-y ELISpot assays are performed using Human IL-4 ELISpot kits purchased from Mabtech. Target peptides are added at 10 μg/ml to triplicate wells containing 250,000 human peripheral blood mononuclear cells in RPM11640 with 10% human serum and incubated for eighteen to twenty-two hours at 37° C. under a 5% CO 2  atmosphere. Triplicate wells are plated with PHA at 10 i.ig/mL. Six wells with no peptide are used for background determination. A response is considered positive if the number of spots in the peptide test wells is statistically different (p&lt;0.05) from that of the control wells by the Mann-Whitney U test. In general, responses are considered positive if the number of spots is at least four times background and greater than 50 spots per one million cells over background (1 response over background per 20,000 splenocytes). Results are recorded as the average number of spots over background and adjusted to spots per one million cells seeded. Suppression rates of 10% or greater, when determined to be statistically significant, are considered statistically significant. 
     Human IL-4 ELISpot, IL-4 ELISpot assays are performed using Human IL-4 ELISpot kits purchased from Mabtech. Target peptides are added at 10 vtg/ml to triplicate wells containing 250,000 human peripheral blood mononuclear cells in RPM11640 with 10% human serum and incubated for eighteen to twenty-two hours at 37° C. under a 5% CO 2  atmosphere. Triplicate wells are plated with PHA at 2 n/mL. Six wells with no peptide are used for background determination. Statistical tests were carried out using a variant permutation test (Hudgens, M. et al.,  J. Immunol. Methods,  288:19-34, 2004). A response is considered positive if the number of spots in the peptide test wells is statistically different (p&lt;0.01) from that of the control wells. In general, responses are considered positive if the number of spots is at least four times background and greater than 50 spots per one million cells over background (1 response over background per 20,000 splenocytes). Results are recorded as the average number of spots over background and adjusted to spots per one million cells seeded. 
     Suppression rates of 10% or greater, when determined to be statistically significant, are considered significant. 
     Human IFN-y ELISA. Target peptides are added at 10 IAg/ml to cultures containing human peripheral blood mononuclear cells in RPM11640 with 10% human serum and incubated for eighteen to twenty-two hours at 37° C. under a 5% CO 2  atmosphere. Cultures stimulated with PHA at 10 ii.g/mL or with no peptide are used as controls. Human IFNI, quantitative sandwich ELISAs were performed using R&amp;D Systems Quantikine ELISA kits. A polyclonal antibody specific for IFN-7 is pre-coated onto a 96-well microtiter plate. Kit-provided standards and cell supernatant samples including PHA and no-peptide controls (100 μl) are pipetted into the wells and any IFN1-7 present is bound by the immobilized antibody over 2 hours at room temperature. After washing away unbound substances, an enzyme-linked polyclonal antibody specific for IFN-.7 is added to the wells for a two hour incubation at room temperature. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells for 30 minutes and color developed in proportion to the amount of bound IFNI-7. The color development is stopped and the intensity of the color at 450 nm measured on a Wallac Victor3. Correction for optical imperfections in the plate is made by subtraction of intensities at 540 nm from the 450 nm values. Differences in cytokine levels between experimental groups were evaluated by t-test. A response is considered positive if the observed difference in cytokine expression between the experimental and control wells is statistically different (p&lt;0.01). 
     Multiplexed human cytokine/chemokine ELISA. Supernatants from PBMC cultures are evaluated for cytokines and chemokine levels using the SearchLight multiplex ELISA technology. Human cytokines that are measured include IL-1p, IL-2, IL-4, IL-5, IL-6, IL-10, IL-12p40, IL-12p70, TNFa and TGFp. Human chemokines that are measured include MCP-1, MIP-1a and MIP-1p. SearchLigbt Proteomic Arrays are a quantitative multiplexed sandwich ELISA containing up to 16 different capture antibodies spotted on the bottom of a 96-well polystyrene microtiter plate. Each antibody captures specific protein detected with a biotinylated antibody, followed by the addition of streptavidin-HRP and lastly, SuperSignal ELISA Femto Chemiluminescent substrate detected with a charge-coupled device (CCD) camera. Differences in cytokine levels between experimental groups were evaluated by t-test. A response is considered positive if the observed difference in cytokine expression between the experimental and control wells is statistically different (p&lt;0.01). 
     Cell separations/depletions methods. Human Treg cell populations are depleted or positively isolated from PBMC using the invitrogen dynabeads system (for human CD4 and CD25) according to manufacturer&#39;s instructions (InVitrogen, Carlsbad, Calif.). 
     (5) Methods for the Suppression of Response to Co-Administered Antigens In Vivo. 
     To measure the immunosuppressive effects of Tregitopes on protein-induced effector responses in a living system, experiments are performed using a murine model. Groups of mice are immunized with an antigen alone, a cocktail of antigen and tregitope, or with an antigen fused to tregitope. A negative control group (solvent alone) is also assessed. One week following the final injection, the mice are sacrificed in accordance with all institutional and federal guidelines and spleens harvested. Freshly isolated mouse splenocytes are used to assay the cellular immune response in vivo. Single splenocyte suspensions are prepared and used in the assays below. Whole blood is also obtained by cardiac puncture and serum collected for use in quantifying antibody response to the co-administered antigen. 
     Murine IFN-y ELISpot. IFN-y ELISpot assays are performed using murine IFN-y ELISpot kits purchased from Mabtech. Target peptides are added at 10 jug/ml to tripliocate wells containing 300,000 murine splenocytes (in RPMI1640 with 10% FCS) and incubated for eighteen to twenty-two hours at 37° C. under a 5% CO 2  atmosphere. Triplicate wells are plated with ConA at 10 pg/mL. Six wells with no peptide are used for background determination. A response is considered positive if the number of spots in the peptide test wells is statistically different (p&lt;0.05) from that of the control wells by the Mann-Whitney U test. In general, responses are considered positive if the number of spots is at least four times background and greater than 50 spots per one million cells over background (1 response over background per 20,000 splenocytes). Results are recorded as the average number of spots over background and adjusted to spots per one million cells seeded. 
     Murine IL-4 ELISpot. IL-4 ELISpot assays are performed using murine IL-4 ELISpot kits purchased from Mabtech. Target peptides are added at 10 μg/ml to triplicate wells containing 300,000 murine splenocytes (in RPM11640 with 10% FCS) and incubated for eighteen to twenty-two hours at 37° C. under a 5% CO 2  atmosphere. Triplicate wells are plated with ConA at 10 j.ig/mL. Six wells with no peptide are used for background determination. Statistical tests were carried out using a variant permutation test (Hudgens, M. et al.,  J. Immunol. Methods,  288:19-34, 2004). A response is considered positive if the number of spots in the peptide test wells is statistically different (p&lt;0.01) from that of the control wells. In general, responses are considered positive if the number of spots is at least four times background and greater than 50 spots per one million cells over background (1 response over background per 20,000 splenocytes). Results are recorded as the average number of spots over background and adjusted to spots per one million cells seeded. 
     Murine IFN-yELISA. Target peptides are added at 10 pg/ml to cultures containing human peripheral blood mononuclear cells in RPM11640 with 10% human serum and incubated for eighteen to twenty-two hours at 37° C. under a 5% CO 2  atmosphere. Cultures stimulated with PHA at 10 μg/mL or with no peptide are used as controls. Mouse IFN-y quantitative sandwich ELISAs were performed using R&amp;D Systems Quantikine ELISA kits. A polyclonal antibody specific for IFN-y is pre-coated onto a 96-well microtiter plate. Kit-provided standards and cell supernatant samples including PHA and no-peptide controls (100 μl) are pipetted into the wells and any IFN-y present is bound by the immobilized antibody over two hours at room temperature. After washing away unbound substances, an enzyme-linked polyclonal antibody specific for IFN-y is added to the wells for a two hour incubation at room temperature. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells for 30 minutes and color developed in proportion to the amount of bound IFN-y. The color development is stopped and the intensity of the color at 450 nm measured on a Wallac Victor3. Correction for optical imperfections in the plate is made by subtraction of intensities at 540 nm from the 450 nm values. Differences in cytokine levels between experimental groups were evaluated by t-test. A response is considered positive if the observed difference in cytokine expression between the experimental and control wells is statistically different (p&lt;0.01). 
     Flow Cytometry. Splenocytes are plated in 96-well tissue culture plates at 2×10 6  cells/well in RPMI 1640 supplemented with 10% FCS, 100 U/mL penicillin, 100 kig/mL streptomycin sulfate. An unstimulated and positive control (ConA) are included in each assay. Cells are incubated overnight at 37° C. at 5% CO 2 . Following incubation, the cells are washed in PBS containing 1% bovine serum albumin and stained with surface antibodies (e.g., CD4, CD25). Cells are then washed and fixed using the Cytofix/Cytoperm kit (BD PharMingen) according to manufacturer&#39;s instructions. Following fixation, the cells are washed twice in Cytoperm buffer and stained with antibodies against intracellular markers (e.g., FOXp3, IL-10). Following staining, the cells are washed and fixed with PBS containing 1% paraformaldehyde in preparation for flow cytometry. Cells are analyzed on a BD Facscalibur machine. 20,000 events are collected per sample. Data analysis is performed using FloJo software. All data are background-subtracted. Comparisons between groups are based on a Wilcoxon rank sum test. A significance of p&lt;0.05 is applied for pairwise comparisons and p&lt;0.01 is used for multiple comparisons. 
     Cell separations/depletions methods. Murine Treg cell populations are depleted or positively isolated from PBMC using the InVitrogen dynabeads system (for murine CD4 and CD25) according to manufacturer&#39;s instructions (InVitrogen, Carlsbad, Calif.). 
     Quantification of antibodies against co administered antigen. Quantification of IgG antibody to antigens was determined by antibody-capture ELISA. Antigen (10 tig/mL) is dissolved in carbonate buffer and placed into a 96-well microtiter plate overnight at 4° C. The plates were then washed with phosphate-buffered saline containing 0.05% Tween 20 (PBST) and blocked for three hours at room temperature with 5% fetal bovine serum (FBS; Gibco) in PBS. Serial dilutions of sera in 0.5% FBS/PBS are added to the plates and incubated at room temperature for two hours. The microtiter plates are then washed with PBST and 100111_goat anti-mouse IgG (gamma-chain specific) conjugated to horseradish peroxidase (Southern Biotechnology Associates) diluted 1:10000 in 0.5% FBS/PBS is added to each well. Microtiter plates are washed in PBST and then developed with 3,3′,5,5′-tetramethylbenzidine (TMB; Moss). Absorbances were read at a wavelength of 450 nm measured on a Wallac Victor3. Correction for optical imperfections in the plate is made by subtraction of intensities at 540 nm from the 450 nm values. 
     Example 1. Identification of a Tregitope Composition 
     Identification of epitopes in Human IgG Proteins as regulatory. After evaluating a large number of antibodies for immunogenic potential, a recurring pattern was observed. Certain epitope clusters were occurring in multiple antibodies. Not wishing to be bound by theory, it was reasoned that highly conserved epitope clusters were unlikely to be promoting anti-antibody immune responses. It was further reasoned that these recurring patterns might be either passively tolerated by the immune system or actively engaging regulatory T cells responsible for suppressing anti-antibody immune response. Comparing the sequences of the recurring epitope clusters to the protein database at GenBank established 19 regions contained in the sequences of IgG antibodies that were both conserved and potentially capable of stimulating regulatory T cells (See  FIGS. 18A and 18B ). 
     As shown in  FIGS. 18A and 18B , according to the EpiMatrix system, all 19 of these regions have significant immune stimulatory potential, each one containing at least one and at most 14 binding motifs and scoring between one and 25 on the EpiVax immunogenicity scale. In addition several of these sequences contained one or more “EpiBars”. EpiBars are single 9 mer frames that are expected to bind to at least 4 different Class II HLA. EpiBars are a marker for increased immuno-stimulatory 
     Conservation. All the IgG derived putative Tregitope sequences were compared to the germline sequences of IgG1, IgG2, IgG3, IgG4, IgA, IgE, IgD and IgM through visual inspection. The IgG-derived Tregitopes were found to be highly conserved in the germline sequences of IgG1, IgG2, IgG3 and IgG4. No homology was found in the germline sequences of IgA, IgE, IgD or IgM. The sequences of the additional Tregitopes are also highly conserved among (variants of human proteins) and are generally present in the circulation in large amounts. 
     Species. Homology analysis of the IgG-derived Tregitopes to non-human species was performed. The sequences were uploaded into the Basic Local Alignment Search Tool (BLAST) via the NCBI website (ncbi.nlm.nih.gov/blast). The BLAST program compares protein sequences to sequence databases and calculates the statistical significance of matches in order to find regions of local similarity between sequences. The IgG-derived Tregitopes were found to be conserved across non-human species such as mouse, rat, cat, camel, cow and non-human primates.  FIG. 19  illustrates a BLAST report of Tregitope-289 (SEQ NO: 4). 
     Identification of regulatory epitopes in common circulating human proteins. In a subsequent analysis EpiVax identified a set of common and circulating proteins that might also contain Tregitopes. The analyzed protein set included isolates of human: Actin, Albumin, Collagen, Fibrinogen, Haptoglobin, Keratin, Myosin, Osteocalcin, Prostaglandin, Superoxide Dismutase, Titin and Transferrin. Common isolates of each protein were analyzed via EpiMatrix and ClustiMer as described above and a set of high scoring and highly conserved putative T cell epitope clusters was selected for further analysis. See  FIGS. 18A and 18B , SEQ ID NOS:38-58. Example 2. Synthesis and characterization of a Tregitope Composition by Binding to HLA Class II Molecules Soluble MHC binding assays were performed on the synthetic IgG Tregitopes according to the methods described above. IC 50  values (μM) were derived by a six point inhibition curve of a strong binding control peptide. As depicted in  FIG. 20 , the Tregitopes identified by in silico analysis bound to human MHC molecules. 
     Additional assays related to structural modifications to amino and carboxy termini. Modifications to the amino and caboxy termini of peptides have been shown to alter MHC binding, proteolytic degradation and T cell activation (Maniere, B. et al.,  MoL ImmunoL,  32:1377-85, 1995; Allen, P. et al.,  Int. ImmunoL,  1:141-50, 1989). If the observed activation of nTregs were indeed due to Tregitope-specific TCR recognition, then fine alterations at the carboxy terminus of the Tregitope peptide should lead to differential suppressive effects. The same Tregitope peptide sequence was synthesized with and without a C-terminal amide cap. The uncapped peptide was evaluated for affinity to DRB1*0101 and DRB1*1501 in HLA binding assays and shown to bind to both alleles with higher affinity than did the capped peptide. Using PBMC from a DRB1*0101 subject, the ability of Tregitope peptides (capped and uncapped) to suppress responses to co-incubated CEF, a MHC class I immunogenic peptide pool, was then investigated. The cells were stimulated on day 1 and cultured for 6 days. On day 7 the cells were collected and half were stained for CD4, CD25 and CD127 and analyzed by flow cytometry. The remaining cells were added to an IFN-y ELISpot plate and re-stimulated with CEF. The co-cultures with the C-terminal amide-capped Tregitope led to an increase in CD4+CD25+CD127low Tregs compared to the uncapped Tregitope-289 ( FIG. 2 , left panel). Consistent with previous studies that have shown that CD4+CD25+CD127low Tregs are highly suppressive, the capped Tregiotpe-289, but not the uncapped Tregitope-289, was able to suppress CEF-specific IFN-y secretion ( FIG. 2 , right panel). 
     Subsequent analysis showed a small 1 dalton change between the capped and uncapped versions of Tregitope-289 (SEQ NO: 4). Tregitope-289 amidated peptide is 1 dalton smaller by mass spectrometry analysis. Amidation of the C-terminus of Tregitope-289 is herein demonstrated to alter its binding and functional characteristics. Because the capped version of Tregitope-289 peptide demonstrated better functionality, the capped (amidated) peptide was used in all subsequent assays. In further support, results displayed here for Tregitope-289 refer to the capped version. Both capped and uncapped versions of the Tregitopes described herein are encompassed by the present invention. 
     Example 3. Characterization of a Tregitope Composition by Stimulation of Natural Regulatory T Cells 
     Human PBMCS were stimulated directly ex vivo for 4 days in the presence of tetanus toxin peptide  17   830-844  alone, Tregitope-289 alone, phytohemagglutinin (a mitogenic positive control) alone, or no stimulus. 1×10 6  cells were stained with anti-CD4-FITC (clone RPA-T4; eBioscience) and anti-CD25-APC (clone BC96; eBioscience) antibodies for 30 minutes on ice in Flow Staining Buffer (eBioscience) and washed twice with buffer. Following cell-surface staining, cells were fixed and permeabilized (eBioscience) and stained intracellulary for Foxp3 (clone PCH101; eBioscience) following manufacturer&#39;s protocol. The frequency of FoxP3 positive CD4+/CD25+ T cells under various culture conditions was enumerated by Flowjo analysis software. There were similar increases in CD25 expression in both the Tetanus- and Tregitope-stimulated samples indicating T cell activation by both peptides ( FIG. 3 ; results shown for Tregitope-289). Expression of FoxP3 within the CD4+CD25+ subset, however, differed significantly depending on the stimulus used. Tetanus stimulation led to a 7% decrease in expression of FoxP3, whereas Tregitope stimulation led to a more than twofold increase in expression, indicating Th and nTreg activation, respectively. 
     Example 4. Characterization of a Tregitope Composition by Suppression of Co-Administered Antigen In Vitro 
     4A: Tregitope-167 and Tregitope-134 down-regulate effector responses and upregulate regulatory responses to coadministered antigens in vitro. 
     PBMCs were cultured for 8 days with either a) pool of immunogenic peptides alone, b) a pool of immunogenic peptides with hTregitope-167, or c) a pool of immunogenic peptides with hTregitope-134. Cells were harvested and washed with PBS Cells (2×10 5  cells/well) were plated into 96-well plate and re-stimulated with the immunogenic peptide pool alone, the immunogenic peptide pool and Tregitope, or no peptide (negative control) for 65 hours. Supernatants were analyzed by multiplexed ELISA analysis as described above. The co-incubation of Tregitope during the initial stimulation led to an increase in secretion of the regulatory cytokines and chemokines, IL-10 and MCP-1 and a decrease in the secretion of helper T cell cytokines and chemokines, IL-5, IL-6, IFN-y and MIP-1q, demonstrating the ability of Tregitopes to engage and activate regulatory T cells ( FIG. 4 ). 
     4B: Tregitope-289 downregulates effector responses and upregulates regulatory responses to co-administered antigen in vitro. 
     PBMCs were cultured for 8 days with either a) pool of immunogenic peptides alone, b) a pool of immunogenic peptides with Tregitope-289, or b) a pool of immunogenic peptides withTregitope-289. The peptides in the immunogenic peptide pool were derived from C3d, an immunogenic autologous protein (Knopf, P. et al.,  Immunol. Cell Biol.,  2008 Jan. 8; doi: 10.1038/sj.icb.7100147). Cells were harvested and washed with PBS. As described, Cells (2×10 5  cells/well) were plated into 96-well plate and re-stimulated in triplicate wells with each condition: C3d pool alone, C3d pool+ Tregitope, PHA control, or no peptide (negative control) for 65 hours. Supernatants were analyzed by multiplexed ELISA analysis. Response to positive control PHA was robust following both culture conditions. The co-incubation of Tregitope during the initial stimulation led to an increase in secretion of the regulatory cytokine IL-10, a slight increase in the regulatory chemokine TGF13, and a decrease in the secretion of the helper T cell cytokines and chemokines IFNy and MIP 1a further demonstrating the ability of Tregitopes to engage and activate regulatory T cells ( FIG. 5 ). 
     4C: A pool of Tregitopes downregulates effector auto-immune responses to co-administered antigen in vitro. 
     Co-incubation with epitopes derived from TSHR, the target antigen of Graves&#39; disease, suppresses immune response to the epitopes in PBMC from a patient with Graves&#39; disease. PBMCs were cultured for 8 days with TSHR peptide pools (pool) with or without a pool of Tregitope peptides (Tregitope-134, Tregitope-167, Tregitope-289). Cells were harvested and washed with PBS. As described above, 2.5×10 5  cells were re-stimulated in an IL-4 ELISpot plate with either 1) individual TSHR epitopes+the pool of Tregitope-134, Tregitope-167, Tregitope-289), 2) a pool of TSHR epitopes+the pool of Tregitope-134, Tregitope-167, Tregitope-289 or 3) no stimulus control. Response to positive control PHA was robust following both culture conditions. 
     The co-incubation of antigen (TSHR peptides) with Tregitope during re-stimulation led to a significant decrease in IL-4 spot-forming cells. This data shows that Tregitopes suppress the cytokine secretion of effector T cells ( FIG. 6 ). 
     4A: Individual Tregitopes downregulate effector responses to CEF, a pool of immunodominant co-administered peptide antigens in vitro. 
     Co-incubation with Tregitope suppresses immune response to CEF, a pool of Immunodominant peptide epitopes derived from common pathogens. PBMCs were cultured for 8 days with or without individual Tregitope peptides: Tregitope-289, Tregitope 294, Tregitope-029, Tregitope-074, Tregitope-009. Cells were harvested and washed with PBS. As described above, 2.5×10 5  cells were re-stimulated in an IFN-y ELISpot plate with either CEF alone, PHA positive control (not shown) or no-stimulus control. Response to positive control PHA was robust following both culture conditions. 
     The co-incubation of antigen (CEF) with Tregitope during incubation led to a significant decrease in IFN-y spot-forming cells in response to restimulation with CEF. These data show that Tregitopes suppress the cytokine secretion of effector T cells ( FIG. 7 ) 
     4B: A pool of Tregitopes downregulates in vitro effector response to co-administered therapeutic protein antigen. 
     Co-incubation with Tregitope suppresses immune response to peptide epitopes derived from Botulinum neurotoxin, a protein used to treat dystonia (movement disorders). PBMCs from a subject with evidence of inhibitors (anti-BoNT antibodies) were cultured for 8 days with or without a pool of Tregitope peptides (Tregitope-167, Tregitope-134, Tregitope-289). Cells were harvested and washed with PBS. As described above, 2.5×10 5  cells were re-stimulated in an IFN-y ELISpot plate with individual BoNT peptides, a pool of BoNT peptides, PHA positive control (not shown) or no-stimulus control. Peptides for which there was no significant baseline response are not shown. Response to positive control PHA was robust following both culture conditions. The co-incubation of antigen (CEF) with Tregitope during incubation led to a significant decrease in IFKI-1(spot-forming cells in response to restimulation with CEF. These data show that Tregitopes suppress the cytokine secretion of effector T cells in response to an immunogenic therapeutic protein ( FIG. 8  and  FIG. 21 ). 
     4F: Tregitope-289 and Tregitope-134 down-regulate proliferation in response to co-administered immunodominant antigens in vitro. 
     CEF is a commercially available pool of immunodominant peptide epitopes from common pathogens. PBMCs were cultured for 8 days with CEF alone, CEF+ Tregitope-134, or CEF+ Tregitope-289. Cells were harvested and washed with PBS. 2×10 6  cells were pre-labeled with CFSE dye (Invitrogen) by standard protocol and re-stimulated for 65 hours with CEF pool, or no peptide (negative control), or PHA mitogen control; supernatants were collected and hIFN-y ELISAs were performed as described above. 
     Response to positive control PHA was robust following both culture conditions. The co-incubation of Tregitope during re-stimulation led to a significant decrease in IFN-y production (left panel), which correlated with the reduction in the proliferation of effector T cells ( FIG. 9 , right panel). 
     4G: Tregitope-289 downregulates proliferation in response to co-administered antigen in vitro. 
     PBMCs from a subject previously immunized with vaccinia were cultured for 8 days with either an immunogenic vaccinia peptide alone or an immunogenic vaccinia peptide with Tregitope-289 as described above. Cells were harvested and washed with PBS. 2×10 6  cells were pre-labeled with CFSE dye (Invitrogen) by standard protocol and re-stimulated with the vaccinia peptide, vaccinia peptide and Tregitope-289, or no peptide (negative control) for 65 hours. The co-incubation of Tregitope during incubation led to a significant decrease in proliferation of the effector T cells further demonstrating the ability of regulatory T cells activated by Tregitope to reduce the proliferation of effector T cells ( FIG. 10 ). 
     4C: Tregitope suppression is mediated by cells with a regulatory phenotype (CD4+CD25Hi T cells) and upregulation of IL-10. 
     Two samples of PBMC from a single dust-mite-allergic individual were prepared. One sample was stained with anti-CD4 and anti-CD25 antibodies and analyzed by flow cytometry. In this sample the CD4+CD25Hi subset of cells were depleted from the remaining PBMC by the methods described above. The other sample was left intact. The two samples were then co-stimulated HDM lysate with or without Tregitope-289. CD4+CD25Hi-depleted PBMC were less able to suppress IFN-y than were non-depleted PBMC, indicating that suppressive effects of Tregitopes are mediated by CD4+CD25Hi cells. In an ancillary analysis in (intact) PBMCs, CD4+ proliferative responses to HDM lysate were suppressed following co-incubation with HDM lysate and Tregitope-289 as compared with incubation with HDM lysate alone. 
       FIG. 11  documents the requirement for CD4+/CD25hi T cells in the initial co-incubation. In the presence of CD4+CD25hi cells, co-stimulation with Tregitope-289 and HDM caused suppression of gamma interferon release following restimulation with HDM alone; in the absence of CD4+CD25hi cells (sorted prior to the incubation, co-stimulation with Tregitope-289 and HDM was associated with a lower amount of suppression (16%: 16.5 to 12.4 pg/ml) as compared with a higher amount of suppression (65%: 33.5 to 11.8 pg/ml) following restimulation with HDM alone.  FIG. 11  show that the cellular subset containing Tregs is necessary for the induction of tolerance to an antigen. 
     4I: Tregitope co-incubation causes expansion of cells with a regulatory phenotype (CD4+CD25Hi T cells) and upregulation of regulatory cytokine IL-10 in response to an allergen. 
     Induction of adaptive tolerance: to determine if Tregitope nTreg activation could lead to generation of allergen-specific aTReg, PBMC (from dust mite allergic individuals) first incubated for 8 days with Dust Mite (DM) antigen alone, dust mite antigen+ Tregitope-289, or dust mite antigen+ Tregitope-167 were analyzed. As shown in the top panel ( FIG. 12 ), co-incubation of PBMC with DM antigen and Tregitope-289 led to a nearly four-fold expansion of CD4+CD25Hi cells; the same was true of PBMC co-incubated with DM antigen and Tregitope-167 (1.6 to 7.5%). In both Tregitope co-incubations, IL-10 secretion was also found to be increased five-fold ( FIG. 12 , bottom panel); a finding consistent with the possibility that the increased CD4+CD25Hi cells may be HDM-specific adaptive Treg. One of skill in the art can confirm that the expanded CD4+CD25hi population is secreting IL-10 in this in vitro assay. The IL-10 secretion in response to the co-incubated antigen, in the presence of an expanded population of CD4+CD25hi Tregulatory cells, indicates that adaptive Tregs were induced during the coincubation with antigen. 
     These data show, in the same patient and the same experiment, the expansion of CD4 CD25hi T cells following co-incubation with Tregitope-289 and DM antigen and following co-incubation with Tregitope-167 and DM antigen; and the amount of IL-10 secreted by the co-incubated cells following restimulation with HDM alone. 
     4J: Tregitope co-incubation causes suppression of antigen-specific allergic Th2 responses. 
     Tregitope co-incubation also led to a significant decrease in expression of CCR4, CD30, CRTH2, and CCR6, which have been shown to be associated with Th2 responses. Modulation of cytokine responses by allergen-specific CD4+ T cells following extended Tregitope co-stimulation was subsequently evaluated. After 30 days in culture, Tregitope co-stimulation contributed to the development of a mixed population of Bet v 1 1141-1155-specific  CD4+ T cells. Following prolonged stimulation with antigen and Tregitope, 42% of these epitope-specific cells were neither IL5 nor IFN-y positive, and 44% demonstrated a shift to a Th-1-like increased interferon response in this prolonged incubation ( FIG. 13 ). 
     Of note, the study subjects were selected for presence of HLA DR*1 1501 to improve the chances of tetramer binding; the effect of Tregitope-167 was more pronounced (five fold increase in Treg induction) than for Tregitope 289 (three fold increase). Tregitope-289 was not shown to bind to DR 1501 in HLB binding assays. In contrast Tregitope-167 binds avidly to HLA 1501 (87% inhibition of binding at 50 ′LIM). 
     Example 5. Characterization of a Tregitope Composition by Suppression of Co-Administered Antigens In Vivo 
     5A: Tregitope co-administration causes suppression of effector responses to co-administered protein therapeutic in vivo. 
     It is shown herein that Tregitopes suppress response to a therapeutic protein of bacterial origin, which is referred to as “ANTIGEN-XX” ( FIG. 14 ). ANTIGEN-XX has caused significant immunogenicity in humans in unpublished studies. Whether the Tregitopes of the invention could suppress the effector immune response protein in vivo was investigated. HLA DR4 Transgenic mice (4-6 wk female) were injected weekly 3× subcutaneously (scruff of the neck) with either 1) 50 pig ANTIGEN-XX alone, 2) 50 lig ANTIGEN-XX+25 μg murine Tregitope-167 and 25 mg murine Tregitope 106 or 3) PBS sham control. Splenocytes were harvested and plated in murine IL-4 elispot plates as described above. 
     Quantification of IgG antibody to ANTIGEN-XX was determined by antibody-capture ELISA as described above. ANTIGEN-XX (10 mg/mL) was dissolved in carbonate buffer (10 mM Na 2 CO 3  and 35 mM NaHCO 3  [pH 9]) and placed into a 96-well microtiter plate overnight at 4° C. The plates were then washed with phosphate-buffered saline containing 0.05% Tween 20 (PBST) and blocked for 3 hours at room temperature with 5% fetal bovine serum (FBS; Gibco) in PBS. Serial dilutions of sera in 0.5% FBS/PBS were added to the plates and incubated at room temperature for 2 hours. The microtiter plates were then washed with PBST and 100 tAL goat anti-mouse IgG (gamma-chain specific) conjugated to horseradish peroxidase (Southern Biotechnology Associates) diluted 1:10000 in 0.5% FBS/PBS is added to each well. Microtiter plates are washed in PBST and then developed with 3,3′,5,5′-tetramethylbenzidine (TMB; Moss). Absorbances were read at a wavelength of 450 nm measured on a Wallac Victor3. Correction for optical imperfections in the plate is made by subtraction of intensities at 540 nm from the 450 nm values. Response to positive control PHA was robust following both immunization conditions and both assay readouts. 
     This study confirms the suppressive effects of the murine homologues of human Tregitopes co-administered with antigen in vivo. 
     5B: Tregitope co-administration causes suppression of effector responses to co-administered allergen in vivo. 
     Dust mites cause significant allergic responses in humans, and the mouse model using house dust mite lysate (HDML) is accepted as a model that is similar to humans. 
     Whether the Tregitopes of the invention could suppress the effector immune response to HDML in vivo was investigated. HLA DR4 Transgenic mice (4-6 wk female) were injected weekly 3× subcutaneously (scruff of the neck) with either 1) 50 lig HDML alone, 2) 50 vtg HDML+50 jug murine homologue of Tregitope-289 or 3) PBS sham control. In a fourth arm, mice were first presensitized to HDML through 3 weekly injections of 50 μg and then treated with coinjections of HDML (50 ttg) and Tregitope-289). One week following the final injections, mice were sacrificed. 
     Splenocytes were harvested and plated in murine IL-4 ELISpot plates as described above; to the plated cells were added (in triplicate): PBS (no stimulus control), HDM Lysate, purified HDM antigen DerP2, and PHA. HDM DerP2 is a component of HDM Lysate. 
     Serum was obtained by cardiac puncture. Quantification of IgG antibody to HDM antigen was determined by antibody-capture ELISA as described above. HDM antigen DerP2 (10 jug/mL) was placed into a 96-well microtiter plate overnight at 4° C. The plates were then washed with phosphate-buffered saline containing 0.05% Tween 20 (PBST) and blocked for three hours at room temperature with 5% fetal bovine serum (FBS; Gibco) in PBS. Serial dilutions of sera in 0.5% FBS/PBS were added to the plates and incubated at room temperature for two hours. The microtiter plates were then washed with PBST and 100 pt goat anti-mouse IgG (gamma-chain specific) conjugated to horseradish peroxidase (Southern Biotechnology Associates) diluted 1:10000 in 0.5% FBS/PBS is added to each well. Microtiter plates are washed in PBST and then developed with 3,3′,5,5′-tetramethylbenzidine (TMB; Moss). Absorbances were read at a wavelength of 450 nm measured on a Wallac Victor3. Correction for optical imperfections in the plate is made by subtraction of intensities at 540 nm from the 450 nm values. Response to positive control PHA was robust following both immunization conditions and both assay readouts ( FIG. 15 ). 
     This study confirms the suppressive effects of the murine equivalents of human Tregitopes co-administered with DM antigen in vivo. 
     5C: Tregitope co-administration causes suppression of effector responses to co-administered therapeutic in vivo. 
     To test whether Tregitope co-administration in vivo would be able to suppress immune responses to an immunogenic therapeutic protein, HLA DRB1*0401 was injected into mice three times weekly with preparations of 50 ttg immunogenic protein therapeutic (“IPT”) alone or in combination with either 50 i_tg Tregitope-289 (murine homologue) or IPT in combination with the murine Fc. Co-administration of IPT with murine Fc region reduced the IL-4 response, however, in vivo co-administration of “IPT” with murine homologue Tregitope-289, led to an even greater decrease in IL-4 by ELISpot ( FIG. 16 ). 
     Example 6. Generation of a FVIII-Tregitope Construct 
     Fusion of Tregitope with an immunogenic protein can lead to the induction of peripheral tolerance of the immunogenic protein. Clotting Factor VIII is immunogenic in people with severe hemophilia A. Chimeric constructs comprised of the coding sequence of Factor VIII and Tregitope are produced (Sambrook et al.,  Molecular Cloning: A Laboratory Manual,  2  ed ., Cold Spring Harbor Laboratory Press, (1989)). Briefly, the Factor VIII coding region fused at the carboxyterminal to a Tregitope is generated by annealing overlapping oligos and sub-cloned into an expression plasmid. The plasmids are transfected into DG44 CHO cells and stable transfectants selected. The chimeric protein is purified over a immunoaffinity column and evaluated for tolergenicity. Table 1 illustrates one embodiment of such a chimeric protein. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Factor VIII-Tregitope (Tregitope bold) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 MQIELSTCFELCLLRFCFSATRRYYLGAVELSWDYMQSDLGELPVDARFP 
               
               
                   
               
               
                 PRVPKSFPFNTSVVYKKTLFVEFTDHLFNIAKPRPPWMGLLGPTIQAEVY 
               
               
                   
               
               
                 DTVVITLKNMASHPVSLHAVGVSYWKASEGAEYDDQTSQREKEDDKVFPG 
               
               
                   
               
               
                 GSHTYVWQVLKENGPMASDPLCLTYSYLSHVDLVKDLNSGLIGALLVCRE 
               
               
                   
               
               
                 GSLAKEKTQTLHKFILLFAVEDEGKSWHSETKNSLMQDRDAASARAWPKM 
               
               
                   
               
               
                 HTVNGYVNRSLPGLIGCHRKSVYWHVIGMGTTPEVHSIFLEGHTFLVRNH 
               
               
                   
               
               
                 RQASLEISPITELTAQTLLMDLGQFLLECHISSHQHDGMEAYVKVDSCPE 
               
               
                   
               
               
                 EPQLRMKNNEEAEDYDDDLTDSEMDVVREDDDNSPSFIQIRSVAKKHPKT 
               
               
                   
               
               
                 WVHYTAAEEEDWDYAPLVLAPDDRSYKSQYLNNGPQRIGRKYKKVREMAY 
               
               
                   
               
               
                 TDETEKTREAIQHESGILGPLLYGEVGDTLLIIFKNQASRPYNTYPHGIT 
               
               
                   
               
               
                 DVRPLYSRRLPKGVKHLKDEPILPGEIFKYKWTVTVEDGPTKSDPRCLTR 
               
               
                   
               
               
                 YYSSEVNMERDLASGLIGPLLICYKESVDQRGNQIMSDKRNVILFSVEDE 
               
               
                   
               
               
                 NRSWYLTENIQRFLPNPAGVQLEDPEFQASNIMHSINGYVEDSLQLSVCL 
               
               
                   
               
               
                 HEVAYWYILSIGAQTDELSVFFSGYTEKHKMVYEDTLTLFPFSGETVFMS 
               
               
                   
               
               
                 MENPGLWILGCHNSDERNRGMTALLKVSSCDKNTGDYYEDSYEDISAYLL 
               
               
                   
               
               
                 SKNNATEPRSFSQNSRHPSTRQKQFNATTIPENDIEKTDPWFAHRTPMPK 
               
               
                   
               
               
                 IQNVSSSDLLMLLRQSPTPHGLSLSDLQEAKYETESDDPSPGAIDSNNSL 
               
               
                   
               
               
                 SEMTHERPQLHHSGDMVETPESGLQLRLNEKLGTTAATELKKLDEKVSST 
               
               
                   
               
               
                 SNNLISTIPSDNLAAGTDNTSSLGPPSMPVHYDSQLDTTLFGKKSSPLTE 
               
               
                   
               
               
                 SGGPLSLSEENNDSKLLESGLMNSQESSWGKNVSSTESGRLFKGKRAHGP 
               
               
                   
               
               
                 ALLTKDNALEKVSISLLKTNKTSNNSATNRKTHIDGPSLLIENSPSVWQN 
               
               
                   
               
               
                 ILESDTEFKKVTPLIHDRMLMDKNATALRLNHMSNKTTSSKNMEMVQQKK 
               
               
                   
               
               
                 EGPIPPDAQNPDMSFFKMLFLPESARWIQRTHGKNSLNSGQGPSPKQLVS 
               
               
                   
               
               
                 LGPEKSVEGQNFLSEKNKVVVGKGEFTKDVGLKEMVEPSSRNLELTNLDN 
               
               
                   
               
               
                 LHENNTHNQEKKIQEETEKKETLIQENVVLPQIHTVTGTKNEMKNLFLLS 
               
               
                   
               
               
                 TRQNVEGSYDGAYAPVLQDFRSLNDSTNRTKKHTAHFSKKGEEENLEGLG 
               
               
                   
               
               
                 NQTKQIVEKYACTTRISPNTSQQNFVTQRSKRALKQERLPLEETELEKRI 
               
               
                   
               
               
                 IVDDTSTQWSKNMKHLTPSTLTQIDYNEKEKGAITQSPLSDCLTRSHSIP 
               
               
                   
               
               
                 QANRSPLPIAKVSSEPSIRPTYLTRVLFQDNSSHLPAASYRKKDSGVQES 
               
               
                   
               
               
                 SHFLQGAKKNNLSLAILTLEMTGDQREVGSLGTSATNSVTYKKVENTVLP 
               
               
                   
               
               
                 KPDLPKTSGKVELLPKVHIYQKDLEPTETSNGSPGHLDLVEGSLLQGTEG 
               
               
                   
               
               
                 AIKWNEANRPGKVPFLRVATESSAKTPSKLLDPLAWDNHYGTQIPKEEWK 
               
               
                   
               
               
                 SQEKSPEKTAFKKKDTILSLNACESNHATAAINEGQNKPEIEVTWAKQGR 
               
               
                   
               
               
                 TERLCSQNPPVLKRHQREITRTTLQSDQEEIDYDDTISVEMKKEDFDIYD 
               
               
                   
               
               
                 EDENQSPRSFQKKTRHYFIAAVERLWDYGMSSSPHVLRNRAQSGSVPQFK 
               
               
                   
               
               
                 KVVFQEFTDGSFTQPLYRGELNEHLGLLGPYIRAEVEDNIMVTERNQASR 
               
               
                   
               
               
                 PYSFYSSLISYEEDQRQGAEPRKNEVKPNETKTYFWKVQHHMAPTKDEFD 
               
               
                   
               
               
                 CKAWAYESDVDLEKDVHSGLIGPLLVCHTNTLNPAHGRQVTVQEFALFFT 
               
               
                   
               
               
                 IFDETKSWYFTENMERNCRAPSNIQMEDPTEKENYRFHAINGYIMDTLPG 
               
               
                   
               
               
                 LVMAQDQRIRWYLLSMGSNENTHSIHFSGHVETVRKKEEYKMALYNLYPG 
               
               
                   
               
               
                 VFETVEMLPSKAGIWRVECLIGEHLHAGMSTLFLVYSNKCQTPLGMASGH 
               
               
                   
               
               
                 IRDFQITASGQYGQWAPKLARLHYSGSINAWSTKEPFSWIKVDLLAPMII 
               
               
                   
               
               
                 HGIKTQGARQKFSSLYISQFIIMYSLDGKKWQTYRGNSTGTLMVFFGNVD 
               
               
                   
               
               
                 SSGIKHNIFNPPITARYIRLHPTHYSIRSTLRMELMGCDLNSCSMPLGME 
               
               
                   
               
               
                 SKAISDAQITASSYFTNMFATWSPSKARLHLQGRSNAWRPQVNNPKEWLQ 
               
               
                   
               
               
                 VDFQKTMKVTGVTTQGVKSLLTSMYVKEFLISSSQDGHQWTLFFQNGKVK 
               
               
                   
               
               
                 VFQGNQDSFTPVVNSLDPPLLTRYLRIHPQSWVHQIALRMEVLGCEAQDL 
               
               
                   
               
               
                 YEEQYNSTYRVVSVLTVLHQDW SEQ ID    
               
               
                   
               
               
                     indicates data missing or illegible when filed 
               
            
           
         
       
     
     Example 7. Generation of a FVIII-Multi-Tregitope Construct 
     Multiple Tregitopes can be present in highly immunogenic proteins to promote adaptive tolerance. Chimeric constructs comprised of the coding sequence of clotting Factor VIII and multiple Tregitope(s) are produced (Sambrook et al.,  Molecular Cloning: A Laboratory Manual,  2 ed., Cold Spring Harbor Laboratory Press, (1989)). Briefly, the Factor VIII coding region fused at the carboxyterminal to a Tregitope is generated by annealing overlapping oligos and sub-cloned into an expression plasmid. The plasmids are transfected into DG44 CHO cells and stable transfectants selected. The chimeric protein is purified over a immunoaffinity column and evaluated for tolergenicity. Table 2 illustrates one embodiment of such a chimeric protein. 
     
       
         
           
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 FactorVIII-multiTregitope (Tregitope (s) bold) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 Docket No. EPV0003NA16 
               
               
                 MQIELSTCFFLCLLRFCFSATRRYYLGAVELSWDYMQSDLGELPVDARFP 
               
               
                   
               
               
                 PRVPKSFPFNTSVVYKKTLFVEFTDHLFNIAKPRPPWMGLLGPTIQAEVY 
               
               
                   
               
               
                 DTVVITLKNMASHPVSLHAVGVSYWKASEGAEYDDQTSQREKEDDKVFPG 
               
               
                   
               
               
                 GSHTYVWQVLKENGPMASDPLCLTYSYLSHVDLVKDLNSGLIGALLVCRE 
               
               
                   
               
               
                 GSLAKEKTQTLHKFILLFAVEDEGKSWHSETKNSLMQDRDAASARAWPKM 
               
               
                   
               
               
                 HTVNGYVNRSLPGLIGCHRKSVYWHVIGMGTTPEVHSIFLEGHTFLVRNH 
               
               
                   
               
               
                 RQASLEISPITFLTAQTLLMDLGQFLLFCHISSHQHDGMEAYVKVDSCPE 
               
               
                   
               
               
                 EPQLRMKNNEEAEDYDDDLTDSEMDVVREDDDNSPSFIQIRSVAKKHPKT 
               
               
                   
               
               
                 WVHYIAAEEEDWDYAPLVLAPDDRSYKSQYLNNGPQRIGRKYKKVRFMAY 
               
               
                   
               
               
                 TDETFKTREAIQHESGILGPLLYGEVGDTLLIIFKNQASRPYNTYPHGIT 
               
               
                   
               
               
                 DVRPLYSRRLPKGVKHLKDFPILPGEIFKYKWTVTVEDGPTKSDPRCLTR 
               
               
                   
               
               
                 YYSSFVNMERDLASGLIGPLLICYKESVDQRGNQIMSDKRNVILFSVEDE 
               
               
                   
               
               
                 NRSWYLTENIQRFLPNPAGVQLEDPEFQASNIMHSINGYVFDSLQLSVCL 
               
               
                   
               
               
                 HEVAYWYILSIGAQTDFLSVFFSGYTFKHKMVYEDTLTLFPFSGETVFMS 
               
               
                   
               
               
                 MENPGLWILGCHNSDERNRGMTALLKVSSCDKNTGDYYEDSYEDISAYLL 
               
               
                   
               
               
                 SKNNAIEPRSFSQNSRHPSTRQKQFNATTIPENDIEKTDPWFAHRTPMPK 
               
               
                   
               
               
                 IQNVSSSDLLMLLRQSPTPHGLSLSDLQEAKYETFSDDPSPGAIDSNNSL 
               
               
                   
               
               
                 SEMTHFRPQLHHSGDMVFTPESGLQLRLNEKLGTTAATELKKLDFKVSST 
               
               
                   
               
               
                 SNNLISTIPSDNLAAGTDNTSSLGPPSMPVHYDSQLDTTLFGKKSSPLTE 
               
               
                   
               
               
                 SGGPLSLSEENNDSKLLESGLMNSQESSWGKNVSSTESGRLFKGKRAHGP 
               
               
                   
               
               
                 ALLTKDNALFKVSISLLKTNKTSNNSATNRKTHIDGPSLLIENSPSVWQN 
               
               
                   
               
               
                 ILESDTEFKKVTPLIHDRMLMDKNATALRLNHMSNKTTSSKNMEMVQQKK 
               
               
                   
               
               
                 EGPIPPDAQNPDMSFFKMLFLPESARWIQRTHGKNSLNSGQGPSPKQLVS 
               
               
                   
               
               
                 LGPEKSVEGQNFLSEKNKVVVGKGEFTKDVGLKEMVFPSSRNLFLTNLDN 
               
               
                   
               
               
                 LHENNTHNQEKKIQEEIEKKETLIQENVVLPQIHTVTGTKNFMKNLFLLS 
               
               
                   
               
               
                 TRQNVEGSYDGAYAPVLQDFRSLNDSTNRTKKHTAHFSKKGEEENLEGLG 
               
               
                   
               
               
                 NQTKQIVEKYACTTRISPNTSQQNFVTQRSKRALKQERLPLEETELEKRI 
               
               
                   
               
               
                 IVDDTSTQWSKNMKHLTPSTLTQIDYNEKEKGAITQSPLSDCLTRSHSIP 
               
               
                   
               
               
                 QANRSPLPIAKVSSEPSIRPTYLTRVLFQDNSSHLPAASYRKKDSGVQES 
               
               
                   
               
               
                 SHFLQGAKKNNLSLAILTLEMTGDQREVGSLGTSATNSVTYKKVENTVLP 
               
               
                   
               
               
                 KPDLPKTSGKVELLPKVHIYQKDLFPTETSNGSPGHLDLVEGSLLQGTEG 
               
               
                   
               
               
                 AIKWNEANRPGKVPFLRVATESSAKTPSKLLDPLAWDNHYGTQIPKEEWK 
               
               
                   
               
               
                 SQEKSPEKTAFKKKDTILSLNACESNHAIAAINEGQNKPEIEVTWAKQGR 
               
               
                   
               
               
                 TERLCSQNPPVLKRHQREITRTTLQSDQEEIDYDDTISVEMKKEDFDIYD 
               
               
                   
               
               
                 EDENQSPRSFQKKTRHYFIAAVERLWDYGMSSSPHVLRNRAQSGSVPQFK 
               
               
                   
               
               
                 KVVFQEFTDGSFTQPLYRGELNEHLGLLGPYIRAEVEDNIMVTFRNQASR 
               
               
                   
               
               
                 PYSFYSSLISYEEDQRQGAEPRKNFVKPNETKTYFWKVQHHMAPTKDEFD 
               
               
                   
               
               
                 CKAWAYFSDVDLEKDVHSGLIGPLLVCHTNTLNPAHGRQVTVQEFALFFT 
               
               
                   
               
               
                 IFDETKSWYFTENMERNCRAPSNIQMEDPTFKENYRFHAINGYIMDTLPG 
               
               
                   
               
               
                 LVMAQDQRIRWYLLSMGSNENIHSIHFSGHVFTVRKKEEYKMALYNLYPG 
               
               
                   
               
               
                 VFETVEMLPSKAGIWRVECLIGEHLHAGMSTLFLVYSNKCQTPLGMASGH 
               
               
                   
               
               
                 IRDFQITASGQYGQWAPKLARLHYSGSINAWSTKEPFSWIKVDLLAPMII 
               
               
                   
               
               
                 HGIKTQGARQKFSSLYISQFIIMYSLDGKKWQTYRGNSTGTLMVFFGNVD 
               
               
                   
               
               
                 SSGIKHNIFNPPIIARYIRLHPTHYSIRSTLRMELMGCDLNSCSMPLGME 
               
               
                   
               
               
                 SKAISDAQITASSYFTNMFATWSPSKARLHLQGRSNAWRPQVNNPKEWLQ 
               
               
                   
               
               
                 VDFQKTMKVTGVTTQGVKSLLTSMYVKEFLISSSQDGHQWTLFFQNGKVK 
               
               
                   
               
               
                 VFQGNQDSFTPVVNSLDPPLLTRYLRIHPQSWVHQIALRMEVLGCEAQDL 
               
               
                   
               
               
                 YEEQYNSTYRVVSVLTVLHQDWEEQYNSTYRVVSVLTVLHQDWEEQYNST 
               
               
                   
               
               
                 YRVVSVLTVLHQDWEEQYNSTYRVVSVLTVLHQDW SEQ ID NO: 2 
               
               
                   
               
            
           
         
       
     
     Example 8. Generation of an Enhanced Vaccine Delivery Vehicle 
     Fc binding to Fc receptors enhance uptake in antigen presenting cells presentation to T and B lymphocytes. Tregitope-289, located in the Fc domain of IgG molecules acts to deliver suppressive signals. The modification of Fc so that Tregitope-289 no longer binds to MHC molecules and regulatory T cells allows for efficient targeting of vaccine candidates while avoiding suppressive effects. Modifications to decrease binding of Tregitopes to MHC molecules are useful.  FIG. 22  illustrates such a modification. Chimeric constructs comprised of various proteins or epitope pseudo-proteins of interest and a Tregitope modified mIgG Fc are designed (Sambrook et al., Molecular Cloning: A Laboratory Manual, 2 ed., Cold Spring Harbor Laboratory Press, (1989)). Briefly, the protein or epitope pseudo-protein of interest is generated by fusion expression plasmid. The plasmids are transfected into DG44 CHO cells and stable transfectants selected. The chimeric protein homodimers are purified over a protein A column and evaluated for immunogenicity.  FIG. 22  illustrates one embodiment of a chimeric protein where the pseudo-protein of interest is a string of immunogenic T cell epitopes derived from the Epstein Barr Virus (EBV) fused to a modified Fc protein in which the Tregitope has been modified to no longer bind MFIC class ii molecules and can not stimulate natural regulatory T cells. EBV-Tregitope modified Fc SEQUENCE (Kb SIGNAL SEQUENCE) in  FIG. 22  is designated as underlined text. The Tregitope is designated as bold text. The Tregitope modified amino acids are designated as shaded text. The human Fc region is designated as italicized text. 
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     EQUIVALENTS 
     While the invention has been described in connection with the specific embodiments thereof, it will be understood that it is capable of further modification. Furthermore, this application is intended to cover any variations, uses, or adaptations of the invention, including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as fall within the scope of the appended claims.