Mannosylated PLP(139-151) induces peptide-specific tolerance to experimental autoimmune encephalomyelitis

Glycovaccinology: The design and engineering of carbohydrate-based vaccine components

Vaccines remain one of the most important pillars in preventative medicine, providing protection against a wide array of diseases by inducing humoral and/or cellular immunity. Of the many possible candidate antigens for subunit vaccine development, carbohydrates are particularly appealing because of their ubiquitous presence on the surface of all living cells, viruses, and parasites as well as their known interactions with both innate and adaptive immune cells. Indeed, several licensed vaccines leverage bacterial cell-surface carbohydrates as antigens for inducing antigen-specific plasma cells secreting protective antibodies and the development of memory T and B cells. Carbohydrates have also garnered attention in other aspects of vaccine development, for example, as adjuvants that enhance the immune response by either activating innate immune responses or targeting specific immune cells. Additionally, carbohydrates can function as immunomodulators that dampen undesired humoral immune responses to entire protein antigens or specific, conserved regions on antigenic proteins. In this review, we highlight how the interplay between carbohydrates and the adaptive and innate arms of the immune response is guiding the development of glycans as vaccine components that act as antigens, adjuvants, and immunomodulators. We also discuss how advances in the field of synthetic glycobiology are enabling the design, engineering, and production of this new generation of carbohydrate-containing vaccine formulations with the potential to prevent infectious diseases, malignancies, and complex immune disorders.

Impact of disease-modifying therapy on dendritic cells and exploring their immunotherapeutic potential in multiple sclerosis

Dendritic cells (DCs) are the most potent professional antigen-presenting cells (APCs), which play a pivotal role in inducing either inflammatory or tolerogenic response based on their subtypes and environmental signals. Emerging evidence indicates that DCs are critical for initiation and progression of autoimmune diseases, including multiple sclerosis (MS). Current disease-modifying therapies (DMT) for MS can significantly affect DCs' functions. However, the study on the impact of DMT on DCs is rare, unlike T and B lymphocytes that are the most commonly discussed targets of these therapies. Induction of tolerogenic DCs (tolDCs) with powerful therapeutic potential has been well-established to combat autoimmune responses in laboratory models and early clinical trials. In contrast to in vitro tolDC induction, in vivo elicitation by specifically targeting multiple cell-surface receptors has shown greater promise with more advantages. Here, we summarize the role of DCs in governing immune tolerance and in the process of initiating and perpetuating MS as well as the effects of current DMT drugs on DCs. We then highlight the most promising cell-surface receptors expressed on DCs currently being explored as the viable pharmacological targets through antigen delivery to generate tolDCs in vivo.

The Mannose Receptor: From Endocytic Receptor and Biomarker to Regulator of (Meta)Inflammation

The mannose receptor is a member of the C-type lectin (CLEC) family, which can bind and internalize a variety of endogenous and pathogen-associated ligands. Because of these properties, its role in endocytosis as well as antigen processing and presentation has been studied intensively. Recently, it became clear that the mannose receptor can directly influence the activation of various immune cells. Cell-bound mannose receptor expressed by antigen-presenting cells was indeed shown to drive activated T cells towards a tolerogenic phenotype. On the other hand, serum concentrations of a soluble form of the mannose receptor have been reported to be increased in patients suffering from a variety of inflammatory diseases and to correlate with severity of disease. Interestingly, we recently demonstrated that the soluble mannose receptor directly promotes macrophage proinflammatory activation and trigger metaflammation. In this review, we highlight the role of the mannose receptor and other CLECs in regulating the activation of immune cells and in shaping inflammatory responses.

Tolerogenic Immunotherapy: Targeting DC Surface Receptors to Induce Antigen-Specific Tolerance

Dendritic cells (DCs) are well-established as major players in the regulation of immune responses. They either induce inflammatory or tolerogenic responses, depending on the DC-subtype and stimuli they receive from the local environment. This dual capacity of DCs has raised therapeutic interest for their use to modify immune-activation via the generation of tolerogenic DCs (tolDCs). Several compounds such as vitamin D3, retinoic acid, dexamethasone, or IL-10 and TGF-β have shown potency in the induction of tolDCs. However, an increasing interest exists in defining tolerance inducing receptors on DCs for new targeting strategies aimed to develop tolerance inducing immunotherapies, on which we focus particular in this review. Ligation of specific cell surface molecules on DCs can result in antigen presentation to T cells in the presence of inhibitory costimulatory molecules and tolerogenic cytokines, giving rise to regulatory T cells. The combination of factors such as antigen structure and conformation, delivery method, and receptor specificity is of paramount importance. During the last decades, research provided many tools that can specifically target various receptors on DCs to induce a tolerogenic phenotype. Based on advances in the knowledge of pathogen recognition receptor expression profiles in human DC subsets, the most promising cell surface receptors that are currently being explored as possible targets for the induction of tolerance in DCs will be discussed. We also review the different strategies that are being tested to target DC receptors such as antigen-carbohydrate conjugates, antibody-antigen fusion proteins and antigen-adjuvant conjugates.

Mannan-MOG35-55 Reverses Experimental Autoimmune Encephalomyelitis, Inducing a Peripheral Type 2 Myeloid Response, Reducing CNS Inflammation, and Preserving Axons in Spinal Cord Lesions

CNS autoantigens conjugated to oxidized mannan (OM) induce antigen-specific T cell tolerance and protect mice against autoimmune encephalomyelitis (EAE). To investigate whether OM-peptides treat EAE initiated by human MHC class II molecules, we administered OM-conjugated murine myelin oligodendrocyte glycoprotein peptide 35-55 (OM-MOG) to humanized HLA-DR2b transgenic mice (DR2b.Ab°), which are susceptible to MOG-EAE. OM-MOG protected DR2b.Ab° mice against MOG-EAE by both prophylactic and therapeutic applications. OM-MOG reversed clinical symptoms, reduced spinal cord inflammation, demyelination, and neuronal damage in DR2b.Ab° mice, while preserving axons within lesions and inducing the expression of genes associated with myelin (Mbp) and neuron (Snap25) recovery in B6 mice. OM-MOG-induced tolerance was peptide-specific, not affecting PLP178-191-induced EAE or polyclonal T cell proliferation responses. OM-MOG-induced immune tolerance involved rapid induction of PD-L1- and IL-10-producing myeloid cells, increased expression of Chi3l3 (Ym1) in secondary lymphoid organs and characteristics of anergy in MOG-specific CD4⁺ T cells. The results show that OM-MOG treats MOG-EAE in a peptide-specific manner, across mouse/human MHC class II barriers, through induction of a peripheral type 2 myeloid cell response and T cell anergy, and suggest that OM-peptides might be useful for suppressing antigen-specific CD4⁺ T cell responses in the context of human autoimmune CNS demyelination.

Autoantigen Tetramer Silences Autoreactive B Cell Populations

Many autoimmune therapies focus on immune suppression to reduce symptom severity and halt disease progression; however, currently approved treatments lack specificity for the autoantigen and rely on more global immune suppression. Multivalent antigen arrays can disarm pathogenic autoimmune B cell populations that specifically recognize the antigen of interest via their B cell receptor (BCR). Disarmament may be achieved by BCR engagement, cross-linking, and sustained receptor occupancy as a result of multivalent, high avidity BCR binding. To engage and explore this mechanism, a tetramer display of the encephalogenic proteolipid peptide (PLP_139-151), referred to as 4-arm PLP_139-151, was synthesized by copper-catalyzed azide-alkyne cycloaddition chemistry. Subcutaneous administration of 4-arm PLP_139-151 completely ameliorated symptoms of paralysis in a mouse model of multiple sclerosis known as experimental autoimmune encephalomyelitis. Competitive binding of 4-arm PLP_139-151 to PLP_139-151-specific IgG in the mouse serum demonstrated the enhanced avidity associated with the multivalent array compared to the free peptide. Furthermore, key PLP_139-151-reactive B cells were depleted following 4-arm PLP_139-151 treatment, resulting in significant reduction of proinflammatory cytokines. Together, these data demonstrate the potential of 4-arm PLP_139-151 to silence autoreactive B cell populations and limit the downstream activation of effector cells.

Mannose receptor induces T-cell tolerance via inhibition of CD45 and up-regulation of CTLA-4

The mannose receptor (MR) is an endocytic receptor involved in serum homeostasis and antigen presentation. Here, we identify the MR as a direct regulator of CD8(+) T-cell activity. We demonstrate that MR expression on dendritic cells (DCs) impaired T-cell cytotoxicity in vitro and in vivo. This regulatory effect of the MR was mediated by a direct interaction with CD45 on the T cell, inhibiting its phosphatase activity, which resulted in up-regulation of cytotoxic T-lymphocyte-associated Protein 4 (CTLA-4) and the induction of T-cell tolerance. Inhibition of CD45 prevented expression of B-cell lymphoma 6 (Bcl-6), a transcriptional inhibitor that directly bound the CTLA-4 promoter and regulated its activity. These data demonstrate that endocytic receptors expressed on DCs contribute to the regulation of T-cell functionality.

Mannan-conjugated myelin peptides prime non-pathogenic Th1 and Th17 cells and ameliorate experimental autoimmune encephalomyelitis

Antigen presenting cells (APC) are critical for regulating immune responses. We tested mannan-peptide conjugates for targeting myelin peptides to APC to induce T cell tolerance and resistance to experimental autoimmune encephalomyelitis (EAE). Myelin peptides conjugated to mannan in oxidized (OM) or reduced (RM) forms protected mice against EAE in prophylactic and therapeutic protocols, with OM-conjugated peptides giving best results. Protection was peptide-specific and associated with reduced antigen-specific T cell proliferation, but not alterations in Th1, Th17 and Treg cell differentiation or T cell apoptosis compared to EAE controls. Bone marrow-derived dendritic cells (DC) loaded with OM-MOG showed up-regulated expression of co-stimulatory molecules, reduced PD-L1 expression and enhanced CD40-inducible IL-12 and IL-23 production compared to MOG DC, features consistent with immunogenic DC. OM-MOG induced active T cell tolerance because i.d. administration or passive transfer of OM-MOG DC suppressed ongoing EAE, while OM-MOG-vaccinated mice did not reduce the proliferation of transferred MOG-specific T cells. As in vivo, MOG-specific T cells cultured with OM-MOG DC showed reduced proliferation and equal Th1 and Th17 cell differentiation compared to those with MOG DC, but surprisingly cytokine production was unresponsive to CD40 engagement. Impaired effector T cell function was further evidenced in spinal cord sections from OM-MOG-vaccinated EAE mice, where markedly reduced numbers of CD3(+) T cells were present, restricted to leptomeninges and exceptional parenchymal lesions. Our results show that mannan-conjugated myelin peptides protect mice against EAE through the expansion of antigen-specific Th1 and Th17 cells with impaired proliferation responses and APC-induced co-stimulatory signals that are required for licensing them to become fully pathogenic T cells.

Glycans of myelin proteins

Human P0 is the main myelin glycoprotein of the peripheral nervous system. It can bind six different glycans, all linked to Asn(93) , the unique glycosylation site. Other myelin glycoproteins, also with a single glycosylation site (PMP22 at Asn(36) , MOG at Asn(31) ), bind only one glycan. The MAG has 10 glycosylation sites; the glycoprotein OMgp has 11 glycosylation sites. Aside from P0, no comprehensive data are available on other myelin glycoproteins. Here we review and analyze all published data on the physicochemical structure of the glycans linked to P0, PMP22, MOG, and MAG. Most data concern bovine P0, whose glycan moieties have an MW ranging from 1,294.56 Da (GP3) to 2,279.94 Da (GP5). The pI of glycosylated P0 protein varies from pH 9.32 to 9.46. The most charged glycan is MS2 containing three sulfate groups and one glucuronic acid; whereas the least charged one is the BA2 residue. All glycans contain one fucose and one galactose. The most mannose rich are the glycans MS2 and GP4, each of them has four mannoses; OPPE1 contains five N-acetylglucosamines and one sulfated glucuronic acid; GP4 contains one sialic acid. Furthermore, human P0 variants causing both gain and loss of glycosylation have been described and cause peripheral neuropathies with variable clinical severity. In particular, the substitution T(95) →M is a very common in Europe and is associated with a late-onset axonal neuropathy. Although peripheral myelin is made up largely of glycoproteins, mutations altering glycosylation have been described only in P0. This attractive avenue of research requires further study.

Enhanced cross-presentation and improved CD8+ T cell responses after mannosylation of synthetic long peptides in mice

The use of synthetic long peptides (SLP) has been proven to be a promising approach to induce adaptive immune responses in vaccination strategies. Here, we analyzed whether the efficiency to activate cytotoxic T cells by SLP-based vaccinations can be increased by conjugating SLPs to mannose residues. We could demonstrate that mannosylation of SLPs results in increased internalization by the mannose receptor (MR) on murine antigen-presenting cells. MR-mediated internalization targeted the mannosylated SLPs into early endosomes, from where they were cross-presented very efficiently compared to non-mannosylated SLPs. The influence of SLP mannosylation was specific for cross-presentation, as no influence on MHC II-restricted presentation was observed. Additionally, we showed that vaccination of mice with mannosylated SLPs containing epitopes from either ovalbumin or HPV E7 resulted in enhanced proliferation and activation of antigen-specific CD8⁺ T cells. These findings demonstrate that mannosylation of SLPs augments the induction of a cytotoxic T cell response in vitro and in vivo and might be a promising approach to induce cytotoxic T cell responses in e.g. cancer therapy and anti-viral immunity.

Generation of hypoallergenic neoglycoconjugates for dendritic cell targeted vaccination: a novel tool for specific immunotherapy

The incidence of allergic disorders and asthma continuously increased over the past decades, consuming a considerable proportion of the health care budget. Allergen-specific subcutaneous immunotherapy represents the only intervention treating the underlying causes of type I allergies, but still suffers from unwanted side effects and low compliance. There is an urgent need for novel approaches improving safety and efficacy of this therapy. In the present study we investigated carbohydrate-mediated targeting of allergens to dermal antigen-presenting cells and its influence on immunogenicity and allergenicity. Mannan, high (40 kDa) and low (6 kDa) molecular weight dextran, and maltodextrin were covalently attached to ovalbumin and papain via mild carbohydrate oxidation resulting in neoglycocomplexes of various sizes. In particular, mannan-conjugates were efficiently taken up by dendritic cells in vivo leading to elevated humoral immune responses against the protein moiety and a shift from IgE to IgG. Beyond providing an adjuvant effect, papain glycocomplexes also proved to mask B-cell epitopes, thus rendering the allergen derivative hypoallergenic.

The present data demonstrate that carbohydrate-modified allergens combine targeting of antigen presenting cells with hypoallergenicity, offering the potential for low dose allergen-specific immunotherapy while concomitantly reducing the risk of side effects.

Liposome-encapsulated peptides protect against experimental allergic encephalitis

Multiple sclerosis (MS) is a severe inflammatory and neurodegenerative disease with an autoimmune background. Despite the variety of therapeutics available against MS, the development of novel approaches to its treatment is of high importance in modern pharmaceutics. In this study, experimental autoimmune encephalomyelitis (EAE) in Dark Agouti rats has been treated with immunodominant peptides of the myelin basic protein (MBP) encapsulated in mannosylated small unilamellar vesicles. The results show that liposome-encapsulated MBP_46–62 is the most effective in reducing maximal disease score during the first attack, while MBP_124–139 and MBP_147–170 can completely prevent the development of the exacerbation stage. Both mannosylation of liposomes and encapsulation of peptides are critical for the therapeutic effect, since neither naked peptides nor nonmannosylated liposomes, loaded or empty, have proved effective. The liposome-mediated synergistic effect of the mixture of 3 MBP peptides significantly suppresses the progression of protracted EAE, with the median cumulative disease score being reduced from 22 to 14 points, compared to the placebo group; prevents the production of circulating autoantibodies; down-regulates the synthesis of Th1 cytokines; and induces the production of brain-derived neurotrophic factor in the central nervous system. Thus, the proposed formulation ameliorates EAE, providing for a less severe first attack and rapid recovery from exacerbation, and offers a promising therapeutic modality in MS treatment.—Belogurov, A. A., Jr., Stepanov, A. V., Smirnov, I. V., Melamed, D., Bacon, A., Mamedov, A. E., Boitsov, V. M., Sashchenko, L. P., Ponomarenko, N. A., Sharanova, S. N., Boyko, A. N., Dubina, M. V., Friboulet, A., Genkin, D. D., Gabibov, A. G. Liposome-encapsulated peptides protect against experimental allergic encephalitis.

[Therapeutic effect of encapsulated into the nanocontainers MBP immunodominant peptides on EAE development in DA rats]

Multiple Sclerosis (MS) is a serve autoimmune neurodegenerative disease. Development of innovative approaches of MS treatment is of a high priority in the modern immunology and pharmacy. In the present study we showed high therapeutic efficiency of immunodominant peptides of myelin basic protein (MBP) incorporated into the monolayer mannosylated liposomes on the development of experimental autoimmune encephalomyelitis (EAE) in DA rats. MBP is a component ofoligodendrocytes' membrane, which form axonal sheath, and is one of the major autoantigens in MS. We analyzed binding pattern ofanti-MBP autoantibodies from MS patients using previously designed MBP epitope library. Utilizing the same approach we investigated pool of anti-MBP antibodies from SJL/J and C57/BL6 mice and DA rats with induced EAE. The most relevant rodent model to MS was EAE in DA rats according to the autoantibodies' binding pattern. We selected three immunodominant MBP fragments encapsulated in monolayer mannosylated liposomes for the following treatment of verified DA rodent model. MBP fragment 46-62 was the most effective in reducing of the first EAE attack, whereas MBP 124-139 and 147-160 inhibited development of pathology during remission stage. Simultaneous administration of these peptides in liposomes significantly decreased level of anti-MBP antibodies. Synergetic therapeutic effect of MBP fragments reduced integral disease score by inhibiting first EAE wave and subsequent remission, thus, our findings disclosure novel approaches for efficient treatment of Multiple Sclerosis.

I-domain-antigen conjugate (IDAC) for delivering antigenic peptides to APC: synthesis, characterization, and in vivo EAE suppression

The objectives of this work are to characterize the identity of I-domain-antigen conjugate (IDAC) and to evaluate the in vivo efficacy of IDAC in suppressing experimental autoimmune encephalomyelitis (EAE) in mouse model. The hypothesis is that the I-domain delivers PLP(139-151) peptides to antigen-presenting cells (APC) and alters the immune system by simultaneously binding to ICAM-1 and MHC-II, blocking immunological synapse formation. IDAC was synthesized by derivatizing the lysine residues with maleimide groups followed by conjugation with PLP-Cys-OH peptide. Conjugation with PLP peptide does not alter the secondary structure of the protein as determined by CD. IDAC suppresses the progression of EAE, while I-domain and GMB-I-domain could only delay the onset of EAE. As a positive control, Ac-PLP-BPI-NH(2)-2 can effectively suppress the progress of EAE. The number of conjugation sites and the sites of conjugations in IDAC were determined using tryptic digest followed by LC-MS analysis. In conclusion, conjugation of I-domain with an antigenic peptide (PLP) resulted in an active molecule to suppress EAE in vivo.

Immune response to controlled release of immunomodulating peptides in a murine experimental autoimmune encephalomyelitis (EAE) model

The effects of controlled release on immune response to an immunomodulating peptide were evaluated in a murine experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS). The peptide, Ac-PLP-BPI-NH(2)-2 (Ac-HSLGKWLGHPDKF-(AcpGAcpGAcp)(2)-ITDGEATDSG-NH(2); Ac = acetyl, Acp = epsilon aminocaproic acid) was designed to suppress T-cell activation in response to PLP(139-151), an antigenic peptide in MS. Poly-lactide-co-glycolide (PLGA) microparticles containing Ac-PLP-BPI-NH(2)-2 (8+/-4 microm, 1.4+/-0.2% (w/w)) were prepared by a powder-in oil-in water emulsion-solvent evaporation method, sterilized and administered subcutaneously (s.c.) to SJL/J (H-2(s)) mice in which EAE had been induced by immunization with PLP(139-151). Treatment groups received Ac-PLP-BPI-NH(2)-2: (i) in solution by repeated i.v. or s.c. injection, (ii) in solution co-administered with blank PLGA microparticles, (iii) in solution co-administered with Ac-PLP-BPI-NH(2)-2 loaded microparticles, and (iv) as Ac-PLP-BPI-NH(2)-2 loaded microparticles. Administration of Ac-PLP-BPI-NH(2)-2 as an s.c. solution produced clinical scores and maintenance of body weight comparable to i.v. solution, but with reduced overall survival, presumably due to anaphylaxis. Administration as s.c. microparticles provided a somewhat less effective reduction in symptoms but with no toxicity during treatment. Thus, the results suggest that s.c. administration of Ac-PLP-BPI-NH(2)-2 microparticles can provide pharmacological efficacy and reduction in dosing frequency without increased toxicity.

Protein/peptide and DNA vaccine delivery by targeting C-type lectin receptors

C-type lectin receptors (CLRs) are a class of pathogen-recognition receptors that are actively investigated in the field of vaccine delivery. Many of their properties have functions linked to the immune system. These receptors are expressed abundantly on antigen-presenting cells and are considered to be the sentinels of immune surveillance owing to their endocytic nature and the ability to recognize a diverse range of pathogens through recognition of pathogen-associated molecular patterns. CLRs are also involved in the processes of antigen presentation mediated through the induction of dendritic cell maturation and cytokine production. These properties engender CLRs to be ideal for vaccine targeting. Conversely, CLRs also function to recognize glycosylated self-antigens to induce homeostatic control and tolerance. In this review, we will describe the various preclinical/clinical vaccination strategies to target antigens and plasmid DNA to this diverse class of receptors.

Prophylactic and therapeutic suppression of experimental autoimmune encephalomyelitis by a novel bifunctional peptide inhibitor

The objective was to optimize and evaluate the in vivo activities of our novel bifunctional peptide inhibitor (BPI), which alters immune response in autoimmune diseases by modulating the immunological synapse formation. Previously, we have designed PLP-BPI and GAD-BPI by conjugating myelin proteolipid protein (PLP)(139-151) and glutamic acid decarboxylase (GAD)(208-217), respectively, with CD11a(237-246) via a spacer peptide. PLP-BPI and GAD-BPI suppressed the disease progression in experimental autoimmune encephalomyelitis (EAE) and in type-1 diabetes, respectively. In this study, various PLP-BPI derivatives were synthesized and evaluated in the EAE model. Intravenous injections of PLP-BPI derivatives prevented the disease progression more efficiently than did unmodified PLP-BPI. Production of IL-17, a potent proinflammatory cytokine found commonly among MS patients, was significantly low in Ac-PLP-BPI-NH(2)-2-treated mice. Treatment given after the disease onset could dramatically ameliorate the disease. BPI induced anaphylactic responses at a lower incidence than PLP(139-151). In conclusion, PLP-BPI derivatives can effectively suppress the disease severity and morbidity of EAE by post-onset therapeutic treatment as well as prophylactic use.

Protein-glycan interactions in the control of innate and adaptive immune responses

The importance of protein glycosylation in the migration of immune cells throughout the body has been extensively appreciated. However, our awareness of the impact of glycosylation on the regulation of innate and adaptive immune responses is relatively new. An increasing number of studies reveal the relevance of glycosylation to pathogen recognition, to the modulation of the innate immune system and to the control of immune cell homeostasis and inflammation. Similarly important is the effect of glycan-containing 'information' in the development of autoimmune diseases and cancer. In this review, we provide an overview of these new directions and their impact in the field of glycoimmunology.

Antigen-specific suppression of experimental autoimmune encephalomyelitis by a novel bifunctional peptide inhibitor

The objective of this study is to evaluate the activity of a novel peptide, i.e., bifunctional peptide inhibitor (BPI), which targets the immunological synapse and inhibits autoimmune responses in an antigen-specific manner. Proteolipid protein (PLP)-BPI was designed by conjugating two peptides, an encephalitogenic epitope of proteolipid protein (PLP(139-151)) and an intercellular adhesion molecule-1-binding peptide derived from alpha(L) integrin (CD11a(237-246)), via a spacer peptide. The therapeutic effect of PLP-BPI was studied in experimental autoimmune encephalomyelitis (EAE) in female SJL/J mice as a model for human multiple sclerosis. Mice that received i.v. injections of PLP-BPI showed significantly lower EAE disease scores and incidence than those treated with vehicle, PLP(139-151) peptide only, CD11a(237-246) peptide only, unlinked mixture of PLP(139-151), and CD11a(237-246) peptides, or other control peptides. Multiple injections of antigenic peptide can produce anaphylactic responses; interestingly, PLP-BPI-treated animals have significantly lower anaphylactic response than do the PLP(139-151)-treated group. Therefore, PLP-BPI can effectively inhibit the disease severity and incidence of EAE with a lower possibility of inducing fatal anaphylaxis. These results suggest that BPI-type molecules can be used to treat different autoimmune diseases in which antigenic epitopes have been identified.

Soluble mannosylated myelin peptide inhibits the encephalitogenicity of autoreactive T cells during experimental autoimmune encephalomyelitis

We have previously shown that immunization with a mannosylated myelin peptide in complete adjuvant induces tolerance instead of disease in experimental autoimmune encephalomyelitis (EAE), a rodent model for multiple sclerosis. In this report we demonstrate that treatment with a soluble mannosylated epitope of proteolipid protein (M-PLP(139-151)) significantly inhibits disease mediated by autoreactive myelin-specific T cells during EAE. Treatment with M-PLP(139-151), applied in different EAE models, significantly reduced the incidence of disease and the severity of clinical symptoms. Delayed-type hypersensitivity responses were abolished after peptide treatment, emphasizing the impact on peripheral T-cell reactivity. Histological analysis of spinal cord tissue from mice treated with M-PLP(139-151) revealed the presence of only few macrophages and T cells. Moreover, little expression of interferon-gamma, interleukin-23, or major histocompatibility complex class II antigen was detected. Immune modulation by M-PLP(139-151) was primarily antigen-specific because an irrelevant mannosylated peptide showed no significant effect on delayed-type hypersensitivity responses or on the course of EAE. Therefore, mannosylated antigens may represent a novel therapeutic approach for antigen-specific modulation of autoreactive T cells in vivo.

Recognition of tumor glycans by antigen-presenting cells

C-type lectin receptors on antigen-presenting cells are potent antigen-uptake receptors with specificity for glycan structures. Glycosylation changes during malignant transformation create tumor-specific carbohydrate structures that interact with C-type lectins on dendritic cells. Recent findings revealed that tumor glycoproteins, such as carcinoembryonic antigen and MUC-1, indeed interact with the C-type lectins DC-SIGN and macrophage galactose-type lectin on antigen-presenting cells. The consequences for anti-cancer immunity or tolerance induction can be extrapolated from the function of C-type lectins in pathogen recognition and antigen presentation. In addition, in vivo studies in mice recently demonstrated the potency of targeting antigens to C-type lectins on antigen-presenting cells for anti-tumor vaccination strategies.