Tolerogenic vaccines for Multiple sclerosis

Extending the in vivo persistence of synthetic glycoconjugates using a serum-protein binder

Synthetic glycoconjugates are used in the development of vaccines and the design of inhibitors for glycan-protein interactions. The in vivo persistence of synthetic glycoconjugates is an important factor in their efficacy, especially when prolonged interactions with specific cell types may be required. In this study, we applied a strategy for non-covalent association of an active compound with serum proteins for extension of glycoconjugate half-life in serum. The small molecule, AG10, has previously been used to extend the half-life of small molecules through its high affinity for transthyretin (TTR), a serum protein. Using a tetravalent polyethylene glycol (PEG)-based scaffold we developed a synthetic strategy for glycoconjugates that allowed for controlled addition of multiple tags, such as a TTR affinity tag or fluorophore. We designed a version of AG10 modified at the pyrazole core, named GD10, amenable to our conjugation strategy and introduced to glycoconjugates using a tri-functional linker. This approach allowed for attachment of GD10 and fluorophore tags, as well as carbohydrate antigens. We then tested the influence of the GD10 tag on glycoconjugate half-life in vivo using a mouse model. Our results suggest that the combination of the GD10 tag and the PEG scaffold extended the half-life of glycoconjugates by as much as 10-fold when compared to proteins of similar molecular weight. The GD10 tag was able to extend the half-life of similar glycoconjugates by as much as 2-fold. We observed a role for the terminal saccharide residue of the carbohydrate antigen and confirmed that conjugates were able to penetrate multiple compartments in vivo including bone marrow, lymph nodes, and other organs. The introduction of the GD10 tag did not obstruct the ability of conjugates to interact with lectin receptors. We conclude that serum protein binders can be used to extend the persistence of glycoconjugates in vivo.

Emerging Therapeutics for Immune Tolerance: Tolerogenic Vaccines, T cell Therapy, and IL-2 Therapy

Autoimmune diseases affect roughly 5-10% of the total population, with women affected more than men. The standard treatment for autoimmune or autoinflammatory diseases had long been immunosuppressive agents until the advent of immunomodulatory biologic drugs, which aimed at blocking inflammatory mediators, including proinflammatory cytokines. At the frontier of these biologic drugs are TNF-α blockers. These therapies inhibit the proinflammatory action of TNF-α in common autoimmune diseases such as rheumatoid arthritis, psoriasis, ulcerative colitis, and Crohn's disease. TNF-α blockade quickly became the "standard of care" for these autoimmune diseases due to their effectiveness in controlling disease and decreasing patient's adverse risk profiles compared to broad-spectrum immunosuppressive agents. However, anti-TNF-α therapies have limitations, including known adverse safety risk, loss of therapeutic efficacy due to drug resistance, and lack of efficacy in numerous autoimmune diseases, including multiple sclerosis. The next wave of truly transformative therapeutics should aspire to provide a cure by selectively suppressing pathogenic autoantigen-specific immune responses while leaving the rest of the immune system intact to control infectious diseases and malignancies. In this review, we will focus on three main areas of active research in immune tolerance. First, tolerogenic vaccines aiming at robust, lasting autoantigen-specific immune tolerance. Second, T cell therapies using Tregs (either polyclonal, antigen-specific, or genetically engineered to express chimeric antigen receptors) to establish active dominant immune tolerance or T cells (engineered to express chimeric antigen receptors) to delete pathogenic immune cells. Third, IL-2 therapies aiming at expanding immunosuppressive regulatory T cells in vivo.

Evidence of a tolerogenic vaccine against AIDS in the Chinese macaque prefigures a potential human vaccine

In 2006 we discovered a new type of mucosal vaccine against simian immunodeficiency virus (SIV) in Chinese macaques. Here, we review 15 years of our published work on this vaccine, which consists of inactivated SIVmac239 particles adjuvanted with Bacillus Calmette-Guérin, Lactobacillus plantarum, or Lactobacillus rhamnosus. Without adjuvant, the vaccine administered by the intragastric route induced the usual SIV-specific humoral and cellular immune responses but provided no protection against intrarectal challenge with SIVmac239. In contrast, out of 24 macaques immunized with the adjuvanted vaccine and challenged intrarectally with SIVmac239 or SIVB670, 23 were sterilely protected for up to five years, while all control macaques were infected. This protection was confirmed by an independent group from the Pasteur Institute. During the past 15 years, we have identified the mechanism of action of the vaccine and discovered that the vaccinated macaques produced a previously unrecognized class of MHC-Ib/E-restricted CD8⁺ T cells (which we refer to as tolerogenic CD8⁺ T cells) that suppressed the activation of SIV-RNA-infected CD4⁺ T cells and thereby inhibited the (activation-dependent) reverse transcription of the virus, which in turn prevented the establishment of SIV infection. Importantly, we discovered also that the tolerogenic CD8⁺ T cell subset observed in vaccinated Chinese macaques could also be found in human elite controllers, a small group of HIV-infected patients in whom these tolerogenic CD8⁺ T cells were shown to naturally suppress viral replication. Given that SIV and HIV require activated immune cells in which to replicate, the specific prevention of activation of SIV-RNA-containing CD4⁺ T cells by a tolerogenic vaccine approach offers an exciting new avenue in HIV vaccine research.

Triggers, Timescales, and Treatments for Cytokine-Mediated Tissue Damage

Inflammation is an essential cytokine-mediated process for generating a neutralizing immune response against pathogens and is generally protective. However, aberrant or excessive production of pro-inflammatory cytokines is associated with uncontrolled local and systemic inflammation, resulting in cell death and often irreversible tissue damage. Uncontrolled inflammation can manifest over timescales spanning hours to years and is primarily dependent on the triggering event. Rapid and potentially lethal increase in cytokine production, or a 'cytokine storm,' develops in hours to days and is associated with cancer cell-based immunotherapies, such as CAR-T cell therapy. On the other hand, some bacterial and viral infections with high microbial replication or highly potent antigens elicit immune responses that result in supraphysiological systemic cytokine concentrations which manifest over days to weeks. Immune dysregulation in autoimmune diseases can lead to chronic cytokine-mediated tissue damage spanning months to years, which often occurs episodically. While the initiating events and cellular participants may differ in these disease processes, many of the cytokines that drive disease progression are shared. For example, upregulation of IL-1, IL-6, IFN-γ, TNF, and GM-CSF frequently coincides with cytokine storm, sepsis, and autoimmune disease. Targeted inhibition of these pro-inflammatory molecules via antagonist monoclonal antibodies has improved clinical outcomes, but the complexity of the underlying immune dysregulation results in high variability. Rather than a "one size fits all" treatment approach, an identification of disease endotypes may permit the development of effective therapeutic strategies that address the contributors of disease progression. Here, we present a literature review of the cytokine-associated etiology of acute and chronic cytokine-mediated tissue damage, describe successes and challenges in developing clinical treatments, and highlight advancements in preclinical therapeutic strategies for mitigating pathological cytokine production.

Low-Zone IL-2 Signaling: Fusion Proteins Containing Linked CD25 and IL-2 Domains Sustain Tolerogenic Vaccination in vivo and Promote Dominance of FOXP3+ Tregs in vitro

Low-zone IL-2 signaling is key to understanding how CD4⁺ CD25^high FOXP3⁺ regulatory T cells (Tregs) exhibit dominance and overgrow conventional effector T cells (Tcons) that typically express lower levels of the IL-2 receptor alpha chain (i.e., CD25). Thus, modalities such as low-dose IL-2 or IL-2/anti-IL-2 antibody complexes have been advanced in the clinic to selectively expand Treg populations as a treatment for chronic inflammatory autoimmune diseases. However, more effective reagents that efficiently lock IL-2 signaling into a low signaling mode are needed to validate and exploit the low-zone IL-2 signaling niche of Tregs. This study focuses on CD25-IL2 and IL2-CD25 fusion proteins (FPs) that were approximately 32 and 320-fold less potent than IL-2. These FPs exhibited transient binding to transmembrane CD25 on human embryonic kidney (HEK) cells, had partially occluded IL-2 binding sites, and formed higher order multimeric conformers that limited the availability of bioactive IL-2. These FPs exhibited broad bell-shaped concentration ranges that favored dominant Treg outgrowth during continuous culture and were used to derive essentially pure long-term Treg monocultures (∼98% Treg purity). FP-induced Tregs had canonical Treg suppressive activity in that these Tregs suppressed antigen-specific proliferative responses of naïve CD4⁺ T cells. The in vivo administration of CD25-IL2/Alum elicited robust increases in circulating Tregs and selectively augmented CD25 expression on Tregs but not on Tcons. A single injection of a Myelin Oligodendrocyte Glycoprotein (MOG35-55)-specific tolerogenic vaccine elicited high levels of circulating MOG-specific Tregs in vivo that waned after 2–3 weeks, whereas boosting with CD25-IL2/Alum maintained MOG-specific CD25^high Tregs throughout the 30-day observation period. However, these FPs did not antagonize free monomeric IL-2 and lacked therapeutic efficacy in experimental autoimmune encephalomyelitis (EAE). In conclusion, these data reveal that CD25-IL2 FPs can be used to select essentially pure long-term lines of FOXP3⁺ CD25^high Tregs. This study also shows that CD25-IL2 FPs can be administered in vivo in synergy with tolerogenic vaccination to maintain high circulating levels of antigen-specific Tregs. Because tolerogenic vaccination and Treg-based adoptive immunotherapy are limited by gradual waning of Tregs, these FPs have potential utility in sustaining tolerogenic Treg responses in vivo.

Tolerogenic vaccines: Targeting the antigenic and cytokine niches of FOXP3+ regulatory T cells

FOXP3+ regulatory T cells (Tregs) constitute a critical barrier that enforces tolerance to both the self-peptidome and the extended-self peptidome to ensure tissue-specific resistance to autoimmune, allergic, and other inflammatory disorders. Here, we review intuitive models regarding how T cell antigen receptor (TCR) specificity and antigen recognition efficiency shape the Treg and conventional T cell (Tcon) repertoires to adaptively regulate T cell maintenance, tissue-residency, phenotypic stability, and immune function in peripheral tissues. Three zones of TCR recognition efficiency are considered, including Tcon recognition of specific low-efficiency self MHC-ligands, Treg recognition of intermediate-efficiency agonistic self MHC-ligands, and Tcon recognition of cross-reactive high-efficiency agonistic foreign MHC-ligands. These respective zones of TCR recognition efficiency are key to understanding how tissue-resident immune networks integrate the antigenic complexity of local environments to provide adaptive decisions setting the balance of suppressive and immunogenic responses. Importantly, deficiencies in the Treg repertoire appear to be an important cause of chronic inflammatory disease. Deficiencies may include global deficiencies in Treg numbers or function, subtle 'holes in the Treg repertoire' in tissue-resident Treg populations, or simply Treg insufficiencies that are unable to counter an overwhelming molecular mimicry stimulus. Tolerogenic vaccination and Treg-based immunotherapy are two therapeutic modalities meant to restore dominance of Treg networks to reverse chronic inflammatory disease. Studies of these therapeutic modalities in a preclinical setting have provided insight into the Treg niche, including the concept that intermediate-efficiency TCR signaling, high IFN-β concentrations, and low IL-2 concentrations favor Treg responses and active dominant mechanisms of immune tolerance. Overall, the purpose here is to assimilate new and established concepts regarding how cognate TCR specificity of the Treg repertoire and the contingent cytokine networks provide a foundation for understanding Treg suppressive strategy.

A GM-CSF-neuroantigen tolerogenic vaccine elicits inefficient antigen recognition events below the CD40L triggering threshold to expand CD4+ CD25+ FOXP3+ Tregs that inhibit experimental autoimmune encephalomyelitis (EAE)

Background

Tolerogenic vaccines represent antigen-specific interventions designed to re-establish self-tolerance and thereby alleviate autoimmune diseases, which collectively comprise over 100 chronic inflammatory diseases afflicting more than 20 million Americans. Tolerogenic vaccines comprised of single-chain GM-CSF-neuroantigen (GMCSF-NAg) fusion proteins were shown in previous studies to prevent and reverse disease in multiple rodent models of experimental autoimmune encephalomyelitis (EAE) by a mechanism contingent upon the function of CD4⁺ CD25⁺ FOXP3⁺ regulatory T cells (Tregs). GMCSF-NAg vaccines inhibited EAE in both quiescent and inflammatory environments in association with low-efficiency T cell receptor (TCR) signaling events that elicited clonal expansion of immunosuppressive Tregs.

Methods

This study focused on two vaccines, including GMCSF-MOG (myelin oligodendrocyte glycoprotein 35–55/MOG^35–55) and GMCSF-NFM (neurofilament medium peptide 13–37/NFM^13–37), that engaged the transgenic 2D2 TCR with either low or high efficiencies, respectively. 2D2 mice were crossed with FOXP3 IRES eGFP (FIG) mice to track Tregs and further crossed with Rag^−/− mice to reduce pre-existing Treg populations.

Results

This study provided evidence that low and high efficiency TCR interactions were integrated via CD40L expression levels to control the Treg/Tcon balance. The high-efficiency GMCSF-NFM vaccine elicited memory Tcon responses in association with activation of the CD40L costimulatory system. Conversely, the low-efficiency GMCSF-MOG vaccine lacked adequate TCR signal strength to elicit CD40L expression and instead elicited Tregs by a mechanism that was impaired by a CD40 agonist. When combined, the low- and high-efficiency GMCSF-NAg vaccines resulted in a balanced outcome and elicited both Tregs and Tcon responses without the predominance of a dominant immunogenic Tcon response. Aside from Treg expansion in 2D2-FIG mice, GMCSF-MOG caused a sustained decrease in TCR-β, CD3, and CD62L expression and a sustained increase in CD44 expression in Tcon subsets. Subcutaneous administration of GMCSF-MOG without adjuvants inhibited EAE in wildtype mice, which had a replete Treg repertoire, but was pathogenic rather than tolerogenic in 2D2-FIG-Rag1^−/− mice, which lacked pre-existing Tregs.

Conclusions

This study provided evidence that the GMCSF-MOG vaccine elicited antigenic responses beneath the CD40L triggering threshold, which defined an antigenic niche that drove dominant expansion of tolerogenic myelin-specific Tregs that inhibited EAE.

Recent Advances in Antigen-Specific Immunotherapies for the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system and is considered to be the leading non-traumatic cause of neurological disability in young adults. Current treatments for MS comprise long-term immunosuppressant drugs and disease-modifying therapies (DMTs) designed to alter its progress with the enhanced risk of severe side effects. The Holy Grail for the treatment of MS is to specifically suppress the disease while at the same time allow the immune system to be functionally active against infectious diseases and malignancy. This could be achieved via the development of immunotherapies designed to specifically suppress immune responses to self-antigens (e.g., myelin antigens). The present study attempts to highlight the various antigen-specific immunotherapies developed so far for the treatment of multiple sclerosis (e.g., vaccination with myelin-derived peptides/proteins, plasmid DNA encoding myelin epitopes, tolerogenic dendritic cells pulsed with encephalitogenic epitopes of myelin proteins, attenuated autologous T cells specific for myelin antigens, T cell receptor peptides, carriers loaded/conjugated with myelin immunodominant peptides, etc), focusing on the outcome of their recent preclinical and clinical evaluation, and to shed light on the mechanisms involved in the immunopathogenesis and treatment of multiple sclerosis.

A GMCSF-Neuroantigen Tolerogenic Vaccine Elicits Systemic Lymphocytosis of CD4+ CD25high FOXP3+ Regulatory T Cells in Myelin-Specific TCR Transgenic Mice Contingent Upon Low-Efficiency T Cell Antigen Receptor Recognition

Previous studies showed that single-chain fusion proteins comprised of GM-CSF and major encephalitogenic peptides of myelin, when injected subcutaneously in saline, were potent tolerogenic vaccines that suppressed experimental autoimmune encephalomyelitis (EAE) in rats and mice. These tolerogenic vaccines exhibited dominant suppressive activity in inflammatory environments even when emulsified in Complete Freund's Adjuvant (CFA). The current study provides evidence that the mechanism of tolerance was dependent upon vaccine-induced regulatory CD25⁺ T cells (Tregs), because treatment of mice with the Treg-depleting anti-CD25 mAb PC61 reversed tolerance. To assess tolerogenic mechanisms, we focused on 2D2-FIG mice, which have a transgenic T cell repertoire that recognizes myelin oligodendrocyte glycoprotein peptide MOG35-55 as a low-affinity ligand and the neurofilament medium peptide NFM13-37 as a high-affinity ligand. Notably, a single subcutaneous vaccination of GMCSF-MOG in saline elicited a major population of FOXP3⁺ Tregs that appeared within 3 days, was sustained over several weeks, expressed canonical Treg markers, and was present systemically at high frequencies in the blood, spleen, and lymph nodes. Subcutaneous and intravenous injections of GMCSF-MOG were equally effective for induction of FOXP3⁺ Tregs. Repeated booster vaccinations with GMCSF-MOG elicited FOXP3 expression in over 40% of all circulating T cells. Covalent linkage of GM-CSF with MOG35-55 was required for Treg induction whereas vaccination with GM-CSF and MOG35-55 as separate molecules lacked Treg-inductive activity. GMCSF-MOG elicited high levels of Tregs even when administered in immunogenic adjuvants such as CFA or Alum. Conversely, incorporation of GM-CSF and MOG35-55 as separate molecules in CFA did not support Treg induction. The ability of the vaccine to induce Tregs was dependent upon the efficiency of T cell antigen recognition, because vaccination of 2D2-FIG or OTII-FIG mice with the high-affinity ligands GMCSF-NFM or GMCSF-OVA (Ovalbumin323-339), respectively, did not elicit Tregs. Comparison of 2D2-FIG and 2D2-FIG-Rag1 ^-/- strains revealed that GMCSF-MOG may predominantly drive Treg expansion because the kinetics of vaccine-induced Treg emergence was a function of pre-existing Treg levels. In conclusion, these findings indicate that the antigenic domain of the GMCSF-NAg tolerogenic vaccine is critical in setting the balance between regulatory and conventional T cell responses in both quiescent and inflammatory environments.

Design and molecular dynamic simulation of a new double-epitope tolerogenic protein as a potential vaccine for multiple sclerosis disease

One of the debilitating diseases affecting the central nervous system is multiple sclerosis (MS). As there is no definitive treatment for MS, researchers have mainly consented with optimization of strategies which slows down the progression of the disease such as specific auto-antigens tolerance induction. In this regard, the aim of this study was design of a new double-epitope protective vaccine based on interleukin (IL)-16-neuroantigens fusion proteins. First, we selected highly antigenic epitopes of myelin basic protein (MBP) (aa 84-104) and myelin oligodendrocyte glycoprotein (MOG) (aa 99-107) from available literature and our bioinformatics analysis. The correct cleavage of our constructs and major histocompatibility complex class II binding affinities of cleaved epitopes were checked and evaluated using Pepcleave and IEDB servers, respectively. Then, different combination of MOG and MBP epitopes with or without fusion to C-terminal active part of IL-16 were designed as constructs. Afterward, Modeller and Gromacs softwares used for the investigation of the MBP, and MOG epitopes antigenicity in these constructs. The results of molecular dynamics simulations showed that IL-16 in MOG + linker + MBP + IL-16 construct does not interfere with final epitopes antigenicity of MOG + linker + MBP construct. To sum up, the construct with IL-16 is suggested as a new double-epitope tolerogenic vaccine for prevention and amelioration of MS in human.

Inflammatory cells and their non-coding RNAs as targets for treating myocardial infarction

Myocardial infarction triggers infiltration of several types of immune cells that coordinate both innate and adaptive immune responses. These play a dual role in post-infarction cardiac remodeling by initiating and resolving inflammatory processes, which needs to occur in a timely and well-orchestrated way to ensure a reestablishment of normalized cardiac functions. Thus, therapeutic modulation of immune responses might have benefits for infarct patients. While such strategies have shown great potential in treating cancer, applications in the post-infarction context have been disappointing. One challenge has been the complexity and plasticity of immune cells and their functions in cardiac regulation and healing. The types appear in patterns that are temporally and spatially distinct, while influencing each other and the surrounding tissue. A comprehensive understanding of the immune cell repertoire and their regulatory functions following infarction is sorely needed. Processes of cardiac remodeling trigger additional genetic changes that may also play critical roles in the aftermath of cardiovascular disease. Some of these changes involve non-coding RNAs that play crucial roles in the regulation of immune cells and may, therefore, be of therapeutic interest. This review summarizes what is currently known about the functions of immune cells and non-coding RNAs during post-infarction wound healing. We address some of the challenges that remain and describe novel therapeutic approaches under development that are based on regulating immune responses through non-coding RNAs in the aftermath of the disease.

Construction of Multivalent Homo- and Heterofunctional ABO Blood Group Glycoconjugates Using a Trifunctional Linker Strategy

The design and synthesis of multivalent ligands displaying complex oligosaccharides is necessary for the development of therapeutics, diagnostics, and research tools. Here, we report an efficient conjugation strategy to prepare complex glycoconjugates with 4 copies of 1 or 2 separate glycan epitopes, providing 4-8 carbohydrate residues on a tetravalent poly(ethylene glycol) scaffold. This strategy provides complex glycoconjugates that approach the size of glycoproteins (15-18 kDa) while remaining well-defined. The synthetic strategy makes use of three orthogonal functional groups, including a reactive N-hydroxysuccinimide (NHS)-ester moiety on the linker to install the first carbohydrate epitope via reaction with an amine. A masked amine functionality on the linker is revealed after the removal of a fluorenylmethyloxycarbonyl (Fmoc)-protecting group, allowing the attachment to the NHS-activated poly(ethylene glycol) (PEG) scaffold. An azide group in the linker was then used to incorporate the second carbohydrate epitope via catalyzed alkyne-azide cycloaddition. Using a known tetravalent PEG scaffold (PDI, 1.025), we prepared homofunctional glycoconjugates that display four copies of lactose and the A-type II or the B-type II human blood group antigens. Using our trifunctional linker, we expanded this strategy to produce heterofunctional conjugates with four copies of two separate glycan epitopes. These heterofunctional conjugates included Neu5Ac, 3'-sialyllactose, or 6'-sialyllactose as a second antigen. Using an alternative strategy, we generated heterofunctional conjugates with three copies of the glycan epitope and one fluorescent group (on average) using a sequential dual-amine coupling strategy. These conjugation strategies should be easily generalized for conjugation of other complex glycans. We demonstrate that the glycan epitopes of heterofunctional conjugates engage and cluster target B-cell receptors and CD22 receptors on B cells, supporting the application of these reagents for investigating cellular response to carbohydrate antigens of the ABO blood group system.

Computational comparison of two new fusion proteins for multiple sclerosis

Multiple sclerosis (MS), as one of the human autoimmune diseases, demyelinates the neurons of the central nervous system (CNS). Activation of the T cells which target the CNS antigens is the first autoimmune event in MS. Myelin oligodendrocyte glycoprotein (MOG) and myelin basic protein (MBP) are two proteins of the myelin sheath and have been shown to be among the high antigens contributing to the pathogenesis of MS. Production of the drugs with high specificity for the immune system diseases is a concern for various researchers. Therefore, tolerogenic vaccines are considered as a new strategy for the treatment of MS by presenting specific antigens. This study aimed to design and compare two fusion proteins by a combination of two neuroantigens linked to interleukin-16 (IL-16) (MOG-Linker-MBP-IL16 and MBP-Linker-MOG-IL16) as vaccines for MS. In this study, at first two models MOG (aa 11-30) linked to MBP (aa 13-32) was made by Modeler 9.10 and simulated for 20 ns via Gromacs 5.1.1 package. Then simulated antigen domains connected to the N-terminal domain of IL-16 and obtained structures simulated for 50 ns. The results revealed that both constructs had stable structures and the linker could keep two antigenic fragments separate enough, preventing undesired interactions. While MOG-Linker-MBP-IL16 showed better solubility, more accessible surface areas, more flexibility of its IL-16 domain, and better functionality of its IL-16 domain as well as more specific cleavage of its related epitopes after endocytosis lead to a better presentation of its antigenic property.

Effects of immunomodulators on the response induced by vaccines against autoimmune diseases

A promising treatment for T-cell-mediated autoimmune diseases is the induction of immune tolerance by modulating the immune response against self-antigens, an objective that may be achieved by vaccination. There are two main types of vaccines currently under development. The tolerogenic vaccines, composed of proteins formed by a cytokine fused to a self-antigen, which usually induce tolerance by eliminating the T-cells that are immune reactive against the self-antigen. The immunogenic vaccines, comprised of a self-antigen plus a sole Th2 adjuvant either free or conjugated, that alleviate autoimmunity by switching the immune response against the self-antigen, from a damaging pro-inflammatory Th1/Th17 to an anti-inflammatory Th2 immunity. Another type of vaccines is the DNA vaccines, where cells transiently express the self-antigen encoded by DNA, which induces a Th2 immunity. Actually, DNA vaccines can benefit from the presence of an adjuvant that elicits a systemic sole Th2 immunity to enhance the initially weak immune response characteristic of these vaccines. While in the tolerogenic vaccines, cytokines are the endogenous immunomodulators, in the immunogenic vaccines, the adjuvants are exogenous agents that elicit Th2 immunity with a production of anti-inflammatory cytokines and antibodies against the self-antigen. Because the commonly used Th2 adjuvant alum, fails to induce an effective immunity in the elderly population, it is unlikely that it would be widely used. Another Th2 adjuvant, the oil/water emulsions mixed with the antigen, while effective in vaccines against infectious agents, due to potential aldehydes in their formulation may be not suitable for autoimmune vaccines. A unique compound is glatiramer, which seems to be both a random polypeptide antigen and an immune modulator that biases the response to Th2 immunity. Its mechanism of action seems to implicate binding to MHC-II, which alters the outcome of T-cell signaling, leading to anergy. Glatiramer, while effective in the treatment of multiple sclerosis has not shown efficacy in other autoimmune diseases. An important new group of promising sole Th2 adjuvants are the fucosylated glycans, which by binding to DC-SIGN bias dendritic cells to Th2 immunity while inhibiting Th1/Th7 immunities. These glycans are similar to those produced by parasitic helminths to prevent inflammatory responses by mammalian hosts. A novel group of sole Th2 adjuvants are some plant-derived fucosylated triterpene glycosides, which share the immune modulatory properties from the fucosylated glycans. These glycosides have also an aldehyde group that delivers an alternative co-stimulatory signal to T-cells, averting the anergy associated with aging due to the loss of the CD28 receptor on T-cells. Hence, the development of vaccines to treat and/or prevent autoimmune conditions and some proteopathies, will significantly benefit from the availability of new sole Th2 adjuvants that while inducing an anti-inflammatory immunity, they do not abrogate pro-inflammatory Th1/Th17 immunities.

IFN-β Facilitates Neuroantigen-Dependent Induction of CD25+ FOXP3+ Regulatory T Cells That Suppress Experimental Autoimmune Encephalomyelitis

This study introduces a flexible format for tolerogenic vaccination that incorporates IFN-β and neuroantigen (NAg) in the Alum adjuvant. Tolerogenic vaccination required all three components, IFN-β, NAg, and Alum, for inhibition of experimental autoimmune encephalomyelitis (EAE) and induction of tolerance. Vaccination with IFN-β + NAg in Alum ameliorated NAg-specific sensitization and inhibited EAE in C57BL/6 mice in pretreatment and therapeutic regimens. Tolerance induction was specific for the tolerogenic vaccine Ag PLP178-191 or myelin oligodendrocyte glycoprotein (MOG)35-55 in proteolipid protein- and MOG-induced models of EAE, respectively, and was abrogated by pretreatment with a depleting anti-CD25 mAb. IFN-β/Alum-based vaccination exhibited hallmarks of infectious tolerance, because IFN-β + OVA in Alum-specific vaccination inhibited EAE elicited by OVA + MOG in CFA but not EAE elicited by MOG in CFA. IFN-β + NAg in Alum vaccination elicited elevated numbers and percentages of FOXP3+ T cells in blood and secondary lymphoid organs in 2D2 MOG-specific transgenic mice, and repeated boosters facilitated generation of activated CD44high CD25+ regulatory T cell (Treg) populations. IFN-β and MOG35-55 elicited suppressive FOXP3+ Tregs in vitro in the absence of Alum via a mechanism that was neutralized by anti-TGF-β and that resulted in the induction of an effector CD69+ CTLA-4+ IFNAR+ FOXP3+ Treg subset. In vitro IFN-β + MOG-induced Tregs inhibited EAE when transferred into actively challenged recipients. Unlike IFN-β + NAg in Alum vaccines, vaccination with TGF-β + MOG35-55 in Alum did not increase Treg percentages in vivo. Overall, this study indicates that IFN-β + NAg in Alum vaccination elicits NAg-specific, suppressive CD25+ Tregs that inhibit CNS autoimmune disease. Thus, IFN-β has the activity spectrum that drives selective responses of suppressive FOXP3+ Tregs.

Immune responses to polyclonal T-cell vaccination in patients with progressive multiple sclerosis

The overall objective of disease management in autoimmune diseases is to suppress chronic inflammation and prevent organ damage. Therapies often revolve around five drug classes: non-steroidal anti-inflammatory drugs (NSAIDS), anti-malarials, steroids, immunosuppressants, and bio-therapies. However, none of these is a 'cure' and each displays a potential for adverse events. In particular, while all of them suppress harmful autoimmune responses, they also impact on useful protective immune responses. T-Cell receptor (TCR) immunogenicity provides a rationale for T-cell vaccinations to induce anti-idiotypic immune responses with the purpose of down-regulating functionality of idiotype-bearing self-reactive T-cells. To explore this, in this study, 39 patients with progressive (chronic) multiple sclerosis (MS) were multiply immunized with autological polyclonal T-cell vaccines (TCVs). None of the TCV-treated patients experienced any significant side-effects during the entire follow-up period (2 years). T-Cell vaccination had no significant effects on T-cell sub-population contents in the blood of MS patients after 2 years of immunotherapy initiation. However, a substantial reduction in the frequency of CD4⁺and CD8⁺memory T-cells able to produce interferon (IFN)-γ following activation were noted in the blood of TCV-treated patients. Moreover, significant and sustained reduction in plasma IFNγ levels and concomitant increases in interleukin (IL)-4 levels were documented in these samples. The TCV-treated subjects, however, exhibited no significant changes in plasma IL-17 and IL-18. More importantly was a significant decline in proliferative T-cell responses to myelin antigens in the TCV-treated patients, indicating attenuation of myelin-specific T-cell activity. Collectively, the results suggest that polyclonal T-cell vaccination is safe to use, able to induce measurable, long-lasting, anti-inflammatory immune effects in patients with advanced MS.

Particulate inorganic adjuvants: recent developments and future outlook

Objectives

To review the state of the art and assess future potential in the use of inorganic particulates as vaccine adjuvants.

Key findings

An adjuvant is an entity added to a vaccine formulation to ensure that robust immunity to the antigen is inculcated. The inclusion of an adjuvant is typically vital for the efficacy of vaccines using inactivated organisms, subunit and DNA antigens. With increasing research efforts being focused on subunit and DNA antigens because of their improved safety profiles, the development of appropriate adjuvants is becoming ever more crucial. Despite this, very few adjuvants are licensed for use in humans (four by the FDA, five by the European Medicines Agency). The most widely used adjuvant, alum, has been used for nearly 90 years, yet its mechanism of action remains poorly understood. In addition, while alum produces a powerful antibody Th2 response, it does not provoke the cellular immune response required for the elimination of intracellular infections or cancers. New adjuvants are therefore needed, and inorganic systems have attracted much attention in this regard.

Summary

In this review, the inorganic adjuvants currently in use are considered, and the efforts made to date to understand their mechanisms of action are summarised. We then move on to survey the literature on inorganic particulate adjuvants, focusing on the most interesting recent developments in this area and their future potential.

GM-CSF-neuroantigen fusion proteins reverse experimental autoimmune encephalomyelitis and mediate tolerogenic activity in adjuvant-primed environments: association with inflammation-dependent, inhibitory antigen presentation

Single-chain fusion proteins comprised of GM-CSF and neuroantigen (NAg) are potent, NAg-specific inhibitors of experimental autoimmune encephalomyelitis (EAE). An important question was whether GMCSF-NAg tolerogenic vaccines retained inhibitory activity within inflammatory environments or were contingent upon steady-state conditions. GM-CSF fused to the myelin oligodendrocyte glycoprotein MOG35-55 peptide (GMCSF-MOG) reversed established paralytic disease in both passive and active models of EAE in C57BL/6 mice. The fusion protein also reversed EAE in CD4-deficient and B cell-deficient mice. Notably, GMCSF-MOG inhibited EAE when coinjected adjacent to the MOG35-55/CFA emulsion. GMCSF-MOG also retained dominant inhibitory activity when directly emulsified with MOG35-55 in the CFA emulsion in both C57BL/6 or B cell-deficient models of EAE. Likewise, when combined with proteolipid protein 139-151 in CFA, GM-CSF fused to proteolipid protein 139-151 peptide inhibited EAE in SJL mice. When deliberately emulsified in CFA with the NAg, GMCSF-NAg inhibited EAE even though NAg was present at >30-fold molar excess. In vitro studies revealed that the GM-CSF domain of GMCSF-MOG stimulated growth and differentiation of inflammatory dendritic cells (DC) and simultaneously targeted the MOG35-55 domain for enhanced presentation by these DC. These inflammatory DC presented MOG35-55 to MOG-specific T cells by an inhibitory mechanism that was mediated in part by IFN-γ signaling and NO production. In conclusion, GMCSF-NAg was tolerogenic in CFA-primed proinflammatory environments by a mechanism associated with targeted Ag presentation by inflammatory DC and an inhibitory IFN-γ/NO pathway. The inhibitory activity of GMCSF-NAg in CFA-primed lymphatics distinguishes GMCSF-NAg fusion proteins as a unique class of inflammation-dependent tolerogens that are mechanistically distinct from naked peptide or protein-based tolerogens.

Interferon-gamma ELISPOT detecting reactivity of T cells to TSH receptor peptides in Graves' disease

OBJECTIVE

While thyrotrophin receptor (TSHR) is recognized as the main autoantigen in Graves' disease (GD), the actual antigen specificity of T cells that infiltrate the thyroid and the orbit is unknown. Identifying T cell responses to TSHR peptides has been difficult in the past due to the low frequency of autoreactive T cells and to the diversity of the putative epitopes identified by proliferation assays.

METHODS

We used the interferon-gamma ELISPOT assay to identify T cell reactivity to TSHR peptides in patients with GD. Peripheral blood T cells were exposed in vitro to four pools of 10 overlapping TSHR peptides.

RESULTS

T cells from 11 of 31 (35%) patients with GD and 1 of 22 (4%) healthy controls reacted to at least one peptide pool (P = 0·009). Mean time since diagnosis was 3·2 years in responder patients and 5·6 years in nonresponders (P = 0·07). In two patients, T cell reactivity was observed shortly after radioiodine treatment and not thereafter.

CONCLUSIONS

Our findings demonstrate that the ELISPOT assay is effective to test T cell reactivity in patients with GD and that patients with GD have significantly more interferon-gamma responses towards TSHR peptides than controls. The data suggest that screening for T cell responses in patients with GD might be more efficient in recent-onset disease or after radioiodine treatment.