Antigen-specific blocking of CD4-specific immunological synapse formation using BPI and current therapies for autoimmune diseases

C-Terminal Region of Caveolin-3 Contains a Stretch of Amino Acid Residues Capable of Diminishing Symptoms of Experimental Autoimmune Encephalomyelitis but Not Rheumatoid Arthritis Modeled in Rats

A short synthetic peptide from the C-terminal part of the caveolin-3 structure was tested for experimental autoimmune encephalomyelitis (EAE) treatment in rats. The structure-function similarity established between the novel synthetic peptide of pCav3 and the well-known immunomodulator immunocortin determined pCav3's ability to reduce EAE symptoms in Dark Agouti (DA) rats injected with pCav3 (500 µg/kg). pCav3 was found to interfere with the proliferation of lymphocytes extracted from the LNs of DA rats primed with homogenate injection, with IC50 = 0.42 μM (2.35 mcg/mL). pCav3 affected EAE in a very similar manner as immunocortin. The high degree of homology between the amino acid sequences of pCav3 and immunocortin corresponded well with the therapeutic activities of both peptides, as demonstrated on EAE. The latter peptide, possessing a homologous structure to pCav3, was also tested on EAE to explore whether there were structural restrictions between these peptides implied by the MHC-involved cell machinery. Consequently, immunocortin was further examined with a different autoimmune disease model, collagen-induced arthritis (CIA), established in Sprague-Dawley rats. CIA was established using an intentionally different genetic platform than EAE. Based on the results, it was concluded that the effectiveness of pCav3 and immunocortin peptides in EAE rat model was almost identical, but differed in the rat model of rheumatoid arthritis; thus, efficacy may be sensitive to the MHC type of animals used to establish the autoimmune disease model.

Quantitative analysis of soluble costimulatory molecules as potential diagnostic biomarkers for rheumatoid arthritis using LC-MS/MS in MRM mode

BACKGROUND AND AIMS

Rheumatoid arthritis (RA) is a chronic autoimmune disease. RA-induced immunological responses are coordinated by T-cell stimulation. The costimulatory signal CD28-B7 is essential for T-cell activation by interacting CD28 with CD80 and CD86 costimulatory proteins. CTLA4 is another costimulatory protein that binds to CD80 and CD86 to inhibit T-cell activity. The soluble costimulatory proteins: sCD80, sCD86, sCD28, and sCTLA-4 were detected and quantified in human plasma and correlated with RA development. As potential diagnostic biomarkers for RA, developing a sensitive, specific, and reproducible method for quantifying these costimulatory molecules in human plasma and establishing quantitative ranges for each protein in healthy and RA patients' plasma is essential for advancing the clinical diagnostic and health outcomes.

MATERIALS AND METHODS

A novel quantitative liquid chromatography-tandem spectrometry (LC-MS/MS) technique using multiple reaction monitoring (MRM) modes was developed and validated to measure soluble costimulatory molecules sCTLA4, sCD28, sCD80, and sCD86 in human plasma samples. Furthermore, the method was applied to determine sCTLA4, sCD28, sCD80, and sCD86 levels in plasma samples from RA patients (n = 23) and healthy controls (n = 21).

RESULTS

The method was successfully developed and validated according to international inter- and intra-assay precision and accuracy guidelines. The linearity of the method was achieved between 0.5 nM and 100 nM for each protein with a correlation coefficient of > 0.998. The plasma level of sCTLA4, sCD80, and sCD86 in RA patients was significantly elevated compared to controls. RA patients had 63.32 ± 17.63 nM sCTLA4 and controls 36.05 ± 18.83 nM; p < 0.0001. The performance of the four proteins was determined using ROC curves, where sCTLA4 showed the highest diagnostic and clinical performance compared to the others.

CONCLUSIONS

This study reports the first use of LC-MS/MS in MRM mode to accurately quantify soluble costimulatory molecules in plasma samples as potential RA diagnostic biomarkers. Determination of the reference range for each protein with high selectivity and sensitivity increases the potential for utilizing this method as a clinical diagnostic.

Immune Modulation by Antigenic Peptides and Antigenic Peptide Conjugates for Treatment of Multiple Sclerosis

The immune system defends our body by fighting infection from pathogens utilizing both the innate and adaptive immune responses. The innate immune response is generated rapidly as the first line of defense. It is followed by the adaptive immune response that selectively targets infected cells. The adaptive immune response is generated more slowly, but selectively, by targeting a wide range of foreign particles (i.e., viruses or bacteria) or molecules that enter the body, known as antigens. Autoimmune diseases are the results of immune system glitches, where the body's adaptive system recognizes self-antigens as foreign. Thus, the host immune system attacks the self-tissues or organs with a high level of inflammation and causes debilitation in patients. Many current treatments for autoimmune diseases (i.e., multiple sclerosis (MS), rheumatoid arthritis (RA)) have been effective but lead to adverse side effects due to general immune system suppression, which makes patients vulnerable to opportunistic infections. To counter these negative effects, many different avenues of antigen specific treatments are being developed to selectively target the autoreactive immune cells for a specific self-antigen or set of self-antigens while not compromising the general immune system. These approaches include soluble antigenic peptides, bifunctional peptide inhibitors (BPI) including IDAC and Fc-BPI, polymer conjugates, and peptide-drug conjugates. Here, various antigen-specific methods of potential treatments, their efficacy, and limitations will be discussed along with the potential mechanisms of action.

Molecular Mechanisms of T Cells Activation by Dendritic Cells in Autoimmune Diseases

The interaction between T cell and dendritic cells (DCs) that leads to T cell activation affects the progression of the immune response including autoimmune diseases. Antigen presentation on immune cell surface, formation of an immunological synapse (IS), and specific identification of complex by T cells including two activating signals are necessary steps that lead to T cell activation. The formation of stimulatory IS involves the inclusion of costimulatory molecules, such as ICAM-1/LFA-1 and CD28/B7-1, and so on. Some fusion proteins and monoclonal antibodies targeting costimulatory molecules have been developed and approved to treat autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), type I diabetes (T1D), inflammatory bowel disease (IBD), and psoriasis. These biological agents, including CTLA-4- and LFA-3-Ig, anti-CD3 monoclonal antibody, could prevent the successful engagement of DCs by T cell with significant efficacy and safety profile. In this article, we reviewed the molecular mechanisms of T cell activation during the interaction between T cells and DCs, and summarized some biological agents that target costimulatory molecules involved in the regulation of T cell activation.

Peptibodies: An elegant solution for a long-standing problem

Chimeric proteins composed of a biologically active peptide and a fragment crystallizable (Fc) domain of immunoglobulin G (IgG) are known as peptibodies. They present an extended half-life due to neonatal Fc receptor (FcRn) salvage pathway, a decreased renal clearance rate owing to its increased size (≈70 kDa) and, depending on the peptide used in the design of the peptibody, an active-targeting moiety. Also, the peptides therapeutic activity is boosted by the number of peptides in the fusion protein (at least two peptides) and to some peptides' alterations. Peptibodies are mainly obtained through recombinant DNA technology. However, to improve peptide properties, "unnatural" changes have been introduced to the original peptides' sequence, for instance, the incorporation of D- or non-natural amino acid residues or even cyclization thus, limiting the application of genetic engineering in the production of peptibodies, since these peptides must be obtained via chemical synthesis. This constrains prompted the development of new methods for conjugation of peptides to Fc domains. Another challenge, subject of intense research, relates to the large-scale production of such peptibodies using these new techniques, which can be minimized by their proved value. To date, two peptibodies, romiplostim and dulaglutide, have been approved and stay as the standard of care in their areas of action. Furthermore, a considerable number of peptibodies are currently in preclinical and clinical development.

Synthesis of a Bifunctional Peptide Inhibitor-IgG1 Fc Fusion That Suppresses Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) is a neurodegenerative disease that is estimated to affect over 2.3 million people worldwide. The exact cause for this disease is unknown but involves immune system attack and destruction of the myelin protein surrounding the neurons in the central nervous system. One promising class of compounds that selectively prevent the activation of immune cells involved in the pathway leading to myelin destruction are bifunctional peptide inhibitors (BPIs). Treatment with BPIs reduces neurodegenerative symptoms in experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. In this work, as an effort to further improve the bioactivity of BPIs, BPI peptides were conjugated to the N- and C-termini of the fragment crystallizable (Fc) region of the human IgG1 antibody. Initially, the two peptides were conjugated to IgG1 Fc using recombinant DNA technology. However, expression in yeast resulted in low yields and one of the peptides being heavily proteolyzed. To circumvent this problem, the poorly expressed peptide was instead produced by solid phase peptide synthesis and conjugated enzymatically using a sortase-mediated ligation. The sortase-mediated method showed near-complete conjugation yield as observed by SDS-PAGE and mass spectrometry in small-scale reactions. This method was scaled up to obtain sufficient quantities for testing the BPI-Fc fusion in mice induced with EAE. Compared to the PBS-treated control, mice treated with the BPI-Fc fusion showed significantly reduced disease symptoms, did not experience weight loss, and showed reduced de-myelination. These results demonstrate that the BPI peptides were highly active at suppressing EAE when conjugated to the large Fc scaffold in this manner.

Pulmonary Administration of Soluble Antigen Arrays Is Superior to Antigen in Treatment of Experimental Autoimmune Encephalomyelitis

Antigen-specific immunotherapy has been used to hyposensitize patients to allergens and offers an enticing approach for attenuating autoimmune diseases. Applying antigen-specific immunotherapy to mucosal surfaces such as the lungs may engage unique immune response pathways to improve efficacy. Pulmonary delivery of soluble antigen arrays (SAgAs) was explored in mice with experimental autoimmune encephalomyelitis (EAE), a multiple sclerosis model. SAgAs were designed to impede immune response to autoantigen epitopes and are composed of a hyaluronan backbone with peptides PLP_139-151 (proteolipid protein) and LABL, a disease-causing proteolipid peptide epitope and an intracellular cell-adhesion molecule-1 ligand, respectively. Pulmonary instillation of SAgAs decreased disease score, improved weight gain, and decreased incidence of disease in EAE mice compared to pulmonary delivery of hyaluronic acid polymer, LABL, or PLP. Interestingly, treating with PLP alone also showed some improvement. Splenocytes from SAgA-treated animals showed increased interferon-gamma levels, and interleukin-6 (IL-6) and IL-17 were elevated in SAgA-treated animals compared to PLP treatments. IL-10, IL-2, and tumor necrosis factor-alpha levels showed no significant difference, yet trends across all cytokines suggested SAgAs induced a very different immune response compared to treatment with PLP alone. This work suggests that codelivery of peptide components is essential when treating EAE via pulmonary instillation, and the immune response may have shifted toward immune tolerance.

Regulatory T cells in multiple sclerosis and myasthenia gravis

Multiple sclerosis (MS) is a chronic debilitating disease of the central nervous system primarily mediated by T lymphocytes with specificity to neuronal antigens in genetically susceptible individuals. On the other hand, myasthenia gravis (MG) primarily involves destruction of the neuromuscular junction by antibodies specific to the acetylcholine receptor. Both autoimmune diseases are thought to result from loss of self-tolerance, which allows for the development and function of autoreactive lymphocytes. Although the mechanisms underlying compromised self-tolerance in these and other autoimmune diseases have not been fully elucidated, one possibility is numerical, functional, and/or migratory deficits in T regulatory cells (Tregs). Tregs are thought to play a critical role in the maintenance of peripheral immune tolerance. It is believed that Tregs function by suppressing the effector CD4+ T cell subsets that mediate autoimmune responses. Dysregulation of suppressive and migratory markers on Tregs have been linked to the pathogenesis of both MS and MG. For example, genetic abnormalities have been found in Treg suppressive markers CTLA-4 and CD25, while others have shown a decreased expression of FoxP3 and IL-10. Furthermore, elevated levels of pro-inflammatory cytokines such as IL-6, IL-17, and IFN-γ secreted by T effectors have been noted in MS and MG patients. This review provides several strategies of treatment which have been shown to be effective or are proposed as potential therapies to restore the function of various Treg subsets including Tr1, iTr35, nTregs, and iTregs. Strategies focusing on enhancing the Treg function find importance in cytokines TGF-β, IDO, interleukins 10, 27, and 35, and ligands Jagged-1 and OX40L. Likewise, strategies which affect Treg migration involve chemokines CCL17 and CXCL11. In pre-clinical animal models of experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune myasthenia gravis (EAMG), several strategies have been shown to ameliorate the disease and thus appear promising for treating patients with MS or MG.

Conjugates of Cell Adhesion Peptides for Therapeutics and Diagnostics Against Cancer and Autoimmune Diseases

Overexpressed cell-surface receptors are hallmarks of many disease states and are often used as markers for targeting diseased cells over healthy counterparts. Cell adhesion peptides, which are often derived from interacting regions of these receptor-ligand proteins, mimic surfaces of intact proteins and, thus, have been studied as targeting agents for various payloads to certain cell targets for cancers and autoimmune diseases. Because many cytotoxic agents in the free form are often harmful to healthy cells, the use of cell adhesion peptides in targeting their delivery to diseased cells has been studied to potentially reduce required effective doses and associated harmful side-effects. In this review, multiple cell adhesion peptides from extracellular matrix and ICAM proteins were used to selectively direct drug payloads, signal-inhibitor peptides, and diagnostic molecules, to diseased cells over normal counterparts. RGD constructs have been used to improve the selectivity and efficacy of diagnostic and drug-peptide conjugates against cancer cells. From this precedent, novel conjugates of antigenic and cell adhesion peptides, called Bifunctional Peptide Inhibitors (BPIs), have been designed to selectively regulate immune cells and suppress harmful inflammatory responses in autoimmune diseases. Similar peptide conjugations with imaging agents have delivered promising diagnostic methods in animal models of rheumatoid arthritis. BPIs have also been shown to generate immune tolerance and suppress autoimmune diseases in animal models of type-1 diabetes, rheumatoid arthritis, and multiple sclerosis. Collectively, these studies show the potential of cell adhesion peptides in improving the delivery of drugs and diagnostic agents to diseased cells in clinical settings.

Sensing of Porcine Reproductive and Respiratory Syndrome Virus-Infected Macrophages by Plasmacytoid Dendritic Cells

Porcine reproductive and respiratory syndrome virus (PRRSV) represents a macrophage (MØ)-tropic virus which is unable to induce interferon (IFN) type I in its target cells. Nevertheless, infected pigs show a short but prominent systemic IFN alpha (IFN-α) response. A possible explanation for this discrepancy is the ability of plasmacytoid dendritic cells (pDC) to produce IFN-α in response to free PRRSV virions, independent of infection. Here, we show that the highly pathogenic PRRSV genotype 1 strain Lena is unique in not inducing IFN-α production in pDC, contrasting with systemic IFN-α responses found in infected pigs. We also demonstrate efficient pDC stimulation by PRRSV Lena-infected MØ, resulting in a higher IFN-α production than direct stimulation of pDC by PRRSV virions. This response was strain-independent, required integrin-mediated intercellular contact, intact actin filaments in the MØ and was partially inhibited by an inhibitor of neutral sphingomyelinase. Although infected MØ-derived exosomes stimulated pDC, an efficient delivery of the stimulatory component was dependent on a tight contact between pDC and the infected cells. In conclusion, with this mechanism the immune system can efficiently sense PRRSV, resulting in production of considerable quantities of IFN-α. This is adding complexity to the immunopathogenesis of PRRSV infections, as IFN-α should alert the immune system and initiate the induction of adaptive immune responses, a process known to be inefficient during infection of pigs.

Antigen-Specific Binding of Multivalent Soluble Antigen Arrays Induces Receptor Clustering and Impedes B Cell Receptor Mediated Signaling

A pressing need exists for autoimmune disease therapies that act in an antigen-specific manner while avoiding global immunosuppression. Multivalent soluble antigen arrays (SAgAPLP:LABL), designed to induce tolerance to a specific multiple sclerosis autoantigen, consist of a flexible hyaluronic acid (HA) polymer backbone cografted with multiple copies of autoantigen peptide (PLP) and cell adhesion inhibitor peptide (LABL). Previous in vivo studies revealed copresentation of both signals on HA was necessary for therapeutic efficacy. To elucidate therapeutic cellular mechanisms, in vitro studies were performed in a model B cell system to evaluate binding and specificity. Compared to HA and HA arrays containing only grafted PLP or LABL, SAgAPLP:LABL displaying both PLP and LABL exhibited greatly enhanced B cell binding. Furthermore, the binding avidity of SAgAPLP:LABL was primarily driven by the PLP antigen, determined via flow cytometry competitive dissociation studies. Fluorescence microscopy showed SAgAPLP:LABL induced mature receptor clustering that was faster than other HA arrays with only one type of grafted peptide. SAgAPLP:LABL molecules also reduced and inhibited IgM-stimulated signaling as discerned by a calcium flux assay. The molecular mechanisms of enhanced antigen-specific binding, mature receptor clustering, and dampened signaling observed in B cells may contribute to SAgAPLP:LABL therapeutic efficacy.

Immune Tolerance Induction against Experimental Autoimmune Encephalomyelitis (EAE) Using A New PLP-B7AP Conjugate that Simultaneously Targets B7/CD28 Costimulatory Signal and TCR/MHC-II Signal

Most of the current therapies used in the treatment of multiple sclerosis (MS) are either ineffective or have adverse side effects. As such, there is a need to develop better therapies that specifically target myelin-specific aberrant immune cells involved in CNS inflammation without compromising the general immune system. In the present study, we developed a new bifunctional peptide inhibitor (BPI) that is effective and specific. Our BPI (PLP-B7AP) is composed of an antigenic peptide from myelin proteolipid protein (PLP139-151) and a B7 antisense peptide (B7AP) derived from CD28 receptor. The main hypothesis is that PLP-B7AP simultaneously targets MHC-II and B7-costimulatory molecules on the surface of antigen presenting cells (APC) and possibly alters the differentiation of naïve T cells from inflammatory to regulatory phenotypes. Results showed that PLP-B7AP was very effective in suppressing experimental autoimmune encephalomyelitis (EAE) compared to various controls in a mouse model. PLP-B7AP was effective when administered both before and after disease induction. Secreted cytokines from splenocytes isolated during periods of high disease severity and remission indicated that PLP-B7AP treatment induced an increased production of anti-inflammatory cytokines and inhibited the production of pro-inflammatory cytokines. Further, analysis of cortical brain tissue sections showed that PLP-B7AP treated mice had significantly lower demyelination compared to the control group. All these taken together indicate that the T cell receptor (TCR) and the CD28 receptor can be targeted simultaneously to improve efficacy and specificity of potential MS therapeutics.

Co-delivery of autoantigen and b7 pathway modulators suppresses experimental autoimmune encephalomyelitis

Autoimmune diseases such as multiple sclerosis (MS) are characterized by the breakdown of immune tolerance to autoantigens. Targeting surface receptors on immune cells offers a unique strategy for reprogramming immune responses in autoimmune diseases. The B7 signaling pathway was targeted using adaptations of soluble antigen array (SAgA) technology achieved by covalently linking B7-binding peptides and disease causing autoantigen (proteolipid peptide (PLP)) to hyaluronic acid (HA). We hypothesized that co-delivery of a B7-binding peptide and autoantigen would suppress experimental autoimmune encephalomyelitis (EAE), a murine model of MS. Three independent B7-targeted SAgAs were created containing peptides to either inhibit or potentially stimulate the B7 signaling pathway. Surprisingly, all SAgAs were found to suppress EAE disease symptoms. Altered cytokine expression was observed in primary splenocytes isolated from SAgA-treated mice, indicating that SAgAs with different B7-binding peptides may suppress EAE through different immunological mechanisms. This antigen-specific immunotherapy using SAgAs can successfully suppress EAE through co-delivery of autoantigen and peptides targeting with the B7 signaling pathway.

Protein 4.1R attenuates autoreactivity in experimental autoimmune encephalomyelitis by suppressing CD4(+) T cell activation

Immune synapse components contribute to multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE) pathogenesis as they play important role in autoreactive T cell activation. Protein 4.1R, a red cell membrane cytoskeletal protein, recently was identified as an important component of immunological synapse (IS) and acted as the negative regulator of CD4(+) T cell activation. However, the pathological role of 4.1R in the MS/EAE pathogenesis is still not elucidated. In this study, we investigated the potential role of protein 4.1R in pathologic processes of EAE by using 4.1R knockout mouse model. Our results suggest that 4.1R can prevent pathogenic autoimmunity in MS/EAE progression by suppressing the CD4(+) T cell activation.

Codelivery of antigen and an immune cell adhesion inhibitor is necessary for efficacy of soluble antigen arrays in experimental autoimmune encephalomyelitis

Autoimmune diseases such as multiple sclerosis (MS) are typified by the misrecognition of self-antigen and the clonal expansion of autoreactive T cells. Antigen-specific immunotherapies (antigen-SITs) have long been explored as a means to desensitize patients to offending self-antigen(s) with the potential to retolerize the immune response. Soluble antigen arrays (SAgAs) are composed of hyaluronic acid (HA) cografted with disease-specific autoantigen (proteolipid protein peptide) and an ICAM-1 inhibitor peptide (LABL). SAgAs were designed as an antigen-SIT that codeliver peptides to suppress experimental autoimmune encephalomyelitis (EAE), a murine model of MS. Codelivery of antigen and cell adhesion inhibitor (LABL) conjugated to HA was essential for SAgA treatment of EAE. Individual SAgA components or mixtures thereof reduced proinflammatory cytokines in cultured splenocytes from EAE mice; however, these treatments showed minimal to no in vivo therapeutic effect in EAE mice. Thus, carriers that codeliver antigen and a secondary “context” signal (e.g., LABL) in vivo may be an important design criteria to consider when designing antigen-SIT for autoimmune therapy.

Suppression of MOG- and PLP-induced experimental autoimmune encephalomyelitis using a novel multivalent bifunctional peptide inhibitor

Previously, bifunctional peptide inhibitors (BPI) with a single antigenic peptide have been shown to suppress experimental autoimmune encephalomyelitis (EAE) in an antigen-specific manner. In this study, a multivalent BPI (MVBMOG/PLP) with two antigenic peptides derived from myelin oligodendrocyte glycoprotein (MOG38-50) and myelin proteolipid protein (PLP139-151) was evaluated in suppressing MOG38-50- and PLP139-151-induced EAE. MVBMOG/PLP significantly suppressed both models of EAE even when there was some evidence of epitope spreading in the MOG38-50-induced EAE model. In addition, MVBMOG/PLP was found to be more effective than PLP-BPI and MOG-BPI in suppressing MOG38-50-induced EAE. Thus, the development of MVB molecules with broader antigenic targets can lead to suppression of epitope spreading in EAE.

Single-step grafting of aminooxy-peptides to hyaluronan: a simple approach to multifunctional therapeutics for experimental autoimmune encephalomyelitis

The immune response to antigens is directed in part by the presence or absence of costimulatory signals. The ability to coincidently present both antigen and, for example, a peptide that inhibits or activates the costimulatory pathway, would be a valuable tool for tolerization or immunization, respectively. A simple reaction scheme utilizing oxime chemistry was identified as a means to efficiently conjugate different peptide species to hyaluronan. Peptides synthesized with an aminooxy N-terminus reacted directly to hyaluronan under slightly acidic aqueous conditions without the need for a catalyst. The resulting oxime bond was found to rapidly hydrolyze at pH2 releasing peptide, but was stable at higher pH values (5.5 and 7). Two different peptide species, a multiple sclerosis antigen (PLP) and an ICAM-1 ligand (LABL) known to block immune cell stimulation, were functionalized with the aminooxy end group. These peptides showed similar reactivity to hyaluronan and were conjugated in an equimolar ratio. The resulting hyaluronan with grafted PLP and LABL significantly inhibited disease in mice with experimental autoimmune encephalomyelitis, a model of multiple sclerosis. Aminooxy-peptides facilitate simple synthesis of multifunctional hyaluronan graft polymers, thus enabling novel approaches to antigen-specific immune modulation.

Controlling immune response and demyelination using highly potent bifunctional peptide inhibitors in the suppression of experimental autoimmune encephalomyelitis

In this study, we investigated the efficacy of new bifunctional peptide inhibitors (BPIs) in suppressing experimental autoimmune encephalomyelitis (EAE) in an animal model. BPI [e.g. proteolipid protein-cyclo(1,8)-CPRGGSVC-NH2 (PLP-cIBR)] is a conjugate between the PLP139-151 peptide derived from proteolipid protein (PLP) and the cIBR7 peptide derived from domain-1 (D1) of intercellular adhesion molecule-1 (ICAM-1). PLP-cIBR is designed to bind to major histocompatibility complex (MHC)-II and leucocyte function-associated antigen-1 (LFA-1) simultaneously to inhibit the formation of the immunological synapse and alter the differentiation and activation of a subpopulation of T cells, thus inducing immunotolerance. The results show that PLP-cIBR is highly potent in ameliorating EAE, even at low concentrations and less frequent injections. Mice treated with PLP-cIBR had a higher secretion of cytokines related to regulatory and/or suppressor cells compared to phosphate-buffered saline (PBS)-treated mice. In contrast, T helper type 1 (Th1) cytokines were higher in mice treated with PBS compared to PLP-cIBR, suggesting that it suppressed Th1 proliferation. Also, we observed significantly less demyelination in PLP-cIBR-treated mice compared to the control, further indicating that PLP-cIBR promoted protection against demyelination.

Vaccinelike and prophylactic treatments of EAE with novel I-domain antigen conjugates (IDAC): targeting multiple antigenic peptides to APC

The objective of this work is to utilize novel I-domain antigenic-peptide conjugates (IDAC) for targeting antigenic peptides to antigen-presenting cells (APC) to simulate tolerance in experimental autoimmune encephalomyelitis (EAE). IDAC-1 and IDAC-3 molecules are conjugates between the I-domain protein and PLP-Cys and Ac-PLP-Cys-NH(2) peptides, respectively, tethered to N-terminus and Lys residues on the I-domain. The hypothesis is that the I-domain protein binds to ICAM-1 and PLP peptide binds to MHC-II on the surface of APC; this binding event inhibits the formation of the immunological synapse at the APC-T-cell interface to alter T-cell differentiation from inflammatory to regulatory phenotypes. Conjugation of peptides to the I-domain did not change the secondary structure of IDAC molecules as determined by circular dichroism spectroscopy. The efficacies of IDAC-1 and -3 were evaluated in EAE mice by administering iv or sc injections of IDAC in a prophylactic or a vaccinelike dosing schedule. IDAC-3 was better than IDAC-1 in suppressing and delaying the onset of EAE when delivered in prophylactic and vaccinelike manners. IDAC-3 also suppressed subsequent relapse of the disease. The production of IL-17 was lowered in the IDAC-3-treated mice compared to those treated with PBS. In contrast, the production of IL-10 was increased, suggesting that there is a shift from inflammatory to regulatory T-cell populations in IDAC-3-treated mice. In conclusion, the I-domain can effectively deliver antigenic peptides in a vaccinelike or prophylactic manner for inducing immunotolerance in the EAE mouse model.

Immune modulating peptides for the treatment and suppression of multiple sclerosis

Multiple sclerosis (MS) is a neurodegenerative disease in which the immune system recognizes proteins of the myelin sheath as antigenic, thus initiating an inflammatory reaction in the central nervous system. This leads to demyelination of the axons, breakdown of the blood-brain barrier, and lesion formation. Current therapies for the treatment of MS are generally non-specific and weaken the global immune system, thus making the individual susceptible to opportunistic infections. Antigenic peptides and their derivatives are becoming more prevalent for investigation as therapeutic agents for MS because they possess immune-specific characteristics. In addition, other peptides that target vital components of the inflammatory immune response have also been developed. Therefore, the objectives of this review are to (a) summarize the immunological basis for the development of MS, (b) discuss specific and non-specific peptides tested in EAE and in humans, and (c) briefly address some problems and potential solutions with these novel therapies.

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.

Vaccine-like controlled-release delivery of an immunomodulating peptide to treat experimental autoimmune encephalomyelitis

The objective of this work is to use colloidal gel from alginate-chitosan-PLGA complex to deliver Ac-PLP-BPI-NH₂-2 peptide in a controlled-release manner as a vaccine-like therapeutic to suppress experimental autoimmune encephalomyelitis (EAE) in the mouse model. Oppositely charged PLGA nanoparticles were prepared by a solvent diffusion method. The carboxyl group of the alginate and the amine group of the chitosan coated the nanoparticles with negative and positive charges, respectively. The peptide (Ac-PLP-BPI-NH₂-2), designed to bind to MHC-II and ICAM-1 simultaneously, was formulated into the colloidal gel by physical mixture. Vaccine-like administration of the peptide-loaded colloidal gel (Ac-PLP-BPI-NH₂-2-NP) was achieved by subcutaneous (sc) injection to EAE mice. Disease severity was measured using clinical scoring and percent change in body weight. Cytokine production was determined using the splenocytes from Ac-PLP-BPI-NH₂-2-NP-treated mice and compared to that of controls. Ac-PLP-BPI-NH₂-2-NP suppressed and delayed the onset of EAE as well as Ac-PLP-BPI-NH₂-2 when delivered in a vaccine-like manner. IL-6 and IL-17 levels were significantly lower in the Ac-PLP-BPI-NH₂-2-NP-treated mice compared to the mouse group treated with blank colloidal gel, suggesting that the mechanism of suppression of EAE is due to a shift in the immune response away from Th17 production. The results of this study suggest that a one-time sc administration of Ac-PLP-BPI-NH₂-2 formulated in a colloidal gel can produce long-term suppression of EAE by reducing Th17 proliferation.

Suppression of EAE and prevention of blood-brain barrier breakdown after vaccination with novel bifunctional peptide inhibitor

The efficacy of bifunctional peptide inhibitor (BPI) in preventing blood-brain barrier (BBB) breakdown during onset of experimental autoimmune encephalomyelitis (EAE) and suppression of the disease was evaluated in mice. The mechanism that defines how BPI prevents the disease was investigated by measuring the in vitro cytokine production of splenocytes. Peptides were injected 5-11 days prior to induction of EAE, and the severity of the disease was monitored by a standard clinical scoring protocol and change in body weight. The BBB breakdown in diseased and treated mice was compared to that in normal control mice by determining deposition of gadolinium diethylenetriaminepentaacetate (Gd-DTPA) in the brain using magnetic resonance imaging (MRI). Mice treated with PLP-BPI showed no or low indication of EAE as well as normal increase in body weight. In contrast, mice treated with the control peptide or PBS showed a decrease in body weight and a high disease score. The diseased mice had high deposition of Gd-DTPA in the brain, indicating breakdown in the BBB. However, the deposition of Gd-DTPA in PLP-BPI-treated mice was similar to that in normal control mice. Thus, PLP-BPI can suppress EAE when administered as a peptide vaccine and maintain the integrity of the BBB.

A fibrinogen-derived peptide provides intercellular adhesion molecule-1-specific targeting and intraendothelial transport of polymer nanocarriers in human cell cultures and mice

Intercellular adhesion molecule-1 (ICAM-1), a transmembrane glycoprotein expressed on activated endothelium and many other cells, represents a suitable target for delivery of drug nanocarriers (NCs) to disease areas. Numerous works have shown efficient targeting and intracellular transport of ICAM-1-targeted NCs, rendering significant therapeutic potential. This is the case for enzyme delivery for treatment of multitissue lysosomal storage disorders. However, those studies used formulations targeted to ICAM-1 by antibodies (anti-ICAM NCs). This poses an obstacle to preclinical evaluation of long-term treatment of such chronic maladies, caused by immunogenicity of foreign proteins administered to animals, compelling development of alternative strategies. In this work, we used radioisotope tracing, fluorescence and electron microscopy, and in vitro, cell cultures, and mouse models to evaluate polymer nanocarriers targeted to ICAM-1 by a 17-mer linear peptide derived from the ICAM-1-binding sequence of fibrinogen (γ3). Our results show that γ3 NCs target ICAM-1 with efficiency and specificity similar to that of anti-ICAM NCs, determined by using immobilized ICAM-1, native ICAM-1 expressed on endothelial cell cultures, and intravenous administration in mice. Furthermore, γ3 NCs are internalized by cells in culture and in vivo and transported to lysosomes via cell adhesion molecule-mediated endocytosis, without apparent disruption of cell junctions, similar to anti-ICAM counterparts. The degree of conservation of fibrinogen γ3 sequence and its cognate site on ICAM-1 among species (e.g., mouse, chimpanzee, and humans) reflects the interspecies targeting found for γ3 NCs, providing an avenue for exploring the translation of ICAM-1-targeting platforms in the preclinical and, perhaps, future clinical realm.