Selective Uptake of Macromolecules to the Brain in Microfluidics and Animal Models Using the HAVN1 Peptide as a Blood-Brain Barrier Modulator

Monoclonal antibodies (mAbs) possess favorable pharmacokinetic properties, high binding specificity and affinity, and minimal off-target effects, making them promising therapeutic agents for central nervous system (CNS) disorders. However, their development as effective therapeutic and diagnostic agents for brain disorders is hindered by their limited ability to efficiently penetrate the blood-brain barrier (BBB). Therefore, it is crucial to develop efficient delivery methods that enhance the penetration of antibodies into the brain. Previous studies have demonstrated the potential of cadherin-derived peptides (i.e., ADTC5, HAVN1 peptides) as BBB modulators (BBBMs) to increase paracellular porosities for penetration of molecules across the BBB. Here, we test the effectiveness of the leading BBBM peptide, HAVN1 (Cyclo(1,6)SHAVSS), in enhancing the permeation of various monoclonal antibodies through the BBB using both in vitro and in vivo systems. In vitro, HAVN1 has been shown to increase the permeability of fluorescently labeled macromolecules, such as a 70 kDa dextran, 50 kDa Fab1, and 150 kDa mAb1, by 4- to 9-fold in a three-dimensional blood-brain barrier (3D-BBB) microfluidics model using a human BBB endothelial cell line (i.e., hCMEC/D3). HAVN1 was selective in modulating the BBB endothelial cell, compared to the pulmonary vascular endothelial (PVE) cell barrier. Co-administration of HAVN1 significantly improved brain depositions of mAb1, mAb2, and Fab1 in C57BL/6 mice after 15 min in the systemic circulation. Furthermore, HAVN1 still significantly enhanced brain deposition of mAb2 when it was administered 24 h after the administration of the mAb. Lastly, we observed that multiple doses of HAVN1 may have a cumulative effect on the brain deposition of mAb2 within a 24-h period. These findings offer promising insights into optimizing HAVN1 and mAb dosing regimens to control or modulate mAb brain deposition for achieving desired mAb dose in the brain to provide its therapeutic effects.

Directing Cell Delivery to Murine Atherosclerotic Aortic Lesions via Targeting Inflamed Circulatory Interface using Nanocarriers

Stem cell therapy holds significant potential for many inflammatory diseases and regenerative medicine applications. However, delivery of therapeutic cells to specific disease sites after systemic administration without indiscriminate trafficking to other non-target tissues is a major limitation of current cell therapies. Here, we describe a novel nanocarrier-directed targeted cell delivery system that enables cell surface coating with dendrimer nanocarriers containing adhesion moieties to serve as a global positioning system "GPS" to guide circulating cells to targeted lesions and mediate the anchoring of cells at the inflammation site. By exploiting cell surface ligands/receptors selectively and/or molecular moieties that are highly expressed on activated endothelium in pathologic disease states, nanocarrier-coated cells containing the counterpart binding receptors/ligands can be enabled to specifically traffic to and dock at vasculature within target lesions. We demonstrate the efficacy of the I-domain fragment of LFA-1 ( id LFA-1) complexed to modified nanocarriers to facilitate homing of mesenchymal stem cells (MSCs) to inflamed luminal endothelial cells on which ICAM-1 is highly expressed in a murine model of aortic atherosclerosis. Our method can overcome challenges imposed by the high velocity and dynamic circulatory flow of the aorta to successfully deliver MSCs to atherosclerotic regions and allow for docking of the potentially therapeutic and immunomodulating cells. This targeted cell-delivery platform can be tailored for selective systemic delivery of various types of therapeutic cells to different disease areas.

Evaluation of LFA-1 Peptide-Methotrexate Conjugates in Modulating Endothelial Cell Inflammation and Cytokine Regulation

Interactions between vascular endothelial cells and inflammatory leukocytes are intermediated via cell adhesion molecules and they become one of the key events for vascular cell injury and development of atherosclerosis. This study evaluated the effects of MTX-peptide conjugates as anti-inflammatory agents on human coronary artery endothelial cells (HCAEC) and Molt-3 T cells. Cyclic peptides, cLABL and cLBEL, were derived from the α- and β-subunits of leukocyte function-associated antigen-1 (LFA-1), respectively. They interact with intercellular adhesion molecule-1 (ICAM-1) to inhibit LFA-1/ICAM-1-mediated homotypic or heterotypic T-cell adhesion. cLABL and cLBEL were linked to the anti-inflammatory drug, methotrexate (MTX), to produce MTX-cLABL and MTX-cLBEL conjugates. This study showed that peptides and MTX-peptide conjugates inhibited T cell adhesion to HCAEC monolayers while MTX alone did not. The conjugates, but not MTX, inhibited binding of anti-ICAM-1 monoclonal antibody (mAb) to ICAM-1 on the HCAEC. This indicates that conjugation of MTX to cLABL and cLBEL peptides did not dramatically change their binding properties to ICAM-1. The conjugates had relatively lower toxicity to cells compared to MTX alone, while they were more toxic than the parent peptides. At low concentrations, MTX, MTX-cLABL and MTX-cLBEL decreased production of IL-6 and IL-8 as inflammatory cytokines. In contrast, higher concentrations of the parent peptides compared to the conjugates were required to inhibit IL-6 and IL-8 productions. Overall, both MTX-cLABL and MTX-cLBEL were more active than both free-peptides. In addition, the conjugates were less toxic than MTX alone. In conclusion, the conjugate can selectively target MTX to ICAM-1-expressing cells to increase cell targeting and to lower MTX toxicity.

M. tuberculosis Transcription Machinery: A Review on the Mycobacterial RNA Polymerase and Drug Discovery Efforts

Mycobacterium tuberculosis (MTB) is the main source of tuberculosis (TB), one of the oldest known diseases in the human population. Despite the drug discovery efforts of past decades, TB is still one of the leading causes of mortality and claimed more than 1.5 million lives worldwide in 2020. Due to the emergence of drug-resistant strains and patient non-compliance during treatments, there is a pressing need to find alternative therapeutic agents for TB. One of the important areas for developing new treatments is in the inhibition of the transcription step of gene expression; it is the first step to synthesize a copy of the genetic material in the form of mRNA. This further translates to functional protein synthesis, which is crucial for the bacteria living processes. MTB contains a bacterial DNA-dependent RNA polymerase (RNAP), which is the key enzyme for the transcription process. MTB RNAP has been targeted for designing and developing antitubercular agents because gene transcription is essential for the mycobacteria survival. Initiation, elongation, and termination are the three important sequential steps in the transcription process. Each step is complex and highly regulated, involving multiple transcription factors. This review is focused on the MTB transcription machinery, especially in the nature of MTB RNAP as the main enzyme that is regulated by transcription factors. The mechanism and conformational dynamics that occur during transcription are discussed and summarized. Finally, the current progress on MTB transcription inhibition and possible drug target in mycobacterial RNAP are also described to provide insight for future antitubercular drug design and development.

Spermidine/Spermine N1-Acetyltransferase 1 (SAT1)-A Potential Gene Target for Selective Sensitization of Glioblastoma Cells Using an Ionizable Lipid Nanoparticle to Deliver siRNA

Spermidine/spermine N1-acetyltransferase 1 (SAT1) responsible for cell polyamine catabolism is overexpressed in glioblastoma multiforme (GB). Its role in tumor survival and promoting resistance towards radiation therapy has made it an interesting target for therapy. In this study, we prepared a lipid nanoparticle-based siRNA delivery system (LNP-siSAT1) to selectively knockdown (KD) SAT1 enzyme in a human glioblastoma cell line. The LNP-siSAT1 containing ionizable DODAP lipid was prepared following a microfluidics mixing method and the resulting nanoparticles had a hydrodynamic size of around 80 nm and a neutral surface charge. The LNP-siSAT1 effectively knocked down the SAT1 expression in U251, LN229, and 42MGBA GB cells, and other brain-relevant endothelial (hCMEC/D3), astrocyte (HA) and macrophage (ANA-1) cells at the mRNA and protein levels. SAT1 KD in U251 cells resulted in a 40% loss in cell viability. Furthermore, SAT1 KD in U251, LN229 and 42MGBA cells sensitized them towards radiation and chemotherapy treatments. In contrast, despite similar SAT1 KD in other brain-relevant cells no significant effect on cytotoxic response, either alone or in combination, was observed. A major roadblock for brain therapeutics is their ability to cross the highly restrictive blood-brain barrier (BBB) presented by the brain microcapillary endothelial cells. Here, we used the BBB circumventing approach to enhance the delivery of LNP-siSAT1 across a BBB cell culture model. A cadherin binding peptide (ADTC5) was used to transiently open the BBB tight junctions to promote paracellular diffusion of LNP-siSAT1. These results suggest LNP-siSAT1 may provide a safe and effective method for reducing SAT1 and sensitizing GB cells to radiation and chemotherapeutic agents.

Structural Design and Synthesis of Novel Cyclic Peptide Inhibitors Targeting Mycobacterium tuberculosis Transcription

Tuberculosis (TB) remains one of the deadliest infectious diseases in the world. Although several established antitubercular drugs have been found, various factors obstruct efforts to combat this disease due to the existence of drug-resistance (DR) TB strains, the need for lengthy treatment, and the occurrence of side effects from drug–drug interactions. Rifampicin (RIF) is the first line of antitubercular drugs and targets RNA polymerase (RNAP) of Mycobacterium tuberculosis (MTB). Here, RIF blocks the synthesis of long RNA during transcription initiation. The efficacy of RIF is low in DR-TB strains, and the use of RIF leads to various side effects. In this study, novel cyclic peptides were computationally designed as inhibitors of MTB transcription initiation. The designed cyclic peptides were subjected to a virtual screening to generate compounds that can bind to the RIF binding site in MTB RNAP subunit β (RpoB) for obtaining a new potential TB drug with a safe clinical profile. The molecular simulations showed that the cyclic peptides were capable of binding with RpoB mutants, suggesting that they can be possibility utilized for treating DR-TB. Structural modifications were carried out by acetylation and amidation of the N- and C-terminus, respectively, to improve their plasma stability and bioavailability. The modified linear and cyclic peptides were successfully synthesized with a solid-phase peptide synthesis method using Fmoc chemistry, and they were characterized by analytical HPLC, LC-ESI-MS⁺, and 1H NMR.

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.

Doxorubicin-loaded iron oxide nanoparticles for glioblastoma therapy: a combinational approach for enhanced delivery of nanoparticles

Although doxorubicin (DOX) is an effective anti-cancer drug with cytotoxicity in a variety of different tumors, its effectiveness in treating glioblastoma multiforme (GBM) is constrained by insufficient penetration across the blood–brain barrier (BBB). In this study, biocompatible magnetic iron oxide nanoparticles (IONPs) stabilized with trimethoxysilylpropyl-ethylenediamine triacetic acid (EDT) were developed as a carrier of DOX for GBM chemotherapy. The DOX-loaded EDT-IONPs (DOX-EDT-IONPs) released DOX within 4 days with the capability of an accelerated release in acidic microenvironments. The DOX-loaded EDT-IONPs (DOX-EDT-IONPs) demonstrated an efficient uptake in mouse brain-derived microvessel endothelial, bEnd.3, Madin–Darby canine kidney transfected with multi-drug resistant protein 1 (MDCK-MDR1), and human U251 GBM cells. The DOX-EDT-IONPs could augment DOX’s uptake in U251 cells by 2.8-fold and significantly inhibited U251 cell proliferation. Moreover, the DOX-EDT-IONPs were found to be effective in apoptotic-induced GBM cell death (over 90%) within 48 h of treatment. Gene expression studies revealed a significant downregulation of TOP II and Ku70, crucial enzymes for DNA repair and replication, as well as MiR-155 oncogene, concomitant with an upregulation of caspase 3 and tumor suppressors i.e., p53, MEG3 and GAS5, in U251 cells upon treatment with DOX-EDT-IONPs. An in vitro MDCK-MDR1-GBM co-culture model was used to assess the BBB permeability and anti-tumor activity of the DOX-EDT-IONPs and DOX treatments. While DOX-EDT-IONP showed improved permeability of DOX across MDCK-MDR1 monolayers compared to DOX alone, cytotoxicity in U251 cells was similar in both treatment groups. Using a cadherin binding peptide (ADTC5) to transiently open tight junctions, in combination with an external magnetic field, significantly enhanced both DOX-EDT-IONP permeability and cytotoxicity in the MDCK-MDR1-GBM co-culture model. Therefore, the combination of magnetic enhanced convective diffusion and the cadherin binding peptide for transiently opening the BBB tight junctions are expected to enhance the efficacy of GBM chemotherapy using the DOX-EDT-IONPs. In general, the developed approach enables the chemotherapeutic to overcome both BBB and multidrug resistance (MDR) glioma cells while providing site-specific magnetic targeting.

Non-invasive Brain Delivery and Efficacy of BDNF in APP/PS1 Transgenic Mice as a Model of Alzheimer's Disease

Neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) have been demonstrated for their potential as a neuroregenerative treatment of Alzheimer's disease (AD). Unfortunately, most proteins cannot be effectively delivered into the brain from the blood stream due to the presence of the blood-brain barrier (BBB). In this study, we delivered BDNF using ADTC5 as BBB modulator (BBBM) into the brains of transgenic APP/PS1 mice, a mouse model for AD. As controls, two groups of APP/PS1 mice were treated with BDNF alone and vehicle, respectively. All three groups were subjected to behavioral/cognitive assessments in Y-maze and novel object recognition (NOR) tests as well as evaluation of the brain markers activated by BDNF. The results showed that BDNF + ADTC5 group performed significantly better in both the Y-maze and NOR assessments compared to mice that received BDNF alone or vehicle. In addition, significant upregulations of NG2 receptors as well as EGR1 and ARC mRNA transcripts were observed in the brain cortex of mice treated with BDNF + ADTC5, further indicating the efficacy of delivered BDNF in the brain. There were high plaque loads in all groups of mice, suggesting no influence of BDNF on the plaque formation. In summary, ADTC5 can deliver BDNF into the brains of APP/PS1 mice and the activity of BDNF in improving cognitive function was likely due to improvement in synaptic plasticity via NG2 glia cells and not by reducing the plaque load.

Noninvasive Brain Delivery and Efficacy of BDNF to Stimulate Neuroregeneration and Suppression of Disease Relapse in EAE Mice

The number of FDA-approved protein drugs (biologics), such as antibodies, antibody-drug conjugates, hormones, and enzymes, continues to grow at a rapid rate; most of these drugs are used to treat diseases of the peripheral body. Unfortunately, most of these biologics cannot be used to treat brain diseases such as Alzheimer's disease (AD), multiple sclerosis (MS), and brain tumors in a noninvasive manner due to their inability to permeate the blood-brain barrier (BBB). Therefore, there is a need to develop an effective method to deliver protein drugs into the brain. Here, we report a proof of concept to deliver a recombinant brain-derived neurotrophic factor (BDNF) to the brains of healthy and experimental autoimmune encephalomyelitis (EAE) mice via intravenous (iv) injections by co-administering BDNF with a BBB modulator (BBBM) peptide ADTC5. Western blot evaluations indicated that ADTC5 enhanced the brain delivery of BDNF in healthy SJL/elite mice compared to BDNF alone and triggered the phosphorylation of TrkB receptors in the brain. The EAE mice treated with BDNF + ADTC5 suppressed EAE relapse compared to those treated with BDNF alone, ADTC5 alone, or vehicle. We further demonstrated that brain delivery of BDNF induced neuroregeneration via visible activation of oligodendrocytes, remyelination, and ARC and EGR1 mRNA transcript upregulation. In summary, we have demonstrated that ADTC5 peptide modulates the BBB to permit noninvasive delivery of BDNF to exert its neuroregeneration activity in the brains of EAE mice.

In Vivo Brain Delivery and Brain Deposition of Proteins with Various Sizes

It is very challenging to develop protein drugs for the treatment of brain diseases; this is due to the difficulty in delivering them into the brain because of the blood-brain barrier (BBB). Thus, alternative delivery methods need further exploration for brain delivery of proteins to diagnose and treat brain diseases. Previously, ADTC5 and HAV6 peptides have been shown to enhance the in vivo brain delivery of small- and medium-size molecules across the BBB. This study was carried out to evaluate the ability of ADTC5 and HAV6 peptides to enhance delivery of proteins of various sizes, such as 15 kDa lysozyme, 65 kDa albumin, 150 kDa IgG mAb, and 220 kDa fibronectin, into the brains of C57BL/6 mice. Each protein was labeled with IRdye800CW, and a quantitative method using near IR fluorescence (NIRF) imaging was developed to determine the amount of protein delivered into the brain. ADTC5 peptide significantly enhanced brain delivery of lysozyme, albumin, and IgG mAb but not fibronectin compared to controls. In contrast, HAV6 peptide significantly enhanced the brain delivery of lysozyme but not albumin and IgG mAb. Thus, there is a cutoff size of proteins that can be delivered by each peptide. The distribution of delivered protein in other organs such as liver, spleen, lung, kidney, and heart could be influenced by HAV6 and ADTC5. In summary, ADTC5 is a better BBB modulator than HAV6 in delivering various sizes of proteins into the brain, and the size of the protein affects its brain delivery.

Improving In Vivo Brain Delivery of Monoclonal Antibody Using Novel Cyclic Peptides

Many proteins can be used to treat brain diseases; however, the presence of the blood–brain barrier (BBB) creates an obstacle to delivering them into the brain. Previously, various molecules were delivered through the paracellular pathway of the BBB via its modulation, using ADTC5 and HAV6 peptides. This study goal was to design new cyclic peptides with N-to-C terminal cyclization for better plasma stability and modulation of the BBB. Cyclic HAVN1 and HAVN2 peptides were derived from a linear HAV6 peptide. Linear and N-to-C terminal cyclic ADTHAV peptides were designed by combining the sequences of ADTC5 and HAV6. These novel cyclic peptides were used to deliver an IRdye800CW-labeled IgG monoclonal antibody into the brain. Cyclic HAVN1 and HAVN2 peptides deliver IgG into the brain, while the parent linear HAV6 peptide does not. Cyclic and linear ADTHAV and ADTC5 peptides enhanced brain delivery of IgG mAb, in which cyclic ADTHAV peptide was better than linear ADTHAV (p = 0.07). Cyclic ADTHAV and ADTC5 influenced the distribution of IgG mAb in other organs while HAV6, HAVN1 and HAVN2 did not. In summary, the novel cyclic peptides are generally better BBB modulators than their linear counterparts for delivering IgG mAb into the brain.

Validation of Cadherin HAV6 Peptide in the Transient Modulation of the Blood-Brain Barrier for the Treatment of Brain Tumors

The blood-brain barrier (BBB) poses a major obstacle by preventing potential therapeutic agents from reaching their intended brain targets at sufficient concentrations. While transient disruption of the BBB has been used to enhance chemotherapeutic efficacy in treating brain tumors, limitations in terms of magnitude and duration of BBB disruption exist. In the present study, the preliminary safety and efficacy profile of HAV6, a peptide that binds to the external domains of cadherin, to transiently open the BBB and improve the delivery of a therapeutic agent, was evaluated in a murine brain tumor model. Transient opening of the BBB in response to HAV6 peptide administration was quantitatively characterized using both a gadolinium magnetic resonance imaging (MRI) contrast agent and adenanthin (Ade), the intended therapeutic agent. The effects of HAV6 peptide on BBB integrity and the efficacy of concurrent administration of HAV6 peptide and the small molecule inhibitor, Ade, in the growth and progression of an orthotopic medulloblastoma mouse model using human D425 tumor cells was examined. Systemic administration of HAV6 peptide caused transient, reversible disruption of BBB in mice. Increases in BBB permeability produced by HAV6 were rapid in onset and observed in all regions of the brain examined. Concurrent administration of HAV6 peptide with Ade, a BBB impermeable inhibitor of Peroxiredoxin-1, caused reduced tumor growth and increased survival in mice bearing medulloblastoma. The rapid onset and transient nature of the BBB modulation produced with the HAV6 peptide along with its uniform disruption and biocompatibility is well-suited for CNS drug delivery applications, especially in the treatment of brain tumors.

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.

Improving Brain Delivery of Biomolecules via BBB Modulation in Mouse and Rat: Detection using MRI, NIRF, and Mass Spectrometry

There is an urgent need to develop new and alternative methods to deliver functional biomolecules to the brain for diagnosis and treatment of brain diseases. The goal of this study was to evaluate the activity of blood-brain barrier (BBB) modulators (i.e., HAV and ADT peptides) to deliver functional biomolecules (i.e., galbumin, IRdye800cw-cLABL, and cIBR7) to the brains of mice and rats. HAV6, cHAVc3, and ADTC5 peptides but not HAV4 peptide significantly enhanced the brain delivery of 65 kDa galbumin compared to control in Balb/c mice as quantified by magnetic resonance imaging (MRI). Ten-minute pretreatment with ADTC5 peptide still significantly increased brain delivery of galbumin; however, no enhancement was observed after 10-min pretreatment with HAV6. There was no enhancement of galbumin deposition following 40-min pretreatment with ADTC5 or HAV6, suggesting a short duration of the BBB opening for large molecules. ADTC5 peptide also improved the brain delivery of IRdye800cw-cLABL peptide about 3.5-fold compared to control in Balb/c mice as detected by near infrared fluorescence (NIRF). The BBB modulator activity of ADTC5 to deliver cIBR7 peptide was also evaluated in vivo using Sprague-Dawley rats. The amount of cIBR7 in the brain was detected by LC-MS/MS. ADTC5 peptide enhanced the delivery of cIBR7 peptide into rat brain about 4-fold compared to control and the intact cIBR7 can be efficiently extracted and detected in rat brain. In conclusion, HAV and ADT peptides enhance the brain delivery of functional peptides (e.g., cLABL and cIBR7) and protein (e.g., 65 kDa galbumin) in two animal models, and the duration of the BBB opening for a large molecule (e.g., galbumin) was short.

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.

Endotoxaemia-augmented murine venous thrombosis is dependent on TLR-4 and ICAM-1, and potentiated by neutropenia

Venous thromboembolism is a major cause of death during and immediately post-sepsis. Venous thrombosis (VT) is mediated by cell adhesion molecules and leukocytes, including neutrophil extracellular traps (NETs). Sepsis, or experimentally, endotoxaemia, shares similar characteristics and is modulated via toll like receptor 4 (TLR4). This study was undertaken to determine if endotoxaemia potentiates early stasis thrombogenesis, and secondarily to determine the role of VT TLR4, ICAM-1 and neutrophils (PMNs). Wild-type (WT), ICAM-1^-/- and TLR4^-/- mice underwent treatment with saline or LPS (10 mg/kg i. p.) alone, or followed by inferior vena cava (IVC) ligation to generate stasis VT. In vivo microscopy of leukocyte trafficking was performed in non-thrombosed mice, and tissue and plasma were harvested during early VT formation. Pre-thrombosis, circulating ICAM-1 was elevated and increased leukocyte adhesion and rolling occurred on the IVC of LPS-treated mice. Post-thrombosis, endotoxaemic mice formed larger, platelet-poor thrombi. Endotoxaemic TLR4^-/- mice did not have an augmented thrombotic response and exhibited significantly decreased circulating ICAM-1 compared to endotoxaemic WT controls. Endotoxaemic ICAM-1^-/- mice had significantly smaller thrombi compared to controls. Hypothesising that PMNs localised to the inflamed endothelium were promoting thrombosis, PMN depletion using anti-Ly6G antibody was performed. Paradoxically, VT formed without PMNs was amplified, potentially related to endotoxaemia induced elevation of PAI-1 and circulating FXIII, and decreased uPA. Endotoxaemia enhanced early VT occurs in a TLR-4 and ICAM-1 dependent fashion, and is potentiated by neutropenia. ICAM-1 and/or TLR-4 inhibition may be a unique strategy to prevent sepsis-associated VT.

Gram-Negative Pneumonia Alters Large-Vein Cell-Adhesion Molecule Profile and Potentiates Experimental Stasis Venous Thrombosis

BACKGROUND/AIMS

Pneumonia is a significant risk factor for the development of venous thrombosis (VT). Cell-adhesion molecules (CAMs) are linked to the pathogenesis of both pneumonia and VT. We hypothesized that remote infection would confer a prothrombogenic milieu via systemic elevation of CAMs.

METHODS

Lung injury was induced in wild-type (C57BL/6) mice by lung contusion or intratracheal inoculation with Klebsiella pneumoniae or saline controls. K. pneumoniae-treated mice and controls additionally underwent inferior vena cava (IVC) ligation to generate VT.

RESULTS

Lung-contusion mice demonstrated no increase in E-selectin or P-selectin whereas mice infected with K. pneumoniae demonstrated increased circulating P-selectin, ICAM-1, VCAM-1 and thrombin-antithrombin (TAT) complexes. Mice with pneumonia formed VT 3 times larger than controls, demonstrated significantly more upregulation of vein-wall and systemic CAMs, and formed erythrocyte-rich thrombi.

CONCLUSION

Elevated CAM expression was identified in mice with pneumonia, but not lung contusion, indicating that the type of inflammatory stimulus and the presence of infection drive the vein-wall response. Elevation of CAMs was associated with amplified VT and may represent an alternate mechanism by which to target the prevention of VT.

Probing the interaction between cHAVc3 peptide and the EC1 domain of E-cadherin using NMR and molecular dynamics simulations

The goal of this work is to probe the interaction between cyclic cHAVc3 peptide and the EC1 domain of human E-cadherin protein. Cyclic cHAVc3 peptide (cyclo(1,6)Ac-CSHAVC-NH₂) binds to the EC1 domain as shown by chemical shift perturbations in the 2D ¹H,-¹⁵N-HSQC NMR spectrum. The molecular dynamics (MD) simulations of the EC1 domain showed folding of the C-terminal tail region into the main head region of the EC1 domain. For cHAVc3 peptide, replica exchange molecular dynamics (REMD) simulations generated five structural clusters of cHAVc3 peptide. Representative structures of cHAVc3 and the EC1 structure from MD simulations were used in molecular docking experiments with NMR constraints to determine the binding site of the peptide on EC1. The results suggest that cHAVc3 binds to EC1 around residues Y36, S37, I38, I53, F77, S78, H79, and I94. The dissociation constants (K_d values) of cHAVc3 peptide to EC1 were estimated using the NMR chemical shifts data and the estimated K_ds are in the range of .5 × 10^-5-7.0 × 10^-5 M.

Brain Delivery of Drug and MRI Contrast Agent: Detection and Quantitative Determination of Brain Deposition of CPT-Glu Using LC-MS/MS and Gd-DTPA Using Magnetic Resonance Imaging

Successful treatment and diagnosis of neurological diseases depend on reliable delivery of molecules across the blood-brain barrier (BBB), which restricts penetration of pharmaceutical drugs and diagnostic agents into the brain. Thus, developing new noninvasive strategies to improve drug delivery across the BBB is critically needed. This study was aimed at evaluating the activity of HAV6 peptide (Ac-SHAVSS-NH2) in improving brain delivery of camptothecin-glutamate (CPT-Glu) conjugate and gadolinium-diethylenetriaminepentaacetate (Gd-DTPA) contrast agent in Sprague-Dawley rats. Brain delivery of both CPT-Glu and Gd-DTPA was evaluated in an in situ rat brain perfusion model in the presence and absence of HAV6 peptide (1.0 mM). Gd-DTPA (0.6 mmol/kg) was intravenously (iv) administered with and without HAV6 peptide (0.019 mmol/kg) in rats. The detection and quantification of CPT-Glu and Gd-DTPA in the brain were carried out by LC-MS/MS and quantitative magnetic resonance imaging (MRI), respectively. Rats perfused with CPT-Glu in combination with HAV6 had significantly higher deposition of drug in the brain compared to CPT-Glu alone. MRI results also showed that administration of Gd-DTPA in the presence of HAV6 peptide led to significant accumulation of Gd-DTPA in various regions of the brain in both the in situ rat brain perfusion and in vivo studies. All observations taken together indicate that HAV6 peptide can disrupt the BBB and enhance delivery of small molecules into the brain.

(1)H, (13)C and (15)N backbone assignment of the EC-1 domain of human E-cadherin

The Extracellular 1 (EC1) domain of E-cadherin has been shown to be important for cadherin-cadherin homophilic interactions. Cadherins are responsible for calcium-mediated cell-cell adhesion located at the adherens junction of the biological barriers (i.e., intestinal mucosa and the blood-brain barrier (BBB)). Cadherin peptides can modulate cadherin interactions to improve drug delivery through the BBB. However, the mechanism of modulating the E-cadherin interactions by cadherin peptides has not been fully elucidated. To provide a basis for subsequent examination of the structure and peptide-binding properties of the EC1 domain of human E-cadherin using solution NMR spectroscopy, the (1)H, (13)C and (15)N backbone resonance of the uniformly labeled-EC1 were assigned and the secondary structure was determined based on the chemical shift values. These resonance assignments are essential for assessing protein-ligand interactions and are reported here.

Modulation of intercellular junctions by cyclic-ADT peptides as a method to reversibly increase blood-brain barrier permeability

It is challenging to deliver molecules to the brain for diagnosis and treatment of brain diseases. This is primarily because of the presence of the blood-brain barrier (BBB), which restricts the entry of many molecules into the brain. In this study, cyclic-ADT peptides (ADTC1, ADTC5, and ADTC6) have been shown to modify the BBB to enhance the delivery of marker molecules [e.g., (14) C-mannitol, gadolinium-diethylenetriaminepentacetate (Gd-DTPA)] to the brain via the paracellular pathways of the BBB. The hypothesis is that these peptides modulate cadherin interactions in the adherens junctions of the vascular endothelial cells forming the BBB to increase paracellular drug permeation. In vitro studies indicated that ADTC5 had the best profile to inhibit adherens junction resealing in Madin-Darby canine kidney cell monolayers in a concentration-dependent manner (IC50 = 0.3 mM) with a maximal response at 0.4 mM. Under the current experimental conditions, ADTC5 improved the delivery of (14) C-mannitol to the brain about twofold compared with the negative control in the in situ rat brain perfusion model. Furthermore, ADTC5 peptide increased in vivo delivery of Gd-DTPA to the brain of Balb/c mice when administered intravenously. In conclusion, ADTC5 has the potential to improve delivery of diagnostic and therapeutic agents to the brain.

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.

Structure, size, and solubility of antigen arrays determines efficacy in experimental autoimmune encephalomyelitis

Presentation of antigen with immune stimulating "signal" has been a cornerstone of vaccine design for decades. Here, the antigen plus immune "signal" of vaccines is modified to produce antigen-specific immunotherapies (antigen-SITs) that can potentially reprogram the immune response toward tolerance of an autoantigen. The codelivery of antigen with a cell adhesion inhibitor using Soluble Antigen Arrays (SAgAs) was previously shown to slow or halt experimental autoimmune encephalomyelitis (EAE), a murine form of multiple sclerosis (MS). SAgAs are comprised of a hyaluronic acid backbone with cografted intercellular cell adhesion molecule-1 ligand derived from αL-integrin (CD11a237-246, "LABL") and an encephalitogenic epitope peptide of proteolipid protein (PLP139-151, "PLP"). Here, the physical characteristics of the carrier were investigated to evaluate how structure, size, and solubility drive the immune response when treating EAE. A bifunctional peptide (small, soluble), SAgAs (large, soluble), and PLGA nanoparticles (large, insoluble) all displaying PLP and LABL in equimolar ratios were compared. Maximum EAE suppression was achieved with coincident display of both peptides on a soluble construct.

Abstract 191: Endothelial Dysfunction Potentiates Deep Venous Thrombosis in a Mouse Model of Sepsis

Objective: Sepsis is a strong risk factor for the development of deep venous thrombosis (DVT). However, little is understood about the underlying pathobiology responsible for this phenomenon. This study was undertaken to evaluate the endothelial response of cellular adhesion molecules (CAM) involved in early thrombogenesis in a mouse model of sepsis.

Methods: Wild-type mice underwent treatment with vehicle or LPS (10mg/kg), or followed by inferior vena cava (IVC) ligation to generate a venous thrombus (VT). Tissue and plasma were harvested at 2 hours post-intervention and were assessed for CAMs, thrombus size, and markers of extracellular DNA (NETs). Pre-treatment (12 hours prior and at time of thrombosis) with P/E selectin (sel) and ICAM exogenous inhibition was undertaken. Antibody depletion was accomplished in selected mice with anti-Ly6G antibody. To understand leukocyte trafficking to the vein wall under sepsis conditions, a separate group of animals underwent LPS or vehicle injection followed by intravital fluorescence microscopy of rhodamine-6G-labeled leukocytes.

Results: Pre-thrombosis, IVC CAMs (P-sel p=0.15, E-sel, p<0.01 and ICAM-1 p=0.11, all n=6) were elevated in mice treated with LPS. Consistently, intravital microscopy of leukocyte behavior revealed increased leukocyte rolling (n=6, p< .0001) and decreased rolling velocity (n=75/group, p<0.0001). Post-thrombosis, LPS treated mice formed larger thrombi (6.4±0.8mg v. 9.9±1.1mg, p=0.03) and exhibited elevations in circulating P-sel, E-sel, and ICAM-1 (all p<0.05, n=10). NETs markers H3 and elastase were not elevated. Pre-treatment with an ICAM-1 inhibitor restored thrombus size (6.6±1.5 mg, n=5) and circulating ICAM-1 levels to that of vehicle treated mice, while P/E sel inhibition resulted in moderately reduced thrombus size (7.3±1.2mg, n=10). Exogenous PMN depletion did not decrease thrombus weight.

Conclusions: In a mouse model of endotoxemia, CAM elevation and leukocyte trafficking occurs in the serum and local vein wall; and with stasis insult, larger VT form. Inhibitor experiments suggest that ICAM may be central to the sepsis related early VT, while PMNs and P/E sel may be less important. CAM inhibition may be a unique strategy to prevent sepsis-associated DVT.

Modulation of blood-brain barrier permeability in mice using synthetic E-cadherin peptide

The present work characterizes the effects of synthetic E-cadherin peptide (HAV) on blood–brain barrier (BBB) integrity using various techniques including magnetic resonance imaging (MRI) and near-infrared fluorescent imaging (NIRF). The permeability of small molecular weight permeability marker gadolinium diethylenetriaminepentaacetate (Gd-DTPA) contrast agent, the large molecular weight permeability marker, IRDye 800CW PEG, and the P-glycoprotein (P-gp) efflux transporter contrast agent, rhodamine 800 (R800), were examined in the presence and absence of HAV peptide. The results consistently demonstrated that systemic iv administration of HAV peptide resulted in a reversible disruption of BBB integrity and enhanced the accumulation of all the dyes examined. The magnitude of increase ranged from 2-fold to 5-fold depending on the size and the properties of the permeability markers. The time frame for BBB disruption with HAV peptide was rapid, occurring within 3–6 min following injection of the peptide. Furthermore, modulation of BBB permeability was reversible with the barrier integrity being restored within 60 min of the injection. The increased BBB permeability observed following HAV peptide administration was not attributable to changes in cerebral blood flow. These studies support the potential use of cadherin peptides to rapidly and reversibly modulate BBB permeability of a variety of therapeutic agents.

Bifunctional Peptide Inhibitors Suppress Interleukin-6 Proliferation and Ameliorates Murine Collagen-Induced Arthritis

The objective of this study is to evaluate the efficacy and potential mechanism of action of type-II collagen bifunctional peptide inhibitor (CII-BPI) molecules in suppressing rheumatoid arthritis in the collagen-induced arthritis (CIA) mouse model. CII-BPI molecules (CII-BPI-1, CII-BPI-2, and CII-BPI-3) were formed through conjugation between an antigenic peptide derived from type-II collagen and a cell adhesion peptide LABL (CD11a_237-246) from the I-domain of LFA-1 via a linker molecule. The hypothesis is that the CII-BPI molecules simultaneously bind to MHC-II and ICAM-1 on the surface of APC and block maturation of the immunological synapse. As a result, the differentiation of naïve T cells is altered from inflammatory to regulatory and/or suppressor T cells. The efficacies of CII-BPI molecules were evaluated upon intravenous injections in CIA mice. Results showed that CII-BPI-1 and CIIBPI-2 suppressed the joint inflammations in CIA mice in a dose-dependent manner and were more potent than the respective antigenic peptides alone. CII-BPI-3 was not as efficacious as CII-BPI-1 and CII-BPI-2. Significantly less joint damage was observed in CII-BPI-2 and CII-2 treated mice than in the control. The production of IL-6 was significantly lower at the peak of disease in mice treated with CII-BPI-2 compared to those treated with CII-2 and control. In conclusion, this is the first proof-of-concept study showing that BPI molecules can be used to suppress RA and may be a potential therapeutic strategy for the treatment of rheumatoid arthritis.

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 (PLP_139-151) 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.

Hyaluronic acid graft polymers displaying peptide antigen modulate dendritic cell response in vitro

A novel oxime grafting scheme was utilized to conjugate an ICAM-1 ligand (LABL), a cellular antigen ovalbumin (OVA), or both peptides simultaneously to hyaluronic acid (HA). Samples of HA only and the various peptide grafted HA were found to bind to dendritic cells (DCs). HA with grafted LABL and OVA showed the greatest binding to DCs. Dendritic cells treated with HA, HA with grafted LABL, or HA with grafted LABL and OVA significantly suppressed T cell and DC conjugate formation and T cell proliferation and reduced proinflammatory cytokine production compared to untreated cells. These results suggest that HA serves as an effective backbone for multivalent ligand presentation for inhibiting T cell response to antigen presentation. In addition, multivalent display of both antigen and an ICAM-1 inhibitor (LABL) may enhance binding to DCs and could potentially disrupt cellular signaling leading to autoimmunity.

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.

Biodegradable Nanoparticles Surface Modification Techniques With cIBR Peptide Targeting to LFA-1 Expressing Leukemic Cells

The lymphocyte function associated antigen-1 (LFA-1) is evaluated for a targeting carrier in leukemia. The cIBR peptide was utilized as the targeting moiety for the drug carrier in direct targeting to LFA-1 expressing cancer cells. This study aims to evaluate the effects of the cIBR peptide conjugation on the specific targeting delivery to the leukemic cell line. Poly (D, L lactide-co-glycolide) (PLGA) nanoparticles were conjugated to the cIBR peptide by three different approaches (coupling, head, and tail) in order to evaluate the nanoparticles' characters, targetability, uptake, drug releasing, and cytotoxicity of each approach. The prepared PLGA nanoparticles were spherical lin shape with a size range of 200–450 nm. The targetability and uptake of three types of cIBR-conjugated nanoparticles (cIBR-NPs) were evidenced and quantified by flow cytometry. The coupling approach presented the highest targetability, uptake, drug releasing, and cytotoxicity followed by the head and tail approaches, respectively. The peptide conjugation method onto the nanoparticles surface was proven to be a key factor for the nanoparticles' physicochemical characteristicss and their efficient delivery.

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.

Methotrexate (MTX)-cIBR conjugate for targeting MTX to leukocytes: conjugate stability and in vivo efficacy in suppressing rheumatoid arthritis

Methotrexate (MTX) has been used to treat rheumatoid arthritis at low doses and leukemia at high doses; however, this drug can produce severe side effects. Our hypothesis is that MTX side effects can be attenuated by directing the drug to the target cells (i.e., leukocytes) using (cyclo(1,12)PenPRGGSVLVTGC) peptide (cIBR). To test this hypothesis, MTX was conjugated to the N-terminus of cIBR peptide to give MTX-cIBR conjugate. MTX-cIBR (5.0 mg/kg) suppressed joint arthritis in adjuvant arthritis rats and prevented periarticular inflammation and bone resorption of the limb joints. In vitro, the toxicity of MTX-cIBR peptide against Molt-3 T cells was inhibited by anti-lymphocyte function-associated antigen-1 (LFA-1) antibody and cIBR peptide in a concentration-dependent manner, suggesting that the uptake of MTX-cIBR was partially mediated by LFA-1. Chemical stability studies indicated that MTX-cIBR was most stable at pH 6.0. The MTX portion of MTX-cIBR was unstable under acidic conditions, whereas the cIBR portion was unstable under basic conditions. In biological media, MTX-cIBR had short half lives in rat plasma (44 min) and homogenized rat heart tissue (38 min). This low plasma stability may contribute to the low in vivo efficacy of MTX-cIBR; therefore, there is a need to design a more stable conjugate to improve the in vivo efficacy.

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.

Autoimmune therapies targeting costimulation and emerging trends in multivalent therapeutics

Proteins participating in immunological signaling have emerged as important targets for controlling the immune response. A multitude of receptor-ligand pairs that regulate signaling pathways of the immune response have been identified. In the complex milieu of immune signaling, therapeutic agents targeting mediators of cellular signaling often either activate an inflammatory immune response or induce tolerance. This review is primarily focused on therapeutics that inhibit the inflammatory immune response by targeting membrane-bound proteins regulating costimulation or mediating immune-cell adhesion. Many of these signals participate in larger, organized structures such as the immunological synapse. Receptor clustering and arrangement into organized structures is also reviewed and emerging trends implicating a potential role for multivalent therapeutics is posited.

Rapid identification of fluorochrome modification sites in proteins by LC ESI-Q-TOF mass spectrometry

Conjugation of either a fluorescent dye or a drug molecule to the ε-amino groups of lysine residues of proteins has many applications in biology and medicine. However, this type of conjugation produces a heterogeneous population of protein conjugates. Because conjugation of fluorochrome or drug molecule to a protein may have deleterious effects on protein function, the identification of conjugation sites is necessary. Unfortunately, the identification process can be time-consuming and laborious; therefore, there is a need to develop a rapid and reliable way to determine the conjugation sites of the fluorescent label or drug molecule. In this study, the sites of conjugation of fluorescein-5'-isothiocyanate and rhodamine-B-isothiocyanate to free amino groups on the insert-domain (I-domain) protein derived from the α-subunit of lymphocyte function-associated antigen-1 (LFA-1) were determined by electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q-TOF MS) along with peptide mapping using trypsin digestion. A reporter fragment of the fluorochrome moiety that is generated in the collision cell of the Q-TOF without explicit MS/MS precursor selection was used to identify the conjugation site. Selected ion plots of the reporter ion readily mark modified peptides in chromatograms of the complex digest. Interrogation of theses spectra reveals a neutral loss/precursor pair that identifies the modified peptide. The results show that one to seven fluorescein molecules or one to four rhodamine molecules were attached to the lysine residue(s) of the I-domain protein. No modifications were found in the metal ion-dependent adhesion site (MIDAS), which is an important binding region of the I-domain.

Utilization of I-domain of LFA-1 to Target Drug and Marker Molecules to Leukocytes

The long-term objective of this project is to utilize the I-domain protein for the α-subunit of LFA-1 to target drugs to lymphocytes by binding to ICAM receptors on the cell surface. The short-term goal is to provide proof-of-concept that I-domain conjugated to small molecules can still bind to and uptake by ICAM-1 on the surface of lymphocytes (i.e., Raji cells). To accomplish this goal, the I-domain protein was labeled with FITC at several lysine residues to produce the FITC-I-domain and CD spectroscopy showed that the FITC-I-domain has a secondary structure similar to that of the parent I-domain. The FITC-I-domain was taken up by Raji cells via receptor-mediated endocytosis and its uptake can be blocked by anti-I-domain mAb but not by its isotype control. Antibodies to ICAM-1 enhance the binding of I-domain to ICAM-1, suggesting it binds to ICAM-1 at different sites than the antibodies. The results indicate that fluorophore modification does not alter the binding and uptake properties of the I-domain protein. Thus, I-domain could be useful as a carrier of drug to target ICAM-1-expressing lymphocytes.

Calcium condensed LABL-TAT complexes effectively target gene delivery to ICAM-1 expressing cells

Targeted gene delivery using nonviral vectors is a highly touted scheme to reduce the potential for toxic or immunological side effects by reducing dose. In previous reports, TAT polyplexes with DNA have shown relatively poor gene delivery. The transfection efficiency has been enhanced by condensing TAT/DNA complexes to a small particle size using calcium. To explore the targetability of these condensed TAT complexes, LABL peptide targeting intercellular cell-adhesion molecule-1 (ICAM-1) was conjugated to TAT peptide using a polyethylene glycol (PEG) spacer. PEGylation reduced the transfection efficiency of TAT, but TAT complexes targeting ICAM-1 expressing cells regained much of the lost transfection efficiency. Targeted block peptides properly formulated with calcium offer promise for gene delivery to ICAM-1 expressing cells at sites of injury or inflammation.

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

In this review, we discuss T-cell activation, etiology, and the current therapies of autoimmune diseases (i.e., MS, T1D, and RA). T-cells are activated upon interaction with antigen-presenting cells (APC) followed by a "bull's eye"-like formation of the immunological synapse (IS) at the T-cell-APC interface. Although the various disease-modifying therapies developed so far have been shown to modulate the IS and thus help in the management of these diseases, they are also known to present some undesirable side effects. In this study, we describe a novel and selective way to suppress autoimmunity by using a bifunctional peptide inhibitor (BPI). BPI uses an intercellular adhesion molecule-1 (ICAM-1)-binding peptide to target antigenic peptides (e.g., proteolipid peptide, glutamic acid decarboxylase, and type II collagen) to the APC and therefore modulate the immune response. The central hypothesis is that BPI blocks the IS formation by simultaneously binding to major histocompatibility complex-II and ICAM-1 on the APC and selectively alters the activation of T cells from T(H)1 to T(reg) and/or T(H)2 phenotypes, leading to tolerance.

Nanoparticles targeting dendritic cell surface molecules effectively block T cell conjugation and shift response

Dendritic cells (DCs) are potent professional antigen presenting cells (APC) that activate naïve T cells. Interaction of ICAM-1 and LFA-1 molecules on each cell is required for T cell conjugation to DCs, which leads to naïve CD4+ T cell activation and proliferation. Nanoparticles capable of blocking LFA-1/ICAM-1 interaction were studied as inhibitors of T cell conjugation to DCs. Primary DCs were primed with ovalbumin, then treated with a peptide that binds ICAM-1 (LABL), a peptide that binds LFA-1 (cIBR), or the same peptides covalently linked to the surface of poly(dl-lactic-co-glycolic acid) nanoparticles (NPs). LABL-NPs and cIBR-NPs rapidly bound to DCs and inhibited T cell conjugation to DCs to a greater extent than the free peptides, unconjugated nanoparticles (NPs), anti-ICAM-1 antibodies, and anti-LFA-1 antibodies. In addition, DCs treated with NPs or with cIBR-NPs stimulated the proliferation of T cells, but DCs treated with LABL-NPs did not stimulate T cell proliferation. Nanoparticles targeting ICAM-1 or LFA-1 also altered cytokine production by DC cocultured with T cells when compared to free ligands, suggesting that these NPs may offer a unique tool for shaping T cell response.