Effect of treatment with glutaraldehyde-fixed myelin basic protein-liposomes on active induction and passive transfer of experimental allergic encephalomyelitis in Lewis rats

An insight into the role of liposomal therapeutics in the reversion of Multiple Sclerosis

INTRODUCTION

Multiple Sclerosis (MS), as an autoimmune disease, has complicated immunopathology, which makes its management relevant to various factors. Novel pharmaceutical vehicles, especially liposomes, can support efficacious handling of this disease both in early detection and prognosis and also in a therapeutic manner. The most well-known trigger of MS onset is the predominance of cellular to humoral immunity and enhancement of inflammatory cytokines level. The installation of liposomes as nanoparticles to control this disease holds great promise up to now.

AREAS COVERED

Various types of liposomes with different properties and purposes have been formulated and targeted immune cells with their surface manipulations. They may be encapsulated with anti-inflammatory, MS-related therapeutics, or immunodominant myelin-specific peptides for attaining a higher therapeutic efficacy of the drugs or tolerance induction. Cationic liposomes are also highly applicable for gene delivery of the anti-inflammatory cytokines or silencing the inflammatory cytokines. Liposomes have also been used as biotools for comprehending MS pathomechanisms or as diagnostic agents.

EXPERT OPINION

The efforts to manage MS through nanomedicine, especially liposomal therapeutics, pave a new avenue to a high-throughput medication of this autoimmune disease and their translation to the clinic in the future for overcoming the challenges that MS patients confront.

Correlation between MRI and clinico-pathological manifestations in Lewis rats protected from experimental allergic encephalomyelitis by acylated synthetic peptide of myelin basic protein

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease of the central nervous system which constitutes an accepted animal model for multiple sclerosis (MS). The disease can take an acute or chronic form depending on the injection route, animal strain and nature of the disease-inducing antigen administered. The neuroinflammation associated with the acute form can be detected with T2-weighted, T1-weighted and diffusion MRI, and blood-brain barrier changes can be investigated with Gd-DTPA-enhanced T1-weighted imaging, similar to that of MS patients. A synthetic peptide of myelin basic protein (MBP) encephalitogenic for the Lewis rat (MBP 68-86) was acylated by the attachment of a palmitoyl residue (PAL68-86), and was shown to confer almost complete protection against EAE, when administered to rats before and after an encephalitogenic challenge. In this study, treatment of Lewis rats with PAL68-86 prevented the appearance of clinical signs (p < 0.0001) after challenge with the native peptide (p68-86) in complete Freund's adjuvant (CFA), and reduced considerably the MRI and histopathological signs of the disease (p < 0.0001). Measurement of the gadolinium leakage due to neuroinflammation revealed a significant decrease in permeability from 4.09 +/- 2.1 to 2.95 +/- 1.79% pixels > mean + 2 SD (p = 0.011). Therefore, quantitative MRI measurements correlate very well with the reduced cellular infiltration in the CNS and the absence of clinical signs in the EAE-protected animal.

Approaches to the treatment of central nervous system autoimmune disease using specific neuroantigen

The ultimate aim in the treatment of autoimmune disease is to restore self-tolerance to the autoantigen(s) in question. In lieu of this ideal result, the conversion of a destructive or pathogenic autoimmune response into one of benign autoimmunity would also be highly desirable. In either case the use of the antigenic epitope, which is the target of the destructive immune response, would ideally be employed so as to give specificity to the protection without the need for long-term immunosuppression. This review describes a number of different approaches using various forms, doses, and routes of injection of specific neuroantigen to inhibit the different clinical varieties of autoimmune encephalomyelitis in a number of animal models; all done with the view to translating the findings into the clinic for the treatment of multiple sclerosis. We conclude that any treatment strategy for multiple sclerosis (MS) must have a number of features: it must be clinically acceptable, specific, long-lasting, require only short-term treatment, able to shunt off ongoing disease, and have the potential to prevent or deal with epitope spreading. Few of the approaches we describe fulfill all of these criteria. We suggest that investigations of new adjunctive agents to be used with a specific antigen be pursued, and that currently the use of chimeric proteins or DNA vaccination with or without the new adjunctives may hold the most hope for the future.

Suppression of experimental allergic encephalomyelitis in the Lewis rat, by administration of an acylated synthetic peptide of myelin basic protein

A Myelin Basic Protein (MBP) epitope encephalitogenic for the Lewis rat (amino acid residues 68-86) was synthesized and acylated by the attachment of a palmitoyl residue. Lewis rats treated intravenously (i.v.) with the palmitoylated peptide alone were better protected against clinical manifestations of experimental allergic encephalomyelitis (EAE) than rats treated with the peptide inserted into liposomes or with the native peptide at similar doses. The administration of the acylated peptide (PAL68 86) conferred excellent protection against a challenge with the encephalitogenic peptide (p68-86) or with the intact MBP molecule, both before and after induction of active disease, and also when administered to recipients after the transfer of lymphocytes from MBP-challenged donors. Histological manifestations were also reduced to a statistically significant degree. Treatment with a palmitoylated peptide from a non-encephalitogenic region of the MBP molecule (PAL44-62) or with a palmitoylated unrelated peptide were ineffective. In vitro Ag-specific proliferative responses as well as the ability to transfer disease to syngeneic recipients, by lymph node lymphocytes from PAL68-86-treated donors, were considerably reduced. Addition of IL-2 to these cultures failed to restore either Ag-specific responsiveness or the ability of the cells to transfer disease. The results suggest that the administration of acylated peptides induces a profound state of unresponsiveness, and thus may provide an effective means for treating T cell-mediated autoimmune inflammatory disorders.

Treatment of spinal cord-induced experimental allergic encephalomyelitis in the Lewis rat with liposomes presenting central nervous system antigens

Chronic-relapsing experimental allergic encephalomyelitis (CR-EAE) in the Lewis rat, induced by the injection of spinal cord tissue in complete Freund's adjuvant (SC/CFA), was studied in vivo by treatment with liposomes containing central nervous tissue antigens, and in vitro by lymphocyte proliferation assays. Intracardiac administration of myelin basic protein (MBP) liposomes, galactocerebroside (GC) liposomes, or MBP + GC liposomes substantially reduced the clinical severity and/or delayed the onset of the initial phase of disease. Liposomes prepared from whole myelin provided even greater protection, and were effective at suppressing both the first disease episode and the relapses. These results indicate that while GC and MBP may play significant roles in the development of CR-EAE in the Lewis rat, immune responses to other antigens are probably also involved. Splenic and lymph node lymphocytes from MBP-GC liposome-treated rats, and splenic lymphocytes from cytochrome-GC (CYT-GC) liposome-treated rats, showed drastically reduced abilities to proliferate in response to MBP in culture. Spleen cells from both the MBP-GC- and CYT-GC-liposome-treated donors were able to actively suppress antigen-induced proliferation of MBP-primed lymphocytes. These findings suggest participation of both clonal anergy, and active suppressor cells in the liposome-mediated suppression of CR-EAE in the Lewis rat.

Suppression of experimental allergic encephalomyelitis by MBP-coupled lymphoid cells and by MBP-liposomes: a comparison

In previous experiments, we showed that administration of myelin basic protein (MBP) inserted into phosphatidyl-serine liposomes, to susceptible animals suppressed the clinical manifestations of both acute and chronic-relapsing EAE. In this report we compare the effectiveness of treatment with MBP-liposomes and with MBP-coupled syngeneic spleen cells in EAE protection. Lewis rats treated with 150 micrograms MBP-liposomes or with 160 micrograms (35 x 10(6] MBP-coupled spleen cells, given 7 days before and 7 days after encephalitogenic challenge were equally protected against clinical EAE, when compared to untreated controls. In addition to clinical protection, in vitro proliferative responses of lymphocytes from treated rats were significantly reduced, but delayed hypersensitivity (DTH) reactions remained unaffected. Proliferation of lymphocytes from MBP-sensitized donors was inhibited by the addition of spleen cells but not of lymph node cells from treated donors. The inhibitory effect was observed with spleen cells regardless of whether the donors were treated or not, was antigen nonspecific, and localized in a radio-resistant, adherent cell population. Adoptive transfers of spleen cells from treated donors, after a 48-hr in vitro incubation with concanavalin A, showed that the cells from donors treated with MBP-coupled spleen cells, but not with MBP-liposomes, suppressed the disease in recipients, following challenge with MBP-complete Freund's adjuvant (CFA). These results suggest that two distinct mechanisms operate in the protection by MBP-coupled cells and MBP-liposomes, respectively.

Chronic-relapsing experimental allergic encephalomyelitis in strain-13 guinea pigs: cell-mediated immunity and IgG isoelectric focusing in myelin basic protein-liposome-treated and untreated animals

Juvenile strain-13 guinea pigs challenged with whole central nervous system (CNS) tissue in complete Freund's adjuvant (CFA) developed chronic-relapsing (CR) experimental allergic encephalomyelitis (EAE). The animals that recovered from the first clinical episode were divided into three groups. One group was left untreated, one group was treated with three intracardiac injections of 100 micrograms glutaraldehyde-fixed myelin basic protein (MBP)-liposomes (MBP-L-GA) given once a week, and one group was treated with cytochrome c-liposomes (CYC-L-GA). The animals treated with MBP-liposomes were very well protected against further relapses. In vitro proliferative responses of peripheral blood lymphocytes (PBL) were performed repeatedly on most animals. The lymphocytes exhibited excellent proliferative responses to MBP, proteolipid apoprotein (PLP) and whole myelin, as well as to purified protein derivative (PPD) and concanavalin-A (ConA). High proliferative responses were recorded over the entire period of observation which lasted 12-22 months, each time the animals were tested in remission or in full relapse. However, a sharp decrease in proliferative responses was observed in most animals when the assay was performed 24-48 h before to 24 h after entering a relapse. The results demonstrate the presence of long-term and sustained cell-mediated responses to two distinct neuroantigens, and show fluctuations of both neuroantigen-specific and nonspecific responses concordant with a well-defined phase of the disease. Isoelectric focusing and immunofixation was performed on sera and cerebrospinal fluids obtained at the time of sacrifice. The pattern showed clear oligoclonal IgG bands (OB) in the samples obtained from untreated, CYC-L-GA-treated as well as in the MBP-L-GA-treated animals.