Therapy of chronic relapsing experimental allergic encephalomyelitis and the role of the blood-brain barrier: elucidation by the action of Brequinar sodium

Combination of cannabinoids, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), mitigates experimental autoimmune encephalomyelitis (EAE) by altering the gut microbiome

Currently, a combination of marijuana cannabinoids including delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD) is used as a drug to treat muscle spasticity in patients with Multiple Sclerosis (MS). Because these cannabinoids can also suppress inflammation, it is unclear whether such patients benefit from suppression of neuroinflammation and if so, what is the mechanism through which cannabinoids act. In the currently study, we used a murine model of MS, experimental autoimmune encephalomyelitis (EAE), to study the role of gut microbiota in the attenuation of clinical signs of paralysis and inflammation caused by cannabinoids. THC + CBD treatment attenuated EAE and caused significant decrease in inflammatory cytokines such as IL-17 and IFN-γ while promoting the induction of anti-inflammatory cytokines such as IL-10 and TGF-β. Use of 16S rRNA sequencing on bacterial DNA extracted from the gut revealed that EAE mice showed high abundance of mucin degrading bacterial species, such as Akkermansia muciniphila (A. muc), which was significantly reduced after THC + CBD treatment. Fecal Material Transfer (FMT) experiments confirmed that THC + CBD-mediated changes in the microbiome play a critical role in attenuating EAE. In silico computational metabolomics revealed that LPS biosynthesis, a key component in gram-negative bacteria such as A. muc, was found to be elevated in EAE mice which was confirmed by demonstrating higher levels of LPS in the brain, while treatment with THC + CBD reversed this trend. EAE mice treated with THC + CBD also had significantly higher levels of short chain fatty acids such as butyric, isovaleric, and valeric acids compared to naïve or disease controls. Collectively, our data suggest that cannabinoids may attenuate EAE and suppress neuroinflammation by preventing microbial dysbiosis seen during EAE and promoting healthy gut microbiota.

Combination of Cannabinoids, Δ9- Tetrahydrocannabinol and Cannabidiol, Ameliorates Experimental Multiple Sclerosis by Suppressing Neuroinflammation Through Regulation of miRNA-Mediated Signaling Pathways

Multiple sclerosis (MS) is a chronic and disabling disorder of the central nervous system (CNS) characterized by neuroinflammation leading to demyelination. Recently a combination of Δ9-tetrahydrocannabinol (THC) and Cannabidiol (CBD) extracted from Cannabis has been approved in many parts of the world to treat MS-related spasticity. THC+CBD combination was also shown to suppresses neuroinflammation, although the mechanisms remain to be further elucidated. In the current study, we demonstrate that THC+CBD combination therapy (10 mg/kg each) but not THC or CBD alone, attenuates murine experimental autoimmune encephalomyelitis (EAE) by reducing neuroinflammation and suppression of Th17 and Th1 cells. These effects were mediated through CB1 and CB2 receptors inasmuch as, THC+CBD failed to ameliorate EAE in mice deficient in CB1 and CB2. THC+CBD treatment also caused a decrease in the levels of brain infiltrating CD4+ T cells and pro-inflammatory molecules (IL-17, INF-γ, TNF-α, IL-1β, IL-6, and TBX21), while increasing anti-inflammatory phenotype such as FoxP3, STAT5b, IL-4, IL-10, and TGF-β. Also, the brain-derived cells showed increased apoptosis along with decreased percentage in G0/G1 phase with increased percentage in G2/M phase of cell cycle. miRNA microarray analysis of brain-derived CD4+ T cells revealed that THC+CBD treatment significantly down-regulated miR-21a-5p, miR-31-5p, miR-122-5p, miR-146a-5p, miR-150-5p, miR-155-5p, and miR-27b-5p while upregulating miR-706-5p and miR-7116. Pathway analysis showed that majority of the down-regulated miRs targeted molecules involved in cycle arrest and apoptosis such as CDKN2A, BCL2L11, and CCNG1, as well as anti-inflammatory molecules such as SOCS1 and FoxP3. Additionally, transfection studies involving miR-21 and use of Mir21-/- mice suggested that while this miR plays a critical role in EAE, additional miRs may also be involved in THC+CBD-mediated attenuation of EAE. Collectively, this study suggests that combination of THC+CBD suppresses neuroinflammation and attenuates clinical EAE development and that this effect is associated with changes in miRNA profile in brain-infiltrating cells.

Plasma cell and B cell-targeted treatments for use in advanced multiple sclerosis

There is increasing evidence that agents that target peripheral B cells and in some instances plasma cells can exhibit marked effects on relapsing multiple sclerosis. In addition, B cells, including plasma cells, within the central nervous system compartment are likely to play an important role in disease progression in both relapsing and progressive MS. However, current B cell-targeting antibodies may not inhibit these, because of poor penetration into the central nervous system and often oligoclonal bands of immunoglobulin persist within the cerebrospinal fluid despite immunotherapy. Through targeting B cells and plasma cells in the CNS, it may be possible to obtain additional benefit above simple peripheral depletion of B cells. As such there are a number of inhibitors of B cell function and B cell depleting agents that have been developed for myeloma and B cell leukaemia and lymphoma, which could potentially be used off-label or as an experimental treatment for advanced (progressive) MS.

Selective Inhibition of the Mitochondrial Permeability Transition Pore Protects against Neurodegeneration in Experimental Multiple Sclerosis

The mitochondrial permeability transition pore is a recognized drug target for neurodegenerative conditions such as multiple sclerosis and for ischemia-reperfusion injury in the brain and heart. The peptidylprolyl isomerase, cyclophilin D (CypD, PPIF), is a positive regulator of the pore, and genetic down-regulation or knock-out improves outcomes in disease models. Current inhibitors of peptidylprolyl isomerases show no selectivity between the tightly conserved cyclophilin paralogs and exhibit significant off-target effects, immunosuppression, and toxicity. We therefore designed and synthesized a new mitochondrially targeted CypD inhibitor, JW47, using a quinolinium cation tethered to cyclosporine. X-ray analysis was used to validate the design concept, and biological evaluation revealed selective cellular inhibition of CypD and the permeability transition pore with reduced cellular toxicity compared with cyclosporine. In an experimental autoimmune encephalomyelitis disease model of neurodegeneration in multiple sclerosis, JW47 demonstrated significant protection of axons and improved motor assessments with minimal immunosuppression. These findings suggest that selective CypD inhibition may represent a viable therapeutic strategy for MS and identify quinolinium as a mitochondrial targeting group for in vivo use.

Experimental autoimmune encephalomyelitis is a good model of multiple sclerosis if used wisely

Although multiple sclerosis is a uniquely human disease, many pathological features can be induced in experimental autoimmune encephalomyelitis (EAE) models following induction of central nervous system-directed autoimmunity. Whilst it is an imperfect set of models, EAE can be used to identify pathogenic mechanisms and therapeutics. However, the failure to translate many treatments from EAE into human benefit has led some to question the validity of the EAE model. Whilst differences in biology between humans and other species may account for this, it is suggested here that the failure to translate may be considerably influenced by human activity. Basic science contributes to failings in aspects of experimental design and over-interpretation of results and lack of transparency and reproducibility of the studies. Importantly issues in trial design by neurologists and other actions of the pharmaceutical industry destine therapeutics to failure and terminate basic science projects. However animal, particularly mechanism-orientated, studies have increasingly identified useful treatments and provided mechanistic ideas on which most hypothesis-led clinical research is based. Without EAE and other animal studies, clinical investigations will continue to be "look-see" exercises, which will most likely provide more misses than hits and will fail the people with MS that they aim to serve.

Imidazol-1-ylethylindazole voltage-gated sodium channel ligands are neuroprotective during optic neuritis in a mouse model of multiple sclerosis

A series of imidazol-1-ylethylindazole sodium channel ligands were developed and optimized for sodium channel inhibition and in vitro neuroprotective activity. The molecules exhibited displacement of a radiolabeled sodium channel ligand and selectivity for blockade of the inactivated state of cloned neuronal Nav channels. Metabolically stable analogue 6 was able to protect retinal ganglion cells during optic neuritis in a mouse model of multiple sclerosis.

Lesional-targeting of neuroprotection to the inflammatory penumbra in experimental multiple sclerosis

Progressive multiple sclerosis is associated with metabolic failure of the axon and excitotoxicity that leads to chronic neurodegeneration. Global sodium-channel blockade causes side effects that can limit its use for neuroprotection in multiple sclerosis. Through selective targeting of drugs to lesions we aimed to improve the potential therapeutic window for treatment. This was assessed in the relapsing-progressive experimental autoimmune encephalomyelitis ABH mouse model of multiple sclerosis using conventional sodium channel blockers and a novel central nervous system-excluded sodium channel blocker (CFM6104) that was synthesized with properties that selectively target the inflammatory penumbra in experimental autoimmune encephalomyelitis lesions. Carbamazepine and oxcarbazepine were not immunosuppressive in lymphocyte-driven autoimmunity, but slowed the accumulation of disability in experimental autoimmune encephalomyelitis when administered during periods of the inflammatory penumbra after active lesion formation, and was shown to limit the development of neurodegeneration during optic neuritis in myelin-specific T cell receptor transgenic mice. CFM6104 was shown to be a state-selective, sodium channel blocker and a fluorescent p-glycoprotein substrate that was traceable. This compound was >90% excluded from the central nervous system in normal mice, but entered the central nervous system during the inflammatory phase in experimental autoimmune encephalomyelitis mice. This occurs after the focal and selective downregulation of endothelial p-glycoprotein at the blood-brain barrier that occurs in both experimental autoimmune encephalomyelitis and multiple sclerosis lesions. CFM6104 significantly slowed down the accumulation of disability and nerve loss in experimental autoimmune encephalomyelitis. Therapeutic-targeting of drugs to lesions may reduce the potential side effect profile of neuroprotective agents that can influence neurotransmission. This class of agents inhibit microglial activity and neural sodium loading, which are both thought to contribute to progressive neurodegeneration in multiple sclerosis and possibly other neurodegenerative diseases.

Immunosuppression with FTY720 is insufficient to prevent secondary progressive neurodegeneration in experimental autoimmune encephalomyelitis

BACKGROUND

There has been poor translation for the use of immunosuppressive agents from experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), into the treatment of MS. This may be due to the fact that most EAE studies examine prophylactic, pre-treatment regimes that prove to be therapeutically-ineffective in long-established, often progressive, MS. FTY720 (fingolimod/Gilenya) is a sphingosine-1-phosphate receptor modulator. This is a new oral agent that markedly reduces the number of relapses in people with MS, compared with currently licensed injectable agents such as the beta interferons. FTY720 has activity against lymphocytes but may also influence oligodendroglia and could therefore have the potential to influence progressive MS, by promoting remyelination.

METHODS

The effect of FTY720 was assessed in relapsing-progressive EAE in mice.

RESULTS

Early intervention during relapsing EAE could completely inhibit subsequent relapses, inhibited the accumulation of neurodegeneration, and facilitated motor recovery. However, when examined in secondary progressive EAE, that develops after the accumulation of deficit from relapsing disease, long-term treatment with FTY720 failed to slow deterioration when initiated late (4 months) into the disease course.

CONCLUSIONS

This study indicates that early intervention with immunosuppressive agents may inhibit the generation of the neurodegenerative microenvironment, which is no longer responsive to potent immunosuppression. However, if treatment is initiated too late, progressive, neurological-disease continues unabated. This suggests that immunosuppression is insufficient to control secondary progression in animals, as has been found so far to be the case in MS, and may warrant early intervention with FTY720 for optimal treatment benefit.

Biozzi mice: Of mice and human neurological diseases

In 1972 Guido Biozzi selectively bred mice to study the immunopathological mechanisms underlying polygenic diseases. One line, the Biozzi antibody high (AB/H) mouse (now designated the ABH strain) was later found to be highly susceptible to many experimentally induced diseases such as autoimmune encephalomyelitis, autoimmune neuritis, autoimmune uveitis, as well as virus-induced demyelination and has thus been a key mouse strain to study human inflammatory neurological diseases. In this paper we discuss the background of the Biozzi ABH mouse and review how studies with these mice have shed light on the pathogenic mechanisms operating in chronic neurological disease.

Autoimmune tolerance eliminates relapses but fails to halt progression in a model of multiple sclerosis

To date there has been poor translation of immunotherapies from rodent models to treatment of progressive multiple sclerosis (MS). In the robust, relapsing Biozzi ABH mouse model of MS, using a combination of a transient deletion of T cells followed by intravenous (i.v.) myelin antigen administration, established relapsing disease in EAE can be effectively silenced. However, when treatment was initiated in late stage chronic-relapsing disease, despite inhibition of further relapses, mice demonstrated evidence of disease progression shown by a deterioration in mobility and development of spasticity and indicates that targeting relapsing, immunological components of MS alone is unlikely to be sufficient to control progression in the late stages of MS.

Cannabinoids inhibit neurodegeneration in models of multiple sclerosis

Multiple sclerosis is increasingly being recognized as a neurodegenerative disease that is triggered by inflammatory attack of the CNS. As yet there is no satisfactory treatment. Using experimental allergic encephalo myelitis (EAE), an animal model of multiple sclerosis, we demonstrate that the cannabinoid system is neuroprotective during EAE. Mice deficient in the cannabinoid receptor CB1 tolerate inflammatory and excitotoxic insults poorly and develop substantial neurodegeneration following immune attack in EAE. In addition, exogenous CB1 agonists can provide significant neuroprotection from the consequences of inflammatory CNS disease in an experimental allergic uveitis model. Therefore, in addition to symptom management, cannabis may also slow the neurodegenerative processes that ultimately lead to chronic disability in multiple sclerosis and probably other diseases.

Gene therapy in autoimmune, demyelinating disease of the central nervous system

Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system (CNS), where suspected autoimmune attack causes nerve demyelination and progressive neurodegeneration and should benefit from both anti-inflammatory and neuroprotective strategies. Although neuroprotection strategies are relatively unexplored in MS, systemic delivery of anti-inflammatory agents to people with MS has so far been relatively disappointing. This is most probably because of the limited capacity of these molecules to enter the target tissue, because of exclusion by the blood-brain barrier. The complex natural history of MS also means that any therapeutic agents will have to be administered long-term. Gene therapy offers the possibility of site-directed, long-term expression, and is currently being preclinically investigated in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. While some immune effects may be targeted in the periphery using DNA vaccination, strategies both viral and nonviral are being developed to target agents into the CNS either via direct delivery or using the trafficking properties of cell-carrier systems. Targeting of leucocyte activation, cytokines and nerve growth factors have shown some promising benefit in animal EAE systems, the challenge will be their application in clinical use.

Lovastatin inhibits brain endothelial cell Rho-mediated lymphocyte migration and attenuates experimental autoimmune encephalomyelitis

Neuroinflammatory diseases, such as multiple sclerosis (MS), result from aberrant leukocyte traffic into the central nervous system (CNS). To breach the specialized blood-brain barrier, activated leukocytes interact with CNS endothelial cells (EC) and activate a CD54-mediated signaling pathway controlling the Rho GTPase. To function correctly Rho requires posttranslational prenylation, and this can be inhibited by depleting the supply of isoprenoids through inhibition of the cholesterol synthesis pathway with 3-hydroxy-3-methylglutaryl CoA reductase (HMG-CoA reductase) inhibitors (statins). Here we show that treatment of brain EC in vitro with lovastatin inhibits Rho-mediated transendothelial T cell migration. This effect can be reversed by supplementation with mevalonolactone, the downstream product of HMG-CoA reductase, or by ectopic expression of myristoylated Rho, which remains active in the absence of prenylation. In a relapsing-remitting mouse model of MS, lovastatin treatment inhibited leukocyte migration into the CNS and significantly attenuated the development of both acute and relapsing clinical disease. These studies demonstrate that the indirect pharmacological inhibition of Rho proteins in brain EC by statins can inhibit a key stage in the pathogenesis of neuroinflammation, namely leukocyte migration across the blood-brain barrier. These studies demonstrate a novel effect of statins in modulating the immune response in neuroinflammtory diseases and may provide additional rationale for their use in the treatment of MS.

Different therapeutic outcomes in experimental allergic encephalomyelitis dependent upon the mode of delivery of IL-10: a comparison of the effects of protein, adenoviral or retroviral IL-10 delivery into the central nervous system

Experimental allergic encephalomyelitis (EAE) is a CNS autoimmune disease mediated by the action of CD4(+) T cells, macrophages, and proinflammatory cytokines. IL-10 is a cytokine shown to have many anti-inflammatory properties. Studies have shown both inhibition and exacerbation of EAE after systemic IL-10 protein administration. We have compared the inhibitory effect in EAE of Il10 gene delivery in the CNS. Fibroblasts transduced with retroviral vectors expressing IL-10 could inhibit EAE. This was not associated with a prevention of cellular recruitment but an alteration in their phenotype, notably an increase in the numbers of CD8(+) T and B cells. In marked contrast, CNS delivery of adenovirus coding for mouse IL-10 or IL-10 protein performed over a wide dose range failed to inhibit disease, despite producing similar or greater amounts of IL-10 protein. Thus the action of IL-10 may differ depending on the local cytokine microenvironment produced by the gene-secreting cell types.

Gene therapy for chronic relapsing experimental allergic encephalomyelitis using cells expressing a novel soluble p75 dimeric TNF receptor

In a murine relapsing experimental allergic encephalomyelitis (EAE) model, gene therapy to block TNF was investigated with the use of a retroviral dimeric p75 TNF receptor (dTNFR) construct. To effectively produce these TNF inhibitors in vivo, a conditionally immortalized syngeneic fibroblast line was established, using a temperature-sensitive SV40 large T Ag-expressing retrovirus. These cells were subsequently infected with a retrovirus expressing soluble dTNFR. CNS-injected cells could be detected 3 mo after transplantation and were shown to produce the transgene product by immunocytochemistry and ELISA of tissue fluids. These levels of dTNFR protein were biologically active and could significantly ameliorate both acute and relapsing EAE. This cell-based gene-vector approach is ideal for delivering proteins to the CNS and has particular relevance to the control of inflammatory CNS disease.

Caspase-1 Regulates the Inflammatory Process Leading to Autoimmune Demyelination

T cell-mediated inflammation is considered to play a key role in the pathogenic mechanisms sustaining multiple sclerosis (MS). Caspase-1, formerly designated IL-1β-converting enzyme, is crucially involved in immune-mediated inflammation because of its pivotal role in regulating the cellular export of IL-1β and IL-18. We studied the role of caspase-1 in experimental autoimmune encephalomyelitis (EAE), the animal model for MS. Caspase-1 is transcriptionally induced during EAE, and its levels correlate with the clinical course and transcription rate of proinflammatory cytokines such as TNF-α, IL-1β, IFN-γ, and IL-6. A reduction of EAE incidence and severity is observed in caspase-1-deficient mice, depending on the immunogenicity and on the amount of the encephalitogenic myelin oligodendrocyte glycoprotein (MOG) peptide used. In caspase-1-deficient mice, reduced EAE incidence correlates with defective development of anti-MOG IFN-γ-producing Th1 cells. Finally, pharmacological blockade of caspase-1 in Biozzi AB/H mice, immunized with spinal cord homogenate or MOG35–55 peptide, by the caspase-1-inhibitor Z-Val-Ala-dl-Asp-fluoromethylketone, significantly reduces EAE incidence in a preventive but not in a therapeutic protocol. These results indicate that caspase-1 plays an important role in the early stage of the immune-mediated inflammatory process leading to EAE, thus representing a possible therapeutic target in the acute phase of relapsing remitting MS.

Local gene therapy with CTLA4-immunoglobulin fusion protein in experimental allergic encephalomyelitis

It has been reported previously that the induction phase of experimental allergic encephalomyelitis (EAE) is highly sensitive to systemic blockade of stimulation via MHC class II molecules and co-stimulation via the CD28:CD80/CD86 pathways. In contrast, the effector phases of EAE were relatively unaffected by similar treatments using MHC class II antigen (Ag)-specific mAb and cytotoxic T lymphocyte antigen (CTLA)4-Ig fusion proteins in some studies. This has been attributed to different sensitivities of effector cell function or the poor penetrance of inhibitory proteins into the central nervous system (CNS). To examine this question further, MHC class II Ag-specific mAb and CTLA4-Ig were delivered directly into the CNS following EAE induction, and both were found to inhibit disease. While it was found that systemic administration of mouse CTLA4-Ig could also inhibit the progression of effector immune responses when administered shortly before or during clinical disease, these were significantly more active when delivered directly into the CNS, which probably involved an action on both CD28 ligands, CD80 and CD86. Although mouse CTLA4-human Ig was therapeutically less efficient than mouse CTLA4-mouse Ig protein, probably due to the enhanced immunogenicity and lower functional activity, gene delivery of CTLA4-human Ig into the CNS using a non-replicating adenoviral vector was more effective than a single injection of CTLA4-human Ig protein. Gene delivery significantly ameliorated the development of EAE, without necessarily inhibiting unrelated peripheral immune responsiveness. Local gene delivery of CTLA4-Ig may thus be an important target for immunotherapy of human autoimmune conditions such as multiple sclerosis.

Cytokine Gene Therapy in Experimental Allergic Encephalomyelitis by Injection of Plasmid DNA-Cationic Liposome Complex into the Central Nervous System

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease of the central nervous system with many similarities to multiple sclerosis. The main effector cells involved are CD4+ T cells, recognizing encephalitogenic epitopes within the central nervous system, and macrophages, both of which secrete proinflammatory cytokines, such as IFN-γ and TNF. Studies have shown that immunomodulation of this inflammatory response by anti-inflammatory cytokines (IL-4, IL-10, IFN-β, and TGF-β) can reduce clinical severity in EAE. The importance of TNF in EAE has been demonstrated by using soluble TNF-receptor molecules to inhibit EAE. However, the limitation of this type of therapy is the necessity for frequent administration of cytokine proteins due to their short biologic half-life. This study demonstrates that EAE can be inhibited by a single injection of therapeutic cytokine (IL-4, IFN-β, and TGF-β) DNA-cationic liposome complex directly into the central nervous system. DNA coding for a novel, dimeric form of human p75 TNF receptor also ameliorated clinical EAE. Local administration of DNA-cationic liposome complex has identified gene targets that may be more efficiently exploited using vectors producing more stable expression for effective treatment of neuroimmunologic disease.

Optic neuritis in chronic relapsing experimental allergic encephalomyelitis in Biozzi ABH mice: demyelination and fast axonal transport changes in disease

The encephalitogenicity of optic nerve tissue was demonstrated in Biozzi ABH (H-2(dq1)) mice. Acute experimental allergic encephalomyelitis (EAE) occurred in 11/14 animals and 4/5 exhibited relapse. The involvement of the optic nerve in spinal cord homogenate induced chronic relapsing EAE (CREAE) was demonstrated by mononuclear cell infiltration and myelin degradation in the optic nerve prior to and during clinical disease. During the relapse phase gross pathological assessment revealed swollen and translucent plaques on the optic nerves. Advanced lesions showed widespread demyelination, astrocytic gliosis and fibrotic changes of the blood vessels. Physiologically, the fast axonal transport of proteins from the retina to the optic nerve and superior colliculus was significantly decreased during relapse. The association of inflammation and demyelination with physiological deficit in the optic nerve highlights the usefulness of this model in the study of multiple sclerosis in which acute monosymptomatic unilateral optic neuritis is a common manifestation. Furthermore, the novel induction of CREAE with optic nerve homogenate suggests that optic neuritis is a common significant role in the pathophysiology and progression of neurological disease in CREAE which may be relevant to studies of optic neuritis in multiple sclerosis.

Recent advances in the pharmacological control of experimental allergic encephalomyelitis (EAE) and the implications for multiple sclerosis treatment

The autoimmune, cell-mediated condition experimental allergic encephalomyelitis (EAE) is the representative model for the inflammatory central nervous system disease MS. EAE has been extensively employed to determine the efficacy of pharmacological agents that may be of ultimate use in the treatment of MS. A wide variety of drugs has been examined for activity in EAE but, over the last decade, three groups of compounds have emerged with clear and reproducible ability to modify significantly the onset and progression of the disease. The immunosuppressants, the modulators of catecholamine activity and the antineoplastic agents have convincingly altered the course of EAE and, as a consequence, provided understanding of the mechanisms of disease expression and offered further insight into the pathogenesis of MS. The article stresses the usefulness of EAE as a model to identify prospective pharmacological treatments for MS and, in particular, considers those compounds subsequently assessed for their ability to interfere with the progression of the human disease.

Control of immune-mediated disease of the central nervous system with monoclonal (CD4-specific) antibodies

Chronic relapsing experimental allergic encephalomyelitis (CREAE) was induced in Biozzi AB/H (H-2dq1) mice by active sensitization with spinal cord antigens. A single i.p. injection of CD8-depleting (YTS169.4) monoclonal antibody (mAb) failed to affect the clinical course of CREAE when administered prior to and during the onset of both the initial clinical and subsequent relapse phase of the disease. By contrast similar treatment with both CD4-depleting (YTS191.1) or CD4-blocking/non-depleting (YTS177.9) mAb significantly inhibited disease progression. Treatment shortly before the anticipated onset of clinical EAE prevented the subsequent development of disease, although disease could be provoked following antigen-rechallenge. In contrast, treatment with these antibodies during post-acute remission phase mainly served to delay the incidence of relapse. This suggests that, unless tolerance can be re-induced, treatment of ongoing neuroimmunological disease will require 'pulse' therapy and thus potentiate the problems of long-term immunosuppresion. Despite the findings that CD4-specific antibodies can rapidly reverse overt clinical disease shortly after the onset of disease exacerbation, once neurological dysfunction becomes established anti-CD4 treatment fails to improve the animals clinically, possibly due to the inability to rapidly reverse established demyelination. Although this study does not exclude the potential central action of the injected mAb, the failure to significantly dissociate therapeutic benefit between mAb administered directly into the CNS and that given systemically suggests that a major action of these agents is probably by selectively removing T cells in the peripheral T cell pool.

Inhibition of chronic relapsing experimental allergic encephalomyelitis in the Biozzi AB/H mouse

Chronic relapsing experimental allergic encephalomyelitis (CREAE) can be reproducibly induced in Biozzi AB/H mice following injection of spinal cord homogenate (SCH) emulsified in complete Freund's adjuvant (CFA). Active clinical disease is associated with mononuclear cell infiltration of the central nervous system (CNS), mainly the spinal cord. Whole brain homogenate (BH), however, failed to induce clinical or histological disease. In contrast, substituting sciatic nerve homogenate in the inoculum induced experimental allergic neuritis (EAN). Clinical disease was manifest earlier (13.1 +/- 0.3 days) than CREAE (16.2 +/- 1.4) and was accompanied by mononuclear infiltration of the peripheral nervous system (PNS). In comparison to CREAE induction, pretreating mice with SCH or BH in incomplete Freund's adjuvant (IFA) suppressed the development of SCH-induced disease. The BH was more tolerogenic than the SCH and this hyporesponsiveness was CNS antigen-specific as PNS tissue failed to inhibit the course of CREAE. Tolerance induced by pretreatment with SCH or BH in IFA was reversed by a single injection of 200 mg/kg cyclophosphamide, 2 days prior to CREAE induction. This suggests that IFA-induced hyporesponsiveness is actively regulated, possibly via the action of suppressor cells. In addition, treatment with neuroantigens in IFA appears to be mainly afferent acting as it serves to prevent initial disease induction. This treatment after immunization for CREAE, however, fails to prevent disease progression. Furthermore, treatment with CNS antigens emulsified in IFA during the post-acute remission stage appeared to synchronize and induce (32 +/- 1 days) the onset of clinical relapse, compared with untreated controls (41 +/- 5 days). This indicates that such IFA treatment has minimal value in controlling an ongoing immune disease of the CNS.

Control of immune-mediated disease of the central nervous system requires the use of a neuroactive agent: elucidation by the action of mitoxantrone

Mitoxantrone was used as an immunosuppressive probe to elucidate a means for the control of experimental allergic encephalomyelitis (EAE) induced in Biozzi AB/H mice following injection of spinal cord homogenate emulsified in Freund's adjuvant. A single i.p. injection of 2.5 mg/kg of mitoxantrone, 1-2 days before the anticipated onset of EAE, failed to prevent the majority of animals from developing clinical disease, whereas when the compound was injected directly into the central nervous system (CNS), at this time point, significantly increased therapeutic benefit was evident, with most animals failing to develop clinical EAE. Although the clinical use of intrathecal mitoxantrone is strongly contraindicated, these data suggest that increased therapeutic benefit may be achieved in immune-mediated disease of the CNS by targeting immunosuppressive doses of suitable agents, on lymphocyte activation within the CNS. In addition, direct administration of immunosuppressive doses into the CNS may reduce potentially unwanted (side) effects in the periphery.