Multiple sclerosis: possible immunological mechanisms

Efficacy, safety, and cost-effectiveness of glatiramer acetate in the treatment of relapsing-remitting multiple sclerosis

The current Multiple Sclerosis (MS) therapeutic landscape is rapidly growing. Glatiramer acetate (GA) remains unique given its non-immunosuppressive mechanism of action as well as its superior long-term safety and sustained efficacy data. In this review, we discuss proposed mechanisms of action of GA. Then we review efficacy data for reduction of relapses and slowing disability as well as long term safety data. Finally we discuss possible future directions of this unique polymer in the treatment of MS.

Glatiramer acetate therapy for multiple sclerosis: a review

The past decade has witnessed a revolution in the treatment of multiple sclerosis (MS), the most common demyelinating disorder of the human CNS. After being considered as an untreatable disease for more than a century, six disease-modifying treatments have been approved between 1993 and 2006. Glatiramer acetate (GA) is a worldwide drug approved for the treatment of relapsing-remitting MS in 1996. The drug is a synthetic copolymer of four amino acids based on the composition of myelin basic protein, one of several putative autoantigens implicated in the pathogenesis of MS. Three separate double-blind, placebo-controlled trials have established its efficacy in relapsing-remitting MS. Observations from an ongoing study, the longest prospective study in MS therapeutics so far, suggest that the effect of GA in reducing the relapse rate and neurological disability is maintained over a 10-year period. Independent investigators have identified several putative immunological mechanisms of action of GA, with the unique observation of the generation of GA-reactive T-helper 2 (anti-inflammatory) polarised lymphocytes within days to weeks of initiating therapy and sustaining an anti-inflammatory milieu for years in the peripheral immune system and, presumably, in the CNS. Emerging data from immunological and imaging studies quantifying axonal injury in the brain point towards neuroprotective abilities of GA. Combined with its remarkable safety and tolerability, long-term efficacy and neuroprotective effect, GA presents it self as a first-line choice in relapsing-remitting MS, and holds immense promise in developing its potential as a combination therapy in MS, as well as extending its indications to other neurodegenerative diseases.

Qualitative evidence of anti-Yo-specific intrathecal antibody synthesis in patients with paraneoplastic cerebellar degeneration

We investigated the presence of anti-Yo-specific oligoclonal antibody bands in cerebrospinal fluid (CSF) and serum samples of 9 patients with anti-Yo syndrome and 11 controls. Isoelectric focusing combined with affinity blotting, revealed anti-Yo-specific intrathecal antibody synthesis in all patients with anti-Yo syndrome: Four patients had positive anti-Yo-specific oligoclonal IgG bands in CSF which were not demonstrable in their sera; five CSF/serum pairs showed additional, more intensive, oligoclonal bands in CSF compared to the corresponding serum. Interestingly, four patients with absence of oligoclonal bands of total IgG in CSF revealed positive anti-Yo-specific oligoclonal bands in the same sample. This speaks for a higher sensitivity of detection of oligoclonal bands using an affinity blot loaded with Yo-specific antigen compared to an affinity blot coated with anti-human IgG used for the detection of oligoclonal bands of total IgG. In conclusion, the presence of anti-Yo-specific oligoclonal IgG bands in CSF which were absent, or less strong, in patients sera provides qualitative evidence of anti-Yo-specific IgG synthesis by intrathecal B-cell clones. These results could be of interest in detection of intrathecal-specific IgG synthesis in nervous system infectious diseases provided that the target antigen is known.

Comparative assessment of immunomodulating therapies for relapsing-remitting multiple sclerosis

The past decade has seen unprecedented advances in the development of disease-modifying therapies for relapsing-remitting multiple sclerosis (RRMS), a disease that has a worldwide prevalence of two million patients. Four agents with the ability to modulate the immune system are now being widely used for RRMS. Of these, three are forms of interferon (IFN)-beta [IFNbeta-1b and two preparations of IFNbeta-1a (Avonex and Rebif], and one is a polypeptide of four amino acids (glatiramer acetate) with a unique mechanism of action. The administration regimens for the IFNbeta-1a products differ, with Avonex being given as 30 microg intramuscularly once a week and Rebif being given as 22 or 44 microg subcutaneously three times a week. It appears safe to predict that both forms of IFNbeta and glatiramer acetate will remain standard treatments for MS for years to come. However, with four therapeutic options available for RRMS, selecting a single therapy is often difficult and necessitates comparisons of the agents, which can be contentious. All four agents have shown superiority over placebo in pivotal phase III trials. Three recent prospective comparative studies have indicated that IFNbeta-1b, Rebif and glatiramer acetate may be more optimal choices than Avonex for patients with RRMS. In a pharmaceutical environment with an estimated worldwide market of $US2.5 billion annually for RRMS, comparative studies are understandably provocative, but at the same time provide meaningful information to clinicians and patients.

Demonstration of anti-HuD specific oligoclonal bands in the cerebrospinal fluid from patients with paraneoplastic neurological syndromes. Qualitative evidence of anti-HuD specific IgG-synthesis in the central nervous system

The presence of HuD-specific oligoclonal IgG bands in the CSF was investigated in five patients with paraneoplastic neurological syndromes. All patients revealed intrathecal synthesis of HuD specific antibodies in the CSF, as estimated from elevated antibody indices (>1.5) in an IgG-ELISA using recombinant HuD-protein as antigen. Isoelectrofocussing combined with affinity blotting showed reactivity of IgG bands with recombinant HuD antigen in all CSF samples. These data support the idea that HuD specific antibodies in the CSF are produced mainly by B-cell clones in the central nervous system. These findings support the hypothesis of autoimmunity in the pathogenesis of anti-Hu associated paraneoplastic neurological syndromes.

Oligodendrocyte-specific protein (OSP) is a major component of CNS myelin

An oligodendrocyte-specific protein (OSP) cDNA was recently identified and found to be expressed primarily in oligodendrocytes and has a deduced amino acid sequence similar to that of peripheral myelin protein 22 (PMP-22). We raised antibodies against a synthetic peptide corresponding to OSP amino acid residues 179-194 which reacted with a 22 kd protein in mouse CNS. OSP immunoreactivity localized to spinal cord white matter tracts using immunohistochemistry in a similar distribution to that of MBP. OSP localized to CNS myelin biochemically with more than a 30-fold enrichment measured in purified myelin. We further purified the proteolipid fraction of myelin and determined that OSP contributes approximately 7% of total myelin protein making it the third most abundant protein in CNS myelin. No binding was found to several agglutinins or a HNK1-specific antibody suggesting that OSP is not a glycoprotein.

Spontaneous and induced remyelination in multiple sclerosis and the Theiler's virus model of central nervous system demyelination

Remyelination in the central nervous system, originally thought to occur rarely, if ever, is now an established phenomena in multiple sclerosis patients. However, the extent of myelin repair is incomplete and limited. Experimental models of central nervous system demyelination provide an opportunity to study the cellular and molecular events involved in remyelination. These models may provide some clue to why remyelination in multiple sclerosis is incomplete as well as suggest potential methods to stimulate central nervous system repair. In this review we examine the morphological aspects of central nervous system remyelination and discuss both spontaneous and induced remyelination in multiple sclerosis and experimental models of central nervous system demyelination. We give special emphasis to the Theiler's virus model of central nervous system demyelination and its usefulness to identify therapeutic agents to promote remyelination. The role of immunoglobulins in promoting remyelination in both the Theiler's model system and in multiple sclerosis is discussed. Finally, we examine the potential physiological role of demyelination and remyelination and its relationship with clinical manifestations of central nervous system disease.

Gamma delta T cell receptor variable region usage during the development of experimental allergic encephalomyelitis

The molecular diversity of gamma delta T cells has not previously been investigated in experimental allergic encephalomyelitis (EAE). This study characterised the gamma delta T cell receptor (TCR) variable (V) region repertoires of T cells infiltrating the brains of EAE mice during development of the disease. TCR gamma- and delta-specific cDNAs were synthesised from total RNA prepared from brain samples and transcription of rearranged V genes was assessed by polymerase chain reaction amplification of TCR V-C transcripts and Southern blot analysis. In the early stages of EAE, the TCR gamma-chain repertoire consisted of V gamma 1-3 and V gamma 6 transcripts and, similarly, a few V delta transcripts that used primarily V delta 1, V delta 4 and V delta 5 gene segments were detected. During the progression of EAE, however, most V gamma and V delta TCR transcripts were observed in the brain. These results indicate that in the course of murine EAE there is an initial infiltration into the brain of a restricted population of gamma delta T cells followed by a heterogeneous gamma delta TCR repertoire as the disease develops. Moreover, the data suggest that gamma delta T cells may play a role in the pathogenesis of demyelinating autoimmune disease.

Analysis of HLA-class II DQA1, DQB1, DRB1 and DPB1 in Italian multiple sclerosis patients

We studied the allelic constitution at the HLA class II DQA1, DQB1, DRB1 and DPB1 in 94 Italian multiple sclerosis (MS) patients and 98 controls. No significant increase in the frequency of DR2 alleles was detected among MS patients, as previously observed both in European and some Italian studies. A slight increase was found for the DQA1*0301 and DQB1*0602 alleles in the MS patients. No significant association was found with the glutamine residue at position 34 of the DQ alpha chain, which was noted previously in MS patients from northern Europe.

Microglial cells qualify as the stimulators of unprimed CD4+ and CD8+ T lymphocytes in the central nervous system

The potential of central nervous system (CNS)-derived cells for initiating T cell responses is not known. Using the capacity of unprimed T cells to respond to allogeneic determinants on antigen-presenting cells (APC), we assessed the ability of microglial cells to act as stimulators of primary T cell responses in vitro. For this purpose, microglial cells were activated with lipopolysaccharide (LPS), interferon-gamma (IFN-gamma), or by phagocytosis of progenitor oligodendrocytes and subsequently tested for their ability to induce a proliferative response of naive, resting T cells. Activated microglial cells induced a significant proliferation of virgin, alloreactive CD4+ and CD8+ T lymphocytes, with a more substantial response of highly purified CD4+ than of CD8-expressing T cells. Phagocytosis activation was the most efficient stimulus to induce this APC competence on microglial cells. By contrast, IFN-gamma-pretreated, MHC-expressing astrocytes were unable to induce similar responses of alloreactive CD4+ or CD8+ T cells under the same experimental conditions. Collectively, our data suggest the role of activated microglia as the fully immunocompetent accessory cell population of the CNS.

Functional defects in peripheral blood T cells of multiple sclerosis patients. Diminished in vitro responsiveness in accessory cell dependent activation systems

Function and phenotype of peripheral blood (PB) T cells in multiple sclerosis (MS) patients were analyzed. In whole blood cultures, T cell proliferation of multiple sclerosis (MS) patients, using soluble CD3 mAb and CD2 mAb as stimulants, was reduced in comparison to healthy controls. A similar difference was seen when isolated PBMC were tested after stimulation with soluble CD3 mAb. However, in accessory cell-independent activation systems, i.e. after stimulation of PBMC with immobilized CD3 mAb or after co-stimulation with CD28 mAb, both patients and controls responded equally well. Phenotypical analysis of the circulating T cell population showed that there were no differences in the percentage of CD26+, 'memory' (CD45R0+) or 'effector' (CD4+CD45R0+CD27-) cells between MS patients and healthy controls. Finally, although MS patients did show an enhanced proportion of 'naive' (CD4+CD45RA+) T cells, this did not correlate with the observed functional defects.

Seasonal variation and sex differences of circulating macrophages, immunoglobulins and lymphocytes in healthy school children

Subpopulations of T and B lymphocytes and levels of serum immunoglobulins G, A, M, E and subclasses G1, G2 and G3 were studied in 45 healthy school children aged 8-16 years during four seasons of the year. There were significant increases in CD4+ T helper cells, total T lymphocytes and CD4+/CD8+ (helper/cytotoxic) T-cell ratio during the spring season. While the levels of CD8+ T cells and total B lymphocytes remained statistically unchanged during all four seasons, the levels of natural (HNK-1) killer cells and macrophages increased significantly during the autumn and summer seasons respectively. The levels of immunoglobulins G, A, M and E remained statistically unchanged during all four seasons. Girls had higher levels of CD4+ T cells and a higher CD4+/CD8+ T-cell ratio than boys. Girls also had slightly higher levels of immunoglobulin G and M. These observations suggest that seasonal variations of some immunological parameters occur in healthy children. This may be an adaptive response to variable climatic and other environmental factors. These natural variations due to seasonal changes should be taken into account when immunological tests are used in clinical investigations.

Natural and experimental transfer of anti-Pertussis antibodies confers resistance to experimental autoimmune encephalomyelitis

Pregnant rats challenged with Bordetela Pertussis vaccine, with or without encephalitogenic antigen during pregnancy, transferred a resistance to induction of experimental autoimmune encephalomyelitis (EAE) to their offspring. Cross-fostering experiments showed that the protection against EAE is conferred during the lactation period through the transfer of anti pertussis antibodies in the milk. The degree of protection correlated with antibody levels. Passive transfer of these antibodies through intraperitoneal injection to naive adult rats also conferred the same degree of protection against EAE induction. It is suggested that such transfer of resistance and antibodies may serve as a model for the study of milk transmitted immunocompetent factors, as well as a model for the mechanisms involved in the resistance to EAE.

Multiple sclerosis susceptibility: population and twin study of polymorphisms in the T-cell receptor beta and gamma genes region. French Group on Multiple Sclerosis

Multiple sclerosis (MS) is a demyelinating auto-immune disease of the central nervous system with a suspected genetic component. Previous publications have demonstrated that MS susceptibility is influenced by Major Histocompatibility Complex (MHC) genes and recent studies have focused on additional susceptibility genes. The accumulation of activated T-cells in demyelinating MS lesions, the possible auto-immune mechanism of this disease and the functional relationship between MHC and T cell receptor (TCR) molecules support the hypothesis that TCR genes are good candidates to influence MS development. Published results in this domain are conflicting and still a matter of controversy. In the present study we analysed the influence of V beta, C beta, P lambda G3 and V gamma gene polymorphisms defined by Restriction Fragments Length Polymorphism (RFLP) on 48 pairs of monozygotic and dizygotic twins with at least one of each pair affected, and also in 63 unrelated MS patients for V gamma gene polymorphism. These results have been compared with those in the non affected twins and with data from a control group (Beall et al., 1989) regarding C beta and V beta polymorphisms and with a local control population for V gamma. No significant correlation between C beta, V gamma or P lambda G3 polymorphisms and MS was found, only a non significant tendency to reduced P lambda G3 allele sharing among dizygotic non concordant twin pairs was observed. However one V beta 11, 25 kb allele and a haplotype defined by V beta 11 and C beta alleles showed a correlation with MS susceptibility of borderline significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic susceptibility to multiple sclerosis linked to myelin basic protein gene

Genetic factors have been implicated in the aetiology of multiple sclerosis (MS), but the genes conferring susceptibility to MS have not been identified. We carried out genetic linkage and association analyses by studying polymorphism of the myelin basic protein (MBP) gene on chromosome 18, a candidate gene for MS, in 21 MS families, 51 additional unrelated patients with definite MS, and 85 controls. All subjects were Finnish, and 14 of the families were from an area with an exceptional familial clustering of MS. Magnetic resonance imaging (MRI) was used to examine subclinical disease in symptom-free family members. In the association analysis, the allele frequencies between MS patients and controls differed significantly, p = 0.000049), the difference being attributable mainly to a higher frequency of a 1.27 kb allele among patients. In the linkage analysis, based on an autosomal dominant model and penetrance 0.05, a maximum LOD score of 3.42 (theta = 0.00) was obtained when patients with optic neuritis and their symptom-free siblings with abnormal MRI findings were classified as "affected". When these subjects were classified as "unknown" the maximum LOD scores ranged from 2.99 to 3.25 (theta = 0.00). The results suggest that in this population genetic predisposition to MS is closely linked to the MBP gene and that polymorphism at the MBP locus or an adjacent locus has a role in the aetiology of MS.

Antibodies to myelin-oligodendrocyte glycoprotein in cerebrospinal fluid from patients with multiple sclerosis and controls

Myelin-oligodendrocyte glycoprotein (MOG) has been implicated as a target for antibody-mediated immune attack in experimental autoimmune encephalomyelitis (EAE) which has been used extensively as an experimental model of multiple sclerosis (MS). We have screened cerebrospinal fluid (CSF) and plasma from 30 patients with MS, 30 with other neurological diseases (OND) and 30 with tension headache for anti-MOG antibodies of IgG isotype by enzyme-linked immunosorbent assay (ELISA). Such antibodies were detected in CSF from seven of the patients with MS, compared to two with OND and one with tension headache. No anti-MOG IgG antibodies were demonstrable in plasma. Antibody specificity was confirmed by Western blot immunostaining. Antibody levels were higher in MS compared to OND and tension headache. No correlation was observed between anti-MOG IgG antibodies and total IgG levels in CSF. The significance of anti-MOG antibodies demonstrated in MS CSF remains to be defined.

Consanguinity and multiple sclerosis in Orkney

For all patients with multiple sclerosis in Orkney who were alive in 1974 or who had died during 1958 to 1974, pedigree data were analysed. The relationship between their parents, expressed by kinship coefficients, was compared with that between parents of matched controls. The closer relationship between parents of patients suggests that it is the genes that are shared by a patient's parents, and that he inherits from both, that influence his susceptibility to multiple sclerosis.

HLA-DQA1 and HLA-DQB1 genes may jointly determine susceptibility to develop multiple sclerosis

Serologic DR typing and genomic DRB1, DQA1, DQB1, DPA1, and DPB1 typing using sequence-specific oligonucleotides were performed in 69 multiple sclerosis (MS) patients and 181 healthy controls on in vitro amplified DNA. The frequencies of DR2 as well as the DR2-associated DQA1*0102 and DQB1*0602 alleles were increased whereas DR7 was decreased among MS patients. The distribution of DR4 subtypes as well as DP alleles were similar in patients and healthy controls. All but one of 23 DR4-positive MS patients carried the DQB1*0302 allele, whereas five of five DR7-positive MS patients carried the DQB1*0303 allele. Of the MS patients, 99% compared to 79% of the controls carried DQA1 alleles encoding glutamine at residue 34, while 97% of the MS patients compared to 72% of the controls carried DQB1 alleles encoding DQ beta chains sharing long polymorphic stretches. A combination of such DQA1 and DQB1 alleles was carried by 96% of the MS patients and 60% of the controls, suggesting an association between MS and a combination of particular DQA1 alleles and DQB1 alleles. The corresponding DQ alpha beta heterodimers may have in common an ability to bind a particular peptide.

Glycosphingolipids in the cerebrospinal fluid of patients with multiple sclerosis

Glycosphingolipids in cerebrospinal fluid (CSF) of individual patients with multiple sclerosis (MS) were analyzed using a glycolipid-overlay technique. The ganglioside composition of CSF of non-MS patients was characterized by an abundance of polysialo species, including GT1b and GQ1b. This pattern is completely different from that of human white or gray matter, in which mono- and disialogangliosides predominate. Increased levels of GM1, either associated with or without increases of other gangliosides, such as GD1a, were observed in 16% of the patients with MS (6 of 37 cases: 1 of 15 progressive progressive stage, 4 of 16 progressive stationary stage, and 1 of 6 relapsing stage). The concentration of GD3 was increased in 23% (3 of 13 cases), whereas 1 of 13 cases (8%) showed a dramatic increase of sulfoglucuronyl paragloboside (SGPG) associated with a high level of GD3. These changes may reflect the cellular changes associated with the known pathological lesions in MS, which are characterized by demyelination, gliosis, and/or remyelination with oligodendrocytic proliferation.

The cellular and molecular events of central nervous system remyelination

Central nervous system (CNS)* regeneration is a subject of great interest, particularly in diseases causing a dramatic loss of neurons. However, some CNS diseases do not affect neurons but damage other cells, such as the myelin-forming cells--called oligodendrocytes--which are also crucial to the harmonious function of the nervous system. Diseases in which oligodendrocytes and myelin are attacked can cause devastating neurological dysfunction which is sometimes followed by recovery and myelin repair or remyelination. The question of the regeneration potential of oligodendrocytes in experimental and human demyelinating diseases such as multiple sclerosis has been debated for a long time. Present evidence suggests that oligodendrocyte precursor cells persist in the adult CNS and that oligodendrocyte regeneration can occur but may be limited by ongoing disease processes. Here we will briefly review recent advances which have broadened our understanding of the cellular and molecular events of CNS remyelination.

Multiple sclerosis: why?

Multiple sclerosis is a chronic inflammatory demyelinating condition of the nervous system. Its etiology is obscure. Something in the environment strikes a susceptible host. Somehow the immune system produces central nervous system lesions. Magnetic resonance imaging scans show far greater "lesion" formation in the brain than was expected from clinical exacerbations. White blood cell changes suggest the disease is not entirely localized to the CNS. Some immunomodulatory treatments temporarily slow the rate of deterioration.