Manganese-Enhanced MRI in Patients with Multiple Sclerosis.

BACKGROUND AND PURPOSE: Cellular uptake of the manganese ion, when administered as a contrast agent for MR imaging, can noninvasively highlight cellular activity and disease processes in both animals and humans. The purpose of this study was to explore the enhancement profile of manganese in patients with multiple sclerosis. MATERIALS AND METHODS: Mangafodipir is a manganese chelate that was clinically approved for MR imaging of liver lesions. We present a case series of 6 adults with multiple sclerosis who were scanned at baseline with gadolinium, then injected with mangafodipir, and followed at variable time points thereafter. RESULTS: Fourteen new lesions formed during or shortly before the study, of which 10 demonstrated manganese enhancement of varying intensity, timing, and spatial pattern. One gadolinium-enhancing extra-axial mass, presumably a meningioma, also demonstrated enhancement with manganese. Most interesting, manganese enhancement was detected in lesions that formed in the days after mangafodipir injection, and this enhancement persisted for several weeks, consistent with contrast coming from intracellular uptake of manganese. Some lesions demonstrated a diffuse pattern of manganese enhancement in an area larger than that of both gadolinium enhancement and T2-FLAIR signal abnormality. CONCLUSIONS: This work demonstrates the first use of a manganese-based contrast agent to enhance MS lesions on MR imaging. Multiple sclerosis lesions were enhanced with a temporal and spatial profile distinct from that of gadolinium. Further experiments are necessary to uncover the mechanism of manganese contrast enhancement as well as cell-specific uptake.

Evidence-based guideline update: Plasmapheresis in neurologic disorders: report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology.

OBJECTIVE: To reassess the role of plasmapheresis in the treatment of neurologic disorders. METHODS: We evaluated the available evidence based on a structured literature review for relevant articles from 1995 through September 2009. In addition, due to revision of the definitions of classification of evidence since the publication of the previous American Academy of Neurology assessment in 1996, the evidence cited in that manuscript was reviewed and reclassified. RESULTS AND RECOMMENDATIONS: Plasmapheresis is established as effective and should be offered in severe acute inflammatory demyelinating polyneuropathy (AIDP)/Guillain-Barré syndrome (GBS) and in the short-term management of chronic inflammatory demyelinating polyneuropathy (Class I studies, Level A). Plasmapheresis is established as ineffective and should not be offered for chronic or secondary progressive multiple sclerosis (MS) (Class I studies, Level A). Plasmapheresis is probably effective and should be considered for mild AIDP/GBS, as second-line treatment of steroid-resistant exacerbations in relapsing forms of MS, and for neuropathy associated with immunoglobulin A or immunoglobulin G gammopathy, based on at least one Class I or 2 Class II studies (Level B). Plasmapheresis is probably not effective and should not be considered for neuropathy associated with immunoglobulin M gammopathy, based on one Class I study (Level B). Plasmapheresis is possibly effective and may be considered for acute fulminant demyelinating CNS disease (Level C). There is insufficient evidence to support or refute the use of plasmapheresis for myasthenia gravis, pediatric autoimmune neuropsychiatric disorders associated with streptococcus infection, and Sydenham chorea (Class III evidence, Level U).

Cross-reactive phage-displayed mimotopes lead to the discovery of mimicry between HSV-1 and a brain-specific protein.

We previously reported the selection of several families of phage-displayed peptide mimics (mimotopes) recognized by oligoclonal immunoglobulins present in the CSF of multiple sclerosis (MS) patients. To search for the natural antigens recognized by these antibodies, anti-sera were raised against one of the mimotopes and used as a probe in ELISA, Western blotting and immunoprecipitation experiments. Anti-mimotope IgG were found to cross-react with an epitope shared by a brain-specific factor conserved from rodents to humans, and the surface glycoprotein gB of HSV-1. These findings support the hypothesis that common viral infections are the triggering agents of self-reactive CSF antibodies, whose role in MS still remains to be elucidated.

Encephalitogenic potential of the myelin basic protein peptide (amino acids 83-99) in multiple sclerosis: results of a phase II clinical trial with an altered peptide ligand.

Myelin-specific T lymphocytes are considered essential in the pathogenesis of multiple sclerosis. The myelin basic protein peptide (a.a. 83-99) represents one candidate antigen; therefore, it was chosen to design an altered peptide ligand, CGP77116, for specific immunotherapy of multiple sclerosis. A magnetic resonance imaging-controlled phase II clinical trial with this altered peptide ligand documented that it was poorly tolerated at the dose tested, and the trial had therefore to be halted. Improvement or worsening of clinical or magnetic resonance imaging parameters could not be demonstrated in this small group of individuals because of the short treatment duration. Three patients developed exacerbations of multiple sclerosis, and in two this could be linked to altered peptide ligand treatment by immunological studies demonstrating the encephalitogenic potential of the myelin basic protein peptide (a.a. 83-99) in a subgroup of patients. These data raise important considerations for the use of specific immunotherapies in general.

Minimal peptide length requirements for CD4(+) T cell clones--implications for molecular mimicry and T cell survival.

CD4(+) T lymphocytes usually recognize peptides of 12-16 amino acids in the context of HLA class II molecules. We have recently used synthetic peptide combinatorial libraries to dissect in detail antigen recognition by autoreactive CD4(+) T cell clones (TCC). The results of these studies demonstrated that antigen recognition by T cells is highly degenerate and that many cross-reactive ligands can be defined, some of which much more potent than the selecting autoantigen. Based on these observations, we examined the response of a myelin basic protein-specific HLA class II-restricted CD4(+) TCC to truncation variants of optimal ligands. Surprisingly, pentapeptides, tetrapeptides and even tripeptides derived from different segments of the optimal ligands were recognized by the TCC, and some were even more potent than the selecting autoantigen. In addition, these peptides enhanced the survival of the TCC at low concentration. The relevance of this finding was supported by the generation of pentapeptide-specific CD4(+) TCC from peripheral blood lymphocytes. These observations not only change existing views on the length requirements for activation of CD4(+) HLA class II-restricted T cells, but also extend our knowledge about the flexibility of TCR recognition and the potential for cross-reactivity in the immune system.

Identification of candidate T-cell epitopes and molecular mimics in chronic Lyme disease.

Elucidating the cellular immune response to infectious agents is a prerequisite for understanding disease pathogenesis and designing effective vaccines. In the identification of microbial T-cell epitopes, the availability of purified or recombinant bacterial proteins has been a chief limiting factor. In chronic infectious diseases such as Lyme disease, immune-mediated damage may add to the effects of direct infection by means of molecular mimicry to tissue autoantigens. Here, we describe a new method to effectively identify both microbial epitopes and candidate autoantigens. The approach combines data acquisition by positional scanning peptide combinatorial libraries and biometric data analysis by generation of scoring matrices. In a patient with chronic neuroborreliosis, we show that this strategy leads to the identification of potentially relevant T-cell targets derived from both Borrelia burgdorferi and the host. We also found that the antigen specificity of a single T-cell clone can be degenerate and yet the clone can preferentially recognize different peptides derived from the same organism, thus demonstrating that flexibility in T-cell recognition does not preclude specificity. This approach has potential applications in the identification of ligands in infectious diseases, tumors and autoimmune diseases.

Effects of early postnatal exposure to low concentrations of carbon monoxide on cognitive functions in rats.

Male Wistar rats were exposed to 75 and 150 ppm of carbon monoxide (CO) from day 1 after birth until postnatal day 10 and their cognitive functions were evaluated at 3 and 18 months of age. The results show that early postnatal exposure to CO does not affect the acquisition and reacquisition of an active avoidance task in both adult and aged rats. Conversely, our previous findings indicate that prenatal exposure to CO (75 and 150 ppm), resulting in maternal blood carboxyhaemoglobin concentrations equivalent to those found in human cigarette smokers, induces long-lasting learning and memory deficits. These findings suggest that neurofunctional sequelae of prenatal CO exposure are notably different from those occurring in response to early postnatal exposure and that the vulnerability of the developing brain to prolonged, relatively mild, decrease in oxygen availability induced by CO critically depends on the particular period of developmental exposure.

Identification of peptides binding to IgG in the CSF of multiple sclerosis patients.

Phage displayed random peptide libraries were screened in order to identify phagotopes reacting with the IgG present in the cerebrospinal fluid (CSF) of multiple sclerosis (MS) patients. Six families of phagotopes each composed of different isolates were identified. These phagotopes were used as reagents, to characterise IgG present in the CSF of MS patients. The following results were obtained: (a) CSF antibodies from different patients display different specificities; (b) anti-phagotope antibodies are also present in the serum of MS patients; (c) Anti-phagotope antibodies are equally frequent in the serum of MS patients and of healthy individuals; (d) some of the anti-phagotope antibodies are enriched in the CSF of MS patients. These data show that the natural antigen(s) recognised by CSF antibodies is rather common in the general population. By using the selected phagotopes as immunogens in rabbits, we have derived large quantities of anti-phagotope antisera which can provide for useful tools toward the identification of the natural antigen(s) recognised by MS CSF antibodies.

Selection of biologically active peptides by phage display of random peptide libraries.

Random peptide libraries displayed on phage are used as a source of peptides for epitope mapping, for the identification of critical amino acids responsible for protein-protein interactions and as leads for the discovery of new therapeutics. Efficient and simple procedures have been devised to select peptides binding to purified proteins, to monoclonal and polyclonal antibodies and to cell surfaces in vivo and in vitro.