[Progressive multifocal leukoencephalopathy. Undesirable side effect of immunotherapy]

[Progressive multifocal leukoencephalopathy under natalizumab. Initial possibilities for risk stratification?]

Natalizumab (Tysabri®) is the first monoclonal antibody approved for the treatment of relapsing forms of multiple sclerosis (MS) but while treatment is highly efficient, it carries the risk of progressive multifocal leukoencephalopathy (PML). Based on reports of confirmed cases of PML, the risk of PML might increase beyond 24 months of treatment. Thus, attempts to stratify patients treated with natalizumab into those carrying higher or lower risk for developing PML are currently being undertaken. Among these strategies JC virus serology might potentially be the first tool available. As a large variety of methods have been published resulting in controversial results for JC virus seroprevalence, standardized testing will be mandatory when applying this method in clinical practice. In addition, risk management strategies for the seropositive majority of patients need to be redefined and optimized further.

Multiple Sklerose

Die multiple Sklerose (MS) ist eine der häufigsten neurologischen Erkrankungen, für deren Ursache es bislang keine einheitliche Erklärung gibt. Grundpfeiler der Diagnostik ist die Klinik, ergänzt durch die Magnetresonanztomographie (MRT). Eine Liquoruntersuchung zum Nachweis der entzündlichen Genese nachgewiesener multifokaler Störungen ist bei allen unklaren Fällen und bei älteren Patienten erforderlich. Zur Bestätigung und Verlaufskontrolle sind elektrophysiologische Verfahren hilfreich.

Animal models of multiple sclerosis--potentials and limitations

Experimental autoimmune encephalomyelitis (EAE) is still the most widely accepted animal model of multiple sclerosis (MS). Different types of EAE have been developed in order to investigate pathogenetic, clinical and therapeutic aspects of the heterogenic human disease. Generally, investigations in EAE are more suitable for the analysis of immunogenetic elements (major histocompatibility complex restriction and candidate risk genes) and for the study of histopathological features (inflammation, demyelination and degeneration) of the disease than for screening of new treatments. Recent studies in new EAE models, especially in transgenic ones, have in connection with new analytical techniques such as microarray assays provided a deeper insight into the pathogenic cellular and molecular mechanisms of EAE and potentially of MS. For example, it was possible to better delineate the role of soluble pro-inflammatory (tumor necrosis factor-α, interferon-γ and interleukins 1, 12 and 23), anti-inflammatory (transforming growth factor-β and interleukins 4, 10, 27 and 35) and neurotrophic factors (ciliary neurotrophic factor and brain-derived neurotrophic factor). Also, the regulatory and effector functions of distinct immune cell subpopulations such as CD4+ Th1, Th2, Th3 and Th17 cells, CD4+FoxP3+ Treg cells, CD8+ Tc1 and Tc2, B cells and γδ+ T cells have been disclosed in more detail. The new insights may help to identify novel targets for the treatment of MS. However, translation of the experimental results into the clinical practice requires prudence and great caution.