Manuela Fluess

Justus-Liebig-Universität Gießen, Gieben, Hesse, Germany

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Publications (3)12.08 Total impact

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    ABSTRACT: The open reading frame III of Borna disease virus (BDV) codes for a protein with a mass of 16 kDa, named p16 or BDV-M. p16 was described as an N-glycosylated protein in several previous publications and therefore was termed gp18, although the amino acid sequence of p16 does not contain any regular consensus sequence for N glycosylation. We examined glycosylation of p16 and studied its membrane topology using antisera raised against peptides, which comprise the N and the C termini. Neither an N- nor a C-terminal peptide is cleaved from p16 during maturation. Neither deglycosylation of p16 by endoglycosidases nor binding of lectin to p16 was detectable. Introduction of typical N-glycosylation sites at the proposed sites of p16 failed in carbohydrate attachment. Flotation experiments with membranes of BDV-infected cells on density gradients revealed that p16 is not an integral membrane protein, since it can be dissociated from membranes. Our experimental data strongly suggest that p16 is a typical nonglycosylated matrix protein associated at the inner surface of the viral membrane, as is true for homologous proteins of other members of the Mononegavirales order.
    Journal of Virology 01/2002; 75(24):12098-104. · 5.08 Impact Factor
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    ABSTRACT: Infection with the neurotropic Borna disease virus (BDV) causes an immune-mediated neurological disease in a broad range of species. In addition to encephalitis, BDV-infected Lewis rats develop a retinitis histologically characterized by the loss of most retinal neurons. By contrast, the dominating retinal macroglia, the Müller cells, do not degenerate. It is known from several models of neurodegeneration that glial cells may survive but undergo significant alterations of their physiological parameters. This prompted us to study the electrophysiology and ATP-induced changes of intracellular Ca2+-concentration ([Ca2+]i) in Müller cells from BDV-infected rat retinae. Freshly isolated cells were used for whole-cell patch-clamp recordings. Whereas neither zero current potentials nor membrane resistances showed significant alterations, the membrane capacitance increased in cells from BDV-infected rats during survival times of up to 8 months. This process was accompanied by a decrease in K+ current densities. Müller cells from BDV-infected rats were characterized by expression of a prominent fast-inactivating A-type K+ current which was rarely found in control cells. Moreover, the number of cells displaying Na+ currents was slightly increased after BDV-infection. ATP evoked increases in [Ca2+]i in Müller cells within retinal wholemounts of both control and BDV-infected animals. However, the number of ATP-responding isolated cells increased from 24% (age-matched controls) to 78% (cells from animals ≥18 weeks after infection). We conclude that in BDV-induced retinopathy, reactive rat Müller cells change their physiological parameters but these changes are different from those in Müller cells during proliferative vitreoretinopathy in man and rabbit. GLIA 35:213–223, 2001. © 2001 Wiley-Liss, Inc.
    Glia 07/2001; 35(3):213 - 223. · 5.07 Impact Factor
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    ABSTRACT: Retinae of Borna disease virus (BDV)-infected Lewis rats were investigated with emphasis on long-term changes in organotypic tissue organization and glia-neuron relationship. Virus inoculation was attained via intracerebral BDV injection. Following survival times ranging between two and eight months, the retinal thickness was reduced up to one third of that of controls. Photoreceptor segments were completely extinguished and the number of neurons was dramatically reduced. The typical laminar organization of the retina was largely dissolved. Electron microscopy revealed severe spongy degeneration. Large numbers of activated microglia and macrophages were found, both cell types performing very active phagocytosis. The microglial cells expressed an extraordinary phenotype as characterized by large numbers of processes, with some of them penetrating the endfeet of Müller cells and others establishing highly complex interdigitations with vacuolized swellings and endings of neuronal processes. Müller cells were not reduced in number but displayed clear indications of gliosis such as alterations in the immunoreactivity for filament proteins and glutamine synthetase, significantly thickened stem processes, and an altered pattern of K(+) currents in patch-clamp recordings. These findings demonstrate for the first time long-term neuron-glia interactions in the retina of BDV-infected rats. Moreover, the data contribute to our knowledge on structural and functional alterations accompanying persisting virus infection in the central nervous system.
    Journal of Neurocytology 01/2001; 30(9-10):801-20. · 1.94 Impact Factor