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The 37/67 kDa laminin receptor (LRP/LR) acts as a receptor for prions providing a promising target for the treatment of prion diseases. Recently, we selected anti-LRP/LR single-chain antibodies (scFvs) and proved a reduction of the peripheral PrP Sc propagation by passive immunotransfer into scrapie-infected mice. Here, we report the development of an in vivo gene delivery system based on adeno-associated virus (AAV) vectors expressing scFvs-S18 and -N3 directed against LRP/LR. Transduction of neuronal and non-neuronal cells with recombinant (r)AAV serotype 2 vectors encoding scFv-S18, -N3 and -C9 verified the efficient secretion of the antibodies. These vectors were administered via stereotactic intracerebral microinjection into the hippocampus of C57BL/6 mice, followed by intracerebral inoculation with 10 % RML at the same site 2 weeks post-injection of rAAV. After 90 days post-infection, scFv-S18 and -N3 expression resulted in the reduction of peripheral PrP Sc propagation by approximately 60 and 32 %, respectively, without a significant prolongation of incubation times and survival. Proof of rAAV vector DNA in spleen samples by real-time PCR strongly suggests a transport or trafficking of rAAV from the brain to the spleen, resulting in rAAV-mediated expression of scFv followed by reduced PrP Sc levels in the spleen most likely due to the blockage of the prion receptor LRP/LR by scFv.Prion diseases are fatal lethal neurodegenerative diseases affecting humans and animals (for review see Weissmann, 2004;Zuber et al., 2007a). None of the affected individuals can be treated or cured effectively (Ludewigs et al., 2007;Vana et al., 2007;Weissmann & Aguzzi, 2005). The abnormal form of the prion protein, PrP Sc , is frequently associated with infectivity and propagates mainly in the brain and the lymphoreticular system (LRS). Accumulation of the aggregated PrP Sc leads to neuronal death. PrP Sc is distinct from the host protein PrP c by its biochemical properties such as proteinase K sensitivity and insolubility, but harbours the same amino acid sequence. The generation of PrP Sc from PrP c involves conformational changes accompanied by modifications in the secondary structure of the protein (for review see Aguzzi & Weissmann, 1998;Prusiner, 1998;Weissmann, 2004).The 37/67 kDa laminin receptor (LRP/LR) is a multifunctional protein (i) playing an important role in cell adhesion, movement and growth of many cell types, (ii) acting as a receptor for some subtypes of adeno-associated 3These authors contributed equally to this work. (Morel et al., 2005). The fact that LRP levels are increased in organs of the LRS and central nervous system (CNS), such as spleen and brain, of infected animals (Rieger et al., 1997) strongly suggests that this receptor is not only essential for prion uptake after oral infection but also plays an important role for PrP Sc propagation and prion pathogenesis in the peripheral nervous system, including the LRS and CNS. Additionally, several laminin receptor isoforms have been found in mouse bra...

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To identify the dynamic transcriptional alterations in CNS during the development of prion disease, brains of scrapieinfected mice and age-matched, mock-inoculated controls were analyzed immediately before inoculation and at different time points post-inoculation using Affymetrix microarray technique. A total of 449 probe sets, representing 430 genes, showed differential expression between scrapie-and mockinoculated mice over the time course. These genes could be separated into two clusters according to expression patterns: the genes in cluster 1 demonstrated lower mRNA levels in scrapie-infected brains when compared with mock-inoculated brains, whereas genes in cluster 2 showed higher mRNA levels in scrapie-infected brains. Functional analysis of differentially expressed genes revealed the most severely affected biological process: cholesterol metabolism. The expression patterns of the cholesterol-related genes indicated an inhibited cholesterol synthesis in the diseased brains. Conspicuously, a number of cluster 1 genes, including some of cholesterol-related genes, showed not only decreasing mRNA levels in scrapie-infected brains but also increasing mRNA levels in mock-inoculated brains with increasing age. Quantitative RT-PCR analysis of some cholesterol-related genes in untreated mice suggested that changes of the examined genes observed in mock-inoculated brains are mainly age related. This finding indicated a link between agerelated genes and scrapie-associated neurodegeneration. Keywords: age-related gene, cholesterol metabolism, microarray, neurodegeneration, prion disease, scrapie. Prion diseases or transmissible spongiform encephalopathies (TSEs) are a class of fatal neurodegenerative diseases which occur in humans and various animal species. The prevalent forms of prion diseases are Creutzfeldt-Jakob disease (CJD) in humans, bovine spongiform encephalopathy in cattle and scrapie in sheep and goats. The neuropathology of prion diseases is characterized by generation and deposition of a misfolded, protease-resistant isoform (PrP Sc ) of a normal host protein, the prion protein (PrP C ), as well as by gliosis, vacuolation or spongiform degeneration, and neuronal cell death (Kretzschmar et al. 1996). So far, a number of experimental models for TSE have been established in animals. A widely used model is infecting mice with mouseadapted scrapie strains, which results in clinical signs and neuropathology associated with prion disease. The incubation interval (the time between inoculation and terminal disease) and the neuropathology depend on the genetic background of the hosts and the inoculated scrapie strains (Bruce 2003).In previous studies, microarray techniques were applied to study the global gene expression alterations in brains of scrapie-infected, terminally diseased mice (Riemer et al. 2004;Xiang et al. 2004) and in brains of post-mortem human CJD patients (Xiang et al. 2005). In brains of infected mice at terminal stages (TS), the up-regulation of genes Received November 17, 2006; revised...

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