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Adriano Aguzzi

Publications and source records attributed to Adriano Aguzzi.

At least 37 records · Page 2Linked to original sources
PubMed2005

No influence of amyloid-beta-degrading neprilysin activity on prion pathogenesis.

Transmissible spongiform encephalopathies are characterized by the accumulation of PrPSc, a protease-resistant form of a host-derived protein termed PrPC. Substantial evidence indicates that PrPSc represents an essential component of the infectious agent, which is termed prion. The accumulation of PrPSc within the central nervous system of prion-infected organisms is a dynamic process that is regulated both by production and by clearance of PrPSc. Although several proteases have been implicated in proteolysis of PrPC, the mechanisms underlying proteolysis of PrPSc remain unclear. Here, it was investigated whether neprilysin, a metalloprotease known to degrade extracellular amyloidogenic proteins such as amyloid-beta, plays a role in prion pathogenesis in vivo. As neprilysin has a broad substrate specificity and is localized subcellularly in the vicinity of PrP, it represents a plausible candidate for prion degradation. Prions were therefore administered to mice lacking or overexpressing neprilysin in brain. However, the gene dosage of neprilysin did not modulate accumulation of PrPSc in brain. Also, incubation times and clinical course of prion disease, as well as brain infectivity titres at terminal stage, were unaffected. These data rule out neprilysin as a major modulator of PrPSc accumulation and prion pathogenesis.

Amyloid beta-Peptides↗
PubMed2005

Paracrine inhibition of prion propagation by anti-PrP single-chain Fv miniantibodies.

Prion diseases are characterized by the deposition of PrP(Sc), an abnormal form of the cellular prion protein PrP(C). A growing body of evidence suggests that antibodies to PrP(C) can antagonize deposition of PrP(Sc). However, host tolerance hampers the induction of immune responses to PrP(C), and cross-linking of PrP(C) by bivalent anti-PrP antibodies is neurotoxic. In order to obviate these problems, we explored the antiprion potential of recombinant single-chain antibody (scFv) fragments. scFv fragments derived from monoclonal anti-PrP antibody 6H4, flagged with c-myc and His6 tags, were correctly processed and secreted by mammalian RD-4 rhabdomyosarcoma cells. When cocultured with cells secreting anti-PrP scFv, chronically prion-infected neuroblastoma cells ceased to produce PrP(Sc), even if antibody-producing cells were physically separated from target cells in transwell cultures. Expression of scFv with irrelevant specificity, or of similarly tagged molecules, was not curative. Therefore, eukaryotically expressed scFv exerts a paracrine antiprion activity. The effector functions encoded by immunoglobulin constant domains are unnecessary for this effect. Because of their small size and their monovalent binding, scFv fragments may represent candidates for gene transfer-based immunotherapy of prion diseases.

Amino Acid Sequence↗
PubMed2005

Circumventing tolerance to the prion protein (PrP): vaccination with PrP-displaying retrovirus particles induces humoral immune responses against the native form of cellular PrP.

Passive immunization with antibodies directed against the cellular form of the prion protein (PrPC) can protect against prion disease. However, active immunization with recombinant prion protein has so far failed to induce antibodies directed against native PrPC expressed on the cell surface. To develop an antiprion vaccine, a retroviral display system presenting either the full-length mouse PrP (PrP209) or the C-terminal 111 amino acids (PrP111) fused to the transmembrane domain of the platelet-derived growth factor receptor was established. Western blot analysis and immunogold electron microscopy of the retroviral display particles revealed successful incorporation of the fusion proteins into the particle membrane. Interestingly, retroviral particles displaying PrP111 (PrPD111 retroparticles) showed higher incorporation efficiencies than those displaying PrP209. Already 7 days after intravenous injection of PrPD111 retroparticles, PrPC-deficient mice (Prnp(o/o)) showed high immunoglobulin M (IgM) and IgG titers specifically binding the native PrPC molecule as expressed on the surface of T cells isolated from PrPC-overexpressing transgenic mice. More importantly, heterozygous Prnp(+/o) mice and also wild-type mice showed PrPC-specific IgM and IgG antibodies upon vaccination with PrPD111 retroparticles, albeit at considerably lower levels. Bacterially expressed recombinant PrP, in contrast, was unable to evoke IgG antibodies recognizing native PrPC in wild-type mice. Thus, our data show that PrP or parts thereof can be functionally displayed on retroviral particles and that immunization with PrP retroparticles may serve as a novel promising strategy for vaccination against transmissible spongiform encephalitis.

Adjuvants, Immunologic↗
PubMed2005

Unchanged survival rates of 14-3-3gamma knockout mice after inoculation with pathological prion protein.

The diagnosis of sporadic Creutzfeldt-Jakob disease (CJD) is based on typical clinical findings and is supported by a positive 14-3-3 Western blot of cerebrospinal fluid. However, it is not clear whether 14-3-3 indicates general neuronal damage or is of pathophysiological relevance in CJD. The fact that the 14-3-3 isoform spectrum in cerebrospinal fluid does not correspond to that found in the brain points to a regulated process. To investigate a possible role of 14-3-3 proteins in transmissible spongiform diseases, we generated a 14-3-3gamma-deficient mutant mouse line by using a classical knockout strategy. The anatomy and cage behavior of the mutant mice were normal. Western blot analyses of brain homogenates revealed no changes in the protein expression of other 14-3-3 isoforms (epsilon, beta, zeta, and eta). Proteomic analyses of mouse brains by two-dimensional differential gel electrophoresis showed that several proteins, including growth hormone, 1-Cys peroxiredoxin, CCT-zeta, glucose-6-phosphate isomerase, GRP170 precursor, and alpha-SNAP, were differentially expressed. Mutant and wild-type mice were inoculated either intracerebrally or intraperitoneally with the Rocky Mountain Laboratory strain of scrapie, but no differences were detected in the postinoculation survival rates. These results indicate that 14-3-3gamma is unlikely to play a causal role in CJD and related diseases.

14-3-3 Proteins↗
PubMed2005

Approaches to therapy of prion diseases.

Devising approaches to the therapy of transmissible spongiform encephalopathies, or prion diseases, is beset by many difficulties. For one, the nature of the infectious agent, the prion, is understood only in outline, and its composition, structure, and mode of replication are still shrouded in mystery. In addition, the mechanism of pathogenesis is not well understood. Because clinical disease affects mainly the brain parenchyme, therapeutic agents must be able to traverse the brain-blood barrier (BBB) or have to be introduced directly into the cerebrospinal fluid or brain tissue. And finally, because the disease is usually recognized only after onset of severe clinical symptoms, the question arises as to whether the neurodegenerative processes can be reversed to any extent after a successful eradication of the agent.

Animals↗
PubMed2004

A pathogenic PrP mutation and doppel interfere with polarized sorting of the prion protein.

Several proteins linked to neurodegenerative diseases, such as the beta-amyloid precursor protein, amyloid beta-peptide, beta-secretase, and tau, undergo selective polarized sorting. We investigated polarized sorting of the mammalian prion protein (PrP(C)) and its homologue doppel (Dpl). In contrast to Dpl, which accumulates on the apical surface, PrP(C) is targeted selectively to the basolateral side in Madin-Darby canine kidney cells. An extensive deletion and domain swapping analysis revealed that the internal hydrophobic domain (HD) of PrP (amino acids 113-133) confers basolateral sorting in a dominant manner. PrP mutants lacking the HD are sorted apically, while Dpl chimeras containing the HD of PrP are directed to the basolateral membrane. Furthermore, a pathogenic PrP missense mutation within the HD leads to aberrant apical sorting of PrP as well.

Animals↗
PubMed2004

Efficient inhibition of prion replication by PrP-Fc(2) suggests that the prion is a PrP(Sc) oligomer.

Soluble dimeric prion protein (PrP-Fc(2)) binds to the disease-associated prion protein PrP(Sc), and inhibits prion replication when expressed in transgenic mice. Prion inhibition is effective even if PrP-Fc(2) is expressed at low levels, suggesting that its affinity for PrP(Sc) is higher than that of monomeric PrP(C). Here, we model prion accumulation as an exponential replication cycle of prion elongation and breakage. The exponential growth rate corresponding to this cycle is reflected in the incubation period of the disease. We use a mathematical model to calculate the exponential growth rate, and fit the model to in vivo data on prion incubation times corresponding to different levels of PrP(C) and PrP-Fc(2). We find an excellent fit of the model to the data. Surprisingly, targeting of PrP(Sc) can be effective at concentrations of PrP-Fc(2) lower than that of PrP(C), even if PrP-Fc(2) and PrP(C) have the same affinity for PrP(Sc). The best fit of our model to data predicts that the replicative prion consists of PrP(Sc) oligomers with a mean size of four to 15 units.

Animals↗
PubMed2004

Humoral immune response to native eukaryotic prion protein correlates with anti-prion protection.

Prion diseases are characterized by the deposition of an abnormal form (termed PrP(Sc)) of the cellular prion protein (PrP(C)). Because antibodies to PrP(C) can antagonize deposition of PrP(Sc) in cultured cells and mice, they may be useful for anti-prion therapy. However, induction of protective anti-prion immune responses in WT animals may be hindered by host tolerance. Here, we studied the cellular and molecular basis of tolerance to PrP(C). Immunization of Prnp(o/o) mice with bacterially expressed PrP (PrP(REC)) resulted in vigorous humoral immune responses to PrP(REC) and native cell-surface PrP(C). Instead, WT mice yielded antibodies that failed to recognize native PrP(C) despite immunoreactivity with PrP(REC), even after immunization with PrP-PrP polyprotein and/or upon administration of anti-OX40 antibodies. Consequently, immunized WT mice experienced insignificantly delayed prion pathogenesis upon peripheral prion challenge. Anti-PrP immune responses in Prnp(o/o) mice were completely abrogated by transgenic expression of PrP(C) in B cells, T cells, neurons, or hepatocytes, but only moderately reduced by expression in myelinating cells, despite additional thymic Prnp transcription in each case. We conclude that tolerance to PrP(C) can coexist with immunoreactivity to PrP(REC) and does not depend on thymic PrP(C) expression. Its circumvention might represent an important step toward the development of effective anti-prion immunotherapy.

Animals↗
PubMed2004

The AP-1 transcription factor c-Jun is required for efficient axonal regeneration.

Nerve injury triggers numerous changes in the injured neurons and surrounding nonneuronal cells that ultimately result in successful target reinnervation or cell death. c-Jun is a component of the heterodimeric AP-1 transcription factor, and c-Jun is highly expressed in response to neuronal trauma. Here we have investigated the role of c-jun during axonal regeneration using mice lacking c-jun in the central nervous system. After transection of the facial nerve, the absence of c-Jun caused severe defects in several aspects of the axonal response, including perineuronal sprouting, lymphocyte recruitment, and microglial activation. c-Jun-deficient motorneurons were atrophic, resistant to axotomy-induced cell death, and showed reduced target muscle reinnervation. Expression of CD44, galanin, and alpha7beta1 integrin, molecules known to be involved in regeneration, was greatly impaired, suggesting a mechanism for c-Jun-mediated axonal growth. Taken together, our results identify c-Jun as an important regulator of axonal regeneration in the injured central nervous system.

Animals↗
PubMed2004

Intrinsic resistance of oligodendrocytes to prion infection.

Within the CNS, the normal form of cellular prion protein (PrP(C)) is expressed on neurons, oligodendrocytes, and astrocytes. The contribution of these cell types to prion replication and pathogenesis is unclear. To assess the role of oligodendrocytes, we expressed PrP(C) under the control of the myelin basic protein (MBP) promoter in mice lacking endogenous PrP(C). PrP(C) was detected in oligodendrocytes and Schwann cells but not in neurons and astrocytes. MBP-PrP mice never developed scrapie after intracerebral, intraperitoneal, or intraocular challenge with scrapie prions. Transgenic brains did not contain protease-resistant prion protein and did not transmit scrapie when inoculated into PrP(C)-overexpressing indicator mice. To investigate whether prion spread within the CNS depends on oligodendrocytic PrP(C), we implanted PrP(C)-overexpressing neuroectodermal grafts into MBP-PrP brains. After intraocular prion inoculation, none of the grafts showed spongiform encephalopathy or prion infectivity. Hence oligodendrocytes do not support cell-autonomous prion replication, establishment of subclinical disease, and neural spread of prions. Prion resistance sets oligodendrocytes aside from both neurons and astrocytes.

Animals↗
PubMed2004

IL-6 is required for glioma development in a mouse model.

The pleiotropic cytokine interleukin-6 (IL-6) contributes to malignant progression and apoptosis resistance of various cancer types. Although IL-6 is elevated in malignant gliomas, and glioma cells respond to IL-6, its functional role in gliomagenesis is unclear. We have investigated this role of IL-6 in a mouse model of spontaneous astrocytoma by crossbreeding glial fibrillary acidic protein (GFAP)-viral src oncogene transgenic mice with IL-6-deficient mice. We show here that ablation of IL-6 prevents tumour formation in these predisposed animals, but did not affect preneoplastic astrogliosis. Moreover, we demonstrate phosphorylation and nuclear translocation of the transcription factor signal transducer and activator of transcription (STAT)3, a prerequisite for IL-6 signalling, in 51 human gliomas WHO grade II-IV and all experimental mouse tumours investigated. Together with the observation that STAT3 activation increases with malignancy, these findings indicate an important role for IL-6 in the development and malignant progression of astrocytomas.

Animals↗
PubMed2004

Disruption of Doppel prevents neurodegeneration in mice with extensive Prnp deletions.

The Prnp gene encodes the cellular prion protein PrP(C). Removal of its ORF does not result in pathological phenotypes, but deletions extending into the upstream intron result in cerebellar degeneration, possibly because of ectopic cis-activation of the Prnd locus that encodes the PrP(C) homologue Doppel (Dpl). To test this hypothesis, we removed Prnd from Prnp(o/o) mice by transallelic meiotic recombination. Balanced loxP-mediated ablation yielded mice lacking both PrP(C) and Dpl (Prn(o/o)), which developed normally and showed unimpaired immune functions but suffered from male infertility. However, removal of the Prnd locus abolished cerebellar degeneration, proving that this phenotype is caused by Dpl upregulation. The absence of compound pathological phenotypes in Prn(o/o) mice suggests the existence of alternative compensatory mechanisms. Alternatively, Dpl and PrP(C) may exert distinct functions despite having partly overlapping expression profiles.

Amyloid↗
PubMed2004

Lymphoid follicle destruction and immunosuppression after repeated CpG oligodeoxynucleotide administration.

DNA containing unmethylated cytidyl guanosyl (CpG) sequences, which are underrepresented in mammalian genomes but prevalent in prokaryotes, is endocytosed by cells of the innate immune system, including macrophages, monocytes and dendritic cells, and activates a pathway involving Toll-like receptor-9 (TLR9). CpG-containing oligodeoxynucleotides (CpG-ODN) are potent stimulators of innate immunity, and are currently being tested as adjuvants of antimicrobial, antiallergic, anticancer and antiprion immunotherapy. Little is known, however, about the consequences of repeated CpG-ODN administration, which is advocated for some of these applications. Here we report that daily injection of 60 microg CpG-ODN dramatically alters the morphology and functionality of mouse lymphoid organs. By day 7, lymphoid follicles were poorly defined; follicular dendritic cells (FDC) and germinal center B lymphocytes were suppressed. Accordingly, CpG-ODN treatment for > or =7 d strongly reduced primary humoral immune responses and immunoglobulin class switching. By day 20, mice developed multifocal liver necrosis and hemorrhagic ascites. All untoward effects were strictly dependent on CpG and TLR9, as neither the CpG-ODN treatment of Tlr9(-/-) mice nor the repetitive challenge of wild-type mice with nonstimulatory ODN (AT-ODN) or with the TLR3 agonist polyinosinic:cytidylic acid (polyI:C) were immunotoxic or hepatotoxic.

Adjuvants, Immunologic↗
PubMed2004

Mammalian prion biology: one century of evolving concepts.

Prions have been responsible for an entire century of tragic episodes. Fifty years ago, kuru decimated the population of Papua New Guinea. Then, iatrogenic transmission of prions caused more than 250 cases of Creutzfeldt-Jakob disease. More recently, transmission of bovine spongiform encephalopathy to humans caused a widespread health scare. On the other hand, the biology of prions represents a fascinating and poorly understood phenomenon, which may account for more than just diseases and may represent a fundamental mechanism of crosstalk between proteins. The two decades since Stanley Prusiner's formulation of the protein-only hypothesis have witnessed spectacular advances, and yet some of the most basic questions in prion science have remained unanswered.

Animals↗
PubMed2004

Creutzfeldt-Jakob disease and inclusion body myositis: abundant disease-associated prion protein in muscle.

Pathologicalprion protein (PrP(Sc)) is the hallmark of prion diseases affecting primarily the central nervous system. Using immunohistochemistry, paraffin-embedded tissue blot, and Western blot, we demonstrated abundant PrP(Sc) in the muscle of a patient with sporadic Creutzfeldt-Jakob disease and inclusion body myositis. Extraneural PrP(C)-PrP(Sc) conversion in Creutzfeldt-Jakob disease appears to become prominent when PrP(C) is abundantly available as substrate, as in inclusion body myositis muscle.

Aged↗