RESUMO
COVID-19 pandemic caused by SARS-CoV-2 infection is a public health emergency. COVID-19 typically exhibits respiratory illness. Unexpectedly, emerging clinical reports indicate that neurological symptoms continue to rise, suggesting detrimental effects of SARS-CoV-2 on the central nervous system (CNS). Here, we show that a Düsseldorf isolate of SARS-CoV-2 enters 3D human brain organoids within 2 days of exposure. We identified that SARS-CoV-2 preferably targets neurons of brain organoids. Imaging neurons of organoids reveal that SARS-CoV-2 exposure is associated with altered distribution of Tau from axons to soma, hyperphosphorylation, and apparent neuronal death. Our studies, therefore, provide initial insights into the potential neurotoxic effect of SARS-CoV-2 and emphasize that brain organoids could model CNS pathologies of COVID-19.
Assuntos
Betacoronavirus/fisiologia , Encéfalo/virologia , Neurônios/virologia , Animais , Morte Celular , Chlorocebus aethiops , Humanos , Doenças do Sistema Nervoso/virologia , Organoides , SARS-CoV-2 , Células Vero , Proteínas tau/metabolismoRESUMO
Neurodegenerative diseases feature specific misfolded or misassembled proteins associated with neurotoxicity. The precise mechanisms by which protein aggregates first arise in the majority of sporadic cases have remained unclear. Likely, a first critical mass of misfolded proteins starts a vicious cycle of a prion-like expansion. We hypothesize that viruses, having evolved to hijack the host cellular machinery for catalyzing their replication, lead to profound disturbances of cellular proteostasis, resulting in such a critical mass of protein aggregates. Here, we investigated the effect of influenza virus (H1N1) strains on proteostasis of proteins associated with neurodegenerative diseases in Lund human mesencephalic dopaminergic cells in vitro and infection of Rag knockout mice in vivo. We demonstrate that acute H1N1 infection leads to the formation of α-synuclein and Disrupted-in-Schizophrenia 1 (DISC1) aggregates, but not of tau or TDP-43 aggregates, indicating a selective effect on proteostasis. Oseltamivir phosphate, an antiinfluenza drug, prevented H1N1-induced α-synuclein aggregation. As a cell pathobiological mechanism, we identified H1N1-induced blocking of autophagosome formation and inhibition of autophagic flux. In addition, α-synuclein aggregates appeared in infected cell populations connected to the olfactory bulbs following intranasal instillation of H1N1 in Rag knockout mice. We propose that H1N1 virus replication in neuronal cells can induce seeds of aggregated α-synuclein or DISC1 that may be able to initiate further detrimental downstream events and should thus be considered a risk factor in the pathogenesis of synucleinopathies or a subset of mental disorders. More generally, aberrant proteostasis induced by viruses may be an underappreciated factor in initiating protein misfolding.
Assuntos
Proteínas de Homeodomínio/fisiologia , Vírus da Influenza A Subtipo H1N1/patogenicidade , Influenza Humana/complicações , Infecções por Orthomyxoviridae/complicações , Proteostase , Sinucleinopatias/etiologia , alfa-Sinucleína/química , Animais , Neurônios Dopaminérgicos/metabolismo , Neurônios Dopaminérgicos/patologia , Feminino , Humanos , Influenza Humana/virologia , Camundongos , Camundongos Knockout , Proteínas do Tecido Nervoso/metabolismo , Infecções por Orthomyxoviridae/virologia , Multimerização Proteica , Sinucleinopatias/metabolismo , Sinucleinopatias/patologia , alfa-Sinucleína/metabolismoRESUMO
OBJECTIVES: The heterogeneity of Amyloid-beta (Aß) plaque load in patients with Alzheimer's disease (AD) has puzzled neuropathology. Since brain Aß plaque load does not correlate with cognitive decline, neurotoxic soluble Aß oligomers have been championed as disease-causing agents in early AD. So far, investigating molecular interactions between soluble oligomeric Aß and insoluble Aß in vivo has been difficult because of the abundance of Aß oligomer species and the kinetic equilibrium in which they coexist. Here, we investigated whether Aß plaque heterogeneity relates to interactions of different Aß conformers. MATERIALS AND METHODS: We took advantage of transgenic mice that generate exclusively Aß dimers (tgDimer mice) but do not develop Aß plaques or neuroinflammation during their lifetime, crossed them to the transgenic CRND8 mice that develop plaques after 90 days and measured Aß plaque load using immunohistochemical and biochemical assays. Furthermore, we performed in vitro thioflavin T (ThT) aggregation assays titrating synthetic Aß42 -S8C dimers into fibril-forming synthetic Aß42 . RESULTS: We observed a lower number of Aß plaques in the brain of double transgenic mice compared to tgCRND8 mice alone while the average plaque size remained unaltered. Corroborating these in vivo findings, synthetic Aß-S8C dimers inhibited fibril formation of wild-type Aß also in vitro, seen by an increased half-time in the ThT assay. CONCLUSIONS: Our study indicates that Aß dimers directly interfere with Aß fibril formation in vivo and in vitro. The variable interaction of Aß dimers with insoluble Aß seeds could thus contribute to the heterogeneity of Aß plaque load in AD patients.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Encéfalo/patologia , Placa Amiloide/metabolismo , Placa Amiloide/patologia , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Animais , Disfunção Cognitiva/patologia , Humanos , Camundongos Transgênicos , Doenças Neuroinflamatórias/metabolismo , Doenças Neuroinflamatórias/patologia , Fragmentos de Peptídeos/metabolismoRESUMO
Genes associated with immune response and inflammation have been identified as genetic risk factors for late-onset Alzheimer´s disease (LOAD). The rare R47H variant within triggering receptor expressed on myeloid cells 2 (TREM2) has been shown to increase the risk for developing Alzheimer's disease (AD) 2-3-fold. Here, we report the generation and characterization of a model of late-onset Alzheimer's disease (LOAD) using lymphoblast-derived induced pluripotent stem cells (iPSCs) from patients carrying the TREM2 R47H mutation, as well as from control individuals without dementia. All iPSCs efficiently differentiated into mature neuronal cultures, however AD neuronal cultures showed a distinct gene expression profile. Furthermore, manipulation of the iPSC-derived neuronal cultures with an Aß-S8C dimer highlighted metabolic pathways, phagosome and immune response as the most perturbed pathways in AD neuronal cultures. Through the construction of an Aß-induced gene regulatory network, we were able to identify an Aß signature linked to protein processing in the endoplasmic reticulum (ER), which emphasized ER-stress, as a potential causal role in LOAD. Overall, this study has shown that our AD-iPSC based model can be used for in-depth studies to better understand the molecular mechanisms underlying the etiology of LOAD and provides new opportunities for screening of potential therapeutic targets.
Assuntos
Doença de Alzheimer/genética , Glicoproteínas de Membrana/genética , Receptores Imunológicos/genética , Idoso , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/genética , Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Diferenciação Celular/genética , Retículo Endoplasmático/genética , Retículo Endoplasmático/metabolismo , Feminino , Redes Reguladoras de Genes/genética , Predisposição Genética para Doença/genética , Variação Genética/genética , Humanos , Masculino , Glicoproteínas de Membrana/metabolismo , Modelos Biológicos , Mutação/genética , Células Mieloides/metabolismo , Neurônios/metabolismo , Células-Tronco Pluripotentes/metabolismo , Células-Tronco Pluripotentes/fisiologia , Receptores Imunológicos/metabolismoRESUMO
Despite amyloid plaques, consisting of insoluble, aggregated amyloid-ß peptides, being a defining feature of Alzheimer's disease, their significance has been challenged due to controversial findings regarding the correlation of cognitive impairment in Alzheimer's disease with plaque load. The amyloid cascade hypothesis defines soluble amyloid-ß oligomers, consisting of multiple amyloid-ß monomers, as precursors of insoluble amyloid-ß plaques. Dissecting the biological effects of single amyloid-ß oligomers, for example of amyloid-ß dimers, an abundant amyloid-ß oligomer associated with clinical progression of Alzheimer's disease, has been difficult due to the inability to control the kinetics of amyloid-ß multimerization. For investigating the biological effects of amyloid-ß dimers, we stabilized amyloid-ß dimers by an intermolecular disulphide bridge via a cysteine mutation in the amyloid-ß peptide (Aß-S8C) of the amyloid precursor protein. This construct was expressed as a recombinant protein in cells and in a novel transgenic mouse, termed tgDimer mouse. This mouse formed constant levels of highly synaptotoxic soluble amyloid-ß dimers, but not monomers, amyloid-ß plaques or insoluble amyloid-ß during its lifespan. Accordingly, neither signs of neuroinflammation, tau hyperphosphorylation or cell death were observed. Nevertheless, these tgDimer mice did exhibit deficits in hippocampal long-term potentiation and age-related impairments in learning and memory, similar to what was observed in classical Alzheimer's disease mouse models. Although the amyloid-ß dimers were unable to initiate the formation of insoluble amyloid-ß aggregates in tgDimer mice, after crossbreeding tgDimer mice with the CRND8 mouse, an amyloid-ß plaque generating mouse model, Aß-S8C dimers were sequestered into amyloid-ß plaques, suggesting that amyloid-ß plaques incorporate neurotoxic amyloid-ß dimers that by themselves are unable to self-assemble. Our results suggest that within the fine interplay between different amyloid-ß species, amyloid-ß dimer neurotoxic signalling, in the absence of amyloid-ß plaque pathology, may be involved in causing early deficits in synaptic plasticity, learning and memory that accompany Alzheimer's disease.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Transtornos Cognitivos/metabolismo , Plasticidade Neuronal/fisiologia , Placa Amiloide/metabolismo , Multimerização Proteica/fisiologia , Peptídeos beta-Amiloides/genética , Animais , Transtornos Cognitivos/genética , Transtornos Cognitivos/patologia , Hipocampo/metabolismo , Hipocampo/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Técnicas de Cultura de Órgãos , Placa Amiloide/genética , Placa Amiloide/patologiaRESUMO
Determining Aß levels in body fluids remains a powerful tool in the diagnostics of Alzheimer's disease. This report delineates a new supramolecular strategy which increases the affinity of antibodies towards Aß to make diagnostic procedures more sensitive. A monoclonal antibody IC16 was generated to an N-terminal epitope of Aß and the variable regions of the heavy and light chains were cloned as a recombinant protein (scFv). A 6 × histidine tag was fused to the C-terminus of IC16-scFv allowing hybridization with a small organic ß-sheet binder via Ni-NTA complexation. On the other hand, a multivalent nitrilotriacetic acid (NTA)-equipped trimeric aminopyrazole (AP) derivative was synthesized based on a cyclam platform; and experimental evidence was obtained for efficient Ni(2+)-mediated complex formation with the histidine-tagged antibody species. In a proof of principle experiment the hybrid molecule showed a strong increase in affinity towards Aß. Thus, the specific binding power of recombinant antibody fragments to their ß-sheet rich targets can be conveniently enhanced by non-covalent hybridization with small organic ß-sheet binders.
Assuntos
Doença de Alzheimer/diagnóstico , Pirazóis/química , Anticorpos de Cadeia Única/química , Peptídeos beta-Amiloides/química , Catálise , Ensaio de Imunoadsorção Enzimática , Epitopos/química , Histidina/química , Humanos , Hidrogênio/química , Concentração de Íons de Hidrogênio , Fragmentos de Imunoglobulinas/química , Imunoterapia , Ligantes , Espectroscopia de Ressonância Magnética , Níquel/química , Ácido Nitrilotriacético/química , Fragmentos de Peptídeos/genética , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Proteínas Recombinantes/químicaRESUMO
We present a novel small molecule antiviral chemotype that was identified by an unconventional cell-free protein synthesis and assembly-based phenotypic screen for modulation of viral capsid assembly. Activity of PAV-431, a representative compound from the series, has been validated against infectious viruses in multiple cell culture models for all six families of viruses causing most respiratory diseases in humans. In animals, this chemotype has been demonstrated efficacious for porcine epidemic diarrhoea virus (a coronavirus) and respiratory syncytial virus (a paramyxovirus). PAV-431 is shown to bind to the protein 14-3-3, a known allosteric modulator. However, it only appears to target the small subset of 14-3-3 which is present in a dynamic multi-protein complex whose components include proteins implicated in viral life cycles and in innate immunity. The composition of this target multi-protein complex appears to be modified upon viral infection and largely restored by PAV-431 treatment. An advanced analog, PAV-104, is shown to be selective for the virally modified target, thereby avoiding host toxicity. Our findings suggest a new paradigm for understanding, and drugging, the host-virus interface, which leads to a new clinical therapeutic strategy for treatment of respiratory viral disease.
Assuntos
Antivirais , Antivirais/farmacologia , Antivirais/química , Humanos , Animais , Proteínas 14-3-3/metabolismo , Complexos Multiproteicos/metabolismo , Interações Hospedeiro-Patógeno/efeitos dos fármacos , Linhagem CelularRESUMO
The aetiology of Alzheimer's disease is thought to include functional impairment of synapses and synapse loss as crucial pathological events leading to cognitive dysfunction and memory loss. Oligomeric amyloid-ß peptides are well known to induce functional damage, destabilization and loss of brain synapses. However, the complex molecular mechanisms of amyloid-ß action resulting ultimately in synapse elimination are incompletely understood, thus limiting knowledge of potential therapeutic targets. Under physiological conditions, long-term synapse stability is mediated by trans-synaptically interacting adhesion molecules such as the homophilically binding N-cadherin/catenin complexes. In this study, we addressed whether inhibition of N-cadherin function affects amyloid-ß-induced synapse impairment. We found that blocking N-cadherin function, both by specific peptides interfering with homophilic binding and by expression of a dominant-negative, ectodomain-deleted N-cadherin mutant, resulted in a strong acceleration of the effect of amyloid-ß on synapse function in cultured cortical neurons. The frequency of AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptor-mediated miniature excitatory postsynaptic currents was reduced upon amyloid-ß application much earlier than observed in controls. We further hypothesized that ectodomain-shed, transmembrane C-terminal fragments that are generated during N-cadherin proteolytic processing might similarly enhance amyloid-ß-induced synapse damage. Indeed, expression of human N-cadherin C-terminal fragment 1 strongly accelerated amyloid-ß-triggered synapse impairment. Ectodomain-shed N-cadherin C-terminal fragment 1 is further proteolytically cleaved by γ-secretase. Therefore, both pharmacological inhibition of γ-secretase and expression of the dominant-negative presenilin 1 mutant L166P were used to increase the presence of endogeneous N-cadherin C-terminal fragment 1. Under these conditions, we again found a strong acceleration of amyloid-ß-induced synapse impairment, which could be compensated by over-expression of full-length N-cadherin. Intriguingly, western blot analysis of post-mortem brains from patients with Alzheimer's disease revealed an enhanced presence of N-cadherin C-terminal fragment 1. Thus, an inhibition of N-cadherin function by proteolytically generated N-cadherin C-terminal fragment 1 might play an important role in Alzheimer's disease progression by accelerating amyloid-ß-triggered synapse damage.
Assuntos
Peptídeos beta-Amiloides/fisiologia , Antígenos CD/fisiologia , Caderinas/fisiologia , Fragmentos de Peptídeos/fisiologia , Processamento de Proteína Pós-Traducional/fisiologia , Sinapses/metabolismo , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/metabolismo , Doença de Alzheimer/fisiopatologia , Secretases da Proteína Precursora do Amiloide/antagonistas & inibidores , Peptídeos beta-Amiloides/farmacologia , Animais , Antígenos CD/biossíntese , Antígenos CD/genética , Caderinas/antagonistas & inibidores , Caderinas/biossíntese , Caderinas/genética , Carbamatos/farmacologia , Células Cultivadas , Dipeptídeos/farmacologia , Feminino , Expressão Gênica/fisiologia , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Potenciais Pós-Sinápticos em Miniatura/efeitos dos fármacos , Potenciais Pós-Sinápticos em Miniatura/fisiologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/fisiologia , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/farmacologia , Presenilina-1/genética , Presenilina-1/fisiologia , ProteóliseRESUMO
The prion agent is the infectious particle causing spongiform encephalopathies in animals and humans and is thought to consist of an altered conformation (PrP(Sc)) of the normal and ubiquitous prion protein PrP(C). The interaction of the prion agent with the immune system, particularly the humoral immune response, has remained unresolved. Here we investigated the immunogenicity of full-length native and infectious prions, as well as the specific biological effects of the resulting monoclonal antibodies (MAbs) on the binding and clearance of prions in cell culture and in in vivo therapy. Immunization of prion knockout (Prnp(0/0)) mice with phosphotungstic acid-purified mouse prions resulted in PrP-specific monoclonal antibodies with binding specificities selective for PrP(Sc) or for both PrP(C) and PrP(Sc). PrP(Sc)-specific MAb W261, of the IgG1 isotype, reacted with prions from mice, sheep with scrapie, deer with chronic wasting disease (CWD), and humans with sporadic and variant Creutzfeldt-Jakob disease (CJD) in assays including a capture enzyme-linked immunosorbent assay (ELISA) system. This PrP(Sc)-specific antibody was unable to clear prions from mouse neuroblastoma cells (ScN2a) permanently infected with scrapie, whereas the high-affinity MAb W226, recognizing both isoforms, PrP(Sc) and PrP(C), did clear prions from ScN2a cells, as determined by a bioassay. However, an attempt to treat intraperitoneally prion infected mice with full-length W226 or with a recombinant variable-chain fragment (scFv) from W226 could only slightly delay the incubation time. We conclude that (i) native, full-length PrP(Sc) elicits a prion-specific antibody response in PrP knockout mice, (ii) a PrP(Sc)-specific antibody had no prion-clearing effect, and (iii) even a high-affinity MAb that clears prions in vitro (W226) may not necessarily protect against prion infection, contrary to previous reports using different antibodies.
Assuntos
Anticorpos Monoclonais/uso terapêutico , Doenças Priônicas/prevenção & controle , Príons/imunologia , Príons/isolamento & purificação , Animais , Anticorpos Monoclonais/isolamento & purificação , Anticorpos Monoclonais/metabolismo , Linhagem Celular , Período de Incubação de Doenças Infecciosas , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Proteínas Priônicas , Ligação Proteica , Fatores de TempoRESUMO
We present a small molecule chemotype, identified by an orthogonal drug screen, exhibiting nanomolar activity against members of all the six viral families causing most human respiratory viral disease, with a demonstrated barrier to resistance development. Antiviral activity is shown in mammalian cells, including human primary bronchial epithelial cells cultured to an air-liquid interface and infected with SARS-CoV-2. In animals, efficacy of early compounds in the lead series is shown by survival (for a coronavirus) and viral load (for a paramyxovirus). The drug target is shown to include a subset of the protein 14-3-3 within a transient host multi-protein complex containing components implicated in viral lifecycles and in innate immunity. This multi-protein complex is modified upon viral infection and largely restored by drug treatment. Our findings suggest a new clinical therapeutic strategy for early treatment upon upper respiratory viral infection to prevent progression to lower respiratory tract or systemic disease. One Sentence Summary: A host-targeted drug to treat all respiratory viruses without viral resistance development.
RESUMO
The primary biological function of the endogenous cellular prion protein has remained unclear. We investigated its biological function in the generation of cellular immune responses using cellular prion protein gene-specific small interfering ribonucleic acid in vivo and in vitro. Our results were confirmed by blocking cellular prion protein with monovalent antibodies and by using cellular prion protein-deficient and -transgenic mice. In vivo prion protein gene-small interfering ribonucleic acid treatment effects were of limited duration, restricted to secondary lymphoid organs and resulted in a 70% reduction of cellular prion protein expression in leukocytes. Disruption of cellular prion protein signalling augmented antigen-specific activation and proliferation, and enhanced T cell receptor signalling, resulting in zeta-chain-associated protein-70 phosphorylation and nuclear factor of activated T cells/activator protein 1 transcriptional activity. In vivo prion protein gene-small interfering ribonucleic acid treatment promoted T cell differentiation towards pro-inflammatory phenotypes and increased survival of antigen-specific T cells. Cellular prion protein silencing with small interfering ribonucleic acid also resulted in the worsening of actively induced and adoptively transferred experimental autoimmune encephalomyelitis. Finally, treatment of myelin basic protein(1-11) T cell receptor transgenic mice with prion protein gene-small interfering ribonucleic acid resulted in spontaneous experimental autoimmune encephalomyelitis. Thus, central nervous system autoimmune disease was modulated at all stages of disease: the generation of the T cell effector response, the elicitation of T effector function and the perpetuation of cellular immune responses. Our findings indicate that cellular prion protein regulates T cell receptor-mediated T cell activation, differentiation and survival. Defects in autoimmunity are restricted to the immune system and not the central nervous system. Our data identify cellular prion protein as a regulator of cellular immunological homoeostasis and suggest cellular prion protein as a novel potential target for therapeutic immunomodulation.
Assuntos
Doenças Autoimunes Desmielinizantes do Sistema Nervoso Central/genética , Inativação Gênica/imunologia , Príons/genética , Receptores de Antígenos de Linfócitos T/fisiologia , Transdução de Sinais/imunologia , Animais , Doenças Autoimunes Desmielinizantes do Sistema Nervoso Central/imunologia , Feminino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Príons/imunologia , RNA Interferente Pequeno/genéticaRESUMO
The ability of viruses to evolve several orders of magnitude faster than their host cells has enabled them to exploit host cellular machinery by selectively recruiting multiprotein complexes (MPCs) for their catalyzed assembly and replication. This hijacking may depend on alternative, 'moonlighting' functions of host proteins that deviate from their canonical functions thereby inducing cellular pathology. Here, we posit that if virus-induced cellular pathology is similar to that of other, unknown (non-viral) causes, the identification and molecular characterization of the host proteins involved in virus-mediated cellular pathology can be leveraged to decipher the non-viral disease-relevant mechanisms. We focus on how virus-induced aberrant proteostasis and protein aggregation resemble the cellular pathology of sporadic neurodegenerative diseases (NDs) and how this can be exploited for drug discovery.
Assuntos
Encéfalo , Vírus , Encéfalo/patologia , Encéfalo/virologia , Humanos , Complexos Multiproteicos , Agregação Patológica de Proteínas , ProteostaseRESUMO
Alzheimer's disease (AD) is a severe neurodegenerative pathology with no effective treatment known. Toxic amyloid-ß peptide (Aß) oligomers play a crucial role in AD pathogenesis. All-d-Enantiomeric peptide D3 and its derivatives were developed to disassemble and destroy cytotoxic Aß aggregates. One of the D3-like compounds is approaching phase II clinical trials; however, high-resolution details of its disease-preventing or pharmacological actions are not completely clear. We demonstrate that peptide D3 stabilizing Aß monomer dynamically interacts with the extracellular juxtamembrane region of a membrane-bound fragment of an amyloid precursor protein containing the Aß sequence. MD simulations based on NMR measurement results suggest that D3 targets the amyloidogenic region, not compromising its α-helicity and preventing intermolecular hydrogen bonding, thus creating prerequisites for inhibition of early steps of Aß conversion into ß-conformation and its toxic oligomerization. An enhanced understanding of the D3 action molecular mechanism facilitates development of effective AD treatment and prevention strategies.
Assuntos
Doença de Alzheimer/tratamento farmacológico , Precursor de Proteína beta-Amiloide/metabolismo , Oligopeptídeos/química , Oligopeptídeos/uso terapêutico , Sequência de Aminoácidos , Animais , Humanos , Camundongos , Simulação de Dinâmica Molecular , Oligopeptídeos/metabolismo , Ligação Proteica , EstereoisomerismoRESUMO
The prion protein, PrP, exists in several stable conformations, with the presence of one conformation, PrP(Sc), associated with transmissible neurodegenerative diseases. Targeting PrP by high-affinity ligands has been proven to be an effective way of preventing peripheral prion infections. Here, we have generated bacterially expressed single chain fragments of the variable domains (scFv) of a monoclonal antibody in Escherichia coli, originally raised against purified PrP(Sc) that recognizes both PrP(C) and PrP(Sc). This scFv fragment had a dissociation constant (K(D)) with recombinant PrP of 2 nM and cleared prions in ScN2a cells at 4 nM, as demonstrated by a mouse prion bioassay. A peptide corresponding to the complementarity determining region 3 of the heavy chain (CDR3H) selectively bound PrP(Sc) but had lost antiprion activity. However, synthesis and application of an improved peptide mimicking side chain topology of CDR3H while exhibiting increased protease resistance, a retro-inverso d-peptide of CDR3H, still bound PrP(Sc) and reinstated antiprion activity. We conclude that (1) scFvW226 is so far the smallest polypeptide with bioassay confirmed antiprion activity, and (2) differential conformation specificity and bioactivity can be regulated by orchestrating the participation of different CDRs.
Assuntos
Regiões Determinantes de Complementaridade/imunologia , Peptídeos/imunologia , Proteínas PrPC/imunologia , Proteínas PrPSc/imunologia , Sequência de Aminoácidos , Animais , Afinidade de Anticorpos/imunologia , Linhagem Celular , Regiões Determinantes de Complementaridade/metabolismo , Camundongos , Camundongos Knockout , Dados de Sequência Molecular , Peptídeos/química , Peptídeos/metabolismo , Proteínas PrPC/metabolismo , Proteínas PrPSc/metabolismo , Conformação ProteicaRESUMO
Prion diseases are transmissible neurodegenerative diseases of humans and animals. The prion agent consists of a misfolded protein, PrPSc (prion protein, scrapie form), of a glycosylphosphatidylinositol-anchored host protein, PrPC (PrP cellular form) of unknown function. During prion replication, PrPSc induces host PrPC to adopt its pathogenic conformation. Some PrPSc may aggregate to microscopically visible, extracellular prion plaques that stain for amyloid. The development of antiprion vaccines presents some challenges. While there is strong self-tolerance to an endogenous antibody response to PrPC and PrPSc, highly potent monoclonal antibodies (mAbs) have been raised in mice in which the prion protein gene has been deleted by gene targeting. These mAbs have been demonstrated to be antiprion-active in permanently scrapie-infected neuroblastoma (ScN2a) cells, primarily when bound to one of four epitopes (the octarepeat region, the region around codons 90-110, helix 1 region codons 145-160, and the extreme C-terminal codons 210-220). The mAbs directed against codon regions 90-110 or 145-160 are also antiprion-active in vivo, but only after intraperitoneal infection with prions, not intracerebral infection, suggesting their blood-brain barrier (BBB) impermeability. The challenge will be to make antibodies, or recombinant derivatives thereof, BBB permeable; this is preferably achieved by monovalent antibody fragments since divalent ones were found to be neurotoxic. Self-tolerance of wild-type animals to PrP immunizations was found to be of extrathymic origin. Even though antibodies raised in wild-type mice were found to display antiprion activity in ScN2a cells, these mice did not have significant extensions of incubation times when challenged intraperitoneally with prions. A general low affinity of these antibody responses to native surface-bound PrPC may account for this. Since wild-type mice were found to develop sufficient T-cell responses to codon regions 145-160 and 210-220, we believe that there is a theoretical chance of a successful vaccination therapy. The influence of the way the immunogen is presented has already been shown to be of major importance for the ensuing immune response, in that presentation of PrP with CpG oligodeoxynucleotides as adjuvant or viral packaging improved antibody responses. Major progress for active immunizations may therefore be expected in this field. Eradication programs will be one of the most important uses of active immunization protocols. For this purpose, vaccines will have to be inexpensive, easy to handle, and effective. In the short term, passive immunizations will likely be most promising for therapy of prion disease, including for human medical interventions. Active immunization protocols are less likely to succeed quickly, and will take years if not decades to be validated for domestic or free-ranging animals.
Assuntos
Doenças Priônicas/terapia , Vacinação/métodos , Vacinas/imunologia , Animais , Anticorpos Monoclonais/administração & dosagem , Anticorpos Monoclonais/imunologia , Modelos Animais de Doenças , Humanos , Doenças Priônicas/imunologia , Doenças Priônicas/prevenção & controle , Príons/imunologiaRESUMO
We examined behaviors and neurotransmitter levels in the tgDimer mouse, a model for early Alzheimer's disease, that expresses exclusively soluble amyloid beta (Aß) dimers and is devoid of Aß plaques, astrogliosis, and neuroinflammation. Seven-month-old mice were subjected to tests of motor activity, attention, anxiety, habituation learning, working memory, and depression-related behaviors. They were impaired in nonselective attention and motor learning and showed anxiety- and despair-related behaviors. In 7- and 12-month-old mice, levels of acetylcholine, dopamine, and serotonin were measured in neostriatum, ventral striatum, prefrontal cortex, hippocampus, amygdala, and entorhinal cortex by high-performance liquid chromatography. The tgDimer mice had lower serotonin turnover rates in hippocampus, ventral striatum, and amygdala relative to wild type controls. The aged tgDimer mice had less hippocampal acetylcholine than adult tgDimers. Stress-test results, based on corticosterone levels, indicated an intact hypothalamus-pituitary-adrenal axis in 12-month-old mice. Since neither Aß plaques nor astrogliosis or neuroinflammation was responsible for these phenotypes, we conclude that Aß dimers contribute to neurotransmitter dysfunction and behavioral impairments, characteristic for the early stages of Alzheimer's disease.
Assuntos
Doença de Alzheimer/metabolismo , Doença de Alzheimer/psicologia , Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Ácido 3,4-Di-Hidroxifenilacético/metabolismo , Acetilcolina/metabolismo , Animais , Comportamento Animal , Química Encefálica , Modelos Animais de Doenças , Dopamina/metabolismo , Ácido Hidroxi-Indolacético/metabolismo , Masculino , Camundongos Transgênicos , Serotonina/metabolismo , Estresse Psicológico/metabolismoRESUMO
Accumulating evidence suggests an important role for the Disrupted-in-Schizophrenia 1 (DISC1) protein in neurodevelopment and chronic mental illness. In particular, the C-terminal 300 amino acids of DISC1 have been found to mediate important protein-protein interactions and to harbor functionally important phosphorylation sites and disease-associated polymorphisms. However, long disordered regions and oligomer-forming subdomains have so far impeded structural analysis. VHH domains derived from camelid heavy chain only antibodies are minimal antigen binding modules with appreciable solubility and stability, which makes them well suited for the stabilizing proteins prior to structural investigation. Here, we report on the generation of a VHH domain derived from an immunized Lama glama, displaying high affinity for the human DISC1 C region (aa 691-836), and its characterization by surface plasmon resonance, size exclusion chromatography and immunological techniques. The VHH-DISC1 (C region) complex was also used for structural investigation by small angle X-ray scattering analysis. In combination with molecular modeling, these data support predictions regarding the three-dimensional fold of this DISC1 segment as well as its steric arrangement in complex with our VHH antibody.
Assuntos
Camelídeos Americanos/imunologia , Proteínas do Tecido Nervoso/imunologia , Anticorpos de Cadeia Única/química , Sequência de Aminoácidos , Animais , Complexo Antígeno-Anticorpo/química , Complexo Antígeno-Anticorpo/genética , Reações Antígeno-Anticorpo , Fenômenos Biofísicos , Camelídeos Americanos/genética , Mapeamento de Epitopos , Feminino , Humanos , Cadeias Pesadas de Imunoglobulinas/química , Cadeias Pesadas de Imunoglobulinas/genética , Camundongos , Modelos Moleculares , Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/genética , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/imunologia , Domínios e Motivos de Interação entre Proteínas , Espalhamento a Baixo Ângulo , Anticorpos de Cadeia Única/genética , Ressonância de Plasmônio de Superfície , Difração de Raios XRESUMO
Alzheimer's disease primarily occurs as sporadic disease and is accompanied with vast socio-economic problems. The mandatory basic research relies on robust and reliable disease models to overcome increasing incidence and emerging social challenges. Rodent models are most efficient, versatile, and predominantly used in research. However, only highly artificial and mostly genetically modified models are available. As these 'engineered' models reproduce only isolated features, researchers demand more suitable models of sporadic neurodegenerative diseases. One very promising animal model was the South American rodent Octodon degus, which was repeatedly described as natural 'sporadic Alzheimer's disease model' with 'Alzheimer's disease-like neuropathology'. To unveil advantages over the 'artificial' mouse models, we re-evaluated the age-dependent, neurohistological changes in young and aged Octodon degus (1 to 5-years-old) bred in a wild-type colony in Germany. In our hands, extensive neuropathological analyses of young and aged animals revealed normal age-related cortical changes without obvious signs for extensive degeneration as seen in patients with dementia. Neither significant neuronal loss nor enhanced microglial activation were observed in aged animals. Silver impregnation methods, conventional, and immunohistological stains as well as biochemical fractionations revealed neither amyloid accumulation nor tangle formation. Phosphoepitope-specific antibodies against tau species displayed similar intraneuronal reactivity in both, young and aged Octodon degus.In contrast to previous results, our study suggests that Octodon degus born and bred in captivity do not inevitably develop cortical amyloidosis, tangle formation or neuronal loss as seen in Alzheimer's disease patients or transgenic disease models.
Assuntos
Doença de Alzheimer , Modelos Animais de Doenças , Octodon , Envelhecimento/metabolismo , Envelhecimento/patologia , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Animais , Western Blotting , Encéfalo/metabolismo , Encéfalo/patologia , Feminino , Humanos , Imuno-Histoquímica , Masculino , Camundongos Transgênicos , Octodon/metabolismo , Proteínas tau/metabolismoRESUMO
Therapeutically active small molecules represent promising nonimmunogenic alternatives to antibodies for specifically targeting disease-relevant receptors. However, a potential drawback compared to antibody-antigen interactions may be the lower affinity of small molecules toward receptors. Here, we overcome this low-affinity problem by coating the surface of nanoparticles (NPs) with multiple ligands. Specifically, we explored the use of gold and platinum nanoparticles to increase the binding affinity of Aß-specific small molecules to inhibit Aß peptide aggregation into fibrils in vitro. The interactions of bare NPs, free ligands, and NP-bound ligands with Aß are comprehensively studied via physicochemical methods (spectroscopy, microscopy, immunologic tests) and cell assays. Reduction of thioflavin T fluorescence, as an indicator for ß-sheet content, and inhibition of cellular Aß excretion are even more effective with NP-bound ligands than with the free ligands. The results from this study may have implications in the development of therapeutics for treating Alzheimer's disease.