Publications by authors named "Emilie Jaumain"

18 Publications

  • Page 1 of 1

PEG-PGA enveloped octaarginine-peptide nanocomplexes: An oral peptide delivery strategy.

J Control Release 2018 04 6;276:125-139. Epub 2018 Mar 6.

Center for Research in Molecular Medicine and Chronic Diseases, IDIS research Institute, Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain. Electronic address:

The objective of this work was the development of a new drug nanocarrier intended to overcome the barriers associated to the oral modality of administration and to assess its value for the systemic or local delivery of peptides. The nanocarrier was rationally designed taking into account the nature of the intestinal barriers and was loaded with insulin, which was selected as a model peptide. The nanocarrier consisted of a complex between insulin and a hydrophobically-modified cell penetrating peptide (CPP), enveloped by a protecting polymer. The selected CPP was octaarginine (r8), chemically conjugated with cholesterol (Chol) or lauric acid (C12), whereas the protecting polymer was poly (glutamic acid)-poly (ethylene glycol) (PGA-PEG). This enveloping material was intended to preserve the stability of the nanocomplex in the intestinal medium and facilitate its diffusion across the intestinal mucus. The enveloped nanocomplexes (ENCPs) exhibited a number of key features, namely (i) a unimodal size distribution with a mean size of 200 nm and a neutral zeta potential, (ii) the capacity to associate insulin (~100% association efficiency) and protect it from degradation in simulated intestinal fluids, (iii) the ability to diffuse through intestinal mucus and, most importantly, (iv) the capacity to interact with the Caco-2 model epithelium, resulting in a massive insulin cell uptake (47.59 ± 5.79%). This enhanced accumulation of insulin at the epithelial level was not translated into an enhanced insulin transport. In fact, only 2% of insulin was transported across the monolayer, and this was correlated with a moderate response of insulin following oral administration to healthy rats. Despite of this, the accumulation of the insulin-loaded nanocarriers in the intestinal mucosa could be verified in vivo upon their labeling with Tc. Overall, these data underline the capacity of the nanocarriers to overcome substantial barriers associated to the oral modality of administration and to facilitate the accumulation of the associated peptide at the intestinal level.
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http://dx.doi.org/10.1016/j.jconrel.2018.03.004DOI Listing
April 2018

Imaging PD-L1 Expression with ImmunoPET.

Bioconjug Chem 2018 01 15;29(1):96-103. Epub 2017 Nov 15.

Department of Radiology and Biomedical Imaging, ‡Department of Medicine, §Helen Diller Family Comprehensive Cancer Center, ∥Department of Pharmaceutical Chemistry, and ⊥Department of Radiation Oncology, University of California, San Francisco , 505 Parnassus Avenue, San Francisco, California 94143, United States.

High sensitivity imaging tools could provide a more holistic view of target antigen expression to improve the identification of patients who might benefit from cancer immunotherapy. We developed for immunoPET a novel recombinant human IgG1 (termed C4) that potently binds an extracellular epitope on human and mouse PD-L1 and radiolabeled the antibody with zirconium-89. Small animal PET/CT studies showed that Zr-C4 detected antigen levels on a patient derived xenograft (PDX) established from a non-small-cell lung cancer (NSCLC) patient before an 8-month response to anti-PD-1 and anti-CTLA4 therapy. Importantly, the concentration of antigen is beneath the detection limit of previously developed anti-PD-L1 radiotracers, including radiolabeled atezolizumab. We also show that Zr-C4 can specifically detect antigen in human NSCLC and prostate cancer models endogenously expressing a broad range of PD-L1. Zr-C4 detects mouse PD-L1 expression changes in immunocompetent mice, suggesting that endogenous PD-1/2 will not confound human imaging. Lastly, we found that Zr-C4 could detect acute changes in tumor expression of PD-L1 due to standard of care chemotherapies. In summary, we present evidence that low levels of PD-L1 in clinically relevant cancer models can be imaged with immunoPET using a novel recombinant human antibody.
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http://dx.doi.org/10.1021/acs.bioconjchem.7b00631DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5773933PMC
January 2018

From Structure-Activity Relationships on Thiazole Derivatives to the In Vivo Evaluation of a New Radiotracer for Cannabinoid Subtype 2 PET Imaging.

Mol Pharm 2017 11 18;14(11):4064-4078. Epub 2017 Oct 18.

UMR 1023 IMIV, Service Hospitalier Frédéric Joliot, CEA, Inserm, Université Paris Sud, CNRS, Université Paris-Saclay , 91405 Orsay, France.

Upregulation of the cannabinoid type 2 receptors (CBR) unveils inflammation processes of pathological disorders, such as cancer, pain, or neurodegenerative diseases. Among others, CBR agonist A-836339 has been labeled with carbon-11 for PET imaging of the CBR and displayed promising results in a mouse model of Alzheimer's disease. The aim of the present work was to develop fluorinated analogs of A-836339 for labeling with fluorine-18 to design a new PET tracer for CBR imaging. Seven fluorinated analogs of A-836339 were synthesized in two to three steps and their binding affinities and selectivities for both the human and the mouse CBR were measured as well as their early ADME profiles. Among them, compound 2f (K = 0.1 nM, K/K = 300) displayed high affinity and selectivity for CBR but also promising lipophilicity, kinetic solubility, and membrane permeation properties and was further selected for in vitro metabolism studies. Incubation of 2f with human or rat liver microsomes followed by LC/MS analysis revealed the presence of six different metabolites mainly resulting from oxidation reactions. A tosylated precursor of 2f was synthesized in two steps and radiolabeled with fluorine-18 to afford [F]2f in 15 ± 5% radiochemical yield and a molar activity of 110 ± 30 GBq/μmol. Autoradiographies of rat spleen and biodistribution studies in healthy rats including pretreatments with either CBR or CBR-specific compounds suggested that [F]2f is a specific tracer for the CBR in vivo. We have therefore demonstrated here that [F]2f is a promising novel tracer for imaging CBR in vivo using PET. Further investigation in animal models of inflammation will follow.
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http://dx.doi.org/10.1021/acs.molpharmaceut.7b00746DOI Listing
November 2017

Using P-MRI of hydroxyapatite for bone attenuation correction in PET-MRI: proof of concept in the rodent brain.

EJNMMI Phys 2017 Dec 2;4(1):16. Epub 2017 May 2.

Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Direction de la Recherche Fondamentale (DRF), Institut d'Imagerie Biomedicale (I2BM), MIRCen, Fontenay-aux-Roses, France.

Background: The correction of γ-photon attenuation in PET-MRI remains a critical issue, especially for bone attenuation. This problem is of great importance for brain studies due to the density of the skull. Current techniques for skull attenuation correction (AC) provide indirect estimates of cortical bone density, leading to inaccurate estimates of brain activity. The purpose of this study was to develop an alternate method for bone attenuation correction based on NMR. The proposed approach relies on the detection of hydroxyapatite crystals by zero echo time (ZTE) MRI of P, providing individual and quantitative assessment of bone density. This work presents a proof of concept of this approach. The first step of the method is a calibration experiment to determine the conversion relationship between the P signal and the linear attenuation coefficient μ. Then P-ZTE was performed in vivo in rodent to estimate the μ-map of the skull. F-FDG PET data were acquired in the same animal and reconstructed with three different AC methods: P-based AC, AC neglecting the bone and the gold standard, CT-based AC, used to comparison for the other two methods.

Results: The calibration experiment provided a conversion factor of P signal into μ. In vivo P-ZTE made it possible to acquire 3D images of the rat skull. Brain PET images showed underestimation of F activity in peripheral regions close to the skull when AC neglected the bone (as compared with CT-based AC). The use of P-derived μ-map for AC leads to increased peripheral activity, and therefore a global overestimation of brain F activity.

Conclusions: In vivo P-ZTE MRI of hydroxyapatite provides μ-map of the skull, which can be used for attenuation correction of F-FDG PET images. This study is limited by several intrinsic biases associated with the size of the rat brain, which are unlikely to affect human data on a clinical PET-MRI system.
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http://dx.doi.org/10.1186/s40658-017-0183-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5413461PMC
December 2017

Absence of Evidence for a Causal Link between Bovine Spongiform Encephalopathy Strain Variant L-BSE and Known Forms of Sporadic Creutzfeldt-Jakob Disease in Human PrP Transgenic Mice.

J Virol 2016 Dec 14;90(23):10867-10874. Epub 2016 Nov 14.

VIM, INRA, Université Paris-Saclay, Jouy-en-Josas, France

Prions are proteinaceous pathogens responsible for subacute spongiform encephalopathies in animals and humans. The prions responsible for bovine spongiform encephalopathy (BSE) are zoonotic agents, causing variant Creutzfeldt-Jakob disease (CJD) in humans. The transfer of prions between species is limited by a species barrier, which is thought to reflect structural incompatibilities between the host cellular prion protein (PrP) and the infecting pathological PrP assemblies (PrP) constituting the prion. A BSE strain variant, designated L-BSE and responsible for atypical, supposedly spontaneous forms of prion diseases in aged cattle, demonstrates zoonotic potential, as evidenced by its capacity to propagate more easily than classical BSE in transgenic mice expressing human PrP and in nonhuman primates. In humanized mice, L-BSE propagates without any apparent species barrier and shares similar biochemical PrP signatures with the CJD subtype designated MM2-cortical, thus opening the possibility that certain CJD cases classified as sporadic may actually originate from L-type BSE cross-transmission. To address this issue, we compared the biological properties of L-BSE and those of a panel of CJD subtypes representative of the human prion strain diversity using standard strain-typing criteria in human PrP transgenic mice. We found no evidence that L-BSE causes a known form of sporadic CJD.

Importance: Since the quasi-extinction of classical BSE, atypical BSE forms are the sole BSE variants circulating in cattle worldwide. They are observed in rare cases of old cattle, making them difficult to detect. Extrapolation of our results suggests that L-BSE may propagate in humans as an unrecognized form of CJD, and we urge both the continued utilization of precautionary measures to eliminate these agents from the human food chain and active surveillance for CJD phenotypes in the general population.
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http://dx.doi.org/10.1128/JVI.01383-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5110181PMC
December 2016

Emergence of two prion subtypes in ovine PrP transgenic mice infected with human MM2-cortical Creutzfeldt-Jakob disease prions.

Acta Neuropathol Commun 2016 Feb 5;4:10. Epub 2016 Feb 5.

INRA (Institut National de la Recherche Agronomique), UR892, Virologie Immunologie Moléculaires, F-78350, Jouy-en-Josas, France.

Introduction: Mammalian prions are proteinaceous pathogens responsible for a broad range of fatal neurodegenerative diseases in humans and animals. These diseases can occur spontaneously, such as Creutzfeldt-Jakob disease (CJD) in humans, or be acquired or inherited. Prions are primarily formed of macromolecular assemblies of the disease-associated prion protein PrP(Sc), a misfolded isoform of the host-encoded prion protein PrP(C). Within defined host-species, prions can exist as conformational variants or strains. Based on both the M/V polymorphism at codon 129 of PrP and the electrophoretic signature of PrP(Sc) in the brain, sporadic CJD is classified in different subtypes, which may encode different strains. A transmission barrier, the mechanism of which remains unknown, limits prion cross-species propagation. To adapt to the new host, prions have the capacity to 'mutate' conformationally, leading to the emergence of a variant with new biological properties. Here, we transmitted experimentally one rare subtype of human CJD, designated cortical MM2 (129 MM with type 2 PrP(Sc)), to transgenic mice overexpressing either human or the VRQ allele of ovine PrP(C).

Results: In marked contrast with the reported absence of transmission to knock-in mice expressing physiological levels of human PrP, this subtype transmitted faithfully to mice overexpressing human PrP, and exhibited unique strain features. Onto the ovine PrP sequence, the cortical MM2 subtype abruptly evolved on second passage, thereby allowing emergence of a pair of strain variants with distinct PrP(Sc) biochemical characteristics and differing tropism for the central and lymphoid tissues. These two strain components exhibited remarkably distinct replicative properties in cell-free amplification assay, allowing the 'physical' cloning of the minor, lymphotropic component, and subsequent isolation in ovine PrP mice and RK13 cells.

Conclusions: Here, we provide in-depth assessment of the transmissibility and evolution of one rare subtype of sporadic CJD upon homologous and heterologous transmission. The notion that the environment or matrix where replication is occurring is key to the selection and preferential amplification of prion substrain components raises new questions on the determinants of prion replication within and between species. These data also further interrogate on the interplay between animal and human prions.
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http://dx.doi.org/10.1186/s40478-016-0284-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4743415PMC
February 2016

White blood cell-based detection of asymptomatic scrapie infection by ex vivo assays.

PLoS One 2014 14;9(8):e104287. Epub 2014 Aug 14.

UMR INRA ENVT 1225, Interactions Hôtes Agents Pathogènes, Ecole Nationale Vétérinaire de Toulouse, Toulouse, France.

Prion transmission can occur by blood transfusion in human variant Creutzfeldt-Jakob disease and in experimental animal models, including sheep. Screening of blood and its derivatives for the presence of prions became therefore a major public health issue. As infectious titer in blood is reportedly low, highly sensitive and robust methods are required to detect prions in blood and blood derived products. The objectives of this study were to compare different methods--in vitro, ex vivo and in vivo assays--to detect prion infectivity in cells prepared from blood samples obtained from scrapie infected sheep at different time points of the disease. Protein misfolding cyclic amplification (PMCA) and bioassays in transgenic mice expressing the ovine prion protein were the most efficient methods to identify infected animals at any time of the disease (asymptomatic to terminally-ill stages). However scrapie cell and cerebellar organotypic slice culture assays designed to replicate ovine prions in culture also allowed detection of prion infectivity in blood cells from asymptomatic sheep. These findings confirm that white blood cells are appropriate targets for preclinical detection and introduce ex vivo tools to detect blood infectivity during the asymptomatic stage of the disease.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0104287PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4133197PMC
April 2015

Accelerated, spleen-based titration of variant Creutzfeldt-Jakob disease infectivity in transgenic mice expressing human prion protein with sensitivity comparable to that of survival time bioassay.

J Virol 2014 Aug 21;88(15):8678-86. Epub 2014 May 21.

INRA (Institut National de la Recherche Agronomique), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France

Unlabelled: The dietary exposure of the human population to the prions responsible for the bovine spongiform encephalopathy (BSE) epizooty has led to the emergence of variant Creutzfeldt-Jakob disease (vCJD). This fatal, untreatable neurodegenerative disorder is a growing public health concern because the prevalence of the infection seems much greater than the disease incidence and because secondary transmission of vCJD by blood transfusion or use of blood products has occurred. A current limitation in variant CJD risk assessment is the lack of quantitative information on the infectivity of contaminated tissues. To address this limitation, we tested the potential of a transgenic mouse line overexpressing human prion protein (PrP), which was previously reported to propagate vCJD prions. Endpoint titration of vCJD infectivity in different tissues was evaluated by two different methods: (i) the "classical" bioassay, based on the appearance of clinical symptoms and the detection of pathological prion protein in tissues of the inoculated mouse, and (ii) a shortened bioassay based on the detection of the protein in the mouse spleen at defined time points. The two methods proved equally sensitive in quantifying infectivity, even after very-low-dose inoculation of infected material, but the time schedule was shortened from ~2.5 years to ~1 year with the spleen bioassay. Compared to the "gold-standard" RIII model routinely used for endpoint titration of vCJD/BSE prions, either method improved the sensitivity by >2 orders of magnitude and allowed reevaluating the infectious titer of spleen from a vCJD individual at disease end stage to >1,000-fold-higher values.

Importance: Here, we provide key reevaluation of the infectious titer of variant CJD brain and spleen tissues. The highly sensitive, accelerated spleen-based assay should thus constitute a key advance for variant CJD epidemiological and risk assessment purposes and should greatly facilitate future titration studies, including, for example, those aimed at validating decontamination procedures. The overlooked notion that the lymphoid tissue exhibits a higher capacity than the brain to replicate prions even after low-dose infection raises new questions about the molecular and/or cellular determinant(s) involved, a key issue regarding potent silent carriers of variant CJD in the lymphoid tissue.
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http://dx.doi.org/10.1128/JVI.01118-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4135959PMC
August 2014

Highly infectious prions generated by a single round of microplate-based protein misfolding cyclic amplification.

mBio 2013 Dec 31;5(1):e00829-13. Epub 2013 Dec 31.

Measurements of the presence of prions in biological tissues or fluids rely more and more on cell-free assays. Although protein misfolding cyclic amplification (PMCA) has emerged as a valuable, sensitive tool, it is currently hampered by its lack of robustness and rapidity for high-throughput purposes. Here, we made a number of improvements making it possible to amplify the maximum levels of scrapie prions in a single 48-h round and in a microplate format. The amplification rates and the infectious titer of the PMCA-formed prions appeared similar to those derived from the in vivo laboratory bioassays. This enhanced technique also amplified efficiently prions from different species, including those responsible for human variant Creutzfeldt-Jakob disease. This new format should help in developing ultrasensitive, high-throughput prion assays for cognitive, diagnostic, and therapeutic applications. IMPORTANCE The method developed here allows large-scale, fast, and reliable cell-free amplification of subinfectious levels of prions from different species. The sensitivity and rapidity achieved approach or equal those of other recently developed prion-seeded conversion assays. Our simplified assay may be amenable to high-throughput, automated purposes and serve in a complementary manner with other recently developed assays for urgently needed antemortem diagnostic tests, by using bodily fluids containing small amounts of prion infectivity. Such a combination of assays is of paramount importance to reduce the transfusion risk in the human population and to identify asymptomatic carriers of variant Creutzfeldt-Jakob disease.
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http://dx.doi.org/10.1128/mBio.00829-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3884057PMC
December 2013

Quaternary structure of pathological prion protein as a determining factor of strain-specific prion replication dynamics.

PLoS Pathog 2013 10;9(10):e1003702. Epub 2013 Oct 10.

INRA (Institut National de la Recherche Agronomique), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France.

Prions are proteinaceous infectious agents responsible for fatal neurodegenerative diseases in animals and humans. They are essentially composed of PrP(Sc), an aggregated, misfolded conformer of the ubiquitously expressed host-encoded prion protein (PrP(C)). Stable variations in PrP(Sc) conformation are assumed to encode the phenotypically tangible prion strains diversity. However the direct contribution of PrP(Sc) quaternary structure to the strain biological information remains mostly unknown. Applying a sedimentation velocity fractionation technique to a panel of ovine prion strains, classified as fast and slow according to their incubation time in ovine PrP transgenic mice, has previously led to the observation that the relationship between prion infectivity and PrP(Sc) quaternary structure was not univocal. For the fast strains specifically, infectivity sedimented slowly and segregated from the bulk of proteinase-K resistant PrP(Sc). To carefully separate the respective contributions of size and density to this hydrodynamic behavior, we performed sedimentation at the equilibrium and varied the solubilization conditions. The density profile of prion infectivity and proteinase-K resistant PrP(Sc) tended to overlap whatever the strain, fast or slow, leaving only size as the main responsible factor for the specific velocity properties of the fast strain most infectious component. We further show that this velocity-isolable population of discrete assemblies perfectly resists limited proteolysis and that its templating activity, as assessed by protein misfolding cyclic amplification outcompetes by several orders of magnitude that of the bulk of larger size PrP(Sc) aggregates. Together, the tight correlation between small size, conversion efficiency and duration of disease establishes PrP(Sc) quaternary structure as a determining factor of prion replication dynamics. For certain strains, a subset of PrP assemblies appears to be the best template for prion replication. This has important implications for fundamental studies on prions.
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http://dx.doi.org/10.1371/journal.ppat.1003702DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3795044PMC
May 2014

Targeted knock-down of cellular prion protein expression in myelinating Schwann cells does not alter mouse prion pathogenesis.

J Gen Virol 2013 Jun 6;94(Pt 6):1435-1440. Epub 2013 Feb 6.

INRA (Institut National de la Recherche Agronomique), UR892, Virologie Immunologie Moléculaires, F-78350, Jouy-en-Josas, France.

In naturally acquired transmissible spongiform encephalopathies, the pathogenic agents or prions spread from the sites of initial peripheral uptake or replication to the brain where they cause progressive and fatal neurodegeneration. Routing via the peripheral nervous system is considered to be one of the main pathways to the central nervous system. Replication of prions in Schwann cells is viewed as a potentially important mechanism for efficient prion spread along nerves. Here we used a Cre-loxP mouse transgenetic approach to disrupt host-encoded prion protein (PrP(C)) specifically in myelinating Schwann cells. Despite the use of infection routes targeting highly myelinated nerves, there was no alteration in mouse prion pathogenesis, suggesting that conversion-dependent, centripetal spread of prions does not crucially rely on PrP(C) expressed by myelinating Schwann cells.
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http://dx.doi.org/10.1099/vir.0.049619-0DOI Listing
June 2013

Endogenous prion protein conversion is required for prion-induced neuritic alterations and neuronal death.

FASEB J 2012 Sep 1;26(9):3854-61. Epub 2012 Jun 1.

UR892, Virologie et Immunologie Moléculaires, Institut National de Recherche Agronomique, Jouy-en-Josas, France.

Prions cause fatal neurodegenerative conditions and result from the conversion of host-encoded cellular prion protein (PrP(C)) into abnormally folded scrapie PrP (PrP(Sc)). Prions can propagate both in neurons and astrocytes, yet neurotoxicity mechanisms remain unclear. Recently, PrP(C) was proposed to mediate neurotoxic signaling of β-sheet-rich PrP and non-PrP conformers independently of conversion. To investigate the role of astrocytes and neuronal PrP(C) in prion-induced neurodegeneration, we set up neuron and astrocyte primary cocultures derived from PrP transgenic mice. In this system, prion-infected astrocytes delivered ovine PrP(Sc) to neurons lacking PrP(C) (prion-resistant), or expressing a PrP(C) convertible (sheep) or not (mouse, human). We show that interaction between neuronal PrP(C) and exogenous PrP(Sc) was not sufficient to induce neuronal death but that efficient PrP(C) conversion was required for prion-associated neurotoxicity. Prion-infected astrocytes markedly accelerated neurodegeneration in homologous cocultures compared to infected single neuronal cultures, despite no detectable neurotoxin release. Finally, PrP(Sc) accumulation in neurons led to neuritic damages and cell death, both potentiated by glutamate and reactive oxygen species. Thus, conversion of neuronal PrP(C) rather than PrP(C)-mediated neurotoxic signaling appears as the main culprit in prion-induced neurodegeneration. We suggest that active prion replication in neurons sensitizes them to environmental stress regulated by neighboring cells, including astrocytes.
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http://dx.doi.org/10.1096/fj.11-201772DOI Listing
September 2012

Integrity of helix 2-helix 3 domain of the PrP protein is not mandatory for prion replication.

J Biol Chem 2012 Jun 16;287(23):18953-64. Epub 2012 Apr 16.

INRA, UR892 Virologie Immunologie Moléculaires, F-78350 Jouy-en-Josas, France.

The process of prion conversion is not yet well understood at the molecular level. The regions critical for the conformational change of PrP remain mostly debated and the extent of sequence change acceptable for prion conversion is poorly documented. To achieve progress on these issues, we applied a reverse genetic approach using the Rov cell system. This allowed us to test the susceptibility of a number of insertion mutants to conversion into prion in the absence of wild-type PrP molecules. We were able to propagate several prions with 8 to 16 extra amino acids, including a polyglycine stretch and His or FLAG tags, inserted in the middle of the protease-resistant fragment. These results demonstrate the possibility to increase the length of the loop between helices H2 and H3 up to 4-fold, without preventing prion replication. They also indicate that this loop probably remains unstructured in PrP(Sc). We also showed that bona fide prions can be produced following insertion of octapeptides in the two C-terminal turns of H2. These insertions do not interfere with the overall fold of the H2-H3 domain indicating that the highly conserved sequence of the terminal part of H2 is not critical for the conversion. Altogether these data showed that the amplitude of modifications acceptable for prion conversion in the core of the globular domain of PrP is much greater than one might have assumed. These observations should help to refine structural models of PrP(Sc) and elucidate the conformational changes underlying prions generation.
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http://dx.doi.org/10.1074/jbc.M112.341677DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3365929PMC
June 2012

Facilitated cross-species transmission of prions in extraneural tissue.

Science 2012 Jan;335(6067):472-5

Institut National de la Recherche Agronomique UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France.

Prions are infectious pathogens essentially composed of PrP(Sc), an abnormally folded form of the host-encoded prion protein PrP(C). Constrained steric interactions between PrP(Sc) and PrP(C) are thought to provide prions with species specificity and to control cross-species transmission into other host populations, including humans. We compared the ability of brain and lymphoid tissues from ovine and human PrP transgenic mice to replicate foreign, inefficiently transmitted prions. Lymphoid tissue was consistently more permissive than the brain to prions such as those causing chronic wasting disease and bovine spongiform encephalopathy. Furthermore, when the transmission barrier was overcome through strain shifting in the brain, a distinct agent propagated in the spleen, which retained the ability to infect the original host. Thus, prion cross-species transmission efficacy can exhibit a marked tissue dependence.
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http://dx.doi.org/10.1126/science.1215659DOI Listing
January 2012

Sheep and goat BSE propagate more efficiently than cattle BSE in human PrP transgenic mice.

PLoS Pathog 2011 Mar 17;7(3):e1001319. Epub 2011 Mar 17.

Centro de Investigación en Sanidad Animal, Madrid, Spain.

A new variant of Creutzfeldt Jacob Disease (vCJD) was identified in humans and linked to the consumption of Bovine Spongiform Encephalopathy (BSE)-infected meat products. Recycling of ruminant tissue in meat and bone meal (MBM) has been proposed as origin of the BSE epidemic. During this epidemic, sheep and goats have been exposed to BSE-contaminated MBM. It is well known that sheep can be experimentally infected with BSE and two field BSE-like cases have been reported in goats. In this work we evaluated the human susceptibility to small ruminants-passaged BSE prions by inoculating two different transgenic mouse lines expressing the methionine (Met) allele of human PrP at codon 129 (tg650 and tg340) with several sheep and goat BSE isolates and compared their transmission characteristics with those of cattle BSE. While the molecular and neuropathological transmission features were undistinguishable and similar to those obtained after transmission of vCJD in both transgenic mouse lines, sheep and goat BSE isolates showed higher transmission efficiency on serial passaging compared to cattle BSE. We found that this higher transmission efficiency was strongly influenced by the ovine PrP sequence, rather than by other host species-specific factors. Although extrapolation of results from prion transmission studies by using transgenic mice has to be done very carefully, especially when human susceptibility to prions is analyzed, our results clearly indicate that Met129 homozygous individuals might be susceptible to a sheep or goat BSE agent at a higher degree than to cattle BSE, and that these agents might transmit with molecular and neuropathological properties indistinguishable from those of vCJD. Our results suggest that the possibility of a small ruminant BSE prion as vCJD causal agent could not be ruled out, and that the risk for humans of a potential goat and/or sheep BSE agent should not be underestimated.
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http://dx.doi.org/10.1371/journal.ppat.1001319DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3060172PMC
March 2011

The physical relationship between infectivity and prion protein aggregates is strain-dependent.

PLoS Pathog 2010 Apr 15;6(4):e1000859. Epub 2010 Apr 15.

INRA (Institut National de la Recherche Agronomique), UR892, Virologie Immunologie Moléculaires, Jouy-en-Josas, France.

Prions are unconventional infectious agents thought to be primarily composed of PrP(Sc), a multimeric misfolded conformer of the ubiquitously expressed host-encoded prion protein (PrP(C)). They cause fatal neurodegenerative diseases in both animals and humans. The disease phenotype is not uniform within species, and stable, self-propagating variations in PrP(Sc) conformation could encode this 'strain' diversity. However, much remains to be learned about the physical relationship between the infectious agent and PrP(Sc) aggregation state, and how this varies according to the strain. We applied a sedimentation velocity technique to a panel of natural, biologically cloned strains obtained by propagation of classical and atypical sheep scrapie and BSE infectious sources in transgenic mice expressing ovine PrP. Detergent-solubilized, infected brain homogenates were used as starting material. Solubilization conditions were optimized to separate PrP(Sc) aggregates from PrP(C). The distribution of PrP(Sc) and infectivity in the gradient was determined by immunoblotting and mouse bioassay, respectively. As a general feature, a major proteinase K-resistant PrP(Sc) peak was observed in the middle part of the gradient. This population approximately corresponds to multimers of 12-30 PrP molecules, if constituted of PrP only. For two strains, infectivity peaked in a markedly different region of the gradient. This most infectious component sedimented very slowly, suggesting small size oligomers and/or low density PrP(Sc) aggregates. Extending this study to hamster prions passaged in hamster PrP transgenic mice revealed that the highly infectious, slowly sedimenting particles could be a feature of strains able to induce a rapidly lethal disease. Our findings suggest that prion infectious particles are subjected to marked strain-dependent variations, which in turn could influence the strain biological phenotype, in particular the replication dynamics.
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http://dx.doi.org/10.1371/journal.ppat.1000859DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2855332PMC
April 2010

Behavior and serotonergic disorders in rats exposed prenatally to valproate: a model for autism.

Neurosci Lett 2010 Feb 28;470(1):55-9. Epub 2009 Dec 28.

CHRU de Tours, Tours, France.

In order to explore whether some aspects of the autistic phenotype could be related to impairment of the serotonergic system, we chose an animal model which mimics a potential cause of autism, i.e. rats exposed to valproate (VPA) on the 9th embryonic day (E9). Previous studies have suggested that VPA exposure in rats at E9 caused a dramatic shift in the distribution of serotonergic neurons on postnatal day 50 (PND50). Behavioral studies have also been performed but on rats that were exposed to VPA later (E12.5). Our aim was to test whether VPA exposure at E9 induces comparable behavioral impairments than at E12.5 and causes serotonergic impairments which could be related to behavioral modifications. The results showed significant behavioral impairments such as a lower tendency to initiate social interactions and hyperlocomotor activity in juvenile male rats. The serotonin levels of these animals at PND50 were decreased (-46%) in the hippocampus, a structure involved in social behavior. This study suggests that VPA could have a direct or indirect action on the serotonergic system as early as the progenitor cell stage. Early embryonic exposure to VPA in rats provides a good model for several specific aspects of autism and should help to continue to explore pathophysiological hypotheses.
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http://dx.doi.org/10.1016/j.neulet.2009.12.054DOI Listing
February 2010

Direct peptide interaction with surface glycosaminoglycans contributes to the cell penetration of maurocalcine.

J Biol Chem 2008 Aug 3;283(35):24274-84. Epub 2008 Jul 3.

INSERM U836, Grenoble Institute of Neurosciences, Research Group 3, Calcium Channels, Functions, and Pathologies Laboratory, Université Joseph Fourier, Grenoble Cedex 9, France.

Maurocalcine (MCa), initially identified from a Tunisian scorpion venom, defines a new member of the family of cell penetrating peptides by its ability to efficiently cross the plasma membrane. The initiating mechanistic step required for the cell translocation of a cell penetrating peptide implicates its binding onto cell surface components such as membrane lipids and/or heparan sulfate proteoglycans. Here we characterized the interaction of wild-type MCa and MCa K20A, a mutant analogue with reduced cell-penetration efficiency, with heparin (HP) and heparan sulfates (HS) through surface plasma resonance. HP and HS bind both to MCa, indicating that heparan sulfate proteoglycans may represent an important entry route of the peptide. This is confirmed by the fact that (i) both compounds bind with reduced affinity to MCa K20A and (ii) the cell penetration of wild-type or mutant MCa coupled to fluorescent streptavidin is reduced by about 50% in mutant Chinese hamster ovary cell lines lacking either all glycosaminoglycans (GAGs) or just HS. Incubating MCa with soluble HS, HP, or chondroitin sulfates also inhibits the cell penetration of MCa-streptavidin complexes. Analyses of the cell distributions of MCa/streptavidin in several Chinese hamster ovary cell lines show that the distribution of the complex coincides with the endosomal marker Lyso-Tracker red and is not affected by the absence of GAGs. The distribution of MCa/streptavidin is not coincident with that of transferrin receptors nor affected by a dominant-negative dynamin 2 K44A mutant, an inhibitor of clathrin-mediated endocytosis. However, entry of the complex is greatly diminished by amiloride, indicating the importance of macropinocytosis in MCa/streptavidin entry. It is concluded that (i) interaction of MCa with GAGs quantitatively improves the cell penetration of MCa, and (ii) GAG-dependent and -independent MCa penetration rely similarly on the macropinocytosis pathway.
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http://dx.doi.org/10.1074/jbc.M709971200DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2701444PMC
August 2008