Maria Eugenia Herva

The Scripps Research Institute, La Jolla, California, United States

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Publications (14)47.26 Total impact

  • Maria E Herva, Charles Weissman
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    ABSTRACT: Prions consist of PrP (Sc) , a misfolded version of the cellular protein PrP (C) . They occur in a variety of strains that share the amino acid sequence of PrP but differ in phenotypic properties, such as cell tropism and pathogenicity; strain-ness is attributed to the conformation of PrP (Sc) . To gain insight as to how susceptibility of cells to a given prion strain comes about, we compared amplification of RML prions by PMCA, using cell lysates from related, RML-resistant and RML-susceptible cell lines as substrate. We found that both lysates supported amplification of RML PrP (Sc) equally well, despite a 280-fold difference in the susceptibility of the cells from which they were derived. Thus, susceptibility is an attribute of the intact cell.
    Prion 09/2012; 6(4):371-4. · 2.13 Impact Factor
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    ABSTRACT: PrP(C), a host protein which in prion-infected animals is converted to PrP(Sc), is linked to the cell membrane by a GPI anchor. Mice expressing PrP(C) without GPI anchor (tgGPI⁻ mice), are susceptible to prion infection but accumulate anchorless PrP(Sc) extra-, rather than intracellularly. We investigated whether tgGPI⁻ mice could faithfully propagate prion strains despite the deviant structure and location of anchorless PrP(Sc). We found that RML and ME7, but not 22L prions propagated in tgGPI⁻ brain developed novel cell tropisms, as determined by the Cell Panel Assay (CPA). Surprisingly, the levels of proteinase K-resistant PrP(Sc) (PrP(res)) in RML- or ME7-infected tgGPI⁻ brain were 25-50 times higher than in wild-type brain. When returned to wild-type brain, ME7 prions recovered their original properties, however RML prions had given rise to a novel prion strain, designated SFL, which remained unchanged even after three passages in wild-type mice. Because both RML PrP(Sc) and SFL PrP(Sc) are stably propagated in wild-type mice we propose that the two conformations are separated by a high activation energy barrier which is abrogated in tgGPI⁻ mice.
    PLoS Pathogens 06/2012; 8(6):e1002746. · 8.14 Impact Factor
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    ABSTRACT: Prion diseases, which are mostly represented in humans by Creutzfeldt-Jakob disease, are transmissible neurodegenerative disorders characterized by vacuolization and neuronal loss, as well as by the accumulation of an abnormal form of the prion protein. These disorders have yet no effective treatment, and drugs that block prion replication in vitro do not significantly slow down the progression of the disease when used in vivo at late stages. Cell therapy that has been already tested in other neurodegenerative disorders therefore represents an interesting alternative approach. In this study, we showed for the first time in prion diseases that intracerebral transplantation of fetal neural stem cells significantly extended both incubation and survival time. This result was dependant on the time window chosen for the engraftment and was obtained with both genetically modified and wild-type stem cells, therefore forging a path toward efficient stem cell therapy for human prion diseases.
    The Journal of Infectious Diseases 10/2011; 204(7):1038-45. · 5.85 Impact Factor
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    ABSTRACT: Neuroblastoma-derived N2a-PK1 cells, fibroblastic LD9 cells, and CNS-derived CAD5 cells can be infected efficiently and persistently by various prion strains, as measured by the standard scrapie cell assay. Swainsonine, an inhibitor of Golgi α-mannosidase II that causes abnormal N-glycosylation, strongly inhibits infection of PK1 cells by RML, 79A and 22F, less so by 139A, and not at all by 22L prions, and it does not diminish propagation of any of these strains in LD9 or CAD5 cells. Misglycosylated PrP(C) formed in the presence of swainsonine is a good substrate for conversion to PrP(Sc), and misglycosylated PrP(Sc) is fully able to trigger infection and seed the protein misfolding cyclic amplification reaction. Distinct subclones of PK1 cells mediate swainsonine inhibition to very different degrees, implicating misglycosylation of one or more host proteins in the inhibitory process. The use of swainsonine and other glycosylation inhibitors described herein enhances the ability of the cell panel assay to differentiate between prion strains. Moreover, as shown elsewhere, the susceptibility of prions to inhibition by swainsonine in PK1 cells is a mutable trait.
    Journal of Biological Chemistry 09/2011; 286(47):40962-73. · 4.65 Impact Factor
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    ABSTRACT: Neuroblastoma-derived N2a-PK1 cells, fibroblastic LD9 cells and CNS-derived CAD5 cells can be infected efficiently and persistently by various prion strains. Swainsonine (swa), an inhibitor of Golgi α-mannosidase II that causes abnormal N-glycosylation, strongly inhibits infection of PK1 cells by RML, 79A and 22F, less so by 139A and not at all by 22L prions, and does not affect propagation of any of these strains in LD9 or CAD5 cells. Misglycosylated PrPC formed in the presence of swa is a good substrate for conversion to PrPSc and misglycosylated PrPSc is fully able to trigger infection and seed the Protein Misfolding Cyclic Amplification (PMCA) reaction. Distinct subclones of PK1 cells mediate swa inhibition to very different degrees, implicating misglycosylation of one or more host proteins in the inhibitory process. The use of swainsonine and other glycosylation inhibitors enhances the ability of the Cell Panel Assay to differentiate between prion strains. Moreover, as shown elsewhere, the susceptibility of prions to inhibition by swainsonine in PK1 cells is a mutable trait.
    Journal of Biological Chemistry 09/2011; · 4.65 Impact Factor
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    ABSTRACT: Until now only a few cell lines have been proved able to propagate prions and only limited prion strains have been replicated in cell models. Neurosphere lines isolated from the brains of mice at embryonic day 14 grow as aggregates and contain CNS stem cells. Others authors have previously reported that cultured neurospheres expressing cellular prion protein (PrP(C)) can be infected with prions. As potential neural progenitors the neurosphere cultures are supposed to differentiate into neurons and astrocytes which represent the main cell types infected by prions in vivo. Here we study the ability of undifferentiated and differentiated neurospheres to replicate several prion strains. Neurosphere cultures were isolated from 129/ola, FVB, Prnp(0/0) and Tga20 mice, which over-express murine PrP. We were not able to detect PrP(res) accumulation in dividing neurosphere cultures after prion exposure to two different mouse adapted scrapie inocula (RML and 22L). In contrast, with differentiated neurosphere cultures expressing PrP(C) (129/ola, FVB and Tga20) a successful PrP(Res) amplification was observed in very short time experiments when infected with the same inocula, implying that cell differentiation improve prion replication in these cultured cells. The mouse BSE adapted inocula (301C) was not amplified in these neurosphere cultures neither before nor after differentiation, suggesting that these cell cultures showed a differential prion strain susceptibility. These results suggest that differentiated neurosphere cultures can complement prion bioassays in mouse models.
    Journal of neuroscience methods 03/2010; 188(2):270-5. · 2.30 Impact Factor
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    ABSTRACT: How susceptible pigs are to infection with sheep prions is unknown. We show, through transmission experiments in transgenic mice expressing porcine prion protein (PrP), that the susceptibility of this mouse model to bovine spongiform encephalopathy (BSE) can be enhanced after its passage in ARQ sheep, indicating that the pathogenicity of the BSE agent is modified after passage in sheep. Transgenic mice expressing porcine PrP were, nevertheless, completely resistant to infection with a broad panel of classical scrapie isolates from different sheep PrP genotypes and with different biochemical characteristics. The atypical (Nor98 like) isolate (SC-PS152) was the only scrapie isolate capable of transmission in these mice, although with a marked transmission barrier. Unexpectedly, the atypical scrapie agent appeared to undergo a strain phenotype shift upon transmission to porcine-PrP transgenic mice and acquired new strain properties, suggesting that atypical scrapie agent may exhibit different phenotypes depending on the host cellular PrP or other genetic factors.
    Emerging Infectious Diseases 08/2009; 15(8):1214-21. · 6.79 Impact Factor
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    ABSTRACT: Faeces from infected animals have been suggested as a potential source of contamination and transmission of prion diseases in the environment. This work describes the development of a procedure for the detection of PrP(res) in stools which is based on a detergent-based extraction and immunoprecipitation (IP). The procedure was evaluated by analyzing TSE-spiked sheep and mice faeces, and proved to be specific for PrP(res) with sensitivities of 5-10 microg of infected brain tissue. In order to analyze the shedding of prions, we studied stools from orally inoculated mice over 4-days post-inoculation and also stools from terminally sick scrapie-infected mice. PrP(res) was only detected in stools shortly after the oral ingestion of TSE agents. The procedure described could be a useful tool for studying the excretion of prions and for evaluating potential environmental contamination by prions.
    Veterinary Microbiology 04/2008; 131(1-2):205-11. · 3.13 Impact Factor
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    ABSTRACT: Sheep can be experimentally infected with bovine spongiform encephalopathy (BSE), and the ensuing disease is similar to scrapie in terms of pathogenesis and clinical signs. BSE infection in sheep is an animal and human health concern. In this study, the transmission in BoPrP-Tg110 mice of prions from BSE-infected sheep was examined and compared to the transmission of original cattle BSE in cattle and sheep scrapie prions. Our results indicate no transmission barrier for sheep BSE prions to infect BoPrP-Tg110 mice, but the course of the disease is accelerated compared to the effects of the original BSE isolate. The shortened incubation period of sheep BSE in the model was conserved in subsequent passage in BoPrP-Tg110 mice, indicating that it is not related to infectious titer differences. Biochemical signature, lesion profile, and PrP(Sc) deposition pattern of both cattle and sheep BSE were similar. In contrast, all three sheep scrapie isolates tested showed an evident transmission barrier and further adaptation in subsequent passage. Taken together, those data indicate that BSE agent can be altered by crossing a species barrier, raising concerns about the virulence of this new prion towards other species, including humans. The BoPrP-Tg110 mouse bioassay should be considered as a valuable tool for discriminating scrapie and BSE in sheep.
    Journal of Virology 02/2007; 81(2):835-43. · 5.08 Impact Factor
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    ABSTRACT: RK13 cell lines generated to express bovine PrP(C) with a four extra octarepeat insertional mutation (Bo-10ORPrP(C)) show partially insoluble PrP(C) and lower rates of cell growth when compared to either the same cells expressing wild type Bo-6ORPrP(C) or the original RK13 cell line. The expression of Bo-10ORPrP(C) in cell cultures was also associated with changes in cell size and reorganization of the actin cytoskeleton. This last process was reversed by Clostridium difficile toxin-B, a specific inhibitor of small GTPase proteins. Further, in clones expressing Bo-10ORPrP(C), increased proportions of cells at cell cycle stage G2/M were observed. Proteasome inhibitors caused a further expansion of G2/M-stage cells that was more marked in cell lines expressing Bo-10ORPrP(C) than those expressing Bo-6ORPrP(C), while this effect was minimal or null in the original RK13 cell line. Hence, the presence of Bo-10ORPrP(C) in RK13 cells promotes cell cycle arrest at G2/M, and the effect is amplified by proteasome inhibition. These findings suggest a role for PrP(C) in cell morphology and cell cycle regulation, and open new avenues for understanding the mechanisms underlying PrP mutation-associated diseases.
    FEBS Letters 08/2006; 580(17):4097-104. · 3.58 Impact Factor
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    ABSTRACT: Bovine spongiform encephalopathy (BSE) is one of several diseases known collectively as transmissible spongiform encephalopathies (TSE) and caused by prions, which are nonconventional infectious agents. The risk of human infection by exposure to a TSE agent is generally considered to be low, because of the species barrier. However, the prions causing BSE in cattle are able to cross the species barrier easily. The appearance of variant Creutzfeldt–Jakob disease (vCJD) after human exposure to BSE prions has highlighted the possible impacts of this infection on human health. Today, a major concern is that the number of BSE cases in many European countries, including the emerging eastern European countries of the EU, is growing. A further concern now emerging is the possibility that BSE could spread to other livestock species, such as sheep or goats. This paper provides an overview of BSE transmission and its potential implications for public health. Prion diseases Bovine spongiform encephalopathy (BSE) is one of several diseases known collectively as transmissible spongiform encephalopathies (TSE), or prion diseases, which are degenera-tive neurological disorders that are presently incurable. There is currently considerable evi-dence to indicate that these diseases are caused by a conformational conversion of the cellular prion protein (PrP C), a membrane glycoprotein of uncertain function, into scrapie prion pro-teins (PrP Sc), a β-rich and protease-resistant iso-form that appears to be infectious in the absence of nucleic acid [1,2]. The generally accepted finding of an abnormally folded pro-tein as the causative agent, able to propagate in a host other than that in which it originated, is changing our view of transmissible diseases. The concept of infection resulting from patho-gen propagation within a susceptible host has been linked traditionally to the ability of nucleic acids to replicate their own coded infor-mation. In prion infections, the information seems to be coded within the conformation of the protein itself. This phenomenon challenges the well-established principles of molecular biology. The propagation of prions is based on strategies previously unrecognized, and depends on prion conformation and/or specific host restrictions. Prion protein PrP C is encoded by the prnp gene, whose sequence is highly conserved among mammals [3]. Ablation of the prnp gene in transgenic mice
    Future Virology 01/2006; 1(1):393-402. · 0.96 Impact Factor
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    MG Mundo ganadero, ISSN 0214-9192, Año 15, Nº. 169, 2004, pags. 65-70. 01/2004;
  • Neurologia 01/2003; Actualizaciones en Neurología, Neurociencias y Envejecimiento(1(3)):172-179.