朊病毒病实验动物脑组织PrPSc样本库的建立

目的 建立朊病毒病实验动物脑组织检测样本库,检测其在特定保存条件下的稳定性,以用于动物和人朊病毒病诊断技术的评估和考核.方法 选用30只经颅内注射感染羊瘙痒因子263K的仓鼠和30只正常仓鼠,每只分别制备10%、1%和0.5%3种浓度的脑组织匀浆,分装冷冻保存.以Western Blot方法 确定脑组织匀浆中PrPSc的存在情况,并分别在建库半年和3年检测PrPSc的稳定性.结果 30只感染仓鼠10%脑组织匀浆全部可检出PrPSc,1%脑组织匀浆有26份为PrPSc阳性,0.5%脑组织匀浆有19份为PrPSc阳性.半年及3年后复检,PrPSc阳性检出率基本不变.所有正常仓鼠脑匀浆均为PrPSc阴性.结论 建立了稳定性良好的含有90份PrPSc阳性标本和90份PrPSc阴性样本的朊病毒病实验动物脑组织检测样本库.     

蛋白质错误折叠循环扩增技术及其应用

可传播性海绵状脑病是一类由朊病毒侵袭中枢神经系统而引起的致死性神经退行性疾病.在朊病毒病的病理过程中,细胞正常朊蛋白PrPc(cellular PrP)转化为异常构象的PrPSc(scrapie PrP)是至关重要的.目前,PrPSc转化增殖及致病机理仍不清楚.蛋白质错误折叠循环扩增(protein misfolding cyclic amplification,PMCA)技术的出现和应用,为研究朊病毒病的发病机制和发展敏感性高、特异性强的检测方法提供了很好的技术平台.     

朊蛋白N端和C端多肽特异性抗体的制备及ELISA检测技术的研究

目的 制备朊蛋白N端和C端多肽特异性抗体，并对ELISA方法在朊病毒病检测中的应用进行研究。方法构建人朊蛋白N端和C端多肽原核表达重组质粒，分别表达纯化融合蛋白。以此为抗原制备朊蛋白N端和C端多肽特异性抗体。ELISA和Western Blot检测所制备抗体与重组和天然的PrP蛋白的免疫反应性。初步建立间接ELISA检测技术。结果 所制备的N端和C端抗体可特异性识别重组全长PrP蛋白和相应的PrP片段，无明显交叉反应。C端抗体还可有效地识别感染羊瘙痒因子263K的仓鼠脑组织中经PK消化后的prp^Se，其Western Blot反应带型与PrP单抗3174相似。5000r／min离心处理脑组织悬液可有效保留上清中PrP^Se成分而不影响ELISA检测。蛋白酶K虽经灭活处理，但可明显抑制重组和天然PrP在液相中与相应抗体的结合。间接ELISA方法可根据反应A值区分正常或感染动物样本。结论 所制备的朊蛋白N端和C端抗体具有良好的特异性，C端抗体可用于实验性朊病毒病的检测。建立的间接ELISA方法可试用于朊病毒病的初步筛查。     

PrP及其缺失突变体与GFAP体外相互作用的初步研究

目的研究PrP蛋白与GFAP蛋白是否发生分子间相互作用以及PrP蛋白多肽链中与GFAP蛋白相互作用的区域。方法制备仓鼠脑组织匀浆上清,通过原核表达系统以及体外翻译系统表达了全长的小鼠GFAP蛋白、人PrP蛋白以及各种缺失突变体,利用Pull-down及免疫共沉淀实验检测PrP与GFAP的分子间相互作用。结果不仅重组的GFAP与PrP发生分子间的相互作用,而且脑组织中的GFAP与PrPC及PrPSc也发生相互作用。PrP与GFAP蛋白相互作用的区域位于PrP的C端第91至231位氨基酸。结论PrP及其缺失突变体与GFAP在体外能够发生分子间的相互作用,提示GFAP可能参与朊蛋白的正常生理功能或者朊病毒病的病理过程。     

朊病毒病实验室生物安全风险控制特点分析

朊病毒病（prion disaese）或可传播性海绵状脑病（transmissible spongiform encephalopathies,TSEs）是一类侵袭人类及多种动物中枢神经系统的退行性脑病,潜伏期长,100％病死率.人类的朊病毒病有克-雅病（Creutzfeldt-Jacob disease,CJD）,包括散发型、家族遗传型、医源型、变异型CJD（variant CJD,vCJD）,另外还有库鲁病（Kuru）、GSS综合征（Gerstmann-Straussler-Scheinker syndrome）、致死性家族型失眠症（fatal familial insomnia,FFI）,其致病因子是朊病毒.朊病毒为微小的蛋白感染颗粒,不包含核酸,与常规病毒不同[1].目前认为朊病毒是由在正常哺乳动物脑组织中存在的PrP蛋白（PrPC）经过构象转变而形成,又称PrPSc.在朊病毒患者中枢神经组织中可以检出异常致病蛋白PrPSc的沉积[1],但不同的朊病毒病具有不同的特点,主要表现在临床特征、潜伏期、脑组织中prpsc的分布、脑组织损伤的特点、能否诱导淀粉样变化,以及朊病毒的分子特征等,具有明显的＆quot;毒株＆quot;差异.鉴于朊病毒不同于传统病毒,具有独特的实验室检测技术[2],因此存在独特的生物风险形式.本文从朊病毒病原学特点和常见实验检测技术方面分析朊病毒实验活动中的生物风险形式,并提出相应的预防措施.     

朊蛋白相关蛋白Shadoo与朊病毒病

朊病毒病,即传染性海绵状脑病(transmissible spongiform encephalopathies,TSEs),是一类传染性、致死性神经退行性疾病.在朊病毒病的病理过程中,细胞正常朊蛋白PrPC转化为异常构象的PrPSc是至关重要的,但是PrPC的正常生理功能仍不清楚.国外学者利用比较基因组学发现了一个新的朊蛋白相关蛋白-Shadoo(Sho).Sho与PrPC在氨基酸序列和细胞定位的相似性及主要在脑组织表达,使它成为一个非常值得研究的PrP相关蛋白.对Sho可能存在的与PrPC重叠的功能甚至直接相互作用的研究工作,将对今后揭示PrPC正常生理功能以及揭示Prion病发病机制具有重要现实意义.     

不同剂量羊瘙痒因子263K颅内感染仓鼠临床终末期脑中GFAP表达的研究

目的 研究不同剂量羊瘙痒因子263 K经颅内注射感染仓鼠后,在发病的终末期星形胶质细胞增生程度是否与注射剂量及潜伏期长短有关.方法 以胶质纤维酸性蛋白(glial fibrill aryacidic protein,GFAP)作为星形胶质细胞增生的分子标志物,采用Western Blot和免疫组化方法检测感染仓鼠终末期脑匀浆和脑组织病理切片中的GFAP表达,经定量分析比较各感染剂量组间是否存在差异.结果与正常对照相比,不同剂量感染仓鼠发病终末期脑组织GFAP阳性细胞数量和总GFAP含量均明显升高,但各感染剂量组间无显著差异.结论 不同感染剂量羊瘙痒因子263K经颅内注射感染仓鼠在发病终末期脑中星形胶质细胞的增生程度相似,与感染剂量及潜伏期无关联性.     

超声处理对羊瘙痒病脑组织中PrPSc聚集状态的影响

目的 研究超声处理对感染羊瘙痒症仓鼠脑组织中PrP^Sc聚集状态的影响，寻找产生PrP^Sc低聚体的条件。方法 裂解液制备脑组织提取物，用各种超声条件处理不同阶段的脑组织提取物；以蛋白酶消化后的Western blot方法和图象分析系统观测PrP^Sc蛋白的分布和聚集状态。结果 适当的超声处理(15s共30次)可增加脑组织匀浆上清中PrP^Sc含量1．29～1．58倍；同样条件下超声处理可明显增加羊瘙痒因子263K感染仓鼠脑组织匀浆上清中PrP蛋白总量，而对正常对照仓鼠脑组织匀浆上清中PrP蛋白总量影响不大；对经常规高速离心获得的PrP^Sc的超声处理显示约90％的PrP^Sc存在于离心上清液中。结论 对感染动物脑组织进行超声处理可增加PrP^Sc的提取量，利于实验室检测。适当的超声处理可破碎大的相对分子质量的PrP^Sc聚集物，产生小的相对分子质量的PrP^Sc产物。     

体外无药物选择压力条件下HIV-1耐药基因突变的演变

目的 分离培养体外稳定传代的原代HIV-1耐药毒株,观察失去药物压力下,耐药毒株的体外生长以及主要耐药突变的演化趋势.方法 采集15例服用拉米夫定+司他夫定+萘韦拉平(3TC+D4T+NVP)的HIV-1感染者的外周血单个核细胞(PBMC),用体外共培养的方法从中分离原代HIV-1毒株;RT-PCR扩增耐药毒株历代培养上清的HIV-1 pol区基因并测序,在Stanford HIV Drug Resistance Database数据库进行耐药性分析.结果 15例患者中病毒载量>1000拷贝/ml的有8例,均成功分离出稳定传代的原代毒株,其中2株为耐药毒株,所携带的主要耐药突变分别是K103N/K238T和M184V/K103N/Y181C/H221Y,分别对NVP和3TC/NVP高度耐药;无药物压力的体外培养过程中,M184V、K103N、Y181C和H221Y等耐药突变可以稳定传代,但是K238T发生了回复突变.结论 分离出2株稳定传代的HIV-1耐药毒株,无药物压力情况下,携带K103N突变的毒株具有较好的复制适应性,可稳定传代;携带M184V和K103N/Y181C/H221Y的毒株也能够稳定复制;本研究中发现K238T耐药突变在失去药物的条件下稳定性差,提示该位点易发生回复突变.     

体外模拟干细胞微环境培养扩增脐血及脐带基质源性间充质干细胞**

背景：建立稳健的扩增体系,在体外扩增时最大限度地获得治疗剂量的干细胞数,同时保存干细胞的特性是临床实验室亟待解决的问题。 目的：建立体外模拟干细胞微环境细胞外基质扩增脐血间充质干细胞及脐带间充质干细胞的方法,并与传统的2-D培养体系比较。 方法：建立体外模拟干细胞微环境细胞外基质,体外分离脐血间充质干细胞及脐带间充质干细胞后分别接种到细胞外基质及传统的2-D塑料培养体系,分别从细胞计数及细胞表面标志物的变化,评估两种扩增体系对脐血间充质干细胞及脐带间充质干细胞体外扩增的优劣。 结果与结论：使用骨髓源性的细胞外基质培养体系单位时间脐血间充质干细胞及脐带间充质干细胞产量是2-D体系的4~6倍,并且流式细胞仪检测显示细胞外基质体系能更好地保持干细胞的表面标记。因此,3-D较2-D培养系更接近生理环境,已建立的骨髓源性细胞外基质培养体系能保持间充质干细胞的特性,为短时间内快速获取更大数目同质、高活性的间充质干细胞提供了可能。 关键词：脐血间充质干细胞;脐带间充质干细胞;细胞外基质;2-D培养板;培养扩增 doi:10.3969/j.issn.1673-8225.2012.10.011     

Molecular interaction between prion protein and GFAP both in native and recombinant forms in vitro

Gliosis of glial fibrillary acidic protein (GFAP) associated astrocytes is considered to be one of the hallmarks of transmissible spongiform encephalopathies (TSEs). In the present study, remarkable GFAP-PrP(Sc) or GFAP-PrP(C) complexes were separately detected in the brain homogenates of 263 K (Scrapie)-infected or normal hamsters by co-immunoprecipitation assay. To get more exact molecular evidences for interaction between prion protein (PrP) and GFAP, various recombinant PrP or GFAP proteins were expressed using prokaryotic-expressing and in vitro translation system. Using pull down and co-immunoprecipitation assays, reliable molecular interaction between PrP and GFAP was observed, and proteinase K (PK)-digested PrP(Sc) molecules were confirmed to be able to bind the recombinant GFAP specifically as well. The region within PrP that was responsible for interaction with GFAP was narrowed to PK-resistant core of PrP (i.e. aa 91-230). The study of the association of PrP with GFAP supplies the molecular evidence for the observation of co-localization of PrP(Sc) and GFAP in the brains of TSEs and may further provide insight into a potential role of GFAP in the biological function of PrP and the pathogenesis of prion diseases.     

Influence of guanidine on proteinase K resistance in vitro and infectivity of scrapie prion protein PrP(Sc)

As the scrapie prion protein PrP(Sc) is rich in beta-sheets it aggregates into prion rods, which show infectivity and proteinase K (PK) resistance. Consequently, dissociation of prion rods and breakdown of beta-sheets in PrP(Sc) by denaturation results in loss of both infectivity and PK-sensitivity. In this study, the effects of guanidine (Gdn), which solubilizes and denatures proteins by breaking down their higher structure, on the solubility, the PK-resistance in vitro and the infectivity of PrP(Sc) of scrapie strain 263K was examined. The infectivity was assayed by intracerebral inoculation into hamsters. Brain tissues of scrapie-infected hamsters were used for preparation of homogenates and crude extracts of PrP(Sc). A treatment of PrP(Sc) with Gdn enhanced its PK-sensitivity in a dose-dependent manner. The PK-resistance in vitro of PrP(Sc) denatured with lower concentrations of Gdn (<2.5 mol/l) could partially resume by renaturation. Gdn markedly reduced or, at higher concentrations, even destroyed the infectivity of PrP(Sc). On the other hand, the infectivity of PrP(Sc) inactivated by denaturation could be partially restored by renaturation. These results confirmed our assumption that all the alternations in the PK-resistance and the infectivity of PrP(Sc) caused by Gdn resulted from changes in its higher structure. However, it should be emphasized that a complete loss of PK-resistance of PrP(Sc) may not necessarily mean its full non-infectivity.     

Detection of ultra-low levels of pathologic prion protein in scrapie infected hamster brain homogenates using real-time immuno-PCR

Pathologic prion protein (PrP(Sc)), implicated in transmissible spongiform encephalopathies, is detected by antibody-based tests or bioassays to confirm the diagnosis of prion diseases. Presently, the Western blot or an ELISA is officially used to screen the brain stem in cattle for the presence of PrP(Sc). The immuno-polymerase chain reaction (IPCR), a technique whereby the exponential amplification ability of PCR is coupled to the detection of proteins by antibodies in an ELISA format, was applied in a modified real-time IPCR method to detect ultra-low levels of prion protein. Using IPCR, recombinant hamster PrP(C) was consistently detected at 1 fg/mL and proteinase K (PK)-digested scrapie infected hamster brain homogenates diluted to 10(-8) (approximately 10-100 infectious units) was detected with a semi-quantitative dose response. This level of detection is 1 million-fold more sensitive than the levels detected by Western blot or ELISA and poises IPCR as a method capable of detecting PrP(Sc) in the pre-clinical phase of infection. Further, the data indicate that unless complete PK digestion of PrP(C) in biological materials is verified, ultrasensitive assays such as IPCR may inaccurately classify a sample as positive.     

Short-term study of the uptake of PrP(Sc) by the Peyer's patches in hamsters after oral exposure to scrapie

The disease-associated prion protein (PrP(Sc)) has been detected in the ileal Peyer's patches of lambs as early as one week after oral exposure to scrapie. In hamsters, the earliest reported time of PrP(Sc) detection in the Peyer's patches after oral exposure to scrapie is 69 days post-infection. To evaluate the acute uptake of inoculum and to investigate whether the Peyer's patches constitute the primary site of entry for scrapie after oral exposure, hamsters were each exposed orally to 1 ml of a 10% brain homogenate from hamsters in the terminal stage of infection with the 263 K strain of the scrapie agent. PrP(Sc) was demonstrated in the Peyer's patches only a few days after exposure, i.e., much earlier than previously reported. This study supports the view that the Peyer's patches constitute at least one of the primary entry sites of PrP(Sc) after oral exposure to scrapie.     

Detection of type 1 prion protein in variant Creutzfeldt-Jakob disease

Molecular typing of the abnormal form of the prion protein (PrP(Sc)) has come to be regarded as a powerful tool in the investigation of the prion diseases. All evidence thus far presented indicates a single PrP(Sc) molecular type in variant Creutzfeldt-Jakob disease (termed type 2B), presumably resulting from infection with a single strain of the agent (bovine spongiform encephalopathy). Here we show for the first time that the PrP(Sc) that accumulates in the brain in variant Creutzfeldt-Jakob disease also contains a minority type 1 component. This minority type 1 PrP(Sc) was found in all 21 cases of variant Creutzfeldt-Jakob disease tested, irrespective of brain region examined, and was also present in the variant Creutzfeldt-Jakob disease tonsil. The quantitative balance between PrP(Sc) types was maintained when variant Creutzfeldt-Jakob disease was transmitted to wild-type mice and was also found in bovine spongiform encephalopathy cattle brain, indicating that the agent rather than the host specifies their relative representation. These results indicate that PrP(Sc) molecular typing is based on quantitative rather than qualitative phenomena and point to a complex relationship between prion protein biochemistry, disease phenotype and agent strain.     

Guanidine hydrochloride extraction and detection of prion proteins in mouse and hamster prion diseases by ELISA

Current detection of transmissible spongiform encephalopathy (TSE) relies on the proteolytic generation of a protease-resistant core from the scrapie isoform of prion protein (PrP(Sc)) followed by immunoblotting. This process is non-quantitative, time-consuming, and technically demanding. Recently, an alternative in vitro test for TSE based on the differential extraction of brain homogenates using guanidine hydrochloride followed by DELFIA (Dissociation Enhanced Lanthanide FluoroImmunoAssay) has been developed. In the present study, this approach was adopted using a panel of anti-PrP monoclonal antibodies (MAbs) in conventional sandwich enzyme-linked immunosorbent assay (ELISA) to investigate hamster and two distinct strains of mouse prion diseases. Although PrP species were present in both soluble and insoluble fractions from normal as well as TSE samples, only the PrP species in the insoluble fractions from the latter samples were protease-resistant. In addition, certain anti-PrP MAb pairs could distinguish the PrP species in infected brains from those in the normal samples. The ability to differentiate disease-associated PrP isoforms without proteinase K digestion could serve as a panacea for developing a reliable and rapid diagnostic test for prion diseases.     

Efficient in vitro amplification of a mouse-adapted scrapie prion protein

Protein misfolding cyclic amplification (PMCA) is a highly sensitive technique used to detect minute amounts of scrapie prion protein (PrP(Sc)), a major protein component of the infectious agents associated with prion diseases. Although exponential in vitro amplification of hamster scrapie PrP(Sc) has been established, the PMCA used was unsuccessful in achieving good amplification of PrP(Sc) from other animals. Here, we have investigated the cause of the insufficient PrP(Sc) amplification in mice and have developed an improved method suitable for amplification of the PrP(Sc) of the mouse-adapted scrapie prion strain Chandler. Mouse PrP(C), the cellular form of the prion protein, tends to become resistant to proteases during incubation independent of sonication. By adding digitonin to the reaction buffer as a lipid detergent, accumulation of the protease-resistant PrP(C) was inhibited; hence, mouse PrP(Sc) could be amplified to infinite levels. The present study is the first report describing effective amplification of PrP(Sc) of the mouse-adapted scrapie prion and this improved PMCA technique will contribute to prion research that uses mice as experimental animals.     

Effect of the E200K mutation on prion protein metabolism. Comparative study of a cell model and human brain

The hallmark of prion diseases is the cerebral accumulation of a conformationally altered isoform (PrP(Sc)) of a normal cellular protein, the prion protein (PrP(C)). In the inherited form, mutations in the prion protein gene are thought to cause the disease by altering the metabolism of the mutant PrP (PrP(M)) engendering its conversion into PrP(Sc). We used a cell model to study biosynthesis and processing of PrP(M) carrying the glutamic acid to lysine substitution at residue 200 (E200K), which is linked to the most common inherited human prion disease. PrP(M) contained an aberrant glycan at residue 197 and generated an increased quantity of truncated fragments. In addition, PrP(M) showed impaired transport of the unglycosylated isoform to the cell surface. Similar changes were found in the PrP isolated from brains of patients affected by the E200K variant of Creutzfeldt-Jakob disease. Although the cellular PrP(M) displayed some characteristics of PrP(Sc), the PrP(Sc) found in the E200K brains was quantitatively and qualitatively different. We propose that the E200K mutation cause the same metabolic changes of PrP(M) in the cell model and in the brain. However, in the brain, PrP(M) undergoes additional modifications, by an age-dependent mechanism that leads to the formation of PrP(Sc) and the development of the disease.     

CpG oligodeoxynucleotide-enhanced humoral immune response and production of antibodies to prion protein PrPSc in mice immunized with 139A scrapie-associated fibrils

Prion diseases are characterized by conversion of the cellular prion protein (PrP(C)) to a protease-resistant conformer, the srapie form of PrP (PrP(Sc)). Humoral immune responses to nondenatured forms of PrP(Sc) have never been fully characterized. We investigated whether production of antibodies to PrP(Sc) could occur in PrP null (Prnp(-/-)) mice and further, whether innate immune stimulation with the TLR9 agonist CpG oligodeoxynucleotide (ODN) 1826 could enhance this process. Whether such stimulation could raise anti-PrP(Sc) antibody levels in wild-type (Prnp(+/+)) mice was also investigated. Prnp(-/-) and Prnp(+/+) mice were immunized with nondenatured 139A scrapie-associated fibrils (SAF), with or without ODN 1826, and were tested for titers of PrP-specific antibodies. In Prnp(-/-) mice, inclusion of ODN 1826 in the immunization regime increased anti-PrP titers more than 13-fold after two immunizations and induced, among others, antibodies to an N-terminal epitope, which were only present in the immune repertoire of mice receiving ODN 1826. mAb 6D11, derived from such a mouse, reacts with the N-terminal epitope QWNK in native and denatured forms of PrP(Sc) and recombinant PrP and exhibits a K(d) in the 10(-)(11) M range. In Prnp(+/+) mice, ODN 1826 increased anti-PrP levels as much as 84% after a single immunization. Thus, ODN 1826 potentiates adaptive immune responses to PrP(Sc) in 139A SAF-immunized mice. These results represent the first characterization of humoral immune responses to nondenatured, infectious PrP(Sc) and suggest methods for optimizing the generation of mAbs to PrP(Sc), many of which could be used for diagnosis and treatment of prion diseases.     

Packaging of prions into exosomes is associated with a novel pathway of PrP processing

Prion diseases are fatal, transmissible neurodegenerative disorders associated with conversion of the host-encoded prion protein (PrP(C)) into an abnormal pathogenic isoform (PrP(Sc)). Following exposure to the infectious agent (PrP(Sc)) in acquired disease, infection is propagated in lymphoid tissues prior to neuroinvasion and spread within the central nervous system. The mechanism of prion dissemination is perplexing due to the lack of plausible PrP(Sc)-containing mobile cells that could account for prion spread between infected and uninfected tissues. Evidence exists to demonstrate that the culture media of prion-infected neuronal cells contain PrP(Sc) and infectivity but the nature of the infectivity remains unknown. In this study we have identified PrP(C) and PrP(Sc) in association with endogenously expressing PrP neuronal cell-derived exosomes. The exosomes from our prion-infected neuronal cell line were efficient initiators of prion propagation in uninfected recipient cells and to non-neuronal cells. Moreover, our neuronal cell line was susceptible to infection by non-neuronal cell-derived exosome PrP(Sc). Importantly, these exosomes produced prion disease when inoculated into mice. Exosome-associated PrP is packaged via a novel processing pathway that involves the N-terminal modification of PrP and selection of distinct PrP glycoforms for incorporation into these vesicles. These data extend our understanding of the relationship between PrP and exosomes by showing that exosomes can establish infection in both neighbouring and distant cell types and highlight the potential contribution of differentially processed forms of PrP in disease distribution. These data suggest that exosomes represent a potent pool of prion infectivity and provide a mechanism for studying prion spread and PrP processing in cells endogenously expressing PrP.