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.     

人PrP特异性多肽抗体的鉴定和应用

目的 为了进一步检测制备的人PrP特异性多肽抗体的免疫反应性和特异性。方法 构建人PrPN端缺失原核表达质粒,表达并纯化N端缺失的PrP蛋白;Western blot检测多肽抗体与纯化的各种人全长、N端缺失以及C端缺失PrP蛋白的反应能力;免疫荧光法检测多肽抗体与真核表达的人PrP蛋白反应能力;提取Creutzfeldt-Jakob病（CJD）病人以及Scrapie感染的仓鼠脑组织,Westen blot检测多肽抗体与致病性PrP－res蛋白的反应能力。结果 所制备的PrP多肽抗体能与原核及真核细胞表达的各种不同长度的PrP蛋白反应,同时还能特异性识别Scrapie感染鼠脑组织中和CJD病人脑组织中的PrP－res蛋白。结论 多肽抗体具备良好的免疫反应性和特异性,可以应用于临床CJD病人的检测。     

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.     

一种朊蛋白错误折叠循环扩增方法的建立

目的建立一种类似于PCR的蛋白质扩增方法-蛋白错误折叠循环扩增技术(PMCA),用于朊病毒病脑组织中PrPSc的检测。方法将不同浓度的羊瘙痒因子263K毒株原液与正常仓鼠脑组织匀浆混合,经反复孵育/超声,共10~15个循环。WesternBlot检测扩增产物中蛋白酶K抗性PrPSc信号。结果在本研究试验体系下,263K毒株可以利用仓鼠脑组织为基质在体外迅速复制。所建立的PrPSc-PMCA技术可检测到10-5稀释的毒株原液中的PrPSc。与常规的脑组织免疫印记方法相比,敏感度提高了105~106倍。研究还显示PrPSc还可利用小脑和脑干为基质进行体外扩增复制。结论成功建立了PrPSc-PMCA技术,为朊病毒病的早期诊断和朊病毒生物学特性的研究提供了一种新的手段。     

耐热可溶性戊型肝炎病毒基因工程抗原的表达

目的 利用硫氧还蛋白融合表达系统表达戊型肝炎病毒（Hepatitis E virus,HEV)结构基因片段，获得耐热，可溶、具有生物活性的HEV基因工程抗原。方法 将HEVORF26964-7126nt基因片段插入硫氧还蛋白融合表达载体pThioHisA，转化大肠埃希菌BL21，经IPTG诱导，表达融合蛋白。裂解细菌后，离心，取上清置于80℃处理10min，再次离心，取上清用ELISA方法测定表达产物的生物活性。结果 SDS-PAGE分析表明，HEV结构基因获得高效表达，相对分子质量约为20000，耐热，水溶性好，ELISA证实具有HEV特异抗原性。结论 应用硫氧还蛋白融合表达系统成功表达了耐热，可溶，具有生物活性的HEV基因工程抗原。     

JNK信号转导通路介导吸烟所致的气道黏液高分泌

目的：探讨香烟对气道黏液分泌的影响及其信号转导机制。方法: 利用香烟提取物条件培养人气道上皮BEAS-2B细胞，以JNK特异性抑制剂SP600125为干预条件。采用RT-PCR技术观察培养细胞黏蛋白(MUC)5AC转录水平的改变。同时分别采用ELISA和Western blotting法检测培养上清液中MUC5AC和细胞表皮生长因子受体（EGFR）的蛋白水平。结果: 香烟刺激下培养细胞MUC5AC mRNA和蛋白分泌水平显著高于正常培养细胞，同时伴激活态EGFR蛋白含量的显著增高，但EGFR蛋白总量未见显著升高。SP600125显著下调香烟所致MUC5AC表达水平和分泌量的升高水平，而未对激活态EGFR水平的上升产生明显影响。结论: 香烟提取物可从转录水平诱导气道上皮细胞呈现黏液高分泌状态；进一步证明其信号转导机制有EGFR的作用，而JNK信号通路也部分参与其中，且不依赖于EGFR。     

苦荞黄酮提取物通过抑制NF-κB信号通路减轻蛛网膜下腔出血模型大鼠神经炎症和氧化应激

目的：探索苦荞黄酮提取物减轻蛛网膜下腔出血（SAH）模型大鼠神经炎症和氧化应激的作用机制。方法：将60只大鼠随机分为假手术组、模型组、尼莫地平组、苦荞黄酮提取物低、中、高剂量组，每组10只。Longa分级评估神经功能缺损；干湿重法测定脑含水量；伊文思蓝染料外渗实验检测大脑血脑屏障通透性；ELISA检测血清TNF-α、IL-6、IL-1β水平和脑组织中上述炎症因子及超氧化物歧化酶（SOD）、丙二醛（MDA）和谷胱甘肽过氧化物酶（GSH-Px）水平；Western blot检测大鼠脑皮质中细胞外调节蛋白激酶/核转录因子κB(ERK/NF-κB)信号通路蛋白表达。结果：与模型组相比，尼莫地平组和苦荞黄酮提取物中、高剂量组大鼠神经功能缺损评分、脑含水量、伊文思蓝渗出量、血清及脑组织TNF-α、IL-6和IL-1β水平、脑组织MDA水平及MMP-9、p-ERK/ERK和p-NF-κB P65/NF-κB P65蛋白量明显下降，脑组织中SOD和GSH-Px水平明显上升（P<0.05）。结论：苦荞黄酮提取物通过抑制ERK/NF-κB信号通路蛋白表达，减缓大鼠神经炎症和氧化应激反应，发挥对SAH...     

去甲肾上腺素诱导严重烧伤大鼠脑组织VEGF表达的实验研究

目的：观察去甲肾上腺素（NE）诱导严重烧 伤后24h大鼠脑组织血管内皮细胞生长因子(VEGF)的表达变化。方法:(1 )采用40%全身总体表面积（TBSA）Ⅲ°烧伤大鼠模型，用干、湿重法检测NE刺激烧伤24h大 鼠脑组织含水量；(2)用高效液相色谱法，检测烧伤大鼠脑组织去甲肾上腺素活性水平的变 化;(3) 用免疫蛋白印迹法（Western blotting）检测NE诱导脑组织VEGF蛋白表达变化。 结果：(1) 烧伤大鼠和NE刺激后的烧伤大鼠脑组织水肿明显；(2)烧伤后2 4 h大鼠脑组织NE活性增加，而NE刺激后的烧伤大鼠，脑组织NE的活性增加显著;(3) NE刺 激剂量增大时，脑组织VEGF的蛋白表达逐渐增加，烧伤后VEGF的蛋白表达增加明显，随NE刺 激剂量增大，烧伤后VEGF的蛋白表达明显增强。结论:NE可诱导严重烧 伤大鼠脑组织VEGF的蛋白表达，提示烧伤后NE水平增高是脑水肿形成的一个重要因素。     

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.     

PrP(Sc) is not detected in peripheral blood leukocytes of scrapie-infected sheep: determining the limit of sensitivity by immunohistochemistry

Peripheral blood leukocytes (PBLs) from scrapie-infected sheep were evaluated for the presence of PrP(Sc) by using dissociated retropharyngeal lymph node (DRLN) cells and immunohistochemistry (IHC). PrP(Sc)-positive cells were detected in 2.05% +/- 0.28% of 3 x 10(6) DRLN cells, but were not detected in 3 x 10(6) PBLs from scrapie-infected sheep. Titration of DRLN cells mixed with PBLs showed that IHC detects a minimum of 0.00205% or 60 PrP(Sc)-positive cells in 3 x 10(6) PBLs.     

信号蛋白14-3-3 β及其缺失突变体与朊蛋白体外相互作用的初步研究

目的 确定PrP蛋白与14-3-3蛋白是否发生分子间的相互作用,以及相互作用区域.方法 表达纯化PrP和人14-3-3 β及其缺失突变体.通过Pull-down和免疫共沉淀方法研究全长人14-3-3 β及缺失突变体与PrP蛋白是否发生分子间相互作用以及相互作用的区域.结果 14-3-3 β能与PrP23-231发生体外的相互作用,且与PrP相互作用的区域位于14-3-3 β N端第1位至38位氨基酸.结论 首次证实人14-3-3 β与PrP相互作用的区域位于14-3-3 β N端第1位至38位氨基酸.     

Detection of PrP(Sc) in rectal biopsy and necropsy samples from sheep with experimental scrapie

Scrapie diagnosis is based on the demonstration of disease-associated prion protein (PrP(Sc)) in brain or, in the live animal, in readily accessible peripheral lymphoid tissue. Lymphatic tissues present at the rectoanal line were readily obtained from sheep without the need for anaesthesia. The presence of PrP(Sc) in such tissue was investigated in sheep infected orally with scrapie-infected brain material. The methods used consisted of immunohistochemistry and histoblotting on biopsy and post-mortem material. PrP(Sc) was detected in animals with PrP genotypes associated with high susceptibility to scrapie from 10 months after infection, i.e., from about the time of appearance of early clinical signs. In the rectal mucosa, PrP(Sc) was found in lymphoid follicles and in cells scattered in the lamina propria, often near and sometimes in the crypt epithelium. By Western blotting, PrP(Sc) was detected in rectal biopsy samples of sheep with the PrP genotype VRQ/VRQ, after electrophoresis of material equivalent to 8 mg of tissue. This study indicated that rectal biopsy samples should prove useful for the diagnosis of scrapie in sheep.     

Prion protein is ubiquitinated after developing protease resistance in the brains of scrapie-infected mice

Although the key event in the pathology of prion diseases is thought to be the conversion of cellular prion protein (PrP(C)) to the protease-resistant scrapie species termed PrP(Sc), the factors that contribute to neurodegeneration in scrapie-infected animals are poorly understood. One probable determinant could be when the accumulation of PrP(Sc) in infected brain overwhelms the ubiquitin-proteasome system and triggers the degenerative cascade. In the present study, it was found that in mouse brains infected with the ME7 scrapie strain, the level of ubiquitin protein conjugates increased significantly at approximately 144 days post-infection (pi) when clinical signs first become apparent. This elevation correlated with the detection of protease-resistant PrP(Sc) and a decline in two endopeptidase activities associated with proteasome function. However, ubiquitination of PrP was only detected at the terminal stage, 3 weeks after the development of clinical symptoms (approximately 165 days pi). These results suggest that ubiquitination of PrP is a late event phenomenon and this conjugation occurs after the formation of protease-resistant PrP(Sc). Whether this post-translational modification and the impairment of proteasome function are pivotal events in the pathogenesis of prion diseases remains to be determined.     

Correlation of polydispersed prion protein and characteristic pathology in the thalamus in variant Creutzfeldt-Jakob disease: implication of small oligomeric species

The vacuolation, neuronal loss and gliosis that characterize human prion disease pathology are accompanied by the accumulation of an aggregated, insoluble and protease-resistant form (termed PrP(Sc)) of the host-encoded normal cellular prion protein (PrP(C)). In variant Creutzfeldt-Jakob disease the frontal cortex and cerebellum exhibit intense vacuolation and the accumulation of PrP(Sc) in the form of amyloid plaques and plaque-like structures. In contrast the posterior thalamus is characterized by intense gliosis and neuronal loss, but PrP(Sc) plaques are rare and vacuolation is patchy. We have used sucrose density gradient centrifugation coupled with conformation dependent immunoassay to examine the biochemical properties of the PrP(Sc) that accumulates in these different brain regions. The results show a greater degree of PrP(Sc) polydisperal in thalamus compared with frontal cortex or cerebellum, including a subpopulation PrP(Sc) molecules in the thalamus that have sedimentation properties resembling those of PrP(C). Much effort has focused on identifying aspects of PrP(Sc) biochemistry that distinguish between different forms of human prion disease and contribute to differential diagnosis. Here we show that PrP(Sc) sedimentation properties, which can depend on aggregation state, correlate with, and may underlie the distinct neurodegenerative processes occurring in different regions of the variant Creutzfeldt-Jakob disease brain.     

A refined method for molecular typing reveals that co-occurrence of PrP(Sc) types in Creutzfeldt-Jakob disease is not the rule

Molecular typing in Creutzfeldt-Jakob disease (CJD) relies on the detection of distinct protease-resistant prion protein (PrP(Sc)) core fragments, which differ in molecular mass or glycoform ratio. However, the definition and correct identification of CJD cases with a co-occurrence of PrP(Sc) types remains a challenge. With antibodies recognizing a linear epitope in the octapeptide repeat PrP region, supposed to distinguish between the two major PrP(Sc) isoforms (ie, types 1 and 2), it was recently shown that all type 2 cases display an associated band with a type 1 migration pattern, which led to the conclusion that multiple PrP(Sc) types regularly coexist in CJD. We studied brain samples from 53 sporadic CJD and 4 variant CJD subjects using a high-resolution electrophoresis, a wide range of proteinase K (PK) activities, the 'type 1-selective' antibody 12B2, and several unselective antibodies. We found that the type 1-like band detected by 12B2 in all CJD subtypes associated with PrP(Sc) type 2 is not a PK-resistant PrP(Sc) core but rather matches the physicochemical properties of partially cleaved fragments, which result from the several PK cleavage sites included in the N-terminal portion of PrP(Sc). Furthermore, using gels with high resolution and a relatively high PK activity, we were able to increase the detection sensitivity of either type 1 or 2, when coexisting, to amount corresponding to 3-5% of the total PrP(Sc) signal (ie, weak band of one type/total PrP(Sc)). Our results show that there are many pitfalls associated with the use of 'type 1 selective' antibodies for CJD typing studies and that co-occurrence of PrP(Sc) types in CJD is not the rule. The present results further validate the rationale basis of current CJD classification and the qualitative nature of molecular typing in CJD.     

Reduction of protein kinase MARK4 in the brains of experimental scrapie rodents and human prion disease correlates with deposits of PrP(Sc)

Microtubule affinity-regulating kinase 4 (MARK4) belongs to a family of kinases that are able to actively phosphorylate the neuronal microtubule-associate proteins (MAPs), such as tau, MAP2 and the ubiquitous MAP4. Abnormal changes in tubulin and the profiles of tau have been previously reported in the human brain and animal transmissible spongiform encephalopathies (TSEs), which may be associated with abnormal alterations of various cellular kinases. To elucidate the possible role of MARK4 in TSE pathogenesis, the MARK4 levels in the brain tissues of scrapie-infected rodents and human prion diseases were evaluated using western blotting and immunohistochemical assays. The results revealed that at terminal stages of the diseases, MARK4 levels in the brain tissues of the scrapie 263K-infected hamsters, 139A-infected mice and a case of Creutzfeldt-Jakob disease (CJD, G114V gCJD) correlated with amounts of PrP(Sc) deposits that were almost undetectable. On the other hand MARK4 signals were noticeable in the brain tissues of a fatal familial insomnia (FFI) patient without PrP(Sc). The reduction of MARK4 was closely related to the prolonged incubation times. These results could be reproduced in SK-N-SH and PC12 cell lines after being exposed to the synthetic peptide PrP106-126. Accordingly, the levels of phosphorylated tau at Ser262 (p-tau262) in cultured cells exposed to PrP106-126, or the ratios of p-tau262/total tau in the brain tissues of 263K-infected hamsters were also significantly decreased. According to our data there is a correlation between a TSE pathological-associated decline of MARK4 in the brain tissues with the deposits of PrP(Sc). Reduction of MARK4 will result in abnormalities of tau phosphorylation, and possibly induce further detachment of microtubules and hinder microtubule transportation.