Characterization of live-attenuated Japanese encephalitis vaccine virus SA14-14-2

The live attenuated Japanese encephalitis (JE) vaccine SA14-14-2 was licensed decades ago and now approved for clinical use in most JE endemic countries. Large-scale clinical trials demonstrate ideal safety and efficacy profile of this Chinese vaccine. The SA14-14-2 vaccine was derived from a virulent strain SA14 after hundreds of serial passaging in cells and animals, concern about virulence reversion remains exist. In the present study, to study the in vitro and in vivo genetic and attenuation stability of the vaccine virus, SA14-14-2 was serially passaged in Vero cells and mouse brain followed by sequence comparison and attenuation phenotype analysis. The results showed that no significant mutation was acquired after serial passaging in Vero cells except a single Ser66Leu mutation within capsid protein, which had no effect on viral virulence in mice. Importantly, serial passaging of SA14-14-2 in suckling mouse brain resulted in emergence of adaptive mutations and increased virulence in mice. Population and plaque-purified clone consensus sequence analysis showed four adaptive mutations in envelope (E) protein, F107L, K138E, T226R and I270T, sequentially occurred and become predominant during serial passaging in suckling mouse brain. Especially, these adaptive mutations were close related with the enhanced neurovirulence and neuroinvasiveness in mice. Our results provide experimental evidence of highly genetic and attenuation stability of SA14-14-2 following passaging in Vero cells, and reveal the potential virulence reversion during passaging in mouse brain in association with critical adaptive mutations in E protein. These findings are important for quality control and evaluation of live JE vaccines and will help understand the attenuation mechanism of flavivirus vaccine.     

海马神经干细胞不同传代方法的比较

背景：体外培养神经干细胞,在悬浮培养时由于自身增殖特性会形成球,传代时将会面临如何将细胞球分离成单细胞的问题。 目的：寻求理想的大鼠海马神经干细胞传代方法,以获得大量可增生的神经干细胞以供研究。 方法：分离新生1 d SD大鼠海马神经干细胞,原代培养至五六天时,分别用机械吹打法、胰蛋白酶、TrypLE和Accutase消化法分离神经干细胞球。之后每7 d传代1次,连续传代3次。分别于每次传代后第1天和传代后第4天计数活细胞比例和细胞球数目,实验重复3次。 结果与结论：神经干细胞球经3种酶消化后获得的均是单细胞;经机械吹打后既有单个细胞,也有小细胞球分布于培养液中。在酶消化法中,Accutase消化法传代后神经干细胞的活细胞比例明显高于胰蛋白酶消化(P < 0.01)和TrypLE消化法 (P < 0.05)。同时,Accutase消化法传代后新形成的细胞球数目也较其余各组多(P < 0.01)。提示在实验条件下,Accutase消化法能够较好地将神经干细胞球分离成存活率较高、能快速形成新的克隆球的单个细胞,是较为理想的神经干细胞分离传代方法。     

二次传代法在产前诊断绒毛核型分析中的应用

目的探讨二次传代法在产前诊断绒毛核型分析中的应用价值。方法 210例有产前诊断指征的孕妇在孕11～14w时B超引导下经腹穿刺抽取少量绒毛组织做核型分析。分别采用了一瓶培养法、两瓶培养法和二次传代法三种长期培养法培养绒毛组织,并对其培养时间和培养成功率进行了比较。结果二次传代法平均培养时间为11.1天,比一瓶培养法延长了1.1天,比两瓶培养法缩短了3.5天;二次传代法培养成功率为98.18%,明显高于一瓶培养法(84.0%),略高于两瓶培养法(96.0%)。结论在产前诊断绒毛培养中,二次传代法需要的绒毛标本量少,同时解决了一瓶培养法分裂相少和两瓶培养法培养时间过长的问题,是一种实用的早期产前诊断绒毛核型分析方法。     

The use of human tumour cell lines in the discovery of new cancer chemotherapeutic drugs

Background: Human tumour cell lines have played a major role in anticancer drug discovery, but cell lines may model only some aspects of tumour behaviour in cancer patients. Growing evidence supports a theory that stem cells with self-renewing properties sustain tumours. Objective: This review considers the extent to which a deeper understanding of the origin and properties of tumour cell lines might lead to new strategies for anticancer drug discovery. Methods: Recent literature on normal and tumour stem cells is reviewed and placed in the context of a discussion on the derivation and properties of tumour cell lines. Results/conclusion: Early-passage cell lines may model the more rapidly proliferating cells in human tumours and, thus, retain some of the properties of tumour stem cells. The effects of anticancer drugs on cell lines should be considered not only with regards to the induction of apoptosis, but also to the induction of senescence or other pathways that lead to host immune and inflammatory responses.     

猪带绦虫重组双歧杆菌疫苗人工传代后的稳定性研究

目的研究猪带绦虫TSO45W-4B基因、TSOL18基因和TSO45W-4B-TSOL18融合基因重组双歧杆菌(Bb)疫苗人工传代后的稳定性。方法分别将猪带绦虫重组质粒pGEX-TSO45W-4B、pGEX-TSOL18和pGEX-TSO45W-4B-TSOL18电转入长双歧杆菌(Bifidobacteria longum),获得阳性菌株pGEX-TSO45W-4B/Bl、pGEX-TSOL18/Bl和pGEX-TSO45W-4B-TSOL18/Bl,分别经人工传代10次后抽提质粒,进行PCR鉴定和稳定性分析。结果经PCR鉴定,从第7代开始,pGEX-TSOL18/Bl菌株出现质粒丢失的现象,随着培养时间的延长,质粒丢失现象越来越严重,第8代,第9代均出现丢失现象。而pGEX-TSO45W-4B/Bl菌株从第8代开始出现质粒丢失现象,随后的第9代,第10代也陆续出现丢失现象。pGEX-TSO45W-4B-TSOL18/Bl菌株相对稳定,但从第10代开始,开始出现了质粒丢失现象。结论重组质粒转化菌pGEX-TSO45W-4B/Bl、pGEX-TSOL18/Bl和pGEX-TSO45W-4B-TSOL18/Bl人工培养时分别从人工传代培养第8代、第7代和第10代开始出现质粒丢失现象,可稳定遗传7代、6代和9代,显示具有不同程度的遗传稳定性,这为猪带绦虫重组Bb疫苗的进一步研究奠定了基础。     

两种传代方法影响人胚胎干细胞转染效率的比较

背景:现有方法将外源分子如DNA导入到人胚胎干细胞用于科学研究的效率普遍较低,如何优化现有条件,提高转染效率显得尤为重要。目的:比较两种不同的传代方法对人胚胎干细胞系H9转染效率的影响,优化胚胎干细胞转染条件。方法:人胚胎干细胞系H9分别采用小克隆传代法和单细胞传代法进行传代,传代后继续培养细胞48 h,用Lipofectamine 3000转染pAdTrack-AKT1荧光质粒2 d后,荧光显微镜下观察荧光质粒的表达,流式细胞仪检测人胚胎干细胞的转染效率;RT-qPCR和Western blot分别检测转染后AKT1在mRNA和蛋白质水平的表达。结果与结论:①荧光显微镜下观察发现单细胞传代组表达荧光质粒的细胞数量更多,流式细胞仪检测单细胞传代法的转染效率[(47.18±2.00)%]高于小克隆传代法的转染效率[(19.52±0.86)%],差异有显著性意义(P<0.01);②单细胞传代组转染后AKT1 mRNA和蛋白的表达均高于小克隆传代组,差异有显著性意义(P<0.01);③结果表明,采用单细胞传代法,增加细胞与转染试剂脂质体的接触面积可提高人胚胎干细胞的转染效率。     

体外持续传代引起小鼠透明软骨细胞表型和细胞外基质平衡变化的研究

目的 研究体外持续传代对透明软骨细胞形态表型、分化特性及细胞外基质（ECM）平衡状态的影响。方法 酶消化法分离培养小鼠透明软骨细胞,连续传代至第5代。采用苏木精-伊红染色观察软骨细胞的形态改变,采用半定量聚合酶链式反应分析软骨细胞特异性基因、常规基因、基质金属蛋白酶家族（MMPs）和基质金属蛋白酶组织抑制剂家族（TIMPs）mRNA水平的变化,采用明胶酶谱分析鉴定软骨细胞明胶酶活性的改变。结果 随着传代次数增加,软骨细胞形态由圆形或多边形变为长梭形,其特异性基因的表达量明显下降（P<0.05）,至第5代已基本丧失。相比而言,常规基因的下调并不明显。MMPs和TIMPs均有下调（P<0.05）,仅MMP-1和TIMP-1改变的差异无统计学意义（P>0.05）;MMPs/TIMPs比值随传代发生紊乱。在蛋白质水平,随传代次数增加,明胶酶的活性下降,P4和P5代细胞下调显著（P<0.05）。结论 软骨细胞在体外培养过程中,其特异性表型特征会随传代次数增加而逐渐丧失,软骨细胞发生反分化而表现出纤维化趋势。同时,ECM的平衡状态被打破,合成与分解代谢紊乱。在利用软骨细胞进行相关疾病的研究或软骨组织工程学实验时,应选用前3代的软骨细胞。