利用杆状病毒表达幽门螺杆菌cagA基因

幽门螺杆菌cagA基因克隆到杆状病毒表达系统的 pBlueBacHis2A转移载体中 ,将重组质粒 pBlueBacHis2A CagA与亲本病毒Bac N blueDNA共转染Sf9细胞 ,以空斑法纯化获得的重组杆状病毒。经PCR法鉴定后进行扩增培养 ,SDS PAGE和Westernbolt检测结果证实所表达的蛋白为CagA蛋白 ,间接ELISA分析表明 ,表达产物可与Hp感染者血清发生特异性的免疫反应     

幽门螺杆菌CagA蛋白N端片段的表达、纯化及其与磷脂酰丝氨酸的亲和力检测

目的:表达和纯化幽门螺杆菌不同菌株的CagA蛋白N端片段,检测其与磷脂酰丝氨酸(PS)的相互作用及亲和力。方法:用PCR方法从幽门螺杆菌3个菌株中扩增出CagA蛋白N端基因,并连接到表达载体pET-28a上;转化大肠杆菌BL21,经IPTG诱导可溶性表达CagA蛋白N端880残基片段;经镍柱亲和纯化后,利用PLOA法检测CagA蛋白与PS的相互作用。结果:构建了3种幽门螺杆菌菌株cagA基因的原核表达质粒pET-28a/cagAJ99、pET-28a/cagA11637及pET-28a/cagASS1,并在大肠杆菌中获得可溶性表达,SDS-PAGE和Western印迹证实得到目标融合蛋白,亲和纯化得到高纯度CagA蛋白。PLOA结果表明,CagA蛋白与PS有明显的相互作用。结论:3种幽门螺杆菌菌株CagA蛋白与PS之间存在相互作用,且不同的CagA与PS有不同的亲和力。     

鼠疫耶尔森氏菌VcrV基因在大肠杆菌中的高效表达

将测序后的鼠疫耶尔森氏菌（Yersinia pestis)LcrV基因重组质粒pGEM－T／ypV酶切,克隆于原核表达载体pBV220,构建成pBV/ypV表达质粒,转化大肠杆菌DH5α,进行PCR及酶切鉴定,筛选阳性克隆,进行温控诱导表达,SDS－PAGE检测表达产物,在相对分子质量38000处有－表达条带,经薄层扫描分析目的蛋白带占全菌蛋白的38．4％以上,主要以可溶形式存在。     

利用杆状病毒表达幽门螺杆菌cagA基因

幽门螺杆菌cagA基因克隆到杆状病毒表达系统的pBlueBacHis2A转移载体中,将重组质粒pBlueBacHis2A-CagA与亲本病毒Bac-N-blue DNA共转染Sf9细胞,以空斑法纯化获得的重组杆状病毒.经PCR法鉴定后进行扩增培养,SDS-PAGE和Western bolt检测结果证实所表达的蛋白为CagA蛋白,间接ELISA分析表明,表达产物可与Hp感染者血清发生特异性的免疫反应.     

共表达ETEC K99、GFP重组大肠杆菌的构建及表达北大核心

[目的]构建K99、GFP基因重组质粒并在大肠杆菌BL21(DE3)感受细胞中表达。[方法]利用PCR扩增技术扩增K99基因和GFP基因,经连接和转化将目的片段克隆到pLA载体上,利用双酶切技术及PCR技术对重组质粒进行鉴定并测序分析,利用Western Blot技术分析蛋白质表达情况。[结果]测序分析结果表明,基因具有正确的阅读框;双酶切和PCR鉴定得到498 bp和720 bp的特异性条带;荧光检测表明重组菌表达了蛋白;Western Blot结果表明重组菌表达为融合蛋白。[结论]成功构建了大肠重组菌,并表达外源融合蛋白。     

共表达ETEC K99、GFP重组大肠杆菌的构建及表达

[目的]构建K99、GFP基因重组质粒并在大肠杆菌BL21(DE3)感受细胞中表达。[方法]利用PCR扩增技术扩增K99基因和GFP基因,经连接和转化将目的片段克隆到pLA载体上,利用双酶切技术及PCR技术对重组质粒进行鉴定并测序分析,利用Western Blot技术分析蛋白质表达情况。[结果]测序分析结果表明,基因具有正确的阅读框;双酶切和PCR鉴定得到498 bp和720 bp的特异性条带;荧光检测表明重组菌表达了蛋白;Western Blot结果表明重组菌表达为融合蛋白。[结论]成功构建了大肠重组菌,并表达外源融合蛋白。     

猪水泡病病毒VP1基因抗原区的原核表达

利用RTPCR和nested PCR(nPCR)技术扩增出猪水泡病病毒VP1基因的抗原区，将其克隆到表达载体pProEXHTb中，获得重组质粒，经PCR、酶切和序列分析鉴定表明，目的基因插入的位置、大小和读码框均正确。将重组质粒导入BL21（DE3），经IPTG诱导表达后SDSPAGE检测表明，重组菌能表达猪水泡病病毒VP1抗原区蛋白；Western blot检测表明，诱导表达的抗原区蛋白能与猪水泡病阳性血清发生特异性反应。     

抗HIV-1白喉免疫毒素的构建及原核表达

目的：构建重组DTA—hS120融合基因表达载体,并诱导其在大肠杆菌中表达。方法：通过PCR扩增,获得只含白喉毒素（DT）活性部位（DTA）的基因片段,将其克隆入原核表达载体pET-28a,转化大肠杆菌BL21（DE3）,IPTG诱导表达,经SDS—PAGE和Western印迹分析鉴定。结果：酶切及DNA序列测定鉴定质粒构建正确;SDS—PAGE和Western印迹分析证实,可表达出相对分子质量为54000的融合蛋白,与DTA—hS-20融合蛋白的分子量一致;经凝胶成像分析,其表达量约占菌体总蛋白的23％,表达形式主要为包涵体。结论：构建了DTA—hS-20重组表达质粒,并获得了高效表达,为进一步研究抗HIV-1治疗药物奠定了基础。     

宫颈癌相关BLCAP基因的原核表达及条件优化

目的利用大肠埃希菌表达系统表达宫颈癌相关BLCAP基因,并优化表达条件。方法利用PCR技术从逆转录病毒重组载体pL（BLCAP）SN中扩增宫颈癌相关BLCAP基因,将其插入到原核表达载体pET-32（a）中,从而构建原核表达重组质粒pET-32（a）-BLCAP,随后将阳性重组质粒转化到表达宿主菌中,通过IPTG诱导表达并优化表达条件,所表达的带有His标签目的融合蛋白经Ni^2＋亲和层析纯化回收,并采用SDS—PAGE和Western印迹对目的蛋白进行分析和鉴定。结果构建的重组表达质粒经PCR、酶切和DNA测序鉴定与预期的结果一致,含有重组质粒的表达宿主菌经过IPTG诱导表达了分子量约为28ku的融合蛋白,并经优化确定了最佳的诱导表达条件。结论成功构建了pET-32（a）-BLCAP原核表达质粒,表达并经纯化得到了BLCAP目的蛋白,为研究该蛋白的性质及其制备针对该蛋白的抗体奠定了基础。     

猪瘟病毒E2基因主要抗原区的克隆及原核表达

利用反转录PCR（RT－PCR）和套式PCR（nest Polymerase Chain Reaction,nPCR)技术扩增出当前猪瘟流行毒（广西玉林株,GXYL)一中国猪瘟兔化弱毒（C－株）兔脾组织毒E2基因的主要抗原区,将其克隆到表达载体pPROEX-HTb中,获得重组质粒pPROEX-GXYL和pPROEX-C,经PCR,酶切和序列分析鉴定表明,插入的位置,大小和读码框均正确。SDS－PAGE,检测表明,经重组质业pPROEX-GXYL和pPROEX-C转化,诱导的受体菌能表达E2基因主要抗原区蛋白,Western-blot检测表明,诱导表达的抗原蛋白能与猪瘟阳性血清发生特异性反应。     

幽门螺杆菌vacA和cagA基因全长分子系统发育分析

文章从GenBank中下载所有含有vacA和cagA基因的H.pylori菌株的VacA和CagA全长氨基酸序列,利用ClastalX 2.0和MEGA 5.05软件构建VacA和CagA分子系统发育树,探讨两基因之间的分子系统发育关系和不同聚类群的临床感染结果与基因型特征。结果显示,VacA和CagA具有高度相似的分子系统发育树,并且所有H.pylori菌株在系统发育树中具有相同的分布特点,分别聚类为东亚株群1、2和西方株群3个聚类群。其中东亚株群1患萎缩性胃炎比例较高,vacA基因型以s1c/m1b和s1a/m1b为主,cagA基因型以EPIYA-ABD为主;东亚株群2患十二指肠溃疡的比例较高,vacA基因型以s1c/m2和s1a/m2为主,cagA基因型以EPIYA-AB’C为主;西方株群患十二指肠溃疡和胃炎的比例相当,萎缩性胃炎比例较低,vacA基因型以s1a/m1a和s1b/m1a为主,cagA基因型以EPIYA-AB/B’CC为主。这些结果说明,vacA和cagA基因可能具有共进化的遗传关系;东亚株群1、2和西方株群分别具有不同的vacA和cagA基因亚型,这可能与其临床感染结果密切相关,因此,在进行H.pylori相关性疾病分析时,有必要结合vacA和cagA基因型的亚型做深入分析。     

The diversity of vacA and cagA genes of Helicobacter pylori in East Asia

It has been reported that Helicobacter pylori infection with the type I strain, which expresses the VacA and CagA antigens, is associated with duodenal ulcer. We examined the diversity of vacA and cagA genes in 143 isolates obtained from patients with duodenal ulcer or chronic gastritis in East Asia (two different areas of Japan, Fukui and Okinawa, and also in Hangzhou, China) by polymerase chain reaction (PCR) and sequence analysis. Diversities of cagA and vacA genes were detected in East Asia. The prevalence of cagA-positive H. pylori was significantly different between Fukui and Okinawa (P=0.0032). The prevalence of Western type CagA was significantly higher in Okinawa than in Fukui (P<0.0001). However, there was no significant association between the genotype of cagA and clinical outcome. In Japan, the predominant vacA genotype was s1c/m1b. In contrast, in Hangzhou, the predominant vacA genotype was s1c/m2, and they were all East Asian CagA-positive. These findings suggest that a distinct distribution of the vacA and cagA genotypes is present in East Asia, regardless of clinical outcome.     

Potential role of CagA in the inhibition of T cell reactivity in Helicobacter pylori infections

The pathogenicity of chronic gastroduodenal diseases is very often related to Helicobacter pylori infections. Most H. pylori strains carry the cagA gene encoding an immunodominant 120- to 128-kDa protein which is considered a virulence marker. The majority of CagA-positive H. pylori isolates also produce a 95-kDa protein cytotoxin (VacA) causing vacuolation and degradation of mammalian cells. In our previous study we have shown that live H. pylori bacteria and their sonicates inhibit PHA-driven proliferation of human T lymphocytes. The H. pylori CagA and VacA proteins were suspected of a paralyzing effect of H. pylori on T cell proliferation. In this report, by using isogenic H. pylori mutant strains defective in CagA and VacA proteins, we determined that CagA is responsible for the inhibition of PHA-induced proliferation of T cells.     

Functional variability of cagA gene in Japanese isolates of Helicobacter pylori

CagA protein of Helicobacter pylori is injected into the epithelium, where CagA undergoes tyrosine phosphorylation and activates proliferation signals. However, the importance of these CagA activities for pathogenesis has yet to be resolved. The aim of this study is to analyze the genetic and functional variability of cagA gene of clinical strains in relation to gastric diseases. Thirty-six H. pylori strains were isolated from Japanese patients with various gastric diseases and examined. All 36 strains were found to contain cagA and cagE gene and to induce CagA phosphorylation upon infection. The intensity of CagA phosphorylation expressed in HeLa cells by transfection was highly correlated to the number of R1 region. The phosphorylation intensity was slightly higher in strains from chronic atrophic gastritis (CG); however, the differences were not statistically significant. These CagA proteins also activated the serum response element (SRE) reporter by 5- to 14-fold, above the level of the control. CagA proteins which lack R2 or R3 region exhibited smaller ability for SRE activation. The average of SRE activation was slightly higher in strains from cases of gastric cancer (GC; 11.4+/-1.6), MALT lymphoma (ML; 10.7+/-1.0), and chronic atrophic gastritis (CG; 11.2+/-1.6) than in those of duodenal ulcer (DU; 8.3+/-1.9) or gastric ulcer (GU; 9.0+/-1.1). In summary, most Japanese H. pylori strains contained CagA transport system and induced CagA phosphorylation, and the levels of the intensity of phosphorylation and the ability to induce SRE varied among strains. Although the association between CagA activities and disease outcome shown in this study is not very strong, variety of CagA structure, which induces variable activities, may be one of the reasons why H. pylori induces distinct diseases on host.     

幽门螺杆菌东、西方株CagA的序列差异及其对胃癌细胞生长与凋亡的影响

【背景】幽门螺杆菌(Helicobacter pylori,H.pylori)是胃癌的主要致病因素,其分泌的细胞毒素相关基因A蛋白(Cytotoxin associated gene A,CagA)是目前已知唯一能被H.pylori注入胃上皮细胞并模拟细胞内蛋白发挥作用的癌蛋白,参与胃癌的发生发展。【目的】比较H.pylori东亚株和西方株CagA结构差异,初步探讨H.pylori-CagA对胃癌细胞增殖与凋亡的影响。【方法】对H.pylori东亚株和西方株CagA的核酸及氨基酸序列进行生物信息学分析,构建含东亚株和西方株cagA基因的真核表达载体,转染胃癌细胞AGS,用Western blot法检测CagA蛋白的表达,用CCK8法测定细胞的生长曲线,流式细胞术检测细胞凋亡。【结果】生物信息学分析发现H.pylori东亚、西方菌株CagA的核酸序列和氨基酸序列均存在特征性差异。构建了含东亚、西方菌株cagA基因的表达载体[命名为GZ7/cagA(东亚株)和26695/cagA(西方株)]。与空载体组比较,GZ7/cagA和26695/cagA转染组均表达CagA蛋白,两组比较表达量无显著性差异,GZ7/cagA转染组细胞生长显著增加,而26695/cagA转染组细胞生长显著降低(P0.05)。GZ7/cagA转染组、26695/cagA转染组细胞的凋亡率分别为7.23±0.96及9.17±1.40,均高于空载体组(5.03±0.63),差异有统计学意义(P0.05)。【结论】东亚株与西方株CagA之间有结构和功能的差异,东亚株CagA能促进细胞增殖,而西方株CagA却抑制细胞增殖,但两者均能促进细胞凋亡。     

Phosphorylation of tyrosine 972 of the Helicobacter pylori CagA protein is essential for induction of a scattering phenotype in gastric epithelial cells

Helicobacter pylori colonizes the human stomach and is the causative agent of a variety of gastric diseases. After bacterial attachment, the H. pylori CagA protein is translocated into gastric epithelial cells and tyrosine phosphorylated. This process is associated with characteristic cytoskeletal rearrangements, resulting in a scatter factor-like ('hummingbird') phenotype. In this study, using a cagA mutant complemented with wild-type cagA and transiently expressing CagA in AGS cells, we have demonstrated that translocated CagA is necessary for rearrangements of the actin cytoskeleton to occur. Anti-phosphotyrosine immunoblotting studies and treatment of infected cells with phosphotyrosine kinase inhibitors suggested that not only translocation but also phosphorylation of CagA is important in this process. Transient expression of CagA-green fluorescent protein (GFP) fusion proteins and two-dimensional gel electrophoresis of CagA protein species demonstrated tyrosine phosphorylation in the C-terminus. Site-directed mutagenesis of CagA revealed that tyrosine residue 972 is essential for induction of the cellular phenotype. We have also demonstrated that translocation and phosphorylation of CagA is necessary but not sufficient for induction of the hummingbird phenotype in AGS cells, indicating the involvement of as yet unidentified bacterial factor(s).     

球形幽门螺杆菌分子生物学研究

为研究幽门螺杆菌（ＨＰ）球形变异本质,作者通过延期培养和采用亚抑菌浓度抗生素,使３株ＨＰ发生球形变异,对弯曲形和球形ＨＰ作了ＳＤＳ－ＰＡＧＥ、免疫印迹及４个毒力基因片段ＰＣＲ和ＰＣＲ－ＳＳＣＰ分析。ＳＤＳ－ＰＡＧＥ图谱显示球形ＨＰ分子量在７４×１０４以上的蛋白含量减少,免疫印迹显示球形ＨＰ１２５×１０４蛋白条带反应减弱,而抗生素诱变的球形ＨＰ分子量为１１×１０４和６３×１０４的蛋白条带反应增强。ＰＣＲ及ＰＣＲ－ＳＳＣＰ结果表明球形ＨＰ的ｈｐａＡ,ＶａｃＡ,ＣａｇＡ和ＵｒｅＡ４个毒力基因片段未发生缺失,但在ｈｐａＡ或ＶａｃＡ基因中存在点突变