CD自杀基因联合GM—CSF基因治疗的抗肿瘤作用及免 …

目的 研究自杀基因与粒细胞－巨噬细胞集落刺激因子（ＧＭ－ＣＳＦ）基因联合治疗抗肿瘤作用及免疫机理。方法 小鼠皮下接种黑色素瘤Ｂ１６Ｆ１０细胞３天后,分别在肿瘤局部直接注射表达小鼠ＧＭ－ＣＳＦ的重组腺病毒ＡｄＧＭ－ＣＳＦ和表达大肠杆菌胞嘧啶脱氨酶（ＣＤ）基因的腺病毒Ａｄ－ＣＤ,然后连续１０天腹腔注射５氟胞嘧啶（５ＦＣ）Ａ（ＡｄＣＤ／５ＦＣ／ＡｄＧＭＣＳＦ组）,单用ＡｄＣＤ／５ＦＣ组,单用ＡｄＧＭ－Ｃ     

rhGM-CSF cDNA直接注射小鼠骨骼肌的体内表达研究

将外源基因直接注入动物体内并获得表达，是近几年发展起来的一种新的基因疗法。该方法操作简便，临床易于接受。天然ＧＭ－ＣＳＦ在体内产生的量极少，本研究将ｈＧＭ－ＣＳＦ基因直接注入小鼠体内，以使小鼠体内产生自身所需要的天然ｈＧＭ－ＣＳＦ。首先将ＰＣＲ扩增的ｈＧＭ－ＣＳＦｃＤＮＡ片段平端插入真核表达质粒ｐＣＤＳ中，构建成重组质粒ｐＣＧＩ；然后采用电击法转染ＣＯＳ－７细胞，ＥＬＩＳＡ法检测结果显示转染后２４，４８，７１和９６小时细胞上清有ｈＧＭ－ＣＳＦ的表达分泌。说明重组质粒ｐＣＧＩ能表达分泌ｈＧＭ－ＣＳ…     

一种N端缺失的rhGM-CSF(7～127)在大肠杆菌中的表达与调控

在ｈＧＭ－ＣＳＦ结构与功能研究的基础之上，通过应用ＰＣＲ介导的缺失与突变和基因重组等技术，构建了表达ｒｈＧＭ－ＣＳＦ（７～１２７）的三种原核表达载体ｐＢＶ２２０／ＧＭ－ＴＧＡ，ｐＢＶ２２０／ＧＭ－ＴＡＡ和ｐＢＶ２２０／ＧＭ－３′ＵＴＲ。在三种载体内，ｈＧＭ－ＣＳＦ（７～１２７）ｃＤＮＡ的５′端均缺失６个氨基酸，３′端则分别为天然终止密码ＴＧＡ，突变终止密码ＴＡＡ和ＴＧＡ加３′ＵＴＲ。ＳＤＳ－ＰＡＧＥ表明三种载体表达ｒｈＧＭ－ＣＳＦ（７～１２７）的水平分别为２１％，１８．８％和２５％。经过用ＰＣｇｅｎｅ软件和Ｚｕｌｃｅｒ算法分析ｈＧＭ－ＣＳＦ（７～１２７）－３′ＵＴＲｍＲＮＡ的二级结构，表明３′ＵＴＲ在终止密码ＴＧＡ附近形成两个茎－环结构，它可能与ｐＢＶ２２０／ＧＭ－３′ＵＴＲ载体高表达ｒｈＧＭ－ＣＳＦ（７～１２７）有关。表达产物ｒｈＧＭ－ＣＳＦ（７～１２７）经弱阴离子ＤＥＡＥ交换层析纯化后，纯度达到９２％，比活性为８×１０７Ｕ／ｍｇ。     

直接从中国人胎肝染色体DNA中克隆粒细胞集落刺激因子（G－CSF）外显子及其在大肠杆菌中的高效表达

利用聚合酶链反应（ＰＣＲ）技术，直接从正常人胎肝染色体ＤＮＡ库中分离克隆了中国人粒细胞集落刺激因子（ｃ－ＣＳＦ）外显子，全长５３７ｂｐ，它包括除信号肽氨基酸外的所有编码区，为了使克隆的Ｇ－ＣＳＦ外显子在大肠杆菌中高效表达，对其５’端进行了修饰，去除第１个编码Ｔｈｒ的密码子，在不改变氨基酸的前提下，变换为ＡＴ丰富的密码子；并将某些密码子换成大肠杆菌喜用的密码子。对于每段目的ＤＮＡ所进行的２次独立的ＰＣＲ反应所获得的产物分别进行了核苷酸序列测定。结果完全一致，证明所克隆的Ｇ－ＣＳＦ外显子的序列是可靠的，与国外发表的Ｇ－ＣＳＦ外显子序列相比，未发现变异。将上述人Ｇ－ＣＳＦ外显于基因插入ｐＢＶ２２０表达载休，构建了ｐＢＶ２２０／Ｇ－ＣＳＦ质粒，将其转化入ＤＨ５ａ菌，ＳＤＳ－ＰＡＧＥ表明其表达量约占菌体总蛋白量的２０％，用依赖性细胞系ＮＦＳ－６０进行测定，活性为５ｘ１０ｖＩＵ／Ｌ。     

CD自杀基因联合GM-CSF基因治疗的抗肿瘤作用及免疫机理

目的研究自杀基因与粒细胞－巨噬细胞集落刺激因子（ＧＭ－ＣＳＦ）基因联合治疗抗肿瘤作用及免疫机理。方法小鼠皮下接种黑色素瘤Ｂ１６Ｆ１０细胞３天后,分别在肿瘤局部直接注射表达小鼠ＧＭ－ＣＳＦ的重组腺病毒ＡｄＧＭ－ＣＳＦ和表达大肠杆菌胞嘧啶脱氨酶（ＣＤ）基因的腺病毒Ａｄ－ＣＤ,然后连续１０天腹腔注射５氟胞嘧啶（５ＦＣ）（ＡｄＣＤ／５ＦＣ／ＡｄＧＭＣＳＦ组）、单用ＡｄＣＤ／５ＦＣ组、单用ＡｄＧＭ－ＣＳＦ组、注射对照病毒ＡｄｌａｃＺ／５ＦＣ组或ＰＢＳ组。结果与接受ＡｄＣＤ／５ＦＣ、ＡｄＧＭ－ＣＳＦ、ＡｄｌａｃＺ／５ＦＣ或ＰＢＳ治疗的荷瘤小鼠比较,经联合治疗后荷瘤小鼠皮下肿瘤结节的生长明显受到抑制,荷瘤小鼠的存活期明显延长（Ｐ＜０．０１）。经ＡｄＣＤ／５ＦＣ／ＡｄＧＭＣＳＦ联合基因治疗后,肿瘤瘤体内或瘤周有大量树突状细胞、ＣＤ８＋Ｔ细胞浸润,黑色素瘤细胞表达ＭＨＣ－Ⅰ和Ｂ７－１分子明显增加,荷瘤小鼠脾细胞对Ｂ１６Ｆ１０黑色素瘤细胞特异性杀伤功能增强。结论联合应用自杀基因和ＧＭ－ＣＳＦ基因转移可以直接杀伤肿瘤细胞,又可提高机体对肿瘤的免疫应答,两者可协同发挥抗肿瘤作用     

一种N端缺失的rhGM—CSF（7～127）在大肠杆菌中的表…

在ｈＧＭ－ＣＳＦ结构与功能研究的基础之上，通过应用ＰＣＲ介导的缺失与突变和基因重组等技术，构建了ｒｈＧＭ－ＣＳＦ（７～１２７）的三种原核表达载体ｐＢＶ２２０／ＧＭ－ＴＧＡ，ｐＢＶ２２０／ＧＭ－ＴＡＡ和ｐＢＶ２２０／ＧＭ－３′ＵＴＲ。在三种载体内，ｈＧＭ－ＣＳＦ（７～１２７）ｃＤＮＡ的５′端块缺失６个氨基酸，３′端则分别为天然终止密码ＴＧＡ，突变终止密码ＴＡＡ和ＴＧＡ加３′ＵＴＲ。ＳＤＳ－ＰＡＧＥ表     

逆转录病毒表达载体N2A／hGM－CSF的构建及其在COS－7细胞的初步表达

用特异性核酸内切酶ＢａｍＨＩ剪切质粒ｐＣＤ／ｈＧＭ－ＣＳＦ，制备人粒细胞巨噬细胞集落刺激因子基因片段，低融点胶回收后，连接至Ｎ２Ａ载体ＢｇｌⅡ位点，转化大肠杆菌ＤＨ５ａ，经快提质粒进行酶切鉴定和核酸打点杂交筛选出重组质粒Ｎ２Ａ／ｈＧＭ－ＣＳＦ。利用ＤＥＡＥ－葡聚糖介导该重组质粒转化ＣＯＳ－７细胞，收集４８ｈ培养上清液，免疫学和生物学活性检测表明该上清中表达产物具有天然ＧＭ－ＣＳＦ的活性，而用质粒Ｎ２Ａ转化ＣＯＳ－７细胞，培养上清中未检测出ＧＭ－ＣＳＦ活性。     

逆转录病毒表达载体N2A／hGM—CSF的构建及其在COS…

用特异性核酸内切酶Ｂａｍ Ｈｉ剪切质粒ｐＣＤ／ｈＧＭ－ＣＳＦ，制备人粒细胞巨噬细胞集落刺激因子基因片段，低融点胶回收后，连接至Ｎ２Ａ载体Ｂｇ１Ⅱ位点，转化大肠杆菌ＤＨ５ａ，经快提质粒进行酶切鉴定和核酸打点杂交筛选出重组质粒Ｎ２Ａ／ｈＧＭ－ＣＳＦ。利用ＤＥＡＥ－葡聚糖介导该重组质粒转化ＣＯＳ－７细胞，收集４８ｈ培养上清液，免疫学和生物学活性检测表明该上清中表达产物具有天然ＧＭ－ＣＳＦ的活性，而用质粒     

白细胞介素10基因转移抑制肾小球系膜细胞诱生炎症细胞因子

目的：通过建立白细胞介素１０（ＩＬ－１０）的重组逆转录病毒载体基因转移系统,观察ＩＬ－１０对脂多糖（ＬＰＳ）诱导的大鼠肾小球系膜细胞（ｇｌｏｍｅｒｕｌａｒｍｅｓｅｎｇｉａｌｃｅｌ,ＧＭＣ）中细胞因子的产生及其基因表达的影响。方法：通过构建的重组逆转录病毒载体ｐＬＸ（ＩＬ－１０）ＳＮ将外源基因ＩＬ－１０转移至大鼠ＧＭＣ：（１）应用聚合酶链反应（ＰＣＲ）,反转录聚合酶链反应（ＲＴ－ＰＣＲ）和ＥＬＩＳＡ检测ＩＬ－１０基因的整合和表达;（２）以ＲＴ－ＰＣＲ观察ＩＬ－１０基因转移对ＬＰＳ诱导的ＧＭＣ肿瘤坏死因子－α（ＴＮＦ－α）的ｍＲＮＡ表达的影响,以ＥＬＩＳＡ测定白细胞介素－１β（ＩＬ－１β）和ＴＮＦ－α的蛋白质表达。结果：外源性ＩＬ－１０基因已整合到靶细胞染色体ＤＮＡ并有效地表达,它能抑制ＬＰＳ诱生ＧＭＣ过度产生ＩＬ－１β,ＴＮＦ－α。结论：外源性ＩＬ－１０基因可以转移到ＧＭＣ并稳定表达,它能抑制ＧＭＣ炎症效应中细胞因子的产生及其基因表达。     

人GM－CSF基因在昆虫细胞中表达的研究

本工作构建的昆虫表达重组体ｐＡＣ６１０－ＧＭＴ，是在ＡｃＭＮＰＶ的Ｐｏｌｙｈｅｄｒｉｎ启动子控制下，表达去除了信号肽编码顺序的人ＧＭ－ＣＳＦ基因（ｃＤＮＡ）的转染载体。它与野生ＡｃＭＮＰＶ病毒ＤＮＡ共转染Ｓｆ２１细胞，经过筛选得到纯化的可表达人ＧＭ－ＣＳＦ的重组病毒株ｖＡｃＧＭＴ。其感染细胞总ＲＮＡ的Ｎｏｒｔｈｅｒｎ分析结果表明，重组病毒在ｍＲＮＡ水平有人ＧＭ－ＣＳＰ特异性表达，其表达水平在感染后４８ｈ时达高峰，７２ｈ未见明显下降。感染细胞裂解物的Ｗｅｓｔｅｒｎ－Ｂｌｏｔ分析和活性测定也证实其蛋白水平的表达，并有人ＧＭ－ＣＳＦ的生物学活性。     

Characterization of the Streptococcus mutans plasmid pva318 cloned into Escherichia coli.

We further characterized the cryptic plasmid pVA318 of Streptococcus mutans. It had a contour length of 5.64 +/- 0.26 kilobases and a guanine-plus-cytosine content of 32 to 34 mol %. Upon cloning the pVA318 plasmid into the vector pBR322 in Escherichia coli, we made the following observations. The expression of tetracycline resistance by HindIII-cloned chimeras, where the insert was in the tetracycline resistance promotor, depended on the orientation of the pVA318 insert. Both HindIII-cloned chimeras segregated from polA(Ts) cells at a nonpermissive temperature. Chimeric molecules cloned with PstI initially showed much instability; the reason for this is unknown, although stable variants were obtained. Both HindIII-cloned variants and a PstI-cloned chimera produced a pVA318-specific protein of approximately 20,000 molecular weight in E. coli minicells. The biological function of this protein is not known; it had no bacteriocin activity against S. mutans or group A Streptococcus indicator strains, and it did not appear in the E. coli periplasm. We constructed a map of pVA318 for restriction endonucleases HindIII, HpaI, PstI, and HaeIII. A previously reported BamHI site in pVA318 did not appear in the pVA318 portion of any of our chimeric clones.     

Characterization of monoclonal antibodies against carcinoembryonic antigen (CEA) and expression in E. coli

Eight monoclonal antibodies (MAbs) against carcinoembryonic antigen (CEA) were characterized. Five clones are IgG(1), two clones are IgM and one clone is IgG(2b); all have kappa light chain. The affinities are in the range of 1.1 x 10(-7) approximately 2.4 x 10(-9) M; the affinities of two IgM clones could not be estimated because of their low enzyme-linked immunoadsorbent assay (ELISA) signal. Each clone was constructed as single-chain Fv (scFv) and expression was performed in E. coli. Four clones out of 8 could express scFv soluble to culture media and the expression was confirmed further by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. The nucleotide and amino acid sequences of V(H) and V(L) of four scFvs were deduced and their family and subgroup were analyzed. We found that the clones that do not express the scFv have aberrant kappa chain (incorrect V/J recombination or stop codon); in contrast, their heavy chain sequences proved correct. The E. coli-expressed scFvs showed 1.5 x 3.4-fold lower affinities (2.8 x 10(-8) approximately 3.6 x 10(-9) M) than those of hybridoma-derived parental antibodies except the one clone (C5), which exhibited approximately 10(-6) M of affinity.     

De novo acquisition of resistance to three antibiotics by Escherichia coli

The acquisition of resistance to amoxicillin, tetracycline, and enrofloxacin by Escherichia coli MG 1655 was examined by exposing growing cells to constant or stepwise increasing concentrations of these compounds. The minimal inhibitory concentration (MIC) of E. coli for amoxicillin increased from 4-8 to 32?μg/ml after growth in the presence of 1.25 or 2.5?μg/ml. By stepwise increasing the exposure, an MIC of 512?μg/ml was reached. This high MIC was maintained after removal of the antibiotics, whereas the lesser increase after exposure to low levels was reversed, indicating that the high MIC was due to a genetic change, but the lower one to phenotypic adaptation only. The MIC for tetracycline increased from 2?μg/ml to maximally 32?μg/ml. The MIC decreased to control levels in the absence of tetracycline, so no genetic changes seem to have occurred. The MIC for enrofloxacin increased from 0.25?μg/ml to maximally 512?μg/ml depending on the concentration during growth. These data mostly support the "radical-based" theory that bactericidal antibiotics induce a common mechanism that contributes to cell killing. Our findings indicate that exposure to low levels of antibiotics causes an increase in MIC above the concentration that the cells were exposed to. The implication is that exposure to low levels of antibiotics should be prevented as much as possible, because this causes resistance far more than high concentrations that inhibit growth or kill the cell and thus prevent acquisition of resistance.     

Functional genomics of Escherichia coli in Japan

Completion of the genome sequence of the model bacterium Escherichia coli has produced nearly 2000 open reading frames (ORFs) that remain to be functionally characterized. To accomplish this goal, we have organized a working project team in Japan and have begun construction of clones containing each of the putative ORFs. The procedure has been conceived such that we shall be able to perform systematic analysis of the shut-off as well as forced expression in vivo of each ORF and purification of its protein product for further biochemical studies. In addition, we have started a collection of various genetic and biochemical data of E. coli published in the past, and analyses of the data from a bio-informatics point of view. Thus, we aim at reaching complete understanding of this model organism in the near future.     

Antimicrobial susceptibility trends among Escherichia coli and Shigella spp. isolated from rural Egyptian paediatric populations with diarrhoea between 1995 and 2000

Antimicrobial susceptibility testing was performed on 3,627 isolates of Escherichia coli and 180 isolates of Shigella spp. collected in rural locations from 875 Egyptian children with diarrhoea between 1995 and 2000. The cumulative rates of resistance for E. coli and Shigella spp. were high (respectively, 68.2% and 54.8% for ampicillin, 24.2% and 23.5% for ampicillin-sulbactam, 57.2% and 42.5% for trimethoprim-sulphamethoxazole, and 50.9% and 75.4% for tetracycline). Non-enterotoxigenic E. coli (NETEC) isolates had a consistently higher level of antimicrobial resistance than did enterotoxigenic E. coli (ETEC) isolates. Trend testing showed significant decreases in resistance to ampicillin, ampicillin-sulbactam and tetracycline among all E. coli isolates. Increasing rates of resistance were observed for trimethoprim-sulphamethoxazole in ETEC isolates and Shigella spp., but not in NETEC isolates. Low levels of resistance were observed for all other antimicrobial agents tested. Overall, high levels, but decreasing trends, of resistance to commonly used antimicrobial agents were detected among isolates of E. coli and Shigella spp. from children in rural Egypt.     

Molecular cloning of paramyosin, a new allergen of Anisakis simplex

BACKGROUND: Anisakis simplex is a fish parasite that, when accidentally ingested by humans, may cause allergic reactions in sensitized individuals. The main objectives of our study were to: (1) construct a cDNA expression library of A. simplex; (2) identify clones producing specific IgE binding protein antigens, and (3) produce and purify the protein/s codified by the isolated clones produced in Escherichia coli. METHODS: An expression cDNA library from the third stage larvae (L3) of A. simplex was constructed. This library was first screened with a rabbit anti A. simplex hyperimmune serum. The positive clones, identified using the rabbit serum, were rescreened with a pool of human sera containing high titers of IgE antibodies against A. simplex. RESULTS: Two positive clones were isolated carrying the genes which codify for paramyosin. The paramyosin protein was produced in E. coli and purified. The partial sequence of a second paramyosin gene was also identified. The frequency of specific IgE binding to the recombinant and native forms of paramyosin using the sera of 26 A. simplex-sensitive individuals was 23 and 88%, respectively. Both paramyosins were able to inhibit 11% of the specific IgE binding to a total extract. CONCLUSIONS: We describe the primary structure of a paramyosin of A. simplex. It can be considered as an allergen based on its IgE binding capacity. We suggest that the recombinant protein does not maintain the complete allergenic properties of the native paramyosin, considering its lower IgE binding capacity of the recombinant protein. However, both proteins have the same specific IgE inhibition capacity. The recombinant protein can be produced in large quantities in E. coli. We propose the term Ani s 2 for this allergen.     

Increased expression of periplasmic Cu,Zn superoxide dismutase enhances survival of Escherichia coli invasive strains within nonphagocytic cells

We have studied the influence of periplasmic Cu,Zn superoxide dismutase on the intracellular survival of Escherichia coli strains able to invade epithelial cells by the expression of the inv gene from Yersinia pseudotuberculosis but unable to multiply intracellularly. Intracellular viability assays, confirmed by electron microscopy observations, showed that invasive strains of E. coli engineered to increase Cu,Zn superoxide dismutase production are much more resistant to intracellular killing than strains containing only the chromosomal sodC copy. However, we have found only a slight difference in survival within HeLa cells between a sodC-null mutant and its isogenic wild-type strain. Such a small difference in survival correlates with the very low expression of this enzyme in the wild-type strain. We have also observed that acid- and oxidative stress-sensitive E. coli HB101(pRI203) is more rapidly killed in epithelial cells than E. coli GC4468(pRI203). The high mortality of E. coli HB101(pRI203), independent of the acidification of the endosome, is abolished by the overexpression of sodC. Our data suggest that oxyradicals are involved in the mechanisms of bacterial killing within epithelial cells and that high-level production of periplasmic Cu,Zn superoxide dismutase provides bacteria with an effective protection against oxidative damage. We propose that Cu,Zn superoxide dismutase could offer an important selective advantage in survival within host cells to bacteria expressing high levels of this enzyme.     

人源性抗乳腺癌单链抗体库的筛选与初步鉴定

目的:本研究旨在已构建的大容量人源性抗乳腺癌噬菌体单链抗体库的基础上,筛选出高亲和力的特异性单链抗体(scFv)并对抗体基本特性进行初步鉴定。方法:以人乳腺癌细胞系MCF-7为靶标,经过4轮淘洗,筛选出高亲和力的特异性抗乳腺癌scFv,并对其结构序列进行分析;通过ELISA和Western blot方法,鉴定scFv的亲和力和特异性,以及其蛋白的基本表达情况。结果:成功构建具有高亲和力的抗乳腺癌单链抗体库,获得scFv的长度约为750 bp,ELISA证实所得抗体对乳腺癌细胞具有良好的亲和力和高度的特异性,IPTG诱导表达及Western blot结果显示,scFv为相对分子质量(Mr)30 000的可溶性蛋白。结论:本研究在已构建的大容量抗乳腺癌单链抗体库的基础上,筛选获得了高亲和力的抗乳腺癌单链抗体库。研究结果为进一步获得可应用于临床诊断和治疗的乳腺癌靶向性抗体奠定了良好的基础。     

人心肌肌钙蛋白I的原核表达及其兔抗体的制备

目的:构建人心肌肌钙蛋白I(hcTnI)基因的原核表达质粒,在大肠杆菌中表达后,并制备兔抗hcTnI抗体。方法:以化学方法合成hcTnI基因并插入融合表达载体pET21a( )的多克隆位点,构建重组表达质粒pET21a( )hcTnI。以重组质粒转化大肠杆菌BL21(DE3)plysS,筛选阳性重组子,经IPTG诱导目的蛋白的表达,表达产物的免疫学活性用Westernblot进行鉴定。以表达的hcTnI蛋白免疫家兔,制备抗hcTnI的抗体并进行纯化及特性鉴定。结果:成功地合成hcTnI基因,测序证实序列正确后亚克隆于表达载体pET21a( )中,经PCR筛选和酶切鉴定获得阳性克隆,序列分析表明其中的插入序列与cTnI基因完全一致。在大肠杆菌中表达出相对分子质量(Mr)为24000的目的蛋白,约占菌体总蛋白的28%,Westernblot分析显示,表达的hcTnI蛋白具有良好的免疫反应性。以纯化的hcTnI免疫家兔后,能有效地刺激特异性抗体的产生,抗血清的效价为3×10-4,且具有良好的特异性。结论:成功地构建hcTnI基因的原核表达载体pET21a( )hcTnI,并在大肠杆菌中获得高效表达。制备出兔抗hcTnI的抗体,且效价及特异性均较良好,为进一步建立酶联免疫吸附法检测hcTnI奠定了基础。