甜味蛋白(brazzein)基因的人工合成及其在大肠杆菌中的重组表达

根据从西非植物Pentadiplandra brazzeana Baillion果实中分离的甜味蛋白brazzein的成熟区氨基酸序列，采用大肠杆菌（Escherichia coli）偏爱的密码子，人工合成了5对寡聚核苷酸序列，经体外连接和PCR扩增后得到了187bp的brazzein的编码序列，将该序列插入pET-28a载体构建成重组表达载体pET-Br。将pET-Br转化至大肠杆菌BL-21细胞，诱导表达后得到了与预计相对分子质量相同的蛋白。该蛋白约占细菌可溶性蛋白的18．9％，分离纯化后通过蛋白复性，得到有微甜味的产物。     

Characterization of enterotoxigenic bovine Escherichia coli.

Among 300 isolates of bovine Escherichia coli, 56 which had been found enterotoxigenic in calf gut loops were characterized on the basis of O and K antigens, colonial morphology and resistance to seven antimicrobial drugs. The 56 isolates enterotoxigenic in the calf were compared with the nonenterotoxigenic ones. Of the 56 enterotoxigenic E. coli the majority possessed the A type of K antigen and had OK groups, O9:K(PS274) or O101:K(RVC118). Fourteen of these isolates had the K99 antigen. None of 27 isolates found enterotoxigenic in the piglet but not in the calf possessed the K99 antigen or belonged to OK groups O9:K(PS274) or O101:K(RVC118). Comparison of the patterns of resistance to seven antimicrobial drugs showed that all enterotoxigenic and nonenterotoxigenic isolates were susceptible to nitrofurantoin and sulphachlorphyridiazine and that there was no significant difference in the patterns between the two groups. The majority of enterotoxigenic isolates were mucoid, whereas most of the nonenterotoxigenic isolates were nonmucoid.     

Recombinant bovine soluble CD14 reduces severity of experimental Escherichia coli mastitis in mice

Endotoxin, or lipopolysaccharide (LPS), is responsible for pathogenesis of infections induced by Gram-negative bacteria, such as E. coli. The cellular response to LPS is modulated by interactions among LPS, LPS-binding protein (LBP) and CD14. Accumulated evidence shows that the soluble form of CD14 (sCD14) competes with membrane-bound CD14 (mCD14) for LPS and plays a pivotal role in regulating bacterial infection and septic shock caused by Gram-negative bacteria. Recombinant bovine sCD14 (rbosCD14) was produced by transfected insect sf/9 cells and its biological function was evaluated in mice. Eighty-one 8-week old BALB/cj female mice were randomly assigned to two groups, and injected intraperitoneally with either LPS (8 microg/g of body weight, n = 41) or LPS plus rbosCD14 (6.8 microg/g of body weight, n = 40). Survival rate at 24 h after injection for mice injected with either LPS or LPS plus rbosCD14 was 30 and 72%, respectively (P < 0.01). At 48 h survival rate was 7 and 37%, respectively (P < 0.01). To investigate the protective effect of rbosCD14 on experimentally induced mastitis in mice, two abdominal contralateral mammary glands of 7 lactating BALB/cj mice were injected through the teat canal with 10-20 colony-forming units (CFU) of Escherichia coli. One gland simultaneously received rbosCD14 (6 microg) and the other saline. At 24 h after challenge, glands that received rbosCD14 had less swelling and hemorrhaging, significantly lower bacterial counts (P < 0.05) and lower concentrations of TNF-alpha (P < 0.05). Results indicate that rbosCD14 is biologically functional and reduces mortality in mice from endotoxin shock and severity of intramammary infection by E. coli.     

Adhesion of Staphylococcus aureus and Escherichia coli to bovine udder epithelial cells

An assay for the adhesion of tritiated thymidine-labelled Staphylococcus aureus and Escherichia coli to bovine mammary ductular epithelial cell lines was developed. The relative adhesion of 15 strains of S. aureus to these cell lines was examined. Four strains did not adhere and the remaining 11 adhered at variable levels. Adhesion to different cell lines was generally similar. Adhesion to freshly collected bovine mammary epithelial cells was significantly greater than that to cells maintained in tissue culture. The system described was demonstrated to be a suitable model for studying adhesion of mastitis-causing organisms to bovine mammary epithelial cells.     

重组人白细胞介素6表达载体的构建及其在大肠杆菌中的高效表达

本研究合成了两个成熟人IL-6cDNA引物.采用PCR法扩增出了成熟人IL-6基因片段,并在其5’端加入了一个Eeo RI部位和ATG,3’端加入了一个Bam HI部位和TAA.利用pBV220质粒构建成功了pBV220 IL-6表达载体.将该重组质粒导入E.coli DH5α中,经30℃扩增和42℃诱导,表达出了分子量为21000的预期蛋白.经SDS-PAGE分析与薄层扫描测定,重组IL-6的含量约占全菌体总蛋白的27％以上.菌体裂解液用7TD_1细胞测定,证明具有明显的IL-6活性.实验还对工程菌的IL-6表达动态和包涵体提取进行了研究,从而为工程菌发酵与IL-6纯化提供了工作基础.     

高效表达重组猪IL-10的基因工程菌株的构建

白细胞介素—10(IL-10)是一种Th2细胞等产生的能抑制Th1细胞释放细胞因子的免疫调节因子。从经脂多糖(LPS)活化的猪外周血单核细胞(PBMC)中提取总RNA，用RT—PCR扩增了猪IL-10(poIL—10)编码基因，克隆并测序验证后，将其亚克隆到表达载体pPROEX^TM HTb中，转化DH5α后，用IPTG诱导培养，经免疫印迹和生物活性检测显示，重组菌株表达了具有活性的重组poIL—10，重组poIL-10表达水平达3mg／ml培养液，占菌体细胞总蛋白的30．2％，本研究为poIL-10的功能研究和临床应用奠定了基础。     

牛病毒性腹泻病毒E2蛋白的截短表达与鉴定

利用牛病毒性腹泻病毒（BVDV）BA株接种MDBK细胞，提取病毒RNA。参照已发表的BVDV基因组序列，利用Oligo6生物学软件设计扩增E2基因的1对引物，引入酶切位点并去掉E2蛋白的跨膜区及疏水区。通过RT-PCR扩增了长约1000bp的E2基因片段，克隆到pMD18-T载体上，酶切并测序鉴定。然后将目的片段进一步定向克隆到pET30a表达载体，转化BL21表达菌。取转化菌培养，并用IPTG诱导，获得了以包涵体形式表达的重组蛋白。将重组蛋白变性、纯化和复性后，用免疫印迹与间接ELISA检测表明纯化的重组蛋白具有良好的免疫原性，为牛病毒性腹泻病毒诊断试剂的研制奠定了基础。     

产肠毒素大肠埃希菌STa-K99融合蛋白重组腺病毒载体的构建及表达

为构建产肠毒素大肠埃希菌(ETEC) STa-K99融合蛋白重组腺病毒载体Ad STa-K99,通过PCR技术分别克隆了STa及K99基因,并与腺病毒穿梭质粒连接构建了穿梭质粒pAd5 STa-K99,将pAd5STa-K99和骨架质粒(含GFP基因)分别用Pac Ⅰ酶切线性化,利用LipofectamineTM LTX&-PLUS共转染293细胞进行同源重组包装重组腺病毒,通过PCR及Western blot对重组腺病毒进行鉴定.结果显示,重组腺病毒Ad5 STa-K99构建正确并表达融合蛋白,且表达的融合蛋白能够被抗体所识别,为研制由ETEC引起的新生动物腹泻重组腺病毒载体疫苗奠定了基础.     

猪卵泡抑制素α模拟肽基因在大肠杆菌中的融合表达

克隆了猪抑制素 α1 - 3 2 基因 (简称抑制素基因 ,INH) ,与 p ET- 32 c载体的 Thioredoxin基因重组 ,表达的 INH-Thioredoxin融合蛋白相对分子质量约 140 0 0 ,在 E.coli DH5α中表达效率较高。在 IPTG浓度为 0 .34 0 m mol/L、诱导16 .8h条件下 ,有最大表达量 ,电泳扫描净灰度达 38.78%。     

牛碱性成纤维细胞生长因子基因在大肠杆菌中的表达及其表达产物的生物学活性

采用巢式PCR方法克隆了牛18ku-bFGF基因完整的编码序列,并构建了原核表达载体pET-28a-bFGF,将其转化大肠杆菌BL21,在25℃低温条件下,用0.5 mmol/L IPTG诱导表达5 h,用Ni-NTA亲和纯化细胞裂解上清液,经Western-blotting检测,结果显示,在特定的诱导条件下,重组牛bFGF基因在大肠杆菌中获得了表达,并且主要以可溶性状态存在于细胞中。经检测,纯化后的重组蛋白能显著促进成纤维细胞的增殖（P〈0.05）,其活性与商品用重组人18ku-bFGF没有差异（P〉0.05）。表明,所获得的可溶性重组牛18ku-bFGF蛋白具有较高的生物学活性,可用于后续研究工作。     

猪A组轮状病毒Vp7基因与乳酸菌非抗性表达载体的重组及在大肠杆菌中的表达

轮状病毒（Rotavirus，RV）属于呼肠孤病毒科（Reoviridae）、轮状病毒属（Rotaviras），作为婴幼儿和动物腹泻的主要病原，在世界范围内广泛流行，每年造成巨大损失。鉴于其危害严重且无有效治疗手段，世界卫生组织将RV疫苗列为最优先发展的疫苗项目之一，尤其是它的基因工程疫苗的研制更为重要。     

Virulence factors of Escherichia coli isolated from bovine clinical mastitis.

Escherichia coli isolates from bovine mastitis were examined for a selection of virulence factors. The strains originated from Finland and Israel, which have differences in the proportion of mastitis caused by E. coli, clinical pictures of coliform mastitis, environmental conditions and herd management. The genes of nine virulence factors were detected by polymerase chain reaction. Presence of K1 and K5 capsules was assessed by use of specific bacteriophages. Serum resistance was tested by a turbidimetric assay. Out of 160 Finnish isolates, 37% had traT, 14% cnf2, 8% cnf1, 11% aer, 9% f17, 8% sfa, 7% pap, 1% afa8D and 1% afa8E. Out of 113 Israeli isolates, 41% had traT, 4% aer, 3% cnf2, 1% cnf1, 1% sfa and 1% f17. Some of the genes were distributed among two major pathotype groups, with either f17 family or sfa, pap and cnf1 as major determinants. Genes for F17a, CS31A, Afa7D and Afa7E were not detected. Altogether 49% of Finnish and 42% of Israeli isolates had at least one virulence gene, but genes other than traT were present in only 24% of Finnish and 5% of Israeli isolates. Serum resistance was more common among Finnish (94/160) than Israeli isolates (19/113). K1 and K5 capsules were not detected.     

HIV—2env基因在大肠杆菌和重组痘苗病毒中的表达

将编码人Ⅱ型免疫缺陷病毒（ＨＩＶ－２）ｅｎｖｇｐ１２０（Ｅ１）和ｇｐ３６（Ｅ２）分别克隆到原核高效表达载体ｐＥＴ１７ｂ、ｐＢＶ２２０和真核表达载体ｐ１０、ｐ１６中,构建成８个重组质粒。经ＳＤＳ－ＰＡＧＥ和Ｗｅｓｔｅｒｎｂｌｏｔ分析证明,在原核表达系统成功地表达了ＨＩＶ－２ｅｎｖ融合蛋白,表达的蛋白分子量分别为３５０００、７００００和５００００,而原核表达质粒ｐＥＴＥ１在ＳＤＳ－ＰＡＧＥ凝胶的３５０００处可见明显的额外蛋白带。经薄层扫描测定,原核系统表达的Ｅｎｖ蛋白（ｇｐ１２０）相对含量为５．８％。在真核细胞中表达的Ｅｎｖ蛋白经Ｗｅｓｔｅｒｎｂｌｏｔ检测分析,分子量分别为６００００、５７０００和４２０００。上述表达的Ｅｎｖ蛋白均能与ＨＩＶ－２阳性血清发生特异性反应。重组痘苗病毒可诱导小鼠产生抗ＨＩＶ－２Ｅｎｖ抗体     

Prevalence of verotoxin-producing Escherichia coli (VTEC) in bovine coli mastitis and their antibiotic resistance patterns.

Between December 1996 and October 1997, milk samples from a total of 145 cows with coli mastitis were screened for the presence of verotoxin-producing E. coli (VTEC). VTEC were found in four (2.8%) out of the 145 samples. The four isolated strains proved to be verotoxin (VT) 1-, VT2- or VT1- and VT2-positive. However, no strain contained all three virulence factors tested. Further strain characterization was carried out by serotyping as well as by resistance pattern analysis.     

重组鸡Cathelicidins类抗菌肽的融合表达及其对金黄色葡萄球菌抗菌活性的研究

Cathelicidins抗菌肽在家禽天然免疫系统中发挥重要作用,本研究将已构建的含Cathelicidins抗菌肽成熟肽的阳性克隆菌株Rosetta(DE3)/pET30-CathL1S、pET30-CathL2S、pET30-CathL3S分别在37℃、1.0 mmol/L IPTG的条件下进行诱导表达。SDS-PAGE和Western blotting分析结果表明,Cathelicidins成熟肽片段均在大肠杆菌中以融合形式成功表达,表达产物的表观分子质量分别为7、8、7.5 ku。琼脂糖孔穴扩散法检测结果显示,表达产物对多种革兰氏阴性菌和阳性菌均具有很好的抑制活性,其对金黄色葡萄球菌(Staphylococcus aureus)、枯草芽孢杆菌(Bacillus subtilis)、藤黄微球菌(Micrococcus luteus)、大肠杆菌(Escherichia coli)、鸡白痢沙门氏菌C79-13 (Salmonella pullorum)、巴氏杆菌、鸭疫里默氏杆菌及绿脓杆菌等供试菌株均有较强的抑制作用,尤其对抗生素耐药菌株有明显的抑制作用。以雏鸡为实验模型研究重组抗菌肽对金黄色葡萄球菌的体内抗菌活性,结果表明,注射中、高剂量CathL-1抗菌肽试验组(5、10 mg/kg),在试验结束后取肝脏组织匀浆液涂布于TMP平板,未分离到葡萄球菌。各抗菌肽试验组平均增重均高于感染对照组,其中低剂量抗菌肽试验组(2.5 mg/kg)体内抑菌效果虽与普通抗生素相当,但其增重效果尤为明显。     

Identification of a bovine mastitis Escherichia coli subset

Eleven Escherichia coli isolates from clinical bovine mastitis cases (mastitic strains) and 11 from the cowshed environment (environmental strains) were compared, to determine if the former were a subset of the latter. The mastitic and environmental strains could not be distinguished according to O antigen and antibiotic sensitivity. All mastitic isolates showed significantly (P<0.0001) faster growth in milk and faster lactose fermentation than most (approximately 64%) environmental strains, but growth rates in nutrient broth did not differ. The rates of lactose fermentation and growth in milk were positively correlated. Adhesion and phagocytosis of mastitic strains by bovine PMN were significantly (P<0.0001) lower than those of environmental strains, and correlated negatively with growth in milk and lactose fermentation. The average percentages of killing by bovine leukocytes in the two sources were not statistically different. All mastitic strains were serum sensitive, whereas most ( approximately 72%) environmental ones were resistant. Finally, pulse-field gel electrophoresis revealed two main pulse type clusters, sharing a similarity coefficient of 79%. Cluster 1 comprised only environmental strains, whereas cluster 2 comprised mostly mastitic strains and only three environmental ones. Four mastitic strains shared a similarity coefficient of less than 74% with the other strains and were not included in the clusters. Our results suggest that clinical bovine mastitis E. coli isolates may form a subset of the general environmental E. coli population; they seem better able to multiply in the udder medium and to evade the host cellular innate immune response, and are genetically distinct from most environmental strains.     

重组Gallinacin-3的克隆及在大肠杆菌中的表达

防御素是昆虫、植物和动物体内抗感染及激发特异性抗感染免疫的重要抗菌肽。Gallinacin-3（gal-3）可能是鸡体内最重要的β-防御素，但它的功能还未得到研究证实。本试验从鸡黏膜表皮组织中克隆了gal-3编码基因，并在大肠杆菌中成功表达了gal-3与谷胱甘肽转硫酶（GST）融合蛋白。经IPTG诱导后，融合蛋白的产量占细菌总蛋白的33．6％左右，主要以包涵体形式存在。用亲合层析技术从大肠杆菌裂解液中纯化出可溶性重组蛋白，并用酶切除目标蛋白的融合伴侣。抑菌试验发现，重组gal-3-GST融合蛋白在未去除融合伴侣时，就与游离的gal-3有着相同的抑菌活性，对沙门氏肠炎杆菌和志贺氏痢疾杆菌的最小杀菌浓度在20μg／mL（相当于约4μg／mL纯gal-3）左右，与其他物种β-防御素的活性相当。     

鸡γ-干扰素基因在大肠杆菌中的高效表达及多克隆抗体的制备

将克隆得到的鸡 IFN- γ基因亚克隆到大肠杆菌原核表达载体 p PROEXTMHT的 Pst 和 Kpn 位点上 ,构建了重组表达质粒 p PROEXTMHT- IFN -γ,经序列分析鉴定 ,确证目的基因克隆入载体的预期位点。将重组质粒转化大肠杆菌 DH5 α,于 37℃不同时间诱导培养 ,SDS- PAGE电泳表明 ,该基因在大肠杆菌中发生高水平表达 ,表达的鸡 IFN- γ融合蛋白相对分子质量约为 2 2 0 0 0。重组蛋白占菌体总蛋白的 33%。经 Western blot鉴定 ,该重组蛋白质具有生物学活性。包涵体被 6 mol/ L 盐酸胍裂解后 ,通过镍离子亲和树脂进行了纯化。用所获得的重组鸡 IFN- γ融合蛋白及其纯化产物经 3次肌肉注射于新西兰白兔 ,制备了兔抗鸡 IFN- γ多克隆抗体。琼脂扩散结果表明 ,多克隆抗体可与纯化的鸡IFN -γ重组蛋白发生特异性反应