不耐热肠毒素和耐热肠毒素基因的融合

用重组基因技术将产肠毒素大肠杆菌（ＥＴＥＣ）的耐热肠毒素（ＳＴａ）基因与不耐热肠毒素Ｂ亚单位（ＬＴ－Ｂ）基因融合。表达的ＬＴＢ／ＳＴａ融合蛋白，既有ＬＴ－Ｂ的抗原性又有ＳＴａ的抗原性。由于基因融合的方式不同，对ＳＴａ的抗原性影响很大，但对ＬＴ－Ｂ的抗原性没有影响。ＬＴ－Ｂ／ＳＴａ融合多肽保留了ＥＴＥｃ肠毒素结合ＧＭ－１神经节甙酯的能力，却仍具有ＳＴａ的生物毒性。     

F10蛋白的原核表达及多克隆抗体的制备

目的：表达F10蛋白，并制备兔抗F10多克隆抗体。方法：利用PCR方法扩增F10基因片段，经BamHⅠ和EcoRⅠ酶切后连接人pET-GST原核表达载体，构建的pET-GST／F10融合重组表达质粒转化大肠杆菌B121，经IPTG诱导表达蛋白，并以亲和层析的方法进行纯化。表达产物用SDS—PAGE电泳和Western blot进行分析鉴定。以纯化的F10蛋白免疫新西兰大白兔，制备兔抗F10的多克隆抗体，并以ELISA法检测抗体效价。结果：经酶切和核酸序列分析证实重组质粒包含有正确编码的F10读码框。SDS—PAGE电泳分析显示pET—GST／F10诱导后表达一相对分子质量（Mr）约为61000的融合蛋白，与预期结果相符。目的蛋白纯化后的纯度达90％以上，Western blot证实该蛋白是GST／F10的融合蛋白。将纯化的GST／F10融合蛋白免疫家兔，得到的兔抗F10抗体效价达1：20000。结论：成功构建了人F10基因原核表达载体，并获得了高纯度的F10重组蛋白及兔抗F10抗体，为下一步研究F10基因功能奠定了实验基础。     

人肝再生磷酸酯酶2(PRL-2)的原核表达及其鸡卵黄抗体的制备

目的 :原核表达人肝再生磷酸酯酶 2 (PRL 2 )与谷胱甘肽S转移酶 (GST)和 6个串联组氨酸 (6×His)的融合蛋白 ,并制备GST PRL 2特异性鸡卵黄抗体。方法 :将人PRL 2cDNA的全长蛋白编码序列 ,克隆入两种原核表达载体pGEX 4T 2和pET2 1a中 ,在大肠杆菌BL2 1中诱导表达融合蛋白。用Glu tathioneSepharose 4B和Ni NTAagarose亲和柱分别纯化目的蛋白。以纯化的GST PRL 2融合蛋白免疫产蛋母鸡制备多克隆抗体 ,应用 6×His PRL 2对抗体进行亲和层析纯化 ,纯化产物用Westernblot进行分析。结果 :得到高表达量的融合蛋白 ,经亲和层析柱纯化后获得较高纯度的GST PRL 2和 6×HisPRL 2融合蛋白。以GST PRL 2融合蛋白免疫鸡得到抗PRL 2的多克隆抗体 ,Westernblot证实 ,经 6×HisPRL 2亲和层析纯化的抗体 ,能够识别 6×His PRL 2和GST PRL 2融合蛋白 ,但不同GST蛋白起反应 ,表明具有较高的特异性。结论 :利用原核表达的人PRL 2融合蛋白制备的抗PRL 2多克隆抗体具有较好的特异性 ,为研究PRL 2蛋白在细胞信号转导过程中的作用提供了重要的技术和材料保障     

用蛋白印迹试验检测精神分裂症患者血清中博尔纳病病毒-p24抗体的研究

目的：探讨博尔纳病病毒（BDV）感染在我国的流行情况及其与精神分裂症的相关性。方法：在对优化表达的GST－BDV－p24融合蛋白进行特异性鉴定的基础上，通过确定融合蛋白与第一抗体、第二抗体间的最佳反应条件，建立可行的检测BDV－p24特异抗体的蛋白印迹（Western-blot）方法，进而对黑龙江地区精神分裂症患者和正常人对照血清中BDV－p24特异性抗体进行了检测，并通过血清－GST蛋白吸收后W estern-blot实验对阳性血清进行了确认。结果：116例精神分裂症患者中检出BDV－p24阳性血清10例，阳性检出率为8.6%，而正常人血清标本中未检出阳性。结论：我国存在博尔纳病病毒的感染，博尔纳病病毒的感染可能与精神分裂症的发生有关。     

乳腺癌易感基因BRCAl的BRCT结构域的融合表达及纯化

乳腺癌易感基因BRCAl在乳腺癌发生、发展中起着重要作用。在其C-末段有两个串联重复的BRCT(BRCTl和BRCT2)结构域。它们与BRCAl的重要功能密切相关，BRCT结构域还存在于其它50多种蛋白中。本文用PCR方法扩增了BRCTl和BRCT2结构域编码序列，并将其以正确相位与pGEX—2T载体中的GST编码序列融合，构建成重组质粒pGST—BRCTl和PGST—BRCT2。将这两种重组质粒分别转化E．coli DH5α后，分别表达了GST—BRCTl和GST—BRCT2两种融合蛋白。Western blot检测结果表明，两种融合蛋白均能与GST抗体反应。表达的GST—BRCTl和GST—BRCT1经GST—Sepharose 4B亲和层析获得了纯化的融合蛋白，为BRCT结构域及其相关蛋白功能研究提供了有用的材料。     

CMTM1-v17/CKLFSF1-v17多克隆抗体的制备、亲合纯化与鉴定

目的：CMTM1-v17是我室克隆的人类新基因，为进一步研究CMTM1-v17的功能，需制备高纯度的CMTM1-v17的抗体。方法：根据生物信息学分析的结果，用PCR法扩增人CMTM1-v17分子C端的cDNA片段（编码118～149位氨基酸），亚克隆到GST融合蛋白表达载体pGEX-4T-2上。将重组质粒pGST-CMTM1-v17导入大肠杆菌BL21，诱导表达GST-CMTM1-v17 C端融合蛋白，经GST亲合层析、凝血酶切割后获得CMTM1-v17 C蛋白作为抗原免疫家兔制备抗血清。抗血清经抗原亲合层析后用Western blot和免疫组化方法进行鉴定。结果：通过重组表达获得抗原蛋白，免疫家兔并纯化抗血清得到特异的抗CMTM1-v17抗体，该抗体能检测到CMTM1-v17超表达和细胞内源性的蛋白。结论：成功制备了抗CMTM1-v17的多克隆抗体，对进一步研究CMTM1-v17的功能提供了一个有用的工具。     

不耐热肠霉素和耐热肠毒素基因的融合

用重组基因技术将产肠毒素大肠杆菌（ＥＴＥＣ）的耐热肠毒素（ＳＴａ）基因与不耐热肠毒素Ｂ亚单位（ＬＴ－Ｂ）基因融合。表达的ＬＴ－Ｂ／ＳＴａ融合蛋白，既有ＬＴ－Ｂ的抗原性又有ＳＴａ的抗原性。由于基因融合的方式不同，对ＳＴａ的抗原性影响很大，但对ＬＴ－Ｂ的抗原性没有影响。ＬＴ－Ｂ／ＳＴａ融合多肽保留了ＥＴＥＣ肠毒素结合ＧＭ－１神经节甙酯的能力，却仍具有ＳＴａ的生物毒性。     

猪瘟病毒E2蛋白重复多表位基因的融合表达及其兔体免疫保护研究

目的：研究猪瘟病毒(CSFV)E2蛋白重复多抗原表位基因的融合表达及其免疫攻毒保护作用。方法：应用PCR方法扩增猪瘟病毒E2蛋白重复多抗原表位基因，构建重复多表位基因的原核重组表达质粒PGEX-3E，进行融合蛋白的表达和纯化。ELISA和Western blot方法测定单表位融合蛋白GST-E和多表位融合蛋白GST-3E与猪抗CSFV的阳性血清和兔抗E2阳性血清的反应性，并进行融合蛋白的兔体免疫及免疫攻毒保护的比较研究。结果：分子克隆和构建了原核重组表达质粒pGEX-3E，表达和纯化了融合蛋白GST-3E；单表位融合蛋白与重复多表位融合蛋白均能够与猪抗CSFV的阳性血清反应和兔抗E2的阳性血清产生免疫反应。在刺激兔体产生抗体方面，单表位融合蛋白刺激兔体产生抗体的能力较弱，而多表位融合蛋白则能够使兔体产生高效价的抗体。接种100MID50剂量猪瘟兔化弱毒(HCLV)进行的兔体免疫攻毒保护试验表明，空白对照组和载体蛋白GST免疫组无保护作用，单表位融合蛋白免疫组具有一定的免疫保护作用，而重复多表位融合蛋白免疫组则完全能够抵抗猪瘟病毒的攻击。结论：猪瘟病毒E2蛋白重复多表位的融合表达具有免疫保护作用，本实验的成功完成为猪瘟病毒多表位抗原的串联及多表位疫苗的研究奠定了基础。     

小鼠肺炎链球菌脂蛋白SPD_1609多克隆抗体的制备

目的制备肺炎链球菌脂蛋白SPD_1609的小鼠多克隆抗体。方法通过PCR扩增肺炎链球菌D39菌株中的spd_1609基因,连接到原核表达载体pGEX-4T-1上,构建重组质粒pGEX-4T-1609。将重组质粒转化大肠杆菌BL21(DE3),用异丙基β-D-硫代半乳糖苷(IPTG)诱导表达谷胱甘肽巯基转移酶-SPD_1609(GST-1609)融合蛋白。利用GST亲和层析柱纯化GST-1609融合蛋白,纯化后的融合蛋白用凝血酶(thrombin)外切酶切掉GST标签,进一步通过GST亲和层析得到SPD_1609蛋白。用纯化的不含GST标签的SPD_1609蛋白免疫小鼠,制备多克隆抗体,用ELISA检测抗体的效价, Western blot法检测抗体的特异性。结果成功构建了原核表达载体pGEX-4T-1609,经GST亲和层析柱分离纯化后可得到相对分子质量(M_r)35 000的SPD_1609蛋白,蛋白纯度在95%以上。ELISA检测结果显示纯化后的SPD_1609蛋白可诱导小鼠产生特异性免疫应答,免疫小鼠血清抗体的效价达1∶40 960, Western blot法检测显示此多克隆抗体可以特异地识别原核表达和肺炎链球菌细胞内表达的SPD_1609蛋白。结论成功制备具有较好特异性的SPD_1609蛋白的小鼠多克隆抗体。     

幽门螺杆菌热休克蛋白A亚单位与大肠杆菌不耐热肠毒素B亚单位融合蛋白表达的研究

目的：获得大肠杆菌不耐热肠毒素B亚单位（LTB）与幽门螺杆菌保护性抗原热休克蛋白A亚单位（HspA）的融合蛋白。方法：PCR扩增ltB和hspA基因，依次构建至表达载体pIM-1，转化大肠杆菌，SDS-PAGE、免疫印迹分析目的蛋白表达情况。采用GM1ELISA和D( )-半乳糖亲和层析方法检测重组LTB-HspA融合蛋白LTB组分与GM1神经节苷脂结合活性。结果：重组LTB-HspA融合蛋白表达量最高可达细菌总蛋白的25％。免疫印迹检测结果证实为重组LTB-HspA融合蛋白。GM1ELISA和D( )-半乳糖亲和层析方法检测结果证实重组LTB-HspA融合蛋白具有与GM1神经节苷脂结合的活性。结论：LTB-HspA融合蛋白的表达研究，为研制幽门螺杆菌分子内佐剂疫苗打下了基础。     

Citrobacter freundii produces an 18-amino-acid heat-stable enterotoxin identical to the 18-amino-acid Escherichia coli heat-stable enterotoxin (ST Ia).

We purified and sequenced the heat-stable enterotoxin produced by Citrobacter freundii. The toxin was detected during purification by reaction with monoclonal antibody to Escherichia coli heat-stable enterotoxin. The C. freundii toxin amino acid sequence was identical to that of the 18-amino-acid heat-stable enterotoxin (STa) produced by toxigenic E. coli.     

Enzyme-linked immunosorbent assay for Escherichia coli heat-stable enterotoxin type II.

The gene for Escherichia coli heat-stable enterotoxin type II (STII) was fused to the genes for protein A from Staphylococcus aureus and beta-galactosidase in two different expression systems. Antibodies raised in rabbits against the protein A-STII fusion protein recognized the beta-galactosidase-STII fusion protein. The latter fusion protein was used as the immobilized antigen in an enzyme-linked immunosorbent assay (ELISA) for detection of STII. The correlation between the results of the ELISA and the intestinal loop test in piglets was 95%, suggesting that the ELISA can be used to reliably detect STII.     

Immunological properties of purified Klebsiella pneumoniae heat-stable enterotoxin

Klebsiella pneumoniae heat-stable enterotoxin was purified to apparent homogenicity by the same techniques used to purify Escherichia coli heat-stable enterotoxin. The two toxins had the same potency in the suckling mouse assay and showed immunological cross-reactivity in enzyme-linked immunosorbent assay, neutralization of secretory activity by specific hyperimmune antisera, and protection against active challenge in rats immunized with a vaccine containing synthetically produced E. coli heat-stable enterotoxin.     

Monoclonal antibodies specific for the Escherichia coli heat-stable enterotoxin STb.

Protein A-STb and STb-alkaline phosphatase protein fusions were used as immunogen and antigen, respectively, for the generation and screening of monoclonal antibodies to the Escherichia coli heat-stable enterotoxin STb. Following immunization with immunoglobulin G-Sepharose-purified protein A-STb and hybridoma construction, STb-alkaline phosphatase hybrid protein was used in a labeled antigen capture assay to detect the production of STb-specific monoclonal antibody. STb-specific monoclonal antibodies were characterized by using a combination of immunoblotting and synthetic-peptide-based enzyme immunoassay techniques. Four distinct anti-STb antibodies were identified and characterized.     

Immunization of swine with heat-stable Escherichia coli enterotoxin coupled to a carrier protein does not protect suckling pigs against an Escherichia coli strain that produces heat-stable enterotoxin.

Pregnant swine were immunized parenterally with purified heat-stable Escherichia coli enterotoxin that was made antigenic by coupling it to bovine immunoglobulin G. Immunized swine had high titers of antitoxin in serum and colostrum as measured by radioimmunoassay. However, the heat-stable enterotoxin neutralizing titers of the serum and colostrum from immunized swine were comparatively low. Newborn pigs suckling their immunized dams were not protected against challenge with porcine enterotoxigenic E. coli that produce heat-stable toxin but do not produce heat-labile toxin.     

Protection in rats immunized with Escherichia coli heat-stable enterotoxin.

Rats immunized with a semipurified preparation of the Escherichia coli heat-stable (ST) enterotoxin conjugated with a protein carrier were protected against challenge with semipurified or purified ST and viable organisms of multiple heterologous serotypes that produce only ST (LT-/ST+), but they were not protected against heal-labile (LT) toxin or viable strains which produce LT either alone (LT+/ST-) or together with ST (LT+/ST+).     

Production of neutralizing monoclonal antibodies to Escherichia coli heat-stable enterotoxin.

In an effort to develop new approaches to the study and control of infectious diarrhea, we prepared murine monoclonal antibodies to the Escherichia coli heat-stable enterotoxin (STa). The toxin was purified from E. coli culture media and conjugated to bovine serum albumin. The STa-bovine serum albumin conjugate was used to immunize BALB/c mice, and the immune spleen cells from these mice were fused with SP2/0 myeloma cells. Resultant hybridomas were screened in an enzyme-linked immunosorbent assay protocol against 500 ng of STa-bovine serum albumin bound to microtiter wells as the solid-phase antigen. Five stable clones were selected and grown further in ascites fluid, which demonstrated anti-STa activity at dilutions of up to 1:500,000 in the enzyme-linked immunosorbent assay for heat-stable enterotoxin. In a competitive enzyme-linked immunosorbent assay format, the antibodies recognized several human and porcine strains of STa to various extents, but did not recognize E. coli heat-labile toxin, cholera toxin, or staphylococcal enterotoxin B. The antibodies were all able to bind lactoperoxidase-labeled [125I]STa, and antibody 20B3 was also able to dissociate [125I]STa bound to toxin receptors on rat jejunal villous cells. Preincubation of STa with antibodies 20B3 or 20F5 led to a concentration-dependent neutralization of toxin activity in a suckling mouse intestinal secretion assay. These antibodies are likely to provide new tools for the continued study of STa structure-function relationships and may lead to improved diagnosis and treatment of E. coli-induced infectious diarrhea.     

抗大肠杆菌耐热性肠毒素ST1 McAb杂交瘤细胞系的建立及应用

目的 耐热性肠毒素ST1单克隆抗体制备及在感染性腹泻诊断中的应用。方法 应用基因工程菌株分泌的肠毒素制备ST1包涵体，免疫Balb／c小鼠，成功制备了3株特异性抗ST1的单克隆抗体细胞株，用其中1株McAb建立了检测ST1的双单克隆抗体夹心ELISA法。结果 检测52株从临床腹泻病人粪便中分离的大肠杆菌，检出ST1阳性率为26．92％，与ST1检测的经典方法乳鼠灌胃法符合率为96．15％。结论 该方法是一种简捷、灵敏和特异的检测方法，具有实际应用价值。     

Purification and partial characterization of heat-stable enterotoxin of enterotoxigenic Escherichia coli.

Heat-stable enterotoxin was purified from a strain of enterotoxigenic Escherichia coli 53402 A-1 from human intestine. The cells were cultured in Casamino Acids-yeast extract-salts medium, and the purification procedure consisted of protamine sulfate treatment of the culture supernatant, ultrafiltration with an Amicon PM-10 membrane, diethylaminoethyl-cellulose column chromatography, hydroxyapatite column chromatography, Bio-Gel P-10 gel filtration, 90% ethanol extraction, and preparative polyacrylamide gel disc electrophoresis. About 300-fold purification was achieved, with a yield of about 12%. However, the homogeneity of the purified heat-stable enterotoxin was not rigorously demonstrated. The purified heat-stable enterotoxin had an absorption maximum at about 275 nm, and its isoelectric point was about 3.90. The molecular weight of the purified heat-stable enterotoxin was ca. 4,000 by Sephadex G-100 gel filtration. The minimum effective dose of purified heat-stable enterotoxin was about 2.5 ng in the suckling mouse assay. The purified heat-stable enterotoxin gave a positive reaction in not only the suckling mouse assay but also the mouse intestinal loop test and the guinea pig skin permeability test.     

Development of an immunoassay using recombinant maltose-binding protein-STa fusions for quantitating antibody responses against STa, the heat-stable enterotoxin of Escherichia coli.

A set of fusion proteins containing heat-stable enterotoxin (STa) and maltose-binding protein were engineered. These molecules were readily purified and used as solid-phase antigens in an enzyme-linked immunosorbent assay to monitor anti-STa responses in mice immunized with a recombinant vaccine composed of STa and the B subunit of heat-labile enterotoxin.