抗重组志贺样毒素ⅡA亚单位单链抗体的构建及表达

目的 构建重组志贺样毒素ⅡA亚单位（SLT2A）单链抗体基因（scFv）,并在大肠杆菌中进行分泌表达。方法 通过连接肽（Gly4Ser）,将已成功扩增的抗SLT2A单克隆抗体（mAb）5F3的VL和Va连接成scFv基因VH-Linker-VL并在Va基因5′端和VL基因3′端引入Sfi Ⅰ和Not Ⅰ的酶切位点,克隆至经改造的分泌性表达载体pCANTAB6His中,转化Ecoli HB2151,IPTG诱导表达。表达产物经亲和层析纯化后,SDS-PAGE和Westem blot分析鉴定。结果 经限制性酶切鉴定及DNA测序分析证实,基因构建正确。SDS-PAGE和Westem blot分析表明scFv基因在大肠杆菌中得到表达,表达产物的相对分子质量为27000,与理论预期值相符,且可与相应抗原特异结合。结论 成功地实现了抗SLT2A scFv基因的原核分泌表达,为探讨0157菌感染的机制及防治研究奠定了基础。     

抗重组人bFGF单克隆抗体可变区基因克隆及单链抗体的构建和表达

目的：从分泌抗重组人碱性成纤维细胞生长因子（bFGF）单克隆抗体（mAb）杂交瘤细胞株B2F3中克隆抗体可变区（V）基因，构建bFGF单链抗体（scFv），并进行可溶性表达。方法：从分泌bFGF mAb杂交瘤细胞株B2F3提取总RNA，用RT-PCR方法扩增抗体重链可变区基因（VH）和轻链的可变区基因（VL）；再通过重叠延伸拼接（SOE）PCR方法，在VH和VL基因之间引入linker（Gly4Ser）3，构建bFGF scFv。将测序正确的scFv基因克隆到表达载体pCANTAB 5E中，选择非抑制型菌株E.coli HB2151进行可溶性表达；经SDS—PAGE检测抗体表达水平，ELISA鉴定其抗原结合活性。结果：测序分析结果显示，VH基因序列全长375碱基对，编码125个氨基酸，VL基因序列全长399碱基对，编码133个氨基酸，二者均符合小鼠免疫球蛋白可变区基因特征，含有4个框架区（FR）、3个抗原互补决定区（CDR）及抗体特征性的2个半胱氨酸残基；构建的scFv全长789碱基对，编码263个氨基酸，连接结构为VH-linker-VL。SDS-PAGE分析表明scFv基因在大肠杆菌为可溶性表达，表达产物主要位于周质腔中，表达产物的Mr为27000，与理论预期值相符；间接ELISA检测结果显示原核表达的scFv具有与bFGF特异性结合的活性。结论：成功地克隆bFGF mAb可变区基因，并构建表达bFGF scFv，为下一步研究bFGF抗体人源化改造奠定实验基础。     

抗SEB单克隆抗体可变区基因克隆及单链抗体的基因构建和表达

目的 从分泌抗SEB的单克隆抗体(FMU-SEB-No.1)杂交瘤细胞中,克隆出FMU-SEB-No.1重链和轻链可变区(VH和VL)基因,构建FMU-SEB-No.1单链抗体(scFv)的原核表达载体,并进行scFv基因的蛋白表达.方法 从FMU-SEB-No.1杂交瘤细胞中提取总RNA,采用RT-PCR扩增出VH和VL基因;通过在引物上设计linker序列,拼接VH和VL为完整FMU-SEB-No.1的scFv基因(FMU-SEB-scFv).将测序正确的scFv基因克隆入PGEX4T-1载体,转化入E.coli BL21(DE3)进行蛋白表达.通过SDS-PAGE,Western blot法分析其表达水平和特异性,酶联免疫吸附试验(ELISA)鉴定其抗原结合活性.结果 测序结果显示,本实验成功克隆出FMU-SEB-No.1重链及轻链可变区基因,并成功构建FMU-SEB-scFv基因,所得的基因全长为750 bp,编码250个氨基酸.SDS-PAGE和Western blot分析表明,PGEX4T1-FMU-SEB-scFv在E.coli BL21(DE3)可表达为Mr约54 000的可溶型scFv/GST融合蛋白.间接ELISA检测结果表明,可溶型scFv/GST融合蛋白与SEB具有较高的抗原结合活性.结论 制备并鉴定了针对SEB的基因工程抗体,为开发出针对SEB的治疗性抗体奠定了实验基础.     

抗重组志贺毒素ⅡB亚基单克隆抗体的制备及生物学特性鉴定

目的 制备出高效价的抗重组志贺毒素ⅡB亚基(rStx2B)单克隆抗体.方法 以融合蛋白EspA-Stx2B作为抗原,免疫Balb/c小鼠,以未免疫的Balb/c小鼠脾细胞为饲养细胞;运用细胞杂交瘤技术制备,运用间接ELISA法筛选产生针对rStx2B的单克隆抗体细胞株;体内诱生法产生腹水,饱和硫酸铵沉淀法初步纯化,再采用HiTrap rProtein A柱进一步纯化,快速定性试纸鉴定McAb的Ig亚型,采用间接ELISA法相加实验鉴定抗原识别表位.结果 获得3株产生针对rStx2B的单克隆抗体细胞株Stx2B-1H9、Stx2B-1H10、Stx2B-3E5,Ig亚型分别为IgG1κ型,IgG2aκ型,IgG2bκ型,亲和力常数分别为7.36×108、6.94×108、5.85×108.结论 成功制备3株稳定分泌抗rStx2B的杂交瘤细胞株,产生的McAb特异性好,亲和力高,为应用这些单克隆抗体建立免疫亲和层析法纯化天然志贺毒素Ⅱ,鉴定Stx2B的表位,研究针对EHEC O157:H7感染的治疗性抗体奠定了基础.     

鼠源性抗人HAAH mAb可变区基因克隆及单链抗体的构建和表达

目的:从分泌抗人类天冬氨酰基β-羟化酶(HAAH)单克隆抗体(mAb)的杂交瘤细胞G3/F11中,克隆出鼠源an-ti-HAAH mAb重、轻链町变区基因,构建Anti-HAAH的单链抗体(scFv),并进行scFv基因的蛋白表达.方法:提取杂交瘤细胞G3/F11的总RNA,通过RT-PCR扩增出VH和VL基因;再利用重叠延伸PCR(SOE-PCR),通过设计在引物上的linker序列,将VH和VL拼接为完整anti-HAAH scFv基因.将测序正确的scFv基因克隆入pHEN 1载体,并利用E.coli HB2151进行蛋白表达;通过SDS-PAGE,Western blot分析其表达状况,ELISA鉴定其抗原结合活性.结果:测序结果显示,本实验成功地构建出鼠源anti-HAAH VH-linker-VL scFv基因,且VH、VL均具有完整正确的小鼠抗体骨架区和互补决定区结构,所得的scFv基因片段全长744 bp,编码248个氨基酸.SDS-PAGE和Western blot分析表明,pHEN 1-anti-HAAH在E.coli HB2151可表达为Mr约27 000的可溶性scFv蛋白,表达量为7.8%.间接ELISA检测显示,可溶性鼠源anti-HAAH scFv蛋白具有较高的抗原结合活性.结论:成功扩增出的鼠源anti-HAAH mAb VH区和VL区基因,并构建为anti-HAAH scFv基因.然后,利用pHEN 1载体对anti-HAAH scFv基因进行成功表达,为进一步研究其生物活性及应用奠定了基础.     

抗Stx2B单链抗体基因的构建及在大肠杆菌中的分泌表达

目的 构建重组志贺样毒素亚Ⅱ结合亚单位（Stx2B）单链抗体基因,并在大肠杆菌中进行分泌表达。方法借助连接肽（Gly4Ser）3将已成功扩增的抗Stx2B单抗1A5轻、重链可变区基因（VL、VH）连接成单链抗体（ScFv）基因VH-Linker-VL,并在VH5’端和VL3’端引入SfiⅠ和Not Ⅰ酶切位点,克隆至经改造的分泌性表达载体pCANTAB6His之中,转化EcoliHB2151,IPTG诱导表达。亲和层析纯化抗体蛋白后,以SDS-PAGE、ELISA等方法分析鉴定表达产物。结果经限制性酶切鉴定及DNA测序分析,证实基因构建正确。SDS-PAGE、ELISA分析表明ScFv基因在大肠杆菌中成功表达,表达产物的相对分子质量（Mr）为27000,与理论预期值相符,且可与相应抗原特异结合。结论成功实现了抗Stx2B单链抗体的原核分泌表达,为探讨O157菌的感染机制及防治研究奠定了基础。     

抗血小板膜糖蛋白单克隆抗体SZ-2单链抗体的构建、表达及功能研究

目的：降低鼠源性抗体的免疫原性及分子量，为其进一步研究、应用奠定基础。方法：应用RT—PCR技术，克隆SZ-2重链、轻链可变基因。应用基因重组技术构建SZ-2单链抗体表达载体pET22-2scFv，导入大肠杆菌BL21(DE3)Plys，诱导表达。流式细胞术、ELISA、Western blot检测SZ-2 scFv与血小板结合能力，瑞斯托霉素、凝血酶和ADP诱导血小板聚集试验对表达产物功能进行研究。结果：克隆基因序列符合小鼠轻、重链可变区基因特征；pET22—2scFv表达质粒拼接正确；表达产物以包涵体形式为主，表达量占菌体总蛋白的25％；纯化、复性后证明表达产物具有与血小板结合的活性，并可抑制瑞斯托霉素、凝血酶诱导的血小板聚集。结论：成功表达了SZ—2单链抗体，该小分子抗体具有与血小板结合的活性，并可抑制瑞斯托霉素、凝血酶诱导的血小板聚集。     

抗血小板膜糖蛋白单克隆抗体SZ—21基因克隆及单链抗体的构建和表达

目的 将能与血小板膜糖蛋白Ⅲa特异结合的单克隆抗体SZ-21构建成单链抗体,为其临床应用奠定基础。方法 通过逆转录及多聚酶甸反应,扩增并克隆SZ-21的可变区基因VH、VL,经测序后构建SZ-21单链抗体（SZ-21AScFv),在大肠杆菌中进行表达,ELISA和Western印迹检测其与血小板的结合特性。结果 VH、VL可变区基因符合小鼠抗体可变区特征,SZ-21ScFv基因拼接正确。表达产物除少量为分泌型外,主要以包涵体形式存在,表达量占菌体蛋白的21%,经过变性和复性后,该单抗体保留了与血小板特异结合的能力。结论 成功表达了SZ-21单链抗体。该小分子抗体具有特异结合血小板的能力,有望用于抗血栓治疗。     

抗登革病毒3型单链抗体的基因克隆表达和免疫学鉴定

目的研究单链抗体在治疗中的免疫反应问题。方法选用对登革病毒四个血清型及部分黄病毒具有中和活性的抗登革３型病毒单克隆抗体３Ｄ３的轻重链可变区基因，通过反转录和聚合酶链反应（ＲＴ－ＰＣＲ）扩增，扩增后的轻重链可变区ＰＣＲ产物通过一个９３个核苷酸连接引物连接成单链抗体基因（ＳｃＦｖ），然后将其基因克隆到噬菌体表达载体ｐＣＡＮＴＡＢ５的外壳蛋白ｇ３ｐ基因中，使单链抗体以融合蛋白的形式表达于噬菌体的表面。结果通过免疫荧光鉴定，这种抗体仍保留着亲代抗体的特性，能与登革３型病毒发生特异性结合。结论这一研究结果为登革３型病毒抗体在登革病毒的诊断和治疗的应用奠定了基础。     

抗志贺样毒素Ⅱ型变异体单克隆抗体的制备及特性鉴定

志贺样毒素Ⅱ变异体(SLT-Ⅱe)是猪水肿病的主要致病因子之一,为了制备SLT-Ⅱe单克隆抗体(mAb),我们从TB1菌中用多粘菌素诱导提取了SLT-Ⅱe蛋白,并且用硫酸铵盐析沉淀法对该蛋白进行了提纯,以提纯蛋白免疫BALB/c小鼠,利用杂交瘤细胞技术制备mAb。细胞融合后,培养上清经间接ELISA检测,共得到3株阳性杂交瘤细胞2E11、2H9和4F3,ELISA效价分别为1∶213、1∶213和1∶28,3株杂交瘤细胞培养上清分泌的mAb在Westernblot试验中均与提纯的毒素蛋白反应,在Vero细胞中和试验中均能够中和毒素对Vero细胞的毒性作用,从而为临床分离株SLT-Ⅱe产生的免疫学检测方法奠定了一定的基础。     

Oral Intoxication of Mice with Shiga Toxin Type 2a (Stx2a) and Protection by Anti-Stx2a Monoclonal Antibody 11E10

Shiga toxin (Stx)-producing Escherichia coli (STEC) strains cause food-borne outbreaks of hemorrhagic colitis and, less commonly, a serious kidney-damaging sequela called the hemolytic uremic syndrome (HUS). Stx, the primary virulence factor expressed by STEC, is an AB₅ toxin with two antigenically distinct forms, Stx1a and Stx2a. Although both toxins have similar biological activities, Stx2a is more frequently produced by STEC strains that cause HUS than is Stx1a. Here we asked whether Stx1a and Stx2a act differently when delivered orally by gavage. We found that Stx2a had a 50% lethal dose (LD₅₀) of 2.9 μg, but no morbidity occurred after oral intoxication with up to 157 μg of Stx1a. We also compared several biochemical and histological parameters in mice intoxicated orally versus intraperitoneally with Stx2a. We discovered that both intoxication routes caused similar increases in serum creatinine and blood urea nitrogen, indicative of kidney damage, as well as electrolyte imbalances and weight loss in the animals. Furthermore, kidney sections from Stx2a-intoxicated mice revealed multifocal, acute tubular necrosis (ATN). Of particular note, we detected Stx2a in kidney sections from orally intoxicated mice in the same region as the epithelial cell type in which ATN was detected. Lastly, we showed reduced renal damage, as determined by renal biomarkers and histopathology, and full protection of orally intoxicated mice with monoclonal antibody (MAb) 11E10 directed against the toxin A subunit; conversely, an irrelevant MAb had no therapeutic effect. Orally intoxicated mice could be rescued by MAb 11E10 6 h but not 24 h after Stx2a delivery.     

Antibody response to Shiga toxins Stx2 and Stx1 in children with enteropathic hemolytic-uremic syndrome

A Western blot (immunoblot) assay (WBA) for the detection of immunoglobulin G antibodies to Shiga toxins Stx2 and Stx1 in sera from 110 patients with enteropathic hemolytic-uremic syndrome (53 culture confirmed to have Shiga toxin-producing Escherichia coli [STEC] infection) and 110 age-matched controls was established by using a chemiluminescence detection system. Thirty-nine (74%) of the 53 culture-confirmed cases were infections with STEC serotype O157, and 14 (26%) were associated with infection by other STEC serotypes. The frequency of an anti-Stx2 response following infection by a Stx2-producing strain (34 of 48 cases; 71%) was higher than that of an anti-Stx1 response following Stx1-producing STEC infection (4 of 10). Furthermore, the frequency of an anti-Stx2 response in 110 control sera (10%) was significantly higher than the frequency of an anti-Stx1 response (1.8%) (P = 0.0325). For STEC O157 culture-confirmed cases WBA for toxin detection had a diagnostic sensitivity of 71% and a specificity of 90%. Because of its high specificity the assay might be a helpful tool for diagnosing suspected STEC infection when tests of stool samples or serological tests against various lipopolysaccharide antigens are negative. Furthermore, the prevalence of anti-Stx antibodies in healthy controls probably reflects the population immunity to systemic Stx-associated disease. It can thus serve as a basis for comparing immunity levels in different populations and for considering future Stx toxoid immunization strategies.     

抗端粒酶蛋白hTERT重链可变区基因的克隆和表达

利用噬菌体表面展示技术制备端粒酶蛋白hTERT抗体，从重组的hTERT免疫的小鼠脾淋巴细胞中提取总RNA，逆转录成cDNA，以逆转录合成的cDNA第一条链为模板，用VHback和VHfor引物，通过PCR扩增出约350bp大小的抗hTERT重链可变区基因，将其克隆到噬菌粒载体PCANTAB 5E中，转化入E.coli TG1宿主菌后，在M13K07辅助噬菌体帮助下，将VH与g3蛋白形成的复合物展示于噬菌体表面，我们利用Dot Blot检测方法筛选出hTERT具有亲和性的VH单功能区抗体，结果提示噬菌体展示技术是制备抗体的一种有效的新途径。抗hTERT VH基因克隆成功，为进一步构建单链抗体SvFv奠定了基础。     

Monoclonal Antibody 11E10, Which Neutralizes Shiga Toxin Type 2 (Stx2), Recognizes Three Regions on the Stx2 A Subunit,Blocks the Enzymatic Action of the Toxin In Vitro,and Alters the Overall Cellular Distribution of the Toxin

Monoclonal antibody (MAb) 11E10 recognizes the Shiga toxin type 2 (Stx2) A₁ subunit. The binding of 11E10 to Stx2 neutralizes both the cytotoxic and lethal activities of Stx2, but the MAb does not bind to or neutralize Stx1 despite the 61% identity and 75% similarity in the amino acids of the A₁ fragments. In this study, we sought to identify the segment or segments on Stx2 that constitute the 11E10 epitope and to determine how recognition of that region by 11E10 leads to inactivation of the toxin. Toward those objectives, we generated a set of chimeric Stx1/Stx2 molecules and then evaluated the capacity of 11E10 to recognize those hybrid toxins by Western blot analyses and to neutralize them in Vero cell cytotoxicity assays. We also compared the amino acid sequences and crystal structures of Stx1 and Stx2 for stretches of dissimilarity that might predict a binding epitope on Stx2 for 11E10. Through these assessments, we concluded that the 11E10 epitope is comprised of three noncontiguous regions surrounding the Stx2 active site. To determine how 11E10 neutralizes Stx2, we examined the capacity of 11E10/Stx2 complexes to target ribosomes. We found that the binding of 11E10 to Stx2 prevented the toxin from inhibiting protein synthesis in an in vitro assay but also altered the overall cellular distribution of Stx2 in Vero cells. We propose that the binding of MAb 11E10 to Stx2 neutralizes the effects of the toxin by preventing the toxin from reaching and/or inactivating the ribosomes.Escherichia coli O157:H7 and other Shiga toxin (Stx)-producing E. coli (STEC) strains cause approximately 110,000 cases of infection and over 90 deaths each year in the United States according to the Centers for Disease Control and Prevention (16). Infections with STEC can lead to diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome (HUS). HUS occurs in about 6 to 15% of individuals after infection with E. coli O157:H7 (15)—but less frequently with other STEC strains (5)—and is characterized by hemolytic anemia, thrombotic thrombocytopenia, and renal failure. The development of this sequela is linked to the expression of Stxs by the bacteria (18).The Stx family comprises two serogroups, Stx/Stx1 and Stx2, and polyclonal antisera raised against either Stx1 or Stx2 do not cross-neutralize the other toxin (29, 30). Stx is produced by Shigella dysenteriae type 1 and differs by only 1 amino acid from the Stx1 made by the prototypic STEC O157:H7 strain, EDL933. A single isolate of STEC can express Stx1 (or one of its variants), Stx2 (or one of its variants), or both toxins. Variants of each toxin type are defined by either a biological or immunological difference from the prototypical toxin (31). Stx1 variants include Stx1c and Stx1d, while the variants of Stx2 are Stx2c, Stx2d, Stx2d-activatable (Stx2d_act), Stx2e, and Stx2f (reviewed in reference 18).Stxs are complex holotoxins with a stoichiometry of five identical binding (B) subunits and a single active (A) domain. These AB₅ molecules are potent cytotoxins with an N-glycosidase activity that stops protein synthesis by inactivation of the 60S ribosome (6); this activity eventually leads to eukaryotic cell death. The ∼32-kDa A subunit contains the enzymatic activity of the toxin with the active site glutamic acid residue at position 167. The A subunit is asymmetrically cleaved by trypsin or furin into an enzymatically active ∼28-kDa A₁ fragment and an ∼4-kDa A₂ peptide. The A₂ peptide remains linked to the large enzymatic domain through a disulfide bond and is encircled by the five identical B subunits of ∼7.7 kDa. The B subunits of the Stxs typically bind to the eukaryotic glycolipid receptor globotriaosylceramide (Gb₃), also known as CD77. The mature A and B subunits of Stx1 and Stx2 are approximately 68 and 73% similar at the amino acid level. The crystal structures of Stx and Stx2 have been resolved, and the two structures are remarkably similar (7, 8). Nevertheless, there are some features of these three-dimensional models that differ (summarized in reference 8).Currently, there are no Food and Drug Administration-approved therapies in the United States to treat STEC infections. However, our research group is one of several that investigate passive immunization strategies to neutralize the Stxs associated with STEC infections (3, 4, 10, 13, 19, 20). Our passive immunization strategy is based on murine monoclonal antibodies (MAbs) developed in this laboratory that specifically bind to and neutralize Stx/Stx1 or Stx2 (21, 28). The MAb 11E10 was generated by immunization of BALB/c mice with Stx2 turned into a toxoid (“toxoided”) by treatment with formaldehyde (21). MAb 11E10 specifically recognizes the A₁ fragment of Stx2 and neutralizes Stx2 for Vero cells and mice but does not bind to or neutralize Stx/Stx1 (21). The murine MAb 11E10 was modified to contain a human constant region to reduce the potential for an antibody recipient to generate an antimouse antibody response (4). This human-mouse chimeric antibody, called cαStx2, successfully underwent phase I clinical testing (3). In this report, we define the epitope on the A subunit of Stx2 recognized by the murine MAb 11E10 (and, therefore, also by cαStx2) and present evidence that the MAb blocks the enzymatic action of the toxin in vitro and also alters toxin trafficking in Vero cells.     

抗肌红蛋白单克隆抗体的制备与鉴定及其初步应用

目的 制备和鉴定抗肌红蛋白(Mb)单克隆抗体,为人肌红蛋白检测试剂的研制奠定基础.方法 用人肌红蛋白抗原免疫BALB/c小鼠,采用杂交瘤技术进行细胞融合,用ELISA方法筛选,有限稀释法进行克隆化培养阳性杂交瘤细胞株.ELISA法测定小鼠腹水滴度,CLIA法对抗体进行配对实验与特异性鉴定.结果 筛选培养出9株分泌抗肌红蛋白单克隆抗体的杂交瘤细胞株,腹水滴度为1∶5×104 ～ 1∶2×105.通过配对实验,有5株抗体6种组合可以成功配对.这5株抗体的亲和常数为6.46×108 ～ 3.68×109 L/mol.用5株抗体所建立的6种化学免疫分析方法与人Hb交叉反应率为7.434×103％ ～2.904×10-2％,与人ALB交叉反应率为4.980×10-7％ ～3.830×10-5％.用Mb17B6与Mb21E8两株抗体建立的CLIA标准曲线的线性系数为0.997,灵敏度为6.02ng/mL.结论 成功制备了可以应用于免疫分析的抗肌红蛋白单克隆抗体.     

Protection of Mice against Shiga Toxin 2 (Stx2)-Associated Damage by Maternal Immunization with a Brucella Lumazine Synthase-Stx2 B Subunit Chimera

Hemolytic-uremic syndrome (HUS) is defined as the triad of anemia, thrombocytopenia, and acute kidney injury. Enterohemorrhagic Shiga toxin (Stx)-producing Escherichia coli (EHEC), which causes a prodromal hemorrhagic enteritis, remains the most common etiology of the typical or epidemic form of HUS. Because no licensed vaccine or effective therapy is presently available for human use, we recently developed a novel immunogen based on the B subunit of Shiga toxin 2 (Stx2B) and the enzyme lumazine synthase from Brucella spp. (BLS) (BLS-Stx2B). The aim of this study was to analyze maternal immunization with BLS-Stx2B as a possible approach for transferring anti-Stx2 protection to the offspring. BALB/c female mice were immunized with BLS-Stx2B before mating. Both dams and pups presented comparable titers of anti-Stx2B antibodies in sera and fecal extracts. Moreover, pups were totally protected against a lethal dose of systemic Stx2 injection up to 2 to 3 months postpartum. In addition, pups were resistant to an oral challenge with an Stx2-producing EHEC strain at weaning and did not develop any symptomatology associated with Stx2 toxicity. Fostering experiments demonstrated that anti-Stx2B neutralizing IgG antibodies were transmitted through breast-feeding. Pups that survived the EHEC infection due to maternally transferred immunity prolonged an active and specific immune response that protected them against a subsequent challenge with intravenous Stx2. Our study shows that maternal immunization with BLS-Stx2B was very effective at promoting the transfer of specific antibodies, and suggests that preexposure of adult females to this immunogen could protect their offspring during the early phase of life.     

CD154 cDNA克隆、单克隆抗体制备及特异性鉴定

本研究目的是获得特异性抗人CD15 4单克隆抗体。利用特异引物 ,通过RT PCR从人外周血淋巴细胞中扩增出编码CD15 4分子的cDNA全长 ,将其克隆在谷胱甘肽巯基转移酶 (GST )融合蛋白表达载体pGEX4T 3中 ,转染大肠杆菌Jm10 9经诱导获得GST CD15 4表达。融合蛋白经分离纯化后 ,免疫Balb/c小鼠 ,应用杂交瘤技术 ,通过ELISA双筛 ,得到 2株抗CD15 4单抗 (1D3和 5H4)。其亚型分别是IgG2a和IgG1。又将CD15 4cDNA全长构建真核表达载体pcDNA3 CD15 4,并转染COS细胞 ,以G418筛选后 ,经RT PCR结果证实pcDNA3 CD15 4已成功转染COS细胞。所获单抗对转染CD15 4的COS细胞和刺激活化的人淋巴细胞有特异性结合反应 ,为进一步研究单抗功能奠定了实验基础。     

恶性淋巴瘤单克隆抗体的制备和初步鉴定

采用人恶性淋巴瘤细胞株Raji细胞作为免疫原免疫BALB/C小鼠, 按常规方法融合并经间接ELISA法筛选, 成功地制备了1株抗Raji细胞单克隆抗体(MAb), 命名为SZ138.用琼脂糖双扩散鉴定其为IgG1类, ELISA法测定其腹水效价为1:3.2×104.MAb流式细胞仪检测表明, 该抗体与Raji和Daudi呈阳性反应;与外周红细胞、白细胞(包括淋巴细胞和中性粒细胞)、未活化血小板、内皮细胞株ECV呈阴性反应.免疫组化SP法显示, MAb SZ138识别的抗原在胃肠道的腺体和肝脏有所表达, 而在心、脑、扁桃体、脾、脂肪组织、动脉血管壁、神经节、横纹肌、平滑肌等组织不表达或表达很低.Western blotting分析显示, MAb SZ138可特异识别还原条件下相对分子量为170kD的蛋白多肽.结果提示: MA SZ138对恶性淋巴瘤的诊断和治疗可能具有一定的临床意义.     

Identification and Characterization of a Newly Isolated Shiga Toxin 2-Converting Phage from Shiga Toxin-Producing Escherichia coli

Shiga toxins 1 (Stx1) and 2 (Stx2) are encoded by toxin-converting bacteriophages of Stx-producing Escherichia coli (STEC), and so far two Stx1- and one Stx2-converting phages have been isolated from two STEC strains (A. D. O’Brien, J. W. Newlands, S. F. Miller, R. K. Holmes, H. W. Smith, and S. B. Formal, Science 226:694–696, 1984). In this study, we isolated two Stx2-converting phages, designated Stx2Φ-I and Stx2Φ-II, from two clinical strains of STEC associated with the outbreaks in Japan in 1996 and found that Stx2Φ-I resembled 933W, the previously reported Stx2-converting phage, in its infective properties for E. coli K-12 strain C600 while Stx2Φ-II was distinct from them. The sizes of the plaques of Stx2Φ-I and Stx2Φ-II in C600 were different; the former was larger than the latter. The restriction maps of Stx2Φ-I and Stx2Φ-II were not identical; rather, Stx2Φ-II DNA was approximately 3 kb larger than Stx2Φ-I DNA. Furthermore, Stx2Φ-I and Stx2Φ-II showed different phage immunity, with Stx2Φ-I and 933W belonging to the same group. Infection of C600 by Stx2Φ-I or 933W was affected by environmental osmolarity differently from that by Stx2Φ-II. When C600 was grown under conditions of high osmolarity, the infectivity of Stx2Φ-I and 933W was greatly decreased compared with that of Stx2Φ-II. Examination of the plating efficiency of the three phages for the defined mutations in C600 revealed that the efficiency of Stx2Φ-I and 933W for the fadL mutant decreased to less than 10⁻⁷ compared with that for C600 whereas the efficiency of Stx2Φ-II decreased to 0.1% of that for C600. In contrast, while the plating efficiency of Stx2Φ-II for the lamB mutant decreased to a low level (0.05% of that for C600), the efficiencies of Stx2Φ-I and 933W were not changed. This was confirmed by the phage neutralization experiments with isolated outer membrane fractions from C600, fadL mutant, or lamB mutant or the purified His₆-tagged FadL and LamB proteins. Based on the data, we concluded that FadL acts as the receptor for Stx2Φ-I and Stx2Φ-II whereas LamB acts as the receptor only for Stx2Φ-II.     

抗HSPC238单克隆抗体的制备和初步鉴定

目的制备抗HSPC238的单克隆抗体，为HSPC238的功能研究奠定基础。方法以纯化的重组蛋白HSPC238为抗原，免疫BALB／c小鼠，运用杂交瘤技术制备HSPC238单克隆抗体，并用间接ELISA法和Western—blot法对单克隆抗体的特性进行鉴定。结果成功建立两株稳定分泌抗HSPC238的单克隆抗体杂交瘤细胞株，分别命名为E001和E002。ELISA检测抗HSPC238单克隆抗体的腹水效价为1：12800和1：25600。两株单克隆抗体的免疫球蛋白亚类均为IgG1。通过Western—blot实验证实，两株单克隆抗体均能特异性结合真核细胞内源性HSPC238蛋白。结论成功制备了两株效价高、特异性好的抗HSPC238单克隆抗体，制备的抗HSPC238单克隆抗体可用于HSPC238蛋白的鉴定，为HSPC238蛋白的生物学功能研究奠定了基础。