鸡源 Bursin-ScFv 噬菌体展示文库的构建及初步筛选

本研究利用抗三肽囊素(Bursin)单克隆抗体免疫SPF来航鸡,获得产生抗独特型抗体的脾细胞,从中提取总RNA,经反转录合成cDNA第一链.以cDNA第一链为模板,根据来航鸡 IgG 抗体重链(VH)、轻链(VL)可变区基因FR设计引物,进行PCR扩增.在体外扩增出该抗体的可变区VH和VL基因(大小分别约为370和320 bp).通过重叠延伸反应(SOE),以(Gly4Ser)3为连接肽,将VH和VL基因连接成为VH-Linker-VL ScFv,将ScFv DNA与噬菌粒载体pHEN1的连接产物转化于大肠杆菌TG1,经辅助噬菌体M13K07感染后,获得重组的鸡源抗三肽囊素独特型抗体全套单链噬菌体抗体库.并测得该库容量约为5×105,噬菌体中ScFv基因的插入率为80%,用辅助噬菌体援救后,得到滴度为1011PFU/mL的初级噬菌体抗体库.用抗Bursin单克隆抗体(2F9-4/HU2)进行4轮"吸附-洗脱-扩增"的淘筛,出现特异性富集.经ELISA、动物试验表明所筛选的5个阳性克隆可与抗Bursin单克隆抗体(2F9-4/HU2)特异性结合,并能促进抗体的生产.     

噬菌体展示三肽囊素模拟肽的研究

本研究分离纯化抗Bursin单克隆抗体(2F9-4/HU2),利用噬菌体环7肽库筛选抗Bursin单克隆抗体(2F9-4/HU2)结合肽,测定阳性克隆ssDNA序列,并与Bursin序列进行同源性分析,通过ELISA法检测其结合活性和竞争ELISA法检测其抗原性,以Busin为对照,验证阳性克隆(№4)在鸡体内的生物学效应.序列分析表明,"LNXT"短肽序列可能为结合抗Bursin单克隆抗体(2F9-4/HU2)的保守序列,但与Bursin无同源性;噬菌体(№1)在序列中含有K、H、G.ELISA和竞争ELISA检测,表明Bursin对阳性克隆1、4、5、6号和抗Bursin单克隆抗体(2F9-4/HU2)的结合有一定的抑制作用:生物学活性初步验证表明,阳性克隆(№4)与Bursin具有类似作用,能促进抗体产生,有望成为一种模拟Bursin新型的免疫增强剂.     

抗三肽囊素单克隆抗体的制备

为研制抗三肽囊素(bursin,KHG-NH₂)的单克隆抗体,本试验采用EDC法将三肽囊素分子赖氨酰(K)上的氨基与载体蛋白(BSA或OVA)定向偶联,分别制备三肽囊素免疫抗原(BSA-KHG-NH₂)和检测抗原(OVA-KHG-NH₂)。以BSA-KHG-NH₂免疫BALB/c小鼠,应用杂交瘤技术,筛选到18株能稳定分泌抗三肽囊素单克隆抗体的杂交瘤细胞株。这18株单克隆抗体与三肽囊素人工抗原的结合均能被三肽囊素、GKHG-NH₂四肽阻断,但不能被KHGK四肽阻断,表明18株单抗与三肽囊素分子的结合具有高度特异性。以本研究制备的单抗2D2建立间接竞争ELISA方法,检测三肽囊素含量,检测下限为4 ng/mL,线性范围为4~500 ng/mL,加标检测回收率为85.0%~92.4%。     

合成三肽囊素阳性噬菌体模拟七肽的免疫活性初步研究

为探讨三肽囊素(Bursin)模拟七肽的免疫活性及其与Brusin的相关性,本研究根据Bursin阳性噬菌体展示七肽库中筛选得到的氨基酸序列(MTTNLQQ)人工合成该七肽.以ELISA和竞争ELISA检验合成七肽与Bursin在体外的免疫学反应的相关性;比较不同剂量的合成七肽(设定Bursin作为对照)对鸡新城疫病毒(NDV)弱毒疫苗(La sota株)在鸡体诱导的特异性免疫应答的影响.结果显示合成七肽与抗Bursin单克隆抗体(2F9-4/HU2)能够特异性结合并且该结合作用可被Bursin阻断;动物试验的结果表明,低剂量(0.09 mg)的合成七肽对疫苗诱导的体液免疫应答的增强作用与Bursin相当,而且高剂量(0.3 mg)的合成七肽对细胞免疫应答具有一定的增强作用.因此,认为七肽序列MTTNLQQ具有与Bursin类似的免疫活性.     

东方田鼠肝脏T7噬菌体展示cDNA文库的构建

本项研究的目的是构建东方田鼠肝脏T7噬菌体展示cDNA文库,为筛选东方田鼠抗血吸虫病抗性相关基因奠定基础.用TRIzol试剂提取东方田鼠肝脏总RNA,分离纯化mRNA,经反转录合成双链cDNA.在双链cDNA末端加上EcoRⅠ/HindⅢ定向接头并用EcoRⅠ和Hind Ⅲ酶切,使其两端分别带EcoRⅠ和HindⅢ粘性末端.用Mini Column纯化、收集300 bp以上的双链cDNA片段,再连接于带有EcoRⅠ和HindⅢ末端的T7 Select 10-3b载体,经体外包装后,以BLT5403为受体菌构建T7噬菌体展示cDNA文库.经测定,库容量为1.3×107 PFU/mL,扩增后文库滴度为1.8×1011 PFU/mL.对从原始文库中随机挑取的100个噬菌斑进行PCR鉴定,重组率为91.7%,阳性克隆片段大小分布在200 bp～1 000 bp,其中有95.5%的插入片段大于300 bp.用日本血吸虫童虫可溶性抗原对文库进行了初筛,得到了21个ESTs,将这些阳性噬菌体克隆和血吸虫童虫共培养,其中大部分克隆诱导的童虫死亡率比阴性噬菌体对照高出2%～13%.     

囊素三肽的研究进展

<正>法氏囊是家禽体内的中枢免疫器官,在免疫反应中发挥着重要作用。Glick[1]首次发现了法氏囊提取液能够使在胚胎期切除法氏囊的小鸡法氏囊复生并且具有恢复产生特异性抗体和免疫球蛋白的能力。Audhya[2]通过高效液相色谱(HPLC)分析发现,法氏囊提取液中发挥主要作用的是一种三肽,是存在于禽法氏     

抗磺胺二甲氧嘧啶VHH抗体噬菌体库的构建和鉴定

旨在制备抗磺胺二甲氧嘧啶(SDM)驼源单域重链(VHH)抗体,用于检测动物源性食品中SDM的残留.采用重氮化法,SDM分别与牛血清白蛋白(BSA)和鸡卵清蛋白(OVA)偶联,合成人工免疫原(SDM-BSA)和包被抗原(SDM-OVA).用SDM-BSA免疫骆驼,在第5 次免疫后1周采集骆驼外周血液,分离外周血淋巴细胞,...     

抗猪流感噬菌体单链抗体库的构建与筛选

利用噬菌体展示技术构建猪流感病毒噬菌体抗体库,并筛选出猪流感高特异性、高亲和力的单链抗体(scFv)。以猪流感病毒免疫BALB/c小鼠,提取脾细胞总RNA,反转录后以cDNA为模板扩增获得VH基因和VL基因,并采用重叠延伸PCR(SOE-PCR),用柔性多肽Linker接头(Gly4Ser)按VH-Linker-VL方式将VH基因和VL基因拼接成scFv基因片段。将scFv基因和pCANTAB5E载体分别双酶切(SfiⅠ/NotⅠ)后连接,转化宿主菌TG1,经过辅助噬菌体M13K07拯救,构建噬菌体单链抗体库。以猪流感病毒为抗原包被96孔酶标板,经过3轮的亲和富集筛选,用Phage-ELISA鉴定阳性重组抗体。本研究成功构建出库容约为4×106cfu/mL抗猪流感病毒的单链抗体库,并筛选出4株特异性抗猪流感病毒的scFv抗体,能够与鼠源阳性多抗进行竞争结合猪流感病毒,为抗猪流感病毒转基因猪的研究奠定基础。     

Isolation of Lawsonia intracellularis specific single-chain Fv antibody fragments from phage display library

Single-chain antibodies (scFv) exhibiting specific binding to Lawsonia intracellularis were isolated from a phagemid library expressing scFvs molecules on the surface of filamentous bacteriophages. For scFv selection whole bacterial cells were used and individual clones were tested in ELISA test. The total of seven unique clones with different fingerprint profiles was isolated. All clones were able to bind specifically in immunofluorescence assay. This is the first report of species specific recombinant antibodies against L. intracellularis.     

Evaluation of a nanobody phage display library constructed from a Brucella-immunised camel

Brucella are invasive gram-negative bacteria that multiply and survive within eukaryotic cells causing brucellosis. Syrian (and Middle East) health and economy sectors are still affected by this disease causing a serious national problem that needs to be solved. Here, a strategy was developed to introduce a new generation of binders, known as Nanobodies (Nbs) in our combat against Brucella. These Nbs, recombinant single-domain variable fragments derived from camelid heavy-chain antibodies are very stable and highly soluble, making them a useful tool in numerous biotechnological and medical applications. In this work and without having access to purified antigens (Ags), a camel was immunised successfully with heat-killed Brucella melitensis strain Riv1 as demonstrated by the high titer of Ag-specific heavy-chain antibodies in the serum. Lymphocytes of the immunised camel were isolated and their Nb genes were cloned in a relatively large library of 10(8) individual transformants, of which 81% contained an insert with the proper size of a Nb gene. Phage display expression of the Nbs from this library and pannings on the Brucella lysate resulted in a clear enrichment of three distinct Nb-displaying phages (phage-Nbs), referred to as NbBruc01, 02 and 03, with specificity for Brucella. Producing these binders in a pure, soluble form, as well as identifying their specific targets, which are likely to be immunodominant Ags in Brucella, is expected to open wide perspectives for following the vaccination, diagnosis and treatment of brucellosis.     

抗鹅细小病毒噬菌体轻链抗体文库的构建

取鹅细小病毒(Goose parvolirus,GPV)免疫过的抗体阳性的试验鹅的脾脏,分离淋巴细胞,提取细胞总RNA后反转录,利用鹅IgG基因特异性引物,分别扩增轻链基因。将鹅轻链基因克隆入噬菌体载体pComb3,经电穿孔法转化大肠杆菌XL1-Blue,再以辅助噬菌体VCSM13超感染,构建抗GPV噬菌体轻链抗体库,筛选阳性克隆,测序分析。结果显示,构建了容量为1×106、重组率为66.6%的轻链抗体库。     

抗牛结核分枝杆菌VHH抗体T7噬菌体库的构建与筛选

为获得抗牛结核分枝杆菌的VHH纳米抗体,本研究利用牛结核分枝杆菌Ag85B蛋白免疫双峰驼,免疫效价达到1∶8 000后采外周血分离淋巴细胞,提取RNA反转录成cDNA,利用巢式PCR方法扩增出编码单域抗体VHH的400 bp基因片段。将目的片段用限制性内切酶EcoRⅠ和HindⅢ双酶切,与T7噬菌体载体臂T7Select 10-3RI Arms连接,再通过体外重新包装含目的片段的噬菌体。对建立的VHH噬菌体抗体库进行鉴定,原始文库库容为5.7×10~8 PFU,库阳性率为85.7%。通过4轮生物亲和淘选,筛选并表达出2株高特异性的VHH抗体,均对牛结核分枝杆菌Ag85B蛋白具有特异性。本研究为进一步探讨VHH抗体在牛结核病的诊断和治疗奠定了基础。     

Identification of antigenic epitopes of the SapA protein of Campylobacter fetus using a phage display peptide library

In this study, we immunized mice with prokaryotically expressed recombinant surface layer protein, SapA, of Campylobacter fetus, generated hybridomas secreting mouse monoclonal antibodies (mAb) targeting SapA, and purified the mAb A2D5 from mouse ascites using saturated ammonium sulfate solution. The mAb A2D5, coated onto ELISA plates, was used to screen the phage random 12-peptide library through three rounds of panning. Following panning, 15 phage clones were randomly chosen and tested for reactivity with mAb A2D5 by indirect ELISA. Single-stranded DNA from positive clones was sequenced and compared with the sequence of SapA to predict the key epitope. ELISA and/or Western blot analyses further validated that synthetic peptides and recombinant peptide mimotopes all interact with mAb A2D5. Nine of ten positive phage clones identified by screening were sequenced successfully. Seven clones shared the same sequence HYDRHNYHWWHT; one had the sequence LSKNLPLTALGN; and the final one had the sequence SGMKEPELRSYS. These three sequences shared high homology with SapA J05577 in the region GNEKDFVTKIYSIALGNTSDVDGINYW, in which the underlined amino acids may serve as key residues in the epitope. ELISA and/or Western blot analyses showed that mAb A2D5 not only interacted with the four synthetic peptide mimotopes, but also with 14 prokaryotically expressed recombinant peptide mimotopes. The mimotopes identified in this study will aid future studies into the pathological processes and immune mechanisms of the SapA protein of C. fetus.     

Identification of antigenic epitopes of the SapA protein of Campylobacter fetus using a phage display peptide library

In this study, we immunized mice with prokaryotically expressed recombinant surface layer protein, SapA, of Campylobacter fetus, generated hybridomas secreting mouse monoclonal antibodies (mAb) targeting SapA, and purified the mAb A2D5 from mouse ascites using saturated ammonium sulfate solution. The mAb A2D5, coated onto ELISA plates, was used to screen the phage random 12-peptide library through three rounds of panning. Following panning, 15 phage clones were randomly chosen and tested for reactivity with mAb A2D5 by indirect ELISA. Single-stranded DNA from positive clones was sequenced and compared with the sequence of SapA to predict the key epitope. ELISA and/or Western blot analyses further validated that synthetic peptides and recombinant peptide mimotopes all interact with mAb A2D5. Nine of ten positive phage clones identified by screening were sequenced successfully. Seven clones shared the same sequence HYDRHNYHWWHT; one had the sequence LSKNLPLTALGN; and the final one had the sequence SGMKEPELRSYS. These three sequences shared high homology with SapA J05577 in the region GNEKDFVTKIYSIALGNTSDVDGINYW, in which the underlined amino acids may serve as key residues in the epitope. ELISA and/or Western blot analyses showed that mAb A2D5 not only interacted with the four synthetic peptide mimotopes, but also with 14 prokaryotically expressed recombinant peptide mimotopes. The mimotopes identified in this study will aid future studies into the pathological processes and immune mechanisms of the SapA protein of C. fetus.