应用噬菌体随机肽库技术筛选丙肝病毒NS3抗原模拟表位

以抗-HCV NS3的单克隆抗体作为固相筛选分子,对人工合成的噬菌体随机12肽库进行5轮"吸附-洗脱-扩增"的筛选过程,随机挑取42个克隆,经噬菌 体酶联免疫吸附法(ELISA)鉴定并进行交叉反应实验以及竞争抑制性结合实验,最后对所选克隆进行DNA序列分析,以确定HCV NS3抗原的模拟表位.经噬菌体富集后,从随机筛选的 42个克隆中得到11个阳性克隆,确定氨基酸序列XXIXXXXMSNXX为HCV NS3的模拟表位.我们用噬菌体12肽库成功筛选得到HCV NS3的模拟表位,为开展用HCV模拟表位探索HCV的防治研究创造了条件.     

脂多糖保守表位模拟肽的筛选与鉴定

用针对脂多糖保守表位的单抗2B4对噬菌体随机12肽库进行亲和筛选,通过噬菌体ELISA实验及脂多糖(LPS)竞争抑制实验鉴定阳性克隆.经三轮筛选后,与抗体结合的噬菌体得到明显富集,噬菌体ELISA结果显示,阳性率达80%.将其中12个阳性噬菌体克隆做鼠伤寒杆菌和大肠杆菌LPS竞争抑制实验,抑制作用非常明显,有良好的剂量依赖关系,证明这12个克隆与LPS具相似表位.DNA测序并推导噬菌体展示肽的氨基酸序列为,GPPQWFFSQPQL（5/12,41.7%）,LPQYFWNTATTA （3/12,25%）,FPQNHWNVPWAT（2/12,16.6%）,HSQSFWNAPLAM和AHPWTHGYFPPL（1/12,8.3%）.实验结果表明,用2B4抗体筛选到的噬菌体短肽克隆可模拟保守表位,即脂多糖的模拟肽（位）.     

脂多糖保守表位模拟肽的筛选与鉴定

用针对脂多糖保守表位的单抗2B4对噬菌体随机12肽库进行亲和筛选,通过噬菌体ELISA实验及脂多糖(LPS)竞争抑制实验鉴定阳性克隆.经三轮筛选后,与抗体结合的噬菌体得到明显富集,噬菌体ELISA结果显示,阳性率达80%.将其中12个阳性噬菌体克隆做鼠伤寒杆菌和大肠杆菌LPS竞争抑制实验,抑制作用非常明显,有良好的剂量依赖关系,证明这12个克隆与LPS具相似表位.DNA测序并推导噬菌体展示肽的氨基酸序列为,GPPQWFFSQPQL（5/12,41.7%）,LPQYFWNTATTA（3/12,25%）,FPQNHWNVPWAT（2/12,16.6%）,HSQSFWNAPLAM和AHPWTHGYFPPL（1/12,8.3%）.实验结果表明,用2B4抗体筛选到的噬菌体短肽克隆可模拟保守表位,即脂多糖的模拟肽（位）.     

利用噬菌体展示肽库筛选鸡传染性支气管炎病毒模拟抗原表位

目的：利用噬菌体展示肽库技术筛选鸡传染性支气管炎病毒（IBV）的模拟抗原表位。方法：用IBV阳性血清纯化IgG作为靶标。对噬菌体展示随机12肽库进行筛选，通过ELISA和竞争抑制ELISA鉴定筛选克隆的结合特性，并对阳性克隆提取ssDNA进行测序分析。结果：3轮生物淘洗后，目标噬菌体得到125倍富集。随机挑选50个克隆进行ELISA和竞争抑制ELISA。其中有12个噬菌体克隆可以与IBV阳性血清高特异性结合。测序分析发现，这12个克隆带有2种氨基酸序列。即KSPKHSSSALHF和SFFQLNLHRPTS。且未发现这2种序列与GenBank中已发表的IBV氨基酸序列有同源性。结论：结果提示。这2个肽可能是IBV抗原的模拟表位。     

噬菌体肽库筛选抗人B7-H4中和抗体的模拟抗原表位及其免疫原性鉴定

目的:用噬菌体呈现随机12肽库筛选能与抗人B7-H4(h B7-H4)中和抗体特异性结合的模拟抗原表位肽,并用其免疫小鼠检测其免疫原性。方法:以抗h B7-H4中和抗体为靶分子,用体外生物淘洗法从噬菌体呈现随机12肽库中筛选与之结合的噬菌体克隆,用竞争性细胞ELISA鉴定阳性噬菌体克隆;化学合成候选多肽,并与钥孔血蓝蛋白或破伤风毒素偶联鉴定多肽的特异性;进一步用融合蛋白免疫小鼠检测其免疫原性和抗血清的补体依赖的细胞杀伤活性(CDC)。结果:经过3轮体外筛选后随机挑取50个阳性噬菌体克隆,其中20个克隆与抗h B7-H4抗体有较强的结合能力,DNA测序得到6组结构相似的肽序列;竞争性ELISA结果显示1号肽噬菌体能与细胞表面的h B7-H4竞争性地结合抗h B7-H4单抗;点杂交结果显示1号肽能特异性结合抗h B7-H4单抗;小鼠免疫实验结果显示1号肽融合蛋白能诱导高滴度的抗h B7-H4抗血清,并且抗血清具有补体依赖的细胞杀伤活性。结论:筛选得到能与抗h B7-H4中和抗体特异性结合的12肽模拟抗原表位序列并且具有免疫原性,为进一步开发h B7-H4相关的多肽疫苗提供了实验依据。     

噬菌体随机肽库筛选抗志贺样毒素Ⅱ结合亚单位Stx2B的单抗的识别表位

目的利用噬菌体随机肽库技术筛选志贺样毒素Ⅱ结合亚单位Stx2B的单抗的识别表位。方法以抗志贺样毒素Ⅱ结合亚单位Stx2B的单克隆抗体筛选噬菌体随机12肽库,挑取阳性克隆测定DNA序列,推导其氨基酸序列并进行同源性分析。通过ELISA鉴定获得的噬菌体短肽与单抗之间的结合特性。结果从噬菌体随机12肽库中筛选出20株可与抗志贺样毒素Ⅱ结合亚单位Stx2B的单抗特异结合的噬菌体克隆,其中多数克隆呈现核心序列WTSRW（Q）,该序列与志贺样毒素Ⅱ结合亚单位Stx2B的一级序列具有一定的同源性。结论WTSRW（Q）序列是志贺样毒素Ⅱ结合亚单位Stx2B单抗的识别表位。     

华支睾吸虫童虫模拟抗原表位的筛选和序列分析

目的 利用噬菌体十二肽库筛选华支睾吸虫童虫模拟抗原表位,以达到早期诊断的目的.方法 用纯化的感染华支睾吸虫童虫的大鼠血清IgG作为靶分子,对噬菌体十二肽库进行3轮筛选,随机挑取19个阳性噬菌体克隆用ELISA法检测其特异性.对吸光度值较高的11个克隆进行DNA测序.结果 19个克隆中有17个能与大鼠华支睾吸虫童虫期感染血清发生免疫反应.11个A值较高的克隆中有9个插入序列,其中5个不同的独立序列.结论 用童虫期感染血清作为靶分子筛选肽库,得到的抗原模拟表位对华支睾吸虫病早期诊断有较高潜在价值.     

抗人白细胞介素15中和抗体识别抗原表位的噬菌体肽库筛选与鉴定

目的:用噬菌体呈现随机七肽库筛选能与抗人白细胞介素15(h IL-15)中和抗体特异性结合的模拟抗原表位肽,并初步鉴定其免疫原性。方法:以抗h IL-15中和抗体为靶分子,用生物淘洗法从噬菌体呈现线性七肽库中筛选与之结合的噬菌体克隆,用噬菌体ELISA和竞争抑制ELISA鉴定阳性噬菌体克隆;化学合成筛选得到的多肽,并与匙孔血蓝蛋白(KLH)偶联免疫BALB/c小鼠,检测其免疫原性。结果:经过3轮体外筛选后随机挑取50个阳性噬菌体克隆,ELISA检测结果显示其中15个克隆与抗h IL-15抗体有较强的结合能力,DNA测序结果得到的结构相似群为MTPFWQK、MSPFNQK、MIPYWQK和MIPFHQK;竞争性ELISA结果显示4个序列均能与IL-15竞争性地结合抗IL-15单抗;小鼠免疫实验结果显示4组多肽均能诱导IL-15特异性免疫反应。结论:筛选得到能与抗h IL-15中和抗体特异性结合,且具有免疫原性的模拟抗原7肽序列,为进一步开发h IL-15相关的多肽疫苗提供了依据。     

用噬菌体随机肽库筛选SARS冠状病毒S蛋白单克隆抗体2C5的模拟表位

SARS-CoVS蛋白特异的单克隆抗体2C5具有病毒中和作用。以单克隆抗体2C5为筛选靶分子,筛选噬菌体展示随机7肽库。经三轮淘洗后随机挑选20个噬菌体克隆进行ELISA分析和序列测定。在10个ELISAOD值大于0.2的阳性噬菌体克隆中,有8个噬菌体克隆展示有共同的7肽序列TPEQQFT。展示有该序列的噬菌体克隆能竞争抑制SARS-CoVS蛋白抗原与单抗2C5的结合。结果表明TPEQQFT为单克隆抗体2C5的模拟表位。该结果可对进一步研究S蛋白结构与功能和设计SARS疫苗有一定的参考意义。     

脑膜炎大肠杆菌IbeA蛋白结合肽序列的亲和筛选

应用噬菌体展示肽库技术,以重组的脑膜炎大肠杆菌致病蛋白IbeA作为靶分子,经过吸附-洗脱-扩增-再吸附的亲和筛选,随机挑选亲和力强的噬菌体克隆,进行ELISA、竞争抑制实验和序列测定。结果显示,经3轮淘选后,间接ELISA鉴定得到高亲和性结合IbeA蛋白的15个阳性克隆。竞争抑制实验结果表明,游离IbeA蛋白能竞争抑制噬菌体结合肽克隆与固相包被的IbeA蛋白的结合,其抑制作用随游离IbeA蛋白浓度的降低而减弱。测序结果得到5种阳性噬菌体克隆展示肽序列。上述结果提示以脑膜炎大肠杆菌IbeA蛋白为靶筛选所获得的噬菌体12肽克隆,具有特异性,其结合肽序列呈现相对保守性。建立的从噬菌体随机肽库筛选IbeA蛋白结合肽的方法具有方便、灵活和高效可行的特点。     

噬菌体展示技术筛选bFGF模拟短肽

目的：通过噬菌体展示技术筛选得到与FGFR结合的bFGF模拟短肽,为bFGF肽类抑制剂的研发提供实验基础。方法：以Balb/c 3T3细胞为靶标,以COS-7细胞作消减,对噬菌体随机七肽库进行4轮生物淘洗,再采用ELISA检测单克隆噬菌体对Balb/c 3T3亲和性和特异性,选取阳性克隆进行DNA测序分析。结果：从富集的噬菌体中获得12个阳性克隆,获得一组疏水性七肽及共同基序PR。结论：利用肽类新药开发的重要工具--噬菌体展示技术,得到2段bFGF的受体结合模拟肽,可望作为bFGF抑制剂的先导肽。     

Interference of HCV replication by cell penetrable human monoclonal scFv specific to NS5B polymerase

A new class of hepatitis C virus (HCV)-targeted therapeutics that is safe, broadly effective and can cope with virus mutations is needed. The HCV's NS5B is highly conserved and different from human protein, and thus it is an attractive target for anti-HCV therapeutics development. In this study, NS5B bound-phage clones selected from a human single chain variable antibody fragment (scFv) phage display library were used to transform appropriate E. coli bacteria. Two scFv inhibiting HCV polymerase activity were selected. The scFvs were linked to a cell penetrating peptide to make cell penetrable scFvs. The transbodies reduced the HCV RNA and infectious virus particles released into the culture medium and inside hepatic cells transfected with a heterologous HCV replicon. They also rescued the innate immune response of the transfected cells. Phage mimotope search and homology modeling/molecular docking revealed the NS5B subdomains and residues bound by the scFvs. The scFv mimotopes matched residues of the NS5B, which are important for nucleolin binding during HCV replication, as well as residues that interconnect the fingers and thumb domains for forming a polymerase active groove. Both scFvs docked on several residues at the thumb armadillo-like fold that could be the polymerase interactive sites of other viral/host proteins for the formation of the replication complex and replication initiation. In conclusion, human transbodies that inhibited HCV RdRp activity and HCV replication and restored the host innate immune response were produced. They are potentially future interferon-free anti-HCV candidates, particularly in combination with other cognates that are specific to NS5B epitopes and other HCV enzymes.     

Interference of HCV replication by cell penetrable human monoclonal scFv specific to NS5B polymerase

A new class of hepatitis C virus (HCV)-targeted therapeutics that is safe, broadly effective and can cope with virus mutations is needed. The HCV''s NS5B is highly conserved and different from human protein, and thus it is an attractive target for anti-HCV therapeutics development. In this study, NS5B bound-phage clones selected from a human single chain variable antibody fragment (scFv) phage display library were used to transform appropriate E. coli bacteria. Two scFv inhibiting HCV polymerase activity were selected. The scFvs were linked to a cell penetrating peptide to make cell penetrable scFvs. The transbodies reduced the HCV RNA and infectious virus particles released into the culture medium and inside hepatic cells transfected with a heterologous HCV replicon. They also rescued the innate immune response of the transfected cells. Phage mimotope search and homology modeling/molecular docking revealed the NS5B subdomains and residues bound by the scFvs. The scFv mimotopes matched residues of the NS5B, which are important for nucleolin binding during HCV replication, as well as residues that interconnect the fingers and thumb domains for forming a polymerase active groove. Both scFvs docked on several residues at the thumb armadillo-like fold that could be the polymerase interactive sites of other viral/host proteins for the formation of the replication complex and replication initiation. In conclusion, human transbodies that inhibited HCV RdRp activity and HCV replication and restored the host innate immune response were produced. They are potentially future interferon-free anti-HCV candidates, particularly in combination with other cognates that are specific to NS5B epitopes and other HCV enzymes.     

从噬菌体随机肽库中筛选流感病毒神经氨酸酶的抑制多肽

目的:从噬菌体呈现12肽库中筛选与流感病毒神经氨酸酶特异性结合的肽。方法:以甲三型流感病毒裂解疫苗原液为靶分子,经过3轮生物淘选,从噬菌体随机肽库中筛选与之结合的噬菌体。用ELISA方法鉴定噬菌体克隆与靶分子的结合力,用荧光方法测定噬菌体克隆对流感病毒A/Sydney/5/97(H3N2)神经氨酸酶的抑制活性。对筛选到的阳性克隆进行DNA序列测定并推导出相应的氨基酸序列。结果:经过3轮筛选后,42个噬菌体克隆与靶分子有高度亲和力,23个噬菌体克隆对流感病毒A/Sydney/5/97(H3N2)神经氨酸酶有抑制活性。对27个噬菌体克隆的测序结果表明,分别有10个和2个克隆的序列是一致的,其氨基酸序列分别为KSLSRHDHIHHH和WPRHHHSASVQT。结论:通过噬菌体肽库筛选到抑制流感病毒神经氨酸酶的12肽,为进一步研究对流感病毒神经氨酸酶有抑制活性的分子药物奠定了基础。     

脓毒症单核巨噬细胞特异性结合肽的筛选

利用噬菌体随机肽库展示技术,筛选出与脓毒症单核/巨噬细胞特异性结合的短肽,探索脓毒症治疗的新方法.分别以经过脂多糖(lipopolysaccharide, LPS)处理的人外周血单核细胞株(THP-1)细胞作为筛选的靶细胞,以未经LPS处理的THP-1细胞作为非特异性噬菌体吸附细胞,对噬菌体随机环七肽库进行4轮“差减"筛选,经过细胞ELISA验证阳性噬菌体克隆,对获得的阳性克隆进行DNA测序及生物信息学分析,并进一步利用免疫荧光实验,鉴定噬菌体克隆与LPS处理THP-1细胞的结合特异性.4轮筛选后,随机挑取的噬菌体克隆,测序后得到可与LPS处理的THP-1细胞特异性结合肽.对去冗余后的七肽进行Clustal W多序列比对分析和BlastP蛋白同源相似性分析,细胞免疫荧光检测确定获得的噬菌体展示七肽可与LPS处理的THP-1细胞特异性结合.噬菌体随机肽库技术为脓毒症单核/巨噬细胞表面靶位的筛选提供了高效、快捷的筛选体系,实验获得的多肽基序具有高度保守性和细胞特异性,这些多肽的生物活性将是下一步的研究内容.     

Identification of epitopes of trichosanthin by phage peptide library

The phage displayed random peptide library has recently emerged as a powerful technique for analyzing Ab-Ag interactions. In this study, the method was employed to identify epitopes of trichosanthin. Two monoclonal Abs (4B5, 2E9) which recognized different epitopes of trichosanthin (TCS) were selected and a phage-peptide library with nine amino acids (9 aa) was used to screen the positive phage clones that have high affinity to the mAbs. Two groups of phage clones that carried peptide-specific binding to mAbs were identified by the screen. The identified phage clones carried peptide-specific binding to 4B5 and 2E9 mAbs were immunized in mice. To evaluate mimotope of selected phages, the specific binding activity to TCS was measured in the serum from phage-immunized mice. They all showed positive results. The conserved interaction motifs were deduced from the peptide sequences of each group of selected phage clones. When compared the motif sequence with the sequence of TCS, it was predicted that 4B5-corresponding epitope was located at 27-37 aa of TCS protein and 2E9-corresponding epitope was located at 41-48 aa of TCS. The predicted sequence of 4B5-corresponding epitope was further confirmed by site-directed mutation of TCS protein. The data showed that the expressed TCS protein mutated in 4B5-corresponding epitope was unable to bind 4B5 mAb. The results suggested that the phage display peptide library is useful to identify Ag epitopes and to raise Ab in disease diagnosis and treatment.     

Screening and Identification of a Specific Binding Peptide to Ovarian Cancer Cells from a Phage-Displayed Peptide Library

To select specific binding peptides for imaging and detection of human ovarian cancer. The phage 12-mer peptide library was used to select specific phage clones to ovarian cancer cells. After four rounds of biopanning, the binding specificity of randomly selected phage clones to ovarian cancer cells was determined by enzyme-linked immunosorbent assay (ELISA). DNA sequencing and homology analysis were performed on specifically bound phages. The binding ability of the selected peptides to SKOV3 cells was confirmed by fluorescence microscopy and flow cytometry. After four rounds of optimized biological panning, phage recovery was 34-fold higher than that of the first round, and the specific phage clones bound to SKOV3 cells were significantly enriched. A total of 32 positive phage clones were preliminarily identified by ELISA from 54 randomly selected clones, and the positive rate was 59.3%. S36 was identified as the clone with best affinity to SKOV3 cells via fluorescence microscopy and flow cytometry. A representative clone of OSP2, S36 is expected to be an effective probe for diagnosis and treatment of ovarian cancer.

     

Investigation and molecular mimicry of the antigen involved in the interaction between the monoclonal antibody 5D10 and the human breast cancer cell line MCF-7

Monoclonal antibody (mAb) 5D10 is directed against the human breast cancer cell line MCF-7. Biochemical characterization of the antibody epitope was attempted and revealed a complex, most likely carbohydrate-linked nature, which prevented isolation and further studies of the interaction. A major goal of this work was to generate structural mimics of the 5D10 epitope to serve as putative substitutes in such studies. A peptide library displayed on filamentous phage was used to select for mimotope peptide sequences. All positive phage clones selected from the library displayed the amino acid sequence H(2)N-QMNPMYYR-CO(2)H. This peptide sequence, as well as a branched form of the peptide, was found to bind mAb 5D10. Moreover, both peptide sequences were able to inhibit the binding of 5D10 to the MCF-7 cells in a concentration-dependent manner, with an EC(50) value in the range of 65 microM. According to these results, random phage peptide libraries can serve to identify mimotopic peptides for unknown complex cell surface epitopes.     

丙型肝炎病毒丝氨酸蛋白酶特异性结合肽的筛选和鉴定

丙型肝炎病毒丝氨酸蛋白酶在病毒复制和包装中的重要作用使其成为特异性抗病毒药物研究的首选靶标。根据丝氨酸蛋白酶晶体结构特点,用柔性连接子连接NS3丝氨酸蛋白酶结构域和NS4A的核心序列,构建成单链丝氨酸蛋白酶基因并且在大肠杆菌中获得高水平的可溶性表达,纯化后的目的蛋白能够切割重组蛋白底物NS5ab。随后,以单链丝氨酸蛋白酶为靶分子对噬菌体展示的随机十二肽库进行了三轮淘筛,挑选的44个克隆中有37个克隆能够特异性地结合丝氨酸蛋白酶,并且这种结合作用为竞争性ELISA试验结果所支持。对13个克隆进行序列测定,得到6种序列,它们在氨基酸组成上存在明显偏性,富含组氨酸和色氨酸,缺乏酸性氨基酸;6种序列存在一个共有序列。