Electron Microscopy of the Major Outer Membrane Protein of Campylobacter jejuni

The surfaces of the disrupted-cell surfaces of the Campylobacter jejuni strains FUM158432 and M1 were examined using the negative-staining technique and electron microscopy. The surfaces of the whole cells and the outer membranes were covered with small dark dots which, in some areas, were arranged in hexagonal patterns. The hexagonal arrangement was more clearly seen in extracted outer membrane. The size of each structure was measured based on a center-to-center distance with the adjacent structure, and was determined to be 9.9±0.9 nm. A profile of the proteins in the outer membrane by SDS-PAGE, performed in 0.1% SDS and at 100 C, showed 42 kDa proteins to comprise the major outer membrane protein of this bacterium. Digestion of the outer membrane materials with proteinase reduced this protein band in the SDS-PAGE, and the amount of dark dots on the electron micrograph indicated the structure to be the major outer membrane protein (porin) of this bacterium. The power spectrogram of a computer-assisted Fourier transformation of the hexagonally arranged porin proteins suggests that the porin has a trimeric structure rather than a monomeric one.     

Cloning of an Outer Membrane Protein Gene from Campylobacter jejuni

An antigen in the outer membrane protein (OMP) fraction of Campylobacter jejuni was identified and characterized. Western blot analysis demonstrated antigenic differences in this protein between two congenic C. jejuni strains. Strain A74/C, which colonizes chickens, expressed the antigen at 34 kDa, while strain A74/O, which poorly colonizes chickens, expressed the antigen at 32 and 34 kDa. A genomic library was constructed in λgt11 with DNA from A74/O and screened with antibody raised against C. jejuni OMPs. A clone that possessed a 1.3-kb insert and expressed an immunoreactive protein fused to β-galactosidase was isolated and purified. DNA sequence analysis revealed the insert contained one open reading frame 864 bases long. The deduced amino acid sequence demonstrated 56.3% similarity with Bacillus steorothermophilus glnH, a glutamine-binding protein, and 54.0% similarity with C. jejuni PEB1, a putative colonization adhesin. Southern hybridization, Northern hybridization, and DNA sequence analyses of the congenic colonizing and noncolonizing strains of C. jejuni failed to distinguish the two strains and revealed only one copy of the gene. Post-translational modification may be an alternate explanation for the antigenic differences seen between the two strains. Received: 15 October 1996 / Accepted: 3 December 1996     

Production and Characterization of Monoclonal Antibodies Specific for a Conserved Epitope within Hepatitis C Virus Hypervariable Region 1

Frequent mutations in hypervariable region 1 (HVR1) of the main envelope protein of hepatitis C virus (HCV) is a major mechanism of persistence by escaping the host immune recognition. HVR1 contains an epitope eliciting neutralizing antibodies. This study was aimed to prepare broadly cross-reacting, high-affinity, monoclonal antibodies (MAb) to the HVR1 C terminus of HCV with potential therapeutic neutralizing capacity. A conserved amino residue group of glycine (G) at position 23 and glutamic acid (Q) at position 26 in HVR1 was confirmed as a key epitope against which two MAbs were selected and characterized. MAbs 2P24 and 15H4 were immunoglobulin G1 kappa chain [IgG1(kappa)], cross-reacted with 32 and 30 of 39 random C-terminal HVR1 peptides, respectively, and did not react with other HCV peptides. The V(H) of 2P24 and 15H4 heavy chains originated from Igh germ line v gene family 1 and 8, respectively. In contrast, the V(L) kappa sequences were highly homologous. The affinity (K(d)) of 2P24 and 15H4 (10(-9) or 10(-8) M with two immunizing peptides and 10(-8) M with two nonimmunizing HVR1 peptides) paralleled the reactivity obtained with peptide enzyme immunoassay. MAbs 2P24 and 15H4 captured 25 of 31 (81%) HCV in unselected patients' plasmas. These antibodies also blocked HCV binding to Molt-4 cells in a dose-dependent fashion. The data presented suggest that broadly cross-reactive MAbs to a conserved epitope within HCV HVR1 can be produced. Clinical application for passive immunization in HCV-related chronic liver disease and after liver transplantation is considered.     

Temperate Bacteriophage Which Causes the Production of a New Major Outer Membrane Protein by Escherichia coli

Under most conditions of growth, the most abundant protein in the outer membrane of most strains of Escherichia coli is a protein designated as “protein 1” or “matrix protein”. In E. coli B, this protein has been shown to be a single polypeptide with a molecular mass of 36,500 and it may account for more than 50% of the total outer membrane protein. E. coli K-12 contains a very similar, although probably not identical, species of protein 1. Some pathogenic E. coli strains contain very little protein 1 and, in its place, make a protein designated as protein 2 which migrates faster on alkaline polyacrylamide gels containing sodium dodecyl sulfate and which gives a different spectrum of CNBr peptides. An E. coli K-12 strain which had been mated with a pathogenic strain was found to produce protein 2, and a temperate bacteriophage was isolated from this K-12 strain after induction with UV light. This phage, designated as PA-2, is similar in morphology and several other properties to phage lambda. When strains of E. coli K-12 are lysogenized by phage PA-2, they produce protein 2 and very little protein 1. Adsorption to lysogenic strains grown under conditions where they produce little protein 1 and primarily protein 2 is greatly reduced as compared to non-lysogenic strains which produce only protein 1. However, when cultures are grown under conditions of catabolite repression, protein 2 is reduced and protein 1 is increased, and lysogenic and non-lysogenic cultures grown under these conditions exhibit the same rate of adsorption. Phage PA-2 does not adsorb to E. coli B, which appears to have a slightly different protein 1 from K-12. These results suggest that protein 1 is the receptor for PA-2, and that protein 2 is made to reduce the superinfection of lysogens.     

Production and Characterization of a Single-Chain Fv Antibody–Alkaline Phosphatase Fusion Protein Specific for Clenbuterol

The production and characterization of an anti-clenbuterol single-chain Fv antibody (CBLscFv)–bacterial alkaline phosphatase (AP) fusion protein are described. The CBLscFv and the phoA gene of Escherichia coli strain K12 chromosomal DNA were cloned by PCR and sequentially inserted into the expression vector pBV220 to express the CBLscFv–AP fusion protein in E. coli strain BL21(DE3)pLysS. SDS–PAGE and western blot analyses revealed that the fusion protein showed a molecular weight of 73 kDa and bound with the antibacterial AP monoclonal antibody. Determination of enzymatic activity indicated that k _cat and K _m values of the fusion protein were 113.60 s⁻¹ and 29.82 μM, respectively. Competitive direct enzyme-linked immunosorbent assay based on the obtained fusion protein indicated that the average concentration required for 50% inhibition of binding (IC₅₀) and the limit of detection for CBL were 4.74 ± 0.003 (n = 3) and 0.54 ± 0.004 (n = 3) μg/l, respectively, and the linear response range extended from 1.13 to 69.68 μg/l. Cross-reactivity studies showed that the fusion protein did not cross-react with CBL analogs. The present findings indicate that the production of the CBLscFv–AP fusion protein in E. coli strain BL21(DE3)pLysS is feasible and suggest that it could be further used to develop a one-step ELISA for the specific detection of CBL.     

Exploring Highly Antigenic Protein of Campylobacter jejuni for Designing Epitope Based Vaccine: Immunoinformatics Approach

International Journal of Peptide Research and Therapeutics - Campylobacter jejuni is a spiral-shaped Gram-negative and microaerophilic bacteria that causes bacterial diarrhea worldwide. Due to its...     

OAS1蛋白单克隆抗体的制备及其表征

目的:用OAS1蛋白免疫小鼠,获得OAS1特异性单克隆抗体,为OAS1的含量测定提供基础。方法:通过全基因合成的方法获得目的基因序列,转化大肠杆菌BL21细胞诱导His-OAS1及OAS1蛋白表达,纯化后用作抗原免疫小鼠,取脾融合,筛选稳定分泌抗体的阳性细胞株,制备并纯化单抗,通过SDS-PAGE,ELISA,Western blot等方法进行检测。结果:体外高效表达OAS1蛋白,并成功制备特异性单克隆抗体,效价在5×10^-11mol/L以上,亲和常数为3.37×10⁸ L·mol^-1。结论:获得高亲和力OAS1单克隆抗体,为其含量的检测奠定了基础。     

猪链球菌2型次黄嘌呤核苷酸脱氢酶单克隆抗体的制备及其识别表位分析

用纯化的硫氧还蛋白-IMPDH融合蛋白免疫BALB/c小鼠,取其脾细胞与SP2/0骨髓瘤细胞融合,对杂交瘤细胞及时筛选,阳性孔经4次有限稀释法克隆,成功获得1A8、1F2、2D2和2D12共4株能稳定传代并分泌抗IMPDH的单克隆抗体(McAb)的杂交瘤细胞株.4株腹水型单克隆抗体间接ELISA效价分别为100x211、100x211、100x210和100x28,经Western-blot分析表明,4株单抗与硫氧还蛋白-IMPDH融合蛋白均具有特异性反应,并且通过4种IMPDH全基因分片段缺失表达的融合蛋白,分析了4株单抗所识别抗原决定簇的差异性,发现1A8、1F2,2D2识别表位的编码基因集中在IMPDH基因片段的627 bp～790 bp之间,2D12识别表位的编码基因则集中在IMPDH基因片段的411 bp～790 bp之间.猪链球菌2型中IMPDH单克隆抗体的获得及相应表位分析为研究IMPDH蛋白的生物学活性及免疫学活性奠定了基础.     

Characterization of a Monoclonal Antibody Specific for Lipoteichoic Acid from Various Gram-Positive Bacteria

A hybrid cell line, 3G6, producing monoclonal antibody (mAb) against the polyglycerophosphate (PGP) backbone of lipoteichoic acids has been derived by the polyethylene glycol-induced fusion of mouse myeloma cells and spleen cells from mice immunized with partially purified glucosyltransferase from culture supernatant of Streptococcus mutans strain 6715. Immunodiffusion tests and ELISA revealed that the antibody reacted with purified PGP from group A Streptococcus pyogenes strain Sv as well as crude phenol-water and saline extracts of various gram-positive bacteria except for a few species such as biotype B S. sanguis, Micrococcus sp., and Actinomyces viscosus. Whole cells of serotype b S. mutans and Staphylococcus epidermidis were agglutinated upon addition of 3G6 mAb, while those of most other species were not significantly affected by this procedure. A hapten inhibition study showed that glycerophosphate was only a potent inhibitor of passive hemagglutination reactions between LTA coated sheep erythrocytes and 3G6 mAb.     

Epitope Characterization of an Aromatase Monoclonal Antibody Suitable for the Assessment of Intratumoral Aromatase Activity

Immunohistochemistry is one of the most suitable methods for the detection of intratumoral aromatase in order to identify patients who may respond to aromatase inhibitor therapy in hormone-dependent breast cancer. Previous studies showed statistically significant correlation between results of immnuohistochemistry and biochemical analysis in carcinoma components stained by aromatase monoclonal antibody 677. In this study, determination of the antigenic peptides recognized by aromatase antibodies through epitope mapping, combined with the new knowledge on aromatase-reductase interaction, provide insights for understanding various immunostaining patterns using different aromatase antibodies. Our studies on aromatase-reductase interaction also provided critical information on how aromatase and reductase interact with each other on the endoplasmic reticulum membrane, and identified key residues, including K108 of aromatase, that are involved in the interaction with reductase. Through epitope mapping and taking into consideration the interference with aromatase immunohistochemical staining by NADPH-cytochrome P450 reductase, we demonstrated that monoclonal antibody 677 is a suitable antibody for an assessment of intratumoral aromatase activity in breast cancer patients for making clinical management decisions. These results also provide valuable information to identify new aromatase antibodies for immunohistochemical diagnosis of hormone-dependent breast cancer in future.     

Production and Epitope Specificky of Monoclonal Antibody against Mouse Peptidylarginine Deiminase Type II

Peptidylarginine deiminase catalyzes the conversion of arginyl residues in proteins to citrullyl residues in the presence of Ca²⁺. We described the preparation of monoclonal antibody (subclass type IgG₁) specific to mouse peptidylarginine deiminase type II. The antibody had no effect on the enzyme activity and its specific epitope was localized in the eight-residue segment at the amino-terminal portion of the enzyme.     

Identification of a Novel Haemophilus parasuis-Specific B Cell Epitope Using Monoclonal Antibody against the OppA Protein

Monoclonal antibody (MAb) 1B3 against Haemophilus parasuis (H. parasuis) was generated by fusing SP2/0 murine myeloma cells and spleen cells from BALB/c mice immunized with the whole-bacterial-cell suspension of H. parasuis HS80 (serotype 5). The MAb 1B3 showed strong reactivity with 15 serotype reference strains of H. parasuis using Dot blot and Western blot analysis. Immunoprecipitation and protein spectral analysis indicated that MAb 1B3 recognized by Oligopeptide permease A (OppA) belongs to the ATP binding cassette transporter family. In addition, a linear B-cell epitope recognized by MAb 1B3 was identified by the screening of a phage-displayed 12-mer random peptide library. Sequence analysis showed that MAb 1B3 was recognized by phages-displaying peptides with the consensus motif KTPSEXR (X means variable amino acids). Its amino acid sequence matched ⁴⁶⁹KTPAEAR⁴⁷⁵ of H. parasuis OppA protein. A series of progressively truncated peptides were synthesized to define the minimal region that was required for MAb 1B3 binding. The epitope was highly conserved in OppA protein sequences from the isolated H. parasuis strains, which was confirmed by alignment analysis. Furthermore, the minimal linear epitope was highly specific among 75 different bacterial strains as shown in sequence alignments. These results indicated MAb 1B3 might be potentially used to develop serological diagnostic tools for H. parasuis.     

群特异性蓝舌病病毒单克隆抗体的制备和鉴定

目的：制备群特异性抗蓝舌病病毒（BTV）单克隆抗体,并对其特性进行鉴定,为建立检测BTV抗原及抗体的ELISA方法奠定基础。方法：用纯化的BTV颗粒为免疫抗原免疫BALB/c鼠,以大肠杆菌表达的VP7蛋白作为筛选抗原,用间接ELISA法筛选杂交瘤细胞株;选取抗体效价最高的一株制备BTV单克隆抗体,以该抗体为捕获抗体与8种不同血清型BTV进行ELISA反应,结果与细胞病变反应进行比对;以该抗体为竞争抗体,与12种不同血清型绵羊BTV抗血清进行竞争ELISA反应,并将结果与参比c-ELISA试剂盒结果进行比对。结果：筛选出5株稳定分泌BTV单克隆抗体的杂交瘤细胞株,并选其中一株（3E2）制备了高纯度的单克隆抗体;该单抗用于检测不同血清型BTV,与细胞病变反应结果完全相符;用于检测不同血清型绵羊BTV抗血清,其结果与参比c-ELISA试剂盒符合率为100%,与鹿流行性出血热病毒抗原和抗体均无交叉反应。结论：制备的BTV单克隆抗体具有良好的群特异性,可用于检测不同血清型BTV抗原及BTV抗体。     

Production and Characterization of Two Monoclonal Antibodies Specific for Plasmopara halstedii

Sunflower downy mildew, caused by the fungus Plasmopara halstedii, is a potentially devastating disease. We produced two monoclonal antibodies (MAbs) (12C9 and 18E2) by immunizing mice with a partially purified extract of P. halstedii race 1. Both MAbs detected in enzyme-linked immunosorbent assay (ELISA) all races of P. halstedii present in France. No cross-reactions were observed with Plasmopara viticola or with other fungi commonly associated with sunflowers. Both MAbs recognized the same three fungal antigens with molecular masses of 68, 140, and 192 kDa. However, the epitopes on the fungal antigens were distinct and repetitive. Seed homogenates from infected plants were incubated in wells coated with MAb 18E2. This resulted in the trapping of P. halstedii antigens that were identified with biotinylated MAb 12C9. No reactions were seen with seed homogenates from healthy plants. Thus, our results suggest that these MAbs might be used to develop a sandwich ELISA detection system for P. halstedii in infected seeds.     

层粘连蛋白受体单克隆抗体抗原性质的鉴定

层粘连蛋白受体（ＬＮ－Ｒ）在癌细胞转移中具有重要作用。ＬＮ－Ｒ的单克隆抗体对于癌转移的基础研究及诊治应用都具有重要意义。本文旨在确定来自人肺巨细胞癌（ＰＧ）细胞ＬＮ－Ｒ的一种单克隆抗体（ＭｃＢ１）的抗原性质。经纯化的ＭｃＢ１能与完整细胞表面、细胞质膜提取物及纯化的ＬＮ－Ｒ制品特异性结合。实验证明经亲和层析纯化的ＬＮ－Ｒ制品中含有膜糖脂,用ＳＤＳ－ＰＡＧＥ及转移电泳将其所复合的膜脂去除后,仍具有与ＭｃＢ１结合的活性,表明此ＭｃＢ１所针对的抗原与其复合的膜糖脂无关。将含ＬＮ－Ｒ的细胞膜提取物经ＰｒｏｎａｓｅＥ消化后,用ＳｅｐｈａｄｅｘＧ５０分离出的糖肽具有与ＭｃＢ１结合的活性,而不含糖的肽则无此活性。含ＬＮ－Ｒ的细胞膜提取物经高碘酸氧化不同时间,其与ＭｃＢ１结合的活性随氧化时间的延长而逐渐减弱乃至完全丧失;而经还原性烷基化反应的ＬＮ－Ｒ仍保持了与ＭｃＢ１结合的活性。用衣霉素（ＴＭ）处理细胞,细胞则丧失了与ＭｃＢ１结合的能力。以上几方面的结果一致证明此ＭｃＢ１的抗原表位确为ＬＮ－Ｒ的糖链部分。     

Cloning and Characterization of a Campylobacter jejuni Iron-Uptake Operon

We report that C. jejuni modifies its outer membrane protein (OMP) repertoire when cultivated under iron-limiting conditions such as during incubation with epithelial cells. To identify genes encoding de novo expressed OMPs, a C. jejuni cosmid library was screened with antisera raised against proteins expressed in the presence of epithelial cells. A single clone was identified encoding an 80-kDa antigen. Sequence analysis of subclones identified an operon of three open reading frames (ORFs) encoding proteins that are homologous to the E. coli ferrichrome uptake system encoded by the fhu locus. Under low-iron conditions, C. jejuni expressed the 80-kDa OMP, indicating that its expression is regulated by the presence of iron. Southern blot analysis indicated that six of eleven isolates of C. jejuni harbor a fhuA homolog which, like all other DNA in this region sequenced thus far, is strikingly GC-rich (65%) compared with the C. jejuni genome (35% G+C). Received: 19 June 2000 / Accepted: 30 August 2000     

Epitope Mapping of a Bactericidal Monoclonal Antibody against the Factor H Binding Protein of Neisseria meningitidis

The factor H binding protein (fHbp) is a 27-kDa membrane-anchored lipoprotein of Neisseria meningitidis that allows the survival of the bacterium in human plasma; it is also a major component of a universal vaccine against meningococcus B.In this study, we used nuclear magnetic resonance spectroscopy, mutagenesis, and in silico modeling to map the epitope recognized by MAb502, a bactericidal monoclonal antibody elicited by fHbp. The data show that the antibody recognizes a conformational epitope within a well-defined area of the immunodominant C-terminal domain of the protein that is formed by two loops connecting different β-strands of a β-barrel and a short α-helix brought in spatial proximity by the protein folding. The identification of the protective epitopes of fHbp is an important factor for understanding the mechanism(s) of an effective immune response and provides valuable guidelines for designing variants of the protein able to induce broadly protective immunity.     

Isolation and Characterization of an Outer Membrane Protein of Chlorobium tepidum

A protein was isolated from membranes of the green sulfur bacterium Chlorobium tepidum. This protein was characterized by gel electrophoresis, gel filtration, analytical ultracentrifugation and amino acid sequencing. The molecular weight of the purified protein was shown to be 26 kDa by SDS-PAGE. HPLC gelfiltration, SDS-PAGE and analytical ultracentrifugation are consistent with the presence of a homogenous protein in the preparations. Amino acid analysis was obtained from the isolated protein after fragmentation with Lys-C, trypsin and cyanogen bromide. The cleavage pattern resulting from these treatments combined with Edman sequencing yield a sequence allowing the identification of an integral membrane agglutinin in Chl. tepidum.