Cloning approach and functional analysis of anti-intimin single-chain variable fragment (scFv)
- Márcio A Menezes†1,
- Karina A Aires†1,
- Christiane Y Ozaki1,
- Renato M Ruiz1,
- Milton CA Pereira1,
- Patrícia AE Abreu1,
- Waldir P Elias1,
- Oscar HP Ramos2 and
- Roxane MF Piazza1Email author
© Menezes et al; licensee BioMed Central Ltd. 2011
Received: 27 August 2010
Accepted: 2 February 2011
Published: 2 February 2011
Intimin is an important virulence factor involved in the pathogenesis of enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic Escherichia coli (EHEC). Both pathogens are still important causes of diarrhea in children and adults in many developing and industrialized countries. Considering the fact that antibodies are important tools in the detection of various pathogens, an anti-intimin IgG2b monoclonal antibody was previously raised in immunized mice with the conserved sequence of the intimin molecule (int388-667). In immunoblotting assays, this monoclonal antibody showed excellent specificity. Despite good performance, the monoclonal antibody failed to detect some EPEC and EHEC isolates harboring variant amino acids within the 338-667 regions of intimin molecules. Consequently, motivated by its use for diagnosis purposes, in this study we aimed to the cloning and expression of the single-chain variable fragment from this monoclonal antibody (scFv).
Anti-intimin hybridoma mRNA was extracted and reversely transcripted to cDNA, and the light and heavy chains of the variable fragment of the antibody were amplified using commercial primers. The amplified chains were cloned into pGEM-T Easy vector. Specific primers were designed and used in an amplification and chain linkage strategy, obtaining the scFv, which in turn was cloned into pAE vector. E. coli BL21(DE3)pLys strain was transformed with pAE scFv-intimin plasmid and subjected to induction of protein expression. Anti-intimin scFv, expressed as inclusion bodies (insoluble fraction), was denatured, purified and submitted to refolding. The protein yield was 1 mg protein per 100 mL of bacterial culture. To test the functionality of the scFv, ELISA and immunofluorescence assays were performed, showing that 275 ng of scFv reacted with 2 mg of purified intimin, resulting in an absorbance of 0.75 at 492 nm. The immunofluorescence assay showed a strong reactivity with EPEC E2348/69.
This study demonstrated that the recombinant anti-intimin antibody obtained is able to recognize the conserved region of intimin (Int388-667) in purified form and the EPEC isolate.
Intimin, a 94-kDa outer membrane protein, mediates the adhesion of enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic Escherichia coli (EHEC) to enterocytes. Both enteropathogens are important causative agents of diarrhea. Besides, EHEC can cause acute gastroenteritis and hemorrhagic colitis , and produce severe/fatal renal and neurological complications as a result of the translocation of Shiga toxins (Stx1 and Stx2) across the intestinal wall.
Intimin is encoded by the E. coli attaching and effacing (eae) gene, which is required for intimate adhesion to epithelial cells and cytoskeletal reorganization . The variable 280-amino acid C-terminal sequence of intimin (Int280) defines many different intimin subtypes [3–5], and up to now, several types and subtypes of intimin have been described and designated by Greek letters [4, 6–17]. In contrast, the N-terminal region of the intimin molecule is conserved and, therefore, has been used as a target for diagnostic purposes [4, 18–20].
Monoclonal antibodies have been used as tools for the detection of different pathogen antigens due to their homogeneity and their unlimited production . Anti-intimin IgG2b monoclonal antibody was raised in immunized mice with purified conserved intimin (int388-667). In immunoblotting assays, it showed excellent specificity and reacted with several serotypes of EPEC isolates. Despite good performance, the monoclonal antibody failed to detect some EPEC and EHEC isolates expressing different intimin subtypes, especially the gamma subtype . In addition, monoclonal production from hybridoma is expensive and requires cell culture facilities.
Recombinant antibody (rAb) technologies involving the handling of key antibody domains constitute an option and have been increasingly used as alternatives to monoclonal antibodies (mAbs) in medical diagnostic and therapeutic applications . A variety of rAb formats have been modified for specific applications, including engineered modifications to antigen binding, valency, and molecular weight (MW). One of the most popular types of rAbs is single-chain variable fragment (scFv), as it has been successfully modified into a number of different Ab formats and is easily expressed by several expression systems.
Several different molecular display formats have also been described, including phage-display , ribosome display [24, 25] and cell-surface display , by which antigen-reactive Abs can be selected and affinity matured. Usually, E. coli is the bacterial production system of choice for small nonglycosylated rAb fragments, including scFv .
Regarding diarrheagenic E. coli, recombinant antibodies were developed against different virulence factors, which were developed for different purposes. Kühne et al.  produced recombinant antibodies that recognize EspA and intimin of EHEC O157:H7. These antibodies were converted to scFv format and cloned into pET22b vector. By immunoblotting, the anti-intimin scFv produced revealed the exclusive recognition of intimin gamma. The anti-EspA scFv produced relatively weak signals in immunoblotting against EspA in whole-cell preparations from serotypes O157 and O111, and no signals were produced with O127 or O86 .
For the treatment of bovine colibacillosis caused by enterotoxigenic E. coli (ETEC), Bhaskaran et al.  developed a recombinant anti-F5 scFv fragment that inhibits the hemmaglutination of horse red blood cells by F5 protein, which would be expected to inhibit the binding of F5-expressing ETEC to intestinal cells. According to these authors, it would provide an effective, less expensive and animal-friendly alternative as a prophylactic agent against colibacillosis. Also for ETEC, but concerning anti-LT monoclonal antibodies, Chung et al.  selected scFvs that specifically reacted with intermediate forms of the B subunit of LT toxin, with the potential to be used to study pentamer assembly in vivo. Thus, the generation of scFvs with differential binding specificities opens up key areas for the development of new therapeutics that can block toxin formation in situ and thus be used for the treatment of diarrheal diseases caused by E. coli and Vibrio cholerae.
Prompted by the potential applications of rAb, we studied the cloning and expression and structural and functional analysis of the recombinant form (scFv) of monoclonal anti-intimin IgG2b antibody, previously obtained from animal immunization employing conserved intimin.
Microorganisms and plasmids
E. coli JM 109  was used for cloning techniques and as negative control for intimin expression. E. coli BL21(DE3)pLys or E. coli C43(DE3) were used to express the recombinant protein. EPEC E2348/69 was used as intimin expression control. pGEM-T Easy vector for cloning was acquired from Promega (Madison, WI, USA). The pAE expression vector was used for expression of recombinant proteins fused with six histidine residues for nickel affinity chromatography .
Cloning of single-chain variable fragment (scFv) of monoclonal anti-intimin antibody
Protocols for DNA manipulation were used as described in . Briefly, mRNA was extracted (Ilustra Quickprep mRNA Purification Kit - GE Healthcare, UK) and reversely transcripted to cDNA (First Strand cDNA Synthesis Kit - GE Healthcare, UK) from anti-intimin hybridoma cells  cultivated in RPMI medium (Invitrogen, Brazil) plus 10% fetal bovine serum in culture flasks (TPP, Switzerland) at 37°C in 5% CO2. Commercially available primers [Light primer mix, Heavy primer1, Heavy primer 2 (GE Healthcare, UK)] were employed to amplify the variable domain of heavy (VH) and light (VL) chains of the antibody following the manufacturer's instructions. The cDNA inserts corresponding to VL and VH were cloned into the pGEM-T Easy vector and sequenced using M13 forward primer (5'-GTAAAACGACGCCCAG-3') and reverse primer (5'-CAGGAAACAGCTATGAC-3'). One set of primers was designed to amplify the heavy chain variable domain, where the forward primer was complementary to the 5' terminal region of the chain and the reverse primer was complementary to the 5' terminal region of the linker (DNA fragment that encodes the [Gly4Ser]3 flexible linker that joins the heavy and light chain variable domains). Also, another set of primers was designed to amplify the light chain variable domain, where the forward primer was complementary to the 3' terminal sequence of the linker and the reverse complementary to the 3' terminal sequence of chain.
Primers designed for scFv cloning and annealing temperatures.
5' GGATCC GTGCAGCTGCAGGAGTCTGG 3'
VH Reverse Linker
5' ACCGCCTCCACCGGAGACGGTGACCGTG 3'
VL Forward Linker
5' GGTGGCGGATCGGACATTGTGCTGACC 3'
5' AAGCTT TTA GTTTGATTTCCAGCTTGGTGCC 3'
Recombinant antibody (anti-intimin scFv) expression, solubility and immunodetection
pAE-scFv was introduced into E. coli BL21(DE3)pLys. The clone was cultivated (37°C, 300 rpm) in 400 ml of 2YT broth containing 100 μg/ml ampicillin and 20 μg/ml chloramphenicol until OD600 = 0.5. At this point, IPTG was added to a final concentration of 1 mM, and the culture was continued for an additional 5 h under the same conditions. The culture was centrifuged (4,500 × g, 15 min, 4°C), the pellet was resuspended in 30 ml of PBS, pH 7.4, and the bacterial cells were disrupted in a French press under 2,000 psi (Thermo Scientific, USA). The bacterial extract was centrifuged (12,000 × g, 30 min, 4°C), and the pellet was resuspended in 30 ml solubilizing buffer (50 mM Tris-HCl, pH 8.0; 200 mM NaCl; 5 mM imidazole; and 8 M urea) for 18 h at 4°C with constant mixing (100 rpm). The bacterial extract before and after induction, as well as soluble and insoluble protein fractions, was analyzed by 12% SDS/PAGE followed by Coomassie Blue staining (Bio-Rad, USA) or transferred to nitrocellulose membrane for Western blot assay (Bio-Rad, USA). The membrane containing the bacterial protein extracts was blocked with blocking buffer (5% skim milk diluted in PBS) at 37°C for 30 min and incubated with 1:3000 anti-histidine mouse antibody (GE Healthcare, UK) diluted in blocking buffer at 37°C for 30 min. The membrane was washed with PBS plus 0.05% Tween 20 (PBST) 3 times for 5 min, followed by 1:2000 goat anti-mouse IgG conjugated to peroxidase (Zymed-Invitrogen, USA) diluted in blocking buffer at 37°C for 30 min. The membrane was then washed and revealed with diaminobenzidine (DAB) plus H2O2.
Purification and refolding of the recombinant scFv anti-intimin antibody obtained
The solubilized recombinant scFv was centrifuged (12,000 × g, 4°C, 30 min) and the supernatant was purified by immobilized metal affinity chromatography (IMAC) using Ni-Sepharose resin (GE Healthcare, UK). The column was washed with solubilization buffer to eliminate nonspecific proteins. Next, the specific protein was eluted with elution buffer (50 mM Tris-HCl, pH 8.0; 200 mM NaCl; 500 mM imidazole; and 8M urea). Purified recombinant scFv antibody was analyzed by 12% SDS/PAGE, as described above.
The purified scFv was dialyzed against solubilization solution containing 5 M urea for 12 h at room temperature using dialysis membrane with 8,000 Da cut-off. Step-wise dialysis was conducted by changing buffers with decreasing urea concentrations (3 M, 2 M, 1 M, 0.5 M and no urea). Considering the 1 M urea step, oxidized glutathione (375 μM) was added to the buffer to facilitate stable disulfide bond formation. The solubilized scFv was concentrated in polyethylene glycol 6000 (PEG 6000) and quantified by the Warburg-Christian method .
Tertiary and quaternary structure predictions
VH, linker and VL nucleotide sequence and predicted amino acid sequence of VH, linker, VL and conserved intimin (Gly388 - Lys667)
Amino Acid Sequences
The functionality of the purified anti-intimin scFv was assayed by ELISA and immunofluorescence.
Sandwich ELISA assay with polyclonal anti-intimin antibody
A polystyrene plate MaxiSorp (Nunc, Denmark) was coated with 0.05 M carbonate/bicarbonate buffer, pH 9.6, containing serial dilutions of recombinant anti-intimin scFv antibody 1:200 (1 μg) to 1:1600 (125 ng) for 18 h at 4°C. The wells were blocked with 5% skim milk diluted in PBS buffer and then, 20 μg/ml purified intimin (Int388-667) was added and incubated for 2 h at 37°C. The polyclonal rabbit anti-intimin IgG enriched fraction was added in serial dilutions from 1:200 (7.5 μg) to 1:3200 (470 ng) and incubated for 30 min at 37°C. The detection was done with goat anti-rabbit IgG conjugated to peroxidase (Invitrogen, USA) diluted 1:5000 and revealed with ο-phenylenediamine (OPD). The absorbance was measured at 492 nm and the reaction without purified intimin was taken for background noise subtraction. Between each reaction step, washing was done with PBS buffer containing 0.05% Tween 20. The purified intimin used in the assays was obtained as described by Menezes et al .
EPEC E2348/69 was cultivated in Luria-Bertani broth (LB) at 37°C for 18 h with constant shaking (250 rpm). One milliliter of the growth culture was centrifuged at 12,000 × g for 10 min and washed three times in PBS buffer. The pellet was permeabilized in 4% Triton X-100 under constant shaking (200 rpm) for 10 min and washed twice in PBS buffer, followed by 1% ρ-formaldehyde incubation for 20 min followed by two washes with PBS. Immunofluorescence reaction was performed using 44 μg/ml recombinant anti-intimin scFv for 1 h at room temperature, followed by anti-histidine mouse antibody incubation at 1:2000 dilutions for 1 h at room temperature. Goat anti-mouse IgG conjugated to fluorescein isothiocyanate (FITC) (Sigma, USA) at 1:100 dilution was added and the mixture incubated for 1 h at room temperature. One drop of the bacterial suspension was placed on a glass slide and examined with a fluorescence microscope (Axioskop-Zeiss, Germany) under 1000× magnification. As negative control, the assay was performed with E. coli K12 JM109.
Cloning strategy of the recombinant anti-intimin scFv
The amplified fragments corresponding to VL and VH were cloned into pGEM-T Easy vector and sequenced using the M13 primers (forward and reverse). The predicted amino acid sequences of VL and VH (Table 2) were analyzed in the NCBI database (blast.ncbi.nlm.nih.gov) using the BLAST tool, and a homology of over 90% was verified with the published data of the variable region of antibodies of the mice species Mus musculus. Conserved regions of heavy and light chain variable domains were used to design new primers containing appropriate restriction sites for subsequent cloning into expression vectors (Table 1).
Amplification products of approximately 300 bp were obtained using these specific primers, corresponding to the variable domains of light and heavy chains (VL and VH). In order to obtain and connect the light and heavy chains variable domains by the linker sequence, four PCR reactions were performed, resulting in a product of approximately 700 bp (Figure 1), corresponding to the anti-intimin scFv (scFv-int), which was subsequently cloned into pAE expression vector. Transformed clones were screened by colony PCR and sequenced (data not shown).
Expression of the recombinant anti-intimin scFv
Purification of the recombinant anti-intimin scFv
Structural and functional analysis of the recombinant anti-intimin scFv
Serotyping has been widely applied in the diagnosis of gastrointestinal diseases caused by EPEC and EHEC, but cannot be used for identifying these groups conclusively . Therefore, identification of the characteristic virulence genes is an obvious choice for detection. PCR to detect one or multiple virulence genes in the same reaction has been a successful method for the detection of EPEC and EHEC, as well as other DEC pathotypes. Nevertheless, gene detection does not assure expression of the corresponding virulence factor [20, 37, 38]. Among the methods for detection of virulence factor expression, immunoassays can be considered the first alternative, for which polyclonal and/or monoclonal antibodies are raised [19, 39–41].
The great genetic diversity of intimin, demonstrated by the description of at least 27 subtypes, makes difficult its molecular detection, which is dependent on the primers sequences [11, 17]. Moreover, a negative PCR result may not indicate that intimin is absent. For this reason the conserved region of this protein (Int388-667) was used as antigen for the development of a potential universal anti-intimin antibody able to detect the current known intimin subtypes and further uncharacterized ones [18–20].
In a previous work, even with an affinity constant of 1.3 × 10-8 M and a good detection limit with purified intimin, monoclonal anti-intimin IgG2b antibody detected 78% of a wide range of EPEC and EHEC intimin-expressing strains . These promising results prompted the objective of this work, the production of a functional scFv (corresponding to monoclonal anti-intimin antibody) intended for diagnosis purposes.
To outline our strategy, the pAE vector was used for scFv expression which was constructed on the basis of the pRSET vector containing the origin of replication of high copy number, with the multiple cloning site containing 6 histidine residues from the pET3-His vector . This vector was used successfully by others [32, 42–48], and despite the fact that in this study the protein was expressed in an insoluble form, a good yield was obtained.
In order to analyze the expression level of recombinant scFv in E. coli, different host strains were used, namely BL21(DE3)pLys and C43(DE3). These strains prevent the escape of expression and contribute to an over expression of the recombinant protein after induction. The analysis of expression in the C43(DE3) strain showed the presence of a protein of predicted molecular weight of 26.5 kDa, and another of smaller size (data not shown). This could be due to action of a protease that could be expressed in this strain. Another hypothesis is that the presence of rare codons in the scFv sequence could lead to truncated protein forms in this strain. On the other hand, despite the presence of some protein before induction, recombinant E. coli BL21(DE3)pLys successfully expressed scFv with the expected molecular weight. These results showed that E. coli BL21(DE3)pLys expressed more protein and only the predicted one. Thus, this strain was chosen for the expression of scFv anti-intimin.
Expression in the reducing environment of the cytoplasm can be achieved at high concentrations but often results in the formation of inclusion bodies (i.e., reduced and unfolded proteins), where the product requires solubilization with denaturing agents (e.g., 8 M urea) and subsequent refolding, by dialysis, of the denaturing agent in the presence of a redox pair (e.g., reduced and oxidized glutathione). Refolding efficiency varies for different antibodies . The anti-intimin scFv obtained in this work was also expressed as insoluble bodies, and thus, it was necessary to perform denaturing solubilization with subsequent refolding steps.
The method chosen for recovering insoluble protein was the solubilization in Tris-HCl buffer containing 8 M urea, followed by purification and step-wise dialysis for the refolding of the purified protein by decreasing urea concentration. Anti-intimin scFv was expressed with 6 histidine residues at the N-terminal, for the purpose of purification by metal affinity. In addition to purification, the His-tag is an epitope for detection using specific antibodies. To demonstrate the functionality of the scFv by ELISA, purified intimin conserved domain (Int388-667) is the best reagent for detection. However, the simple fact that the purified intimin also contains His-tag clearly impairs scFv detection, since the former could create false positive results.
To overcome this technical limitation, the strategy used was the sandwich indirect ELISA assay using the rabbit IgG enriched fraction or monoclonal anti-intimin. This protocol consisted of coating the plate with anti-intimin scFv, followed by incubation with purified intimin and rabbit polyclonal anti-intimin IgG, without the use of anti-His. Results showed that anti-intimin scFv is a functional antibody, and as expected, the polyclonal antibody does not compete with the scFv for the same epitope. On the other hand, no reactivity was observed when the monoclonal anti-intimin antibody was used, suggesting that this antibody competes with the scFv for the same intimin epitope (data not shown). Moreover, anti-intimin scFv was tested by immunofluorescence. This antibody recognized the EPEC E2348/69 strain but not E. coli K-12 after outer membrane permeabilization, showing its specificity for intimin.
The results of this study allow us to conclude that recombinant anti-intimin scFv was able to recognize the conserved region of purified intimin (Int388-667) and intimin in an EPEC isolate. Subsequent tests underway in our laboratory could demonstrate if the scFv reacts with the different types of intimin expressed by EPEC and EHEC. These data will be extremely important, since the recombinant scFv described so far is derived from spleen cell-cDNA from rabbits immunized with the intimin variable portion of O157:H7 and recognize only gamma intimin . It is worth mentioning that our previous results already showed that monoclonal anti-intimin antibody recognizes a broad variety of EPEC and EHEC strains , and as the anti-intimin scFv described herein is derived from it, this rAb is a promising tool for EPEC/EHEC diagnosis.
In conclusion, we successfully obtained a recombinant anti-intimin scFv with high specificity for intimin, detecting the conserved region of intimin (Int388-667) in the purified form and intimin on an EPEC isolate. Thus, this rAb is a very promising tool for EPEC/EHEC diagnosis and research purposes. Also, the deduced amino acid sequences of CDRs may also help us to create other scFv fragments with even higher affinity and specificity for intimin by site-directed mutagenesis.
enteropathogenic Escherichia coli
enterohemorrhagic Escherichia coli
enterotoxigenic Escherichia coli
- eae E. coli :
attaching and effacing
single chain variable fragment
heavy chain variable domain
light chain variable domain
E. coli secreted protein A
National Center for Biotechnology Information
Basic Local Alignment Search Tool
polymerase chain reaction
immobilized metal affinity chromatography
sodium dodecyl sulfate
polyacrylamide gel electrophoresis
complementarity determining region
enzyme-linked immunosorbent assay
recombinant phage antibody system
Roswell Park Memorial Institute
PBS plus Tween 20
This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (Grants 04/12136-5 and fellowship to MAM) and FINEP.
- O'Brien AD, Newland JW, Miller SF, Holmes RK, Smith HW, Formal SB: Shiga-like toxin-converting phages from Escherichia coli strains that cause hemorrhagic colitis or infantile diarrhea. Science. 1984, 226: 694-696.PubMedView ArticleGoogle Scholar
- Jerse AE, Yu J, Tall BD, Kaper JB: A genetic locus of enteropathogenic Escherichia coli necessary for the production of attaching and effacing lesions on tissue culture cells. Proc Natl Acad Sci USA. 1990, 87: 7839-7843. 10.1073/pnas.87.20.7839.PubMedPubMed CentralView ArticleGoogle Scholar
- Frankel G, Candy DC, Everest P, Dougan G: Characterization of the C-terminal domains of intimin-like proteins of enteropathogenic and enterohemorrhagic Escherichia coli, Citrobacter freundii, and Hafnia alvei. Infect Immun. 1994, 62: 1835-1842.PubMedPubMed CentralGoogle Scholar
- Adu-Bobie J, Trabulsi LR, Carneiro-Sampaio MMS, Dougan G, Frankel G: Identification of immunodominant regions within the C-terminal cell binding domain of intimin α an intimin β from enteropathogenic Escherichia coli. Infect Immun. 1998, 66: 5643-5649.PubMedPubMed CentralGoogle Scholar
- Lacher DW, Steinsland H, Whittam TS: Allelic subtyping of the intimin locus (eae) of pathogenic Escherichia coli by fluorescent RFLP. FEMS Microbiol Lett. 2006, 261: 80-87. 10.1111/j.1574-6968.2006.00328.x.PubMedView ArticleGoogle Scholar
- Agin TS, Wolf MK: Identification of a family of intimins common to Escherichia coli causing attaching-effacing lesions in rabbits, humans, and swine. Infect Immun. 1997, 65: 320-326.PubMedPubMed CentralGoogle Scholar
- China B, Jacquemin E, Devrin AC, Pirson V, Mainil J: Heterogeneity of the eae genes in attaching/effacing Escherichia coli from cattle: comparison with human strains. Res Microbiol. 1999, 150: 323-332. 10.1016/S0923-2508(99)80058-8.PubMedView ArticleGoogle Scholar
- Reid SD, Betting DJ, Whittam TS: Molecular detection and identification of intimin alleles in pathogenic Escherichia coli by multiplex PCR. J Clin Microbiol. 1999, 37: 2719-2722.PubMedPubMed CentralGoogle Scholar
- Oswald E, Schmidt H, Morabito S, Karch H, Marches O, Caprioli A: Typing of intimin genes in human and animal enterohemorrhagic and enteropathogenic Escherichia coli: characterization of a new intimin variant. Infect Immun. 2000, 68: 64-71. 10.1128/IAI.68.1.64-71.2000.PubMedPubMed CentralView ArticleGoogle Scholar
- Tarr CL, Whittam TS: Molecular evolution of the intimin gene in O111 clones of pathogenic Escherichia coli. J Bacteriol. 2002, 184: 479-487. 10.1128/JB.184.2.479-487.2002.PubMedPubMed CentralView ArticleGoogle Scholar
- Zhang WL, Köhler B, Oswald E, Beutin L, Karch H, Morabito S, Caprioli A, Suerbaum S, Schmidt H: Genetic diversity of intimin genes of attaching and effacing Escherichia coli strains. J Clin Microbiol. 2002, 40: 4486-4492. 10.1128/JCM.40.12.4486-4492.2002.PubMedPubMed CentralView ArticleGoogle Scholar
- Ramachandran V, Brett K, Hornitzky MA, Dowton M, Bettelheim KA, Walker MJ, Djordjevic SP: Distribution of intimin subtypes among Escherichia coli isolates from ruminant and human sources. J Clin Microbiol. 2003, 41: 5022-5032. 10.1128/JCM.41.11.5022-5032.2003.PubMedPubMed CentralView ArticleGoogle Scholar
- Beutin L, Krause G, Zimmermann S, Kaulfuss S, Gleier K: Characterization of Shiga toxin-producing Escherichia coli strains isolated from human patients in Germany over a 3-year period. J Clin Microbiol. 2004, 42: 1099-1108. 10.1128/JCM.42.3.1099-1108.2004.PubMedPubMed CentralView ArticleGoogle Scholar
- Garrido P, Blanco M, Moreno-Paz M, Briones C, Dahbi G, Blanco J, Blanco J, Parro V: STEC-EPEC oligonucleotide microarray: a new tool for typing genetic variants of the LEE pathogenicity island of human and animal Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) strains. Clin Chem. 2006, 52: 192-201. 10.1373/clinchem.2005.059766.PubMedView ArticleGoogle Scholar
- Blanco JE, Blanco M, Alonso MP, Mora A, Dahbi G, Coira MA, Blanco J: Serotypes, virulence genes, and intimin types of Shiga toxin (verotoxin)-producing Escherichia coli isolates from human patients: prevalence in Lugo, Spain, from 1992 through 1999. J Clin Microbiol. 2004, 42: 311-319. 10.1128/JCM.42.1.311-319.2004.PubMedPubMed CentralView ArticleGoogle Scholar
- Blanco M, Schumacher S, Tasara T, Zweifel C, Blanco JE, Dahbi G, Blanco J, Stephan R: Serotypes, intimin variants and other virulence factors of eae positive Escherichia coli strains isolated from healthy cattle in Switzerland. Identification of a new intimin variant gene (eae-eta2). BMC Microbiol. 2005, 5: 23-10.1186/1471-2180-5-23.PubMedPubMed CentralView ArticleGoogle Scholar
- Blanco M, Blanco JE, Dahbi G, Alonso MP, Mora A, Coira MA, Madrid C, Juárez A, Bernárdez MI, González EA, Blanco J: Identification of two new intimin types in atypical enteropathogenic Escherichia coli. Int Microbiol. 2006, 9: 103-110.PubMedGoogle Scholar
- Batchelor M, Knutton S, Caprioli A, Huter V, Zanial M, Dougan G, Frankel G: Development of a universal intimin antiserum and PCR primers. J Clin Microbiol. 1999, 37: 3822-3827.PubMedPubMed CentralGoogle Scholar
- Koga PCM, Menezes CA, Lima FA, Nara JM, Magalhães CA, Cianciarullo AM, Ferreira-Júnior JMC, Trabulsi LR, Mendes-Ledesma MRB, Piazza RMF: Polyclonal anti-intimin antibody: immunological characterization and its use in EPEC diagnosis. Braz J Microbiol. 2003, 34: 5-7. 10.1590/S1517-83822003000500002.View ArticleGoogle Scholar
- Menezes MA, Rocha LB, Koga PC, Fernandes I, Nara JM, Magalhães CA, Abe CM, Ayala CO, Burgos YK, Elias WP, Castro AF, Piazza RM: Identification of enteropathogenic and enterohaemorrhagic Escherichia coli strains by immunoserological detection of intimin. J Appl Microbiol. 2010, 108: 878-887. 10.1111/j.1365-2672.2009.04484.x.PubMedView ArticleGoogle Scholar
- Svennerholm AM, Wikström M, Lindbald M, Holmgren J: Monoclonal antibodies against Escherichia coli heat-stabile toxin (STa) and their use in a diagnostic ST ganglioside GM1-Enzime-linked immunosorbent assay. J Clin Microbiol. 1986, 24: 585-590.PubMedPubMed CentralGoogle Scholar
- Weisser NE, Hall JC: Applications of single-chain variable fragment antibodies in therapeutics and diagnostics. Biotechnol Adv. 2009, 27: 502-520. 10.1016/j.biotechadv.2009.04.004.PubMedView ArticleGoogle Scholar
- McCafferty J, Griffiths AD, Winter G, Chiswell DJ: Phage antibodies: filamentous phage displaying antibody variable domains. Nature. 1990, 348: 552-554. 10.1038/348552a0.PubMedView ArticleGoogle Scholar
- Hanes J, Plückthun A: In vitro selection and evolution of functional proteins by using ribosome display. Proc Natl Acad Sci USA. 1997, 94: 4937-4942. 10.1073/pnas.94.10.4937.PubMedPubMed CentralView ArticleGoogle Scholar
- He M, Taussig MJ: Antibody-ribosome-mRNA (ARM) complexes as efficient selection particles for in vitro display and evolution of antibody combining sites. Nucleic Acids Res. 1997, 25: 5132-5134. 10.1093/nar/25.24.5132.PubMedPubMed CentralView ArticleGoogle Scholar
- Francisco JA, Stathopoulos C, Warren RA, Kilburn DG, Georgiou G: Specific adhesion and hydrolysis of cellulose by intact Escherichia coli expressing surface anchored cellulase or cellulose binding domains. Biotechnology (N Y). 1993, 11: 491-495. 10.1038/nbt0493-491.View ArticleGoogle Scholar
- Wang SH, Zhang JB, Zhang ZP, Zhou YF, Yang RF, Chen J, Guo YC, You F, Zhang XE: Construction of single chain variable fragment (ScFv) and BiscFv-alkaline phosphatase fusion protein for detection of Bacillus anthracis. Anal Chem. 2006, 78: 997-1004. 10.1021/ac0512352.PubMedView ArticleGoogle Scholar
- Kühne SA, Hawes WS, La Ragione RM, Woodward MJ, Whitelam GC, Gough KC: Isolation of recombinant antibodies against EspA and intimin of Escherichia coli O157:H7. J Clin Microbiol. 2004, 42: 2966-2976.PubMedPubMed CentralView ArticleGoogle Scholar
- Bhaskaran S, Jay CM, Berghman LR, Wagner GG, Waghela SD: A single-chain fragment variable recombinant antibody against F5 fimbria of enterotoxigenic Escherichia coli inhibits agglutination of horse red blood cells induced by F5 protein. Vet Res Commun. 2005, 29: 463-476. 10.1007/s11259-005-1432-z.PubMedView ArticleGoogle Scholar
- Chung WY, Sack M, Carter R, Spiegel H, Fischer R, Hirst TR, Williams NA, James RF: Phage-display derived single-chain fragment variable (scFv) antibodies recognizing conformational epitopes of Escherichia coli heat-labile enterotoxin B-subunit. J Immunol Methods. 2008, 339: 115-123. 10.1016/j.jim.2008.08.005.PubMedView ArticleGoogle Scholar
- Sambrook J, Fritsch EF, Maniatis T: Molecular cloning: a laboratory manual. 1989, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NYGoogle Scholar
- Ramos CR, Abreu PA, Nascimento AL, Ho PL: A high-copy T7 Escherichia coli expression vector for the production of recombinant proteins with a minimal N-terminal His-tagged fusion peptide. Braz J Med Biol Res. 2004, 37: 1103-1109. 10.1590/S0100-879X2004000800001.PubMedView ArticleGoogle Scholar
- Warburg O, Christian W: Isolierung und kristallisation des gärungsferments enolase. Biochem Z. 1942, 310: 384-421.Google Scholar
- Hwang H, Pierce B, Mintseris J, Janin J, Weng Z: Protein-protein docking benchmark version 3.0. Proteins. 2008, 73: 705-709. 10.1002/prot.22106.PubMedPubMed CentralView ArticleGoogle Scholar
- Chaudhury S, Sircar A, Sivasubramanian A, Berrondo M, Gray JJ: Incorporating biochemical information and backbone flexibility in RosettaDock for CAPRI rounds 6-12. Proteins. 2007, 69: 793-800. 10.1002/prot.21731.PubMedView ArticleGoogle Scholar
- Trabulsi LR, Keller R, Gomes TAT: Typical and Atypical Enteropathogenic Escherichia coli. Emerg Infect Dis. 2002, 8: 508-513.PubMedPubMed CentralView ArticleGoogle Scholar
- Vilhena-Costa AB, Piazza RM, Nara JM, Trabulsi LR, Martinez MB: Slot blot immunoassay as a tool for plasmid-encoded toxin detection in enteroaggregative Escherichia coli culture supernatants. Diagn Microbiol Infect Dis. 2006, 55: 101-106. 10.1016/j.diagmicrobio.2006.01.008.PubMedView ArticleGoogle Scholar
- Nara JM, Cianciarullo AM, Culler HF, Bueris V, Horton DS, Menezes MA, Franzolin MR, Elias WP, Piazza RM: Differentiation of typical and atypical enteropathogenic Escherichia coli using colony immunoblot for detection of bundle-forming pilus expression. J Appl Microbiol. 2010, 109: 35-43.PubMedGoogle Scholar
- Menezes CA, Gonçalves DS, Amianti J, Fernandes I, Taddei CR, Koga PCM, Trabulsi LR, Martinez MB, Piazza RMF: Capture immunoassay for LT detection produced by enterotoxigenic Escherichia coli in bacterial isolates. Braz J Microbiol. 2003, 34: 11-13. 10.1590/S1517-83822003000500004.View ArticleGoogle Scholar
- Menezes CA, Imamura SY, Trabulsi LR, Fernandes-Filho A, Martinez MB, Guth BE, Girão DM, Piazza RM: Production, characterization, and application of antibodies against heat-labile type-I toxin for detection of enterotoxigenic Escherichia coli. Mem Inst Oswaldo Cruz. 2006, 101: 875-880.PubMedGoogle Scholar
- Mendes-Ledesma MR, Rocha LB, Bueris V, Krause G, Beutin L, Franzolin MR, Trabulsi LR, Elias WP, Piazza RM: Production and characterization of rabbit polyclonal sera against Shiga toxins Stx1 and Stx2 for detection of Shiga toxin-producing Escherichia coli. Microbiol Immunol. 2008, 52: 484-491. 10.1111/j.1348-0421.2008.00068.x.PubMedView ArticleGoogle Scholar
- Neves FO, Ho PL, Raw I, Pereira CA, Moreira C, Nascimento AL: Overexpression of a synthetic gene encoding human alpha interferon in Escherichia coli. Protein Expr Purif. 2004, 35: 353-359. 10.1016/j.pep.2004.02.005.PubMedView ArticleGoogle Scholar
- Reis CV, Andrade SA, Ramos OH, Ramos CR, Ho PL, Batista IF, Chudzinski-Tavassi AM: Lopap, a prothrombin activator from Lonomia obliqua belonging to the lipocalin family: recombinant production, biochemical characterization and structure-function insights. Biochem J. 2006, 398: 295-302. 10.1042/BJ20060325.PubMedPubMed CentralView ArticleGoogle Scholar
- Silva M, Cabrera-Crespo J, Sbrogio-Almeida ME, Miyaji EN, Ho PL, Leite LC, Lopes AP: Optimizing expression of Streptococcus pneumoniae surface protein a, PspA: serocross-reactivity within families of antisera induced against clades 1 and 3. Mol Biotechnol. 2007, 37: 146-154. 10.1007/s12033-007-0043-z.PubMedView ArticleGoogle Scholar
- Vieira ML, D'Atri LP, Schattner M, Habarta AM, Barbosa AS, de Morais ZM, Vasconcellos SA, Abreu PA, Gómez RM, Nascimento AL: A novel leptospiral protein increases ICAM-1 and E-selectin expression in human umbilical vein endothelial cells. FEMS Microbiol Lett. 2007, 276: 172-180. 10.1111/j.1574-6968.2007.00924.x.PubMedView ArticleGoogle Scholar
- Longhi MT, Oliveira TR, Romero EC, Gonçales AP, de Morais ZM, Vasconcellos SA, Nascimento AL: A newly identified protein of Leptospira interrogans mediates binding to laminin. J Med Microbiol. 2009, 58: 1275-1282. 10.1099/jmm.0.011916-0.PubMedView ArticleGoogle Scholar
- Atzingen MV, Gómez RM, Schattner M, Pretre G, Gonçales AP, de Morais ZM, Vasconcellos SA, Nascimento AL: Lp95, a novel leptospiral protein that binds extracellular matrix components and activates e-selectin on endothelial cells. J Infect. 2009, 59: 264-276. 10.1016/j.jinf.2009.07.010.PubMedView ArticleGoogle Scholar
- Vieira ML, de Morais ZM, Gonçales AP, Romero EC, Vasconcellos SA, Nascimento AL: Lsa63, a newly identified surface protein of Leptospira interrogans binds laminin and collagen IV. J Infect. 2010, 60: 52-64. 10.1016/j.jinf.2009.10.047.PubMedView ArticleGoogle Scholar
- Guo JQ, You SY, Li L, Zhang YZ, Huang JN, Zhang CY: Construction and high-level expression of a single-chain Fv antibody fragment specific for acidic isoferritin in Escherichia coli. J Biotechnol. 2003, 102: 177-189. 10.1016/S0168-1656(03)00020-8.PubMedView ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.