Biosensing Cytokine IL-6: A Comparative Analysis of Natural and Synthetic Receptors.

Cytokines are a family of proteins which play a major role in the regulation of the immune system and the development of several diseases, from rheumatoid arthritis to cancer and, more recently, COVID-19. Therefore, many efforts are currently being developed to improve therapy and diagnosis, as well as to produce inhibitory drugs and biosensors for a rapid, minimally invasive, and effective detection. In this regard, even more efficient cytokine receptors are under investigation. In this paper we analyze a set of IL-6 cytokine receptors, investigating their topological features by means of a theoretical approach. Our results suggest a topological indicator that may help in the identification of those receptors having the highest complementarity with the protein, a feature expected to ensure a stable binding. Furthermore, we propose and discuss the use of these receptors in an idealized experimental setup.

Direct Determination of Antibody Chain Pairing by Top-down and Middle-down Mass Spectrometry Using Electron Capture Dissociation and Ultraviolet Photodissociation.

One challenge associated with the discovery and development of monoclonal antibody (mAb) therapeutics is the determination of heavy chain and light chain pairing. Advances in MS instrumentation and MS/MS methods have greatly enhanced capabilities for the analysis of large intact proteins yielding much more detailed and accurate proteoform characterization. Consequently, direct interrogation of intact antibodies or F(ab')2 and Fab fragments has the potential to significantly streamline therapeutic mAb discovery processes. Here, we demonstrate for the first time the ability to efficiently cleave disulfide bonds linking heavy and light chains of mAbs using electron capture dissociation (ECD) and 157 nm ultraviolet photodissociation (UVPD). The combination of intact mAb, Fab, or F(ab')2 mass, intact LC and Fd masses, and CDR3 sequence coverage enabled determination of heavy chain and light chain pairing from a single experiment and experimental condition. These results demonstrate the potential of top-down and middle-down proteomics to significantly streamline therapeutic antibody discovery.

Human recombinant Fab fragment from combinatorial libraries of a B-cell lymphoma patient recognizes core protein of chondroitin sulphate proteoglycan 4.

CD antigens are well known as therapeutic targets of B-cell lymphoma. To isolate therapeutic antibodies that recognize novel targets other than CD antigens, we constructed a phage display combinatorial antibody Fab library from bone marrow lymphocytes of B-cell lymphoma patient. To eliminate antibodies reactive with known B-cell lymphoma antigen, non-hematopoietic and patient's sera reactive HeLaS3 cells was selected as a target of whole cell panning. Five rounds of panning against live HeLaS3 cells retrieved single Fab clone, termed AHSA (Antibody to HeLa Surface Antigen). Using phage display random peptide library, LSYLEP was identified as an epitope sequence of AHSA. LC-MS/MS analysis of AHSA-precipitated HeLaS3 cell lysates detected several fragments corresponding to the sequence of chondroitin sulphate proteoglycan 4 (CSPG4) core protein. Since LSYLEP sequence was at the position of 313-318 of CSPG4, we considered that CSPG4 was AHSA-associated antigen. Double staining of CSPG4-postive MDA-MB-435S cells with AHSA and anti-CSPG4 rabbit antibody showed identical staining position, and reduced AHSA reactivity was observed in CSPG4-siRNA treated MDA-MB-435S cells. In conclusion, we retrieved a human Fab from antibody library of B-cell lymphoma patient, and identified CSPG4 as a recognizing antigen. AHSA may have potential benefits for development of CSPG4-targeting theranostics for B-cell lymphoma.

Quality of horse F(ab)2 antitoxins and antirabies immunoglobulins: protein content and anticomplementary activity

Background Among other applications, immunotherapy is used for the post-exposure treatment and/or prophylaxis of important infectious diseases, such as botulism, diphtheria, tetanus and rabies. The effectiveness of serum therapy is widely proven, but improvements on the immunoglobulin purification process and on the quality control are necessary to reduce the amount of protein aggregates. These may trigger adverse reactions in patients by activating the complement system and inducing the generation of anaphylatoxins. Herein, we used immunochemical methods to predict the quality of horse F(ab)2 anti-botulinum AB, anti-diphtheric, antitetanic and anti-rabies immunoglobulins, in terms of amount of proteins and protein aggregates. Methods Samples were submitted to protein quantification, SDS-PAGE, Western blot analysis and molecular exclusion chromatography. The anticomplementary activity was determined in vitro by detecting the production of C5a/C5a desArg, the most potent anaphylatoxin. Data were analyzed by one-way ANOVA followed by Tukey's post-test, and differences were considered statistically significant when p 0.05. Results Horse F(ab)2 antitoxins and anti-rabies immunoglobulin preparations presented different amounts of protein. SDS-PAGE and Western blot analyses revealed the presence of protein aggregates, non-immunoglobulin contaminants and, unexpectedly, IgG whole molecules in the samples, indicating the non-complete digestion of immunoglobulins. The chromatographic profiles of antitoxins and anti-rabies immunoglobulins allowed to estimate the percentage of contaminants and aggregates in the samples. Although protein aggregates were present, the samples were not able to induce the generation of C5a/C5a desArg in vitro, indicating that they probably contain acceptable levels of aggregates...

Selective disulfide reduction for labeling and enhancement of Fab antibody fragments.

Many methods have been developed for chemical labeling and enhancement of the properties of antibodies and their common fragments, including the Fab and F(ab')2 fragments. Somewhat selective reduction of some antibody disulfide bonds has been previously achieved, yielding antibodies and antibody fragments that can be labeled at defined sites, enhancing their utility and properties. Selective reduction of the two hinge disulfide bonds present in F(ab')2 fragments using mild reduction has been useful. However, such reduction is often not quantitative and results in the reduction of multiple disulfide bonds, and therefore subsequent multiple labeling or conjugation sites are neither homogenous nor stoichiometric. Here, a simple and efficient selective reduction of the single disulfide bond linking the partial heavy chain and the intact light chain which compose the Fab fragment is accomplished utilizing tris(2-carboxyethyl)phosphine (TCEP) immobilized on agarose beads. The resultant reduced cysteine residues were labeled with several cysteine-selective fluorescent reagents, as well as by cysteine-directed PEGylation. These two cysteine residues can also be re-ligated by means of a bifunctional cysteine cross-linking agent, dibromobimane, thereby both restoring a covalent linkage between the heavy and light chains at this site, far removed from the antigen binding site, and also introducing a fluorescent probe. There are many other research and clinical uses for these selectively partially reduced Fab fragments, including biotinylation, toxin and drug conjugation, and incorporation of radioisotopes, and this technique enables simple generation of very useful Fab fragment derivatives with many potential applications.

Fab fragment glycosylated IgG may play a central role in placental immune evasion.

STUDY QUESTION: How does the placenta protect the fetus from immune rejection by the mother? SUMMARY ANSWER: The placenta can produce IgG that is glycosylated at one of its Fab arms (asymmetric IgG; aIgG) which can interact with other antibodies and certain leukocytes to affect local immune reactions at the junction between the two genetically distinct entities. WHAT IS KNOWN ALREADY: The placenta can protect the semi-allogenic fetus from immune rejection by the immune potent mother. aIgG in serum is increased during pregnancy and returns to the normal range after giving birth. aIgG can react to antigens to form immune complexes which do not cause a subsequent immune effector reaction, including fixing complements, inducing cytotoxicity and phagocytosis, and therefore has been called 'blocking antibody'. STUDY DESIGN, SIZE, DURATION: Eighty-eight human placentas, four trophoblast cell lines (TEV-1, JAR, JEG and BeWo), primary culture of human placental trophoblasts and a gene knock-out mouse model were investigated in this study. PARTICIPANTS/MATERIALS, SETTING, METHODS: The general approach included the techniques of cell culture, immunohistochemistry, in situ hybridization, immuno-electron microscopy, western blot, quantitative PCR, protein isolation, glycosylation analysis, enzyme digestion, gene sequencing, mass spectrophotometry, laser-guided microdissection, enzyme-linked immunosorbent assay, pulse chase assay, double and multiple staining to analyze protein and DNA and RNA analysis at the cellular and molecular levels. MAIN RESULTS AND THE ROLE OF CHANCE: Three major discoveries were made: (i) placental trophoblasts and endothelial cells are capable of producing IgG, a significant portion of which is aberrantly glycosylated at one of its Fab arms to form aIgG; (ii) the asymmetrically glycosylated IgG produced by trophoblasts and endothelial cells can react to immunoglobulin molecules of human, rat, mouse, goat and rabbit at the Fc portion; (iii) asymmetrically glycosylated IgG can react to certain leukocytes in the membrane and cytoplasm, while symmetric IgG from the placenta does not have this property. LIMITATIONS, REASONS FOR CAUTION: Most of the experiments were performed in vitro. The proposed mechanism calls for verification in normal and abnormal pregnancy. WIDER IMPLICATIONS OF THE FINDINGS: This study identified a number of new phenomena suggesting that aIgG produced by the placenta would be able to react to detrimental antibodies and leukocytes and interfere with their immune reactions against the placenta and the fetus. This opens a new dimension for further studies on pregnancy physiology and immunology. Should the mechanism proposed here be confirmed, it will have a direct impact on our understanding of the physiology and pathology of human reproduction and offer new possibilities for the treatment of many diseases including spontaneous abortion, infertility and pre-eclampsia. It also sheds light on the mechanism of immune evasion in general including that of cancer.

Renal brush border enzyme-cleavable linkages for low renal radioactivity levels of radiolabeled antibody fragments.

We previously demonstrated that Fab fragments labeled with 3'-[(131)I]iodohippuryl N(ε)-maleoyl-l-lysine ([(131)I]HML) showed low renal radioactivity from early postinjection time, due to a liberation of m-[(131)I]iodohippuric acid by the action of renal brush border enzymes. Since there are lots of enzymes on renal brush border membrane, peptide linkages other than the glycyl-l-lysine were evaluated as the cleavable linkages to explore the chemical design. In this study, we evaluated four peptide linkages with a general formula of m-iodobenzoyl-glycyl-X (X: l-tyosine O-methyl, l-asparagine, l-glutamine, and N(ε)-Boc-l-lysine). In vitro studies using renal brush border membrane vesicles (BBMVs) demonstrated that 3'-[(125)I]iodohippuryl O-methyl-l-tyrosine (2c) liberated the highest amount of m-[(125)I]iodohippuric acid among the four substrates and the change in the linkage structure altered enzyme species responsible for the hydrolysis reaction. To further assess the applicability of the linkage, a radioiodination reagent containing a glycyl-tyrosine linkage, 3'-[(125)I]iodohippuryl O-((2-maleimidoethyl)carbamoyl)methyl-l-tyrosine (HMT, 12c), was designed, synthesized, and subsequently conjugated to an Fab fragment. [(125)I]HMT-Fab exhibited renal radioactivity levels similar to and significantly lower than [(125)I]HML-Fab and directly radioiodinated Fab, while the blood clearance rates of the three were similar. The analyses of urine for 24 h postinjection of [(125)I]HMT-Fab showed that m-[(125)I]iodohippuric acid was excreted as the major radiometabolite. The findings indicated that glycyl-tyrosine linkage is also available to reduce renal radioactivity levels of radioiodinated Fab fragments, due to liberation of m-iodohippuric acid by the action of enzymes present on renal brush border membrane. These findings suggest that an appropriate selection of peptide linkages would allow the liberation of a designed radiolabeled compound from covalently conjugated polypeptides to prepare radiolabeled polypeptides of low renal radioactivity levels. For the selection of the most appropriate peptide linkage, the in vitro system using BBMVs would be useful to narrow the candidates to just a few.

Structure of the Fab-labeled "breathing" state of native poliovirus.

At 37°C, the structure of poliovirus is dynamic, and internal polypeptides VP4 and N terminus of VP1 (residues 1 to 53) externalize reversibly. An Fab fragment of a monospecific antibody, which binds to residues 39 to 55 of VP1, was utilized to locate the N termini of VP1 in native (160S) particles in this "breathing" state. Fab and virus were mixed and imaged via cryogenic electron microscopy. The resulting reconstruction showed the capsid expands similarly to the irreversibly altered cell entry intermediate (135S) particle, but the N terminus of VP1 is located near the 2-fold axes, instead of the "propeller tip" as in 135S particles.

AFM imaging of ALYGNSA polymer-protein surfaces: evidence of antibody orientation.

Previous investigations found the combination of recombinant bacterial protein G (rProG) and poly(methyl methacrylate) (PMMA) to produce a greater proportion of oriented antibodies. PMMA-rProG yielded a sixfold greater availability of antibody Fab regions compared with other bacterial affinity linker protein and polymer pairings, including commercially available polystyrene (PS) high-binding 96-well microplates. Given the name ALYGNSA, the PMMA-rProG combination was developed into a fluorescence assay and evaluated in conjunction with commercially available cancer biomarker enzyme-linked immunosorbent assays (ELISAs). In each study, a lower limit of detection was seen with the ALYGNSA assay. The purpose of this investigation was to examine the ALYGNSA substrate in contrast with a commonly used ELISA substrate and analyze the affinity-immobilized antibodies for additional evidence of orientation. Non-contact atomic force microscopy is a logical method as it operates in ambient conditions, can be used directly on biological samples without modification, and offers the resolution necessary to identify the position of the antibody on the surface. Dynamic contact angle studies were employed to examine untreated PMMA and PS samples and revealed important differences in their surface characters. Comparative height threshold grain analysis of the prepared ALYGNSA surface, a similarly treated mica surface, and a gold colloid sizing standard evaluated and confirmed the antibody orientation of the ALYGNSA system.

Radiolabeling of fab and f(ab')2 antibody fragments with 99mTc(I) tricarbonyl core using a new bifunctional tridentate ligand.

The objective of this study was to design and evaluate a new histidine-modified tridentate chelator for labeling antimesothelin fab and f(ab')2 antibody fragments with the Tc(I) tricarbonyl ([Tc(CO)3]) core. N-(ortho-phenol)-histidine chelator was synthesized by modifying the single amino acid L-histidine, a natural amino acid, with an additional phenol group to obtain the bifunctional tridentate ligand after reductive amination. Bioconjugation was based on the carbodiimide activation of the carboxylate of chelator and on further reaction with the amine groups present on the antibody fragments. Radiolabeling was accomplished by replacing the three aqua ligands of the complex precursor [Tc(CO)3(H2O)3] with the tridentate chelator. The antibody fragments radiolabeled with [Tc(CO)3] core were tested for stability by the cysteine challenge test. The immunoreactivity and binding affinity of the radiolabeled fragments were studied using in-vitro cell-binding assays. Radiochemical yields achieved for [Tc(CO)3] core labeling of fab and f(ab')2 were 91.6±9.1% and 80.7±8.5%, respectively. Stability studies of radiolabeled antibody fragments showed that the Tc label was stable to transchelation by cysteine. Both Tc-fab and Tc-f(ab')2 retained their reactivity and affinity to the mesothelin antigen. From our studies, it can be concluded that the newly synthesized N-(ortho-phenol)-histidine chelator is a promising candidate for [Tc(CO)3] labeling of biomolecules and for developing other novel Tc radiopharmaceuticals.

Digoxin immune fab treatment for severe preeclampsia.

We evaluated the efficacy, safety, and biological mechanisms of digoxin immune Fab (DIF) treatment of severe preeclampsia. Fifty-one severe preeclamptic patients were randomized in double-blind fashion to DIF ( N = 24) or placebo ( N = 27) for 48 hours. Primary outcomes were change in creatinine clearance (CrCl) at 24 to 48 hours and antihypertensive drug use. Serum sodium pump inhibition, a sequela of endogenous digitalis-like factors (EDLF), was also assessed. CrCl in DIF subjects was essentially unchanged from baseline versus a decrease with placebo (-3 +/- 10 and -34 +/- 10 mL/min, respectively, P = 0.02). Antihypertensive use was similar between treatments (46 and 52%, respectively, P = 0.7). Serum sodium pump inhibition was decreased with DIF compared with placebo at 24 hours after treatment initiation (least squares mean difference, 19 percentage points, P = 0.03). DIF appeared to be well tolerated. These results suggest DIF prevents a decline in renal function in severe preeclampsia by neutralizing EDLF. Sodium pump inhibition was significantly improved. Further research is warranted.

Use of biofluorescence imaging to compare the distribution of certolizumab pegol, adalimumab, and infliximab in the inflamed paws of mice with collagen-induced arthritis.

Exposure to a drug at the site of inflammation may be an important consideration for the effective treatment of inflammatory disorders such as rheumatoid arthritis (RA). The purpose of this in vivo study was to identify a methodology to enable effective quantification of antibody-type reagents in normal and inflamed tissue by investigating the distribution of the tumor necrosis factor-alpha (TNF-alpha) inhibitors, certolizumab pegol, adalimumab, and infliximab, in healthy and inflamed murine tissue using a novel non-invasive biofluorescence method. Certolizumab pegol, adalimumab, and infliximab were labeled with the low molecular weight dye alexa680. The agents were administered intravenously at a dose of 2mg/kg in naïve DBA/1 mice and in DBA/1 mice with ongoing collagen-induced arthritis. Concentrations of the TNF inhibitors in the hind paws were measured using a Xenogen IVIS200 biofluorescence imager at multiple time points up to 26h post-administration. In 2 independent experiments, the distribution of certolizumab pegol was compared with that of adalimumab and infliximab. Certolizumab pegol, adalimumab, and infliximab all distributed more effectively into inflamed tissue than non-inflamed tissue in this animal model of arthritis. However, the ratio of penetration of certolizumab pegol into inflamed arthritic paws compared with normal tissue was greater than that observed with adalimumab and infliximab. Furthermore, the duration of exposure in the inflamed versus normal tissue was more prolonged for certolizumab pegol than for both adalimumab and infliximab, and the accumulation of certolizumab pegol in diseased tissue was more responsive to the severity of inflammation when compared with adalimumab and infliximab. It is probable that these features of certolizumab pegol are conferred on the molecule by PEGylation. It is important to assess exposure to drug at the site of inflammation, because distinct structural features of certain agents may affect efficacy, tolerability, rapidity and/or sustainability of effect. The novel non-invasive biofluorescence method used in this study is an effective tool for comparing tissue penetration of therapeutic agents.

A peptide-based, ratiometric biosensor construct for direct fluorescence detection of a protein analyte.

We present the design, synthesis, and functional evaluation of peptide-based fluorescent constructs for wavelength-ratiometric biosensing of a protein analyte. The concept was shown using the high-affinity model interaction between the 18 amino acid peptide pTMVP and a recombinant antibody fragment, Fab57P. pTMVP was functionalized in two different positions with 6-bromomethyl-2-(2-furanyl)-3-hydroxychromone, an environmentally sensitive fluorophore with a two-band emission. The equilibrium dissociation constant of the interaction between pTMVP and Fab57P was largely preserved upon labeling. The biosensor ability of the labeled peptide constructs was evaluated in terms of the relative intensity change of the emission bands from the normal (N*) and tautomer (T*) excited-state species of the fluorophore ( I(N*)/I(T*)) upon binding of Fab57P. When the peptide was labeled in the C terminus, the I(N*)/I(T*) ratio changed by 40% upon analyte binding, while labeling close to the residues most important for binding resulted in a construct that completely lacked ratiometric biosensor ability. Integrated biosensor elements for reagentless detection, where peptides and ratiometric fluorophores are combined to ensure robustness in both recognition and signaling, are expected to become an important contribution to the design of future protein quantification assays in immobilized formats.

A cancer protein microarray platform using antibody fragments and its clinical applications.

Antibody microarrays have shown great potential for measurement of either a spectrum of target proteins in proteomics or disease-associated antigens in molecular diagnostics. Despite its importance, the applications of antibody microarrays are still limited by a variety of fundamental problems. Among them, cross-reactivity significantly limits the multiplexing ability in parallel sandwich immunoassays. As a result, it is very important to design new capture probes in order to incorporate a universal label into the assay configuration. In this report, an antibody fragments (F(ab')2) microarray platform for serum tumor markers was developed. Each antigen was detected at different concentrations to assemble its calibration curve, and combinations of different markers were tested to examine the specificity of simultaneous detection based on the F(ab')2 microarrays. Diagnostics of serum samples with this cancer antibody microarray platform and immunoradiometric assays (IRMA) were also performed. Wide range calibration curves (0-1280 U mL(-1)) were obtained for each tumor marker. Comparative studies demonstrated that such F(ab')2 microarrays exhibited both moderately improved sensitivity and better specificity than full-sized monoclonal antibody microarrays. It is also demonstrated that this microarray platform is quantitative, highly specific and reasonably sensitive. More importantly, clinical applications of our F(ab')2 microarray platform for upwards of 100 patient serum samples clearly show its potential in cancer diagnostics.

Effects of cell-permeating peptide binding on the distribution of 125I-labeled Fab fragment in rats.

The peptides comprising the sequence of HIV-1 Tat protein (positions 48-60), Antennapedia (positions 43-58), and HIV-1 Rev protein (positions 34-50) are known to be cell-permeating. In this study, we examined how the distribution of Fab fragments in rats is affected by conjugation with these peptides. Fab fragment was iodinated by a chloramine-T method and then chemically conjugated with cell-permeating peptide. The complex of 125I-Fab and cell-permeating peptide was administered to male rats intravenously at a dose of 1 mg/kg, and whole-body autoradiography was performed at 4 and 24 h after administration. The patterns of distribution of 125I-Fab exhibited remarkable variation depending on the cell-permeating peptide used. In particular, at 4 h, high concentrations of radioactivity were observed in the spleen, adrenal gland, renal medulla, and liver with Rev peptide-Fab complex, in the liver and spleen with Tat peptide-Fab complex, and in the spleen, adrenal gland, and liver with Antennapedia peptide-Fab complex. Even at 24 h, high concentrations of radioactivity were still observed in the spleen and renal medulla of rat with Rev peptide-Fab complex, and in the spleen and renal cortex of rat with Antennapedia peptide-Fab complex. These findings demonstrate that the patterns of distribution of peptide-125I-Fab complexes can be modulated by selection of cell-penetrating peptides. Moreover, the patterns of retention of peptide-125I-Fab complexes in internal organs also differed at 24 h after administration. These findings provide valuable information for the development of novel antibody pharmaceuticals and therapeutic systems.

[Secretory expression of chimeric Fab antibody HAb18 against human hepatocellular carcinoma in Pichia pastoris].

AIM: To express secretively chimeric Fab antibody HAb18 (cFab) against human hepatocellular carcinoma in Pichia pastoris. METHODS: Genes encoding CL chain and Fd fragment of cFab antibody HAb18 were subcloned into vectors pPIC9K and pPICZalphaA, respectively. After confirmed by DNA sequence analysis, the recombinant plasmids pPIC9K/CL and pPICZalphaA/Fd were transformed into the genome of Pichia pastoris GS115. Mut(+) multiple insert transformants were screened by G418 and Zeocin and then induced with 5 mL/L methanol to express cFab. RESULTS: 4 days after methanol induction, 26 mg/L of the cFab fragment was detected in the culture supernatant. Western blot proved that the expressed protein could specifically bind with HAb18GEF antigen. CONCLUSION: The successful expression of cFab/HAb18 in Pichia pastoris lays the foundation for large-scale production and further application of the antibody.

Vascular cell adhesion molecule-1-targeted detection of endothelial activation in human microvasculature.

The hallmark of endothelial activation, an early and critical step in many alloimmune and inflammatory responses, is the transcriptional induction and expression of endothelial adhesion molecules (eg, vascular cell adhesion molecule-1 [VCAM-1]). We assessed the feasibility of VCAM-1-targeted in vivo detection of endothelial activation using I-125-labeled-F(ab')2 fragments of E1/6, a monoclonal antibody against human but not murine VCAM-1. The Kd and Bmax, determined by saturation binding in tumor necrosis factor (TNF)-activated human endothelial cells (ECs), were 3.2 +/- 0.6 nmol/L and 5600 +/- 300 binding sites per EC, respectively. Biodistribution and in vivo binding characteristics of I-125-E1/6 F(ab')2 were assessed in a novel chimeric human/mouse model, in which human skin (as a source of human microvasculature) is grafted onto SCID/beige mice. I-125-E1/6 F(ab')2 localized to TNF-activated human skin grafts as detected by autoradiography and gamma well-counting. Relative uptakes (uptake in human skin graft/uptake in the surrounding mouse skin) were, respectively, 2.6 +/- 0.8 (n = 14) and 1.6 +/- 0.3 (n = 12) for E1/6 and MOPC-21, an isotype-matched control antibody (P < .01). The preferential uptake in human skin graft was not due to differences in tissue vascularity assessed by Tc-99m-labeled murine red blood cells. In conclusion, the chimeric human/mouse model is a novel experimental tool for in vivo evaluation of human endothelial cell-specific radiopharmaceuticals. Although I-125-E1/6 F(ab')2 localized to human skin grafts, the limited number of VCAM-1 molecules/endothelial cell adversely affects its suitability as a target for in vivo imaging of endothelial activation.

Improved solid-phase microextraction device for use in on-line immunoaffinity capillary electrophoresis.

A simple solid-phase microextraction device was fabricated for use in on-line immunoaffinity capillary electrophoresis (CE). The device, designed in the form of a four-part cross-shaped or cruciform configuration, includes a large-bore tube to transport samples and washing buffers and a small-bore fused-silica capillary for separation of analytes. At the intersection of the transport and separation tubes, a small cavity was fabricated, termed the analyte concentrator-microreactor, which contains four porous walls or semipermeable membranes (one for each inlet and outlet of the tubes) permitting the confinement of beads or suitable microstructures. The surface of the beads in the analyte concentrator carried a molecular recognition adsorbing chemical or affinity ligand material. The improved cruciform configuration of the analyte concentrator-microreactor device, designed for use in on-line immunoaffinity CE, enables it to specifically trap, enrich, and elute an analyte from any biological fluid or tissue sample extract without any sample pretreatment except filtration, centrifugation, and/or dilution allowing the separation and characterization of target analyte(s) with improved speed, sensitivity, and lower cost than existing techniques. As a model system, Fab' fragments derived from a purified immunoglobulin G (IgG) antibody were covalently bound to controlled-porosity glass and used as constituents of the analyte-microreactor device. The high-specificity polyclonal antibodies employed in these experiments were individually raised against the acidic nonsteroidal anti-inflammatory drugs ibuprofen and naproxen, and the neuropeptides angiotensin II, and neurotensin. These compounds, which were present in simple and complex matrices were captured by and eluted from the analyte concentrator-microreactor using a 50 mM sodium tetraborate buffer solution, pH 9.0, followed by a 100 nL plug of 300 mM glycine buffer, pH 3.4. Two analyte concentrators were tested independently: one containing Fab' fragments derived from antibodies raised against ibuprofen and naproxen; the other containing Fab' fragments derived from antibodies raised against angiotensin II and neurotensin. Each resulting electropherogram demonstrated the presence of two eluted materials in less than 20 min. Immunoaffinity CE performed in a cruciform structure was simpler and faster than previously reported in the literature using on-line microextraction devices designed in a linear format. The new concentration-separation system operated consistently for many runs, maintaining reproducible migration times and peak areas for every analyte studied.

[Prokaryotic expression and bioactivity identification of Fab against human gamma-seminoprotein].

AIM: To construct the expression vector containing cDNA encoding Fab against human gamma-seminoprotein and express it in E. coli. METHODS: The genes encoding K chain and Fd against gamma-seminoprotein were acquired from pUC19-K and pBluescript KS( M13-)-Fd by restrictive enzyme digestion and then cloned into the expression vector pComb3 to construct recombinant expression vector pComb3-Fab. pComb3-Fab was transfected into and expressed in XLI-Blue. RESULTS: Fab against r-semino-protein was expressed in. XLI-Blue. Western blot analysis and immunocytochemical staining demonstrated that ex-pressed Fab could specifically bind to gamma-seminoprotein. CONCLUSION: Fab against gamma -seminoprotein has been expressed successfully with biological activity, which create favourable condition for further study on targeted therapy of prostate cancer.

Targeting of human breast cancer by a bispecific antibody directed against two tumour-associated antigens: ErbB-2 and carcinoembryonic antigen.

Carcinoembryonic antigen (CEA) and ErbB-2 are expressed in about 50 and 30% of breast cancers, respectively. We hypothesised that targeting of these two antigens by a bispecific antibody (BAb) might provide efficient tumour uptake and prolonged tumour residence time. In the present study, we first studied the expression of CEA and ErbB-2 on primary breast tumours screened by immunohistochemistry. Of 106 primary breast cancers, 69 (65%) were positive for CEA, 20 (19%) were positive for ErbB-2, and 13 (12%) expressed both antigens. We then prepared and evaluated a BAb directed against CEA and ErbB-2. Using BIACORE technology, we showed that the BAb recognised both CEA and ErbB-2 with affinities of 0.9 x 10 and 0.8 x 10 M(-1), respectively. In vivo, BAb tumour localisation was compared with that of its parental homodimeric F(ab')(2)-ORTHO-phenylene- dimaleimide (PDM) fragments. Uptake of (125)I-BAb was lower than that of (131)I-35A7F(ab')(2)-PDM in LS174T tumours, used as a model of CEA expressing tumours, and was similar to that of (131)I-FWP51 F(ab')(2)-PDM in SKOv3 tumours, used as a model of ErbB-2 expressing tumours. In a double-positive model, the SKOv3-CEA-1B9 tumour, BAb showed a similar uptake to that of 35A7 F(ab')(2)-PDM and we demonstrated that, although BAb had double specificity, it internalised as a homodimeric anti-ErbB-2 antibody. BAb showed a greater uptake than that of FWP51 F(ab')(2)-PDM and this difference was even more important 72 h after injection with an uptake of 7.3 +/- 2.1 vs. 1.4 +/- 0.5% of the injected dose per gram of tissue. The results obtained with the BAb in the double-positive tumour-bearing nude mice suggest that targeting two distinct tumour-associated antigens on the same cell could improve tumour localisation.