Single chain antibody fragment (scFv) is a small molecule composed of a variable region of heavy chain (VH) and a variable region of light chain (VL) of an antibody, and these two chains are connected by a flexible short peptide. scFv is the smallest functional fragment with complete antigen-binding activity, which contains both the antibody-recognizing site and the antigen-binding site. Compared with other antibodies, scFv has the advantages of small molecular weight, strong penetration, low immunogenicity, and easy expression. Currently, the most commonly used display systems for scFv mainly include the phage display system, ribosome display system, mRNA display system, yeast cell surface display system and mammalian cell display system. In recent years, with the development of scFv in the field of medicine, biology, and food safety, they have also attracted much attention in the sectors of biosynthesis and applied research. This review summarizes the advances of scFv display systems in recent years in order to facilitate scFv screening and application.
Animals ; Immunoglobulin Variable Region/genetics* ; Immunoglobulin Fragments/metabolism* ; Single-Chain Antibodies/metabolism* ; Peptide Library ; Mammals/genetics*

Macrolide and corticosteroid resistance has been reported in patients with Mycoplasma pneumoniae (MP) pneumonia (MPP). MP clearance is difficult to achieve through antibiotic treatment in sensitive patients with severe MPP (SMPP). SMPP in children might progress to airway remodeling and even bronchiolitis/bronchitis obliterans. Therefore, identifying serum biomarkers that indicate MPP progression and exploring new targeted drugs for SMPP treatment require urgency. In this study, serum samples were collected from patients with general MPP (GMPP) and SMPP to conduct proteomics profiling. The Fc fragment of the IgG-binding protein (FCGBP) was identified as the most promising indicator of SMPP. Biological enrichment analysis indicated uncontrolled inflammation in SMPP. ELISA results proved that the FCGBP level in patients with SMPP was substantially higher than that in patients with GMPP. Furthermore, the FCGBP levels showed a decreasing trend in patients with GMPP but the opposite trend in patients with SMPP during disease progression. Connectivity map analyses identified 25 possible targeted drugs for SMPP treatment. Among them, a mechanistic target of rapamycin kinase (mTOR) inhibitor, which is a macrolide compound and a cell proliferation inhibitor, was the most promising candidate for targeting SMPP. To our knowledge, this study was the first proteomics-based characterization of patients with SMPP and GMPP.
Biomarkers ; Carrier Proteins ; Child ; Humans ; Immunoglobulin Fc Fragments ; Immunoglobulin G ; Macrolides ; Mycoplasma pneumoniae ; Pneumonia, Mycoplasma/drug therapy* ; Proteomics

Entero virus 71 (EV71) causes hand, foot, and mouth disease (HFMD) and occasionally leads to severe neurological complications and even death. Scavenger receptor class B member 2 (SCARB2) is a functional receptor for EV71, that mediates viral attachment, internalization, and uncoating. However, the exact binding site of EV71 on SCARB2 is unknown. In this study, we generated a monoclonal antibody (mAb) that binds to human but not mouse SCARB2. It is named JL2, and it can effectively inhibit EV71 infection of target cells. Using a set of chimeras of human and mouse SCARB2, we identified that the region containing residues 77-113 of human SCARB2 contributes significantly to JL2 binding. The structure of the SCARB2-JL2 complex revealed that JL2 binds to the apical region of SCARB2 involving α-helices 2, 5, and 14. Our results provide new insights into the potential binding sites for EV71 on SCARB2 and the molecular mechanism of EV71 entry.
Amino Acid Sequence ; Animals ; Antibodies, Monoclonal ; chemistry ; genetics ; metabolism ; Binding Sites ; Cell Line ; Crystallography, X-Ray ; Enterovirus A, Human ; drug effects ; genetics ; growth & development ; immunology ; Fibroblasts ; drug effects ; virology ; Gene Expression ; HEK293 Cells ; Humans ; Immunoglobulin Fab Fragments ; chemistry ; genetics ; metabolism ; Lysosome-Associated Membrane Glycoproteins ; chemistry ; genetics ; immunology ; Mice ; Models, Molecular ; Protein Binding ; Protein Conformation, alpha-Helical ; Protein Conformation, beta-Strand ; Protein Interaction Domains and Motifs ; Receptors, Scavenger ; chemistry ; genetics ; immunology ; Receptors, Virus ; chemistry ; genetics ; immunology ; Recombinant Fusion Proteins ; chemistry ; genetics ; immunology ; Sequence Alignment ; Sequence Homology, Amino Acid ; Sf9 Cells ; Spodoptera ; Thermodynamics

Systemic light chain amyloidosis (AL amyloidosis) is the most common type of amyloidosis, in which deposition of misfolded monoclonal light chain secreted by underlying clonal plasma cells leads to organ dysfunction. Tissue biopsy of involved organ is needed to confirm the type of amyloid deposits, thus proper treatment could be applied. Laser microdissection followed by mass spectrometry, performed on formalin-fixed paraffin-embedded specimens, has been proven superior to traditional methods on accurate diagnosis of amyloidosis. Prognosis depends on the extent of cardiac involvement. The Mayo staging system using NT-ProBNP, cardiac troponin-T and free light chain, is the most robust method for risk stratification and treatment guidance. The introduction of autologous stem cell transplantation (auto-ASCT) resulted in long-term survival in responders, while treatment-related toxicity substantially limited the number of eligible candidates. Novel agents, especially bortezomib, thalidomide and lenalidomide hold promise to achieve comparable hematological responses with auto-ASCT, which might play significant role in treatment of recurrent or refractory AL amyloidosis.
Amyloidosis ; Bortezomib ; Hematopoietic Stem Cell Transplantation ; Humans ; Immunoglobulin Light Chains ; Immunoglobulin Light-chain Amyloidosis ; Natriuretic Peptide, Brain ; Peptide Fragments ; Prognosis

OBJECTIVETo prepare polyclonal antibodies against sodium pump alpha 2 subunit M1-M2 extramembrane fragment (NKAα2 EM1) for studying the pathogenesis of hypertension.

METHODSAccording to the GenBank data, the amino acid sequence of NKAα2 EM1 was obtained and the target peptide (LAAMEDEPSNDN) was synthesized using a peptide synthesizer with Fmoc method and purified with high-performance liquid chromatography. The synthesized peptide was then coupled to KLH for immunizing New Zealand white rabbits for 4 times to obtain the antiserum. The IgG antibodies against the synthetic peptide, after affinity purification with Protein A, were used for detecting NKAα2 EM1 expression in rat aortic vascular smooth muscle cells by enzyme-linked immunosorbent assay and immunocytochemistry (ICC).

RESULTSThe synthesized peptide fragment , which consisted of 13 amino acid residues including one derivatized cysteine residue in the N-terminal (LAAMEDEPSNDN-C), had a theoretical relative molecular mass of 1408.48 D with a measured relative molecular mass of 1407.90 D and a purity exceeding 85.5%. The titer of the antiserum was more than 1:512 000, and the purified IgG antibody concentration was 0.965 mg/ml after purification with Protein A. At a 1:1000 dilution (final concentration of 1 µg/ml), the titer of the purified IgG antibody was more than 1:256 000. The purified IgG antibody could be used at 1:100 to 1:200 dilutions for for immunocytological examination of formalin-fixed cells.

CONCLUSIONThe anti-NKAα2 EM1 polyclonal antibodies obtained can be used in ELISA and immunocytochemistry for detecting the sodium pump alpha 2 subunit in formalin-fixed tissue or cells to facilitate investigation of the relationship between sodium pump and hypertension.

Amino Acid Sequence ; Animals ; Antibodies ; Chromatography, Affinity ; Enzyme-Linked Immunosorbent Assay ; Hypertension ; Immune Sera ; Immunoglobulin G ; Immunohistochemistry ; Peptide Fragments ; Rabbits ; Rats ; Sodium-Potassium-Exchanging ATPase ; immunology

To obtain human antibodies against the Gn protein of Severe fever with thrombocytopenia syndrome virus (SFTSV) with phage display technology, this study aimed to screen anti-Gn protein antibodies from an anti-SFTSV Fab human phage display library. Antibody genes were identified by sequence analysis and the specificity of antibodies was confirmed by ELISA. The Fab antibody genes were cloned into the HL51-14 vector and expressed in a mammalian cell expression system. IgG antibodies were then purified by protein A affinity chromatography,and the results were further confirmed by ELISA,IFA,western blotting assays and micro-neutralization tests. The results showed that, after three rounds of panning, there were 390 human Fab antibodies against SFTSV particles, of which 364 were specific for nucleoprotein. Coated with the Gn protein, eight different Fab antibodies specific for Gn protein were obtained after the determination of the subtype and subclass of antibodies by gene sequencing; five of these antibodies were from the Lambda library and three were from the Kappa library. The eight IgG antibodies could specifically bind to Gn protein according to the ELISA, IFA and Western blotting assays. The micro-neutralization test showed that these eight antibodies had no neutralizing activity,but they could still provide a reference for research in human monoclonal antibodies against SFTSV.
Antibodies ; genetics ; immunology ; Bunyaviridae Infections ; genetics ; immunology ; virology ; Cell Line ; Cloning, Molecular ; Humans ; Immunoglobulin Fab Fragments ; genetics ; immunology ; Immunoglobulin G ; genetics ; immunology ; Neutralization Tests ; Phlebovirus ; genetics ; immunology ; Viral Proteins ; genetics ; immunology

BACKGROUNDMonoclonal antibodies (mAbs) such as DD3, raised against progastrin-releasing peptide(31-98) (ProGRP (31-98)) antigen, have been used to target small cell lung cancer (SCLC). However, as an intact mAb, DD3 is cleared slowly from the body, with an optimal radioimmunoimaging time of 72 hours. More recently, a single-chain antibody fragment has demonstrated reduced excretion time in blood and normal tissues and is increasingly used in diagnostic cancer research. Thereby, it potentially increases the radioimmunoimaging efficacy. However, there have been few studies with this antibody fragment. The aim of this study was to characterize the preliminary radioimmunoimaging and biodistribution of (131)I-anti-ProGRP(31-98) scFv in nude mice bearing SCLC xenografts.

METHODSAnti-ProGRP(31-98) scFv was used to detect ProGRP expression by flow cytometry analysis and immunohistochemistry. (131)I-anti-ProGRP(31-98) scFv was injected intravenously into healthy Kunming mice and the percentage injected dose per gram (%ID/g) in various organs was calculated. Similarly, the %ID/g and tumor/non-tumor ratio in xenograft-bearing mice was calculated. After injection of (131)I-anti-ProGRP(31-98) scFv, treated mice were imaged at 1, 24, and 30 hours. Then the tumor/base ratios were calculated.

RESULTSProGRP was highly expressed in NCI-H446 cells and xenograft tissue. The metabolism of (131)I-anti-ProGRP(31-98) scFv in healthy mice was consistent with a first-order and two-compartment model; T1/2α and T1/2β were 10.2 minutes and 5 hours 18 minutes, respectively. The %ID/g of (131)I-anti-ProGRP(31-98) scFv in xenografts was much higher than in healthy tissues at 12 hours after injection, reaching a maximum of (5.38±0.92) %ID/g at 24 hours. Successful imaging of xenograft tissue was achieved as early as 1 hour post-injection and persisted until 30 hours, with 24 hours proving optimal.

CONCLUSION(131)I-anti-ProGRP(31-98) scFv shows highly selective tumor uptake with low accumulation in normal tissues and rapid blood clearance, indicating that it could be a promising agent for SCLC radioimmunoimaging.

Animals ; Female ; Flow Cytometry ; Humans ; Immunoglobulin Fragments ; immunology ; Male ; Mice ; Mice, Inbred BALB C ; Mice, Nude ; Peptide Fragments ; immunology ; Radioimmunodetection ; methods ; Recombinant Proteins ; immunology ; Small Cell Lung Carcinoma ; diagnostic imaging ; metabolism ; Xenograft Model Antitumor Assays

PURPOSE: We aimed to investigate whether combination therapy using intracoronary (IC) abciximab and aspiration thrombectomy (AT) enhances myocardial perfusion compared to each treatment alone in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). MATERIALS AND METHODS: We enrolled 40 patients with STEMI, who presented within 6 h of symptom onset and had Thrombolysis in MI flow 0/1 or a large angiographic thrombus burden (grade 3/4). Patients were randomly divided into 3 groups: 10 patients who received a bolus of IC abciximab (0.25 mg/kg); 10 patients who received only AT; and 20 patients who received both treatments. The index of microcirculatory resistance (IMR) was measured with a pressure sensor/thermistor-tipped guidewire following successful PCI. Microvascular obstruction (MVO) was assessed using cardiac magnetic resonance imaging on day 5. RESULTS: IMR was lower in the combination group than in the IC abciximab group (23.5+/-7.4 U vs. 66.9+/-48.7 U, p=0.001) and tended to be lower than in the AT group, with barely missed significance (23.5+/-7.4 U vs. 37.2+/-26.1 U, p=0.07). MVO was observed less frequently in the combination group than in the IC abciximab group (18.8% vs. 88.9%, p=0.002) and tended to occur less frequently than in the AT group (18.8% vs. 66.7%, p=0.054). No difference of IMR and MVO was found between the IC abciximab and the AT group (66.9+/-48.7 U vs. 37.2+/-26.1 U, p=0.451 for IMR; 88.9% vs. 66.7%, p=0.525 for MVO, respectively). CONCLUSION: Combination treatment using IC abciximab and AT may synergistically improve myocardial perfusion in patients with STEMI undergoing primary PCI (Trial Registration: clinicaltrials. gov Identifier: NCT01404507).
Adolescent ; Adult ; Aged ; Angioplasty, Balloon, Coronary/*methods ; Antibodies, Monoclonal/*therapeutic use ; Female ; Humans ; Immunoglobulin Fab Fragments/*therapeutic use ; Male ; Middle Aged ; Myocardial Infarction/*drug therapy/*surgery ; Thrombectomy/*methods ; Young Adult

BACKGROUND AND OBJECTIVES: We investigated the effect of the additional use of abciximab during percutaneous coronary intervention (PCI) on the level of procoagulant microparticles (MPs) in patients with ST-segment elevation myocardial infarction (STEMI) who had undergone primary PCI. SUBJECTS AND METHODS: In this study, we studied 86 patients with STEMI (72 men, age 58+/-13) who had undergone primary PCI. The decision to administer abciximab immediately prior to PCI was left to the discretion of the operator. Blood samples for analysis of MPs were obtained from the femoral artery before and after PCI. MPs with procoagulant potential were measured using a commercial kit. The cellular origins of MPs were determined by antigenic capture with specific antibodies. RESULTS: Procoagulant MPs captured onto annexin V were not changed significantly after PCI {13.4+/-13.2 nM vs. 13.2+/-16.1 nM phosphatidylserine equivalent (PS eq), p=0.479}. Abciximab was used in 30 of 86 patients (35%) immediately prior to PCI. In patients who had undergone PCI without abciximab, no significant change in the level of MPs was observed after PCI. However, in the abciximab group, the level of circulating MPs was significantly decreased after PCI (12.0+/-10.7 nM vs. 7.8+/-11.7 nM PS eq, p=0.018). Levels of endothelial- and platelet-derived MPs also showed a significant reduction after PCI in the abciximab group. CONCLUSION: Primary PCI with additional abciximab significantly reduced the level of procoagulant MPs regardless of their cellular origins in patients with STEMI.
Angioplasty ; Annexin A5 ; Antibodies, Monoclonal ; Cell-Derived Microparticles ; Femoral Artery ; Humans ; Immunoglobulin Fab Fragments ; Male ; Myocardial Infarction ; Percutaneous Coronary Intervention ; Platelet Aggregation Inhibitors

To identify human monoclonal HIV-l-neutralizing antibodies from an HIV-1 CRF07BC specific phage display antibody library by cell-based screening. 293T cells were transfected by pCH064. 2-Env plas mid and then used to biopan the phage antibody library. The positive phage clones were screened by cell based ELISA and sequenced for the variable region of heavy (VH) and light (VL) chains. The expressed Fabs were purified by Ni(+2) -NTA column and analyzed by SDS-PAGE. The cell- and gp120 protein-based ELISA as well as flow cytometry were used to measure Fab's binding activity. The neutralizing activity of Fabs was assessed by HIV-1 pseudoviruses. After 4-round biopanning, the binding phages to transfected cells were enriched about 650-folds. A total of 28 positive clones were screened out by cell ELISA and sequence analysis identified 5 different Fabs possessing unique VH and VL (2801, 2837, 2863, 2870 and 2920). Interestingly, these Fabs reacted with the Env-transfected 293T cells but not soluble gp120 proteins, suggesting that they might target conformation-dependent epitopes presenting on viral Env complex. We found that three Fabs (2801, 2863, 2870) exhibited potent neutralizing activity against CRF07_BC isolate CH120. 6 with IC50 of 2.24, 0.89 and 3.09 microg/mL respectively, and that 2801 and 2863 cross-neutral ized the subtype B isolate SF162 at IC50 of 0.69 and 3.52 microg/mL respectively. In conclusion, the HIV-1 Env-transfected 293T cells can be used to efficiently enrich and screen the phage antibody library and isolate human monoclonal HIV-1-neutralizing Fabs that target the Env complex-dependent conformational epitopes. Therefore, our studies provide a powerful platform for exploring the mechanism of HIV-1 neu tralizing response and for designing AIDS vaccines.
Antibodies, Monoclonal ; genetics ; immunology ; Antibodies, Neutralizing ; genetics ; immunology ; Enzyme-Linked Immunosorbent Assay ; methods ; HEK293 Cells ; HIV Antibodies ; genetics ; immunology ; HIV Envelope Protein gp120 ; genetics ; immunology ; HIV Infections ; immunology ; virology ; HIV-1 ; genetics ; immunology ; isolation & purification ; Humans ; Immunoglobulin Fab Fragments ; genetics ; immunology ; Neutralization Tests ; Peptide Library ; Transfection