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Objective:To establish an in vivo infection model of H5N1 pseudovirus and to detect the neutralizing activity of FHA3 antibody using this model. Methods:Based on the sequence information of hemagglutinin (HA) and neuraminidase (NA) of A/Anhui/1/2005/H5N1 strain, two recombinant plasmids of pcDNA3.1-HA5 and pcDNA3.1-NA1 were constructed. The two plasmids and plasmid pNL4-3.Luc.R-E- were co-transfected into 293T cells to prepare H5N1 pseudovirus supernatant. The morphology of pseudovirus particles in the supernatant was observed by electron microscopy. MDCK cells were infected with the pseudovirus supernatant and the virus titer was detected. BALB/c mice were injected with the pseudovirus supernatant by intraperitoneal injection and subjected to bioluminescence imaging at 2, 5, 8, and 12 d after infection to detect the pseudovirus infection in vivo. The functional activity of FHA3 antibody in vivo was evaluated using the established mouse infection model. Results:The recombinant plasmids pcDNA3.1-HA5 and pcDNA3.1-NA1 were correctly constructed and could be used to prepare pseudovirus supernatants of high titer by co-transfecting 293T cells with the plasmid pNL4-3.Luc.R-E-. The virus particles were round under electron microscope. H5N1 pseudovirus-infected mice exhibits strong fluorescence signals, which were attenuated by FHA3 treatment before challenge.Conclusions:The in vivo infection model of H5N1 pseudovirus was successfully constructed and FHA3 antibody was proved to be protective against the pseudovirus infection.
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Objective:To prepare and identify a functional antibody FNA1 targeting the neuraminidase (NA) of influenza A virus N1 subtype.Methods:According to single-chain antibody fragment (scFv) sequence, the heavy chain and light chain variable region sequences of FNA1 were synthesized, and the recombinant expression plasmid pFRT-IgG1κ-FNA1 was constructed by linking the expression vector pFRT-IgG1κ. The FNA1 antibody was expressed in ExpiCHO cells and purified using affinity purification technique. The binding ability of FNA1 to the target proteins, influenza A virus N1 subtype NA antigens, was detected by ELISA. Flow cytometry was performed to analyze the binding ability of FNA1 to the NA antigens expressed on the surface of cell membrane. The in vitro activity of FNA1 against NA was evaluated by infecting 293T cells with pseudovirus. Results:Protein electrophoresis showed that FNA1 with high purity was obtained. FNA1 specifically recognized and bound to N1 subtype NA antigens in a concentration-dependent manner. FNA1 could effectively block NA activity by binding to N1 subtype NA protein expressed on the surface of cell membrane, thus inhibiting the release of packaged pseudovirus from cell surface and further inhibiting target cell infection.Conclusions:An antibody FNA1 targeting influenza A virus N1 subtype NA with in vitro functional activity was obtained.
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Objective:To prepare and identify a broad-spectrum antibody FHA3 targeting influenza A virus hemagglutinin (HA).Methods:According to the single-chain antibody fragment (scFv) sequence, the heavy chain (VH) and light chain (VL) variable regions of FHA3 were amplified by PCR and a recombinant plasmid pFRT-IgG1κ-FHA3 was constructed by linking the expression vector pFRT-IgG1κ. FHA3 was expressed in the ExpiCHO system and purified by affinity purification. The binding activity of FHA3 to influenza A virus HA was detected by ELISA. The neutralizing activity of FHA3 was detected in vitro by infecting host cells with pseudovirus. Results:SDS-PAGE showed that high-purity FHA3 was obtained. FHA3 could bind to H1N1 HA, H2N2 HA, H3N2 HA, H5N1 HA, H7N9 HA and H9N2 HA in a concentration-dependent manner. FHA3 had good neutralizing activity in vitro that was it could effectively block the invasion of H5N1 and H7N9 pseudoviruses into target cells at a low concentration of 5 μg/ml and H1N1 pseudovirus at 0.012 5 μg/ml. Conclusions:A broad spectrum antibody targeting HA protein of influenza A virus with neutralizing activity in vitro was obtained.
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Camelidae possess a special type of antibody,namely heavy-chain antibody. It consists of a homodimer comprising three domains:CH2,CH3 and one variable region of heavy chain(VH),but CH1 and light chain are absent. The VH of heavy-chain an-tibody is named nanobody. Compared to the traditional antibody,nanobody has many advantages. For example it has small molecular weight,better stability and can cross blood brain barrier(BBB). More and more application of nanobodies have been reported in scien-tific fields,such as biological detection,diagnosis,and pharmacy. In this paper we review structural characteristics and physicochemi-cal properties of nanobodies,and investigate their development in biomedicine researches as well.
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Objective To ascertain whether estrogen could induce B cell to produce interleukin(IL)-10. Methods C57BL/6 splenic B cells were purified by magnetic activated cell sorting(MACS)method,followed by estrogen treatment for 3 days. The secretion of IL-10 from cultured cell supernatant was tested by ELISA technique. The abundance of mRNA for IL-10、PD-L1 and RBM47 in B cells with estrogen treatment was tested by real-time PCR method. The intracellular IL-10 expression and the surface PD-L1 expression of treated B cells were tested by fluorescence activated cell sorting(FACS)method. And the expression of RBM47 in B cells by estrogen treatment was tested using Western blotting method. Results Estrogen could induce B cell to produce IL-10 in a dose-dependent manner. Estrogen treatment could increase the percentage of IL-10+B cells,the abundance of mRNA for IL-10,PD-L1 and RBM47 in B cells,as well as the expression of PD-L1 on B cell surface. Furthermore,our experimental result indicated the upreg?ulation of RBM47 expression in B cells by estrogen treatment. Conclusion Estrogen treatment in vitro can induce the upregulation of IL-10+regulatory B cells(Breg). Upregulation of RBM47 in the treated B cells might participate in this process by stabilizing IL-10 mRNA.
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Objective To examine whether Tim-3 plays a protective role in paraquat poisoning induced excessive immune response and tissue damage based on the critical roles of Tim-3 controlling inflammatory response.Methods A paraquat poisoning model was established in wild type and in Tim-3 transgenic C57BL/6 mice by intraperitoneal injection of paraquat (40 mg/kg) .In addition, C57BL/6 mice with paraquat poisoning were injected with Tim-3 soluble protein( sTim-3) or control protein to see the effect of Tim-3 blocking on the progression of paraquat poisoning.Samples were collected at 6 and 24 h after paraquat injection respectively and were examined for tissue damage, cytokine expression and paraquat metabolism.Results After paraquat poisoning, there was significantly attenuated tissue damage in the lungs and kidneys and decreased TNF-α,IL-6 and IL-1 beta expression in the PBMCs or in the serum from Tim-3 transgenic mice compared to wild type mice.The serum concentration of paraquat in Tim-3 transgenic mice was also significantly decreased.However, in sTim-3 treated paraquat poisoning mice, there was significantly increased cytokine expression and tissue damage compared to control protein treated mice.The in vitro data showed that Tim-3 signaling negatively regulated macrophages mediated inflammatory response.Conclusion Tim-3 plays a critical role in maintaining the homeostasis after paraquat poisoning. Further investigation on the regulatory roles of Tim-3 in inflammation will shed new light on the pathogenesis of paraquat poisoning and provide new therapeutic strategies.
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Objective To study the intrinsic relationships between the binding energy of the antibody light and heavy chains and the conformational characteristics , physical and chemical properties , and to establish a corresponding mathemat-ical model and evaluate the thermal stability of the antibody molecules , which contribute to the antibody design , optimiza-tion and affinity maturation .Methods Based on bioinformatics and computational biology methods , the antibody′s structur-al information with the crystal diffraction data was analyzed .The conformational character of the variable domain of the antibody was studied using distance geometry and computer graphics technology .With the aid of the intermolecular hydrogen bond formation theory and the reaction free energy theory , the dynamic structure and energy characteristics be-tween the heavy and light chain variable regions of the antibody were studied .Furthermore , using nonlinear fitting and regression analysis, a mathematical model was set up .Results According to simulation and statistic analysis , there was a linear relationship between the binding energy and the number of the intermolecular hydrogen bonding , Van der Waals interaction of the heavy and light chains of the antibody .There was polynomial correlation between the binding energy and the physicochemical properties of the antibody .Using the frequency of amino acid position and the established model , the humanized anti-ricin antibody , which could not obtain the stable engineering cell line , was evaluated and optimized .The stable engineering cell line of the humanized anti-ricin antibody was obtained in the experiment .Conclusion The self structure of the antibody variable region ( conformation and physicochemical properties ) has much effect on its stability . The antibody stability can be improved by structural optimization .
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Objective To develop a human Tim-3 specific monoclonal antibody and evaluate its biological activity and possible use in clinical diseases associated with dysregulated Tim-3 expression .Methods The BALB/c mice were immu-nized by conventional method, and positive clones were used to develop anti-human Tim-3 antibody, the binding and neutralization activities of which in vitro and in vivo were investigated.Results ①A monoclonal antibody (clone L3D) which could specifically bind to human Tim-3 protein in ELISA assay was obtained and the subtype of the monoclonal antibody was IgG2a .②Flow cytometry indicated that the monoclonal antibody could bind to Tim-3 expressed in human U937 cells.This antibody also showed a cross activity to mice′Tim-3.③The monoclonal antibody inhibited the apoptosis of THP1 cells induced by Gal-9, the ligand of Tim-3.④Injection of Tim-3 antibody exacerbated sepsis in mice as marked by the decreased survival rate and increased expression of pro-inflammatory cytokines .Conclusion An anti-human Tim-3 monoclonal antibody is successfully obtained.The excellent binding and neutralization activities of this antibody enable it to be widely used in clinical diseases associated with deregulated Tim-3 expression .
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B cell maturation antigen (BCMA) is a receptor of B lymphocyte stimulator (BLyS). Human IgG1Fc fusion proteins with the extracellular domain of BCMA(eBCMA), also called decoy receptors, have beenused as a potential BLyS antagonists to block BLyS activities. In order to design novel BLyS antagonistpeptides, computer-aided homologue modeling was used to construct an eBCMA-Fc fusion protein based on thecrystal structures of BCMA and Fc fragmant. To ensure the activity of eBCMA not to be interfered by Fcfusion, the root mean square distance (RMSD) for eBCMA and Fc were calculated to be 0.036 nm and 0.064nm, respectively, based on molecular docking modeling. An eBCMA-Fc fusion gene was constructed andintroduced into E. coli for expression. As expected, the purified 36 kD eBCMA-Fc fusion protein was able tobind BLyS in vitro at a dosage-dependent manner and demonstrated an anti-proliferative activity induced byBLyS in Daudi cells. The results have provided useful information on the evaluation of computer modeling andthe in vitro biological activity for the design of potential BLyS antagonist peptides.
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Objective To design and express a novel peptide based on ricin toxin antibody in E. coli, and to evaluate its biological activity. Methods Based on the crystal structure of ricin toxin A chain (RTA) and the RTA-rRNA interact in the complex model, the steric conformation of RTA was theoretical modeled and its functional domain was preliminarily determined. The humanized single-domain RTA antibody was designed rationally by computer-guidod molecular design method. Its coding sequence was ob- tained by overlapping extension PCR, and cloned into the pET-32a vector. The fusion protein was then ex-pressed in E. coli BL21 (DE3), identified by Western blot, and purified with Ni-NTA agarose. The binding and neutralizing activity of this novel peptide for riein was evaluated by competitive ELlSA assay and MTT assay. Results A recombinant human single-domain antibody expressing a polypeptide against RTA in the CDR3 loop was designed. The fusion protein was successfully expressed in E. coll. The purified protein can bind to ricin, and neutralize its activity in SP2/0 viability assay. Conclusion The success of the novel pep-tide based on riein toxin antibody provides a novel method to develop new generation of ricin antagonists.
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Objective To establish a stable cell line secreting human IgE Cε2-4 protein, and in-vestigate the binding capacity of receptor FcεR Ⅰ Methods The E24 gene was derived from SKO-O07 cell line, and was then cloned into pcDNA3.1 (+) (signal peptides were synthesized and fused at the 5'-end of E24 gene) or pCMV-L vector. After transient transfection into 293T cell, the secreted F24 protein was ana-lyzed by sandwich ELISA. The best vector was chosen to be transfected into CHO cells with LipofectAMI-NETM 2000 reagent. After being selected by G418 and subcloned three times by limited-dilution method, two stable cell lines were established. E24 gene was amplified by RT-PCR, and the E24 protein in the superna-tant was identified by ELISA. Besides, the binding capacity of FceR ⅠⅡ was analyzed by flow cytometry method. Results Three mammalian expression vector SP-E24-F3. 1, SP lI-E24-P3.1 and E24-PL were constructed and transient transfected to 293T cells. The output of E24 protein in the supernatant were 19.1, 19.4 and 8.7 μg/ml, respectively. Then the vector SP IX-E24-P3.1 was transfected into CHO cells. Final-ly, two single clones secreting E24 protein were stably obtained. The output of E24 were all at least 25 μg/ml. RT-PCR could detect the E24 gene from one of the two clones. Furthermore, flow cytometry results showed that E24 could bind the receptor in a dose-dependent manner. Conclusion Two stable cell line se- creting E24 protein were obtained, while E24 could specifically bind FcεR Ⅰ.
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A three-dimensional (3D) graphic model of a single-chain Fv (scFv) which was derived from an anti-human placental acidic isoferritin (PAF) monoclonal antibody (Mab) was constructed by a homologous protein-predicting computer algorithm on Silicon graphic computer station.The structure, surface static electricity and hydrophobicity of scFv were investigated. Computer graphic modelling indicated that all regions of scFv including the linker, variable regions of the heavy (VH) and light (VL) chains were suitable. The VH region and the VL region were involved in composing the "hydrophobic pocket". The linker was drifted away VH and VL regions. The complementarity determining regions (CDRs) of VH and VL regions surrounded the "hydrophobic pocket". This study provides a theory basis for improving antibody affinity, investigating antibody structure and analyzing the functions of VH and VL regions in antibody activity.
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A three-dimensional (3D) graphic model of a single-chain Fv (scFv) which was derived from an anti-human placental acidic isoferritin (PAF) monoclonal antibody (Mab) was constructed by a homologous protein-predicting computer algorithm on Silicon graphic computer station.The structure, surface static electricity and hydrophobicity of scFv were investigated. Computer graphic modelling indicated that all regions of scFv including the linker, variable regions of the heavy (VH) and light (VL) chains were suitable. The VH region and the VL region were involved in composing the "hydrophobic pocket". The linker was drifted away VH and VL regions. The complementarity determining regions (CDRs) of VH and VL regions surrounded the "hydrophobic pocket". This study provides a theory basis for improving antibody affinity, investigating antibody structure and analyzing the functions of VH and VL regions in antibody activity.