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The variable domain of heavy-chain antibody (VHH) has been developed widely in drug therapy, diagnosis, and research. Escherichia coli is the most popular expression system for VHH production, whereas low bioactivity occurs sometimes. Mammalian cells are one of the most ideal hosts for VHH expression at present. To improve the yield of VHH in Expi293F cells, we optimized the signal peptide (SP) and codons of VHH. Firstly, the fusion protein VHH1-Fc was used to screen SPs. The SP IFN-α2 showed the highest secretion as quantified by enzyme-linked immunosorbent assay (ELISA). Subsequently, codon optimization by improving GC3 and GC content doubled the yield of VHH1 and kept its binding activity to Senecavirus A (SVA). Finally, the mean yields of other 5 VHHs that fused with SP IFN-α2 and codon-optimized were over 191.6 mg/L, and these VHHs had high recovery and high purity in the culture supernatant. This study confirms that SP IFN-α2 and codon optimization could produce VHHs in Expi293F cells efficiently, which provides a reference for the large-scale production of VHHs.

Objective: To domesticate adherent Chinese hamster ovary (CHO) cells into suspension CHO cells (CHO-S) cultured in serum-free medium,and evaluate the application of the CHO-S cells in antibody expression., Methods: Adherent CHO cells were domesticated into CHO-S cells through suspension culture and gradually decreasing the serum concentration, and eventually the cells were cultured in serum-free medium. Based on the anti-prostate-specific membrane antigen ( PSMA) single chain antibody fragment ( Sc Fv) gene sequence obtained from a phage display library, the genes of heavy and light chains were designed, synthesized and cloned into the pc DNA3. 1 vector,and the products were named pc DNA3. 1-HC and pc DNA3. 1-LC respectively. The plasmids were transiently transfected at the ratio of light and heavy chain 3 ∶ 1 into CHO-S cells using Free Style MAX transfection reagent, and the supernatants were harvested at day 7 after transfection. SDS-PAGE and Western blotting were used to detect the antibody expression,and flow cytometry was applied to evaluate its binding activity to PSMA positive cells., Results: The adherent CHO cells were successfully domesticated into CHO-S cells. Expression plasmids for anti-PSMA antibody heavy chain and light chain were successfully constructed,and anti-PSMA antibody could be secretively expressed in CHO-S cells. Flow cytometry showed that the expressed antibody could specifically bind to PSMA positive cells., Conclusion: CHO-S cel s were successful y domesticated from adherent CHO cells, and could be used for antibody expression. This study provided a useful tool for further antibody expression, purification and function study.

The Ebola virus is highly infectious and can result in death in ≤ 90% of infected subjects. Detection of the Ebola virus and diagnosis of infection are extremely important for epidemic control. Presently, Chinese laboratories detect the nucleic acids of the Ebola virus by real-time reverse transcription-polymerase chain reaction (RT-PCR). However, such detection takes a relatively long time and necessitates skilled personnel and expensive equipment. Enzyme-linked immunosorbent assay (ELISA) of serum is simple, easy to operate, and can be used to ascertain if a patient is infected with the Ebola virus as well as the degree of infection. Hence, ELISA can be used in epidemiological investigations and is a strong complement to detection of nucleic acids. Cases of Ebola hemorrhagic fever have not been documented in China, so quality-control material for positive serology is needed. Construction and expression of human-mouse chimeric antibodies against the nucleoprotein of the Ebola virus was carried out. Genes encoding variable heavy (VH) and variable light (VL) chains were extracted and amplified from murine hybridoma cells. Genes encoding the VH and VL chains of monoclonal antibodies were amplified by RT-PCR. According to sequence analyses, a primer was designed to amplify functional sequences relative to VH and VL chain. The eukaryotic expression vector HL51-14 carrying some human antibody heavy chain- and light chain-constant regions was used. IgG antibodies were obtained by transient transfection of 293T cells. Subsequently, immunological detection and immunological identification were identified by ELISA, immunofluorescence assay, and western blotting. These results showed that we constructed and purified two human- mouse chimeric antibodies.

To rapidly select potent anti-VSTM1-v2 scFv (single-chain antibody fragment) by construction and screening of a humanized scFv library in which a murine VH-CDR3 library was grafted onto a human scFv framework. A murine VH-CDR3 library was amplified from anti-VSTM1-v2 murine cDNA and grafted on human scFv (VH3-VK1) framework. Anti-VSTM1-v2 scFv templates were selected and enriched through ribosome display, TA-cloned into expression vector, and transformed into BL21 (DE3) for soluble expression of target scFv. A total of 1000 clones were randomly picked. Positive ones were first identified using colony PCR, indirect ELISA, Western blotting and then verified with sequencing and dose response ELISA. At last an anti-VSTM1-v2 humanized scFv with good binding affinity (EC50 = 21.35 nmol x L(-1)) was selected from the humanized library of 10(12) members generated in this study. This scFv antibody might have potential applications. This study provides a new approach for rapid screening of humanized antibodies.

Objective: To construct dengue virus-specific full-length fully human antibody libraries using mammalian cell surface display technique., Methods: Total RNA was extracted from peripheral blood mononuclear cells (PBMCs) from convalescent patients with dengue fever. The reservoirs of the light chain and heavy chain variable regions (LCκ and VH) of the antibody genes were amplified by RT-PCR and inserted into the vector pDGB-HC-TM separately to construct the light chain and heavy chain libraries. The library DNAs were transfected into CHO cells and the expression of full-length fully human antibodies on the surface of CHO cells was analyzed by flow cytometry., Results: Using 1.2 µg of the total RNA isolated from the PBMCs as the template, the LCκ and VH were amplified and the full-length fully human antibody mammalian display libraries were constructed. The kappa light chain gene library had a size of 1.45×10(4) and the heavy chain gene library had a size of 1.8×10(5). Sequence analysis showed that 8 out of the 10 light chain clones and 7 out of the 10 heavy chain clones randomly picked up from the constructed libraries contained correct open reading frames. FACS analysis demonstrated that all the 15 clones with correct open reading frames expressed full-length antibodies, which could be detected on CHO cell surfaces. After co-transfection of the heavy chain and light chain gene libraries into CHO cells, the expression of full-length antibodies on CHO cell surfaces could be detected by FACS analysis with an expressible diversity of the antibody library reaching 1.46×10(9) [(1.45×10(4)×80%)×(1.8×10(5)×70%)]., Conclusion: Using 1.2 µg of total RNA as template, the LCκ and VH full-length fully human antibody libraries against dengue virus have been successfully constructed with an expressible diversity of 10(9).

Aim: To Construct Fab antibody against Rh antigen., Methods: The variable regions of light and heavy chains were amplified by RT-PCR from the PBMCs of volunteers with high titer (1:256-512 by inditect agglutation) antibody to Rh antigen. Meanwhile, the genes of constant regions of light and heavy chains were isolated from pComb3xTT and pComb3xlambda phagmid carrying the templates respectively. Vkappa light chain and Fd heavy chain were linked by the first splicing overlapping extension PCR (SOE), and a full-length Fab gene was created by the second SOE. The Fab gene was ligated to phagmid pComb3HxSS and transformed to E.coli XL1-Blue by electroporation. The obtained human Fab phage antibody library was panned using Rh(-)/Rh(+) RBC four times. the phage antibodies against Rh antigen were highly enriched. Indirect agglutation test, western blot analysis and sequencing analysis were performed to detect the specificity of Fab against Rh., Results: The repertoire of human phage display Fab library was 7.4 x 10(6);. After panning, A Fab clone which could bind to Rh antigen specifically was obtained., Conclusion: A Fab antibody that specifically aggulated Rh(+) RBC is obtained, this makes it possible to produce Rh antibody with high quantity and effection in our country.

Aim: To prepare distinct human McAbs to TNF-alpha with high neutralizing potency using ribosome display technology., Methods: The immunoglobulin heavy and light chain variable (VH, VL) genes were prepared from the peripheral blood lymphocytes in three arthritis patients by PCR. The genes encoding VH/K fragments were prepared by randomly combining VH and VL genes by SOE PCR. TNF-alpha binding fragments were selected over three cycles of ribosome display and the selected VH/Ks genes were cloned into pET22b(+)/BL21(DE3), from which soluble VH/K fragments were prepared. The expressed products of selected clones were analyzed by ELISA. Then the positive clones were characterized., Results: A human VH/K gene library with 6.7x10(12) numbers used for ribosome display was constructed. Among the 180 selected clones, two clones TRB21 and TRB409 exhibiting the highest ELISA signals were isolated. The analysis of the sequence of TRB21 and TRB409 showed that they were new human immunoglobulin V genes to TNF-alpha and they recognize TNF-alpha specifically and antagonize the cytolytic effect of TNF-alpha on 1929 cell., Conclusion: The selected VH/Ks to TNF-alpha will be useful for constructing engineering antibodies with high affinity against arthritis. Ribosome display is a rapid means of generating fully human antibody fragments in vitro.

The N-terminal segment (FR-1) of the heavy chain (VH) of antibodies may have a great impact on IgG secretion in Escherichia coli and other hosts. Decrease in secretion may be caused by a single amino acid change in the framework region. To investigate the high antibody expression in mammalian cells, we designed the site-directed mutagenesis of the FR-I of the pCMV-RV/VH gene,which expressed the immunoglobulin heavy chain of human anti-Rabies virus antibody. Mutating Glu (H6) to Gln could improve both antibody secretion and affinity. The immunofluorescence assay indicated that both the secretion-deficient antibodies and the secretion- efficient antibodies could be transcribed and translated intracellularly, and led into ER,then transferred to Golgi apparatus,and the difference in secretion may relate to the contribution of the FR-I to the folding and assembly of the antibody. In this study, we have confirmed experimentally that the nature of residues H6 in antibody heavy chains indeed determines the antibody secretion in mammalian cells. These results also provide the basis for antibody production.

Aim: To construct and express the single chain antibody (scFv) in E.coli HB2151 by cloning the variable region genes from hybridoma against bFGF., Methods: Total RNA was extracted from hybridoma cell line B2F3 secreting mAbs against bFGF and the cDNA was amplified by retropolymerase chain reaction (RT-PCR). V(L) and V(H) were fused by a short peptide linker containing 15 amino acids (Gly(4)Ser)(3) using splice-overlap extension PCR to construct the scFv gene. The sequences of the scFv were analyzed by Shanghai Sangon Biological Engineering Technology and Services Co. Ltd and Ig Blast data base in GenBank. The scFv gene was inserted into pCANTAB-5E vector and expressed in E.coli HB2151., Results: The V(H) gene contained 375 base pairs and encoded 125 amine acid residues. The V(L) gene contained 399 base pairs and encoded 133 amine acid residues. There were four FRs, three CDRs and two characteristic cysteine residues in the V(H) gene and the V(L) gene, respectively. The scFv gene contained 789 base pairs and encoded 263 amine acid residues with the structure of V(H)-linker-V(L). Restriction endonuclease digestion and DNA sequencing proved that the expression vector of pCANTAB-5E-scFv was constructed correctly. SDS-PAGE and ELISA analysis showed that scFv was successfully expressed in E.coli HB2151 and the expression protein had specific antigen binding activity., Conclusion: The variable region genes of anti-bFGF mAbs have been cloned successfully and single chain antibody fragments have been constructed and expressed, which will be a great help to the study of humanized antibodies against bFGF.

Aim: To construct and express the single chain variable fragments (scFv) gene against human CD33 antigen, and characterize its bioactivity., Methods: The genes encoding the light and heavy chain variable regions were cloned by RT-PCR from a murine hybridoma cell line, which could produce monoclonal antibody(mAb) against human CD33 antigen. Then the light and heavy chain variable regions were fused together by a short peptide linker containing 15 amino acid (Gly(4)Ser)(3) using splice-overlap extensive PCR. The recombinant anti-CD33 scFv was subcloned into the expression vector pET28a(+) and expressed in E.coli Rosetta after induction by IPTG., Results: SDS-PAGE and Western blot analysis showed that the recombinant anti-CD33 scFv gene was expressed in the form of inclusion body in E.coli Rosetta, and the purified fusion protein was obtained after a series of purification steps including cell lysis, inclusion body solubilization, Ni(2+) metal affinity chromatography and protein refolding. Flow cytometry(FCM) analysis showed that the scFv could react with human CD33 antigen., Conclusion: Recombinant anti-CD33 scFv gene has been successfully constructed and expressed in E.coli Rosetta, which could provide foundation for the future target therapy to the myeloid leukemia.

In order to investigate the expression of heavy chain of HLA-B * 2705 in prokaryotic system and identify its activity, the extra-membrane gene fragment of HLA-B * 2705 was amplified from full-length HLA-B*2705 cDNA by PCR and cloned into pGEM-T vector. After identification by sequencing, the prokaryotic expressing vector pET32a (+)-B * 2705 was constructed. The antigenic activity of expressed protein was identified by Western blot and antibody blocking reaction. The results indicated that the fused HLA-B * 2705 protein expression with high efficiency was obtained. The expressed product was more than 50% of the total bacteria protein. The antigenic activity of expressed protein was confirmed by Western blot and antibody blocking reaction. It is concluded that HLA-B * 2705 fusion protein are obtained as basis for the further studies.

Aim: To express and characterize an active form of a single-chain antibody (scFv) from the gene of human phage antibodies which is specific for hepatocellular cancer., Methods: The complementary DNAs encoding the variable regions of the light chain (V(L)) and heavy chain (V(H)) were connected by a (Gly(4)Ser)(3) linker using a splicing by overlap extension polymerase chain reaction. The resultant scFv gene was cloned to the pET28a(+) vector and expressed in E.coli as inclusion bodies. Then the inclusion bodies were solubilized, denatured and renatured. Finally, the affinity constant of scFv was determined by noncompetitive enzyme immunoassay., Results: The target protein amounted 26% of the total protein in the condition of A(600) at 0.8 for 6 hours. After renatured, the purity of target protein was 95% and the affinity constant of the scFv was 3.6x10(7) mol/L., Conclusion: An active form of scFv which is specific for hepatocellular cancer can bind selectively with hepatocellular cancer cells, which provides a theoretical basis for immunological detection and clinical use of scFv.

Aim: To investigate the relation of the affinity activity to the structure of recombinant Fab., Methods: The human anti-HBsAg single chain Fab gene was obtained by overlaping PCR from the H and L chains of Fab, and was introduced into the expression system of Pichia pastoris. The expression vector of single chain Fab was transformed into GS115 cells by the method of LiCl transformation. The transformants were obtained and cultured in shake flask. The culture supernatant of the recombinant yeast was deposited in (NH(4))(2)SO(4) and purified by affinity chromatography. The affinity of culture supernatant of recombinant yeast and purified single chain Fab was analyzed by ELISA., Results: The analysis of SDS-PAGE and Western blot showed that the single chain Fab gene was expressed successfully in Pichia pastoris, and the expression quantity was about 5-10 mg/L in shake flask. The recombinant Fab was purified by affinity chromatography and the purity reached 97.8%. The ELISA analysis showed that the recombinant single chain Fab had good HBsAg binding properties., Conclusion: The single chain Fab gene could be expressed successfully in Pichia pastoris and the recombinant single chain Fab can efficiently bind with HBsAg.

Objective: To identify immune epitopes existed in the framework region (FR) of the IgHV protein of B-cell malignance, and explore the use of these FR-derived peptides to induce the family specific immune response in vitro, in order to explore the possibility of a new IgHV gene family-specific immunotherapy for B-cell malignance., Methods: Bioinformatics was used for predicting T cell epitopes in IgHV protein. Peptides of interest were synthesized in vitro. T2 cell binding assay was performed to determine the binding ability of the peptides to HLA-A*0201 molecules. Peptide/HLA tetramer staining was used to detect the number of peptide-specific cytotoxic T lymphocytes (CTLs). Cytotoxicity assay was used to determine killing activity., Results: Twelve peptides that were common to seven IgHV gene subfamilies were identified, and 10 (83%) of them were located in the FR of IgHV protein. The synthesized peptides up-regulated HLA*0201 molecules fluorescence intensity on cell surfaces of T2. By using an antigen-specific T-cell expansion system in vitro, the peripheral blood mononuclear cells (PBMNC) from a healthy HLA-A0201 donor were stimulated weekly by autologous PBMNC loaded with the peptide as antigen presenting cells (APC), and the peptide-specific CTLs were demonstrated to be generated successfully in the healthy donors. The frequency of CD8 and peptide/HLA tetramer double positive cells in the gated lymphocyte population was 0.38% before stimulation and increased to 49.38 % after four times stimulation. Cytotoxicity assay indicated that these CTLs were capable of killing the HLA-A*0201, IgHV1 (+) lymphoma cells. Furthermore, the generated CTL could not kill the target cell loaded with the IgHV3 peptide, indicating that the cytotoxicity is family-specific., Conclusion: Peptides derived from the IgHV protein FR can successfully induce the generation of peptide-specific CTLs in vitro. These CTLs are capable of killing the lymphoma cell belonged to the same subfamily in a peptide-specific and MHC-restricted way. These findings could potentially form the basis of broadening application of immunoglobulin-directed immunotherapy in B-cell malignancies.

Objective: To induce anti-B-cell acute lymphoblastic leukemia (B-ALL) cytotoxic T lymphocyte response against immunoglobulin heavy chain frame-derived nonapeptide., Methods: The peptide, QLVQSGAEV, containing IgHV1 frame region 3rd-11th amino acids (IgHV1(3-11)), was synthesized. IgHV1(3-11)-T2 binding tests were performed. HLA-A * 0201-positive normal peripheral blood mononuclear cells (PBMNC) were stimulated by IgHV1(3-11)-loaded antigen presenting cells three times at weekly intervals. HLA-A * 0201/IgHV1(3-11) tetramers were used to detect the proliferation of IgHV1(3-11)-specific CD8(+) T cells in the culture. Seven IgHV gene families of B-ALL patients were respectively amplified by PCR and the PCR products were sequenced to select IgHV1 and IgHV3 family monoallelic functional rearrangements. Among them, HLA-A * 0201 positive individuals were subsequently identified. Cytotoxicity of IgHV1(3-11)-specific CD8(+) T cells against HLA-A * 0201-positive IgHV1/IgHV3 family B-ALL cells was measured by MTT assay., Results: The synthesized IgHV1(3-11) up-regulated HLA-A * 0201 expression on T2 cell surface by 1.63-folds. The percentage of IgHV1(3-11)-specific CD8(+) T cells in HLA-A * 0201-positive normal PBMNC was increased from 1.64% after second stimulation to 82.57% after third stimulation. At effector: target ratio of 20:1, the killing rate of IgHV1(3-11)-specific CD8(+) T cells against IgHV1 family B-ALL cells was 18.24%, being 1.8-folds as that against IgHV3 family B-ALL cells (P = 0.01)., Conclusion: Cytolytic T lymphocytes generated in vitro against immunoglobulin heavy chain frame-derived nonapeptides can kill B-ALL cells expressing these peptides.

Aim: To screen human scFv against IL-8 from phage antibody library., Methods: IL-8-His fusion protein was expressed in E.coli BL21 (DE3) transfected with prokaryotic expression vector pRSET-IL-8 and was purified by affinity chromatography. Specific antibody was screened by 3 rounds of panning of phage antibody library with the fusion protein. The antigen binding activity and DNA sequences of positive clones were determined and analyzed., Results: After 3 rounds of panning, 2 positive clones were obtained which could bind IL-8 specifically. DNA sequence analysis showed both of the 2 VH genes belonged to human IgG VH3 subgroup, and the Vlambda gene belonged to human VlambdaDPL5 and VlambdaDPL2 subgroups,respectively., Conclusion: It is feasible to obtain human anti-IL-8 antibody by phage display technique, which provides the basis for further research on psoriasis and other related diseases.

Objective: To clone IgHV genes from childhood B-ALL cells and identify CTL epitopes deduced from IgHV gene., Methods: Seven IgHV gene families were respectively amplified by PCR and directly sequenced for 37 childhood B-ALL cases. Bioinformatics were applied for analyzing characteristics of sequences available and predicting HLA-A*0201 molecule-binding nonapeptides derived from IgHV. The predicted nonapeptide QLVQSGAEV was synthesized and its binding affinity to T2 cells determined. CD8+ T cells from a healthy HLA-A*0201+ donor peripheral blood were stimulated repeatedly with QLVQSGAEV-loaded antigen presenting cells., Results: IgHV gene rearrangements were identified in 37 B-ALL. Forty IgHV gene sequences available preferentially utilized V(H)4-59 and V(H)4-34 gene segments. Increased frequency (15.4%) of D7-27 in B-ALL IgHV was found compared to that reported for adult PBLs (P = 0.02); 20.0% DJ(H) junctions in B-ALL lacked non-encoding nucleotides, a frequency higher than that reported for adult PBLs (P = 0.02). 17.5% B-ALL IgHV contained < 2% replacement mutations. Forty B-ALL IgHV sequences acquired 12 high HLA-A*0201-binding nonapeptides, 10 (83.0%) peptides were located in frame region (FR)1 and 3. The synthesized peptide QLVQSGAEV up-regulated HLA-A*0201 expression 1.63 fold on the surface of T2 cells. The frequency of QLVQSGAEV-specific CD8+ T cells in a healthy HLA-A*0201+ donor peripheral blood increased from 1.6% and 82.6% after two-round and 3-round stimulations, respectively., Conclusion: IgHV genes in childhood B-ALL are of germline characteristics. Their heavy chain framework regions contain HLA-A*0201-binding nonapeptides. These peptides are capable of inducing specific CD8+ T cells to activate and proliferate.

Aim: To develop rAAV2 containing cDNA of GAD-Ig fusion gene [GAD-Ig fusion gene is constructed by inserting glutamic acid decarboxylase(GAD) into N-terminal of murine IgG3 heavy chain(Ig)], and to study whether rAAV2 mediated GAD-Ig fusion gene expression could induce specific tolerance in IDDM animal model-nonobese diabetic (NOD) mice., Methods: GAD-Ig cDNA was amplified by PCR from the plasmid BSSK-GAD-Ig and inserted into an eukaryotic expression plasmid pSNAV to construct a recombinant expression plasmid pSNAV/GAD-Ig. Plasmid pSNAV-GAD-Ig was then transfected into the rAAV2 packaging cell-BHK-21 cells using LipofectAMINE TM 2000 to produce rAAV-GAD-Ig. Target gene expression in BHK-21 cells infected by rAAV-GAD-Ig was confirmed by RT-PCR, Western blot and ELISA respectively. Then rAAV-GAD-Ig was injected into intramuscularly NOD mice. Antigen-specific tolerance in NOD mice was detected by specific lymphocytic proliferation reaction to GAD antigen., Results: GAD-Ig gene was inserted into the genome of target cells. Target cells transfected by rAAV2-GAD-Ig could secret GAD-Ig. rAAV2-GAD-Ig induced specific tolerance in NOD mice., Conclusion: rAAV2-GAD-Ig was obtained, which can be used in IDDM gene therapy in NOD mice.

Aim: To clone and sequence V(H) and V(L) genes of anti-idiotype monoclonal antibody (mAb) against vibrio alginolyticus., Methods: Total RNA was extracted from hybridoma cell AL1 secreting mAb against vibrio alginolyticus and cDNA was amplified by RT-PCR. Then the cDNA was inserted into PMD18-T vector and its sequence was analyzed., Results: The V(H) gene contained 369 bp and encoded 123 amino acid residues; the V(L) gene contained 339 bp and encoded 113 amino acid residues. There were four FRs, three CDRs and two characteristic cysteine residues in the V(H) and V(L) genes, respectively., Conclusion: The successful cloning of the V(H) and V(L) genes of anti-idiotype mAb against vibrio alginolyticus provides a sound basis for construction of gene-engineering vaccine of the anti-idiotype mAb against vibrio alginolyticus.

Aim: To construct a human phage displayed single chain Fv antibody (scFv) library and screen specific scFv against rabies virus., Methods: Using a phage-display technique, IgVH and IgVL genes were cloned from peripheral blood lymphocytes from three donors immunized with the WISTAR PM strain vaccine. Genes encoding scFv fragments were constructed by random linkage of VH gene and VL gene by SOE PCR, and then the constructed scFv genes were cloned into phagemid vector and transfected into E. coli TG1. The recombinant phages were screened by four rounds of panning with rabies virus vaccine. The positive recombinant phages were sequenced and antigen-binding activity of recombinant scFv was detected by competition ELISA., Results: A human phage-displayed scFv library with about 7 x 10(8) sink size was constructed. A new human scFv was selected, which bound specifically to rabies virus and had higher affinity., Conclusion: The results lay a solid foundation for preparation of human engineering antibody to rabies virus reported herein with higher affinity.

Objective: To identify that immunoglobulin heavy chain framework regions-derived peptides function as cytotoxic T lymphocytes epitopes., Methods: Seven IgHV gene families were respectively amplified by PCR and directly sequenced for 108 acute lymphoblastic leukemia cases. Sequences available were translated into amino acid sequences. Bioinformatics were applied for analyzing recombination patterns and gene mutations of the IgHV genes. Softwares SYFPEITHI and BIMAS were used for predicting the T cell epitopes in the immunoglobulin heavy chain variable regions. To determine whether the predicted peptides have immunogenicity, a IgHV1 family nonapeptide QLVQSGAEV was synthesized as a representation and T2 binding assay of this peptide was performed, inducing proliferation of T cells from normal HLA-A * 0201 peripheral blood lymphocytes (PBLs) with QLVQSGAEV-loaded antigen presenting cells, and detecting the proliferating T cells by HLA-A * 0201/QLVQSGAEV tetramers., Results: Complete IgHV gene rearrangements were identified in 66% cases. Among 40 B-ALL IgHV sequences available, 26 were predicted for antigenic nonapeptides that are likely to bind to HLA-A * 0201 molecule. Twelve peptides were acquired. Except one peptide derived from CDR3, 10 (83%) peptides were located in the immunoglobulin heavy chain framework regions. Moreover B-ALL belonging to the same IgHV family shared 1 - 2 peptides. Synthesized peptide QLVQSGAEV up-regulated HLA-A * 0201 expression 1.63 times on T2 cell surface. PBLs from a normal HLA-A * 0201 donor were stimulated with QLVQSGAEV-loaded autologous PBMCs and T2, the CD8(+) tetramer(+) cells in gated lymphocyte population increased from 1.64% after the first stimulation to 82.57% after the third stimulation., Conclusion: Immunoglobulin heavy chain framework region genes encode IgHV family-specific peptides recognized by CTLs. Specific CTLs remain in human peripheral T cell repertoire. Immunoglobulin heavy chain framework-derived peptides function as T cell epitopes to induce the proliferation of specific CTLs.

Objective: To construct the gene co-expression vector of immunoglobulin heavy chain variable region (IgHV) gene and GM-CSF or IL-2 as IgHV family specific nucleic acid vaccine to lymphoma, and study the immune response of the immunized mice against lymphoma., Methods: Six clones with significantly different length in gene fragments were selected from a gene bank constructed from normal fetal umbilical cord blood. These gene fragments in the clones were sequenced. The sequences were translated into IgHV peptides. T cell epitopes in the IgHV were predicted by bioinformatics. Meanwhile 6 clones of IgHV1 constructed before were analyzed. The most typical clone of IgHV1 and IgHV3 containing most of the T cell epitopes were selected. The IgHV gene fragments whose complementary determining region 3 (CDR3) was cut out and composed mainly of framework region were cloned into eukaryotic expression vector. The gene fragments of framework region of IgHV linking with gene of GM-CSF or IL-2 were cloned into pcDNA3.0 to form fusion genes of IgHV (FR)-GM-CSF/IL-2. Then they were transected into COS cells, African green monkey renal cells, by Lipofectin and their transient expression product was detected by ELISA. Twenty male Balb/c mice were randomly divided into 5 groups of 4 mice to be injected with different vectors at the weeks 0, 2, and 4: with IgHV3 (FR)/pcDNA3.0, with IgHV3 (FR)-IL-2/pcDNA 3.0, with blank vector pcDNA3.0 as control, with IgHV1 (FR)/pcDNA3.0, and with IgHV1 (FR)-IL-2/pcDNA3.0. At the weeks 0, 2, 4, 6, and 8 serum was collected from the mice to undergo indirect immunofluorescence examination to detect the antibodies against Namalwa cells, lymphoma cells from Africa green monkey, and normal lymphocytes. ELISA was used to examine the serum interferon (IFN)-gamma., Results: About 30 of T cell epitopes existed in each IgHV peptides predicted by bioinformatics. Among the bioinformatics prediction, about 90% of the T cell epitopes were in the framework region (FR) of IgHV, and the first 10% with higher prediction score were in FR. The CDR3 of two typical IgHV sequences were cut down and the remaining sequences, mainly composed of FR, were used to construct the IgHV (FR)/pcDNA3.0 expression vectors. The 3' end of IgHV1 (FR) and IgHV3 (FR) were linked to GM-CSF or IL-2 gene successfully. The expression of GM-CSF in the group transfected with IgHV (FR)-GM-CSF/pcDNA3.0 were 200 times higher than in the group transfected with control pcDNA3.0. The expression of IL-2 in the group transfected with IgHV (FR)-IL-2/pcDNA3.0 were 60 times higher than in the group transfected with control pcDNA3.0. The antibody against IgHV1 family lymphoma cell line Namalwa could be detected since the second week in the mice immunized with IgHV1 (FR)-IL-2/pcDNA3.0. The antibody could be detected since the fourth week in the mice immunized with IgHV1 (FR). The antibody against lymphocyte line of IgHV3 family could be detected since the second week in the mice immunized with IgHV3 (FR)-IL-2/pcDNA3.0. The antibody could be detected since the fourth week in the mice immunized with IgHV3 (FR)/pcDNA3.0. The contents of serum IFN-gamma the mice immunized with IgHV1 (FR)-IL-2/pcDNA3.0 and with IgHV3 (FR)-IL-2/pcDNA3.0 was significantly higher than those of the mice immunized with IgHV (FR)/pcDNA3.0 or pcDNA3.0 (all P < 0.01)., Conclusion: The gene fragments of IgHV (FR) can be used to construct IgHV family specific nucleic acid vaccine that induces anti-lymphoma immune response in mice by muscle injection. The expressing vectors of IgHV (FR)-GM-CSF/IL-2 induces stronger immunoreaction.

The anti-CD3 antibody can improve success rate of organs transplant. HIT3a, a mouse anti-CD3 antibody, was chimerized by using gene engineering methods to decrease its immunogenity. The anti-CD3 genes, heavy chain and light chain, were cloned using PCR from the vector pCANTAB 5E containing anti-CD3 scFv gene fragment, and two PCR fragments were recombined into the expression vector pKN100 with human antibody light constant domain and pG1D105 with human antibody heavy constant domain, respectively. The two vectors were co-transfected into CHO cells using liposome. The anti-CD3 antibody was detected by ELISA and Western blot assay in supernatant of transfected CHO cells culture. The primary results of competitive assays by FACS showed that anti-CD3 antibody could partially block the sites through which parent antibody (HIT3a) bind to CD3+ Jurkat cells. The result of 3H-TdR incorporation showed that the chimeric anti-CD3 antibody could stimulated proliferation of peripheral blood mononuclear cells (PBMC) as the parent antibody. In this thesis, the results of some experiments indicated that the chimeric anti-CD3 antibody expressed in CHO cells was an antibody with native biological activity, and it is possible to apply to in clinic in the future.

Objective: To explore the feasibility of construction of the universal nucleic acid vaccine against B-cell lymphoma., Methods: RT-PCR was employed to obtain the immuncy losulin heavy chain variable region (IgHV1) gene fragments of the Namalwa cell, normal fetal umbilical cord blood and adult peripheral blood. Then these RT-PCR products were cloned into the eukaryotic expression vector pcDNA3.0 and sequenced. Six plasmids that had high identities with the germ line genes were mixed to serve as vaccines. Eighteen Balb/c mice were divided randomly into three groups and were immunized respectively with the six mixed plasmids, the specific IgHV1 fragment of the Namalwa cell and the blank plasmid pcDNA3.0. 100 microg plasmid and 5 microg hIL-6 per mouse were injected into the muscle, 3 times in 4 weeks. Western blotting and indirect immunofluorescence staining were used to assess the humoral immune responses against the Namalwa cell., Results: The specific humoral immune responses against the Namalwa lymphoma cell could be induced in both the IgHV1-mix group and the Na-IgHV1 group, and the antibodies could recognize the nature antigenic determinants in the surface of the Namalwa cell. The antibodies could be detected since the fourth week after the first immunization, and reached the climax at the sixth week. There was no significant difference of the titers of the antibodies between the two groups. The antibody couldn't be found in the negative control group., Conclusion: The mixed IgHV plasmids can be used as the universal nucleic acid vaccine against the B-cell lymphoma which expresses the same IgHV1 family genes.

This study was to investigate the anti-lymphocytic malignancy immunologic effects induced by two types of the idiotypic nucleic acid vaccines which were constructed from the genomic DNA and RNA of the human B lymphoma cell line respectively. Namalwa cell line and BALB/c mice were used as the models. The gene fragments of the IgH variable region (IgHV), which were obtained from the genomic DNA and RNA of Namalwa cell respectively, were cloned into the eukaryocytic expression vector pcDNA 3.0 to be used as the idiotypic nucleic acid vaccines. After transfecting COS cells with one of vaccines constructed from the genomic DNA by using LipofectAMINE, the result of transcription was identified by using RT-PCR. The experimental mice were immunized by intramuscular injection with two types of vaccines. The specific anti-idiotypic antibody was detected by indirect immunofluorescence assay. The results showed that the nucleic acid vaccine constructed from the genomic DNA can be transcribed in COS cells, the transcription product turned shorter, and the intron region of 86 bp was spliced accurately. When immunizing the mice, two vaccines both induced the anti-idiotypic antibody against Namalwa cell, the anti-idiotypic antibody could be detected since detected since after immunization, and got to the peak of titer on the sixth week. It was concluded that the nucleic acid vaccines against lymphoma can be constructed from both the genomic DNA and RNA.

The VH and VL genes from a hybridoma cell line producing mouse McAb against alpha-toxin of Clostridium perfringens type A were amplified by RT-PCR. The VH and VL genes were connected thought a flexible linker (Gly4Ser)3 and the VH-linker-VL (ScFv) gene was cloned into a vector pGEM-T. The ScFv gene consists of 726 bp encoding 242 amino acid residues. Both VH and VL genes were confirmed as functionally rearranged mouse immunoglobulin variable region. According to kabat classed method, the VH and VL gene segments belong to mouse Ig heavy chain subgroup II (B) and kappa light chain subgroup III respectively. The ScFv gene was amplified inserted the expression vector pHOG21 and transformed into E coli XL1-BLUE. The ScFv protein was highly expressed in recombinant strain XL1-BLUE (pHOG-2E3) and the expression level of the ScFv was about 25% of total bacteria protein by SDS-PAGE. The neutralization assay showed that the expressed ScFv protein could neutralize the phospholipase C activities of alpha-toxin.

Objective: To select anti-VEGF (vascular endothelial growth factor) antibodies (Fab fragments) from human phage display antibody library and to identify their specification and activities., Methods: Human immunoglobulin heavy chain and light chain genes were separately amplified by RT-PCR from human peripheral lymphocytes using family specific primers and signal sequences of immunoglobulin. Human antibody library was constructed by phage display technology, and phage Fab antibodies to VEGF were screened from this library. ELISA, Western blot and (3)H-thymidine incorporation assays were used for the specification and neutralization activities of these Fab antibodies. Sequencing analysis was carried out for further identification of the antibodies., Results: The repertoire of human phage display Fab library was 1.5 x 10(8). After 4 round panning with VEGF(121), 280 clones were checked for their binding activities with ELISA and 12 clones could bind to VEGF(121) specifically. Western blot demonstrated that bacterially expressed soluble Fab could specifically recognize VEGF. Results of (3)H- thymidine incorporation showed that one clone of soluble Fab could neutralize the mitogenic activity of VEGF(165) on HUVEC. Sequencing analysis showed that the obtained V(H) gene belonged to human VH6 subgroup and the light chain was VJC rearranged human VL4 gene., Conclusions: Human anti-VEGF antibodies can be obtained from human phage display library, which provides a basis for preparation of high affinity human anti-VEGF monoclonal antibodies through antibody engineer technique.

Objective: To obtain the minimum molecule having activity to bind human fibrin., Methods: The immunoglobulin heavy- and light-chain variable region (VH and Vkappa) genes were isolated from 8E5 hybridoma cells, which secreted a monoclonal antibody against human fibrin, by RT-PCR. An expression vector pOPE51-8E5 was constructed for the recombinant VH-Vkappa expression. The transformed E. coli JM 109 cells were propagated and induced by IPTG., Results and Conclusion: Expression product was found in the periplasmic space and inclusion bodies by SDS-PAGE and immunobloting. It was a 30000 single chain fragment (scFv) with antigen-binding specificity. The yield of the scFv was 28.9% of the total bacterial proteins.