[Relationship between Early Peak Temperature and Neutropenia Duration in Acute Leukemia Patients after Chemotherapy and Its Mechanism].

OBJECTIVE: To investigate the relationship between early peak body temperature and neutropenia duration and its potential mechanism. METHODS: A total of 111 patients with CR1 phase acute leukemia (AL) with neutropenia infection were enrolled in this study. The relationship between early peak body temperature and neutropenia duration was analyzed retrospectively, and the IL-6 serum level in patients with different peak of body temperature was detected, and the single cell culture system in vitro was established, the incorparation rate of EdU in vivo was detected, and the effect of IL-6 on mouse hematopoietic stem cells /progenitor cells was analyzed. RESULTS: Out of 111 patients with nentropenia, the body temperature <38 °C and the neutropenia duration 9.5±3.69 d were observed in 44 patients, while the body temperature >38 °C and neutropenia duration 7.33±4.20 d were observed in 69 patients, the differences between 2 groups was statistically signficant (P<0.05). The EdU test showed that the number of EdU+ hematopoietic stem cells and progenitor cells increased. The IL-6 level was different in patients with different peaks of initial bady temperature (P<0.05). The results of amimal experiment showed that the IL-6 could promote the proliferation of hematopoietic stem cells/ progenitor cells in vitro and in vivo. CONCLUSION: For patients with neutropenic infection when initial body temperature peak is <38 °C, the probability of neutropenia duration prolonging after chamotherapy increases, which may relate with promotive effect of pro-inflammatory cytokins on prliferation of hematopoietic stem cells/progenitor cells.

[Sensitivity to chemotherapeutic drugs of polyploid tumor cells induced by a spindle poison nocodazole].

OBJECTIVE: To investigate the changes of drug sensitivity of spindle poison-induced polyploid tumor cells to chemotherapeutic agents and its possible mechanism. METHODS: Nocodazole in a dose of 100 ng/ml was used to induce polyploidization in a breast cancer cell line MDA-MB-231 cells. The polyploid cells (T-MDA-MB-231) were sorted by flow cytometry. The morphological changes and proliferation of T-MDA-MB-231 cells were compared with that of MDA-MB-231 cells. The cell growth inhibition was assessed by MTT assay. The cells were treated with paclitaxel, docetaxel, vincristine, epirubicin, 5-Fu, VP16 and oxaliplatin, respectively. Those cells were labeled with annexin V-FITC/PI and analyzed by flow cytometry. Bcl-2 was knocked down in T-MDA-MB-231 cells using SiRNA and their growth inhibition was evaluated by MTT assay to evaluate the reversing effect of Bcl-2-silencing on drug resistance. RESULTS: The polyploid T-MDA-MB-231 cells grew in vitro continuously and maintained constant DNA content. They had a larger cell size, and grew more slowly than MDA-MB-231 cells. The IC(50(s)) of T-MDA-MB-231 cells were significantly higher than that of the MDA-MB-231 cells: paclitaxel: (6.37 ± 0.07) vs. (2.05 ± 0.83) µmol/L; docetaxel: (32.98 ± 1.48) vs. (11.95 ± 0.98) µmol/L; vincristine: (35.28 ± 1.66) vs. (14.58 ± 0.94) µmol/L; oxaliplatin: (19.07 ± 0.45) vs. (9.75 ± 1.05) µmol/L; 5-Fu: (85.49 ± 3.21) vs. (31.35 ± 1.51) µmol/L; and epirubicin: (0.53 ± 0.06) vs. (0.15 ± 0.01) µmol/L, (all P < 0.05). The IC(50(s)) of VP16 in T-MDA-MB-231 cells was (2.85 ± 0.50)µmol/L, significantly lower than the (12.20 ± 1.55) µmol/L in MDA-MB-231 cells (P < 0.05), and that of T-MDA-MB-231 cells after Bcl-2-knocked down by siRNA was (19.59 ± 0.48) µmol/L, significantly higher than the (12.20 ± 1.55) µmol/L in the MDA-MB-231 cells (P < 0.05). The IC(50(s)) of docetaxel of T-MDA-MB-231 cells after Bcl-2-knocked down by siRNA was (21.52 ± 0.68) µmol/L, significantly decreased and lower than that before Bcl-2 silencing (32.98 ± 1.48) µmol/L. CONCLUSIONS: Our results indicate that polyploid tumor cells induced by spindle poison Nocodazole are more resistant to most of chemotherapeutic drugs. Downregulation of Bcl-2 increases the sensitivity of polyploid cells to docetaxel. The high expression of Bcl-2 may be one of the drug resistance mechanisms of polyploid tumor cells. The polyploid tumor cells are relatively sensitive to VP16, suggesting that VP16 might be an effective candidate drug for treatment of chemoresistant polyploid tumors.

[Preparation and identification of monoclonal antibody against human Flt-1].

AIM: To prepare functional monoclonal antibodies(mAb)against recombinant human Flt-1(rhFlt-1). METHODS: A cell line stable secreting mAb was established by using FLT-1 extracellular domain III as antigen and hybridoma technique. Then it was purified in large-scale from mouse ascites by protein G affinity chromatography. The characteristics of mAb were then determined by ELISA, Western blotting and FACS. RESULTS: The immunoglobin subtype of mAb XA12 was IgG1 with kappa (κ) light chains, and it could recognize rhFlt-1 specifically. Furthermore, mAb XA12 could bind to rhFlt-1with high affinity (K=1.28±0.05 nmol/L). It could also be used to detect Flt-1-positive cells, such as human umbilical vascular endothelial cells (HUVECs) and K562/A02 in a dose-dependent fashion. CONCLUSION: A hybridoma cell line secreting functional anti-rhFlt-1 mAb was successfully prepared. The antibody can be used to study the function of Flt-1 and further potentially optimized for clinical purpose.

[The influence of Ara-C on anti-CD3/anti-Pgp mediating T-lymphocytes activities against multi-drug resistant leukemia cells.].

OBJECTIVE: To investigate the role of Ara-C in regulating anti-CD3/anti-Pgp mediating T-lymphocytes activities against multi-drug resistant leukemia cells. METHODS: The diabody of anti-CD3/anti-Pgp was purified by E-tag affinity chromatography. K562 and K562/A02 cells were treated with Ara-C. The expressions of B7-1 and B7-2 on K562 and K562/AO2 cells were detected by FACS. The cytotoxicity of T-lymphocytes combined with anti-CD3/anU-Pgp plus Ara-C was analyzed by CytoTox 96 nonradioactive method. RESULTS: The expressions of B7-1 and B7-2 on K562 and K562/A02 cells treated by Ara-C was significantly higher than those untreated. The effect/target ratio was from 0.39:1 to 25:1, and the killing rate of activated T cells to anti-drug-resistant leukemia cells was from (16.44 +/- 1.20)% to (60.49 +/- 2.90)%. The killing rates were increased gradually, with both the effect/target ratio and the antibody concentration increasing (P < 0.05). CONCLUSION: Ara-C may be an important adjuvant for improving anti-CD3/anti-Pgp mediating T-lymphocytes activities against multi-drug resistant leukemia cells.

[Preparation and activity detection of monoclonal antibody against anti-CD3 ScFv].

OBJECTIVE: To prepare monoclonal antibody (McAb) against anti-CD3 ScFv for purifying and detecting serum anti-CD3 antibody concentration. METHODS: McAb against anti-CD3 ScFv was prepared by hybridoma technique and used to prepare affinity chromatography column, which was used to purify anti-CD3 ScFv and Diabody [CD3 x Pgp] without E-tag. The binding activities of anti-CD3 ScFv, Diabody [CD3 x Pgp] without E-tag, and Diabody [CD3 x Pgp] purified by anti-CD3 affinity chromatography column or anti-E-tag affinity chromatography column against K562/A02 cell and Jurket cells were detected by fluorescence activated cell sorting (FACS) method. ELISA was used to identify the specificity of the McAb. RESULTS: McAb against anti-CD3 ScFv specifically detected serum anti-CD3 ScFv without reacting with sera. The anti-CD3 ScFv purified by anti-CD3 affinity chromatography column and purified by anti-E-tag affinity chromatography column had the same specific binding activity with Jurkat cells. The positive binding rates of Diabody [CD3 x Pgp] without E-tag to K562/A02 and Jurkat cells were 89.87% and 83.95%, respectively. In the competitive binding experiments with K562/A02 and Jurkat cells, the binding rates of Diabody [CD3 x Pgp] without E-tag decreased to 56.30% and 43.78%, respectively. CONCLUSION: The McAb against anti-CD3 ScFv prepared in our lab can be used to purify and detect serum anti-CD3 antibody concentration.

[The role of extracellular domain of human 4-1BBL in regulating activities of human peripheral blood lymphocytes in vitro].

AIM: To investigate the role of the extracellular domain of human 4-1BBL (ex4-1BBL) in regulating the in vitro activities of peripheral blood lymphocytes (PBL). METHODS: Viable cells were quantified with Trypan-blue exclusion assay. CytoTox 96 Nonradioactive Cytotoxicity Assay Kit was used for measuring LDH levels of supernatant. ELISA kit was used for measuring IL-2 level. In vitro cytotoxity of PBL combined with anti-CD3/anti-Pgp bispecific diabody plus ex4-1BBL was analyzed with CytoTox 96 nonradioactive method. RESULTS: Ex4-1BBL can increase the proliferation of PBL, reduce cell death, promote IL-2 secretion, and the experimental group with ex4-1BBL showed obviously enhanced cytotoxic effect toward K562/A02 cells. CONCLUSION: Ex4-1BBL may be an important adjuvant for improving activities of PBL.

[Mechanism of synergistic anti-tumor effect of PH II -7 with doxorubicin on multi-drug resistant HL-60/ADR cells].

OBJECTIVE: To study the synergistic mechanism between PH II -7 and doxorubicin against multi-drug resistant HL-60/ADR cells and its parent HL-60 cells. METHODS: The anti-tumor activity of doxorubicin alone and combined with PH II -7 were measured by MTT assay. RNA was extracted from the cells treated with PH II -7 for different times or doses then the expression of MRP gene was measured by RT-PCR. Confocal laser scanning microscopy and FACS were used to detect the intracellular cumulation of doxorubicin in PH II -7 treated HL-60 and HL-60/ADR cells. RESULTS: PH II -7 has anti-tumor effect with IC50 of (0.83 +/- 0.08) micromol/L and (1.74 +/- 0.56) micromol/L for HL-60 and HL-60/ADR, respectively. It could potentiate the anti-tumor effect of doxorubicin with CDI of 0.7 and 0.43 for HL-60 and HL-60/ADR, respectively. PH II -7 and doxorubicin act synergistically in inhibiting the proliferation of HL-60 and HL-60/ADR cells and down-regulating the expression of MRP gene in a dose and time dependent manner. PH II -7 restored the intracellular cumulation of doxorubicin in HL-60/ADR cells to 55% of that in HL-60 cells. CONCLUSION: PH II -7 can significantly hasten the cytotoxicity of doxorubicin to HL-60 and HL-60/ADR cells through down-regulating the expression of MRP. The synergistic effect was more obvious in HL-60/ADR cells.

[Cloning and expression of the extracellular domain of 4-1BBL].

RT-PCR was used to clone DNA fragment of the extracellular domain of 4-1BBL from human THP-1 cells (human monocyte), and the expression vector pAYZ4-1BBL was constructed by cloning the extracellular domain of 4-1BBL into the expression vector pAYZ. The extracellular domain of 4-1BBL was expressed in E. coli 16C9 and purified by affinity chromatography. SDS-PAGE and Western blot analysis showed that the relativae molecular weight of soluble 4-1BBL is 22kD which was consistent with the theoretically predicted value. So far as we know, it is the first time that the soluble expression of 4-1BBL in E. coli was achieved 4-1BBL induced a significant release of IL-2 in stimulated Jurkat cells after 48h incubation, especially in the presence of tumor cell. At the same time the apoptosis level of Jurkat cell reduce more than 50%. In conclusion, 4-1BBL may be useful in cancer immunotherapy.

[Specific targeting cytotoxicity to resistant leukemia cells mediated by anti-Pgp/anti-CD3 diabody].

OBJECTIVE: To study the specific targeting cytotoxicity to drug-resistant leukemia cells mediated by anti-Pgp/anti-CD3 diabody. METHODS: The diabody was purified by affinity chromatography and identified by SDS-PAGE and FACS. The effect of the anti-Pgp/anti-CD3 diabody mediated lysis of Pgp-expressing tumor cells was assayed by human leukemia nude mice xenograft model in vivo. RESULTS: The diabody was produced in E.coli in a soluble functional form and could bind both Jurkat cells (CD3(+)) and K562/A02 cells (Pgp(+)). The binding rates were 86.25% and 86.26%, respectively. It could inhibit tumor growth by 98.57% and prolonged the survival of mice bearing xenografted K562/A02 cells. CONCLUSION: The diabody was proved to be a potent agent for mediating T lymphocyte cytotoxicity to lyse Pgp expressing tumor cells in vitro and in vivo.

[Effect of monoclonal antibody against extracellular domain III of vascular endothelial growth factor receptor KDR on proliferation of vascular endothelial cells].

OBJECTIVE: To prepare a neutralizing monoclonal antibody (McAb) against vascular endothelial growth factor receptor KDR and study its biological activity. METHODS: Extracellular immunoglobulin (Ig)-like domain III of KDR (KDR III) was expressed in E. coli and purified by affinity chromatograph. Monoclonal antibody against KDR III was prepared by hybridoma technique. ELISA and FACS analysis were used to identify its specificity. Immunoprecipitation and [(3)H]-TdR incorporation assay were also used to detect the activity of anti-KDR McAb blocking the phosphorylation of KDR tyrosine kinase receptor and the influence on VEGF-induced mitogenesis of human endothelial cells. RESULTS: McAb Ycom1D3 against KDR III was prepared which bound specifically to both the soluble KDR III and the cell-surface expressed KDR. It effectively blocked VEGF/KDR interaction and inhibited VEGF-stimulated activation of KDR expression on human endothelial cells. Furthermore, Ycom1D3 efficiently neutralized VEGF-induced mitogenesis of human umbilical vascular endothelial cells. CONCLUSION: McAb Ycom1D3 against KDR III may suppress the action of VEGF by blocking native vascular endothelial growth factor receptor KDR. It has potential clinical applications in the treatment of cancers and other diseases where pathological angiogenesis is involved.

[Prokaryotic expression and characterization of an anti-KDR single chain antibody].

AIM: To construct and express a single chain antibody (scFv) against human vascular endothelial growth factor (VEGF) receptor KDR and characterize its biological activity. METHODS: The restriction enzyme sites were added to the previously cloned V(H) and V(L) genes of mAb Ycom1D3 against KDR by PCR. The anti-KDR scFv gene was constructed by the splicing overlap extensive (SOE) PCR and then inserted into fusion expression vector pAYZH. The recombinant protein was expressed in E.coli 16C9 and purified with His-tag affinity chromatography. The specificity of the purified scFv was examined by ELISA and FACS. RESULTS: DNA sequencing indicated that the cloned scFv gene consisted of 729 bp, encoding 243 amino acids. After induction in low-phosphate medium of AP5, a new protein band with relative molecular mass (M(r)) of 30 000 appeared on gel of SDS-PAGE and on nitrocellulose membrane of Western blot, which was consistent with the theoretically predicted value. Anti-KDR scFv was expressed in the form of inclusion body, which accounted for 20% of total bacterial protein. ELISA and competitive immunofluorescence binding test showed that the anti-KDR scFv had the same binding activity as mAb Ycom1D3 and that it could block VEGF/KDR interaction effectively. CONCLUSION: Recombinant anti-KDR scFv gene has been successfully constructed and expressed in E.coli 16C9, which lays the foundation for its diagnostic and therapeutic application.

[An anti-P-gp/anti-CD3 bispecific antibody cytotoxic to human multidrug resistant KB cells].

OBJECTIVE: To study the specific cytotoxicity mediated by anti-P-gp/anti-CD(3) diabodies in multidrug resistant solid tumor using P-gp as target. METHODS: The anti-P-gp/anti-CD(3) diabodies were secreted from E. coli strain 16C9 containing the expression plasmid PAYZDCP, grown at 30 degrees C in a shaker flask; the diabodies were purified by affinity chromatography and identified by SDS-PAGE; the effect of the anti-P-gp/anti-CD(3) diabody mediated lysis of P-gp-expressing tumor cells was assayed by (51)Cr release assay in vitro, and by human KB nude mouse xenograft models in vivo. RESULTS: The diabodies were generated by bacteria as a soluble functional form and purified by one-step affinity chromatography with a yield > 4 mg/L culture medium. In (51)Cr release assay, the diabodies targeted human activated T cells to lyse P-gp(+)-KB/MDR cells in a dose-dependent manner. It suggested that the diabody was able to induce an efficient lysis of the target cells by human T cells in vitro. When combined with activated human T cells, the diabody significantly inhibited the growth of KB/MDR, but had no effect on KB xenografts. CONCLUSION: The anti-P-gp/anti-CD(3) bispecific antibody is a potent agent for targeting human T lymphocytes to lyse solid tumor cells overexpressing P-gp in vitro and in vivo.

Production of neutralizing monoclonal antibody against human vascular endothelial growth factor receptor II.

AIM: To prepare neutralizing monoclonal antibody (mAb) against extracellular immunoglobulin (Ig)-like domain III of vascular endothelial growth factor receptor KDR and study its biological activity. METHODS: Soluble KDR Ig domain III (KDR-III) fusion protein was expressed in E Coli and purified from the bacterial periplasmic extracts via an affinity chromatography. Monoclonal antibodies against KDR-III were prepared by hybridoma technique. ELISA and FACS analysis were used to identify its specificity. Immunoprecipitation and [3H]-thymidine incorporation assay were also used to detect the activity of anti-KDR mAb blocking the phosphorylation of KDR tyrosine kinase receptor and the influence on vascular endothelial growth factor-induced mitogenesis of human endothelial cells. RESULTS: A monoclonal antibody, Ycom1D3 (IgG1), was generated from a mouse immunized with the recombinant KDR-III protein. Ycom1D3 bound specifically to both the soluble KDR-III and the cell-surface expressed KDR. Ycom1D3 effectively blocked VEGF/KDR interaction and inhibited VEGF-stimulated KDR activation in human endothelial cells. Furthermore, the antibody efficiently neutralized VEGF-induced mitogenesis of human endothelial cells. CONCLUSION: Our results suggest that the anti-KDR mAb, Ycom1D3, has potential applications in the treatment of cancer and other diseases where pathological angiogenesis is involved.

[Construction and expression of single chain Fv gene against domain II of human VEGF receptor II].

The genes encoding for the light and heavy chain variable regions (V(H) and V(L)) has been cloned by RT-PCR from a murine hybridoma that produced monoclonal antibody (mAb) Ycom1D3, which was against domain III of human vascular endothelial growth factor receptor II (KDRIII) and were then connected to each other by a short peptide linker containing 15 amino acids (Gly4Ser)3 using splice-overlap extensive PCR. The recombinant Ycom1D3-ScFv gene was cloned into the expression vector pAYZ and induced to express in E. coli 16C9. SDS-PAGE and Western blot analysis showed that the recombinant Ycom1D3-ScFv gene was expressed in E. coli 16C9 and the relative molecular weight of the fusion protein is 30kD which was consistent with the theoretically predicted value. ScFv expression was in the form of an inclusion body and the purified fusion protein was obtained after a series of purification steps including cell breakage, inclusion body solubilization, TALON metal affinity chromatography and protein refolding. Flow cytometric analysis showed that the ScFv fragment can react with human umbilical vein endothelial cells (HUVECs) which express KDR on the cell surface. In Conclusion, Recombinant Ycom1D3-ScFv gene has been successfully constructed and expressed in E. coli 16C9, which could be useful in both diagnostic and therapeutic applications.

[High level expression of chimeric antibody fragment F(ab')2 directed against CD20 in Escherichia coli].

The use of tumor antigen specific antibody for the delivery of therapeutic agents offers the possibility of targeting therapy with reduced toxicity to normal tissues compared to conventional treatments. In previous work, the human-mouse chimeric antibody fragment Fab' directed against CD20 was constructed from the new anti-CD20 antibody HI47 (a mouse IgG3, K). The chimeric antibody fragment Fab' could reduce its antigenicity, but the yield, quality and affinity of chimeric antibody fragment Fab' restrict its use. To improve affinity of chimeric antibody fragment Fab', a new phasmid pYZcpp3, which expresses chimeric antibody fragment F(ab')2, was constructed by adding a sequence encoding a small peptide, (CPP)3, to C-terminus of heavy chain constant region of chimeric antibody fragment Fab'. Using the pYZcpp3 to transform E. coli. 16c9, the genetically engineered bacteria 10916# was obtained. 10916# can secret the soluble chimeric antibody fragment Fab' and F(ab')2 into periplasmic. The yield was up to 360 mg/L with the percent of F(ab')2 up to 45% in 19L fermentor by the high density fermentation technology. Without denaturation and renaturation, the F(ab')2 has possessed the native three-dimensional structure. The purity of F(ab')2 was more than 90% after the purification of protein G affinity chromatography and S200 size exclusion chromatography. The F(ab')2 could distinguish and bind to Raji cells (CD20+) by FACS. F(ab')2 could inhibit the proliferation of Raji cells in vitro by MTT, IC50 was 22.8 microg/mL. HI47 and its chimeric fragments F(ab')2 induced a significant level of apoptosis (23.5%, 20.8%, respectively), independent of any cross-linking agents, in Raji cells after 24 h incubation. The chimeric antibody fragment F(ab')2 directed against CD20 is possible to apply to tumor therapy in clinic in the future.

[Apoptosis of human B cell lymphoma Raji cells induced by monovalent anti-CD20 antibody].

BACKGROUND & OBJECTIVE: The anti-CD20 antibodies and fragments have been applied for treatment of non-Hodgkin's lymphomas (NHL) in clinic. The new anti-CD20 antibodies and their fragments (unmodified or radiolabeled) yet have been exploited for those patients with incomplete response to rituximab. The chimeric antibody fragments Fab and F(ab) '(2) derived from HI(47)(a mouse anti-CD20 antibody) have been constructed. The present study was designed to determine the effect of HI(47) and chimeric anti-CD20 antibody fragments on growth inhibition and apoptosis of lymphoma cells. METHODS: The binding of anti-CD20 antibodies to CD20 positive human B cell lymphoma Raji cells was examined using immunofluorescence assay. MTT method was used to evaluate the effect of chimeric antibody fragments on Raji cells growth. Annexin V staining and DNA ladder were used to examine the apoptosis of Raji cells induced by chimeric antibody fragments. RESULTS: HI(47) and its chimeric antibody fragments were capable of binding to CD20 positive Raji cells with the binding rate of above 90%. HI(47) did not compete with rituximab in binding with Raji cells. The growth of Raji cells was inhibited by HI(47) and its fragments with the inhibition rates of (57+/-1.5)%, (65.2+/-2.5)%,and (77.2+/-3.2)%, respectively, at the concentration of 100 microg/ml. The monovalent antibody fragment Fab (20 microg/ml) induced the apoptosis of Raji cells with early apoptosis rate of 17%. CONCLUSION: The chimeric anti-CD20 antibody fragments derived from HI(47) have inhibitory effect on Raji cells and can induce apoptosis of Raji cells.

[One amino acid mutation in an anti-CD20 antibody fragment that affects the yield bacterial secretion and the affinity].

Monoclonal antibodies (mAb) directed against CD20, either unmodified or in radiolabeled forms, have been successfully exploited in clinic as effective therapeutic agents in the management of non-Hodgkin's B-cell lymphoma. The antibody fragment is a potential agent in image and therapy of tumor. To further improve the soluble expression of anti-CD20 antibody Fab' fragment, PCR was used to mutate the anti-CD20 VL and VH genes and its biological activity was identified. The expression vector of chimeric antibody Fab' was constructed and expressed in E. coli. The data of mutant clone DNA sequence showed that the amino acid of light chain gene of the parent anti-CD20 antibody (H47) was successful mutated as Ser (GAG)-Asn (CAG). The soluble expression of mutated anti-CD20 Fab' (CD20-7) was 3.8 mg/g dry cell weight, while the parent (CD20-2) was 1.3 mg/g dry cell weight. The affinity constant Ka of CD20-7 was 2.2 x 10(9) L/mol. The primary results of competitive assays by FACS showed that CD20-7 could partially block the sites through which parent antibody (HI47) bind to Raji cells. There was difference in the Raji cells (CD20+)-binding activity between the mutant CD20-7 and parent CD20-2. The site mutation of anti-CD20 Fab' gene make it possible that the anti-CD20 antibody fragment was succeeded to obtain higher expression. In this thesis, we succeeded in completing mutation and expression of anti-CD20 Fab' genes, distinguishing its biological activity, and obtaining its highly expression. These period results will lay a foundation for development of other kind of anti-CD20 engineering antibody (for instance: Fab' Diabody and miniantibody), and make it possible for anti-CD20 antibody to be applied to tumor therapy in civil in the future.

[Construction and expression of anti-CD3/ anti-Pgp Diabody].

The use of tumor antigen specific antibodies for the delivery of therapeutic agents offers the possibility of targeting therapy with reduced toxicity to normal tissues compared to conventional treatments. However, several factors restrict the use of anti-PGP monoclonal antibodies(Mabs). First, Pgp is expressed in normal tissues, particularly in epithelial and endothelial cells of the gastrointestinal tract, liver, kidney, blood brain barrier, choroids plexus and other organs. It plays a significant role to transport drugs and toxins in these organs. Therefore, anti-PGP antibodies in combination with cytotoxic compounds or radiolabelled antibodies should neither inhibit the activity of PGP, nor harm the cells which expressed PGP normally. BiMab exploit the specificity of Mab and ensures activation of cellular cytotoxic mechanisms which kill tumor cells only, but not harm normal cells. It will provide a strategy for resistant cancer therapy using anti-PGP antibodies. Second, Repeated administration of murine antibodies generates a strong human anti-mouse immune (HAMA) response in up to 50% of patients after the first dose, and appro ximately 90% following a second treatment. In an effort to reduce the toxicity and antigenicity, we focus to produce anti-PGP antibodies which have the binding activity only, but not inhibit the function of the "pump", and to construct a small and partially humanized recombinant molecule with dual specificity for both PGP and CD3 complex to activate the host immune response toward the tumour. PCR and overlap PCR were used to construct anti-CD3/ anti-Pgp Diabody. DNA sequence was analyzed by the Terminus of Dideoxy Nucleotide. The product was purified by affinity chromatography and analyzed by both the detection of western blot and size exclusion chromatography; its antigen-binding activity was examined by FACS, cellular RIA. Plasmid pAYZDCP which expressed the anti-CD3/anti-Pgp Diabody was constructed correctly. The diabody was recovered in high yield( up to 2mg/ L) after E-taq purification and predominantly(90%) as a dimer. The diabody can bind to Jurkat cells (CD3+) and K562/A02 cells(Pgp+). The affinities of the diabody were similar with the anti-CD3 ScFv or anti-Pgp ScFv, respectively. The anti-CD3/ anti-Pgp BsF(ab')2 was first recast into the diabody format and succeeded to obtain high level expression. The results of some biological activity experiments indicated that the diabody could bind to Jurkat cells and K562/A02 cells. Multidrug resistance can be reversed experimentally by a variety of drugs, among which the best known are verapamil and trifluoperazine, which unfortunately are of limited use in practice due to severe collateral cardiac toxicity. Anti-PGP x anti-CD3 diabody will provide another therapeutic strategy against multidrug resistance cancer.

[Expression of chimeric anti-CD3 IgG antibody in mammalian cells and analysis of its biological activity].

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.