Effects of B7-2 gene RNAi lentiviral vector on dendritic cells and T lymphocytes proliferation induced by dendritic cells in vitro / 中国免疫学杂志

Objective: To generate mouse B7-2 gene RNAi lentivirus and study its interference effects on B7-2 expression and T lymphocytes proliferation induced by dendritic cells. Methods: Three sequences specific targeting B7-2 gene and one non-specific sequence were respectively synthesized, and inserted into lentiviral vector, then the recombinant vectors were sequencing. 293 T cells were co-transfected with lentiviral expression plasmid and packaging plasmids to produce recombinant lentivirus which titre was checked according to the expression level of green fluorescent protein ( GFP). Bone marrow cells from C57 BL/6 mice were isolated to differentiate into DCs at the present of GM-CSF, IL-4 and LPS for 48 h, then morphology and phenotypic was identified. DCs were infected by recombinant RNAi lentivirus and then the efficiency of infection and the expression of B7-2 on the surface of DCs were detected by flow cytometry. Effects on the proliferation of T cells were detected by co-culturing with DCs which were infected by B7-2 RNAi lentivirus and murine spleen T cells in vitro. Results: DNA sequencing confirmed that three B7-2 RNAi and one non-specific recombinant lentiviral transfer plasmids were successfully constructed, the titer of recombinant lentivirus was ( 2-4) × 108 TU/ml. The recombinant lentivirus could effectively infect DC and inhibit the expression of B7-2. After the B7-2 recombinant lentivirus infection, the ability of DCs to stimulate the proliferation of T cells decreased obviously ( P＜0. 05). Conclusion: The lentiviral B7-2 gene RNAi vector can effectively silence the expression of B7-2 on the surface of DCs and inhibit the proliferation effect of T cells induced by DCs.

Construction of anti-CD28 single chain antibody genes and expression of the ScFv in BmN cells and the larvae of Bombyx mori / 生物工程学报

The V(H) and V(L) gene fragments of anti-CD28 mAb were combined to form anti-CD28 ScFv gene by using TP-PCR method. Sequence analysis showed that 6 x His tag was added to it for the ease of purification and the V(H), and V(L) gene fragments were connected by a linker containing 15 amino acids which are biased by the baculovirus promoter, ph. Then ScFv gene fragment was inserted into baculovirus transfer vector pBacPAK8. The recombinant transfer vector, pBacPAK8/CD28-ScFv was constructed successfully. The pBacPAK8/CD28-ScFv and the linear Bm-BacPAK6 were co-transfected into the cell line of Bombyx mori (BmN) with the help of Lipofectin,then the product was purified by plaque assay and identified by PCR method. The recombinant virus, Bm-BacPAK6 CD28-ScFv, was obtained successfully. The BmN cells and the larvae of Bombyx mori were infected by the recombinant baculovirus and harvested every 24h postinfection. SDS-PAGE and Western Blotting analysis confirmed the expression of ScFv with the molecular weight of about 28 kD. The expression in BmN cells was detected 24h post infection and it peaked at 72 h, while in the larvae of Bombyx mori, the expression was detected 48 h post infection and it peaked at 120 h.

Two-step Tandem Chromatography Purification of Anti-human CD80 Monoclonal Antibody 4E5 from Mouse Ascites / 中国生物工程杂志

A two-step method for the purification of blocking-type anti-human CD80 monoclonal antibody 4E5 from mouse ascites was developed using anion exchange and gel filtration in combination. The ascites was first purified by anion exchange after centrifugation and filtration. The experimental parameters of sample loading and elution were optimized. The optimized loading condition was pH 8.0,50 mmol/L Tris-HCl and satisfactory results were obtained using a 0~0.5mol/L NaCl step elution. The fraction containing the protein of interest was directly loaded on gel filtration column and eluted using a 20 mmol/L phosphate buffer at pH 7.2. The purity of the obtained monoclonal antibody was up to 95% with a recovery of 61%. The purity of mAb could efficiently inhibit the growth of Daudi cells. The amplification of the method was also studied using a Bio-Scale Q5 column and the result was satisfied.

Construction of a recombinant baculovirus transfer vector with two promoters expressing the anti-human CD28 chimeric antibody by using TP-PCR method / 生物工程学报

CD28, a cell surface glycoprotein, predominantly expressed on T cells, belongs to the Ig superfamily and provides critical co-stimulatory signals. The data which have published indicate that the monoclonal antibody against CD28 can decrease curative effects when it was applied in vivo for a long time. In order to avoid the human-anti-mouse action, anti-CD28 mAb must be humanized before it can be used in clinical study. Chimeric antibody, consisting of variable regions of mouse antibody and the constant regions of human IgG1, is often chosen by designers in generating humanized antibody. In this study, to prepare the anti-human CD28 chimeric antibody, the genes coding variable regions of anti-CD28 mAb and the constant regions of human IgG1 were cloned by PCR method. Then, the target genes were assembled by TP-PCR, a novel method developed for fusing genes without designing endonuclease sites at the both end of the target genes, and inserted into the baculovirus transfer vector pAcUW3 respectively. Thus, the recombinant baculovirus transfer vector with two strong promoters, ph and p10 was successfully constructed, which can express two different foreign genes at the same time. The recombinant vector was identified by the methods of restriction digesting, electrophoresis, PCR amplification and further verified by DNA sequence analysis. This work will contribute to expressing the chimeric CD28 antibody in insect cells.