Optimization of transduction conditions of recombinant adeno-associated virus into NK92 cells / 中国药科大学学报

@#To improve the transduction efficiency of recombinant adeno-associated virus (rAAV) in NK92 cells, the number of cells, concentration of IL-2 in the medium, and serotype and dosage of rAAV were explored to optimize cell state and viral transfection conditions.Then, zinc chloride (ZnCl2), chloroquine, polyvinyl alcohol (PVA) and genistein with different concentration were added separately during transfection to further improve the viral transduction efficiency.The results showed that, at cell number of 5 × 105, the expression efficiency of enhanced green fluorescent protein (EGFP) was relatively high.When the IL-2 concentration was 1 000 IU/mL, NK92 cells were most suitable for virus transfection. The transduction efficiency of different serotypes of rAAV in NK92 cells was rAAV6, rAAV2 and rAAV9 in descending order.Pretreatment of NK92 cells with genistein could significantly increase the viral transduction efficiency, while the addition of other reagents had no significant effect.Through the optimization of the above conditions, the transduction efficiency of rAAV to NK92 cells could be significantly improved, which provided evidence for functional genetic modification of NK92 cells by rAAV.

Tropisms of rAAV2, 6, 8, 9 serotypes for intravitreal injection in the mouse retina / 中华实验眼科杂志

Objective:To compare the tropism of different adeno-associated virus (AAV) serotypes in retinal cells.Methods:The plasmids pFastBacDual-inCap and pFastBacDual-ITR-CMV-EGFP were constructed for AAV packaging with the baculovirus expression system.Recombinant adeno-associated virus type 2(rAAV2), 6, 8 and 9 serotypes were packaged, and the infectivity of rAAV was evaluated by infecting HEK293T cells at multiplicity of infection(MOI)2000.Twenty-five C57BL/6 mice were divided into five groups, with five mice per group.In the three experimental groups, both eyes of each mouse were injected 1 μl rAAV intravitreally, and 1 μl phosphate buffered saline (PBS) for the eyes of the control group.Two weeks after injection, the retinal tissues were collected for preparing flat mounts and cryosections.Enhanced green fluorescent protein (EGFP) gene expression was observed via fluorescence microscopy and laser scanning confocal microscopy.The study protocol was approved by the Ethics Committee of Suzhou Institute of Biomedical Engineering and Technology.Results:The infection efficiency of the recombinant virus to HEK293T cells was rAAV2>rAAV6>rAAV8>rAAV9, and the transduction efficiency was 39.5%, 18.4%, 8.7% and 4.6%, respectively.In mouse retinal transduction, rAAV2 and rAAV6 were highly expressed in the ganglion cells, and rAAV8 and rAAV9 were highly expressed in the retinal pigment epithelium (RPE) and photoreceptor cells.rAAV2-mediated EGFP expression in retinas was stable within three months after injection.Conclusions:Different rAAV serotypes have varying tropism and transduction efficiencies in retinal cells through intravitreal injection, rAAV2 has a high transduction efficiency and it can be stably expressed in retinas within three months after injection.

Ultra-sensitive quantification of the colorectal cancer-specific NDRG4 gene methylation levels in stool / 医学研究生学报

Objective The NDRG4 gene methylation in stool is a candidate biomarker for non?invasive diagnosis of colorectal cancer. However, the traditional methods for methylation detection could not be well applied to stool samples due to the low sensitivity and low specificity. The aim of this study was to develop a highly sensitive and specific method for quantifying the methylated NDRG4 gene in stools. Methods Forty one stool samples were collected from 12 colorectal cancer patients, 4 adenoma patients and 25 nor?mal persons. The invasive reaction was combined with real?time PCR and the relative quantification was performed by 2-ΔCT method to develop the highly sensitive and specific methylated DNA detection method, which was used for detecting NDRG4 methylation levels in 41 of stool samples. Results The sensitivity of the method was as low as 10 copies of methylated NDRG4 gene fragments. The specificity was high enough to distinguish 0.01% of methylated fragments from un?methylated fragments and 105 copies of unmethylated NDRG4 fragments gave noamplification signals. The detection results from 41 of stool samples showed that detection rate of the NDRG4 gene in stool from adenoma and colorectal cancer groups had a significant difference comparing to that from the normal group. Conclusion The 2-ΔCT method could accurately quantify the methylation levels of the NDRG4 gene in stool samples, and provide an efficient tool for non?invasive colorectal cancer detection.

Preparation of a novel AAV-ITR gene expression mini vector in Sf9 insect cells via baculovirus / 生物工程学报

AAV-ITR gene expression mini vector is a double-strand or single-strand DNA that only contains inverted terminal repeats of adeno-associated virus, cis-elements and gene of interest and does not contain any other foreign DNA sequences. We prepared Bac-ITR-EGFP and Bac-inrep. Spodoptera frugiperda cells were infected with Bac-ITR-EGFP (P3) and Bac-inrep (P3). Up to 100 μg of AAV-ITR-EGFP gene expression mini vectors were extracted from 2 x 10(7) cells of Sf9 72 h after infection. The gel electrophoresis analysis shows that most forms of AAV-ITR-EGFP gene expression mini vector were monomer and dimer. The mini vector expression efficacy was examined in vitro with HEK 293T cells. The EGFP expression was observed at 24 h after transfection, and the positive ratio reached 65% at 48 h after transfection.

Generation of a chimeric plasmin-resistant VEGF165/VEGF183 (132-158) protein and its comparative activity.

Vascular endothelial growth factor-A (VEGF) is a potentially ideal angiogenic agent in tissue repair, however, various side effects still limit its application in clinical practice. If VEGF could be localized and activated in a specific region, its side effects would be minimized. A VEGF variant was designed by fusing the peptide VEGF183 (132-158), which contains plasmin and matrix metalloproteinases (MMPs ) cleavage sites, as well as extracellular matrix (ECM) binding sequences to the COOH-terminus of plasmin-resistant VEGF165 (designated as VEGF192). These were then expressed in Pichia pastoris and mouse breast cancer EMT-6 cells. Its stimulation of dermal vessel permeability in rats, mitogenic activity in cultured human umbilical vein endothelial cells (HUVECs), affinity for ECM, as well as its half-life in rats were compared with those of VEGF165. The results show that VEGF192 has weaker vessel permeabilization activity and mitogenic activity for HUVECs only at lower concentrations. It also has a longer half-life and a higher ECM-binding affinity compared with those of VEGF165. However, the plasmin-cleaved VEGF192 could stimulate HUVEC proliferation in a dose-dependent manner. Different functional peptide combinations should have potential applications for VEGF modifications and VEGF192 might be used in tissue engineering and the treatment of ischemia-related diseases.

Effects of nasal immunization of multi-target preventive vaccines on atherosclerosis.

Previous investigations have demonstrated that anti-inflammatory or lipid-lowering treatments could be useful for alleviating morbidity and mortality of atherosclerotic cardiovascular diseases. However, whether a vaccine designed to target inflammation and lipid simultaneously is more powerful to control the process of atherosclerosis remain to be unknown. Here, a vaccine was designed to target heat shock protein-65(Hsp65) and cholesteryl ester transfer protein (CETP) simultaneously and the effects of nasal immunization of multi-target vaccine on high-cholesterol-diet-driven rabbit atherosclerosis lesions were evaluated. Sera, nasal lavages and lung washes were used to ELISA assay for the analysis of IgG and IgA against Hsp65 and CETP. Sera were also used to the analysis of the avidity of combination of anti-Hsp65 and anti-CETP IgG antibodies with corresponding antigen, cytokines IL-10 and IFN-γ, and lipoproteins. In addition, aortas were harvested for analysis of atherosclerotic lesions. The results showed that lower and lasting specific anti-Hsp65 IgG and high anti-CETP IgG in sera and protective anti-Hsp65 and anti-CETP IgA in nasal cavity and lung were induced, the avidity of combination of anti-Hsp65 and anti-CETP IgG with antigen were higher, and more protective IL-10 and less adverse IFN-γ were produced. In addition, sera TC, and LDL-C were decreased. As a result, the size of aorta atherosclerotic plaques was significantly reduced. We conclude that multifaceted vaccine combining lipid-regulating with anti-inflammation was a potential remedy, especially for atherosclerosis with complicated etiology.

Cloning, expressing of exendin-4 analogue and bioactivity analysis in vivo / 生物工程学报

To construct, express and purify Exendin-4 analogue and detect its biological activity in vivo. Insert gene sequence into fusion partner ofpED plasmid which is helped to purification, entitled the new recombinant plasmid 5 Exendin-4 analogue polypeptide gene and fusion partner gene was linked by acid hydrolysisgene, transformed to E. coli BL21 and the fusion protein was induced by lactose. After acid hydrolysis, the Exendin-4 analogue polypeptide separated from fusion chaperon. Anion charge chromatography were used to further purification. 6 to 8 week-old ICR mice were injected (s.c) with Exendin-4 analogue, blood glucose and plasma insulin level was detected in different period after oral glucose tolerance test. The results show that high expression of inclusion body was induced by lactose, which accounted for 40% of germ proteins, the Exendin-4 analogue was obtained with the purity of 91.8% after being purified by anion charge chromatography. Bioactivity assay showed that the level of blood glucose of mouse which treated with exendin-4 analogue was obviously decreased to normal (P < 0.01), and the level of plasma insulin was increased obviously (P < 0.01).

Oral administration of Lactococcus lactis delivered heat shock protein 65 attenuates atherosclerosis in low-density lipoprotein receptor-deficient mice.

Lactococcus is a genus of Gram positive food-grade bacteria that has been widely used as a vaccine platform for the safe delivery of heterologous antigens. Many reports support the involvement of inflammation and immunity in atherosclerosis as well as the role of autoimmunity to heat shock proteins (HSPs) in the progression of atherogenesis. In this study, experiments were specifically designed to investigate the effect of oral administration of mycobacterial heat shock protein 65 (HSP65) delivered by Lactococcus lactis (L. lactis) on atherogenesis. Two types of HSP65-encoding plasmids for intracellular expression or secretion were constructed, and then transformed into L. lactis NZ9000. Oral administration of two recombinant L. lactis strains both induced suppression of HSP65-specific proliferation, accompanied by elevation of Interleukin-10 (IL-10) production and reduction of interferon-gamma (IFN-γ) level. Inducible HSP65-specific tolerance exerted a protective effect on atherosclerotic lesion formation and endothelial damage in low-density lipoprotein receptor-deficient (LDL-RD) mice model, while no obvious pathological abnormalities were observed. In conclusion, delivery of HSP65 at the intestinal mucosa by recombinant L. lactis provides a novel approach for the prevention of atherosclerosis. The results further illustrate the potential of using genetically modified L. lactis as a safe and effective vaccine delivery to elicit antigen-specific tolerance for treatment of autoimmune diseases.

Immunization with P277 induces vascular leak syndrome in C57BL/6 mice via endothelial damage.

Accumulating evidence established a positive association of anti-heat shock protein 60 (HSP60) autoantibodies and the presence of atherosclerosis. However, whether anti-P277 (HSP60 437-460) autoantibodies may lead to the pathological increase in vascular permeability, a vascular leak syndrome (VLS), is unknown. In the present study, anti-P277 immunity was effectively induced in C57BL/6 mice, causing a marked increase in VLS in both normal mice and those bearing melanoma as well. Further analysis of the pathological role of anti-P277 immunity revealed that the B-cell epitopes located in P277 played a causal role in the development of VLS. Moreover, studies on endothelial cells (ECs) showed that the anti-P277 antibodies could cross-react with HSP60, highly expressed in both normal and stressed ECs, and mediate damage to cells in the presence of complement. These data suggested that humoral immune response induced by anti-P277 immunity mediates EC damage and induces VLS. These negative effects may cast shadows on P277, used as a peptide vaccine.

Study on preparation and unique properties of a novel insulin analogue with N-terminal Arg-4, Pro-3, Lys-2, Pro-1extension at insulin B-chain.

A novel insulin analog, PIns, with N-terminal Arg-4, Pro-3, Lys-2, Pro-1extension at human regular insulin B-chain was acquired through gene engineering. Preproinsulin for PIns was cloned and expressed using a bacterial expression system at a high level (72.1%) as fusion protein carrying a modified thioredoxin N-terminal region (1-21) linked to N-terminus of proinsulin by a lysine residue. Purified fusion protein was refolded and converted into PIns by a single enzymatic reaction. After PIns was purified, the homogeneity of it was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis, isoelectronic focusing electrophoresis, amino acid composition analysis and mass spectrometry methods. A decreased tendency of self-association of PIns as compared with regular insulin was demonstrated by the size exclusion HPLC analysis. When subcutaneously administrated into normal rats, the PIns showed a faster rate of onset of action and a shorter duration of action compared with regular insulin, similar to the pharmacokinetic characteristics of insulin Lispro. These results showed that PIns is a rapid insulin analog. Furthermore, the N-terminal Arg-4, Pro-3, Lys-2, Pro-1extension at insulin B-chain can be excised by DPPIV and recombinant peptidase with DPPIV-like activities. It is suggested that PIns serves as an artificial insulin precursor and can be transformed to regular insulin in vivo due to the truncation of N-terminal sequence of PIns B-chain by DPPIV.

Construction, expression, purification and immunology effect of an anti-atherosclerosis chimeric enzyme vaccine in Escherichia coli.

In order to prevent atherosclerosis, a chimeric enzyme vaccine of AnsB-TTP-PADRE-CETPC was successfully constructed, expressed and purified to immunize New Zealand white rabbits for inducing high titers of anti-CETP antibodies to improve lipid abnormality. The protein was expressed as soluble protein in Escherichia coli and purified by anion exchange column and Sephadex G-100 size-exclusion chromatography. After immunizing rabbits with the purified protein, high titer anti-CETP antibodies were induced and lasted more than nineteen weeks in vivo; High density lipoprotein cholesterol (HDL-C) content in the serum was elevated to 61% while decreased low density lipoprotein cholesterol (LDL-C) to 37.2% compared with control rabbits in the presence of Al(OH) (3).

A novel vaccine targeting gastrin-releasing peptide: efficient inhibition of breast cancer growth in vivo.

Gastrin-releasing peptide (GRP), a bombesin-like peptide, is an autocrine growth factor that can stimulate the growth of various cancer cells. We developed a novel protein vaccine HSP65-(GRP-10)(6) (HG6) that consists of six copies of a 10-amino acid residue epitope of GRP C-terminal fragment carried by mycobacterial 65 kDa HSP65 and then immunized mice via subcutaneous injection. Strong humoral and cell-mediated immune responses were induced. High titer of anti-GRP antibodies was detected in immunized mice sera by ELISA and verified by Western blot analysis. Activity of CD4+T lymphocytes, especially high levels of interferon (INF)-gamma, were developed in mice immunized with HG6 when compared with HSP65 or PBS. We found that immunogene tumor therapy with a vaccine based on GRP was effective at both protective and therapeutic antitumor immunity in breast tumor models in mice. The purified GRP monoclonal antibody (McAb) was proved to be potential in inhibiting EMT-6 tumor cell proliferation in vitro. The attenuation induced by active immune responses on tumor-induced angiogenesis was observed with an intradermal tumor model in mice. Taken together, we demonstrate for the first time that immune responses that are elicited by a novel chimeric protein vaccine targeting GRP can suppress the proliferation of breast tumor cell EMT-6 in mice, and it may be of importance in the further exploration of the applications of other autocrine growth factor identified in human and other animal in cancer therapy.

Improved efficacy of P277 fused to heat shock protein 65 of Mycobacterium tuberculosis against diabetes in nonobese diabetic mice / 生物工程学报

To improve the efficacy of peptide P277 in preventing autoimmune diabetes, heat shock protein 65 kD (HSP65) of Mycobacterium tuberculosis var. bovis was fused with linear polypeptide epitope of P277 and expressed as soluble protein in Escherichia coli. The fusion protein HSP65-P277 was purified by anion exchange column chromatography and then used to immunize prediabetic NOD mice with three ip inoculations in absence of adjuvants. Serum samples from the immunized mice were collected monthly and the concentration of blood glucose was measured. The study showed that administration of HSP65-P277 to NOD mice could prevent the development of diabetes more efficiently than the peptide P277 itself or HSP65. Fused to heat shock protein 65 of Mycobacterium tuberculosis could improve the efficacy of diabetes prevention of P277 in nonobese diabetic mice. The results suggest the fusion protein of HSP65-P277 would be useful for treating insulin-dependent diabetes mellitus.

Study on preparation and activity of a novel recombinant human parathyroid hormone(1-34) analog with N-terminal Pro-Pro extension.

A recombinant human parathyroid hormone fragment, Pro-Pro-hPTH(1-34), with molecular weight of 4311.46 was acquired through gene engineering. It was then isolated and purified. The homogeneity of this fragment was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), high performance liquid chromatography(HPLC), isoelectronic focusing (IEF) electrophoresis and mass spectrometry(MS) methods. Its isoelectric point is 8.0 which was determined by IEF. It was found that the hormone fragment significantly induced calcium increment as compared to the control group (P<0.001) in Parsons's Chicken Assay, an established bioassay for the evaluation of the PTH effect. After the 3-month-old ovariectomized (OVXed) rats, the OVXed rat is one of the two models required by the U.S. Food and Drug Administration for the preclinical assessment of drugs for treating osteoporosis [DeLuca PP, Dani BA. Skeletal effects of parathyroid hormone (1-34) in ovariectomized rats with or without concurrent administration of salmon calcitonin. Am Assoc Pharm Sci 2001;3(4):E27 [1]]. Sprague-Dawley rats were fed for 14 weeks, daily subcutaneous injections of Pro-Pro-hPTH(1-34) for 16 weeks (0.4, 0.6 or 0.9 nmol/100 g body weight), reduced the ovariectomy (OVX)-triggered mass loss of vertebral trabecular bone. The mean Bone Material Density (BMD) increased to 29.2-34.5% in 3-month-old OVXed rats compared to control-vehicle group (P<0.001) and increased to 17.5-22.3% compared to sham-operated groups (P<0.01). In short, A recombinant Pro-Pro-hPTH(1-34) was harvested in purified form and its physico-chemical characterization was determined. It showed significantly enhanced activity upon two typical models for PTH fragments. It can increase the mineral density of vertebral trabecular bone just as synthetic hPTH(1-34), and the functional activity of Pro-Pro-hPTH(1-34) should be due to the removing of Pro-Pro- by Dipeptidyl peptidase IV (DPPIV). This study opened out a simplified method which was cheaper, faster than the conventional one for producing active hPTH fragment, and its applied prospect would be good; Furthermore, it may open up our own path in finding new methods for post-processing of gene-engineering product.

Effect of Displaying P277 Peptide on Surface of L-asparaginase on Its Antigenicity and Efficacy of Autoimmune Diabetes Prevention in NOD Mice / 中国生物化学与分子生物学报

The recombinant chimeric enzyme of AnsB-TTP-P277 comprising L-asparaginase, a tetanus toxin peptide spacer and P277 was expressed as a soluble protein in Escherichia coli. The purified chimeric enzyme exhibited primary activity of the native asparaginase. Prediabetic NOD mice immunized with the chimeric enzyme could induce specific antibodies against P277 and the specificity of anti-P277 antibodies was verified by Western blot assay. The study showed that displaying the P277 epitope on the surface of asparaginase could effectively overcome the weak antigenicity of the P277 epitope and evoke a strong P277-specific immune response in mice. Moreover, the concentration of blood glucose was measured by an automated analyzer.Histochemical analysis of mice pancreas tissues showed that the administration of the chimeric enzyme to NOD mice could prevent the development of diabetes more efficiently than the peptide P277 itself.

Ten tandem repeats of beta-hCG 109-118 enhance immunogenicity and anti-tumor effects of beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65.

The beta-subunit of human chorionic gonadotropin (beta-hCG) is secreted by many kinds of tumors and it has been used as an ideal target antigen to develop vaccines against tumors. In view of the low immunogenicity of this self-peptide,we designed a method based on isocaudamer technique to repeat tandemly the 10-residue sequence X of beta-hCG (109-118), then 10 tandemly repeated copies of the 10-residue sequence combined with beta-hCG C-terminal 37 peptides were fused to mycobacterial heat-shock protein 65 to construct a fusion protein HSP65-X10-betahCGCTP37 as an immunogen. In this study, we examined the effect of the tandem repeats of this 10-residue sequence in eliciting an immune by comparing the immunogenicity and anti-tumor effects of the two immunogens, HSP65-X10-betahCGCTP37 and HSP65-betahCGCTP37 (without the 10 tandem repeats). Immunization of mice with the fusion protein HSP65-X10-betahCGCTP37 elicited much higher levels of specific anti-beta-hCG antibodies and more effectively inhibited the growth of Lewis lung carcinoma (LLC) in vivo than with HSP65-betahCGCTP37, which should suggest that HSP65-X10-betahCGCTP37 may be an effective protein vaccine for the treatment of beta-hCG-dependent tumors and multiple tandem repeats of a certain epitope are an efficient method to overcome the low immunogenicity of self-peptide antigens.

Improved efficacy of DNA vaccination against breast cancer by boosting with the repeat beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65.

Studies have demonstrated that active-specific immunotherapy has potential for controlling mammary tumor progression. Human chorionic gonadotropin (hCG) is expressed and extremely sensitive, easily detectable and highly correlated with breast cancer. We developed a gene vaccine using a plasmid vector to deliver the six copies of 10-amino acid residues of beta-hCG 109-118 and beta hCG C-terminal 37-amino acid (CTP37). BALB/c female mice were immunized with a combination of pCR-HBc-X6-betahCGCTP37 DNA vaccine and HSP-X6-betahCGCTP37 protein vaccine. pCR-HBc-X6-betahCGCTP37 DNA vaccine were injected intramuscularly three times, on days -46,-25 and -11 and HSP-X6-betahCGCTP37 protein were applied two times, 21 and 14 days before tumor cell challenge. We assessed a combined DNA and protein vaccine for its effect of against murine EMT6 mammary tumor cells. In this study, animals vaccinated DNA vaccination boosting with the repeat beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65 induced higher avidity antibodies and effectively inhibited the growth of tumor, compared with treatment using DNA alone or BCG priming HSP-X6-betahCGCTP37 protein boosting. The data presented demonstrate that improve immunogenicity of DNA vaccination by boosting with the repeat beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65, which should prove useful in the development of new DNA vaccine against growth factors for cancer immunotherapy.

Low temperature and glucose enhanced T7 RNA polymerase-based plasmid stability for increasing expression of glucagon-like peptide-2 in Escherichia coli.

The high activity of T7 RNA polymerase has made the T7 RNA polymerase-based expression system very powerful for high-level expression of recombinant protein. However, the overactivity of T7 RNA polymerase would also bring about negative effects on plasmid stability and protein production, especially when expressing a toxic protein. If the latter role is dominant, it is necessary to adopt some measures to attenuate the activity or the amount of T7 RNA polymerase in the cells. Apart from the stringent regulation by inserting some genes reducing the amount or the activity of T7 RNA polymerase into plasmids, optimizing the culture conditions would be another way. In this work, we have studied the effects of various culture conditions on the plasmid stability and the target protein yield including selective pressure, culture temperature, toxicity of the target protein and the catabolite repression caused by glucose. The results have indicated that adding antibiotic after induction has little effect in increasing plasmid stability, but inducing expression at low temperature and adding glucose to the medium improved the plasmid stability and the protein yield to a large extent.