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@#Objective To develop and verify an anion-exchange high-performance liquid chromatography(AEX-HPLC)method for the determination of empty capsid ratio of recombinant adeno-associated virus type 9(rAAV9).Methods AEXHPLC based on the differences in surface charge was used to establish a method for detecting the ratio of empty and full capsid rAAV9 by optimizing the elution gradient of mobile phase,pH,column temperature,flow rate,sample concentration,injection volume and detection wavelength of fluorescence detector. The specificity,linearity,limit of detection(LOD),limit of quantitation(LOQ),precision and accuracy of the method were verified to confirm the feasibility.Results Using a CIMac AAV full/empty-0. 1 mL column,20 mmol/L BIS-Tris propane(BTP)as mobile phase A and 20 mmol/L BTP+1 mol/L NaCl as mobile phase B,gradient elution was performed with pH of 9.0,column temperature of 20 ℃,flow rate of1 mL/min,sample concentration of 4×10~(12)vg/mL,injection volume of 10 μL,excitation wavelength of 280 nm and emission wavelength of 330 nm,which realised the baseline isolation and quantitative detection of empty and full capsid rAAV9. The verification results of the method showed that the preparation buffer had no interference with good specificity;rAAV9 showed a good linear relationship in the range of(1.6-8)×10~(12)vg/mL,r = 0. 993;the LOD was 5×10~(10)vg/mL,and the LOQ was 1×10~(11)vg/mL;the RSD of repeatability and intermediate precision were 2. 95% and 2. 10%,respectively;the accuracy rates were not less than 80%.Conclusion A highly sensitive and rapid AEX-HPLC method for determination of the ratio of empty capsid to full capsid rAAV9 was developed,which could be used for the analysis of empty capsid rate and quality control in gene therapy products.
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@#Objective To explore a method for detecting the integrity of target nucleic acid in recombinant adeno-associated virus(rAAV),and establish a preliminary analysis algorithm.Methods The free DNA fragment of rAAV was digested,and the virus genome was extracted.Five pairs of overlapping primers were designed,using the orthogonal array method,which were detected by digital PCR respectively,with conventional conditions:20 μL reaction system with EveGreen and4 μL template,and digital PCR conditions:95 ℃ 5 min;95 ℃ 15 s,55 ℃ 30 s,72 ℃ 90 s for 45 cycles.The enhancement condition of ultra-long nucleic acid fragment was 25 μL reaction system with Mix B-2 000 bp and 2 μL template,and the quantitative analysis was performed by using the software attached to the instrument.Using the least square method,the number of full-length fragments was fitted and analyzed,and then the integrity distribution of target nucleic acid was interpreted.Results The fragments with the distance between primers of no more than 1 200 nt were amplified effectively,and a series of effective copies of fragments with a length of about 1 000 nt were obtained by systematic analysis.The copy number of common fragments was fitted and analyzed by the least square method.It was estimated that the full-length fragments in the sample were no more than 1 234 copies/μL,and there was a signficant difference(P < 0.05)between this value and the maximum measured value of 1 443 copies/μL,with the difference of approximately 16.9%.Conclusion A preliminary detection method for the integrity of target nucleic acid in rAAV has been developed,and a certain amount of incomplete target nucleic acids were analyzed in the test sample,laying a foundation for further in-depth research.
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@#Objective To establish and validate a method for the determination of the interesting protein expression level of recombinant adeno-associated virus(rAAV)infected cells,so as to monitor the product quality in different stages of rAAV9production process.Methods After incubation of serial diluted rAAV samples with infection enhancer Envirus-AAV,the human malignant glioblastoma cells(U87-MG)pretreated with hydroxyurea(HU)were infected.Using rAAV9 reference as the standard,the expression level of glutaryl-CoA dehydrogenase(GCDH)was detected by ELISA,and the specificity,accuracy,precision,linear range,limit of quantitation(LOQ)and durability of the method were verified.Eight batches of rAAV9 samples were detected by the established method.Results The A_(450)-A_(630) value of the sample buffer was 0.3,which was slightly lower than the lowest dilution point(1 ng/mL)of the four-parameter standard curve for protein quantification.The average recoveries of samples with 150%,100% and 50% theoretical relative titer levels were in the range of 100.0%-107.3%.The RSDs of the target protein expression level of the samples with three theoretical relative titer levels detected by the same experimenter three times and different experimenters were all less than 25%.There was a good linear relationship between rAAV9 samples and the target protein expression levels in the range of 50%-150% theoretical relative titer levels,and the linear regression equation was y = 1.077 x-0.022,R~2= 0.984.The LOQ of the method was 0.59,namely 6.0×10~(12) vg/mL.After U87-MG cells were incubated with HU for different time(18,21,24 h),and the culture supernatant was stored under different conditions(room temperature for 0.5 h,below-60 ℃ for 12 h,below-60 ℃ for 24 h).The RSDs of target protein expression levels were all less than 25%.The target protein expression levels of 1-8 batches of rAAV9 samples were 111%,121%,72%,65%,86%,75%,102% and 91%,respectively.Conclusion The established method for the determination of the target protein expression level after rAAV infection has good specificity,accuracy,precision and durability,and can be used for the quality control of products in different stages of rAAV9 production.
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@#Objective To investigate the feasibility of using quantitative PCR(qPCR)technology to detect large fragments of host cell residual DNA(HCD)in recombinant adeno-associated virus(rAAV)gene therapy products.Methods Four different serotypes of rAAV were extracted for the nucleic acids,two fragment sequences of 244 bp and 562 bp within the long terminal repeat sequence(LTR)in the genome of host cells HEK293 were specifically quantified by qPCR,and the proportion of HCD in the total nucleic acids was calculated.Results Large fragments of HCD in qPCR quantifiable range were detected in four different serotype rAAV products,with the abundance ranging from 0. 3% to 5. 4%. As the length of the detected fragment increased,the abundance of HCD fragments showed a decreasing trend.Conclusion qPCR technology can be used to determine the presence of large fragments of HCD in rAAV products.
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OBJECTIVE@#Melittin, a cell-penetrating peptide, improves the efficiency of many non-viral gene delivery vectors, yet its application in viral vectors has not been well studied. The non-pathogenic recombinant adeno-associated virus (rAAV) vector is an ideal in vivo gene delivery vector. However, its full potential will only be achieved after improvement of its transduction efficiency. To improve the transduction efficiency of rAAV2 vectors, we attempted to develop a melittin-based rAAV2 vector delivery strategy.@*METHODS@#The melittin peptide was inserted into the rAAV2 capsid either in the loop VIII of all viral proteins (VPs) or at the N terminus of VP2. Various rAAV2-gfp or -fluc vectors were subjected to quantitative real-time polymerase chain reaction and Western blot assays to determine their titers and integrity of capsid proteins, respectively. Alternatively, the vectors based on wild-type capsid were pre-incubated with melittin, followed by transduction of cultured cells or tail vein administration of the mixture to C57BL/6 and BALB/c nude mice. In vivo bioluminescence imaging was performed to evaluate the transgene expression.@*RESULTS@#rAAV2 vectors with melittin peptide inserted in the loop VIII of VPs had low transduction efficiency, probably due to dramatically reduced ability to bind to the target cells. Fusing the melittin peptide at the N-terminus of VP2 produced vectors without the VP2 subunit. Interestingly, among the commonly used rAAV vectors, pre-incubation of rAAV2 and rAAV6 vectors with melittin significantly enhanced their transduction efficiency in HEK293 and Huh7 cells in vitro. Melittin also had the ability to increase the rAAV2-mediated transgene expression in mouse liver in vivo. Mechanistically, melittin did not change the vector-receptor interaction. Moreover, cell counting kit-8 assays of cultured cells and serum transaminase levels indicated melittin had little cytotoxicity.@*CONCLUSION@#Pre-incubation with melittin, but not insertion of melittin into the rAAV2 capsid, significantly enhanced rAAV2-mediated transgene expression. Although further in vivo evaluations are required, this research not only expands the pharmacological potential of melittin, but also provides a new strategy to improve gene therapy mediated by rAAV vectors.
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Mice , Animals , Humans , Melitten/genetics , Dependovirus/genetics , Serogroup , HEK293 Cells , Mice, Nude , Mice, Inbred C57BL , Transgenes , Genetic Vectors/geneticsABSTRACT
@#ObjectiveTo develop a national standard for genomic titer determination of recombinant type 5 adeno-associated virus(rAAV5).MethodsThe rAAV5-GFP stock solution prepared by the three-plasmid system was identified and verified for the appearance,pH,sterility,genomic titer,purity and infection titer according to the relevant requirements of Chinese Pharmacopoeia(Volume Ⅲ,2020 edition),which was diluted and subpackaged to prepare candidate standards according to the results;The stability of candidate standards was investigated by thermal acceleration test;Three laboratories were organized to collaboratively calibrate the candidate standards using droplet digital PCR(ddPCR).ResultsAll the detection indexes of the candidate standard and the stock solution met the relevant requirements;The genomic titer showed no significant decrease at 25,4,-20,-40,-80 ℃ for 1,3,4,6 months;Through collaborative calibration by three laboratories,the candidate standard was assigned a value of 2. 56 × 10(12)copies/mL,and the 95% confidence interval was 2. 48 ×10(12)copies/mL,and the 95% confidence interval was 2. 48 ×10(12)copies/mL ～ 2. 64 × 10(12)copies/mL ～ 2. 64 × 10(12)copies/mL.ConclusionThe developed national standard for the determination of rAAV5 genomic titer had good stability and might be used for the quality evaluation of rAAV5 related products.
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Objective To construct the recombinant adeno-associated virus vector carrying cancerous inhibitor of PP2A (CIP2A)short hairpin RNA (shRNA)for preparation of high-titer viruses.Methods The small hairpin RNA of CIP2A (CIP2A shRNA)was designed,synthesized and cloned into pDC31 6-EGFP-U6 plasmid which was double digested by Bam HⅠ and Hin dⅢ.The resultant plasmid pDC31 6-EGFP-shRNA was confirmed and served as template to appraise primers.EGFP-CIP2A shRNA sequence was amplified by PCR,double digested with Eco RⅠand Sal Ⅰ and ligated to pSNAV2.0 plasmid digested with the same enzyme pair.pSNAV2.0-EGFP-CIP2A shRNA plasmid DNA was prepared,purified,identified and transfected into BHK-21 cells.BHK-21 cells expressing CIP2A shRNA (BHK-21/CIP2A-shRNA ) were obtained and subsequently infected with VGTC’s proprietary AAV packaging system to package the rAAV2-CIP2A shRNA.After purification,the functional and infectious virus was obtained and the titer of virus was detected.Real-time PCR and Western blot methods were used to detect the expression of CIP2A after infection with HepG2 cells,and the empty viral vector rAAV2-EGFP was used as control. Results A recombinant adeno-associated virus-2 vector carrying CIP2A shRNA was constructed successfully.The presence of the target sequence in the vector was confirmed by double enzyme digestion and sequencing.By transfecting the pSNAV2.0-EGFP-CIP2A shRNA plasmid into BHK-21 cells,BHK-21/CIP2A shRNA cells were infected with helper virus HSV1-rc/ΔUL2 to package the rAAV2-CIP2A shRNA to obtain a functional and infectious virus.The titer of the recombinant virus was 0.25×10 1 2 v.g./mL.The expression of CIP2A mRNA and screening value of 1×10 5 MOI effected HepG2 cells.Conclusion A high-titer recombinant adeno-associated virus-2 vector carrying CIP2A shRNA has been constructed successfully.
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Objective To clear, amplify and detect the activity of the recombinant adeno-assoeiated virus vector with adiponectin( rAAV2/1-Aerp30 ). Methods Recombinant plasmid pSNAV2.0-Acrp30 was obtained. The recombinant plasmid was then transfected into BHK21 cells using LipofectAMINETM 2000. The G418 resistant cells were obtained consequently. These cells were infected with HSVI-rc/△UL2 which has the function of packaging and copying recombinant AAV. After purification, the construction of recombinant rAAV2/1-Aerp30 was collected. Results The construction of recombinant pSNAV2.0-Acrp30 was confirmed by PCR electrophoresis and digestion with restriction enzyme. The gene sequencing showed that the recombinant pSNAV2.0-Acrp30 was correct. The virus titer was about 1.0×1012 μg/ml. The purity f the recombinant AAV2/1 was fairly high using the SDS-PAGE method. Conclusion With this method, rAAV2/-Aerp30 with high virus titers and purity can be acquired successfully and it can meet the demands of the experimental study of Acrp30 gene therapy of GK rats.
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Background and purpose: Hepatocellular carcinoma (HCC) is a hypervascular tumor associated with a poor prognosis and lack of effective treatments. Consequently, identifying novel therapeutic strategies are urgently needed. We have previously shown that the kringle 1 domain of human hepatocyte growth factor (HGFK1) is a more effective anti-angiogenesis molecule than angiostatin. In this study, we observed the effects and mechanisms of HGFK1 gene on the HCC. Methods: A recombinant adeno-associated vires carrying the HGFK1 gene (rAAV-HGFK1) was constructed.HCC of rat was induced by McA-RH7777. rAAV-HGFK1 was used to treat the rat, median survival time and metastasis rate were observed. Results: Ten days after tumor cell inoculation, surgery were performed to confirm the tumor formation, PBS, rAAV-EGFP or rAAV-HGFK1 was injected directly into the tumor nodule followed by portal vein injection. Results from our study demonstrated that rAAV-HGFK1 treatment significantly prolonged the median survival time of the HCC bearing rats from 30 days (PBS and rAAV-EGFP groups) to 49 days (rAAV-HGFK1 group). More importantly rAAV-HGFK1 inhibited tumor growth and completely prevented liver, lung and peritoneal metastasis. In the controlled PBS and AAV-EGFP group, liver and peritoneal metastasis rate were both 100%, and lung metastasis rate was 100% and 83%, respectively. While there was no metastasis found in treatment group, with only 33% of ascites happened. This was most possibly due to the primary tumor in liver but not due to the metastasis. Moreover, at a higher magnification (1000×), it was clear that the HGFK1 protein was expressed mainly in the cytoplasma of liver cells. In parallel, IHC staining of CD31 also demonstrated a significantly lower level of microvessel density (MVD) (6.21±1.6) in the liver tumor of the AAV-HGFK1 treatment group, as compared to the two control PBS and AAV-EGFP groups (25.1±2.1 and 26.8±2.5, respectively, P<0.01). HE staining showed that AAV-HGFK1 treatment induced large areas of necrosis in the tumor tissues, while minimal areas of necrosis were observed in the tumor tissue in the control groups. In addition, no toxicity appeared when high dosage (4.8× 1012 vg/rat) of rAAV-HGFK1 was administered in rats. Conclusion: Results from this study demonstrated that HGFK1 inhibited the growth and metastasis of HCC and prolonged the survival time of animals with HCC through anti-angiogenesis effects. No obvious toxicity was observed. It might be the novel promising treatment for HCC and other cancers.
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Objective To observe the in vivo gene expression profile of the recombinant adenoassociated-2 virus mediated human GM-CSF, mouse GM-CSF (rAAV-2-hGM-CSF, rAAV-2-mGM-CSE )vector modified bone marrow mesenchymal stem cell (BMSC). Methods We transduced the BMSC by rAAV-2-hGM-CSF, rAAV-2-mGM-CSF at the condition which have acquired before respectively, then transfused the in vitro gene modified BMSC after 12 days proliferation in vitro to 6 weeks old nude mice through tail vein,while the BMSC transfused in control group hadn' t been gene modified. 2, 4, 6, 8 weeks after transfusion, count the total white blood cells and detect the hGM-CSF, mGM-CSF concentration in nude mice serum at that time point. Results Nude mice serum hGM-CSF levels were 23.77, 25.32, 19.77, 15.25 ng/L at 2, 4, 6, 8 weeks after transfusion compare to 36.25 ng/L, the in vitro level before transfusion; mGM-CSF levels were 34.96, 34.84, 35.50, 32.93 ng/L at 2, 4, 6, 8 weeks after transfusion compare to 25.14 ng/L, the in vitro level before transfusion; at the same time point the nude mice serum mGM-CSF levels were 17.34,17.44, 14.68, 16.85 ng/L in control group, rAAV-2-mGM-CSF transduced BMSC made the nude mice white blood cell count increased, but no changes in nude mice white blood cell count at rAAV-2-hGM-CSFtransduced BMSC and control group. Conclusion BMSC as a gene therapy vehicle, it can be gene modified in vitro, then the gene modified BMSC could let the therapeutic gene to have therapeutic effects in vivo.
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Objective:To investigate the effective mechanism for transfection of rat brain derived neurotrophic factor(BDNF) gene by recombinant adeno-associated virus in the cultured hippocampal neurons.Methods:rAAV-BDNF was injected into the serum free-induced neurons.DAPI,PI and Actin stain was performed to measure the apoptosis cells and morphogenesis of the cells.Results:After the gene transfer,the survival rate of the serum free-induced neurons was increased by 65%.Conclusion:The recombinant adeno-associated virus vector can protect the serum free-induced neurons from Apoptosis.