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@#Objective To compare the application of two pretreatment methods,deoxyribonuclease(DNase)treatment and ligand affinity,in detecting the residual amount of free and mispackaged host cell DNA(HCDNA)in recombinant adenoassociated virus(rAAV).Methods Free and mispackaged HCDNA were isolated by DNase treatment and ligand affinity respectively,and then the nucleic acid was extracted and detected by qPCR. The accuracy and reproducibility of two pretreatment methods for detecting HCDNA residues were compared.Results Using DNase treatment,the result of nucleic acid quantitative detection in non-DNase-treated group was the total residual amount of HCDNA,that in DNase-treated group was the amount of mispackaged HCDNA,and the difference between them was the residual amount of free HCDNA. The recovery rates of both the untreated and treated groups were more than 75%,and the RSD of reproducibility was less than 30%. Using affinity extraction method,with the affinity ligand combined with rAAV,the result of recovery rate of mispackaged HCDNA was over 75%,and that of free HCDNA was only 36%.Conclusion DNase treatment method can effectively detect free and mispackaged HCDNA,laying a foundation for further research.
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@#Objective To characterize the capsid proteins of recombinant adeno-associated virus 6(rAAV6)vectors by reversed phase liquid chromatography-mass spectrometry(RPLC-MS),including primary structure and post-translational modification(PTM).Methods The mobile phase A consisted of 0. 1% aqueous solution of difluoroacetic acid(DFA),while the mobile phase B was 0. 1% DFA acetonitrile solution. The column temperature was maintained at 80 ℃,and the gradient elution lasted for 10 min(0→10 min,mobile phase B 15%→45%). The ESI-Q-TOF mass spectrometry detection operated in positive ion mode with the scanning range of 400-4 000 m/z,the scanning frequency of 2 Hz,the cone voltage at 80 V,the capillary voltage at 3. 0 kV,and the ion source temperature at 120 ℃.Results The measured relative molecular mass of the AAV capsid proteins VP1,VP2,and VP3 was 81 255. 9,66 062. 9,and 59 488. 6,respectively. The deviations from the theoretical values were 8. 1 ppm for VP1,3. 8 ppm for VP2,and 36 ppm for VP3. Mass peptide profile analysis of the enzymatically digested rAAV6 sample indicated a sequence coverage of about 89% with detected PTMs mainly including deamidation,N-terminal acetylation,ubiquitination,and phosphorylation;no glycosylation modification sites were found. Tandem mass spectrometry confirmed the N-terminal and C-terminal sequences of the rAAV6 capsid protein as well as the N-terminal PTM.Conclusion The complete relative molecular mass of rAAV6 capsid protein was analyzed by RPLCMS technique,and the PTM of rAAV6 capsid protein was analyzed by tandem mass spectrometry at the peptide level,which has a certain significance for the quality control of AAV gene therapy products and the improvement of production process.
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@#Adeno-associated virus (AAV) is a common viral vector used in gene therapy.Because of its high safety and its ability to target a variety of cells, it has been widely used in preclinical and clinical studies.However, during the design and production, AAV vectors have many key quality attributes that affect their safety and efficacy.The development and application of biological mass spectrometry technology provides a convenient platform for the research on biological macromolecules, especially in the aspects of protein sequence, structure and interaction.For AAV vectors, mass spectrometry can facilitate the determination or characterization of capsid protein ratio, post-translational modification, serotype, and empty capsid ratio, thus assisting in the quality control of AAV vectors.Compared with the existing methods, mass spectrometry has the advantages of smaller amount of sample size, faster and more sensitive analysis, being more suitable for the analysis of complete AAV vectors with higher mass resolution, and can distinguish empty capsids, full capsids and partial capsids.In the future, mass spectrometry technology is expected to play a more important role in the design and production of AAV vectors through the coupling of more efficient protein separation technology with mass spectrometry, the development of new information processing software platforms and new mass spectrometry detection techniques.
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Objective To evaluate the effects of adeno-associated virus-enhanced green fluorescent protein (AAV-EGFP)on the biologic behavior of rabbit's bone marrow stromal cells(BMSCs)by means of a simple method of culturing and osteogenic induction in vitro so as to find an ideal viral vector and cell tracing mark for tissue en- gineering.Methods Total bone marrow culture was conducted to obtain rabbit BMSCs which were then induced in the osteogenic direction.The morphology of the cells was observed continuously,and their surface antigen and ossification were detected by alkali phosphatase stain and Von Kossa stain.On the basis of the above results, AAV-EGFP was transfected into the induced cells.The morphologic changes of the cells,the expression time and intensity of fluorescent light were observed.The transfection efficiency was detected to find the best multiplicity of infection(MOI)value.The cell growth curves were drawn to evaluate the biologic effects of AAV-EGFP on the cyto-activity.Results The morphology and purity of the rabbit BMSCs obtained were good.The ossification of the cells was significant after osteogenic induction.The best MOI value was found to be 1?10~5.The expression intensity of fluorescent light was strong with the expression time more than eight weeks so that the fluorescent light could be observed after cell generations.The transfection efficiency of AAV was high without significant biologic effects on the cyto-activity.Conclusions The total bone marrow culture and in vitro cell induction can satisfy the requirements for seeding cells in tissue engineering.AAV is an ideal viral vector for tissue engineering.Transfection of AAV-EGFP to cells could be an ideal method for cell tracing mark.