Name: Autore in primo piano: Isolamento efficiente dei virus adeno-associati per applicazioni precliniche
Uploaded: 2024-02-09T14:30:00
Description: Watch this Scientific Journal Video about Author Spotlight: Efficient Adeno-Associated Virus Isolation for Pre-Clinical Applications at JoVE.com

La composizione delle soluzioni e dei tamponi utilizzati in questo protocollo è fornita nella Tabella 1.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always"><tbody><tr><td>Soluzione</td>
			<td colspan="2">Composizione</td>
		</tr><tr><td rowspan="4">Tampone di lisi AAV</td>
			<td colspan="2">1,2 mL di soluzione 5 M di NaCl</td>
		</tr><tr><td colspan="2">2 mL di soluzione 1 M Tris-HCl pH 8,5</td>
		</tr><tr><td colspan="2">80 uL di soluzi...

Isolamento AAV mediante centrifugazione in gradiente a doppia densità di iodipanolo

<ol>
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A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multiyear+factor+VIII+expression+after+AAV+gene+transfer+for+hemophilia+A.">Multiyear factor VIII expression after AAV gene transfer for hemophilia A.</a> N Engl J Med. 385 (21), 1961-1973 (2021).</li><li>Naso, M. F., Tomkowicz, B., Perry, W. L., Strohl, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adeno-Associated+Virus+(AAV)+as+a+vector+for+gene+therapy.">Adeno-Associated Virus (AAV) as a vector for gene therapy.</a> Biodrugs. 31 (4), 317-334 (2017).</li><li>Atchison, R. W., Casto, B. C., Hammon, W. M. c. 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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+purified+recombinant+adeno-associated+virus+vectors+are+biologically+active+and+free+of+detectable+helper+and+wild-type+viruses.">Highly purified recombinant adeno-associated virus vectors are biologically active and free of detectable helper and wild-type viruses.</a> Hum Gene Ther. 10 (6), 1031-1039 (1999).</li><li>Debelak, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cation-exchange+high-performance+liquid+chromatography+of+recombinant+adeno-associated+virus+type+2.">Cation-exchange high-performance liquid chromatography of recombinant adeno-associated virus type 2.</a> J Chromatogr B Biomed Sci App. 740 (2), 195-202 (2000).</li><li>Burova, E., Ioffe, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chromatographic+purification+of+recombinant+adenoviral+and+adeno-associated+viral+vectors:+methods+and+implications.">Chromatographic purification of recombinant adenoviral and adeno-associated viral vectors: methods and implications.</a> Gene Ther. 12 (1), S5-S17 (2005).</li><li>Adams, B., Bak, H., Tustian, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Moving+from+the+bench+towards+a+large+scale,+industrial+platform+process+for+adeno-associated+viral+vector+purification.">Moving from the bench towards a large scale, industrial platform process for adeno-associated viral vector purification.</a> Biotechnol Bioeng. 117 (10), 3199-3211 (2020).</li><li>Grieger, J. C., Choi, V. W., Samulski, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+and+characterization+of+adeno-associated+viral+vectors.">Production and characterization of adeno-associated viral vectors.</a> Nat Protoc. 1 (3), 1412-1428 (2006).</li><li>Florea, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-efficiency+purification+of+divergent+AAV+serotypes+using+AAVX+affinity+chromatography.">High-efficiency purification of divergent AAV serotypes using AAVX affinity chromatography.</a> Mol Ther Methods Clin Dev. 28, 146-159 (2022).</li><li>Chamberlain, K., Riyad, J. M., Weber, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expressing+transgenes+that+exceed+the+packaging+capacity+of+adeno-associated+virus+capsids.">Expressing transgenes that exceed the packaging capacity of adeno-associated virus capsids.</a> Hum Gene Ther Methods. 27 (1), 1-12 (2016).</li><li>Green, E. A., Hamaker, N. K., Lee, K. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+vector+elements+and+process+conditions+in+transient+and+stable+suspension+HEK293+platforms+using+SARS-CoV-2+receptor+binding+domain+as+a+model+protein.">Comparison of vector elements and process conditions in transient and stable suspension HEK293 platforms using SARS-CoV-2 receptor binding domain as a model protein.</a> BMC Biotechnol. 23 (1), 7 (2023).</li><li>Erbacher, P., Zou, S., Bettinger, T., Steffan, A. M., Remy, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chitosan-based+vector/DNA+complexes+for+gene+delivery:+Biophysical+characteristics+and+transfection+ability.">Chitosan-based vector/DNA complexes for gene delivery: Biophysical characteristics and transfection ability.</a> Pharm Res. 15 (9), 1332-1339 (1998).</li><li>Vandenberghe, L. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Efficient+serotype-dependent+release+of+functional+vector+into+the+culture+medium+during+adeno-associated+virus+manufacturing.">Efficient serotype-dependent release of functional vector into the culture medium during adeno-associated virus manufacturing.</a> Hum Gene Ther. 21 (10), 1251-1257 (2010).</li><li>Summerford, C., Samulski, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane-associated+heparan+sulfate+proteoglycan+is+a+receptor+for+adeno-associated+virus+type+2+virions.">Membrane-associated heparan sulfate proteoglycan is a receptor for adeno-associated virus type 2 virions.</a> J Virol. 72 (2), 1438-1445 (1998).</li><li>Wright, J. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+factors+that+contribute+to+recombinant+AAV2+particle+aggregation+and+methods+to+prevent+its+occurrence+during+vector+purification+and+formulation.">Identification of factors that contribute to recombinant AAV2 particle aggregation and methods to prevent its occurrence during vector purification and formulation.</a> Mol Ther. 12 (1), 171-178 (2005).</li><li>Gruntman, A. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stability+and+compatibility+of+recombinant+adeno-associated+virus+under+conditions+commonly+encountered+in+human+gene+therapy+trials.">Stability and compatibility of recombinant adeno-associated virus under conditions commonly encountered in human gene therapy trials.</a> Hum Gene Ther Methods. 26 (2), 71-76 (2015).</li><li>Srivastava, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rationale+and+strategies+for+the+development+of+safe+and+effective+optimized+AAV+vectors+for+human+gene+therapy.">Rationale and strategies for the development of safe and effective optimized AAV vectors for human gene therapy.</a> Mol Ther Nucleic Acids. 32, 949-959 (2023).</li><li>Mullard, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FDA+approves+first+gene+therapy+for+Duchenne+muscular+dystrophy,+despite+internal+objections.">FDA approves first gene therapy for Duchenne muscular dystrophy, despite internal objections.</a> Nat Rev Drug Discov. 22 (8), 610-610 (2023).</li><li>Center for Biologics Evaluation and Research. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Approved+Cellular+and+Gene+Therapy+Products.">Approved Cellular and Gene Therapy Products.</a> US Food Drug Adm. , (2023).</li><li>Kang, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AAV+vectors+applied+to+the+treatment+of+CNS+disorders:+Clinical+status+and+challenges.">AAV vectors applied to the treatment of CNS disorders: Clinical status and challenges.</a> J Control Release Off J Control Release Soc. 355, 458-473 (2023).</li><li>De Wolf, D., Singh, K., Chuah, M. 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Il protocollo di purificazione a gradiente di densità a doppio iodixanolo è il metodo universale perché è applicabile a qualsiasi variante mutante AAV, indipendentemente dalla loro specificità recettoriale. I primi metodi di purificazione dell'AAV si basavano sulla densità delle particelle e includevano la centrifugazione isopicnica in CsCl e la centrifugazione continua a gradiente di densità del saccarosio19. Successivamente, sono stati sviluppati approcci sierotipo-specifici, che hanno fa...

I vettori virali adeno-associati ricombinanti (rAAV) sono strumenti ampiamente utilizzati per il trattamento di malattie genetiche, tra cui l'atrofia muscolare spinale, la distrofia retinica e l'emofilia A 1,2,3. I vettori rAAV sono ingegnerizzati per mancare dei geni virali presenti nell'AAV4 wild-type, un piccolo virus icosaedrico senza involucro con un genoma lineare di DNA a singolo filamento di 4,7 kb. L'AAV è stato scoperto per la prima volta negli anni '60 come contaminante dei preparati di adenovirus5. Nonostante le sue piccole dimensioni del capside, che limitano la dimensione del transgene che può essere impacchettato a un massimo di 4,9 kb escludendo ITRs6, l'AAV è utile per il rilascio del transgene perché non è patogeno nell'uomo, consente l'espressione del transgene in molti tipi di cellule in divisione e non in divisione e ha effetti immunogenici limitati7.
Come membri del genere dependoparvovirus, la produzione di rAAV si basa sull'espressione di geni helper presenti nell'adenovirus o nel virus dell'herpes simplex8. Sono state sviluppate diverse strategie per produrre rAAV, ma la produzione in cellule HEK293 trasformate con i geni adenovirali E1A/E1B helper è il metodo più consolidato utilizzato oggi9. L'approccio generale alla produzione di rAAV inizia con la trasfezione di cellule HEK293 con tre plasmidi contenenti il transgene all'interno di ripetizioni terminali invertite (ITR), geni AAV rep e cap e geni helper adenovirali aggiuntivi, rispettivamente. Settantadue ore dopo la trasfezione, le cellule vengono raccolte e processate per purificare rAAV contenente il transgene.
Nello sviluppo di nuovi vettori rAAV per scopi terapeutici, un obiettivo importante è la produzione di vettori con una maggiore efficienza di trasduzione. Un aumento dell'efficienza di trasduzione delle cellule bersaglio significherebbe una diminuzione della dose clinica necessaria di rAAV, diminuendo così la probabilità di effetti immunogenici avversi che vanno dalla neutralizzazione mediata da anticorpi a tossicità acute10,11. Per migliorare l'efficacia di trasduzione dei vettori rAAV, è possibile apportare modifiche al genoma impacchettato o al capside. I metodi praticabili per regolare l'efficacia della trasduzione attraverso la progettazione del genoma impacchettato includono l'incorporazione di promotori forti e tessuto-specifici, una selezione ponderata degli elementi di elaborazione dell'mRNA e l'ottimizzazione della sequenza codificante per migliorare l'efficienza della traduzione12. Le alterazioni del capside vengono effettuate con l'obiettivo di aumentare il tropismo per i tipi di cellule umane bersaglio. Gli sforzi verso lo sviluppo di nuovi capsidi vettoriali di trasporto del transgene rAAV sono generalmente caratterizzati da un focus sulla progettazione razionale di capsidi AAV con mutazioni specifiche che hanno come bersaglio specifici recettori cellulari o sull'evoluzione diretta per identificare capsidi con tropismo per specifici tipi di cellule da librerie di capsidi combinatori ad alta complessità senza mirare a un recettore specifico (sebbene alcuni gruppi combinino questi approcci)13, 14,15. Nell'approccio dell'evoluzione diretta, le librerie combinatorie del capside sono costruite utilizzando una particolare spina dorsale del sierotipo con regioni variabili mutate all'esterno del capside16. Le librerie combinatorie di capsidi sono spesso costruite a partire da sierotipi AAV non originati nell'uomo, riducendo il rischio di immunità preesistente durante l'uso clinico10. Pertanto, i metodi di purificazione che possono essere applicati a qualsiasi sierotipo sono ideali per eliminare la necessità di un'ottimizzazione sierotipo-specifica per i sierotipi meno comunemente usati che fungono da spina dorsale per queste librerie.
La centrifugazione a gradiente di densità dello iodixanolo viene utilizzata per purificare titoli elevati di rAAV con elevata infettività17. In questo protocollo, l'rAAV viene prodotto in coltura cellulare in sospensione per ridurre la quantità di lavoro necessaria per produrre grandi titoli di AAV. È inclusa anche una fase di centrifugazione per eliminare il lisato cellulare per ridurre la presenza di proteine contaminanti e diminuire il rischio di precipitazione del virus. Questo protocollo è un metodo economico per produrre preparati di rAAV ad alta purezza adatti all'uso preclinico.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>5810 R benchtop centrifuge</td>
			<td>Eppendorf</td>
			<td>22625501</td>
			<td></td>
		</tr>
		<tr>
			<td>8-channel peristaltic pump&#160;</td>
			<td>Watson-Marlow</td>
			<td>020.3708.00A</td>
			<td></td>
		</tr>
		<tr>
			<td>Automated cell counter&#160;</td>
			<td>NanoEntek</td>
			<td>EVE-MC</td>
			<td></td>
		</tr>
		<tr>
			<td>Avanti J-E high-speed centrifuge</td>
			<td>Beckman Coulter</td>
			<td>369001</td>
			<td></td>
		</tr>
		<tr>
			<td>Benzonase</td>
			<td>Thermo Scientific</td>
			<td>88701</td>
			<td></td>
		</tr>
		<tr>
			<td>Biological safety cabinet</td>
			<td>Labconco</td>
			<td>322491101</td>
			<td></td>
		</tr>
		<tr>
			<td>CO2 incubator with shaker&#160;</td>
			<td></td>
			<td></td>
			<td>Set at 8% CO2 and 37 &#176;C</td>
		</tr>
		<tr>
			<td>Conical centrifuge tubes</td>
			<td>Thermo Scientific</td>
			<td>339652</td>
			<td>50 mL</td>
		</tr>
		<tr>
			<td>Conical centrifuge tubes</td>
			<td>Thermo Scientific</td>
			<td>339650</td>
			<td>15 mL</td>
		</tr>
		<tr>
			<td>Disposable micro-pipets</td>
			<td>Fisherbrand</td>
			<td>21-164-2G</td>
			<td>Capillaries</td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s phosphate buffered saline without CaCl2 and MgCl2&#160; (DPBS) (10x)</td>
			<td>Sigma-Aldrich</td>
			<td>D1408</td>
			<td></td>
		</tr>
		<tr>
			<td>ECLIPSE Ts2R-FL inverted microscope</td>
			<td>Nikon</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Expi293 Expression Medium</td>
			<td>Gibco</td>
			<td>A1435101</td>
			<td></td>
		</tr>
		<tr>
			<td>Expi293F cells</td>
			<td>Gibco</td>
			<td>A14527</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter tips</td>
			<td>USA Scientific</td>
			<td>1126-7810</td>
			<td>1000 &#181;L</td>
		</tr>
		<tr>
			<td>Filter tips</td>
			<td>USA Scientific</td>
			<td>1120-8810</td>
			<td>200 &#181;L</td>
		</tr>
		<tr>
			<td>Filter tips</td>
			<td>USA Scientific</td>
			<td>1120-1810</td>
			<td>20 &#181;L</td>
		</tr>
		<tr>
			<td>Filter tips</td>
			<td>USA Scientific</td>
			<td>1121-3810</td>
			<td>10 &#181;L</td>
		</tr>
		<tr>
			<td>Hypodermic needles</td>
			<td>Tyco Healthcare</td>
			<td>820112</td>
			<td>20 GA x 1-1/2 A</td>
		</tr>
		<tr>
			<td>Ice bucket with lid</td>
			<td>VWR</td>
			<td>10146-184</td>
			<td></td>
		</tr>
		<tr>
			<td>JS-5.3 rotor</td>
			<td>Beckman Coulter</td>
			<td>368690</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium chloride solution (1 M)</td>
			<td>Millipore Sigma</td>
			<td>M1028-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Metal stand and clamp&#160;</td>
			<td>Fisherbrand</td>
			<td>05-769-6Q</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcentrifuge tubes</td>
			<td>Eppendorf</td>
			<td>22600028</td>
			<td>1.5 mL</td>
		</tr>
		<tr>
			<td>Needle nose pliers</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Optima XE-90 ultracentrifuge</td>
			<td>Beckman Coulter</td>
			<td>A94471</td>
			<td></td>
		</tr>
		<tr>
			<td>Opti-MEM I Reduced-Serum Medium</td>
			<td>Gibco</td>
			<td>31985062</td>
			<td></td>
		</tr>
		<tr>
			<td>OptiPrep density gradient media (iodixanol)</td>
			<td>Serumwerk</td>
			<td>AXS-1114542</td>
			<td>60% iodixanol solution</td>
		</tr>
		<tr>
			<td>P1000 Pipet</td>
			<td>Gilson</td>
			<td>F144059M</td>
			<td></td>
		</tr>
		<tr>
			<td>P2 Pipet</td>
			<td>Gilson</td>
			<td>F144054M</td>
			<td></td>
		</tr>
		<tr>
			<td>P20 Pipet</td>
			<td>Gilson</td>
			<td>F144056M</td>
			<td></td>
		</tr>
		<tr>
			<td>P200 Pipet</td>
			<td>Gilson</td>
			<td>F144058M</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenol red&#160;solution</td>
			<td>Sigma-Aldrich</td>
			<td>P0290</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffered saline (PBS)</td>
			<td>Sigma-Aldrich</td>
			<td>P4474</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipet-Aid XP pipette controller</td>
			<td>Drummond Scientific</td>
			<td>4-000-101</td>
			<td></td>
		</tr>
		<tr>
			<td>Plasmid pCapsid</td>
			<td>De novo or Addgene, etc.&#160;</td>
			<td>N/A</td>
			<td>We used pACGrh74.&#160;</td>
		</tr>
		<tr>
			<td>Plasmid pHelper</td>
			<td>Addgene</td>
			<td>112867</td>
			<td></td>
		</tr>
		<tr>
			<td>Plasmid pTransgene</td>
			<td>De novo or Addgene, etc.&#160;</td>
			<td>N/A</td>
			<td>We used pdsAAV-GFP.</td>
		</tr>
		<tr>
			<td>Pluronic F-68 polyol solution (10%)</td>
			<td>Mp Biomedicals</td>
			<td>92750049</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylene glycol 8000</td>
			<td>Research Products International</td>
			<td>P48080-500.0</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylenimine HCl Max (PEI-Max)</td>
			<td>Polysciences</td>
			<td>NC1038561</td>
			<td>Dilute in water to 40 &#956;M</td>
		</tr>
		<tr>
			<td>Polypropylene centrifuge tubes, sterile</td>
			<td>Corning</td>
			<td>431123</td>
			<td>500 mL</td>
		</tr>
		<tr>
			<td>Polypropylene centrifuge tubes, sterile</td>
			<td>Corning</td>
			<td>430776</td>
			<td>250 mL</td>
		</tr>
		<tr>
			<td>Polypropylene Optiseal tubes</td>
			<td>Beckman Coulter</td>
			<td>361625</td>
			<td></td>
		</tr>
		<tr>
			<td>Serological pipettes</td>
			<td>Alkali Scientific</td>
			<td>SP250-B</td>
			<td>50 mL</td>
		</tr>
		<tr>
			<td>Serological pipettes</td>
			<td>Alkali Scientific</td>
			<td>SP225-B</td>
			<td>25 mL</td>
		</tr>
		<tr>
			<td>Serological pipettes</td>
			<td>Alkali Scientific</td>
			<td>SP210-B</td>
			<td>10 mL</td>
		</tr>
		<tr>
			<td>Serological pipettes</td>
			<td>Alkali Scientific</td>
			<td>SP205-B</td>
			<td>5 mL</td>
		</tr>
		<tr>
			<td>Shaker flasks</td>
			<td>Fisherbrand</td>
			<td>PBV1000</td>
			<td>1 L</td>
		</tr>
		<tr>
			<td>Shaker flasks</td>
			<td>Fisherbrand</td>
			<td>PBV50-0</td>
			<td>500 mL</td>
		</tr>
		<tr>
			<td>Shaker flasks</td>
			<td>Fisherbrand</td>
			<td>PBV250</td>
			<td>250 mL</td>
		</tr>
		<tr>
			<td>Shaker flasks</td>
			<td>Fisherbrand</td>
			<td>PBV12-5</td>
			<td>125 mL</td>
		</tr>
		<tr>
			<td>Sodium chloride solution (5 M)</td>
			<td>Fisher Scientific</td>
			<td>NC1752640</td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile syringes</td>
			<td>Fisherbrand</td>
			<td>14-955-458</td>
			<td>5 mL</td>
		</tr>
		<tr>
			<td>Syringe filter</td>
			<td>Millipore</td>
			<td>SLGV013SL</td>
			<td>0.22 micron</td>
		</tr>
		<tr>
			<td>Tris-HCl pH 8.5 (1 M)</td>
			<td>Kd Medical</td>
			<td>RGE3363</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan blue solution</td>
			<td>Gibco</td>
			<td>15250061</td>
			<td></td>
		</tr>
		<tr>
			<td>Tube rack assembly</td>
			<td>Beckman Coulter</td>
			<td>361646</td>
			<td></td>
		</tr>
		<tr>
			<td>Tube spacers (x4)</td>
			<td>Beckman Coulter</td>
			<td>361669</td>
			<td></td>
		</tr>
		<tr>
			<td>Tubing for peristaltic pump</td>
			<td>Fisher Scientific</td>
			<td>14190516</td>
			<td></td>
		</tr>
		<tr>
			<td>Type 70 Ti fixed-angle titanium rotor</td>
			<td>Beckman Coulter</td>
			<td>337922</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultra low temperature freezer</td>
			<td></td>
			<td></td>
			<td>Set at -70 &#176;C</td>
		</tr>
		<tr>
			<td>Vivaspin 20 centrifugal concentrator</td>
			<td>Sartorius</td>
			<td>VS2041</td>
			<td></td>
		</tr>
		<tr>
			<td>Water bath&#160;</td>
			<td></td>
			<td></td>
			<td>Set at 37 &#176;C</td>
		</tr>
	</tbody>
</table>

suspension culture production and purification of adeno-associated virus by iodixanol density gradient centrifugation for in vivo applications

Questo protocollo descrive la produzione e la purificazione di virus adeno-associati ricombinanti (rAAV) mediante centrifugazione a gradiente di densità dello iodio, un metodo sierotipo-agnostico di purificazione dell'AAV descritto per la prima volta nel 1999. I vettori rAAV sono ampiamente utilizzati nelle applicazioni di terapia genica per veicolare transgeni a vari tipi di cellule umane. In questo lavoro, il virus ricombinante è prodotto dalla trasfezione di cellule Expi293 in coltura in sospensione con plasmidi che codificano per il transgene, il capside vettore e i geni helper adenovirali. La centrifugazione a gradiente di densità dello iodixanolo purifica le particelle AAV complete in base alla densità delle particelle. Inoltre, in questa metodologia ormai onnipresente sono incluse tre fasi al fine di aumentare la resa totale del virus, diminuire il rischio di precipitazione a causa della contaminazione delle proteine e concentrare ulteriormente il prodotto virale finale, rispettivamente: precipitazione di particelle virali da terreni cellulari utilizzando una soluzione di polietilenglicole (PEG) e cloruro di sodio, l'introduzione di un secondo ciclo di centrifugazione a gradiente di densità dello iodixanolo, e lo scambio di tamponi tramite un filtro centrifugo. Utilizzando questo metodo, è possibile ottenere costantemente titoli nell'intervallo di10-12 particelle virali/mL di eccezionale purezza per l'uso in vivo .

Recombinant adeno-associated viral (rAAV) vectors are widely used tools for the treatment of genetic diseases, including spinal muscular atrophy, retinal dystrophy, and hemophilia A1,2,3. rAAV vectors are engineered to lack viral genes present in wild-type AAV4, a small, non-envelope icosahedral virus with a linear single-stranded 4.7 kb DNA genome. AAV was first discovered in the 1960s as a contaminant of adenovirus preparations5. Despite its small capsid size, which limits the size of the transgene that can be packaged to a maximum of 4.9 kb excluding ITRs6, AAV is useful for transgene delivery because it is non-pathogenic in humans, allows expression of transgene in many dividing and nondividing cell types, and has limited immunogenic effects7.
As members of the genus dependoparvovirus, the production of rAAVs relies on the expression of helper genes present in adenovirus or herpes simplex virus8. Several strategies to produce rAAV have been developed, but production in HEK293 cells transformed with the adenoviral E1A/E1B helper genes is the most established method used today9. The general approach of rAAV production begins with the transfection of HEK293 cells with three plasmids containing the transgene within inverted terminal repeats (ITRs), AAV rep and cap genes, and additional adenoviral helper genes, respectively. Seventy-two hours after transfection, cells are harvested and processed to purify rAAV containing the transgene.
In the development of new rAAV vectors for therapeutic purposes, a major goal is producing vectors with increased transduction efficiency. An increase in the transduction efficiency of target cells would mean a decrease in the necessary clinical dose of rAAV, thus decreasing the likelihood of adverse immunogenic effects ranging from antibody-mediated neutralization to acute toxicities10,11. To improve the transduction efficacy of rAAV vectors, alterations can be made to the packaged genome or to the capsid. Viable methods to tune transduction efficacy via packaged genome design include the incorporation of strong and tissue-specific promoters, thoughtful selection of mRNA processing elements, and coding sequence optimization to improve translation efficiency12. Alterations to the capsid are made with the goal of increasing tropism for target human cell types. Efforts towards developing new rAAV transgene delivery vector capsids are generally characterized by a focus on either rational design of AAV capsids with specific mutations targeting specific cell receptors or directed evolution to identify capsids with tropism for specific cell types from high-complexity combinatorial capsid libraries without targeting one specific receptor (although some groups combine these approaches)13,14,15. In the directed evolution approach, combinatorial capsid libraries are constructed using a particular serotype backbone with mutated variable regions on the capsid exterior16. Combinatorial capsid libraries are often constructed from AAV serotypes not originating in humans, decreasing the risk of preexisting immunity during clinical use10. Therefore, purification methods that can be applied to any serotype are ideal to eliminate the need for serotype-specific optimization for the less commonly used serotypes serving as backbones for these libraries.
Iodixanol density gradient centrifugation is utilized to purify high titers of rAAV with high infectivity17. In this protocol, rAAV is produced in suspension cell culture to decrease the amount of labor needed to produce large titers of AAV. A centrifugation step is also included to clear cell lysate to reduce the presence of contaminating proteins and decrease the risk of virus precipitation. This protocol is a cost-effective method to produce preparations of high-purity rAAV suitable for pre-clinical use.

Autore in primo piano: Isolamento efficiente dei virus adeno-associati per applicazioni precliniche

Produzione e purificazione in coltura in sospensione di virus adeno-associati mediante centrifugazione a gradiente di densità di iodixanolo per applicazioni in vivo

We use a directed evolution approach to identify adeno-associated viral capits with higher tropism for target human cell types. Through this research, we aim to produce recombinant adeno-associated viral vectors with improved target cell transduction and clinical relevance within the field of gene therapy. Our group recently de-targeted several AAV serotypes from the liver by incorporating capsid residues original to an AAV serotype that naturally possesses decreased liver tropism.If successfully expanded to additional serotypes, this provides the groundwork to decrease necessary RAAV clinical dose by peripheral injection and reduce adverse patient outcomes. The IODIXanol purification method while being cost effective is difficult to scale up. Additionally, in downstream applications, the directed evolution approach is performed with animal models or in vitro.So capsid isolated by directed evolution may not transduce in vivo targets in humans to the same extent as in preclinical models. This protocol is affordable and accessible for smaller labs. Additionally, this method yields high purity, recombinant adeno-associated virus that can be used for downstream preclinical in vivo applications.

Questo metodo può essere utilizzato per ottenere titoli di almeno10-12 particelle virali per ml. Un titolo può essere ottenuto (Figura 3) mediante qPCR utilizzando i primer ITR forniti nella Tabella supplementare 1, mediante ddPCR o con qualsiasi altro metodo di titolazione. Titoli non ottimali potrebbero derivare dall'uso di un gene cap che codifica per un capside con scarsa efficienza di confezionamento.
Un'altra possibile ...

Watch this Scientific Journal Video about Author Spotlight: Efficient Adeno-Associated Virus Isolation for Pre-Clinical Applications at JoVE.com

Il virus adeno-associato viene prodotto in coltura cellulare in sospensione e purificato mediante centrifugazione a gradiente di densità a doppio iodixanolo. Sono incluse misure per aumentare la resa totale del virus, diminuire il rischio di precipitazione del virus e concentrare ulteriormente il prodotto finale del virus. I titoli finali attesi raggiungono10-12 particelle virali/mL e sono adatti per l'uso preclinico in vivo .

This protocol describes recombinant adeno-associated virus (rAAV) production and purification by iodixanol density gradient centrifugation, a ...

Utilizziamo un approccio di evoluzione diretta per identificare i capiti virali adeno-associati con un tropismo più elevato per i tipi di cellule umane bersaglio. Attraverso questa ricerca, miriamo a produrre vettori virali adeno-associati ricombinanti con una migliore trasduzione delle cellule bersaglio e rilevanza clinica nel campo della terapia genica. Il nostro gruppo ha recentemente de-targettizzato diversi sierotipi di AAV dal fegato incorporando residui di capside originali di un sierotipo AAV che possiede naturalmente un ridotto trofismo epatico.Se esteso con successo ad altri sierotipi, questo fornisce le basi per ridurre la dose clinica di RAAV necessaria mediante iniezione periferica e ridurre gli esiti avversi per i pazienti. Il metodo di purificazione IODIXanol, pur essendo conveniente, è difficile da scalare. Inoltre, nelle applicazioni a valle, l'approccio dell'evoluzione diretta viene eseguito con modelli animali o in vitro.Quindi il capside isolato dall'evoluzione diretta potrebbe non trasdurre bersagli in vivo nell'uomo nella stessa misura dei modelli preclinici. Questo protocollo è conveniente e accessibile per i laboratori più piccoli. Inoltre, questo metodo produce virus adeno-associati ricombinanti ad alta purezza che possono essere utilizzati per applicazioni precliniche in vivo a valle.

suspension-culture-production-purification-adeno-associated-virus

Research

JoVE Journal

Medicine

Suspension Culture Production and Purification of Adeno-Associated Virus by Iodixanol Density Gradient Centrifugation for In Vivo Applications

This protocol describes recombinant adeno-associated virus (rAAV) production and purification by iodixanol density gradient centrifugation, a serotype-agnostic method of purifying AAV first described in 1999. rAAV vectors are widely used in gene therapy applications to deliver transgenes to various human cell types. In this work, the recombinant virus is produced by transfection of Expi293 cells in suspension culture with plasmids encoding the transgene, vector capsid, and adenoviral helper genes. Iodixanol density gradient centrifugation purifies full AAV particles based on particle density. Additionally, three steps are included in this now-ubiquitous methodology in order to increase total virus yield, decrease the risk of precipitation due to contaminating proteins, and further concentrate the final virus product, respectively: precipitation of viral particles from cell media using a solution of polyethylene glycol (PEG) and sodium chloride, the introduction of a second round of iodixanol density gradient centrifugation, and buffer exchange via a centrifugal filter. Using this method, it is possible to consistently achieve titers in the range of 1012 viral particles/mL of exceptional purity for in vivo use.

Adeno-associated virus is produced in suspension cell culture and purified by double iodixanol density gradient centrifugation. Steps are included to increase total virus yield, decrease the risk of virus precipitation, and further concentrate the final virus product. Expected final titers reach 1012 viral particles/mL and are suitable for pre-clinical in vivo use.