悬浮培养物生产和纯化腺相关病毒的碘克沙醇密度梯度离心用于体内应用
Summary
腺相关病毒在悬浮细胞培养物中产生，并通过双碘克沙醇密度梯度离心纯化。包括提高总病毒产量、降低病毒沉淀风险和进一步浓缩最终病毒产物的步骤。预期最终滴度达到 1012 个病毒颗粒/mL，适用于临床前 体内 使用。
Abstract
该协议描述了通过碘克沙醇密度梯度离心产生和纯化的重组腺相关病毒（rAAV），这是一种与血清型无关的纯化AAV的方法，于1999年首次描述。rAAV载体广泛用于基因治疗应用，将转基因递送至各种人类细胞类型。在这项工作中，重组病毒是通过用编码转基因、载体衣壳和腺病毒辅助基因的质粒在悬浮培养物中转染 Expi293 细胞来生产的。碘克沙醇密度梯度离心法根据颗粒密度纯化完整的AAV颗粒。此外，这种现在无处不在的方法还包括三个步骤，以提高病毒总产量，降低由于污染蛋白质而沉淀的风险，并进一步浓缩最终病毒产物，分别：使用聚乙二醇（PEG）和氯化钠溶液从细胞培养基中沉淀病毒颗粒，引入第二轮碘克沙醇密度梯度离心， 以及通过离心过滤器进行缓冲液置换。使用这种方法，可以在体内使用时始终如一地达到 1012 个病毒颗粒/mL 的异常纯度。
Introduction
重组腺相关病毒 （rAAV） 载体是治疗遗传性疾病（包括脊髓性肌萎缩症、视网膜营养不良症和 A 型血友病）的广泛使用工具 1,2,3。rAAV 载体经过工程设计，缺乏野生型 AAV 4 中存在的病毒基因，野生型 AAV4 是一种具有线性单链 4.7 kb DNA 基因组的小型非包膜二十面体病毒。AAV 于 1960 年代首次被发现是腺病毒制剂的污染物5。尽管其衣壳尺寸小，将可包装的转基因的大小限制为最大 4.9 kb（不包括ITRs 6），但 AAV 可用于转基因递送，因为它在人类中无致病性，允许在许多分裂和非分裂细胞类型中表达转基因，并且免疫原性作用有限7。
作为依赖细小病毒属的成员，rAAV 的产生依赖于腺病毒或单纯疱疹病毒8 中存在的辅助基因的表达。已经开发了几种产生 rAAV 的策略，但在用腺病毒 E1A/E1B 辅助基因转化的 HEK293 细胞中生产是当今使用的最成熟的方法9。rAAV 生产的一般方法始于 HEK293 细胞的转染，其中三种质粒分别含有反转末端重复序列 （ITR）、AAV 代表 和 帽 基因以及其他腺病毒辅助基因中的转基因。转染后 72 小时，收获并处理细胞以纯化含有转基因的 rAAV。
在开发用于治疗目的的新型rAAV载体时，一个主要目标是生产具有更高转导效率的载体。靶细胞转导效率的提高意味着 rAAV 必要临床剂量的降低，从而降低从抗体介导的中和到急性毒性的不良免疫原性反应的可能性10,11。为了提高rAAV载体的转导功效，可以对包装的基因组或衣壳进行改变。通过包装基因组设计调整转导功效的可行方法包括掺入强效和组织特异性启动子、深思熟虑地选择 mRNA 加工元件以及编码序列优化以提高翻译效率12。对衣壳进行改变的目的是增加目标人类细胞类型的趋向性。开发新的 rAAV 转基因递送载体衣壳的努力通常以专注于合理设计具有靶向特定细胞受体的特定突变的 AAV 衣壳或定向进化以从高复杂性组合衣壳库中识别具有特定细胞类型嗜性的衣壳，而不靶向一种特定受体（尽管有些小组结合了这些方法）13，14,15.在定向进化方法中，组合衣壳文库是使用在衣壳外部具有突变可变区域的特定血清型骨架构建的 16。组合衣壳文库通常由非源自人类的 AAV 血清型构建，从而降低临床使用期间预先存在免疫的风险10。因此，可应用于任何血清型的纯化方法都是理想的选择，可以消除对作为这些文库骨架的不太常用的血清型进行血清型特异性优化的需要。
碘克沙醇密度梯度离心用于纯化高滴度的具有高感染性的 rAAV17。在该方案中，rAAV在悬浮细胞培养物中产生，以减少生产大滴度AAV所需的劳动力。还包括一个离心步骤，以澄清细胞裂解物，以减少污染蛋白质的存在并降低病毒沉淀的风险。该方案是一种具有成本效益的方法，用于生产适合临床前使用的高纯度rAAV制剂。
Protocol
表1提供了该协议中使用的溶液和缓冲液的组成。 溶液 组成 AAV裂解缓冲液 1.2 mL 5 M NaCl 溶液 2 mL 1 M Tris-HCl pH 8.5 溶液 80 uL 1 M MgCl2 溶液 mQ 水至 40 mL…
Representative Results
该方法可用于获得每mL至少10-12个病毒颗粒的滴度。使用补充表1中提供的ITR引物通过qPCR获得滴度（图3），通过ddPCR或任何其他滴度方法。使用包装效率低下的衣壳的帽基因可能导致滴度欠佳。 结果欠佳的另一个可能来源是 Expi293 细胞的转导效率差。建议在转染当天的细胞密度为 3-4 x 106 vc/mL，并且细胞活力接近 98%。在…
Discussion
双碘克沙醇密度梯度纯化方案是通用方法，因为它适用于任何AAV突变体变体，无论其受体特异性如何。早期的AAV纯化方法依赖于颗粒密度，包括CsCl中的等脁离心和连续蔗糖密度梯度离心19。后来，开发了血清型特异性方法，该方法利用与琼脂糖柱20 结合的单克隆抗体。1999 年开发了一种使用不连续碘克沙醇梯度的基于密度的新型纯化方法，并产生了比从 CsCl 梯?…
Divulgations
The authors have nothing to disclose.
Acknowledgements
没有。
Materials
| 5810 R benchtop centrifuge | Eppendorf | 22625501 | |
| 8-channel peristaltic pump | Watson-Marlow | 020.3708.00A | |
| Automated cell counter | NanoEntek | EVE-MC | |
| Avanti J-E high-speed centrifuge | Beckman Coulter | 369001 | |
| Benzonase | Thermo Scientific | 88701 | |
| Biological safety cabinet | Labconco | 322491101 | |
| CO2 incubator with shaker | Set at 8% CO2 and 37 °C | ||
| Conical centrifuge tubes | Thermo Scientific | 339652 | 50 mL |
| Conical centrifuge tubes | Thermo Scientific | 339650 | 15 mL |
| Disposable micro-pipets | Fisherbrand | 21-164-2G | Capillaries |
| Dulbecco's phosphate buffered saline without CaCl2 and MgCl2 (DPBS) (10x) | Sigma-Aldrich | D1408 | |
| ECLIPSE Ts2R-FL inverted microscope | Nikon | ||
| Expi293 Expression Medium | Gibco | A1435101 | |
| Expi293F cells | Gibco | A14527 | |
| Filter tips | USA Scientific | 1126-7810 | 1000 µL |
| Filter tips | USA Scientific | 1120-8810 | 200 µL |
| Filter tips | USA Scientific | 1120-1810 | 20 µL |
| Filter tips | USA Scientific | 1121-3810 | 10 µL |
| Hypodermic needles | Tyco Healthcare | 820112 | 20 GA x 1-1/2 A |
| Ice bucket with lid | VWR | 10146-184 | |
| JS-5.3 rotor | Beckman Coulter | 368690 | |
| Magnesium chloride solution (1 M) | Millipore Sigma | M1028-100ML | |
| Metal stand and clamp | Fisherbrand | 05-769-6Q | |
| Microcentrifuge tubes | Eppendorf | 22600028 | 1.5 mL |
| Needle nose pliers | |||
| Optima XE-90 ultracentrifuge | Beckman Coulter | A94471 | |
| Opti-MEM I Reduced-Serum Medium | Gibco | 31985062 | |
| OptiPrep density gradient media (iodixanol) | Serumwerk | AXS-1114542 | 60% iodixanol solution |
| P1000 Pipet | Gilson | F144059M | |
| P2 Pipet | Gilson | F144054M | |
| P20 Pipet | Gilson | F144056M | |
| P200 Pipet | Gilson | F144058M | |
| Phenol red solution | Sigma-Aldrich | P0290 | |
| Phosphate buffered saline (PBS) | Sigma-Aldrich | P4474 | |
| Pipet-Aid XP pipette controller | Drummond Scientific | 4-000-101 | |
| Plasmid pCapsid | De novo or Addgene, etc. | N/A | We used pACGrh74. |
| Plasmid pHelper | Addgene | 112867 | |
| Plasmid pTransgene | De novo or Addgene, etc. | N/A | We used pdsAAV-GFP. |
| Pluronic F-68 polyol solution (10%) | Mp Biomedicals | 92750049 | |
| Polyethylene glycol 8000 | Research Products International | P48080-500.0 | |
| Polyethylenimine HCl Max (PEI-Max) | Polysciences | NC1038561 | Dilute in water to 40 μM |
| Polypropylene centrifuge tubes, sterile | Corning | 431123 | 500 mL |
| Polypropylene centrifuge tubes, sterile | Corning | 430776 | 250 mL |
| Polypropylene Optiseal tubes | Beckman Coulter | 361625 | |
| Serological pipettes | Alkali Scientific | SP250-B | 50 mL |
| Serological pipettes | Alkali Scientific | SP225-B | 25 mL |
| Serological pipettes | Alkali Scientific | SP210-B | 10 mL |
| Serological pipettes | Alkali Scientific | SP205-B | 5 mL |
| Shaker flasks | Fisherbrand | PBV1000 | 1 L |
| Shaker flasks | Fisherbrand | PBV50-0 | 500 mL |
| Shaker flasks | Fisherbrand | PBV250 | 250 mL |
| Shaker flasks | Fisherbrand | PBV12-5 | 125 mL |
| Sodium chloride solution (5 M) | Fisher Scientific | NC1752640 | |
| Sterile syringes | Fisherbrand | 14-955-458 | 5 mL |
| Syringe filter | Millipore | SLGV013SL | 0.22 micron |
| Tris-HCl pH 8.5 (1 M) | Kd Medical | RGE3363 | |
| Trypan blue solution | Gibco | 15250061 | |
| Tube rack assembly | Beckman Coulter | 361646 | |
| Tube spacers (x4) | Beckman Coulter | 361669 | |
| Tubing for peristaltic pump | Fisher Scientific | 14190516 | |
| Type 70 Ti fixed-angle titanium rotor | Beckman Coulter | 337922 | |
| Ultra low temperature freezer | Set at -70 °C | ||
| Vivaspin 20 centrifugal concentrator | Sartorius | VS2041 | |
| Water bath | Set at 37 °C |
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Citer Cet Article
Harris, K. K., Kondratov, O., Zolotukhin, S. Suspension Culture Production and Purification of Adeno-Associated Virus by Iodixanol Density Gradient Centrifugation for In Vivo Applications. J. Vis. Exp. (204), e66460, doi:10.3791/66460 (2024).