BioVector® pSG3 delta env (pSG3ΔEnv) HIV-1 伪病毒假型骨架质粒载体

BioVector® pSG3 delta env (pSG3ΔEnv) HIV-1 Pseudovirus Backbone Vector

第一部分 中文说明

一 载体基本信息与科研用途

• 载体名称：BioVector® pSG3 delta env (通常写作 pSG3ΔEnv 或 pSG3.1Δenv)

• 载体类型：人类免疫缺陷病毒1型（HIV-1）复制缺陷型报告/骨架质粒载体（伪病毒骨架）。

• 核心用途：专门用于体外高通量重组HIV-1单轮感染伪病毒（Single-round infection pseudovirus）的制备，广泛部署于艾滋病毒中和抗体（Nab）效价测定、病毒入侵抑制剂筛选及包膜蛋白功能鉴定。

• 抗性标记：

  • 大肠杆菌筛选：氨苄青霉素抗性（Ampicillin，$Amp^R$）。

• 常用宿主菌：大肠杆菌 DH5a、Top10 或针对长末端重复序列（LTR）具备防重组优化能力的 Stbl3 感受态细胞。

二 关键结构域与分子改构特征

• 亲本背景：该质粒衍生自全长、具备完整感染活性的 HIV-1  proviral clone 基因组质粒 pSG3 (GenBank 保藏号：L02317)。它保留了 HIV-1 的全套顺式作用元件（如两端的 $5'$-LTR 和 $3'$-LTR 启动/加工序列、$\psi$ 病毒包装信号）以及内部除外膜蛋白外的核心结构和酶类基因。

• env 基因失活机制（$\Delta env$ 突变）：

  • 改构方法：通过使用限制性内切酶 SpeI 对亲本质粒的 env 开放阅读框进行局部单位点切割，随后利用 DNA 聚合酶 Klenow 片段进行末端补平（Klenow filling），最后重新无缝连接。

  • 分子效应：此操作精确定向地在 env 编码区内部引入了 4个碱基（CTAG）的插入突变。这一移码突变直接导致在包膜糖蛋白 env 的第 142 位氨基酸残基后自发产生了一个翻译提前终止密码子（Stop codon）。

  • 安全性与功能表型：当该质粒单独转染哺乳动物宿主细胞（如 HEK293T）时，病毒基因组能够正常转录和剪接，高效表达 HIV-1 所有的核心结构蛋白（Gag）、酶类（Pol，包括反转录酶、蛋白酶、整合酶）以及辅助调节因子（Tat, Rev 等）。然而，由于 env 基因被彻底阻断，细胞完全无法合成外膜 gp160 糖蛋白。因此，单独包装排出的病毒颗粒由于缺乏“钥匙”（外膜锚定蛋白），表现为绝对的单轮感染性（Single-round infection only），完全丧失了自主复制与二次扩散传代的能力。

三 标准单轮伪病毒制备与中和测定步骤

1. 重组伪病毒包装（Co-transfection）：

   • 采用经典的二质粒系统（Two-plasmid system）。将高纯度无内毒素的 BioVector® pSG3 delta env 骨架质粒 与 表达特定 HIV-1 临床分离株或突变株的 Env 膜蛋白表达质粒（如 pcDNA3.1-Env） 按 1比1 至 2比1 的质量比例混合。

   • 利用磷酸钙法或脂质体（如 Lipofectamine 3000）共转染处于对数生长期的 HEK293T/17 细胞。

   • 转染 48 小时后，收获富含伪病毒颗粒的培养基上清，经过低速离心和 0.45 μm 滤膜过滤，分装并冻存于 -80 摄氏度。

2. 靶细胞感染与中和测定（TZM-bl 测定体系）：

   • 将待测的患者血清（抗体）或小分子进入抑制剂（如 T-20 融合抑制剂）进行梯度稀释。

   • 将稀释后的抗体与定量的重组 HIV-1 伪病毒液在 96 孔板中 37 摄氏度孵育 1 小时，使抗体充分结合外膜糖蛋白。

   • 随后在孔中加入标准的 TZM-bl 指示细胞（该细胞稳定集成了受 HIV-1 Tat 蛋白严格驱动的荧光素酶 Luciferase 和 $\beta$-半乳糖苷酶报告基因）。

   • 孵育 48 小时后，裂解细胞并加入荧光素酶底物，通过测定相对荧光单位（RLU）的下调幅度，精确计算出该中和抗体或药物的 $IC_{50}$ 值。

四 核心科研应用方向

1. 全球 HIV-1 中和抗体谱系（bNAbs）的分子分型与 Tier 分级评价：BioVector® pSG3 delta env 联合质粒系统是国际艾滋病疫苗研究（CAVD/EDCMA）公认的金标准骨架。通过与不同进化分支（Clade A, B, C, E等）及不同临床病程阶段（Tier 1, Tier 2, Tier 3）的 env 表达载体搭配，搭建覆盖全球毒株变异的伪病毒库，用于高通量评估广谱中和抗体（如 VRC01, 10E8）的广谱杀伤效能。

2. 耐药突变株（如融合抑制剂耐药）的适应性风险评估：当 HIV-1 感染者在接受 gp41 融合抑制剂（如 Enfuvirtide）单药治疗出现耐药时，科研人员常通过 PCR 扩增患者体内的 env 变异序列，将其克隆并与 pSG3 delta env 共包装，在安全的 BSL-2 实验室环境中快速测定外膜特定位点突变（如 gp41 的 G36D 突变）对药物敏感性的定量改变。

3. 病毒学基因重组与逃逸动力学基础研究：作为一类无膜蛋白表达的 proviral 脱壳骨架，该质粒也常被用于反向遗传学实验，用来研究在特定人工选择压力或共感染状态下，缺陷型 env 基因骨架与外源野生型片段之间发生高频同源重组、从而恢复复制能力的分子演化轨迹。

PART 2 ENGLISH SECTION

I General Information and Applications

• Vector Name: BioVector® pSG3 delta env (frequently cataloged as pSG3ΔEnv or pSG3.1Δenv)

• Vector Type: Human Immunodeficiency Virus Type 1 (HIV-1) Replication-Deficient Reporter/Backbone Pseudovirus Vector.

• Primary Application: Heavily prioritized for the high-throughput reconstitution of heterologous HIV-1 single-round infection pseudoviruses in vitro. It is a cornerstone platform for measuring neutralizing antibody (Nab) titers, screening HIV entry/fusion inhibitors, and characterizing envelope glycoprotein fitness.

• Selection Flags:

  • Bacterial Selection: Ampicillin resistance gene (AmpR) for routine expansion inside standard E. coli strains.

• Common Host Systems: E. coli DH5a, Top10, or Stbl3 competent cells optimized to suppress homologous recombination across viral Long Terminal Repeats (LTRs).

II Vector Anatomy and Component Configuration

• Parental Genetic Architecture: Synthesized from the full length, replication competent HIV-1 proviral molecular clone pSG3 (GenBank Accession: L02317). It maintains all critical HIV-1 cis-acting elements (including functional $5'$ and $3'$ LTR driving/processing complexes, the $\psi$ genomic packaging cascade) and internal structural and enzymatic code.

• Env Inactivation Mechanism ($\Delta env$ Alignment):

  • Molecular Engineering: Developed by subjecting the parental plasmid framework to a targeted restriction digestion within the env open reading frame utilizing the endonuclease SpeI, followed by a Klenow polymerase filling reaction to blunt the 3' recessed ends, and subsequent self-religation.

  • Transcriptional Impact: This precise modification introduces a 4-nucleotide insertion mutation (CTAG) directly into the env sequence. This frame-shift event creates a premature translational stop codon immediately following amino acid residue 142 of the envelope precursor.

  • Safety and Functional Phenotype: Upon transfection into mammalian packaging cells (such as HEK293T), the structural proviral system transcribes normally, expressing the full suite of internal core components (Gag), replication machinery (Pol: reverse transcriptase, protease, integrase), and early regulatory factors (Tat, Rev). However, because gp160 translation is terminated early, the cells are entirely unable to manufacture the envelope spike. Consequently, the resulting particles can package and egress but remain restricted to single-round infection trajectories, possessing zero autonomous replication or secondary transmission risks.

III Single-Round Pseudovirus Production and Neutralization Assay Protocols

1. Pseudovirus Packaging Pipeline (Two-Plasmid System):

   • Co-transfect mid-log phase HEK293T/17 cells with highly purified, endotoxin-free BioVector® pSG3 delta env backbone plasmid alongside a secondary expression vector carrying the desired target variant env open reading frame (e.g., pcDNA3.1-Env) at a 1:1 to 2:1 mass ratio.

   • Deploy established calcium phosphate or lipid-mediated (e.g., Lipofectamine 3000) transfection chemistry.

   • Harvest the virus-laden supernatant 48 hours post-transfection, clarify the media via low-speed centrifugation, pass it through a 0.45 μm syringe filter module, and archive aliquots at -80 degrees Celsius.

2. Neutralization Testing via TZM-bl Indicator Matrices:

   • Prepare serial dilutions of target patient sera, monoclonal antibodies, or small-molecule entry blockers within a 96-well assay array.

   • Mix the diluted blockers with a calibrated volume of the harvested single-round pseudovirus and incubate at 37 degrees Celsius for 1 hour to allow antibody-envelope spike engagement.

   • Introduce standard TZM-bl reporter cells (engineered to express Tat-responsive Luciferase and $\beta$-galactosidase genes upon viral entry and integration).

   • Quantitate relative luciferase units (RLU) 48 hours post-infection using a luminometer, calculating exact $IC_{50}$ values based on signal reduction curves.

IV Strategic Research Applications

1. Global Profiling of Broadly Neutralizing Antibody (bNAb) Lineages: The BioVector® pSG3 delta env framework serves as an international benchmark system across major vaccine validation networks (e.g., CAVD). By pairing this single backbone against diverse panels of env functional clones representing multiple geographic clades (A, B, C, CRF01_AE) and tiered neutralization sensitivities (Tier 1, 2, and 3), researchers can systematically map the breath and potency of emergent biologics (e.g., VRC01, 10E8).

2. Resistance Mapping & Entry Inhibitor Fitness Diagnostics: When HIV-1 positive cohorts develop non-responsive outcomes against clinical fusion blockers like Enfuvirtide (T-20), the patient's native env sequence is amplified via RT-PCR, cloned into an expression vector, and paired with pSG3 delta env. This permits quantitative measurement of $EC_{50}$ shifts under standard BSL-2 containment controls, bypassing the biohazards of growing live patient isolates.

3. Elucidating Viral Recombination Mechanics & Evolutionary Escapes: Serving as an env-defective proviral reporter platform, this vector is utilized in reverse genetics to track how defective viral strands interact with flanking envelope sequences during co-infection events, mapping the precise multi-step homologous crossover t

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