BioVector? pSG3 delta env (pSG3ΔEnv) HIV-1 偽病毒假型骨架質(zhì)粒載體

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

第一部分 中文說明

一 載體基本信息與科研用途

• 載體名稱：BioVector? pSG3 delta env (通常寫作 pSG3ΔEnv 或 pSG3.1Δenv)

• 載體類型：人類免疫缺陷病毒1型（HIV-1）復制缺陷型報告/骨架質(zhì)粒載體（偽病毒骨架）。

• 核心用途：專門用于體外高通量重組HIV-1單輪感染偽病毒（Single-round infection pseudovirus）的制備，廣泛部署于艾滋病毒中和抗體（Nab）效價測定、病毒入侵抑制劑篩選及包膜蛋白功能鑒定。

• 抗性標記：

  • 大腸桿菌篩選：氨芐青霉素抗性（Ampicillin，$Amp^R$）。

• 常用宿主菌：大腸桿菌 DH5a、Top10 或針對長末端重復序列（LTR）具備防重組優(yōu)化能力的 Stbl3 感受態(tài)細胞。

二 關(guān)鍵結(jié)構(gòu)域與分子改構(gòu)特征

• 親本背景：該質(zhì)粒衍生自全長、具備完整感染活性的 HIV-1  proviral clone 基因組質(zhì)粒 pSG3 (GenBank 保藏號：L02317)。它保留了 HIV-1 的全套順式作用元件（如兩端的 $5'$-LTR 和 $3'$-LTR 啟動/加工序列、$\psi$ 病毒包裝信號）以及內(nèi)部除外膜蛋白外的核心結(jié)構(gòu)和酶類基因。

• env 基因失活機制（$\Delta env$ 突變）：

  • 改構(gòu)方法：通過使用限制性內(nèi)切酶 SpeI 對親本質(zhì)粒的 env 開放閱讀框進行局部單位點切割，隨后利用 DNA 聚合酶 Klenow 片段進行末端補平（Klenow filling），最后重新無縫連接。

  • 分子效應：此操作精確定向地在 env 編碼區(qū)內(nèi)部引入了 4個堿基（CTAG）的插入突變。這一移碼突變直接導致在包膜糖蛋白 env 的第 142 位氨基酸殘基后自發(fā)產(chǎn)生了一個翻譯提前終止密碼子（Stop codon）。

  • 安全性與功能表型：當該質(zhì)粒單獨轉(zhuǎn)染哺乳動物宿主細胞（如 HEK293T）時，病毒基因組能夠正常轉(zhuǎn)錄和剪接，高效表達 HIV-1 所有的核心結(jié)構(gòu)蛋白（Gag）、酶類（Pol，包括反轉(zhuǎn)錄酶、蛋白酶、整合酶）以及輔助調(diào)節(jié)因子（Tat, Rev 等）。然而，由于 env 基因被徹底阻斷，細胞完全無法合成外膜 gp160 糖蛋白。因此，單獨包裝排出的病毒顆粒由于缺乏“鑰匙”（外膜錨定蛋白），表現(xiàn)為絕對的單輪感染性（Single-round infection only），完全喪失了自主復制與二次擴散傳代的能力。

三 標準單輪偽病毒制備與中和測定步驟

1. 重組偽病毒包裝（Co-transfection）：

   • 采用經(jīng)典的二質(zhì)粒系統(tǒng)（Two-plasmid system）。將高純度無內(nèi)毒素的 BioVector? pSG3 delta env 骨架質(zhì)粒 與 表達特定 HIV-1 臨床分離株或突變株的 Env 膜蛋白表達質(zhì)粒（如 pcDNA3.1-Env） 按 1比1 至 2比1 的質(zhì)量比例混合。

   • 利用磷酸鈣法或脂質(zhì)體（如 Lipofectamine 3000）共轉(zhuǎn)染處于對數(shù)生長期的 HEK293T/17 細胞。

   • 轉(zhuǎn)染 48 小時后，收獲富含偽病毒顆粒的培養(yǎng)基上清，經(jīng)過低速離心和 0.45 μm 濾膜過濾，分裝并凍存于 -80 攝氏度。

2. 靶細胞感染與中和測定（TZM-bl 測定體系）：

   • 將待測的患者血清（抗體）或小分子進入抑制劑（如 T-20 融合抑制劑）進行梯度稀釋。

   • 將稀釋后的抗體與定量的重組 HIV-1 偽病毒液在 96 孔板中 37 攝氏度孵育 1 小時，使抗體充分結(jié)合外膜糖蛋白。

   • 隨后在孔中加入標準的 TZM-bl 指示細胞（該細胞穩(wěn)定集成了受 HIV-1 Tat 蛋白嚴格驅(qū)動的熒光素酶 Luciferase 和 $\beta$-半乳糖苷酶報告基因）。

   • 孵育 48 小時后，裂解細胞并加入熒光素酶底物，通過測定相對熒光單位（RLU）的下調(diào)幅度，精確計算出該中和抗體或藥物的 $IC_{50}$ 值。

四 核心科研應用方向

1. 全球 HIV-1 中和抗體譜系（bNAbs）的分子分型與 Tier 分級評價：BioVector? pSG3 delta env 聯(lián)合質(zhì)粒系統(tǒng)是國際艾滋病疫苗研究（CAVD/EDCMA）公認的金標準骨架。通過與不同進化分支（Clade A, B, C, E等）及不同臨床病程階段（Tier 1, Tier 2, Tier 3）的 env 表達載體搭配，搭建覆蓋全球毒株變異的偽病毒庫，用于高通量評估廣譜中和抗體（如 VRC01, 10E8）的廣譜殺傷效能。

2. 耐藥突變株（如融合抑制劑耐藥）的適應性風險評估：當 HIV-1 感染者在接受 gp41 融合抑制劑（如 Enfuvirtide）單藥治療出現(xiàn)耐藥時，科研人員常通過 PCR 擴增患者體內(nèi)的 env 變異序列，將其克隆并與 pSG3 delta env 共包裝，在安全的 BSL-2 實驗室環(huán)境中快速測定外膜特定位點突變（如 gp41 的 G36D 突變）對藥物敏感性的定量改變。

3. 病毒學基因重組與逃逸動力學基礎(chǔ)研究：作為一類無膜蛋白表達的 proviral 脫殼骨架，該質(zhì)粒也常被用于反向遺傳學實驗，用來研究在特定人工選擇壓力或共感染狀態(tài)下，缺陷型 env 基因骨架與外源野生型片段之間發(fā)生高頻同源重組、從而恢復復制能力的分子演化軌跡。

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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