Pseudotyping Service of Lentiviral Vectors with Hepacivirus
Glycoprotein is one of the major components of human pathogenic viruses. They have been shown to play an important role in infection and immunity. The development of novel diagnostic antibodies against these antigenic viral glycoproteins has also demonstrated potential in the field of infectious disease treatment. Since viral envelope glycoproteins are a key consideration in the interaction of receptors with neutralizing antibodies, it is necessary to design glycoprotein optimization strategies.
Creative Biolabs has a team of professional gene therapy scientists who are experienced in the optimization of viral envelope glycoproteins. Our advanced variant optimization technology platform enables the optimized Lentiviral vectors (LVs) to remain active to meet the customer's research needs.
Hepacivirus Introdcution
The origin of GaLV has been assumed to be a murine retrovirus derived from a local South East Asian rodent host. The host cell receptor for GaLV Env has been identified as a sodium-dependent phosphate transporter protein. Similar to other retroviruses, GaLV encodes a single transmembrane surface glycoprotein (GaLV Env), which is cleaved into surface (SU) and transmembrane (TM) subunits. The TM domain of GaLV Env contains a short 30-amino-acid C-terminal cytoplasmic tail. The Env protein from GaLV has been shown to be incompatible with HIV-1 in the production of infectious pseudotyped particles. This incompatibility has been mapped to the C-terminal cytoplasmic tail of GaLV Env and the HIV-1 accessory protein Vpu modulates this incompatibility. Glycoproteins containing the cytoplasmic tail from GaLV Env are prevented from being incorporated into HIV-1 particles by Vpu, effectively reducing infectious particle production by 50- to 100-fold.
Figure 1. Schematic representation of the cell-free hepatitis C virus (HCV) entry pathway.1
Why Use Hepacivirus Envelope Proteins?
LVs are inherently flexible. By replacing the native HIV-1 envelope (gp120/gp41) with Hepacivirus E1/E2, we create a chimeric particle that possesses the stable integration and large cargo capacity of a lentivirus but the "key" to the liver held by HCV.
The Mechanism of Entry
Unlike the pH-dependent fusion of VSV-G that occurs in the early endosome, Hepacivirus-pseudotyped LVs mimic the authentic HCV lifecycle:
- Initial Attachment: Interaction with glycosaminoglycans and SR-BI.
- Receptor Engagement: High-affinity binding of E2 to the large extracellular loop of CD81.
- Endocytosis: Clathrin-mediated uptake into the cell.
- Membrane Fusion: Triggered by the acidic environment of the endosome, leading to the release of the lentiviral capsid into the cytosol.
Distinction from VSV-G and Others
VSV-G relies on the LDL receptor (LDLR), which is expressed on nearly every nucleated cell. While efficient, this leads to significant "off-target" sequestration in vivo. Hepacivirus pseudotypes offer a physiologically relevant model for studying liver-specific entry that VSV-G cannot replicate.
Advantages of Hepacivirus-Pseudotyped Lentiviral Vectors
- Specific Cellular Entry Mechanism: As outlined, HCV E1/E2-mediated entry relies on a receptor complex predominantly expressed on hepatocytes. Pseudotyped LV particles "hijack" this precise recognition system, effectively restricting gene delivery to hepatocytes and related models.
- Distinct Membrane Fusion Process: HCV membrane fusion occurs in the acidic endosomal environment, driven by the E1 glycoprotein. This differs from the direct plasma membrane fusion mediated by VSV-G, offering an intracellular routing pathway closer to that of the native virus, which may influence transgene expression kinetics and fate.
- Unique Platform for Virus-Host Interaction Studies: Pseudotyping with specific E1/E2 mutants or envelopes from different genotypes enables precise investigation of the roles of particular receptor-binding domains or neutralising antibody epitopes in viral entry, making it an ideal tool for screening entry inhibitors.
Application Fields of Hepacivirus-Pseudotyped Lentiviral Vectors
- High-Throughput Screening of HCV Entry Inhibitors: Construction of reporter gene vectors for rapid screening and evaluation of anti-HCV entry candidate drugs or neutralizing antibodies.
- Liver-Specific Gene Function Studies: Delivery of shRNA, CRISPR/Cas9 components, or cDNA to study gene function in a physiologically relevant hepatocyte context.
- Liver Disease Modelling: Introduction of pathogenic genes or mutations into hepatocytes to establish in vitro models of inherited liver disorders.
- Development of Liver-Targeted Gene Therapy Vectors: Serves as a delivery tool to validate the efficacy of liver-specific promoters or therapeutic transgenes, paving the way for in vivo gene therapy.
Services at Creative Biolabs
Pseudotyped viruses play an important role in the study of virus entry process, receptor identification, neutralizing antibody detection, vaccine evaluation and the like. Creative Biolabs provides pseudotyping services of lentiviral vector for targeting CD81+ cells using envelope proteins derived from hepacivirus. Pseudotype virus is produced by a combination of exogenous viral envelope proteins, which has been shown to have several compelling advantages compared to traditional lentiviruses:
- Single cycle replication in cells
- Good safety
- Has a wide range of hosts
- Higher transfection efficiency
- Easier to concentrate to high titers
- Resistance to serum complement
- Non-cell cycle-dependent transfection
Hepacivirus Envelope Protein Design & Optimisation
The efficacy of a pseudotyped vector begins with the envelope. We don't simply use "wild-type" sequences; we optimise them for the human expression environment.
- Strain Selection: Choose from multiple Hepacivirus genotypes (1a, 1b, 2a, 3a, etc.) to match your specific research focus.
- Codon Optimisation: We utilise proprietary algorithms to optimise GC content and remove cryptic splice sites, significantly increasing E1 and E2 expression levels in producer cells.
- Structural Engineering: To improve the incorporation of E1/E2 into the lentiviral membrane, we offer truncation or mutation of the transmembrane domains and cytoplasmic tails, which often enhances the resulting viral titer.
Hepacivirus-Pseudotyped Lentiviral Vector Construction
Our molecular biology suite addresses the complexity of vector design, ensuring the genetic payload remains stable and is expressed at the desired levels.
- Modular Backbones: Based on 3rd-generation HIV-1 transfer vectors.
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Versatile Cargo Options:
- Reporter Genes: GFP, Luciferase, mCherry for tracking.
- Gene Modulation: shRNA and miRNA.
- Therapeutic Sequences: Full-length cDNA for gene replacement therapies.
- Promoter Customisation: While CMV is standard, we highly recommend liver-specific promoters to ensure expression is restricted to your target cells.
Lentiviral Packaging & Production
Our production process is scaled to your needs, from small-scale discovery to pilot-plant manufacturing.
- High-Efficiency Transfection: Optimised multi-plasmid transfection in HEK293T/17 suspension or adherent cultures.
- Serum-Free Options: Available for projects requiring minimal protein interference.
- Safety Compliance: Every batch is designed to be replication-incompetent and meets BSL-2 requirements.
Titer Determination & Functional Validation
We provide clarity on the potency of your vector through a dual-titer approach:
- Physical Titer: Measured via p24 ELISA or qPCR/ddPCR for viral RNA copies (VP/mL).
- Functional Titer: Measured via transduction in permissive cells
Result Delivery
| Service Module | Core Deliverables | Key Output |
|---|---|---|
| Envelope Design & Optimization | Genotype selection, codon optimization, protein engineering, custom sequence support. | Sequence-verified, high-expression envelope plasmid. |
| Lentiviral Vector Construction | Cloning of your gene of interest into LV backbone, mono-/bi-cistronic design, promoter customization (incl. liver-specific). | High-purity, validated transfer plasmid. |
| Viral Packaging & Production | Co-transfection using 3rd/4th generation systems, small to pilot scale production under strict BSL-2 protocols. | Crude viral supernatant. |
| Viral Purification & Concentration | Ultracentrifugation or chromatography purification, buffer exchange, concentration to high titer. | Purified, concentrated viral stock. |
| Titer Determination & Functional Validation | Physical titer and hepatocyte-specific functional titer (TU/mL) determination. | Comprehensive titer analysis report. |
| Custom Project Solutions | End-to-end project design based on specific goals. | Custom project report, technical consultation, and ongoing support. |
Collaboration Workflow
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Consultation & Project Design
Our expert team designs a customised proposal based on your research objectives.
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Agreement & Project Initiation
Finalisation of the proposal, timeline, and budget.
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Execution & Production
We perform vector construction, virus packaging, purification, and QC.
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Data & Delivery
Provision of a detailed experimental report, all data, and the final viral product.
Frequently Asked Questions
Q: Are Hepacivirus-pseudotyped lentiviruses replication-competent?
A: No. We produce third-generation lentiviral vectors. Essential viral genes are deleted from the vector genome and provided in trans on separate plasmids. The resulting viral particles are capable of a single round of infection and transgene expression but cannot produce new progeny virus, ensuring biosafety.
Q: Are they suitable for in vivo studies?
A: Yes. High-purity, concentrated Hepacivirus-pseudotyped vectors can be used for liver-targeted in vivo studies in models like mice (e.g., via hydrodynamic tail vein injection). We can provide formulations suitable for in vivo applications.
Q: How does their infection efficiency in hepatocytes compare to VSV-G pseudotypes?
A: In most hepatocyte models, particularly primary human hepatocytes, Hepacivirus-pseudotyped vectors typically demonstrate significantly higher transduction efficiency than VSV-G pseudotypes, as they utilise the highly efficient, hepatocyte-specific natural entry pathway.
Q: Do you support client-provided custom E1/E2 gene sequences?
A: Absolutely. We can clone and produce vectors pseudotyped with your specific mutant or chimeric envelope sequences for your personalised mechanistic studies.
Connect with Us Anytime!
After glycoprotein optimization of the virus you are interested, Creative Biolabs performs binding assays to ensure the effect of glycosylation of the protein on viral function. Based on structural optimization, we also offer a range of downstream services such as Potency Tests, Safety and Toxicology Analysis, Delivery Systems Development, etc. to meet your needs. Please feel free to contact us and our experienced technicians will give you the most detailed answers to your questions.
Reference
- Colpitts C C, Tsai P L, Zeisel M B. Hepatitis C virus entry: An intriguingly complex and highly regulated process. International journal of molecular sciences, 2020, 21(6): 2091. https://doi.org/10.3390/ijms21062091 (Distributed under Open Access license CC BY 4.0, without modification.)
