The choice of gene delivery tools is the key to successful gene therapy. Whether the drug can ultimately exert efficacy in the human body depends to a large extent on a stable and efficient delivery system. At present, the commonly used vectors for gene therapy include viral vectors and non-viral vectors. Viral vectors have the advantages of a wide host range, long acting time, and they can perform overexpression, interference, knockout, endogenous activation of coding or non-coding genes, so they are more and more widely used in gene therapy research. Adeno-associated virus (AAV), adenovirus (ADV) and lentivirus (LV) are all commonly used viral vectors with different infection characteristics. Among them, AAV is currently the most widely used delivery vector in gene transduction and gene therapy due to its advantages of good tissue specificity, low immunogenicity, and high safety.
AAV Type |
Vector Production Scale |
Virus amount |
Titer |
Turnaround |
Over-expression |
Purified pilot |
≥1*10^12 GC |
≥1*10^12 GC/mL |
5~6 weeks |
Purified medium |
≥5*10^12 GC |
≥1*10^13 GC/mL |
||
Interference |
Purified pilot(3+1) |
≥1*10^12 GC |
≥1*10^12 GC/mL |
|
Purified medium(3+1) |
≥5*10^12 GC |
≥1*10^13 GC/mL |
||
Knock-out |
Purified pilot |
≥1*10^12 GC |
≥1*10^12 GC/mL |
|
Purified medium |
≥5*10^12 GC |
≥1*10^13 GC/mL |
Serotype |
Target tissue |
Serotype |
Target tissue |
AAV1 |
muscles, heart, nerves, skeletal muscles |
AAV rh10 |
liver, blood, heart, extracorporeal cells |
AAV2 |
muscles, liver, brain tissue, eyes, nerves |
AAV2-retro |
nerve cell (reverse non-transsynaptic) |
AAV5 |
lungs, eyes, nerves, pancreas |
AAV-DJ |
retina, lung, kidney, cells in vitro |
AAV6 |
mungs, heart |
AAV-DJ-8 |
liver, eyes, central nervous system |
AAV7 |
muscle, liver |
AAV9-CNS |
central nervous system |
AAV8 |
muscles, liver, nerves, eyes |
AAV9-PNS |
peripheral nervous system |
AAV9 |
heart, muscles, lungs, liver, nerves |
More serotypes |
|
Advantages of Cyagen’s AAV virus packaging service:
Type |
Titer |
Turnaround |
|
Lentivirus (LV) |
Standard |
≥1*10^8 TU/mL |
5-8 weeks |
Purified |
≥1*10^9 TU/mL |
||
Adenovirus (ADV) |
Standard |
≥1*10^10 PFU/mL |
7-10 weeks |
Purified |
≥1*10^12 PFU/mL |
Q1: What is the difference between AAV, LV, and ADV viral vectors?
Project |
AAV |
ADV |
LV |
Particle diameter |
20-30nm |
90-100nm |
80-100nm |
Genome |
4.7kb single-stranded DNA or 2.4kb double-stranded DNA |
36 kb double-stranded DNA |
9.3 kb double-stranded RNA |
Capacity |
≤4.5kb |
8.3kb |
≤6kb |
Expression |
Phased expression at medium to high level |
High-level transient expression |
Moderately stable expression |
Expression Duration |
Begin to express within 7-14 days, |
Begin to express in 1-2 days, |
Begin to express in 2-4 days, |
Generally 6 months to 24 months |
Lasts ≤ (2-4) weeks |
Lasts ≥6 months |
|
Diffusion capacity in vivo |
High |
High |
Ordinary |
Immunogenicity |
Very low |
High |
Low |
Integration method |
Small amount of targeted integration |
No integration |
High frequency random integration |
Advantages |
High yield, simple composition, good safety |
High yield and easy purification |
Low yield, stable expression |
Application |
Animal experiments |
Cell/animal larger gene overexpression |
Cell experiments |
Q2: Why is AAV the most popular vector in the field of gene therapy?
Because AAV has the following advantages:
1. Wide host range: dividing and non-dividing cells;
2. High safety: No pathogenic AAV is found; ITR and rep/cap are expressed on independent plasmids;
3. Low immunogenicity: The immune response to AAV in animals or humans is the smallest among several viral vectors;
Q3: What are the key points that need to be paid attention to when implementing AAV expression in animals?
1. Selection of serotype. The serotype of AAV is mainly determined by the structure of the AAV capsid protein. Different capsid protein structures recognize different cell surface receptors. Therefore, the choice of serotype will affect the infection efficiency, tissue affinity, and start time of AAV expression.
2. The choice of promoter. Broad-spectrum promoter or specific promoter? Compared with the broad tissue specificity of serotypes, specific promoters can achieve specificity by cell type. Therefore, for studies with higher specificity requirements, a certain cell-specific promoter can be selected.
3. Injection method. For tissues and organs that can be injected locally, local multipoint injection of target organs can achieve better specificity and expression effects.
4. Virus amount and titer. The recommended amount of AAV injected differs according to the target organs/tissues and AAV serotypes used (different diffusion capacity), and the amount of virus particles delivered to the tissue has a great influence on the infection effect. However, the amount of AAV used is not as much as possible — too much virus may sometimes even reduce expression. If you want to know the best viral administration process for a specific application target, you can contact us for consultation.
Q4: How much virus is sufficient for AAV injection in mice?
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