Table 2.
General properties of the most commonly used viral vectors.
| Properties | Adenoviruses | AAV | Retroviruses | Lentiviruses |
|---|---|---|---|---|
| Wild type viruses | 36 kb ds linear DNA | 4.7 kb ssDNA | 9.2 kb Diploid +ssRNA | 8-10 kb Diploid +ssRNA |
| Pre-existing host antibodies | Yes | Yes | Unlikely | Unlikely but (may be in HIV +ve individuals) |
| Packaging capacity | 8-30 kb | 4 kb | <8 kb | 8 kb expected |
| Viral titre (particles/ml) | >1013 | >1012 | >109 | 109 |
| Stability | Good | Good | Good | Not tested |
| Integration | No | <10% integrated | Yes | Yes |
| Cellular localisation | Nuclear | Nuclear | Nuclear | Nuclear |
| Cell range | Non-replicating and replicating | Non-replicating and replicating | Replicating only | Non-replicating and replicating |
| Levels of expression | Very high | Moderate | Moderate | Moderate |
| Duration of expression | Transient | Long | Long, but subject to shutdown | Long |
| Immune response | Extensive | Not known | Few neutralis-ing antibodies | Not known |
| Safety issues | Inflammatory and toxicity | Rearrangement and inflammatory | Insertional mutagenesis | Insertional mutagenesis |
| Main advantages | Extremely efficient transduction of most tissues | Non-inflammatory Non-pathogenic | Long-term gene transfer in dividing cells | Long-term gene transfer in dividing cells |
| Main disadvantages | Capsid mediates a potent inflammatory response | Small packaging capacity | Transduces only dividing cells and potential for oncogenesis | Potential for oncogenesis |
kb, kilo base; ssDNA, single stranded DNA; dsDNA, double stranded DNA.