Retrovirus-based vectors for transient and permanent cell modification

• Retroviral platforms encompass vectors for permanent and transient gene expression.
• Possible biological entities for transfer or expression include DNA, RNA and proteins.
• Transient technologies allow an exact adjustment of expression level and duration.
• Advanced protocols have enhanced the potency of retroviral platforms.
• First generation systems have been improved by genetic elements and small molecules.

Retroviral vectors are commonly employed for long-term transgene expression via integrating vector technology. However, three alternative retrovirus-based platforms are currently available that allow transient cell modification. Gene expression can be mediated from either episomal DNA or RNA templates, or selected proteins can be directly transferred through retroviral nanoparticles. The different technologies are functionally graded with respect to safety, expression magnitude and expression duration. Improvement of the initial technologies, including modification of vector designs, targeted increase in expression strength and duration as well as improved safety characteristics, has allowed maturation of retroviral systems into efficient and promising tools that meet the technological demands of a wide variety of potential application areas.