Your Safety is our priority
The risks are largely defined by the vector system used and the transgene insert encoded by the lentiviral vectors. The biosafety issues associated with using recombinant lentiviral vectors can be greatly reduced by cautiously considering the nature of the transgene insert and by ensuring that viral replication is highly limited. The two major risks of using lentiviral vectors are:
- the potential generation of replication competent lentivirus (RCL)
- the potential for oncogenesis through insertional mutagenesis
The third generation lentiviral vectors are replication incompetent
To increase the safety of lentivirus, the components necessary for virus production are split across multiple plasmids.
Vectalys lentiviral packaging systems are of the 3rd generation. They utilize split-genes to provide the viral packaging elements for each plasmid to physically separate the viral envelope env sequence from the gag-pol sequences. These split-gene packaging strategies reduce the risk of generating RCL.
Multiple recombination events are necessary to create a virus that harbors the sequences required for independent replication. The components necessary for virus production are split in three plasmids as follows:
- Lentiviral transfer plasmid encoding your insert of interest. This sequence is flanked by long terminal repeats (LTRs) that facilitate host genome integration. To improve safety, transfer vectors additionally contain a deletion in the 3' LTR, rendering the virus “self-inactivating” (SIN) after integration.
- Packaging plasmid (gag-pol)
- Envelope plasmid (env)
Moreover, Tat is eliminated from our 3rd generation system through the addition of a chimeric 5' LTR associated with a heterologous promoter on the transfer plasmid. Expression of the transgene from this promoter is no longer dependent on Tat transactivation. This approach further reduces the possibility of creating RCL. In fact, the emergence of RCL is not detected from systems using this approach (split of components + SIN modifications).
These improvements significantly increase the safety profile of our lentiviral vectors.
Oncogenesis depends on the nature of the insert
Because the site of insertion is random, there is a small chance that insertion interferes with normal cellular functions and gives rise to uncontrolled cell proliferation. This risk may be very minimal for polycistronic cells.
An oncogenesis event may appear in such cell culture leading to the death of one cell population only.
The other cell populations in the cell culture will not be affected by oncogenesis. In the case of monocistronic cell culture, oncogenesis phenomenon in target cells will be avoided by selection of the cell population.
Moreover, the potential for oncogenesis is largely based on the specific insert contained within the lentiviral transfer vector (dependent upon whether or not it is an oncogene) and should be considered on a case by case basis.
Biosafety should always be considered with respect to the precise nature of experiments being performed, and your biosafety office can provide more information on your organization’s best practices with regard to lentiviral research. It is imperative to fully understand the potential hazards and take the necessary precautions for laboratory use of lentiviral vectors.
Vectalys advises you to contact your health and safety facilities for local guidelines and regulations, and strongly recommends that new users of all viral technologies receive training from experienced personnel. For more details, the NIH has provided additional information on lentiviral safety considerations.