The use of lentiviral vectors has been increasing in biomedical research due to the attractive features of infecting both dividing and nondividing cells, which is a very effective tool in human gene therapy. However, the biosafety of HIV-based vectors requires a careful evaluation with a major concern involving the possibility that the HIV could self-replicate and could be produced during manufacture of the vector in the packaging cell line or in the target cells by a process of recombination. In order to clarify the University’s position on the biosafety assessment and requirement for replication competent lentivirus (RCL) testing, the Institutional Biosafety Committee (IBC) has created the following policy.
According to Recombinant DNA Advisory Committee (RAC) Guidance Document “Biosafety Considerations for Research with Lentiviral Vectors,” the major risks to be considered for research with HIV-1 based lentivirus vectors are potential for generation of RCL and potential for oncogenesis. The risk can be lowered by the nature of the vector system (and its safety features) or elevated by the nature of the inserted transgene.
Guidance Policy for Risk Assessment and RCL Testing
At the February IBC 2004 meeting, the IBC has adopted general criteria for risk assessment of lentivirus vectors in determining containment and practices. Lentivirus vectors can be used/made following Biosafety Level 2(BSL2) containment criteria if:
- The vector is minimal containing LTRs, packaging sequencing, and no coding gene sequences;
- A heterologous envelope is used (not HIV or SIV);
- The packaging plasmid has no sequences on the LTR that could recombine; and
- Genes inserted do not code for oncogenes, oncogene precursor, or highly toxic molecules.
In consideration of the aforementioned guidance document from RAC and other additional factors, the UCLA IBC has added the following criteria for RCL testing:
- Work with Lentivirus (2nd generation or higher) without high risk inserts (e.g., oncogene, highly toxic molecules) can be conducted at BSL2 condition without the requirement of RCL testing. However, if this gene product is used for human clinical trials, RCL testing will be required.
- Work with Lentivirus (2nd generation or higher) with high risk inserts such as oncogenes can be conducted at BSL2+ (Biosafety Level 2 facility using the practices of BSL2) condition without the requirement of RCL testing. However, if this gene product is used for human clinical trials, RCL testing will be required.
- Recombinant DNA Advisory Committee Guidance Document “Biosafety Considerations for Research with Lentiviral Vectors” (March RAC 2006 meeting)
- UCLA IBC Special Action “Review to Lower Biosafety Level Containment for SIN Lentivirus vector from Biosafety Level 2+ to Biosafety Level 2” (February 2004)