shRNA expression constructs are delivered to cells by viral infection or transduction. Since the shRNAs are designed for use with mammalian cells, there are biosafety concerns for researchers handling the material. These concerns are addressed both with viral engineering and enhanced lab protocols.
To produce lentivirus and retrovirus for infection of cells, an expression vector that is missing the viral structural genes is used. This creates virus that is able to infect cells and integrate the desired gene, but is unable to replicate within the cells. The lentiviral system also has several genes removed to minimize its similarity to the human HIV-1 virus, and contains a deletion in the long terminal repeat (LTR) resulting in self-inactivation of the lentivirus following transduction. Finally, infectious lentivirus and retrovirus are classified as Biosafety Level 2 (BSL-2) agents and therefore all researchers working with them must have additional infectious agent training. In addition, access to the lab is limited while work is in progress, contaminated sharp items are treated with extreme precaution, and any work which could generate aerosols must be completed in a biosafety cabinet.