RECOMBINANT LENTIVIRAL VECTORS
Lentiviral vectors are made by transiently transfecting the producer cell line with three plasmids encoding the vector components (see diagram two).
Diagram Two: Lentiviral Vector
The transfer plasmid contains the gene expression cassette encoding the therapeutic gene and packaging signal flanked by the retroviral LTRs. The packaging plasmid encodes all the components required for packaging and assembly of viral particles, with the packaging signal removed to prevent formation of RCL. The pseudo-typing plasmid contains an envelope protein that allows the lentiviral vector in target specific cellular populations, e.g. VSV-G. Splitting the components on three separate plasmids reduces the chances of homologous recombination and allows lower expression of the components of the viral genes known to limit viral yield. The latest generation of lentiviral vectors are considered quite safe, and are often the vector of choice when trying to target cell lines that have been traditionally refractive to gene transfer, such as neuronal, haematopoietic and stem cell populations.
