CAG-Null Lentivirus

As a simple retrovirus, HIV-1-derived lentivirus is able to hijack host-mediated mechanisms to maintain efficient nuclear import across the intact nuclear membrane. This property enables it to efficiently transduce non-dividing and terminally differentiated cells (e.g., post-mitotic neurons, hepatocytes, or macrophages). The lentiviral genome occupies approximately 10.7 kb of single-stranded RNA (ssRNA) enclosed in a lipid-rich spherical capsid of approximately 100 nm in diameter. The viral genome encodes structural and enzymatic genes, including gag and pol. The polycistronic gag gene encodes three products, namely matrix protein (MA), capsid protein (CA), and nucleoprotein (NC). The polycistronic pol gene provides three viral enzymes, namely reverse transcriptase (RT), protease (PR), and integrase (IN). Lentivirus (LV) is an enveloped virus that uses a glycoprotein envelope to attach to and enter host cells. The creation of heterologous envelopes for pseudotyping viral particles was one of the major advances in the field, which significantly enriched and expanded the tropism for transduction. In addition, the addition of heterologous envelopes to viral particles also had a positive impact on vector safety. Lentiviruses can be effectively pseudotyped with a variety of heterologous envelopes, allowing for a broad range of viral tropisms. For example, lentiviruses with added Mokola virus (MV), Ross River virus (RRV), and rabies virus (RV) showed strong tropism for neuronal cell transduction. However, the most commonly used envelope for pseudotyping viral particles is vesicular stomatitis virus protein G (VSV-G). This envelope has been shown to have an extremely broad tropism and can therefore be used for transduction into most cells and tissues. In addition to gag and pol, lentiviruses carry six complementary genes: rev and tat, which are involved in viral transcription and export, respectively; and nef, vif, vpr, and vpu, which are involved in viral entry, assembly, replication, particle formation, and release. It is important to note that the last four complementary genes are not essential for vector production and can therefore be omitted from the vector packaging cassette.