Retrovirus: It is an RNA virus. When replicating, it must first convert RNA into cDNA under the action of reverse transcriptase, and then amplify under the action of proteases such as DNA replication, transcription, and translation. It mainly includes three subfamilies: RNA tumor virus, lentivirus, and foamy virus. Lentivirus: It belongs to the Retroviridae family. The name comes from the virus's long-term incubation period of several years. The classic lentivirus is modified from HIV virus, and the HIV-1/HIV-2 system has also been widely used. In addition to the HIV virus system, there are also simian immunodeficiency virus (SIV) vector system, feline immunodeficiency virus (FIV) vector system, sheep Maedi-Visna virus (MMV) vector system, and equine infectious anemia (EIA) vector system.
Advantages of lentivirus:
1. The genome carried by lentivirus can be integrated into the host genome, allowing host cells to stably express exogenous genes for a long time;
2. It can infect dividing and non-dividing cells;
3. Low immunogenicity, direct injection into living tissue is not likely to cause immune response, suitable for animal experiments;
4. Specific promoters can be replaced;
5. The size of wild-type HIV is about 9.8 kb, and the inserted fragment can be as long as 5-6 kb;
Lentivirus vector
Lentivirus is a type of viral vector modified from human immunodeficiency virus (HIV). It is a type of retrovirus. Its genome is RNA, and its toxic genes have been removed and replaced by exogenous target genes. It is a pseudotype virus. Reverse transcriptase can be used to integrate exogenous genes into the genome for stable expression, and it has the characteristics of infecting dividing and non-dividing cells.
Advantages of lentivirus vector:
1. Long-term stable gene expression: Since the gene is integrated into the host cell genome, lentivirus vectors can provide long-term and stable exogenous gene expression, which is suitable for experiments or treatments that require long-term observation.
2. Wide range of cell infection ability: Lentivirus can infect many types of cells, including both dividing and non-dividing cells, making it an ideal choice for studying complex cell types.
3. Low immunogenicity: The immune response induced by lentiviral vectors is relatively weak, so it is safer in in vivo experiments or gene therapy, reducing the risk of adverse reactions caused by immune response.
4. Suitable for primary cells and difficult-to-transfect cells: Lentivirus can effectively transduce primary cells and other cells that are difficult to transfect by traditional methods, such as stem cells and neurons.
5. Relatively large gene vector capacity: Lentivirus vectors can carry large exogenous gene fragments and can meet the needs of more complex gene operations.
6. Suitable for gene therapy: Due to its long-term stable gene expression ability and low immunogenicity, lentiviral vectors have been widely used in gene therapy research, especially for the treatment of chronic diseases and genetic diseases.
Application prospects:
1. Construction of stable expression cell lines: Lentivirus vectors can infect various cells and carry signals such as fluorescent markers. They are commonly used effective vectors for constructing cell lines.
2. RNA interference technology: RNA interference (RNAi) technology is a molecular silencing mechanism mediated by small molecule double-stranded RNA, which can effectively downregulate the expression of target genes and is a new means of antiviral treatment. As an effective auxiliary means of RNAi research, lentiviral vectors can infect various cells in the division period and achieve stable expression. On the basis of understanding the viral virulence protein, shRNA targeting a certain viral pathogenic gene site is constructed with lentivirus as a vector for cell experiments or animal regression experiments. The gene silencing effect and the inhibition of viral replication ability can be determined by detecting mRNA replication levels and virus titer determination.
3. Target gene and pathway screening: Viruses need to recognize specific receptor sites to invade hosts, and interact with target genes to activate complex signal pathways such as signal transmission, material metabolism, and cycle regulation, which is conducive to the replication and survival of viruses in the host. Therefore, finding target genes can provide a new idea for the treatment of viral diseases. The lentiviral vector system has a high expression rate, can carry longer gene fragments, and rarely induces immune responses in the host. It is an ideal expression vector for screening target genes.
4. Gene therapy: Gene therapy refers to the introduction of exogenous genes into cells to correct or compensate for diseases caused by gene defects. The introduced exogenous genes are mainly divided into normal genes, therapeutic genes and "suicide genes". The introduction of normal genes or gene fragments that can function normally can make up for congenital gene deficiencies and thus play a therapeutic role. They are mainly used for the treatment of various genetic diseases; while therapeutic genes mainly refer to the introduction of target genes that have obvious therapeutic effects on diseases; "Suicide genes" mainly refer to cytosine deaminase genes (CD) and genes encoding thymidine kinase (TK), which can catalyze non-toxic drug precursors into cytotoxic substances and kill receptor cells.
5. Vaccine development: When a disease occurs, vaccine immune prevention and control is an effective way to avoid its large-scale prevalence, and plays an important role in the prevention and treatment of infectious diseases in humans and animals. , lentiviral vectors can infect non-dividing cells, and there is no need to directly target pathogenic antigens, and can be used to inhibit autoimmune diseases.
6. Production of transgenic animals: Using lentivirus as a vector and microinjection technology to introduce exogenous genes into animal embryos can significantly increase the stable expression rate of the target gene, and even achieve stable genetic traits, reducing the production cost of transgenic animals.
7. Bioreactor Lentivirus vectors have become the preferred tool for building bioreactors with their natural advantages of stability, high efficiency, and gene integration. The transgenic animals produced can also form stable genetic traits of offspring
References:
1. https://bpsbioscience.com/lentiviruses
2. https://resources.amsbio.com/Catalog/Viral%20Delivery%20systems%200522.pdf
3. Milone, M.C., O’Doherty, U. Clinical use of lentiviral vectors. Leukemia 32, 1529–1541 (2018). https://doi.org/10.1038/s41375-018-0106-0