Viral vector

Viral vectors are tools commonly used by molecular biologists to deliver genetic material into cells. This process can be performed inside a living organism (in vivo) or in cell culture (in vitro). Viruses have evolved specialized molecular mechanisms to efficiently transport their genomes inside the cells they infect. Delivery of genes or other genetic material by a vector is termed transduction and the infected cells are described as transduced. Molecular biologists first harnessed this machinery in the 1970s. Paul Berg used a modified SV40 virus containing DNA from the bacteriophage λ to infect monkey kidney cells maintained in culture. In addition to their use in molecular biology research, viral vectors are used for gene therapy and the development of vaccines. Vectors can either integrate into a cell's genome or transiently express a gene with non-integrative vectors. Viral Vectors are tailored to their specific applications but generally share a few key properties. Safety: Although viral vectors are occasionally created from pathogenic viruses, they are modified in such a way as to minimize the risk of handling them. This usually involves the deletion of a part of the viral genome critical for viral replication. Such a virus can efficiently infect cells but, once the infection has taken place, requires a helper virus to provide the missing proteins for production of new virions. Low toxicity: The viral vector should have a minimal effect on the physiology of the cell it infects. Stability: Some viruses are genetically unstable and can rapidly rearrange their genomes. This is detrimental to predictability and reproducibility of the work conducted using a viral vector and is avoided in their design. Cell type specificity: Most viral vectors are engineered to infect as wide a range of cell types as possible. However, sometimes the opposite is preferred. The viral vector can be modified to target the virus to a specific kind of cell. Viruses modified in this manner are said to be pseudotyped.