Virus Expression Vector for Mammalian Cells

Virus Expression Vector for Mammalian Cells - A number of viruses have also been used as transfer or expression vectors for mammalian cells.

These include the following

(i)The first viruses used for mamalian cells included DNA viruses like papovaviruses (SY40 and polyoma) and adenoviruses, but since their capacity for foreign genes is small, they can not be used for the expression of many genes which are fairly large in size

(ii)Retroviruses (murine and avian retroviruses) are very useful vectors, since they can infect broad variety of cell types and can be used for cloning large genes; however, being single stranded RNA , they can not replicate without being integrated so that we will need replicating cells for expression or alternatively high titer (high concentration) for fully differentiated cells (e.g. neurons, hepatocytes, etc.)

(i)adeno associated virus (AAY) overcomes the limitations associated with retroviruses even though, like retroviruses, it is an integrating virus, with 5kb single stranded DNA, it is nonpathogenic, and can be concentrated to high titer (109 particles/µl)

(ii)Herpes virus, is another important non integrating virus of large size (150 kb), which can be used' for expression of large intact genes.

Several of the above viruses have already been used and showed expression of cloned genes, but they need to be further characterized for their long term usage.