Vectors recombinant virus production

An important safety issue of viral vectors is whether or not the recombinant viruses are able to replicate in the infected cells. Replication of viral vectors is unwanted in most gene-therapy approaches. Therefore, replication-defective vectors have been designed, which are able to perform only one initial infectious cycle within the target cell. In addition, replication-competent vectors have been designed, which are able to productively infect the target cell and to spread in the target tissue. 

The lack of human pathogenicity of plant viruses rules out the risks of human infection by exposure in the field or in food products to a plant virus. However, biological containment of the virus expression vector remains a primary safety concern as it can be considered a risk to the environment. This includes the spread of recombinant viruses to weeds... 

Other protocols involve cell lines with integrated rep/cap cassettes (Clark et al., 1995 Gao et al., 1998 Liu et al., 1999 Chadeuf et al., 2000 Mathews et al., 2002 Qiao et al., 2002a,b) infected with adenovirus or, alternatively, a recombinant herpesvirus system has been used to provide both helper virus function and rep/cap (Conway et al., 1997, 1999). In a switch away from using mammalian cell and helper virus production systems, rAAV vectors have been made in insect cells where the AAV genes are expressed under the control of insect promoters and the traditional helper virus gene products are not required (Urabe et al., 2002). Stable producer cell... 

Conway, J. E. et al. (1999). High-titer recombinant adeno-associated virus production utilizing a recombinant herpes simplex vims type I vector expressing AAV-2 Rep and Cap. Gene Ther. 6, 986-993. 

King, L.A., Mann, S.G., Lawrie, A.M. and Possee, R.D. (1994). Baculo-virus expression vector system Production and isolation of recombinant viruses. In Cell Biology A Laboratory Handbook, Vol. 3 (Celis, J.E., ed.), Academic Press, San Diego, pp. 148-154. 

Baculovirus Expression Vector System Production and Isolation of Recombinant Viruses... 

The use of recombinant viral vectors as vaccination tools displays considerable clinical promise. One potential complicating factor, however, centres around the possibility that previous recipient exposure to the virus being used as a vector would negate the therapeutic efficacy of the product. Such prior exposure would likely indicate the presence of circulating immune memory... 

Recombinant DNA drug production has been a success story, but the technology does have its drawbacks and disadvantages. For example, the use of bacterial plasmids and, less commonly, viruses, as vectors for the insertion of genes into host cells has its limitations. While such methods work well for smaller drug molecules, such as insulin, they are much less effective in the production of larger, more complex proteins that constitute many of the drugs that chemists would like to manufacture synthetically. 

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