Helper adenovirus

Xiao, X., Li, J. and Samulski, R. J. (1998). Production of high-titer recombinant adeno-associated virus vectors in the absence of helper adenovirus. 

Adeno-associated viruses are naturally defective viruses that require a helper adenovirus to replicate normally. However, they are capable of infecting a range of cells and can integrate at specific sites in human chromatin. Adeno-associated viruses have been used experimentally to kill certain forms of breast, cervical, and prostate cancer cells. As viral vectors, they have been used to introduce a gene for production of insulin and the genes for both Factor VIII and Factor IX, lacking in humans with certain forms of hemophilia (hemophilia A and B, respectively). 

It is not known whether one or both of the two types of AAV virions is individually capable of initiating a productive infection in the presence of adenovirus or whether both types of AAV particles are required. Titration studies of AAV infectivity in the presence of excess adenovirus have suggested single-hit kinetics for infection this would imply that it is not essential for both types of co-infect a cell (Blacklow et al., 1967). Attempts to productively infect cells with physically separated particles (Berns and Adler, 1972) have been made but the data have not been of sufficient precision to resolve this problem (Hoggan and Berns, unpublished data). Purified AAV DNA has been shown to be infectious in the presence of helper adenovirus (Hoggan et al., 1968). The infectivity of the DNA was increased by the addition of... 

Adsorption, penetration, and uncoating occurred to the same extent regardless of the presence or absence of helper adenovirus (Rose and Koczox, 1972 Berns and Adler, unpublished data). 

Casto, B. C., Atchinson, R. W., Hammon, W. McD. Studies on the relationship between adeno-associated virus type 1 (AAV-l) and adenovirus. I. Replication of AAV-l in certain cell cultures and its effect on helper adenovirus. Virology 32, 52-59 (1967). 

Hoggan, M. D., Thomas, G. F., Johnson, F. B. Continuous carriage of adenovirus associated virus genome in cell cultures in the absence of helper adenoviruses. In The Proceedings of the Fourth Lepetit Colloquium, Cocoyac, Mexico, 1972. Amsterdam North Holland Publ. 1972,... 

Sandig, V, R. YouU, A.J. Belt, L.L. Franlin, M. Oshima, D. Maione, F. Wang, M.L. Metzker, R. Savino, and C.T. Caskey, Optimization of the helper-dependent adenovirus system for production and potency in vivo. Proc Natl Acad Sci USA, 2000. 97(3) 1002-7. 

AAV2 and its helper viruses like HSV, AAY2 interacts with the cell surface via heparin sulfate, and AAV internalization is mediated by aV/ 5 integrin, which is also required by adenovirus for uptake. Serotypes other than AAV2 exhibit different tropisms and interact with different cell surface molecules. Some of the cell surface receptors have been identified for AAV3 (HSPG Rabinowitz et al.,... 

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... 

Qiao, C., Li, J., Skold, A., Zhang, X. and Xiao, X. (2002a). Feasibility of generating adeno-associated virus packaging cell lines containing inducible adenovirus helper genes. J. Virol. 76, 1904-1913. 

Fallaux FJ, Bout A, van der Wollenberg DJ, Hehir KM, Keegan J, Auger C, Cramer SJ, van Ormondt H, van der Eb AJ, Valerio D, Hoeben RC (1998), New helper cells and matched early region 1-deleted adenovirus vectors prevent generation of replication-competent adenoviruses, Hum. Gene Ther. 9 1909-1917. 

Cregan SP, MacLaurin J, Gendron TF, Callaghan SM, Park DS, Parks RJ, Graham FL, Morley P, Slack RS (2000) Helper-dependent adenovirus vectors Their use as a gene delivery system to neurons. Gene Ther 7 1200-1209. 

Mitani K, Graham EL, Caskey CT, Kochanek S (1995) Rescue, propagation, and partial purification of a helper virus-dependent adenovirus vector. Proc Natl Acad Sci USA 92 3854-3858. 

Parks RJ, Chen L, Anton M, Sankar U, Rudnicki MA, Graham FL (1996) A helper-dependent adenovirus vector system Removal of helper virus by Cre-mediated excision of the viral packaging signal. Proc Natl Acad Sci USA 93 13565-13570. 

Haj-Ahmad Y, Graham FL. 1986. Development of a helper-independent human adenovirus vector and its use in the transfer of the herpes simplex virus thymidine kinase gene. J. Virol. 57 267-74... 

Parks RJ, Bramson JL, Wan Y, Addison CL, Graham FL. 1999. Effects of staffer DNA on transgene expression from helper-dependent adenovirus vectors. J. Virol. 73 8027-34... 

Fig. Z3 Viral vector production. The rAAV Vector plasmid contains the therapeutic gene flanked by the ITRs, usually of AAV2. The helper plasmid contains the rep and cap genes, as well as the adenoviral genes needed for replication. Both plasmids are transiently transfected into HEK293 cells that express the adenovirus ElA and ElB gene products...

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