ABSTRACT
To some extent comparative toxicity will depend on viral doses used for each type of vector, i.e. usually retroviral vectors and AAV vectors are used at much lower doses than adenovirus vectors. Murine retroviral vectors contaminated with RCR have been shown to be tumorigenic in non-human primates raising concerns over the risk to humans. As the current retroviral vectors are based on murine viruses the likelihood of producing replication competent virus, through recombination with endogenous human retroviruses, is reduced. Retroviral vectors generated in packaging cell lines, which do not express an galactosyltransferase, are resistant to human serum and the construction of vector systems based on these retroviruses would be advantageous for in vivo applications. Alternative strategies for increasing gene transfer efficiency include the modification of envelope proteins to express N-terminal binding domains or functional antibody fragments in order to target retroviral vectors to specific cell types.
