The expression profile with first generation. Ad vectors is not suitable for the long-term correction of chronic diseases but is adequate for direct cell killing, for most immunotherapy strategies and for some acute diseases. The first generation vectors have an insert –size limit of ~7.5kb.
The promoter used most frequently with Ad (and indeed all other vectors) is derived from cytomegalovirus(CMV), which gives strong expression in many cell types.
Ad gives particularly, efficient gene transfer to the liver, such that dissemination form the site of local injection(such as tumours) and consequent liver transfection is the most serious safety concern. The most serious limitation of Ad vectors stems from their tendency to elicit strong immune and (at high doses) inflammatory responses. Single, large doses of Ad provoke neutralizing antibody response directed to proteins of the viral particle, which prevent binding to target cells and abrogate gene transfer upon repeat dosing by systemic administration routes in animals.


