Recombinant Adenovirus vector System (Adenovirus packaging System -AdMax system)

Since wild-type adenovirus is associated with a wide range of illnesses and enlists a variety of immune responses, so recombinant replication deficiency virus has been an attractive vector for gene therapy [20]. To date, there have been many different generations of adenovirus vectors, differing in the extent to which the genome from wild-type adenovirus is attenuated, among them, most studies involving adenovirus vectors utilize the simple E1-deleted, first-generation adenovirus vector. Due to the induction of strong innate and adaptive immune responses and limited the duration of transgene expression of first-generation adenovirus vector, researchers have further developed the second-generation adenovirus vectors by deleting the E2 or E4 coding sequences, resulting in some beneficial effects of reducing the expression of viral proteins and vector-directed immune responses. However, because of their limited evidence of enhanced efficacy over first generation vectors, the third-generation adenovirus vectors have been designed by deletion of all viral protein coding sequences, which can only be propagated in the presence of a second virus that provides all of the replication and packaging functions in trans, for which the third-generation adenovirus vectors are also known as fully-deleted, gutted, or helper-dependent Ad (hdAd) vectors [15].

Traditionally, recombinant adenovirus vectors used in gene delivery were prepared with a plasmid containing the transgene flanked by inverted terminal repeats (ITRs), co-transfected with packaging plasmid pAd-BHGlox(delta)E1, E3. Once packaged into a E1-complementing cell line, such as QBI 293A cells, recombinant viral will be easily propagated.