A human designer cell line for the efficient development and large-scale manufacturing of biopharmaceutical products [e.g., vaccines, monoclonal antibodies and gene therapy products]. The PER.C6® cell line is made from a single healthy, human cell that has been purposefully immortalized so that it can grow indefinitely and can be expanded efficiently without the need for materials that allow cell attachment (i.e. microcarriers) or the need for serum derived from non-human sources
Based on the PDF document, I believe the single, healthy, "immortal" cell referred to above may be the one that is created from human retina cells -- particularly fetal retina cells using E1 produced from Ad5. The immortal cell is then used to create a master cell bank for vaccine and biopharmaceutical product production. Per Crucell, "PER.C6® cells can replicate indefinitely..."
Nevertheless, this is where my ignorance in genetics is going to cause me to leave the highway, because I cannot make an educated opinion without that knowledge. However, if you have expertise in that area, I believe that the article Size and location of the transforming region in human adenovirus type 5 DNA gives background on what Ad5 is. Perhaps AD5 is a Crucell proprietary version of the human adenovirus type 5 DNA.
For further reading: The human cell line PER.C6 provides a new manufacturing system for the production of influenza vaccines
Remixx World! briefly discussed vaccines created from human retina cells last year in What Ingredients are in the H1N1 "Swine Flu" Vaccine? (Yes, Intranasal Contains Live H1N1 Virus)(Updated as of 11/30/2009)