"Packaging" is the process by which AAV preparations are generated — meaning the production procedure by which a linear single-stranded DNA sequence derived from a plasmid is encapsidated within a viral protein coat. At Addgene, AAV preparations are generated using a helper virus-free (fully plasmid-based) packaging protocol in 293T cells. For a table with these AAV production plasmids, please see our AAV Plasmids page.
The plasmids are delivered to the producer cells via triple co-transfection of the following plasmid types: 1.) the transfer plasmid which contains AAV2 ITRs, 2.) a packaging plasmid encoding the AAV2 Rep gene plus a serotype-specific Cap gene, and finally a third plasmid 3.) called the helper plasmid, encoding necessary adenoviral (AdV) sequences. The viral particles produced by the cells are therefore a "pseudotype" that is a hybrid between the AAV2 genomic packaging signals (the ITRs), the recombinant transgene, and the AAV capsid from the serotype of your choice. Its name can be denoted by AAV2/x — where "x" is the serotype conferred by the Cap (capsid) portion of the aforementioned Rep/Cap plasmid. Because all of the AAV preparations in our catalog are based on the AAV2 packaging signals we use a shorthand, and they are called simply "AAVx" particles — namely by indexing the transfer plasmid catalog ID numbers with this suffix. In other words, the AAV2/5 preparation of plasmid 49055 would have a catalog ID of "49055-AAV5."
More information regarding our general AAV production protocol and quality control can be found on our Viral Production page.