AAV expressing cells can be differentiated based on their ability to produce high or low levels of AAV. The high AAV expressing cells can efficiently produce viral particles, while the low AAV expressing cells produce few viral particles. The two types of cells also differ in their transfection efficiency. The high AAV expressing cells are more efficient at transfecting target cells than the low AAV expressing cells.
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The reason for these differences is not well understood, but may have to do with the way the viruses bind to their targets and the level of expression of specific proteins on the surface of the target cell.
In one embodiment, the number of AAV particles produced by the high AAV expressing cells is much greater than the low AAV expressing cells. The increased production of viral particles by the higher expressing cell may be due to a difference in levels of expression of certain proteins on their surface.
For example, in human embryonic kidney 293 cells, high-level expression of GFP can increase production of more particles (a reduction in particle size) (Miller et al., 2007), and a reduction in p24 generation increases virus production (Losev et al., 2003). There are many different types of AAV vectors available that can transfect various types of target cells.