AAV Vector Genome Metabolism

A complex pathway of events[1] impact the function of AAV vectors such as the availability of specific cell-surface receptors, cellular trafficking, and potential diversion of AAV particles into a ubiquitin-mediated proteosome degradation pathway, and delay in uncoating in the cell nucleus. The uncoated single-strand genome must be converted to a duplex molecule. Following this, a succession of additional events result in the vector genome being converted into larger, mostly circular concatemeric molecules.

Single-strand to double-strand conversion step may be rate-limiting, but this can be overcome by using self-complementary vector genomes that are not more than half the size of the AAV genome. These genomes are packaged as a dimeric molecule equivalent to a RF formed during vector genome replication. Upon uncoating, these molecules reassociate (''snap back'') to duplex molecules with pseudo zero-order kinetics.[7] The ability of AAV vectors to form concatemers also extends the capacity of AAV vectors in a ''dual-vector'' system. Expression cassettes up to 9 kb in size can be divided between two AAV vectors, and coinfection forms concatemers to generate an intact expression cassette.[8]

Wild-type AAV, in cell culture, integrates into human chromosome 19, but this process requires the rep gene which is not present in AAV vectors. In contrast, a variety of animal models show that, in the absence of selective pressure, AAV vectors persist predominantly as circular concatemers. The circularization appears to involve recombination between ITRs.[9] The majority of these concatemers are episomal and integrated copies of vector in organs such as liver or muscle may be rare.[10,11] The relative rarity of integration is of importance in assessing the safety profile of AAV vectors for clinical applications.

Getting Started With Dumbbells

Getting Started With Dumbbells

The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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