Adeno-Associated Virus (AAV) is a nonpathogenic virus species that belongs to the Parvoviridae family. AAV is classified as small (25nm) and contains a single-stranded nonenveloped DNA genome. Infection with AAV occurs only with the help of other viruses, either herpesvirus or adenovirus (hence adeno-associated virus), causing only a very mild immune response in humans. There are twelve serotypes of human AAV but the number of nonhuman AAVs exceeds 100. AAV2 is the only mammalian DNA virus that is known to integrate in a specific site of the genome.
The low immunogenicity and the ability to infect dividing as well as non-dividing cells with stable expression make the adeno-associated virus an attractive vector for the application in gene therapy. AAV has successfully been proven as gene therapy vector with the ability to attach and enter the target cell, transfer to the nucleus and express the transgene in a stable manner over a sustained period of time. In several clinical trials (e.g. FIX, CFTR, Parkinsons’s, Canavan disease) AAV did not show any serious vector-related adverse effects. Clinically relevant tissues have, however, revealed a diversified susceptibility to AAV infection. The gene transduction with AAV2 vector in muscle, retina, liver and heart resulted in lower gene expression compared to AAV serotypes 1, 5, 8 and 9 transduction in the respective tissues. The challenge of using AAV as gene therapy vector, however, lies in the resistance of some tissues to transduction with the available AAV serotypes.
With the increasing importance of AAV vectors in the field of gene therapy there is an increasing demand for robust & reliable methods for rAAV characterization. At this moment, quantification methods for rAAV vector preparations currently include quantitative PCR (qPCR) & digital droplet PCR (ddPCR) for the determination of the DNA titer as well as dot blot & Titration ELISA for the determination of the total capsid titer (assembled viral capsids proteins). Methods using electron microscopy, protein chromatography, flow cytometry, or virus particle counting instruments have also been described, but are generally only applicable for highly skilled users and/or require specialised and expensive equipment. Find out more about currently used methods and a comparison of AAV quantification methods.
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For more information about PROGEN´s antibodies and AAV titration ELISAs, see PROGEN´s posters and application note in the download area.
Check out PROGEN´s posters about the development of reliable AAV standards, the new recombinant AAV2 antibody and comparison of negative staining EM and cryo-EM for the determination of the ratio of full and empty AAV capsids or download the application note on the quantification of AAV8 titers for standardized gene delivery.