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February 12, 2025
by Alias Chacko
Adeno-Associated Virus (AAV)
Adeno-associated virus (AAV) was discovered in 1965, as a contaminant of adenovirus (Ad) preparations, hence the name. It is replication-defective, non-enveloped small viruses (20nm) with a genome of single stranded DNA, from the parvovirus family. As 80-90% of humans are sero-positive with AAV2, most people treated with AAVs are non-pathogenic. Recombinant AAVs can infect both dividing and non-dividing cells and persist in an extrachromosomal state without integrating into the genome of the host cell.
The advantages of AAV compared to other viral vectors
● Long-term gene expression. rAAV genomes do not integrate into the host cellular genome, it persist in the nucleus in episomal forms. As cells replicate and divide, these episome will be lost. However, It can be expressed continuously for more than 6 months in tissues where cell division is not vigorous.
● Strong diffusivity. Due to small size and higher titer, rAAV has much higher diffusivity than adenovirus and lentivirus. And AAV can cross the blood-brain barrier, it is an ideal tool for neuron and glial cell infection.
● Specific expression can be achieved. AAV has a wide variety of promoters and serotypes, This enables AAV to recognize and infect different organs and cells, which make AAV as the first choice for animal experiments.
● High safety. AAV has not been found to cause disease to humans, and it is the safest viral vector approved by the FDA in US that can be directly used in human for gene therapy.
● low immunogenicity: When AAV is used to infect muscle, brain, eye and many others with local high dose, it is not easy to cause immune response;
● High stability. rAAV virus can be stored for 1 week at 4°C, and it is resistant to some reagents such as chloroform.
The advantages of AAV compared to other viral vectors
● Long-term gene expression. rAAV genomes do not integrate into the host cellular genome, it persist in the nucleus in episomal forms. As cells replicate and divide, these episome will be lost. However, It can be expressed continuously for more than 6 months in tissues where cell division is not vigorous.
● Strong diffusivity. Due to small size and higher titer, rAAV has much higher diffusivity than adenovirus and lentivirus. And AAV can cross the blood-brain barrier, it is an ideal tool for neuron and glial cell infection.
● Specific expression can be achieved. AAV has a wide variety of promoters and serotypes, This enables AAV to recognize and infect different organs and cells, which make AAV as the first choice for animal experiments.
● High safety. AAV has not been found to cause disease to humans, and it is the safest viral vector approved by the FDA in US that can be directly used in human for gene therapy.
● low immunogenicity: When AAV is used to infect muscle, brain, eye and many others with local high dose, it is not easy to cause immune response;
● High stability. rAAV virus can be stored for 1 week at 4°C, and it is resistant to some reagents such as chloroform.