The adeno-associated Virus (AAV) has remained the leading platform for gene delivery for treating different human diseases. The recent advances in developing clinically desirable AAV capsids, optimizing genome designs, and harnessing revolutionary biotechnologies have added significantly to the gene therapy field growth and addgene AAV purification.

Adeno-Associated viruses (AAV) are the small viruses responsible for infecting humans and other eutherian species. AAV is in the class of genus Dependoparvovirus and also in the family of Parvoviridae. AAVs are small 20 nm replication-defective and non-enveloped viruses. They have a linear single-stranded DNA genome of 4.8 kilobases in approximate. Adeno-Associated Virus does not cause diseases, it only causes a very mild immune response, and it’s an attractive virus for creating viral vectors for gene therapy. It is also used for the creation of isogenic human disease models.

Adeno-associated virus vector as a platform for gene therapy delivery |  Nature Reviews Drug Discovery

AAV, a non-enveloped virus, can be choreography to get DNA to target cells, and it has been a major focus, especially in the clinical-stage experimental therapeutic strategies. One of the proven safest gene therapy strategies is the ability to generate recombinant AAV particles that lack any viral genes and contain DNA sequences of interest suitable for various therapeutic applications.

Having the understanding of AAV Gene Therapy

The pattern for the human body is the gene because it dictates to the body’s cells how to make proteins critical to their functions. Many diseases are easy to relate to, and those that are not known and disorders result from the faulty expression of proteins. And this emanates from corrupted or missing genes or environmental modification of genes or even proteins. 

Gene therapy uses modified viruses or other technologies to deliver therapeutic genes to cells or tissues to reference genetic diseases at their source. How Adeno-Associated Virus (AAV) can be used as an effective delivery system for therapeutic genetic material into living tissue is one of the advances in modern medicine discovery. AAV gene therapy through the AAV expression system has broad therapeutic implications for many diseases. 

Adeno-Associated Virus (AAV) is one of the gene therapy vehicles that is mostly investigated. And it was initially discovered to be a contaminant of adenovirus preparations, which brought about its name. Initially, distinguished serological molecular cloning of AAV genes has identified many unique AAV strains in multiple species. Three genes are contained in the single-stranded genome: Replication, Capsid, and Assembly. Nine gene products were birthed from these three genes through three promoters, alternative translation start sites, and differential splicing.

Adeno-associated viral vector (AAV) for Duchenne muscular dystrophy... |  Download Scientific Diagram

The Replication gene encodes four proteins which are Rep78, Rep68, Rep52, and Rep40, which are required for viral genome replication and packaging. For capsid expression, it gives rise to the viral capsid proteins such as VP; VP1/VP2/VP3. They form the outer capsid shell that protects the viral genome and is actively involved in cell binding and internalization. Sixty proteins arranged into an icosahedral structure with the capsid proteins are estimated to be compromised in the viral coat in a molar ratio of 1:1:10 (VP1:VP2:VP3). 

The Assembly (AAP) gene encodes the assembly-activating protein (AAP) in an alternate reading frame that overlaps the cap gene. This nuclear protein is thought to provide a scaffolding function for capsid assembly. As AAP is essential for nucleolar localization of VP proteins and capsid assembly in AAV2, the subnuclear localization of AAP varies among 11 other serotypes and is nonessential in AAV4, AAV5, and AAV11.

One of the first AAV serotypes identified and characterized is AAV2, which includes its genome sequence. Due to the detailed understanding of AAV2 biology from the early work, most rAAV vectors generated utilize the AAV2 ITRs in their vector designs.

Benefits of using AAV as the main means of gene therapeutics delivery

AAV is the dominant form of gene therapy for genetic diseases. In today’s therapeutic discoveries, AAV has become the driving force in the field, and with addgene aav guide, important benefits have been attached to its importance for its use which are;

  • AAV is a virus that is not known to result in human diseases. 
  • AAV does not have the capability of making more of itself without external help. With this, it will not replicate in the body the way normal viruses do, which has made scientists adequately control the amount of AAV that will be given.

How AAV works

Adeno-Associated Virus (AAV) can be transformed from a naturally occurring virus into a mechanism for gene therapy delivery. The viral DNA will be replaced with new DNA, making it a precisely coded vector. AAV will no longer be considered a virus when this happens because most of the viral components have been replaced. The AAV vector will deliver regular copies of genes to the appropriate tissues or organs in the body. And now, it will deliver the therapy configured into it. The advancement in AAV technology can target a wide range of tissues and cells to treat many genetic diseases. Two copies of the gene can be combined into a vector with some diseases. These vectors are known as self-complementary AAV or scAAV.