Research Trend   |   May 25, 2018

AAV – The king of viral vectors?

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Adeno-associated virus (AAV) has recently been surging in popularity as a vector system. The recent wave of gene therapy successes and powerful new genome editing technologies, such as CRISPR/Cas9, have increased public and scientific awareness of the advantages of using safe, non-pathogenic, and non-mutagenic viral vectors. When combined with AAV’s amazing customizability for precise cell-type specific transgene expression, this may make AAV the ideal vector system for both clinical and laboratory uses.

In terms of biosafety, AAV is in a class by itself compared to other viral vectors. Even in as an unmodified, wild-type virus, AAV is entirely nonpathogenic in humans, causing no human diseases. The virus is also inherently non-replicative, since its natural replication is dependent on co-infection with other viruses such as adenovirus. The cytotoxicity of AAV is significantly lower than for adenovirus or lentivirus, and in AAV-transduced animals the systemic immune response is minor or nonexistent in most cases.

An additional advantage is that recombinant AAV vectors do not randomly integrate into the host genome, preventing disruption of host genes, which is a risk with lentivirus and other retroviruses. The AAV viral genome persists as extra-chromosomal concatemers, which have been shown to produce effective, stable transgene expression for years in many cases2-4.

The final feature that makes AAV such a powerful vector system is that it can be packaged using a wide variety of serotype capsid proteins, directing customized, tissue-specific vector targeting. This provides an additional level of gene expression specificity, along with cell type-specific promoters, making AAV vectors more precise in their in vivo gene expression patterns than other vector systems.

Perhaps the single drawback of AAV is that its cargo space is limited compared to other viruses. Often this is not an issue, since AAV can incorporate ~4kb of DNA, which is more than enough for many uses, but researchers have begun to push even this limit. New methods utilizing dual AAV vectors have shown promising results for transgenes well over the cargo capacity of a single AAV virion5-7.

Together, these qualities have driven AAV to the forefront of recent waves of gene therapy and gene editing applications in clinical trials, as well as to become a common vector system for use in cell culture and animal model basic research. The inevitable improvements to AAV vectors, such as new serotypes or increased cargo capacity, will make AAV an even more powerful vector system.

VectorBuilder provides design and packaging of custom AAV vectors for your research. Choose from a wide variety of serotypes and promoters, tailored to your experiments. We also have AAV vectors for inducible or conditional expression, noncoding RNAs, shRNA, miRNAs, and CRISPR/Cas9.

References

  1. Naso MF, Tomkowicz B, Perry WL 3rd, Strohl WR. Adeno-Associated Virus (AAV) as a Vector for Gene Therapy. BioDrugs. 2017 Aug;31(4):317-334.
  2. Arruda VR, Stedman HH, Nichols TC, Haskins ME, Nicholson M, Herzog RW, Couto LB, High KA. Regional intravascular delivery of AAV-2-F.IX to skeletal muscle achieves long-term correction of hemophilia B in a large animal model. Blood. 2005 May 1;105(9):3458-64.
  3. Rivera VM, Gao GP, Grant RL, Schnell MA, Zoltick PW, Rozamus LW, Clackson T, Wilson JM. Long-term pharmacologically regulated expression of erythropoietin in primates following AAV-mediated gene transfer. Blood. 2005 Feb 15;105(4):1424-30.
  4. Xiao X, Li J, Samulski RJ. Efficient long-term gene transfer into muscle tissue of immunocompetent mice by adeno-associated virus vector. J Virol. 1996 Nov;70(11):8098-108.
  5. McClements ME, MacLaren RE. Adeno-associated Virus (AAV) Dual Vector Strategies for Gene Therapy Encoding Large Transgenes. Yale J Biol Med. 2017 Dec 19;90(4):611-623.
  6. Chamberlain K, Riyad JM, Weber T. Expressing Transgenes That Exceed the Packaging Capacity of Adeno-Associated Virus Capsids. Hum Gene Ther Methods. 2016 Feb;27(1):1-12.
  7. Hirsch ML, Wolf SJ, Samulski RJ. Delivering Transgenic DNA Exceeding the Carrying Capacity of AAV Vectors. Methods Mol Biol. 2016;1382:21-39.
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