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Adeno-associated virus (AAV) is a small virus with a single stranded DNA genome that requires a helper virus to infect humans and animals. More than 100 documented AAV serotypes exist, each with unique properties that allow AAVs to selectively target and infect specific tissues and cell types. Because of these properties, AAVs are commonly used to package and deliver genetic material, transgenes, into cells.

AAV Gene Therapy Offers New Treatment Pathways for Genetic Disorders.
Gene therapy holds enormous promise for treating genetic disorders by empowering researchers and clinicians to successfully deliver genetic material to specific tissues in living organisms. Gene therapy uses vectors, like AAV, to deliver transgenes to add, delete or correct genetic material in cells to control gene expression. AAVs have become the most commonly used vector for gene delivery in animal research and testing.1,2 Some AAV gene therapies have received regulatory approval to treat genetic disorders in humans.3,4 Looking ahead, continued research on AAV hopes to unlock new possibilities for more precise, targeted treatments in both animal and human medicine, potentially revolutionizing how we approach genetic disorders.

Detecting Pre-existing AAV Neutralizing Antibodies is Crucial for Effective Gene Therapy Research in Animals.
Although most AAVs do not cause disease, exposure to the virus generates an immune response that results in antibodies that can bind the AAV serotype it was exposed to. Some antibodies that bind the virus may also neutralize the virus by preventing it from reaching or entering the target cells. Environmental exposure, placental transfer of maternal antibodies, and age can affect the presence and levels of preexisting AAV antibodies.5

The presence of preexisting antibodies can hinder the effectiveness of AAV-based therapies and stimulate complement activation and immune based toxicities. Antibody testing can inform on the presence and quantities of preexisting antibodies.

Preexisting AAV antibody testing is a critical part of gene therapy research and development in animal models. All animals should be tested for preexisting antibodies prior to use in AAV-based gene therapy studies. Additionally, animals that are housed in groups should be routinely tested to monitor population health and help expose trends in disease exposure patterns. Working with an experienced animal health diagnostic laboratory can significantly improve the quality of gene therapy and xenotransplantation studies.6

Optimized assays precisely detect and quantify preexisting antibodies
Preexisting antibody testing can be used to detect or quantify the total amount of antibodies that recognize an AAV serotype or the antibodies capable of neutralizing an AAV serotype. Immunosorbent and/or cell-based assays are robust tools for evaluating the presence of antibodies in animal serum or other biological samples.

Qualitative assays provide quick screening in a rapid format. This type of screening is ideal for initial assessments, saving time and resources by quickly identifying positive or negative cases without the need for extensive processing.

Quantitative assays provide a more in-depth analysis. Neutralizing antibody titer assays offer a quantified measure, a titer, of the potency of an antibody to block an AAV serotype. This level of testing precision is crucial for accurately gauging antibody strength and tailoring treatment plans, especially in cases where therapeutic efficacy may depend on precise antibody levels.

Partnering with experts to strengthen AAV studies.
An expert animal health diagnostic partner can help overcome challenges associated with AAV-based study outcomes. Surveillance before a study is important because numerous AAV serotypes are present in nature and potentially in animal research facilities. Surveillance can help optimize animal care practices and study planning. AAV serotype variability can complicate assay development because preexisting antibodies may bind and neutralize multiple AAV serotypes and require additional examination.

Qualitative assays that screen for a panel of serotypes can provide information on a wide variety of serotypes. Testing panels can be curated to match the needs of a specific laboratory, animal population, species, or biological matrix. Neutralizing antibody tests should be designed to confirm and quantify the results of panel testing. The quality of AAV-based studies can be significantly improved with support and expertise from a highly skilled animal diagnostic laboratory with customizable and robust assay development platforms.

  1. Gao GP, Alvira MR, Wang L, Calcedo R, Johnston J, Wilson JM. Novel adeno-associated viruses from rhesus monkeys as vectors for human gene therapy. Proc Natl Acad Sci U S A. Sep 3 2002;99(18):11854-9. doi:10.1073/pnas.182412299
  2. Dunbar CE, High KA, Joung JK, Kohn DB, Ozawa K, Sadelain M. Gene therapy comes of age. Science. Jan 12 2018;359(6372)doi:10.1126/science.aan4672
  3. Keeler AM, Flotte TR. Recombinant Adeno-Associated Virus Gene Therapy in Light of Luxturna (and Zolgensma and Glybera): Where Are We, and How Did We Get Here? Annu Rev Virol. Sep 29 2019;6(1):601-621. doi:10.1146/annurev-virology-092818-015530
  4. Wang D, Tai PWL, Gao G. Adeno-associated virus vector as a platform for gene therapy delivery. Nat Rev Drug Discov. May 2019;18(5):358-378. doi:10.1038/s41573-019-0012-9
  5. Niewiesk S. Maternal antibodies: clinical significance, mechanism of interference with immune responses, and possible vaccination strategies. Front Immunol. 2014;5:446. doi:10.3389/fimmu.2014.00446
  6. Jacobsen KR, Mota J, Salerno M, Willis A, Pitts D, Denner J. Prevalence of Antibodies against Adeno-Associated Viruses (AAVs) in Gottingen Minipigs and Its Implications for Gene Therapy and Xenotransplantation. Viruses. Oct 15 2024;16(10)doi:10.3390/v16101613