A Guide to AAV Serotype Selection

By Abhilasha Gupta, PhD – Senior Application Scientist

Introduction

As a molecular biologist I repeatedly encountered a few questions when designing my AAV constructs. Which serotype should I select? Which promoter should I use? What is the WPRE, and is it necessary? This is the first in a series of reviews intended as an aid to the research community. At Vector Biolabs we’ve produced tens of thousands of custom AAVs and would like to apply that experience to your development challenges.

For a more general overview of AAV biology see our “Intro to AAV” page.

Over the past 20 years, AAV has been actively investigated as a preferred vector that can be modified to deliver transgenes (DNA/RNA) safely into a variety of cell- and tissue-types across many species including murine, rodent, canine, and non-human primates. There are approved AAV-based gene therapies to treat hemophilia type B, spinal muscular atrophy, retinal dystrophy, and macular-age degeneration. AAV infection of target tissue and cells depends on several factors: their serotype (differentiated by the antigenic properties of the different viral capsid proteins), transducibility (cell receptor and mode of cell entry) and the type of promoter driving expression of the transgene. This review will summarize the tissue tropism and transducibility of the different AAV serotypes. It is important to note that no one AAV serotype is exclusive to a particular tissue or cell-type. However, some AAV serotypes transduce certain tissues more effectively than other serotypes.

Below we have summarized a few notable features of each naturally occurring serotype and included a table summarizing their tissue tropism.

Tissue Tropism

Tissue
Cell Type
AAV
Transduction Efficiency
Species
Brain – Neurons Neurons AAV1 +++ Efficient transduction Murine
AAV2 +/++ Natural Tropism
AAV7 ++++ High transduction Murine
AAV9 +++++ Superior transduction (and non-neuronal) Murine, NHP, Feline
Golgi neurons AAV5 + Not well characterized Murine
Brain – Non Neuronal Cells Astrocytes AAV9 ++++ High transduction
AAV11 + Not well characterized Murine
Basketum AAV5 + Not well characterized Murine
Cerebrum AAV11 + Mild tropism NHP
Ependymal cells AAV1 +++ Efficient transduction Murine
AAV4 + Specific tropism
Glial cells AAV1 +++ Efficient transduction Murine
Oligodendrocytes AAV1 +++ Efficient transduction
AAV9 ++++ High transduction
Purkinje cells AAV5 + Not well characterized Murine
Stellate AAV5 + Not well characterized Murine
Ventricular epithelium AAV5 + Not well characterized Murine
Projection neurons AAV11 + Not well characterized Murine
Inferior colliculus AAV5 + Not well characterized Murine
Primary motor cortex AAV/DJ8 +++ High transduction Murine (P0)
Non-mitotic cells AAV2 + Natural Tropism
Ocular Retinal cells AAV1 +++ Efficient transduction
AAV2 +++ Efficient tranduction
AAV8 ++ Efficient tranduction
AAV10 + Not well characterized
Retinal pigmented epithelium AAV1 +++ Efficient tranduction Murine (Subretinal injection)
AAV2 +++ Efficient tranduction Murine (Subretinal injection)
AAV4 +++ Stable transduction Rodent, Canine, NHP
AAV5 +++ Efficient tranduction Murine (Subretinal injection)
AAV7 +++ Efficient tranduction Murine (Subretinal injection)
AAV8 +++ Efficient tranduction Murine (Subretinal injection)
AAV9 +++ Efficient tranduction Murine (Subretinal injection)
AAV10 + Not well characterized
Photoreceptor cells AAV2 +++ Efficient tranduction Murine (Subretinal injection)
AAV5 +++ Efficient tranduction Murine (Subretinal injection)
AAV7 ++++ High transduction Murine (Subretinal injection)
AAV8 +++ Efficient tranduction Murine (Subretinal injection)
AAV9 +++ Efficient tranduction Murine
AAV10 + Not well characterized
Amacrine AAV8 +++ Efficient tranduction
Muller AAV2 ++ Significant tranduction Murine
AAV8 ++++ High tranduction Murine (Subretinal injection)
AAV9 ++++ High tranduction Murine (Subretinal injection)
Putative bipolar AAV8 +++ Efficient tranduction
Ganglion cell layer AAV2 +++ Efficient tranduction Murine (Intravitreal injection)
AAV8 +++ Efficient transduction Murine (Intravitreal injection)
AAV10 + Not well characterized
Inner nuclear layer AAV10 + Not well characterized
Horizontal cells AAV10 ++++ High trandsuction
Lungs alveolar epithelial cells AAV4 ++ Significant transduction Murine
AAV5 +++ Efficient transduction Murine
AAV6 ++++ High transduction Murine, Canine
AAV9 ++++ High transduction
AAV10 + Not well characterized Murine (IV injection)
Heart cardiomyocytes AAV1 +++ Efficient transduction Murine (Local injection)
AAV2 + Not well characterized
AAV4 ++ Significant transduction Murine
AAV6 ++ Higher transduction efficiency than AAV2 Murine, Porcine, Canine, Sheep
AAV8 ++++ Most efficient transduction by systemic delivery
AAV9 +++++ Best (5-10 fold higher than AAV8) Murine, NHP, Porcine
epicardium AAV7 ++++ High transduction
Cardiac muscle AAVrh74 ++++ High transduction Murine, NHP
Liver Hepatocytes AAV2 +++ Natural tropism and stable transduction Murine
AAV5 ++ Significant transduction Murine
AAV6 + Not well characterized Murine
AAV7 ++++ Strong tropism Murine, Human
AAV8 +++++ Strong and best tropism with superior transduction than AAV2 Murine
AAV9 ++++ Higher transduction efficiency than AAV2 Murine
AAV10 + Not well characterized Murine (IV injection)
Kidneys AAV4 ++ Significant transduction Murine
AAV8 ++++ High transduction efficiency by direct injection
Renal tubular epithelium AAV9 +++ Efficient transduction Murine (IV injection)
Juxtaglomerular cells AAV9 +++ Specific and efficient transduction Murine (IV injection)
Intestines Small intestines AAV10 +++ Natural Tropism Murine, NHP
AAV11 +++ Natural tropism NHP
Colon AAV9 ++++ High transduction Murine
AAV10 +++++ Best transduction Murine (SMA injection)
Muscle Skeletal muscle AAV1 +++ Most efficient transduction Murine, Canine, NHP
AAV2 +++ Natural tropism
AAV6 ++++ High transduction Murine (Tibialis anterior injection)
AAV7 ++++ Similar transduction efficincy to AAV1, higher than AAV2 Murine
AAV8 +++ Most efficient transduction Murine (Systemic delivery)
AAV9 ++++ High transduction Murine (Tibialis anterior injection)
AAVrh74 ++++ High tropism Murine, NHP
Smooth muscles AAV1 +++ Efficient transduction
AAV5 ++ Sufficient transduction Murine
Vascular endothelial muscles AAV1 +++ Efficient transduction
AAV2 +++ Natural tropism
AAV5 ++ Sufficient transduction Murine
AAV9 ++++ High transduction
Lymph nodes Unspecified AAV10 + Not well characterized NHP
AAV11 + Not well characterized NHP
Spinal tissues AAV7 ++++ Robust tropism and high transduction NHP (Intrathecal injection)
AAV9 ++++ High transduction NHP (Intrathecal injection)
Spinal cord AAV11 + Mild tropism, not well characterized NHP
Salivary glands AAV12 + Strong tropism, not well characterized NHP
Ears Cochlear inner hair cells AAV3 ++++ High transduction Murine
AAV8 ++++ Specific tropism and high transduction Murine
Pancreas AAV8 ++ Significant transduction Murine
AAV9 ++ Significant transduction Murine
Testicular tissue Leydig cells AAV2 +++ Efficient transduction Murine
AAV10 +++ Efficient transduction Murine
AAV9 ++++ Specific tropism and high transduction Murine (neuraminidase)

Naturally Occurring Serotypes

Serotype
Notable Features
AAV1 First viral vector approved for use in gene therapy
Primary cell surface receptor is sialic acid
Does not bind to heparin
AAV2 Discovered in 1965
Most studied of all AAV serotypes
Primary cellular receptor is heparin sulfate proteoglycan (HSPG: R585 and R588) – but remains insufficient for cell entry. Hence, AAV2 uses other coreceptors (Laminin receptor (LR); Fibroblast Growth Factor Receptor (FGFR1); integrins (αVβ5, α5β1) and CD9)
Has tropism for Murine, Canine, NHP, Avian
AAV3 Transduces cells that cannot be transduced with AAV2
Binding receptors: HSPG, FGFR1, LR, and hHGFR)
AAV4 Most antigenically distinct serotype
Primary cell surface receptor is a-2.3-O-linked sialic acid
AAV5 Most genetically divergent of all AAVs
Uses HSV as its helper virus, and an atypical endocytic pathway for cell transduction
Transduces cells that cannot be transduced with AAV2
AAV6 High genomic similarity with both AAV1 (99% coding homology) and AAV2 (multiple regions identical)
Coreceptor is epidermal growth factor (EGFR)
AAV7 First isolated in 2002 from Rhesus macaque monkeys
Coreceptor and cell entry pathways are unknown. Does not bind to heparin nor any glycans
AAV8 First isolated in 2002 from Rhesus macaque monkeys
Binds to the same receptor as AAV2 and AAV3 – LR
Is able to cross the blood vessel barrier
Transduction efficiency is susceptible to proteosome levels in some tissues – must use proteosome inhibitors to increase
AAV9 First identified in 2004 from human isolates.
Binds to coreceptors: N-linked galactose, putative integrin, LR
Crosses the blood-brain barrier (BBB)
AAV10 Isolated from cynomolgus monkeys in 2004
Capsid protein is highly similar to AAV4 and AAV8
Mode of host entry remains unknown
AAV11 Isolated from cynomolgus monkeys in 2004
Capsid protein is highly similar to AAV4 and AAV8
Mode of host entry remains unknown
AAV12 Isolated from simian adenovirus
Novel serotype with distinct biological and serological properties
Mode of cell entry is unknown
Does not bind to HSPG nor sialic acids
AAV13 Isolated from simian adenovirus
Primary cell surface receptor is unknown; can bind to HSPG
Structurally similar to AAV2 and AAV3
Limited data
Rh74 Isolated from rhesus macaque monkey lymph nodes and spleen
Low immunogenicity compared to other AAV serotypes
Primary coreceptor is unknown
Attractive serotype for gene therapy of Duchenne Muscular Dystrophy (DMD)
* A universal receptor, KIAA0319 or AAVR, has been identified that mediates rapid endocytosis after cell binding and attachment for all AAV serotypes (http://doi.org/10.1371/journal.pone.0188830)

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