How to Select AAV Serotypes for Neurological Research?
Adeno-associated virus (AAV) is regarded as the most promising vector for gene research because of its variety, extremely low immunogenicity, high safety, strong diffusion capacity, and persistence of gene expression in vivo. Different AAVs have different capsid protein spatial structures, sequence, and tissue specificity, which leads to the generation of multiple serotypes in vivo. Various serotypes have their functions, and their infection efficiency and transmission ability to different sites and cells are also different, accordingly, the selection of the appropriate serotype determines the results of subsequent experiments.
Creative Biolabs is pleased to share our extensive expertise in AAV serotype selection to facilitate research and project development for our clients.
AAV Applications in the Nervous System
The application of AAV in the nervous system mainly includes two main categories, neuronal tracing tools, and gene manipulation tools.
- Neuronal Tracing Tools
Accurate labeling of neural circuits with AAV requires consideration of reversibility, including neuronal anterograde, and retrograde labeling.
Fig. 1 Modalities of AAV labeling of neurons. (Bostan, et al., 2020)
- Neuronal Anterograde Labeling
Currently, there are only two serotypes that can be used for neuronal anterograde labeling, AAV9, and AAV1.
- Neuronal Retrograde Labeling
The only retrograde labeling available is the Retro serotype, a mutant of AAV2 that can be used when exploring the source of nerve fiber projections in a brain region.
The existence of the blood-brain barrier (BBB) has a strong protective effect on the central nervous system (CNS), but it can also block the transmission and absorption of drugs. AAV9, AAVPHP.B, AAVPHP.eB, and AAVPHP.S can effectively mediate the translocation of genes from the periphery to the CNS, and then deliver genetic material to the brain or spinal cord.
Fig. 2 Serotypes that can cross the BBB. (Chan, et al., 2017)
- Gene Manipulation Tools
As a genetic manipulation tool, there are many serotypes that can be selected. Appropriate serotypes are often selected according to different parts of peripheral nerves, spinal cord, brain regions and cell types.
Table1. Selection of different serotypes.
| Area | Serotypes | |
| Peripheral nervous system | AAVPHP. S, AAVrh10, AAV9 | |
| Spinal cord | AAVPHP. eB, AAVPHP.B, AAVrh10, AAV9 | |
| Brain | Whole brain | AVPHP. eB, AAVPHP.B, AAV9, AAVrh10 |
| Brain regions | Striatum | AAV5, AAV-DJ |
| Hippocampus | AAV9, AAV-DJ, AAV2 | |
| Cortex | AAV9, AAV8, AAV6, AAV5 | |
| Substantia Nigra | AAV5 | |
| Thalamus | AAV5 | |
| Amygdala | AAV1, AAV6, AAV7, AAV8, AAV-DJ, AAVrh10 | |
Fig. 3 Spinal cord(left) and amygdala(right) infection by different serotypes of AAV. (Park, et al., 2017)
In addition, nervous system-specific promoters can also be combined with serotypes to more efficiently and specifically gene expression.
Table2. Selection of different promoters.
| Promoter | Characteristics | Size | Species |
| hSyn | Neuron-specific promoter | 0.5 kb | human |
| mecp2 | Short neuron-specific promoter | 0.2 kb | mouse |
| TUBA1A | Early neuron-specific promoter | 1.2 kb | mouse |
| CaMKIIa | Glutamatergic neuron-specific promoter in forebrain | 1.1 kb | mouse |
| hVGAT | GABAergic neuron /interneuron specific promoter | 1.8 kb | human |
| Slc6a3 | Dopamine neuron-specific expression promoter | 1.2 kb | mouse |
| gfaABC1D | Astrocyte-specific promoter | 0.9 kb | human |
| Iba1 | Microglia-specific promoter | 1.5 kb | mouse |
| CNP | Oligodendrocyte or Schwann cell-specific expression promoter | 1.5 kb | mouse |
| F4/80 | Microglia-specific promoter | 0.6 kb | mouse |
| CD68 | Microglia-specific promoter | 0.7 kb | mouse |
Creative Biolabs is a leading supplier of custom neuroscience solutions to our partners worldwide. Our services range from gene function research to mechanism research. We are pleased to share our expertise in neuroscience research, please contact us for more technical support.
References
- Bostan, A. C.; et al. The cerebellum and basal ganglia are interconnected. Neuropsychol Rev. 2010, 20(3), 261-270.
- Chan, K.Y.; et al. Engineered AAVs for efficient noninvasive gene delivery to the central and peripheral nervous systems. Nat Neurosci. 2017, 20(8), 1172-1179.
- Park, S.H.; et al. Adeno-associated virus serotype rh10 is a useful gene transfer vector for sensory nerves that innervate bone in immunodeficient mice. Sci Rep. 2017, 7(1), 17428.
