Adeno-associated virus (AAV) vector-mediated gene delivery was recently approved for the treatment of inherited blindness and spinal muscular atrophy, and long-term therapeutic effects have been achieved for other rare diseases, including haemophilia and Duchenne muscular dystrophy. However, current research indicates that the genetic modification of AAV vectors may further facilitate the success of AAV gene therapy. Vector engineering can increase AAV transduction efficiency (by optimizing the transgene cassette), vector tropism (using capsid engineering) and the ability of the capsid and transgene to avoid the host immune response (by genetically modifying these components), as well as optimize the large-scale production of AAV.
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The authors thank A. Dobbins for critical reading of the manuscript. This work was supported by National Institutes of Health Grants R01AI117408, R01HL125749, P01HL112761, R01AI072176 and R01HL144661. The authors apologize to any research group that feels their work was overlooked in this Review; we had to be extremely selective owing to space restrictions.
R.J.S. is the founder and a shareholder at Asklepios BioPharmaceutical and Bamboo Therapeutics, Inc. He holds patents that have been licensed by University of North Carolina to Asklepios Biopharmaceutical, for which he receives royalties. He has consulted for Baxter Healthcare and has received payment for speaking. C.L. is a cofounder of Bedrock Therapeutics, Inc. He holds patents licensed by University of North Carolina and has received royalties from Bedrock Therapeutics and Asklepios Biopharmaceutical.
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FDA approves innovative gene therapy to treat pediatric patients with spinal muscular atrophy: https://www.fda.gov/news-events/press-announcements/fda-approves-innovative-gene-therapy-treat-pediatric-patients-spinal-muscular-atrophy-rare-disease
Pfizer presents initial clinical data on phase 1b gene therapy study for duchenne muscular dystrophy (DMD): https://www.pfizer.com/news/press-release/press-release-detail/pfizer_presents_initial_clinical_data_on_phase_1b_gene_therapy_study_for_duchenne_muscular_dystrophy_dmd
Solid Biosciences announces FDA removes clinical hold on SGT-001: https://investors.solidbio.com/news-releases/news-release-details/solid-biosciences-announces-fda-removes-clinical-hold-sgt-001
Statement by FDA Commissioner Scott Gottlieb, M.D., and Biologics Center Director Peter Marks, M.D., Ph.D. on FDA’s continued efforts to stop stem cell clinics and manufacturers from marketing unapproved products that put patients at risk: https://www.fda.gov/news-events/press-announcements/statement-fda-commissioner-scott-gottlieb-md-and-peter-marks-md-phd-director-centre-biologics
- Leber congenital amaurosis
A rare genetic eye disease caused by the deficiency of various genes.
A genetic disorder with progressive vision loss due to a deficiency in Rab escort protein-1 (REP-1) owing to mutations in the CHM gene.
- Retinitis pigmentosa
A genetic disorder that causes progressive vision loss due to inherited retinal degeneration.
- Leber’s hereditary optic neuropathy
An inherited mitochondrial disorder involving the loss of central vision caused by the degeneration of retinal ganglion cells and their axons owing to point mutations in mitochondrial DNA.
Autosomal recessive congenital vision loss due to malfunction of the retinal phototransduction pathway.
- X-linked retinoschisis
A congenital eye disorder caused by mutations in the gene encoding retinoschisin, which plays a role in intercellular adhesion.
- Innate immune response
A general or non-specific defence mechanism that is the first-line defence against infection from viruses, bacteria, parasites and other foreign particles.
- Codon usage bias
A bias that results from background substitution biases and natural selection, and refers to the fact that, among species, some codons are more frequently used than other synonymous codons during translation.
- Stargardt disease
A common inherited retinal disease due to mutations in ABCA4, the gene encoding ATP-binding cassette transporter (ABCA4).
A truncated form of dystrophin that retains its function despite deletion of ~75% of the central rod domain (19 of the 24 rods; two of the four hinges) and the distal C-terminal domain (exons 71–78).
- Usher syndrome
A genetic disease caused by a deficiency in various genes that results in partial or total hearing and vision loss.
- AAV helper plasmids
Plasmids containing adeno-associated virus (AAV) rep and cap genes without inverted terminal repeats.
Antibodies produced from B cells after exposure to the individual’s own proteins.
- Major histocompatibility complex (MHC) class I pathway
MHC class I molecules are expressed on the cell surface of all nucleated cells. When peptide fragments generated from intracellular proteins bind MHC class I, the MHC class I–peptide complex is transported to the cell surface to induce the production of, and/or be recognized and killed by, cytotoxic T lymphocytes.
- Plasma apheresis
A procedure to remove the plasma from blood outside the body and reinfuse it back into patients.
- Adenovirus helper plasmid
A plasmid containing most adenovirus genes that helps the production of adeno-associated virus (AAV) Rep and AAV replication.
- Stable HeLa cell line–adenovirus method
A HeLa cell line contains adeno-associated virus (AAV) rep and cap genes, with or without integration of the AAV vector genome. When transduced with wild-type adenovirus and AAV vector, AAV Rep and Cap will be produced and the AAV vector genome will replicate and be packaged to produce a large amount of AAV vector.
- Herpesvirus helper method
Recombinant herpesvirus vectors (one contains adeno-associated virus (AAV) rep and cap, another contains AAV vector genome) are used to deliver the rep and cap genes, as well as the AAV vector genome, into HeLa cells for AAV vector production. Helper genes for helping AAV Rep and Cap production are provided by the herpes simplex virus genome.
- Kozak sequence
A sequence with the consensus ACCAUGG and a critical role in translation initiation.
- Leaky ribosomal scanning
A mechanism for regulating gene expression during the initiation phase of eukaryotic translation, in which a suboptimal translational initiation codon on mRNA is skipped by the small 40S ribosome subunit in translation initiation.
- Complement activation
Complement is a system made up of plasma proteins that can be activated by a pathogen or the antigen–antibody complex. Complement activation enhances the ability of antibodies or phagocytic cells to clear invading microorganisms or damaged cells.
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Li, C., Samulski, R.J. Engineering adeno-associated virus vectors for gene therapy. Nat Rev Genet 21, 255–272 (2020). https://doi.org/10.1038/s41576-019-0205-4
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