AAV is a non-enveloped icosahedral parvovirus, about 25 nm. The capsid is composed of 60 VP subunits; the unique region of VP1 is involved in endosomal escape, and VP3 constitutes the main structural skeleton. The wild-type genome contains rep, cap and ITR at both ends; recombinant AAV usually retains only the ITR, and provides rep/cap and auxiliary functions in the production system, thereby separating the replication ability from the transgene expression cassette. [4-1 to 4-4]
Function chain determined by structure
|
Level |
Key components |
Direct impact on the experiment |
|
Capsid |
VP1/VP2/VP3 and surface variable regions |
Receptor binding, cell entry, antibody recognition, tissue tropism and production of aptamers |
|
Vector genome |
ITR-promoter-transgene-regulatory element-polyA-ITR |
Capacity, expression intensity, specificity, genome integrity |
|
Cell entrance |
Glycans, AAVR and other dependent factors |
The same capsid may produce different results in different cells and species |
|
Production components |
rep/cap, auxiliary genes, production cells |
Yield, empty/solid shell ratio, residue and batch-to-batch consistency |
The 2023 biophysical review emphasized that transduction is a continuous process of receptor binding, endocytosis, endosomal escape, nuclear transport, uncoating, and second-strand formation; the structure of the Rep packaging complex in 2026 further showed that packaging is not a simple "DNA loading into an empty shell", but a dynamic process of collaboration between Rep, ITR and capsid interface. [4-3,4-4]
References for this chapter
[4-1] Pillay S, et al. An essential receptor for adeno-associated virus infection. Nature. 2016;530:108-112. DOI:10.1038/nature16465. PMID:26814968. [H]
[4-2] Bennett A, Mietzsch M, Agbandje-McKenna M. Understanding capsid assembly and genome packaging for adeno-associated viruses. Future Virol. 2017;12:283-297. DOI:10.2217/fvl-2017-0011. PMID:36776482. [H]
[4-3] Xiang YS, Hao GG. Biophysical characterization of adeno-associated virus capsid through the viral transduction life cycle. Biophys Rev. 2023;21:62. DOI:10.1186/s43141-023-00518-5. PMID:37195476. [N]
[4-4] Xu V, et al. Structural basis for Rep-mediated adeno-associated virus packaging. Cell Rep. 2026;45:117044. DOI:10.1016/j.celrep.2026.117044. PMID:41790558. [N]