Structure of adeno-associated virus type 4

Area of Science:

• Structural biology
• Virology
• Biochemistry

Background:

• Adeno-associated virus (AAV) is a versatile tool in gene therapy, with various serotypes targeting different cells.
• Understanding AAV capsid structure is crucial for engineering targeted delivery systems.
• AAV4 is an antigenically distinct serotype with potential therapeutic applications.

Purpose of the Study:

• To determine the high-resolution structure of the AAV4 capsid.
• To build a pseudoatomic model of AAV4 and compare it with other AAV serotypes.
• To identify structural features responsible for AAV4's unique properties.

Main Methods:

• Cryo-electron microscopy and image reconstruction were used to determine the AAV4 structure at 13-Å resolution.
• A pseudoatomic model was constructed using structure-based sequence alignment with AAV2.
• The model was constrained by the reconstructed density envelope.

Main Results:

• The AAV4 capsid structure revealed variations in surface loops compared to AAV2.
• These structural differences likely explain the distinct receptor binding and antigenicity of AAV4.
• Unexpected structural similarities were found between AAV4 and autonomous parvoviruses (e.g., Aleutian mink disease virus, human parvovirus B19).

Conclusions:

• The determined AAV4 structure provides a basis for understanding its unique biological characteristics.
• Structural insights can guide the rational design of AAV-based gene therapy vectors.
• AAV4's structural relationships challenge existing classifications within the Parvoviridae family.