Adeno-Associated Virus (AAV) belongs to the Parvoviridae family and is a non-enveloped, single-stranded linear DNA virus. Due to its advantages such as a wide host range, high safety, low immunogenicity, stable expression, and stable physical characteristics, AAV has been widely used in basic research and clinical trials. Consequently, AAV vectors have become one of the most commonly used gene therapy vectors in the world.
Adenovirus (AdV) is a non-enveloped linear double-stranded DNA virus that is widely used in gene therapy and basic life science research. Current adenoviral vectors are primarily derived from human adenovirus type 5 (Ad5), which has a genome of approximately 36 kb of linear double-stranded DNA. Adenoviruses enter cells via receptor-mediated endocytosis using their fiber proteins and subsequently transfer from endosomes to the cytoplasm and nucleus, utilizing the cell’s transcription and translation machinery to initiate viral replication and assembly.
Lentivirus vectors are gene therapy vectors developed based on HIV-1 (Human Immunodeficiency Virus type 1). They have a broad infection spectrum, can effectively infect both dividing and non-dividing cells, and provide long-term stable expression of exogenous genes, making them a powerful tool for introducing foreign genes.
AAV is an ideal vector for expressing small gene sequences and is widely applied in in vivo studies. They are typically used to deliver exogenous genes, fluorescent markers, calcium indicators, and physiological control tools to the brains and various tissues/organs of mammals. When utilizing AAV vectors for in vivo gene delivery, the method of virus injection, injection volume, and serotype selection are particularly important. AAV has many serotypes, each with different capsid protein structures, sequences, and tissue specificities. Therefore, the recognition and binding to cell surface receptors also differ significantly, resulting in varied tissue types, cell types, and transduction efficiencies among different serotypes. It is essential to choose the corresponding serotype of AAV virus based on the specific tissues and organs being targeted.
Advantages of AAV: low immunogenicity suitable for in vivo studies; ability to express small gene sequences; multiple serotypes; stable expression with long duration.
The adenoviral infection process is mediated by receptor-mediated endocytosis, where the genome does not integrate into the host cell genome but is expressed in a free state within the nucleus. Thus, gene delivery based on adenoviral vectors features transient expression. Adenoviruses can achieve rapid expression in a short time, typically reaching peak levels within 1 to 3 days.
Adenoviruses have broad cellular and tissue infection capabilities, and their capacity for carrying gene segments is large (up to about 7 kb). In vitro, adenoviral vectors exhibit high transduction efficiency (close to 100%) and can transduce various types of cells, making them an excellent tool for gene delivery to many hard-to-transfect cell types. In vivo, adenoviruses tend to target the liver due to their liver tropism and can infect the liver when injected via the tail vein. However, because of their high immunogenicity and intense infections, adenoviruses often induce local tissue inflammation and immune responses in animals, which can affect the objectivity of animal signs and experimental results. Therefore, consideration of dosage is necessary when using adenoviruses for in vivo studies.
Advantages of adenovirus: suitable for infecting hard-to-infect cells; rapid expression time; transient expression; large vector capacity; can undergo animal experiments post-purification.
Lentivirus vectors are characterized by a broad host range and large gene capacity. In vitro, lentivirus vectors can effectively infect various types of primary cells, such as cultured neurons, hepatocytes, cardiomyocytes, tumor cells, endothelial cells, and stem cells, as well as most cell lines. Due to the integrative nature of lentiviral infections, they can effectively integrate exogenous genes into the host chromosomes, allowing for persistent expression and the establishment of stable cell lines for cellular function studies of genes.
In vivo, the application of lentivirus vectors is not as widespread as that of AAV vectors due to their immunogenic properties and the potential for random integration, which may lead to abnormal cell functioning. Compared to AAV, lentivirus has a smaller diffusion range but offers faster expression and a greater gene capacity (up to 4 kb), making it suitable for large-capacity gene delivery.
Advantages of lentivirus: stable expression, establishment of stable cell lines; broad infection range, capable of infecting both dividing and non-dividing cells.
