Adeno-associated virus (AAV) is a highly efficient gene therapy vector that is utilized to deliver transgenes to a variety of different tissues in vivo, and it is currently being evaluated for using in the research of acute and chronic lung diseases including those caused by single gene defects such as cystic fibrosis, alpha-1 antitrypsin deficiency and surfactant protein B deficiency. The transduction efficiency of adeno-associated virus (AAV) vectors in Lung tissues is related to the AAV serotype and the route of administration. Here, we briefly provide some information that you need think about when get started with AAVs in lung.

Adeno-associated virus (AAV) with serotype2, serotype5, serotype6 and serotype9 can archive high transduction efficiency of target genes in lung, but the specificity of infected cells is different. AAV2 capsids is mainly transduction Airway smooth muscle, those having AAV type 5 or 6 capsids show high transduction rates in airway epithelial cells, in a range that should be sufficient for treating lung disease.

Serotype	Infection	Infection site and degree	Receptor
AAV2	basal layer >>surface	Airway cell: Low level or none Alveolar cell: Low level or none Bronchial epithelium: Low level or none Airway smooth muscle: Medium level	Heparin sulfate
AAV5	basal layer >surface	Airway cell: Medium level Alveolar cell: Medium level	PDGFR, 2-5 sialic acid receptor
AAV6	surface	Airway cell: Medium level Alveolar cell: High level Bronchial epithelium: Medium level Airway smooth muscle: Low level	Sialic acid glycoprotein
AAV9	basal layer&surface	Airway cell: Low level Alveolar cell: Medium level	Galactosyl glucose

Meyer-Berg, H., et al., Stem Cell Res Ther, 2020. 

Which Promoter need to be selected in lung?

Promoters can be organism or tissue type-specific, which can help you restrict the expression of your transgene to a specific species or location. Promoters can also drive different levels of expression. CMV is a strong promoter that drives very high, ubiquitous expression in lungs. In addition, if you want to infect specific types of cells in the lung, you can also consider choosing a cell-specific promoter, such as the endothelial cell promoter ICAM2 or the smooth muscle cell promoter SM22α, which can achieve specific infection of endothelial cells or smooth muscle cells.

Injection Method

There are many methods for AAV to infect the lungs. The more commonly used methods include intranasal instillation, endotracheal intubation, and intratracheal injection. If the specific requirements for AAV infection in the lungs are low, intravenous injection, intraperitoneal injection, etc. Intratumoral injection can also be used when lung cancer tumorigenesis experiments are performed. The following table shows a comparison of different injection ways. If you want to know more, you can check the reference article or contact us at [email protected].

Method	Targeting site	Advantages	Disadvantages	Reference
intranasal instillation	Nasal epithelial cells Tracheal epithelium proximal and middle lobes	Fast; easy to operate; Low equipment requirements; multiple doses possible	Two people are required; Unable to deliver to the distal lobe	Reference 2 Reference 3
endotracheal intubation	Nasal epithelial cells Tracheal epithelium cells Proximal, middle and distal lobes	Can reach to the distal lobe	difficult in operation; Special equipment required; time consuming	Reference 4
intratracheal injection	Nasal epithelial cells Tracheal epithelium cells proximal and middle lobes May target distal lobes	Mainly for lower respiratory tract; Limited delivery to nasal epithelium	difficult in operation; surgical skills required; Invasive	Reference 2