AAV Tropism for Lung Tissues

In the lungs, AAV tropism is divided between the airway epithelium (the lining of the tubes like the trachea and bronchi) and the alveoli (the deep air sacs where gas exchange happens).

Because the lung has a thick layer of mucus and specialized barriers, natural AAVs often require high doses or specific delivery methods (like intranasal or intratracheal) to be effective.

Serotype	Target Tissue/Cells	Transduction Efficiency	Best Use Case	Notes
AAV6	Airway Epithelium	Very High	Cystic Fibrosis research	Widely considered the “gold standard” for the lining of the lungs; targets ciliated and club cells.
AAV5	Airway & Alveoli	High	Global lung delivery	Effective at targeting both the upper airways and the deep alveolar type-2 (AT2) stem cells.
AAV1	Airway Epithelium	Moderate	Local airway delivery	Similar to AAV6 but often slightly less efficient in the lung.
AAV9	Alveoli & Parenchyma	High	Systemic lung targeting	Best for reaching the deep lung via the bloodstream; also targets lung fibroblasts and endothelial cells.
AAV4	Small Airway / RPE	Moderate	Small airway progenitor cells	Interestingly, while great for the eye, it has shown specific affinity for distal/small airway cells in some animal models.
AAVrh10	Global Lung	High	Widespread transduction	A rhesus primate strain that shows robust, widespread expression across large and small airways.
AAV2	Alveoli	Low/Mixed	Deep lung (limited)	Poor at passing through the airway mucus; tends to stay in the alveoli if delivered directly.

Delivery Method vs. Target

In lung gene therapy, the route of administration often dictates which cells get infected:

• Intranasal / Intratracheal (Inhalation): Best for targeting the Airway Epithelium. This route is preferred for diseases like Cystic Fibrosis or COPD where the lining of the lungs is the problem. AAV6 and AAV5 excel here.
• Intravenous (Systemic): Best for targeting the Lung Vasculature (blood vessels) or the Parenchyma (deep tissue). AAV9 is the top choice for this route.

Specific Cell Types Targeted

To further refine your research, you can pair these serotypes with specific promoters to target individual cell populations:

• KRT5 (Keratin 5): Targets Basal Cells in the airways.
• SPC (Surfactant Protein C): Restricts expression to Alveolar Type 2 (AT2) cells.
• Foxj1: Targets Ciliated Cells.

The AAV6.2 Variant

It is worth noting that a specific engineered variant called AAV6.2 (which differs from natural AAV6 by a single amino acid) was created specifically to increase lung transduction efficiency even further. It is often cited in recent pulmonary gene therapy literature.