6.1 Lung tissue structure
Accessibility of airway epithelium, alveolar type I/II cells, endothelium, and immune cells is affected by the distribution of mucus, barriers, and drug deposits.
6.2 AAV serotype selection
Both AAV5/6/9 and lung screening capsids can be evaluated; in vitro airway models are not a substitute for in vivo deposition validation.
6.3 Lung-specific promoter
SFTPC is used for alveolar type II cells, SCGB1A1 is used for club cells, and FOXJ1 is used for ciliated cells.
6.4 Administration method and dosage reference
Intratracheal instillation (i.t.): Targeting the lower lung parenchyma. Mice 4×10^11-1×10^12 vg/mouse, 25-50 μL, video laryngoscope + Penn-Century nebulizer or 31 G tracheostomy needle; rats 1×10^11-5×10^12 vg/mouse, 100-300 μL, 22 G-ball head gavage needle; mainly transduces AT2, AT1 and bronchial epithelium, with more deposition in the lower lobe of the right lung, and peak expression in 1-2 weeks [6-4,6-5].
Intranasal instillation (i.n.): full respiratory tract coverage. Mice were divided into 25-50 μL into both nostrils and kept in a supine position for 1 minute; the upper respiratory tract (nasal mucosa) was additionally transduced, and there was much residue in the nasal cavity [6-4].
Aerosol inhalation: close to physiological exposure. NHP atomization is about 3 mL/animal (Aerogen Solo vibrating mesh), general anesthesia + mechanical ventilation is about 30 minutes; sheep 10 mL/time via mask or intubation, repeated for 9 months, has good tolerance; distribution is more uniform but the efficiency is only 10-30%. High doses (>2×10^12 vg) can penetrate the alveolar-capillary barrier and enter the blood, causing liver expression [6-4,6-5].
6.5 Key research evidence
Akahori et al. established a non-invasive AAV airway pathway to target lung parenchymal cells and constructed a SARS-CoV-2 susceptible mouse model [6-4]; Wootton et al. systematically compared the AAV distribution in the mouse respiratory tract of four administration methods [6-5]; Körbelin et al. achieved lung targeting through NGS-guided capsid library screening [6-1]; Kang et al. lung-tropic AAV improved the survival of surfactant protein B-deficient mice [6-2]. The atomization/drip method, inhalation efficiency, lobar distribution and liver off-target should be recorded.
6.6 References for this chapter
[6-1] Körbelin J, et al. Pulmonary targeting by NGS-guided AAV capsid library screening. Mol Ther. 2016;24:1050-1061. DOI:10.1038/mt.2016.62. [H]
[6-2] Kang MH, et al. A lung-tropic AAV vector in surfactant B deficiency. Nat Commun. 2020;11:3929. [H]
[6-3] Wu H, et al. Tropism of AAV serotypes in mouse lungs via intratracheal instillation. Virol J. 2024;21:302. [N]
[6-4] Akahori Y, et al. Non-invasive administration of AAV to target lung parenchymal cells and develop SARS-CoV-2-susceptible mice. Commun Biol. 2022;5:45. DOI:10.1038/s42003-021-02984-3. [N]
[6-5] Wootton SK, et al. AAV vector distribution in the mouse respiratory tract following four different methods of administration. BMC Biotechnol. 2017;17:43. DOI:10.1186/s12896-017-0365-2. [H]