Adenovirus disrupts paediatric airway epithelium and impairs regeneration - 09/05/26

Human adenoviruses (HAdV), especially HAdV-7, are major causes of severe respiratory illness in young immunocompetent children and are linked to post-infectious bronchiolitis obliterans, though pathogenic mechanisms remain unclear. We analysed the bronchial epithelial response to HAdV-7 infection in healthy children. We also evaluated in this model the effect of cidofovir, an antiviral drug used in HAdV infection. Then, we compared the impact of HAdV and rhinovirus (RV) infection in ex vivo nasal brushing cultures and in vitro paediatric bronchial epithelial cells differentiated at the air-liquid interface (ALI).

Primary bronchial epithelial cells from paediatric lung resections (CERC-SFCTCV-2023-11-21_31945) were expanded and differentiated at ALI before infection with HAdV-7 ( n = 6). Antiviral effects of cidofovir were assessed at different concentrations. Viral load (RT-qPCR and TCID ₅₀ ), cytotoxicity, transepithelial electrical resistance (TEER), cytokine release profiling and specific immunostaining were analysed. Nasal brushings from hospitalised children with lower respiratory infection due to HAdV or RV (ClinicalTrial.gov ID NCT06140901) were also cultured at ALI. For comparison, HAdV-7 and RVA16-infected ALI cultures were re-seeded to assess whether similar effects could be reproduced.

HAdV-7 infection of ALI-differentiated paediatric bronchial epithelial cells caused a significant decrease in TEER by 7 days post infection (dpi), indicating impaired barrier integrity. Histological analysis showed disrupted epithelial architecture at 5 dpi, while ciliated cells remained present. Immunofluorescence confirmed adenoviral protein expression at 5 and 13 dpi. Viral replication showed a strong correlation between RT-q PCR and TCID ₅₀ assays, with cytopathologic effect from 13 dpi and cytotoxicity exceeding 10% at 21 dpi. Infection induced upregulation of IP-10, IFN-λ1 and lf-TSLP at both gene and protein levels, while IL-33 remained unchanged. Cidofovir treatment showed a strong, dose-dependent antiviral effect, with significant cytotoxicity only at 100 μM. Among nasal samples, 27 RV brushing-derived cultures established ALI differentiation successfully, while 7 HAdV-infected samples failed to adhere. Similarly, re-seeded HAdV-infected bronchial cells failed to re-establish epithelial layers, contrary to RVA16-infected cells. These findings highlight HAdV-7's strong cytopathic effects and its detrimental impact on epithelial regeneration and immune responses.

This HAdV-7 infection model in paediatric bronchial epithelial ALI cultures reveals marked epithelial damage, impaired regeneration and sustained immune activation. It offers a relevant platform to investigate pathogenesis and evaluate potential antiviral treatments.