Rapid generation of a murine RSV infectious model by transducing a conditional knock-in mouse harboring human IGF1 receptor with adenoviral vector.

Human respiratory syncytial virus (RSV) remains the leading viral cause of severe lower respiratory tract disease in infants and young children worldwide. Despite decades of research, RSV vaccine development remains hindered by the lack of animal models that accurately recapitulate pediatric susceptibility and allow rigorous assessment of protective efficacy and safety. Recent studies have identified the human insulin-like growth factor 1 receptor (hIGF1R) as a critical host receptor that facilitates RSV fusion and entry. Using a novel conditional knock-in mouse model, lung-specific hIGF1R expression achieved through Ad5 vector transduction enables rapid generation of a pediatric-relevant mouse model, offering a promising route to close this gap. Following intranasal challenge with RSV A2 (1.62 × 105 TCID50), four-week-old Ad5-hIGF1R mice exhibited higher pulmonary viral loads, marked peribronchiolar and perivascular inflammation, interstitial thickening and a tendency toward alveolar wall coalescence compared with wild-type controls, thereby recapitulating severe pediatric RSV disease. Transcriptomic analysis revealed 12 chemokine genes, upregulated in RSV-infected lungs of Ad5-hIGF1R mice relative to mock controls, that are involved in immune-inflammatory pathways and may serve as practical biomarkers for detecting dysregulated host responses during vaccine or antiviral-drug assessment. Furthermore, A mid-dose prefusion F (pre-F) vaccination regimen significantly reduced viral loads and moderately attenuated neutrophil infiltration in the lungs of Ad5-hIGF1R mice. In summary, the young Ad5-hIGF1R mice demonstrate that hIGF1R expression enhances RSV replication and immunopathology in vivo. This model not only overcomes the limited RSV susceptibility of conventional young mice but also provides a platform for evaluating RSV vaccines.