Pathological Characteristics of the Lung and Brain in Cotton Rats and BALB/c Mice Infected with Respiratory Syncytial Virus.

To compare the respiratory lesions and nervous system damage in cotton rats and BALB/c mice following respiratory syncytial virus (RSV) infection, and to evaluate their suitability as models for RSV-related respiratory and nervous system diseases, cotton rats and BALB/c mice were infected with RSV via intranasal instillation, monitored daily for weight and temperature. At 3, 5, and 7 days post-infection (dpi), viral loads in the nasal turbinates, lungs, and brain tissues were quantified. Pathological changes and neuroinflammatory responses in the lungs and brain were assessed using hematoxylin and eosin (H&E) staining, Nissl staining, immunofluorescence, and Western blotting analysis, while the mRNA expression levels of inflammatory factors were specifically analyzed at 5 dpi. The results showed that viral loads in the nasal turbinates and lungs of cotton rats were significantly higher than those in BALB/c mice, accompanied by more extensive pulmonary inflammatory factor gene upregulation at 5 dpi and more pronounced lung histopathological alterations. In contrast, RSV RNA and antigens were detected in the brain tissues of BALB/c mice, at levels markedly lower than those in respiratory tissues, along with viral antigens primarily localized to the choroid plexus epithelium. No significant pathological or neuroinflammatory changes were observed in the brains of cotton rats at any examined time point. In conclusion, cotton rats provide advantages for modeling RSV-associated respiratory tract infection and pulmonary pathology, whereas under the experimental conditions of this study, BALB/c mice may be more appropriate for investigating RSV-associated CNS inflammatory responses, although the clinical relevance of these findings remains to be further validated.