Long COVID Model Reveals Distinct Lung and Brain Changes Compared to Flu
New research utilizing a mouse model suggests that the long-term effects of SARS-CoV-2 infection, resembling long COVID, differ significantly from those observed after influenza A infection. The study, published in Frontiers in Immunology, highlights distinct patterns of lung and brain injury following sublethal doses of each virus, offering potential insights into the underlying mechanisms of persistent symptoms.
Distinct Lung Injury Patterns
Both SARS-CoV-2 (MA30 strain) and influenza A (PR8 strain) caused prolonged inflammation and collagen deposition in the lungs of infected mice, indicative of subchronic inflammatory lung injury and fibrotic remodeling. But, the recovery patterns differed. Influenza A infection demonstrated signs of epithelial regeneration, with persistent basal epithelial markers suggesting active repair processes. In contrast, SARS-CoV-2 infection was characterized by sustained activation of inflammatory, complement, and coagulation pathways, alongside extracellular matrix remodeling and continued barrier dysfunction, hindering restoration of normal lung function.
These findings suggest that breathlessness following viral infection may stem from different underlying mechanisms. The influenza-like trajectory aligns with a repair-dominant recovery, while the SARS-CoV-2 trajectory points towards persistent inflammation, vascular signaling issues, and ongoing remodeling.
Neuroinflammation Without Direct Brain Infection
Interestingly, neither virus directly infected the brain. Despite this, SARS-CoV-2 infection uniquely led to increased microhemorrhage frequency early in the infection and persistent neuroinflammation throughout the 28-day observation period. Brain profiling of mice infected with SARS-CoV-2 revealed enrichment of pathways associated with vascular dysfunction, extracellular matrix remodeling, and IL-6 related signaling. The virus disrupted hypothalamic-pituitary-axis programs, a finding not observed with influenza A.
Implications for Long COVID
The study suggests that neurological symptoms associated with long COVID may arise from inflammatory and microvascular mechanisms rather than direct viral invasion of the brain. This reinforces the need for monitoring neurocognitive and neuropsychiatric complaints in patients even after acute SARS-CoV-2 infection has resolved. The research provides a foundation for understanding the diverse and persistent symptoms experienced by individuals with long COVID and may inform the development of targeted therapies.
Study Details
Researchers longitudinally characterized C57BL/6 mice infected with sublethal doses of mouse-adapted SARS-CoV-2 (MA30) or influenza A (PR8). Lung and brain tissues were analyzed at 14, 21, and 28 days post-infection using histological analysis and bulk-RNA sequencing. Reference: Currey J et al. Characterization of subchronic lung and brain consequences caused by mouse-adapted SARS-CoV-2 and influenza A infection of C57BL6 mice. Frontiers in Immunology. 2026;DOI:10.3389/fimmu.2026.1755141
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