A108-07 Single-cell Profiling of Airway Immune Dysregulations in Post-Covid-19 Lung Injury

Abstract Rationale Long COVID poses a pressing global health challenge, with persistent lung pathology lacking mechanistic understanding and targeted therapy. Objectives To systematically profile local immune responses underlying respiratory sequelae after COVID-19 and identify therapeutic targets. Methods Single-cell RNA sequencing was performed on paired peripheral blood mononuclear cells (PBMCs) and bronchoalveolar lavage fluid (BALF) from 21 individuals exhibiting persistent respiratory symptoms or CT abnormalities three years after COVID-19. Immune profiling was correlated with clinical parameters, adjusting for age and sex. Measurements and Main Results Analysis of 152,403 PBMCs and 12,634 BALF cells identified six major cell types and 60 clusters. GZMB+ and GZMK+ CD8+ tissue-resident memory T (TRM) cells persisted in BALF for up to three years. Their abundance was negatively correlated with forced vital capacity (FVC): GZMB+ (r=-0.59, p = 0.0052) and GZMK+ (r=-0.52, p = 0.015). In contrast, the abundance of alveolar SPP1+ macrophages (r = 0.5, p = 0.021) and LAMP3+ conventional dendritic cells (cDCs, r = 0.53, p = 0.014) correlated positively with FVC. CD8+ TRM cells exhibited high PD-1, while SPP1+ macrophages and LAMP3+ cDCs expressed PD-L1. Ligand-receptor analysis implicated SPP1+ macrophages, via SPP1-CD44 and PD-L1/PD-1 axis, in promoting CD8+ Trm exhaustion. In vitro, SPP1 treatment increased PD-1+CD8+ T cells and suppressed IL-2, IFN-γ, and TNF-α production. Conclusion This study uncovers a novel immune circuit in long COVID lungs where SPP1+ macrophages and LAMP3+ cDCs may drive CD8+ TRM exhaustion, potentially restraining immunopathology while supporting lung repair. The findings highlight SPP1+ macrophages as a potential therapeutic target for modulating immune-repair balance in persistent lung injury post viral infection. This abstract is funded by: None