Deciphering HTLV-1-associated Lung Pathology through Integrated in vitro and Multi-cohort Multi-omics Analysis: Inflammation, Monocyte Recruitment and Differentiation Triggered by HTLV-1-exposed Alveolar Epithelial Cells.

BACKGROUND: Human T-lymphotropic virus type 1 (HTLV-1) infects up to ten million people worldwide, and causes severe diseases, including adult T-cell leukemia/lymphoma and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Individuals with HAM/TSP are prone to pulmonary complications (e.g., bronchiectasis). Their bronchoalveolar lavage fluid typically shows increased levels of inflammatory cytokines, chemokines and cell adhesion molecules contributing to chronic inflammation. RESULTS: This study assessed the impact of HTLV-1 infection on lung inflammation by analyzing the alveolar transcriptome of A549 epithelial cells following exposure to HTLV-1. Co-culture with HTLV-1-infected MT-2 cells caused transcriptomic changes related to viral response, NF-κB activation, and inflammation. RT-qPCR confirmed elevated expression of the chemokine monocyte chemotactic protein-1 (MCP-1/CCL2) and colony stimulating factor 1 (CSF-1) in A549 MT-2 co-cultures. Increased CSF-1 expression was mechanistically linked to NF-κB signaling, using CRISPR/Cas9 RELA knockout. Supernatant from A549 MT-2 co-cultures triggered chemotaxis and macrophage differentiation of THP-1 and primary monocytes. Systems biology analysis revealed enrichment in pathways associated with monocyte infiltration and bronchiectasis. Finally, we validate the in vivo relevance of our in vitro model through multi-cohort multi-omics analysis combining bulk and single-cell transcriptomics, viral interactomics and multi-ancestry GWAS. CONCLUSIONS: We describe an in vitro co-culture model that recapitulates HTLV-1-triggered lung inflammation, through RELA/NF-kB-dependent release of pro-inflammatory cytokines and chemokines resulting in monocyte chemotaxis, activation and differentiation. Integrated multi-omics analysis confirmed the in vivo relevance of our in vitro model.