Identification and functional role of medulla germinal centers during SARS-CoV-2 infection and reinfection in a macaque model using Xenium in situ spatial transcriptomics 9127

Abstract Description Germinal centers (GCs) generally form in the cortex of lymph nodes (LNs), supporting memory B cells differentiation and high-affinity antibody production. Recent studies have identified GCs in the medulla (mGC), challenging conventional understanding, though limited by methodological constraints. This study investigated mGCs in the mediastinal LNs of SARS-CoV-2-infected macaques during infection (3 dpi), convalescence (21 dpi), and reinfection (31 dpi; 3 days post-reinfection). Using Xenium in situ spatial transcriptomics, we resolved single-cell transcriptomic landscapes to characterize mGCs and their pathways. mGC were most abundant during convalescence but decreased during reinfection compared to cortex GCs (cGCs). Gene ontology analysis revealed enrichment pathways such as ‘B cell activation’ and ‘Lymphocyte differentiation’ during convalescence. During reinfection, mGCs exhibited metabolic adaptations with upregulation of ‘fatty acid metabolic processes’. Unlike cGC, mGC had higher proportions of plasma cells, fibroblasts, vascular endothelial cells, and lymphatic endothelial cells, with upregulated pathways for ‘Extracellular matrix structural constituent’ during both convalescence and reinfection. These findings underscore the distinct role of mGCs in humoral immunity, including plasma cell survival and metabolic adaptation. Xenium provide novel insights into GC heterogeneity and LN immune responses during SARS-CoV-2 infection, advancing our understanding of mGCs. Funding Sources Supported by KRIBB Research Initiative Program (KGM 4572431), KHIDI the Ministry of Health and Welfare (RS-2023-00302794), and The Bio and Medical Technology Development Program of the NRF MSIT (No 2022M3A9J1072296) Topic Categories Lymphocyte Differentiation and Peripheral Maintenance (LYM)