OR12

1:International Center for Infectious Disease Research (CIRI), Lyon, France; 2:Lyon University Hospital, Bacteriology Laboratory, Lyon, France; 3:Lyon University Hospital, Department of Infectious and Tropical Diseases, Lyon, France

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a major global health concern. Granulomas are central to TB pathology, serving as sites of bacterial control and persistence. In vitro granuloma models offer a controlled platform to study host-pathogen interactions, yet the impact of Mtb lineage and host variability remains poorly understood. Peripheral blood mononuclear cells (PBMCs) from three active TB patients were used to generate ex vivo granulomas, infected with autologous or heterologous Mtb clinical isolates from lineages 1, 2, 3, and 4 (L1-L4), as well as the reference strain H37Rv. Bacterial growth (CFU counting), Mtb dormancy (differentially culturable bacteria) and cytokine production were assessed at 7, 14, and 21 days post-infection (dpi). Bacterial growth and cytokine response were mainly Mtb isolate-dependent. The L4 isolate showed the highest bacterial burden and sustained inflammatory response. In contrast, the L2 isolate showed significant bacterial reduction, associated with increased dormancy and a weaker cytokine profile. Autologous infections showed reduced bacterial loads at 7-dpi compared to heterologous infections, accompanied by enhanced early Th1-type cytokine responses, including elevated IFN-γ and TNF-α levels, and high IFN-γ/IL-10 ratio. These early advantages did not persist at later time points. Mtb lineage and host-pathogen specificity shape granuloma dynamics, influencing bacterial control and immune responses. These findings underscore the utility of ex vivo granuloma models in TB research and highlight the need to account for pathogen diversity and host context. Future studies using single-cell approaches could further unravel early immune mechanisms driving infection outcomes.