Comprehensive CyTOF and lipidomic analysis of splenic immune and serum lipid responses to BCG vaccination and H37Rv challenge in BALB/c mice

The protective efficacy of the Bacillus Calmette-Guérin (BCG) vaccine against Mycobacterium tuberculosis (Mtb) is variable, and the systemic mechanisms linking cellular immunity with host metabolism remain poorly understood. This study employed high-dimensional mass cytometry (CyTOF) within the splenic compartment and serum lipidomics to map the integrated immuno-metabolic landscape in BCG-vaccinated and non-vaccinated mice following infection with the H37Rv strain. We report that BCG vaccination was associated with a distinct phenotype characterised by the priming of antimicrobial myeloid subsets (CD11b+ Mac2+/Mac3+) and lipidomic pathways away from stress-induced inflammatory responses. In contrast, non-vaccinated hosts exhibited a dysregulated response, characterised by a systemic cortisol surge, a lipidomic profile suggestive of reduced bioactive lipids (including PPARγ ligands such as 13-HODE and 19,20-DiHDPA), and the reactive mobilisation of CD103 + CD4+/CD8 + T cells and activated B cell subsets to the spleen. These findings reveal that protection is not solely cellular but relies on a stable metabolic environment that supports immune function. While infection in naive hosts drives a resource-depleting stress response that likely compromises macrophage efficacy, BCG vaccination establishes an integrated multiparametric defence, preventing pathogen-driven metabolic manipulation and maintaining the necessary lipid mediators for effective inflammation resolution and bacterial control.