IFN-γ-induced trained immunity enhances killing of priority pathogens in healthy and genetically vulnerable individuals.

Infectious diseases remain a global health challenge, driven by increasing antimicrobial resistance and the threat of emerging epidemics. Mycobacterium tuberculosis and Staphylococcus aureus are leading causes of mortality worldwide. Trained immunity - a form of innate immune memory - offers a promising approach to enhance pathogen clearance. Here, we demonstrate that IFN-γ induces trained immunity in human monocytes through a mechanism involving mTORC1 activation, glutaminolysis, and epigenetic remodeling. Macrophages derived from IFN-γ-trained monocytes exhibited increased glycolytic activity with enhanced cytokine and chemokine responses upon stimulation or infection. Crucially, trained macrophages had increased production of reactive oxygen species, which mediated enhanced bactericidal activity against methicillin-resistant S. aureus and M. tuberculosis. Furthermore, ATAC-sequencing analysis of IFN-γ-trained macrophages revealed increased chromatin accessibility in regions associated with host defense. Last, IFN-γ training restored impaired innate responses in macrophages from individuals homozygous for the TIRAP 180L polymorphism, a genetic variant associated with increased susceptibility to infection. These findings establish IFN-γ as a potent inducer of trained immunity in human monocytes and support its potential as a host-directed strategy to strengthen antimicrobial defenses, particularly in genetically susceptible individuals and high-risk clinical contexts.