T. pallidum achieves immune evasion by blocking autophagic flux in microglia through hexokinase 2.

Increasing evidence suggests that immune cell clearance is closely linked to cellular metabolism. Neurosyphilis, a severe neurological disorder caused by Treponema pallidum (T. pallidum) infection, significantly impacts the brain. Microglia, the innate immune cells of the central nervous system, play a critical role in neuroinflammation and immune surveillance. However, the inability of the nervous system to fully eliminate T. pallidum points to a compromised clearance function of microglia. This study investigates how T. pallidum alters the immune clearance ability of microglia and explores the underlying metabolic mechanisms. RNA sequencing (RNA seq), LC-MS metabolomics, and XFe96 Seahorse assays were employed to assess metabolic activity in microglial cells. Western blotting, qPCR, and immunofluorescence imaging were utilized to evaluate autophagy flux and extent of T. pallidum infections. Transcriptomic analysis revealed that T. pallidum alters the transcription expression of key glycolytic enzymes, including hexokinase 1 (HK1), hexokinase 2 (HK2), and lactate dehydrogenase A (LDHA), leading to significant metabolic dysregulation. Specifically, metabolomic analysis showed reduced levels of phosphoenolpyruvate and citrate, while lactate production was notably increased. Functional assays confirmed that T. pallidum impairs glycolytic activity in microglial, as evidenced by decreased glycolytic flux, glycolytic reserve capacity, and maximum glycolytic capacity. Moreover, our results indicate that HK2, a crucial glycolytic enzyme, is closely associated with the autophagy. T. pallidum infection inhibits HK2 expression, which in turn suppresses autophagic flux by reducing the formation of lysosome-associated membrane protein 2 (LAMP2) and disrupting autophagosome-lysosome fusion. These findings suggest that T. pallidum hijacks microglial metabolic pathways, specifically glycolysis, to evade immune clearance. By inhibiting the glycolytic enzyme HK2, T. pallidum modulates autophagy and enhances immune evasion, providing a novel insight into the pathogenesis of neurosyphilis. This study paves the way for further investigations into the role of metabolic reprogramming in the immune escape mechanisms of T. pallidum.