Our data suggests that PTX3-deficient macrophages infected with A. fumigatus exhibit a defective metabolic reprogramming, which is essential for the antifungal effector functions of these cells. In fact, PTX3 deficiency is associated with a dysregulated glucose metabolism, with an accumulation of pentose phosphate pathway metabolites, linked to a reduced capacity to produce pro-inflammatory cytokines and to control fungal killing and germination by macrophages.
TLR4, a PRR expressed in the cell membrane of macrophages and other immune cells, has been previously linked with the function of PTX3 in the context of A. fumigatus infection. In fact, our preliminary data suggest that an unbalanced TLR4 signalling in the absence of PTX3 could in fact affect the metabolic and functional activation of macrophages against A. fumigatus.
Our lab has previously shown that the glycolytic metabolic rewiring of macrophages in response to A. fumigatus is dependent on melanin. Specifically, fungal melanin impairs intracellular calcium signalling and the recruitment of molecular mediators to the phagosome. Importantly, the regulation of phagosome biogenesis and other essential processes for the intracellular killing of A. fumigatus by macrophages, show substantial overlap with these cellular metabolic pathways. Despite these observations, the mechanistic links between PTX3 function, cellular metabolism, and fungal clearance remain poorly understood. Unpublished data from our lab showed that PTX3 was essential for the optimal activation of a specific intracellular mechanisms of fungal elimination in human macrophages, raising the hypothesis that PTX3 could promote fungal clearance by regulating cell metabolism. Thus, our current investigation intends to determine the role of PTX3 in the metabolic regulation of phagosome biogenesis and the different steps of maturation, as well as intracellular fungal elimination.
In order to understand the dynamic contribution of PTX3 to antifungal effector functions and immunometabolic responses of macrophages in a disease-relevant context, we proposed to use physiologically representative model systems. In vivo mouse models cannot recapitulate all the aspects of the human infection, due to morphological and immune differences between mice and humans. A human lung-on-a-chip organ model that can be used to recapitulate the physiology of the alveolus, allowing the dissection of host-fungus interaction during fungal infection with unprecedented resolution, has been developed. After a specific training at Dr. Alexander Mosig laboratory (Jena, Germany), we have successfully established an Aspergillosis-on-chip model in our lab. In HSCT patients, specific PTX3 genetic variants are associated with an increased risk of infection. Thus, we will now assess the contribution of PTX3 by including macrophages from carriers of selected PTX3 genotypes in lung-on-chip systems.
