Inhibition of Cryptococcus neoformans-mediated phagolysosome damage by induced lysosomal renitence constrains fungal growth. (P3106)

Abstract Cryptococcus neoformans (C.neo) is a pathogenic yeast which primarily infects the lungs. The mechanisms which enable intracellular replication in unactivated macrophages by C.neo and the strategies employed by classically activated macrophages to combat this replication are incompletely understood. In this work we explore lysosomal damage as an important intracellular survival strategy of C.neo. We measured lysosome damage in C.neo infected murine bone marrow-derived macrophages using ratiometric-epifluorescence microscopy. C.neo growth inhibition data were confirmed by in vitro growth assay. C.neo-mediated lysosome damage was observed in a significant portion of the infected macrophages. The damage increased in frequency and average magnitude with time and replication of the intracellular yeast. Lysosome damage was significantly reduced in macrophages which had phagocytosed heat killed C.neo. Increased lysosome damage correlated with increased C.neo replication and reduced yeast killing. Finally, macrophage activation with IFN-γ but not IL-4 protected macrophages from lysosome damage and promoted increased killing of C.neo. Thus, we conclude that Lysosome damage may be important to the C.neo survival strategy in the host and that classically-activated host macrophages counter this strategy by inducing lysosome renitence. Thus, therapeutic strategies which decrease the ability of C.neo to cause lysosomal damage may be valuable in treating these infections.