Gene expression profiling of murine macrophages in response to infection with Cryptococcus neoformans yeast cells at distinct physiological states, including the dormant state known as viable but non-culturable (VBNC)

Macrophages play a pivotal role in determining the fate of invading Cryptococcus neoformans cells, and this outcome is highly dependent on how the pathogen modulates phagocyte activation and function. A common consequence of the C. neoformans-host interaction is the establishment of a latent infection, in which the yeast enters a dormant state. In this study, we investigated whether dormant cells could modulate murine bone marrow-derived macrophages (BMDMs) differently from non-dormant cells, thereby providing mechanistic insights into latent infection. To accomplish this, we examined the transcriptional responses of BMDMs upon in vitro infection with distinct physiological states of C. neoformans – exponential phase, stationary phase, or viable but non-culturable (VBNC; equivalent of dormant) cells – over a period of 6 hours. Our findings unveiled a relationship between the physiological state of the yeast and its impact on the transcriptome of BMDMs. Compared to non-dormant cells, particularly those in the logarithm phase, VBNC cells trigger a modest disruption in the host transcriptome, regulating a reduced number of genes, which clustered in far fewer Gene Ontology terms, many of which were unique to this specific condition. Nevertheless, VBNC cells retained the ability to regulate genes that are important for immune response, such as NLRP3 inflammasome-related genes. Our results suggest that VBNC cells retain the low immunostimulatory profile that is critical for the persistence of this fungal pathogen within the host. Overall design: Comparative gene expression profiling analysis of mouse bone marrow-derived macrophages cultured alone (uninfected control; Uni) or co-cultured with logarithm-phase (E-Cn), stationary-phase (S-Cn), or dormant yeast cells (viable but non-culturable cells; D-Cn) of Cryptococcus neoformansstrain H99O.