Transcriptional responses of primary murine macrophages to four Candida species
Candidiasis is an infection caused by yeasts of the genus Candida that ranges in severity from debilitating mucosal infections to disseminated disease with high mortality rates. C. albicans is the most common cause of infection, but non-albicans species collectively represent a significant disease burden. Disseminated disease rarely affects immunocompetent individuals, largely due to the action of innate immune cells, including macrophages, in controlling infection. The interaction of C. albicans with macrophages has been subject to extensive study, but there has been little investigation of the macrophage response to non-albicans Candida species. Here, we used RNA-seq to investigate global transcriptional changes within primary murine macrophages after one hour in response to four species: C. albicans, C. parapsilosis, C. tropicalis and Clavispora lusitaniae. We identified a strong pro-inflammatory response to C. albicans that was largely independent of fungal variability and found that this was highly correlated with the response to C. parapsilosis and C. tropicalis. In contrast, C. lusitaniae elicited a broadly weaker response, including reduced induction of cytokine genes. Several chemokine genes also showed weaker induction in response to both C. lusitaniae and C. parapsilosis than to C. albicans, although significantly reduced secretion of CCL3 protein was only evident in response to C. lusitaniae. These data indicate a high degree of similarity in early macrophage recognition of multiple important Candida pathogens, but also suggest that weaker recognition of C. lusitaniae by immune cells may aid immune evasion by this species. Overall design: Macrophages were differentiated from murine bone marrows using 10 ng/ml macrophage colony stimulating factor (M-CSF) for seven days, before being distributed into 12-well plates and incubated overnight. Macrophages were then stimulated with medium only, live Candida (C. albicans, C. lusitaniae, C. parapsilosis, C. tropicalis) or UV-killed C. albicans (all in a 3:1 Candida:macrophage ratio). For the LPS/IFN-gamma condition, macrophages were treated overnight with 100 U/ml IFN-gamma, then during the experiment were stimulated with 100 ng/ml LPS. After 1 hr treatment, macrophage RNA was isolated using the Qiagen RNeasy Micro kit. RNA samples were obtained from macrophages derived from three individual mice. Sequencing and library preparation was performed by Macrogen, Inc.