Vomocytosis of Cryptococcus neoformans cells from murine, bone marrow-derived dendritic cells

Abstract

Cryptococcus neoformans (CN) cells survive within the acidic phagolysosome of macrophages for extended times, then escape without impacting the viability of the host cell via a phenomenon that has been coined vomocytosis. Through this mechanism, CN disseminate throughout the body, sometimes resulting in a potentially fatal condition - Cryptococcal Meningitis (CM). Justifiably, vomocytosis studies have focused primarily on macrophages, as alveolar macrophages within the lung act as first responders that ultimately expel this fungal pathogen. Herein, we hypothesize that dendritic cells (DCs), an innate immune cell with attributes that include phagocytosis and antigen presentation, can also act as vomocytes. Presciently, this report shows that vomocytosis of CN indeed occurs from DCs. Primarily through time-lapse microscopy imaging, we show that rates of vomocytosis events from DCs are comparable to those seen from macrophages and further, are independent of the presence of the CN capsule and infection ratios. Moreover, phagosome-altering drugs such as chloroquine and bafilomycin A, as well as the actin-modifying drug, cytochalasin B inhibit this phenomenon from DCs. Although DC immunophenotype does not affect the total number of vomocytic events, we observed differences in the numbers of CN per phagosome and expulsion times. Interestingly, these observations were similar in primary, murine macrophages. Understanding the vomocytic behavior of different phagocytes and their phenotypic subtypes is needed to help elucidate the full picture of the dynamic interplay between CN and the immune system. Critically, deeper insight into vomocytosis could reveal novel approaches to treat CM, as well as other immune-related conditions.