Antifungal activity of dendritic cell lysosomal proteins against Cryptococcus neoformans

Abstract

Cryptococcal meningitis is a life-threatening disease among immune compromised individuals that is caused by the opportunistic fungal pathogen Cryptococcus neoformans. Previous studies have shown that the fungus is phagocytosed by dendritic cells (DCs) and trafficked to the lysosome where it is killed by both oxidative and non-oxidative mechanisms. While certain molecules from the lysosome are known to kill or inhibit the growth of C. neoformans, the lysosome is an organelle containing many different proteins and enzymes that are designed to degrade phagocytosed material. We hypothesized that multiple lysosomal components, including cysteine proteases and antimicrobial peptides, could inhibit the growth of C. neoformans. Our study identified the contents of the DC lysosome and examined the anti-cryptococcal properties of different proteins found within the lysosome. Results showed several DC lysosomal proteins affected the growth of C. neoformans in vitro. The proteins that killed or inhibited the fungus did so in a dose-dependent manner. Furthermore, the concentration of protein needed for cryptococcal inhibition was found to be non-cytotoxic to mammalian cells. These data show that many DC lysosomal proteins have antifungal activity and have potential as immune-based therapeutics.

Transcriptional Changes in Pulmonary Phagocyte Subsets Dictate the Outcome Following Interaction With The Fungal Pathogen Cryptococcus neoformans

“…Each subset of pulmonary macrophages or DCs was purified (as described above), and 2x10 5 cells/ml of each subset were incubated with 1µg/ml anti-GXM antibody (kind gift from Tom Kozel, University of Nevada Reno) and 1x10 4 cells/ml of C. neoformans strain H99 (20:1 ratio) in 100 µl in triplicate wells for 24 hours at 37°C, 5% CO 2 , as previously described ( 18 , 60 , 81 , 82 ). After 24 hours, the samples were centrifuged, and supernatants were removed.…”

Antifungal activity of eumelanin-inspired indoylenepheyleneethynylene against Cryptococcus neoformans

“…Checkerboard assays were conducted using a method previously described, to determine the antifungal activity of EIPE-1 in combination with AmB ( Bonifácio et al, 2019 ; Nelson et al, 2021 ). EIPE-1 or AmB were evaluated in a two-fold dilution as described in the MIC protocol above.…”

“…FICIs were defined as the sum of individual FICs (FICI = FIC Am B + FIC EIPE-1 ), with FICs being defined as the MIC derived from the combination therapy divided by their MIC alone (FIC = MIC Combination /MIC Alone ). Off-scale MICs were considered to be the highest or lowest concentration tested in the microdilution assay ( Bonifácio et al, 2019 ; Nelson et al, 2021 ).…”

Cryptococcus escapes host immunity: What do we know?

“…and migrate to T-cell-rich lymphoid organs, where the major histocompatibility complex class II (MHC-II) on their surface presents the processed antigenic component to the initial T cells, namely mannoprotein (MP), initiating the subsequent T lymphocyte immune response. DCs engulf cryptococci and recruit lysosomes to fuse with them, which are independently segregated within the phagocytosed lysosomes and killed by oxidative and nonoxidative mechanisms, while cathepsin B forms pores in the cryptococci cell wall and accelerates cryptococci lysis ( Nelson et al., 2021 ).…”