TY  - JOUR
A1  - Prauße, Maria T. E.
A1  - Lehnert, Teresa
A1  - Timme, Sandra
A1  - Hünniger, Kerstin
A1  - Leonhardt, Ines
A1  - Kurzai, Oliver
A1  - Figge, Marc Thilo
T1  - Predictive Virtual Infection Modeling of Fungal Immune Evasion in Human Whole Blood
JF  - Frontiers in Immunology
N2  - Bloodstream infections by the human-pathogenic fungi Candida albicans and Candida glabrata increasingly occur in hospitalized patients and are associated with high mortality rates. The early immune response against these fungi in human blood comprises a concerted action of humoral and cellular components of the innate immune system. Upon entering the blood, the majority of fungal cells will be eliminated by innate immune cells, i.e., neutrophils and monocytes. However, recent studies identified a population of fungal cells that can evade the immune response and thereby may disseminate and cause organ dissemination, which is frequently observed during candidemia. In this study, we investigate the so far unresolved mechanism of fungal immune evasion in human whole blood by testing hypotheses with the help of mathematical modeling. We use a previously established state-based virtual infection model for whole-blood infection with C. albicans to quantify the immune response and identified the fungal immune-evasion mechanism. While this process was assumed to be spontaneous in the previous model, we now hypothesize that the immune-evasion process is mediated by host factors and incorporate such a mechanism in the model. In particular, we propose, based on previous studies that the fungal immune-evasion mechanism could possibly arise through modification of the fungal surface by as of yet unknown proteins that are assumed to be secreted by activated neutrophils. To validate or reject any of the immune-evasion mechanisms, we compared the simulation of both immune-evasion models for different infection scenarios, i.e., infection of whole blood with either C. albicans or C. glabrata under non-neutropenic and neutropenic conditions. We found that under non-neutropenic conditions, both immune-evasion models fit the experimental data from whole-blood infection with C. albicans and C. glabrata. However, differences between the immune-evasion models could be observed for the infection outcome under neutropenic conditions with respect to the distribution of fungal cells across the immune cells. Based on these predictions, we suggested specific experimental studies that might allow for the validation or rejection of the proposed immune-evasion mechanism.
KW  - immune evasion
KW  - state-based model
KW  - innate immune response
KW  - polymorphonuclear neutrophils
KW  - whole-blood infection assay
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197493
SN  - 1664-3224
VL  - 9
IS  - 560
ER  - 
TY  - JOUR
A1  - Dasari, Prasad
A1  - Koleci, Naile
A1  - Shopova, Iordana A.
A1  - Wartenberg, Dirk
A1  - Beyersdorf, Niklas
A1  - Dietrich, Stefanie
A1  - Sahagún-Ruiz, Alfredo
A1  - Figge, Marc Thilo
A1  - Skerka, Christine
A1  - Brakhage, Axel A.
A1  - Zipfel, Peter F.
T1  - Enolase from Aspergillus fumigatus is a moonlighting protein that binds the human plasma complement proteins factor H, FHL-1, C4BP, and plasminogen
JF  - Frontiers in Immunology
N2  - The opportunistic fungal pathogen Aspergillus fumigatus can cause severe infections, particularly in immunocompromised individuals. Upon infection, A. fumigatus faces the powerful and directly acting immune defense of the human host. The mechanisms on how A. fumigatus evades innate immune attack and complement are still poorly understood. Here, we identify A. fumigatus enolase, AfEno1, which was also characterized as fungal allergen, as a surface ligand for human plasma complement regulators. AfEno1 binds factor H, factor-H-like protein 1 (FHL-1), C4b binding protein (C4BP), and plasminogen. Factor H attaches to AfEno1 via two regions, via short conserved repeats (SCRs) 6–7 and 19–20, and FHL-1 contacts AfEno1 via SCRs 6–7. Both regulators when bound to AfEno1 retain cofactor activity and assist in C3b inactivation. Similarly, the classical pathway regulator C4BP binds to AfEno1 and bound to AfEno1; C4BP assists in C4b inactivation. Plasminogen which binds to AfEno1 via lysine residues is accessible for the tissue-type plasminogen activator (tPA), and active plasmin cleaves the chromogenic substrate S2251, degrades fibrinogen, and inactivates C3 and C3b. Plasmin attached to swollen A. fumigatus conidia damages human A549 lung epithelial cells, reduces the cellular metabolic activity, and induces cell retraction, which results in exposure of the extracellular matrix. Thus, A. fumigatus AfEno1 is a moonlighting protein and virulence factor which recruits several human regulators. The attached human regulators allow the fungal pathogen to control complement at the level of C3 and to damage endothelial cell layers and tissue components.
KW  - complement factor H
KW  - moonlighting
KW  - immune evasion
KW  - plasminogen
KW  - blocking phagocytosis
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-195612
SN  - 1664-3224
VL  - 10
ER  - 
TY  - JOUR
A1  - Al-Zaben, Naim
A1  - Medyukhina, Anna
A1  - Dietrich, Stefanie
A1  - Marolda, Alessandra
A1  - Hünniger, Kerstin
A1  - Kurzai, Oliver
A1  - Figge, Marc Thilo
T1  - Automated tracking of label-free cells with enhanced recognition of whole tracks
JF  - Scientific Reports
N2  - Migration and interactions of immune cells are routinely studied by time-lapse microscopy of in vitro migration and confrontation assays. To objectively quantify the dynamic behavior of cells, software tools for automated cell tracking can be applied. However, many existing tracking algorithms recognize only rather short fragments of a whole cell track and rely on cell staining to enhance cell segmentation. While our previously developed segmentation approach enables tracking of label-free cells, it still suffers from frequently recognizing only short track fragments. In this study, we identify sources of track fragmentation and provide solutions to obtain longer cell tracks. This is achieved by improving the detection of low-contrast cells and by optimizing the value of the gap size parameter, which defines the number of missing cell positions between track fragments that is accepted for still connecting them into one track. We find that the enhanced track recognition increases the average length of cell tracks up to 2.2-fold. Recognizing cell tracks as a whole will enable studying and quantifying more complex patterns of cell behavior, e.g. switches in migration mode or dependence of the phagocytosis efficiency on the number and type of preceding interactions. Such quantitative analyses will improve our understanding of how immune cells interact and function in health and disease.
KW  - image processing
KW  - software
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-221093
VL  - 9
ER  - 
TY  - JOUR
A1  - Dasari, Prasad
A1  - Shopova, Iordana A.
A1  - Stroe, Maria
A1  - Wartenberg, Dirk
A1  - Martin-Dahse, Hans
A1  - Beyersdorf, Niklas
A1  - Hortschansky, Peter
A1  - Dietrich, Stefanie
A1  - Cseresnyés, Zoltán
A1  - Figge, Marc Thilo
A1  - Westermann, Martin
A1  - Skerka, Christine
A1  - Brakhage, Axel A.
A1  - Zipfel, Peter F.
T1  - Aspf2 From Aspergillus fumigatus Recruits Human Immune Regulators for Immune Evasion and Cell Damage
JF  - Frontiers in Immunology
N2  - The opportunistic fungal pathogen Aspergillus fumigatus can cause life-threatening infections, particularly in immunocompromised patients. Most pathogenic microbes control host innate immune responses at the earliest time, already before infiltrating host immune cells arrive at the site of infection. Here, we identify Aspf2 as the first A. fumigatus Factor H-binding protein. Aspf2 recruits several human plasma regulators, Factor H, factor-H-like protein 1 (FHL-1), FHR1, and plasminogen. Factor H contacts Aspf2 via two regions located in SCRs6–7 and SCR20. FHL-1 binds via SCRs6–7, and FHR1 via SCRs3–5. Factor H and FHL-1 attached to Aspf2-maintained cofactor activity and assisted in C3b inactivation. A Δaspf2 knockout strain was generated which bound Factor H with 28% and FHL-1 with 42% lower intensity. In agreement with less immune regulator acquisition, when challenged with complement-active normal human serum, Δaspf2 conidia had substantially more C3b (>57%) deposited on their surface. Consequently, Δaspf2 conidia were more efficiently phagocytosed (>20%) and killed (44%) by human neutrophils as wild-type conidia. Furthermore, Aspf2 recruited human plasminogen and, when activated by tissue-type plasminogen activator, newly generated plasmin cleaved the chromogenic substrate S2251 and degraded fibrinogen. Furthermore, plasmin attached to conidia damaged human lung epithelial cells, induced cell retraction, and caused matrix exposure. Thus, Aspf2 is a central immune evasion protein and plasminogen ligand of A. fumigatus. By blocking host innate immune attack and by disrupting human lung epithelial cell layers, Aspf2 assists in early steps of fungal infection and likely allows tissue penetration.
KW  - complement
KW  - blocking opsonization
KW  - phagocytosis
KW  - acquisition of host regulators
KW  - immune evasion
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197013
SN  - 1664-3224
VL  - 9
IS  - 1635
ER  -