Viktoria Szeifert

All Publications

• Mac-1 Receptor Clustering Initiates Production of Pro-Inflammatory, Antibacterial Extracellular Vesicles From Neutrophils FRONTIERS IN IMMUNOLOGY Szeifert, V., Kolonics, F., Bartos, B., Khamari, D., Vagi, P., Barna, L., Ligeti, E., Lorincz, A. M. 2021; 12: 671995

  Abstract

  Depending on the prevailing environmental conditions, neutrophilic granulocytes release extracellular vesicles (EV) which have either anti-inflammatory effects on other neutrophils or pro-inflammatory and antibacterial effects. In the present study we investigated the molecular mechanisms underlying the biogenesis of functionally heterogenic EVs. We show that selective stimulation of Mac-1 integrin (complement receptor 3) by specific ligands initiates the generation of EVs which are able to impair bacterial growth and to induce the secretion of the pro-inflammatory cytokine IL-8 (aEV). However, direct Mac-1 stimulation results in aEV release only if neutrophils were activated on ligand coated surfaces whereas soluble ligands are ineffective. Using total internal reflection fluorescence (TIRF) microcopy, an increased clustering of Mac-1 molecules could be visualized in neutrophils added to C3bi coated surfaces; moreover antibody induced cluster formation triggers aEV release as well. Mac-1 induced production of aEV apparently necessitates a strong calcium signal as it fully depends on the presence of extracellular calcium. However, initiation of a strong calcium signal by an ionophore only results the generation of EV devoid of any antibacterial or pro-inflammatory effect. Our results thus demonstrate that stimulation and clustering of Mac-1 is necessary and sufficient for initiation of aEV biogenesis. In contrast, an intracellular calcium signal is necessary but by itself not sufficient for the production of antibacterial and pro-inflammatory EVs.

  View details for DOI 10.3389/fimmu.2021.671995

  View details for Web of Science ID 000693835500001

  View details for PubMedID 34456905

  View details for PubMedCentralID PMC8397541

• The Functional Heterogeneity of Neutrophil-Derived Extracellular Vesicles Reflects the Status of the Parent Cell CELLS Kolonics, F., Szeifert, V., Timar, C., Ligeti, E., Lorincz, A. M. 2020; 9 (12)

  Abstract

  Similar to other cell types, neutrophilic granulocytes also release extracellular vesicles (EVs), mainly medium-sized microvesicles/microparticles. According to published data, authors have reached a consensus on the physical parameters (size, density) and chemical composition (surface proteins, proteomics) of neutrophil-derived EVs. In contrast, there is large diversity and even controversy in the reported functional properties. Part of the discrepancy may be ascribed to differences in the viability of the starting cells, in eliciting factors, in separation techniques and in storage conditions. However, the most recent data from our laboratory prove that the same population of neutrophils is able to generate EVs with different functional properties, transmitting pro-inflammatory or anti-inflammatory effects on neighboring cells. Previously we have shown that Mac-1 integrin is a key factor that switches anti-inflammatory EV generation into pro-inflammatory and antibacterial EV production. This paper reviews current knowledge on the functional alterations initiated by neutrophil-derived EVs, listing their effects according to the triggering agents and target cells. We summarize the presence of neutrophil-derived EVs in pathological processes and their perspectives in diagnostics and therapy. Finally, the functional heterogeneity of differently triggered EVs indicates that neutrophils are capable of producing a broad spectrum of EVs, depending on the environmental conditions prevailing at the time of EV genesis.

  View details for DOI 10.3390/cells9122718

  View details for Web of Science ID 000601808900001

  View details for PubMedID 33353087

  View details for PubMedCentralID PMC7766779

• Human Neutrophils Produce Antifungal Extracellular Vesicles against Aspergillus fumigatus MBIO Shopova, I. A., Belyaev, I., Dasari, P., Jahreis, S., Stroe, M. C., Cseresnyes, Z., Zimmermann, A., Medyukhina, A., Svensson, C., Krueger, T., Szeifert, V., Nietzsche, S., Conrad, T., Blango, M. G., Kniemeyer, O., von Lilienfeld-Toal, M., Zipfel, P. F., Ligeti, E., Figge, M., Brakhage, A. A. 2020; 11 (2)

  Abstract

  Polymorphonuclear granulocytes (PMNs) are indispensable for controlling life-threatening fungal infections. In addition to various effector mechanisms, PMNs also produce extracellular vesicles (EVs). Their contribution to antifungal defense has remained unexplored. We reveal that the clinically important human-pathogenic fungus Aspergillus fumigatus triggers PMNs to release a distinct set of antifungal EVs (afEVs). Proteome analyses indicated that afEVs are enriched in antimicrobial proteins. The cargo and the release kinetics of EVs are modulated by the fungal strain confronted. Tracking of afEVs indicated that they associated with fungal cells and even entered fungal hyphae, resulting in alterations in the morphology of the fungal cell wall and dose-dependent antifungal effects. To assess as a proof of concept whether the antimicrobial proteins found in afEVs might contribute to growth inhibition of hyphae when present in the fungal cytoplasm, two human proteins enriched in afEVs, cathepsin G and azurocidin, were heterologously expressed in fungal hyphae. This led to reduced fungal growth relative to that of a control strain producing the human retinol binding protein 7. In conclusion, extracellular vesicles produced by neutrophils in response to A. fumigatus infection are able to associate with the fungus, limit growth, and elicit cell damage by delivering antifungal cargo. This finding offers an intriguing, previously overlooked mechanism of antifungal defense against A. fumigatusIMPORTANCE Invasive fungal infections caused by the mold Aspergillus fumigatus are a growing concern in the clinic due to the increasing use of immunosuppressive therapies and increasing antifungal drug resistance. These infections result in high rates of mortality, as treatment and diagnostic options remain limited. In healthy individuals, neutrophilic granulocytes are critical for elimination of A. fumigatus from the host; however, the exact extracellular mechanism of neutrophil-mediated antifungal activity remains unresolved. Here, we present a mode of antifungal defense employed by human neutrophils against A. fumigatus not previously described. We found that extracellular vesicles produced by neutrophils in response to A. fumigatus infection are able to associate with the fungus, limit growth, and elicit cell damage by delivering antifungal cargo. In the end, antifungal extracellular vesicle biology provides a significant step forward in our understanding of A. fumigatus host pathogenesis and opens up novel diagnostic and therapeutic possibilities.

  View details for DOI 10.1128/mBio.00596-20

  View details for Web of Science ID 000531071300112

  View details for PubMedID 32291301

  View details for PubMedCentralID PMC7157820

• Role of Mac-1 integrin in generation of extracellular vesicles with antibacterial capacity from neutrophilic granulocytes JOURNAL OF EXTRACELLULAR VESICLES Lorincz, A. M., Bartos, B., Szombath, D., Szeifert, V., Timar, C. I., Turiak, L., Drahos, L., Kittel, A., Veres, D. S., Kolonics, F., Mocsai, A., Ligeti, E. 2020; 9 (1): 1698889

  Abstract

  Production of extracellular vesicles (EVs) involved in intercellular communication is a common capacity of most cell types. Upon encountering opsonized microorganisms, neutrophilic granulocytes release EVs that compromise bacterial growth. We carried out a systematic investigation of the involvement of potential opsonin receptors in EV-generation from human and murine neutrophils. Applying flow cytometric, proteomic and functional analysis as well as using genetically modified mice, we demonstrate that formation of antibacterial EVs depends upon stimulation of the multifunctional Mac-1 integrin complex, also called as complement receptor 3 (CR3), whereas activation of immunoglobulin binding Fc receptors or pattern recognition receptors alone or in combination is ineffective. Mac-1/CR3 stimulation and downstream tyrosine kinase signalling affect both the numbers, the cargo content and the antibacterial capacity of the produced vesicles. In contrast, Mac-1/CR3 signalling is not required for spontaneous EV formation, clearly indicating the existence of separate molecular pathways in EV biogenesis. We propose that EVs are "tailor-made" with different composition and functional properties depending on the environmental circumstances.

  View details for DOI 10.1080/20013078.2019.1698889

  View details for Web of Science ID 000615322900001

  View details for PubMedID 31853340

  View details for PubMedCentralID PMC6913618

• Different Calcium and Src Family Kinase Signaling in Mac-1 Dependent Phagocytosis and Extracellular Vesicle Generation FRONTIERS IN IMMUNOLOGY Lorincz, A. M., Szeifert, V., Bartos, B., Szombath, D., Mocsai, A., Ligeti, E. 2019; 10: 2942

  Abstract

  Encountering opsonized particles by neutrophils results in phagocytosis of the particle and generation of extracellular vesicles with antibacterial property (aEV). The aim of the present study is to compare the involvement of different receptors and receptor-proximal signaling pathways in these two parallel processes. Investigating human neutrophils from peripheral blood, we show that complement receptors are decisive for both processes whereas immunoglobulin binding Fc receptors (FcR) only participate moderately in phagocytosis and pattern recognition receptors induce mild EV production but only minimal phagocytosis. Studying bone marrow derived neutrophils of genetically modified animals we verify that the involved complement receptor is CR3, also known as the β2 integrin Mac-1. We show that genetic deletion of the adaptor molecules FcRγ chain or DAP12 does not influence either process, suggesting potential redundant function. Combined absence of the Src family kinases Hck, Fgr, and Lyn drastically impairs phagocytosis but does not influence aEV production. In contrast, deletion of PLCγ2 has no influence on phagocytosis, but reduces aEV formation. In accord with the essential role of PLCγ2, aEV biogenesis both from murine and from human neutrophils is dependent on presence of extracellular calcium. Absence of external calcium prevented the generation of antibacterial EVs, whereas the spontaneous EV formation was not influenced. We thus show that phagocytosis and biogenesis of antibacterial EVs are independent processes and proceed on different signaling pathways although the same receptor plays the critical role in both. Our data reveal the possibility in neutrophilic granulocytes to modulate aEV production without disturbing the phagocytic process.

  View details for DOI 10.3389/fimmu.2019.02942

  View details for Web of Science ID 000505009900001

  View details for PubMedID 31921192

  View details for PubMedCentralID PMC6928112

• New flow cytometry-based method for the assessment of the antibacterial effect of immune cells and subcellular particles JOURNAL OF LEUKOCYTE BIOLOGY Lorincz, A. M., Szeifert, V., Bartos, B., Ligeti, E. 2018; 103 (5): 955-963

  Abstract

  Techniques currently used for assessment of bacterial count or growth are time-consuming, offer low throughput, or they are complicated or expensive. The aim of the present work was to elaborate a new method that is able to detect the antibacterial effect of cells, subcellular particles, and soluble compounds in a fast, cost, and labor effective way. Our proposed technique is based on flow cytometry (FC) optimized for detection of small particles and on fluorescently labeled bacteria. It allows direct determination of the bacterial count in 3 hours. The effect of various human phagocytes and extracellular vesicles on gram-positive and gram-negative bacteria is investigated in parallel with the new, FC-based method, with colony counting and with our previous, OD-based method. Comparing the killing effect of wild type and NADPH oxidase-deficient murine neutrophils presents an example of detection of a clinically important deficiency. Strong correlation was obtained between the results of the different techniques, but the reproducibility of the FC-based test was superior to the OD-based test. The major advantages of the new technique are: rapidity, low cost, high throughput, and simplicity.

  View details for DOI 10.1002/JLB.4TA0817-317R

  View details for Web of Science ID 000431501700015

  View details for PubMedID 29513908