Our projects

SARS-CoV-2 is a novel virus of the +ssRNA class that is responsible for the sometimes severe sequelae of COVID-19 infection - such as fever, cough, respiratory distress, limb pain, myalgia. SARS-CoV-2 primarily affects the lungs and can also lead to death from multi-organ failure in older, predominantly male patients with pre-existing conditions. Although often asymptomatic in young individuals, elevated cytokine levels have been described in cases of Covid-19 infection with severe progression, indicating that a so-called cytokine storm ("Cytokine Storm") plays a crucial role in the pathogenesis of SARS-CoV-2 infections, as has been observed previously in SARS and MERS. Excessive lung injury in patients with severe disease progression has recently been associated with increased neutrophil to lymphocyte ratios, which in turn could be correlated with increased cytokine levels. The cytokine storm triggered by coronaviruses can lead to viral sepsis and inflammation-related lung damage and subsequently to complications such as pneumonia, acute respiratory failure, shock, multiple organ failure or even death. Ultimately, immune cells mobilized by cytokines are responsible for the organ damage, with cell surface glycans (so-called glycosaminoglycans, GAGs for short) serving as co-receptors for the cytokines.

Our research group is investigating glycan/chemokine interactions and is developing compounds to modulate immune cell migration, especially in inflammatory diseases. However, the mechanism of action of these substances also plays a role in viral diseases, as they can have an inhibitory effect on virus entry on the one hand and a positive influence on the dysregulated immune system on the other.

Based on previous research results, an important approach is pursued: upon virus entry, the virus first docks to glycosaminoglycans of the target cell before it uses the ACE2 receptor to invade the cell, where it then proceeds to viral replication. By adding external sugar molecules, the virus particles should be competitively displaced from the surface of the target cell, thus inhibiting virus entry with subsequent replication.

In cooperation with Kurt Zatloukal of the Diagnostic and Research Institute of Pathology of the Medical University of Graz, the antiviral effect of these substances will be investigated in the BSL3 zone in order to be able to select a clinical candidate for the treatment of SARS-COV2 patients as soon as possible.

The accumulation of eosinophilic granulocytes in the tissue (eosinophilia) is directly related to chronic inflammatory diseases of the gastrointestinal tract whose prevalence is continuously increasing, such as eosinophilic esophagitis (EoE), colitis or gastroenteritis. While healthy esophageal tissue does not show any eosinophils, biopsies from EoE patients show high infiltration numbers of this granulocyte subtype, leading to chronic esophagitis accompanied by typical disease symptoms such as dysphagia, bolus obstruction, heartburn and vomiting. In this context, CCL26, also known as eotaxin-3, is considered to be the chemokine that is significantly involved in the migration of eosinophil granulocytes into inflamed tissues through its interaction with the CCR3 receptor on the surface. However, the interaction of CCL26 with glycosaminoglycans on the surface of epithelial cells of inflamed tissues also influences the recruitment potential of this chemokine.

In this project, the GAG dependence of inflammatory responses elicited by CCL26-mobilized eosinophilia will be investigated. For this purpose, various CCL26 mutants have already been recombinantly expressed, purified and characterized. This spectrum includes a number of so-called "knock-out" and "knock-in" mutants, which differ in glycan binding behavior as well as in their CCR3 receptor activation potential. In collaboration with Cincinnati Children's Hospital, these mutants will now help to elucidate the mechanism of action of the glycans involved in these inflammations. To this end, in addition to various in vitro interaction studies, eosinophil migration and cocultivation studies will be performed in cell-based assay systems as well as in animal experiments.

As the sole representative of the 4th and smallest CX3C subclass of chemokines, CX3CL1, also known as fractalkine, represents an unusual but highly interesting member of the chemokine family. Unlike other chemokines, fractalkine is expressed as a membrane-bound molecule consisting of an extracellular N-terminal chemokine domain anchored to the endothelium via a mucin-like tail and a transmembrane domain. CX3CL1 resolves its chemotactic activity through the interaction of the CX3CL1 domain with its specific CX3CR1 receptor, primarily on the surface of monocytes and macrophages, but also on T cells, NK cells, and dendritic cells. Due to its dual nature, fractalkine not only assumes the role of a chemotactically active messenger, but also that of an adhesion molecule for leukocytes. In addition to the membrane-bound form, CX3CL1 also exists in a "hedged," soluble form that is also capable of triggering leukocyte migration, but is less abundant than the bound form.

In inflammatory kidney diseases such as glomerulonephritis, tumor diseases and lupus nephritis, infiltration of immune cells such as monocytes and macrophages into the kidney contributes significantly to disease progression. In addition to the well-studied CCL2, which is responsible for the majority of monocyte migration in inflammatory kidney disease, recent studies show the potential involvement of the CX3CL1 axis in these processes4.

In the course of this project, considering the therapeutic potential of the CX3CL1 axis in general, the studies will be particularly focused on lupus nephritis. The structural and functional characterization of CX3CL1, especially in relation to glycosaminoglycans, co-receptors of chemokines, is the main focus and will be tested in subsequent cell-based assays as well as in appropriate animal experiments.

Glycosaminoglycans on the surface of cells and especially tissues represent one of the first interaction points of migrating endogenous cells but also pathogens. The structural diversity of glycoasminoglycans in particular and glycans in general requires very selective and specific methods in analytics. Using state-of-the-art high-resolution mass spectrometry coupled to high-performance liquid chromatography, insights into the responses of cells to specific stimuli can be gained. The additional dimension of ion mobility provides even deeper insights into the proteome of cells and tissues and allows the identification of very similar, potentially disease-relevant proteoforms.

In the corresponding experiments, cells in culture are treated at different time points with substances of interest and different substance concentrations. These treated cells are subsequently digested using physical and chemical reactions. In the next step, specific endopeptidases are used to generate smaller peptide fragments, whose mass-to-charge ratio is determined after separation on a reversed phase using an ion-mobility coupled quadrupole time-of-flight mass spectrometer.

The high sample throughput achieved by partial automation and the resulting data volumes place high demands on subsequent data evaluation and interpretation. With the aid of special programs and using biostatistical methods, changes in protein expression can be determined and thus the response of glycosaminoglycan-mediated signals can be interpreted and disease-specific targets for active substances can be found and tested.

The extracellular matrix (ECM) describes a complex, three-dimensional network of non-cellular components that occur in all healthy as well as pathologically altered organs and tissues in a wide variety of compositions. These are mainly proteoglycans and fibrous proteins such as collagens, fibronectin, tenascin, elastin, etc.. These components are formed and secreted by the cells embedded in them, resulting in a functional as well as structural diversity of the individual tissue structures due to the different cell types.

The ECM shapes and influences the mechanical as well as biochemical properties of the organs and tissues by fixing their cells and forming bonds with various growth factors, cytokines, chemokines and cells via their surface receptors. Through these interactions, it has a great influence on diverse biochemical mechanisms such as morphogenesis, differentiation, homeostasis, cell migration as well as communication. Therefore, ECM also plays a major role in pathological changes and offers potential targets for innovative therapeutic approaches.

Our project focuses on the matrix protein tenascin-C, which is highly expressed not only in embryonic development but also in pathological changes such as cancer, chronic inflammation and atherosclerosis and is involved in the migration of various immune cells.

Tenascin-C occurs in a wide variety of isoforms (a total of 511 are known) and is present as a hexamer, with a monomer having a molecular weight of 180-250kDa. The diversity and size of the protein are two challenges that affect many of the necessary steps and often call for extraordinary ideas.

The function of tenascin-C is tissue dependent and still largely unknown. The aim of this project is predominantly the biophysical and biochemical characterization of the protein itself as well as its interactions with diverse chemokines and other macromolecules such as glycosaminoglycans. A wide variety of methods will be used to analyze the functional properties and potential diagnostic or therapeutic approaches.

Cystic fibrosis (ZF) is the most common mono-genetic inherited disease in the Caucasian population. Currently, there are 70,000 known cases worldwide with an average life expectancy of 40 years. The cause of the disease is a mutation in the CFTR gene. This gene is essential for the synthesis of an ion channel, which is responsible for the normal hydration of the lung tissue, for example. If the function of this ion channel is disturbed, the viscosity of the naturally occurring mucus in the lungs increases. As a result, the mucus is difficult to excrete and pathogens settle in the lungs. These pathogens cause lung inflammation, which over time damages the lung tissue and leads to loss of lung function. In ZF, the function of other organ systems is also disturbed, but the dysfunction of the lungs is the most serious for life expectancy.

In pneumonia, there is a massive influx of immune cells into the lungs, which then damage the lung tissue, among other things. One of the main mediators of immune cell immigration is the protein CXCL8. CXCL8 functions by interacting with G protein-coupled receptors on one side and glycosaminoglycan (GAG) co-receptors on the other. Both interactions are essential for an in vivo effect.

The compounds we are developing are novel peptide constructs based on the CXCL8 sequence that are designed to therapeutically interfere with the interaction between CXCL8 and its co-receptors. This should minimize the excessive influx of immune cells into the lung tissue, which would have an anti-inflammatory effect and ultimately minimize irreversible damage to the lung tissue.

Mannose-binding lectin (MBL) binds to coronaviruses and can thereby reduce infectivity. The extent to which this property of MBL also applies to SARS-CoV-2 has not yet been shown. The aim of this project is to demonstrate the inactivation of SARS-CoV-2 by MBL in in vitro experiments. This could lead the basis for novel bioactive filters to prevent SARS-CoV-2 infections. Another application of MBL and SARS-CoV-2 is based on the observation that MBL can both enhance or inhibit an immune response to antigens in a dose-dependent manner. In this context, it is planned to investigate whether MBL-SARS-CoV-2 spike protein complexes induce the formation of neutralizing antibodies better than spike protein without MBL. If successful, this would provide a new efficient methodology for producing vaccines against SARSCoV-2.

The lectin metabolic pathway of the complement system plays a crucial role in the defense against infectious microorganisms. It is triggered by the binding of so-called pattern recognition molecules (PRMs) to sugar molecules or acetylated side chains on the surface of microorganisms (so-called PAMPs = Pathogen-Associated Molecular Patterns). Different PRMs activate the lectin metabolic pathway, including oligomers of mannose-binding lectin (MBL). These MBL oligomers recognize highly conserved structures on the surface of many microorganisms, such as glycoproteins of viruses, including the so-called spike protein of SARS-CoV-2 (MBL oligomers also bind to modified sugar structures on the surface of apoptotic and necrotic as well as tumor cells). Subsequently, dimers of MBL-associated serine proteases 1 and 2 (MASP-1 and MASP-2) bind to MBL oligomers, which activate a proteolytic cascade that culminates in the formation of a membrane-attacking complex and lysis of the pathogen.