AG Marco Binder

Cell-intrinsic antiviral immunity is pivotal to combat virus infections. Sensing of conserved pathogen-associated molecular patterns (PAMPS) by cellular receptors such as RIG-I results in the production and release of interferons and massive expression of interferon-stimulated genes (ISGs), conferring an antiviral state. Notably, this response not only comprises antiviral effectors but also displays cytostatic and anti-tumorigenic properties, inducing apoptosis, and suppressing proliferation and migration. Upon continued triggering of a very slight RIG-I signal, we observed significantly inhibited cell growth, which could be reversed by knockout of the transcription factor IRF3. Initial results indicated that this cytostatic effect was not (only) mediated by secreted interferons but rather was an intrinsic effect of the "infected" cell (Urban 2020). We are currently investigating whether prolonged stimulation of this antiviral system, as it occurs during chronic viral infection, would lead to selection and preferential outgrowth of interferon resistant cells. This could have significant implications for both viral persistence as well as the development of tumors in the long run. This project is part of a large DFG-funded "transregional" Collaborative Research Center, TRR179. 

Recent literature has furthermore shown that antiviral innate immune signaling is directly involved in tumor development and/or immune control of emerging tumors, albeit the molecular mechanisms are not at all understood yet. Surprisingly, two studies (Sistigu et al., Nature Medicine 2014; Ranoa et al., Oncotarget 2016) have also demonstrated a direct involvement of the RIG-I/interferon axis in the induction of tumor-cell death in at least a subset of chemotherapies, e.g. doxorubicin. Based on these anecdotal reports, our research aims to identify and characterize the components and the mechanism of RIG-I mediated cell-death upon doxorubicin-induced DNA damage. We generated A549 CRISPR/Cas9 knockout cell lines targeting different components of innate immunity and determined rates of cell death upon treatment with cytostatics or also γ-irradiation by life cell imaging. We confirmed that doxorubicin treatment induces cell death dependent on a functioning RIG-I/MAVS axis, including the transcription factors IRF3 and NFkB, while the interferon system appeared dispensable (see figure), but a third antiviral transcription factor, IRF1, turned out to be surprisingly important (Zander 2022).

• Hiebinger F., Kudulyte A., Chi H, Burbano De Lara S, Ilic D, Helm B, Welsch H, Dao Thi VL, Klingmüller U, Binder M (2023, in press) Tumour cells can escape antiproliferative pressure by interferon-β through immunoediting of interferon receptor expression. Cancer Cell International doi:10.1186/512935-023-03150-y
• Pecori R, Ren W, Pirmoradian M, Wang X, Liu D, Berglund M, Li W, Tasakis RN, Di Giorgio S, Ye X, Li X, Arnold A, Wüst S, Schneider M, Selvasaravanan KD, Fuell Y, Stafforst T, Amini RM, Sonnevi K, Enblad G, Sander B, Wahlin BE, Wu K, Zhang H, Helm D, Binder M, Papavasiliou FN, Pan-Hammarström Q. (2023) ADAR1-mediated RNA editing promotes B cell lymphomagenesis. iScience 26(6):106864
• Zander DY, Burkart S, Wüst S, Gonçalves Magalhães V, Binder M. (2022) Cooperative Effects of RIG-I-like Receptor Signaling and IRF1 on DNA Damage-Induced Cell Death. Cell Death Dis. 13, 364
• Urban C, Welsch H, Heine K, Wüst S, Haas DA, Dächert C, Pandey A, Pichlmair A, Binder M. (2020) Persistent Innate Immune Stimulation Results in IRF3-Mediated but Caspase-Independent Cytostasis. Viruses 12(6):635

The interplay between virus infection, establishment of replication and the induction of the cell-intrinsic antiviral defense program is at the core of the decision of whether a virus will be efficiently cleared or leads to productive infection and disease. The dynamics, i.e. promptness and vigor, of the two processes is critical– if the cell-intrinsic response is quick enough, it can kill off the virus before it enters its exponential replication phase. In the contrary, as most (if not all) viruses encode factors that potently antagonize the cellular defense program, once the virus is one step ahead, it may effectively block the induction of the RIG-I/interferon response and manage to establish robust replication within the host cell. In order to understand this complex interplay, we teamed up with biomathematicians (Prof. Lars Kaderali, Greifswald) who together with us establish mathematical models (based on systems of ordinary differential equations) accurately simulating molecular pathways or virus replication cycles.

Several years ago, we have established the most detailed model of intracellular replication of the Hepatitis C virus (HCV) (Binder 2013). This model comprises every single major step of genome replication, beginning with translation of viral proteins, setting up replication organelles and replicating the viral RNA genome. Recently, we have been extending this original model by the extracellular steps of the HCV life cycle, i.e. the production and secretion of infectious viral particles from the host cell, and the infection of new "naive" host cells (figure 3A). The mathematical model is trained and validated against ample sets of experimental data. Generating this data required tedious measurements of viral parameters in our BSL-3 laboratory. The model can very precisely predict the course of amplification of a given amount of viral inoculum (figure 3B), and can be used to predict and understand the effects of various antiviral substances. In the future, we propose such modeling approaches to be used for establishing optimal drug regimens, meaning combinations of optimal doses of differently acting antiviral compounds.

We are going to set up models for further viruses; a model for Dengue virus has already been set up in collaboration with the team of Ralf Bartenschlager (Zitzmann 2020), and a more general model for the replication of plus-strand RNA viruses has currently been submitted (Zitzmann bioRxiv 2022). In parallel, we are setting up mathematical models of cellular antiviral pathways, most importantly the RIG-I signaling pathway. Based on previous biochemical studies of the pathway in our lab, we have recently published a model of RIG-I activation (Schweinoch 2020). Currently, we are finalizing a very large combined model of the RIG-I and the interferon JAK/STAT signaling cascades, allowing for the simulation of the full antiviral response over the course of 24 hours post infection (Burkart bioRxiv 2022, see above).

Our longer-term goal is to combine the models of viral replication with models of cell-intrinsic antiviral responses. This will eventually permit studying the mutual interactions as described above and potentially allow for a better understanding of the essential parameters determining the outcome of infection. A particular focus will be the difference between acute, self-limiting infections and infections that establish persistence, such as HCV, where a delicate balance of viral and antiviral processes must exist. This line of research is currently paused, but we nevertheless plan to work on it in the future! Please note that our lab is almost exclusively doing experimental work, with the modelling being done by the group of Lars Kaderali!

• Zitzmann C, Dächert C, Schmid B, van der Schaar H, van Hemert M, Perelson AS, van Kuppeveld FJM, Bartenschlager R, Binder M, Kaderali L (2023) Mathematical modeling of plus-strand RNA virus replication to identify broad-spectrum antiviral treatment strategies. PLoS Computational Biology 19(4):e1010423
• Schweinoch D, Bachmann P, Clausznitzer D, Binder M, Kaderali L (2020) Mechanistic modeling explains the dsRNA length-dependent activation of the RIG-I mediated immune response. J Theor Biol 500:110336
• Zitzmann C, Schmid B, Ruggieri A, Perelson AS, Binder M, Bartenschlager R, Kaderali L. (2020) A Coupled Mathematical Model of the Intracellular Replication of Dengue Virus and the Host Cell Immune Response to Infection. Front Microbiol. 11:725
• Binder, M., Sulaimanov, N., Clausznitzer, D., Schulze, M., Hüber, C. M., Lenz, S. M., Schlöder, J. P., Trippler, M., Bartenschlager, R., Lohman, V. and Kaderali L. (2013). Replication vesicles are load- and choke-points in the hepatitis C virus lifecycle. PLoS Pathog 9, e1003561