Early Determinants of DNA-Virus Lytic or Latent Infection (eDEVILLI)

Viruses that are able to persist can undergo reactivation in immunocompromised patients and cause life-threatening diseases. The eDEVILLI project will contribute to the understanding of the cellular and systemic immune control of infection with pathogenic human DNA viruses that hide as chromatin repressed DNA in a reservoir of latently infected cells (e.g. Cytomegaloviruses, CMV and Epstein-Barr virus, EBV). Hence, eDEVILLI will provide the basis for novel strategies to contain the consequences of virus reactivation. There is evidence suggesting that the decision between latent and productive infection is made at the single cell level within the first few hours of infection. We postulate that this decision is shaped by the interplay between cell-intrinsic, cell-extrinsic and viral modulators, which our consortium aims to identify and characterize. Cutting-edge combinatorial methods will be employed to identify the viral chromatin structures (ATAC-seq) and the viral genome- and virion-associated proteomes (EdU-CLAP and mass spectrometry). In vivo imaging with super-resolution microscopy allows to follow individual viral genomes in due course of the infection process and genetically modified mouse models enable the translation of the molecular and cellular findings into the organismic context. The research consortium is composed of five groups from Germany (coordinator + 1), Sweden, France and Austria. The determination of the pattern of viral chromatin organization and the composition of the viral DNA- as well as the virion-associated proteomes and its association with quiescent and productive infection (Aim1 and 2) will be performed by the groups of Germany, Sweden and France. For the validation of the identified targets the consortiums uses in vivo and ex vivo models provided by the Austrian group. In addition mouse models will help to explore the mechanisms by which extrinsic signals influence the silencing of viral gene expression and the establishment of latency (Aim3). The Austrian group will contribute its expertise in the interferon (IFN) system and the genetic engineering of mice. IFNs are key components of the innate immune defence against infections and promote viral genome silencing or clearance. STAT1 with the two isoforms, STAT1a and STAT1ß, is the key transcription factor in the regulation of IFN-dependent transcriptional programs. On the one hand, we will address the question how the STAT1 isoforms shape the IFN effects by investigating recognition and silencing of incoming non- chromatinized viral DNA in human and murine cell culture systems. We will in vivo validate the effects in mice with constitutive STAT1a or STAT1ß knockouts as well as in mice lacking STAT1 in a cell type-specific manner. On the other hand, we will study IFN-induced cellular factors that associate with incoming viral DNA. IFI16 was recently identified as a key player in the recognition and silencing of non-chromatinized DNA. We will analyze the biological relevance of IFI16 in early infection by generating an IFI16 knockout mouse. The eDEVILLI consortium assembles a broad spectrum of interdisciplinary methods and biological systems, well established in each of the research laboratories. The organization of the research in work packages and specific tasks will ensure the rapid transfer of technologies and findings to the entire program. Our joint effort will identify novel principles shaping the decision between lytic and latent infection of DNA viruses on the molecular, cellular and organismal level. This will foster our knowledge and understanding of the control of infection by pathogenic human DNA viruses. It will provide the basis for the translation of this knowledge into novel strategies for containing the potentially severe consequences of virus reactivation. 1

The international research consortium eDEVILLI comprised groups from Germany, Austria, France and Sweden aimed at the basic understanding of herpesvirus host cell interactions. Infections with herpesviruses do not lead a priori to disease symptoms because virus in infected cells can stay in latency, becomes activated at later timepoints and than leads to severe disease. In patients, virus activation occurs upon immune-deficiencies (e.g. caused by age or pregnancy) or upon medicamentous immunosuppression (e.g. during auto-immune diseases, transplantations, HIV infections) and can be life-threatening. The cellular systems and protein interactions underlying herpesvirus infection, latency and reactivation were the focus of the research consortium. The Austrian project part investigated the interferon (IFN) system and its impact on herpesvirus infection in mouse models. IFNs are key components of the innate immunity against viruses and inactivate or destroy viral genomes. STAT1 is a central transcription factor governing the IFN-dependent transcriptional programs. The detailed molecular mechanisms of cellular recognition and IFN-induction by Herpes viruses are not clear; the PHYIN protein family is known to recognise foreign DNA and thus might be central in the cellular responses to herpesvirus infection. Using complex genetic mouse models we identified myeloid-specific STAT1 signaling as a crucial control mechanism for Herpesvirus spread. Myeloid STAT1 also drives extramedullar virus- and stress-induced haematopoiesis (EMH). The results identify STAT1 as a potential therapeutic target in hematopoietic failures caused be virus infection or stress conditions. The long-term expertise of the Viennese group in genetic engineering was used to generate a mouse model for studying the PHYIN family member Mnda.