Influenza is one of the most common infectious diseases in humans, occurring as seasonal epidemic and sporadic pandemic outbreaks. Annually, influenza A viruses (IAV) cause 3-5 million clinical infections and 250000-500000 fatal cases. Thus, those viruses are of great concern to human health. The recent emergence of resistant influenza strains to the current antiviral drugs highlights the necessity for a better understanding of the molecular mechanisms of IAV pathogenesis and subsequent development of new therapeutics against influenza. Detrimental inflammation of the lungs is a hallmark of severe influenza virus infections, although the mechanisms underlying these inflammatory processes are poorly understood. Extensive crosstalk exists between inflammation and hemostasis (ie: primary hemostasis, coagulation and fibrinolysis). Accordingly disturbance in their interplay is inevitably linked to human diseases. Numerous lines of evidence point to a link between the hemostatic system, endothelial barrier function and inappropriate inflammation in several models of injuries such as bacterial infections. Up to now, the role of hemostasis during viral infections has been mainly unexplored. The question is: do influenza viruses lead to exaggerated inflammation via inappropriate activation of hemostatic response? Along with the deleterious host inflammatory response, significant abnormalities in hemostasis were revealed during severe IAV infections in humans. Although the clinical association between hemostasis disorders and pathogenicity of influenza virus infections has emerged, experimental evidence for the active contribution of hemostasis in the cytokine storm following influenza virus infection is still limited. Recently, our results revealed the fundamental importance of hemostatic factors in severe lung inflammation and pathogenesis of IAV infections in mice. Activation of Protease-activated-receptor 1 (PAR1), a receptor activated by the coagulation factor thrombin interacts with the fibrinolytic molecule plasminogen and plays a role in inflammation induced by IAV. Also, we found that plasminogen activation impairs fibrin deposits, which act as a physical barrier to prevent cytokine storm in the lungs upon IAV infection. Consistently, recent reports provided evidence that endothelial cells are central orchestrators of IAV-mediated lung deleterious inflammation. Altogether, crosstalk exists between the dysregulation of hemostasis and inflammation during influenza virus infection, although this remains to be fully established. The present project aims at a better understanding of the intricate relationship between hemostasis and inflammation in the pathogenesis of IAV infections. In this project, we will first study whether hemostasis is differentially activated upon mice infection with low or highly pathogenic influenza strains and the consequence of hemostasis activation in term of IAV pathogenicity. In the second and third part of the project we will evaluate the specific contribution of protease-activated-receptors (PAR4) and protease-nexin1 to inflammation of the lungs, and outcome of influenza virus infections. Finally, the last part of our project will be dedicated to the development of new clinical and therapeutic applications. Of special interest, the protective role for commercialized drugs will be tested against a broad range of influenza strains, including those of the H5N1 (highly pathogenic) and pandemic H1N1 viruses. Altogether, this project will represent a crucial step toward understanding the mechanism that underlie influenza cytokine storm during influenza A virus infections. It may also point at novel intervention strategies that could mitigate the host inflammatory response after infection as well as the definition of new clinical markers for severe influenza infections.

In 2012, a novel human coronavirus (MERS-CoV) was identified in the Middle East as the causative agent of a severe acute and/or fatal respiratory syndrome. Since its identification, it has been responsible for 211 laboratory-confirmed cases including 88 deaths. Most cases are sporadic but human-to-human transmission has been documented both in hospital settings and community clusters. Emergence of this new coronavirus in humans raises concerns about a possible widespread outbreak, similar to the one previously caused by SARS-CoV in 2003. Control of such emerging viral pathogens constitutes a major public health issue. However, despite the urgent need for efficient and safe therapeutics, there is currently no antiviral treatment nor vaccine available as yet and there is no evidence that they may become available nor when. Innovative strategies are thus required to fight against these emerging hazardous coronaviruses adequately. In this context, the main objective of the CoV-SigN project is to identify innovative efficient antiviral compounds against MERS-CoV and SARS-CoV that target the host cell instead of viral molecular determinants. Based on the postulate that gene expression profiling can be considered as a global “fingerprint” of the disease/drug effect, this innovative strategy was already successfully achieved by the coordinator partner with seasonal influenza A viruses. This proof-of-concept led to an ongoing clinical trial that evaluate a marketed drug for new antiviral indication. In term of experimental strategy, the CoV-SigN project aims to identify in vitro and in vivo host transcriptomic signatures associated with viral infections, followed by the in silico screening of large databases for existing compounds that can counteract these viral signatures. Next, candidates will be evaluated by using in vitro cellular assays for their expected antiviral properties against MERS-CoV and SARS-CoV. Sample from the two patients collected in hospital settings (CHRU Lille), will constitute a pivotal added value to the project by comparison with the initial proof-of-concept pilot study. By bringing additional physiological data (such as immune and inflammatory responses, different steps of pathology progression), in vivo signatures of infections will add more biological relevance to the project by implementing in vitro signatures analysis and strengthening the selection of candidate compounds to test for their antiviral property. Use of such new antivirals should considerably decrease the risk of emergence of drug resistance and would be well adapted for short treatment duration and therefore should not impact cellular functions permanently. Thus, the CoV-SigN project constitutes an ideal approach to characterize inhibitors particularly adapted to target acute respiratory pathogenesis demonstrated by MERS-CoV and SARS-CoV viruses. This project is part of a drug-repurposing concept and could provide important financial and regulatory advantages compared to the time-consuming and expensive development of de novo antiviral molecules. The strength of the proposal relies on the complementary and synergistic fundamental, technological, translational and clinical expertise of the four partners. Moreover, the combination of pre-existing collaborations between partners, established proof-of concept and preliminary experimental setup/results from patients’ samples will constitute key parameters for the successful achievement of the CoV-SigN project in terms of scientific output and medical applied perspectives.