Broadly Active Antiviral Compounds Disturb Zika Virus Progeny Release Rescuing Virus-Induced Toxicity in Brain Organoids.

RNA viruses have gained plenty of attention during recent outbreaks of Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), Zika virus (ZIKV), and Ebola virus. ZIKV is a vector borne Flavivirus that is spread by mosquitoes and it mainly infects neuronal progenitor cells. One hallmark of congenital ZIKV disease is a reduced brain size in fetuses, leading to severe neurological defects. The World Health Organization (WHO) is urging the development of new antiviral treatments against ZIKV, as there are no efficient countermeasures against ZIKV disease. Previously, we presented a new class of host-targeting antivirals active against a number of pathogenic RNA viruses, such as SARS-CoV-2. Here, we show the transfer of the image-based phenotypic antiviral assay to ZIKV-infected brain cells, followed by mechanism-of-action studies and a proof-of-concept study in a three-dimensional (3D) organoid model. The novel antiviral compounds showed a therapeutic window against ZIKV in several cell models and rescued ZIKV-induced neurotoxicity in brain organoids. The compound's mechanism-of-action was pinpointed to late steps in the virus life cycle, impairing the formation of new virus particles. Collectively, in this study, we expand the antiviral activity of new small molecule inhibitors to a new virus class of Flaviviruses, but also uncover compounds' mechanism of action, which are important for the further development of antivirals.

Novel Broad-Spectrum Antiviral Inhibitors Targeting Host Factors Essential for Replication of Pathogenic RNA Viruses.

Recent RNA virus outbreaks such as Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Ebola virus (EBOV) have caused worldwide health emergencies highlighting the urgent need for new antiviral strategies. Targeting host cell pathways supporting viral replication is an attractive approach for development of antiviral compounds, especially with new, unexplored viruses where knowledge of virus biology is limited. Here, we present a strategy to identify host-targeted small molecule inhibitors using an image-based phenotypic antiviral screening assay followed by extensive target identification efforts revealing altered cellular pathways upon antiviral compound treatment. The newly discovered antiviral compounds showed broad-range antiviral activity against pathogenic RNA viruses such as SARS-CoV-2, EBOV and Crimean-Congo hemorrhagic fever virus (CCHFV). Target identification of the antiviral compounds by thermal protein profiling revealed major effects on proteostasis pathways and disturbance in interactions between cellular HSP70 complex and viral proteins, illustrating the supportive role of HSP70 on many RNA viruses across virus families. Collectively, this strategy identifies new small molecule inhibitors with broad antiviral activity against pathogenic RNA viruses, but also uncovers novel virus biology urgently needed for design of new antiviral therapies.