The increasing prevalence of tick-borne arboviral infections worldwide necessitates advanced control strategies, particularly those targeting vectors, to mitigate the disease burden. However, the cellular interactions between arboviruses and ticks, especially for negative-strand RNA viruses, remain largely unexplored. Here, we employ a proteomics informed by transcriptomics approach to elucidate the cellular response of the Rhipicephalus microplus-derived BME/CTVM6 cell line to severe fever with thrombocytopenia syndrome virus (SFTSV) infection. We generate the de novo transcriptomes and proteomes of SFTSV- and mock-infected tick cells, identifying key host responses and regulatory pathways. Additionally, interactome analysis of the viral nucleoprotein (N) integrated host responses with viral replication and dsRNA-mediated gene silencing screen reveals two anti-SFTSV effectors: the N interacting RNA helicases DHX9 and UPF1. Collectively, our results provide insights into the antiviral responses of R. microplus vector cells and highlight critical SFTSV restriction factors, while enriching transcriptomic and proteomic resources for future research.

The commitment to replicate the RNA genome of flaviviruses without a primer involves RNA–protein interactions that have been shown to include the recognition of the stem–loop A (SLA) in the 5′ untranslated region (UTR) by the nonstructural protein NS5. We show that DENV2 NS5 arginine 888, located within the carboxy-terminal 18 residues, is completely conserved in all flaviviruses and interacts specifically with the top-loop of 3′SL in the 3′UTR which contains the pentanucleotide 5′-CACAG-3′ previously shown to be critical for flavivirus RNA replication. We present virological and biochemical data showing the importance of this Arg 888 in virus viability and de novo initiation of RNA polymerase activity in vitro. Based on our binding studies, we hypothesize that ternary complex formation of NS5 with 3′SL, followed by dimerization, leads to the formation of the de novo initiation complex that could be regulated by the reversible zipping and unzipping of cis-acting RNA elements.

Axonal degeneration (AxD) is a pathological hallmark of many neurodegenerative diseases. Deciphering the morphological patterns of AxD will help to understand the underlying mechanisms and develop effective therapies. Here, we evaluated the progression of AxD in cortical neurons using a novel microfluidic device together with a deep learning tool that we developed for the enhanced-throughput analysis of AxD on microscopic images. The trained convolutional neural network (CNN) sensitively and specifically segmented the features of AxD including axons, axonal swellings, and axonal fragments. Its performance exceeded that of the human evaluators. In an in vitro model of AxD in hemorrhagic stroke induced by the hemolysis product hemin, we detected a time-dependent degeneration of axons leading to a decrease in axon area, while axonal swelling and fragment areas increased. Axonal swellings preceded axon fragmentation, suggesting that swellings may be reliable predictors of AxD. Using a recurrent neural network (RNN), we identified four morphological patterns of AxD (granular, retraction, swelling, and transport degeneration). These findings indicate a morphological heterogeneity of AxD in hemorrhagic stroke. Our EntireAxon platform enables the systematic analysis of axons and AxD in time-lapse microscopy and unravels a so-far unknown intricacy in which AxD can occur in a disease context.

Dengue virus (DENV), a member of the Flaviviridae family, is the most prevalent and medically important mosquito-borne viral pathogen. Infected cells secrete the viral non-structural protein 1 (NS1) into the bloodstream, where it can interact with endothelial cells to induce vascular leak. Host factors involved in NS1-mediated endothelial dysfunction are incompletely understood, leading us to investigate the host interactome of DENV NS1 in endothelial cells via a comparative mass spectrometry approach. We identified ephrin B1 (EFNB1) as a critical host factor in NS1-mediated endothelial barrier dysfunction and show that phosphorylation of EFNB1 is necessary for induction of barrier dysfunction. Further, we map the interface of the EFNB1-NS1 complex through biochemical and computational approaches, and we show that EFNB1-Fc-fusion proteins can act as decoys to block NS1-induced barrier dysfunction in vitro and in vivo . This study provides insights into the mechanism of flavivirus NS1-mediated endothelial barrier dysfunction and new avenues to target vascular leak.

In recent years, arboviral infections have surged dramatically due to the geographic expansion of Aedes and Culex mosquitoes, their main vector mosquitoes. Despite significant efforts to uncover arbovirus-host interactions and viral protein effector functions in mammals, systematic studies aiming to characterize virus-vector interactions in arthropods are largely missing, and the functions and cellular targets of many arboviral proteins in mosquitoes remain elusive. Here, we applied a multi-omic approach to systematically evaluate the ability of arboviral capsids to interact with the Ae. aegypti proteome. This extensive multi-modal atlas across 12 pathogenic arboviral species spanning three viral genera revealed shared and distinct host factor specificities, uncovering species-, genus- and vector preference-specific patterns of host usage in mosquitoes. Functional phenotypic screening of 110 newly discovered host proteins across three prototypic arboviruses (La Crosse virus, dengue virus and West Nile virus) identified several novel host dependency factors, including a new role for the chromatin-remodeling Brahma complex in orthoflavivirus replication. Using a combination of biochemical and sequencing approaches, we characterized the cellular determinants of these interactions and profiled their functional consequences on the chromatin landscape. Altogether, this study provides a multi-layered repository to categorize and characterize arboviral capsid effector functions in invertebrates, providing important cues on novel mechanisms of transcriptional regulation via capsid-mediated modulation of chromatin accessibility in insects.