Probes for LONG

Many enveloped animal viruses produce a variety of particle shapes, ranging from small spherical to long filamentous types. Characterization of how the shape of the virion affects infectivity has been difficult because the shape is only partially genetically encoded, and most pleomorphic virus structures have no selective advantage in vitro. Here, we apply virus fractionation using low-force sedimentation, as well as antibody neutralization coupled with RNAScope, single-particle membrane fusion experiments and stochastic simulations to evaluate the effects of differently shaped influenza A viruses and influenza viruses pseudotyped with Ebola glycoprotein on the infection of cells. Our results reveal that the shape of the virus particles determines the probability of both virus attachment and membrane fusion when viral glycoprotein activity is compromised. The larger contact interface between a cell and a larger particle offers a greater probability that several active glycoproteins are adjacent to each other and can cooperate to induce membrane merger. Particles with a length of tens of micrometres can fuse even when 95% of the glycoproteins are inactivated. We hypothesize that non-genetically encoded variable particle shapes enable pleomorphic viruses to overcome selective pressure and may enable adaptation to infection of cells by emerging viruses such as Ebola. Our results suggest that therapeutics targeting filamentous virus particles could overcome antiviral drug resistance and immune evasion in pleomorphic viruses.

The human-pathogenic Kasokero virus (KASV; genus Orthonairovirus) has been isolated from the sera of Egyptian rousette bats (ERBs; Rousettus aegyptiacus) captured in Uganda and unengorged Ornithodoros (Reticulinasus) faini ticks collected from the rock crevices of ERB colonies in South Africa and Uganda. Although evidence suggests that KASV is maintained in an enzootic transmission cycle between O. (R.) faini ticks and ERBs with potential for incidental virus spillover to humans through the bite of an infected tick, the vertebrate reservoir status of ERBs for KASV has never been experimentally evaluated. Furthermore, the potential for bat-to-bat and bat-to-human transmission of KASV is unknown. Herein, we inoculate two groups of ERBs with KASV; one group of bats is serially sampled to assess viremia, oral, fecal, and urinary shedding and the second group of bats is serially euthanized to assess virus-tissue tropism. Throughout the study, none of the bats exhibit overt signs of clinical disease. Following the detection of high KASV loads of long duration in blood, oral, fecal, and urine specimens collected from ERBs in the serial sampling group, all bats seroconvert to KASV. ERBs from the serial euthanasia group exhibit high KASV loads indicative of virus replication in the skin at the inoculation site, spleen, and inguinal lymph node tissue, and histopathology and in situ hybridization reveal virus replication in the liver and self-limiting, KASV-induced lymphohistiocytic hepatitis. The results of this study suggest that ERBs are competent, natural vertebrate reservoir hosts for KASV that can sustain viremias of appropriate magnitude and duration to support virus maintenance through bat-tick-bat transmission cycles. Viral shedding data suggests that KASV might also be transmitted bat-to-bat and highlights the potential for KASV spillover to humans through contact with infectious oral secretions, feces, or urine.

Introduction Le virus ZIKA (ZIKV) est un virus transmis par les moustiques et par le sperme, avec un fort potentiel d’émergence. Lors d’une infection pendant la grossesse, ce virus peut entraîner des anomalies fœtales cérébrales mais aussi uro-génitales, comme révélé lors de l’épidémie de 2015-2016 dans les Amériques. Description L’objectif de notre étude est de déterminer la permissivité du rein fœtal au ZIKV et les conséquences de cette infection. Méthodes Pour cela nous avons infecté ex vivo avec ZIKV des cultures organotypiques de reins fœtaux disséqués à partir de produits d’IVG obtenus entre 11 et 14 semaines d’aménorrhée. Résultats Nos résultats montrent que le ZIKV se réplique efficacement dans le rein fœtal, comme attesté par l’augmentation de l’ARN viral dans les cultures au cours du temps et par la détection in situ en RNAscope de l’ARN brin négatif produit lors de la réplication du virus. L’ARN réplicatif du ZIKV a été retrouvé dans le tissu interstitiel ainsi que dans des tubules et des glomérules en formation. Les cellules cibles du virus ont été identifiées par immunohistochimie à l’aide d’anticorps contre la protéine virale non structurale NS2b et contre des marqueurs cellulaires. Le virus est retrouvé au niveau du compartiment interstitiel dans des macrophages CD68+ et des fibroblastes SMA+ et au niveau des cellules épithéliales tubulaires CK18+. La localisation dans des cellules glomérulaires WT1+ reste à déterminer. L’infection virale n’a pas d’effet délétère majeur sur la morphologie, la viabilité et la prolifération cellulaire du rein à 6 jours post-infection. Conclusion En conclusion, ces résultats révèlent pour la première fois que le rein fœtal est permissif au virus Zika. Il serait nécessaire d’évaluer l’effet à plus long terme de l’infection sur le rein en développement. Notre modèle ex vivo pourrait permettre de tester l’efficacité d’antiviraux visant à empêcher la réplication du ZIKV dans le rein foetal.

As the global prototypical zoonotic hantavirus, Hantaan virus (HTNV) is prevalent in Asia and is the leading causative agent of severe hemorrhagic fever with renal syndrome (HFRS), which has profound morbidity and mortality. Macrophages are crucial components of the host innate immune system and serve as the first line of defense against HTNV infection. Previous studies indicated that the viral replication efficiency in macrophages determines hantavirus pathogenicity, but it remains unknown which factor manipulates the macrophage activation pattern and the virus-host interaction process. Here, we performed the transcriptomic analysis of HTNV-infected mouse bone marrow-derived macrophages and identified the long noncoding RNA (lncRNA) nuclear enriched abundant transcript 1 (NEAT1), especially the isoform NEAT1-2, as one of the lncRNAs that is differentially expressed at the early phase. Based on coculture experiments, we revealed that silencing NEAT1-2 hinders inflammatory macrophage activation and facilitates HTNV propagation, while enhancing NEAT1-2 transcription effectively restrains viral replication. Furthermore, sterol response element binding factor-2 (SREBP2), which controls the cholesterol metabolism process, was found to stimulate macrophages by promoting the production of multiple inflammatory cytokines upon HTNV infection. NEAT1-2 could potentiate SREBP2 activity by upregulating Srebf1 expression and interacting with SREBP2, thus stimulating inflammatory macrophages and limiting HTNV propagation. More importantly, we demonstrated that the NEAT1-2 expression level in patient monocytes was negatively correlated with viral load and HFRS disease progression. Our results identified a function and mechanism of action for the lncRNA NEAT1 in heightening SREBP2-mediated macrophage activation to restrain hantaviral propagation and revealed the association of NEAT1 with HFRS severity.