With no available therapies, infections with Zika virus (ZIKV) constitute a major public health concern as they can lead to congenital microcephaly. In order to generate an intracellular environment favourable to viral replication, ZIKV induces endomembrane remodelling and the morphogenesis of replication factories via enigmatic mechanisms. In this study, we identified the AAA+ type ATPase valosin‐containing protein (VCP) as a cellular interaction partner of ZIKV non‐structural protein 4B (NS4B). Importantly, its pharmacological inhibition as well as the expression of a VCP dominant‐negative mutant impaired ZIKV replication. In infected cells, VCP is relocalised to large ultrastructures containing both NS4B and NS3, which are reminiscent of dengue virus convoluted membranes. Moreover, short treatment with the VCP inhibitors NMS‐873 or CB‐5083 drastically decreased the abundance and size of ZIKV‐induced convoluted membranes. Furthermore, NMS‐873 treatment inhibited ZIKV‐induced mitochondria elongation previously reported to be physically and functionally linked to convoluted membranes in case of the closely related dengue virus. Finally, VCP inhibition resulted in enhanced apoptosis of ZIKV‐infected cells strongly suggesting that convoluted membranes limit virus‐induced cytopathic effects. Altogether, this study identifies VCP as a host factor required for ZIKV life cycle and more precisely, for the maintenance of viral replication factories. Our data further support a model in which convoluted membranes regulate ZIKV life cycle by impacting on mitochondrial functions and ZIKV‐induced death signals in order to create a cytoplasmic environment favourable to viral replication.

Dengue fever, caused by dengue virus (DENV) is the most prevalent arthropod-borne viral disease, and is endemic in many tropical and sub-tropical parts of the world with an increasing incidence in temperate regions. The closely related flavivirus Zika virus (ZIKV) can be transmitted vertically in utero and causes congenital Zika syndrome and other birth defects. In adults, ZIKV is associated with Guillain-Barré syndrome. There are no approved antiviral therapies against neither viruses. Effective antiviral compounds are urgently needed. Amaryllidaceae alkaloids (AAs) are a specific class of nitrogen-containing compounds produced by plants of the Amaryllidaceae family with numerous biological activities. Recently, the AA lycorine was shown to present strong antiflaviviral properties. Previously, we demonstrated that Crinum jagus contained lycorine and several alkaloids of cherylline, crinine and galanthamine-types with unknown antiviral potential. In this study, we explored their biological activities. We show that C. jagus crude alkaloid extract inhibited DENV infection. Among the purified AAs, cherylline inhibited efficiently both DENV (EC 50 =8.8 μM) and ZIKV replication (EC 50 =20.3 μM), but had no effect on HIV-1 infection. Time-of-drug-addition and -removal experiments identified a post-entry step as the one targeted by cherylline. Consistently, using subgenomic replicons and replication-defective genomes, we demonstrate that cherylline specifically hinders the viral RNA-synthesis step but not viral translation. In conclusion, AAs are an underestimated source of antiflavivirus compounds, including the effective inhibitor cherylline that could be optimized for new therapeutic approaches.

With 40% of the world population at risk, infections with dengue virus (DENV) constitute a serious threat to public health. While there is no antiviral therapy available against this potentially lethal disease, the efficacy of the only approved vaccine is not optimal and its safety has been recently questioned. In order to develop better vaccines based on attenuated and/or chimeric viruses, one must consider how the human immune system is engaged during DENV infection. The activation of the innate immunity through the detection of viruses by cellular sensors is the first line of defence against those pathogens. This triggers a cascade of events which establishes an antiviral state at the cell level and leads to a global immunological response. However, DENV has evolved to interfere with the innate immune signalling at multiple levels, hence dampening antiviral responses and favouring viral replication and dissemination. This review elaborates on the interplay between DENV and the innate immune system. A special focus is given on the viral countermeasure mechanisms reported over the last decade which should be taken into consideration during vaccine development.Vaccines 2019, 7, 145 2 of 21 serotypes (1-4) in one given restricted geographic area [4,5]. While there is an unmet medical need regarding strategies against dengue, the incidence of this disease is expected to geographically expand in the future considering that the arthropod vector is colonizing northern European and American territories with temperate climates. Clinical ManifestationDENV infection is characterized by a mixed clinical presentation that ranges from an asymptomatic disease to a mild febrile prodrome all the way to a severe hemorrhagic fever and shock syndrome. All infected individuals, asymptomatic or not, can transmit DENV to Aedes mosquitoes during a blood meal, making it difficult to precisely estimate the actual size of the reservoir at any given time. DENV infection severity is classified according to the World Health Organization (WHO) 1997 and 2009 guidelines [6]. Dengue "without warning signs" (or dengue fever) regroups at-risk individuals with fever and at least two of the following signs and symptoms: nausea/vomiting, rash, headaches, eye pain, muscle aches, joint pain, leukopenia, or positivity at the tourniquet test. Dengue "with warning signs of severe infection" (or dengue hemorrhagic fever) includes in addition to the previous signs and symptoms abdominal pain, persistent vomiting, ascites, pleural effusion, mucosal bleeding, lethargy or restlessness, hepatomegaly, and an increase in hematocrit paired with rapid decrease in platelet count. Lastly, severe dengue (or dengue shock) occurs when the infection leads to severe plasma leakage, massive bleeding, and multiple organ failures. As of now, the therapeutic arsenal against DENV infection is fairly limited and only consists of supportive care and intravenous fluid therapy.From a host-pathogen interaction point of view, it is interesting to note that, in the majority of DENV-...

Flaviviridae infections represent a major global health burden. By deciphering mechanistic aspects of hepatitis C virus (HCV)-host interactions, one could discover common strategy for inhibiting the replication of related flaviviruses. By elucidating the HCV interactome, we identified the 17-beta-hydroxysteroid dehydrogenase type 12 (HSD17B12) as a human hub of the very-long-chain fatty acid (VLCFA) synthesis pathway and core interactor. Here we show that HSD17B12 knockdown (KD) impairs HCV replication and reduces virion production. Mechanistically, depletion of HSD17B12 induces alterations in VLCFA-containing lipid species and a drastic reduction of lipid droplets (LDs) that play a critical role in virus assembly. Oleic acid supplementation rescues viral RNA replication and production of infectious particles in HSD17B12 depleted cells, supporting a specific role of VLCFA in HCV life cycle. Furthermore, the small-molecule HSD17B12 inhibitor, INH-12, significantly reduces replication and infectious particle production of HCV as well as dengue virus and Zika virus revealing a conserved requirement across Flaviviridae virus family. Overall, the data provide a strong rationale for the advanced evaluation of HSD17B12 inhibition as a promising broad-spectrum antiviral strategy for the treatment of Flaviviridae infections.