Santos-Ferreira, N. | bioRxiv Science

bioRxiv2022

Ex vivo midgut cultures of Aedes aegypti are efficiently infected by mosquito-borne alpha- and flaviviruses

Aedes aegypti mosquitoes can transmit several arboviruses, including chikungunya virus (CHIKV), dengue virus (DENV), and Zika virus (ZIKV). When blood-feeding on a virus-infected human, the mosquito ingests the virus into the midgut (stomach), where it replicates and must overcome the midgut barrier to disseminate to other organs and ultimately be transmitted via the saliva. Current tools to study mosquito-borne viruses (MBVs) include 2D-cell culture systems and in vivo mosquito infection models, which offer great advantages, yet have some limitations. Here, we describe a long-term ex vivo culture of Ae. aegypti midguts. Cultured midguts were metabolically active for 7 days in a 96-well plate at 28{degrees}C and were permissive to ZIKV, DENV, Ross River virus (RRV) and CHIKV. Ex vivo midguts from Culex pipiens mosquitoes were found to be permissive to Usutu virus (USUV). Immunofluorescence staining confirmed viral protein synthesis in CHIKV-infected midguts of Ae. aegypti. Furthermore, fluorescence microscopy revealed replication and spread of a reporter DENV in specific regions of the midgut. In addition, two known antiviral molecules, {beta}-D-N4-hydroxycytidine (NHC) and 7-deaza-2-C-methyladenosine (7DMA), were able to inhibit CHIKV and ZIKV replication, respectively, in the ex vivo model. Together, our results show that ex vivo midguts can be efficiently infected with mosquito-borne alpha- and flaviviruses and employed to evaluate antiviral drugs. Furthermore, the setup can be extended to other mosquito species. Ex vivo midgut cultures could thus be a new model to study MBVs, offering the advantage of reduced biosafety measures compared to infecting living mosquitoes. ImportanceMosquito-borne viruses (MBVs) are a significant global health threat since they can cause severe diseases in humans, such as hemorrhagic fever, encephalitis, and chronic arthritis. MBVs rely on the mosquito vector to infect new hosts and perpetuate virus transmission. No therapeutics are currently available. The study of arbovirus infection in the mosquito vector can greatly contribute to elucidating strategies for controlling arbovirus transmission. This work investigated the infection of midguts from Aedes aegypti mosquitoes in an ex vivo platform. We found several MBVs capable of replicating in the midgut tissue, including viruses of major health importance, such as dengue, chikungunya, and Zika viruses. Additionally, antiviral compounds reduced arbovirus infection in the cultured midgut tissue. Overall, the midgut model emerges as a useful tool for diverse applications such as studying tissue-specific responses to virus infection and screening potential anti-arboviral molecules.

molecular biology↗

bioRxiv2022

Human norovirus efficiently replicates in differentiated 3D-human intestinal enteroids

Human norovirus (HNoV) accounts for one fifth of all acute viral gastroenteritis worldwide and an economic burden of [~]$60 billion globally. The lack of treatment options against HNoV is in part due to the lack of cultivation systems. Recently, a model of infection in biopsies-derived human intestinal enteroids (HIE) has been described: 3D-HIE are first dispersed in 2D-monolayers and differentiated prior to infection, resulting in a labor-intensive, time-consuming procedure. Here, we present an alternative protocol for HNoV infection of 3D-HIE. We found that 3D-HIE differentiate as efficiently as 2D-monolayers. In addition, immunofluorescence-based quantification of UEA-1, a lectin that stains the villus brush border, revealed that over 90% of differentiated 3D-HIE spontaneously undergo polarity inversion, allowing for viral infection without the need for microinjection. Infection with HNoV GII.4-positive stool samples attained a fold-increase over inoculum of [~]2 Log10 at 2 days post infection or up to 3.5 Log10 when ruxolitinib, a JAK1/2-inhibitor, was added. Treatment of GII.4-infected 3D-HIE with the polymerase inhibitor 2-C-Methylcytidine (2CMC), other antivirals, or with a HNoV-neutralizing antibody showed a reduction in viral infection, suggesting that 3D-HIE are an excellent platform to test anti-infectives. The host response to HNoV was then investigated by RNA sequencing in infected versus uninfected 3D-HIE, in the presence of ruxolitinib to focus on viral-associated signatures. The analysis revealed upregulated hormones and neurotransmitter signal transduction pathways and downregulated inflammatory pathways upon HNoV infection. Overall, 3D-HIE have proven to be a more robust model to study HNoV infection, screen antivirals and investigate host response to HNoV infection. ImportanceHuman norovirus (HNoV) clinical and socio-economic impact calls for immediate actions in the development of anti-infectives. Physiologically-relevant in vitro models are hence needed to study HNoV biology, tropism and mechanism of viral-associated disease but also as a platform to identify antiviral agents. Biopsy-derived human intestinal enteroids are a biomimetic of the intestine and recently described as a model that supports HNoV infection. The established protocol is time-consuming and labor-intensive. Therefore, we sought to develop a simplified and robust alternative model of infection in 3D enteroids that undergo differentiation and spontaneous polarity inversion. Advantages of this model are the shorter experimental time, better infection yield and spatial integrity of the intestinal epithelium. This model is potentially suitable for the study of pathogens that infect intestinal cells from the apical surface but also for unraveling the interactions between intestinal epithelium and indigenous bacteria of the human microbiome.

microbiology↗