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Microbiology spectrum ; : e0298922, 2022.
Article in English | MEDLINE | ID: covidwho-2008769


Zika virus (ZIKV) is a mosquito-borne flavivirus that emerged in the Pacific islands in 2007 and spread to the Americas in 2015. The infection remains asymptomatic in most cases but can be associated with severe neurological disorders. Despite massive efforts, no specific drug or vaccine against ZIKV infection is available to date. Claudins are tight-junction proteins that favor the entry of several flaviviruses, including ZIKV. In this study, we identified two peptides derived from the N-terminal sequences of claudin-7 and claudin-1, named CL7.1 and CL1.1, respectively, that inhibited ZIKV infection in a panel of human cell lines. Using cell-to-cell fusion assays, we demonstrated that these peptides blocked the ZIKV E-mediated membrane fusion. A comparison of the antiviral efficacy of CL1.1 and CL7.1 pointed to the importance of the peptide amphipathicity. Electron microscopic analysis revealed that CL1.1 altered the ultrastructure of the viral particles likely by binding the virus lipid envelope. However, amphipathicity could not fully explain the antiviral activity of CL1.1. In silico docking simulations suggested that CL1.1 may also interact with the E protein, near its stem region. Overall, our data suggested that claudin-derived peptides inhibition may be linked to simultaneous interaction with the E protein and the viral lipid envelope. Finally, we found that CL1.1 also blocked infection by yellow fever and Japanese encephalitis viruses but not by HIV-1 or SARS-CoV-2. Our results provide a basis for the future development of therapeutics against a wide range of endemic and emerging flaviviruses. IMPORTANCE Zika virus (ZIKV) is a flavivirus transmitted by mosquito bites that have spread to the Pacific Islands and the Americas over the past decade. The infection remains asymptomatic in most cases but can cause severe neurological disorders. ZIKV is a major public health threat in areas of endemicity, and there is currently no specific antiviral drug or vaccine available. We identified two antiviral peptides deriving from the N-terminal sequences of claudin-7 and claudin-1 with the latter being the most effective. These peptides block the envelope-mediated membrane fusion. Our data suggested that the inhibition was likely achieved by simultaneously interacting with the viral lipid envelope and the E protein. The peptides also inhibited other flaviviruses. These results could provide the basis for the development of therapies that might target a wide array of flaviviruses from current epidemics and possibly future emergences.

Virologie ; 26(2):120, 2022.
Article in English | EMBASE | ID: covidwho-1913246


Bulk transcriptomic analyses of virus-cell interactions are commonly performed on mixed populations of infected and uninfected bystander cells and may thus lead to inaccurate interpretations. Moreover, they generally focus on the expression of the coding genome and not on the total transcriptome, which is largely composed of long non-coding RNAs (lncRNAs). We performed polyA+ and whole transcriptome analysis of lung epithelial A549 cells infected with SARS-CoV-2, which were sorted based on the expression of the viral protein Spike (S). To increase the sequencing depth and ameliorate the robustness of the analysis, the samples were depleted of viral transcripts, which constituted up to 85% of total reads in the S-positive cells. Results highlighted a high number of down-regulated genes upon infection, an indication of massive host transcription shutdown. We also noticed an increased level of intronic reads in infected cells as compared to control cells, suggesting a defect in mRNA splicing. Among the upregulated coding genes in S-positive cells, we recovered candidates previously identified by analysis performed on non-sorted cells, such as CXCL8 and CCL20, but also novel candidates, including IL- 32, ITGAM and the down-regulated FEN1. Comparison of mRNA abundances of few coding, non-coding and unannotated genes between non-sorted cells and sorted ones confirmed the accuracy of the approach. We also observed that S-negative bystander cells and mock-infected control cells exhibited very similar transcriptomic profiles. This was not due to a lack of communication between infected and bystander cells: transcripts related to inflammatory cytokines underwent normal splicing and maturation in infected cells, with concomitant high levels of protein secretion. The observed lack of major transcriptomic changes in the bystander population can be linked to the insufficient interferon response in infected cells. Finally, we explored the functional implications of genes selectively upregulated in the infected subpopulation and observed previously uncharacterized proviral activities of lncRNA ADIRFAS1 and endogenous Interleukin 32 (IL-32), making them attractive targets for putative therapeutic strategies. Thus, analyzing the whole transcriptome of pure populations of infected lung cells allowed the accurate identification of cellular functions that are directly affected by infection and recovery of coding and non-coding genes relevant for SARS-CoV-2 replication.

Virologie ; 26(2):111, 2022.
Article in French | EMBASE | ID: covidwho-1913051


The interferon (IFN) response is a critical arm of the innate immune response and a major host defense mechanism against viral infections. Numerous genes that contribute to this antiviral state remain to be identified and characterized. Using large-scale loss-of-function strategies, we screened siRNAs or gRNAs libraries targeting hundreds of IFNstimulated genes (ISGs) in IFN-treated cells infected with human RNA viruses, including SARS-CoV-2, Zika virus or tick-borne encephalitis virus. We recovered previously unrecognized human genes able to modulate the replication of these RNA viruses in an IFN-dependent manner. For instance, we identified the chromatin remodeling protein MTA2 as a potent flavivirus-specific antiviral factor. Mechanistic studies to decipher the molecular mechanisms by which these novel antiviral genes are functioning are on-going. We are also expanding our studies to the identification and characterization of ISGs in animal species that serve as viral reservoirs, such as bats. Our work should open new perspectives to target weakness points in the life cycle of these emerging RNA viruses.

Virologie ; 26(2):120, 2022.
Article in English | EMBASE | ID: covidwho-1912931


Establishment of the interferon (IFN)-mediated antiviral state provides a crucial initial line of defense against viral infection. Numerous genes that contribute to this antiviral state remain to be identified. Using a loss-of-function strategy, we screened an original library of 1156 siRNAs targeting 386 individual curated human genes in stimulated microglial cells infected with Zika virus (ZIKV), an emerging RNA virus that belongs to the flavivirus genus. The screen recovered twenty-one potential host proteins that modulate ZIKV replication in an IFN-dependent manner, including the previously known IFITM3 and LY6E. Further characterization contributed to delineate the spectrum of action of these genes towards other pathogenic RNA viruses, including Hepatitis C virus and SARS-CoV-2. Our data revealed that APOL3 acts as a proviral factor for ZIKV and several other related and unrelated RNA viruses. In addition, we showed that MTA2, a chromatin remodeling factor, possesses potent flavivirus-specific antiviral functions. We are currently investigating the molecular mechanisms behind IFN-dependent flaviviral restriction of MTA2. Our work identified previously unrecognized genes that modulate the replication of RNA viruses in an IFN-dependent way, opening new perspectives to target weakness points in the life cycle of these viruses.

Virologie ; 26(2):186, 2022.
Article in English | EMBASE | ID: covidwho-1912865


Bats are natural reservoirs for numerous coronaviruses, including the potential ancestor of SARS-CoV-2. Knowledge concerning the interaction of coronaviruses and bat cells is, however, sparse. There is thus a need to develop bat cellular models to understand cell tropism, viral replication and virus-induced cell responses. Here, we report the first molecular study of SARS-CoV-2 infection in chiropteran cells. We investigated the ability of primary cells from Rhinolophus and Myotis species, as well as of established and novel cell lines from Myotis myotis, Eptesicus serotinus, Tadarida brasiliensis and Nyctalus noctula, to support SARS-CoV-2 replication. None of these cells were permissive to infection, not even the ones expressing detectable levels of angiotensin-converting enzyme 2 (ACE2), which serves as the viral receptor in many mammalian species including humans. The resistance to infection was overcome by expression of human ACE2 (hACE2) in three cell lines, suggesting that the restriction to viral replication was due to a low expression of bat ACE2 (bACE2) or absence of bACE2 binding in these cells. By contrast, multiple restriction factors to viral replication exist in the three N. noctula cells since hACE2 expression was not sufficient to permit infection. Infectious virions were produced but not released from hACE2-transduced M. myotis brain cells. E. serotinus brain cells and M. myotis nasal epithelial cells expressing hACE2 efficiently controlled viral replication, which correlated with a potent interferon response. Together, our data highlight the existence of species-specific molecular barriers to viral replication in bat cells. Our newly developed chiropteran cellular models are useful tools to investigate the interplay between viruses belonging to the SARS-CoV- 2 lineage and their natural reservoir, including the identification of factors responsible for viral restriction.