The Unfolded Protein Response is required early during TBEV infection to trigger the interferon response

Flaviviruses are a major cause of disease in humans and animals worldwide. Tick-borne encephalitis virus (TBEV) is the most relevant arthropod-borne flavivirus endemic in Europe and is the etiological agent of tick-borne encephalitis, a potentially fatal infection of the central nervous system. In our recent work we demonstrated that TBEV is able to trigger the stress response of infected cells leading to the formation of stress granules (SG) (Albornoz et al. 2014). We also found that the formation of SG in TBEV infected cells is delayed, following the same delayed kinetic of the IFN response (Miorin et al. 2012). Indeed, while TBEV replication is evident at early time points post infection, SG and IFN-\u3b2 mRNA become detectable only after 16 hours. Transcriptome analysis of TBEV infected cells showed that, in addition to interferon and interferon stimulated genes, also genes of the unfolded protein response (UPR) were activated. Interestingly, the spliced form of XBP1 and phosphorylation of PERK occurred early during infection (<12h) indicating that the UPR occurs before induction of interferon. We then investigated the role of the UPR as an early cellular response to the infection and as a possible trigger of the interferon response. Interestingly, when cells were infected following treatment with Tunicamycin, a known inducer of the UPR, the IFN response was already active at 8 hours post-infection and the virus titres were significantly decreased. In this condition formation of stress granules was also anticipated with the same kinetic. These data suggest that TBEV is able to evade both the stress and interferon responses and that the UPR may play a critical and unexpected role in the delayed activation of both

Cellular Targets for the Treatment of Flavivirus Infections

Classical antiviral therapy targets viral functions, mostly viral enzymes or receptors. Successful examples include precursor herpesvirus drugs, antiretroviral drugs that target reverse transcriptase and protease, influenza virus directed compounds as well as more recent direct antiviral agents (DAA) applied in the treatment of hepatitis C virus (HCV). However, from early times, the possibility of targeting the host cell to contain the infection has frequently re-emerged as an alternative and complementary antiviral strategy. Advantages of this approach include an increased threshold to the emergence of resistance and the possibility to target multiple viruses. Major pitfalls are related to important cellular side effects and cytotoxicity. In this mini-review, the concept of host directed antiviral therapy will be discussed with a focus on the most recent advances in the field of Flaviviruses, a family of important human pathogens for which we do not have antivirals available in the clinics

A new laser device for ultra-rapid and sustainable aerosol sterilization

The current COVID-19 pandemic has highlighted the importance of aerosol-based transmission of human pathogens; this therefore calls for novel medical devices which are able to sterilize contaminated aerosols. Here we describe a new laser device able to sterilize droplets containing either viruses or bacteria. Using engineered viral particles, we determined the 10,600 nm wavelength as the most efficient and exploitable laser source to be manufactured in a commercial device. Given the lack of existing working models to reproduce a human aerosol containing living microbial particles, we developed a new system mimicking human droplet formation and preserving bacterial and viral viability. This evidenced the efficacy of 10,600 nm laser light to kill two aerosol transmitted human pathogens, Legionella pneumophila and SARS-CoV-2. The minimal exposure time of &lt;15 ms was required for the inactivation of over 99% pathogens in the aerosol; this is a key element in the design of a device that is safe and can be used in preventing inter-individual transmission. This represents a major advantage over existing devices, which mainly aim at either purifying incoming air by filters or sterilizing solid surfaces, which are not the major transmission routes for airborne communicable diseases

Viral priming of cell intrinsic innate antiviral signaling by the unfolded protein response

The innate response to a pathogen is critical in determining the outcome of the infection. However, the interplay of different cellular responses that are activated following viral infection and their contribution to innate antiviral signalling has not been clearly established. This work shows that flaviviruses, including Dengue, Zika, West Nile and Tick-borne encephalitis viruses, activate the unfolded protein response before transcription of interferon regulatory factor 3 induced genes. Infection in conditions of unfolded protein response priming leads to early activation of innate antiviral responses and cell intrinsic inhibition of viral replication, which is interferon regulatory factor 3 dependent. These results demonstrate that the unfolded protein response is not only a physiological reaction of the cell to viral infection, but also synergizes with pattern recognition sensing to mount a potent antiviral response

A method for the detection of virus infectivity in single cells and real time: towards an automated fluorescence neutralization test

Virus neutralizing antibodies are critical correlates of protection in vaccine development and are discriminatory in the plaque reduction neutralization test when used for the diagnosis of viral infections. However, neutralization assays are time consuming, labor intensive and highly variable, thus limiting their use. Advances in automated live imaging of cells opened new possibilities for standard virus diagnostic techniques such as neutralization assays. To this end, a reporter cell line based on the translocation of the transcription factor IRF3 in response to infection is proposed. Image acquisition of signal in a microplate format allowed the setup of a rapid, semi-automated and high-throughput fluorescent neutralization test. The study is extended to the live imaging of IRF3 translocations that could potentially cut the time of analysis to few hours. The fluorescent neutralization test is suitable for high-throughput assays and expandable to other viruses of global importance such as Zika virus

Persistent viremia and urine shedding of tick-borne encephalitis virus in an infected immunosuppressed patient from a new epidemic cluster in North-Eastern Italy

A persistent tick-borne encephalitis virus infection in an immune-suppressed patient is presented. Such an unusual clinical case offers the unique chance of detecting persistent viremia associated to the erythrocyte fraction and shedding of the virus in the urine for more than six weeks. The infection occurred in a new area of the Friuli Venezia-Giulia region (North Eastern Italy) where two additional cases are also being reported

Broad spectrum anti-flavivirus pyridobenzothiazolones leading to less infective virions

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