Rift Valley fever virus modulates apoptosis and immune response during infection of human astrocytes

International audienceRift Valley fever (RVF) is an arboviral disease of zoonotic origin that causes recurrent epidemics in Africa, the Arabic Peninsula, and islands of the South West of the Indian Ocean. RVF occurs mainly in livestock but also affects humans with severe clinical manifestations, including neurological disorders. However, human neuropathogenesis of Rift Valley fever virus (RVFV) is still poorly characterized. To study the interactions between RVFV and the central nervous system (CNS), we focused on RVFV infection of astrocytes, the major glial cells of the CNS that have several supporting roles including immune response regulation. We confirmed the permissiveness of astrocytes to RVFV infection and highlighted a strain-dependent infectivity. We showed that RVFV infection of astrocytes induced cell apoptosis and observed that the RVFV Non-Structural protein NSs, a known virulence factor, potentially delayed apoptosis by sequestrating activated-caspase 3 in the nucleus. Our study also showed that RVFV-infected astrocytes upregulated expression of genes associated with inflammatory and type I interferon responses at the mRNA level, but not at the protein level. This inhibition of immune response is potentially due to a NSs-dependent mechanism of mRNA nuclear export inhibition. Together, these results highlighted the direct impact of RVFV infection on the human CNS through the induction of apoptosis and a possible inhibition of early-onset immune responses that are crucial for the host survival

Effect of high pressure on the antimicrobial activity and secondary structure of the bacteriocin nisin

International audienceEffect of high pressure (HP) treatment on the antimicrobial properties and the structure of nisin was evaluated. Nisin solutions at pH 2.8 or 6.1 were treated by HP at 500 MPa – 10 min – 20 °C and their antimicrobial potency was determined. It appeared that HP clearly impacted the antimicrobial activity of nisin, with respective activity loss of 22.5% and 49.9% at pH 2.8 and 6.1. Structural analysis of nisin by circular dichroism and Fourier transform-infrared spectroscopies revealed that the decrease of nisin antimicrobial activity was likely due to the unfolding of the protein induced by HP. A loss of nisin β-turns structure, particularly significant at neutral pH, was linked to the drastic drop in antimicrobial activity, as these structures are implicated in the nisin interaction with the bacterial membrane.Industrial relevanceThe combination of nisin and high pressure (HP) can be use at an industrial scale to inactivate bacteria. Nisin is allowed as a food additive (E234) and can be added at a final concentration ranging from 120 to 500 IU/g, depending on the product. In this work, we showed that HP can induce a significant reduction of nisin activity (-22.5% at pH 2.8 and -49.9% at pH 6.1). Therefore, this activity loss could be taken into account to manage the final nisin concentration in HP-treated food products

Les nécropoles de l’âge du Bronze de Courcelles (Loiret). Approches des pratiques funéraires au début du Bronze final dans le Gâtinais occidental

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Les nécropoles de l’âge du Bronze de Courcelles (Loiret). Approches des pratiques funéraires au début du Bronze final dans le Gâtinais occidental

International audienc