[en] Highlights: • Amino-terminal 40 amino acids of HPIV3 P restrict and regulate N⁰-P interaction. • P_A28P fails to support RNA synthesis of HPIV3 minigenome replicon. • Recombinant HPIV3 with mutation of A28P in P failed to be rescued. The phosphoprotein (P) of human parainfluenza virus type 3 (HPIV3) plays a pivotal role in viral RNA synthesis, which interacts with the nucleoprotein (N) to form a soluble N⁰-P complex (N⁰, free of RNAs) to prevent the nonspecific RNA binding and illegitimate aggregation of N. Functional regions within P have been studied intensively. However, the precise site (s) within P directly involved in N⁰-P interaction still remains unclear. In this study, using a series of deleted and truncated mutants of P of HPIV3, we demonstrate that amino-terminal 40 amino acids (aa) of P restrict and regulate N⁰-P interaction. Furthermore, using in vivo HPIV3 minigenome replicon assay, we identify a critical P mutant (P_A28P) located in amino-terminal 40 aa, which fails to support RNA synthesis of HPIV3 minigenome replicon. Although P_A28P maintains an enhanced N-P interaction, it is unable to form N⁰-P complex and keep N soluble, thus, resulting in aggregation and functional abolishment of N-P complex. Moreover, we found that recombinant HPIV3 with mutation of A28P in P failed to be rescued. Taken together, we identified a residue within the extreme amino-terminus of P, which plays a critical role in restricting the excessively N-P interaction and keeping a functional N⁰-P complex formation.

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[en] Highlights: • We report for the first time viperin antiviral activity against Junin arenavirus. • Viperin N-terminal is necessary for the interaction with Junin viral nucleoprotein. • Interplay between lipid droplets and JUNV reveals new targets for virus intervention. Junín arenavirus infections are associated with high levels of interferons in both severe and fatal cases. Upon Junín virus (JUNV) infection a cell signaling cascade initiates, that ultimately attempts to limit viral replication and prevent infection progression through the expression of host antiviral proteins. The interferon stimulated gene (ISG) viperin has drawn our attention as it has been highlighted as an important antiviral protein against several viral infections. The studies of the mechanistic actions of viperin have described important functional domains relating its antiviral and immune-modulating actions through cellular lipid structures. In line with this, through silencing and overexpression approaches, we have identified viperin as an antiviral ISG against JUNV. In addition, we found that lipid droplet structures are modulated during JUNV infection, suggesting its relevance for proper virus multiplication. Furthermore, our confocal microscopy images, bioinformatics and functional results also revealed viperin-JUNV protein interactions that might be participating in this antiviral pathway at lipid droplet level. Altogether, these results will help to better understand the factors mediating innate immunity in arenavirus infection and may lead to the development of pharmacological agents that can boost their effectiveness thereby leading to new treatments for this viral disease.

[en] Highlights: • A recombinant protein vaccine to parrot bornavirus was tested in cockatiels. • The vaccine failed to protect birds from infection but did block disease development. • Cyclosporin A treatment of birds also blocked disease development. • We propose that proventricular dilation disease in cockatiels is immune mediated. We have demonstrated that vaccination of cockatiels (Nymphicus hollandicus) with killed parrot bornavirus (PaBV) plus recombinant PaBV-4 nucleoprotein (N) in alum was protective against disease in birds challenged with a virulent bornavirus isolate (PaBV-2). Unvaccinated birds, as well as birds vaccinated after challenge, developed gross and histologic lesions typical of proventricular dilatation disease (PDD). There was no evidence that vaccination either before or after challenge made the infection more severe. Birds vaccinated prior to challenge largely remained free of disease, despite the persistence of the virus in many organs. Similar results were obtained when recombinant N, in alum, was used for vaccination. In some rodent models, Borna disease is immune mediated thus we did an additional study whereby cyclosporine A was administered to unvaccinated birds starting 1 day prior to challenge. This treatment also conferred complete protection from disease, but not infection.

[en] Highlights: • Arenaviruses lacking the Z protein can be rescued and cultivated in BHK-21 cells. • Arenaviruses without Z still produce a low amount of infectious particles. • The lack of Z appears to be compensated by late domains found into the NP protein. Mammarenaviruses bud out of infected cells via the recruitment of the endosomal sorting complex required for transport through late domain motifs localized into their Z protein. Here, we demonstrated that mammarenaviruses lacking this protein can be rescued and are replicative, despite a 3-log reduction in virion production, in BHK-21 cells, but not in five other cell lines. Mutations of putative late domain motifs identified into the viral nucleoprotein resulted in the almost complete abolition of infectious virion production by Z-deleted mammarenaviruses. This result strongly suggested that the nucleoprotein may compensate for the deletion of Z. These observations were primarily obtained using the Lymphocytic choriomeningitis virus, and further confirmed using the Old World Lassa and New World Machupo viruses, responsible of human hemorrhagic fevers. Z-deleted viruses should prove very useful tools to investigate the biology of Mammarenaviruses.

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[en] Published in summary form only

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[en] CD8 T cells play an important role in controlling Ebola infection and in mediating vaccine-induced protective immunity, yet little is known about antigenic targets in Ebola that are recognized by CD8 T cells. Overlapping peptides were used to identify major histocompatibility complex class I-restricted epitopes in mice immunized with vectors encoding Ebola nucleoprotein (NP). CD8 T-cell responses were mapped to a H-2^d-restricted epitope (NP279-288) and two H-2^b-restricted epitopes (NP44-52 and NP288-296). The identification of these epitopes will facilitate studies of immune correlates of protection and the evaluation of vaccine strategies in murine models of Ebola infection