Setup of Aerosol Delivery System to Prevent Measles Virus Infection in Nonhuman Primate Model.

Measles virus is one of the most contagious airborne human viruses which keeps causing outbreaks in numerous countries over the world despite the existence of an efficient vaccine. Fusion inhibitory lipopeptides were shown to inhibit viral entry into target cells, and their adequate administration into the respiratory tract may provide a novel preventive approach against airborne infections. Aerosol delivery presents the best administration route to deliver such preventive compounds to the upper and lower respiratory tract. This approach offers a conceptually new strategy to protect the population at risk against infection by respiratory viruses, including measles. It is a noninvasive needle-free approach, which may be used when antiviral protection is required, without any medical assistance. In this chapter, we describe the nebulization approach of lipopeptide compounds in nonhuman primates and the subsequent measles virus challenge.

A vaccine targeting antigen-presenting cells through CD40 induces protective immunity against Nipah disease.

Nipah virus (NiV) has been recently ranked by the World Health Organization as being among the top eight emerging pathogens likely to cause major epidemics, whereas no therapeutics or vaccines have yet been approved. We report a method to deliver immunogenic epitopes from NiV through the targeting of the CD40 receptor of antigen-presenting cells by fusing a selected humanized anti-CD40 monoclonal antibody to the Nipah glycoprotein with conserved NiV fusion and nucleocapsid peptides. In the African green monkey model, CD40.NiV induces specific immunoglobulin A (IgA) and IgG as well as cross-neutralizing responses against circulating NiV strains and Hendra virus and T cell responses. Challenge experiments using a NiV-B strain demonstrate the high protective efficacy of the vaccine, with all vaccinated animals surviving and showing no significant clinical signs or virus replication, suggesting that the CD40.NiV vaccine conferred sterilizing immunity. Overall, results obtained with the CD40.NiV vaccine are highly promising in terms of the breadth and efficacy against NiV.

Interplay of Ebola Virus With Immune Cells Leading to Their Death by Diverse Mechanisms.

Inflammation and cytopenia are commonly observed during Ebola virus (EBOV) infection; however, mechanisms responsible for EBOV-induced cell death remain obscure. While apoptosis and necrosis are already identified as mechanisms of cell death induced by the virus, our study demonstrates that THP-1 monocytes and SupT1 T cells exposed to EBOV undergo pyroptosis and necroptosis, respectively, through a direct contact with EBOV, and also mediate pyroptosis or necroptosis of uninfected bystander cells via indirect effects associated with secreted soluble factors. These results emphasize novel aspects of interactions between EBOV and immune cell populations and provide a better understanding of the immunopathogenesis of EBOV disease.

Measles Virus-Induced Host Immunity and Mechanisms of Viral Evasion.

The immune system deploys a complex network of cells and signaling pathways to protect host integrity against exogenous threats, including measles virus (MeV). However, throughout its evolutionary path, MeV developed various mechanisms to disrupt and evade immune responses. Despite an available vaccine, MeV remains an important re-emerging pathogen with a continuous increase in prevalence worldwide during the last decade. Considerable knowledge has been accumulated regarding MeV interactions with the innate immune system through two antagonistic aspects: recognition of the virus by cellular sensors and viral ability to inhibit the induction of the interferon cascade. Indeed, while the host could use several innate adaptors to sense MeV infection, the virus is adapted to unsettle defenses by obstructing host cell signaling pathways. Recent works have highlighted a novel aspect of innate immune response directed against MeV unexpectedly involving DNA-related sensing through activation of the cGAS/STING axis, even in the absence of any viral DNA intermediate. In addition, while MeV infection most often causes a mild disease and triggers a lifelong immunity, its tropism for invariant T-cells and memory T and B-cells provokes the elimination of one primary shield and the pre-existing immunity against previously encountered pathogens, known as "immune amnesia".

Nebulized fusion inhibitory peptide protects cynomolgus macaques from measles virus infection.

Measles is the most contagious airborne viral infection and the leading cause of child death among vaccine-preventable diseases. We show here that aerosolized lipopeptide fusion inhibitor, derived from heptad-repeat regions of the measles virus (MeV) fusion protein, blocks respiratory MeV infection in a non-human primate model, the cynomolgus macaque. We use a custom-designed mesh nebulizer to ensure efficient aerosol delivery of peptide to the respiratory tract and demonstrate the absence of adverse effects and lung pathology in macaques. The nebulized peptide efficiently prevents MeV infection, resulting in the complete absence of MeV RNA, MeV-infected cells, and MeV-specific humoral responses in treated animals. This strategy provides an additional means to fight against respiratory infection in non-vaccinated people, that can be readily translated to human trials. It presents a proof-of-concept for the aerosol delivery of fusion inhibitory peptides to protect against measles and other airborne viruses, including SARS-CoV-2, in case of high-risk exposure.

Nebulized fusion inhibitory peptide protects cynomolgus macaques from measles virus infection.

Measles is the most contagious airborne viral infection and the leading cause of child death among vaccine-preventable diseases. We show here that aerosolized lipopeptide fusion inhibitors, derived from heptad-repeat regions of the measles virus (MeV) fusion protein, block respiratory MeV infection in a non-human primate model, the cynomolgus macaque. We used a custom-designed mesh nebulizer to ensure efficient aerosol delivery of peptides to the respiratory tract and demonstrated the absence of adverse effects and lung pathology in macaques. The nebulized peptide efficiently prevented MeV infection, resulting in the complete absence of MeV RNA, MeV-infected cells, and MeV-specific humoral responses in treated animals. This strategy provides an additional shield which complements vaccination to fight against respiratory infection, presenting a proof-of-concept for the aerosol delivery of fusion inhibitory peptides to protect against measles and other airborne viruses, including SARS-CoV-2, in case of high-risk exposure, that can be readily translated to human trials.

Fruit bats as natural reservoir of highly pathogenic henipaviruses: balance between antiviral defense and viral toleranceInteractions between Henipaviruses and their natural host, fruit bats.

Bats are the natural reservoir host for a number of zoonotic viruses, including Hendra and Nipah viruses of Henipavirus genus, which are highly pathogenic in humans and numerous other mammalian species. Despite being infected, bats present limited signs of disease but still retain the ability to transmit the infection to other susceptible hosts, presenting thus a permanent source of new viral outbreaks. Different mechanisms have evolved in fruit bats permitting them to efficiently control the Henipavirus infection. These mechanisms likely allow bats to establish an adequate equilibrium between viral tolerance and antiviral defense, enabling them thus to avoid both uncontrollable virus expansion as well as immunopathology linked to excessive antiviral responses.

[Crimean-Congo hemorrhagic fever, a future health problem in France?] / La fièvre hémorragique de Crimée-Congo, une future problématique de santé en France ?

The Crimean-Congo hemorrhagic fever virus (CCHFV) is the etiological agent of a severe hemorrhagic fever affecting Africa, Asia and southern Europe. Climate changes of recent decades have recently led to a rise in the distribution of this virus. Still few scientific data are available on the biology of its vector, the tick, or its own biology, but the proven presence of human infections observed in Spain and animals with positive serology in Corsica should focus our attention on this pathogen. This review takes stock of the epidemiologic evolution of CCHF in Europe, notably in France.

TITLE: La fièvre hémorragique de Crimée-Congo, une future problématique de santé en France ? ABSTRACT: Le virus de la fièvre hémorragique de Crimée-Congo (CCHFV) est l'agent étiologique d'une fièvre hémorragique grave affectant l'Afrique, l'Asie et le sud de l'Europe. Les modifications climatiques de ces dernières décennies induisent depuis peu une remontée de l'aire de distribution de ce virus. Encore peu de données scientifiques sont disponibles sur les interactions avec son vecteur, la tique, ou sur sa biologie propre. Cependant, la présence avérée d'infections humaines en Espagne et des sérologies positives dans le cheptel corse pourraient bien concentrer l'attention sur ce pathogène. Cette revue fait le point sur l'évolution des connaissances éco-épidémiologiques de ce virus, notamment en Europe et plus particulièrement en France.

Molecular rationale for antibody-mediated targeting of the hantavirus fusion glycoprotein.

The intricate lattice of Gn and Gc glycoprotein spike complexes on the hantavirus envelope facilitates host-cell entry and is the primary target of the neutralizing antibody-mediated immune response. Through study of a neutralizing monoclonal antibody termed mAb P-4G2, which neutralizes the zoonotic pathogen Puumala virus (PUUV), we provide a molecular-level basis for antibody-mediated targeting of the hantaviral glycoprotein lattice. Crystallographic analysis demonstrates that P-4G2 binds to a multi-domain site on PUUV Gc and may preclude fusogenic rearrangements of the glycoprotein that are required for host-cell entry. Furthermore, cryo-electron microscopy of PUUV-like particles in the presence of P-4G2 reveals a lattice-independent configuration of the Gc, demonstrating that P-4G2 perturbs the (Gn-Gc)4 lattice. This work provides a structure-based blueprint for rationalizing antibody-mediated targeting of hantaviruses.

[Ebola, the first vaccines available]. / Ebola, des premiers vaccins disponibles.

In the recent years, Ebola virus has been responsible for several major epidemics. Research efforts have allowed the development and evaluation in the field of several vaccine candidates. At present, two of them are already approved and used in the fight against the virus in the Democratic Republic of Congo. This review aims to describe the different candidates, the clinical trials that have been conducted as well as the first results in the field.

TITLE: Ebola, des premiers vaccins disponibles. ABSTRACT: Ces dernières années, le virus Ebola a été responsable d'épidémies de grande ampleur. Les efforts de recherche ont permis la mise au point et l'évaluation sur le terrain de plusieurs candidats vaccins. À l'heure actuelle, deux sont déjà homologués et utilisés dans la lutte contre le virus en République démocratique du Congo. Cette revue se propose de faire le point sur les différents candidats vaccins, les essais cliniques qui ont été menés et les premiers résultats de terrain.

High Pathogenicity of Nipah Virus from Pteropus lylei Fruit Bats, Cambodia.

We conducted an in-depth characterization of the Nipah virus (NiV) isolate previously obtained from a Pteropus lylei bat in Cambodia in 2003 (CSUR381). We performed full-genome sequencing and phylogenetic analyses and confirmed CSUR381 is part of the NiV-Malaysia genotype. In vitro studies revealed similar cell permissiveness and replication of CSUR381 (compared with 2 other NiV isolates) in both bat and human cell lines. Sequence alignments indicated conservation of the ephrin-B2 and ephrin-B3 receptor binding sites, the glycosylation site on the G attachment protein, as well as the editing site in phosphoprotein, suggesting production of nonstructural proteins V and W, known to counteract the host innate immunity. In the hamster animal model, CSUR381 induced lethal infections. Altogether, these data suggest that the Cambodia bat-derived NiV isolate has high pathogenic potential and, thus, provide insight for further studies and better risk assessment for future NiV outbreaks in Southeast Asia.

Involvement of Surfactant Protein D in Ebola Virus Infection Enhancement via Glycoprotein Interaction.

Since the largest 2014⁻2016 Ebola virus disease outbreak in West Africa, understanding of Ebola virus infection has improved, notably the involvement of innate immune mediators. Amongst them, collectins are important players in the antiviral innate immune defense. A screening of Ebola glycoprotein (GP)-collectins interactions revealed the specific interaction of human surfactant protein D (hSP-D), a lectin expressed in lung and liver, two compartments where Ebola was found in vivo. Further analyses have demonstrated an involvement of hSP-D in the enhancement of virus infection in several in vitro models. Similar effects were observed for porcine SP-D (pSP-D). In addition, both hSP-D and pSP-D interacted with Reston virus (RESTV) GP and enhanced pseudoviral infection in pulmonary cells. Thus, our study reveals a novel partner of Ebola GP that may participate to enhance viral spread.

Mannoside Glycolipid Conjugates Display Antiviral Activity Against Ebola Virus.

The West African outbreak of Ebola virus (EBOV) infection during 2013-2016 highlighted the need for development of field-applicable therapeutic drugs for this infection. Here we report that mannoside glycolipid conjugates (MGCs) consisting of a trimannose head and a lipophilic chain assembled by a linker inhibit EBOV infection not only of human monocyte-derived dendritic cells and macrophages, but also of a number of susceptible cells. Analysis of the mode of action leads us to conclude that MGCs act directly on cells, notably by preventing virus endocytosis.

Filovirus proteins for antiviral drug discovery: Structure/function of proteins involved in assembly and budding.

There are no approved medications for the treatment of Marburg or Ebola virus infection. In two previous articles (Martin et al., 2016, Martin et al., 2017), we reviewed surface glycoprotein and replication proteins structure/function relationship to decipher the molecular mechanisms of filovirus life cycle and identify antiviral strategies. In the present article, we recapitulate knowledge about the viral proteins involved in filovirus assembly and budding. First we describe the structural data available for viral proteins associated with virus assembly and virion egress and then, we integrate the structural features of these proteins in the functional context of the viral replication cycle. Finally, we summarize recent advances in the development of innovative antiviral strategies to target filovirus assembly and egress. The development of such prophylactic or post-exposure treatments could help controlling future filovirus outbreaks.

Interference with the production of infectious viral particles and bimodal inhibition of replication are broadly conserved antiviral properties of IFITMs.

IFITMs are broad antiviral factors that block incoming virions in endosomal vesicles, protecting target cells from infection. In the case of HIV-1, we and others reported the existence of an additional antiviral mechanism through which IFITMs lead to the production of virions of reduced infectivity. However, whether this second mechanism of inhibition is unique to HIV or extends to other viruses is currently unknown. To address this question, we have analyzed the susceptibility of a broad spectrum of viruses to the negative imprinting of the virion particles infectivity by IFITMs. The results we have gathered indicate that this second antiviral property of IFITMs extends well beyond HIV and we were able to identify viruses susceptible to the three IFITMs altogether (HIV-1, SIV, MLV, MPMV, VSV, MeV, EBOV, WNV), as well as viruses that displayed a member-specific susceptibility (EBV, DUGV), or were resistant to all IFITMs (HCV, RVFV, MOPV, AAV). The swapping of genetic elements between resistant and susceptible viruses allowed us to point to specificities in the viral mode of assembly, rather than glycoproteins as dominant factors of susceptibility. However, we also show that, contrarily to X4-, R5-tropic HIV-1 envelopes confer resistance against IFITM3, suggesting that viral receptors add an additional layer of complexity in the IFITMs-HIV interplay. Lastly, we show that the overall antiviral effects ascribed to IFITMs during spreading infections, are the result of a bimodal inhibition in which IFITMs act both by protecting target cells from incoming viruses and in driving the production of virions of reduced infectivity. Overall, our study reports for the first time that the negative imprinting of the virion particles infectivity is a conserved antiviral property of IFITMs and establishes IFITMs as a paradigm of restriction factor capable of interfering with two distinct phases of a virus life cycle.

Modeling Ebolavirus Budding with Virus Like Particles.

About 15 years ago, several groups initially described the release of virus like particles (VLPs) upon expression of Ebola virus VP40 in mammalian cells. Further development of the protocol later allowed for the dissection of the Ebola virus budding mechanism and for the identification of critical VP40 residues involved in this process. VLPs are now produced routinely in several laboratories as a tool to study virus entry or egress and have even been proposed as vaccine candidates against Ebola virus disease. Here we described protocols for the production and the analysis of Ebola virus VLP release.

Human transmission of Ebola virus.

Ever since the first recognised outbreak of Ebolavirus in 1976, retrospective epidemiological analyses and extensive studies with animal models have given us insight into the nature of the pathology and transmission mechanisms of this virus. In this review focusing on Ebolavirus, we present an outline of our current understanding of filovirus human-to-human transmission and of our knowledge concerning the molecular basis of viral transmission and potential for adaptation, with particular focus on what we have learnt from the 2014 outbreak in West Africa. We identify knowledge gaps relating to transmission and pathogenicity mechanisms, molecular adaptation and filovirus ecology.

Characterization of the Unconventional Secretion of the Ebola Matrix Protein VP40.

While most secreted proteins use the classical endoplasmic reticulum (ER)-Golgi secretion pathway to reach the extracellular medium, a few proteins are secreted through unconventional secretary pathways. Viral proteins can be secreted through unconventional secretion pathways. Here, we describe how we have recently demonstrated that the Ebola virus (EBOV) matrix protein VP40 is released from transfected and infected cells in a soluble form through an unconventional secretion pathway.

Anti-EBOV GP IgGs Lacking α1-3-Galactose and Neu5Gc Prolong Survival and Decrease Blood Viral Load in EBOV-Infected Guinea Pigs.

Polyclonal xenogenic IgGs, although having been used in the prevention and cure of severe infectious diseases, are highly immunogenic, which may restrict their usage in new applications such as Ebola hemorrhagic fever. IgG glycans display powerful xenogeneic antigens in humans, for example α1-3 Galactose and the glycolyl form of neuraminic acid Neu5Gc, and IgGs deprived of these key sugar epitopes may represent an advantage for passive immunotherapy. In this paper, we explored whether low immunogenicity IgGs had a protective effect on a guinea pig model of Ebola virus (EBOV) infection. For this purpose, a double knock-out pig lacking α1-3 Galactose and Neu5Gc was immunized against virus-like particles displaying surface EBOV glycoprotein GP. Following purification from serum, hyper-immune polyclonal IgGs were obtained, exhibiting an anti-EBOV GP titer of 1:100,000 and a virus neutralizing titer of 1:100. Guinea pigs were injected intramuscularly with purified IgGs on day 0 and day 3 post-EBOV infection. Compared to control animals treated with IgGs from non-immunized double KO pigs, the anti-EBOV IgGs-treated animals exhibited a significantly prolonged survival and a decreased virus load in blood on day 3. The data obtained indicated that IgGs lacking α1-3 Galactose and Neu5Gc, two highly immunogenic epitopes in humans, have a protective effect upon EBOV infection.

Enhancement of Ebola Virus Infection via Ficolin-1 Interaction with the Mucin Domain of GP Glycoprotein.

UNLABELLED: Ebola virus infection requires the surface viral glycoprotein to initiate entry into the target cells. The trimeric glycoprotein is a highly glycosylated viral protein which has been shown to interact with host C-type lectin receptors and the soluble complement recognition protein mannose-binding lectin, thereby enhancing viral infection. Similarly to mannose-binding lectin, ficolins are soluble effectors of the innate immune system that recognize particular glycans at the pathogen surface. In this study, we demonstrate that ficolin-1 interacts with the Zaire Ebola virus (EBOV) glycoprotein, and we characterized this interaction by surface plasmon resonance spectroscopy. Ficolin-1 was shown to bind to the viral glycoprotein with a high affinity. This interaction was mediated by the fibrinogen-like recognition domain of ficolin-1 and the mucin-like domain of the viral glycoprotein. Using a ficolin-1 control mutant devoid of sialic acid-binding capacity, we identified sialylated moieties of the mucin domain to be potential ligands on the glycoprotein. In cell culture, using both pseudotyped viruses and EBOV, ficolin-1 was shown to enhance EBOV infection independently of the serum complement. We also observed that ficolin-1 enhanced EBOV infection on human monocyte-derived macrophages, described to be major viral target cells,. Competition experiments suggested that although ficolin-1 and mannose-binding lectin recognized different carbohydrate moieties on the EBOV glycoprotein, the observed enhancement of the infection likely depended on a common cellular receptor/partner. In conclusion, ficolin-1 could provide an alternative receptor-mediated mechanism for enhancing EBOV infection, thereby contributing to viral subversion of the host innate immune system. IMPORTANCE: A specific interaction involving ficolin-1 (M-ficolin), a soluble effector of the innate immune response, and the glycoprotein (GP) of EBOV was identified. Ficolin-1 enhanced virus infection instead of tipping the balance toward its elimination. An interaction between the fibrinogen-like recognition domain of ficolin-1 and the mucin-like domain of Ebola virus GP occurred. In this model, the enhancement of infection was shown to be independent of the serum complement. The facilitation of EBOV entry into target host cells by the interaction with ficolin-1 and other host lectins shunts virus elimination, which likely facilitates the survival of the virus in infected host cells and contributes to the virus strategy to subvert the innate immune response.