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See detailThe alpha2,3-Sialyltransferase Encoded by Myxoma Virus Is a Virulence Factor that Contributes to Immunosuppression.
Boutard, Berengere; Vankerckhove, Sophie; Markine-Goriaynoff, Nicolas et al

in PloS one (2015), 10(2), 0118806

Myxoma virus (MYXV) induces a lethal disease called Myxomatosis in European rabbits. MYXV is one of the rare viruses that encodes an alpha2,3-sialyltransferase through its M138L gene. In this study, we ... [more ▼]

Myxoma virus (MYXV) induces a lethal disease called Myxomatosis in European rabbits. MYXV is one of the rare viruses that encodes an alpha2,3-sialyltransferase through its M138L gene. In this study, we showed that although the absence of the enzyme was not associated with any in vitro deficit, the M138L deficient strains are highly attenuated in vivo. Indeed, while all rabbits infected with the parental and the revertant strains died within 9 days post-infection from severe myxomatosis, all but one rabbit inoculated with the M138L deficient strains survived the infection. In primary lesions, this resistance to the infection was associated with an increased ability of innate immune cells, mostly neutrophils, to migrate to the site of virus replication at 4 days post-infection. This was followed by the development of a better specific immune response against MYXV. Indeed, at day 9 post-infection, we observed an important proliferation of lymphocytes and an intense congestion of blood vessels in lymph nodes after M138L knockouts infection. Accordingly, in these rabbits, we observed an intense mononuclear cell infiltration throughout the dermis in primary lesions and higher titers of neutralizing antibodies. Finally, this adaptive immune response provided protection to these surviving rabbits against a challenge with the MYXV WT strain. Altogether, these results show that expression of the M138L gene contributes directly or indirectly to immune evasion by MYXV. In the future, these results could help us to better understand the pathogenesis of myxomatosis but also the importance of glycans in regulation of immune responses. [less ▲]

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See detailA gammaherpesvirus infection protects against allergic asthma.
Machiels, Bénédicte ULg; Dourcy, Mickael ULg; Sabatel, Catherine ULg et al

Poster (2014, December 12)

The “hygiene hypothesis” proposes that the augmentation of allergic diseases in developed countries could be linked to a reduced exposure to infections during childhood. Surprisingly, the potential ... [more ▼]

The “hygiene hypothesis” proposes that the augmentation of allergic diseases in developed countries could be linked to a reduced exposure to infections during childhood. Surprisingly, the potential protective role of herpesvirus infections against allergy development has never been addressed directly. In this study, we used the Murid herpesvirus 4 (MuHV-4) to study the impact of a persistent gammaherpesvirus infection on the development of House Dust Mites (HDM)-induced allergic asthma. Our results revealed that MuHV-4 infection affects both the sensitization and the challenging phases of HDM-induced airway allergy. In particular, we highlighted that MuHV-4 infection strongly impacts the lung innate immune response. Indeed, while the dendritic cells remained competent to uptake antigens and to migrate to the draining lymph nodes, MuHV-4 infection impaired their ability to trigger HDM sensitization. In the future, these results could allow us to develop strategies to prevent the development of TH2-skewed responses against respiratory allergens. [less ▲]

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See detailLa virothérapie oncolytique médiée par le virus de la myxomatose
Krygier, David; Gillet, Laurent ULg; Marlier, Didier ULg

in Annales de Médecine Vétérinaire (2013), 157(1), 5-14

Le virus de la myxomatose est un poxvirus du genre Leporipoxvirus qui induit une pathologie spécifique, la myxomatose, chez le lapin européen (Oryctolagus cuniculus). Ce virus a la particularité d’être ... [more ▼]

Le virus de la myxomatose est un poxvirus du genre Leporipoxvirus qui induit une pathologie spécifique, la myxomatose, chez le lapin européen (Oryctolagus cuniculus). Ce virus a la particularité d’être non pathogène pour les autres espèces de vertébrés y compris l’homme. Le virus de la myxomatose (MYXV) présente aussi, de manière inattendue, un tropisme pour les cellules cancéreuses humaines in vitro ainsi qu’un potentiel oncolytique in vivo. La tolérance de ces cellules au MYXV est intimement liée au niveau intracellulaire d’Akt phosphorylée. Cette enzyme, est une serine/thréonine protéine kinase qui joue un rôle essentiel dans de nombreux processus cellulaires et fait partie de la voie de signalisation PI3k/Akt/mTOR (mammalian target of rapamycin), fréquemment amplifiée par l’oncogénèse. La protéine virale à répétitions ankyrines, M-T5, interagit avec Akt ce qui module le tropisme du MYXV pour les cellules tumorales humaines. Un régulateur de la croissance cellulaire et du métabolisme situé en aval d’Akt, mTOR, est spécifiquement inhibé par la rapamycine. Ainsi, l’utilisation de la rapamycine en combinaison avec le MYXV permet d’augmenter la concentration d’Akt phosphorylée, et par conséquent, d’amplifier l’oncolyse. Un meilleur contrôle chimique de la voie de signalisation d’Akt ou de la modification génétique de son génome constituera une étape décisive pour que le MYXV devienne l’un des nouveaux traitements des cancers chez l’homme [less ▲]

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See detailIllumination of murine gammaherpesvirus-68 cycle reveals a sexual transmission route from females to males in laboratory mice.
Francois, Sylvie; Vidick, Sarah ULg; Sarlet, Mickael et al

in PLoS Pathogens (2013), 9(4), 1003292

Transmission is a matter of life or death for pathogen lineages and can therefore be considered as the main motor of their evolution. Gammaherpesviruses are archetypal pathogenic persistent viruses which ... [more ▼]

Transmission is a matter of life or death for pathogen lineages and can therefore be considered as the main motor of their evolution. Gammaherpesviruses are archetypal pathogenic persistent viruses which have evolved to be transmitted in presence of specific immune response. Identifying their mode of transmission and their mechanisms of immune evasion is therefore essential to develop prophylactic and therapeutic strategies against these infections. As the known human gammaherpesviruses, Epstein-Barr virus and Kaposi's Sarcoma-associated Herpesvirus are host-specific and lack a convenient in vivo infection model; related animal gammaherpesviruses, such as murine gammaherpesvirus-68 (MHV-68), are commonly used as general models of gammaherpesvirus infections in vivo. To date, it has however never been possible to monitor viral excretion or virus transmission of MHV-68 in laboratory mice population. In this study, we have used MHV-68 associated with global luciferase imaging to investigate potential excretion sites of this virus in laboratory mice. This allowed us to identify a genital excretion site of MHV-68 following intranasal infection and latency establishment in female mice. This excretion occurred at the external border of the vagina and was dependent on the presence of estrogens. However, MHV-68 vaginal excretion was not associated with vertical transmission to the litter or with horizontal transmission to female mice. In contrast, we observed efficient virus transmission to naive males after sexual contact. In vivo imaging allowed us to show that MHV-68 firstly replicated in penis epithelium and corpus cavernosum before spreading to draining lymph nodes and spleen. All together, those results revealed the first experimental transmission model for MHV-68 in laboratory mice. In the future, this model could help us to better understand the biology of gammaherpesviruses and could also allow the development of strategies that could prevent the spread of these viruses in natural populations. [less ▲]

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See detailProteomic characterization of murid herpesvirus 4 extracellular virions.
Vidick, Sarah ULg; Leroy, Baptiste; Gonon Rodrigues Palmeira, Leonor ULg et al

in PloS one (2013), 8(12), 83842

Gammaherpesvirinae, such as the human Epstein-Barr virus (EBV) and the Kaposi's sarcoma associated herpesvirus (KSHV) are highly prevalent pathogens that have been associated with several neoplastic ... [more ▼]

Gammaherpesvirinae, such as the human Epstein-Barr virus (EBV) and the Kaposi's sarcoma associated herpesvirus (KSHV) are highly prevalent pathogens that have been associated with several neoplastic diseases. As EBV and KSHV are host-range specific and replicate poorly in vitro, animal counterparts such as Murid herpesvirus-4 (MuHV-4) have been widely used as models. In this study, we used MuHV-4 in order to improve the knowledge about proteins that compose gammaherpesviruses virions. To this end, MuHV-4 extracellular virions were isolated and structural proteins were identified using liquid chromatography tandem mass spectrometry-based proteomic approaches. These analyses allowed the identification of 31 structural proteins encoded by the MuHV-4 genome which were classified as capsid (8), envelope (9), tegument (13) and unclassified (1) structural proteins. In addition, we estimated the relative abundance of the identified proteins in MuHV-4 virions by using exponentially modified protein abundance index analyses. In parallel, several host proteins were found in purified MuHV-4 virions including Annexin A2. Although Annexin A2 has previously been detected in different virions from various families, its role in the virion remains controversial. Interestingly, despite its relatively high abundance in virions, Annexin A2 was not essential for the growth of MuHV-4 in vitro. Altogether, these results extend previous work aimed at determining the composition of gammaherpesvirus virions and provide novel insights for understanding MuHV-4 biology. [less ▲]

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See detailGlycoprotein B cleavage is important for murid herpesvirus 4 to infect myeloid cells.
Glauser, Daniel L.; Milho, Ricardo; Frederico, Bruno et al

in Journal of Virology (2013)

Glycoprotein B (gB) is a conserved herpesvirus virion component implicated in membrane fusion. As with many - but not all - herpesviruses, the gB of murid herpesvirus 4 (MuHV-4) is cleaved into disulfide ... [more ▼]

Glycoprotein B (gB) is a conserved herpesvirus virion component implicated in membrane fusion. As with many - but not all - herpesviruses, the gB of murid herpesvirus 4 (MuHV-4) is cleaved into disulfide-linked subunits, apparently by furin. Preventing gB cleavage for some herpesviruses causes minor infection deficits in vitro, but what the cleavage contributes to host colonization has been unclear. To address this we mutated the furin cleavage site (R-R-K-R) of the MuHV-4 gB. Abolishing gB cleavage did not affect its expression levels, glycosylation or antigenic conformation. In vitro, mutant viruses entered fibroblasts and epithelial cells normally, but had a significant entry deficit in myeloid cells such as macrophages and bone marrow-derived dendritic cells. The deficit in myeloid cells was not due to reduced virion binding or endocytosis, suggesting that gB cleavage promotes infection at a post-endocytic entry step, presumably viral membrane fusion. In vivo, viruses lacking gB cleavage showed reduced lytic spread in the lungs. Alveolar epithelial cell infection was normal, but alveolar macrophage infection was significantly reduced. Normal long-term latency in lymphoid tissue was established nonetheless. [less ▲]

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See detailAlternative splicing switches tropism of a gammaherpesvirus
Machiels, Bénédicte ULg; Gillet, Laurent ULg

Conference (2012, November)

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See detailMethod for producing antibody using "naked" expression vector expressing type II transmembrane fusion protein
Renauld, Jean Christophe; Lemaire, Muriel; Dumoutier, Laurie et al

Patent (2012)

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See detailFeeding Cyprinus carpio with infectious materials mediates cyprinid herpesvirus 3 entry through infection of pharyngeal periodontal mucosa
Fournier, Guillaume ULg; Boutier, Maxime ULg; Victor, Stalin Raj et al

in Veterinary Research (2012), 43(6),

Cyprinid herpesvirus 3 (CyHV-3), also known as Koi herpesvirus, is the etiological agent of a mortal disease in common and koi carp. Recently, we investigated the entry of CyHV-3 in carp using ... [more ▼]

Cyprinid herpesvirus 3 (CyHV-3), also known as Koi herpesvirus, is the etiological agent of a mortal disease in common and koi carp. Recently, we investigated the entry of CyHV-3 in carp using bioluminescence imaging and a CyHV-3 recombinant strain expressing luciferase (LUC). We demonstrated that the skin is the major portal of entry after inoculation of carp by immersion in water containing CyHV-3. While this model of infection mimics some natural conditions in which infection takes place, other epidemiological conditions could favour entry of virus through the digestive tract. Here, we investigated whether ingestion of infectious materials mediates CyHV-3 entry through the digestive tract. Carp were fed with materials contaminated with the CyHV-3 LUC recombinant (oral contamination) or immersed in water containing the virus (contamination by immersion). Bioluminescence imaging analyses performed at different times post-infection led to the following observations: (i) the pharyngeal periodontal mucosa is the major portal of entry after oral contamination, while the skin is the major portal of entry after contamination by immersion. (ii) Both modes of inoculation led to the spreading of the infection to the various organs tested. However, the timing and the sequence in which some of the organs turned positive were different between the two modes of inoculation. Finally, we compared the disease induced by the two inoculation modes. They led to comparable clinical signs and mortality rate. The results of the present study suggest that, based on epidemiological conditions, CyHV-3 can enter carp either by skin or periodontal pharyngeal mucosal infection. [less ▲]

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See detailMyeloid infection links epithelial and B cell tropisms of murid herpesvirus-4.
Frederico, Bruno; Milho, Ricardo; May, Janet S. et al

in PLoS Pathogens (2012), 8(9), 1002935

Gamma-herpesviruses persist in lymphocytes and cause disease by driving their proliferation. Lymphocyte infection is therefore a key pathogenetic event. Murid Herpesvirus-4 (MuHV-4) is a rhadinovirus that ... [more ▼]

Gamma-herpesviruses persist in lymphocytes and cause disease by driving their proliferation. Lymphocyte infection is therefore a key pathogenetic event. Murid Herpesvirus-4 (MuHV-4) is a rhadinovirus that like the related Kaposi's Sarcoma-associated Herpesvirus persists in B cells in vivo yet infects them poorly in vitro. Here we used MuHV-4 to understand how virion tropism sets the path to lymphocyte colonization. Virions that were highly infectious in vivo showed a severe post-binding block to B cell infection. Host entry was accordingly an epithelial infection and B cell infection a secondary event. Macrophage infection by cell-free virions was also poor, but improved markedly when virion binding improved or when macrophages were co-cultured with infected fibroblasts. Under the same conditions B cell infection remained poor; it improved only when virions came from macrophages. This reflected better cell penetration and correlated with antigenic changes in the virion fusion complex. Macrophages were seen to contact acutely infected epithelial cells, and cre/lox-based virus tagging showed that almost all the virus recovered from lymphoid tissue had passed through lysM(+) and CD11c(+) myeloid cells. Thus MuHV-4 reached B cells in 3 distinct stages: incoming virions infected epithelial cells; infection then passed to myeloid cells; glycoprotein changes then allowed B cell infection. These data identify new complexity in rhadinovirus infection and potentially also new vulnerability to intervention. [less ▲]

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See detailBovine Herpesvirus Type 4 Glycoprotein L Is Nonessential for Infectivity but Triggers Virion Endocytosis during Entry
Lété, Céline ULg; Machiels, Bénédicte ULg; Stevenson, P. G. et al

in Journal of Virology (2012)

The core entry machinery of mammalian herpesviruses comprises glycoproteins B, H and L (gB, gH and gL). gH and gL form a heterodimer with a central role in viral membrane fusion. When archetypal alpha- or ... [more ▼]

The core entry machinery of mammalian herpesviruses comprises glycoproteins B, H and L (gB, gH and gL). gH and gL form a heterodimer with a central role in viral membrane fusion. When archetypal alpha- or beta-herpesviruses lack gL, gH misfolds and progeny virions are non-infectious. However, the gL of the rhadinovirus Murid herpesvirus 4 (MuHV-4) is non-essential for infection. In order to define more generally what role gL plays in rhadinovirus infections, we disrupted its coding sequence in Bovine herpesvirus-4 (BoHV-4). BoHV-4 lacking gL showed altered gH glycosylation and incorporated somewhat less gH into virions but remained infectious. However, gL- virions showed poor growth associated with an entry deficit. Moreover a major part of their entry defect appeared to reflect impaired endocytosis, which occurs upstream of membrane fusion itself. Thus, the rhadinovirus gL may be more important for driving virion endocytosis than for incorporating gH into virions, and is non-essential for membrane fusion. [less ▲]

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See detailProteomic characterization of bovine herpesvirus 4 extracellular virions.
Lété, Céline ULg; Palmeira, Leonor ULg; Leroy, Baptiste et al

in Journal of Virology (2012), 86(21), 11567-80

Gammaherpesviruses are important pathogens in human and animal populations. During early events of infection, these viruses manipulate preexisting host cell signaling pathways to allow successful ... [more ▼]

Gammaherpesviruses are important pathogens in human and animal populations. During early events of infection, these viruses manipulate preexisting host cell signaling pathways to allow successful infection. The different proteins that compose viral particles are therefore likely to have critical functions not only in viral structures and in entry into target cell but also in evasion of the host's antiviral response. In this study, we analyzed the protein composition of bovine herpesvirus 4 (BoHV-4), a close relative of the human Kaposi's sarcoma-associated herpesvirus. Using mass spectrometry-based approaches, we identified 37 viral proteins associated with extracellular virions, among which 24 were resistant to proteinase K treatment of intact virions. Analysis of proteins associated with purified capsid-tegument preparations allowed us to define protein localization. In parallel, in order to identify some previously undefined open reading frames, we mapped peptides detected in whole virion lysates onto the six frames of the BoHV-4 genome to generate a proteogenomic map of BoHV-4 virions. Furthermore, we detected important glycosylation of three envelope proteins: gB, gH, and gp180. Finally, we identified 38 host proteins associated with BoHV-4 virions; 15 of these proteins were resistant to proteinase K treatment of intact virions. Many of these have important functions in different cellular pathways involved in virus infection. This study extends our knowledge of gammaherpesvirus virions composition and provides new insights for understanding the life cycle of these viruses. [less ▲]

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See detailVirion endocytosis is a major target for Murid Herpesvirus-4 neutralization.
Glauser, D; Gillet, Laurent ULg; Stevenson, PG

in Journal of General Virology (The) (2012)

Herpesviruses consistently transmit from immunocompetent carriers, implying that their neutralization is hard to achieve. Murid Herpesvirus-4 (MuHV-4) exploits host IgG Fc receptors to bypass blocks to ... [more ▼]

Herpesviruses consistently transmit from immunocompetent carriers, implying that their neutralization is hard to achieve. Murid Herpesvirus-4 (MuHV-4) exploits host IgG Fc receptors to bypass blocks to cell binding, and pH-dependent protein conformation changes to unveil its fusion machinery only after endocytosis. Nevertheless neutralization remains possible by targeting the virion glycoprotein H (gH) / gL heterodimer, and the neutralizing antibody responses of MuHV-4 carriers are improved by boosting with recombinant gH/gL. We analysed here how gH/gL-directed neutralization works. The MuHV-4 gH/gL binds to heparan sulfate. However most gH/gL-specific neutralizing antibodies did not block this interaction. Nor did they act directly on fusion. Instead they blocked virion endocytosis and transport to the late endosomes where membrane fusion normally occurs. The poor endocytosis of gH/gL-neutralized virions was recapitulated precisely by virions genetically lacking gL. Therefore driving virion uptake appears to be an important function of gH/gL that provides a major target for antibody-mediated neutralization. [less ▲]

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See detailGenital re-excretion of Murid gammaherpesvirus 4 following intranasal infection
François, Sylvie ULg; Vidick, Sarah ULg; Sarlet, Michaël ULg et al

in Proceedings of the 1st Scientific Meeting of the Faculty of Veterinary Medicine (2011, December 09)

Gammaherpesviruses are the archetypes of persistent viruses that have been identified in a range of animals from mice to man. As the human gammaviruses have no well-established in vivo infection model ... [more ▼]

Gammaherpesviruses are the archetypes of persistent viruses that have been identified in a range of animals from mice to man. As the human gammaviruses have no well-established in vivo infection model, related animal gammaherpesviruses are an important source of information. We are studying Murid herpesvirus 4 (MuHV-4) in inbred laboratory mouse strains which are commonly accepted as a good model for studying gammaherpesviruses in vivo. To date, it has however never been possible to monitor viral reexcretion and virus transmission in this species. In order to identify potential re-excretion sites, intranasally infected mice were followed through global luciferase imaging for up to six months after infection. Surprisingly, we detected transient viral replication in mice genital tract at various times after latency establishment. Ex vivo imaging, quantitative PCR and immunohistochemistry revealed that virus genomes were present in high quantity in the vaginal tissue and that viral replication occurred mainly at the vaginal external border. Moreover, we highlighted the presence of free infectious viruses in the vaginal cavity at the moment of the observation of viral replication. As this ephemeral viral reexcretion could reveal a link with reproductive cycle, we compared reexcretion in normal and ovariectomized mice. Interestingly, no viral reactivation was observed in absence of hormonal cycle. In conclusion, we experimentally indentified for the first time a reexcretion site for MuHV-4 in mice that had been intranasaly infected. In the future, these results could help us to better understand the biology of gammaherpesviruses but should also allow us to develop strategies that could prevent the spread of these viruses in natural populations. [less ▲]

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See detailGenital re-excretion of Murid gammaherpesvirus 4 following intranasal infection
François, Sylvie ULg; Vidick, Sarah ULg; Sarlet, Michaël ULg et al

Poster (2011, November 16)

Gammaherpesviruses are the archetypes of persistent viruses that have been identified in a range of animals from mice to man. As the human gammaviruses have no well-established in vivo infection model ... [more ▼]

Gammaherpesviruses are the archetypes of persistent viruses that have been identified in a range of animals from mice to man. As the human gammaviruses have no well-established in vivo infection model, related animal gammaherpesviruses are an important source of information. We are studying Murid herpesvirus 4 (MuHV-4) in inbred laboratory mouse strains which are commonly accepted as a good model for studying gammaherpesviruses in vivo. To date, it has however never been possible to monitor viral reexcretion and virus transmission in this species. In order to identify potential re-excretion sites, intranasally infected mice were followed through global luciferase imaging for up to six months after infection. Surprisingly, we detected transient viral replication in mice genital tract at various times after latency establishment. Ex vivo imaging, quantitative PCR and immunohistochemistry revealed that virus genomes were present in high quantity in the vaginal tissue and that viral replication occurred mainly at the vaginal external border. Moreover, we highlighted the presence of free infectious viruses in the vaginal cavity at the moment of the observation of viral replication. As this ephemeral viral reexcretion could reveal a link with reproductive cycle, we compared reexcretion in normal and ovariectomized mice. Interestingly, no viral reactivation was observed in absence of hormonal cycle. In conclusion, we experimentally indentified for the first time a reexcretion site for MuHV-4 in mice that had been intranasaly infected. In the future, these results could help us to better understand the biology of gammaherpesviruses but should also allow us to develop strategies that could prevent the spread of these viruses in natural populations. [less ▲]

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