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See detailORF9p phosphorylation by ORF47p is crucial for the formation and egress of the Varicella-zoster virus (VZV) viral particles.
Riva, Laura ULg; Thiry, Marc ULg; BONTEMS, Sébastien ULg et al

in Journal of Virology (2013), 87(5), 2868-2881

The role of the tegument during the herpesvirus lytic cycle is still not clearly established, particularly at the late phase of infection, when the newly produced viral particles need to be fully ... [more ▼]

The role of the tegument during the herpesvirus lytic cycle is still not clearly established, particularly at the late phase of infection, when the newly produced viral particles need to be fully assembled before being released from the infected cell. The Varicella-zoster virus (VZV) protein coded by ORF9 (ORF9p) is an essential tegument protein and, even though its mRNA is the most expressed during the productive infection, little is known about its functions. Using a GalK positive/negative selection technique, we modified a BAC containing the complete VZV genome creating viruses expressing mutant versions of ORF9p.We showed that ORF9p is hyper-phosphorylated during the infection, especially through its interaction with the viral Ser/Thr kinase ORF47p; we identified a consensus site within ORF9p recognized by ORF47p and demonstrated its importance for ORF9p phosphorylation. Strikingly, an ultra-structural analysis revealed that the mutation of this consensus site (Glutamate 85 to Arginine) strongly affects viral assembly and release, reproducing ORF47 kinase dead VZV phenotype. It also slightly diminishes the infectivity towards immature dendritic cells. Taken together, our results identify ORF9p as a new viral substrate of ORF47p and suggest a determinant role of this phosphorylation for viral infectivity, especially during the process of viral particle formation and egress. [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 detailViral expression directs the fate of B cells in BLV-infected sheep.
Florins, Arnaud-Francois ULg; De Brogniez, Alix ULg; Elemans, M. et al

in Journal of Virology (2012), 86(1), 621-624

The host immune response is believed to tightly control viral replication of deltaretroviruses such as human T-lymphotropic virus type 1 (HTLV-1) and bovine leukemia virus (BLV). However, this assumption ... [more ▼]

The host immune response is believed to tightly control viral replication of deltaretroviruses such as human T-lymphotropic virus type 1 (HTLV-1) and bovine leukemia virus (BLV). However, this assumption has not been definitely proven in vivo. In order to further evaluate the importance of immune response in the BLV model, we studied the fate of cells in which viral expression was transiently induced. Using a dual fluorochrome labeling approach, we show that ex vivo induction of viral expression induces higher death rates of B cells in vivo. Furthermore, cyclosporine treatment of these animals indicated that an efficient immune response is required to control virus expressing cells. [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 detailPersistent infection of thymic epithelial cells with coxsackievirus B4 results in a decreased expression of insulin-like growth factor 2
Jaïdane, Hela; Caloone, Delphine; Lobert, Pierre-Emmanuel et al

in Journal of Virology (2012), 86

It has been hypothesized that a disturbance of central self-tolerance to islet β-cell may play a role in the enteroviral pathogenesis of type 1 diabetes. Whether enteroviruses can induce an impaired ... [more ▼]

It has been hypothesized that a disturbance of central self-tolerance to islet β-cell may play a role in the enteroviral pathogenesis of type 1 diabetes. Whether enteroviruses can induce an impaired expression of β-cell self-antigens in thymic epithelial cells has been investigated in a murine thymic epithelial (MTE) cell line. This cell line was permissive to the diabetogenic strain CV-B4 E2 and spontaneously expressed type 2 insulin-like growth factor (Igf2), the dominant self-antigen of the insulin family. In this model, a persistent replication of CV-B4 E2 was obtained as attested by the prolonged detection of intracellular positive and negative-strand viral RNA by RT-PCR, and capsid protein VP1 by IF and by the release of infectious particles in culture supernatant fluids. The chronic stage of the infection was characterized by a low proportion of VP1-positive cells (1-2%) whereas many cells harbored enteroviral RNA as displayed by RT-PCR without extraction applied directly on a few cells. Igf2 mRNA and IGF-2 protein were dramatically decreased in CV-B4 E2-infected MTE cultures compared with mock-infected cultures, whereas housekeeping and Il6 genes expression were maintained and Igf1 mRNA was decreased but at a lower extent. Inoculation of CV-B3-, CV-B4 JVB- or Echovirus 1 resulted in a low level of IGF-2 in culture supernatant fluids as well, whereas HSV-1 stimulated the production of the protein. Thus, a persistent infection of a thymic epithelial cell line with enteroviruses, like CV-B4 E2 can result in a disturbed production of IGF-2, a protein involved in central self-tolerance towards islet β-cells. [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 detailComplete genome sequence of a novel bovine norovirus: Evidence for slow genetic evolution in genogroup III genotype 2 noroviruses
Mauroy, Axel ULg; Scipioni, A.; Mathijs, E. et al

in Journal of Virology (2012), 86(22), 12449-12450

A new genogroup III genotype 2 bovine norovirus, B309/2003/BE, was entirely sequenced and genetically compared to the original Newbury2/1976/UK strain and to Dumfries/1994/UK, detected in 1976 and 1994 ... [more ▼]

A new genogroup III genotype 2 bovine norovirus, B309/2003/BE, was entirely sequenced and genetically compared to the original Newbury2/1976/UK strain and to Dumfries/1994/UK, detected in 1976 and 1994, respectively. Interestingly, except in welldefined coding regions (N-terminal protein, 3A-like protease, hypervariable region of the capsid protein, and C-terminal part of the minor structural protein), very low genetic differences were noted between the entire genomes of these three strains along a 30-year-long period. It allowed some hypotheses of hotspots of genetic evolution through a low genetic evolution background in genotype 2 genogroup III bovine noroviruses. © 2012, American Society for Microbiology. [less ▲]

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See detailEx vivo bioluminescent detection of Alcelaphine herpesvirus 1 infection during malignant catarrhal fever.
Dewals, Benjamin G ULg; Myster, Françoise ULg; Palmeira, Leonor ULg et al

in Journal of Virology (2011), 85(14), 6941-54

Alcelaphine herpesvirus 1 (AlHV-1), carried by wildebeest asymptomatically, causes malignant catarrhal fever (WD-MCF) when cross-species transmitted to a variety of susceptible species of the Artiodactyla ... [more ▼]

Alcelaphine herpesvirus 1 (AlHV-1), carried by wildebeest asymptomatically, causes malignant catarrhal fever (WD-MCF) when cross-species transmitted to a variety of susceptible species of the Artiodactyla order. Experimentally, WD-MCF can be reproduced in rabbits. WD-MCF is described as a combination of lymphoproliferation and degenerative lesions in virtually all organs and caused by unknown mechanisms. Recently, we demonstrated that WD-MCF is associated with the proliferation of CD8(+) cells supporting a latent type of infection in lymphoid tissues. Here, we investigated the macroscopic distribution of AlHV-1 infection using ex vivo bioluminescence imaging in rabbit to determine whether it correlates with the distribution of lesions in lymphoid and non-lymphoid organs. To reach that goal, a recombinant AlHV-1 strain was produced by insertion of a luciferase expression cassette (luc) in an intergenic region. In vitro, the reconstituted AlHV-1 luc(+) strain replicated comparably to the parental strain and luciferase activity was detected by bioluminescence imaging. In vivo, rabbits infected with the AlHV-1 luc(+) strain developed WD-MCF comparably to the parental wild-type strain with hyperthermia and increase of both CD8(+) T cells frequencies and viral genomic charge over time in peripheral blood mononuclear cells and in lymph nodes at time of euthanasia. Bioluminescent imaging revealed that AlHV-1 infection could be detected ex vivo in lymphoid organs but also in lung, liver and kidney during WD-MCF, demonstrating that AlHV-1 infection is prevalent in tissue lesions. Finally, we show that the infiltrating mononuclear leukocytes in non-lymphoid organs are mainly CD8(+) T cells and that latency is predominant during WD-MCF. [less ▲]

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See detailBovine Herpesvirus 4 Bo10 gene encodes a nonessential viral envelope protein that regulates viral tropism through both positive and negative effects.
Machiels, Bénédicte ULg; Lété, Céline ULg; Defays, Katalin et al

in Journal of Virology (2011), 85(2), 1011-1024

All gammaherpesviruses encode a glycoprotein positionally homologous to the Epstein-Barr virus gp350 and the Kaposi's Sarcoma associated herpesvirus (KSHV) K8.1. In this study, we characterized that of ... [more ▼]

All gammaherpesviruses encode a glycoprotein positionally homologous to the Epstein-Barr virus gp350 and the Kaposi's Sarcoma associated herpesvirus (KSHV) K8.1. In this study, we characterized that of Bovine Herpesvirus-4 (BoHV-4), encoded by the Bo10 gene. We identified a 180 kDa gene product, gp180, which was incorporated into the virion envelope. A Bo10 deletion virus was viable, but showed a growth deficit associated with reduced binding to epithelial cells. This seemed to reflect an interaction of gp180 with glycosaminoglycans (GAGs), since the Bo10 mutant was both less infectious for GAG(+) cells than the wild-type and more infectious for GAG(-) cells. However, we could not identify a direct interaction between gp180 and GAGs, implying that any direct interaction must be of low affinity. This function of gp180 was very similar to that previously identified for the Murid Herpesvirus 4 gp150, and also to the Epstein-Barr virus gp350 that promotes CD21(+) cell infection and inhibits CD21(-) cell infection. We propose that such proteins generally regulate virion attachment both by binding to cells and by covering another receptor-binding protein until they are displaced. Thus they regulate viral tropism both positively and negatively depending upon the presence or absence of their receptor. [less ▲]

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See detailCo-infection with two closely related alphaherpesviruses results in a highly diversified recombination mosaic displaying negative genetic interference
Muylkens, Benoît ULg; Farnir, Frédéric ULg; Meurens, François et al

in Journal of Virology (2009), 83(7), 3127-3137

Phylogenetic studies of the emergence and spread of natural recombinants in herpesviruses infecting humans and animals have been reported recently. However, despite an ever-increasing amount of evidence ... [more ▼]

Phylogenetic studies of the emergence and spread of natural recombinants in herpesviruses infecting humans and animals have been reported recently. However, despite an ever-increasing amount of evidence of recombination in herpesvirus history, the recombination process and the consequences on the genetic diversity of the progeny remain poorly characterized. We addressed this issue by using multiple single-nucleotide polymorphisms (SNPs) differentiating the two subtypes of an alphaherpesvirus, bovine herpesvirus 1 (BoHV-1). Analysis of a large sample of progeny virions obtained in a single growth cycle of coinfected BoHV-1 strains provided a prospective investigation of the recombination dynamics by using SNPs as recombination markers. We found that the simultaneous infection with two closely related herpesviruses results in a highly diversified recombination mosaic. From the analysis of multiple recombinants arising in the progeny, we provide the first evidence of genetic interference influencing the recombination process in herpesviruses. In addition, we report striking differences in the levels of recombination frequency observed along the BoHV-1 genome. With particular emphasis on the genetic structure of a progeny virus population rising in vitro, our data show to which extent recombination participates to the genetic diversification of herpesviruses [less ▲]

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See detailThe major portal of entry of koi herpesvirus in cyprinus carpio is the skin.
Costes, Bérénice ULg; Stalin Raj, V.; Michel, Benjamin ULg et al

in Journal of Virology (2009)

Koi herpesvirus (KHV), recently designated in the species Cyprinid Herpesvirus 3, is the causative agent of a lethal disease in koi and common carp. In the present study, we investigated the portal of ... [more ▼]

Koi herpesvirus (KHV), recently designated in the species Cyprinid Herpesvirus 3, is the causative agent of a lethal disease in koi and common carp. In the present study, we investigated the portal of entry of KHV in carp using bioluminescence imaging. Taking profit of the recent cloning of the KHV genome as a bacterial artificial chromosome (BAC), we produced a recombinant plasmid encoding a firefly luciferase (LUC) expression cassette inserted in the intergenic region between ORF 136 and ORF 137. Two viral strains were then reconstituted from the modified plasmid: the FL BAC 136 LUC excised strain and the FL BAC 136 LUC TK revertant strain encoding a disrupted and a wild-type thymidine kinase (TK) locus, respectively. In vitro, the two recombinant strains replicated comparably to the parental FL strain. The FL BAC 136 LUC TK revertant strain was shown in vitro to induce a bioluminescent signal allowing the detection of single positive cells as early as 24 hours post-infection; while in vivo, it induced KHV infection in carp that was indistinguishable from that induced by the parental FL strain. To identify the KHV portal of entry, carp were analyzed by bioluminescence imaging at different time post-infection with the FL BAC 136 LUC TK revertant strain. These analyses demonstrated that the skin of the fish, covering the fins and also the body, is the major portal of entry of KHV in carp. Finally, to further demonstrate the role of the skin as the KHV portal of entry, we constructed an original system nicknamed "U-tube" to perform per-cutaneous infection restricted to the posterior part of the fish. All the data obtained in the present study demonstrate that the skin and not the gills is the major portal of entry of KHV in carp. [less ▲]

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See detailCloning of the koi herpesvirus genome as an infectious bacterial artificial chromosome demonstrates that disruption of the thymidine kinase locus induces partial attenuation in Cyprinus carpio koi.
Costes, Bérénice ULg; Fournier, Guillaume ULg; Michel, Benjamin ULg et al

in Journal of Virology (2008), 82(10), 4955-4964

Koi herpesvirus (KHV) is the causative agent of a lethal disease in koi and common carp. In the present study, we describe the cloning of the KHV genome as a stable and infectious bacterial artificial ... [more ▼]

Koi herpesvirus (KHV) is the causative agent of a lethal disease in koi and common carp. In the present study, we describe the cloning of the KHV genome as a stable and infectious bacterial artificial chromosome (BAC) clone that can be used to produce KHV recombinant strains. This goal was achieved by the insertion of a loxP-flanked BAC cassette into the thymidine kinase (TK) locus. This insertion led to a BAC plasmid that was stably maintained in bacteria and was able to regenerate virions when permissive cells were transfected with the plasmid. Reconstituted virions free of the BAC cassette but carrying a disrupted TK locus (the FL BAC-excised strain) were produced by the transfection of Cre recombinase-expressing cells with the BAC. Similarly, virions with a wild-type revertant TK sequence (the FL BAC revertant strain) were produced by the cotransfection of cells with the BAC and a DNA fragment encoding the wild-type TK sequence. Reconstituted recombinant viruses were compared to the wild-type parental virus in vitro and in vivo. The FL BAC revertant strain and the FL BAC-excised strain replicated comparably to the parental FL strain. The FL BAC revertant strain induced KHV infection in koi carp that was indistinguishable from that induced by the parental strain, while the FL BAC-excised strain exhibited a partially attenuated phenotype. Finally, the usefulness of the KHV BAC for recombination studies was demonstrated by the production of an ORF16-deleted strain by using prokaryotic recombination technology. The availability of the KHV BAC is an important advance that will allow the study of viral genes involved in KHV pathogenesis, as well as the production of attenuated recombinant candidate vaccines. [less ▲]

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See detailGlycoprotein L disruption reveals two functional forms of the murine gammaherpesvirus 68 glycoprotein H.
Gillet, Laurent ULg; May, Janet S; Colaco, Susanna et al

in Journal of Virology (2007), 81(1), 280-91

The herpesvirus glycoprotein H (gH) and gL associate to form a heterodimer that plays a central role in virus-driven membrane fusion. When archetypal alpha- or betaherpesviruses lack gL, gH misfolds and ... [more ▼]

The herpesvirus glycoprotein H (gH) and gL associate to form a heterodimer that plays a central role in virus-driven membrane fusion. When archetypal alpha- or betaherpesviruses lack gL, gH misfolds and progeny virions are noninfectious. In order to define the role that gL plays in gamma-2 herpesvirus infections, we disrupted its coding sequence in murine gammaherpesvirus-68 (MHV-68). MHV-68 lacking gL folded gH into a conformation antigenically distinct from the form that normally predominates on infected cells. gL-deficient virions bound less well than the wild type to epithelial cells and fibroblasts. However, they still incorporated gH and remained infectious. The cell-to-cell spread of gL-deficient viruses was remarkably normal, as was infection, dissemination, and latency establishment in vivo. Viral membrane fusion was therefore gL independent. The major function of gL appeared to be allowing gH to participate in cell binding prior to membrane fusion. This function was most important for the entry of MHV-68 virions into fibroblasts and epithelial cells. [less ▲]

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See detailEvidence for a multiprotein gamma-2 herpesvirus entry complex.
Gillet, Laurent ULg; Stevenson, Philip G

in Journal of Virology (2007), 81(23), 13082-91

Herpesviruses use multiple virion glycoproteins to enter cells. How these work together is not well understood: some may act separately or they may form a single complex. Murine gammaherpesvirus 68 (MHV ... [more ▼]

Herpesviruses use multiple virion glycoproteins to enter cells. How these work together is not well understood: some may act separately or they may form a single complex. Murine gammaherpesvirus 68 (MHV-68) gB, gH, gL, and gp150 all participate in entry. gB and gL are involved in binding, gB and gH are conserved fusion proteins, and gp150 inhibits cell binding until glycosaminoglycans are engaged. Here we show that a gH-specific antibody coprecipitates gB and thus that gH and gB are associated in the virion membrane. A gH/gL-specific antibody also coprecipitated gB, implying a tripartite complex of gL/gH/gB, although the gH/gB association did not require gL. The association was also independent of gp150, and gp150 was not demonstrably bound to gB or gH. However, gp150 incorporation into virions was partly gL dependent, suggesting that it too contributes to a single entry complex. gp150- and gL- gp150- mutants bound better than the wild type to B cells and readily colonized B cells in vivo. Thus, gp150 and gL appear to be epithelial cell-adapted accessories of a core gB/gH entry complex. The cell binding revealed by gp150 disruption did not require gL and therefore seemed most likely to involve gB. [less ▲]

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See detailDNA immunization with plasmids encoding fusion and nucleocapsid proteins of bovine respiratory syncytial virus induces a strong cell-mediated immunity and protects calves against challenge.
Boxus, Mathieu ULg; Tignon, Marylene; Roels, Stefan et al

in Journal of Virology (2007), 81(13), 6879-89

Respiratory syncytial viruses (RSV) are one of the most important respiratory pathogens of humans and cattle, and there is currently no safe and effective vaccine prophylaxis. In this study, we designed ... [more ▼]

Respiratory syncytial viruses (RSV) are one of the most important respiratory pathogens of humans and cattle, and there is currently no safe and effective vaccine prophylaxis. In this study, we designed two codon-optimized plasmids encoding the bovine RSV fusion (F) and nucleocapsid (N) proteins and assessed their immunogenicity in young calves. Two administrations of both plasmids elicited low antibody levels but primed a strong cell-mediated immunity characterized by lymphoproliferative response and gamma interferon production in vitro and in vivo. Interestingly, this strong cellular response drastically reduced viral replication, clinical signs, and pulmonary lesions after a highly virulent challenge. Moreover, calves that were further vaccinated with a killed-virus vaccine developed high levels of neutralizing antibody and were fully protected following challenge. These results indicate that DNA vaccination could be a promising alternative to the classical vaccines against RSV in cattle and could therefore open perspectives for vaccinating young infants. [less ▲]

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See detailVaricella-zoster virus modulates NF-kappaB recruitment on selected cellular promoters.
El Mjiyad, Nadia ULg; Bontems, Sébastien ULg; Gloire, Geoffrey ULg et al

in Journal of Virology (2007), 81(23), 13092-104

Intercellular adhesion molecule 1 (ICAM-1) expression is down-regulated in the center of cutaneous varicella lesions despite the expression of proinflammatory cytokines such as gamma interferon and tumor ... [more ▼]

Intercellular adhesion molecule 1 (ICAM-1) expression is down-regulated in the center of cutaneous varicella lesions despite the expression of proinflammatory cytokines such as gamma interferon and tumor necrosis factor alpha (TNF-alpha). To study the molecular basis of this down-regulation, the ICAM-1 induction of TNF-alpha was analyzed in varicella-zoster virus (VZV)-infected melanoma cells (MeWo), leading to the following observations: (i) VZV inhibits the stimulation of icam-1 mRNA synthesis; (ii) despite VZV-induced nuclear translocation of p65, p52, and c-Rel, p50 does not translocate in response to TNF-alpha; (iii) the nuclear p65 present in VZV-infected cells is no longer associated with p50 and is unable to bind the proximal NF-kappaB site of the icam-1 promoter, despite an increased acetylation and accessibility of the promoter in response to TNF-alpha; and (iv) VZV induces the nuclear accumulation of the NF-kappaB inhibitor p100. VZV also inhibits icam-1 stimulation of TNF-alpha by strongly reducing NF-kappaB nuclear translocation in MRC5 fibroblasts. Taken together, these data show that VZV interferes with several aspects of the immune response by inhibiting NF-kappaB binding and the expression of target genes. Targeting NF-kappaB activation, which plays a central role in innate and adaptive immune responses, leads to obvious advantages for the virus, particularly in melanocytes, which are a site of viral replication in the skin. [less ▲]

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See detailEven attenuated bovine leukemia virus proviruses can be pathogenic in sheep.
Florins, Arnaud-Francois ULg; Gillet, Nicolas ULg; Boxus, Mathieu ULg et al

in Journal of virology (2007), 81(18), 10195-200

Based on a reverse genetics approach, we previously reported that bovine leukemia virus (BLV) mutants harboring deletions in the accessory R3 and G4 genes persist at very low proviral loads and are unable ... [more ▼]

Based on a reverse genetics approach, we previously reported that bovine leukemia virus (BLV) mutants harboring deletions in the accessory R3 and G4 genes persist at very low proviral loads and are unable to induce leukemia or lymphoma in sheep, indicating that these R3 and G4 gene sequences are required for pathogenesis. We now show that lymphoma can occur, albeit infrequently (1 case of 20) and after extended periods of latency (7 years). Direct sequencing and reinfection experiments demonstrated that lymphomagenesis was not due to the reversion of the mutant to the wild type. Similar observations with another type of attenuated mutant impaired in the transmembrane protein (TM) YXXL signaling motifs were made. We conclude that the R3 and G4 genes and the TM YXXL motifs are not strictly required for pathogenesis but that their integrity contributes to disease frequency and latency. [less ▲]

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See detailSpleen-dependent turnover of CD11b peripheral blood B lymphocytes in bovine leukemia virus-infected sheep.
Florins, Arnaud-Francois ULg; Gillet, Nicolas ULg; Asquith, Becca et al

in Journal of virology (2006), 80(24), 11998-2008

Lymphocyte homeostasis is determined by a critical balance between cell proliferation and death, an equilibrium which is deregulated in bovine leukemia virus (BLV)-infected sheep. We have previously shown ... [more ▼]

Lymphocyte homeostasis is determined by a critical balance between cell proliferation and death, an equilibrium which is deregulated in bovine leukemia virus (BLV)-infected sheep. We have previously shown that an excess of proliferation occurs in lymphoid tissues and that the peripheral blood population is prone to increased cell death. To further understand the mechanisms involved, we evaluated the physiological role of the spleen in this accelerated turnover. To this end, B lymphocytes were labeled in vivo using a fluorescent marker (carboxyfluorescein diacetate succinimidyl ester), and the cell kinetic parameters (proliferation and death rates) of animals before and after splenectomy were compared. We show that the enhanced cell death observed in BLV-infected sheep is abrogated after splenectomy, revealing a key role of the spleen in B-lymphocyte dynamics. [less ▲]

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See detailPeripheral blood B-cell death compensates for excessive proliferation in lymphoid tissues and maintains homeostasis in bovine leukemia virus-infected sheep.
Debacq, Christophe; Gillet, Nicolas ULg; Asquith, Becca et al

in Journal of Virology (2006), 80(19), 9710-9719

The size of a lymphocyte population is primarily determined by a dynamic equilibrium between cell proliferation and death. Hence, lymphocyte recirculation between the peripheral blood and lymphoid tissues ... [more ▼]

The size of a lymphocyte population is primarily determined by a dynamic equilibrium between cell proliferation and death. Hence, lymphocyte recirculation between the peripheral blood and lymphoid tissues is a key determinant in the maintenance of cell homeostasis. Insights into these mechanisms can be gathered from large-animal models, where lymphatic cannulation from individual lymph nodes is possible. In this study, we assessed in vivo lymphocyte trafficking in bovine leukemia virus (BLV)-infected sheep. With a carboxyfluorescein diacetate succinimidyl ester labeling technique, we demonstrate that the dynamics of lymphocyte recirculation is unaltered but that accelerated proliferation in the lymphoid tissues is compensated for by increased death in the peripheral blood cell population. Lymphocyte homeostasis is thus maintained by biphasic kinetics in two distinct tissues, emphasizing a very dynamic process during BLV infection. [less ▲]

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