Barbara Adler

Publications of Barbara Adler

• Virus progeny of murine cytomegalovirus bacterial artificial chromosome pSM3fr show reduced growth in salivary Glands due to a fixed mutation of MCK-2.

  Authors: Stefan Jordan, Johannes Krause, Adrian Prager, Maja Mitrovic, Stipan Jonjic, Ulrich H Koszinowski, Barbara Adler

  Journal of virology. 08/2011; 85(19):10346-53.

  Murine cytomegalovirus (MCMV) Smith strain has been cloned as a bacterial artificial chromosome (BAC) named pSM3fr and used for analysis of virus gene functions in vitro and in vivo. When sequencingMurine cytomegalovirus (MCMV) Smith strain has been cloned as a bacterial artificial chromosome (BAC) named pSM3fr and used for analysis of virus gene functions in vitro and in vivo. When sequencing the complete BAC genome, we identified a frameshift mutation within the open reading frame (ORF) encoding MCMV chemokine homologue MCK-2. This mutation would result in a truncated MCK-2 protein. When mice were infected with pSM3fr-derived virus, we observed reduced virus production in salivary glands, which could be reverted by repair of the frameshift mutation. When looking for the source of the mutation, we consistently found that virus stocks of cell culture-passaged MCMV Smith strain are mixtures of viruses with or without the MCK-2 mutation. We conclude that the MCK-2 mutation in the pSM3fr BAC is the result of clonal selection during the BAC cloning procedure.

• HCMV spread and cell tropism are determined by distinct virus populations.

  Authors: Laura Scrivano, Christian Sinzger, Hans Nitschko, Ulrich H Koszinowski, Barbara Adler

  PLoS pathogens. 01/2011; 7(1):e1001256.

  Human cytomegalovirus (HCMV) can infect many different cell types in vivo. Two gH/gL complexes are used for entry into cells. gH/gL/pUL(128,130,131A) shows no selectivity for its host cell, whereasHuman cytomegalovirus (HCMV) can infect many different cell types in vivo. Two gH/gL complexes are used for entry into cells. gH/gL/pUL(128,130,131A) shows no selectivity for its host cell, whereas formation of a gH/gL/gO complex only restricts the tropism mainly to fibroblasts. Here, we describe that depending on the cell type in which virus replication takes place, virus carrying the gH/gL/pUL(128,130,131A) complex is either released or retained cell-associated. We observed that virus spread in fibroblast cultures was predominantly supernatant-driven, whereas spread in endothelial cell (EC) cultures was predominantly focal. This was due to properties of virus released from fibroblasts and EC. Fibroblasts released virus which could infect both fibroblasts and EC. In contrast, EC released virus which readily infected fibroblasts, but was barely able to infect EC. The EC infection capacities of virus released from fibroblasts or EC correlated with respectively high or low amounts of gH/gL/pUL(128,130,131A) in virus particles. Moreover, we found that focal spread in EC cultures could be attributed to EC-tropic virus tightly associated with EC and not released into the supernatant. Preincubation of fibroblast-derived virus progeny with EC or beads coated with pUL131A-specific antibodies depleted the fraction that could infect EC, and left a fraction that could predominantly infect fibroblasts. These data strongly suggest that HCMV progeny is composed of distinct virus populations. EC specifically retain the EC-tropic population, whereas fibroblasts release EC-tropic and non EC-tropic virus. Our findings offer completely new views on how HCMV spread may be controlled by its host cells.

• The m74 gene product of murine cytomegalovirus (MCMV) is a functional homolog of human CMV gO and determines the entry pathway of MCMV.

  Authors: Laura Scrivano, Jasmina Esterlechner, Hermine Mühlbach, Nicole Ettischer, Christoph Hagen, Kay Grünewald, Christian A Mohr, Zsolt Ruzsics, Ulrich Koszinowski, Barbara Adler

  Journal of virology. 02/2010; 84(9):4469-80.

  The glycoprotein gO (UL74) of human cytomegalovirus (HCMV) forms a complex with gH/gL. Virus mutants with a deletion of gO show a defect in secondary envelopment with the consequence that virusThe glycoprotein gO (UL74) of human cytomegalovirus (HCMV) forms a complex with gH/gL. Virus mutants with a deletion of gO show a defect in secondary envelopment with the consequence that virus spread is restricted to a cell-associated pathway. Here we report that the positional homolog of HCMV gO, m74 of mouse CMV (MCMV), codes for a glycosylated protein which also forms a complex with gH (M75). m74 knockout mutants of MCMV show the same spread phenotype as gO knockout mutants of HCMV, namely, a shift from supernatant-driven to cell-associated spread. We could show that this phenotype is due to a reduction of infectious virus particles in cell culture supernatants. m74 knockout mutants enter fibroblasts via an energy-dependent and pH-sensitive pathway, whereas in the presence of an intact m74 gene product, entry is neither energy dependent nor pH sensitive. This entry phenotype is shared by HCMV expressing or lacking gO. Our data indicate that the m74 and UL74 gene products both codetermine CMV spread and CMV entry into cells. We postulate that MCMV, like HCMV, expresses alternative gH/gL complexes which govern cell-to-cell spread of the virus.

• A gammaherpesvirus complement regulatory protein promotes initiation of infection by activation of protein kinase Akt/PKB.

  Authors: Beatrix Steer, Barbara Adler, Stipan Jonjic, James P Stewart, Heiko Adler

  PloS one. 01/2010; 5(7):e11672.

  Viruses have evolved to evade the host's complement system. The open reading frames 4 (ORF4) of gammaherpesviruses encode homologs of regulators of complement activation (RCA) proteins, which inhibitViruses have evolved to evade the host's complement system. The open reading frames 4 (ORF4) of gammaherpesviruses encode homologs of regulators of complement activation (RCA) proteins, which inhibit complement activation at the level of C3 and C4 deposition. Besides complement regulation, these proteins are involved in heparan sulfate and glycosaminoglycan binding, and in case of MHV-68, also in viral DNA synthesis in macrophages. Here, we made use of MHV-68 to study the role of ORF4 during infection of fibroblasts. While attachment and penetration of virions lacking the RCA protein were not affected, we observed a delayed delivery of the viral genome to the nucleus of infected cells. Analysis of the phosphorylation status of a variety of kinases revealed a significant reduction in phosphorylation of the protein kinase Akt in cells infected with ORF4 mutant virus, when compared to cells infected with wt virus. Consistent with a role of Akt activation in initial stages of infection, inhibition of Akt signaling in wt virus infected cells resulted in a phenotype resembling the phenotype of the ORF4 mutant virus, and activation of Akt by addition of insulin partially reversed the phenotype of the ORF4 mutant virus. Importantly, the homologous ORF4 of KSHV was able to rescue the phenotype of the MHV-68 ORF4 mutant, indicating that ORF4 is functionally conserved and that ORF4 of KSHV might have a similar function in infection initiation. In summary, our studies demonstrate that ORF4 contributes to efficient infection by activation of the protein kinase Akt and thus reveal a novel function of a gammaherpesvirus RCA protein.

• Endothelial cells in human cytomegalovirus infection: one host cell out of many or a crucial target for virus spread?

  Authors: Barbara Adler, Christian Sinzger

  Thrombosis and haemostasis. 12/2009; 102(6):1057-63.

  Endothelial cells (EC) are assumed to play a central role in the spread of human cytomegalovirus (HCMV) throughout the body. Results from in-situ analyses of infected tissues and data from cellEndothelial cells (EC) are assumed to play a central role in the spread of human cytomegalovirus (HCMV) throughout the body. Results from in-situ analyses of infected tissues and data from cell culture systems together strongly suggest that vascular EC can support productive replication of HCMV and thus contribute to its haematogeneous dissemination. By inducing an angiogenic response, HCMV may even promote growth of its own habitat. The particular role of EC is further supported by the fact that entry of HCMV into EC is dependent on a complex of the envelope glycoproteins gH and gL with a set of proteins (UL128-131A) which is dispensable for HCMV entry into most other cell types. These molecular requirements may also be reflected by cell type-dependent differences in entry routes, i.e. endocytosis versus fusion at the plasma membrane. An animal model with trackable murine CMV is now available to clarify the pathogenetic role of EC during haematogeneous dissemination of this virus.

• UL74 of human cytomegalovirus contributes to virus release by promoting secondary envelopment of virions.

  Authors: Xiao Jing Jiang, Barbara Adler, Kerstin Laib Sampaio, Margarete Digel, Gerhard Jahn, Nicole Ettischer, York-Dieter Stierhof, Laura Scrivano, Ulrich Koszinowski, Michael Mach, Christian Sinzger

  Journal of virology. 04/2008; 82(6):2802-12.

  The glycoprotein (g) complex gH/gL represents an essential part of the herpesvirus fusion machinery mediating entry of cell-free virions and cell-associated viral spread. In some herpesvirusesThe glycoprotein (g) complex gH/gL represents an essential part of the herpesvirus fusion machinery mediating entry of cell-free virions and cell-associated viral spread. In some herpesviruses additional proteins are associated with gH/gL contributing to the cell tropism of the respective virus. Human cytomegalovirus (HCMV) gH/gL forms complexes with either gO (UL74) or proteins of the UL128-131A gene locus. While a contribution of UL128-131A to endothelial cell tropism is known, the role of gO is less clear. We studied the role of gH/gL-associated proteins in HCMV replication in human foreskin fibroblasts (HFF) and human umbilical vein endothelial cells (HUVEC). Deletions of UL74 alone or in combination with mutations of the UL128-131A gene region were introduced into bacterial artificial chromosome vectors derived from the endotheliotropic strain TB40/E. Deletion of UL74 caused a profound defect regarding virus release from infected HFF and HUVEC. Large numbers of capsids accumulated in the cytoplasm of infected HFF but failed to acquire an envelope. Clear cell type differences were observed in the cell-associated spread of the UL74-defective virus. In HFF, focal growth was severely impaired, whereas it was normal in HUVEC. Deletion of UL131A abolished focal growth in endothelial cells. UL74/UL128-131A dual mutants showed severely impaired reconstitution efficiency. Our data suggest that gO plays a critical role in secondary envelopment and release of cell-free virions independent of the cell type but affects cell-associated growth specifically in HFF, whereas UL128-131A contributes to cell-associated spread in HFF and HUVEC.

• Cloning and sequencing of a highly productive, endotheliotropic virus strain derived from human cytomegalovirus TB40/E.

  Authors: Christian Sinzger, Gabriele Hahn, Margarete Digel, Ruth Katona, Kerstin Laib Sampaio, Martin Messerle, Hartmut Hengel, Ulrich Koszinowski, Wolfram Brune, Barbara Adler

  The Journal of general virology. 03/2008; 89(Pt 2):359-68.

  Human cytomegalovirus (HCMV) strain TB40/E, replicates efficiently, exhibits a broad cell tropism and is widely used for infection of endothelial cells and monocyte-derived cells yet has not beenHuman cytomegalovirus (HCMV) strain TB40/E, replicates efficiently, exhibits a broad cell tropism and is widely used for infection of endothelial cells and monocyte-derived cells yet has not been available in a phenotypically homogeneous form compatible with genetic analysis. To overcome this problem, we cloned the TB40/E strain into a bacterial artificial chromosome (BAC) vector. Both highly endotheliotropic and poorly endotheliotropic virus clones, representing three distinct restriction fragment patterns, were reconstituted after transfection of BAC clones derived from previously plaque-purified strain TB40/E. For one of the highly endotheliotropic clones, TB40-BAC4, we provide the genome sequence. Two BACs with identical restriction fragment patterns but different cell tropism were further analysed in the UL128-UL131A gene region. Sequence analysis revealed one coding-relevant adenine insertion at position 332 of UL128 in the BAC of the poorly endotheliotropic virus, which caused a frameshift in the C-terminal part of the coding sequence. Removal of this insertion by markerless mutagenesis restored the highly endotheliotropic phenotype, indicating that the loss of endothelial cell tropism was caused by this insertion. In conclusion, HCMV strain TB40/E, which combines the high endothelial cell tropism of a clinical isolate with the high titre growth of a cell culture adapted strain, is now available as a BAC clone suitable for genetic engineering. The results also suggest BAC cloning as a suitable method for selection of genetically defined virus clones.

  Download

• Random screening for dominant-negative mutants of the cytomegalovirus nuclear egress protein M50.

  Authors: Brigitte Rupp, Zsolt Ruzsics, Christopher Buser, Barbara Adler, Paul Walther, Ulrich H. Koszinowski

  Journal of virology. 07/2007; 81(11):5508-17.

  Inactivation of gene products by dominant-negative (DN) mutants is a powerful tool to assign functions to proteins. Here, we present a two-step procedure to establish a random screen for DN alleles,Inactivation of gene products by dominant-negative (DN) mutants is a powerful tool to assign functions to proteins. Here, we present a two-step procedure to establish a random screen for DN alleles, using the essential murine cytomegalovirus gene M50 as an example. First, loss-of-function mutants from a linker-scanning library were tested for inhibition of virus reconstitution with the help of FLP-mediated ectopic insertion of the mutants into the viral genome. Second, DN candidates were confirmed by conditional expression of the inhibitory proteins in the virus context. This allowed the quantification of the inhibitory effect, the identification of the morphogenesis block, and the construction of DN mutants with improved activity. Based on these observations a DN mutant of the homologous gene (UL50) in human cytomegalovirus was predicted and constructed. Our data suggest that a proline-rich sequence motif in the variable region of M50/UL50 represents a new functional site which is essential for nuclear egress of cytomegalovirus capsids.

  Download

• Role of human cytomegalovirus UL131A in cell type-specific virus entry and release.

  Authors: Barbara Adler, Laura Scrivano, Zsolt Ruzcics, Brigitte Rupp, Christian Sinzger, Ulrich Koszinowski

  The Journal of general virology. 10/2006; 87(Pt 9):2451-60.

  The human cytomegalovirus (HCMV) genes UL128, UL130 and UL131A are essential for endothelial cell infection. Complementation of the defective UL131A gene of the non-endotheliotropic HCMV strain AD169The human cytomegalovirus (HCMV) genes UL128, UL130 and UL131A are essential for endothelial cell infection. Complementation of the defective UL131A gene of the non-endotheliotropic HCMV strain AD169 with wild-type UL131A in cis in an ectopic position restored endothelial cell tropism. The UL131A protein was found in virions in a complex with gH. Coinfection of fibroblasts with UL131A-negative and -positive viruses restored the endothelial cell tropism of UL131A-negative virions by complementing the virions with UL131A protein. Virus entry into endothelial cells, but not into fibroblasts, was blocked by an antipeptide antiserum to pUL131A. AD169, cis-complemented with wild-type UL131A, showed an impaired release of infectious particles from fibroblasts. A comparable defect in virus release was observed when UL131A was expressed ectopically in a virus background already expressing an intact copy of UL131A. In contrast, virus release from infected endothelial cells was not affected by UL131A. These data suggest a dual role for pUL131A in virus entry and virus exit from infected cells.

• IL-28A and IL-29 mediate antiproliferative and antiviral signals in intestinal epithelial cells and murine CMV infection increases colonic IL-28A expression.

  Authors: Stephan Brand, Florian Beigel, Torsten Olszak, Kathrin Zitzmann, Sören T Eichhorst, Jan-Michel Otte, Joachim Diebold, Helmut Diepolder, Barbara Adler, Christoph J Auernhammer, Burkhard Göke, Julia Dambacher

  American journal of physiology. Gastrointestinal and liver physiology. 12/2005; 289(5):G960-8.

  Human cytomegalovirus virus (CMV) is a major cause of morbidity and mortality in immunocompromised individuals. Recently, a novel group of cytokines [interleukin (IL)-28A/B and IL-29, also termedHuman cytomegalovirus virus (CMV) is a major cause of morbidity and mortality in immunocompromised individuals. Recently, a novel group of cytokines [interleukin (IL)-28A/B and IL-29, also termed interferon (IFN)-lambdas] has been described. Here, we demonstrate that intestinal epithelial cell (IEC) lines as well as murine and human colonic tissue express the IFN-lambda receptor subunits IL-28R and IL-10R2. IL-28A and IL-29 binding to their receptor complex activates ERK-1/2 and stress-activated protein kinase/c-Jun NH2-terminal kinase MAPKs and Akt, resulting in increased IL-8 protein expression. IFN-lambdas also induce phosphorylation of signal transducer and activator of transcription 1 and significantly increase mRNA expression of suppressor of cytokine signaling 3 and the antiviral proteins myxovirus resistance A and 2',5'-oligoadenylate synthetase. These signals result in an up to 83% reduction of cells positive for human CMV immediate-early protein after human CMV infection. In mice, IL-28A mRNA expression is upregulated after infection with murine CMV in vivo. Both IL-28A and IL-29 significantly decrease cell proliferation but have no effect on Fas-induced apoptosis. In conclusion, IECs express functional receptors for IFN-lambdas, which mediate antiviral and antiproliferative signals in IECs, suggesting a potential for therapeutic use in certain viral infections and as (antiproliferative) anticancer therapy.

• Epstein-Barr virus latent membrane protein 2A mimics B-cell receptor-dependent virus reactivation.

  Authors: Eveline Schaadt, Barbara Baier, Josef Mautner, Georg W Bornkamm, Barbara Adler

  The Journal of general virology. 04/2005; 86(Pt 3):551-9.

  Latent membrane protein 2A (LMP2A) of Epstein-Barr virus (EBV) shares protein motifs with the B-cell receptor that play a role in B-cell receptor signalling and has been shown to mimic an activatedLatent membrane protein 2A (LMP2A) of Epstein-Barr virus (EBV) shares protein motifs with the B-cell receptor that play a role in B-cell receptor signalling and has been shown to mimic an activated B-cell receptor by providing a survival signal for mature B cells in transgenic mice. Conversely, LMP2A has been reported not to support but to inhibit B-cell receptor signalling with respect to virus reactivation and to block lytic virus induction after anti-Ig treatment of EBV-infected B cells. To solve this apparent paradox, the role of LMP2A in lytic-cycle induction was re-examined in B cells conditionally immortalized by EBV. It was shown that, in the absence of other stimuli, LMP2A expression alone could lead to induction of the virus lytic cycle. Similarly to B-cell receptor stimulation by anti-Ig treatment, this LMP2A-mediated reactivation was dependent on the mitogen-activated protein kinase pathway and could be inhibited by the viral LMP1. Our data reinforce the notion that LMP2A is a functional homologue of the B-cell receptor, not only with respect to B-cell survival but also with respect to regulation of the lytic cycle.

• Functional analysis of the mutated Epstein-Barr virus oncoprotein LMP1(69del): implications for a new role of naturally occurring LMP1 variants.

  Authors: Clara Larcher, David Bernhard, Eveline Schaadt, Barbara Adler, Michael J Ausserlechner, Manfred Mitterer, Hartwig P Huemer

  Haematologica. 01/2004; 88(12):1324-35.

  BACKGROUND AND OBJECTIVES: The role of carboxyterminal deletions of the latent membrane protein-1 (LMP1) in Epstein-Barr virus (EBV) infection and oncogenesis is unclear. Here we describe functionalBACKGROUND AND OBJECTIVES: The role of carboxyterminal deletions of the latent membrane protein-1 (LMP1) in Epstein-Barr virus (EBV) infection and oncogenesis is unclear. Here we describe functional properties of a rare 69-bp LMP1 deletion mutant (LMP1(69del)) isolated from a patient with polyclonal B-cell lymphocytosis. DESIGN AND METHODS: Colony focus assay was used to evaluate the transforming capacity of LMP1(69del) in comparison to that of wild-type LMP1 from EBV strain B95/8. Transient transfectants of B-, T-, epithelial and 3T3 cells, and stable transfectants with ecdysone-inducible LMP1 expression were produced. The signaling capacity of both LMP1s on nuclear transcription factors NFkappaB and AP-1 were studied. Secretion of matrix metalloproteinase MMP-9, apoptosis, and EBV lytic and latent gene expression were also investigated. RESULTS: LMP(69del) showed transforming properties comparable to those of the wild-type oncoprotein. Induction of NFkappaB but a markedly reduced influence on AP-1 were observed. Both oncoproteins induced secretion of MMP-9, and enhanced pre-apoptotic effects in Jurkat-T cells leading to increased Fas/Apo-1 and doxorubicin-mediated apoptosis. Furthermore, LMP1(69del) showed a more effective down-regulation of the EBV lytic cycle master gene BZLF1(Zebra) than did wild-type LMP1. INTERPRETATION AND CONCLUSIONS: (i) LMP1(69del) possesses oncogenic properties, (ii) the observed impaired activity on AP-1 does not interfere with MMP-9 induction, (iii) the enhanced inhibition of BZLF1 could compensate for previously described mutations of our isolate leading to a more lytic phenotype and may be responsible for counteracting permanent virus replication in the chronic active EBV syndrome observed in this patient.

• Control of Epstein-Barr virus reactivation by activated CD40 and viral latent membrane protein 1.

  Authors: Barbara Adler, Eveline Schaadt, Bettina Kempkes, Ursula Zimber-Strobl, Barbara Baier, Georg W Bornkamm

  Proceedings of the National Academy of Sciences of the United States of America. 02/2002; 99(1):437-42.

  In humans, Epstein-Barr virus (EBV) establishes a persistent latent infection in peripheral resting B lymphocytes. Virus reactivation is highly restricted. Whereas in healthy humans the infectionIn humans, Epstein-Barr virus (EBV) establishes a persistent latent infection in peripheral resting B lymphocytes. Virus reactivation is highly restricted. Whereas in healthy humans the infection usually is benign, immunocompromised patients show an increased risk for EBV-associated malignancies, accompanied by an increase in virus replication and in the number of virus-infected cells. To search for viral and host factors regulating virus reactivation, we used conditionally EBV-immortalized B cells. We found that CD40-CD40 ligand interaction and the viral mimic of activated CD40, EBV latent membrane protein 1, suppress virus reactivation. Both inhibit anti-IgM or phorbolester-induced transcription of the viral immediate early protein BZLF1, which controls entry into the viral lytic cycle. The finding that latent membrane protein 1 and CD40 contribute to the regulation of latency may have important implications for the balance between EBV and its host in normal as well as in immunocompromised individuals.