Emmanuel J H J Wiertz

University Medical Center Utrecht, Utrecht, Provincie Utrecht, Netherlands

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Publications (99)606.64 Total impact

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    ABSTRACT: CD8(+) CTLs detect virus-infected cells through recognition of virus-derived peptides presented at the cell surface by MHC class I molecules. The cowpox virus protein CPXV012 deprives the endoplasmic reticulum (ER) lumen of peptides for loading onto newly synthesized MHC class I molecules by inhibiting the transporter associated with Ag processing (TAP). This evasion strategy allows the virus to avoid detection by the immune system. In this article, we show that CPXV012, a 9-kDa type II transmembrane protein, prevents peptide transport by inhibiting ATP binding to TAP. We identified a segment within the ER-luminal domain of CPXV012 that imposes the block in peptide transport by TAP. Biophysical studies show that this domain has a strong affinity for phospholipids that are also abundant in the ER membrane. We discuss these findings in an evolutionary context and show that a frameshift deletion in the CPXV012 gene in an ancestral cowpox virus created the current form of CPXV012 that is capable of inhibiting TAP. In conclusion, our findings indicate that the ER-luminal domain of CPXV012 inserts into the ER membrane, where it interacts with TAP. CPXV012 presumably induces a conformational arrest that precludes ATP binding to TAP and, thus, activity of TAP, thereby preventing the presentation of viral peptides to CTLs.
    Journal of immunology (Baltimore, Md. : 1950). 07/2014;
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    ABSTRACT: Viral infection triggers an early host response through activation of pattern recognition receptors, including Toll-like receptors (TLR). TLR signaling cascades induce production of type I interferons and proinflammatory cytokines involved in establishing an anti-viral state as well as in orchestrating ensuing adaptive immunity. To allow infection, replication, and persistence, (herpes)viruses employ ingenious strategies to evade host immunity. The human gamma-herpesvirus Epstein-Barr virus (EBV) is a large, enveloped DNA virus persistently carried by more than 90% of adults worldwide. It is the causative agent of infectious mononucleosis and is associated with several malignant tumors. EBV activates TLRs, including TLR2, TLR3, and TLR9. Interestingly, both the expression of and signaling by TLRs is attenuated during productive EBV infection. Ubiquitination plays an important role in regulating TLR signaling and is controlled by ubiquitin ligases and deubiquitinases (DUBs). The EBV genome encodes three proteins reported to exert in vitro deubiquitinase activity. Using active site-directed probes, we show that one of these putative DUBs, the conserved herpesvirus large tegument protein BPLF1, acts as a functional DUB in EBV-producing B cells. The BPLF1 enzyme is expressed during the late phase of lytic EBV infection and is incorporated into viral particles. The N-terminal part of the large BPLF1 protein contains the catalytic site for DUB activity and suppresses TLR-mediated activation of NF-κB at, or downstream of, the TRAF6 signaling intermediate. A catalytically inactive mutant of this EBV protein did not reduce NF-κB activation, indicating that DUB activity is essential for attenuating TLR signal transduction. Our combined results show that EBV employs deubiquitination of signaling intermediates in the TLR cascade as a mechanism to counteract innate anti-viral immunity of infected hosts.
    PLoS Pathogens 02/2014; 10(2):e1003960. · 8.14 Impact Factor
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    ABSTRACT: Misfolded ER proteins are retrotranslocated into the cytosol for degradation via the ubiquitin-proteasome system. The human cytomegalovirus protein US11 exploits this ER-associated protein degradation (ERAD) pathway to downregulate HLA class I molecules in virus-infected cells, thereby evading elimination by cytotoxic T-lymphocytes. US11-mediated degradation of HLA class I has been instrumental in the identification of key components of mammalian ERAD, including Derlin-1, p97, VIMP and SEL1L. Despite this, the process governing retrotranslocation of the substrate is still poorly understood. Here using a high-coverage genome-wide shRNA library, we identify the uncharacterized protein TMEM129 and the ubiquitin-conjugating E2 enzyme UBE2J2 to be essential for US11-mediated HLA class I downregulation. TMEM129 is an unconventional C4C4-type RING finger E3 ubiquitin ligase that resides within a complex containing various other ERAD components, including Derlin-1, Derlin-2, VIMP and p97, indicating that TMEM129 is an integral part of the ER-resident dislocation complex mediating US11-induced HLA class I degradation.
    Nature Communications 01/2014; 5:3832. · 10.74 Impact Factor
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    ABSTRACT: Misfolded MHC class I heavy chains (MHC I HCs) are targeted for endoplasmic reticulum (ER)-associated degradation (ERAD) by the ubiquitin E3 ligase HRD1, and E2 ubiquitin conjugating enzyme UBE2J1, and represent one of the few known endogenous ERAD substrates. The mechanism by which misfolded proteins are dislocated across the ER membrane into the cytosol is unclear. Here, we investigate the requirements for MHC I ubiquitination and degradation and show that endogenous misfolded MHC I HCs are recognized in the ER lumen by EDEM1 in a glycan-dependent manner and targeted to the core SEL1L/HRD1/UBE2J1 complex. A soluble MHC I HC lacking its transmembrane domain and cytosolic tail uses the same ERAD components and is degraded as efficiently as wild-type MHC I. Unexpectedly, HRD1-dependent polyubiquitination is preferentially targeted to the ER luminal domain of full-length MHC I HCs, despite the presence of an exposed cytosolic C-terminal tail. MHC I luminal domain ubiquitination occurs before p97 ATPase-mediated extraction from the ER membrane and can be targeted to nonlysine, as well as lysine, residues. A subset of integral membrane proteins, therefore, requires an early dislocation event to expose part of their luminal domain to the cytosol, before HRD1-mediated polyubiquitination and dislocation.
    Proceedings of the National Academy of Sciences 08/2013; · 9.81 Impact Factor
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    ABSTRACT: Genomic variation and related evolutionary dynamics of human respiratory syncytial virus (RSV), a common causative agent of severe lower respiratory tract infections, may affect its transmission behavior. RSV evolutionary patterns are likely to be influenced by a precarious interplay between selection favoring variants with higher replicative fitness and variants that evade host immune responses. Studying RSV genetic variation can reveal both genes and individual codons within these genes that are most crucial for RSV survival. This study conducts genetic diversity and evolutionary rate analyses on 36 RSV subgroup B whole genome sequences. The attachment protein, G, was the most variable protein and, accordingly, the G gene had a higher substitution rate than other RSV-B genes. Overall, less genetic variability was found amongst the available RSV-B genome sequences than that amongst a comparable sample of RSV-A genome sequences. The mean substitution rates of both subgroups were, however, similar (A: 6.47 x 10(-4) [Credible interval (CI): 5.56, 7.38 x 10(-4)], B: 7.76 x 10(-4) [CI: 6.89, 8.58 x 10(-4)] substitution/site/yr), with the time to their most recent common ancestors (TMRCAs) being much lower for RSV-B (19 yrs) than for RSV-A (46.8 yrs). The more recent RSV-B TMRCA is apparently the result of a genetic bottleneck that, over longer time-scales, is still compatible with neutral population dynamics. Whereas the immunogenic G protein seems to require high substitution rates to ensure immune evasion, strong purifying selection in conserved proteins such as the fusion protein and nucleocapsid protein is likely essential to preserve RSV viability.
    Journal of Virology 05/2013; · 5.08 Impact Factor
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    ABSTRACT: Coevolution of herpesviruses and their hosts has driven the development of both host antiviral mechanisms to detect and eliminate infected cells and viral ploys to escape immune surveillance. Among the immune-evasion strategies used by the lymphocryptovirus (γ(1)-herpesvirus) EBV is the downregulation of surface HLA class I expression by the virally encoded G protein-coupled receptor BILF1, thereby impeding presentation of viral Ags and cytotoxic T cell recognition of the infected cell. In this study, we show EBV BILF1 to be expressed early in the viral lytic cycle. BILF1 targets a broad range of HLA class I molecules, including multiple HLA-A and -B types and HLA-E. In contrast, HLA-C was only marginally affected. We advance the mechanistic understanding of the process by showing that the cytoplasmic C-terminal tail of EBV BILF1 is required for reducing surface HLA class I expression. Susceptibility to BILF1-mediated downregulation, in turn, is conferred by specific residues in the intracellular tail of the HLA class I H chain. Finally, we explore the evolution of BILF1 within the lymphocryptovirus genus. Although the homolog of BILF1 encoded by the lymphocryptovirus infecting Old World rhesus primates shares the ability of EBV to downregulate cell surface HLA class I expression, this function is not possessed by New World marmoset lymphocryptovirus BILF1. Therefore, this study furthers our knowledge of the evolution of immunoevasive functions by the lymphocryptovirus genus of herpesviruses.
    The Journal of Immunology 01/2013; · 5.52 Impact Factor
  • Daniëlle Horst, Maaike E Ressing, Arend Mulder, Emmanuel J H J Wiertz
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    ABSTRACT: The peptide content of MHC class I molecules present at the cell surface is monitored by surveilling CD8(+) cytotoxic T cells. In case of a viral infection, a proportion of the MHC class I molecules will carry peptides derived from viral proteins. This allows the CD8(+) T cells to recognize and eliminate virus-infected cells. This highly sensitive detection system of the host is counteracted by viruses, which have acquired functions to downregulate cell surface expression of MHC class I molecules. In this chapter, we describe a flow cytometry-based method to identify viral gene product(s) responsible for evasion from MHC class I-restricted antigen presentation. To this end, cells are transiently transfected using polyethylenimine (PEI) as a transfection reagent, followed by cell surface staining with MHC class I-specific monoclonal antibodies. Once viral proteins responsible for MHC class I downregulation have been identified, their mechanism of action can be characterized. Identification and characterization of virus-encoded MHC class I inhibitors augments our understanding of virus-host interactions and often provides new insights into antigen processing and presentation pathways, including related cellular processes such as protein trafficking and degradation.
    Methods in molecular biology (Clifton, N.J.) 01/2013; 960:127-136. · 1.29 Impact Factor
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    ABSTRACT: Processing and presentation of antigen on MHC-I class I molecules serves to present peptides derived from cytosolic proteins to CD8(+) T cells. Infection with bacteria that remain in phagosomal compartments, such as Mycobacterium tuberculosis (Mtb), provides a challenge to this immune recognition as bacterial proteins are segregated from the cytosol. Previously we identified the Mtb phagosome itself as an organelle capable of loading MHC Class I molecules with Mtb antigens. Here, we find that the TAP transporter, responsible for importing peptides into the ER for loading in Class I molecules, is both present and functional in Mtb phagosomes. Furthermore, we describe a novel peptide reagent, representing the N-terminal domain of the bovine herpes virus UL49.5 protein, which is capable of specifically inhibiting the lumenal face of TAP. Together, these results provide insight into the mechanism by which peptides from intra-phagosomal pathogens are loaded onto Class I molecules.
    PLoS ONE 01/2013; 8(11):e79571. · 3.53 Impact Factor
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    ABSTRACT: Following primary infection, herpesviruses persist for life in their hosts, even when vigorous anti-viral immunity has been induced. Failure of the host immune system to eliminate infected cells is facilitated by highly effective immune evasion strategies acquired by these herpesviruses during millions of years of co-evolution with their hosts. Here, we review the mechanisms of action of viral gene products that lead to cytotoxic T cell evasion through interference with the function of the transporter associated with antigen processing, TAP. The viral TAP inhibitors impede transport of peptides from the cytosol into the ER lumen, thereby preventing peptide loading onto MHC class I complexes. Recent insights have revealed a pattern of functional convergent evolution. In every herpesvirus subfamily, inhibitors of TAP function have been identified that are, surprisingly, unrelated in genome location, structure, and mechanism of action. Recently, cowpox virus has also been found to encode a TAP inhibitor. Expanding our knowledge on how viruses perturb antigen presentation, in particular by targeting TAP, not only provides information on viral pathogenesis, but also reveals novel aspects of the cellular processes corrupted by these viruses, notably the translocation of peptides by the ATP-binding cassette (ABC) transporter TAP. As the various TAP inhibitors are anticipated to impede discrete conformational transitions it is expected that crystal structures of TAP-inhibitor complexes will reveal valuable structural information on the actual mechanism of peptide translocation by TAP. Viral TAP inhibitors are also used for various (clinical) applications, for example, as effective tools in antigen presentation studies and as immunomodulators in immunotherapy for cancer, heterologous vaccination, and transplant protection.
    Molecular Immunology 11/2012; · 2.65 Impact Factor
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    ABSTRACT: CD4(+) T cells play a central role in adaptive immunity. The acknowledgment of their cytolytic effector function and the finding that endogenous antigens can enter the HLA class II processing pathway make CD4(+) T cells promising tools for immunotherapy. Expression of HLA class II and endogenous antigen, however, does not always correlate with T-cell recognition. We therefore investigated processing and presentation of endogenous HLA class II epitopes that induced CD4(+) T cells during in vivo immune responses. We demonstrate that the peptide editor HLA-DM allowed antigen presentation of some (DM-resistant antigens) but abolished surface expression of other natural HLA class II epitopes (DM-sensitive antigens). DM sensitivity was shown to be epitope specific, mediated via interaction between HLA-DM and the HLA-DR restriction molecule, and reversible by HLA-DO. Because of the restricted expression of HLA-DO, presentation of DM-sensitive antigens was limited to professional antigen-presenting cells, whereas DM-resistant epitopes were expressed on all HLA class II-expressing cells. In conclusion, our data provide novel insights into the presentation of endogenous HLA class II epitopes and identify intracellular antigen processing and presentation as a critical factor for CD4(+) T-cell recognition. This opens perspectives to exploit selective processing capacities as a new approach for targeted immunotherapy.
    Blood 08/2012; 120(16):3246-55. · 9.78 Impact Factor
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    ABSTRACT: Replication of the human herpesvirus Epstein-Barr virus drastically impairs cellular protein synthesis. This shutoff phenotype results from mRNA degradation upon expression of the early lytic-phase protein BGLF5. Interestingly, BGLF5 is the viral DNase, or alkaline exonuclease, homologues of which are present throughout the herpesvirus family. During productive infection, this DNase is essential for processing and packaging of the viral genome. In contrast to this widely conserved DNase activity, shutoff is only mediated by the alkaline exonucleases of the subfamily of gammaherpesviruses. Here, we show that BGLF5 can degrade mRNAs of both cellular and viral origin, irrespective of polyadenylation. Furthermore, shutoff by BGLF5 induces nuclear relocalization of the cytosolic poly(A) binding protein. Guided by the recently resolved BGLF5 structure, mutants were generated and analyzed for functional consequences on DNase and shutoff activities. On the one hand, a point mutation destroying DNase activity also blocks RNase function, implying that both activities share a catalytic site. On the other hand, other mutations are more selective, having a more pronounced effect on either DNA degradation or shutoff. The latter results are indicative of an oligonucleotide-binding site that is partially shared by DNA and RNA. For this, the flexible "bridge" that crosses the active-site canyon of BGLF5 appears to contribute to the interaction with RNA substrates. These findings extend our understanding of the molecular basis for the shutoff function of BGLF5 that is conserved in gammaherpesviruses but not in alpha- and betaherpesviruses.
    Journal of Virology 06/2012; 86(17):9175-87. · 5.08 Impact Factor
  • Molecular Immunology. 05/2012; 51(1):11.
  • Molecular Immunology. 05/2012; 51(1):36.
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    ABSTRACT: Viral gene carriers are being widely used as gene transfer systems in (trans)differentiation and reprogramming strategies. Forced expression of key regulators of pancreatic differentiation in stem cells, liver cells, pancreatic duct cells, or cells from the exocrine pancreas, can lead to the initiation of endocrine pancreatic differentiation. While several viral vector systems have been employed in such studies, the results reported with adenovirus vectors have been the most promising in vitro and in vivo. In this study, we examined whether the viral vector system itself could impact the differentiation capacity of human bone-marrow derived mesenchymal stem cells (hMSCs) toward the endocrine lineage. Lentivirus-mediated expression of Pdx-1, Ngn-3, and Maf-A alone or in combination does not lead to robust expression of any of the endocrine hormones (i.e. insulin, glucagon and somatostatin) in hMSCs. Remarkably, subsequent transduction of these genetically modified cells with an irrelevant early region 1 (E1)-deleted adenoviral vector potentiates the differentiation stimulus and promotes glucagon gene expression in hMSCs by affecting the chromatin structure. This adenovirus stimulation was observed upon infection with an E1-deleted adenovirus vector, but not after exposure to helper-dependent adenovirus vectors, pointing at the involvement of genes retained in the E1-deleted adenovirus vector in this phenomenon. Lentivirus mediated expression of the adenovirus E4-ORF3 mimics the adenovirus effect. From these data we conclude that E1-deleted adenoviral vectors are not inert gene-transfer vectors and contribute to the modulation of the cellular differentiation pathways.
    PLoS ONE 01/2012; 7(10):e48093. · 3.53 Impact Factor
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    ABSTRACT: Human respiratory syncytial virus (RSV) is an important cause of severe lower respiratory tract infections in infants and the elderly. In the vast majority of cases, however, RSV infections run mild and symptoms resemble those of a common cold. The immunological, clinical, and epidemiological profile of severe RSV infections suggests a disease caused by a virus with typical seasonal transmission behavior, lacking clear-cut virulence factors, but instead causing disease by modifying the host's immune response in a way that stimulates pathogenesis. Yet, the interplay between RSV-evoked immune responses and epidemic behavior, and how this affects the genomic evolutionary dynamics of the virus, remains poorly understood. Here, we present a comprehensive collection of 33 novel RSV subgroup A genomes from strains sampled over the last decade, and provide the first measurement of RSV-A genomic diversity through time in a phylodynamic framework. In addition, we map amino acid substitutions per protein to determine mutational hotspots in specific domains. Using Bayesian genealogical inference, we estimated the genomic evolutionary rate to be 6.47×10(-4) (credible interval: 5.56×10(-4), 7.38×10(-4)) substitutions/site/year, considerably slower than previous estimates based on G gene sequences only. The G gene is however marked by elevated substitution rates compared to other RSV genes, which can be attributed to relaxed selective constraints. In line with this, site-specific selection analyses identify the G gene as the major target of diversifying selection. Importantly, statistical analysis demonstrates that the immune driven positive selection does not leave a measurable imprint on the genome phylogeny, implying that RSV lineage replacement mainly follows nonselective epidemiological processes. The roughly 50 years of RSV-A genomic evolution are characterized by a constant population size through time and general co-circulation of lineages over many epidemic seasons - a conclusion that might be taken into account when developing future therapeutic and preventive strategies.
    PLoS ONE 01/2012; 7(12):e51439. · 3.53 Impact Factor
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    ABSTRACT: The Epstein-Barr virus (EBV)-encoded immune evasion protein BNLF2a inhibits the transporter associated with antigen processing (TAP), thereby downregulating HLA class I expression at the cell surface. As a consequence, recognition of EBV-infected cells by cytotoxic T cells is impaired. Here, we show that sequence polymorphism of the BNLF2a protein is observed with natural EBV isolates, with evidence for positive selection. Despite these mutations, the BNLF2a variants efficiently reduce cell surface HLA class I levels. This conservation of BNLF2a function during evolution of EBV implies an important role for the viral TAP inhibitor in preventing T cell recognition during viral infection.
    Journal of Virology 01/2012; 86(1):572-7. · 5.08 Impact Factor
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    ABSTRACT: Viral infections are counteracted by virus-specific cytotoxic T cells that recognize the infected cell via MHC class I (MHC I) molecules presenting virus-derived peptides. The loading of the peptides onto MHC I molecules occurs in the endoplasmic reticulum (ER) and is facilitated by the peptide loading complex. A key player in this complex is the transporter associated with antigen processing (TAP), which translocates the viral peptides from the cytosol into the ER. Herpesviruses have developed many strategies to evade cytotoxic T cells. Several members of the genus Varicellovirus encode a UL49.5 protein that prevents peptide transport through TAP. These include bovine herpesvirus (BoHV) 1, BoHV-5, bubaline herpesvirus 1, cervid herpesvirus 1, pseudorabies virus, felid herpesvirus 1, and equine herpesvirus 1 and 4. BoHV-1 UL49.5 inhibits TAP by preventing conformational changes essential for peptide transport and by inducing degradation of the TAP complex. UL49.5 consists of an ER luminal N-terminal domain, a transmembrane domain and a cytosolic C-terminal tail domain. In this study, the following features of UL49.5 were deciphered: (1) chimeric constructs of BoHV-1 and VZV UL49.5 attribute the lack of TAP inhibition by VZV UL49.5 to its ER-luminal domain, (2) the ER-luminal and TM domains of UL49.5 are required for efficient interaction with and inhibition of TAP, (3) the C-terminal RXRX sequence is essential for TAP degradation by BoHV-1 UL49.5, and (4) in addition to the RXRX sequence, the cytoplasmic tail of BoHV-1 UL49.5 carries a motif that is required for efficient TAP inhibition by the protein. A model is presented depicting how the different domains of UL49.5 may block the translocation of peptides by TAP and target TAP for proteasomal degradation.
    Molecular Immunology 07/2011; 48(15-16):2038-51. · 2.65 Impact Factor
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    ABSTRACT: The lifelong infection by varicelloviruses is characterized by a fine balance between the host immune response and immune evasion strategies used by these viruses. Virus-derived peptides are presented to cytotoxic T lymphocytes by major histocompatibility complex (MHC) class I molecules. The transporter associated with antigen processing (TAP) transports the peptides from the cytosol into the endoplasmic reticulum, where the loading of MHC-I molecules occurs. The varicelloviruses bovine herpesvirus 1 (BoHV-1), pseudorabies virus, and equid herpesviruses 1 and 4 have been found to encode a UL49.5 protein that inhibits TAP-mediated peptide transport. To investigate to what extent UL49.5-mediated TAP inhibition is conserved within the family of Alphaherpesvirinae, the homologs of another five varicelloviruses, one mardivirus, and one iltovirus were studied. The UL49.5 proteins of BoHV-5, bubaline herpesvirus 1, cervid herpesvirus 1, and felid herpesvirus 1 were identified as potent TAP inhibitors. The varicella-zoster virus and simian varicellovirus UL49.5 proteins fail to block TAP; this is not due to the absence of viral cofactors that might assist in this process, since cells infected with these viruses did not show reduced TAP function either. The UL49.5 homologs of the mardivirus Marek's disease virus 1 and the iltovirus infectious laryngotracheitis virus did not block TAP, suggesting that the capacity to inhibit TAP via UL49.5 has been acquired by varicelloviruses only. A phylogenetic analysis of viruses that inhibit TAP through their UL49.5 proteins reveals an interesting hereditary pattern, pointing toward the presence of this capacity in defined clades within the genus Varicellovirus.
    Journal of Virology 03/2011; 85(5):2351-63. · 5.08 Impact Factor
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    ABSTRACT: Herpesviruses escape elimination by cytotoxic T lymphocytes through specific interference with the antigen-presenting function of MHC class I (MHC I) molecules. The transporter associated with antigen processing (TAP) forms a bottleneck in the MHC I antigen presentation pathway. The fact that multiple viruses, especially herpesviruses, encode molecules blocking TAP function is a case in point. The action of these viral immuno evasins is usually potent and very specific, making these proteins valuable tools for studying the cell biology of antigen presentation, including alternative antigen processing pathways. Yet, no dedicated TAP inhibitor has been described for any of the mouse herpesviruses. To permit the use of immuno evasins derived from non-mouse herpesviruses in mouse models, we assessed the cross-species activity of four TAP inhibitors and one tapasin inhibitor in the context of three different mouse haplotypes, H-2(b), H-2(d), and H-2(k). Two of the four TAP inhibitors, the bovine herpesvirus 1-encoded UL49.5 and the human cytomegalovirus (HCMV)-encoded US6 protein, potently inhibited mouse TAP. ICP47 and BNLF2a, encoded by herpes simplexvirus 1 and Epstein-Barr virus, respectively, failed to inhibit TAP in all mouse cells tested. Previous work, however, demonstrated that US6 did not cross the mouse species barrier. We now show that substitution of the cysteine residue at position 108 was responsible for this lack of activity. The HCMV-encoded tapasin inhibitor US3 efficiently downregulated H-2(d) molecules on 3T3 cells, but not in other cell lines tested. Finally, we show that synthetic peptides comprising the functional domain of US6 can be exploited as a versatile TAP inhibitor. In conclusion, a complete overview is presented of the applicability of herpesvirus-encoded TAP and tapasin inhibitors in mouse cells of different genetic background.
    Molecular Immunology 03/2011; 48(6-7):835-45. · 2.65 Impact Factor
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    ABSTRACT: EBV, the prototypic human γ(1)-herpesvirus, persists for life in infected individuals, despite the presence of vigorous antiviral immunity. CTLs play an important role in the protection against viral infections, which they detect through recognition of virus-encoded peptides presented in the context of HLA class I molecules at the cell surface. The viral peptides are generated in the cytosol and are transported into the endoplasmic reticulum (ER) by TAP. The EBV-encoded lytic-phase protein BNLF2a acts as a powerful inhibitor of TAP. Consequently, loading of antigenic peptides onto HLA class I molecules is hampered, and recognition of BNLF2a-expressing cells by cytotoxic T cells is avoided. In this study, we characterize BNLF2a as a tail-anchored (TA) protein and elucidate its mode of action. Its hydrophilic N-terminal domain is located in the cytosol, whereas its hydrophobic C-terminal domain is inserted into membranes posttranslationally. TAP has no role in membrane insertion of BNLF2a. Instead, Asna1 (also named TRC40), a cellular protein involved in posttranslational membrane insertion of TA proteins, is responsible for integration of BNLF2a into the ER membrane. Asna1 is thereby required for efficient BNLF2a-mediated HLA class I downregulation. To optimally accomplish immune evasion, BNLF2a is composed of two specialized domains: its C-terminal tail anchor ensures membrane integration and ER retention, whereas its cytosolic N terminus accomplishes inhibition of TAP function. These results illustrate how EBV exploits a cellular pathway for TA protein biogenesis to achieve immune evasion, and they highlight the exquisite adaptation of this virus to its host.
    The Journal of Immunology 02/2011; 186(6):3594-605. · 5.52 Impact Factor

Publication Stats

5k Citations
606.64 Total Impact Points


  • 2009–2013
    • University Medical Center Utrecht
      • Department of Medical Microbiology
      Utrecht, Provincie Utrecht, Netherlands
  • 2012
    • Queensland Institute of Medical Research
      Brisbane, Queensland, Australia
  • 2001–2012
    • Leiden University Medical Centre
      • • Department of Molecular Cell Biology
      • • Department of Medical Microbiology
      Leiden, South Holland, Netherlands
    • Maastricht University
      • Medische Microbiologie
      Maastricht, Provincie Limburg, Netherlands
  • 2011
    • University Joseph Fourier - Grenoble 1
      Grenoble, Rhône-Alpes, France
    • National Institute of Allergy and Infectious Diseases
      Maryland, United States
  • 2007–2009
    • University of Birmingham
      • • School of Cancer Sciences
      • • Centre for War Studies
      Birmingham, ENG, United Kingdom
  • 2002
    • Academisch Medisch Centrum Universiteit van Amsterdam
      • Department of Experimental Immunology (EXIM)
      Amsterdam, North Holland, Netherlands
  • 1998–2001
    • Harvard Medical School
      • Department of Pathology
      Boston, Massachusetts, United States
  • 1997–2001
    • National Institute for Public Health and the Environment (RIVM)
      Utrecht, Utrecht, Netherlands
  • 1996–1997
    • Massachusetts Institute of Technology
      • Department of Biology
      Cambridge, MA, United States