0000000000050264
AUTHOR
Rafaela Holtappels
Peptide Processing Is Critical for T-Cell Memory Inflation and May Be Optimized to Improve Immune Protection by CMV-Based Vaccine Vectors.
Cytomegalovirus (CMV) elicits long-term T-cell immunity of unparalleled strength, which has allowed the development of highly protective CMV-based vaccine vectors. Counterintuitively, experimental vaccines encoding a single MHC-I restricted epitope offered better immune protection than those expressing entire proteins, including the same epitope. To clarify this conundrum, we generated recombinant murine CMVs (MCMVs) encoding well-characterized MHC-I epitopes at different positions within viral genes and observed strong immune responses and protection against viruses and tumor growth when the epitopes were expressed at the protein C-terminus. We used the M45-encoded conventional epitope HGI…
Subdominant CD8 T-Cell Epitopes Account for Protection against Cytomegalovirus Independent of Immunodomination▿ †
ABSTRACTCytomegalovirus (CMV) infection continues to be a complication in recipients of hematopoietic stem cell transplantation (HSCT). Preexisting donor immunity is recognized as a favorable prognostic factor for the reconstitution of protective antiviral immunity mediated primarily by CD8 T cells. Furthermore, adoptive transfer of CMV-specific memory CD8 T (CD8-TM) cells is a therapeutic option for preventing CMV disease in HSCT recipients. Given the different CMV infection histories of donor and recipient, a problem may arise from an antigenic mismatch between the CMV variant that has primed donor immunity and the CMV variant acquired by the recipient. Here, we have used the BALB/c mouse…
Insufficient Antigen Presentation Due to Viral Immune Evasion Explains Lethal Cytomegalovirus Organ Disease After Allogeneic Hematopoietic Cell Transplantation.
Reactivation of latent cytomegalovirus (CMV) poses a clinical problem in transiently immunocompromised recipients of hematopoietic cell (HC) transplantation (HCT) by viral histopathology that results in multiple organ manifestations. Compared to autologous HCT and to syngeneic HCT performed with identical twins as HC donor and recipient, lethal outcome of CMV infection is more frequent in allogeneic HCT with MHC/HLA or minor histocompatibility loci mismatch between donor and recipient. It is an open question if a graft-versus-host (GvH) reaction exacerbates CMV disease, or if CMV exacerbates GvH disease (GvHD), or if interference is mutual. Here we have used a mouse model of experimental HC…
Early gene m18, a novel player in the immune response to murine cytomegalovirus
The identification of all antigenic peptides encoded by a pathogen, its T cell ‘immunome’, is a research aim for rational vaccine design. Screening of proteome-spanning peptide libraries or computational prediction is used to identify antigenic peptides recognized by CD8 T cells. Based on their high coding capacity, cytomegaloviruses (CMVs) could specify numerous antigenic peptides. Yet, current evidence indicates that the memory CD8 T cell response in a given haplotype is actually focused on a few viral proteins. CMVs actively interfere with antigen processing and presentation by the expression of immune evasion proteins. In the case of murine CMV (mCMV), these proteins are effectual in th…
Adoptive CD8 T Cell Control of Pathogens Cannot Be Improved by Combining Protective Epitope Specificities
Adoptive transfer of CD8 T cells has the potential to cure infectious or malignant diseases that are refractory to conventional chemotherapy. A practically important but still unanswered question is whether mixtures of protective CD8 T cells with different epitope specificities mediate more efficient effector cell functions than do the monospecific individual CD8 T cell populations. In this study, we have addressed this issue for models of viral and bacterial infection. CD8 T cell-mediated cytotoxicity in vitro and protection in vivo were assessed to test whether CD8 T cell lines cooperate in target cell lysis and control of infection, respectively. Our data clearly show that mixtures of cy…
Thy-1 (CD90) regulates the extravasation of leukocytes during inflammation.
Human Thy-1 (CD90) has been shown to mediate adhesion of inflammatory cells to activated microvascular endothelial cells via interaction with Mac-1 (CD11b/CD18) in vitro. Since there are no data showing the physiological relevance of Thy-1 for the recruitment of inflammatory cells in vivo, different inflammation models were investigated in Thy-1-deficient mice and littermate controls. In thioglycollate-induced peritonitis, the number of neutrophils and monocytes was significantly diminished in Thy-1-deficient mice. During acute lung inflammation, the extravasation of eosinophils and monocytes into the lung was significantly reduced in Thy-1-deficient mice. Moreover, during chronic lung infl…
Control of cytomegalovirus in bone marrow transplantation chimeras lacking the prevailing antigen-presenting molecule in recipient tissues rests primarily on recipient-derived CD8 T cells
ABSTRACT Cytomegalovirus (CMV) infection during the transient immunodeficiency after bone marrow transplantation (BMT) develops into disease unless antiviral CD8 T cells are restored in due course. Histoincompatibility between donor and recipient is associated with increased risk. Complications may include a rejection response against the foreign major histocompatibility complex (MHC) antigens and a lack of antiviral control resulting from a misfit between donor-derived T cells and the antigenic viral peptides presented in recipient tissues. Here we have established a murine model of CMV disease after experimental BMT performed across a single MHC class I disparity. Specifically, BALB/c bon…
Immunodominant Cytomegalovirus Epitopes Suppress Subdominant Epitopes in the Generation of High-Avidity CD8 T Cells
CD8+ T-cell responses to pathogens are directed against infected cells that present pathogen-encoded peptides on MHC class-I molecules. Although natural responses are polyclonal, the spectrum of peptides that qualify for epitopes is remarkably small even for pathogens with high coding capacity. Among those few that are successful at all, a hierarchy exists in the magnitude of the response that they elicit in terms of numbers of CD8+ T cells generated. This led to a classification into immunodominant and non-immunodominant or subordinate epitopes, IDEs and non-IDEs, respectively. IDEs are favored in the design of vaccines and are chosen for CD8+ T-cell immunotherapy. Using murine cytomegalov…
Coincident airway exposure to low-potency allergen and cytomegalovirus sensitizes for allergic airway disease by viral activation of migratory dendritic cells
Despite a broad cell-type tropism, cytomegalovirus (CMV) is an evidentially pulmonary pathogen. Predilection for the lungs is of medical relevance in immunocompromised recipients of hematopoietic cell transplantation, in whom interstitial CMV pneumonia is a frequent and, if left untreated, fatal clinical manifestation of human CMV infection. A conceivable contribution of CMV to airway diseases of other etiology is an issue that so far attracted little medical attention. As the route of primary CMV infection upon host-to-host transmission in early childhood involves airway mucosa, coincidence of CMV airway infection and exposure to airborne environmental antigens is almost unavoidable. For i…
CD8 T Cells Control Cytomegalovirus Latency by Epitope-Specific Sensing of Transcriptional Reactivation
ABSTRACT During murine cytomegalovirus (mCMV) latency in the lungs, most of the viral genomes are transcriptionally silent at the major immediate-early locus, but rare and stochastic episodes of desilencing lead to the expression of IE1 transcripts. This low-frequency but perpetual expression is accompanied by an activation of lung-resident effector-memory CD8 T cells specific for the antigenic peptide 168-YPHFMPTNL-176, which is derivedfrom the IE1 protein. These molecular and immunological findings were combined in the “silencing/desilencing and immune sensing hypothesis” of cytomegalovirus latency and reactivation. This hypothesis proposes that IE1 gene expression proceeds to cell surfac…
Experimental Preemptive Immunotherapy of Murine Cytomegalovirus Disease with CD8 T-Cell Lines Specific for ppM83 and pM84, the Two Homologs of Human Cytomegalovirus Tegument Protein ppUL83 (pp65)
ABSTRACTCD8 T cells are the principal antiviral effectors controlling cytomegalovirus (CMV) infection. For human CMV, the virion tegument protein ppUL83 (pp65) has been identified as a source of immunodominant peptides and is regarded as a candidate for cytoimmunotherapy and vaccination. Two sequence homologs of ppUL83 are known for murine CMV, namely the virion protein ppM83 (pp105) expressed late in the viral replication cycle and the nonstructural protein pM84 (p65) expressed in the early phase. Here we show that ppM83, unlike ppUL83, is not delivered into the antigen presentation pathway after virus penetration before or in absence of viral gene expression, while other virion proteins o…
Immune Evasion Proteins Enhance Cytomegalovirus Latency in the Lungs
ABSTRACT CD8 T cells control cytomegalovirus (CMV) infection in bone marrow transplantation recipients and persist in latently infected lungs as effector memory cells for continuous sensing of reactivated viral gene expression. Here we have addressed the question of whether viral immunoevasins, glycoproteins that specifically interfere with antigen presentation to CD8 T cells, have an impact on viral latency in the murine model. The data show that deletion of immunoevasin genes in murine CMV accelerates the clearance of productive infection during hematopoietic reconstitution and leads to a reduced latent viral genome load, reduced latency-associated viral transcription, and a lower inciden…
Virally Infected Mouse Liver Endothelial Cells Trigger CD8+ T-Cell Immunity
Background & Aims Dendritic cell activation through ligation of pattern recognition receptors leading to full functional maturation causes induction of CD8 + T-cell immunity through increased delivery of costimulatory signals instead of tolerance. Here we investigate whether organ-resident antigen-presenting cells, such as liver sinusoidal endothelial cells (LSECs), also switch from tolerogenic to immunogenic CD8 + T-cell activation upon such stimulation. Methods Murine LSECs were isolated by immunomagnetic separation and analyzed for functional maturation upon triggering pattern recognition receptors or viral infection employing gene expression analysis and T cell coculture assays. In vivo…
Superresolution imaging of biological nanostructures by spectral precision distance microscopy
For the improved understanding of biological systems on the nanoscale, it is necessary to enhance the resolution of light microscopy in the visible wavelength range beyond the limits of conventional epifluorescence microscopy (optical resolution of about 200 nm laterally, 600 nm axially). Recently, various far-field methods have been developed allowing a substantial increase of resolution ("superresolution microscopy", or "lightoptical nanoscopy"). This opens an avenue to 'nano-image' intact and even living cells, as well as other biostructures like viruses, down to the molecular detail. Thus, it is possible to combine light optical spatial nanoscale information with ultrastructure analyses…
Highly protective in vivo function of cytomegalovirus IE1 epitope-specific memory CD8 T cells purified by T-cell receptor-based cell sorting.
ABSTRACTReconstitution of antiviral CD8 T cells is essential for controlling cytomegalovirus (CMV) infection after bone marrow transplantation. Accordingly, polyclonal CD8 T cells derived from BALB/c mice infected with murine CMV protect immunocompromised adoptive transfer recipients against CMV disease. The protective population comprises CD8 T cells with T-cell receptors (TCRs) specific for defined and for as-yet-unknown viral epitopes, as well as a majority of nonprotective cells with unrelated specificities. Defined epitopes include IE1/m123 and m164, which are immunodominant in terms of the magnitude of the CD8 T-cell response, and a panel of subordinate epitopes (m04, m18, M45, M83, a…
Inactivation of an Enveloped Virus by Immobilized Antimicrobial Peptides.
Infections caused by viruses are difficult to treat due to their life cycle, which depends on the replication machinery of the respective host cells. Commonly used antiviral strategies are based upon the application of, e.g., entry inhibitors and other compounds that interfere with virus replication. Besides possible side effects, the rapid occurrence of viral resistance poses a great challenge. Antimicrobial peptides (AMPs), as a component of the innate immunity, are able to kill bacteria and fungi and, in addition, may inactivate enveloped viruses. Many AMPs exert their biological function by impairing microbial and viral membranes. As a result, membrane integrity is lost, leading to bact…
Dynamic Antigen Presentation Patterns of Listeria monocytogenes-Derived CD8 T Cell Epitopes In Vivo
Abstract Little information exists regarding the presentation of antigenic peptides in infected tissues. In this study the in vivo presentation of four different CD8 T cell epitopes of Listeria monocytogenes was monitored. Peptide presentation was measured by a new, highly sensitive, ex vivo Ag presentation assay that was based on the testing of freshly isolated cells from infected spleens with peptide-specific CD8 T cell lines in an IFN-γ-specific ELISPOT assay. Remarkably, the peptide presentation pattern of splenocytes and that of macrophages purified from spleens of L. monocytogenes-infected mice were different from those of in vitro infected macrophage-like cell lines. The in vivo Ag p…
Enrichment of Immediate-Early 1 (m123/pp89) Peptide-Specific CD8 T Cells in a Pulmonary CD62LloMemory-Effector Cell Pool during Latent Murine Cytomegalovirus Infection of the Lungs
ABSTRACTInterstitial cytomegalovirus (CMV) pneumonia is a clinically relevant complication in recipients of bone marrow transplantation (BMT). Recent data for a model of experimental syngeneic BMT and concomitant infection of BALB/c mice with murine CMV (mCMV) have documented the persistence of tissue-resident CD8 T cells after clearance of productive infection of the lungs (J. Podlech, R. Holtappels, M.-F. Pahl-Seibert, H.-P. Steffens, and M. J. Reddehase, J. Virol. 74:7496–7507, 2000). It was proposed that these cells represent antiviral “standby” memory cells whose functional role might be to help prevent reactivation of latent virus. The pool of pulmonary CD8 T cells was composed of two…
Cytomegalovirus Misleads Its Host by Priming of CD8 T Cells Specific for an Epitope Not Presented in Infected Tissues
Cytomegaloviruses (CMVs) code for several proteins that inhibit the presentation of antigenic peptides to CD8 T cells. Although the molecular mechanisms of CMV interference with the major histocompatibility complex class I pathway are long understood, surprisingly little evidence exists to support a role in vivo. Here we document the first example of the presentation of an antigenic peptide being blocked by a CMV immune evasion protein in organs relevant to CMV disease. Although this Db-restricted peptide, which is derived from the antiapoptotic protein M45 of murine CMV (mCMV), is classified as an immunodominant peptide based on response magnitude and long-term memory, adoptive transfer of…
Therapeutic Vaccination of Hematopoietic Cell Transplantation Recipients Improves Protective CD8 T-Cell Immunotherapy of Cytomegalovirus Infection
Reactivation of latent cytomegalovirus (CMV) endangers the therapeutic success of hematopoietic cell transplantation (HCT) in tumor patients due to cytopathogenic virus spread that leads to organ manifestations of CMV disease, to interstitial pneumonia in particular. In cases of virus variants that are refractory to standard antiviral pharmacotherapy, immunotherapy by adoptive cell transfer (ACT) of virus-specific CD8+ T cells is the last resort to bridge the “protection gap” between hematoablative conditioning for HCT and endogenous reconstitution of antiviral immunity. We have used the well-established mouse model of CD8+ T-cell immunotherapy by ACT in a setting of experimental HCT and mu…
Stalemating a clever opportunist: lessons from murine cytomegalovirus.
Abstract Cytomegaloviruses and their specific hosts have come to an arrangement that avoids disease but allows the viruses to persist in the individual host and to spread in the host species. Recent work has uncovered some of the molecular details of this evolutionary “contract for mutual survival.” Cytomegaloviruses encode proteins, referred to as “immunoevasins,” which are specifically committed to subvert the immune defense of the host for evading virus elimination. In reply, the hosts have evolved countermeasures to overcome the viral immunoevasins and present antigenic peptides to an extent that is sufficient for confining virus replication to below a harmful level. Accordingly, cytome…
Antigen-presenting cells of haematopoietic origin prime cytomegalovirus-specific CD8 T-cells but are not sufficient for driving memory inflation during viral latency
Expansion of the CD8 T-cell memory pool, also known as ‘memory inflation’, for certain but not all viral epitopes in latently infected host tissues is a special feature of the immune response to cytomegalovirus. The Ld-presented murine cytomegalovirus (mCMV) immediate–early (IE) 1 peptide is the prototype of an epitope that is associated with memory inflation. Based on the detection of IE1 transcripts in latently infected lungs it was previously proposed that episodes of viral gene expression and antigenic activity due to desilencing of a limited number of viral genes may drive epitope-specific memory inflation. This would imply direct antigen presentation through latently infected host tis…
Processing and Presentation of Murine Cytomegalovirus pORFm164-Derived Peptide in Fibroblasts in the Face of All Viral Immunosubversive Early Gene Functions
ABSTRACTCD8 T cells are the principal effector cells in the resolution of acute murine cytomegalovirus (mCMV) infection in host organs. This undoubted antiviral and protective in vivo function of CD8 T cells appeared to be inconsistent with immunosubversive strategies of the virus effected by early (E)-phase genesm04,m06, andm152. The so-called immune evasion proteins gp34, gp48, and gp37/40, respectively, were found to interfere with peptide presentation at different steps in the major histocompatibility complex (MHC) class I pathway of antigen processing and presentation in fibroblasts. Accordingly, they were proposed to prevent recognition and lysis of infected fibroblasts by cytolytic T…
Reconstitution of the Complement Function in C1q-Deficient (C1qa−/−) Mice with Wild-Type Bone Marrow Cells
Abstract Besides Ab-independent and Ab-dependent activation of the complement classical pathway in host defense, C1q plays a key role in the processing of immune complexes and in the clearance of apoptotic cells. In humans, C1q deficiency leads to systemic lupus erythematosus-like symptoms in over 90% of the cases, thus making this defect a strong disease susceptibility factor. Similarly, C1q-deficient mice (C1qa−/−) develop systemic lupus erythematosus-like symptoms, such as autoantibodies and glomerulonephritis. We have previously provided evidence that C1q is produced by cells of the monocyte-macrophage lineage. In this study, we have tested whether transplantation of bone marrow cells w…
In vivo impact of cytomegalovirus evasion of CD8 T-cell immunity: Facts and thoughts based on murine models
Cytomegaloviruses (CMVs) co-exist with their respective host species and have evolved to avoid their elimination by the hosts' immune effector mechanisms and to persist in a non-replicative state, known as viral latency. There is evidence to suggest that latency is nevertheless a highly dynamic condition during which episodes of viral gene desilencing, which can be viewed as incomplete reactivations, cause intermittent antigenic activity that stimulates CD8 memory-effector T cells and drives their clonal expansion. These T cells are supposed to terminate reactivation before completion of the productive viral cycle. In this view, CMVs do not "evade" their respective host's immune response bu…
Macrophages Escape Inhibition of Major Histocompatibility Complex Class I-Dependent Antigen Presentation by Cytomegalovirus
ABSTRACTThe mouse cytomegalovirus (MCMV)m152- andm06-encoded glycoproteins gp40 and gp48, respectively, independently downregulate major histocompatibility complex (MHC) class I surface expression during the course of productive MCMV infection in fibroblasts. As a result, presentation of an immediate-early protein pp89-derived nonapeptide toH-2Ld-restricted CD8+cytotoxic T cells is completely prevented in fibroblasts. Here we demonstrate that MCMV-infected primary bone marrow macrophages and the macrophage cell line J774 constitutively present pp89 peptides during permissive MCMV infection to cytotoxic T lymphocytes (CTL). In contrast to fibroblasts, expression of them152andm06genes in macr…
Control of Murine Cytomegalovirus Infection by γδ T Cells
Infections with cytomegalovirus (CMV) can cause severe disease in immunosuppressed patients and infected newborns. Innate as well as cellular and humoral adaptive immune effector functions contribute to the control of CMV in immunocompetent individuals. None of the innate or adaptive immune functions are essential for virus control, however. Expansion of γδ T cells has been observed during human CMV (HCMV) infection in the fetus and in transplant patients with HCMV reactivation but the protective function of γδ T cells under these conditions remains unclear. Here we show for murine CMV (MCMV) infections that mice that lack CD8 and CD4 αβ-T cells as well as B lymphocytes can control a MCMV i…
Non-cognate bystander cytolysis by clonal epitope-specific CTL lines through CD28-CD80 interaction inhibits antibody production: A potential caveat to CD8 T-cell immunotherapy.
Abstract Adoptive transfer of virus epitope-specific CD8 T cells is an immunotherapy option to control cytomegalovirus (CMV) infection and prevent CMV organ disease in immunocompromised solid organ transplantation (SOT) and hematopoietic cell transplantation (HCT) recipients. The therapy aims at an early, selective recognition and cytolysis of infected cells for preventing viral spread in tissues with no adverse immunopathogenic side-effects by attack of uninfected bystander cells. Here we describe that virus epitope-specific, cloned T-cell lines lyse target cells that present the cognate antigenic peptide to the TCR, but simultaneously have the potential to lyse uninfected cells expressing…
Proliferation and MHC-unrestricted bystander lysis by virus-specific cytotoxic T cells following antigen self-presentation.
Cytotoxic T cells (CTL) not only act as effector cells, but can also serve as antigen-presenting cells (APC) for other CTL due to their expression of major histocompatibility complex (MHC) class I molecules. In the present study we show that independently derived CTL lines (CTLL) with specificity for an L(d)-presented nonapeptide corresponding to amino acids 168-176 of the immediate-early 1 (IE1) protein of murine cytomegalovirus not only lyse syngeneic but also allogeneic target cells, if the peptide is present during the cytolytic assay. Whereas a short peptide pulse is sufficient to render syngeneic cells susceptible to lysis, continued presence of soluble peptide is mandatory for the ly…
Consequence of Histoincompatibility beyond GvH-Reaction in Cytomegalovirus Disease Associated with Allogeneic Hematopoietic Cell Transplantation: Change of Paradigm
Hematopoietic cell (HC) transplantation (HCT) is the last resort to cure hematopoietic malignancies that are refractory to standard therapies. Hematoablative treatment aims at wiping out tumor cells as completely as possible to avoid leukemia/lymphoma relapse. This treatment inevitably co-depletes cells of hematopoietic cell lineages, including differentiated cells that constitute the immune system. HCT reconstitutes hematopoiesis and thus, eventually, also antiviral effector cells. In cases of an unrelated donor, that is, in allogeneic HCT, HLA-matching is performed to minimize the risk of graft-versus-host reaction and disease (GvHR/D), but a mismatch in minor histocompatibility antigens …
Murine model of interstitial cytomegalovirus pneumonia in syngeneic bone marrow transplantation: persistence of protective pulmonary CD8-T-cell infiltrates after clearance of acute infection.
ABSTRACTInterstitial pneumonia (IP) is a severe organ manifestation of cytomegalovirus (CMV) disease in the immunocompromised host, in particular in recipients of bone marrow transplantation (BMT). Diagnostic criteria for the definition of CMV-IP include clinical evidence of pneumonia together with CMV detected in bronchoalveolar lavage or lung biopsy. We have used the model of syngeneic BMT and simultaneous infection of BALB/c mice with murine CMV for studying the pathogenesis of CMV-IP by controlled longitudinal analysis. A disseminated cytopathic infection of the lungs with fatal outcome was observed only when reconstituting CD8 T cells were depleted. Neither CD8 nor CD4 T cells mediated…
The Efficacy of Antigen Processing Is Critical for Protection against Cytomegalovirus Disease in the Presence of Viral Immune Evasion Proteins▿
ABSTRACT Cytomegaloviruses (CMVs) code for immunoevasins, glycoproteins that are specifically dedicated to interfere with the presentation of antigenic peptides to CD8 T cells. Nonetheless, the biological outcome is not an immune evasion of the virus, since CD8 T cells can control CMV infection even when immunoevasins are expressed. Here, we compare the processing of a protective and a nonprotective epitope derived from the same viral protein, the antiapoptotic protein M45 in the murine model. The data provide evidence to conclude that protection against CMVs critically depends on antigenic peptides generated in an amount sufficient to exhaust the inhibitory capacity of immunoevasins.
Reconstitution of CD8 T cells is essential for the prevention of multiple-organ cytomegalovirus histopathology after bone marrow transplantation.
Cytomegalovirus (CMV) infection in the period of temporary immunodeficiency after haematoablative treatment and bone marrow transplantation (BMT) is associated with a risk of graft failure and multiple-organ CMV disease. The efficacy of immune system reconstitution is decisive for the prevention of CMV pathogenesis after BMT. Previous data in murine model systems have documented a redundancy in the immune effector mechanisms controlling CMV. CD8 T cells proved to be relevant but not irreplaceable as antiviral effectors. Specifically, in a state of long-term in vivo depletion of the CD8 T-cell subset, CD4 T cells were educed to become deputy effectors controlling CMV by a mechanism involving…
The Putative Natural Killer Decoy Early Genem04(gp34) of Murine Cytomegalovirus Encodes an Antigenic Peptide Recognized by Protective Antiviral CD8 T Cells
ABSTRACTSeveral early genes of murine cytomegalovirus (MCMV) encode proteins that mediate immune evasion by interference with the major histocompatibility complex class I (MHC-I) pathway of antigen presentation to cytolytic T lymphocytes (CTL). Specifically, them152gene product gp37/40 causes retention of MHC-I molecules in the endoplasmic reticulum (ER)-Golgi intermediate compartment. Lack of MHC-I on the cell surface should activate natural killer (NK) cells recognizing the “missing self.” The retention, however, is counteracted by them04early gene product gp34, which binds to folded MHC-I molecules in the ER and directs the complex to the cell surface. It was thus speculated that gp34 mi…
The Immune Evasion Paradox: Immunoevasins of Murine Cytomegalovirus Enhance Priming of CD8 T Cells by Preventing Negative Feedback Regulation▿
ABSTRACTCytomegaloviruses express glycoproteins that interfere with antigen presentation to CD8 T cells. Although the molecular modes of action of these “immunoevasins” differ between cytomegalovirus species, the convergent biological outcome is an inhibition of the recognition of infected cells. In murine cytomegalovirus, m152/gp40 retains peptide-loaded major histocompatibility complex class I molecules in acis-Golgi compartment, m06/gp48 mediates their vesicular sorting for lysosomal degradation, and m04/gp34, although not an immunoevasin in its own right, appears to assist in the concerted action of all three molecules. Using the Ld-restricted IE1 epitope YPHFMPTNL in the BALB/c mouse m…
Cytomegalovirus Encodes a Positive Regulator of Antigen Presentation
ABSTRACT Murine cytomegalovirus encodes three regulators of antigen presentation to antiviral CD8 T cells. According to current paradigms, all three regulators are committed to the inhibition of the presentation of antigenic peptides. Whereas m152/gp40 catalyzes the retention of peptide-loaded major histocompatibility complex (MHC) class I molecules in a cis -Golgi compartment, m06/gp48 binds stably to class I molecules and directs them into the cellular cargo-sorting pathway of lysosomal degradation. Regulator m04/gp34 also binds stably to class I molecules, but unlike m152 and m06, it does not downmodulate MHC class I cell surface expression. It has entered the literature as a direct inhi…
Animal models: Murine cytomegalovirus
Publisher Summary This chapter focuses on murine cytomegalovirus (CMV) animal models. Multiple-organ cytomegalovirus disease, interstitial pneumonia in particular, is a major concern in the therapy of hematopoietic malignancies by hematoablative treatment and bone marrow transplantation (BMT). Human CMV (hCMV) is the prototype member of the subfamily, Betaherpesvirinae, of the virus family, Herpesviridae . Its genome is a linear, double-stranded DNA with a coding capacity of ca. 165 open reading frames. During an aeon of co-evolution, CMVs have adapted themselves to their respective hosts; therefore, CMV biology is most reliably studied in a natural virus-host combination. Even though hCMV …
TCR-Ligand koff rate correlates with the protective capacity of antigen-specific CD8+ T cells for adoptive transfer.
Adoptive immunotherapy is a promising therapeutic approach for the treatment of chronic infections and cancer. Thereby, T cells within a certain range of high avidity for their cognate ligand are believed to be most effective. T cell receptor (TCR) transfer experiments indicate that a major part of avidity is hard-wired within the structure of the TCR. Unfortunately, rapid measurement of structural avidity of TCRs is difficult on living T cells. We developed a technology, where dissociation (koff-rate) of truly monomeric peptide major histocompatibility complex (pMHC) molecules bound to surface expressed TCRs can be monitored by real-time microscopy in a highly reliable manner. A first eval…
In Vivo Replication of Recombinant Murine Cytomegalovirus Driven by the Paralogous Major Immediate-Early Promoter-Enhancer of Human Cytomegalovirus
ABSTRACT Transcription of the major immediate-early (MIE) genes of cytomegaloviruses (CMV) is driven by a strong promoter-enhancer (MIEPE) complex. Transactivator proteins encoded by these MIE genes are essential for productive infection. Accordingly, the MIEPE is a crucial control point, and its regulation by activators and repressors is pertinent to virus replication. Since the MIEPE contains multiple regulatory elements, it was reasonable to assume that specific sequence motifs are irreplaceable for specifying the cell-type tropism and replication pattern. Recent work on murine CMV infectivity (A. Angulo, M. Messerle, U. H. Koszinowski, and P. Ghazal, J. Virol. 72:8502–8509, 1998) has do…
Revisiting CD8 T-cell ‘Memory Inflation’: New Insights with Implications for Cytomegaloviruses as Vaccine Vectors
Murine models of cytomegalovirus (CMV) infection have revealed an exceptional kinetics of the immune response. After resolution of productive infection, transient contraction of the viral epitope-specific CD8 T-cell pool was found to be followed by a pool expansion specific for certain viral epitopes during non-productive &lsquo
Two Antigenic Peptides from Genes m123 and m164 of Murine Cytomegalovirus Quantitatively Dominate CD8 T-Cell Memory in the H-2 d Haplotype
ABSTRACT The importance of CD8 T cells for the control of cytomegalovirus (CMV) infection has raised interest in the identification of immunogenic viral proteins as candidates for vaccination and cytoimmunotherapy. The final aim is to determine the viral “immunome” for any major histocompatibility complex class I molecule by antigenicity screening of proteome-derived peptides. For human CMV, there is a limitation to this approach: the T cells used as responder cells for peptide screening are usually memory cells that have undergone in vivo selection. On this basis, pUL83 (pp65) and pUL123 (IE1 or pp68 to -72) were classified as immunodominant proteins. It is an open question whether this li…
Preemptive CD8 T-Cell Immunotherapy of Acute Cytomegalovirus Infection Prevents Lethal Disease, Limits the Burden of Latent Viral Genomes, and Reduces the Risk of Virus Recurrence
ABSTRACT In the immunocompetent host, primary cytomegalovirus (CMV) infection is resolved by the immune response without causing overt disease. The viral genome, however, is not cleared but is maintained in a latent state that entails a risk of virus recurrence and consequent organ disease. By using murine CMV as a model, we have shown previously that multiple organs harbor latent CMV and that reactivation occurs with an incidence that is determined by the viral DNA load in the respective organ (M. J. Reddehase, M. Balthesen, M. Rapp, S. Jonjic, I. Pavic, and U. H. Koszinowski. J. Exp. Med. 179:185–193, 1994). This predicts that a therapeutic intervention capable of limiting the load of lat…
Identification of a Kd-restricted antigenic peptide encoded by murine cytomegalovirus early gene M84
The two sister cytomegaloviruses (CMVs), human and murine CMV, have both evolved immune evasion functions that interfere with the major histocompatibility complex class I (MHC-I) pathway of antigen processing and presentation and are effectual in the early (E) phase of virus gene expression. However, studies on murine CMV have shown that E-phase immune evasion is leaky. An E-phase protein involved in immune evasion, namely m04-gp34, was found to simultaneously account for an antigenic peptide presented by the MHC-I molecule Dd. Recent work has demonstrated the induction of protective immunity specific for the E-phase protein M84-p65, one of two murine CMV homologues of the human CMV matrix …
Exogenous TNFR2 activation protects from acute GvHD via host T reg cell expansion
Activation of TNFR2 with a novel agonist expands T reg cells in vivo and protects allo-HCT recipients from acute GvHD while sparing antilymphoma and antiinfectious properties of transplanted donor T cells.
Control of murine cytomegalovirus in the lungs: Relative but not absolute immunodominance of the immediate-early 1 nonapeptide during the antiviral cytolytic T-lymphocyte response in pulmonary infiltrates
Effective control by the immune system is a hallmark of cytomegalovirus (CMV) infection. Accordingly, human CMV disease is a medical problem restricted to the immunologically immature or immunocompromised host (for a review, see reference 21). Murine models have implicated natural killer (NK) cells and CD8 T cells in the control of CMV infection. While NK cells mediate early protection in genetically resistant mouse inbred strains (4, 5, 31, 51), CD8 T cells establish enduring protective memory and function as principal antiviral effectors in susceptible strains (31). Specifically, in the BALB/c strain, major histocompatibility complex (MHC) class I-restricted antiviral CD8 T cells resolve …
CD8 T-Cell Immunotherapy of Cytomegalovirus Disease in the Murine Model
Publisher Summary Cytomegaloviruses (CMVs) are conditional pathogens that are strictly species specific and are usually well controlled in their respective mammalian hosts by the effector mechanisms of both innate and adaptive immunity. Human CMV (hCMV) is mostly acquired perinatally as well as in early childhood and is transmitted, for instance, through breast milk and saliva. Whilst the immune response in an immunocompetent host prevents an overt CMV disease and rapidly terminates the productive acute infection, viral genome is maintained in most tissues for the life span of the infected host in a state known as viral latency. Latency implies that infectious virions are no longer produced…