Virally Infected Mouse Liver Endothelial Cells Trigger CD8+ T-Cell Immunity

Cytomegalovirus (CMV) is a ubiquitous beta-herpesvirus whose reactivation from latency is a major cause of morbidity and mortality in immunocompromised hosts. Mouse CMV (MCMV) is a well-established model virus to study virus-host interactions. We showed in this study that the CD8-independent antiviral function of myeloid dendritic cells (mDC) is biologically relevant for the inhibition of MCMV replication in vivo and in vitro. In vivo ablation of CD11c ؉ DC resulted in higher viral titers and increased susceptibility to MCMV infection in the first 3 days postinfection. We developed in vitro coculture systems in which we cocultivated MCMV-infected endothelial cells or fibroblasts with T cell subsets and/or dendritic cells. H uman cytomegalovirus (HCMV) is a betaherpesvirus which establishes a lifelong latent infection in immunocompetenthosts. Latent HCMV is present in the majority of people worldwide, but the primary infection is usually asymptomatic. The primary infection is well contained by the immune cells, such as natural killer (NK) cells and T cells, which also prevent viral reactivation from latency (1, 2).Their activation depends on cross talk with dendritic cells (DC) (3, 4), and this interaction plays an important role in CMV control (5-7). The direct effect of DC on viral replication remains, however, unclear.In immunocompromised hosts, like AIDS patients or people undergoing transplantation, the virus cannot be contained, and its reactivation from latency has been associated with severe disease (8). Therefore, to develop new therapeutic approaches against CMV disease, it is exceedingly important to understand the immune mechanisms that drive the virus into latency.Murine cytomegalovirus (MCMV) is a natural pathogen of the mouse. It shows numerous analogies in latency and reactivation to the human virus, and its genome displays substantial similarity to the HCMV one (9). Therefore, MCMV is a widely used model for CMV infection and immunity (10)(11)(12).During primary infection, MCMV infects various different cell types, such as macrophages and DC but also nonhematopoietic cells, including endothelial and epithelial cells (13). On the other hand, the establishment of latency appears to be restricted to certain cell types. Latent HCMV was found in blood monocytes and in progenitor cells of the myeloid lineage (14-19), whereas liver sinusoidal endothelial cells (LSEC) were shown to be a site of MCMV latency and reactivation (20, 21), although myeloid cells might also present a latent reservoir in the mouse (22, 23).

Section: Discussionsupporting

confidence: 81%

Type I Interferon Released by Myeloid Dendritic Cells Reversibly Impairs Cytomegalovirus Replication by Inhibiting Immediate Early Gene Expression

Holzki

Dağ

Dekhtiarenko

et al. 2015

“…In addition, EC have recently been identified as sites of virus latency (65), and at least liver EC are able to directly stimulate a cytotoxic T-cell response (36). Using MCMV-⌬M94 constructs for conditional gene expression, we noticed substantial differences in the abilities of EC and Hc to activate a CD8 ϩ T-cell response.…”

Section: Discussionmentioning

confidence: 90%

“…ϩ T-cell response via cross presentation against MCMV infection (36). In addition to EC, other cell types seem to contribute to CD8 ϩ T-cell stimulation, as antigen expression in most infected cells led to a stronger T-cell response than expression in infected EC only.…”

Section: Discussionmentioning

confidence: 99%

A Spread-Deficient Cytomegalovirus for Assessment of First-Target Cells in Vaccination

Mohr

Arapović

Mühlbach

et al. 2010

Self Cite

Human cytomegalovirus (HCMV) is a human pathogen that causes severe disease primarily in the immunocompromised or immunologically immature individual. To date, no vaccine is available. We describe use of a spread-deficient murine CMV (MCMV) as a novel approach for betaherpesvirus vaccination. To generate a spread-deficient MCMV, the conserved, essential gene M94 was deleted. Immunization with MCMV-⌬M94 is apathogenic and protective against wild-type challenge even in highly susceptible IFN␣␤R ؊/؊ mice. MCMV-⌬M94 was able to induce a robust CD4؉ and CD8 ؉ T-cell response as well as a neutralizing antibody response comparable to that induced by wild-type infection. Endothelial cells were identified as activators of CD8 ؉ T cells in vivo. Thus, the vaccination with a spread-deficient betaherpesvirus is a safe and protective strategy and allows the linkage between cell tropism and immunogenicity. Furthermore, genomes of MCMV-⌬M94 were present in lungs 12 months after infection, revealing first-target cells as sites of genome maintenance.

“…We employed such a strategy previously for the antigenic IE1 peptide of mCMV (79). We are not the first to have generated a recombinant mCMV that specifies SIINFEKL as a reporter peptide, but our concept differs in that mCMV-SIINFEKL, unlike the mCMV-Ova viruses (43,80), does not ectopically express the foreign protein ovalbumin as the source for the peptide. Instead, the nonessential but abundantly synthesized viral protein gp36.5/m164, an ER-resident type I glycoprotein expressed in the early (E) phase of the viral replicative cycle, was used as a carrier protein in which the 9-codon sequence of the D d -restricted immunodominant intrinsic peptide 167-AG PPRYSRI-175 (33, 35, 39) (amino acid positions are given relative to the start site of the primary translation product, p36) was replaced with the 8-codon sequence of SIINFEKL or, in the controls, SIINFEKA.…”

Section: Resultsmentioning

confidence: 99%

Immune Evasion Proteins of Murine Cytomegalovirus Preferentially Affect Cell Surface Display of Recently Generated Peptide Presentation Complexes

Lemmermann

Gergely

Böhm

et al. 2010

Self Cite

For recognition of infected cells by CD8 T cells, antigenic peptides are presented at the cell surface, bound to major histocompatibility complex class I (MHC-I) molecules. Downmodulation of cell surface MHC-I molecules is regarded as a hallmark function of cytomegalovirus-encoded immunoevasins. The molecular mechanisms by which immunoevasins interfere with the MHC-I pathway suggest, however, that this downmodulation may be secondary to an interruption of turnover replenishment and that hindrance of the vesicular transport of recently generated peptide-MHC (pMHC) complexes to the cell surface is the actual function of immunoevasins. Here we have used the model of murine cytomegalovirus (mCMV) infection to provide experimental evidence for this hypothesis. To quantitate pMHC complexes at the cell surface after infection in the presence and absence of immunoevasins, we generated the recombinant viruses mCMV-SIINFEKL and mCMV-⌬m06m152-SIINFEKL, respectively, expressing the K b -presented peptide SIINFEKL with early-phase kinetics in place of an immunodominant peptide of the viral carrier protein gp36.5/m164. The data revealed ϳ10,000 K b molecules presenting SIINFEKL in the absence of immunoevasins, which is an occupancy of ϳ10% of all cell surface K b molecules, whereas immunoevasins reduced this number to almost the detection limit. To selectively evaluate their effect on preexisting pMHC complexes, cells were exogenously loaded with SIINFEKL peptide shortly after infection with mCMV-SIINFEKA, in which endogenous presentation is prevented by an L174A mutation of the C-terminal MHC-I anchor residue. The data suggest that pMHC complexes present at the cell surface in advance of immunoevasin gene expression are downmodulated due to constitutive turnover in the absence of resupply. CD8 T cells recognize infected cells by interaction of theirT-cell receptor (TCR) with a cell surface presentation complex composed of a cognate antigenic peptide bound to a presenting allelic form of a major histocompatibility complex class I (MHC-I) glycoprotein (77,85,97,98). The number of such "peptide receptors" per cell has been estimated to be on the order of 10 5 to 10 6 for each MHC-I allomorph (for a review, see reference 82). Viral antigenic peptides are generated within infected cells by proteolytic processing of viral proteins, usually in the proteasome, and associate with nascent MHC-I proteins in the endoplasmic reticulum (ER) before the peptide-MHC (pMHC) complexes travel to the cell surface with the cellular vesicular flow (for reviews, see references 13, 87, 92, and 93). CD8 T cells have long been known to protect against cytomegalovirus (CMV) infection and disease in animal models (60, 72; reviewed in references 33 and 36) and in humans (9,61,67,75,76). As shown only recently in the murine CMV (mCMV) model of infection of immunocompromised mice by adoptive transfer of epitope-specific CD8 T cells, antiviral protection against CMV is indeed TCR mediated and epitope dependent. Specifically, memory cells purified by TCR-bas...