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Cytomegalovirus misleads its host by priming of CD8 T cells specific for an epitope not presented in infected tissues.

Holtappels R, Podlech J, Pahl-Seibert MF, Jülch M, Thomas D, Simon CO, Wagner M, Reddehase MJ - J. Exp. Med. (2003)

Bottom Line: 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.Notably, the same cells protected C57BL/6 mice infected with an mCMV mutant in which immune evasion protein m152/gp40 is deleted.These data indicate that direct presentation or cross-presentation of an antigenic peptide by professional antigen-presenting cells can efficiently prime CD8 T cells that fail in protection against CMV organ disease because m152/gp40 prevents presentation of this peptide in pathogenetically relevant tissue cells.

View Article: PubMed Central - PubMed

Affiliation: Institute for Virology, Johannes Gutenberg-University, Hochhaus am Augustusplatz, 55101 Mainz, Germany.

ABSTRACT
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 M45 epitope-specific CD8 T cells did not protect against infection with wild-type mCMV. Notably, the same cells protected C57BL/6 mice infected with an mCMV mutant in which immune evasion protein m152/gp40 is deleted. These data indicate that direct presentation or cross-presentation of an antigenic peptide by professional antigen-presenting cells can efficiently prime CD8 T cells that fail in protection against CMV organ disease because m152/gp40 prevents presentation of this peptide in pathogenetically relevant tissue cells.

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M45 peptide is only presented in cells infected with immune evasion gene deletion mutants. An M45 epitope-specific, polyclonal CTLL was derived from mCMV-WT–infected C57BL/6 mice. (A) Cytolytic effector function and affinity of M45-CTLL. EL4 target cells were pulsed with the indicated molar concentrations of M45 peptide. Lysis of target cells was measured at an E/T ratio of 15. Dot symbols represent mean values of triplicate assay cultures. (B) Presentation of M45 peptide measured by the number of M45-CTLs that respond in the ELISPOT assay. For stimulator cells and statistical analysis, see the legend of Fig. 1.
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fig2: M45 peptide is only presented in cells infected with immune evasion gene deletion mutants. An M45 epitope-specific, polyclonal CTLL was derived from mCMV-WT–infected C57BL/6 mice. (A) Cytolytic effector function and affinity of M45-CTLL. EL4 target cells were pulsed with the indicated molar concentrations of M45 peptide. Lysis of target cells was measured at an E/T ratio of 15. Dot symbols represent mean values of triplicate assay cultures. (B) Presentation of M45 peptide measured by the number of M45-CTLs that respond in the ELISPOT assay. For stimulator cells and statistical analysis, see the legend of Fig. 1.

Mentions: The T cell line M45-CTLL was generated by repetitive restimulation of spleen-derived memory cells with M45 peptide. After the fifth round of stimulation, M45-specific cytolytic activity (Fig. 2 A) and induction of IFN-γ secretion (Fig. 2 B) were tested. Half-maximal lysis was observed with target cells pulsed with M45 peptide at a concentration of 10−12 M (Fig. 2 A), which indicates an affinity that is ∼100-fold higher than that of the in vivo protective IE1-CTLL and m164-CTLL specific for the two immunodominant mCMV peptides in the H-2d haplotype (11). A high and comparable proportion of the cells secreted IFN-γ after CD3ɛ-mediated signaling and after stimulation with the cognate peptide, which indicates monospecificity (Fig. 2 B). Despite the high sensitivity of M45-CTLs, fibroblasts infected with mCMV-WT were not recognized. In contrast, peptide presentation occurred in fibroblasts infected with the mutant viruses mCMV-Δm152 and mCMV-Δm04+06+152, but did not engage all M45-specific cells. This finding shows that stimulation with infected fibroblasts, even after deletion of the three immunoevasins, underestimates the number of epitope-specific effector cells.


Cytomegalovirus misleads its host by priming of CD8 T cells specific for an epitope not presented in infected tissues.

Holtappels R, Podlech J, Pahl-Seibert MF, Jülch M, Thomas D, Simon CO, Wagner M, Reddehase MJ - J. Exp. Med. (2003)

M45 peptide is only presented in cells infected with immune evasion gene deletion mutants. An M45 epitope-specific, polyclonal CTLL was derived from mCMV-WT–infected C57BL/6 mice. (A) Cytolytic effector function and affinity of M45-CTLL. EL4 target cells were pulsed with the indicated molar concentrations of M45 peptide. Lysis of target cells was measured at an E/T ratio of 15. Dot symbols represent mean values of triplicate assay cultures. (B) Presentation of M45 peptide measured by the number of M45-CTLs that respond in the ELISPOT assay. For stimulator cells and statistical analysis, see the legend of Fig. 1.
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Related In: Results  -  Collection

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fig2: M45 peptide is only presented in cells infected with immune evasion gene deletion mutants. An M45 epitope-specific, polyclonal CTLL was derived from mCMV-WT–infected C57BL/6 mice. (A) Cytolytic effector function and affinity of M45-CTLL. EL4 target cells were pulsed with the indicated molar concentrations of M45 peptide. Lysis of target cells was measured at an E/T ratio of 15. Dot symbols represent mean values of triplicate assay cultures. (B) Presentation of M45 peptide measured by the number of M45-CTLs that respond in the ELISPOT assay. For stimulator cells and statistical analysis, see the legend of Fig. 1.
Mentions: The T cell line M45-CTLL was generated by repetitive restimulation of spleen-derived memory cells with M45 peptide. After the fifth round of stimulation, M45-specific cytolytic activity (Fig. 2 A) and induction of IFN-γ secretion (Fig. 2 B) were tested. Half-maximal lysis was observed with target cells pulsed with M45 peptide at a concentration of 10−12 M (Fig. 2 A), which indicates an affinity that is ∼100-fold higher than that of the in vivo protective IE1-CTLL and m164-CTLL specific for the two immunodominant mCMV peptides in the H-2d haplotype (11). A high and comparable proportion of the cells secreted IFN-γ after CD3ɛ-mediated signaling and after stimulation with the cognate peptide, which indicates monospecificity (Fig. 2 B). Despite the high sensitivity of M45-CTLs, fibroblasts infected with mCMV-WT were not recognized. In contrast, peptide presentation occurred in fibroblasts infected with the mutant viruses mCMV-Δm152 and mCMV-Δm04+06+152, but did not engage all M45-specific cells. This finding shows that stimulation with infected fibroblasts, even after deletion of the three immunoevasins, underestimates the number of epitope-specific effector cells.

Bottom Line: 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.Notably, the same cells protected C57BL/6 mice infected with an mCMV mutant in which immune evasion protein m152/gp40 is deleted.These data indicate that direct presentation or cross-presentation of an antigenic peptide by professional antigen-presenting cells can efficiently prime CD8 T cells that fail in protection against CMV organ disease because m152/gp40 prevents presentation of this peptide in pathogenetically relevant tissue cells.

View Article: PubMed Central - PubMed

Affiliation: Institute for Virology, Johannes Gutenberg-University, Hochhaus am Augustusplatz, 55101 Mainz, Germany.

ABSTRACT
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 M45 epitope-specific CD8 T cells did not protect against infection with wild-type mCMV. Notably, the same cells protected C57BL/6 mice infected with an mCMV mutant in which immune evasion protein m152/gp40 is deleted. These data indicate that direct presentation or cross-presentation of an antigenic peptide by professional antigen-presenting cells can efficiently prime CD8 T cells that fail in protection against CMV organ disease because m152/gp40 prevents presentation of this peptide in pathogenetically relevant tissue cells.

Show MeSH
Related in: MedlinePlus