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Updated: Aug 6, 2026
Dissecting Innate Immune Signaling in Viral Evasion of Cytokine Production
Published on: March 2, 2014
Coordinated function of murine cytomegalovirus genes completely inhibits CTL lysis
Amelia K Pinto1, Michael W Munks, Ulrich H Koszinowski
1Oregon Health and Science University, Molecular Microbiology and Immunology, Portland, OR 97239, USA.
Abstract:
Murine CMV (MCMV) encodes three viral genes that interfere with Ag presentation (VIPRs) to CD8 T cells, m04, m06, and m152. Because the functional impact of these genes during normal infection of C57BL/6 mice is surprisingly modest, we wanted to determine whether the VIPRs are equally effective against the entire spectrum of H-2(b)-restricted CD8 T cell epitopes. We also wanted to understand how the VIPRs interact at a functional level. To address these questions, we used a panel of MCMV mutants lacking each VIPR in all possible combinations, and CTL specific for 15 H-2(b)-restricted MCMV epitopes. Only expression of all three MCMV VIPRs completely inhibited killing by CTL specific for all 15 epitopes, but removal of any one VIPR enabled lysis by at least some CTL. The dominant interaction between the VIPRs was cooperation: m06 increased the inhibition of lysis achieved by either m152 or m04. However, for 1 of 15 epitopes m04 functionally antagonized m152. There was little differential impact of any of the VIPRs on K(b) vs D(b), but a surprising degree of differential impact of the three VIPRs for different epitopes. These epitope-specific differences did not correlate with functional avidity, or with timing of VIPR expression in relation to Ag expression in the virus replication cycle. Although questions remain about the molecular mechanism and in vivo role of these genes, we conclude that the coordinated function of MCMV's three VIPRs results in a powerful inhibition of lysis of infected cells by CD8 T cells.
Insights
Murine cytomegalovirus (MCMV) uses three viral gene products (VIPRs) to block CD8 T cell immunity. Coordinated action of all three MCMV VIPRs is required for complete inhibition of T cell killing, highlighting their cooperative immune evasion.
Area of Science:
- Immunology
- Virology
- Molecular Biology
Background:
- Murine cytomegalovirus (MCMV) possesses three viral immune evasion genes, known as viral immune Презентация (VIPRs) - m04, m06, and m152.
- These VIPRs interfere with antigen presentation to CD8 T cells.
- The individual impact of these VIPRs during normal C57BL/6 mouse infection appears modest.
Purpose of the Study:
- To investigate the effectiveness of MCMV VIPRs against a broad range of H-2(b)-restricted CD8 T cell epitopes.
- To elucidate the functional interactions between the three MCMV VIPRs.
Main Methods:
- Utilized a panel of MCMV mutants lacking individual or combinations of VIPRs (m04, m06, m152).
- Employed cytotoxic T lymphocytes (CTLs) specific for 15 distinct H-2(b)-restricted MCMV epitopes.
- Assessed the inhibition of target cell lysis by CTLs in the presence of different VIPR combinations.
Main Results:
- Complete inhibition of CTL-mediated lysis against all 15 epitopes required the expression of all three MCMV VIPRs.
- Removal of any single VIPR allowed lysis by at least some CTLs.
- The VIPRs primarily exhibited cooperation, with m06 enhancing the inhibitory effect of m04 or m152.
- A single epitope showed functional antagonism between m04 and m152.
- VIPR effects showed significant epitope-specific differences but minimal differential impact between H-2K(b) and H-2D(b) alleles.
- Epitope-specific differences did not correlate with CTL functional avidity or VIPR expression timing.
Conclusions:
- The coordinated function of MCMV's three VIPRs leads to potent inhibition of CD8 T cell-mediated lysis of infected cells.
- While cooperation is the dominant interaction, specific antagonistic relationships and epitope-specific effects exist.
- Further research is needed to fully understand the molecular mechanisms and in vivo significance of these VIPRs.
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